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Sample records for frequency magnetoelectric coupling

  1. Low moment NiCr radio frequency magnetic films for multiferroic heterostructures with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Beguhn, S.; Lou, J.; Rand, S.; Li, M.; Yang, X.; Li, S. D.; Liu, M.; Sun, N. X.

    2012-05-01

    Magnetic/piezoelectric multiferroic heterostructures with a magnetic thin film on a piezoelectric slab provides a great opportunity to achieve a strong converse magnetoelectric coupling with great potential for voltage tunable magnetic devices. Efforts have been made in developing highly magnetostrictive RF magnetic materials with low magnetization using magnetic/piezoelectric heterostructures to generate large electric-field induced effective magnetic fields. In this work, we report on NiCr films having low magnetization and relatively large magnetostriction. Strong converse magnetoelectric coupling and large electric field tunable ferromagnetic resonance (FMR) bandwidths are achieved in layered NiCr/lead zirconate titanate (PZT) and NiCr/lead zinc niobate lead titanate (PZN-PT) multiferroic heterostructures. A large electric field induced effective magnetic field of 260 Oe for NiCr/PZT and 756 Oe for NiCr/PZN-PT was observed, corresponding to a giant magnetoelectric coupling coefficient of 13 Oe cm/kV in NiCr/PZT and 75.6 Oe cm/kV in NiCr/PZN-PT multiferroic heterostructures. A high voltage tunable FMR frequency range was observed, with fmax/fmin being 124 and 325% for NiCr/PZT and NiCr/PZN-PT. The strong converse magnetoelectric coupling of NiCr/PZT and NiCr/PZN-PT heterostructures provide great opportunities for electric field tunable RF magnetic devices.

  2. Magnetoelectric coupling at metal surfaces

    SciTech Connect

    Gerhard, Lukas; Yamada, T.K.; Balashov, T.; Takacs, A. F.; Wesselink, R.J.H.; Daene, Markus W; Fechner, M.; Ostanin, S.; Ernst, Arthur; Mertig, I.; Wulfhekel, Wulf

    2010-10-01

    Magnetoelectric coupling allows the magnetic state of a material to be changed by an applied electric field. To date, this phenomenon has mainly been observed in insulating materials such as complex multiferroic oxides. Bulk metallic systems do not exhibit magnetoelectric coupling, because applied electric fields are screened by conduction electrons. We demonstrate strong magnetoelectric coupling at the surface of thin iron films using the electric field from a scanning tunnelling microscope, and are able to write, store and read information to areas with sides of a few nanometres. Our work demonstrates that high-density, non-volatile information storage is possible in metals.

  3. Synthetic magnetoelectric coupling in a nanocomposite multiferroic

    DOE PAGESBeta

    Jain, P.; Wang, Q.; Roldan, M.; Glavic, A.; Lauter, V.; Urban, C.; Bi, Z.; Ahmed, T.; Zhu, J.; Varela, M.; et al

    2015-03-13

    Given the paucity of single phase multiferroic materials (with large ferromagnetic moment), composite systems seem an attractive solution to realize magnetoelectric coupling between ferromagnetic and ferroelectric order parameters. Despite having antiferromagnetic order, BiFeO₃ (BFO) has nevertheless been a key material due to excellent ferroelectric properties at room temperature. We studied a superlattice composed of 8 repetitions of 6 unit cells of La₀.₇Sr₀.₃MnO₃ (LSMO) grown on 5 unit cells of BFO. Significant net uncompensated magnetization in BFO, an insulating superlattice, is demonstrated using polarized neutron reflectometry. Remarkably, the magnetization enables magnetic field to change the dielectric properties of the superlattice, whichmore » we cite as an example of synthetic magnetoelectric coupling. Importantly, controlled creation of magnetic moment in BFO is a much needed path toward design and implementation of integrated oxide devices for next generation magnetoelectric data storage platforms.« less

  4. Quantitative investigation of magnetoelectric coupling in various forms of multiferroics

    NASA Astrophysics Data System (ADS)

    Kim, Kee Hoon

    2009-03-01

    Magnetoelectric susceptibility (MES) is probably the most direct way of estimating the magnitude of magnetoelectric coupling in many forms of magnetoelectric and/or multiferroic materials. Historically, the MES has been measured in numerous existing magnetoelectric materials in broad field, frequency, and temperature ranges and their MES values have been tabulated [1]. With growing interest worldwide toward applications of multiferroics for novel memory and sensor devices, however, there have been ever-increasing demands to measure quantitatively the MES of multiferroic thin films. Yet, the measurements of thin film MES become challenging in spite of its large MES value because the magnetoelectric voltages, proportional to the film thickness, usually get too small to be measured reliably. Herein, we introduce a highly sensitive magnetoelectric susceptometer that can detect the charge variation down to ˜10-17C in a few gauss oscillating magnetic field. Using this specific setup, we could measure the MES of multiferroic thin films or single crystals with unprecedented accuracy and sensitivity in cryogenic (down to 2 K) and magnetic field (up to 9 T) environments. In this talk, we summarize a number of key results based on this technique; (1) MES of a 300 nm BiFeO3-CoFe2O4 nanopillar structure as well as those of a 250 nm BiFeO3 film and of a BiFeO3 single crystal. (2) MES of (Pb,Zr)TiO3-NiFe2O4 nanocomposite films, and (3) temperature- and field-dependent MES in representative multiferroic crystals/films including TbMn2O5 , GaFeO3, and Cr2O3. In particular, we demonstrate that the MES of the film with the nanopillar structure is enhanced by approximately one order of magnitude reaching 2×10-10 s/m at room temperature, compared with those of a pure BiFeO3 film and a single crystal. Furthermore, based on detailed field and temperature dependent MES studies, we show that magnetoelectric coupling in TbMn2O5 has been mediated and amplified by the large magnetoelastic

  5. Nonlinear resonant magnetoelectric interactions and efficient frequency doubling in a ferromagnetic-ferroelectric layered structure

    NASA Astrophysics Data System (ADS)

    Fetisov, L. Y.; Fetisov, Y. K.; Sreenivasulu, G.; Srinivasan, G.

    2013-03-01

    Mechanical strain mediated non-linear magnetoelectric (NLME) coupling is studied in layered composites of ferromagnetic FeBSiC and piezoelectric lead zirconate titanate (PZT) bimorph. The NLME manifests as frequency doubling in the voltage response of the sample to an applied ac magnetic field. It is shown that NLME is strong (i) in the absence of DC magnetic bias, (ii) when the frequency of h is tuned to half the frequency for bending oscillations, and (iii) a PZT bimorph (instead of a single layer of PZT) is used. A model is discussed for the non-linear magnetoelectric coupling that is of interest for RF frequency doublers.

  6. Giant magnetoelectric effect at low frequencies in polymer-based thin film composites

    SciTech Connect

    Kulkarni, A.; Meurisch, K.; Strunskus, T.; Faupel, F.; Teliban, I.; Jahns, R.; Knöchel, R.; Piorra, A.

    2014-01-13

    A polymer-based magnetoelectric 2-2 composite was fabricated in a thin film approach by direct spin coating of polyvinylidenefluoride-co-trifluoroethylene onto a Metglas substrate without the usage of an adhesive for the mechanical coupling between the piezoelectric and magnetostrictive materials. For a prototype single-sided clamped cantilever, a magnetoelectric coefficient as high as 850 V cm{sup −1} Oe{sup −1} is observed at its fundamental bending mode resonance frequency at 27.8 Hz and a detection limit of 10 pTHz{sup −1/2} at its second bending mode resonance frequency at 169.5 Hz.

  7. Theoretical study on perpendicular magnetoelectric coupling in ferroelectromagnet system

    NASA Astrophysics Data System (ADS)

    Zhong, Chonggui; Jiang, Qing

    2002-06-01

    We apply the Heisenberg model for antiferromagnetic interaction and Diffour model for ferroelectric interaction to analyze the magnetic, electric, magnetoelectric property in the system with the spontaneous coexistence of the ferroelectric and antiferromagnetic orders below a certain temperature. The soft mode theory is used to calculate the on-site polarization and mean field theory is applied to deal with the on-site magnetization. We also present the perpendicular magnetoelectric susceptibility χme⊥, polarization susceptibility χp as a function of temperature, and discuss the effect of the inherent magnetoelectric coupling on them. In addition, it is found that an anomaly appears in the curve of the polarization susceptibility due to the coupling between the ferroelectric and antiferromagnetic orders.

  8. Large magnetoelectric coupling in Co4Nb2O9

    PubMed Central

    Fang, Y.; Song, Y. Q.; Zhou, W. P.; Zhao, R.; Tang, R. J.; Yang, H.; Lv, L. Y.; Yang, S. G.; Wang, D. H.; Du, Y. W.

    2014-01-01

    Magnetoelectric materials which simultaneously exhibit electric polarization and magnetism have attracted more and more attention due to their novel physical properties and promising applications for next-generation devices. Exploring new materials with outstanding magnetoelectric performance, especially the manipulation of magnetization by electric field, is of great importance. Here, we demonstrate the cross-coupling between magnetic and electric orders in polycrystalline Co4Nb2O9, in which not only magnetic-field-induced electric polarization but also electric field control of magnetism is observed. These results reveal rich physical phenomenon and potential applications in this compound. PMID:24463631

  9. Nomograph method for predicting magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Bichurin, Mirza; Petrov, Vladimir; Petrov, Roman; Tatarenko, Alexander; Leontiev, Viktor; Lavrentieva, Ksenia

    2016-08-01

    Magnetoelectric (ME) composites are known to enable the achievement of ME voltage coefficients many orders of magnitude larger than previously reported values for single phase materials. The advancements have opened up many possibilities in applications of sensors, transformers, and microwave devices. We presented here a new quick test of ME composites using nomographs and showed its use in applications where an approximate answer is appropriate and useful. To draw the graphs for ME voltage coefficients, we derived approximate expressions in explicit form for magnetically induced ME effect for different operational modes and laminate composite configurations including symmetrical and asymmetrical structures.

  10. Magnetoelectric coupling in 4,4'-stilbenedinitrene

    NASA Astrophysics Data System (ADS)

    Günaydın-Şen, Ö.; Chen, P.; Fosso-Tande, J.; Allen, T. L.; Cherian, J.; Tokumoto, T.; Lahti, P. M.; McGill, S.; Harrison, R. J.; Musfeldt, J. L.

    2013-05-01

    We investigated the optical properties of 4,4'-stilbenedinitrene at low temperature and in high magnetic fields and compared the results with complementary first principles calculations. Both physical tuning parameters allow us to manipulate the singlet-triplet equilibrium, and by doing so, control the optical contrast (which is on the order of -2.5 × 102 cm-1 at 555 nm and 35 T). Moreover, analysis of the magneto-optical response using a combined population and Beer's law framework reveals the singlet-triplet spin gap and identifies particular features in the absorption difference spectrum as deriving from singlet or triplet state excitations. These findings deepen our understanding of coupling in open shell molecules and show how chemical structure modification can modulate charge-spin interactions in organic biradicals.

  11. Magnetoelectric coupling in 4, 4'-stilbenedinitrene

    NASA Astrophysics Data System (ADS)

    Musfeldt, J. L.; Gunaydin-Sen, O.; Chen, P.; Fosso-Tande, J.; Allen, T.; Cherian, J.; Tokumoto, T.; McGill, S.; Lahti, P. M.; Harrison, R. J.

    2013-03-01

    We investigated the optical properties of 4,4'-stilbenedinitrene at low temperature and in high magnetic fields and compared the results with complementary first principles calculations. Both physical tuning parameters allow us to manipulate the singlet-triplet equilibrium, and by so doing, control the optical contrast (which is on the order of -2.5 ×102 cm-1 at 555 nm and 35 T). Moreover, analysis of the magneto-optical response using a combined population and Beer's law framework reveals the singlet-triplet spin gap and identifies particular features in the absorption difference spectrum as deriving from singlet or triplet state excitations. These findings deepen our understanding of coupling in open shell molecules and show how highlight opportunities where chemical structure modification can amplify charge-spin interactions in organic biradicals. This work is supported by the National Science Foundation.

  12. Tunable characteristics of bending resonance frequency in magnetoelectric laminated composites

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Li, Ping; Wen, Yu-Mei; Zhu, Yong

    2013-07-01

    As the magnetoelectric (ME) effect in piezoelectric/magnetostrictive laminated composites is mediated by mechanical deformation, the ME effect is significantly enhanced in the vicinity of resonance frequency. The bending resonance frequency (fr) of bilayered Terfenol-D/PZT (MP) laminated composites is studied, and our analysis predicts that (i) the bending resonance frequency of an MP laminated composite can be tuned by an applied dc magnetic bias (Hdc) due to the ΔE effect; (ii) the bending resonance frequency of the MP laminated composite can be controlled by incorporating FeCuNbSiB layers with different thicknesses. The experimental results show that with Hdc increasing from 0 Oe (1 Oe=79.5775 A/m) to 700 Oe, the bending resonance frequency can be shifted in a range of 32.68 kHz <= fr <= 33.96 kHz. In addition, with the thickness of the FeCuNbSiB layer increasing from 0 μm to 90 μm, the bending resonance frequency of the MP laminated composite gradually increases from 33.66 kHz to 39.18 kHz. This study offers a method of adjusting the strength of dc magnetic bias or the thicknesses of the FeCuNbSiB layer to tune the bending resonance frequency for ME composite, which plays a guiding role in the ME composite design for real applications.

  13. Negative refraction with low absorption using Raman transitions with magnetoelectric coupling

    SciTech Connect

    Sikes, D. E.; Yavuz, D. D.

    2010-07-15

    We suggest a scheme for obtaining negative refraction that does not require the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency. The key idea of the scheme is to obtain a strong electric response by using far-off-resonant Raman transitions. We propose to use a pair of electric-dipole Raman transitions and utilize magneto-electric cross coupling to achieve a negative index of refraction without requiring negative permeability. The interference of the two Raman transitions allows tunable negative refraction with low absorption.

  14. Quantification of strain and charge co-mediated magnetoelectric coupling on ultra-thin Permalloy/PMN-PT interface.

    PubMed

    Nan, Tianxiang; Zhou, Ziyao; Liu, Ming; Yang, Xi; Gao, Yuan; Assaf, Badih A; Lin, Hwaider; Velu, Siddharth; Wang, Xinjun; Luo, Haosu; Chen, Jimmy; Akhtar, Saad; Hu, Edward; Rajiv, Rohit; Krishnan, Kavin; Sreedhar, Shalini; Heiman, Don; Howe, Brandon M; Brown, Gail J; Sun, Nian X

    2014-01-01

    Strain and charge co-mediated magnetoelectric coupling are expected in ultra-thin ferromagnetic/ferroelectric multiferroic heterostructures, which could lead to significantly enhanced magnetoelectric coupling. It is however challenging to observe the combined strain charge mediated magnetoelectric coupling, and difficult in quantitatively distinguish these two magnetoelectric coupling mechanisms. We demonstrated in this work, the quantification of the coexistence of strain and surface charge mediated magnetoelectric coupling on ultra-thin Ni0.79Fe0.21/PMN-PT interface by using a Ni0.79Fe0.21/Cu/PMN-PT heterostructure with only strain-mediated magnetoelectric coupling as a control. The NiFe/PMN-PT heterostructure exhibited a high voltage induced effective magnetic field change of 375 Oe enhanced by the surface charge at the PMN-PT interface. Without the enhancement of the charge-mediated magnetoelectric effect by inserting a Cu layer at the PMN-PT interface, the electric field modification of effective magnetic field was 202 Oe. By distinguishing the magnetoelectric coupling mechanisms, a pure surface charge modification of magnetism shows a strong correlation to polarization of PMN-PT. A non-volatile effective magnetic field change of 104 Oe was observed at zero electric field originates from the different remnant polarization state of PMN-PT. The strain and charge co-mediated magnetoelectric coupling in ultra-thin magnetic/ferroelectric heterostructures could lead to power efficient and non-volatile magnetoelectric devices with enhanced magnetoelectric coupling.

  15. Inversion of Ferrimagnetic Magnetization by Ferroelectric Switching via a Novel Magnetoelectric Coupling

    NASA Astrophysics Data System (ADS)

    Weng, Yakui; Lin, Lingfang; Dagotto, Elbio; Dong, Shuai

    2016-07-01

    Although several multiferroic materials or heterostructures have been extensively studied, finding strong magnetoelectric couplings for the electric field control of the magnetization remains challenging. Here, a novel interfacial magnetoelectric coupling based on three components (ferroelectric dipole, magnetic moment, and antiferromagnetic order) is analytically formulated. As an extension of carrier-mediated magnetoelectricity, the new coupling is shown to induce an electric-magnetic hysteresis loop. Realizations employing BiFeO3 bilayers grown along the [111] axis are proposed. Without involving magnetic phase transitions, the magnetization orientation can be switched by the carrier modulation driven by the field effect, as confirmed using first-principles calculations.

  16. Inversion of ferrimagnetic magnetization by ferroelectric switching via a novel magnetoelectric coupling

    DOE PAGESBeta

    Weng, Yakui; Lin, Lingfang; Dagotto, Elbio; Dong, Shuai

    2016-07-12

    Although several multiferroic materials or heterostructures have been extensively studied, finding strong magnetoelectric couplings for the electric field control of the magnetization remains challenging. Here, a novel interfacial magnetoelectric coupling based on three components (ferroelectric dipole, magnetic moment, and antiferromagnetic order) is analytically formulated. As an extension of carrier-mediated magnetoelectricity, the new coupling is shown to induce an electric-magnetic hysteresis loop. In addition, realizations employing BiFeO3 bilayers grown along the [111] axis are proposed. Without involving magnetic phase transitions, the magnetization orientation can be switched by the carrier modulation driven by the field effect, as confirmed using first-principles calculations.

  17. Magnetoelectric coupling in hexagonal LuFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Liu, Hao

    The magnetic and polar properties of single-crystalline hexagonal LuFeO3 films have been studied. Both theoretical and experimental approaches indicated the coexisting of multiple ferroic orders. The spontaneous electric polarization is associated with a structural change, which also influences the magnetic properties, predicting a strong magnetoelectric coupling in these films. To investigate the magnetoelectric coupling, the micro capacitance structures were fabricated by photolithography combined with Ar ion beam etching method. The capacitance vs voltage curves show significant magnetic field effect, indicating strong magnetoelectric coupling in this system.

  18. Tensor properties of the magnetoelectric coupling in hexaferrites

    NASA Astrophysics Data System (ADS)

    Vittoria, Carmine; Somu, Sivasubramanian; Widom, Allan

    2014-04-01

    Recent data reported on magnetoelectric coupling parameter α for hexaferrite materials are very high; hence, these materials are expected to potentially impact future technologies in a major way. At this juncture, it is imperative to address the fundamental question, "What does α depend on?" in order to advance the design of new hexaferrite materials with even higher α. A complete mathematical formulation of a microscopic model would be rather complicated, especially for complex crystal structures such as the Z-type hexaferrites. Herein we present a simple, yet elegant thermodynamic argument by which we derive a functional relationship between α and the material parameters. We show that α is best described as a tensor proportional to the product of magnetostriction and piezoelectric strain tensors. Using this relationship, quantitative values for α are estimated and compared to experimentally measured values for various hexaferrites, composites, and Cr2O3.

  19. Magnetoelectric Coupling in Cobalt Zinc Ferrite - Lead Zirconate Titanate Composites

    NASA Astrophysics Data System (ADS)

    Srinivasan, G.; Hayes, R.; Mantese, J. V.

    2003-03-01

    This report is on the observation of zinc-assisted enhancement in magnetoelectric (ME) coupling in cobalt zinc ferrite, Co(1-x)ZnxFe2O4(x=0-0.5) (CZFO)-lead zirconate titanate (PZT) composites. In such ferromagnetic-piezoelectric composites, an applied ac magnetic field produces dynamic deformation in ferrites due to magnetostriction and results in an induced electric field due to piezoelectric effect in PZT [1]. Important findings are as follows. (i) Bulk samples of pure CFO and PZT prepared either by traditional ceramic processing or by microwave sintering show very weak ME coupling. (iii) Enhancement in ME coupling, by a factor of five, is observed in a layered structure of thick films of CFO and PZT. (iv) Substitution of Zn in CFO is observed to strengthen magneto-mechanical and ME couplings in multilayers. (v) The interface coupling parameter, obtained from our theoretical model [2], shows an increase with x and a peak value for x=0.4. --- Research supported by a grant from the NSF (DMR-0072144) 1. G. Srinivasan, E. T. Rasmussen, J. Gallegos, R. Srinivasan, Yu. I. Bokhan, and V. M. Laletin, Phys. Rev. B 64, 214408 (2001). 2. M. I. Bichurin, V. M. Petrov, and G. Srinivasan, in press, J. Appl. Phys. (Jan. 2003)

  20. A pencil-like magnetoelectric sensor exhibiting ultrahigh coupling properties

    NASA Astrophysics Data System (ADS)

    Lin, Lizhi; Li, Yingwei; Soh, Ai-Kah; Li, Faxin

    2013-04-01

    A one-dimensional pencil-like magnetoelectric (ME) sensor prototype is proposed which consists of a magnetostrictive cylinder, a truncated conical spacer, and a piezoelectric disk assembled in a rigid frame. By adopting the displacement-transfer mode in this sensor, not only the strain loss at the ME interface is avoided but also the volume fractions of both phases can be adjusted in a broader range. Using a nonlinear magnetostrictive model and linear piezoelectric model, the ME coupling performance of this sensor is systematically analyzed using lead titanate zirconate (PZT) disks and Terfenol-D cylinder as the components. Results show that such a sensor can practically exhibit giant quasi-static ME field coefficients (αE) and charge density coefficients (αD) as high as 455 V /cm Oe and 480×10-6 C/m2 Oe, which is about 10 times and 100 times higher than the best reported values, respectively. Furthermore, the ME coupling properties will decrease considerably when the stiffness of the frame is reduced. The proposed pencil-like ME sensor in this work could be very helpful in the design of ultrasensitive magnetic-field sensors and other ME coupling devices.

  1. Quantification of strain and charge co-mediated magnetoelectric coupling on ultra-thin Permalloy/PMN-PT interface

    PubMed Central

    Nan, Tianxiang; Zhou, Ziyao; Liu, Ming; Yang, Xi; Gao, Yuan; Assaf, Badih A.; Lin, Hwaider; Velu, Siddharth; Wang, Xinjun; Luo, Haosu; Chen, Jimmy; Akhtar, Saad; Hu, Edward; Rajiv, Rohit; Krishnan, Kavin; Sreedhar, Shalini; Heiman, Don; Howe, Brandon M.; Brown, Gail J.; Sun, Nian X.

    2014-01-01

    Strain and charge co-mediated magnetoelectric coupling are expected in ultra-thin ferromagnetic/ferroelectric multiferroic heterostructures, which could lead to significantly enhanced magnetoelectric coupling. It is however challenging to observe the combined strain charge mediated magnetoelectric coupling, and difficult in quantitatively distinguish these two magnetoelectric coupling mechanisms. We demonstrated in this work, the quantification of the coexistence of strain and surface charge mediated magnetoelectric coupling on ultra-thin Ni0.79Fe0.21/PMN-PT interface by using a Ni0.79Fe0.21/Cu/PMN-PT heterostructure with only strain-mediated magnetoelectric coupling as a control. The NiFe/PMN-PT heterostructure exhibited a high voltage induced effective magnetic field change of 375 Oe enhanced by the surface charge at the PMN-PT interface. Without the enhancement of the charge-mediated magnetoelectric effect by inserting a Cu layer at the PMN-PT interface, the electric field modification of effective magnetic field was 202 Oe. By distinguishing the magnetoelectric coupling mechanisms, a pure surface charge modification of magnetism shows a strong correlation to polarization of PMN-PT. A non-volatile effective magnetic field change of 104 Oe was observed at zero electric field originates from the different remnant polarization state of PMN-PT. The strain and charge co-mediated magnetoelectric coupling in ultra-thin magnetic/ferroelectric heterostructures could lead to power efficient and non-volatile magnetoelectric devices with enhanced magnetoelectric coupling. PMID:24418911

  2. Quantification of strain and charge co-mediated magnetoelectric coupling on ultra-thin Permalloy/PMN-PT interface.

    PubMed

    Nan, Tianxiang; Zhou, Ziyao; Liu, Ming; Yang, Xi; Gao, Yuan; Assaf, Badih A; Lin, Hwaider; Velu, Siddharth; Wang, Xinjun; Luo, Haosu; Chen, Jimmy; Akhtar, Saad; Hu, Edward; Rajiv, Rohit; Krishnan, Kavin; Sreedhar, Shalini; Heiman, Don; Howe, Brandon M; Brown, Gail J; Sun, Nian X

    2014-01-01

    Strain and charge co-mediated magnetoelectric coupling are expected in ultra-thin ferromagnetic/ferroelectric multiferroic heterostructures, which could lead to significantly enhanced magnetoelectric coupling. It is however challenging to observe the combined strain charge mediated magnetoelectric coupling, and difficult in quantitatively distinguish these two magnetoelectric coupling mechanisms. We demonstrated in this work, the quantification of the coexistence of strain and surface charge mediated magnetoelectric coupling on ultra-thin Ni0.79Fe0.21/PMN-PT interface by using a Ni0.79Fe0.21/Cu/PMN-PT heterostructure with only strain-mediated magnetoelectric coupling as a control. The NiFe/PMN-PT heterostructure exhibited a high voltage induced effective magnetic field change of 375 Oe enhanced by the surface charge at the PMN-PT interface. Without the enhancement of the charge-mediated magnetoelectric effect by inserting a Cu layer at the PMN-PT interface, the electric field modification of effective magnetic field was 202 Oe. By distinguishing the magnetoelectric coupling mechanisms, a pure surface charge modification of magnetism shows a strong correlation to polarization of PMN-PT. A non-volatile effective magnetic field change of 104 Oe was observed at zero electric field originates from the different remnant polarization state of PMN-PT. The strain and charge co-mediated magnetoelectric coupling in ultra-thin magnetic/ferroelectric heterostructures could lead to power efficient and non-volatile magnetoelectric devices with enhanced magnetoelectric coupling. PMID:24418911

  3. Spin-phonon coupling and ferroelectricity in magnetoelectric gallium ferrite

    NASA Astrophysics Data System (ADS)

    Mukherjee, Somdutta

    2014-03-01

    Gallium ferrite (GaFeO3 or GFO) is a low temperature ferrimagnet and room temperature piezoelectric wherein the magnetic transition temperature (TC) could be tailored to room temperature and above by tuning the stoichiometry and processing conditions. Such tunability of the magnetic transition temperature renders GFO a unique perspective in the research of multiferroics to potentially demonstrate room temperature magnetoelectric effect attractive for futuristic digital memory applications. Recent studies in several transition metal oxides highlight the importance of spin-phonon coupling in designing novel multiferroics by means of strain induced phase transition. In the present work, we have systematically studied the evolution of phonons in good quality samples of GFO across the TC using Raman spectroscopy. Using the phonon softening behavior and nearest neighbor spin-spin correlation function below TC we estimated spin-phonon coupling strength in the magnetically ordered state. In the process, we also show, for the first time, the presence of a spin glass phase in GFO where the spin-glass transition has a signature of abrupt change in spin-phonon coupling strength. Though GFO is piezoelectric and crystallizes in polar Pc21n symmetry, its ferroelectric nature remained controversial probably due to the large leakage current in the bulk material. To address this issue, we deposited epitaxial thin film on single crystalline yttria stabilized zirconia (YSZ) substrate using indium tin oxide (ITO) as a bottom conducting layer. We demonstrate clear evidence of room temperature ferroelectricity in the thin films from the 180o phase shift of the piezoresponse upon switching the electric field. Further, suppression of dielectric anomaly in presence of an external magnetic field clearly reveals a pronounced magneto-dielectric coupling across the magnetic transition temperature. In addition, using first principles calculations we elucidate that Fe ions are not only

  4. Magnetoelectric Coupling, Ferroelectricity, and Magnetic Memory Effect in Double Perovskite La3Ni2NbO9.

    PubMed

    Dey, K; Indra, A; De, D; Majumdar, S; Giri, S

    2016-05-25

    We observe ferroelectricity in an almost unexplored double perovskite La3Ni2NbO9. Ferroelectricity appears below ∼60 K, which is found to be correlated with the significant magnetostriction. A reasonably large value of spontaneous electric polarization is recorded to be ∼260 μC/m(2) at 10 K for E = 5 kV/cm, which decreases signifi- cantly upon application of a magnetic field (H), suggesting considerable magnetoelectric coupling. The dielectric permittivity is also influenced by H below the ferroelectric transition. The magnetodielectric response scales linearly to the squared magnetization, as described by the Ginzburg-Landau theory. Meticulous studies of static and dynamic features of dc magnetization and frequency dependent ac susceptibility results suggest spin-glass state below 29 K. Intrinsic magnetic memory effect is observed from zero-field cooled magnetization and isothermal remanent magnetization studies, also pointing spin-glass state below 29 K. Appearance of ferroelectricity together with a significant magnetoelectric coupling in absence of conventional long-range magnetic order is promising for searching new magnetoelectric materials. PMID:27136317

  5. Resonant and nonresonant magnetoelectric effects in multilayer composites at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Bichurin, M. I.; Kiliba, Yu. V.; Srinivasan, G.

    2002-03-01

    A phenomenological theory is presented on the effect of an external electric field on magnetic and magnetoelectric (ME) susceptibilities of ferroelectric/ferromagnetic composites, such as lithium ferrite lead zirconate titanate (PZT), at microwave frequencies. Expressions have been obtained relating the magnetic susceptibility tensor components of the composite (symmetry point group 3m and 4mm) to ME coupling constants. Estimates of linear and bilinear ME susceptibilities at high frequencies are given and are extended to include ferromagnetic resonance (FMR) conditions [1]. Both magnetic and ME susceptibilities reveal a resonance in the electric field dependence. Three methods for measurements of ME susceptibility at microwave frequencies are considered: electric dipole transitions, resonance ME effects at ferromagnetic resonance and off-resonance method. Using the theory and experimental data on ferromagnetic resonance line shift in external electric field, the ME constants for lithium ferrite-PZT multilayer composite are determined. The theory is useful for measurements of ME constants and for the design and analysis of electrically controlled high frequency magnetic devices. - work supported by a grant from the National Science Foundation (DMR-0072144) 1. M.I. Bichurin, I. A. Kornev, V. M. Petrov, A. S. Tatarenko, Yu. V. Kiliba, and G. Srinivasan, Phys. Rev. B 64, 094409 (2001).

  6. Giant self-biased magnetoelectric coupling in co-fired textured layered composites

    NASA Astrophysics Data System (ADS)

    Yan, Yongke; Zhou, Yuan; Priya, Shashank

    2013-02-01

    Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response.

  7. Magnetoelectric coupling characteristics in multiferroic heterostructures with different thickness of nanocrystalline soft magnetic alloy

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Wang, Yao

    2016-05-01

    Magnetoelectric(ME) coupling characteristics in multiferroic heterostructures with different thickness of nanocrystalline soft magnetic alloy has been investigated at low frequency. The ME response with obvious hysteresis, self-biased and dual-peak phenomenon is observed for multiferroic heterostructures, which results from strong magnetic interactions between two ferromagnetic materials with different magnetic properties, magnetostrictions and optimum bias magnetic fields Hdc,opti. The proposed multiferroic heterostructures not only enhance ME coupling significantly, but also broaden dc magnetic bias operating range and overcomes the limitations of narrow bias range. By optimizing the thickness of nanocrystalline soft magnetic alloy Tf, a significantly zero-biased ME voltage coefficient(MEVC) of 14.8mV/Oe (185 mV/cmṡ Oe) at Tf = 0.09 mm can be obtained, which is about 10.8 times as large as that of traditional PZT/Terfenol-D composite with a weak ME coupling at zero bias Hdc,zero. Furthermore, when Tf increases from 0.03 mm to 0.18 mm, the maximum MEVC increases nearly linearly with the increased Tf at Hdc,opti. Additionally, the experimental results demonstrate the ME response for multiferroic heterostructures spreads over a wide magnetic dc bias operating range. The excellent ME performance provides a promising and practicable application for both highly sensitive magnetic field sensors without bias and ME energy harvesters.

  8. Comment on "Canonical magnetic insulators with isotropic magnetoelectric coupling"

    NASA Astrophysics Data System (ADS)

    Perez-Mato, J. M.; Gallego, Samuel V.; Tasci, E. S.; Elcoro, L.; Aroyo, M. I.

    2014-10-01

    Coh et al. presented in [Phys. Rev. B 88, 121106(R) (2013), 10.1103/PhysRevB.88.121106] a systematic search of the simplest so-called "canonical" structures allowing isotropic magnetoelectric response, and reported a total of 30 such magnetic configurations. Using magnetic symmetry we show in this Comment that this listing is severely incomplete, and 14 additional distinct cases satisfying the same conditions should be added. The complete list of these elementary magnetic arrangements is then presented in a short and efficient form as distinct Wyckoff positions of some cubic magnetic space groups.

  9. The influence of low-level pre-stressing on resonant magnetoelectric coupling in Terfenol-D/PZT/Terfenol-D laminated composite structure

    NASA Astrophysics Data System (ADS)

    Chen, Zhengxin; Su, Yu

    2014-05-01

    The resonant magnetoelectric coupling behavior in a Terfenol-D/PZT/Terfenol-D laminated composite structure is experimentally studied with specific interest in the dependence on the pre-applied low-level mechanical stress up to 1.25 MPa. A laminated composite consisting of two Terfenol-D plates and one transversely polarized sandwiched-in PZT plate is fabricated in lab followed by pre-stressing along the direction of length, width, and thickness, respectively. It is observed that resonant magnetoelectric coupling develops in such pre-stressed composite when magnetically excited in each of the orthogonal directions, and the longitudinal mode of principle vibration can be confirmed. The action of pre-stresses generally elevates the frequency of resonance through the ΔE effect in Terfenol-D. In the meanwhile, the increased pre-stress lowers the value of the resonance magnetoelectric coefficient. This is partly attributed to the decrease of the effective quality factor of the structure along the increase of pre-stress, and partly attributed to the piezomagnetic coefficient of Terfenol-D, which either decreases or remains constant depending on the magnetizing state. In addition to the resonant behaviors, the tunability of the magnetoelectric coefficient of the pre-stressed structure is examined at fixed excitation frequency. For the structure excited in the length or width direction, the magnetoelectric coupling can reach the maximum at an optimal bias field. When excited in thickness, however, the magnetoelectric coupling becomes very weak, and the value of the coefficient increases monotonically with the pre-stresses. The increase of the pre-stress causes degradation of the maximum magnetoelectric coefficient for the structure when excited in length or width direction. This observation can be explained via the upshift of the resonance frequency of the structure caused by increased pre-stresses. Alternatively, it can be viewed as the consequence of the change in the

  10. Dipolar glass and strong magneto-electric coupling within a purely organic system

    NASA Astrophysics Data System (ADS)

    Berlie, Adam; Terry, Ian; Liu, Yun; Szablewski, Marek

    There is much interest in the search for novel materials that show ferroelectric as well as magneto-electric coupling, such as that observed in multiferroics. Within organic based materials the electronic polarisation can come from a charge distribution across a molecule or molecules and so one must search for systems that have a electronic (and magnetic) dipole that is intrinsic. One such material is tetraethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)2) which is a charge transfer system where there is a single electron delocalised across a TCNQ dimer. We show that dielectric measurements yield anomalies at the Peierls structural distortion and on going through the spin-Peierls transition. In both cases the electric response is glassy and at low temperature the corresponding magnetic measurements evidence the strong magneto-electric coupling within the material showing analogies to spin glass systems.

  11. Local two-way magnetoelectric couplings in multiferroic composites via scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Xie, S. H.; Liu, Y. M.; Liu, X. Y.; Zhou, Q. F.; Shung, K. K.; Zhou, Y. C.; Li, J. Y.

    2010-09-01

    Local two-way magnetoelectric (ME) couplings of a multiferroic composite have been characterized at nanoscale using novel scanning probe microscopy techniques we developed. A bilayer multiferroic composite consisting of lead zirconate titanate (PZT) and TbDyFe (TDF) has been fabricated, and the evolution of ferroelectric domains in PZT induced by an external magnetic field is observed by piezoresponse force microscopy, while the evolution of magnetic domains in TDF induced by an external electric field is observed by magnetic force microscopy, confirming the two-way ME couplings in the multiferroic composite. The technique will be useful in characterizing nanoscale ME couplings in a wide range of multiferroic composites.

  12. Enhanced Magnetoelectric Coupling in Layered Structure of Piezoelectric Bimorph and Metallic Alloy

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Bichurin, M. I.; Lavrentyeva, K. V.; Leontiev, V. S.

    2016-08-01

    We have investigated the enhanced magnetoelectric (ME) coupling in a layered structure of piezoelectric bimorph and magnetostrictive metallic alloy. The observed ME coefficient in the piezoelectric bimorph-based structure was found to be two times higher than in the traditional piezoelectric/magnetostrictive bilayer. The observed enhancement in ME coupling strength is related to equal signs of induced voltage in both lead zirconate titanate layers with opposite poling directions due to the flexural deformations. The piezoelectric bimorph-based structure has promising potential for sensor and technological applications.

  13. Giant and universal magnetoelectric coupling in soft materials and concomitant ramifications for materials science and biology.

    PubMed

    Liu, Liping; Sharma, Pradeep

    2013-10-01

    Magnetoelectric coupling-the ability of a material to magnetize upon application of an electric field and, conversely, to polarize under the action of a magnetic field-is rare and restricted to a rather small set of exotic hard crystalline materials. Intense research activity has recently ensued on materials development, fundamental scientific issues, and applications related to this phenomenon. This tantalizing property, if present in adequate strength at room temperature, can be used to pave the way for next-generation memory devices such as miniature magnetic random access memories and multiple state memory bits, sensors, energy harvesting, spintronics, among others. In this Rapid Communication, we prove the existence of an overlooked strain mediated nonlinear mechanism that can be used to universally induce the giant magnetoelectric effect in all (sufficiently) soft dielectric materials. For soft polymer foams-which, for instance, may be used in stretchable electronics-we predict room-temperature magnetoelectric coefficients that are comparable to the best known (hard) composite materials created. We also argue, based on a simple quantitative model, that magnetoreception in some biological contexts (e.g., birds) most likely utilizes this very mechanism.

  14. Phonon excitations and magnetoelectric coupling in multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Bahoosh, Safa Golrokh; Wesselinowa, Julia M.; Trimper, Steffen

    2013-05-01

    Multiferroic rare-earth manganites are theoretically studied by focusing on the coupling to the lattice degrees of freedom. We demonstrate analytically that the phonon excitations in the multiferroic phase are strongly affected by the magnetoelectric coupling, the spin-phonon interaction and the anharmonic phonon-phonon interaction. Based on a microscopic model, the temperature dependence of the phonon dispersion relation is analyzed. It offers an anomaly at both the ferroelectric and the magnetic transition indicating the mutual coupling between multiferroic orders and lattice distortions. Depending on the sign of the spin-phonon coupling the phonon modes become softer or harder in accordance with experimental observations. We show that the phonon spectrum can be also controlled by an external magnetic field. The phonon energy is enhanced by increasing that field. The applied Green's function technique allows the calculation of the macroscopic magnetization depending on both the phonon-phonon and the spin-phonon couplings.

  15. Magnetoelectric coupling in ordered arrays of multilayered heteroepitaxial BaTiO₃/CoFe₂O₄ nanodots.

    PubMed

    Lu, Xiaoli; Kim, Yunseok; Goetze, Silvana; Li, Xiaoguang; Dong, Sining; Werner, Peter; Alexe, Marin; Hesse, Dietrich

    2011-08-10

    Fully epitaxial BaTiO(3)/CoFe(2)O(4) ferroelectric/ferromagnetic multilayered nanodot arrays, a new type of magnetoelectric (ME) nanocomposite with both horizontal and vertical orderings, were fabricated via a stencil-derived direct epitaxy technique. By reducing the clamping effect, ferroelectric domain modification and distinct magnetization change proportional to different interfacial area around the BaTiO(3) phase transition temperatures were found, which may pave the way to quantitative introducing of ME coupling at nanoscale and build high density multistate memory devices. PMID:21749120

  16. Magneto-optical Kerr effect investigation on magnetoelectric coupling in ferromagnetic/antiferroelectric multilayer thin film structures

    NASA Astrophysics Data System (ADS)

    Mirshekarloo, Meysam Sharifzadeh; Yakovlev, Nikolai; Wong, Meng Fei; Yao, Kui; Sritharan, Thirumany; Bhatia, Charanjit Singh

    2012-10-01

    Magnetoelectric (ME) membranes comprising soft ferromagnetic Ni and antiferroelectric (AFE) (Pb,La)(Zr,Sn,Ti)O3 (PLZST) layers were proposed and fabricated through a bulk micro-machining process on silicon wafers. An AC-mode magneto-optical Kerr effect technique was proposed to examine the magnetoelectric coupling in the multilayer membranes, in which the electric field-induced magnetization rotation was analyzed for understanding the underlying coupling mechanisms. The AFE to ferroelectric phase transformation of PLZST induced a rotation of magnetization of about 0.5° in Ni, persuaded by strain-induced anisotropy of about -0.5 kJ/m3.

  17. Analysis of the low-frequency magnetoelectric performance in three-phase laminate composites with Fe-based nanocrystalline ribbon

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Li, Ping; Wen, Yumei; Zhu, Yong

    2013-11-01

    The theoretical analysis of magnetoelectric (ME) performance in three-phase Terfenol-D/PZT/FeCuNbSiB (MPF) laminate composite is presented in this paper. The ME couplings at low frequency for ideal and less than ideal interface couplings are studied, respectively, and our analysis predicts that (i) the ME voltage coefficient for ideal interface coupling increases with the increasing layers (n) of Fe-based nanocrystalline ribbon FeCuNbSiB (Fe73.5Cu1Nb3Si13.5B9) while the sizes of PZT (Pb(Zr1-xTix)O3) and Terfenol-D (Tb1-xDyxFe2-y) are kept constant, and then it tends to be a constant when the layers of FeCuNbSiB are >100 (ii) by introducing the interface coupling factor k and considering the degradation of d33m,f with n, the ME voltage coefficient for a less than ideal interface condition is predicted. As the FeCuNbSiB layer increases, it first increases and reaches to a maximum value, and then slowly decreases. Various MPF laminates are fabricated and tested. It is found that the theoretical predictions for the consideration of actual boundary conditions at the interface are in agreement with the experimental observations. This study plays a guiding role for the design of MPF composite in real applications.

  18. The memory effect of magnetoelectric coupling in FeGaB/NiTi/PMN-PT multiferroic heterostructure

    PubMed Central

    Zhou, Ziyao; Zhao, Shishun; Gao, Yuan; Wang, Xinjun; Nan, Tianxiang; Sun, Nian X.; Yang, Xi; Liu, Ming

    2016-01-01

    Magnetoelectric coupling effect has provided a power efficient approach in controlling the magnetic properties of ferromagnetic materials. However, one remaining issue of ferromagnetic/ferroelectric magnetoelectric bilayer composite is that the induced effective anisotropy disappears with the removal of the electric field. The introducing of the shape memory alloys may prevent such problem by taking the advantage of its shape memory effect. Additionally, the shape memory alloy can also “store” the magnetoelectric coupling before heat release, which introduces more functionality to the system. In this paper, we study a FeGaB/NiTi/PMN-PT multiferroic heterostructure, which can be operating in different states with electric field and temperature manipulation. Such phenomenon is promising for tunable multiferroic devices with multi-functionalities. PMID:26847469

  19. The memory effect of magnetoelectric coupling in FeGaB/NiTi/PMN-PT multiferroic heterostructure.

    PubMed

    Zhou, Ziyao; Zhao, Shishun; Gao, Yuan; Wang, Xinjun; Nan, Tianxiang; Sun, Nian X; Yang, Xi; Liu, Ming

    2016-02-05

    Magnetoelectric coupling effect has provided a power efficient approach in controlling the magnetic properties of ferromagnetic materials. However, one remaining issue of ferromagnetic/ferroelectric magnetoelectric bilayer composite is that the induced effective anisotropy disappears with the removal of the electric field. The introducing of the shape memory alloys may prevent such problem by taking the advantage of its shape memory effect. Additionally, the shape memory alloy can also "store" the magnetoelectric coupling before heat release, which introduces more functionality to the system. In this paper, we study a FeGaB/NiTi/PMN-PT multiferroic heterostructure, which can be operating in different states with electric field and temperature manipulation. Such phenomenon is promising for tunable multiferroic devices with multi-functionalities.

  20. The memory effect of magnetoelectric coupling in FeGaB/NiTi/PMN-PT multiferroic heterostructure

    NASA Astrophysics Data System (ADS)

    Zhou, Ziyao; Zhao, Shishun; Gao, Yuan; Wang, Xinjun; Nan, Tianxiang; Sun, Nian X.; Yang, Xi; Liu, Ming

    2016-02-01

    Magnetoelectric coupling effect has provided a power efficient approach in controlling the magnetic properties of ferromagnetic materials. However, one remaining issue of ferromagnetic/ferroelectric magnetoelectric bilayer composite is that the induced effective anisotropy disappears with the removal of the electric field. The introducing of the shape memory alloys may prevent such problem by taking the advantage of its shape memory effect. Additionally, the shape memory alloy can also “store” the magnetoelectric coupling before heat release, which introduces more functionality to the system. In this paper, we study a FeGaB/NiTi/PMN-PT multiferroic heterostructure, which can be operating in different states with electric field and temperature manipulation. Such phenomenon is promising for tunable multiferroic devices with multi-functionalities.

  1. The memory effect of magnetoelectric coupling in FeGaB/NiTi/PMN-PT multiferroic heterostructure.

    PubMed

    Zhou, Ziyao; Zhao, Shishun; Gao, Yuan; Wang, Xinjun; Nan, Tianxiang; Sun, Nian X; Yang, Xi; Liu, Ming

    2016-01-01

    Magnetoelectric coupling effect has provided a power efficient approach in controlling the magnetic properties of ferromagnetic materials. However, one remaining issue of ferromagnetic/ferroelectric magnetoelectric bilayer composite is that the induced effective anisotropy disappears with the removal of the electric field. The introducing of the shape memory alloys may prevent such problem by taking the advantage of its shape memory effect. Additionally, the shape memory alloy can also "store" the magnetoelectric coupling before heat release, which introduces more functionality to the system. In this paper, we study a FeGaB/NiTi/PMN-PT multiferroic heterostructure, which can be operating in different states with electric field and temperature manipulation. Such phenomenon is promising for tunable multiferroic devices with multi-functionalities. PMID:26847469

  2. Magnetoelectric control of spin currents

    NASA Astrophysics Data System (ADS)

    Gómez, J. E.; Vargas, J. M.; Avilés-Félix, L.; Butera, A.

    2016-06-01

    The ability to control the spin current injection has been explored on a hybrid magnetoelectric system consisting of a (011)-cut ferroelectric lead magnesium niobate-lead titanate (PMNT) single crystal, a ferromagnetic FePt alloy, and a metallic Pt. With this PMNT/FePt/Pt structure we have been able to control the magnetic field position or the microwave excitation frequency at which the spin pumping phenomenon between FePt and Pt occurs. We demonstrate that the magnetoelectric heterostructure operating in the L-T (longitudinal magnetized-transverse polarized) mode couples the PMNT crystal to the magnetostrictive FePt/Pt bilayer, displaying a strong magnetoelectric coefficient of ˜140 Oe cm kV-1. Our results show that this mechanism can be effectively exploited as a tunable spin current intensity emitter and open the possibility to create an oscillating or a bistable switch to effectively manipulate spin currents.

  3. Magnetoelectric coupling of laminated composites under combined thermal and magnetic loadings

    NASA Astrophysics Data System (ADS)

    Fang, F.; Xu, Y. T.; Yang, W.

    2012-01-01

    Laminated magnetoelectric (ME) composites are suitable for applications such as magnetic field sensors, transformers, and microwave resonators. Such applications frequently involve environments where the temperature alters. The present work investigates the temperature dependent ME coupling for three kinds of laminates, namely, Terfenol-D/PZT/Terfenol-D, Ni/PZT/Ni, and Metglas/PZT/Metglas. The Terfenol-D/PZT/Terfenol-D is shown to exhibit the best temperature stability. The peak value of the ME coefficient versus temperature curve is predicted for the laminates based on the equivalent circuit model, as well as the measurements of temperature dependent magnetostriction for Terfenol-D, Ni, and Metglas. The predictions agree well with the experimental data, implying that the piezomagnetic coefficient, d11,m, of the magnetic layer plays an important role in the temperature dependent ME coupling of the laminate.

  4. First principles study of magnetoelectric coupling in Co2FeAl/BaTiO3 tunnel junctions.

    PubMed

    Yu, Li; Gao, Guoying; Zhu, Lin; Deng, Lei; Yang, Zhizong; Yao, Kailun

    2015-06-14

    Critical thickness for ferroelectricity and the magnetoelectric effect of Co2FeAl/BaTiO3 multiferroic tunnel junctions (MFTJs) are investigated using first-principles calculations. The ferroelectric polarization of the barriers can be maintained upto a critical thickness of 1.7 nm for both the Co2/TiO2 and FeAl/TiO2 interfaces. The magnetoelectric effect is derived from the difference in the magnetic moments on interfacial atoms, which is sensitive to the reversal of electric polarization. The magnetoelectric coupling is found to be dependent on the interfacial electronic hybridizations. Compared with the Co2/TiO2 interface, more net magnetization change is achieved at the FeAl/TiO2 interface. In addition, the in-plane strain effect shows that in-plane compressive strain can lead to the enhancement of ferroelectric polarization stability and intensity of magnetoelectric coupling. These findings suggest that Co2FeAl/BaTiO3 MFTJs could be utilized in the area of electrically controlled magnetism, especially the MFTJ with loaded in-plane compressive strain with the FeAl/TiO2 interface. PMID:25987345

  5. Magnetoelectric coupling of multiferroic chromium doped barium titanate thin film probed by magneto-impedance spectroscopy

    SciTech Connect

    Shah, Jyoti Kotnala, Ravinder K. E-mail: rkkotnala@gmail.com

    2014-04-07

    Thin film of BaTiO{sub 3} doped with 0.1 at. % Cr (Cr:BTO) has been prepared by pulsed laser deposition technique. Film was deposited on Pt/SrTiO{sub 3} substrate at 500 °C in 50 mTorr Oxygen gas pressure using KrF (298 nm) laser. Polycrystalline growth of single phase Cr:BTO thin film has been confirmed by grazing angle X-ray diffraction. Cr:BTO film exhibited remnant polarization 6.4 μC/cm{sup 2} and 0.79 MV/cm coercivity. Magnetization measurement of Cr:BTO film showed magnetic moment 12 emu/cc. Formation of weakly magnetic domains has been captured by magnetic force microscopy. Theoretical impedance equation fitted to experimental data in Cole-Cole plot for thin film in presence of transverse magnetic field resolved the increase in grain capacitance from 4.58 × 10{sup −12} to 5.4 × 10{sup −11} F. Film exhibited high value 137 mV/cm-Oe magneto-electric (ME) coupling coefficient at room temperature. The high value of ME coupling obtained can reduce the typical processing steps involved in multilayer deposition to obtain multiferrocity in thin film. Barium titanate being best ferroelectric material has been tailored to be multiferroic by non ferromagnetic element, Cr, doping in thin film form opens an avenue for more stable and reliable spintronic material for low power magnetoelectric random excess memory applications.

  6. Magnetoelectric coupling of multiferroic composites under combined magnetic and mechanical loadings

    NASA Astrophysics Data System (ADS)

    Fang, F.; Zhou, Y. Y.; Xu, Y. T.; Jing, W. Q.; Yang, W.

    2013-07-01

    Multiferroic composites are of particular interest because of their high magnetoelectric (ME) coupling at room temperature. In multiferroic composites, ME coupling is a strain mediated effect achieved via the interfaces between the magnetic and electrical subsystems through elastic deformation. In this paper, ME coupling of laminate composites is investigated under combined magnetic and mechanical loadings. Three types of laminate composites are used, with piezoelectric phase layers of PZT plates and the magnetic phase layers comprising Terfenol-D, Ni and Metglas, respectively. As the applied compressive stress increases, the ME coefficient (αME) decreases monotonically for Terfenol-D/PZT/Terfenol-D and Metglas/PZT/Metglas, while it slightly increases for Ni/PZT/Ni laminate. To reveal the influence of the magnetic layers on the ME coupling, measurements of magnetostriction under combined magnetic and compressive loadings are carried out for Terfenol-D, Ni and Metglas. Based on the equivalent circuit model, the peak values of the ME coefficient for different compressive stresses are predicted for the laminate composites; these agree well with the experimental data. It is suggested that the compressive stress-induced strain, as well as the magnetostrictive response of the magnetic material, mainly contribute to the mechanical-magnetic-electrical coupling behavior of the multiferroic composites.

  7. Tuning the competition between ferromagnetism and antiferromagnetism in a half-doped manganite through magnetoelectric coupling

    SciTech Connect

    Yi, Di; Liu, Jian; Okamoto, Satoshi; Jagannatha, Suresha; Chen, Yi-Chun; Yu, Pu; Chu, Ying-Hao; Arenholz, Elke; Ramesh, Ramamoorthy

    2013-01-01

    We investigate the possibility of controlling the magnetic phase transition of the heterointerface between a half-doped manganite La0:5Ca0:5MnO3 and a multiferroic BiFeO3 (BFO) through magnetoelectric coupling. Using macroscopic magnetometry and element-selective x-ray magnetic circular dichroism at the Mn and Fe L edges, we discover that the ferroelectric polarization of BFO controls simultaneously the magnetization of BFO and La0.5Ca0.5MnO3 (LCMO). X-ray absorption spectra at the oxygen K edge and linear dichroism at the Mn L edge suggest that the interfacial coupling is mainly derived from the superexchange between Mn and Fe t2g spins. The combination of x-ray absorption spectroscopy and mean-field theory calculations reveals that the d-electron modulation of Mn cations changes the magnetic coupling in LCMO, which controls the enhanced canted moments of interfacial BFO via the interfacial coupling. Our results demonstrate that the competition between ferromagnetic and antiferromagnetic instability can be modulated by an electric field at the heterointerface, providing another pathway for the electrical field control of magnetism.

  8. Strain-mediated converse magnetoelectric coupling strength manipulation by a thin titanium layer

    NASA Astrophysics Data System (ADS)

    Yang, Wei-Gang; Morley, Nicola A.; Sharp, Joanne; Tian, Ye; Rainforth, W. Mark

    2016-01-01

    The manipulation of the strain-mediated magnetoelectric (ME) coupling strength is investigated by inserting a thin Ti layer (0-10 nm) between a 50 nm Co50Fe50 layer and a (011) oriented lead magnesium niobate-lead titanate (PMN-PT) substrate. A record high remanence ratio (Mr/Ms) tunability of 100% has been demonstrated in the 50 nm CoFe/8 nm Ti/PMN-PT heterostructure, when a total in-plane piezoelectric strain of -1821 ppm was applied at an electric field (E-field) of 16 kV/cm. The ME coupling strength is gradually optimized as the Ti layer thickness increases. Magnetic energy calculation showed that with increasing Ti layer thickness the uniaxial magnetic anisotropy energy (Euni) was reduced from 43 ± 1 kJ/m3 to 29.8 ± 1 kJ/m3. The reduction of Euni makes the strain effect dominant in the total magnetic energy, thus gives an obvious enhanced ME coupling strength.

  9. Magnetoelectric response of the antiferromagnetic insulator phase in a three-dimensional correlated system with spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Sekine, Akihiko; Nomura, Kentaro

    2015-03-01

    We theoretically investigate the antiferromagnetic insulator phase in a threedimensional correlated system with spin-orbit coupling, the Fu-Kane-Mele-Hubbard model at half-filling. We focus on the topological magnetoelectric effect which is described by the theta term. A low-energy effective Hamiltonian is derived in the antiferromagnetic insulator phase. Then with the use of a field-theoretical method, the theta term is derived as a consequence of the chiral anomaly.

  10. The effect of field-orientation on the magnetoelectric coupling in Terfenol-D/PZT/Terfenol-D laminated structure

    NASA Astrophysics Data System (ADS)

    Chen, Zhengxin; Su, Yu; Meguid, S. A.

    2014-11-01

    The field-orientation dependent magnetoelectric coupling is experimentally studied for a rectangular Terfenol-D/PZT/Terfenol-D laminated structure. The considered magnetic field, namely the dc-bias magnetic field or the ac-excitation magnetic field, is allowed to be spatially re-orientated between two orthogonal geometric dimensions of the composite. In the study, the direction of the excitation can be fixed in the longitudinal (Scheme-I) or thickness (Scheme-II) directions, while considering the bias orientation. Alternatively, the bias field can be restricted to the longitudinal (Scheme-III) or thickness (Scheme-IV) directions, while the excitation orientation is considered. The variation in magnetoelectric coefficient as a function of the bias magnitude is studied with special attention paid to the field-orientation dependency. For the testing schemes of I and II, the direction of the dc-bias field can be re-oriented by forming an angle with the fixed direction of the ac-excitation field. As the angle changes from 0° to 90°, the magnetoelectric coupling evolves from L-T mode to S-T surface shear for Scheme-I, and from T-T mode to S-T thickness shear for Scheme-II. The bias-field-orientation dependence demonstrates a complex pattern due to the varying overall state of anisotropy in Terfenol-D. In Scheme-I with low bias magnitude, the orientation dependence can be represented by the measured effective longitudinal piezomagnetic coefficient. In addition, the optimal bias field for maximum magnetoelectric coefficient is observed to linearly increase with the bias orientation angle. Alternatively, the orientation dependence in Schemes III and IV is more predictable due to the barely changed overall state of anisotropy. In this case, Scheme-III shows that the magnetoelectric coefficient decreases monotonically with the orientation angle and Scheme-IV indicates that the maximum coefficient is attained at around 60°. The dependence of the magnetoelectric coupling on

  11. Self-Biased 215MHz Magnetoelectric NEMS Resonator for Ultra-Sensitive DC Magnetic Field Detection

    PubMed Central

    Nan, Tianxiang; Hui, Yu; Rinaldi, Matteo; Sun, Nian X.

    2013-01-01

    High sensitivity magnetoelectric sensors with their electromechanical resonance frequencies < 200 kHz have been recently demonstrated using magnetostrictive/piezoelectric magnetoelectric heterostructures. In this work, we demonstrate a novel magnetoelectric nano-electromechanical systems (NEMS) resonator with an electromechanical resonance frequency of 215 MHz based on an AlN/(FeGaB/Al2O3) × 10 magnetoelectric heterostructure for detecting DC magnetic fields. This magnetoelectric NEMS resonator showed a high quality factor of 735, and strong magnetoelectric coupling with a large voltage tunable sensitivity. The admittance of the magnetoelectric NEMS resonator was very sensitive to DC magnetic fields at its electromechanical resonance, which led to a new detection mechanism for ultra-sensitive self-biased RF NEMS magnetoelectric sensor with a low limit of detection of DC magnetic fields of ~300 picoTelsa. The magnetic/piezoelectric heterostructure based RF NEMS magnetoelectric sensor is compact, power efficient and readily integrated with CMOS technology, which represents a new class of ultra-sensitive magnetometers for DC and low frequency AC magnetic fields. PMID:23760520

  12. Enhanced magnetoelectric effect for flexible current sensor applications

    NASA Astrophysics Data System (ADS)

    Le, Minh-Quyen; Belhora, Fouad; Cornogolub, Alexandru; Cottinet, Pierre-Jean; Lebrun, Laurent; Hajjaji, Abdelouahed

    2014-05-01

    This article focuses on the magnetoelectric (ME) effect that could be obtained in a bilayered structure consisting of the Cytop polymer and a magnetic tape filled with magnetically soft particles. The ME behavior was characterized by measuring the amplitude of the magnetoelectric current versus various input parameters that appear in theoretical expressions, i.e., the bias magnetic field, the alternative magnetic field, and the applied frequency. Experimental results were investigated together with theoretical models in order to determine the ME coupling value. It was found that the laminate material of a transversely charging electret along with bias magnetic tape could attain significant magnetoelectric properties, which were the result of the mechanical contacts between the layers and the electric-mechanical and magnetic-mechanical coupling in each phase. All the results demonstrated a possibility to realize a low-cost flexible current sensor while achieving an improved magnetoelectric response.

  13. A dual-peak phenomenon of magnetoelectric coupling in laminated Terfenol-D/PZT/Terfenol-D composites

    NASA Astrophysics Data System (ADS)

    Zhao, C. P.; Fang, F.; Yang, W.

    2010-12-01

    Magnetoelectric (ME) composite materials find many applications due to their high magnetoelectric (ME) coefficient (αME) at room temperature. A dual-peak phenomenon is reported in the curves of the magnetoelectric coefficient (αME) versus the static magnetic field (HS) for Terfenol-D/PZT/Terfenol-D tri-layered composites of rectangular shape. The first peak corresponds to the maximum of the piezomagnetic coefficient d33, m of the Terfenol-D plate, and the second is caused by the resonance of the laminate under the applied alternating magnetic field. The position of the first peak in the αME versus HS curve shifts slightly as the frequency increases. The position of the second peak, however, moves considerably toward higher HS values as the frequency increases. An analysis based on the equivalent circuit method is proposed, which incorporates the constitutive model and the change in Young's modulus with the applied static magnetic field (ΔE effect) for Terfenol-D. The theoretical prediction agrees well with the experimental observations. This finding is of importance for both the basic understanding of the ME composites and for device applications such as detection of magnetic materials.

  14. Gauge-discontinuity contributions to the Chern-Simons orbital magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Liu, Jianpeng; Vanderbilt, David

    We propose a new method for calculating the Chern-Simons orbital magnetoelectric coupling, conventionally parametrized in terms of a phase angle θ. We propose to relax the periodicity condition in one direction (kz) so that a gauge discontinuity is introduced on a 2D k plane normal to kz. The total θ response then has contributions from both the integral of the Chern-Simons 3-form over the 3D bulk BZ and the gauge discontinuity expressed as a 2D integral over the k plane. Sometimes the boundary plane may be further divided into subregions by 1D ``vortex loops'' which make a third kind of contribution to the total θ, expressed as a combination of Berry phases around the vortex loops. The total θ thus consists of three terms which can be expressed as integrals over 3D, 2D and 1D manifolds. When time-reversal symmetry is present and the gauge in the bulk BZ is chosen to respect this symmetry, both the 3D and 2D integrals vanish; the entire contribution then comes from the vortex-loop integral, which is either 0 or π corresponding to the ℤ2 classification of 3D time-reversal invariant insulators. We demonstrate our method by applying it to the Fu-Kane-Mele model with an applied staggered Zeeman field.

  15. Multiferroic Ni0.6Zn0.4Fe2O4-BaTiO3 nanostructures: Magnetoelectric coupling, dielectric, and fluorescence

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Singh, Sukhdeep; Tripathi, S. K.; Kotnala, R. K.

    2014-09-01

    Multiferroic nanostructures of Ni0.6Zn0.4Fe2O4-BaTiO3 (NZF/BT) have been prepared by two synthesis routes, i.e., chemical combustion (CNZF/BT) and hydrothermal (HNZF/BT). The synthesis of CNZF/BT results in nanoparticles of average size 4 nm at 500 °C annealing. However, the synthesis of HNZF/BT with hydrolysis temperature 180 °C/48 h shows nanowires of diameter 3 nm and length >150 nm. A growth mechanism in the fabrication of nanoparticles and wires is given. X-ray diffraction is used to identify the crystalline phase. The transmission electron microscopy shows the dimensions of NZF/BT nanostructures. The ferromagnetism, ferroelectricity, and magnetoelectric coupling show more enhancements in HNZF/BT nanowires than CNZF/BT nanoparticles. The observed polarization depends upon shape of nanostructures, tetragonal phase, and epitaxial strain. The tension induced by the surface curvature of nanowire counteracts the near-surface depolarizing effect and meanwhile leads to unusual enhancement of polarization. The ferromagnetism depends upon superficial spin canting, spin pinning of nanocomposite, and oxygen vacancy clusters. The magnetoelectric coefficient as the function of applied dc magnetizing field under ac magnetic field 5 Oe and frequency 1093 Hz is measured. The nanodimensions of NZF/BT are observed dielectric constant up to 120 MHz. The optical activity of NZF/BT nanostructures is shown by Fluorescence spectra.

  16. Giant magnetoelectric coupling interaction in BaTiO{sub 3}/BiFeO{sub 3}/BaTiO{sub 3} trilayer multiferroic heterostructures

    SciTech Connect

    Kotnala, R. K. E-mail: rkkotnala@gmail.com; Gupta, Rekha; Chaudhary, Sujeet

    2015-08-24

    Multiferroic trilayer thin films of BaTiO{sub 3}/BiFeO{sub 3}/BaTiO{sub 3} were prepared by RF-magnetron sputtering technique at different thicknesses of BiFeO{sub 3} layer. A pure phase polycrystalline growth of thin films was confirmed from X-ray diffraction results. The film showed maximum remnant electric polarization (2P{sub r}) of 13.5 μC/cm{sup 2} and saturation magnetization (M{sub s}) of 61 emu/cc at room temperature. Thermally activated charge transport dominated via oxygen vacancies as calculated by their activation energy, which was consistent with current–voltage characteristics. Magnetic field induced large change in resistance and capacitance of grain, and grain boundary was modeled by combined impedance and modulus spectroscopy in the presence of varied magnetic fields. Presence of large intrinsic magnetoelectric coupling was established by a maximum 20% increase in grain capacitance (C{sub g}) with applied magnetic field (2 kG) on trilayer having 20 nm BiFeO{sub 3} layer. Substantially higher magnetoelectric coupling in thinner films has been observed due to bonding between Fe and Ti atoms at interface via oxygen atoms. Room temperature magnetoelectric coupling was confirmed by dynamic magnetoelectric coupling, and maximum longitudinal magnetoelectric coupling of 515 mV/cm-Oe was observed at 20 nm thickness of BiFeO{sub 3}. The observed magnetoelectric properties are potentially useful for novel room temperature magnetoelectric and spintronic device applications for obtaining higher voltage at lower applied magnetic field.

  17. Gauge-discontinuity contributions to Chern-Simons orbital magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Liu, Jianpeng; Vanderbilt, David

    2015-12-01

    We propose a method for calculating Chern-Simons orbital magnetoelectric coupling, conventionally parametrized in terms of a phase angle θ . According to previous theories, θ can be expressed as a three-dimensional (3D) Brillouin-zone (BZ) integral of the Chern-Simons 3-form defined in terms of the occupied Bloch functions. Such an expression is valid only if a smooth and periodic gauge has been chosen in the entire Brillouin zone, and even then, convergence with respect to the k -space mesh density can be difficult to obtain. In order to solve this problem, we propose to relax the periodicity condition in one direction (say, the kz direction) so that a gauge discontinuity is introduced on a two-dimensional (2D) k plane normal to kz. The total θ response then has contributions from both the integral of the Chern-Simons 3-form over the 3D bulk BZ and the gauge discontinuity expressed as a 2D integral over the k plane. Sometimes, the boundary plane may be further divided into subregions by 1D "vortex loops" which make a third kind of contribution to the total θ , expressed as a combination of Berry phases around the vortex loops. The total θ thus consists of three terms which can be expressed as integrals over 3D, 2D, and 1D manifolds. When time-reversal symmetry is present and the gauge in the bulk BZ is chosen to respect this symmetry, both the 3D and 2D integrals vanish; the entire contribution then comes from the vortex-loop integral, which is either 0 or π corresponding to the Z2 classification of 3D time-reversal-invariant insulators. We demonstrate our method by applying it to the Fu-Kane-Mele model with an applied staggered Zeeman field.

  18. Strain mediated magnetoelectric coupling in a NiFe2O4-BaTiO3 multiferroic composite

    NASA Astrophysics Data System (ADS)

    Gorige, Venkataiah; Kati, Raju; Yoon, D. H.; Kumar, P. S. Anil

    2016-10-01

    In this paper we demonstrate significant magnetoelectric coupling in ferrimagnetic, NiFe2O4, and ferroelectric, BaTiO3, multiferroic composite bulk materials by measuring temperature dependent magnetization. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy data show that the two phases coexist with a highly crystalline and sharp interface without any detectable impurities, which enables significant magnetoelectric (ME) coupling. The temperature dependent magnetization data of the composite clearly show the jumps in magnetization curves at the structural phase transitions of BaTiO3, thereby indicating their origin in ME coupling. The change in coercivity of composite sample in different ferroelectric phases of BaTiO3 has been observed compared to the NiFe2O4 sample. The different lattice strains corresponding to different ferroelectric phases of BaTiO3 could be the driving force for modulating the magnetization and coercivity of the composite material. This is clear evidence of strain mediated ME coupling in ferrimagnetic and ferroelectric composite materials.

  19. Giant low-frequency multipeak self-biased magnetoelectric properties in four-phase structure with stepped ultrasonic horn

    NASA Astrophysics Data System (ADS)

    Li, Jie; Lu, Caijiang

    2016-11-01

    This paper develops a self-biased magnetoelectric (ME) heterostructure FeCuNbSiB/terfenol-d/ultrasonic-horn/PZT by sandwiching a piezoelectric Pb(Zr,Ti)O3 (PZT) plate and a magnetization-graded FeCuNbSiB/terfenol-d layer on a rectangular-stepped ultrasonic horn substrate. The rectangular-stepped ultrasonic horn substrate severs as the resonance frequency determining element of the ME heterostructure, converges and amplifies the vibration excited by the magnetization-graded FeCuNbSiB/terfenol-d layer. The experiments show that fifteen large peaks of ME response with magnitudes of 0.2–7.5 V/(cm·Oe) in 0.5–50 kHz range are observed at zero-biased magnetic field. This demonstrates that the proposed multi-peak self-biased heterostructure may be useful for multifunctional devices for multi-frequency operation.

  20. Ferrimagnetic resonance and magnetoelastic excitations in magnetoelectric hexaferrites

    NASA Astrophysics Data System (ADS)

    Vittoria, Carmine

    2015-08-01

    Static field properties of magnetoelectric hexaferrites have been explored extensively in the past five years. In this paper, dynamic properties of magnetoelectric hexaferrites are being explored. In particular, effects of the linear magnetoelectric coupling (α ) on ferrimagnetic resonance (FMR) and magnetoelastic excitations are being investigated. A magnetoelastic free energy which includes Landau-Lifshitz mathematical description of a spin spiral configuration is proposed to calculate FMR and magnetoelastic excitations in magnetoelectric hexaferrites. It is predicted that the ordinary uniform precession FMR mode contains resonance frequency shifts that are proportional to magnetoelectric static and dynamic fields. The calculated FMR fields are in agreement with experiments. Furthermore, it is predicted at low frequencies (approximately megahertz ranges), near zero magnetic field FMR frequencies, there is an extra uniform precession FMR mode besides the ordinary FMR mode which can only be accounted by dynamic magnetoelectric fields. Whereas the FMR frequency shifts in the ordinary FMR mode due to the α coupling scale as α , the shifts in the new discovered FMR mode scale as α2. Also, magnetoelastic dispersions were calculated, and it is predicted that the effect of the α coupling are the following: (1) The strength of admixture of modes and splitting in energy between spin waves and transverse acoustic waves is proportional to α . (2) The degeneracy of the two transverse acoustic wave modes is lifted even for relatively low values of α . Interestingly, at low frequencies near zero field FMR frequencies, the surface spin wave mode branch flip-flops with the volume spin wave branch whereby one branch assumes real values of the propagation constant and the other purely imaginary upon the application of a static electric field.

  1. Giant and universal magnetoelectric coupling in soft materials and concomitant ramifications for materials science and biology

    NASA Astrophysics Data System (ADS)

    Liu, Liping; Sharma, Pradeep

    2013-10-01

    Magnetoelectric coupling—the ability of a material to magnetize upon application of an electric field and, conversely, to polarize under the action of a magnetic field—is rare and restricted to a rather small set of exotic hard crystalline materials. Intense research activity has recently ensued on materials development, fundamental scientific issues, and applications related to this phenomenon. This tantalizing property, if present in adequate strength at room temperature, can be used to pave the way for next-generation memory devices such as miniature magnetic random access memories and multiple state memory bits, sensors, energy harvesting, spintronics, among others. In this Rapid Communication, we prove the existence of an overlooked strain mediated nonlinear mechanism that can be used to universally induce the giant magnetoelectric effect in all (sufficiently) soft dielectric materials. For soft polymer foams—which, for instance, may be used in stretchable electronics—we predict room-temperature magnetoelectric coefficients that are comparable to the best known (hard) composite materials created. We also argue, based on a simple quantitative model, that magnetoreception in some biological contexts (e.g., birds) most likely utilizes this very mechanism.

  2. Negative index of refraction in a four-level system with magnetoelectric cross coupling and local field corrections

    SciTech Connect

    Bello, F.

    2011-07-15

    This research focuses on a coherently driven four-level atomic medium with the aim of inducing a negative index of refraction while taking into consideration local field corrections as well as magnetoelectric cross coupling (i.e.,chirality) within the material's response functions. Two control fields are used to render the medium transparent for a probe field which simultaneously couples to an electric and a magnetic dipole transition, thus allowing one to test the permittivity and permeability of the material at the same time. Numerical simulations show that a negative index of refraction with low absorption can be obtained for a range of probe detunings while depending on number density and the ratio between the intensities of the control fields.

  3. Magnetoelectric coupling and spin-dependent tunneling in Fe/PbTiO3/Fe multiferroic heterostructure with a Ni monolayer inserted at one interface

    NASA Astrophysics Data System (ADS)

    Dai, Jian-Qing; Zhang, Hu; Song, Yu-Min

    2015-08-01

    We report on first-principles calculations of a Ni monolayer inserted at one interface in the epitaxial Fe/PbTiO3/Fe multiferroic heterostructure, focusing on the magnetoelectric coupling and the spin-dependent transport properties. The results of magnetoelectric coupling calculations reveal an attractive approach to realize cumulative magnetoelectric effects in the ferromagnetic/ferroelectric/ferromagnetic superlattices. The underlying physics is attributed to the combinations of several different magnetoelectric coupling mechanisms such as interface bonding, spin-dependent screening, and different types of magnetic interactions. We also demonstrate that inserting a Ni monolayer at one interface in the Fe/PbTiO3/Fe multiferroic tunnel junction is an efficient method to produce considerable tunneling electroresistance effect by modifying the tunnel potential barrier and the interfacial electronic structure. Furthermore, coexistence of tunneling magnetoresistance and tunneling electroresistance leads to the emergence of four distinct resistance states, which can be served as a multistate-storage device. The complicated influencing factors including bulk properties of the ferromagnetic electrodes, decay rates of the evanescent states in the tunnel barrier, and the specific interfacial electronic structure provide us promising opportunities to design novel multiferroic tunnel junctions with excellent performances.

  4. Magnetoelectric coupling and spin-dependent tunneling in Fe/PbTiO{sub 3}/Fe multiferroic heterostructure with a Ni monolayer inserted at one interface

    SciTech Connect

    Dai, Jian-Qing Zhang, Hu; Song, Yu-Min

    2015-08-07

    We report on first-principles calculations of a Ni monolayer inserted at one interface in the epitaxial Fe/PbTiO{sub 3}/Fe multiferroic heterostructure, focusing on the magnetoelectric coupling and the spin-dependent transport properties. The results of magnetoelectric coupling calculations reveal an attractive approach to realize cumulative magnetoelectric effects in the ferromagnetic/ferroelectric/ferromagnetic superlattices. The underlying physics is attributed to the combinations of several different magnetoelectric coupling mechanisms such as interface bonding, spin-dependent screening, and different types of magnetic interactions. We also demonstrate that inserting a Ni monolayer at one interface in the Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction is an efficient method to produce considerable tunneling electroresistance effect by modifying the tunnel potential barrier and the interfacial electronic structure. Furthermore, coexistence of tunneling magnetoresistance and tunneling electroresistance leads to the emergence of four distinct resistance states, which can be served as a multistate-storage device. The complicated influencing factors including bulk properties of the ferromagnetic electrodes, decay rates of the evanescent states in the tunnel barrier, and the specific interfacial electronic structure provide us promising opportunities to design novel multiferroic tunnel junctions with excellent performances.

  5. The Origin and Coupling Mechanism of the Magnetoelectric Effect in TM Cl 2 -4SC(NH 2 ) 2 ( TM = Ni and Co)

    DOE PAGESBeta

    Mun, Eundeok; Wilcox, Jason; Manson, Jamie L.; Scott, Brian; Tobash, Paul; Zapf, Vivien S.

    2014-01-01

    Most research on multiferroics and magnetoelectric effects to date has focused on inorganic oxides. Molecule-based materials are a relatively new field in which to search for magnetoelectric multiferroics and to explore new coupling mechanisms between electric and magnetic order. We present magnetoelectric behavior in NiCl 2 -4SC(NH 2 ) 2 (DTN) and CoCl 2 -4SC(NH 2 ) 2 (DTC). These compounds form tetragonal structures where the transition metal ion (Ni or Co) is surrounded by four electrically polar thiourea molecules [SC(NH 2 ) 2 ]. By tracking the magnetic and electric properties of these compounds as a function ofmore » magnetic field, we gain insights into the coupling mechanism by observing that, in DTN, the electric polarization tracks the magnetic ordering, whereas in DTC it does not. For DTN, all electrically polar thiourea molecules tilt in the same direction along the c -axis, breaking spatial-inversion symmetry, whereas, for DTC, two thiourea molecules tilt up and two tilt down with respect to c -axis, perfectly canceling the net electrical polarization. Thus, the magnetoelectric coupling mechanism in DTN is likely a magnetostrictive adjustment of the thiourea molecule orientation in response to magnetic order.« less

  6. Magnetoelectric coupling effect in lead-free Bi4Ti3O12/CoFe2O4 composite films derived from chemistry solution deposition

    NASA Astrophysics Data System (ADS)

    Tang, Zhehong; Chen, Jieyu; Bai, Yulong; Zhao, Shifeng

    2016-08-01

    Lead-free magnetoelectric composite films combining Bi4Ti3O12 and CoFe2O4 were synthesized by chemical solution deposition on Pt (100)/Ti/SiO2/Si substrate. Morphological and electrical domain structure, ferroelectric, leakage, dielectric, piezoelectric, magnetic and magnetoelectric properties were investigated for Bi4Ti3O12/CoFe2O4 composite films. Well-defined interfaces between Bi4Ti3O12 and CoFe2O4 film layers and electrical domain structure were observed. The composite films show the coexistence of ferroelectric and ferromagnetic orders at room temperature. Larger piezoelectric coefficient and magnetization are obtained for the composite films, which is contributed to the magnetoelectric effect since it originates from the interface coupling through mechanical strain transfer. This work presents a feasible way to modulate the magnetoelectric coupling in ferromagnetic/ferroelectric composite films for developing lead-free micro-electro-mechanical system and information storage devices.

  7. Annular bilayer magnetoelectric composites: theoretical analysis.

    PubMed

    Guo, Mingsen; Dong, Shuxiang

    2010-01-01

    The laminated bilayer magnetoelectric (ME) composites consist of magnetostrictive and piezoelectric layers are known to have giant ME coefficient due to the high coupling efficiency in bending mode. In our previous report, the bar-shaped bilayer composite has been investigated by using a magnetoelectric-coupling equivalent circuit. Here, we propose an annular bilayer ME composite, which consists of magnetostrictive and piezoelectric rings. This composite has a much lower resonance frequency of bending mode compared with its radial mode. In addition, the annular bilayer ME composite is expected to respond to vortex magnetic field as well as unidirectional magnetic field. In this paper, we investigate the annular bilayer ME composite by using impedance-matrix method and predict the ME coefficients as a function of geometric parameters of the composites. PMID:20178914

  8. Modeling of resonant magneto-electric effect in a magnetostrictive and piezoelectric laminate composite structure coupled by a bonding material

    NASA Astrophysics Data System (ADS)

    Hasanyan, D.; Wang, Y.; Gao, J.; Li, M.; Shen, Y.; Li, J.; Viehland, D.

    2012-09-01

    The harmonic magneto-electro-elastic vibration of a thin laminated composite was considered. A theoretical model, including shear lag and vibration effects was developed for predicting the magneto-electric (ME) effect in a laminate composite consisting of magnetostrictive and piezoelectric layers. To avoid bending, we assumed that the composite was geometrically symmetric. For finite length symmetrically fabricated laminates, we derived the dynamic strain-stress field and ME coefficients, including shear lag and vibration effects for several boundary conditions. Parametric studies are presented to evaluate the influences of material properties and geometries on the strain distribution and the ME coefficient. Analytical expressions indicate that the shear lag and the vibration frequency strongly influence the strain distribution in the laminates and these effects strongly influence the ME coefficients.

  9. Theoretical and experimental investigation of magnetoelectric effect for bending-tension coupled modes in magnetostrictive-piezoelectric layered composites

    NASA Astrophysics Data System (ADS)

    Hasanyan, D.; Gao, J.; Wang, Y.; Viswan, R.; Li, M.; Shen, Y.; Li, J.; Viehland, D.

    2012-07-01

    In this paper, we discuss a theoretical model with experimental verification for the resonance enhancement of magnetoelectric (ME) interactions at frequencies corresponding to bending-tension oscillations. A dynamic theory of arbitrary laminated magneto-elasto-electric bars was constructed. The model included bending and longitudinal vibration effects for predicting ME coefficients in laminate bar composite structures consisting of magnetostrictive, piezoelectric, and pure elastic layers. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account, as such the bending deformations should be considered in an applied magnetic or electric field. The frequency dependence of the ME voltage coefficients has obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to free vibrations at both ends. As a demonstration, our theory for multilayer ME composites was then applied to ferromagnetic-ferroelectric bilayers, specifically Metglas-PZT ones. A theoretical model is presented for static (low-frequency) ME effects in such bilayers. We also performed experiments for these Metglas-PZT bilayers and analyzed the influence of Metglas geometry (length and thickness) and Metglas/PZT volume fraction on the ME coefficient. The frequency dependence of the ME coefficient is also presented for different geometries (length, thickness) of Metglas. The theory shows good agreement with experimental data, even near the resonance frequency.

  10. Diverse interface effects on ferroelectricity and magnetoelectric coupling in asymmetric multiferroic tunnel junctions: the role of the interfacial bonding structure.

    PubMed

    Liu, X T; Chen, W J; Jiang, G L; Wang, B; Zheng, Yue

    2016-01-28

    Interface and size effects on electric/magnetic orders and magnetoelectric coupling are vital in the modern application of quantum-size functional devices based on multiferroic tunnel junctions. In order to give a comprehensive study of the interface and size effects, the properties of a typical asymmetric multiferroic tunnel junction, i.e., Fe/BaTiO3/Co, have been calculated using the first-principles simulations. Most importantly, all of the eight possible structures with four combinations of electrode/ferroelectric interfaces (i.e., Fe/BaO, Fe/TiO2, Co/BaO and Co/TiO2) and a series of barrier thicknesses have been taken into account. In this work, the equilibrium configurations, polarization, charge density, spin density and magnetic moments, etc., have been completely simulated and comprehensively analyzed. It is found that the ferroelectric stability is determined as a competition outcome of the strength of short-range chemical bondings and long-range depolarization/built-in fields. M/BaO (M = magnetic metal) terminations show an extraordinary enhancement of local polarization near the interface and increase the critical thickness of ferroelectricity. The bistability of polarization is well kept at the M/TiO2 interface. At the same time, the induced magnetic moment on atoms at the interfaces is rather localized and dominated by the local interfacial configuration. Reversing electric polarization can switch the induced magnetic moments, wherein atoms in M-O-Ti and M-Ti-O chains show preference for being magnetized. In addition, the difference between the sum of the interfacial magnetic moments is also enlarged with the increase of the barrier thickness. Our study provides a comprehensive and detailed reference to the manipulation and utilization of the interface, size and magnetoelectric effects in asymmetric multiferroic tunnel junctions.

  11. Magnetoelectric coupling in multiferroic BaTiO3-CoFe2O4 composite nanofibers via electrospinning

    NASA Astrophysics Data System (ADS)

    Fu, Bi; Lu, Ruie; Gao, Kun; Yang, Yaodong; Wang, Yaping

    2015-07-01

    Magnetoelectric (ME) coupling in Pb-based multiferroic composites has been widely investigated due to the excellent piezoelectric property of lead zirconate titanate (PZT). In this letter, we report a strategy to create a hybrid Pb-free ferroelectric and ferromagnetic material and detect its ME coupling at the nanoscale. Hybrid Pb-free multiferroic BaTiO3-CoFe2O4 (BTO-CFO) composite nanofibers (NFs) were generated by sol-gel electrospinning. The perovskite structure of BTO and the spinel structure of CFO nanograins were homogenously distributed in the composite NFs and verified by bright-field transmission electron microscopy observations along the perovskite [111] zone axis. Multiferroicity was confirmed by amplitude-voltage butterfly curves and magnetic hysteresis loops. ME coupling was observed in terms of a singularity on a dM/dT curve at the ferroelectric Curie temperature (TC) of BaTiO3. The lateral ME coefficient was investigated by the evolution of the piezoresponse under an external magnetic field of 1000 Oe and was estimated to be α31 =0.78× 104 \\text{mV cm}-1 \\text{Oe}-1 . These findings could enable the creation of nanoscale Pb-free multiferroic composite devices.

  12. Tuning magnetoelectric coupling using porosity in multiferroic nanocomposites of ALD-grown Pb(Zr,Ti)O3 and templated mesoporous CoFe2O4

    NASA Astrophysics Data System (ADS)

    Chien, Diana; Buditama, Abraham N.; Schelhas, Laura T.; Kang, Hye Yeon; Robbennolt, Shauna; Chang, Jane P.; Tolbert, Sarah H.

    2016-09-01

    In this manuscript, we examine ways to create multiferroic composites with controlled nanoscale architecture. We accomplished this by uniformly depositing piezoelectric lead zirconate titanate (PZT) into templated mesoporous, magnetostrictive cobalt ferrite (CFO) thin films to form nanocomposites in which strain can be transferred at the interface between the two materials. To study the magnetoelectric coupling, the nanostructure was electrically poled ex situ prior to magnetic measurements. No samples showed a change in in-plane magnetization as a function of voltage due to substrate clamping. Out-of-plane changes were observed, but contrary to expectations based on total PZT volume fraction, mesoporous CFO samples partially filled with PZT showed more change in out-of-plane magnetization than the sample with fully filled pores. This result suggests that residual porosity in the composite adds mechanical flexibility and results in greater magnetoelectric coupling.

  13. Multipeak self-biased magnetoelectric coupling characteristics in four-phase Metglas/Terfenol-D/Be-bronze/PMN-PT structure

    NASA Astrophysics Data System (ADS)

    Huang, Dongyan; Lu, Caijiang; Bing, Han

    2015-04-01

    This letter develops a self-biased magnetoelectric (ME) structure Metglas/Terfenol-D/Be-bronze/PMN-PT (MTBP) consisting of a magnetization-graded Metglas/Terfenol-D layer, a elastic Be-bronze plate, and a piezoelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) plate. By using the magnetization-graded Metglas/Terfenol-D layer and the elastic Be-bronze plate, multi-peak self-biased ME responses are obtained in MTBP structure. The experimental results show that the MTBP structure with two layers of Metglas foil has maximum zero-biased ME voltage coefficient (MEVC). As frequency increases from 0.5 to 90 kHz, eleven large peaks of MEVC with magnitudes of 0.75-33 V/(cm Oe) are observed at zero-biased magnetic field. The results demonstrate that the proposed multi-peak self-biased ME structure may be useful for multifunctional devices such as multi-frequency energy harvesters or low-frequency ac magnetic field sensors.

  14. Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films.

    PubMed

    Alberca, A; Munuera, C; Azpeitia, J; Kirby, B; Nemes, N M; Perez-Muñoz, A M; Tornos, J; Mompean, F J; Leon, C; Santamaria, J; Garcia-Hernandez, M

    2015-12-09

    We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30-40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2-5) · 10(-7) s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite.

  15. Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films.

    PubMed

    Alberca, A; Munuera, C; Azpeitia, J; Kirby, B; Nemes, N M; Perez-Muñoz, A M; Tornos, J; Mompean, F J; Leon, C; Santamaria, J; Garcia-Hernandez, M

    2015-01-01

    We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30-40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2-5) · 10(-7) s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite. PMID:26648002

  16. Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films

    PubMed Central

    Alberca, A.; Munuera, C.; Azpeitia, J.; Kirby, B.; Nemes, N. M.; Perez-Muñoz, A. M.; Tornos, J.; Mompean, F. J.; Leon, C.; Santamaria, J.; Garcia-Hernandez, M.

    2015-01-01

    We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30–40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2–5)·10−7 s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite. PMID:26648002

  17. Controlled extrinsic magnetoelectric coupling in BaTiO3/Ni nanocomposites: Effect of compaction pressure on interfacial anisotropy

    NASA Astrophysics Data System (ADS)

    Brosseau, C.; Castel, V.; Potel, M.

    2010-07-01

    The dynamical control of the dielectric response in magnetoelectric (ME) nanocomposites (NCs) renders an entire additional degree of freedom to the functionality of miniaturized magnetoelectronics and spintronics devices. In composite materials, the ME effect is realized by using the concept of product properties. Through the investigation of the microwave properties of a series of BaTiO3/Ni NCs fabricated by compaction of nanopowders, we present experimental evidence that the compaction (uniaxial) pressure in the range 33-230 MPa affects significantly the ME features. The Ni loading was varied from zero (BaTiO3 only) to 63 vol %. Our findings revealed that the ME coupling coefficient exhibits a large enhancement for specific values of the Ni volume fraction and compaction pressure. The coupling effects in the NCs were studied by looking at the relationships among the crystallite orientation and the magnetic properties. The magnetization curves for different directions of the applied magnetic field cannot be superimposed. We suggest that the average magnetization measurements on these NCs under compressive stress are dominated by strain anisotropy rather than magnetocrystalline anisotropy. Overall, these observations are considered to be evidence of stress-induced microstructural changes under pressure which strongly affect the elastic interaction between the magnetostrictive and piezoelectric phases in these NCs. These results have a potential technological impact for designing precise tunable ME NCs for microwave devices such as tunable phase shifters, resonators, and delay lines.

  18. Tailoring the magnetoelectric coupling in the Co2Y type hexaferrite single crystals by systematic doping control

    NASA Astrophysics Data System (ADS)

    Shin, Kwangwoo; Park, Chang Bae; Chun, Sae Hwan; Kim, Kee Hoon

    2015-03-01

    Hexagonal ferrites have shown gigantic magnetoelectric (ME) coupling in a broad temperature range including room temperature, which draws great interests due to their rich physics and various application potential. Here, we report the variations of the ME coupling and electrical phase boundary in the Sr and Al doped Co2Y type single crystal. As the doping ratio of Sr and Al ions increased, not only the transition temperature of the heliconical spin ordering increased up to 430 K, but also the ferroelectric phase boundary became closer to the zero magnetic field. These two main effects lead us to observe the large direct and converse ME effects at room temperature and near zero magnetic field. In particular, in an optimally doped sample, the ME susceptibility reaches to 28,000 ps/m at 10 K and the magnetization direction could be reversed by an external electric field even at 250 K without any bias magnetic field. These results clearly show that the Co2Y type hexaferrite is a promising material system that might realize the magnetization reversal even at room temperature.

  19. Electro-optic switching in iron oxide nanoparticle embedded paramagnetic chiral liquid crystal via magneto-electric coupling

    SciTech Connect

    Goel, Puja; Arora, Manju; Biradar, Ashok M.

    2014-03-28

    The variation in optical texture, electro-optic, and dielectric properties of iron oxide nanoparticles (NPs) embedded ferroelectric liquid crystal (FLC) with respect to change in temperature and electrical bias conditions are demonstrated in the current investigations. Improvement in spontaneous polarization and response time in nanocomposites has been attributed to magneto-electric (ME) coupling resulting from the strong interaction among the ferromagnetic nanoparticle's exchange field (due to unpaired e{sup −}) and the field of liquid crystal molecular director. Electron paramagnetic resonance spectrum of FLC material gives a broad resonance signal with superimposed components indicating the presence of a source of spin. This paramagnetic behavior of host FLC material had been a major factor in strengthening the guest host interaction by giving an additional possibility of (a) spin-spin interaction and (b) interactions between magnetic-dipole and electric-dipole moments (ME effects) in the composite materials. Furthermore, the phenomenon of dielectric and static memory effect in these composites are also observed which yet again confirms the coupling of magnetic NP's field with FLC's director orientation. We therefore believe that such advanced soft materials holding the optical and electrical properties of conventional LCs with the magnetic and electronic properties of ferromagnetic nanoparticles are going to play a key role in the development of futuristic multifunctional optical devices.

  20. Piezoelectric single crystal and magnetostrictive Metglas composites: Linear and nonlinear magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Wang, Yaojin; Finkel, P.; Li, Jiefang; Viehland, D.

    2014-04-01

    Both the linear (αV) and nonlinear (αV,n) magnetoelectric coefficients were systemically studied in laminated composites of Metglas and [001]-orientated piezoelectric single crystals of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Mn-doped PMN-PT. The coefficients were close in value in both cases at quasistatic mode (i.e., 3.8 V/Oe relative to 3.5 V/Oe) and were enhanced by factors of ×18 (Metglas/PMN-PT) and ×32 (Metglas/Mn-doped PMN-PT) at the electromechanical resonance (EMR). The use of Mn-doped PMN-PT crystals results in a higher gain factor due to a larger mechanical quality factor (i.e., 20.9 relative to 40.6). Accordingly, both types of laminates had similar values of αV,n when modulated at 1 kHz, but Mn-doped PMN-PT ones had a higher value when modulated at the EMR.

  1. Giant magnetoelectric effect in thin magnetic films utilizing inter-ferroelectric transitions

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Staruch, Margo

    There has recently been much interest to multiferroic magnetoelectric composites based on relaxor ferroelectric single crystals as potential candidates for devices such as magnetic field sensors, energy harvesters, or transducers. Large magnetoelectric coupling coefficient is prerequisite for superior device performance in a broad range of frequencies and functioning conditions. In magnetoelectric heterostructures based on ternary relaxors Pb(In1/2Nb1/2) O3-Pb(Mg1/3Nb2/3) O3-PbTiO3 (PIN-PMN-PT) crystal better operational range and temperature stability as compared to binary relaxors can be achieved. Giant linear converse magnetoelectric coupling up to 2 x 10-6 s m-1 were observed in heterostructural composites with multilayered FeCo/Ag deposited on (011) PIN-PMN-PT crystals. Further enhancement of magnetoelectric coupling is demonstrated by utilizing inter-ferroelctric rhombohedral - orthorhombic phase transitions in PIN-PMN-PT Mechanical clamping was a precondition to utilize this inter-ferroelectric transition mode to bring the crystal to a point just below its transformation threshold when very small perturbations at the input will cause large swings at the output generating a sharp uniaxial increase in strain (~0.5 %) and polarization change, giving rise to nonlinear effects. Details of these results and their implications will be presented. Giant magnetoelectric effect in thin magnetic fillms utilizing inter-ferroelectric transitions.

  2. Dynamical magnetoelectric phenomena of multiferroic skyrmions.

    PubMed

    Mochizuki, Masahito; Seki, Shinichiro

    2015-12-23

    Magnetic skyrmions, vortex-like swirling spin textures characterized by a quantized topological invariant, realized in chiral-lattice magnets are currently attracting intense research interest. In particular, their dynamics under external fields is an issue of vital importance both for fundamental science and for technical application. Whereas observations of magnetic skyrmions has been limited to metallic magnets so far, their realization was also discovered in a chiral-lattice insulating magnet Cu2OSeO3 in 2012. Skyrmions in the insulator turned out to exhibit multiferroic nature with spin-induced ferroelectricity. Strong magnetoelectric coupling between noncollinear skyrmion spins and electric polarizations mediated by relativistic spin-orbit interaction enables us to drive motion and oscillation of magnetic skyrmions by application of electric fields instead of injection of electric currents. Insulating materials also provide an environment suitable for detection of pure spin dynamics through spectroscopic measurements owing to the absence of appreciable charge excitations. In this article, we review recent theoretical and experimental studies on multiferroic properties and dynamical magnetoelectric phenomena of magnetic skyrmions in insulators. We argue that multiferroic skyrmions show unique coupled oscillation modes of magnetizations and polarizations, so-called electromagnon excitations, which are both magnetically and electrically active, and interference between the electric and magnetic activation processes leads to peculiar magnetoelectric effects in a microwave frequency regime. PMID:26624202

  3. Absence of strain-mediated magnetoelectric coupling at fully epitaxial Fe/BaTiO{sub 3} interface (invited)

    SciTech Connect

    Radaelli, G. Petti, D.; Cantoni, M.; Rinaldi, C.; Bertacco, R.

    2014-05-07

    Interfacial MagnetoElectric coupling (MEC) at ferroelectric/ferromagnetic interfaces has recently emerged as a promising route to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO{sub 3} (BTO) system, various MEC mechanisms have been theoretically predicted. Experimentally, it is well established that using BTO single crystal substrates MEC is dominated by strain-mediated mechanisms. In case of ferromagnetic layers epitaxially grown onto BTO films, instead, no direct evidence for MEC has been provided, apart from the results obtained on tunneling junction sandwiching a BTO tunneling barrier. In this paper, MEC at fully epitaxial Fe/BTO interface is investigated by Magneto-Optical Kerr Effect and magnetoresistance measurements on magnetic tunnel junctions fabricated on BTO. We find no evidence for strain-mediated MEC mechanisms in epitaxial systems, likely due to clamping of BTO to the substrate. Our results indicate that pure electronic MEC is the route of choice to be explored for achieving the electrical writing of information in epitaxial ferromagnet-ferroelectric heterostructures.

  4. Magnetoacoustic resonance in magnetoelectric bilayers

    NASA Astrophysics Data System (ADS)

    Filippov, D. A.; Bichurin, M. I.; Petrov, V. M.; Srinivasan, G.

    2004-03-01

    Layered composites of ferrite and ferroelectric single crystal thin films are of interest for studies on magnetoelectric interactions [1,2]. Such interactions result in unique and novel effects that are absent in single phase materials. For example, in a single crystal composite it is possible to control the ferromagnetic resonance (FMR) parameters for the ferrite by means of hypersonic oscillations induced in the ferroelectric phase. The absorption of acoustic oscillations by the ferrite results in variation in FMR line shape and power absorbed. One anticipates resonance absorption of elastic waves when the frequency of elastic waves coincides with the precession frequency of magnetization vector. This work is concerned with the nature of FMR under the influence of acoustic oscillations with the same frequency as FMR. Bilayers of ferrite and piezoelectric single crystals are considered. Hypersonic waves induced in the piezoelectric phase transmit acoustic power into ferrite due to mechanical connectivity between the phases. That transmission depends strongly on interface coupling [3]. We estimate the resulting variations in ferromagnetic resonance line shape. Estimates of magnetoelectric effect at magnetoacoustic resonance are also given. In addition, dependence of absorption of acoustic power on sample dimensions and compliances, electric and magnetic susceptibilities, piezoelectric and magnetostriction coefficients is discussed. The theory provided here is important for an understanding of interface coupling and the nature of magnetoelastic interactions in the composites. 1. M. I. Bichurin and V. M. Petrov, Zh. Tekh. Fiz. 58, 2277 (1988) [Sov. Phys. Tech. Phys. 33, 1389 (1988)]. 2. M.I. Bichurin, I. A. Kornev, V. M. Petrov, A. S. Tatarenko, Yu. V. Kiliba, and G. Srinivasan. Phys. Rev. B 64, 094409 (2001). 3. M. I. Bichurin, V. M. Petrov, and G. Srinivasan, J. Appl. Phys. 92, 7681 (2002). This work was supported by grants from the Russian Ministry of Education (

  5. Properties of magnetoelectric susceptibility

    NASA Astrophysics Data System (ADS)

    Zhai, Junyi; Li, Jiefang; Viehland, Dwight; Bichurin, M. I.

    2006-03-01

    The magnetoelectric (ME) susceptibility is the principle property of ME materials, determining the connection between polarization (or electric induction) and an external magnetic field. Since measurement of the ME susceptibility over a wide frequency range [1] and the design of new ME devices require more information about the ME susceptibility, the present work has focused on this property in detail. First, we consider the ME susceptibility as a complex parameter with both real and the imaginary parts, advancing a methodology for measurement of these values. Second, we have analyzed the ME susceptibility, for example a trilayer laminate composite of Terfenol-D/PZT, Terfenol-D, and found a maximum value of ˜3.5x10-7s/m in the electromechanical resonance range. In addition, we have studied the internal structure of the ME susceptibility: i.e., its dependencies on phase volume fractions, layer thickness, and choice of materials couple. Our results for the ME susceptibility will allow it to be more correctly used both as a fundamental materials property and also in potential ME device applications. [1] M.I. Bichurin, V.M. Petrov,Yu.V. Kiliba, and G. Srinivasan. Phys. Rev. B 66, 134404 (2002).

  6. Composition-driven enhanced magnetic properties and magnetoelectric coupling in Gd substituted BiFeO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Vijayasundaram, S. V.; Suresh, G.; Mondal, R. A.; Kanagadurai, R.

    2016-11-01

    Bi1-xGdxFeO3 (x=0, 0.05 and 0.1) samples were synthesized by modified sol-gel process. X-ray diffraction studies confirmed that the crystal structures of Gd substituted samples remain stable for x<0.1, while compositional-driven structural phase transition from rhombohedral to orthorhombic was observed in the case of x=0.1. The average particle sizes of pure and Gd substituted BiFeO3 nanoparticles were found to be in the range 62-46 nm. The size of the oblate spherical particles decreased with increasing Gd concentration. XPS studies revealed the trivalent oxidation states of Bi and Fe ions along with sample purity. Pure BiFeO3 exhibited linear M-H loop indicating its antiferromagnetic characteristics, whereas obvious non-linear M-H loops were observed in Gd substituted samples. In contrast to the observed room temperature magnetization (0.36 emu/g) under 40 kOe for BiFeO3, the sample with 10% Gd exhibited appreciable enhancement of magnetization (1.88 emu/g). A leaky type P-E hysteresis loop was observed for the pure one, whereas concave-like ferroelectric loops were obtained for Gd substituted samples. The possible origins of enhanced multiferroic properties have been explained on the basis of substituent, its concentration, phase purity, particle size, structural distortion and the modified magnetic structure. The measurement of magnetoelectric studies at room temperature revealed the coupling between magnetic and ferroelectric ordering, which is desirable for multifunctional device applications of multiferroics.

  7. Magnetoelectric Control of Exchange Coupling in Monodomain BiFeO3 Heterostructures

    NASA Astrophysics Data System (ADS)

    Irwin, Julian; Saenrang, W.; Davidson, B.; Ryu, S.; Baek, S.-B.; Eom, C. B.; Rzchowski, M. S.; Freeland, J.

    2014-03-01

    The electric field control of magnetization via the exchange bias coupling of a ferromagnetic and antiferromagnetic orderings has exciting applications in spintronic devices such as magnetic tunnel junctions. We investigate the exchange coupling between the monodomain multiferroic BiFeO3(BFO) thin film and a ferromagnetic Co layer. Recently, X-ray magnetic circular dichromism (XMCD) has been used to observe a ~20° rotation in the magnetization of the Co when the electric polarization of the BFO is reversed. Due to the formation of an antiferromagnetic surface ``dead layer'' at high temperatures, observed using X-ray linear magnetic dichromism, this rotation is only seen at temperatures below ~150K. Here we investigate the exchange coupling using anisotropic magnetoresistance (AMR) measurements that detect changes in the magnetization of the Co layer. Out approach using AMR can be applied more generally to study exchange coupling in multiferroic systems. This work is supported by the Army Research Office under Grant No. W911NF-10-1-0362.

  8. The origin and coupling mechanism of magnetoelectric effect in TMCl2-4SC(NH2)2 (TM = Ni and Co)

    NASA Astrophysics Data System (ADS)

    Mun, E.; Wilcox, J.; Manson, J.; Scott, B.; Tobash, P.; Bauer, E.; Sengupta, P.; Batista, C.; Zapf, V.

    2012-02-01

    Most research on multiferroics and magnetoelectric effects to date has focused on inorganic oxides. Metal organic frameworks (MOF) are a new field in which to search for ferroelectricity and explore new coupling mechanisms between electricity and magnetism. We will present the magnetic and electric properties of NiCl2-4SC(NH2)2, DTN, and CoCl2-4SC(NH2)2, DTC, compounds as a function of temperature, magnetic, and electric field. We gain insights into the coupling mechanism by observing that in DTN the electric polarization closely tracks the magnetic ordering whereas in DTC it does not. For DTN, all electrically polar thiourea, SC(NH2)2, molecules are tilted in the same direction along the c-axis, breaking spatial inversion symmetry, whereas for DTC, two thiourea molecules are pointing up and the other two thiourea molecules are pointing down direction with respect to c-axis, perfectly canceling the net electrical polarization. Thus the magnetoelectric coupling mechanism is likely magnetostrictive adjustments of the thiourea molecule orientation in response to magnetic order.

  9. In-plane anisotropic effect of magnetoelectric coupled PMN-PT/FePt multiferroic heterostructure: Static and microwave properties

    NASA Astrophysics Data System (ADS)

    Vargas, Jose M.; Gómez, Javier

    2014-10-01

    The effects of the electric and magnetic field variation on multiferroic heterostructure were studied in this work. Thin films of polycrystalline Fe50Pt50 (FePt) were grown by dc-sputtering on top of the commercial slabs of lead magnesium niobate-lead titanate (PMN-PT). The sample was a (011)-cut single crystal and had one side polished. In this condition, the PMN-PT/FePt operates in the L-T (longitudinal magnetized-transverse polarized) mode. A FePt thin film of 20 nm was used in this study to avoid the characteristic broad microwave absorption line associated with these films above thicknesses of 40 nm. For the in-plane easy magnetization axis (01-1), a microwave magnetoelectric (ME) coupling of 28 Oe cm kV -1 was estimated, whereas a value of 42 Oe cm kV -1 was obtained through the hard magnetization axis (100). Insight into the effects of the in-plane strain anisotropy on the ME coupling is obtained from the dc-magnetization loops. It was observed that the trend was opposite along the easy and hard magnetic directions. In particular, along the easy-magnetic axis (01-1), a square and narrow loop with a factor of Mr/MS of 0.96 was measured at 10 kV/cm. Along the hard-magnetic axis, a factor of 0.16 at 10 kV/cm was obtained. Using electric tuning via microwave absorption at X-band (9.78 GHz), we observe completely different trends along the easy and hard magnetic directions; Multiple absorption lines along the latter axis compared to a single and narrower absorption line along the former. In spite of its intrinsic complexity, we propose a model which gives good agreement both for static and microwave properties. These observations are of fundamental interest for future ME microwave components, such as filters, phase-shifters, and resonators.

  10. Substructure coupling in the frequency domain

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Frequency domain analysis was found to be a suitable method for determining the transient response of systems subjected to a wide variety of loads. However, since a large number of calculations are performed within the discrete frequency loop, the method loses it computational efficiency if the loads must be represented by a large number of discrete frequencies. It was also discovered that substructure coupling in the frequency domain work particularly well for analyzing structural system with a small number of interface and loaded degrees of freedom. It was discovered that substructure coupling in the frequency domain can lead to an efficient method of obtaining natural frequencies of undamped structures. It was also found that the damped natural frequencies of a system may be determined using frequency domain techniques.

  11. Tuning of magnetoelectric coupling in (1-y)Bi0.8Dy0.2FeO3-yNi0.5Zn0.5Fe2O4 multiferroic composites

    NASA Astrophysics Data System (ADS)

    Mazumdar, S. C.; Khan, M. N. I.; Islam, Md. Fakhrul; Hossain, A. K. M. Akther

    2016-03-01

    Magnetoelectric composites (1-y)Bi0.8Dy0.2FeO3 (BDFO)-yNi0.5Zn0.5Fe2O4 (NZFO) with y=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 are synthesized by conventional solid state reaction route. The X-ray diffraction analysis confirms the coexistence of orthorhombic perovskite BDFO and spinel NZFO phases with no third phase. Microstructural and surface morphology are studied by Field Emission Scanning Electron Microscopy. Quantitative elemental analysis of the samples is carried out by Energy Dispersive X-ray Spectroscopy. The real part of the initial permeability increases and relative quality peak broadens with the ferrite content in the composites. Dielectric constant, loss tangent, relative quality factor and ac conductivity are measured as a function of frequency at room temperature. The dielectric constant shows usual dielectric dispersion at lower frequencies due to Maxwell-Wagner type interfacial polarization. The complex impedance spectroscopy is used to distinguish between the grain and grain boundary contribution to the total resistance. The modulus study reveals the ease of polaron hopping and negligibly small contribution of electrode effect. The magnetic hysteresis has been studied to know the response of NZFO phase to the applied magnetic field in the composite. The saturation and remanent magnetization are found to increase with increase in NZFO in the composite. The magnetoelectric voltage coefficient, αME is measured as a function of applied dc magnetic field. The tuning of ferrite percentage and dc magnetic field results in highest αME (~66 mV/cm Oe) for the composite with 40% NZFO at 4.7 kOe which is attributed to the enhanced mechanical coupling between the two phases. The incorporation of BDFO and NZFO enhances the multiferroic properties in the present composite which are quite promising from application point of view.

  12. Strain-mediated elastic coupling in magnetoelectric nickel/barium-titanate heterostructures

    NASA Astrophysics Data System (ADS)

    Streubel, Robert; Köhler, Denny; Schäfer, Rudolf; Eng, Lukas M.

    2013-02-01

    Multiferroic nanomaterials bear the potential for assembling a manifold of novel and smart devices. For room temperature (RT) applications, however, only the BiFeO3 single-phase perovskites are potential candidates to date. Nevertheless, vertical heterostructures separating magnetic and ferroelectric functionality into different layers are now widely proposed to circumvent this lack in materials’ availability. We show here that the second approach is very profitable as illustrated by the strain-mediated coupling between such two layers, i.e., a ferroelectric barium titanate single-crystal (BTO) and a magnetostrictive nickel (Ni) thin film. Applying an electric field across the BTO substrate forces the magnetic easy axis in the Ni film to rotate by 90∘, resulting in a magnetic anisotropy in the range of -1.2 to -33 kJ/m3. We show that local switching proceeds through the nucleation and growth of straight Néel-domain walls at a cost of zigzag walls. The process is fully reversible and continuously tunable as investigated with magnetooptical Kerr microscopy and magnetic force microscopy probing the local in-plane and out-of-plane magnetizations, respectively. Moreover, the degree of anisotropy can be pre-engineered by depositing the Ni film either at RT, above the Curie temperature Tc of BTO, or at an intermediate temperature. Our findings give evidence for using the reported coupling in modern devices, such as magnetoresistive random access memories, spin valves, spin-polarized electron emission, but equally for the bottom-up assembling of magnetizable molecular nanostructures through magnetic domain wall engineering.

  13. Magnetoelectric coupling study in multiferroic Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} ceramics through small and large electric signal standard measurements

    SciTech Connect

    Raymond, Oscar; Siqueiros, Jesus M.; Font, Reynaldo; Portelles, Jorge

    2011-05-01

    Multifunctional multiferroic materials such as the single phase compound Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} (PFN), where ferroelectric and antiferromagnetic order coexist, are very promising and have great interest from the academic and technological points of view. In this work, coupling of the ferroelectric and magnetic moments is reported. For this study, a combination of the small signal response using the impedance spectroscopy technique and the electromechanical resonance method with the large signal response through standard ferroelectric hysteresis measurement, has been used with and without an applied magnetic field. The measurements to determine the electrical properties of the ceramic were performed as functions of the bias and poling electric fields. A simultaneous analysis of the complex dielectric constant {epsilon}-tilde, impedance Z-tilde, electric modulus M-tilde, admittance Y-tilde, and the electromechanical parameters and coupling factors is presented. The results are correlated with a previous study of structural, morphological, small signal dielectric frequency-temperature response, and the ferroelectric hysteretic, magnetic and magnetodielectric behaviors. The observed shifts of the resonance and antiresonance frequency values can be associated with change of the ferroelectric domain size favored by the readjustment of the oxygen octahedron when the magnetic field is applied. From P-E hysteresis loops obtained without and with an external applied magnetic field, a dc magnetoelectric coupling effect with maximum value of 4 kV/cm T (400 mV/cm Oe) was obtained.

  14. Magnetoelectric coupling tuned by competing anisotropies in Mn1-xNixTiO3

    DOE PAGESBeta

    Chi, Songxue; Ye, Feng; Zhou, H. D.; Choi, E. S.; Hwang, J.; Cao, Huibo; Fernandez-Baca, Jaime A.

    2014-10-24

    A flop of electric polarization from Pmore » $$\\|$$c (Pc) to P$$\\|$$ a (Pa) is observed in MnTiO3 as a spin flop transtion is triggered by a c-axis magnetic field, H$$\\|$$c=7 T. The critical magnetic field for Pa is significantly reduced in Mn1-xNixTiO3 (x=0.33). Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and inter-planar neighbors. In the x=0.33 system, the single ion anisotropies of Mn2+ and Ni2+ compete and give rise to an additional spin reorientation transition at TR. A magnetic field, Hc, aligns the spins along c for TRN. The rotation of the collinear spins away from the c-axis for TR alters the magnetic point symmetry and gives rise to new ME susceptibility tensor form. Such linear ME response provides satisfactory explanation for behavior of field-induced electric polarization in both compositions. As the Ni content increases to x=0.5 and 0.68, the ME effect disappears as a new magnetic phase emerges.« less

  15. Equivalent circuit model of converse magnetoelectric effect for the tri-layer magnetoelectric laminates with thermal and stress loadings

    NASA Astrophysics Data System (ADS)

    Zhou, Hao-Miao; Li, Meng-Han; Liu, Hui; Cui, Xiao-Le

    2015-12-01

    For the converse magnetoelectric coupling effect of the piezoelectric/magnetostrictive/piezoelectric tri-layer symmetric magnetoelectric laminates, based on the nonlinear thermo-magneto-mechanical constitutive equations of the giant magnetostrictive materials and the thermo-electro-mechanical constitutive equations of the piezoelectric materials, according to Newton's second law and the magnetic circuit theorem, an equivalent circuit is established. Then an expression of the converse magnetoelectric coefficient describing nonlinear thermo-magneto-electro-mechanical coupling is established. The curve of the nonlinear converse magnetoelectric coefficient versus the bias magnetic field, is predicted effectively by the expression, and the predictions are in good agreement with the experimental result both qualitatively and quantitatively. Furthermore, the model can predict the complex influences of the bias magnetic field, the stress and the ambient temperature on the converse magnetoelectric coefficient. It can be found from these predictions that the converse magnetoelectric coefficient decreases with the increasing temperature and increases with the increasing tensile stress. Under the common effect of the ambient temperature and the stress, it is also found that the converse magnetoelectric coefficient changes sharply with the ambient temperature when the tensile stress is applied on the laminates, but it has a good stability of temperature when a large compressive stress is applied. Therefore, this work contributes to the researches on the giant converse magnetoelectric coefficient and the designs of magnetoelectric devices based on the converse magnetoelectric coupling.

  16. Effect of thickness on the stress and magnetoelectric coupling in bilayered Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3}-CoFe{sub 2}O{sub 4} films

    SciTech Connect

    Wang, Jing E-mail: cwnan@tsinghua.edu.cn; Li, Zheng; Wang, Jianjun; Nan, Cewen E-mail: cwnan@tsinghua.edu.cn; He, Hongcai

    2015-01-28

    Magnetoelectric bilayered Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3}-CoFe{sub 2}O{sub 4}(PZT-CFO) films with different PZT thicknesses were grown on (111)Pt/Ti/SiO{sub 2}/Si substrates using chemical solution spin-coating. Structural characterization by X-ray diffraction and electron microscopy shows pure phases and well-defined interfaces between the PZT and CFO films. The CFO-PZT-substrate structure effectively alleviates the substrate clamping effect for the CFO layer, showing appreciable magnetoelectric responses in the composite films. Both the direct magnetoelectric effect and the magnetic field-induced Raman shifts in the A{sub 1}(TO{sub 1}) soft mode of PZT demonstrate the magnetic-mechanical-electric coupling in the films. The results also indicate that with a constant CFO layer thickness, the thickness of the PZT layer plays an important role in the stress relaxation and strong magnetoelectric coupling. The coupling could be further enhanced by increasing the CFO thickness, optimizing the volume (thickness) fraction of the PZT thickness, and releasing the clamping effect from the substrate.

  17. Magnetoelectric sensor excitations in hexaferrite slabs

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Izadkhah, Hessam; Somu, Sivasubramanian; Vittoria, Carmine

    2015-06-01

    We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite slabs in the frequency range of 100 Hz to 10 MHz. Novel circuit designs incorporating both spiral and solenoid coils and single and multi-capacitor banks were developed to probe the physics and properties of ME hexaferrites and explore ME effects for sensor detections. Fundamental measurements of the anisotropic tensor elements of the magneto-electric coupling parameter were performed using these novel techniques. In addition, for H-field sensing experiments we measured sensitivity of about 3000 Vm-1/G using solenoid coils and 8000 Vm-1/G using spiral coils. For E-field, sensing the sensitivity was 10-4 G/Vm-1 and using single capacitor detector. Sensitivity for multi-capacitor detectors was measured to be in the order of 10-3 G/Vm-1 and frequency dependent exhibiting a maximum value at ˜1 MHz. Tunability of 0.1%-90% was achieved for tunable inductor applications using both single and multi-capacitors excitation. We believe that significant (˜106) improvements in sensitivity and tunability are feasible with simple modifications of the fabrication process.

  18. Magnetoelectric polymer nanocomposite for flexible electronics

    SciTech Connect

    Alnassar, M. Alfadhel, A.; Ivanov, Yu. P.; Kosel, J.

    2015-05-07

    This paper reports the fabrication and characterization of a new type of magnetoelectric polymer nanocomposite that exhibits excellent ferromagnetism and ferroelectricity simultaneously at room temperature. The multiferroic nanocomposite consists of high aspect ratio ferromagnetic iron nanowires embedded inside a ferroelectric co-polymer poly(vinylindene fluoride-trifluoroethylene), P(VDF-TrFE). The nanocomposite has been fabricated via a simple low temperature spin coating technique. Structural, ferromagnetic, ferroelectric, and magnetoelectric properties of the developed nanocomposite have been characterized. The nanocomposite films showed isotropic magnetic properties due to the random orientation of the iron nanowires inside the film. In addition, the embedded nanowires did not hinder the ferroelectric phase development of the nanocomposite. The developed nanocomposite showed a high magnetoelectric coupling response of 156 mV/cmOe measured at 3.1 kOe DC bias field. This value is among the highest reported magnetoelectric coupling in two phase particulate polymer nanocomposites.

  19. Large magnetoelectric response in multiferroic polymer-based composites

    NASA Astrophysics Data System (ADS)

    Nan, Ce-Wen; Cai, N.; Shi, Z.; Zhai, J.; Liu, G.; Lin, Y.

    2005-01-01

    A type of multiferroic polymer-based composite is presented which exhibits a giant magnetoelectric sensitivity. Such a multiferroic composite prepared via a simple low-temperature hot-molding technique for common polymer-based composites has a laminate structure with one lead-zirconate-titanate (PZT)/polyvinylidene-fluoride (PVDF) composite layer sandwiched between two TbDyFe alloy (Terfenol-D)/PVDF composite layers. The PZT/PVDF layer in the middle dominates the dielectric and piezoelectric behavior of the polymer based composites. The coupling elastic interaction between two outer Terfenol-D/PVDF layers and the middle PZT/PVDF layer in such polymer-based composites produces the giant magnetoelectric response as demonstrated by the experimental results, especially at high frequency at which the electromechanical resonance appears. The maximum magnetoelectric sensitivity of the composites can reach up to as high as about 300mV/cmOe at frequency below 50kHz and about 6000mV/cmOe at the resonance frequency of around 80kHz .

  20. Magnetoelectric coupling in lead-free piezoelectric Lix(K0.5Na0.5)1 - xNb1 - yTayO3 and magnetostrictive CoFe2O4 laminated composites

    NASA Astrophysics Data System (ADS)

    Fu, Jiyong; Santa Rosa, Washington; M'Peko, Jean Claude; Algueró, Miguel; Venet, Michel

    2016-04-01

    To replace lead zirconium titanate in magnetoelectric (ME) composites owing to concerns regarding its toxicity, we investigate the ME coupling in bilayer composites comprising lead-free Lix(K0.5Na0.5)1 - xNb1 - yTayO3 (LKNNT) (piezoelectric) and CoFe2O4 (magnetostrictive) phases. We prepare the LKNNT ceramics and measure its piezoelectric coefficient d31, a crucial ingredient determining ME couplings, for several Li (x = 0.03 , 0.035 , 0.04) and Ta (y = 0.15 , 0.2 , 0.25) concentrations, and find that the highest d31 occurs at y = 0.2 for all the values of x studied here. We then evaluate both the transverse (αE,31) and the longitudinal (αE,33) low-frequency ME coupling coefficients of our composites, for each the above composition of (x , y). At x = 0.03, we find the usual scenario of αE,31 and αE,33, i.e., the strongest ME coupling occurs when d31 is maximal, namely at y = 0.2. On the other hand, interestingly, we also obtain the strongest ME coupling when the LKNNT layer has a relatively weaker d31, e.g., at y = 0.25 for x = 0.035 and y = 0.15 for x = 0.04, following from the interplay of d31 and other ingredients (e.g., dielectric constant). Our calculated ME couplings, with αE,31 in magnitude around twice of αE,33, are comparable to those in lead-based composites. The effect of the volume fraction and interface parameter on the ME coupling is also discussed.

  1. Magnetoelectric coupling at the interface of BiFeO3/La0.7Sr0.3MnO3 multilayers

    SciTech Connect

    Calderon, M. J.; Liang, Shuhua; Yu, Rong; Salafranca, Juan; Scalapino, D. J.; Dong, Shuai; Yunoki, Seiji; Brey, L.; Moreo, Adriana; Dagotto, Elbio R

    2011-01-01

    Electric-field controlled exchange bias in a heterostructure composed of the ferromagnetic manganite La0.7Sr0.3MO3 and the ferroelectric antiferromagnetic BiFeO3 has recently been demonstrated experimentally. By means of a model Hamiltonian, we provide a possible explanation for the origin of this magnetoelectric coupling. We find, in agreement with experimental results, a net ferromagnetic moment at the BiFeO3 interface. The induced ferromagnetic moment is the result of the competition between the eg-electron double exchange and the t2g-spin antiferromagnetic superexchange that dominates in bulk BiFeO3. The balance of these simultaneous ferromagnetic and antiferromagnetic tendencies is strongly affected by the interfacial electronic charge density, which, in turn, can be controlled by the BiFeO3 ferroelectric polarization.

  2. High-resolution structure studies and magnetoelectric coupling of relaxor multiferroic Pb (F e0.5N b0.5) O3

    NASA Astrophysics Data System (ADS)

    Sim, Hasung; Peets, Darren C.; Lee, Sanghyun; Lee, Seongsu; Kamiyama, T.; Ikeda, K.; Otomo, T.; Cheong, S.-W.; Park, Je-Geun

    2014-12-01

    Pb (F e0.5N b0.5) O3 (PFN), one of the few relaxor multiferroic systems, has a G -type antiferromagnetic transition at TN=143 K and a ferroelectric transition at TC=385 K . By using high-resolution neutron-diffraction experiments and a total scattering technique, we paint a comprehensive picture of the long- and short-range structures of PFN: (i) a clear sign of short-range structural correlation above TC, (ii) no sign of the negative thermal expansion behavior reported in a previous study, and (iii) clearest evidence thus far of magnetoelectric coupling below TN. We conclude that at the heart of the unusual relaxor multiferroic behavior lies the disorder between Fe3 + and Nb5 + atoms. We argue that this disorder gives rise to short-range structural correlations arising from O disorder in addition to Pb displacement.

  3. Optical characterization of Bi2Se3 in a magnetic field: Infrared evidence for magnetoelectric coupling in a topological insulator material

    NASA Astrophysics Data System (ADS)

    Laforge, A. D.; Frenzel, A.; Pursley, B. C.; Lin, Tao; Liu, Xinfei; Shi, Jing; Basov, D. N.

    2010-03-01

    We present an infrared magneto-optical study of the highly thermoelectric narrow-gap semiconductor Bi2Se3 . Far-infrared and midinfrared (IR) reflectance and transmission measurements have been performed in magnetic fields oriented both parallel and perpendicular to the trigonal c axis of this layered material and supplemented with UV-visible ellipsometry to obtain the optical conductivity σ1(ω) . With lowering of temperature we observe narrowing of the Drude conductivity due to reduced quasiparticle scattering, as well as an increase in the absorption edge due to direct electronic transitions. Magnetic fields H∥c dramatically renormalize and asymmetrically broaden the strongest far-IR optical phonon, indicating interaction of the phonon with the continuum free-carrier spectrum and significant magnetoelectric coupling. For the perpendicular field orientation, electronic absorption is enhanced, and the plasma edge is slightly shifted to higher energies. In both cases the direct transition energy is softened in magnetic field.

  4. Correlation of magnetoelectric coupling in multiferroic BaTiO{sub 3}-BiFeO{sub 3} superlattices with oxygen vacancies and antiphase octahedral rotations

    SciTech Connect

    Lorenz, Michael Schwinkendorf, Peter; Grundmann, Marius; Wagner, Gerald; Oeckler, Oliver; Lazenka, Vera; Modarresi, Hiwa; Vantomme, André; Temst, Kristiaan; Van Bael, Margriet J.

    2015-01-05

    Multiferroic (BaTiO{sub 3}-BiFeO{sub 3}) × 15 multilayer heterostructures show high magnetoelectric (ME) coefficients α{sub ME} up to 24 V/cm·Oe at 300 K. This value is much higher than that of a single-phase BiFeO{sub 3} reference film (α{sub ME} = 4.2 V/cm·Oe). We found clear correlation of ME coefficients with increasing oxygen partial pressure during growth. ME coupling is highest for lower density of oxygen vacancy-related defects. Detailed scanning transmission electron microscopy and selected area electron diffraction microstructural investigations at 300 K revealed antiphase rotations of the oxygen octahedra in the BaTiO{sub 3} single layers, which are an additional correlated defect structure of the multilayers.

  5. Magnetoelectric Coupling in Well-Ordered Epitaxial BiFeO3/CoFe2O4/SrRuO3 Heterostructured Nanodot Array.

    PubMed

    Tian, Guo; Zhang, Fengyuan; Yao, Junxiang; Fan, Hua; Li, Peilian; Li, Zhongwen; Song, Xiao; Zhang, Xiaoyan; Qin, Minghui; Zeng, Min; Zhang, Zhang; Yao, Jianjun; Gao, Xingsen; Liu, Junming

    2016-01-26

    Multiferroic magnetoelectric (ME) composites exhibit sizable ME coupling at room temperature, promising applications in a wide range of novel devices. For high density integrated devices, it is indispensable to achieve a well-ordered nanostructured array with reasonable ME coupling. For this purpose, we explored the well-ordered array of isolated epitaxial BiFeO3/CoFe2O4/SrRuO3 heterostructured nanodots fabricated by nanoporous anodic alumina (AAO) template method. The arrayed heterostructured nanodots demonstrate well-established epitaxial structures and coexistence of piezoelectric and ferromagnetic properties, as revealed by transmission electron microscopy (TEM) and peizoeresponse/magnetic force microscopy (PFM/MFM). It was found that the heterostructured nanodots yield apparent ME coupling, likely due to the effective transfer of interface couplings along with the substantial release of substrate clamping. A noticeable change in piezoelectric response of the nanodots can be triggered by magnetic field, indicating a substantial enhancement of ME coupling. Moreover, an electric field induced magnetization switching in these nanodots can be observed, showing a large reverse ME effect. These results offer good opportunities of the nanodots for applications in high-density ME devices, e.g., high density recording (>100 Gbit/in.(2)) or logic devices. PMID:26651132

  6. Multiferroic magnetoelectric composites: Historical perspective, status, and future directions

    NASA Astrophysics Data System (ADS)

    Nan, Ce-Wen; Bichurin, M. I.; Dong, Shuxiang; Viehland, D.; Srinivasan, G.

    2008-02-01

    Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. An electric polarization is induced by a weak ac magnetic field oscillating in the presence of a dc bias field, and/or a magnetization polarization appears upon applying an electric field. So far, three kinds of bulk magnetoelectric composites have been investigated in experimental and theoretical, i.e., composites of (a) ferrite and piezoelectric ceramics (e.g., lead zirconate titanate), (b) magnetic metals/alloys (e.g., Terfenol-D and Metglas) and piezoelectric ceramics, and (c) Terfenol-D and piezoelectric ceramics and polymer. The elastic coupling interaction between the magnetostrictive phase and piezoelectric phase leads to giant magnetoelectric response of these magnetoelectric composites. For example, a Metglas/lead zirconate titanate fiber laminate has been found to exhibit the highest magnetoelectric coefficient, and in the vicinity of resonance, its magnetoelectric voltage coefficient as high as 102V/cmOe orders has been achieved, which exceeds the

  7. Multiferroicity and magnetoelectric coupling enhanced large magnetocaloric effect in DyFe{sub 0.5}Cr{sub 0.5}O{sub 3}

    SciTech Connect

    Yin, L. H.; Yang, J.; Dai, J. M.; Song, W. H.; Zhang, R. R.; Sun, Y. P.

    2014-01-20

    DyFe{sub 0.5}Cr{sub 0.5}O{sub 3} has been synthesized using a sol-gel method. It exhibits ferroelectricity at the antiferromagnetic ordering temperature T{sub N1}∼261 K. Large magnetocaloric effect (MCE) (11.3 J/kg K at 4.5 T) enhanced by magnetoelectric coupling due to magnetic field and temperature induced magnetic transition was observed. Temperature-dependent Raman study shows an anomalous behavior near T{sub N1} in the phonon modes related to the vibration of Dy atoms and stretching of CrO{sub 6}/FeO{sub 6} octahedra, suggesting the ferroelectricity in DyFe{sub 0.5}Cr{sub 0.5}O{sub 3} is associated with the spin-phonon coupling with respect to both Dy and Cr/Fe ions. These results suggest routes to obtain high-temperature multiferroicity and large MCE for practical applications.

  8. Magnetic field-induced ferroelectric domain structure evolution and magnetoelectric coupling for [110]-oriented PMN-PT/Terfenol-D multiferroic composites

    NASA Astrophysics Data System (ADS)

    Fang, F.; Jing, W. Q.

    2016-01-01

    Magnetic field-induced polarization rotation and magnetoelectric coupling effects are studied for [110]-oriented (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3/Tb0.3Dy0.7Fe2(PMN-xPT/Terfenol-D) multiferroic composites. Two compositions of the [110]-oriented relaxor ferroelectric single crystals, PMN-28PT and PMN-33PT, are used. In [110]-oriented PMN-28PT, domains of rhombohedral (R) and monoclinic (MB) phases coexist prior to the magnetic loadings. Upon the applied magnetic loadings, phase transition from monoclinic MB to R phase occurs. In [110]-oriented PMN-33PT, domains are initially of mixed orthorhombic (O) and MB phases, and the phase transition from O to MB phase takes place upon the external magnetic loading. Compared to PMN-28PT, the PMN-33PT single crystal exhibits much finer domain boundary structure prior to the magnetic loadings. Upon the magnetic loadings, more domain variants are induced via the phase transition in PMN-33PT than that in PMN-28PT single crystal. The finer domain band structure and more domain variants contribute to stronger piezoelectric activity. As a result, the composite of PMN-33PT/Terfenol-D manifests a stronger ME coupling than PMN-28PT/Terfenol-D composite.

  9. First-principles approach to the dynamic magnetoelectric couplings for the non-reciprocal directional dichroism in BiFeO3

    NASA Astrophysics Data System (ADS)

    Lee, Jun Hee; Kézsmáki, István; Fishman, Randy S.

    2016-04-01

    Due to the complicated magnetic and crystallographic structures of BiFeO3, its magnetoelectric (ME) couplings and microscopic model Hamiltonian remain poorly understood. By employing a first-principles approach, we uncover all possible ME couplings associated with the spin-current (SC) and exchange-striction (ES) polarizations, and construct an appropriate Hamiltonian for the long-range spin-cycloid in BiFeO3. First-principles calculations are used to understand the microscopic origins of the ME couplings. We find that inversion symmetries broken by ferroelectric and antiferroelectric distortions induce the SC and the ES polarizations, which cooperatively produce the dynamic ME effects in BiFeO3. A model motivated by first principles reproduces the absorption difference of counter-propagating light beams called non-reciprocal directional dichroism. The current paper focuses on the spin-driven (SD) polarizations produced by a dynamic electric field, i.e. the dynamic ME couplings. Due to the inertial properties of Fe, the dynamic SD polarizations differ significantly from the static SD polarizations. Our systematic approach can be generally applied to any multiferroic material, laying the foundation for revealing hidden ME couplings on the atomic scale and for exploiting optical ME effects in the next generation of technological devices such as optical diodes. This manuscript has been written by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.

  10. Magnetic spin structure and magnetoelectric coupling in BiFeO{sub 3}-BaTiO{sub 3} multilayer

    SciTech Connect

    Lazenka, Vera Modarresi, Hiwa; Bisht, Manisha; Vantomme, André; Temst, Kristiaan; Lorenz, Michael; Bonholzer, Michael; Grundmann, Marius; Rüffer, Rudolf; Van Bael, Margriet J.

    2015-02-23

    Magnetic spin structures in epitaxial BiFeO{sub 3} single layer and an epitaxial BaTiO{sub 3}/BiFeO{sub 3} multilayer thin film have been studied by means of nuclear resonant scattering of synchrotron radiation. We demonstrate a spin reorientation in the 15 × [BaTiO{sub 3}/BiFeO{sub 3}] multilayer compared to the single BiFeO{sub 3} thin film. Whereas in the BiFeO{sub 3} film, the net magnetic moment m{sup →} lies in the (1–10) plane, identical to the bulk, m{sup →} in the multilayer points to different polar and azimuthal directions. This spin reorientation indicates that strain and interfaces play a significant role in tuning the magnetic spin order. Furthermore, large difference in the magnetic field dependence of the magnetoelectric coefficient observed between the BiFeO{sub 3} single layer and multilayer can be associated with this magnetic spin reorientation.

  11. Microscopic evidence of strain-mediated magnetoelectric coupling in Co/Pt multilayers/PMN-PT(011) heterostructures

    NASA Astrophysics Data System (ADS)

    Sun, Ying; Wang, Wenbo; Wu, Weida; Zheng, Xiaoli; Cai, Jianwang; Zhao, Yonggang; Liu, Ming

    A promising way to control magnetization(M) via an electric field(E-field) is using magnetoelectric(ME) effect in FM/FE heterostructures. We use magnetic(electric) force microscopy(M(e)FM) to study the strain-mediated E-field modulation of M in (Co/Pt)n with perpendicular magnetic anisotropy(PMA) or in-plane anisotropy on PMN-PT(011) substrates. MFM were performed on (Co/Pt)n with an DC E-field applied to PMN-PT. In MeFM, we superimpose an AC modulation on a DC one and utilize lock-in technique to detect weak ME effect. For (Co/Pt)n with PMA, MFM images show stripe domains with no obvious changes at varied DC E-fields. However, MeFM shows interesting structures and the image contrast reverses sign at opposite strain slopes of the PMN-PT substrate. For sample with in-plane anisotropy, both MFM and MeFM images show dipole-like domains. Interestingly, the MeFM image contrast reverses sign at opposite strain slopes of the substrate. The sign reversal of MeFM contrast indicates that features revealed by MeFM are intrinsic local ME effect. Our MeFM data are consistent with the ferromagnetic resonance results showing that strain-induced anisotropy change will cause part of M switching to the in-plane direction. Possible scenarios will be discussed.

  12. Ab initio study of magnetoelectric coupling in La0.66Sr0.33MnO3 / PbZr0.2Ti0.8O3 multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Hammouri, Mahmoud; Fohtung, Edwin; Vasiliev, Igor

    2016-10-01

    Multiferroic heterostructures composed of thin layers of ferromagnetic and ferroelectric perovskites have attracted considerable attention in recent years. We apply ab initio computational methods based on density functional theory to study the magnetoelectric coupling at the (0 0 1) interface between \\text{L}{{\\text{a}}0.66}\\text{S}{{\\text{r}}0.33}\\text{Mn}{{\\text{O}}3} (LSMO) and \\text{PbZ}{{\\text{r}}0.2}\\text{T}{{\\text{i}}0.8}{{\\text{O}}3} (PZT). Our study demonstrates that the ferroelectric polarization of PZT has a strong influence on the distribution of magnetization in LSMO. The presence of polarized PZT changes the balance between the ferromagnetic and antiferromagnetic states of LSMO. The observed interfacial magnetoelectric effect can be explained by the variation of the charge density across the LSMO/PZT interface and by the change of the magnetic order in the LSMO layer adjacent to PZT.

  13. Self-biased magnetoelectric coupling characteristics of three-phase composite transducers with nanocrystallin soft magnetic alloy

    NASA Astrophysics Data System (ADS)

    Huang, Dongyan; Lu, Caijiang; Bing, Han

    2015-07-01

    This paper reports the self-biased magnetoelectric (ME) effects in composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB), pure nickel (Ni) and piezoelectric lead zirconate titanate (PZT). The FeCuNbSiB ribbons are fabricated on traditional laminates Ni/PZT/Ni through two modes: the attached mode (F-NPN-F) and the laminated mode (F/NPN/F). The F-NPN-F composite sufficiently reveals that the high-permeability FeCuNbSiB ribbons concentrate more magnetic flux in magnetostrictive Ni, which results in the self-biased ME effects of F-NPN-F. For the F/NPN/F composite, the FeCuNbSiB acts as the dynamic driver to enhance the effective piezomagnetic coefficient of Ni. The giant self-biased ME effects of F/NPN/F are because of the internal magnetic field between Ni and FeCuNbSiB due to their different magnetic characteristics. The influences of the numbers of FeCuNbSiB layers ( L) on the resonant ME voltage coefficients ( α ME ,r ) for F-NPN-F and F/NPN/F composites are investigated in detail. The experiments demonstrate that the maximum α ME ,r at zero-biased field is 80 V/cm Oe for F-NPN-F with L = 2, and 85 V/cm Oe for F/NPN/F with L = 4. This paper demonstrates that these two ME composites are suitable for achieving zero-biased ME transducers, power-free magnetic field sensors and energy harvesters.

  14. Multiferroism and Magnetoelectric Coupling in Nano-Microscale Lead-Free Composite by 0.3Co-FERRITE and 0.7(K0.5Na0.5)NbO3-BASED Ferroelectric Matrix

    NASA Astrophysics Data System (ADS)

    Zhou, Yun; Wang, Xinyan; Li, Li; Su, Yuling; Zhang, Jincang; Cao, Shixun

    Nontoxic lead-free multiferroic composites are synthesized by incorporating the dispersed 0.3CoFe2O4 (CFO) ferromagnetic nanoparticles into 0.7(K0.5Na0.5) NbO3-LiSbO3 (KNN-LS5.2) ferroelectric micromatrix. The multiferroicity of the composite can be verified by polarization-electric field hysteresis loop and magnetic hysteresis loop. The composite exhibits excellent magnetic properties. A dilution effect is observed in magnetic hysteresis loops. The field dependence of ME voltage coefficient is given as a function of magnetic field from -4 kOe to 4 kOe with a maximum magnetoelectric voltage coefficient of 10.7 mVṡcm-1ṡOe-1 at the frequency of 1 kHz. It is a very high value in the lead-free magnetoelectric composites system for the potential use on multifunctional devices.

  15. Effect of divalent Ba cation substitution with Sr on coupled 'multiglass' state in the magnetoelectric multiferroic compound Ba3NbFe3Si2O14.

    PubMed

    Rathore, Satyapal Singh; Vitta, Satish

    2015-01-01

    (Ba/Sr)3NbFe3Si2O14 is a magneto-electric multiferroic with an incommensurate antiferromagnetic spiral magnetic structure which induces electric polarization at 26 K. Structural studies show that both the compounds have similar crystal structure down to 6 K. They exhibit a transition, TN at 26 K and 25 K respectively, as indicated by heat capacity and magnetization, into an antiferromagnetic state. Although Ba and Sr are isovalent, they exhibit very different static and dynamic magnetic behaviors. The Ba-compound exhibits a glassy behavior with critical slowing dynamics with a freezing temperature of ~35 K and a critical exponent of 3.9, a value close to the 3-D Ising model above TN, in addition to the invariant transition into an antiferromagnetic state. The Sr-compound however does not exhibit any dispersive behavior except for the invariant transition at TN. The dielectric constant reflects magnetic behavior of the two compounds: the Ba-compound has two distinct dispersive peaks while the Sr-compound has a single dispersive peak. Thus the compounds exhibit coupled 'multiglass' behavior. The difference in magnetic properties between the two compounds is found to be due to modifications to super exchange path angle and length as well as anti-site defects which stabilize either ferromagnetic or antiferromagnetic interactions. PMID:25988657

  16. First-principles approach to the dynamic magnetoelectric couplings for the non-reciprocal directional dichroism in BiFeO3

    DOE PAGESBeta

    Kezsmarki, I.; Fishman, Randy Scott

    2016-04-18

    Due to the complicated magnetic and crystallographic structures of BiFeO3, its magnetoelectric (ME) couplings and microscopic model Hamiltonian remain poorly understood. By employing a firstprinciples approach, we uncover all possibleMEcouplings associated with the spin-current (SC) and exchange-striction (ES) polarizations, and construct an appropriate Hamiltonian for the long-range spin-cycloid in BiFeO3. First-principles calculations are used to understand the microscopic origins of theMEcouplings.Wefind that inversion symmetries broken by ferroelectric and antiferroelectric distortions induce the SC and the ES polarizations, which cooperatively produce the dynamicME effects in BiFeO3. A model motivated by first principles reproduces the absorption difference of counter-propagating light beams calledmore » non-reciprocal directional dichroism. The current paper focuses on the spin-driven (SD) polarizations produced by a dynamic electric field, i.e. the dynamic MEcouplings. Due to the inertial properties of Fe, the dynamic SD polarizations differ significantly from the static SD polarizations. Our systematic approach can be generally applied to any multiferroic material, laying the foundation for revealing hiddenMEcouplings on the atomic scale and for exploiting opticalMEeffects in the next generation of technological devices such as optical diodes.« less

  17. A multilevel nonvolatile magnetoelectric memory

    PubMed Central

    Shen, Jianxin; Cong, Junzhuang; Shang, Dashan; Chai, Yisheng; Shen, Shipeng; Zhai, Kun; Sun, Young

    2016-01-01

    The coexistence and coupling between magnetization and electric polarization in multiferroic materials provide extra degrees of freedom for creating next-generation memory devices. A variety of concepts of multiferroic or magnetoelectric memories have been proposed and explored in the past decade. Here we propose a new principle to realize a multilevel nonvolatile memory based on the multiple states of the magnetoelectric coefficient (α) of multiferroics. Because the states of α depends on the relative orientation between magnetization and polarization, one can reach different levels of α by controlling the ratio of up and down ferroelectric domains with external electric fields. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure confirm that the states of α can be well controlled between positive and negative by applying selective electric fields. Consequently, two-level, four-level, and eight-level nonvolatile memory devices are demonstrated at room temperature. This kind of multilevel magnetoelectric memory retains all the advantages of ferroelectric random access memory but overcomes the drawback of destructive reading of polarization. In contrast, the reading of α is nondestructive and highly efficient in a parallel way, with an independent reading coil shared by all the memory cells. PMID:27681812

  18. Theory of magnetoelectric effect in multilayer nanocomposites on a substrate: Resonant bending-mode response

    NASA Astrophysics Data System (ADS)

    Krantz, Matthias C.; Gerken, Martina

    2013-05-01

    Resonant bending-mode magnetoelectric (ME) coefficients of magnetostrictive-piezoelectric multilayer cantilevers are calculated analytically using a model developed for arbitrary multilayers on a substrate. Without quality factor effects the ME coefficient maxima in the four-dimensional parameter space of layer numbers, layer sequences, piezoelectric volume fractions, and substrate thicknesses are found to be essentially constant for nonzero substrate thickness. Global maxima occur for bilayers without substrates. Vanishing magnetoelectric response regions result from voltage cancellation in piezoelectric layers or absence of bending-mode excitation. They are determined by the neutral plane position in the multilayer stack. With Q-factor effects dominated by viscous air damping ME coefficients strongly increase with cantilever thickness primarily due to increasing resonance frequencies. The results yield a layer specific prediction of ME coefficients, resonance frequencies, and Q-factors in arbitrary multilayers and thus distinction of linear-coupling and Q-factor effects from exchange interaction, interface, or nonlinear ME effects.

  19. The role of the relative voltage and phase for frequency coupling in a dual-frequency capacitively coupled plasma

    SciTech Connect

    O'Connell, D.; Gans, T.; Semmler, E.; Awakowicz, P.

    2008-08-25

    Frequency coupling in multifrequency discharges is a complex nonlinear interaction of the different frequency components. An alpha-mode low pressure rf capacitively coupled plasma operated simultaneously with two frequencies is investigated and the coupling of the two frequencies is observed to greatly influence the excitation and ionization within the discharge. Through this, plasma production and sustainment are dictated by the corresponding electron dynamics and can be manipulated through the dual-frequency sheath. These mechanisms are influenced by the relative voltage and also the relative phase of the two frequencies.

  20. Evidence for weak ferromagnetism, isostructural phase transition, and linear magnetoelectric coupling in the multiferroic Bi0.8Pb0.2Fe0.9Nb0.1O3 solid solution

    NASA Astrophysics Data System (ADS)

    Patel, Jay Prakash; Senyshyn, Anatoliy; Fuess, Hartmut; Pandey, Dhananjai

    2013-09-01

    Magnetization, dielectric, and calorimetric studies on Bi0.8 Pb0.2 Fe0.9 Nb0.1O3 (BF-0.2PFN) reveal very weak ferromagnetism but strong dielectric anomaly at the antiferromagnetic transition temperature (TN) characteristic of magnetoelectric coupling. We correlate these results with nuclear and magnetic structure studies using x-ray and neutron powder diffraction techniques, respectively. Rietveld refinements using x-ray powder diffraction data in the temperature range 300 to 673 K reveal pronounced anomalies in the unit cell parameters at TN, indicating strong magnetoelastic coupling. The nuclear and magnetic structures of BF-0.2PFN were determined from neutron powder diffraction data using a representation theory approach. They show the occurrence of a first-order isostructural phase transition (IPT) accompanying the magnetic ordering below TN˜566 K, leading to significant discontinuous change in the ionic polarization (ΔPz˜1.6(3) μC/cm2) and octahedral tilt angle (˜0.3°) at TN. The ionic polarization obtained from refined positional coordinates of the nuclear structure and Born effective charges is shown to scale linearly with sublattice magnetization, confirming the presence of linear magnetoelectric coupling in BF-0.2PFN at the atomic level, despite the very low value of remanent magnetization (Mr).

  1. Magnetodielectric effect and electric-induced magnetic permeability in magnetoelectric laminate composite under low inspiring signal

    NASA Astrophysics Data System (ADS)

    Zhou, Jian-Ping; Zhang, Yu-Xiang; Zhang, Guang-Bin; Liu, Peng

    2013-01-01

    A theory based on equivalent circuit was proposed to demonstrate that magnetodielectric (MDE) effect and electric-induced magnetic permeability (EIMP) exist in the magnetoelectric composite. Both MDE and EIMP are sensitive to the amplitude of inspiring signal. They were researched in a simple Pb(Zr,Ti)O3/Terfenol-D laminate composite experimentally. A large MDE coefficient over 85% was found near the resonance frequency under a low magnetic field of 40 Oe. The EIMP was also observed in the composite. They are mainly originated from the magnetoelectric coupling between the piezoelectric and magnetostrictive components. These results are significant in the device applications of modulating dielectric constant and magnetic permeability at room temperature.

  2. Magneto-electric coupling in antiferromagnet/ferroelectric Mn2Au/BaTiO3 interface

    NASA Astrophysics Data System (ADS)

    Plekhanov, Evgeny; Stroppa, Alessandro; Picozzi, Silvia

    2016-08-01

    Within the crucial issue of the electric field control of magnetism, the use of antiferromagnets (AFMs) coupled to ferroelectrics is much less explored than the ferromagnets counterpart, although the first choice might lead to better performances and larger stability with respect to external perturbations (such as magnetic fields). Here, we explore the possibility to control the magnetic anisotropy of a Mn2Au layer by reversing the ferroelectric polarization of BaTiO3 in Mn2Au/BaTiO3 interfaces. By means of a thorough exploration of many possible geometry configurations, we identify the two most stable, corresponding to compressive and tensile strain at the interface. The first appears to be easy-axis, while the second—easy-plane—with a large induced moment on the interface Ti atom. The reversal of ferroelectric polarization changes the anisotropy by approximately 50%, thus paving the way to the control of AFM properties with an electric field.

  3. High temperature magneto-electric effect in yittrium iron garnet (YIG)

    NASA Astrophysics Data System (ADS)

    Saha, J.; Chaudhary, S.; Majumdar, P.; Kuanr, B. K.; Patnaik, S.

    2016-05-01

    We report a study on potential multiferroic characteristics of Yttrium Iron Garnet (YIG). The emergence of ferroelectricity in YIG is in debate but we provide evidence for strong magneto-electric coupling above room temperature from dielectric constant measurement with and without magnetic field. We find that the apparent pseudo-ferroelectric crossover temperature in YIG varies with frequency. For higher frequency the transition shifts towards higher temperature. This is indicative of relaxor behavior. We have also measured the dielectric constant in the presence of external magnetic field at high temperature that confirms interdependence of magnetic and dielectric properties.

  4. Magnetoelectric domain wall dynamics and its implications for magnetoelectric memory

    DOE PAGESBeta

    Belashchenko, K. D.; Tchernyshyov, O.; Kovalev, Alexey A.; Tretiakov, O. A.

    2016-03-30

    Domain wall dynamics in a magnetoelectric antiferromagnet is analyzed, and its implications for magnetoelectric memory applications are discussed. Cr2O3 is used in the estimates of the materials parameters. It is found that the domain wall mobility has a maximum as a function of the electric field due to the gyrotropic coupling induced by it. In Cr2O3, the maximal mobility of 0.1 m/(s Oe) is reached at E≈0.06 V/nm. Fields of this order may be too weak to overcome the intrinsic depinning field, which is estimated for B-doped Cr2O3. These major drawbacks for device implementation can be overcome by applying amore » small in-plane shear strain, which blocks the domain wall precession. Domain wall mobility of about 0.7 m/(s Oe) can then be achieved at E = 0.2 V/nm. Furthermore, a split-gate scheme is proposed for the domain-wall controlled bit element; its extension to multiple-gate linear arrays can offer advantages in memory density, programmability, and logic functionality.« less

  5. Magnetoelectric domain wall dynamics and its implications for magnetoelectric memory

    NASA Astrophysics Data System (ADS)

    Belashchenko, K. D.; Tchernyshyov, O.; Kovalev, Alexey A.; Tretiakov, O. A.

    2016-03-01

    Domain wall dynamics in a magnetoelectric antiferromagnet is analyzed, and its implications for magnetoelectric memory applications are discussed. Cr2O3 is used in the estimates of the materials parameters. It is found that the domain wall mobility has a maximum as a function of the electric field due to the gyrotropic coupling induced by it. In Cr2O3, the maximal mobility of 0.1 m/(s Oe) is reached at E ≈0.06 V/nm. Fields of this order may be too weak to overcome the intrinsic depinning field, which is estimated for B-doped Cr2O3. These major drawbacks for device implementation can be overcome by applying a small in-plane shear strain, which blocks the domain wall precession. Domain wall mobility of about 0.7 m/(s Oe) can then be achieved at E = 0.2 V/nm. A split-gate scheme is proposed for the domain-wall controlled bit element; its extension to multiple-gate linear arrays can offer advantages in memory density, programmability, and logic functionality.

  6. Mesoscale Interfacial Dynamics in Magnetoelectric Nanocomposites

    SciTech Connect

    Khachaturyan, Armen G.

    2009-08-06

    Theory and modeling of chessboard-like self-assembling of vertically aligned columnar nanostructures in films has been developed. By means of modeling and three-dimensional computational simulations, we proposed a novel self-assembly process that can produce good chessboard nanostructure architectures through a pseudo-spinodal decomposition of an epitaxial film under optimal thermodynamic and crystallographic conditions (appropriate choice of the temperature, composition of the film, and crystal lattice parameters of the film and substrate). These conditions are formulated. The obtained results have been published on Nano Letters. Based on the principles of the formation of chessboard nanostructured films, we are currently trying to find good decomposing material systems that satisfy the optimal conditions to produce the chessboard nanostructure architecture. In addition we are under way doing 'computer experiments' to look for the appropriate materials with the chessboard columnar nanostructures, as a potential candidate for engineering of optical devices, high-efficiency multiferroics, and high-density magnetic perpendicular recording media. We are also currently to investigate the magnetoelectric response of multiferroic chessboard nanostructures under applied electric/magnetic fields. A unified 3-dimensional phase field theory of the strain-mediated magnetoelectric effect in magnetoelectric composites is developed. The theory is based on the established equivalency paradigm: we proved that by using a variational priciple the exact values of the electric, magnetic and strain fields in a magnetoelectric composite of arbitrary morphology and their coupled magneto-electric-mechanical response can be evaluated by considering an equivalent homogeneous system with the specially chosen effective eigenstrain, polarization and magnetization. These equivalency parameters are spatially inhomogeneous fields, which are obtained by solving the time-dependent Ginzburg

  7. Optical Measurements on Magnetoelectric LSMO/PZT Bilayers

    NASA Astrophysics Data System (ADS)

    Chen, Disheng; Polisetty, Srinivas; Wolfe, Evan; Zhou, Jinling; Holcomb, Mikel; Tra Vu, Thanh; Yang, Jan-Chi; Chu, Ying-Hao

    2012-02-01

    Fairly weak magnetoelectric coupling observed in the only single phase material (BeFiO3) exhibiting magnetism and ferroelectricity at room temperature has pushed scientists to consider alternative systems. Multilayers prove promising theoretically and experimentally, however, most modern techniques are blind to the interfacial mechanisms causing the coupling. Without a full understanding of the physical mechanism for these effects, significant improvements in the design and multiple potential applications of magnetoelectric coupling will be difficult to achieve. Optical measurements including second harmonic generation are crucial tools to solve this problem, as they provide complementary insight into the magnetic/ferroelectric properties and resulting carrier dynamics. For example, angular dependence SHG of magnetic LaSrMnO3 and ferroelectric PbZrTiO3 bilayers indicates the symmetry and magnetization as we vary thicknesses of the magnetic and ferroelectric layers and its implication to magnetoelectric coupling.

  8. Frequency response enhancement in integrated coupled-cavity DBR lasers.

    SciTech Connect

    Wendt, Joel Robert; Vawter, Gregory Allen; Tauke-Pedretti, Anna; Alford, Charles Fred; Skogen, Erik J.; Chow, Weng Wah; Cajas, Florante G.; Overberg, Mark E.; Torres, David L.; Yang, Zhenshan; Peake, Gregory Merwin

    2010-11-01

    We present a photonic integrated circuit (PIC) composed of two strongly coupled lasers. This PIC utilizes the dynamics of mutual injection locking to increase the relaxation resonance frequency from 3 GHz to beyond 30 GHz.

  9. Magnetoelectric ‘spin’ on stimulating the brain

    PubMed Central

    Guduru, Rakesh; Liang, Ping; Hong, J; Rodzinski, Alexandra; Hadjikhani, Ali; Horstmyer, Jeffrey; Levister, Ernest; Khizroev, Sakhrat

    2015-01-01

    Aim: The in vivo study on imprinting control region mice aims to show that magnetoelectric nanoparticles may directly couple the intrinsic neural activity-induced electric fields with external magnetic fields. Methods: Approximately 10 µg of CoFe2O4–BaTiO3 30-nm nanoparticles have been intravenously administrated through a tail vein and forced to cross the blood–brain barrier via a d.c. field gradient of 3000 Oe/cm. A surgically attached two-channel electroencephalography headmount has directly measured the modulation of intrinsic electric waveforms by an external a.c. 100-Oe magnetic field in a frequency range of 0–20 Hz. Results: The modulated signal has reached the strength comparable to that due the regular neural activity. Conclusion: The study opens a pathway to use multifunctional nanoparticles to control intrinsic fields deep in the brain. PMID:25953069

  10. Ultraviolet single-frequency coupled optofluidic ring resonator dye laser.

    PubMed

    Tu, Xin; Wu, Xiang; Li, Ming; Liu, Liying; Xu, Lei

    2012-08-27

    Ultraviolet single-frequency lasing is realized in a coupled optofluidic ring resonator (COFRR) dye laser that consists of a thin-walled capillary microfluidic ring resonator and a cylindrical resonator. The whispering gallery modes (WGMs) in each resonator couple to each other and generate single-frequency laser emission. Single-frequency lasing occurs at 386.75 nm with a pump threshold of 5.9 μJ/mm. The side-mode-suppression ratio (SMSR) is about 20 dB. Moreover, the laser emits mainly in two directions, and each of them has a divergence of only 10.5°.

  11. Magnetoelectric Coupling Characteristics of the La0.67Sr0.33MnO3/PbZr0.2Ti0.8O3(001) Interface

    NASA Astrophysics Data System (ADS)

    Hammouri, Mahmoud; Karpov, Dmitry; Fohtung, Edwin; Vasiliev, Igor

    Multiferroic heterostructures composed of thin layers of ferromagnetic and ferroelectric perovskites have attracted considerable attention in recent years. We apply ab initio computational methods based on density functional theory to study the characteristics of the magnetoelectric coupling at the (001) interface between La0.67Sr0.33MnO3 (LSMO) and PbZr0.2Ti0.8O3(PZT). The calculations are carried out using the Quantum ESPRESSO electronic structure code combined with Vanderbilt ultrasoft pseudopotentials. Our study shows that the interfacial interaction between LSMO and PZT and the polarization of PZT have a strong influence on the distribution of magnetization within the LSMO layer. A significant change in the magnetization of the LSMO layer adjacent to PZT is observed after reversal of the direction of polarization of PZT. Supported by NMSU GREG award. EF is funded by the DoD-AFOSR under Award No FA9550-14-1-0363.

  12. Different coupling modes mediate cortical cross-frequency interactions.

    PubMed

    Helfrich, Randolph F; Herrmann, Christoph S; Engel, Andreas K; Schneider, Till R

    2016-10-15

    Cross-frequency coupling (CFC) has been suggested to constitute a highly flexible mechanism for cortical information gating and processing, giving rise to conscious perception and various higher cognitive functions in humans. In particular, it might provide an elegant tool for information integration across several spatiotemporal scales within nested or coupled neuronal networks. However, it is currently unknown whether low-frequency (theta/alpha) or high-frequency gamma oscillations orchestrate cross-frequency interactions, raising the question of who is master and who is slave. While correlative evidence suggested that at least two distinct CFC modes exist, namely, phase-amplitude-coupling (PAC) and amplitude-envelope correlations (AEC), it is currently unknown whether they subserve distinct cortical functions. Novel non-invasive brain stimulation tools, such as transcranial alternating current stimulation (tACS), now provide the unique opportunity to selectively entrain the low- or high-frequency component and study subsequent effects on CFC. Here, we demonstrate the differential modulation of CFC during selective entrainment of alpha or gamma oscillations. Our results reveal that entrainment of the low-frequency component increased PAC, where gamma power became preferentially locked to the trough of the alpha oscillation, while gamma-band entrainment enhanced AECs and reduced alpha power. These results provide causal evidence for the functional role of coupled alpha and gamma oscillations for visual processing. PMID:26608244

  13. Different coupling modes mediate cortical cross-frequency interactions.

    PubMed

    Helfrich, Randolph F; Herrmann, Christoph S; Engel, Andreas K; Schneider, Till R

    2016-10-15

    Cross-frequency coupling (CFC) has been suggested to constitute a highly flexible mechanism for cortical information gating and processing, giving rise to conscious perception and various higher cognitive functions in humans. In particular, it might provide an elegant tool for information integration across several spatiotemporal scales within nested or coupled neuronal networks. However, it is currently unknown whether low-frequency (theta/alpha) or high-frequency gamma oscillations orchestrate cross-frequency interactions, raising the question of who is master and who is slave. While correlative evidence suggested that at least two distinct CFC modes exist, namely, phase-amplitude-coupling (PAC) and amplitude-envelope correlations (AEC), it is currently unknown whether they subserve distinct cortical functions. Novel non-invasive brain stimulation tools, such as transcranial alternating current stimulation (tACS), now provide the unique opportunity to selectively entrain the low- or high-frequency component and study subsequent effects on CFC. Here, we demonstrate the differential modulation of CFC during selective entrainment of alpha or gamma oscillations. Our results reveal that entrainment of the low-frequency component increased PAC, where gamma power became preferentially locked to the trough of the alpha oscillation, while gamma-band entrainment enhanced AECs and reduced alpha power. These results provide causal evidence for the functional role of coupled alpha and gamma oscillations for visual processing.

  14. Multifunctional magnetoelectric materials for device applications

    NASA Astrophysics Data System (ADS)

    Ortega, N.; Kumar, Ashok; Scott, J. F.; Katiyar, Ram S.

    2015-12-01

    Over the past decade magnetoelectric (ME) mutiferroic (MF) materials and their devices are one of the highest priority research topics that has been investigated by the scientific ferroics community to develop the next generation of novel multifunctional materials. These systems show the simultaneous existence of two or more ferroic orders, and cross-coupling between them, such as magnetic spin, polarisation, ferroelastic ordering, and ferrotoroidicity. Based on the type of ordering and coupling, they have drawn increasing interest for a variety of device applications, such as magnetic field sensors, nonvolatile memory elements, ferroelectric photovoltaics, nano-electronics etc. Since single-phase materials exist rarely in nature with strong cross-coupling properties, intensive research activity is being pursued towards the discovery of new single-phase multiferroic materials and the design of new engineered materials with strong magneto-electric (ME) coupling. This review article summarises the development of different kinds of multiferroic material: single-phase and composite ceramic, laminated composite and nanostructured thin films. Thin-film nanostructures have higher magnitude direct ME coupling values and clear evidence of indirect ME coupling compared with bulk materials. Promising ME coupling coefficients have been reported in laminated composite materials in which the signal to noise ratio is good for device fabrication. We describe the possible applications of these materials.

  15. Theoretical investigation of magnetoelectric surface acoustic wave characteristics of ZnO/Metglas layered composite

    NASA Astrophysics Data System (ADS)

    Huang, Liang; Lyu, Qingqing; Wen, Dandan; Zhong, Zhiyong; Zhang, Huaiwu; Bai, Feiming

    2016-01-01

    The surface acoustic wave properties of piezoelectric/magnetostrictive layered structures consisting of insulating ZnO and metallic Metglas with giant Δ E effect were studied based on a stable scattering matrix method. Only the first Rayleigh mode was found with phase velocity between 2200 m/s and 2650 m/s, and the maximum electro-mechanical coupling coefficient about 1%. It was found that the center frequency of ZnO/Metglas is highly sensitive on the change of magnetic field, up to 440 MHz/Oe. However, there is a cutoff Young's modulus of Metglas for different designs of SAW, below which the Rayleigh mode will disappear. For a magnetoelectric SAW design with the center frequency of 335 MHz and covering a full magnetic field range from -1.4 to +1.4 Oe, the frequency sensitivity is 212 MHz/Oe, equivalent to a magnetic field sensitivity of 5 × 10-12 Tesla. Unlike conventional magnetoelectric bulk laminates or film stacks, the detection of frequency shift instead of electrical charge allows not only shrinkage of device volume but also a broad frequency band detection of weak magnetic field.

  16. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, G.; Qu, P.; Piskulich, E.; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.; Qu, Hongwei; Srinivasan, G.

    2014-07-01

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  17. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    SciTech Connect

    Sreenivasulu, G.; Piskulich, E.; Srinivasan, G.; Qu, P.; Qu, Hongwei; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.

    2014-07-21

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  18. Laser frequency bandwidth narrowing by photorefractive two-beam coupling.

    PubMed

    Chomsky, D; Sternklar, S; Zigler, A; Jackel, S

    1992-04-01

    We present a theoretical analysis and experimental demonstration of a new method for spectral narrowing of laser radiation. The bandwidth narrowing is experienced by a laser beam subjected to a photorefractive two-beam coupling process. Contrary to the conventional method of frequency filtering by a Fabry-Perot étalon, this technique has no intrinsic finesse limitation on its resolution. A factor of 2 in frequency bandwidth narrowing is achieved with an argon-ion laser.

  19. Dynamics of the locomotor-respiratory coupling at different frequencies.

    PubMed

    Hoffmann, Charles P; Bardy, Benoît G

    2015-05-01

    The locomotor-respiratory coupling (LRC) is a universal phenomenon reported for various forms of rhythmic exercise. In this study, we investigated the effect of movement and respiratory frequencies on LRC. Participants were instructed to cycle or breath in synchrony with a periodic auditory stimulation at preferred and non-preferred frequencies. LRC stability was assessed by frequency and phase coupling indexes using the theory of nonlinear coupled oscillators through the sine circle map model, and the Farey tree. Results showed a stabilizing effect of sound on LRC for all frequencies and for the two systems paced. The sound-induced effect was more prominent when the rhythm of the stimulation corresponded to the preferred frequencies. The adoption of cycling or respiratory frequencies far off preferential ones led to a loss of stability in LRC. Contrary to previous findings, our results suggest that LRC is not unidirectional-from locomotion onto respiration-but bidirectional between the two systems. They also suggest that auditory information plays an important role in the modulation of LRC. PMID:25796188

  20. Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

    SciTech Connect

    Waskoenig, J.; Gans, T.

    2010-05-03

    Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

  1. A magnetoelectric composite based signal generator

    NASA Astrophysics Data System (ADS)

    Fetisov, Y. K.; Serov, V. N.; Fetisov, L. Y.; Makovkin, S. A.; Viehland, D.; Srinivasan, G.

    2016-05-01

    Self-oscillations in an active loop consisting of a wide-band amplifier and a magnetoelectric composite in the feedback circuit have been observed. The composite with a ferroelectric lead zirconate titanate bimorph and ferromagnetic Metglas serves as a resonator that determines the frequency of oscillations and provides the feedback voltage. Under amplitude balance and phase matching conditions, the device generated signals at 2.3 kHz, at the bending resonance frequency of the composite. The oscillations were observed over a specific range of magnetic bias H. The shape of the signal generated is dependent on electrical circuit parameters and magnitude and orientation of H.

  2. Broadband/Wideband Magnetoelectric Response

    DOE PAGESBeta

    Park, Chee-Sung; Priya, Shashank

    2012-01-01

    A broadband/wideband magnetoelectric (ME) composite offers new opportunities for sensing wide ranges of both DC and AC magnetic fields. The broadband/wideband behavior is characterized by flat ME response over a given AC frequency range and DC magnetic bias. The structure proposed in this study operates in the longitudinal-transversal (L-T) mode. In this paper, we provide information on (i) how to design broadband/wideband ME sensors and (ii) how to control the magnitude of ME response over a desired frequency and DC bias regime. A systematic study was conducted to identify the factors affecting the broadband/wideband behavior by developing experimental models andmore » validating them against the predictions made through finite element modeling. A working prototype of the sensor with flat bands for both DC and AC magnetic field conditions was successfully obtained. These results are quite promising for practical applications such as current probe, low-frequency magnetic field sensing, and ME energy harvester.« less

  3. Coupled whispering gallery mode resonators in the Terahertz frequency range.

    PubMed

    Preu, S; Schwefel, H G L; Malzer, S; Döhler, G H; Wang, L J; Hanson, M; Zimmerman, J D; Gossard, A C

    2008-05-12

    We report on coupling of two whispering gallery mode resonators in the Terahertz frequency range. Due to the long wavelength in the millimeter to submillimeter range, the resonators can be macroscopic allowing for accurate size and shape control. This is necessary to couple specific modes of two or more resonators. Sets of polyethylene (PE) and quartz disk resonators are demonstrated, with medium (loaded) quality (Q)-factors of 40-800. Both exhibit coinciding resonance frequency spectra over more than ten times the free spectral range. Loading effects of single resonators are investigated which provide strong Q-factor degradation and red-shifts of the resonances in the 0.2% range. By coupling two resonators of the same size, we observe mode splitting, in very good agreement with our numerical calculations.

  4. Electric Field Control of the Resistance of Multiferroic Tunnel Junctions with Magnetoelectric Antiferromagnetic Barriers

    NASA Astrophysics Data System (ADS)

    Merodio, P.; Kalitsov, A.; Chshiev, M.; Velev, J.

    2016-06-01

    Based on model calculations, we predict a magnetoelectric tunneling electroresistance effect in multiferroic tunnel junctions consisting of ferromagnetic electrodes and magnetoelectric antiferromagnetic barriers. Switching of the antiferromagnetic order parameter in the barrier in applied electric field by means of the magnetoelectric coupling leads to a substantial change of the resistance of the junction. The effect is explained in terms of the switching of the orientations of local magnetizations at the barrier interfaces affecting the spin-dependent interface transmission probabilities. Magnetoelectric multiferroic materials with finite ferroelectric polarization exhibit an enhanced resistive change due to polarization-induced spin-dependent screening. These results suggest that devices with active barriers based on single-phase magnetoelectric antiferromagnets represent an alternative nonvolatile memory concept.

  5. Deterministic coherence resonance in coupled chaotic oscillators with frequency mismatch.

    PubMed

    Pisarchik, A N; Jaimes-Reátegui, R

    2015-11-01

    A small mismatch between natural frequencies of unidirectionally coupled chaotic oscillators can induce coherence resonance in the slave oscillator for a certain coupling strength. This surprising phenomenon resembles "stabilization of chaos by chaos," i.e., the chaotic driving applied to the chaotic system makes its dynamics more regular when the natural frequency of the slave oscillator is a little different than the natural frequency of the master oscillator. The coherence is characterized with the dominant component in the power spectrum of the slave oscillator, normalized standard deviations of both the peak amplitude and the interpeak interval, and Lyapunov exponents. The enhanced coherence is associated with increasing negative both the third and the fourth Lyapunov exponents, while the first and second exponents are always positive and zero, respectively.

  6. Magnetoelectric polarizability and axion electrodynamics in crystalline insulators.

    PubMed

    Essin, Andrew M; Moore, Joel E; Vanderbilt, David

    2009-04-10

    The orbital motion of electrons in a three-dimensional solid can generate a pseudoscalar magnetoelectric coupling theta, a fact we derive for the single-particle case using a recent theory of polarization in weakly inhomogeneous materials. This polarizability theta is the same parameter that appears in the "axion electrodynamics" Lagrangian DeltaL_{EM}=(thetae;{2}/2pih)E.B, which is known to describe the unusual magnetoelectric properties of the three-dimensional topological insulator (theta=pi). We compute theta for a simple model that accesses the topological insulator and discuss its connection to the surface Hall conductivity. The orbital magnetoelectric polarizability can be generalized to the many-particle wave function and defines the 3D topological insulator, like the integer quantum Hall effect, in terms of a topological ground-state response function.

  7. Adiabatic frequency conversion with a sign flip in the coupling

    NASA Astrophysics Data System (ADS)

    Hristova, H. S.; Rangelov, A. A.; Montemezzani, G.; Vitanov, N. V.

    2016-09-01

    Adiabatic frequency conversion is a method recently developed in nonlinear optics [H. Suchowski, D. Oron, A. Arie, and Y. Silberberg, Phys. Rev. A 78, 063821 (2008), 10.1103/PhysRevA.78.063821], using ideas from the technique of rapid adiabatic passage (RAP) via a level crossing in quantum physics. In this method, the coupling coefficients are constant and the phase mismatch is chirped adiabatically. In this work, we propose another method for adiabatic frequency conversion, in which the phase mismatch is constant and the coupling is a pulse-shaped function with a sign flip (i.e., a phase step of π ) at its maximum. Compared to the RAP method, our technique has comparable efficiency but it is simpler to implement for it only needs two bulk crystals with opposite χ(2 ) nonlinearity. Moreover, because our technique requires constant nonzero frequency mismatch and has zero conversion efficiency on exact frequency matching, it can be used as a frequency filter.

  8. Frequency shifts in a rubidium frequency standard due to coupling to another standard

    NASA Technical Reports Server (NTRS)

    Jaduszliwer, Bernardo; Cook, R. A.; Frueholz, R. P.

    1990-01-01

    Highly reliable timing system, such as used on board satellites, may incorporate a hot standby atomic clock besides the active one. RF couplings between them may affect the performance of the active clock. The effect of such couplings between two rubidium atomic clocks was investigated, and it was found that they will add an oscillatory term to the Allan Variance of the active clock, degrading its frequency stability, and that under certain circumstances they may also shift the active clock's operating frequency. These two effects are discussed in detail, and the level of isolation required to render them negligible is established.

  9. Controlled self-assembly of multiferroic core-shell nanoparticles exhibiting strong magneto-electric effects

    SciTech Connect

    Sreenivasulu, Gollapudi; Hamilton, Sean L.; Lehto, Piper R.; Srinivasan, Gopalan; Popov, Maksym; Chavez, Ferman A.

    2014-02-03

    Ferromagnetic-ferroelectric composites show strain mediated coupling between the magnetic and electric sub-systems due to magnetostriction and piezoelectric effects associated with the ferroic phases. We have synthesized core-shell multiferroic nano-composites by functionalizing 10–100 nm barium titanate and nickel ferrite nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst. The core-shell structure was confirmed by electron microscopy and magnetic force microscopy. Evidence for strong strain mediated magneto-electric coupling was obtained by static magnetic field induced variations in the permittivity over 16–18 GHz and polarization and by electric field induced by low-frequency ac magnetic fields.

  10. Magnetoelectric Glass Nature in Magnetoplumbite-Type BaCo6Ti6O19

    NASA Astrophysics Data System (ADS)

    Tonomoto, Hayato; Kimura, Kenta; Kimura, Tsuyoshi

    2016-03-01

    The magnetoelectric coupling in the spin glass BaCo6Ti6O19 with the magnetoplumbite structure was examined. We have successfully grown single crystals of this compound and revealed the XY-like spin glass nature with a glass transition at Tg ≈ 14 K. It was found that the electric polarization P gradually develops below about 50 K and shows a substantial anomaly at around Tg. Furthermore, the magnitude of P strongly depends on the magnetoelectric cooling condition below Tg and shows a memory effect coupled with the spin sector. The present result indicates that BaCo6Ti6O19 exhibits a magnetoelectric glass nature in which a frozen state of electric dipoles is coupled with that of magnetic ones and can be modulated magnetoelectrically.

  11. Magnetoelectric interactions in single crystal ferrite-piezoelectric bilayers

    NASA Astrophysics Data System (ADS)

    Srinivasan, G.; Petrov, V. M.; Zhai, J.

    2005-03-01

    The nature of low-frequency (10-2 - 10^4 Hz) magnetoelectric (ME) coupling has been investigated in bilayers of single crystal Ni-Zn ferrites and polycrystalline lead zirconate titanate or single crystal lead magnesium niobate-lead titanate. Important observations are as follows. (i) The ME coupling in the bilayers is found to be stronger than in polycrystalline multilayers [1]. (ii) Zn substitution in ferrite is found to enhance the strength of ME interactions. (iii) ME voltage coefficients show significant variation with the orientation of the bias magnetic field. (iv) Data analysis using our model reveals that superior magneto-mechanical coupling in the ferrites is the cause of strong ME interactions [2]. 1. G. Srinivasan, E. T. Rasmussen, and R. Hayes Phys. Rev. B. 67, 014418 (2003). 2. M. I. Bichurin, V. M. Petrov and G. Srinivasan. Phys. Rev. B. 68, 054402 (2003). - supported by grants from the the National Science Foundation (DMR-0302254), Russian Ministry of Education (Å02-3.4-278), and the Universities of Russia Foundation (UNR 01.01.026).

  12. Understanding the dynamic magnetization process for the magnetoelectric effect in multiferroic composites

    NASA Astrophysics Data System (ADS)

    Gualdi, A. J.; Zabotto, F. L.; Garcia, D.; Bhalla, A.; Guo, R.; de Camargo, P. C.; de Oliveira, A. J. A.

    2016-03-01

    Based on a magnetic relaxation model, an approach that includes the spin dynamics is proposed and applied to describe the magnetoelectric (ME) effect frequency dependence for a 0-3 type composite at low temperatures. Our results show that the ME coefficient, in low temperatures, for PMN-PT/CFO ( (1 -x )P b (M g1 /3N b2 /3)-x P b T i O3/C o F e2O4 ) composite has a step-like behavior on the hysteresis loop for frequency of 1 kHz, contrasting with the results at low frequencies (10 Hz). This approach assumes that the ferromagnetic and ferroelectric phases are coupled through the interactions of the spins of the ferromagnetic phase with the composite phonons by spin/lattice relaxation.

  13. Synchronization of phase oscillators with frequency-weighted coupling

    PubMed Central

    Xu, Can; Sun, Yuting; Gao, Jian; Qiu, Tian; Zheng, Zhigang; Guan, Shuguang

    2016-01-01

    Recently, the first-order synchronization transition has been studied in systems of coupled phase oscillators. In this paper, we propose a framework to investigate the synchronization in the frequency-weighted Kuramoto model with all-to-all couplings. A rigorous mean-field analysis is implemented to predict the possible steady states. Furthermore, a detailed linear stability analysis proves that the incoherent state is only neutrally stable below the synchronization threshold. Nevertheless, interestingly, the amplitude of the order parameter decays exponentially (at least for short time) in this regime, resembling the Landau damping effect in plasma physics. Moreover, the explicit expression for the critical coupling strength is determined by both the mean-field method and linear operator theory. The mechanism of bifurcation for the incoherent state near the critical point is further revealed by the amplitude expansion theory, which shows that the oscillating standing wave state could also occur in this model for certain frequency distributions. Our theoretical analysis and numerical results are consistent with each other, which can help us understand the synchronization transition in general networks with heterogenous couplings. PMID:26903110

  14. Subterahertz excitations and magnetoelectric effects in hexaferrite-piezoelectric bilayers

    SciTech Connect

    Ustinov, Alexey B.; Srinivasan, G.

    2008-10-06

    A frequency-agile hexaferrite-piezoelectric composite for potential device applications at subterahertz frequencies is studied. The bilayer is composed of aluminum substituted barium hexagonal ferrite (BaAl{sub 2}Fe{sub 10}O{sub 19}) and lead zirconate titanate (PZT). A dc electric field applied to PZT results in mechanical deformation of the ferrite, leading to a frequency shift in ferromagnetic resonance. The bilayer demonstrates magnetoelectric interaction coefficient of about 0.37 Oe cm/kV.

  15. Remote power transfer using magneto-electric devices

    NASA Astrophysics Data System (ADS)

    Sinha, K.; Tabib-Azar, M.

    2015-12-01

    We report remote power transfer using magneto-electric devices. The experiments were performed at room temperature for piezoelectric beam coupled with electromagnet. Neodymium magnet was used as mass loading. We observed the output power of the order +19.3 to -71.1 dB given the gap between the input and output source was varied from 4 mm to 12 mm for the device (21.3 mm × 3.59 mm × 0.57 mm) with best performance at the resonance peak. We tested the device for frequency sweeps of 10-100 Hz and 100-5000 Hz. This enabled us to figure out the output power for the device at resonant frequencies over a wide frequency range. The device has high input impedance (as opposed to coils) and can be miniaturized aggressively to below 100 μm linear dimensions. The piezoelectric beams have much higher quality factors (Q) larger than 1000 while coils have low Qs (∼ 20) and the harvesting efficiency is proportional to Q.

  16. Self-biased large magnetoelectric coupling in co-sintered Bi{sub 0.5}Na{sub 0.5}TiO{sub 3} based piezoelectric and CoFe{sub 2}O{sub 4} based magnetostrictive bilayered composite

    SciTech Connect

    Kumari, Mukesh; Singh, Amrita; Chatterjee, Ratnamala E-mail: ratnamalac@gmail.com; Gupta, Arti; Prakash, Chandra

    2014-12-28

    In this work, magnetoelectric properties of a co-sintered bilayered composite of non-lead based piezoelectric 0.97(Bi{sub 0.5}Na{sub 0.5}TiO{sub 3})–0.03(K{sub 0.47}Na{sub 0.47}Li{sub 0.06}Nb{sub 0.74}Sb{sub 0.06}Ta{sub 0.2}O{sub 3}) and magnetostrictive Co{sub 0.6}Zn{sub 0.4}Fe{sub 1.7}Mn{sub 0.3}O{sub 4} are presented. Similar optimal sintering conditions of the individual components lead to a very clean interface as evidenced in the scanning electron microscopy, angle dispersive X-ray diffraction, and energy-dispersive X-ray (EDX) results. Clean interface results in strong intimate mechanical coupling between both components and causes a maximum transfer of induced strain, leading to a large magnetoelectric coupling ∼142 mV/cm·Oe measured in longitudinally magnetized-transversely polarized configuration (L-T mode). Remnant polarization ∼32 μC/cm{sup 2}, remnant magnetization ∼0.50 emu/g, and sufficiently high self biased magnetoelectricity ∼135 mV/cm Oe (L-T mode) were observed for this composite.

  17. Room temperature nonlinear magnetoelectric effect in lead-free and Nb-doped AlFeO{sub 3} compositions

    SciTech Connect

    Cótica, Luiz F.; Santos, Guilherme M.; Santos, Ivair A.; Freitas, Valdirlei F.; Coelho, Adelino A.; Pal, Madhuparna; Guo, Ruyan; Bhalla, Amar S.; Garcia, Ducinei; Eiras, José A.

    2015-02-14

    It is still a challenging problem to obtain technologically useful materials displaying strong magnetoelectric coupling at room temperature. In the search for new effects and materials to achieve this kind of coupling, a nonlinear magnetoelectric effect was proposed in the magnetically disordered relaxor ferroelectric materials. In this context, the aluminum iron oxide (AlFeO{sub 3}), a room temperature ferroelectric relaxor and magnetic spin glass compound, emerges as an attractive lead-free magnetoelectric material along with nonlinear magnetoelectric effects. In this work, static, dynamic, and temperature dependent ferroic and magnetoelectric properties in lead-free AlFeO{sub 3} and 2 at. % Nb-doped AlFeO{sub 3} multiferroic magnetoelectric compositions are studied. Pyroelectric and magnetic measurements show changes in ferroelectric and magnetic states close to each other (∼200 K). The magnetoelectric coefficient behavior as a function of H{sub bias} suggests a room temperature nonlinear magnetoelectric coupling in both single-phase and Nb-doped AlFeO{sub 3}-based ceramic compositions.

  18. Magnetoelectric Effect in Ceramics Based on Bismuth Ferrite.

    PubMed

    Jartych, Elżbieta; Pikula, Tomasz; Kowal, Karol; Dzik, Jolanta; Guzdek, Piotr; Czekaj, Dionizy

    2016-12-01

    Solid-state sintering method was used to prepare ceramic materials based on bismuth ferrite, i.e., (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions and the Aurivillius Bi5Ti3FeO15 compound. The structure of the materials was examined using X-ray diffraction, and the Rietveld method was applied to phase analysis and structure refinement. Magnetoelectric coupling was registered in all the materials using dynamic lock-in technique. The highest value of magnetoelectric coupling coefficient α ME was obtained for the Bi5Ti3FeO15 compound (α ME ~ 10 mVcm(-1) Oe(-1)). In the case of (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions, the maximum α ME is of the order of 1 and 2.7 mVcm(-1) Oe(-1), respectively. The magnitude of magnetoelectric coupling is accompanied with structural transformation in the studied solid solutions. The relatively high magnetoelectric effect in the Aurivillius Bi5Ti3FeO15 compound is surprising, especially since the material is paramagnetic at room temperature. When the materials were subjected to a preliminary electrical poling, the magnitude of the magnetoelectric coupling increased 2-3 times. PMID:27129686

  19. Magnetoelectric Effect in Ceramics Based on Bismuth Ferrite.

    PubMed

    Jartych, Elżbieta; Pikula, Tomasz; Kowal, Karol; Dzik, Jolanta; Guzdek, Piotr; Czekaj, Dionizy

    2016-12-01

    Solid-state sintering method was used to prepare ceramic materials based on bismuth ferrite, i.e., (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions and the Aurivillius Bi5Ti3FeO15 compound. The structure of the materials was examined using X-ray diffraction, and the Rietveld method was applied to phase analysis and structure refinement. Magnetoelectric coupling was registered in all the materials using dynamic lock-in technique. The highest value of magnetoelectric coupling coefficient α ME was obtained for the Bi5Ti3FeO15 compound (α ME ~ 10 mVcm(-1) Oe(-1)). In the case of (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions, the maximum α ME is of the order of 1 and 2.7 mVcm(-1) Oe(-1), respectively. The magnitude of magnetoelectric coupling is accompanied with structural transformation in the studied solid solutions. The relatively high magnetoelectric effect in the Aurivillius Bi5Ti3FeO15 compound is surprising, especially since the material is paramagnetic at room temperature. When the materials were subjected to a preliminary electrical poling, the magnitude of the magnetoelectric coupling increased 2-3 times.

  20. Large self-biased and multi-peak magnetoelectric coupling in transducer of Pb(Zr,Ti)O3 plates and H-type magnetization-graded ferromagnetic fork

    NASA Astrophysics Data System (ADS)

    Shen, Yongchun; Ling, Zhihao; Lu, Caijiang

    2015-12-01

    This paper develops a self-biased magnetoelectric (ME) composite Metglas/H-type-FeNi/PZT (MHFP) of H-type magnetization-graded Metglas/H-type-FeNi fork and piezoelectric Pb(Zr,Ti)O3 (PZT) plate. By using the magnetization-graded magnetostrictive layer and symmetrical H-type structure, giant self-biased ME coupling and multi-peak phenomenon are observed. The zero-biased ME voltage coefficient of MHFP composite reaches ˜63.8 V/cm Oe, which is ˜37.5 times higher than that of traditional FeNi/PZT laminate. The output ME voltage has a good near linear relation with Hac and is determined to be ˜5.1 V/Oe and ˜10.6 mV/Oe at ˜65 kHz and 1 kHz, respectively. These indicate that the proposed composite show promising applications for ME transducers and high-sensitivity self-biased magnetic sensors.

  1. Properties of epitaxial (210) iron garnet films exhibiting the magnetoelectric effect

    SciTech Connect

    Arzamastseva, G. V.; Balbashov, A. M.; Lisovskii, F. V. Mansvetova, E. G.; Temiryazev, A. G.; Temiryazeva, M. P.

    2015-04-15

    The properties of epitaxial magnetic (LuBi){sub 3}(FeGa){sub 5}O{sub 12} iron garnet films grown on (210) substrates, which exhibit the magnetoelectric effect, are experimentally studied. The induced anisotropy and the behavior of the domain structure in the films are investigated in uniform and nonuniform external fields. The existing hypotheses about the nature of the magnetoelectric coupling in such films are critically analyzed.

  2. Multi-frequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

    NASA Astrophysics Data System (ADS)

    Andersen, Christian Kraglund; Mølmer, Klaus

    2015-03-01

    A SQUID inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency side bands. We calculate the multi-frequency eigenmodes and these can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application, we determine their coupling to transmon qubits with different frequencies and we present a bi-chromatic scheme for entanglement and gate operations. In this calculation, we obtain a maximally entangled state with a fidelity F = 95 % . Our proposal is competitive with the achievements of other entanglement-gates with superconducting devices and it may offer some advantages: (i) There is no need for additional control lines and dephasing associated with the conventional frequency tuning of qubits. (ii) When our qubits are idle, they are far detuned with respect to each other and to the resonator, and hence they are immune to cross talk and Purcell-enhanced decay.

  3. Coupled vibro-acoustic model updating using frequency response functions

    NASA Astrophysics Data System (ADS)

    Nehete, D. V.; Modak, S. V.; Gupta, K.

    2016-03-01

    Interior noise in cavities of motorized vehicles is of increasing significance due to the lightweight design of these structures. Accurate coupled vibro-acoustic FE models of such cavities are required so as to allow a reliable design and analysis. It is, however, experienced that the vibro-acoustic predictions using these models do not often correlate acceptably well with the experimental measurements and hence require model updating. Both the structural and the acoustic parameters addressing the stiffness as well as the damping modeling inaccuracies need to be considered simultaneously in the model updating framework in order to obtain an accurate estimate of these parameters. It is also noted that the acoustic absorption properties are generally frequency dependent. This makes use of modal data based methods for updating vibro-acoustic FE models difficult. In view of this, the present paper proposes a method based on vibro-acoustic frequency response functions that allow updating of a coupled FE model by considering simultaneously the parameters associated with both the structural as well as the acoustic model of the cavity. The effectiveness of the proposed method is demonstrated through numerical studies on a 3D rectangular box cavity with a flexible plate. Updating parameters related to the material property, stiffness of joints between the plate and the rectangular cavity and the properties of absorbing surfaces of the acoustic cavity are considered. The robustness of the method under presence of noise is also studied.

  4. Cross-Frequency Coupling of Plasma Waves in the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Khazanov, G. V.

    2014-12-01

    Wave-particle and wave-wave interactions are crucial elements of magnetosphere and ionosphere plasma dynamics. Such interactions provide a channel of energy redistribution between different plasma populations, and lead to connections between physical processes developing on different spatial and temporal scales. The lower hybrid waves (LHWs) are particularly interesting for plasma dynamics, because they couple well with both electrons and ions. The excitation of LHWs is a widely discussed mechanism of interaction between plasma species in space and is one of the unresolved questions of magnetospheric multi-ion plasmas. It is demonstrated that large-amplitude Alfven and/or EMIC waves, in particular those associated with lower frequency (LF) turbulence, may generate LHWs in the auroral zone and ring current region and in some cases this serves as the Alfven and/or EMIC waves saturation mechanism. We believe that this described scenario, as well as some other cross-frequency coupling of plasma waves processes that will be discussed in this presentation, can play a vital role in various parts of the magnetospheric plasma, especially in the places under investigation by the NASA THEMIS and Van Allen Probes (formerly known as the Radiation Belt Storm Probes (RBSP)) missions.

  5. Efficient thermal energy harvesting using nanoscale magnetoelectric heterostructures

    NASA Astrophysics Data System (ADS)

    Etesami, S. R.; Berakdar, J.

    2016-02-01

    Thermomechanical cycles with a ferroelectric working substance convert heat to electrical energy. As shown here, magnetoelectrically coupled ferroelectric/ferromagnetic composites (also called multiferroics) allow for an efficient thermal energy harvesting at room temperature by exploiting the pyroelectric effect. By virtue of the magnetoelectric coupling, external electric and magnetic fields can steer the operation of these heat engines. Our theoretical predictions are based on a combination of Landau-Khalatnikov-Tani approach (with a Ginzburg-Landau-Devonshire potential) to simulate the ferroelectric dynamics coupled to the magnetic dynamics. The latter is treated via the electric-polarization-dependent Landau-Lifshitz-Gilbert equation. By performing an adapted Olsen cycle we show that a multiferroic working substance is potentially much more superior to the sole ferroelectrics, as far as the thermal energy harvesting using pyroelectric effect is concerned. Our proposal holds promise not only for low-energy consuming devices but also for cooling technology.

  6. Cross-frequency coupling in real and virtual brain networks

    PubMed Central

    Jirsa, Viktor; Müller, Viktor

    2013-01-01

    Information processing in the brain is thought to rely on the convergence and divergence of oscillatory behaviors of widely distributed brain areas. This information flow is captured in its simplest form via the concepts of synchronization and desynchronization and related metrics. More complex forms of information flow are transient synchronizations and multi-frequency behaviors with metrics related to cross-frequency coupling (CFC). It is supposed that CFC plays a crucial role in the organization of large-scale networks and functional integration across large distances. In this study, we describe different CFC measures and test their applicability in simulated and real electroencephalographic (EEG) data obtained during resting state. For these purposes, we derive generic oscillator equations from full brain network models. We systematically model and simulate the various scenarios of CFC under the influence of noise to obtain biologically realistic oscillator dynamics. We find that (i) specific CFC-measures detect correctly in most cases the nature of CFC under noise conditions, (ii) bispectrum (BIS) and bicoherence (BIC) correctly detect the CFCs in simulated data, (iii) empirical resting state EEG show a prominent delta-alpha CFC as identified by specific CFC measures and the more classic BIS and BIC. This coupling was mostly asymmetric (directed) and generally higher in the eyes closed (EC) than in the eyes open (EO) condition. In conjunction, these two sets of measures provide a powerful toolbox to reveal the nature of couplings from experimental data and as such allow inference on the brain state dependent information processing. Methodological advantages of using CFC measures and theoretical significance of delta and alpha interactions during resting and other brain states are discussed. PMID:23840188

  7. Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor

    SciTech Connect

    Stalnaker, Jason E.; Mbele, Vela; Gerginov, Vladislav; Fortier, Tara M.; Diddams, Scott A.; Hollberg, Leo; Tanner, Carol E.

    2010-04-15

    We report measurements of absolute transition frequencies and hyperfine coupling constants for the 8S{sub 1/2}, 9S{sub 1/2}, 7D{sub 3/2}, and 7D{sub 5/2} states in {sup 133}Cs vapor. The stepwise excitation through either the 6P{sub 1/2} or 6P{sub 3/2} intermediate state is performed directly with broadband laser light from a stabilized femtosecond laser optical-frequency comb. The laser beam is split, counterpropagated, and focused into a room-temperature Cs vapor cell. The repetition rate of the frequency comb is scanned and we detect the fluorescence on the 7P{sub 1/2,3/2{yields}}6S{sub 1/2} branches of the decay of the excited states. The excitations to the different states are isolated by the introduction of narrow-bandwidth interference filters in the laser beam paths. Using a nonlinear least-squares method we find measurements of transition frequencies and hyperfine coupling constants that are in agreement with other recent measurements for the 8S state and provide improvement by 2 orders of magnitude over previously published results for the 9S and 7D states.

  8. Electrophysiological low-frequency coherence and cross-frequency coupling contributes to BOLD connectivity

    PubMed Central

    Wang, Liang; Saalmann, Yuri B.; Pinsk, Mark A.; Arcaro, Michael J.; Kastner, Sabine

    2012-01-01

    SUMMARY Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD) signals in different brain areas. Although evidence suggests that gamma band (30–100 Hz) neural activity contributes to local BOLD signals, the neural basis of inter-areal BOLD correlations is unclear. We first defined a visual network in monkeys based on converging evidence from inter-areal BOLD correlations during a fixation task, task-free state and anesthesia, and then simultaneously recorded local field potentials (LFPs) from the same four network areas in the task-free state. Low frequency oscillations (< 20 Hz), and not gamma activity, predominantly contributed to inter-areal BOLD correlations. The low frequency oscillations also influenced local processing by modulating gamma activity within individual areas. We suggest that such cross-frequency coupling links local BOLD signals to BOLD correlations across distributed networks. PMID:23217748

  9. Crystal growth of hexaferrite architecture for magnetoelectrically tunable microwave semiconductor integrated devices

    NASA Astrophysics Data System (ADS)

    Hu, Bolin

    Hexaferrites (i.e., hexagonal ferrites), discovered in 1950s, exist as any one of six crystallographic structural variants (i.e., M-, X-, Y-, W-, U-, and Z-type). Over the past six decades, the hexaferrites have received much attention owing to their important properties that lend use as permanent magnets, magnetic data storage materials, as well as components in electrical devices, particularly those operating at RF frequencies. Moreover, there has been increasing interest in hexaferrites for new fundamental and emerging applications. Among those, electronic components for mobile and wireless communications especially incorporated with semiconductor integrated circuits at microwave frequencies, electromagnetic wave absorbers for electromagnetic compatibility, random-access memory (RAM) and low observable technology, and as composite materials having low dimensions. However, of particular interest is the magnetoelectric (ME) effect discovered recently in the hexaferrites such as SrScxFe12-xO19 (SrScM), Ba2--xSrxZn 2Fe12O22 (Zn2Y), Sr4Co2Fe 36O60 (Co2U) and Sr3Co2Fe 24O41 (Co2Z), demonstrating ferroelectricity induced by the complex internal alignment of magnetic moments. Further, both Co 2Z and Co2U have revealed observable magnetoelectric effects at room temperature, representing a step toward practical applications using the ME effect. These materials hold great potential for applications, since strong magnetoelectric coupling allows switching of the FE polarization with a magnetic field (H) and vice versa. These features could lead to a new type of storage devices, such as an electric field-controlled magnetic memory. A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25--40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the

  10. Magnetoelectric and multiferroic properties in layered 3D transition metal oxides

    NASA Astrophysics Data System (ADS)

    Hwang, Jungmin

    Functional ferroelectric and magnetic materials have played an important role of modern technology in the sensor or storage device industries. Ferroelectricity and ferromagnetism emerge from different origins. However, it is discovered that these two seemingly unrelated phenomena can actually coexist in materials called multiferroics. Since current trends toward device miniaturization have increased interests in combining electronic and magnetic properies into multifunctional materials, multiferroics have attracted great attention. Ferromagnetic ferroelectric multiferroics are especially fascinating not only because they have both ferroic properties, but also because of the magnetoelectric coupling which leads the interaction between the magnetic and electric polarization. Recent theoretical breakthroughs in understanding the coexistence of magnetic and electrical ordering have regenerated a great interests in research of such magnetoelectric multiferroics. The long-sought control of electric polarization by magnetic fields was recently discovered in 'frustrated magnets', for example the perovskites RMnO3, RMn 2O5 (R: rare earth elements), Ni3V 2O8, delafossite CuFeO2, spinel CoCr2O 4, MnWO4, etc. In this dissertation, I have explored several magnetoelectric materials and multiferroics, which show significant magnetoelectric interactions between electric and magnetic orderings. The objects of my projects are focused on understanding the origins of such magnetoelectric couplings and establishing the magnetic/electric phase diagrams and the spin structures. I believe that my works would help to understand the mechanisms of magnetoelectric effects and multiferroics.

  11. Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

    NASA Astrophysics Data System (ADS)

    Polzikova, N. I.; Alekseev, S. G.; Pyataikin, I. I.; Kotelyanskii, I. M.; Luzanov, V. A.; Orlov, A. P.

    2016-05-01

    We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

  12. Dual-phase self-biased magnetoelectric energy harvester

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan; Apo, Daniel J.; Priya, Shashank

    2013-11-01

    We report a magnetoelectric energy harvester structure that can simultaneously scavenge magnetic and vibration energy in the absence of DC magnetic field. The structure consisted of a piezoelectric macro-fiber composite bonded to a Ni cantilever. Large magnetoelectric coefficient ˜50 V/cm Oe and power density ˜4.5 mW/cm3 (1 g acceleration) were observed at the resonance frequency. An additive effect was realized when the harvester operated under dual-phase mode. The increase in voltage output at the first three resonance frequencies under dual-phase mode was found to be 2.4%, 35.5%, and 360.7%. These results present significant advancement toward high energy density multimode energy harvesting system.

  13. A tightly coupled non-equilibrium model for inductively coupled radio-frequency plasmas

    NASA Astrophysics Data System (ADS)

    Munafò, A.; Alfuhaid, S. A.; Cambier, J.-L.; Panesi, M.

    2015-10-01

    The objective of the present work is the development of a tightly coupled magneto-hydrodynamic model for inductively coupled radio-frequency plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State approach. A multi-temperature formulation is used to account for thermal non-equilibrium between translation of heavy-particles and vibration of molecules. Excited electronic states of atoms are instead treated as separate pseudo-species, allowing for non-Boltzmann distributions of their populations. Free-electrons are assumed Maxwellian at their own temperature. The governing equations for the electro-magnetic field and the gas properties (e.g., chemical composition and temperatures) are written as a coupled system of time-dependent conservation laws. Steady-state solutions are obtained by means of an implicit Finite Volume method. The results obtained in both LTE and NLTE conditions over a broad spectrum of operating conditions demonstrate the robustness of the proposed coupled numerical method. The analysis of chemical composition and temperature distributions along the torch radius shows that: (i) the use of the LTE assumption may lead to an inaccurate prediction of the thermo-chemical state of the gas, and (ii) non-equilibrium phenomena play a significant role close the walls, due to the combined effects of Ohmic heating and macroscopic gradients.

  14. A tightly coupled non-equilibrium model for inductively coupled radio-frequency plasmas

    SciTech Connect

    Munafò, A. Alfuhaid, S. A. Panesi, M.; Cambier, J.-L.

    2015-10-07

    The objective of the present work is the development of a tightly coupled magneto-hydrodynamic model for inductively coupled radio-frequency plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State approach. A multi-temperature formulation is used to account for thermal non-equilibrium between translation of heavy-particles and vibration of molecules. Excited electronic states of atoms are instead treated as separate pseudo-species, allowing for non-Boltzmann distributions of their populations. Free-electrons are assumed Maxwellian at their own temperature. The governing equations for the electro-magnetic field and the gas properties (e.g., chemical composition and temperatures) are written as a coupled system of time-dependent conservation laws. Steady-state solutions are obtained by means of an implicit Finite Volume method. The results obtained in both LTE and NLTE conditions over a broad spectrum of operating conditions demonstrate the robustness of the proposed coupled numerical method. The analysis of chemical composition and temperature distributions along the torch radius shows that: (i) the use of the LTE assumption may lead to an inaccurate prediction of the thermo-chemical state of the gas, and (ii) non-equilibrium phenomena play a significant role close the walls, due to the combined effects of Ohmic heating and macroscopic gradients.

  15. Note: Self-biased magnetic field sensor using end-bonding magnetoelectric heterostructure

    NASA Astrophysics Data System (ADS)

    Zhao, Yaoxia; Lu, Caijiang

    2015-03-01

    A high sensitivity magnetic field sensor based on magnetoelectric (ME) coupling is presented. The ME sensor FeCuNbSiB/Nickel-PZT-FeCuNbSiB/Nickel is made by bonding magnetization-graded magnetostrictive materials FeCuNbSiB/Nickel at the free ends of the piezoelectric Pb(Zr1-x,Tix)O3 (PZT) plate. Experiments indicate that the proposed sensor has a zero-bias field sensitivity of 14.7 V/Oe at resonance, which is ˜41.6 times larger than that of previous FeCuNbSiB-PZT-FeCuNbSiB. Furthermore, without external biased field, it can detect dc magnetic field changes as small as ˜9 nT near the resonant frequency. This proposed ME sensor provides new pathways to reducing or even eliminating the need of bias fields for ME sensors.

  16. Note: self-biased magnetic field sensor using end-bonding magnetoelectric heterostructure.

    PubMed

    Zhao, Yaoxia; Lu, Caijiang

    2015-03-01

    A high sensitivity magnetic field sensor based on magnetoelectric (ME) coupling is presented. The ME sensor FeCuNbSiB/Nickel-PZT-FeCuNbSiB/Nickel is made by bonding magnetization-graded magnetostrictive materials FeCuNbSiB/Nickel at the free ends of the piezoelectric Pb(Zr1-x,Tix)O3 (PZT) plate. Experiments indicate that the proposed sensor has a zero-bias field sensitivity of 14.7 V/Oe at resonance, which is ∼41.6 times larger than that of previous FeCuNbSiB-PZT-FeCuNbSiB. Furthermore, without external biased field, it can detect dc magnetic field changes as small as ∼9 nT near the resonant frequency. This proposed ME sensor provides new pathways to reducing or even eliminating the need of bias fields for ME sensors.

  17. Magnetoelectric interactions in hot-pressed nickel zinc ferrite and lead zirconante titanate composites

    SciTech Connect

    Srinivasan, G.; DeVreugd, C.P.; Flattery, C.S.; Laletsin, V.M.; Paddubnaya, N.

    2004-09-27

    The synthesis by hot pressing and wide-band (10 Hz-1 MHz) magnetoelectric (ME) characterization of bulk composites of nickel zinc ferrite Ni{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} (NZFO) (x=0-0.5) and lead zirconate titanate (PZT) are reported. Hot-pressed samples show an order of magnitude improvement in ME voltage coefficient compared to sintered samples. Frequency dependence of ME coefficients show a three order of magnitude enhancement at electromechanical resonance. The ME coupling is maximum for samples with equal volume of ferrite and PZT. The strongest ME interactions are measured for samples of NZFO (x=0.2) and PZT.

  18. Mesoscale Interfacial Dynamics in Magnetoelectric Nanocomposites

    SciTech Connect

    Shashank, Priya

    2009-12-14

    Biphasic composites are the key towards achieving enhanced magnetoelectric response. In order understand the control behavior of the composites and resultant symmetry of the multifunctional product tensors, we need to synthesized model material systems with the following features (i) interface formation through either deposition control or natural decomposition; (ii) a very high interphase-interfacial area, to maximize the ME coupling; and (iii) an equilibrium phase distribution and morphology, resulting in preferred crystallographic orientation relations between phases across the interphase-interfacial boundaries. This thought process guided the experimental evolution in this program. We initiated the research with the co-fired composites approach and then moved on to the thin film laminates deposited through the rf-magnetron sputtering and pulsed laser deposition process

  19. Multiferroic and magnetoelectric properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 core-shell nanocomposite

    NASA Astrophysics Data System (ADS)

    Kumar, Ajith S.; Lekha, C. S. Chitra; Vivek, S.; Saravanan, Venkata; Nandakumar, K.; Nair, Swapna S.

    2016-11-01

    Lead-free magnetoelectric (ME) composites with remarkable ME coupling are required for the realization of eco-friendly multifunctional devices. This work demonstrates the ME properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 (BCZT-CFO) core-shell composites synthesized via co-sol-gel technique. Room temperature ferroelectric and ferromagnetic characterization have shown that the samples are magnetic and ferroelectric along with an adequate magnetoelectric coupling of 12.15 mV/(cm Oe). The strong dependence of electric parameters on applied magnetic DC bias fields demonstrated in ferroelectric and magnetoelectric measurements provide a framework for the development of potential magnetoelectric devices. Also, the high sensitivity of magnetoelectric coupling towards the applied AC magnetic field can be used for its application in magnetoelectric sensors.

  20. Magnetoelectric sensor excitations in hexaferrite films

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Rabinowitz, Jake; Izadkhah, Hessam; Somu, Sivasubramanian; Vittoria, Carmine

    2015-05-01

    We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite thin films in the frequency range of 1 kHz to 10 MHz. The technique incorporating solenoid coils and multi-capacitors bank was developed to probe the physics and properties of ME hexaferrite film and explore ME effects for sensor detections and tunable device applications. For H-field sensing, we obtained sensitivity of 4 × 10-4 V/Gm and for E-field sensing the sensitivity was 10-3 Gm/V. Tunability of up to 6% was achieved for tunable inductor applications. The proposed fabrication designs lend themselves to significant (˜106) improvements in sensitivity and tunability.

  1. Magnetoelectric properties of 500-nm C r2O3 films

    NASA Astrophysics Data System (ADS)

    Borisov, P.; Ashida, T.; Nozaki, T.; Sahashi, M.; Lederman, D.

    2016-05-01

    The linear magnetoelectric effect was measured in 500-nm C r2O3 films grown by radio frequency sputtering on A l2O3 substrates between top and bottom thin film Pt electrodes. Magnetoelectric susceptibility was measured directly by applying an alternating current (ac) electric field and measuring the induced ac magnetic moment using superconducting quantum interference device magnetometry. A linear dependence of the induced ac magnetic moment on the ac electric field amplitude was found. The temperature dependence of the magnetoelectric susceptibility agreed qualitatively and quantitatively with prior measurements of bulk single crystals, but the characteristic temperatures of the film were lower than those of single crystals. It was also possible to reverse the sign of the magnetoelectric susceptibility by reversing the sign of the magnetic field applied during cooling through the Néel temperature. A competition between total magnetoelectric and Zeeman energies is proposed to explain the difference between film and bulk C r2O3 regarding the cooling field dependence of the magnetoelectric effect.

  2. Magnetoelectric effect in layered ferrite/PZT composites. Study of the demagnetizing effect on the magnetoelectric behavior

    NASA Astrophysics Data System (ADS)

    Loyau, V.; Morin, V.; Chaplier, G.; LoBue, M.; Mazaleyrat, F.

    2015-05-01

    We report the use of high magnetomechanical coupling ferrites in magnetoelectric (ME) layered composites. Bilayer samples combining (Ni0.973 Co0.027)1-xZnxFe2O4 ferrites (x = 0-0.5) synthesized by non conventional reactive Spark Plasma Sintering and commercial lead zirconate titanate (PZT) were characterized in term of ME voltage coefficients measured at sub-resonant frequency. Strong ME effects are obtained and we show that an annealing at 1000 °C and a quenching in air improve the piezomagnetic behavior of Zn-rich compositions. A theoretical model that predicts the ME behavior was developed, focusing our work on the demagnetizing effects in the transversal mode as well as the longitudinal mode. The model shows that: (i) high ME coefficients are obtained when ferrites with high magnetomechanical coupling are used in bilayer ME composites, (ii) the ME behavior in transversal and longitudinal modes is quite similar, and differences in the shapes of the ME curves are mainly due the demagnetizing effects, (iii) in the transversal mode, the magnetic field penetration depends on the ferrite layer thickness and the ME coefficient is affected accordingly. The two later points are confirmed by measurements on ME samples and calculations. Performances of the ME composites made with high magnetomechanical coupling ferrites are compared to those obtained using Terfenol-D materials in the same conditions of size, shape, and volume ratio. It appears that a ferrite with an optimized composition has performances comparable to those obtained with Terfenol-D material. Nevertheless, the fabrication processes of ferrites are quite simpler. Finally, a ferrite/PZT based ME composite was used as a current sensor.

  3. Room-temperature magnetoelectric coupling in single-phase BaTiO{sub 3}-BiFeO{sub 3} system

    SciTech Connect

    Yang, Su-Chul; Kumar, Ashok; Priya, Shashank; Petkov, Valeri

    2013-04-14

    In this paper, single-phase multiferroic ceramics of (1 - x) BaTiO{sub 3}-x BiFeO{sub 3} (BT - x BFO) were synthesized by solid-solution method in the wide range of material composition (x = 0.025 - 1.0). The changes in crystal structure were confirmed via X-ray diffractions (XRD) and atomic pair distribution functions (PDFs). The room-temperature ME coupling was found to exhibit significant magnitude in the narrow composition window (x = 0.71 - 0.8) where the average crystal structure was found to be rhombohedral. Especially, the BT - 0.725 BFO ceramics containing local monoclinic distortions within rhombohedral phase were found to exhibit high room-temperature ME coefficient ({alpha}{sub ME}) of 0.87 mV/cm{center_dot}Oe with high piezoelectric properties (g{sub 33} = 18.5 Multiplication-Sign 10 mV m N{sup -1} and d{sub 33} = 124 pC N{sup -1}). We believe that the high room-temperature ME coupling in single-phase lead-free BT-BFO ceramics provides a possibility of developing electrically or magnetically tunable thin-film devices.

  4. Ferroic Properties in Individual and Multi-Component Nanostructures: The Influence of Size, Shape, and Interfacial Coupling

    NASA Astrophysics Data System (ADS)

    Johnson, Stephanie Howell

    nanoscale, the functional properties of individual ferroelectric nanocubes of varying sizes were measured at elevated temperature using local ferroelectric piezoelectric amplitude and phase switching analysis. Experimental evidence of the direct magnetoelectric effect within a single integrated nanostructure is presented. The synthesis, fabrication, and functional property characterization of highly tunable magnetoelectric coupling within individual multiferroic nanowires is described. The direct magnetoelectric response is distinctively enhanced by extreme curvature of the ferroelectric shell in relation to planar heterostructures, the geometric dominance of the interface as a fraction of the total volume of the nanowire, and magnetic shape anisotropy of the ferromagnetic nanowire core. This study of geometry aided direct magnetoelectric coupling can help the development of a future study and design of a magnetoelectric proximity sensor. One solution to address the issues associated with current magnetic field sensors, such as cost, durability, and detection range, is to develop a mesoscale magnetoelectric resonator device. Magnetoelectric resonator structures have a resonant frequency which will shift in the presence of an applied magnetic field due to the magnetostrictive properties of the ferromagnetic material. The resonator detection range can be tuned by pre-straining the piezoelectric layer. Two suggested resonator designs which are promising candidates for magnetic field proximity sensors are the fixed-fixed beam design and the membrane design.

  5. Influence of constant and ac electric fields on ferromagnetic resonance in magnetoelectric composites

    NASA Astrophysics Data System (ADS)

    Tatarenko, A. S.; Bichurin, M. I.; Petrov, V. M.; Fillipov, D. A.; Srinivasan, G.

    2004-03-01

    A composite of ferromagnetic and ferroelectric phases is expected to show magnetoelectric coupling that is mediated by mechanical deformation. For such composites, we proposed a model to treat the magnetoelectric (ME) coupling at frequencies corresponding to ferromagnetic resonance (FMR) [1,2]. The effect manifests as a shift in the resonance field when subjected to a constant electric field. Here we discuss a theory for the influence of both dc and high frequency electric fields on FMR in the composites. The model predicts a significant increase in the strength of ME coupling when the electric field is tuned to the electromechanical resonance (EMR) frequency. We assume the composite to be a homogeneous medium. By solving combined elastostatics, electrostatics and magnetostatics equations, we estimate the ME constants using effective parameters. The calculations are for 3-0, 0-3 and 2-2 connectivities. Expressions for ME coefficients are obtained as a function of interface coupling and the volume fraction for the piezoelectric phase. Under the influence of a constant electric field E, our model predicts a shift in the ferromagnetic resonance field that is proportional to ME constants. In the presence of an ac electric field, we estimate a strong ME coupling when the frequency is tuned to EMR. As an example, the FMR field shift at 9.3 GHz due an ac electrical field tuned to EMR at 350 kHz is determined for multilayer and bulk composites of nickel ferrite - lead zirconate titanate. It is shown that ME interactions are enhanced by several orders of magnitude compared to off resonance values. 1. M.I. Bichurin, I. A. Kornev, V. M. Petrov, A. S. Tatarenko, Yu. V. Kiliba, and G. Srinivasan. Phys. Rev. B 64, 094409 (2001). 2. M.I. Bichurin, V. M. Petrov, Yu. V. Kiliba, and G. Srinivasan. Phys. Rev. B 66, 134404 (2002). - supported by grants from the Russian Ministry of Education (Å02-3.4-278), the Universities of Russia Foundation (UNR 01.01.007), and the National Science

  6. The structural, electrical and magnetoelectric properties of soft-chemically-synthesized SmFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Sahoo, Sushrisangita; Mahapatra, P. K.; Choudhary, R. N. P.

    2016-01-01

    The structural, electrical and magnetoelectric properties of SmFeO3 ceramic samples, synthesized using a soft-chemical method, were studied. A structural analysis of the material was carried out by the Rietveld refinement of room temperature x-ray diffraction data. The temperature dependence of the dielectric peaks was analyzed by fitting them with two Gaussian peaks corresponding to two phase transitions—one being electric, and the other being magnetic in nature. The depression angle of the semicircles in a Nyquist plot representing the grain and grain boundary contributions in the sample was estimated. The grain boundary effect, appearing at temperatures above 75 °C, is explained using the Maxwell-Wagner mechanism. The impedance study reveals a semi-conducting grain with an insulating grain boundary, leading to the formation of surface and internal barrier layer capacitors and resulting in a very high dielectric constant. The effect of dc conductivity on the loss tangent at low frequencies and high temperature has been analyzed. The frequency dependence of ac conductivity in the two different regions can be explained on the basis of correlated barrier hopping and quantum mechanical tunneling models. The material is found to exhibit canted antiferromagnetism and improper ferroelectric characteristics. The value of the magnetoelectric voltage-coupling coefficient (α) of a SmFeO3 ceramic is found to be 2.2 mV cm-1 Oe-1.

  7. Commissioning of helium injector for coupled radio frequency quadrupole and separated function radio frequency quadrupole accelerator

    SciTech Connect

    Peng, Shixiang Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Zhang, Ailing; Chen, Jia'er

    2014-02-15

    A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 π mm mrad and the fraction of He+ is about 99%.

  8. Commissioning of helium injector for coupled radio frequency quadrupole and separated function radio frequency quadrupole accelerator.

    PubMed

    Peng, Shixiang; Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Zhang, Ailing; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Chen, Jia'er

    2014-02-01

    A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 π mm mrad and the fraction of He+ is about 99%.

  9. Effects of interelectrode gap on high frequency and very high frequency capacitively coupled plasmas

    SciTech Connect

    Bera, Kallol; Rauf, Shahid; Ramaswamy, Kartik; Collins, Ken

    2009-07-15

    Capacitively coupled plasma (CCP) discharges using high frequency (HF) and very high frequency (VHF) sources are widely used for dielectric etching in the semiconductor industry. A two-dimensional fluid plasma model is used to investigate the effects of interelectrode gap on plasma spatial characteristics of both HF and VHF CCPs. The plasma model includes the full set of Maxwell's equations in their potential formulation. The peak in plasma density is close to the electrode edge at 13.5 MHz for a small interelectrode gap. This is due to electric field enhancement at the electrode edge. As the gap is increased, the plasma produced at the electrode edge diffuses to the chamber center and the plasma becomes more uniform. At 180 MHz, where electromagnetic standing wave effects are strong, the plasma density peaks at the chamber center at large interelectrode gap. As the interelectrode gap is decreased, the electron density increases near the electrode edge due to inductive heating and electrostatic electron heating, which makes the plasma more uniform in the interelectrode region.

  10. Spin-lattice coupling in iron jarosite

    SciTech Connect

    Buurma, A.J.C.; Handayani, I.P.; Mufti, N.; Blake, G.R.; Loosdrecht, P.H.M. van; Palstra, T.T.M.

    2012-11-15

    We have studied the magnetoelectric coupling of the frustrated triangular antiferromagnet iron jarosite using Raman spectroscopy, dielectric measurements and specific heat. Temperature dependent capacitance measurements show an anomaly in the dielectric constant at T{sub N}. Specific heat data indicate the presence of a low frequency Einstein mode at low temperature. Raman spectroscopy confirms the presence of a new mode below T{sub N} that can be attributed to folding of the Brillouin zone. This mode shifts and sharpens below T{sub N}. We evaluate the strength of the magnetoelectric coupling using the symmetry unrestricted biquadratic magnetoelectric terms in the free energy. - Graphical abstract: Sketch of two connected triangles formed by Fe{sup 3+} spins (red arrows) in the hexagonal basal plane of potassium iron jarosite. An applied magnetic field (H) below the antiferromagnetic ordering temperature induces shifts of the hydroxy ligands, giving rise to local electrical dipole moments (blue arrows). These electric displacements cancel out in pairwise fashion by symmetry. Ligand shifts are confined to the plane and shown by shadowing. Highlights: Black-Right-Pointing-Pointer Evidence has been found for spin-lattice coupling in iron jarosite. Black-Right-Pointing-Pointer A new optical Raman mode appears below T{sub N} and shifts with temperature. Black-Right-Pointing-Pointer The magnetodielectric coupling is mediated by superexchange. Black-Right-Pointing-Pointer Symmetry of Kagome magnetic lattice causes local electrical dipole moments to cancel.

  11. Influence of the linear magneto-electric effect on the lateral shift of light reflected from a magneto-electric film

    NASA Astrophysics Data System (ADS)

    Dadoenkova, Yu S.; Bentivegna, F. F. L.; Dadoenkova, N. N.; Petrov, R. V.; Lyubchanskii, I. L.; Bichurin, M. I.

    2016-08-01

    We present a theoretical investigation of the lateral shift of an infrared light beam reflected from a magnetic film deposited on a non-magnetic dielectric substrate, taking into account the linear magneto-electric interaction in the magnetic film. We use the stationary phase method to evaluate the lateral shift. It is shown that the magneto-electric coupling leads to a six-fold enhancement of the lateral shift amplitude of a p-(s-) polarized incident beam reflected into a s-(p-) polarized beam. A reversal of the magnetization in the film leads to a nonreciprocal sign change of the lateral shift.

  12. Peak divergence in the curve of magnetoelectric coefficient versus dc bias magnetic field at resonance region for bi-layer magnetostrictive/piezoelectric composites

    SciTech Connect

    Zuo, Z. J.; Pan, D. A. Zhang, S. G.; Qiao, L. J.; Jia, Y. M.

    2013-12-15

    Magnetoelectric (ME) coefficient dependence on the bias magnetic field at resonance frequencies for the bi-layered bonded Terfenol-D/Pb(Zr,Ti)O{sub 3} composite was investigated. The resonance frequency decreases first and then increases with the bias magnetic field (H{sub DC}), showing a “V” shape in the range of 0 ∼ 5 kOe. Below the resonance frequency, the pattern of ME coefficient dependence on the H{sub DC} shows a single peak, but splits into a double-peak pattern when the testing frequency increases into a certain region. With increasing the frequency, a divergent evolution of the H{sub DC} patterns was observed. Domain motion and ΔE effect combined with magnetostriction-piezoelectric coupling effect were employed to explain this experimental result.

  13. Magnetoelectric Effect and Magnetodielectric Effect in Magnetic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Hyungsuk

    Nano-sized magnetic particles represent considerable interests in modern science because their properties are advantageous to applications such as data storage and medical science. In particular, superparamagnetism is a magnetic property which is found in nano-sized (approximately less than 20 nm) ferromagnetic or ferrimagnetic particles. Studies have shown that superparamagnetic material shows ferromagnetic magnetization only with an external magnetic field; without an external magnetic field, it loses magnetic properties even at ambient temperature overcoming its intrinsic anisotropy energy. From a magnetic memory standpoint, as bit size decreases, superparamagnetism is a major obstacle to thermal stability due to this volatility, resulting in a loss of information. If it is possible to modulate the superparamagnetic properties of magnetic nanoparticles, this might provide a solution to this critical issue. In this dissertation, we studied the modulation of superparamagnetic properties by applying an electric field on a magnetoelectric composite composed of magnetic nanoparticles and a piezoelectric substrate. The magnetoelectric effect might present an additional solution to memory device in terms of reducing writing energy by using an electric field rather than an electric current. Additionally, for systems lacking a significant magnetoelectric coupling (for instance, magnetic nanoparticles incased in polymer resin), the relationship between the dielectric constant, which is intrinsically related to ferroelectric order, and magnetic anisotropy energy was investigated.

  14. Low-frequency RF Coupling To Unconventional (Fat Unbalanced) Dipoles

    SciTech Connect

    Ong, M M; Brown, C G; Perkins, M P; Speer, R D; Javedani, J B

    2010-12-07

    The report explains radio frequency (RF) coupling to unconventional dipole antennas. Normal dipoles have thin equal length arms that operate at maximum efficiency around resonance frequencies. In some applications like high-explosive (HE) safety analysis, structures similar to dipoles with ''fat'' unequal length arms must be evaluated for indirect-lightning effects. An example is shown where a metal drum-shaped container with HE forms one arm and the detonator cable acts as the other. Even if the HE is in a facility converted into a ''Faraday cage'', a lightning strike to the facility could still produce electric fields inside. The detonator cable concentrates the electric field and carries the energy into the detonator, potentially creating a hazard. This electromagnetic (EM) field coupling of lightning energy is the indirect effect of a lightning strike. In practice, ''Faraday cages'' are formed by the rebar of the concrete facilities. The individual rebar rods in the roof, walls and floor are normally electrically connected because of the construction technique of using metal wire to tie the pieces together. There are two additional requirements for a good cage. (1) The roof-wall joint and the wall-floor joint must be electrically attached. (2) All metallic penetrations into the facility must also be electrically connected to the rebar. In this report, it is assumed that these conditions have been met, and there is no arcing in the facility structure. Many types of detonators have metal ''cups'' that contain the explosives and thin electrical initiating wires, called bridge wires mounted between two pins. The pins are connected to the detonator cable. The area of concern is between the pins supporting the bridge wire and the metal cup forming the outside of the detonator. Detonator cables usually have two wires, and in this example, both wires generated the same voltage at the detonator bridge wire. This is called the common-mode voltage. The explosive component

  15. Correlation of magnetoelectric and delta-E effects in ferromagnetic-piezoelectric layered composites

    NASA Astrophysics Data System (ADS)

    Laletin, V. M.; Srinivasan, G.; Bichurin, M. I.

    2005-03-01

    Magnetoelectric (ME) coupling and its dependence on delta-E-effect have been studied in trilayers of ferromagnetic metals and lead zirconate titanate (PZT). Measurements on samples with PZT and Fe, Co, Ni or permendur (an alloy of Co-Fe-V) show evidence for strong ME interactions. Our theoretical model for bias magnetic field H dependence of ME effect predicts contributions due to two mechanisms: variation of piezomagnetic and compliance coefficients with H. The individual contributions from the two sources can be measured in the electromechanical resonance (EMR) region for the composite. Data on frequency dependence of ME coefficient reveal a giant coupling at electromechanical resonance (EMR), at 200-300 kHz for radial modes and at ˜2.7 MHz for thickness modes. Variation of compliance coefficients with H (delta-E-effect) results in a frequency shift of peak ME voltage coefficient. Theoretical profiles of ME coefficient vs. frequency agree with the data. These results are of importance for the design of signal processing devices that requires fine tuning. 1. M. I. Bichurin, D.A. Filippov, V. M. Petrov, V. M. Laletin, N. Paddubnaya, and G. Srinivasan, Phys. Rev. B 68, 132408 (2003). - supported by grants from the Russian Ministry of Education (Å02-3.4-278), the Universities of Russia Foundation (UNR 01.01.026) and the National Science Foundation (DMR-0302254).

  16. Locomotor-respiratory coupling patterns and oxygen consumption during walking above and below preferred stride frequency.

    PubMed

    O'Halloran, Joseph; Hamill, Joseph; McDermott, William J; Remelius, Jebb G; Van Emmerik, Richard E A

    2012-03-01

    Locomotor respiratory coupling patterns in humans have been assessed on the basis of the interaction between different physiological and motor subsystems; these interactions have implications for movement economy. A complex and dynamical systems framework may provide more insight than entrainment into the variability and adaptability of these rhythms and their coupling. The purpose of this study was to investigate the relationship between steady state locomotor-respiratory coordination dynamics and oxygen consumption [Formula: see text] of the movement by varying walking stride frequency from preferred. Twelve male participants walked on a treadmill at a self-selected speed. Stride frequency was varied from -20 to +20% of preferred stride frequency (PSF) while respiratory airflow, gas exchange variables, and stride kinematics were recorded. Discrete relative phase and return map techniques were used to evaluate the strength, stability, and variability of both frequency and phase couplings. Analysis of [Formula: see text] during steady-state walking showed a U-shaped response (P = 0.002) with a minimum at PSF and PSF - 10%. Locomotor-respiratory frequency coupling strength was not greater (P = 0.375) at PSF than any other stride frequency condition. The dominant coupling across all conditions was 2:1 with greater occurrences at the lower stride frequencies. Variability in coupling was the greatest during PSF, indicating an exploration of coupling strategies to search for the coupling frequency strategy with the least oxygen consumption. Contrary to the belief that increased strength of frequency coupling would decrease oxygen consumption; these results conclude that it is the increased variability of frequency coupling that results in lower oxygen consumption.

  17. Misidentifications of specific forms of cross-frequency coupling: three warnings

    PubMed Central

    Hyafil, Alexandre

    2015-01-01

    Cross-frequency coupling (CFC) between neural oscillations has received increased attention over the last decade, as it is believed to underlie a number of cognitive operations in different brain systems. Coupling can take different forms as it associates the phase, frequency, and/or amplitude of coupled oscillations. These specific forms of coupling are a signature for the underlying network physiology and probably relate to distinct cognitive functions. Here I discuss three caveats in data analysis that can lead to mistake one specific form of CFC for another: (1) bicoherence assesses the level of phase-amplitude and not of phase-phase coupling (PPC) as commonly accepted; (2) a test for phase-amplitude coupling (PAC) can indeed signal phase-frequency coupling (PFC) when the higher frequency signal is extracted using a too narrow band; (3) an oscillation whose frequency fluctuates may induce spurious amplitude anticorrelations between neighboring frequency bands. I indicate practical rules to avoid such misidentifications and correctly identify the specific nature of cross-frequency coupled signals. PMID:26500488

  18. Magnetoelectric interfaces and spin transport.

    PubMed

    Burton, J D; Tsymbal, E Y

    2012-10-28

    Engineered heterostructures designed for electric control of magnetic properties, the so-called magnetoelectric interfaces, present a novel route towards using the spin degree of freedom in electronic devices. Here, we review how a subset of such interfaces, namely ferromagnet-ferroelectric heterostructures, display electronically mediated control of magnetism and, in particular, emphasis is placed on how these effects manifest themselves as detectable spin-dependent transport phenomena. Examples of these effects are given for a variety of material systems on the basis of ferroelectric oxides, manganese and ruthenium magnetic complex oxides and elemental ferromagnetic metals. Results from both theory and experiment are discussed. PMID:22987031

  19. Polar domain walls trigger magnetoelectric coupling

    PubMed Central

    Fontcuberta, Josep; Skumryev, Vassil; Laukhin, Vladimir; Granados, Xavier; Salje, Ekhard K. H.

    2015-01-01

    Interface physics in oxides heterostructures is pivotal in material’s science. Domain walls (DWs) in ferroic systems are examples of naturally occurring interfaces, where order parameter of neighboring domains is modified and emerging properties may develop. Here we show that electric tuning of ferroelastic domain walls in SrTiO3 leads to dramatic changes of the magnetic domain structure of a neighboring magnetic layer (La1/2Sr1/2MnO3) epitaxially clamped on a SrTiO3 substrate. We show that the properties of the magnetic layer are intimately connected to the existence of polar regions at twin boundaries of SrTiO3, developing at , that can be electrically modulated. These findings illustrate that by exploiting the responsiveness of DWs nanoregions to external stimuli, even in absence of any domain contribution, prominent and adjustable macroscopic reactions of neighboring layers can be obtained. We conclude that polar DWs, known to exist in other materials, can be used to trigger tunable responses and may lead to new ways for the manipulation of interfacial emerging properties. PMID:26387597

  20. Topological properties of microwave magnetoelectric fields.

    PubMed

    Berezin, M; Kamenetskii, E O; Shavit, R

    2014-02-01

    Collective excitations of electron spins in a ferromagnetic sample dominated by the magnetic dipole-dipole interaction strongly influence the field structure of microwave radiation. A small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillation spectra can behave as a source of specific fields in vacuum, termed magnetoelectric (ME) fields. A coupling between the time-varying electric and magnetic fields in the ME-field structures is different from such a coupling in regular electromagnetic fields. The ME fields are characterized by strong energy confinement at a subwavelength region of microwave radiation, topologically distinctive power-flow vortices, and helicity parameters [E. O. Kamenetskii, R. Joffe, and R. Shavit, Phys. Rev. E 87, 023201 (2013)]. We study topological properties of microwave ME fields by loading a MDM ferrite particle with different dielectric samples. We establish a close connection between the permittivity parameters of dielectric environment and the topology of ME fields. We show that the topology of ME fields is strongly correlated with the Fano-resonance spectra observed at terminals of a microwave structure. We reveal specific thresholds in the Fano-resonance spectra appearing at certain permittivity parameters of dielectric samples. We show that ME fields originated from MDM ferrite disks can be distinguished by topological portraits of the helicity parameters and can have a torsion degree of freedom. Importantly, the ME-field phenomena can be viewed as implementations of space-time coordinate transformations on waves.

  1. Topological properties of microwave magnetoelectric fields.

    PubMed

    Berezin, M; Kamenetskii, E O; Shavit, R

    2014-02-01

    Collective excitations of electron spins in a ferromagnetic sample dominated by the magnetic dipole-dipole interaction strongly influence the field structure of microwave radiation. A small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillation spectra can behave as a source of specific fields in vacuum, termed magnetoelectric (ME) fields. A coupling between the time-varying electric and magnetic fields in the ME-field structures is different from such a coupling in regular electromagnetic fields. The ME fields are characterized by strong energy confinement at a subwavelength region of microwave radiation, topologically distinctive power-flow vortices, and helicity parameters [E. O. Kamenetskii, R. Joffe, and R. Shavit, Phys. Rev. E 87, 023201 (2013)]. We study topological properties of microwave ME fields by loading a MDM ferrite particle with different dielectric samples. We establish a close connection between the permittivity parameters of dielectric environment and the topology of ME fields. We show that the topology of ME fields is strongly correlated with the Fano-resonance spectra observed at terminals of a microwave structure. We reveal specific thresholds in the Fano-resonance spectra appearing at certain permittivity parameters of dielectric samples. We show that ME fields originated from MDM ferrite disks can be distinguished by topological portraits of the helicity parameters and can have a torsion degree of freedom. Importantly, the ME-field phenomena can be viewed as implementations of space-time coordinate transformations on waves. PMID:25353595

  2. An introduction to the use of representation analysis for studying magnetoelectrics and multiferroics

    NASA Astrophysics Data System (ADS)

    Chapon, L. C.

    2012-03-01

    This lecture is an introduction to the theory of representations applied to the study of magnetoelectric and multiferroic materials. It is intended for students or newcomers in the field and explains the key concepts required to understand phenomenologically the coupling between magnetic phase transitions in crystals and dielectric properties. Symmetry properties of some prototypal magnetoelectrics and multiferroics are analysed, including the treatment of incommensurate spin-driven ferroelectrics. It is deliberately written with a minimal use of mathematical formulation or a strict group theoretical approach.

  3. Calculation of coupled secular oscillation frequencies and axial secular frequency in a nonlinear ion trap by a homotopy method.

    PubMed

    Doroudi, Alireza

    2009-11-01

    In this paper the homotopy perturbation method is used for calculation of the frequencies of the coupled secular oscillations and axial secular frequencies of a nonlinear ion trap. The motion of the ion in a rapidly oscillating field is transformed to the motion in an effective potential. The equations of ion motion in the effective potential are in the form of a Duffing-like equation. The homotopy perturbation method is used for solving the resulted system of coupled nonlinear differential equations and the resulted axial equation for obtaining the expressions for ion secular frequencies as a function of nonlinear field parameters and amplitudes of oscillations. The calculated axial secular frequencies are compared with the results of Lindstedt-Poincare method and the exact results. PMID:20365087

  4. Design and characterization of broadband magnetoelectric sensor

    NASA Astrophysics Data System (ADS)

    Park, Chee-Sung; Ahn, Cheol-Woo; Ryu, Jungho; Yoon, Woon-Ha; Park, Dong-Soo; Kim, Hyoun-Ee; Priya, Shashank

    2009-05-01

    In this study, we present a broadband magnetoelectric (ME) sensor design comprising of Metglas and piezoelectric ceramic laminate composite. A systematic study was conducted to elucidate the role of various composite variables toward the ME response [longitudinal-transverse (LT) mode] over the applied range of magnetic dc bias. The broadband behavior was characterized by flat ME responses over a wide range of magnetic dc bias at frequency of 1 kHz. The variation in ME coefficient as a function of magnetic dc bias was found to be significantly dependent on the size and shape of the laminate composites, the number of Metglas layers, and composite structure of sandwich versus unimorph. By adjusting these variables, we were able to achieve near-flat ME response over a magnetic bias range of 90-220 Oe. ME coefficient was also measured as a function of frequency, and at electromechanical resonance the peak value was found to be almost independent of applied magnetic bias in the range of 90-220 Oe.

  5. Acoustic analysis of the frequency-dependent coupling between the frog's ears.

    PubMed

    Shofner, William P

    2015-09-01

    The ears of anurans are coupled through the Eustachian tubes and mouth cavity. The degree of coupling varies with frequency showing a bandpass characteristic, but the characteristics differ between empirically measured data based on auditory nerve responses and tympanic membrane vibration. In the present study, the coupling was modeled acoustically as a tube connected with a side branch. This tube corresponds to the Eustachian tubes, whereas the side branch corresponds to the mouth cavity and nares. The analysis accounts for the frequency dependency shown by the empirical data and reconciles the differences observed between the coupling as measured by tympanic membrane vibration and auditory nerve responses.

  6. Large magnetoelectric effect in mechanically mediated structure of TbFe{sub 2}, Pb(Zr,Ti)O{sub 3}, and nonmagnetic flakes

    SciTech Connect

    Bi, K.; Wang, Y. G.; Wu, W.; Pan, D. A.

    2011-03-28

    Magnetoelectric (ME) effect has been studied in a structure of a magnetostrictive TbFe{sub 2} alloy, two piezoelectric Pb(Zr,Ti)O{sub 3} (PZT) ceramics, and two nonmagnetic flakes. The ME coupling originates from the magnetic-mechanical-electric transform of the magnetostrictive effect in TbFe{sub 2} and the piezoelectric effect in PZT by end bonding, instead of interface bonding. Large ME coefficients of 10.5 and 9.9 V cm{sup -1} Oe{sup -1} were obtained at the first planar acoustic and third bending resonance frequencies, which are larger than that of conventional layered TbFe{sub 2}/PZT composites. The results show that the large ME coupling can be achieved without interface coupling.

  7. Reviving oscillation with optimal spatial period of frequency distribution in coupled oscillators

    NASA Astrophysics Data System (ADS)

    Deng, Tongfa; Liu, Weiqing; Zhu, Yun; Xiao, Jinghua; Kurths, Jürgen

    2016-09-01

    The spatial distributions of system's frequencies have significant influences on the critical coupling strengths for amplitude death (AD) in coupled oscillators. We find that the left and right critical coupling strengths for AD have quite different relations to the increasing spatial period m of the frequency distribution in coupled oscillators. The left one has a negative linear relationship with m in log-log axis for small initial frequency mismatches while remains constant for large initial frequency mismatches. The right one is in quadratic function relation with spatial period m of the frequency distribution in log-log axis. There is an optimal spatial period m0 of frequency distribution with which the coupled system has a minimal critical strength to transit from an AD regime to reviving oscillation. Moreover, the optimal spatial period m0 of the frequency distribution is found to be related to the system size √{ N } . Numerical examples are explored to reveal the inner regimes of effects of the spatial frequency distribution on AD.

  8. Nonvolatile Memory Based on Nonlinear Magnetoelectric Effects

    NASA Astrophysics Data System (ADS)

    Shen, Jianxin; Cong, Junzhuang; Chai, Yisheng; Shang, Dashan; Shen, Shipeng; Zhai, Kun; Tian, Ying; Sun, Young

    2016-08-01

    The magnetoelectric effects in multiferroics have a great potential in creating next-generation memory devices. We use an alternative concept of nonvolatile memory based, on a type of nonlinear magnetoelectric effects showing a butterfly-shaped hysteresis loop. The principle is to utilize the states of the magnetoelectric coefficient, instead of magnetization, electric polarization, or resistance, to store binary information. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure clearly demonstrate that the sign of the magnetoelectric coefficient can be repeatedly switched between positive and negative by applying electric fields, confirming the feasibility of this principle. This kind of nonvolatile memory has outstanding practical virtues such as simple structure, easy operation in writing and reading, low power, fast speed, and diverse materials available.

  9. Surface magnetoelectric effect in ferromagnetic metal films.

    PubMed

    Duan, Chun-Gang; Velev, Julian P; Sabirianov, R F; Zhu, Ziqiang; Chu, Junhao; Jaswal, S S; Tsymbal, E Y

    2008-09-26

    A surface magnetoelectric effect is revealed by density-functional calculations that are applied to ferromagnetic Fe(001), Ni(001), and Co(0001) films in the presence of an external electric field. The effect originates from spin-dependent screening of the electric field which leads to notable changes in the surface magnetization and the surface magnetocrystalline anisotropy. These results are of considerable interest in the area of electrically controlled magnetism and magnetoelectric phenomena. PMID:18851486

  10. Magnetoelectric excitations in hexaferrites utilizing solenoid coil for sensing applications

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Izadkhah, Hessam; Somu, Sivasubramanian; Vittoria, Carmine

    2015-11-01

    We have developed techniques for H- and E-field sensors utilizing single phase magnetoelectric hexaferrite materials in the frequency range of 100 Hz to 10 MHz. Novel excitation method incorporating solenoid coils and single and multi-capacitor banks were developed and tested for sensor detections. For H-field sensing we obtained sensitivity of about 3000 V/mG and for E-field sensing the sensitivity was 10-4 G/Vm-1. Tunability of about 0.1% was achieved for tunable inductor applications. However, the proposed designs lend themselves to significant (~106) improvements in sensitivity and tunability.

  11. Two pulse-coupled non-identical, frequency-different BZ oscillators with time delay.

    PubMed

    Lavrova, Anastasia I; Vanag, Vladimir K

    2014-04-14

    Two non-identical, frequency-different pulse-coupled oscillators with time delay have been systematically studied using four-variable model of the Belousov-Zhabotinsky (BZ) reaction at mutual inhibitory, mutual excitatory, and mixed excitatory-inhibitory types of coupling. Different resonances like 1 : 2, 2 : 3, 1 : 3, etc., as well as complex rhythms and abrupt changes between them occur depending on the coupling strengths, time delay, and frequency ratio. Analogously to in-phase and anti-phase oscillations for 1 : 1 resonance, a similar phase locking exists for 1 : 2 resonance in the case of inhibitory coupling. For excitatory coupling, a bursting regime is found. The number of spikes in a single burst can be tuned by both the frequency ratio and time delay. For excitatory-inhibitory coupling, a region where one oscillator is suppressed (OS zone) has been found. Boundary of the OS zone depends on the frequency ratio. For weakly coupled oscillators, Farey sequence has been found for excitatory-inhibitory and mutual excitatory coupling.

  12. Metal-ceramic laminate composite magnetoelectric gradiometer.

    PubMed

    Bedekar, V; Bichurin, M I; Ivanov, S N; Pukinski, Y J; Priya, S

    2010-03-01

    Gradiometer resembles in functionality a magnetic field sensor where it measures the magnetic field gradient and its sensitivity is determined by the ability to quantify differential voltage change with respect to a reference value. Magnetoelectric (ME) gradiometer designed in this study is based upon the nickel (Ni)-Pb(Zr,Ti)O(3) (PZT) composites and utilizes the ring-dot piezoelectric transformer structure working near the resonance as the basis. The samples had the ring-dot electrode pattern printed on the top surface of PZT, where ring acts as the input while dot acts as the output. There is an insulation gap between the input and output section of 1.2 mm. The generated magnetic field due to converse ME effect interacts with the external applied magnetic field producing flux gradient, which is detected through the frequency shift and output voltage change in gradiometer structure. The measurements of output voltage dependence on applied magnetic field clearly illustrate that the proposed design can provide high sensitivity and bandwidth.

  13. Distributed coupling and multi-frequency microwave accelerators

    DOEpatents

    Tantawi, Sami G.; Li, Zenghai; Borchard, Philipp

    2016-07-05

    A microwave circuit for a linear accelerator has multiple metallic cell sections, a pair of distribution waveguide manifolds, and a sequence of feed arms connecting the manifolds to the cell sections. The distribution waveguide manifolds are connected to the cell sections so that alternating pairs of cell sections are connected to opposite distribution waveguide manifolds. The distribution waveguide manifolds have concave modifications of their walls opposite the feed arms, and the feed arms have portions of two distinct widths. In some embodiments, the distribution waveguide manifolds are connected to the cell sections by two different types of junctions adapted to allow two frequency operation. The microwave circuit may be manufactured by making two quasi-identical parts, and joining the two parts to form the microwave circuit, thereby allowing for many manufacturing techniques including electron beam welding, and thereby allowing the use of un-annealled copper alloys, and hence greater tolerance to high gradient operation.

  14. Structural, magnetic and transport properties of magnetoelectric composites

    NASA Astrophysics Data System (ADS)

    Rahman, M. Azizar; Gafur, M. A.; Hossain, A. K. M. Akther

    2013-11-01

    Magnetoelectric composites of nominal chemical compositions (y)Mn0.45Ni0.05Zn0.50Fe2O4+(1-y)BaZr0.52Ti0.48O3 (where y varies from 0 to 1.0 in steps of 0.20) were prepared by the standard solid state reaction technique. The samples were sintered at various temperatures. X-ray diffraction patterns confirm the presence of the constituent phases. The initial permeability increases with increasing ferrite content and also with increasing sintering temperature. However, there is a slight decrease in initial permeability value for samples sintered above 1573 K. The dielectric dispersion is observed at lower frequencies (<103 Hz) due to interfacial polarization. The dielectric constant is almost independent at high frequencies (>104 Hz) for a particular composition because of the inability of electric dipoles to follow the fast variation of the alternating applied electric field. The ac electrical conductivity increases with increasing frequency, suggesting that the conduction is due to small polaron hopping. The increase in dielectric constant and dielectric loss corresponds to the increase in ac electric conductivity with increasing sintering temperature up to 1573 K. The magnetoelectric voltage coefficient of the composites decreases with increasing ferrite content and dc magnetic field.

  15. Marginal chimera state at cross-frequency locking of pulse-coupled neural networks

    NASA Astrophysics Data System (ADS)

    Bolotov, M. I.; Osipov, G. V.; Pikovsky, A.

    2016-03-01

    We consider two coupled populations of leaky integrate-and-fire neurons. Depending on the coupling strength, mean fields generated by these populations can have incommensurate frequencies or become frequency locked. In the observed 2:1 locking state of the mean fields, individual neurons in one population are asynchronous with the mean fields, while in another population they have the same frequency as the mean field. These synchronous neurons form a chimera state, where part of them build a fully synchronized cluster, while other remain scattered. We explain this chimera as a marginal one, caused by a self-organized neutral dynamics of the effective circle map.

  16. Frequency dependent plasma characteristics in a capacitively coupled 300 mm wafer plasma processing chamber.

    SciTech Connect

    Hebner, Gregory Albert; Holland, J.P.; Paterson, A.M.; Barnat, Edward V.; Miller, Paul Albert

    2006-01-01

    Argon plasma characteristics in a dual-frequency, capacitively coupled, 300 mm-wafer plasma processing system were investigated for rf drive frequencies between 10 and 190 MHz. We report spatial and frequency dependent changes in plasma parameters such as line-integrated electron density, ion saturation current, optical emission and argon metastable density. For the conditions investigated, the line-integrated electron density was a nonlinear function of drive frequency at constant rf power. In addition, the spatial distribution of the positive ions changed from uniform to peaked in the centre as the frequency was increased. Spatially resolved optical emission increased with frequency and the relative optical emission at several spectral lines depended on frequency. Argon metastable density and spatial distribution were not a strong function of drive frequency. Metastable temperature was approximately 400 K.

  17. An effective model of magnetoelectricity in multiferroics RMn2O5

    NASA Astrophysics Data System (ADS)

    Fang, Chen; Hu, Jiangping

    2008-06-01

    An effective model is developed to explain the phase diagram and the mechanism of magnetoelectric coupling in multiferroics, RMn2O5. We show that the nature of magnetoelectric coupling in RMn2O5 is a coupling between two Ising-type orders, namely, the ferroelectric order in the b-axis, and the.coupled magnetic order between two frustrated antiferromagnetic chains. The frustrated magnetic structure drives the system to a commensurate-incommensurate phase transition, which can be understood as a competition between a collinear order stemming from the "order by disorder" mechanism and a chiral symmetry order. The low-energy excitation is calculated and it quantitatively matches experimental results. Distinct features and the effects of external magnetic field in the electromagnon spectra in the incommensurate phase are predicted.

  18. On the Bending Coupled Natural Frequencies of a Spinning, Multispan Timoshenko Shaft Carrying Elastic Disks

    NASA Astrophysics Data System (ADS)

    Jia, H. S.

    1999-04-01

    Vibration problems of spinning shafts with attached disks occur quite frequently, but until recently the analyses were generally restricted to the flexible-shaft/rigid-disk models, which lost at least two-thirds of the vibrational characteristics to a certain extent. In the present paper, a substructure synthesis technique is applied to the modelling of the bending coupled dynamics of a spinning shaft/disk system with disk flexibility considered. The shaft is treated as a Timoshenko beam. The coupled equations of motion are derived analytically. A numerical study is performed to demonstrate the method developed. The bending coupled natural frequencies, both in view of the shaft transverse vibration and in view of the disk transverse vibration, and the coupled mode shapes are obtained as spin speed varies. The disk flexibility has important effects on the system vibrational behavior, especially at the frequency range near the natural frequencies of single disks.

  19. Enhanced magnetoelectric properties of BiFeO3 on formation of BiFeO3/SrFe12O19 nanocomposites

    NASA Astrophysics Data System (ADS)

    Das, Anusree; Chatterjee, Souvik; Bandyopadhyay, Sudipta; Das, Dipankar

    2016-06-01

    Nanocomposites (NCs) comprising (1-x) BiFeO3 (BFO) and x SrFe12O19 (SRF) (x = 0.1, 0.2, 0.3, and 0.4) have been prepared by a sol-gel route. Presence of pure phases of both BiFeO3 (BFO) and SrFe12O19 (SRF) in the NCs for x = 0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data though a minor impurity phase is observed in the case of x = 0.1 and 0.2 NCs. Transmission electron micrographs of the NCs show that particles are mostly spherical with average size of 30 nm. M-H measurements at 300 and 10 K indicate predominantly ferrimagnetic behavior of all the NCs with an increasing trend of saturation magnetization values with increasing content of SRF. Dielectric constant (ɛr) of the NCs at room temperature shows a dispersive behavior with frequency and attains a constant value at higher frequency. ɛr - T measurements reveal an increasing trend of dielectric constant of the NCs with increasing temperature and show an anomaly around the antiferromagnetic transition temperature of BFO, which indicates magnetoelectric coupling in the NCs. The variation of capacitance in the presence of magnetic field confirms the enhancement of magnetoelectric effect in the NCs. 57Fe Mössbauer spectroscopy results indicate the presence of only Fe3+ ions in usual crystallographic sites of BFO and SRF.

  20. Strong magnetoelectric coupling in sol-gel derived multiferroic (Pb0.76Ca0.24)TiO3-CoFe2O4 composite films

    NASA Astrophysics Data System (ADS)

    Cheng, T. D.; Tang, X. G.; Wang, Yu; Chan, H. L. W.

    2012-10-01

    A multilayer heterostructure composite thin films consisting of alternating layers (Pb0.76Ca0.24)TiO3 (PCT) and CoFe2O4 (CFO) were grown on Pt/Ti/SiO2/Si(100) substrate by a sol-gel process. X-ray measurements indicated high quality of crystallization of both PCT and CFO layers. The magnetic and ferroelectric properties of the composite were investigated. Well-defined polarization vs. electric field (P-E) and magnetic hysteresis (M-H) loops were obtained. A strong magnetoelectric (ME) response was observed in the sample which was subjected to an alternating magnetic field, and a high ME voltage coefficient αE = 870 mV/Oe cm was obtained for the composite thin films when applied magnetic field parallel to the sample plane.

  1. Characteristics of pulsed dual frequency inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Seo, Jin Seok; Kim, Kyoung Nam; Kim, Ki Seok; Kim, Tae Hyung; Yeom, Geun Young

    2015-01-01

    To control the plasma characteristics more efficiently, a dual antenna inductively coupled plasma (DF-ICP) source composed of a 12-turn inner antenna operated at 2 MHz and a 3-turn outer antenna at 13.56 MHz was pulsed. The effects of pulsing to each antenna on the change of plasma characteristics and SiO2 etch characteristics using Ar/C4F8 gas mixtures were investigated. When the duty percentage was decreased from continuous wave (CW) mode to 30% for the inner or outer ICP antenna, decrease of the average electron temperature was observed for the pulsing of each antenna. Increase of the CF2/F ratio was also observed with decreasing duty percentage of each antenna, indicating decreased dissociation of the C4F8 gas due to the decreased average electron temperature. When SiO2 etching was investigated as a function of pulse duty percentage, increase of the etch selectivity of SiO2 over amorphous carbon layer (ACL) was observed while decreasing the SiO2 etch rate. The increase of etch selectivity was related to the change of gas dissociation characteristics, as observed by the decrease of average electron temperature and consequent increase of the CF2/F ratio. The decrease of the SiO2 etch rate could be compensated for by using the rf power compensated mode, that is, by maintaining the same time-average rf power during pulsing, instead of using the conventional pulsing mode. Through use of the power compensated mode, increased etch selectivity of SiO2/ACL similar to the conventional pulsing mode could be observed without significant decrease of the SiO2 etch rate. Finally, by using the rf power compensated mode while pulsing rf powers to both antennas, the plasma uniformity over the 300 mm diameter substrate could be improved from 7% for the CW conditions to about around 3.3% with the duty percentage of 30%.

  2. Nonlinear Magnetoelectric Response of Planar Ferromagnetic-Piezoelectric Structures to Sub-Millisecond Magnetic Pulses

    PubMed Central

    Kreitmeier, Florian; Chashin, Dmitry V.; Fetisov, Yury K.; Fetisov, Leonid Y.; Schulz, Irene; Monkman, Gareth J.; Shamonin, Mikhail

    2012-01-01

    The magnetoelectric response of bi- and symmetric trilayer composite structures to pulsed magnetic fields is experimentally investigated in detail. The structures comprise layers of commercially available piezoelectric (lead zirconate titanate) and magnetostrictive (permendur or nickel) materials. The magnetic-field pulses have the form of a half-wave sine function with duration of 450 μs and amplitudes ranging from 500 Oe to 38 kOe. The time dependence of the resulting voltage is presented and explained by theoretical estimations. Appearance of voltage oscillations with frequencies much larger than the reciprocal pulse length is observed for sufficiently large amplitudes (∼1–10 kOe) of the magnetic-field pulse. The origin of these oscillations is the excitation of bending and planar acoustic oscillations in the structures. Dependencies of the magnetoelectric voltage coefficient on the excitation frequency and the applied magnetic field are calculated by digital signal processing and compared with those obtained by the method of harmonic field modulation. The results are of interest for developing magnetoelectric sensors of pulsed magnetic fields as well as for rapid characterization of magnetoelectric composite structures. PMID:23202188

  3. Enhancement in Magnetoelectric Effects at Thickness Modes of Layered Ferromagnets and Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Filippov, D. A.; Bichurin, M. I.; Petrov, V. M.; Laletsin, V. M.; Srinivasan, G.; Nan, C. W.

    2006-03-01

    Magnetoelectric (ME) effects in magnetic - piezoelectric heterostructures are caused by mechanical coupling between magnetic and piezoelectric layers. We reported earlier on the theory and observation of a resonant enhancement in the ME effects when the electrical subsystem is driven to resonance, i.e., electromechanical resonance (EMR) associated with radial acoustic modes [1]. Here we discuss the theory and data for ME effects associated with thickness EMR modes. Profiles of ME voltage coefficients versus frequency were estimated for trilayers based lead zirconate titanate and the following ferromagnetic phases: cobalt ferrite, nickel ferrite and lithium ferrite and Fe, Co and Ni. The results are compared with data on samples 10 mm in diameter and 2 mm in thickness. An enhacement in the ME voltage due to radial modes is observed at 350 kHz. A similar behavior due to the thickness mode is observed at 1.5-2 MHz, in agreement with the theory. Calculated ME voltage coefficients versus frequency profiles are in excellent agreement with data. - supported by an NSF grant. [1] D. A. Filippov, M. I. Bichurin, V. M. Petrov, V. M. Laletin, G. Srinivasan, Phys. Solid State 46, 1674, (2004).

  4. Vibrational and librational frequency coupling in stimulated scattering spectra of liquid water

    NASA Astrophysics Data System (ADS)

    Dorkenoo, K. D.; Rivoire, G.

    2002-02-01

    Evolution of the backward stimulated Raman spectrum in liquid water when the focusing point of the exciting beam is moved progressively in the bulk from the entrance surface to the bottom shows modulation structures. Proof has been made by using Fourier transform on the spectra that a low frequency structure is present when the focal point is near the entrance window. This structure coexists with a periodical high frequency structure when the focal point is moved inside the bulk. Propagative effects explain the high frequency modulation, while the low frequency modulation (quasi-period 20 cm-1) is explained by coupling of librational and vibrational molecular movements.

  5. Two generalized algorithms measuring phase-amplitude cross-frequency coupling in neuronal oscillations network.

    PubMed

    Li, Qun; Zheng, Chen-Guang; Cheng, Ning; Wang, Yi-Yi; Yin, Tao; Zhang, Tao

    2016-06-01

    An increasing number of studies pays attention to cross-frequency coupling in neuronal oscillations network, as it is considered to play an important role in exchanging and integrating of information. In this study, two generalized algorithms, phase-amplitude coupling-evolution map approach and phase-amplitude coupling-conditional mutual information which have been developed and applied originally in an identical rhythm, are generalized to measure cross-frequency coupling. The effectiveness of quantitatively distinguishing the changes of coupling strength from the measurement of phase-amplitude coupling (PAC) is demonstrated based on simulation data. The data suggest that the generalized algorithms are able to effectively evaluate the strength of PAC, which are consistent with those traditional approaches, such as PAC-PLV and PAC-MI. Experimental data, which are local field potentials obtained from anaesthetized SD rats, have also been analyzed by these two generalized approaches. The data show that the theta-low gamma PAC in the hippocampal CA3-CA1 network is significantly decreased in the glioma group compared to that in the control group. The results, obtained from either simulation data or real experimental signals, are consistent with that of those traditional approaches PAC-MI and PAC-PLV. It may be considered as a proper indicator for the cross frequency coupling in sub-network, such as the hippocampal CA3 and CA1. PMID:27275379

  6. Two generalized algorithms measuring phase-amplitude cross-frequency coupling in neuronal oscillations network.

    PubMed

    Li, Qun; Zheng, Chen-Guang; Cheng, Ning; Wang, Yi-Yi; Yin, Tao; Zhang, Tao

    2016-06-01

    An increasing number of studies pays attention to cross-frequency coupling in neuronal oscillations network, as it is considered to play an important role in exchanging and integrating of information. In this study, two generalized algorithms, phase-amplitude coupling-evolution map approach and phase-amplitude coupling-conditional mutual information which have been developed and applied originally in an identical rhythm, are generalized to measure cross-frequency coupling. The effectiveness of quantitatively distinguishing the changes of coupling strength from the measurement of phase-amplitude coupling (PAC) is demonstrated based on simulation data. The data suggest that the generalized algorithms are able to effectively evaluate the strength of PAC, which are consistent with those traditional approaches, such as PAC-PLV and PAC-MI. Experimental data, which are local field potentials obtained from anaesthetized SD rats, have also been analyzed by these two generalized approaches. The data show that the theta-low gamma PAC in the hippocampal CA3-CA1 network is significantly decreased in the glioma group compared to that in the control group. The results, obtained from either simulation data or real experimental signals, are consistent with that of those traditional approaches PAC-MI and PAC-PLV. It may be considered as a proper indicator for the cross frequency coupling in sub-network, such as the hippocampal CA3 and CA1.

  7. Beating frequency and amplitude modulation of the piano tone due to coupling of tones

    NASA Astrophysics Data System (ADS)

    Cartling, Bo

    2005-04-01

    The influence on a piano tone from weak coexcitation of damped adjacent tones due to coupling via the bridge is studied. The frequency and amplitude modulation of the sound resulting from coexcitation of one strong and one or two weak tones is analyzed. One weak tone causes frequency and amplitude modulation of the sound, and two weak tones produce beating frequency and amplitude modulation, where the beatings of the two modulations are of opposite phase. By digital recording of the sound of piano tones, the appearance of these phenomena is verified. The audibility of the observed frequency and amplitude modulation is discussed in terms of previously determined detection thresholds. The beating character of both frequency and amplitude modulations, however, distinguishes the phenomena from those previously studied and prompts further psychoacoustic investigations. It is shown that detuning of unison strings may significantly increase the frequency deviation of the frequency modulation in conjunction with affected amplitude modulation. The modulatory effects of coupling to adjacent tones therefore may possibly be utilized in the tuning process. A coupling of tones analogous to the situation in a piano may arise in other stringed musical instruments transferring string vibrations to a soundboard via a bridge. .

  8. Beating frequency and amplitude modulation of the piano tone due to coupling of tones.

    PubMed

    Cartling, Bo

    2005-04-01

    The influence on a piano tone from weak coexcitation of damped adjacent tones due to coupling via the bridge is studied. The frequency and amplitude modulation of the sound resulting from coexcitation of one strong and one or two weak tones is analyzed. One weak tone causes frequency and amplitude modulation of the sound, and two weak tones produce beating frequency and amplitude modulation, where the beatings of the two modulations are of opposite phase. By digital recording of the sound of piano tones, the appearance of these phenomena is verified. The audibility of the observed frequency and amplitude modulation is discussed in terms of previously determined detection thresholds. The beating character of both frequency and amplitude modulations, however, distinguishes the phenomena from those previously studied and prompts further psychoacoustic investigations. It is shown that detuning of unison strings may significantly increase the frequency deviation of the frequency modulation in conjunction with affected amplitude modulation. The modulatory effects of coupling to adjacent tones therefore may possibly be utilized in the tuning process. A coupling of tones analogous to the situation in a piano may arise in other stringed musical instruments transferring string vibrations to a soundboard via a bridge. PMID:15898666

  9. Magnetoelectric effect in simple collinear antiferromagnetic spinels

    NASA Astrophysics Data System (ADS)

    Saha, Rana; Ghara, Somnath; Suard, Emmanuelle; Jang, Dong Hyun; Kim, Kee Hoon; Ter-Oganessian, N. V.; Sundaresan, A.

    2016-07-01

    We report the discovery of the linear magnetoelectric effect in a family of spinel oxides, C o3O4 and Mn B2O4 (B =Al ,Ga) with simple collinear antiferromagnetic spin structure. An external magnetic field induces a dielectric anomaly at TN, accompanied by the generation of electric polarization that varies linearly with magnetic field. Magnetization and magnetoelectric measurements on a single crystal of MnG a2O4 together with a phenomenological theory suggest that the easy axis direction is [111] with the corresponding magnetic symmetry R 3¯'m' . The proposed theoretical model of single-ion contribution of magnetic ions located in a noncentrosymmetric crystal environment stands for a generic mechanism for observing magnetoelectric effects in these and other similar materials.

  10. Coupling of Helmholtz resonators to improve acoustic liners for turbofan engines at low frequency

    NASA Technical Reports Server (NTRS)

    Dean, L. W.

    1975-01-01

    An analytical and test program was conducted to evaluate means for increasing the effectiveness of low frequency sound absorbing liners for aircraft turbine engines. Three schemes for coupling low frequency absorber elements were considered. These schemes were analytically modeled and their impedance was predicted over a frequency range of 50 to 1,000 Hz. An optimum and two off-optimum designs of the most promising, a parallel coupled scheme, were fabricated and tested in a flow duct facility. Impedance measurements were in good agreement with predicted values and validated the procedure used to transform modeled parameters to hardware designs. Measurements of attenuation for panels of coupled resonators were consistent with predictions based on measured impedance. All coupled resonator panels tested showed an increase in peak attenuation of about 50% and an increase in attenuation bandwidth of one one-third octave band over that measured for an uncoupled panel. These attenuation characteristics equate to about 35% greater reduction in source perceived noise level (PNL), relative to the uncoupled panel, or a reduction in treatment length of about 24% for constant PNL reduction. The increased effectiveness of the coupled resonator concept for attenuation of low frequency broad spectrum noise is demonstrated.

  11. Resonance Frequency Analysis for Surface-Coupled AFM Cantilever in Liquids

    SciTech Connect

    Mirman, B; Kalinin, Sergei V

    2008-01-01

    Shifts in the resonance frequencies of surface-coupled atomic force microscope (AFM) probes are used as the basis for the detection mechanisms in a number of scanning probe microscopy techniques including atomic force acoustic microscopy (AFAM), force modulation microscopy, and resonance enhanced piezoresponse force microscopy (PFM). Here, we analyze resonance characteristics for AFM cantilever coupled to surface in liquid environment, and derive approximate expressions for resonant frequencies as a function of vertical and lateral spring constant of the tip-surface junction. This analysis provides a simplified framework for the interpretation of AFAM and PFM data in ambient, liquid, and vacuum environments.

  12. Spurious cross-frequency amplitude-amplitude coupling in nonstationary, nonlinear signals

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Lo, Men-Tzung; Hu, Kun

    2016-07-01

    Recent studies of brain activities show that cross-frequency coupling (CFC) plays an important role in memory and learning. Many measures have been proposed to investigate the CFC phenomenon, including the correlation between the amplitude envelopes of two brain waves at different frequencies - cross-frequency amplitude-amplitude coupling (AAC). In this short communication, we describe how nonstationary, nonlinear oscillatory signals may produce spurious cross-frequency AAC. Utilizing the empirical mode decomposition, we also propose a new method for assessment of AAC that can potentially reduce the effects of nonlinearity and nonstationarity and, thus, help to avoid the detection of artificial AACs. We compare the performances of this new method and the traditional Fourier-based AAC method. We also discuss the strategies to identify potential spurious AACs.

  13. Simulation of dust particles in dual-frequency capacitively coupled silane discharges

    SciTech Connect

    Liu Xiangmei; Song Yuanhong; Xu Xiang; Wang Younian

    2010-01-15

    The behavior of nanoparticles in dual-frequency capacitively coupled silane discharges is investigated by employing a one-dimensional self-consistent fluid model. The numerical simulation tries to trace the formation, charging, growth, and transport of dust particles during the discharge, under the influences of the high- and low-frequency electric sources, as well as the gas pressure. The effects of the presence of the nanoparticles and larger anions on the plasma properties are also discussed, especially, for the bulk potential, electron temperature, and densities of various particles. The calculation results show that the nanoparticle density and charge distribution are mainly influenced by the voltage and frequency of the high-frequency source, while the voltage of the low-frequency source can also exert an effect on the nanoparticle formation, compared with the frequency. As the discharge lasts, the electric potential and electron density keep decreasing, while the electron temperature gets increasing after a sudden drop.

  14. Magnetoelectric Composite Based Microwave Attenuator

    NASA Astrophysics Data System (ADS)

    Tatarenko, A. S.; Srinivasan, G.

    2005-03-01

    Ferrite-ferroelectric composites are magnetoelectric (ME) due to their response to elastic and electromagnetic force fields. The ME composites are characterized by tensor permittivity, permeability and ME susceptibility. The unique combination of magnetic, electrical, and ME interactions, therefore, opens up the possibility of electric field tunable ferromagnetic resonance (FMR) based devices [1]. Here we discuss an ME attenuator operating at 9.3 GHz based on FMR in a layered sample consisting of lead magnesium niobate-lead titanate bonded to yttrium iron garnet (YIG) film on a gadolinium gallium garnet substrate. Electrical tuning is realized with the application of a control voltage due to ME effect; the shift is 0-15 Oe as E is increased from 0 to 3 kV/cm. If the attenuator is operated at FMR, the corresponding insertion loss will range from 25 dB to 2 dB. 1. S. Shastry and G. Srinivasan, M.I. Bichurin, V.M. Petrov, A.S. Tatarenko. Phys. Rev. B, 70 064416 (2004). - supported by grants the grants from the National Science Foundation (DMR-0302254), from Russian Ministry of Education (Å02-3.4-278) and from Universities of Russia Foundation (UNR 01.01.026).

  15. Radio frequency coupling apparatus and method for measuring minority carrier lifetimes in semiconductor materials

    DOEpatents

    Johnston, Steven W.; Ahrenkiel, Richard K.

    2002-01-01

    An apparatus for measuring the minority carrier lifetime of a semiconductor sample using radio-frequency coupling. The measuring apparatus includes an antenna that is positioned a coupling distance from a semiconductor sample which is exposed to light pulses from a laser during sampling operations. A signal generator is included to generate high frequency, such as 900 MHz or higher, sinusoidal waveform signals that are split into a reference signal and a sample signal. The sample signal is transmitted into a sample branch circuit where it passes through a tuning capacitor and a coaxial cable prior to reaching the antenna. The antenna is radio-frequency coupled with the adjacent sample and transmits the sample signal, or electromagnetic radiation corresponding to the sample signal, to the sample and receives reflected power or a sample-coupled-photoconductivity signal back. To lower impedance and speed system response, the impedance is controlled by limiting impedance in the coaxial cable and the antenna reactance. In one embodiment, the antenna is a waveguide/aperture hybrid antenna having a central transmission line and an adjacent ground flange. The sample-coupled-photoconductivity signal is then transmitted to a mixer which also receives the reference signal. To enhance the sensitivity of the measuring apparatus, the mixer is operated to phase match the reference signal and the sample-coupled-photoconductivity signal.

  16. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

    PubMed Central

    Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

    2016-01-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 − 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 −CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

  17. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

    NASA Astrophysics Data System (ADS)

    Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

    2016-08-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 ‑ 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 ‑CoFe2O4 bulk composites with similar content of the ferrite phase.

  18. First observation of magnetoelectric effect in M-type hexaferrite thin films

    SciTech Connect

    Mohebbi, Marjan; Ebnabbasi, Khabat; Vittoria, Carmine

    2013-05-07

    The magnetoelectric (ME) effect in M-type hexaferrite thin films is reported. Prior to this work, the ME effect in hexaferrite materials was observed only in bulk polycrystalline materials. Thin films of SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19} were grown on sapphire (0001) using pulsed laser deposition. The thin films were characterized by X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy, vibrating sample magnetometer, and ferromagnetic resonance. We measured saturation magnetization of 1250 G, g-factor of 2.66, and coercive field of 20 Oe for these magnetoelectric M-type hexaferrite thin films. The magnetoelectric effect was confirmed by monitoring the change rate in remanence magnetization with the application of DC voltage at room temperature and it gave rise to changes in remanence in the order of 12.8% with the application of only 1 V (DC voltage). We deduced a magnetoelectric coupling, {alpha}, of 6.07 Multiplication-Sign 10{sup -9} s m{sup -1} in SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19} thin films.

  19. Continuous Magnetoelectric Control in Multiferroic DyMnO3 Films with Twin-like Domains

    PubMed Central

    Lu, Chengliang; Deniz, Hakan; Li, Xiang; Liu, Jun-Ming; Cheong, Sang-Wook

    2016-01-01

    The magnetic control of ferroelectric polarization is currently a central topic in the multiferroic researches, owing to the related gigantic magnetoelectric coupling and fascinating physics. Although a bunch of novel magnetoelectric effect have been discovered in multiferroics of magnetic origin, the manipulation of polarization was found to be fundamentally determined by the microscopic origin in a certain multiferroic phase, hindering the development of unusual magnetoelectric control. Here, we report emergent magnetoelectric control in DyMnO3/Nb:SrTiO3 (001) films showing twin-like domain structure. Our results demonstrate interesting magnetically induced partial switch of polarization due to the coexistence of polarizations along both the a-axis and c-axis enabled by the twin-like domain structure in DyMnO3 films, despite the polarization-switch was conventionally believed to be a one-step event in the bulk counterpart. Moreover, a continuous and periodic control of macroscopic polarization by an in-plane rotating magnetic field is evidenced in the thin films. This distinctive magnetic manipulation of polarization is the consequence of the cooperative action of the twin-like domains and the dual magnetic origin of polarization, which promises additional applications using the magnetic control of ferroelectricity. PMID:26829899

  20. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect.

    PubMed

    Naveed-Ul-Haq, M; Shvartsman, Vladimir V; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C

    2016-01-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 - 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 -CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

  1. Continuous Magnetoelectric Control in Multiferroic DyMnO3 Films with Twin-like Domains

    NASA Astrophysics Data System (ADS)

    Lu, Chengliang; Deniz, Hakan; Li, Xiang; Liu, Jun-Ming; Cheong, Sang-Wook

    2016-02-01

    The magnetic control of ferroelectric polarization is currently a central topic in the multiferroic researches, owing to the related gigantic magnetoelectric coupling and fascinating physics. Although a bunch of novel magnetoelectric effect have been discovered in multiferroics of magnetic origin, the manipulation of polarization was found to be fundamentally determined by the microscopic origin in a certain multiferroic phase, hindering the development of unusual magnetoelectric control. Here, we report emergent magnetoelectric control in DyMnO3/Nb:SrTiO3 (001) films showing twin-like domain structure. Our results demonstrate interesting magnetically induced partial switch of polarization due to the coexistence of polarizations along both the a-axis and c-axis enabled by the twin-like domain structure in DyMnO3 films, despite the polarization-switch was conventionally believed to be a one-step event in the bulk counterpart. Moreover, a continuous and periodic control of macroscopic polarization by an in-plane rotating magnetic field is evidenced in the thin films. This distinctive magnetic manipulation of polarization is the consequence of the cooperative action of the twin-like domains and the dual magnetic origin of polarization, which promises additional applications using the magnetic control of ferroelectricity.

  2. Magnetoelectric effect in Cr2O3 thin films

    NASA Astrophysics Data System (ADS)

    He, Xi; Wang, Yi; Sahoo, Sarbeswar; Binek, Christian

    2008-03-01

    Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic compounds like Cr2O3 (max. αzz 4ps/m ) and also cross- coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. A straightforward approach is to increase the electric field at constant voltage by reducing the thickness of the ME material to thin films of a few nm. Since magnetism is known to be affected by geometrical confinement thickness dependence of the ME effect in thin film Cr2O3 is expected. We grow (111) textured Cr2O3 films with various thicknesses below 500 nm and study the ME effect for various ME annealing conditions as a function of temperature with the help of Kerr-magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh and Nicola A. Spaldin 2007 Nature Materials 6 21.

  3. Topological magnetoelectric effects in microwave far-field radiation

    NASA Astrophysics Data System (ADS)

    Berezin, M.; Kamenetskii, E. O.; Shavit, R.

    2016-07-01

    Similar to electromagnetism, described by the Maxwell equations, the physics of magnetoelectric (ME) phenomena deals with the fundamental problem of the relationship between electric and magnetic fields. Despite a formal resemblance between the two notions, they concern effects of different natures. In general, ME-coupling effects manifest in numerous macroscopic phenomena in solids with space and time symmetry breakings. Recently, it was shown that the near fields in the proximity of a small ferrite particle with magnetic-dipolar-mode (MDM) oscillations have the space and time symmetry breakings and the topological properties of these fields are different from the topological properties of the free-space electromagnetic fields. Such MDM-originated fields—called magnetoelectric (ME) fields—carry both spin and orbital angular momenta. They are characterized by power-flow vortices and non-zero helicity. In this paper, we report on observation of the topological ME effects in far-field microwave radiation based on a small microwave antenna with a MDM ferrite resonator. We show that the microwave far-field radiation can be manifested with a torsion structure where an angle between the electric and magnetic field vectors varies. We discuss the question on observation of the regions of localized ME energy in far-field microwave radiation.

  4. Dispersion of Electric-Field-Induced Faraday Effect in Magnetoelectric Cr2O3

    NASA Astrophysics Data System (ADS)

    Wang, Junlei; Binek, Christian

    2016-03-01

    The frequency dependence of the electric-field-induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility α and the antiferromagnetic order parameter η . The relative strength of these contributions is determined by the frequency of the probing light and can be tuned between extreme characteristics following the temperature dependence of α or η . The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3 + crystal-field states. The results allow us to measure voltage-controlled selection, isothermal switching, and temperature dependence of η in a tabletop setup. The voltage-specific Faraday rotation is independent of the sample thickness, making the method scalable and versatile down to the limit of dielectric breakdown.

  5. A novel in-line frequency sensor based on coupling capacitance for X-band application

    NASA Astrophysics Data System (ADS)

    Yan, Jiabin; Liao, Xiaoping; Yi, Zhenxiang

    2016-05-01

    This paper presents a novel in-line frequency sensor, based on coupling capacitance, for X-band applications. The novel frequency sensor can achieve absolute frequency measurement with a simple structure and no DC power consumption. Fabrication of the frequency sensor is completely compatible with the GaAs monolithic microwave integrated circuit process. A well-designed metal-insulator-metal capacitor is employed to couple a certain percentage of incident power and a thermoelectric power sensor is used to measure the coupled power. The sensor design is guided by HFSS simulation and a lumped circuit model. The results validate the effectiveness of the simulation and model, and show relatively good performance of the frequency sensor with simple and reliable components. The net sensitivity of the frequency sensor is about 1.43 mV (W•GHz)-1, and the measured S 11 and S 21 are better than  -14.8 dB and  -1.39 dB at X-band.

  6. Assessment of cross-frequency coupling with confidence using generalized linear models

    PubMed Central

    Kramer, M. A.; Eden, U. T.

    2013-01-01

    Background Brain voltage activity displays distinct neuronal rhythms spanning a wide frequency range. How rhythms of different frequency interact – and the function of these interactions – remains an active area of research. Many methods have been proposed to assess the interactions between different frequency rhythms, in particular measures that characterize the relationship between the phase of a low frequency rhythm and the amplitude envelope of a high frequency rhythm. However, an optimal analysis method to assess this cross-frequency coupling (CFC) does not yet exist. New Method Here we describe a new procedure to assess CFC that utilizes the generalized linear modeling (GLM) framework. Results We illustrate the utility of this procedure in three synthetic examples. The proposed GLM-CFC procedure allows a rapid and principled assessment of CFC with confidence bounds, scales with the intensity of the CFC, and accurately detects biphasic coupling. Comparison with Existing Methods Compared to existing methods, the proposed GLM-CFC procedure is easily interpretable, possesses confidence intervals that are easy and efficient to compute, and accurately detects biphasic coupling. Conclusions The GLM-CFC statistic provides a method for accurate and statistically rigorous assessment of CFC. PMID:24012829

  7. Source-Space Cross-Frequency Amplitude-Amplitude Coupling in Tinnitus

    PubMed Central

    Zobay, Oliver; Adjamian, Peyman

    2015-01-01

    The thalamocortical dysrhythmia (TCD) model has been influential in the development of theoretical explanations for the neurological mechanisms of tinnitus. It asserts that thalamocortical oscillations lock a region in the auditory cortex into an ectopic slow-wave theta rhythm (4–8 Hz). The cortical area surrounding this region is hypothesized to generate abnormal gamma (>30 Hz) oscillations (“edge effect”) giving rise to the tinnitus percept. Consequently, the model predicts enhanced cross-frequency coherence in a broad range between theta and gamma. In this magnetoencephalography study involving tinnitus and control cohorts, we investigated this prediction. Using beamforming, cross-frequency amplitude-amplitude coupling (AAC) was computed within the auditory cortices for frequencies (f1, f2) between 2 and 80 Hz. We find the AAC signal to decompose into two distinct components at low (f1, f2 < 30 Hz) and high (f1, f2 > 30 Hz) frequencies, respectively. Studying the correlation of AAC with several key covariates (age, hearing level (HL), tinnitus handicap and duration, and HL at tinnitus frequency), we observe a statistically significant association between age and low-frequency AAC. Contrary to the TCD predictions, however, we do not find any indication of statistical differences in AAC between tinnitus and controls and thus no evidence for the predicted enhancement of cross-frequency coupling in tinnitus. PMID:26665004

  8. THz-range generation frequency growth in semiconductor superlattice coupled to external high-quality resonator

    NASA Astrophysics Data System (ADS)

    Makarov, Vladimir V.; Maksimenko, Vladimir A.; Khramova, Marina V.; Pavlov, Alexey N.; Hramov, Alexander E.

    2016-03-01

    We investigate effects of a linear resonator on spatial electron dynamics in semiconductor superlattice. We have shown that coupling the external resonant system to superlattice leads to occurrence of the additional area of negative differential conductance on the current-voltage characteristic, which does not occur in autonomous system. Furthermore, this region shows great increase of generation frequency, that contains practical interest.

  9. Good Vibrations: Cross-Frequency Coupling in the Human Nucleus Accumbens during Reward Processing

    ERIC Educational Resources Information Center

    Cohen, Michael X.; Axmacher, Nikolai; Lenartz, Doris; Elger, Christian E.; Sturm, Volker; Schlaepfer, Thomas E.

    2009-01-01

    The nucleus accumbens is critical for reward-guided learning and decision-making. It is thought to "gate" the flow of a diverse range of information (e.g., rewarding, aversive, and novel events) from limbic afferents to basal ganglia outputs. Gating and information encoding may be achieved via cross-frequency coupling, in which bursts of…

  10. Effects of gas pressure on 60/13.56 MHz dual-frequency capacitively coupled plasmas

    SciTech Connect

    Yuan, Q. H.; Yin, G. Q.; Xin, Y.; Ning, Z. Y.

    2011-05-15

    The electron energy probability functions (EEPFs) were measured with increasing gas pressure in 60/13.56 MHz dual-frequency capacitively coupled plasma (DF-CCP) using compensated Langmiur electrostatic probe. The transition pressure of heating mode from collisionless to collisional heating in 60/13.56 MHz DF-CCP is found to be significantly lower than that in 13.56 MHz single-frequency CCP. As the pressure increases, the EEPFs change from bi-Maxwellian to Druyvesteyn type which is similar with that in 60 MHz single-frequency CCP. The pressure dependence of electron densities, effective electron temperatures, floating potentials, and plasma potentials in 60/13.56 MHz DF-CCP were measured and were compared with that in 60 MHz single-frequency CCP. The pressure dependence of these plasma parameters in 60/13.56 MHz DF-CCP is similar with that in 60 MHz single-frequency CCP.

  11. Magneto-electric effect for multiferroic thin film by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Wang, Zidong; Grimson, Malcolm J.

    2015-06-01

    Magneto-electric (ME) effect in a multiferroic heterostructure film, i.e., a coupled ferromagnetic-ferroelectric thin film, has been investigated through the use of the Metropolis algorithm in Monte Carlo simulations. A classical Heisenberg model describes the energy stored in the ferromagnetic (FM) film, and we use a pseudo-spin model with a transverse Ising Hamiltonian to characterise the energy of electric dipoles in the ferroelectric (FE) film. The purpose of this article is to demonstrate the dynamic response of polarisation is driven by an external magnetic field, when there is a linear magneto-electric coupling at the interface between the ferromagnetic and ferroelectric components. Contribution to the topical issue "Advanced Electromagnetics Symposium (AES 2014) - Elected submissions", edited by Adel Razek

  12. Enhanced bending-resonance magnetoelectric response in end-bonding magnetostrictive/piezoelectric heterostructure

    NASA Astrophysics Data System (ADS)

    Peng, Jinshuan; Lu, Caijiang; Xu, Changbao; Gao, Jipu; Gui, Junguo; Lin, Chenhui

    2015-05-01

    In this paper, we present a magnetoelectric (ME) heterostructure made by attaching two magnetostrictive Nickel (Ni) plates at the two free ends of a piezoelectric Pb(Zr1-xTix)O3 (PZT) plate. With this configuration, the Ni and the PZT plates vibrate more freely due to the absence of an interfacial epoxy layer, which results in a larger bending deformation of the PZT plate. The Ni and the PZT plates couple to each other by mechanical magnetic forces, instead of shear forces. In addition, the two Ni plates act as proof masses for the PZT plate, which can reduce the bending resonant frequency ( f r) the of PZT plate. The experimental results demonstrate that the bendingresonance ME voltage coefficient ( aME,r) is 2.82 times larger than that of the traditional bilayer laminate Ni/PZT. As the length of the Ni plates (L) increases, the fr decreases and can be shifted in a range of 34.6 kHz ≤ fr ≤ 61.02 kHz. The maximum aME,r of 49.84 V/cm Oe is observed at dc bias magnetic field H dc = 158 Oe when L = 18 mm. This heterostructure is of interest for high-sensitive dc magnetic-field sensors, ME transducers.

  13. Investigation of optimized end-bonding magnetoelectric heterostructure for sensitive magnetic field sensor.

    PubMed

    Lu, Caijiang; Xu, Changbao; Wang, Lei; Gao, Jipu; Gui, Junguo; Lin, Chenghui

    2014-11-01

    This paper reports an optimized end-bonding magnetoelectric (ME) heterostructure FeCuNbSiB-PZT-FeCuNbSiB (FPF) for sensitive magnetic field sensor. The heterostructure is made by attaching magnetostrictive Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB) foils at the free ends of piezoelectric Pb(Zr1-x,Tix)O3 (PZT) plates. Due to the structural advantages, the FPF has ∼3.12 times larger resonance voltage coefficient (αME,r) than traditional FeCuNbSiB/PZT laminate. And compared with the Metglas-PZT-Metglas heterostructure, the FPF heterostructure has stronger ME responses for the excellent magnetic characteristics of FeCuNbSiB. In experiments, the FPF heterostructure is optimal designed through adjusting the thickness of PZT plate (tp) and the length of FeCuNbSiB foil (L). The results demonstrate that the maximum αME,r of 662.1 (V/cm Oe) is observed at 13 Oe DC bias magnetic field when L = 15 mm and tp = 0.6 mm. Based on the giant ME coupling, the DC magnetic field sensitivity for the optimized FPF heterostructure is 3.89 nT at resonant frequency. These results are very promising for the cheap room-temperature magnetic field sensing technology.

  14. A loop-gap resonator for chirality-sensitive nuclear magneto-electric resonance (NMER).

    PubMed

    Garbacz, Piotr; Fischer, Peer; Krämer, Steffen

    2016-09-14

    Direct detection of molecular chirality is practically impossible by methods of standard nuclear magnetic resonance (NMR) that is based on interactions involving magnetic-dipole and magnetic-field operators. However, theoretical studies provide a possible direct probe of chirality by exploiting an enantiomer selective additional coupling involving magnetic-dipole, magnetic-field, and electric field operators. This offers a way for direct experimental detection of chirality by nuclear magneto-electric resonance (NMER). This method uses both resonant magnetic and electric radiofrequency (RF) fields. The weakness of the chiral interaction though requires a large electric RF field and a small transverse RF magnetic field over the sample volume, which is a non-trivial constraint. In this study, we present a detailed study of the NMER concept and a possible experimental realization based on a loop-gap resonator. For this original device, the basic principle and numerical studies as well as fabrication and measurements of the frequency dependence of the scattering parameter are reported. By simulating the NMER spin dynamics for our device and taking the (19)F NMER signal of enantiomer-pure 1,1,1-trifluoropropan-2-ol, we predict a chirality induced NMER signal that accounts for 1%-5% of the standard achiral NMR signal. PMID:27634253

  15. Combinatorial bulk ceramic magnetoelectric composite libraries of strontium hexaferrite and barium titanate.

    PubMed

    Pullar, Robert C

    2012-07-01

    Bulk ceramic combinatorial libraries were produced via a novel, high-throughput (HT) process, in the form of polycrystalline strips with a gradient composition along the length of the library. Step gradient ceramic composite libraries with 10 mol % steps of SrFe12O19-BaTiO3 (SrM-BT) were made and characterized using HT methods, as a proof of principle of the combinatorial bulk ceramic process, and sintered via HT thermal processing. It was found that the SrM-BT libraries sintered at 1175 °C had the optimum morphology and density. The compositional, electrical and magnetic properties of this library were analyzed, and it was found that the SrM and BT phases did not react and remained discrete. The combinatorial synthesis method produced a relatively linear variation in composition. The magnetization of the library followed the measured compositions very well, as did the low frequency permittivity values of most compositions in the library. However, with high SrM content of ≥80 mol %, the samples became increasingly conductive, and no reliable dielectric measurements could be made. Such conductivity would also greatly inhibit any ferroelectricity and magnetoelectric coupling with these composites with high levels of the SrM hexagonal ferrite. PMID:22676556

  16. A loop-gap resonator for chirality-sensitive nuclear magneto-electric resonance (NMER)

    NASA Astrophysics Data System (ADS)

    Garbacz, Piotr; Fischer, Peer; Krämer, Steffen

    2016-09-01

    Direct detection of molecular chirality is practically impossible by methods of standard nuclear magnetic resonance (NMR) that is based on interactions involving magnetic-dipole and magnetic-field operators. However, theoretical studies provide a possible direct probe of chirality by exploiting an enantiomer selective additional coupling involving magnetic-dipole, magnetic-field, and electric field operators. This offers a way for direct experimental detection of chirality by nuclear magneto-electric resonance (NMER). This method uses both resonant magnetic and electric radiofrequency (RF) fields. The weakness of the chiral interaction though requires a large electric RF field and a small transverse RF magnetic field over the sample volume, which is a non-trivial constraint. In this study, we present a detailed study of the NMER concept and a possible experimental realization based on a loop-gap resonator. For this original device, the basic principle and numerical studies as well as fabrication and measurements of the frequency dependence of the scattering parameter are reported. By simulating the NMER spin dynamics for our device and taking the 19F NMER signal of enantiomer-pure 1,1,1-trifluoropropan-2-ol, we predict a chirality induced NMER signal that accounts for 1%-5% of the standard achiral NMR signal.

  17. Coupling and tuning of modal frequencies in direct current biased microelectromechanical systems arrays

    SciTech Connect

    Kambali, Prashant N.; Swain, Gyanadutta; Pandey, Ashok Kumar; Buks, Eyal; Gottlieb, Oded

    2015-08-10

    Understanding the coupling of different modal frequencies and their tuning mechanisms has become essential to design multi-frequency MEMS devices. In this work, we fabricate a MEMS beam with fixed boundaries separated from two side electrodes and a bottom electrode. Subsequently, we perform experiments to obtain the frequency variation of in-plane and out-of-plane mechanical modes of the microbeam with respect to both DC bias and laser heating. We show that the frequencies of the two modes coincide at a certain DC bias, which in turn can also be varied due to temperature. Subsequently, we develop a theoretical model to predict the variation of the two modes and their coupling due to a variable gap between the microbeam and electrodes, initial tension, and fringing field coefficients. Finally, we discuss the influence of frequency tuning parameters in arrays of 3, 33, and 40 microbeams, respectively. It is also found that the frequency bandwidth of a microbeam array can be increased to as high as 25 kHz for a 40 microbeam array with a DC bias of 80 V.

  18. Experimental evidence of deterministic coherence resonance in coupled chaotic systems with frequency mismatch

    NASA Astrophysics Data System (ADS)

    García-Vellisca, M. A.; Pisarchik, A. N.; Jaimes-Reátegui, R.

    2016-07-01

    We present the experimental evidence of deterministic coherence resonance in unidirectionally coupled two and three Rössler electronic oscillators with mismatch between their natural frequencies. The regularity in both the amplitude and the phase of chaotic fluctuations is experimentally proven by the analyses of normalized standard deviations of the peak amplitude and interpeak interval and Lyapunov exponents. The resonant chaos suppression appears when the coupling strength is increased and the oscillators are in phase synchronization. In two coupled oscillators, the coherence enhancement is associated with negative third and fourth Lyapunov exponents, while the largest first and second exponents remain positive. Distinctly, in three oscillators coupled in a ring, all exponents become negative, giving rise to periodicity. Numerical simulations are in good agreement with the experiments.

  19. Electric field modulation of ultra-high resonance frequency in obliquely deposited [Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011)/FeCoZr heterostructure for reconfigurable magnetoelectric microwave devices

    NASA Astrophysics Data System (ADS)

    Phuoc, Nguyen N.; Ong, C. K.

    2014-07-01

    The multiferroic heterostructure of FeCoZr/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) (PMN-PT) prepared by oblique sputtering deposition technique shows a large electrical tunability of ultra-high ferromagnetic resonance frequency from 7.4 GHz to 12.3 GHz. Moreover, we experimentally demonstrate the possibility of realizing electrically reconfigurable magnetoelectric microwave devices with ultra-low power consumption by employing the heterostructure under different resetting electric fields through a reconfiguration process. In particular, the tunability of the FeCoZr/PMN-PT heterostructure from 8.2 GHz to 11.6 GHz can retain in a remanent state after releasing the resetting electric field. This suggests that the tunable microwave devices based on such heterostructures are permanently reconfigurable by simply using a trigger electric field double-pulse which requires much less energy than that of the conventional ones wherein an electric field needs to be constantly applied during operation.

  20. Off-resonance frequency operation for power transfer in a loosely coupled air core transformer

    DOEpatents

    Scudiere, Matthew B

    2012-11-13

    A power transmission system includes a loosely coupled air core transformer having a resonance frequency determined by a product of inductance and capacitance of a primary circuit including a primary coil. A secondary circuit is configured to have a substantially same product of inductance and capacitance. A back EMF generating device (e.g., a battery), which generates a back EMF with power transfer, is attached to the secondary circuit. Once the load power of the back EMF generating device exceeds a certain threshold level, which depends on the system parameters, the power transfer can be achieved at higher transfer efficiency if performed at an operating frequency less than the resonance frequency, which can be from 50% to 95% of the resonance frequency.

  1. Ultralow-Frequency Collective Compression Mode and Strong Interlayer Coupling in Multilayer Black Phosphorus

    NASA Astrophysics Data System (ADS)

    Dong, Shan; Zhang, Anmin; Liu, Kai; Ji, Jianting; Ye, Y. G.; Luo, X. G.; Chen, X. H.; Ma, Xiaoli; Jie, Yinghao; Chen, Changfeng; Wang, Xiaoqun; Zhang, Qingming

    2016-02-01

    The recent renaissance of black phosphorus (BP) as a two-dimensional (2D) layered material has generated tremendous interest, but its unique structural characters underlying many of its outstanding properties still need elucidation. Here we report Raman measurements that reveal an ultralow-frequency collective compression mode (CCM) in BP, which is unprecedented among similar 2D layered materials. This novel CCM indicates an unusually strong interlayer coupling, and this result is quantitatively supported by a phonon frequency analysis and first-principles calculations. Moreover, the CCM and another branch of low-frequency Raman modes shift sensitively with changing number of layers, allowing an accurate determination of the thickness up to tens of atomic layers, which is considerably higher than previously achieved by using high-frequency Raman modes. These findings offer fundamental insights and practical tools for further exploration of BP as a highly promising new 2D semiconductor.

  2. Tunable coupling between fixed-frequency superconducting transmon qubits, Part I: Concept, design, and prospects

    NASA Astrophysics Data System (ADS)

    Filipp, Stefan; McKay, David C.; Magesan, Easwar; Mezzacapo, Antonio; Chow, Jerry M.; Gambetta, Jay M.

    The controlled realization of qubit-qubit interactions is essential for both the physical implementation of quantum error-correction codes and for reliable quantum simulations. Ideally, the fidelity and speed of corresponding two-qubit gate operations is comparable to those of single qubit operations. In particular, in a scalable superconducting qubit architecture coherence must not be compromised by the presence of additional coupling elements mediating the interaction between qubits. Here we present a coupling method between fixed-frequency transmon qubits based on the frequency modulation of an auxiliary circuit coupling to the individual transmons. Since the coupler remains in its ground state at all times, its coherence does not significantly influence the fidelity of consequent entangling operations. Moreover, with the possibility to create interactions along different directions, our method is suited to engineer Hamiltonians with adjustable coupling terms. This property can be utilized for quantum simulations of spins or fermions in transmon arrays, in which pairwise couplings between adjacent qubits can be activated on demand. We acknowledge support from ARO under Contract W911NF-14-1-0124.

  3. Palladacycle-Catalyzed Carbonylative Suzuki-Miyaura Coupling with High Turnover Number and Turnover Frequency.

    PubMed

    Gautam, Prashant; Bhanage, Bhalchandra M

    2015-08-01

    This work reports the carbonylative Suzuki-Miyaura coupling of aryl iodides catalyzed by palladacycles. More importantly, the palladacycles have been used to generate high turnover numbers (TON's) and turnover frequencies (TOF's). A range of aryl iodides can be coupled with arylboronic acids, generating TON's in the range of 10(6) to 10(7) and TOF's in the range of 10(5) to 10(6) h(-1). Comparison of the palladacycles with a conventional palladium source shows their superiority in generating high TON's and TOF's. PMID:26166246

  4. Finite size effect on spread of resonance frequencies in arrays of coupled vortices

    SciTech Connect

    Vogel, Andreas; Drews, André; Im, Mi-Young; Fischer, Peter; Meier, Guido

    2011-01-25

    Dynamical properties of magnetic vortices in arrays of magnetostatically coupled ferromagnetic disks are studied by means of a broadband ferromagnetic-resonance (FMR) setup. Magnetic force microscopy and magnetic transmission soft X-ray microscopy are used to image the core polarizations and the chiralities which are both found to be randomly distributed. The resonance frequency of vortex-core motion strongly depends on the magnetostatic coupling between the disks. The parameter describing the relative broadening of the absorption peak observed in the FMR transmission spectra for a given normalized center-to-center distance between the elements is shown to depend on the size of the array.

  5. A Generalized Fast Frequency Sweep Algorithm for Coupled Circuit-EM Simulations

    SciTech Connect

    Ouyang, G; Jandhyala, V; Champagne, N; Sharpe, R; Fasenfest, B J; Rockway, J D

    2004-12-14

    An Asymptotic Wave Expansion (AWE) technique is implemented into the EIGER computational electromagnetics code. The AWE fast frequency sweep is formed by separating the components of the integral equations by frequency dependence, then using this information to find a rational function approximation of the results. The standard AWE method is generalized to work for several integral equations, including the EFIE for conductors and the PMCHWT for dielectrics. The method is also expanded to work for two types of coupled circuit-EM problems as well as lumped load circuit elements. After a simple bisecting adaptive sweep algorithm is developed, dramatic speed improvements are seen for several example problems.

  6. Magnetoelectric laminate composite based tachometer for harsh environment applications

    SciTech Connect

    Myers, Robert; Islam, Rashed Adnan; Karmarkar, Makarand; Priya, Shashank

    2007-09-17

    This study reports the design, fabrication, and characterization of a tachometer utilizing magnetoelectric (ME) laminate composites with sandwich structure consisting of Pb(Zr,Ti)O{sub 3} (PZT) and Galfenol. High temperature characterization of Galfenol shows that it can sustain the magnetic property over 500 deg. C. The Curie temperature of PZT compositions was in the range of 325-340 deg. C. The magnitude of the ME coefficient was found to scale with the dimensionless ratio (d g/S), where d is the piezoelectric strain constant, g is the piezoelectric voltage constant, and S is the elastic compliance. The tachometer design is based on the principle that when ME composite is exposed to oscillating magnetic field, it generates voltage with the same frequency.

  7. Room-temperature magnetoelectric multiferroic thin films and applications thereof

    DOEpatents

    Katiyar, Ram S; Kuman, Ashok; Scott, James F.

    2014-08-12

    The invention provides a novel class of room-temperature, single-phase, magnetoelectric multiferroic (PbFe.sub.0.67W.sub.0.33O.sub.3).sub.x (PbZr.sub.0.53Ti.sub.0.47O.sub.3).sub.1-x (0.2.ltoreq.x.ltoreq.0.8) (PFW.sub.x-PZT.sub.1-x) thin films that exhibit high dielectric constants, high polarization, weak saturation magnetization, broad dielectric temperature peak, high-frequency dispersion, low dielectric loss and low leakage current. These properties render them to be suitable candidates for room-temperature multiferroic devices. Methods of preparation are also provided.

  8. A study of sexual satisfaction and frequency of sex among Hong Kong Chinese couples.

    PubMed

    Cheung, Mike W-L; Wong, Paul W-C; Liu, Ka Y; Yip, Paul S-F; Fan, Susan Yun-Sun; Lam, Tai-Hing

    2008-01-01

    There have been several studies in Western societies on the causes and consequences of sexual satisfaction within marriage. Little is known, however about the marital sexual relationship in Chinese societies. Moreover, most published studies used married individuals rather than married couples as participants. The present study examined data from a well-established knowledge, attitude, and practice (KAP) survey of 1,124 Hong Kong Chinese couples on martial sexual relationship. A conceptual model was tested using structural equation modeling (SEM). Interest in sex was found to be the strongest predictor of both sexual satisfaction and frequency of sex for both husbands and wives. Among the sociodemographic variables, the following two were significantly associated with lower frequencies of sex: for wives, that of having a full-time job; and for husbands, the factor of age. Theoretical implications for research on the interplay among culture, marriage, and sex in non-Western societies are discussed.

  9. Lower Bounds on the Frequency Estimation Error in Magnetically Coupled MEMS Resonant Sensors.

    PubMed

    Paden, Brad E

    2016-02-01

    MEMS inductor-capacitor (LC) resonant pressure sensors have revolutionized the treatment of abdominal aortic aneurysms. In contrast to electrostatically driven MEMS resonators, these magnetically coupled devices are wireless so that they can be permanently implanted in the body and can communicate to an external coil via pressure-induced frequency modulation. Motivated by the importance of these sensors in this and other applications, this paper develops relationships among sensor design variables, system noise levels, and overall system performance. Specifically, new models are developed that express the Cramér-Rao lower bound for the variance of resonator frequency estimates in terms of system variables through a system of coupled algebraic equations, which can be used in design and optimization. Further, models are developed for a novel mechanical resonator in addition to the LC-type resonators.

  10. High-frequency Born synthetic seismograms based on coupled normal modes

    USGS Publications Warehouse

    Pollitz, F.

    2011-01-01

    High-frequency and full waveform synthetic seismograms on a 3-D laterally heterogeneous earth model are simulated using the theory of coupled normal modes. The set of coupled integral equations that describe the 3-D response are simplified into a set of uncoupled integral equations by using the Born approximation to calculate scattered wavefields and the pure-path approximation to modulate the phase of incident and scattered wavefields. This depends upon a decomposition of the aspherical structure into smooth and rough components. The uncoupled integral equations are discretized and solved in the frequency domain, and time domain results are obtained by inverse Fourier transform. Examples show the utility of the normal mode approach to synthesize the seismic wavefields resulting from interaction with a combination of rough and smooth structural heterogeneities. This approach is applied to an ~4 Hz shallow crustal wave propagation around the site of the San Andreas Fault Observatory at Depth (SAFOD). ?? The Author Geophysical Journal International ?? 2011 RAS.

  11. High-frequency Born synthetic seismograms based on coupled normal modes

    USGS Publications Warehouse

    Pollitz, Fred F.

    2011-01-01

    High-frequency and full waveform synthetic seismograms on a 3-D laterally heterogeneous earth model are simulated using the theory of coupled normal modes. The set of coupled integral equations that describe the 3-D response are simplified into a set of uncoupled integral equations by using the Born approximation to calculate scattered wavefields and the pure-path approximation to modulate the phase of incident and scattered wavefields. This depends upon a decomposition of the aspherical structure into smooth and rough components. The uncoupled integral equations are discretized and solved in the frequency domain, and time domain results are obtained by inverse Fourier transform. Examples show the utility of the normal mode approach to synthesize the seismic wavefields resulting from interaction with a combination of rough and smooth structural heterogeneities. This approach is applied to an ∼4 Hz shallow crustal wave propagation around the site of the San Andreas Fault Observatory at Depth (SAFOD).

  12. Experimental observation of three-frequency quasiperiodic solution in a ring of unidirectionally coupled oscillators.

    PubMed

    Borkowski, L; Perlikowski, P; Kapitaniak, T; Stefanski, A

    2015-06-01

    The subject of the experimental research supported with numerical simulations presented in this paper is an analog electrical circuit representing the ring of unidirectionally coupled single-well Duffing oscillators. The research is concentrated on the existence of the stable three-frequency quasiperiodic attractor in this system. It is shown that such solution can be robustly stable in a wide range of parameters of the system under consideration in spite of a parameter mismatch which is unavoidable during experiment. PMID:26172771

  13. Different modes of a capacitively coupled radio-frequency discharge in methane.

    PubMed

    Schweigert, I V

    2004-04-16

    The transition between different regimes of a capacitevely coupled radio-frequency gas discharge in methane is studied with a combined particle-in-cell Monte Carlo collision algorithm over a wide range of gas pressure P and discharge current j. The results of this study are compared with known experimental and numerical results and summarized on a P-j phase diagram, which constitutes the areas of existence of different discharge regimes.

  14. Different Modes of a Capacitively Coupled Radio-Frequency Discharge in Methane

    NASA Astrophysics Data System (ADS)

    Schweigert, I. V.

    2004-04-01

    The transition between different regimes of a capacitevely coupled radio-frequency gas discharge in methane is studied with a combined particle-in-cell Monte Carlo collision algorithm over a wide range of gas pressure P and discharge current j. The results of this study are compared with known experimental and numerical results and summarized on a P-j phase diagram, which constitutes the areas of existence of different discharge regimes.

  15. Direct measurement of voltage-controlled reversal of the antiferromagnetic spin structure in magnetoelectric Cr2O3

    NASA Astrophysics Data System (ADS)

    Wang, Junlei; Binek, Christian

    The frequency dependence of the electric field induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility and the antiferromagnetic order parameter. The relative strength of these contributions is determined by the frequency of the probing light beam. It allows tuning the Faraday signal between extreme characteristics which follow the temperature dependence of the magnetoelectric susceptibility or solely that of the antiferromagnetic order parameter. The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3 + crystal-field states. The results lead to a table-top set-up allowing to measure voltage-controlled selection and temperature dependence of the antiferromagnetic order parameter. The Faraday rotation per applied voltage is independent of the sample thickness making the method scalable and versatile for thin film investigations. Scalability, compactness, and simplicity of the data analysis combined with low photon flux requirements make the Faraday approach advantageous for the investigation of the otherwise difficult to access voltage-controlled switching of antiferromagnetic domain states in magnetoelectric thin films. This project is supported by NRI via CNFD through tasks SRC 2398.001 and 2587.001, by C-SPIN, a SRC program, sponsored by MARCO and DARPA, and by NSF through Nebraska MRSEC DMR-1420645.

  16. Coupled analysis of multi-impact energy harvesting from low-frequency wind induced vibrations

    NASA Astrophysics Data System (ADS)

    Zhu, Jin; Zhang, Wei

    2015-04-01

    Energy need from off-grid locations has been critical for effective real-time monitoring and control to ensure structural safety and reliability. To harvest energy from ambient environments, the piezoelectric-based energy-harvesting system has been proven very efficient to convert high frequency vibrations into usable electrical energy. However, due to the low frequency nature of the vibrations of civil infrastructures, such as those induced from vehicle impacts, wind, and waves, the application of a traditional piezoelectric-based energy-harvesting system is greatly restrained since the output power drops dramatically with the reduction of vibration frequencies. This paper focuses on the coupled analysis of a proposed piezoelectric multi-impact wind-energy-harvesting device that can effectively up-convert low frequency wind-induced vibrations into high frequency ones. The device consists of an H-shape beam and four bimorph piezoelectric cantilever beams. The H-shape beam, which can be easily triggered to vibrate at a low wind speed, is originated from the first Tacoma Narrows Bridge, which failed at wind speeds of 18.8 m s-1 in 1940. The multi-impact mechanism between the H-shape beam and the bimorph piezoelectric cantilever beams is incorporated to improve the harvesting performance at lower frequencies. During the multi-impact process, a series of sequential impacts between the H-shape beam and the cantilever beams can trigger high frequency vibrations of the cantilever beams and result in high output power with a considerably high efficiency. In the coupled analysis, the coupled structural, aerodynamic, and electrical equations are solved to obtain the dynamic response and the power output of the proposed harvesting device. A parametric study for several parameters in the coupled analysis framework is carried out including the external resistance, wind speed, and the configuration of the H-shape beam. The average harvested power for the piezoelectric cantilever

  17. Synthesis and properties of novel tunable ferroic and magneto-electric meta-materials composites

    NASA Astrophysics Data System (ADS)

    Agrawal, Shashnk

    The aim of the research was to develop composite materials for low temperature and room temperature applications in the high frequency areas. For tunable dielectric materials, (Ba1-x,Srx)TiO3 (BST) with various weight ratios with cubic-tetragonal phase transition peak below or around room temperature were used. Micron sized Ba0.4Sr 0.6TiO3 and Ba0.6Sr0.4TiO3 and nano size Ba0.5Sr0.5TiO3 were used for ferroelectric phase and both micron and nano sized MgO was used as non-ferroelectric phase. The magneto-electric composites were prepared with both micron sized Ba0.6Sr0.4TiO3 and PMN-PT as ferroelectric/piezoelectric phase and CoFe2O4 (nano), NiMn0.1Fe 1.9O4 (micron) and Mn0.1Zn0.9Fe 2O4 (nano) as magnetic components. The ferroelectric composite materials were processed using multi mode microwave sintering technique. The microwave sintering resulted in lower sintering time compared to the conventional sintering and also the higher density composites with good connectivity of grains. The connectivity pattern of 0-3 was obtained in the resulted composites with good connectivity of ferroic grains and isolating the non-ferroelectric grains giving very low dielectric constant and appreciable tunability. Using nano particle size of both BST and MgO, a maximum tunability of 48% at 80 KV/cm was achieved with dielectric constant of 89 at 200 K at 100 KHz. The microwave sintering resulted in very dense composites and low dielectric losses providing composites with high break down strength. The maximum DC electric field applied to the samples was 80 KV/cm. The addition of MgO resulted in the shift of maximum dielectric peak to lower phase transition temperature without shifting the ferroelectric nature of BST. Additional experiments were carried out for pyroelectric measurements to confirm the phase transitions temperatures in the composites. High frequency measurements were done at room temperature with modified cavity perturbation technique where a special cavity was designed

  18. Decoherence of coupled Josephson charge qubits due to partially correlated low-frequency noise

    SciTech Connect

    Hu, Yong; Zhou, Zheng-Wei; Cai, Jian-Ming; Guo, Guang-Can

    2007-05-15

    Josephson charge qubits are promising candidates for scalable quantum computing. However, their performances are strongly degraded by decoherence due to low-frequency background noise, typically with a 1/f spectrum. In this paper, we investigate the decoherence process of two Cooper pair boxes (CPBs) coupled via a capacitor. Going beyond the common and uncorrelated noise models and the Bloch-Redfield formalism of previous works, we study the coupled system's quadratic dephasing under the condition of partially correlated noise sources. Based on reported experiments and generally accepted noise mechanisms, we introduce a reasonable assumption for the noise correlation, with which the calculation of multiqubit decoherence can be simplified to a problem on the single-qubit level. For the conventional Gaussian 1/f noise case, our results demonstrate that the quadratic dephasing rates are not very sensitive to the spatial correlation of the noises. Furthermore, we discuss the feasibility and efficiency of dynamical decoupling in the coupled CPBs.

  19. Using High Frequency Focused Water-Coupled Ultrasound for 3-D Surface Depression Profiling

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Whalen, Mike F.; Hendricks, J. Lynne; Bodis, James R.

    1999-01-01

    Surface topography is an important variable in the performance of many industrial components and is normally measured with diamond-tip profilometry over a small area or using optical scattering methods for larger area measurement. A prior study was performed demonstrating that focused air-coupled ultrasound at 1 MHz was capable of profiling surfaces with 25 micron depth resolution and 400 micron lateral resolution over a 1.4 mm depth range. In this article, the question of whether higher-frequency focused water-coupled ultrasound can improve on these specifications is addressed. 10 and 25 MHz focused ultrasonic transducers were employed in the water-coupled mode. Time-of-flight images of the sample surface were acquired and converted to depth / surface profile images using the simple relation (d = V*t/2) between distance (d), time-of-flight (t), and the velocity of sound in water (V). Results are compared for the two frequencies used and with those from the 1 MHz air-coupled configuration.

  20. Computational IR spectroscopy of water: OH stretch frequencies, transition dipoles, and intermolecular vibrational coupling constants

    NASA Astrophysics Data System (ADS)

    Choi, Jun-Ho; Cho, Minhaeng

    2013-05-01

    The Hessian matrix reconstruction method initially developed to extract the basis mode frequencies, vibrational coupling constants, and transition dipoles of the delocalized amide I, II, and III vibrations of polypeptides and proteins from quantum chemistry calculation results is used to obtain those properties of delocalized O-H stretch modes in liquid water. Considering the water symmetric and asymmetric O-H stretch modes as basis modes, we here develop theoretical models relating vibrational frequencies, transition dipoles, and coupling constants of basis modes to local water configuration and solvent electric potential. Molecular dynamics simulation was performed to generate an ensemble of water configurations that was in turn used to construct vibrational Hamiltonian matrices. Obtaining the eigenvalues and eigenvectors of the matrices and using the time-averaging approximation method, which was developed by the Skinner group, to calculating the vibrational spectra of coupled oscillator systems, we could numerically simulate the O-H stretch IR spectrum of liquid water. The asymmetric line shape and weak shoulder bands were quantitatively reproduced by the present computational procedure based on vibrational exciton model, where the polarization effects on basis mode transition dipoles and inter-mode coupling constants were found to be crucial in quantitatively simulating the vibrational spectra of hydrogen-bond networking liquid water.

  1. High-mechanical-frequency characteristics of optomechanical crystal cavity with coupling waveguide

    PubMed Central

    Huang, Zhilei; Cui, Kaiyu; Bai, Guoren; Feng, Xue; Liu, Fang; Zhang, Wei; Huang, Yidong

    2016-01-01

    Optomechanical crystals have attracted great attention recently for their ability to realize strong photon-phonon interaction in cavity optomechanical systems. By far, the operation of cavity optomechanical systems with high mechanical frequency has to employ tapered fibres or one-sided waveguides with circulators to couple the light into and out of the cavities, which hinders their on-chip applications. Here, we demonstrate larger-centre-hole nanobeam structures with on-chip transmission-coupling waveguide. The measured mechanical frequency is up to 4.47 GHz, with a high mechanical Q-factor of 1.4 × 103 in the ambient environment. The corresponding optomechanical coupling rate is calculated and measured to be 836 kHz and 1.2 MHz, respectively, while the effective mass is estimated to be 136 fg. With the transmission waveguide coupled structure and a small footprint of 3.4 μm2, this simple cavity can be directly used as functional components or integrated with other on-chip devices in future practical applications. PMID:27686419

  2. High-mechanical-frequency characteristics of optomechanical crystal cavity with coupling waveguide

    NASA Astrophysics Data System (ADS)

    Huang, Zhilei; Cui, Kaiyu; Bai, Guoren; Feng, Xue; Liu, Fang; Zhang, Wei; Huang, Yidong

    2016-09-01

    Optomechanical crystals have attracted great attention recently for their ability to realize strong photon-phonon interaction in cavity optomechanical systems. By far, the operation of cavity optomechanical systems with high mechanical frequency has to employ tapered fibres or one-sided waveguides with circulators to couple the light into and out of the cavities, which hinders their on-chip applications. Here, we demonstrate larger-centre-hole nanobeam structures with on-chip transmission-coupling waveguide. The measured mechanical frequency is up to 4.47 GHz, with a high mechanical Q-factor of 1.4 × 103 in the ambient environment. The corresponding optomechanical coupling rate is calculated and measured to be 836 kHz and 1.2 MHz, respectively, while the effective mass is estimated to be 136 fg. With the transmission waveguide coupled structure and a small footprint of 3.4 μm2, this simple cavity can be directly used as functional components or integrated with other on-chip devices in future practical applications.

  3. Detecting phase-amplitude coupling with high frequency resolution using adaptive decompositions

    PubMed Central

    Pittman-Polletta, Benjamin; Hsieh, Wan-Hsin; Kaur, Satvinder; Lo, Men-Tzung; Hu, Kun

    2014-01-01

    Background Phase-amplitude coupling (PAC) – the dependence of the amplitude of one rhythm on the phase of another, lower-frequency rhythm – has recently been used to illuminate cross-frequency coordination in neurophysiological activity. An essential step in measuring PAC is decomposing data to obtain rhythmic components of interest. Current methods of PAC assessment employ narrowband Fourier-based filters, which assume that biological rhythms are stationary, harmonic oscillations. However, biological signals frequently contain irregular and nonstationary features, which may contaminate rhythms of interest and complicate comodulogram interpretation, especially when frequency resolution is limited by short data segments. New method To better account for nonstationarities while maintaining sharp frequency resolution in PAC measurement, even for short data segments, we introduce a new method of PAC assessment which utilizes adaptive and more generally broadband decomposition techniques – such as the empirical mode decomposition (EMD). To obtain high frequency resolution PAC measurements, our method distributes the PAC associated with pairs of broadband oscillations over frequency space according to the time-local frequencies of these oscillations. Comparison with existing methods We compare our novel adaptive approach to a narrowband comodulogram approach on a variety of simulated signals of short duration, studying systematically how different types of nonstationarities affect these methods, as well as on EEG data. Conclusions Our results show: (1) narrowband filtering can lead to poor PAC frequency resolution, and inaccuracy and false negatives in PAC assessment; (2) our adaptive approach attains better PAC frequency resolution and is more resistant to nonstationarities and artifacts than traditional comodulograms. PMID:24452055

  4. Nonlinear magnetoelectric behavior of Terfenol-D/PZT-5A laminate composites

    NASA Astrophysics Data System (ADS)

    Wang, Yezuo; Atulasimha, Jayasimha; Prasoon, Ruchir

    2010-12-01

    In this paper, a comprehensive experimental study and modeling of the nonlinear behavior of Terfenol-D/PZT-5A magnetoelectric laminate composites is reported. Magnetostriction versus magnetic field of an individual Terfenol-D sample of dimensions length = 22 mm, width = 19 mm, thickness = 0.683 mm, and polarization versus electric field as well as strain versus electric field of an individual PZT-5A sample of dimensions length = 22 mm, width = 19 mm, thickness = 0.127 mm were characterized. These samples were bonded to form a symmetric PZT-5A/Terfenol-D/PZT-5A laminate composite to avoid bending-extension coupling. Electric response of this composite to magnetic input was comprehensively characterized to include major loop and minor loop behavior. A modeling approach that structurally couples the nonlinear magnetostrictive Terfenol-D behavior and linear PZT-5A behavior to predict the magnetoelectric response was developed and validated against experimental results. This analysis, with further refinements, could prove to be a useful tool to model and design magnetoelectric sensors.

  5. Influence of frequency on the characteristics of VHF capacitively coupled plasmas in a 300 mm chamber

    NASA Astrophysics Data System (ADS)

    Hebner, G. A.; Barnat, E. V.; Miller, P. A.; Paterson, A.; Holland, J.; Lill, T.

    2004-09-01

    We have investigated the characteristics of VHF capacitively coupled plasmas produced in a modified Applied Materials chamber. The chamber had a 14-inch diameter upper electrode (source) that was driven at 10 to 160 MHz and a 300 mm diameter electrostatic chuck with a ceramic process kit that was driven at 13.56 MHz (bias). Diagnostics employed include a microwave interferometer to measure the line-integrated electron density, a hairpin microwave resonator to measure the spatially resolved electron density, absorption spectroscopy to determine the argon metastable temperature and density, laser induced fluorescence (LIF) to determine the spatial distribution of the excited species, and spatially resolved optical emission. We found that for constant source rf power, the electron density increased with rf frequency. The argon 1s5 metastable temperature was slightly above room temperature (300 - 400K), significantly cooler than our previous measurements in inductively coupled plasmas. The metastable density was not a strong function of source frequency or rf power. The metastable spatial distribution was always peaked in the center of the chamber and had a weak dependence on frequency. Scaling of the plasma parameters with frequency, power and pressure, and implications to energy deposition models will be discussed. This work was supported by Applied Materials and Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  6. Numerical investigation on electrical characterization of a capacitive coupled radio-frequency plasma

    NASA Astrophysics Data System (ADS)

    Yao, H.; He, X.; Chen, J. P.; Zhang, Y. C.

    2015-05-01

    This paper presents the main electrical features of capacitive coupled radio-frequency (CCRF) discharges in gas. A two-dimensional, time-dependent fluid model was established. Capacitive coupled plasmas (CCP) were produced by applying radio-frequency voltage to a pair of parallel plate electrodes which are separated from the plasma by dielectric layers. The electron equation and the electron transport equations were solved and yielded the electron number density and electron temperature. The electrostatic field was obtained by the solution of the Poisson equation. The distribution of electron temperature and electron number density was studied under different conditions: radio-frequency applied voltages (VRF=100-2000V), frequencies (f=3.0-40.68MHz), pressures (p=0.001-1torr), and gas species (O2, Ar, He, N2). The results show that electron number density presents a minimum near the electrodes, and presents a maximum between the positive and the negative electrodes. The distinguishing feature of CCP is the presence of oscillating sheaths near electrodes where displacement current dominates conduction current. These informations will help us to analyze the characters of CCP for application.

  7. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-14

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  8. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-01

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  9. Piezoelectric and Magnetoelectric Thick Films for Fabricating Power Sources in Wireless Sensor Nodes

    PubMed Central

    Priya, Shashank; Ryu, Jungho; Park, Chee-Sung; Oliver, Josiah; Choi, Jong-Jin; Park, Dong-Soo

    2009-01-01

    In this manuscript, we review the progress made in the synthesis of thick film-based piezoelectric and magnetoelectric structures for harvesting energy from mechanical vibrations and magnetic field. Piezoelectric compositions in the system Pb(Zr,Ti)O3–Pb(Zn1/3Nb2/3)O3 (PZNT) have shown promise for providing enhanced efficiency due to higher energy density and thus form the base of transducers designed for capturing the mechanical energy. Laminate structures of PZNT with magnetostrictive ferrite materials provide large magnitudes of magnetoelectric coupling and are being targeted to capture the stray magnetic field energy. We analyze the models used to predict the performance of the energy harvesters and present a full system description. PMID:22454590

  10. Magnetoelectric effects in the skyrmion host material Cu2OSeO3

    PubMed Central

    Ruff, E.; Lunkenheimer, P.; Loidl, A.; Berger, H.; Krohns, S.

    2015-01-01

    Insulating helimagnetic Cu2OSeO3 shows sizeable magnetoelectric effects in its skyrmion phase. Using magnetization measurements, magneto-current analysis and dielectric spectroscopy, we provide a thorough investigation of magnetoelectric coupling, polarization and dielectric constants of the ordered magnetic and polar phases of single-crystalline Cu2OSeO3 in external magnetic fields up to 150 mT and at temperatures below 60 K. From these measurements we construct a detailed phase diagram. Especially, the skyrmion phase and the metamagnetic transition of helical to conical spin order are characterized in detail. Finally we address the question if there is any signature of polar order that can be switched by an external electric field, which would imply multiferroic behaviour of Cu2OSeO3. PMID:26446514

  11. Piezoelectric and magnetoelectric thick films for fabricating power sources in wireless sensor nodes.

    PubMed

    Priya, Shashank; Ryu, Jungho; Park, Chee-Sung; Oliver, Josiah; Choi, Jong-Jin; Park, Dong-Soo

    2009-01-01

    In this manuscript, we review the progress made in the synthesis of thick film-based piezoelectric and magnetoelectric structures for harvesting energy from mechanical vibrations and magnetic field. Piezoelectric compositions in the system Pb(Zr,Ti)O(3)-Pb(Zn(1/3)Nb(2/3))O(3) (PZNT) have shown promise for providing enhanced efficiency due to higher energy density and thus form the base of transducers designed for capturing the mechanical energy. Laminate structures of PZNT with magnetostrictive ferrite materials provide large magnitudes of magnetoelectric coupling and are being targeted to capture the stray magnetic field energy. We analyze the models used to predict the performance of the energy harvesters and present a full system description. PMID:22454590

  12. Voltage-impulse-induced nonvolatile tunable magnetoelectric inductor based on multiferroic bilayer structure

    NASA Astrophysics Data System (ADS)

    Su, Hua; Tang, Xiaoli; Zhang, Huaiwu; Sun, Nian X.

    2016-07-01

    In this study, we developed a voltage-impulse-induced nonvolatile tunable magnetoelectric inductor, which used an amorphous magnetic ribbon/lead zirconate titanate (PZT) multiferroic bilayer structure as a magnetic core. The PZT substrate, which contained defect dipoles through acceptor doping, was used in the bilayer structure to obtain an asymmetric strain-E “butterfly” curve. Different and stable voltage-impulse-induced in-plane residual stain states could be obtained by applying specific voltage impulse excitation modes. These residual strain states induced a nonvolatile inductance variation in the inductor through strain-mediated magnetoelectric coupling. This method provided a promising approach to realize nonvolatile tunable inductors for miniaturized circuits and systems.

  13. Voltage-impulse-induced nonvolatile tunable magnetoelectric inductor based on multiferroic bilayer structure

    NASA Astrophysics Data System (ADS)

    Su, Hua; Tang, Xiaoli; Zhang, Huaiwu; Sun, Nian X.

    2016-07-01

    In this study, we developed a voltage-impulse-induced nonvolatile tunable magnetoelectric inductor, which used an amorphous magnetic ribbon/lead zirconate titanate (PZT) multiferroic bilayer structure as a magnetic core. The PZT substrate, which contained defect dipoles through acceptor doping, was used in the bilayer structure to obtain an asymmetric strain–E “butterfly” curve. Different and stable voltage-impulse-induced in-plane residual stain states could be obtained by applying specific voltage impulse excitation modes. These residual strain states induced a nonvolatile inductance variation in the inductor through strain-mediated magnetoelectric coupling. This method provided a promising approach to realize nonvolatile tunable inductors for miniaturized circuits and systems.

  14. Giant self-biased converse magnetoelectric effect in multiferroic heterostructure with single-phase magnetostrictive materials

    NASA Astrophysics Data System (ADS)

    Zhang, Jitao; Li, Ping; Wen, Yumei; He, Wei; Yang, Aichao; Wang, Decai; Yang, Chao; Lu, Caijiang

    2014-10-01

    Giant self-biased converse magnetoelectric (CME) effects with obvious hysteretic behaviors are systematically investigated in two-phase SmFe2/PZT [Pb(Zr1-x, Tix)O3] multiferroic laminates at room temperature. Taking advantage of the huge anisotropic field of SmFe2 plate, large remnant CME coupling is provoked by this field instead of permanent magnets to bias the laminate. Consequently, bitable magnetization status switching is realized through a smaller ac voltage far below the electric coercive field in the absence of magnetic bias field. Experiments demonstrate that a large remnant CME coefficient (αCME) of 0.007 mG/V is achieved, exhibiting ˜50 times higher CME coefficient than the previous laminate composite multi-phase magnetostrictive plates. These results provide promising applications for realization of high-density magnetoelectric random access memories (MERAMs) devices with lower energy consumption.

  15. Magnetism and magnetoelectricity in the polar oxide α-Cu2V2O7

    NASA Astrophysics Data System (ADS)

    Lee, Y.-W.; Jang, T.-H.; Dissanayake, S. E.; Lee, Seunghun; Jeong, Yoon H.

    2016-01-01

    Single crystals of the orthorhombic polar oxide α-Cu2V2O7 with space group Fdd2 are synthesized and their physical properties are measured. Neutron powder diffraction is also performed on a polycrystal sample to extract the magnetic structure. The ground state is shown to be weakly ferromagnetic, that is, collinearly antiferromagnetic in the a-direction with a small remanent magnetization in the c-direction. When an external magnetic field is applied in the c-direction, further spin canting, accompanied by the induced electric polarization, occurs. It is demonstrated that the magnetoelectric effect in α-Cu2V2O7 is adequately described if spin-dependent p\\text-d hybridization due to spin-orbit coupling as well as magnetic domain effects are simultaneously taken into account. We discuss the implication of the present result in the search for materials with multiferroicity and/or magnetoelectricity.

  16. Frequency stabilization of spin-torque-driven oscillations by coupling with a magnetic nonlinear resonator

    SciTech Connect

    Kudo, Kiwamu Suto, Hirofumi; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie

    2014-10-28

    The fundamental function of any oscillator is to produce a waveform with a stable frequency. Here, we show a method of frequency stabilization for spin-torque nano-oscillators (STNOs) that relies on coupling with an adjacent nanomagnet through the magnetic dipole–dipole interaction. It is numerically demonstrated that highly stable oscillations occur as a result of mutual feedback between an STNO and a nanomagnet. The nanomagnet acts as a nonlinear resonator for the STNO. This method is based on the nonlinear behavior of the resonator and can be considered as a magnetic analogue of an optimization scheme in nanoelectromechanical systems. The oscillation frequency is most stabilized when the nanomagnet is driven at a special feedback point at which the feedback noise between the STNO and resonator is completely eliminated.

  17. NiCo-lead zirconium titanate-NiCo trilayered magnetoelectric composites prepared by electroless deposition

    NASA Astrophysics Data System (ADS)

    Zhou, M. H.; Fan, H. P.; Zhao, Z. S.; Wang, Y. G.; Bi, K.

    2015-04-01

    The NiCo layers with various Ni/Co atomic ratio have been successfully electroless deposited on PZT layers by varying the bath composition. As the cobalt atomic ratio in the deposited layer increases from 17.2 to 54.8 wt%, the magnetostrictive coefficient decreases. The magnetoelectric effect depends strongly on the magnetostrictive properties of magnetostrictive phase. The magnetoelectric coefficient of NiCo/PZT/NiCo trilayers increases with Ni/Co atomic ratio of the deposited NiCo layers increasing from 45:55 to 83:17. A maximum ME voltage coefficient of αE,31 = 2.8 V ṡ cm-1 ṡ Oe-1 is obtained at a frequency of about 88 kHz, which makes these trilayers suitable for applications in actuators, transducers and sensors.

  18. NiCo-lead zirconium titanate-NiCo trilayered magnetoelectric composites prepared by electroless deposition

    SciTech Connect

    Zhou, M. H.; Wang, Y. G.; Bi, K.; Fan, H. P.; Zhao, Z. S.

    2015-04-15

    The NiCo layers with various Ni/Co atomic ratio have been successfully electroless deposited on PZT layers by varying the bath composition. As the cobalt atomic ratio in the deposited layer increases from 17.2 to 54.8 wt%, the magnetostrictive coefficient decreases. The magnetoelectric effect depends strongly on the magnetostrictive properties of magnetostrictive phase. The magnetoelectric coefficient of NiCo/PZT/NiCo trilayers increases with Ni/Co atomic ratio of the deposited NiCo layers increasing from 45:55 to 83:17. A maximum ME voltage coefficient of α{sub E,31} = 2.8 V ⋅ cm{sup −1} ⋅ Oe{sup −1} is obtained at a frequency of about 88 kHz, which makes these trilayers suitable for applications in actuators, transducers and sensors.

  19. DC magnetic field sensing based on the nonlinear magnetoelectric effect in magnetic heterostructures

    NASA Astrophysics Data System (ADS)

    Burdin, Dmitrii; Chashin, Dmitrii; Ekonomov, Nikolai; Fetisov, Leonid; Fetisov, Yuri; Shamonin, Mikhail

    2016-09-01

    Recently, highly sensitive magnetic field sensors using the magnetoelectric effect in composite ferromagnetic-piezoelectric layered structures have been demonstrated. However, most of the proposed concepts are not useful for measuring dc magnetic fields, because the conductivity of piezoelectric layers results in a strong decline of the sensor’s sensitivity at low frequencies. In this paper, a novel functional principle of magnetoelectric sensors for dc magnetic field measurements is described. The sensor employs the nonlinear effect of voltage harmonic generation in a composite magnetoelectric structure under the simultaneous influence of a strong imposed ac magnetic field and a weak dc magnetic field to be measured. This physical effect arises due to the nonlinear dependence of the magnetostriction in the ferromagnetic layer on the magnetic field. A sensor prototype comprising of a piezoelectric fibre transducer sandwiched between two layers of the amorphous ferromagnetic Metglas® alloy was fabricated. The specifications regarding the magnetic field range, frequency characteristics, and noise level were studied experimentally. The prototype showed the responsivity of 2.5 V mT-1 and permitted the measurement of dc magnetic fields in the range of ~10 nT to about 0.4 mT. Although sensor operation is based on the nonlinear effect, the sensor response can be made linear with respect to the measured magnetic field in a broad dynamic range extending over 5 orders of magnitude. The underlying physics is explained through a simplified theory for the proposed sensor. The functionality, differences and advantages of the magnetoelectric sensor compare well with fluxgate magnetometers. The ways to enhance the sensor performance are considered.

  20. DC magnetic field sensing based on the nonlinear magnetoelectric effect in magnetic heterostructures

    NASA Astrophysics Data System (ADS)

    Burdin, Dmitrii; Chashin, Dmitrii; Ekonomov, Nikolai; Fetisov, Leonid; Fetisov, Yuri; Shamonin, Mikhail

    2016-09-01

    Recently, highly sensitive magnetic field sensors using the magnetoelectric effect in composite ferromagnetic-piezoelectric layered structures have been demonstrated. However, most of the proposed concepts are not useful for measuring dc magnetic fields, because the conductivity of piezoelectric layers results in a strong decline of the sensor’s sensitivity at low frequencies. In this paper, a novel functional principle of magnetoelectric sensors for dc magnetic field measurements is described. The sensor employs the nonlinear effect of voltage harmonic generation in a composite magnetoelectric structure under the simultaneous influence of a strong imposed ac magnetic field and a weak dc magnetic field to be measured. This physical effect arises due to the nonlinear dependence of the magnetostriction in the ferromagnetic layer on the magnetic field. A sensor prototype comprising of a piezoelectric fibre transducer sandwiched between two layers of the amorphous ferromagnetic Metglas® alloy was fabricated. The specifications regarding the magnetic field range, frequency characteristics, and noise level were studied experimentally. The prototype showed the responsivity of 2.5 V mT‑1 and permitted the measurement of dc magnetic fields in the range of ~10 nT to about 0.4 mT. Although sensor operation is based on the nonlinear effect, the sensor response can be made linear with respect to the measured magnetic field in a broad dynamic range extending over 5 orders of magnitude. The underlying physics is explained through a simplified theory for the proposed sensor. The functionality, differences and advantages of the magnetoelectric sensor compare well with fluxgate magnetometers. The ways to enhance the sensor performance are considered.

  1. Untangling Cortico-Striatal Connectivity and Cross-Frequency Coupling in L-DOPA-Induced Dyskinesia

    PubMed Central

    Belić, Jovana J.; Halje, Pär; Richter, Ulrike; Petersson, Per; Hellgren Kotaleski, Jeanette

    2016-01-01

    We simultaneously recorded local field potentials (LFPs) in the primary motor cortex and sensorimotor striatum in awake, freely behaving, 6-OHDA lesioned hemi-parkinsonian rats in order to study the features directly related to pathological states such as parkinsonian state and levodopa-induced dyskinesia. We analyzed the spectral characteristics of the obtained signals and observed that during dyskinesia the most prominent feature was a relative power increase in the high gamma frequency range at around 80 Hz, while for the parkinsonian state it was in the beta frequency range. Here we show that during both pathological states effective connectivity in terms of Granger causality is bidirectional with an accent on the striatal influence on the cortex. In the case of dyskinesia, we also found a high increase in effective connectivity at 80 Hz. In order to further understand the 80-Hz phenomenon, we performed cross-frequency analysis and observed characteristic patterns in the case of dyskinesia but not in the case of the parkinsonian state or the control state. We noted a large decrease in the modulation of the amplitude at 80 Hz by the phase of low frequency oscillations (up to ~10 Hz) across both structures in the case of dyskinesia. This may suggest a lack of coupling between the low frequency activity of the recorded network and the group of neurons active at ~80 Hz. PMID:27065818

  2. Studies on the effect of finite geometrical asymmetry in dual capacitively coupled radio frequency plasma

    NASA Astrophysics Data System (ADS)

    Bora, B.

    2015-10-01

    In recent years, dual capacitively coupled radio frequency (CCRF) glow discharge plasma has been widely studied in the laboratory because of its simpler design and high efficiency for different material processing applications such as thin-film deposition, plasma etching, sputtering of insulating materials etc. The main objective of studies on dual frequency CCRF plasma has been the independent control of ion energy and ion flux using an electrical asymmetry effect (EAE). Most studies have been reported in electrode configurations that are either geometrically symmetric (both electrodes are equal) or completely asymmetric (one electrode is infinitely bigger than the other). However, it seems that most of the laboratory CCRF plasmas have finite electrode geometry. In addition, plasma series resonance (PSR) and electron bounce resonance (EBR) heating also come into play as a result of geometrical asymmetry as well as EAE. In this study, a dual frequency CCRF plasma has been studied in which the dual frequency CCRF has been coupled to the lumped circuit model of the plasma and the time-independent fluid model of the plasma sheath, in order to study the effect of finite geometrical asymmetry on the generation of dc-self bias and plasma heating. The dc self-bias is found to strongly depend on the ratio of the area between the electrodes. The dc self-bias is found to depend on the phase angle between the two applied voltage waveforms. The EAE and geometrical asymmetry are found to work differently in controlling the dc self-bias. It can be concluded that the phase angle between the two voltage waveforms in dual CCRF plasmas has an important role in determining the dc self-bias and may be used for controlling the plasma properties in the dual frequency CCRF plasma.

  3. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    NASA Technical Reports Server (NTRS)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  4. Capacitively coupled radio-frequency hydrogen discharges: The role of kinetics

    NASA Astrophysics Data System (ADS)

    Marques, L.; Jolly, J.; Alves, L. L.

    2007-09-01

    This paper presents a systematic characterization of capacitively coupled radio-frequency hydrogen discharges, produced within a parallel plate cylindrical setup at different rf applied voltages (Vrf=50-600V), frequencies (f=13.56-40.68MHz), and pressures (p=0.2-1torr). A two-dimensional, time-dependent fluid model for charged particle transport is self-consistently solved coupled to a homogeneous kinetic model for hydrogen, including vibrationally excited molecular species and electronically excited atomic species. Numerical simulations are compared with experimental measurements of various plasma parameters. A good quantitative agreement is found between simulations and experiment for the coupled electrical power and the plasma potential. The model underestimates the values of the electron density, the self-bias potential, and the H(n =1) atom density with respect to measurements, but agrees with experiment when predicting that all these parameters increase with either Vrf, f, or p. The dissociation degree is about 10-3 for the work conditions considered. Simulations adopt a wall recombination probability for H atoms that was experimentally measured, thus accounting for surface modification with discharge operating conditions. Results show the key role played by the atomic wall recombination mechanism in plasma description.

  5. Fiber Grating Coupled Light Source Capable of Tunable, Single Frequency Operation

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A. (Inventor); Duerksen, Gary L. (Inventor)

    2001-01-01

    Fiber Bragg grating coupled light sources can achieve tunable single-frequency (single axial and lateral spatial mode) operation by correcting for a quadratic phase variation in the lateral dimension using an aperture stop. The output of a quasi-monochromatic light source such as a Fabry Perot laser diode is astigmatic. As a consequence of the astigmatism, coupling geometries that accommodate the transverse numerical aperture of the laser are defocused in the lateral dimension, even for apsherical optics. The mismatch produces the quadratic phase variation in the feedback along the lateral axis at the facet of the laser that excites lateral modes of higher order than the TM(sub 00). Because the instability entails excitation of higher order lateral submodes, single frequency operation also is accomplished by using fiber Bragg gratings whose bandwidth is narrower than the submode spacing. This technique is particularly pertinent to the use of lensed fiber gratings in lieu of discrete coupling optics. Stable device operation requires overall phase match between the fed-back signal and the laser output. The fiber Bragg grating acts as a phase-preserving mirror when the Bragg condition is met precisely. The phase-match condition is maintained throughout the fiber tuning range by matching the Fabry-Perot axial mode wavelength to the passband center wavelength of the Bragg grating.

  6. Tailoring alphabetical metamaterials in optical frequency: plasmonic coupling, dispersion, and sensing.

    PubMed

    Zhang, Jun; Cao, Cuong; Xu, Xinlong; Liow, Chihao; Li, Shuzhou; Tan, Pingheng; Xiong, Qihua

    2014-04-22

    Tailoring optical properties of artificial metamaterials, whose optical properties go beyond the limitations of conventional and naturally occurring materials, is of importance in fundamental research and has led to many important applications such as security imaging, invisible cloak, negative refraction, ultrasensitive sensing, and transformable and switchable optics. Herein, by precisely controlling the size, symmetry, and topology of alphabetical metamaterials with U, S, Y, H, U-bar, and V shapes, we have obtained highly tunable optical response covering visible-to-infrared (vis-NIR) optical frequency. In addition, we show a detailed study on the physical origin of resonance modes, plasmonic coupling, the dispersion of resonance modes, and the possibility of negative refraction. We have found that all the electronic and magnetic modes follow the dispersion of surface plasmon polaritons; thus, essentially they are electronic- and magnetic-surface-plasmon-polaritons-like (ESPP-like and MSPP-like) modes resulted from diffraction coupling between localized surface plasmon and freely propagating light. On the basis of the fill factor and formula of magnetism permeability, we predict that the alphabetical metamaterials should show the negative refraction capability in visible optical frequency. Furthermore, we have demonstrated the specific ultrasensitive surface enhanced Raman spectroscopy (SERS) sensing of monolayer molecules and femtomolar food contaminants by tuning their resonance to match the laser wavelength, or by tuning the laser wavelength to match the plasmon resonance of metamaterials. Our tunable alphabetical metamaterials provide a generic platform to study the electromagnetic properties of metamaterials and explore the novel applications in optical frequency.

  7. Coupled rotor-fuselage vibration reduction with multiple frequency blade pitch control

    NASA Technical Reports Server (NTRS)

    Papavassiliou, I.; Friedmann, P. P.; Venkatesan, C.

    1991-01-01

    A nonlinear coupled rotor/flexible fuselage analysis has been developed and used to study the effects of higher harmonic blade pitch control on the vibratory hub loads and fuselage acceleration levels. Previous results, obtained with this model have shown that conventional higher harmonic control (HHC) inputs aimed at hub shear reduction cause an increase in the fuselage accelerations and vice-versa. It was also found that for simultaneous reduction of hub shears and fuselage accelerations, a pitch input representing a combination of two higher harmonic components of different frequencies was needed. Subsequently, it was found that this input could not be implemented through a conventional swashplate. This paper corrects a mistake originally made in the representation of the multiple frequency pitch input and shows that such a pitch input can be only implemented in the rotating reference frame. A rigorous mathematical solution is found, for the pitch input in the rotating reference frame, which produces simultaneous reduction of hub shears and fuselage acceleration. New insight on vibration reduction in coupled rotor/fuselage systems is obtained from the sensitivity of hub shears to the frequency and amplitude of the open loop HHC signal in the rotating reference frame. Finally the role of fuselage flexibility in this class of problems is determined.

  8. Tunable electromagnetically induced transparency at terahertz frequencies in coupled graphene metamaterial

    NASA Astrophysics Data System (ADS)

    Ding, Guo-Wen; Liu, Shao-Bin; Zhang, Hai-Feng; Kong, Xiang-Kun; Li, Hai-Ming; Li, Bing-Xiang; Liu, Si-Yuan; Li, Hai

    2015-11-01

    A graphene-based metamaterial with tunable electromagnetically induced transparency (EIT)-like transmission is numerically studied in this paper. The proposed structure consists of a graphene layer composed of coupled cut-wire pairs printed on a substrate. The simulation confirms that an EIT-like transparency window can be observed due to indirect coupling in a terahertz frequency range. More importantly, the peak frequency of the transmission window can be dynamically controlled over a broad frequency range by varying the Fermi energy levels of the graphene layer through controlling the electrostatic gating. The proposed metamaterial structure offers an additional opportunity to design novel applications such as switches or modulators. Project supported by the National Natural Science Foundation of China (Grant No. 61307052), the Youth Funding for Science & Technology Innovation in Nanjing University of Aeronautics and Astronautics, China (Grant No. NS2014039), the Chinese Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20123218110017), the Innovation Program for Graduate Education of Jiangsu Province, China (Grant Nos. KYLX_0272, CXZZ13_0166, and CXLX13_155), the Open Research Program in National State Key Laboratory of Millimeter Waves of China (Grant No. K201609), and the Fundamental Research Funds for the Central Universities of China (Grant No. kfjj20150407).

  9. Breaking the symmetry of forward-backward light emission with localized and collective magnetoelectric resonances in arrays of pyramid-shaped aluminum nanoparticles.

    PubMed

    Rodriguez, S R K; Bernal Arango, F; Steinbusch, T P; Verschuuren, M A; Koenderink, A F; Gómez Rivas, J

    2014-12-12

    We propose aluminum nanopyramids (ANPs) as magnetoelectric optical antennas to tailor the forward versus backward luminescence spectrum. We present light extinction and emission experiments for an ANP array wherein magnetoelectric localized resonances couple to in-plane diffracted orders. This coupling leads to spectrally sharp collective resonances. Luminescent molecules drive both localized and collective resonances, and we experimentally demonstrate an unconventional forward versus backward luminescence spectrum. Through analytical calculations, we show that the magnetic, magnetoelectric, and quadrupolar moments of ANPs—which lie at the origin of the observed effects—are enhanced by their tapering and height. Full-wave simulations show that localized and delocalized magnetic surface waves, with an excitation strength depending on the plane wave direction, direct the forward versus backward emitted intensity.

  10. Cavity mode frequencies and strong optomechanical coupling in two-membrane cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Li, Jie; Xuereb, André; Malossi, Nicola; Vitali, David

    2016-08-01

    We study the cavity mode frequencies of a Fabry-Pérot cavity containing two vibrating dielectric membranes. We derive the equations for the mode resonances and provide approximate analytical solutions for them as a function of the membrane positions, which act as an excellent approximation when the relative and center-of-mass position of the two membranes are much smaller than the cavity length. With these analytical solutions, one finds that extremely large optomechanical coupling of the membrane relative motion can be achieved in the limit of highly reflective membranes when the two membranes are placed very close to a resonance of the inner cavity formed by them. We also study the cavity finesse of the system and verify that, under the conditions of large coupling, it is not appreciably affected by the presence of the two membranes. The achievable large values of the ratio between the optomechanical coupling and the cavity decay rate, g/κ , make this two-membrane system the simplest promising platform for implementing cavity optomechanics in the strong coupling regime.

  11. Active loaded plasmonic antennas at terahertz frequencies: Optical control of their capacitive-inductive coupling

    NASA Astrophysics Data System (ADS)

    Georgiou, G.; Tserkezis, C.; Schaafsma, M. C.; Aizpurua, J.; Gómez Rivas, J.

    2015-03-01

    We demonstrate the photogeneration of loaded dipole plasmonic antennas resonating at THz frequencies. This is achieved by the patterned optical illumination of a semiconductor surface using a spatial light modulator. Our experimental results indicate the existence of capacitive and inductive coupling of localized surface plasmon polaritons. By varying the load in the antenna gap we are able to switch between both coupling regimes. Furthermore, we determine experimentally the effective impedance of the antenna load and verify that this load can be effectively expressed as a LC resonance formed by a THz inductor and capacitor connected in a parallel circuit configuration. These findings are theoretically supported by full electrodynamic calculations and by simple concepts of lumped circuit theory. Our results open new possibilities for the design of active THz circuits for optoelectronic devices.

  12. Numerical evaluation of aperture coupling in resonant cavities and frequency perturbation analysis

    NASA Astrophysics Data System (ADS)

    Dash, R.; Nayak, B.; Sharma, A.; Mittal, K. C.

    2014-01-01

    This paper presents a general formulation for numerical evaluation of the coupling between two identical resonant cavities by a small elliptical aperture in a plane common wall of arbitrary thickness. It is organized into two parts. In the first one we discuss the aperture coupling that is expressed in terms of electric and magnetic dipole moments and polarizabilities using Carlson symmetric elliptical integrals. Carlson integrals have been numerically evaluated and under zero thickness approximation, the results match with the complete elliptical integrals of first and second kind. It is found that with zero wall thickness, the results obtained are the same as those of Bethe and Collin for an elliptical and circular aperture of zero thickness. In the second part, Slater's perturbation method is applied to find the frequency changes due to apertures of finite thickness on the cavity wall.

  13. Multi-ferroic and magnetoelectric materials and interfaces.

    PubMed

    Velev, J P; Jaswal, S S; Tsymbal, E Y

    2011-08-13

    The existence of multiple ferroic orders in the same material and the coupling between them have been known for decades. However, these phenomena have mostly remained the theoretical domain owing to the fact that in single-phase materials such couplings are rare and weak. This situation has changed dramatically recently for at least two reasons: first, advances in materials fabrication have made it possible to manufacture these materials in structures of lower dimensionality, such as thin films or wires, or in compound structures such as laminates and epitaxial-layered heterostructures. In these designed materials, new degrees of freedom are accessible in which the coupling between ferroic orders can be greatly enhanced. Second, the miniaturization trend in conventional electronics is approaching the limits beyond which the reduction of the electronic element is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, without further size reduction, is to use multi-functional materials that would enable new device capabilities. Here, we review the field of multi-ferroic (MF) and magnetoelectric (ME) materials, putting the emphasis on electronic effects at ME interfaces and MF tunnel junctions. PMID:21727115

  14. Towards spatial frequency domain optical imaging of neurovascular coupling in a mouse model of Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Lin, Alexander J.; Konecky, Soren D.; Rice, Tyler B.; Green, Kim N.; Choi, Bernard; Durkin, Anthony J.; Tromberg, Bruce J.

    2012-02-01

    Early neurovascular coupling (NVC) changes in Alzheimer's disease can potentially provide imaging biomarkers to assist with diagnosis and treatment. Previous efforts to quantify NVC with intrinsic signal imaging have required assumptions of baseline optical pathlength to calculate changes in oxy- and deoxy-hemoglobin concentrations during evoked stimuli. In this work, we present an economical spatial frequency domain imaging (SFDI) platform utilizing a commercially available LED projector, camera, and off-the-shelf optical components suitable for imaging dynamic optical properties. The fast acquisition platform described in this work is validated on silicone phantoms and demonstrated in neuroimaging of a mouse model.

  15. Frequency tuning, nonlinearities and mode coupling in circular mechanical graphene resonators.

    PubMed

    Eriksson, A M; Midtvedt, D; Croy, A; Isacsson, A

    2013-10-01

    We study circular nanomechanical graphene resonators by means of continuum elasticity theory, treating them as membranes. We derive dynamic equations for the flexural mode amplitudes. Due to the geometrical nonlinearity the mode dynamics can be modeled by coupled Duffing equations. By solving the Airy stress problem we obtain analytic expressions for the eigenfrequencies and nonlinear coefficients as functions of the radius, suspension height, initial tension, back-gate voltage and elastic constants, which we compare with finite element simulations. Using perturbation theory, we show that it is necessary to include the effects of the non-uniform stress distribution for finite deflections. This correctly reproduces the spectrum and frequency tuning of the resonator, including frequency crossings. PMID:24008430

  16. Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping

    SciTech Connect

    Coffer, J.; Encalada, N.; Huang, M.; Camparo, J.

    2014-10-28

    We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

  17. High-Frequency Coupling to Cables for Plane Wave and Random Wave Conditions

    NASA Astrophysics Data System (ADS)

    Pissoort, D.; Vanhee, F.; Boesman, B.; Catrysse, J.; Vandenbosch, G.; Gielen, G.

    2012-05-01

    In this paper, the high-frequency coupling from electromagnetic fields to cables is studied and this under (i) plane-wave conditions representing a susceptibility test in a semi-anechoic room and (ii) random wave conditions representing a more realistic environment with many reflections. Two set-ups are considered. First, a s imple wire above an infinite ground plane. Second, a more realistic set-up representing a desktop device with attached cables whose layout is according to EN 55016-2-3:2006 [1]. It is shown that for frequencies above 1 GHz the induced (worst-case) current at the side of the device under test can differ significantly between plane-wave and random wave conditions. Moreover, the random wave condition does necessarily not lead to the highest induced currents.

  18. Broadening the Frequency Bandwidth of Piezoelectric Energy Harvesters Using Coupled Linear Resonators

    NASA Astrophysics Data System (ADS)

    Sadeqi, Soheil

    The desire to reduce power consumption of current integrated circuits has led design engineers to focus on harvesting energy from free ambient sources such as vibrations. The energy harvested this way can eliminate the need for battery replacement, particularly, in low-energy remote sensing and wireless devices. Currently, most vibration-based energy harvesters are designed as linear resonators, therefore, they have a narrow resonance frequency. The optimal performance of such harvesters is achieved only when their resonance frequency is matched with the ambient excitation. In practice, however, a slight shift of the excitation frequency will cause a dramatic reduction in their performance. In the majority of cases, the ambient vibrations are totally random with their energy distributed over a wide frequency spectrum. Thus, developing techniques to extend the bandwidth of vibration-based energy harvesters has become an important field of research in energy harvesting systems. This thesis first reviews the broadband vibration-based energy harvesting techniques currently known in some detail with regard to their merits and applicability under different circumstances. After that, the design, fabrication, modeling and characterization of three new piezoelectric-based energy harvesting mechanism, built typically for rotary motion applications, is discussed. A step-by-step procedure is followed in order to broaden the bandwidth of such energy harvesters by introducing a coupled spring-mass system attached to a PZT beam undergoing rotary motion. It is shown that the new strategies can indeed give rise to a wide-band frequency response making it possible to fine-tune their dynamical response. The numerical results are shown to be in good agreement with the experimental data as far as the frequency response is concerned.

  19. Giant strain control of magnetoelectric effect in Ta|Fe|MgO.

    PubMed

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 10(3) fJV(-1)m(-1). We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d-Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d-O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

  20. Giant strain control of magnetoelectric effect in Ta|Fe|MgO

    NASA Astrophysics Data System (ADS)

    Odkhuu, Dorj

    2016-09-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 103 fJV‑1m‑1. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d–Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d–O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments.

  1. Giant strain control of magnetoelectric effect in Ta|Fe|MgO

    PubMed Central

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 103 fJV−1m−1. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d–Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d–O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

  2. Incommensurate crystal supercell and polarization flop observed in the magnetoelectric ilmenite MnTiO3

    DOE PAGESBeta

    Silverstein, Harlyn J.; Skoropata, Elizabeth; Sarte, Paul M.; Mauws, Cole; Aczel, Adam A.; Choi, Eun Sang; van Lierop, Johan; Wiebe, Christopher R.; Zhou, Haidong

    2016-02-19

    In the last few years the magnetoelectric behavior of MnTiO3 has been observed even though its been studied for many decades. We use neutron scattering on two separately grown single crystals and two powder samples to show the presence of a supercell that breaks R (3) over bar symmetry. We also present the temperature and field dependence of the dielectric constant and pyroelectric current and show evidence of nonzero off-diagonal magnetoelectric tensor elements (forbidden by R (3) over bar symmetry) followed by a polarization flop accompanying the spin flop transition at mu H-0(SF) = 6.5T. Mossbauer spectroscopy on MnTiO3 gentlymore » doped with Fe-57 was used to help shed light on the impact of the supercell on the observed behavior. Moreover, the full supercell structure could not be solved at this time due to a lack of visible reflections, the full scope of the results presented here suggest that the role of local spin-lattice coupling in the magnetoelectric properties of MnTiO3 is likely more important than previously thought.« less

  3. Emissive Probe Measurements in a Dual-Frequency-Confined Capacitively-Coupled-Plasma System

    NASA Astrophysics Data System (ADS)

    Linnane, Shane; Ellingboe, Albert R.

    2002-10-01

    Dual frequency confined capacitively coupled plasmas (DFC-CCP) are increasingly used in semiconductor manufacturing for dielectric etching, allowing greater (and independent) control of ion energies and ion flux on the etched substrate. The powered electrode is driven with the summation of 27MHz and 2MHz sinusoidal voltages, while the other electrode is grounded. The electrode areas are similar in size, giving an electrode aspect ratio less than 2. Because of this low aspect ratio, there are large oscillations in the plasma potential. The expectation is for sinusoidal oscillations at the higher driving frequency, due to capacitive sheaths, while a rectified oscillation is expected at the lower driving frequency.(E. Kawamura, V. Vahedi, M. A. Lieberman and C. K. Birdsall, Plasma Sources Sci. Technology. 8 (1999) R45-R64 Work Supported by EURATOM.) Measurements of rf oscillation in the plasma potential taken with a floating emissive probe will be presented. The emissive probe and circuitry allows direct realtime measurement of plasma potential oscillation at both driving frequencies and the harmonics of each, thus allowing measurement of the actual potential on the driven electrode and ion energy incident on grounded electrode.

  4. Spectroscopy diagnostic of dual-frequency capacitively coupled CHF{sub 3}/Ar plasma

    SciTech Connect

    Liu, Wen-Yao; Du, Yong-Quan; Liu, Yong-Xin; Liu, Jia; Zhao, Tian-Liang; Wang, You-Nian; Xu, Yong; Li, Xiao-Song; Zhu, Ai-Min

    2013-11-15

    A combined spectroscopic method of absorption, actinometry, and relative optical emission intensity is employed to determine the absolute CF{sub 2} density, the relative F and H densities, H atom excitation temperature and the electron density in dual-frequency (60/2 MHz) capacitively coupled CHF{sub 3}/Ar plasmas. The effects of different control parameters, such as high-frequency (HF) power, low-frequency (LF) power, gas pressure, gap length and content of CHF{sub 3}, on the concentration of radical CF{sub 2}, F, and H and excitation temperature are discussed, respectively. It is found that the concentration of CF{sub 2} is strongly dependent on the HF power, operating pressure and the proportion of CHF{sub 3} in feed gas, while it is almost independent of the LF power and the gap length. A higher concentration ratio of F to CF{sub 2} could be obtained in dual-frequency discharge case. Finally, the generation and decay mechanisms of CF{sub 2} and F were also discussed.

  5. Room temperature multiferroic properties and magnetoelectric coupling in Sm and Ni substituted Bi{sub 4−x}Sm{sub x}Ti{sub 3−x}Ni{sub x}O{sub 12±δ} (x = 0, 0.02, 0.05, 0.07) ceramics

    SciTech Connect

    Paul, Joginder Bhardwaj, Sumit; Sharma, K. K.; Kotnala, R. K.; Kumar, Ravi

    2014-05-28

    Lead free multiferroic Bi{sub 4−x}Sm{sub x}Ti{sub 3−x}Ni{sub x}O{sub 12±δ} (x = 0.02, 0.05, and 0.07) samples have been synthesized by conventional solid state route. X-ray diffraction analysis reveals single phase up to x = 0.07, and a secondary phase appears at x > 0.07. Raman spectroscopy confirms the local distortions in the crystal. Field emission scanning electron microscopy shows plate like grains. Substitution has increased the orthorhombic distortion, grain size, and hence the ferroelectric transition temperature (T{sub c}). A significant reduction in the values of dielectric constant (ε′) and loss tangent (tan δ) has been observed with the increase of Sm and Ni ions. The increase in dc resistivity at room temperature has been found with substitution. Enhancement in the values of remnant polarization (2P{sub r}) and magnetization (2M{sub r}) is observed. Magnetoelectric coupling coefficient (α) values of 0.60 mV/cm/Oe are achieved in Bi{sub 4−x}Sm{sub x}Ti{sub 3−x}Ni{sub x}O{sub 12±δ} ceramic samples. Hence, we have successfully converted the ferroelectric Bi{sub 4}Ti{sub 3}O{sub 12} into a multiferroic, which is a new lead free multiferroic material, can be useful for future electromagnetic devices.

  6. Simulation and evaluation of dielectric and magnetoelectric properties of diphasic and layered ferroic composites

    NASA Astrophysics Data System (ADS)

    Wang, Hsiao-Yuan

    The present demand in the development of tunable devices and meta-materials require better understanding of the composite systems. Ferroelectric based composites with solubility or impurities doped interstitially satisfied the specific condition necessary for applications of e.g. frequency, bias, temperature, etc. On the other hand, many composite materials using coupling phenomena have been reported to have their effective properties surpassing the natural materials. The improvement of the properties of composite materials lies on the better understanding of their coupling effects. Conventional science tries to derive theories based on observation and materials characterizations. Taken advantage of the rapid growing computer technology, one used to say "impossible to be measured" or "impossible to see" can now be virtually characterized and visualized by simulation models. In this thesis, computer models of dielectric properties, piezoelectricity, magnetostriction and magnetoelectricity were constructed and verified. And subsequently the materials of interest were simulated and discussed. First, a three dimensional finite element model on dielectric properties of two phases or materials mixture was constructed. The effective permittivity and tan(delta) of Ba0.5Sr0.5 TiO3:MgO composite were simulated and compared with the experimental results. Structural design parameters concepts such as layers stacking, geometry effect, and effect of size of inclusion were visualized and then discussed. Subsequently, dielectric properties of Ba0.5Sr0.5TiO 3:MgO composite were examined changing their volume fraction using Monte Carlo simulation. The type of connectivity of the Ba0.5Sr 0.5TiO3:MgO composite was also discussed. On the other hand, finite element method with Monte Carlo simulation was conducted for the composition (x)Pb0.2Sr0.8TiO3:(1-x)MgO from x=0 to 1 in the paraelectric phase (from -50°C to 200°C), and the results were computed and compared with the experimental

  7. Suspended Rectangular/Circular Patch Antennas With Electromagnetically Coupled Inverted Microstrip Feed for Dual Polarization/Frequency

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.

    2000-01-01

    The paper demonstrates suspended rectangular and circular patch antennas with electromagnetically coupled inverted microstrip feed for linear as well as dual linear polarization/frequency applications. The measured results include the return loss and the impedance bandwidth of the antennas.

  8. Suspended Rectangular/Circular Patch Antennas with Electromagnetically Coupled Inverted Microstrip Feed for Dual Polarization/Frequency

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.

    2000-01-01

    The paper demonstrates suspended rectangular and circular patch antennas with electromagnetically coupled inverted microstrip feed for linear as well as dual linear polarization/frequency applications. The measured results include the return loss and the impedance bandwidth of the antennas.

  9. High-Frequency Focused Water-Coupled Ultrasound Used for Three-Dimensional Surface Depression Profiling

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Whalen, Mike F.; Hendricks, J. Lynne; Bodis, James R.

    2001-01-01

    To interface with other solids, many surfaces are engineered via methods such as plating, coating, and machining to produce a functional surface ensuring successful end products. In addition, subsurface properties such as hardness, residual stress, deformation, chemical composition, and microstructure are often linked to surface characteristics. Surface topography, therefore, contains the signatures of the surface and possibly links to volumetric properties, and as a result serves as a vital link between surface design, manufacturing, and performance. Hence, surface topography can be used to diagnose, monitor, and control fabrication methods. At the NASA Glenn Research Center, the measurement of surface topography is important in developing high-temperature structural materials and for profiling the surface changes of materials during microgravity combustion experiments. A prior study demonstrated that focused air-coupled ultrasound at 1 MHz could profile surfaces with a 25-m depth resolution and a 400-m lateral resolution over a 1.4-mm depth range. In this work, we address the question of whether higher frequency focused water-coupled ultrasound can improve on these specifications. To this end, we employed 10- and 25-MHz focused ultrasonic transducers in the water-coupled mode. The surface profile results seen in this investigation for 25-MHz water-coupled ultrasound, in comparison to those for 1-MHz air-coupled ultrasound, represent an 8 times improvement in depth resolution (3 vs. 25 m seen in practice), an improvement of at least 2 times in lateral resolution (180 vs. 400 m calculated and observed in practice), and an improvement in vertical depth range of 4 times (calculated).

  10. Modelling Tropical Cyclones-Ocean interactions: the role of the Atmophere - Ocean coupling frequency

    NASA Astrophysics Data System (ADS)

    Scoccimarro, Enrico; Fogli, Pier Giuseppe; Gualdi, Silvio; Masina, Simona; Navarra, Antonio

    2016-04-01

    The interaction between Tropical Cyclones (TCs) and ocean is a major mechanism responsible for energy exchange between the atmosphere and the ocean. TCs affect the thermal and dynamical structure of the ocean, but the magnitude of the impact is still uncertain. Very few CMIP5 models demonstrated ability in representing TCs, mainly due to their horizontal resolution. We aim to improve TCs representation in next CMIPs experiments through the new CMCC-CM2VHR General Circulation Model, having a horizontal resolution of 1/4 degree in both atmospheric and ocean components. The model is capable to represent realistically TCs up to Cat-5 Typhoons. A good representation of the TC-Ocean interaction strongly depends on the coupling frequency between the atmospheric and the ocean components. In this work, we found that a better representation of the negative Sea Surface Temperature - TC induced feedback, through a high (hourly) coupling frequency, ensures the reduction of the TC induced Power Dissipation Index (PDI) bias of one order of magnitude. In addition, a cat-5 storm case study is deeply investigated also in terms of TC effects on the deep ocean.

  11. Simulation and Measurement of Medium-Frequency Signals Coupling From a Line to a Loop Antenna

    PubMed Central

    Damiano, Nicholas W.; Li, Jingcheng; Zhou, Chenming; Brocker, Donovan E.; Qin, Yifeng; Werner, Douglas H.; Werner, Pingjuan L.

    2016-01-01

    The underground-mining environment can affect radio-signal propagation in various ways. Understanding these effects is especially critical in evaluating communications systems used during normal mining operations and during mine emergencies. One of these types of communications systems relies on medium-frequency (MF) radio frequencies. This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating MF coupling between a transmission line (TL) and a loop antenna in an underground coal mine. Two different types of measurements were completed: 1) line-current distribution and 2) line-to-antenna coupling. Measurements were taken underground in an experimental coal mine and on a specially designed surface test area. The results of these tests are characterized by current along a TL and voltage induced in the loop from a line. This paper concludes with a discussion of issues for MF TLs. These include electromagnetic fields at the ends of the TL, connection of the ends of the TL, the effect of other conductors underground, and the proximity of coal or earth. These results could help operators by providing examples of these challenges that may be experienced underground and a method by which to measure voltage induced by a line. PMID:27784954

  12. Altered cross-frequency coupling in resting-state MEG after mild traumatic brain injury.

    PubMed

    Antonakakis, Marios; Dimitriadis, Stavros I; Zervakis, Michalis; Micheloyannis, Sifis; Rezaie, Roozbeh; Babajani-Feremi, Abbas; Zouridakis, George; Papanicolaou, Andrew C

    2016-04-01

    Cross-frequency coupling (CFC) is thought to represent a basic mechanism of functional integration of neural networks across distant brain regions. In this study, we analyzed CFC profiles from resting state Magnetoencephalographic (MEG) recordings obtained from 30 mild traumatic brain injury (mTBI) patients and 50 controls. We used mutual information (MI) to quantify the phase-to-amplitude coupling (PAC) of activity among the recording sensors in six nonoverlapping frequency bands. After forming the CFC-based functional connectivity graphs, we employed a tensor representation and tensor subspace analysis to identify the optimal set of features for subject classification as mTBI or control. Our results showed that controls formed a dense network of stronger local and global connections indicating higher functional integration compared to mTBI patients. Furthermore, mTBI patients could be separated from controls with more than 90% classification accuracy. These findings indicate that analysis of brain networks computed from resting-state MEG with PAC and tensorial representation of connectivity profiles may provide a valuable biomarker for the diagnosis of mTBI.

  13. The role of coupled resistance-compliance in upper tracheobronchial airways under high frequency oscillatory ventilation.

    PubMed

    Alzahrany, Mohammed; Banerjee, Arindam; Salzman, Gary

    2014-12-01

    A large eddy simulation (LES) based computational fluid dynamics (CFD) study was conducted to investigate lung lobar ventilation and gas exchange under high frequency oscillatory ventilation conditions. Time-dependent pressure coupled with the airways resistance and compliance (R&C) were imposed as boundary conditions (BCs) in the upper tracheobronchial tree of patient-specific lung geometry. The flow distribution in the left and right lungs demonstrated significant variations compared to the case in which traditional BCs based on mass flow rate fractions was used and is in agreement with the in vivo data available in the literature. The gas transport due to the pendelluft mechanism was captured in the different lung lobes and units. The computed pendelluft elapsed time was consistent with available physiological data. In contrast to in vivo studies, our simulations were able to predict the volume associated with the pendelluft elapsed time at different frequencies. Significant differences in coaxial counter flow and flow structures were observed between different BCs. The consistency of the results with the physiological in vivo data indicates that computations with coupled R&C BCs provide a suitable alternative tool for understanding the gas transport, diagnosing lung pathway disease severity, and optimizing ventilation management techniques. PMID:25248986

  14. Microwave Magnetoelectric Effects in Single Crystal YIG/PMN-PT Bilayers

    NASA Astrophysics Data System (ADS)

    Shastry, S.; Srinivasan, G.; Mantese, J. V.

    2004-03-01

    Layered magnetostrictive/piezoelectric structures are multifunctional due to mechanical force mediated electromagnetic coupling. This study is concerned with microwave magnetoelectric (ME) interactions in layered ferrite-piezoelectric oxides. Ferromagnetic resonance (FMR) is a powerful tool for such studies. An electric field E applied to the composite produces a mechanical deformation in PZT that in turn is coupled to the ferrite, resulting in a shift in the resonance field. Information on the nature of high frequency ME coupling could therefore be obtained from data on field shift vs E. Since the measurement accuracy depends very much on the FMR line width, bilayers consisting of single crystal or epitaxial low-loss ferrites are ideal for the investigations. Studies were performed at 9.4 GHz on bilayers consisting of (100), (110) or (111) epitaxial yttrium iron garnet (YIG) films (1-130 micron) and (100) lead magnesium niobate-lead titanate (PMN-PT). The samples were positioned outside a hole at the bottom or side of a TE102-reflection type cavity. Resonance absorption vs bias magnetic field H were obtained as a function of E = 0-8 kV/cm for both in-plane and out-of-plane H. Important results are as follows. (i) The ME coupling is stronger for H perpendicular to the bilayer than for in-plane H. (ii) The coupling strength is maximum for E and H along <111> in YIG. (iii) The ME constant varies from a maximum of 6 Oe cm/kV for bilayers with 4 micron YIG to a minimum of 3 Oe cm/kV for 110 micron YIG. (iv) The variation of resonance field shift with the volume ratio for the two phases is in agreement with theory [1,2]. 1. M. I. Bichurin, I. A. Kornev, V. M. Petrov, A. S. Tatarenko, Yu. V. Kiliba, and G. Srinivasan, Phys. Rev. B 64, 094409 (2001). 2. M. I. Bichurin, V. M. Petrov, Yu. V. Kiliba, G. Srinivasan, Phys. Rev. B 66, 134404 (2002). This work was supported by a grant from the National Science Foundation (DMR-0322254)

  15. Tailored voltage waveform capacitively coupled plasmas in electronegative gases: frequency dependence of asymmetry effects

    NASA Astrophysics Data System (ADS)

    Schüngel, E.; Korolov, I.; Bruneau, B.; Derzsi, A.; Johnson, E.; O’Connell, D.; Gans, T.; Booth, J.-P.; Donkó, Z.; Schulze, J.

    2016-07-01

    Capacitively coupled radio frequency plasmas operated in an electronegative gas (CF4) and driven by voltage waveforms composed of four consecutive harmonics are investigated for different fundamental driving frequencies using PIC/MCC simulations and an analytical model. As has been observed previously for electropositive gases, the application of peak-shaped waveforms (that are characterized by a strong amplitude asymmetry) results in the development of a DC self-bias due to the electrical asymmetry effect (EAE), which increases the energy of ions arriving at the powered electrode. In contrast to the electropositive case (Korolov et al 2012 J. Phys. D: Appl. Phys. 45 465202) the absolute value of the DC self-bias is found to increase as the fundamental frequency is reduced in this electronegative discharge, providing an increased range over which the DC self-bias can be controlled. The analytical model reveals that this increased DC self-bias is caused by changes in the spatial profile and the mean value of the net charge density in the grounded electrode sheath. The spatio-temporally resolved simulation data show that as the frequency is reduced the grounded electrode sheath region becomes electronegative. The presence of negative ions in this sheath leads to very different dynamics of the power absorption of electrons, which in turn enhances the local electronegativity and plasma density via ionization and attachment processes. The ion flux to the grounded electrode (where the ion energy is lowest) can be up to twice that to the powered electrode. At the same time, while the mean ion energies at both electrodes are quite different, their ratio remains approximately constant for all base frequencies studied here.

  16. Fluid modelling of capacitively coupled radio-frequency discharges: a review

    NASA Astrophysics Data System (ADS)

    Alves, L. L.; Marques, L.

    2012-12-01

    This paper reviews the basis and the successes with the fluid modelling of capacitively coupled radio-frequency discharges, produced within a parallel-plate cylindrical setup at (single) 13.56-80 MHz frequencies, 6 × 10-2-6 Torr pressures and 50-1000 V rf-applied voltages, in SiH4-H2, H2 and N2. The two-dimensional, time-dependent model used in the simulations accounts for the production, transport and destruction of the charged particles (via the electron and ion continuity and momentum-transfer equations, and the electron mean energy transport equations), and of the excited species and/or radicals (via their rate balance equations, including very complete kinetic descriptions with several collisional-radiative production/destruction mechanisms, coupled to the two-term electron Boltzmann equation), accounting also for the self-consistent development of the rf field (via the solution to Poisson's equation). The charged particle transport equations are solved with and without corrective flux terms (due to inertia and friction effects), whose influence on results is discussed. In the case of silane-hydrogen mixtures, the model further includes a phenomenological description of the plasma-substrate interaction to calculate the deposition rate of a-Si : H thin films. In general, the model gives good predictions for the self-bias voltage, the coupled power and the intensities of radiative emission transitions (both average and spatially resolved), underestimating the electron density by a factor of 3-4.

  17. Cross-frequency coupling in deep brain structures upon processing the painful sensory inputs.

    PubMed

    Liu, C C; Chien, J H; Kim, J H; Chuang, Y F; Cheng, D T; Anderson, W S; Lenz, F A

    2015-09-10

    Cross-frequency coupling has been shown to be functionally significant in cortical information processing, potentially serving as a mechanism for integrating functionally relevant regions in the brain. In this study, we evaluate the hypothesis that pain-related gamma oscillatory responses are coupled with low-frequency oscillations in the frontal lobe, amygdala and hippocampus, areas known to have roles in pain processing. We delivered painful laser pulses to random locations on the dorsal hand of five patients with uncontrolled epilepsy requiring depth electrode implantation for seizure monitoring. Two blocks of 40 laser stimulations were delivered to each subject and the pain-intensity was controlled at five in a 0-10 scale by adjusting the energy level of the laser pulses. Local-field-potentials (LFPs) were recorded through bilaterally implanted depth electrode contacts to study the oscillatory responses upon processing the painful laser stimulations. Our results show that painful laser stimulations enhanced low-gamma (LH, 40-70 Hz) and high-gamma (HG, 70-110 Hz) oscillatory responses in the amygdala and hippocampal regions on the right hemisphere and these gamma responses were significantly coupled with the phases of theta (4-7 Hz) and alpha (8-1 2 Hz) rhythms during pain processing. Given the roles of these deep brain structures in emotion, these findings suggest that the oscillatory responses in these regions may play a role in integrating the affective component of pain, which may contribute to our understanding of the mechanisms underlying the affective information processing in humans.

  18. Tropical Cyclones-Ocean Interactions in a High Resolution GCM: the Role of the Coupling Frequency

    NASA Astrophysics Data System (ADS)

    Scoccimarro, E.; Fogli, P. G.; Masina, S.; Gualdi, S.; Navarra, A.

    2015-12-01

    The interaction between Tropical Cyclones (TCs) and ocean is a major mechanism responsible for energy exchange between the atmosphere and the ocean. TCs affect the thermal and dynamical structure of the ocean, but the magnitude of the impact is still uncertain. Very few CMIP5 models demonstrated ability in representing TCs, mainly due to their horizontal resolution. We aim to improve TCs representation in next CMIPs experiments through the new CMCC-CESM-NEMO General Circulation Model, having a horizontal resolution of ¼ degree in both atmospheric and ocean components. The model is capable to represent realistically TCs up to Cat-4 Typhoons. The wind structure associated with TCs is responsible for two important atmosphere-ocean feedbacks: the first feedback — positive — is driven by the latent heat associated with the enhanced evaporation rate and leads to an increase of the available energy for TC. The second feedback — negative — is due to the cold water upwelling induced by the increased wind stress at the ocean surface and by the shear-induced mixing at the base of the mixed layer. The second feedback is responsible for a significant cooling of the sea surface, leading to a weakening of the cyclone intensity due to the reduction of the total heat flux into the atmosphere. Furthermore TC intensification, intensity, and lifetime strongly depend on their transitional speed. A good representation of the TC-Ocean interaction strongly depends on the coupling frequency between the atmospheric and the ocean components, especially when simulating fast moving TCs. In this work, we investigate the role of the coupling frequency in representing the two mentioned feedbacks using the new fully coupled General Circulation Model developed at CMCC.

  19. A close-coupling multi-antenna type radio frequency driven ion source

    SciTech Connect

    Oka, Y.; Shoji, T.

    2012-02-15

    A newly close coupling multi-antenna type radio frequency driven ion source is tested for the purpose of essentially improving plasma coupling on the basis of our old type ion source, which reuses a NNBI (negative ion source for neutral beam injection) ion source used in 1/5th scale of the Large Helical Device NNBI. The ion source and the antenna structure are described, and the efficient plasma production in terms of the positive ion saturation current (the current density) is studied. The source is made of a metal-walled plasma chamber which is desirable from the point of view of the structural toughness for fusion and industrial application, etc. At around 160 kW of rf input power, the ion saturation current density successfully reaches the 5 A/cm{sup 2} level with a gas pressure of 0.6-2 Pa in hydrogen for 10 ms pulse duration. The rf power efficiency of the plasma production with a close coupling configuration of the antenna is improved substantially compared to that with the previous antenna unit in the old type ion source. The power efficiency is assessed as competing with that of other types of sources.

  20. Tailoring alphabetical metamaterials in optical frequency: plasmonic coupling, dispersion, and sensing.

    PubMed

    Zhang, Jun; Cao, Cuong; Xu, Xinlong; Liow, Chihao; Li, Shuzhou; Tan, Pingheng; Xiong, Qihua

    2014-04-22

    Tailoring optical properties of artificial metamaterials, whose optical properties go beyond the limitations of conventional and naturally occurring materials, is of importance in fundamental research and has led to many important applications such as security imaging, invisible cloak, negative refraction, ultrasensitive sensing, and transformable and switchable optics. Herein, by precisely controlling the size, symmetry, and topology of alphabetical metamaterials with U, S, Y, H, U-bar, and V shapes, we have obtained highly tunable optical response covering visible-to-infrared (vis-NIR) optical frequency. In addition, we show a detailed study on the physical origin of resonance modes, plasmonic coupling, the dispersion of resonance modes, and the possibility of negative refraction. We have found that all the electronic and magnetic modes follow the dispersion of surface plasmon polaritons; thus, essentially they are electronic- and magnetic-surface-plasmon-polaritons-like (ESPP-like and MSPP-like) modes resulted from diffraction coupling between localized surface plasmon and freely propagating light. On the basis of the fill factor and formula of magnetism permeability, we predict that the alphabetical metamaterials should show the negative refraction capability in visible optical frequency. Furthermore, we have demonstrated the specific ultrasensitive surface enhanced Raman spectroscopy (SERS) sensing of monolayer molecules and femtomolar food contaminants by tuning their resonance to match the laser wavelength, or by tuning the laser wavelength to match the plasmon resonance of metamaterials. Our tunable alphabetical metamaterials provide a generic platform to study the electromagnetic properties of metamaterials and explore the novel applications in optical frequency. PMID:24670107

  1. Novel hybrid multifunctional magnetoelectric porous composite films

    NASA Astrophysics Data System (ADS)

    Martins, P.; Gonçalves, R.; Lopes, A. C.; Venkata Ramana, E.; Mendiratta, S. K.; Lanceros-Mendez, S.

    2015-12-01

    Novel multifunctional porous films have been developed by the integration of magnetic CoFe2O4 (CFO) nanoparticles into poly(vinylidene fluoride)-Trifuoroethylene (P(VDF-TrFE)), taking advantage of the synergies of the magnetostrictive filler and the piezoelectric polymer. The porous films show a piezoelectric response with an effective d33 coefficient of -22 pC/N-1, a maximum magnetization of 12 emu g-1 and a maximum magnetoelectric coefficient of 9 mV cm-1 Oe-1. In this way, a multifunctional membrane has been developed suitable for advanced applications ranging from biomedical to water treatment.

  2. Study of xCo0.8Ni0.2Fe2O4+(1-x) Pb0.99625 La0.0025Zr0.55Ti0.45O3 magnetoelectric composites

    NASA Astrophysics Data System (ADS)

    Dipti; Singh, Sangeeta; Juneja, J. K.; Raina, K. K.; Kotnala, R. K.; Prakash, Chandra

    2016-06-01

    We are reporting here, the studies of the structural, dielectric, ferroelectric and magnetic properties of magnetoelectric composites of La modified lead zirconate titanate (PLZT) and Ni modified cobalt ferrite (CNFO) with compositional formula xCo0.8Ni0.2Fe2O4+(1-x) Pb0.99625La0.0025Zr0.55Ti0.45O3 (x=0.00, 0.05, 0.10, 0.15 and 1.00 by weight) prepared by the solid state reaction method. Coexistence of both the phases in composites was confirmed by X-Ray diffraction technique. The microstructure and average grain size were determined from Scanning Electron Micrograph (SEM) in backscattered mode. Both the phases could be observed clearly. The variations of dielectric properties with frequency and temperature were also studied. P-E and M-H hysteresis measurements were carried. Magnetoelectric coupling (ME) coefficient for samples with x=0.05 and 0.10 were measured as a function of DC magnetic field. Maximum value of ME coefficient (1.2 mV/cm Oe) and piezoelectric coefficient (96 pC/N) for x=0.05 were observed.

  3. Floquet topological system based on frequency-modulated classical coupled harmonic oscillators

    NASA Astrophysics Data System (ADS)

    Salerno, Grazia; Ozawa, Tomoki; Price, Hannah M.; Carusotto, Iacopo

    2016-02-01

    We theoretically propose how to observe topological effects in a generic classical system of coupled harmonic oscillators, such as classical pendula or lumped-element electric circuits, whose oscillation frequency is modulated fast in time. Making use of Floquet theory in the high-frequency limit, we identify a regime in which the system is accurately described by a Harper-Hofstadter model where the synthetic magnetic field can be externally tuned via the phase of the frequency modulation of the different oscillators. We illustrate how the topologically protected chiral edge states, as well as the Hofstadter butterfly of bulk bands, can be observed in the driven-dissipative steady state under a monochromatic drive. In analogy with the integer quantum Hall effect, we show how the topological Chern numbers of the bands can be extracted from the mean transverse shift of the steady-state oscillation amplitude distribution. Finally, we discuss the regime where the analogy with the Harper-Hofstadter model breaks down.

  4. Frequency-Specific Coupling in the Cortico-Cerebellar Auditory System

    PubMed Central

    Pastor, M. A.; Vidaurre, C.; Fernández-Seara, M. A.; Villanueva, A.; Friston, K. J.

    2008-01-01

    Induced oscillatory activity in the auditory cortex peaks at around 40 Hz in humans. Using regional cerebral blood flow and positron emission tomography we previously confirmed frequency-selective cortical responses to 40-Hz tones in auditory primary cortices and concomitant bilateral activation of the cerebellar hemispheres. In this study, using functional magnetic resonance imaging (fMRI) we estimated the influence of 40-Hz auditory stimulation on the coupling between auditory cortex and superior temporal sulcus (STS) and Crus II, using a dynamic causal model of the interactions between medial geniculate nuclei, auditory superior temporal gyrus (STG)/STS, and the cerebellar Crus II auditory region. Specifically, we tested the hypothesis that 40-Hz-selective responses in the cerebellar Crus II auditory region could be explained by frequency-specific enabling of interactions in the auditory cortico–cerebellar–thalamic loop. Our model comparison results suggest that input from auditory STG/STS to cerebellum is enhanced selectively at gamma-band frequencies around 40 Hz. PMID:18684912

  5. Transient plasma potential in pulsed dual frequency inductively coupled plasmas and effect of substrate biasing

    NASA Astrophysics Data System (ADS)

    Mishra, Anurag; Yeom, Geun Young

    2016-09-01

    An electron emitting probe in saturated floating potential mode has been used to investigate the temporal evolution of plasma potential and the effect of substrate RF biasing on it for pulsed dual frequency (2 MHz/13.56 MHz) inductively coupled plasma (ICP) source. The low frequency power (P2MHz) has been pulsed at 1 KHz and a duty ratio of 50%, while high frequency power (P13.56MHz) has been used in continuous mode. The substrate has been biased with a separate bias power at (P12.56MHz) Argon has been used as a discharge gas. During the ICP power pulsing, three distinct regions in a typical plasma potential profile, have been identified as `initial overshoot', pulse `on-phase' and pulse `off-phase'. It has been found out that the RF biasing of the substrate significantly modulates the temporal evolution of the plasma potential. During the initial overshoot, plasma potential decreases with increasing RF biasing of the substrate, however it increases with increasing substrate biasing for pulse `on-phase' and `off-phase'. An interesting structure in plasma potential profile has also been observed when the substrate bias is applied and its evolution depends upon the magnitude of bias power. The reason of the evolution of this structure may be the ambipolar diffusion of electron and its dependence on bias power.

  6. Parametric coupling of low frequency whistler to Alfven wave in a plasma

    SciTech Connect

    Ahmad, Nafis; Tripathi, V. K.; Rafat, M.; Husain, Mudassir M.

    2009-12-15

    The parametric decay of a large amplitude electromagnetic wave in the ion cyclotron range of frequency into a compressional Alfven wave and an electromagnetic sideband wave in a magnetized plasma is investigated. The pump wave propagates in the direction of ambient magnetic field whereas the decay waves propagate at oblique angles. When the pump wave is left circularly polarized the decay is not permitted kinematically as the momentum of pump photon always exceeds the sum of momenta of the decay wave photons. For the right circularly polarized whistler mode pump the decay is permitted with sideband nearly right circularly polarized. The density perturbation associated with the Alfven wave couples with the pump driven oscillatory velocities of ions and electrons to produce a current driving the sideband. The sideband and the pump exert pondermotive force on ions and electrons that drive the Alfven wave. The frequency and growth rate of the Alfven wave increase with the normalized pump frequency. The threshold power density, determined by the collisional damping rates of the decay waves is rather modest.

  7. Analysis and modeling of time-variant amplitude-frequency couplings of and between oscillations of EEG bursts.

    PubMed

    Witte, Herbert; Putsche, Peter; Hemmelmann, Claudia; Schelenz, Christoph; Leistritz, Lutz

    2008-08-01

    Low-frequency (0.5-2.5 Hz) and individually defined high-frequency (7-11 or 8-12 Hz; 11-15 or 14-18 Hz) oscillatory components of the electroencephalogram (EEG) burst activity derived from thiopental-induced burst-suppression patterns (BSP) were investigated in seven sedated patients (17-26 years old) with severe head injury. The predominant high-frequency burst oscillations (>7 Hz) were detected for each patient by means of time-variant amplitude spectrum analysis. Thereafter, the instantaneous envelope (IE) and the instantaneous frequency (IF) were computed for these low- and high-frequency bands to quantify amplitude-frequency dependencies (envelope-envelope, envelope-frequency, and frequency-frequency correlations). Time-variant phase-locking, phase synchronization, and quadratic phase couplings are associated with the observed amplitude-frequency characteristics. Additionally, these time-variant analyses were carried out for modeled burst patterns. Coupled Duffing oscillators were adapted to each EEG burst and by means of these models data-based burst simulations were generated. Results are: (1) strong envelope-envelope correlations (IE courses) can be demonstrated; (2) it can be shown that a rise of the IE is associated with an increase of the IF (only for the frequency bands 0.5-2.5 and 7-11 or 8-12 Hz); (3) the rise characteristics of all individually averaged envelope-frequency courses (IE-IF) are strongly correlated; (4) for the 7-11 or 8-12 Hz oscillation these associations are weaker and the variation between the time courses of the patients is higher; (5) for both frequency ranges a quantitative amplitude-frequency dependency can be shown because higher IE peak maxima are accompanied by stronger IF changes; (6) the time range of significant phase-locking within the 7-11 or 8-12 Hz frequency bands and of the strongest quadratic phase couplings (between 0.5-2.5 and 7-11 or 8-12 Hz) is between 0 and 1,000 ms; (7) all phase coupling characteristics of the

  8. Comparing Two Types of Magnetically-Coupled Adjustable Speed Drives with Variable Frequency Drives in Pump and Fan Applications

    SciTech Connect

    Anderson, Kenneth J.; Chvala, William D.

    2003-05-30

    This paper presents the results from laboratory tests on MagnaDrive Corporation’s fixed magnet, magnetically-coupled adjustable speed drive and Coyote Electronics electromagnetic, magnetically-coupled adjustable speed drive, compared to a typical variable frequency drive (VFDs) for fan and pump loads. It also discusses advantages and disadvantages of using mechanical magnetically-coupled adjustable speed drives versus variable frequency drives, and it provides field experience with VFDs in food storage as well as adjustable speed drives in wastewater and other field applications.

  9. High precision frequency calibration of tunable diode lasers stabilized on an internally coupled Fabry-Perot interferometer.

    PubMed

    Clar, H J; Schieder, R; Reich, M; Winnewisser, G

    1989-05-01

    For very high precision molecular spectroscopy we use a tunable diode laser which is frequency locked to an internally coupled Fabry-Perot interferometer (icFPI). The spectra are calibrated by means of the interference pattern of an iodine stabilized He-Ne reference laser which is simultaneously coupled into the icFPI. In this paper the exact relation between the diode laser frequency and the He-Ne fringe number is derived and a convenient calibration procedure yielding a frequency accuracy of 5 x 10(-5) cm(-1) at 10 microm is described.

  10. A generalized lumped element modeling of electrically and magnetically dual-tunable microwave magnetoelectric resonators

    NASA Astrophysics Data System (ADS)

    Zhou, Hao-Miao; Li, Chao; Zhu, Feng-Jie; Qu, Shao-Xing

    2013-08-01

    According to the microwave transmission principle and the mechanism of ferromagnetic resonance (FMR), a generalized lumped element modeling for magnetoelectric tunable resonators based on the inverse magnetoelectric effect is established taking the impact of equivalent factors of piezoelectric layer into consideration. The lumped element modeling is used to analyze the electrically and magnetically dual-tunable FMR frequency drift of the magnetoelectric tunable resonator; the prediction results have a good agreement with the experimental results and the electromagnetic simulation results in quality and quantity. On this basis, this lumped element modeling is used to predict the effect of the applied electric field, the microstrip's width, the substrate's thickness, and the size of ferrite-piezoelectric layered structure on the ferromagnetic resonance. The results show that with the increase of applied electric field, the values of equivalent resistance R, inductor L, and turns ratio n increase slightly, while the value of C decreases slightly, the FMR frequency fr positively shifts; with the increase of the microstrip's width and substrate's thickness, the values of equivalent resistance R, inductor L, and turns ratio n decrease, while the value of C increases, the FMR bandwidth becomes narrower, and the ferromagnetic resonance attenuation becomes stronger at the same time. When the applied electric field is determined, with the increase of the length or thickness of layered structure, the FMR frequency shifts forward, the FMR peak point decreases first and then increases; with the width of layered structure increases, the FMR frequency of the resonator shifts backward, the FMR peak point decreases first and then increases.

  11. Magnetoelectric Properties in Piezoelectric and Magnetostrictive Laminate Composites

    NASA Astrophysics Data System (ADS)

    Ryu, Jungho; Carazo, Alfredo Vázquez; Uchino, Kenji; Kim, Hyoun-Ee

    2001-08-01

    Magnetoelectric laminate composites of piezoelectric-magnetostrictive materials were investigated. The composites were prepared by stacking and bonding Pb(Zr, Ti)O3 (PZT) and Terfenol-D disks. Experimental results indicated that the magnetoelectric voltage coefficient, dE/dH, increased with decreasing thickness and increasing piezoelectric voltage constant (g31) of the PZT layer. We obtained the highest magnetoelectric voltage coefficient of 4.68 V/cm\\cdotOe at room temperature for the sample with high g33 PZT of 0.5 mm in thickness. This value is about 36 times higher than the best reported value.

  12. Ferroelectric ordering and magnetoelectric effect of pristine and Ho-doped orthorhombic DyMnO{sub 3} by dielectric studies

    SciTech Connect

    Magesh, J.; Murugavel, P.; Mangalam, R. V. K.; Singh, K.; Simon, Ch.; Prellier, W.

    2015-08-21

    In this paper, the magnetoelectric coupling and ferroelectric ordering of the orthorhombic Dy{sub 1-x}Ho{sub x}MnO{sub 3} (x = 0 and 0.1) are studied from the magnetodielectric response of the polycrystalline samples. The dielectric study on the DyMnO{sub 3} reveals ferroelectric transition at 18 K along with an addition transition at 12 K. We suggest that the transition at 12 K could have originated from the polarization flop rather than being the rare earth magnetic ordering. The magnetodielectric study reveals a magnetoelectric coupling strength of 10%, which is stronger by two orders of magnitude in comparison to the hexagonal manganites. Surprisingly, the Ho{sup 3+} substitution in DyMnO{sub 3} suppresses the magnetoelectric coupling strength via the suppression of the spiral magnetic ordering. In addition, it also reduces the antiferromagnetic ordering and ferroelectric ordering temperatures. Overall, the studies show that the rare earth plays an important role in the magnetoelectric coupling strength through the modulation of spiral magnetic structure.

  13. Theory of domain wall motion mediated magnetoelectric effects in a multiferroic composite

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Srinivasan, G.

    2014-10-01

    A model is discussed for magnetoelectric (ME) interactions originating from the motion of magnetic domain walls (DWs) in a multiferroic composite of orthoferrites RFeO3 (RFO) with magnetic stripe domains and a piezoelectric such as lead magnesium niobate-lead titanate (PMN-PT). The DWs in RFO can be set in motion with an ac magnetic field up to a critical speed of 20 km/s, the highest for any magnetic system, leading to the excitation of bulk and shear magnetoacoustic waves. Thus, the ME coupling will arise from flexural deformation associated with DW motion (rather than the Joule magnetostriction mediated coupling under a static or quasistatic condition). A c plane orthoferrite with a single Néel-type DW in the bc plane and an ac magnetic field H along the c axis is assumed. The deflection in the bilayer due to DW motion is obtained when the DW velocity is a linear function H and the resulting induced voltage across PMN-PT is estimated. It is shown that a combination of spatial and time harmonics of the bending deformation leads to (i) a linear ME coefficient defined by αE=E/H and (ii) a quadratic ME coefficient αEQ=E/H2. The model is applied to yttrium orthoferrites (YFO) and a PMN-PT bilayer since YFO has one of the highest DW mobility amongst the orthoferrites. The coefficient αE is dependent on the DW position, and it is maximum when the DW equilibrium position is at the center of the sample. In YFO/PMN-PT the estimated low-frequency αE ˜ 30 mV/cm Oe and resonance value is 1.5 V/(cm Oe). Since orthoferrites (and PMN-PT) are transparent in the visible region and have a large Faraday rotation, the DW dynamics and the ME coupling could be studied simultaneously. The theory discussed here is of interest for studies on ME coupling and for applications such as magnetically controlled electro-optic devices.

  14. Single-frequency blue light generation by single-pass sum-frequency generation in a coupled ring cavity tapered laser

    NASA Astrophysics Data System (ADS)

    Bjarlin Jensen, Ole; Michael Petersen, Paul

    2013-09-01

    A generic approach for generation of tunable single frequency light is presented. 340 mW of near diffraction limited, single-frequency, and tunable blue light around 459 nm is generated by sum-frequency generation (SFG) between two tunable tapered diode lasers. One diode laser is operated in a ring cavity and another tapered diode laser is single-passed through a nonlinear crystal which is contained in the coupled ring cavity. Using this method, the single-pass conversion efficiency is more than 25%. In contrast to SFG in an external cavity, the system is entirely self-stabilized with no electronic locking.

  15. Pulsed radio-frequency discharge inductively coupled plasma mass spectrometry for oxide analysis

    NASA Astrophysics Data System (ADS)

    Li, Weifeng; Yin, Zhibin; Hang, Wei; Li, Bin; Huang, Benli

    2016-08-01

    A direct solid sampling technique has been developed based on a pulsed radio-frequency discharge (RFD) in mixture of N2 and Ar environment at atmospheric pressure. With an averaged input power of 65 W, a crater with the diameter of 80 μm and depth of 50 μm can be formed on sample surface after discharge for 1 min, suggesting the feasibility of the pulsed RFD for sampling nonconductive solids. Combined with inductively coupled plasma mass spectrometry (ICPMS), this technique allows to measure elemental composition of solids directly with relative standard deviation (RSD) of ~ 20%. Capability of quantitative analysis was demonstrated by the use of soil standards and artificial standards. Good calibration linearity and limits of detection (LODs) in range of 10- 8-10- 9 g/g were achieved for most elements.

  16. Ultra sensitive magnetic sensors integrating the giant magnetoelectric effect with advanced microelectronics

    NASA Astrophysics Data System (ADS)

    Fang, Zhao

    This dissertation investigates approaches to enhance the performance, especially the sensitivity and signal to noise ratio of magnetoelectric sensors, which exploits the magnetoelectric coupling in magnetostrictive and piezoelectric laminate composites. A magnetic sensor is a system or device that can measure the magnitude of a magnetic field or each of its vector components. Usually the techniques encompass many aspects of physics and electronics. The common technologies used for magnetic field sensing include induction coil sensors, fluxgate, SQUID (superconducting quantum interference device), Hall effect, giant magnetoresistance, magnetostrictive/piezoelectric composites, and MEMS (microelectromechanical systems)-based magnetic sensors. Magnetic sensors have found a broad range of applications for many decades. For example, ultra sensitive magnetic sensors are able to detect tiny magnetic fields produced outside the brain by the neuronal currents which can be used for diagnostic application. Measuring the brain's magnetic field is extremely challenging because they are so weak, have strengths of 0.1--1 pT and thus requiring magnetic sensors with sub-picotesla sensitivity. In fact, to date, these measurements can only performed with the most sensitive magnetic sensors, i.e., SQUID. However, such detectors need expensive and cumbersome cryogenics to operate. Additionally, the thermal insulation of the sensors prevents them from being placed very closed to the tissues under study, thereby preventing high-resolution measurement capability. All of these severely limit their broad usage and proliferation for biomedical imaging, diagnosis, and research. A novel ultra-sensitive magnetic sensor capable of operating at room temperature is investigated in this thesis. Magnetoelectric effect is a material phenomenon featuring the interchange between the magnetic and electric energies or signals. The large ME effect observed in ME composites, especially the ME laminates

  17. The giant magnetoelectric effect in Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites

    NASA Astrophysics Data System (ADS)

    Qiu, Jing; Wen, Yumei; Li, Ping; Chen, Hengjia

    2015-05-01

    The Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites with excellent magnetoelectric (ME) coupling effect were synthesized by electrostatic spray depositing. The ME coupling characteristics of Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites were investigated. It is found that the appropriate thickness ratio between magnetostrictive layers and piezoelectric layers (tm/tp) will be favorable to raise the resonance ME field output performance. The resonance frequency of ME field coefficient can be tuned by controlling tm/tp. The optimum resonance ME field coefficient of Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites achieves 259.2 V/cm Oe at mechanical resonance frequency at 11.5 kHz with the dc bias magnetic field is 60 Oe. Remarkably, the proposed composites exhibit a giant ME effect and a higher ME voltage coefficient than the previous Terfenol-D/PZT laminated composites. It indicates that the mentioned Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites have great potential for the application of highly sensitive magnetic field sensing and vibration energy harvesting.

  18. Electric polarization, magnetoelectric effect, and orbital state of a layered iron oxide with frustrated geometry.

    PubMed

    Nagano, A; Naka, M; Nasu, J; Ishihara, S

    2007-11-23

    A layered iron oxide RFe2O4 (R denotes rare-earth-metal elements) is an exotic dielectric material with charge-order (CO) driven electric polarization and magnetoelectric effect caused by spin-charge coupling. In this paper, a theory of electronic structure and dielectric property in RFe2O4 is presented. Charge frustration in paired-triangular lattices allows a charge imbalance without inversion symmetry. Spin frustration induces reinforcement of this polar CO by a magnetic ordering. We also analyze an orbital model for the Fe ion which does not show a conventional long-range order.

  19. Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

    NASA Astrophysics Data System (ADS)

    Bruneau, B.; Korolov, I.; Lafleur, T.; Gans, T.; O'Connell, D.; Greb, A.; Derzsi, A.; Donkó, Z.; Brandt, S.; Schüngel, E.; Schulze, J.; Johnson, E.; Booth, J.-P.

    2016-04-01

    We report investigations of capacitively coupled carbon tetrafluoride (CF4) plasmas excited with tailored voltage waveforms containing up to five harmonics of a base frequency of 5.5 MHz. The impact of both the slope asymmetry, and the amplitude asymmetry, of these waveforms on the discharge is examined by combining experiments with particle-in-cell simulations. For all conditions studied herein, the discharge is shown to operate in the drift-ambipolar mode, where a comparatively large electric field in the plasma bulk (outside the sheaths) is the main mechanism for electron power absorption leading to ionization. We show that both types of waveform asymmetries strongly influence the ion energy at the electrodes, with the particularity of having the highest ion flux on the electrode where the lowest ion energy is observed. Even at the comparatively high pressure (600 mTorr) and low fundamental frequency of 5.5 MHz used here, tailoring the voltage waveforms is shown to efficiently create an asymmetry of both the ion energy and the ion flux in geometrically symmetric reactors.

  20. Evidence of Resonant Mode Coupling and the Relationship between Low and High Frequencies in a Rapidly Rotating a Star

    NASA Astrophysics Data System (ADS)

    Breger, M.; Montgomery, M. H.

    2014-03-01

    In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day-1 (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of "normal" combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day-1 in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.

  1. Evidence of resonant mode coupling and the relationship between low and high frequencies in a rapidly rotating a star

    SciTech Connect

    Breger, M.; Montgomery, M. H.

    2014-03-10

    In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day{sup –1} (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of 'normal' combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day{sup –1} in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.

  2. The Double Jones Birefringence in Magneto-electric Medium

    PubMed Central

    Mahmood, Waqas; Zhao, Qing

    2015-01-01

    In this paper, the Maxwell’s equations for a tensorial magneto-electric (ME) medium are solved, which is an extension to the work on the uniaxial anisotropic nonmagnetic medium. The coefficients of the dielectric permittivity, magnetic permeability, and of the magneto-electric effect are considered as tensors. The polarization is shown lying in the plane of two perpendicular independent vectors, and the relationship for the transverse polarization is given. The propagation of an electromagnetic wave through a ME medium gives rise to double Jones birefringence. Besides, the condition for an independent phenomenon of D’yakonov surface wave in a magneto-isotropic but with magneto-electric medium is given, which is measurable experimentally when the incident angle is . Lastly, it is shown that the parameter for the magneto-electric effect plays a role in the damping of the wave. PMID:26354609

  3. Vortex magnetic field sensor based on ring-type magnetoelectric laminate

    NASA Astrophysics Data System (ADS)

    Dong, Shuxiang; Li, Jie-Fang; Viehland, D.

    2004-09-01

    It has been found that ring-type magnetoelectric laminate composites of circumferentially magnetized magnetostrictive TERFENOL-D and a circumferentially poled piezoelectric Pb(Zr ,Ti)O3 have high sensitivity to a vortex magnetic field. At room temperature, an induced output voltage from this ring laminate exhibited a near-linear response to an alternating current (ac) vortex magnetic field Hac over a wide magnetic field range of 10-9frequencies between sub-Hz and kHz.

  4. Non-contact magnetically coupled rectilinear-rotary oscillations to exploit low-frequency broadband energy harvesting with frequency up-conversion

    NASA Astrophysics Data System (ADS)

    Deng, Wei; Wang, Ya

    2016-09-01

    Ambient vibrations have a rectilinear and broadband nature and are particularly rich in the low-frequency regions. This letter reports an electromagnetic energy harvester to transform low-frequency broadband rectilinear vibrations into electricity with frequency up-conversion. The harvester consists of a rectilinear oscillator and a rotary oscillator coupled through magnetic force induced by four arc permanent magnets centrosymmetrically distributed on each oscillator. The rotary oscillator also includes two repulsive magnets and six stationary coils with steel screws inside to obtain and maintain four equilibrium positions with shallowed potential wells. The magnetic interaction between the rectilinear oscillator and the rotary oscillator is formulated using a magnetic dipole model. The restoring torque induced by the steel screws on the rotor is experimentally measured. Magnetically coupled governing equations are derived and their numerical solutions are used to characterize the dynamic response of the harvester under chirp excitations. Experimental results demonstrate its excellent harvesting capability of scavenging low-frequency wideband vibrational energy under slow-frequency-drifted excitations, simple harmonic excitations, and mixed-frequency excitations. Under harmonic excitations, the rectilinear oscillator vibrates non-harmonically but approximately periodically, while the rotary counterpart oscillates in a more complex pattern varying with the excitation frequency, which leads to the frequency up-conversion (up to 10 times increase) and broadened bandwidth (25% increase from its resonant frequency). Experiments show an output voltage of 5 V (RMS)/40 V (Peak to Peak) and an output power of 55 mW (RMS)/950 mW (Peak) at an optimal load of 465 Ω under harmonic excitation of 4 Hz at 0.7 g.

  5. Optimization of the magnetoelectric response of poly(vinylidene fluoride)/epoxy/Vitrovac laminates.

    PubMed

    Silva, M; Reis, S; Lehmann, C S; Martins, P; Lanceros-Mendez, S; Lasheras, A; Gutiérrez, J; Barandiarán, J M

    2013-11-13

    The effect of the bonding layer type and piezoelectric layer thickness on the magnetoelectric (ME) response of layered poly(vinylidene fluoride) (PVDF)/epoxy/Vitrovac composites is reported. Three distinct epoxy types were tested, commercially known as M-Bond, Devcon, and Stycast. The main differences among them are their different mechanical characteristics, in particular the value of the Young modulus, and the coupling with the polymer and Vitrovac (Fe39Ni39Mo4Si6B12) layers of the laminate. The laminated composites prepared with M-Bond epoxy exhibit the highest ME coupling. Experimental results also show that the ME response increases with increasing PVDF thickness, the highest ME response of 53 V·cm(-1)·Oe(-1) being obtained for a 110 μm thick PVDF/M-Bond epoxy/Vitrovac laminate. The behavior of the ME laminates with increasing temperatures up to 90 °C shows a decrease of more than 80% in the ME response of the laminate, explained by the deteriorated coupling between the different layers. A two-dimensional numerical model of the ME laminate composite based on the finite element method was used to evaluate the experimental results. A comparison between numerical and experimental data allows us to select the appropriate epoxy and to optimize the piezoelectric PVDF layer width to maximize the induced magnetoelectric voltage. The obtained results show the critical role of the bonding layer and piezoelectric layer thickness in the ME performance of laminate composites.

  6. Magneto-electric interactions at bending resonance in an asymmetric multiferroic composite: Theory and experiment on the influence of electrode position

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, G.; Qu, P.; Petrov, V. M.; Qu, Hongwei; Srinivasan, G.

    2015-05-01

    In magnetostrictive-piezoelectric bilayers the strength of mechanical strain mediated magneto-electric (ME) interactions shows a resonance enhancement at bending modes. Such composites when operating under frequency modulation at bending resonance have very high ME sensitivity and are of importance for ultrasensitive magnetometers. This report provides an avenue for further enhancement in the ME sensitivity by strategic positioning of the electrodes in the bilayer. We discuss the theory and measurements on the dependence of ME coupling on the position of electrodes in a lead zirconate titanate-permendur bilayer. Samples of effective length L with full electrodes and partial electrodes of length l = L/3 are studied. A five-fold increase in ME voltage coefficient (MEVC) at bending resonance and a 75% increase in low-frequency MEVC are measured as the partial electrode position is moved from the free-end to clamped-end of the bilayer. When the partial electrode is close to the clamped end, the low-frequency and resonance MEVC are 22% and 45% higher, respectively, than for fully electroded bilayer. According to the model discussed here these observations could be attributed to non-uniform stress along the sample length under flexural deformation. Such deformations are stronger at the free-end than at the clamped-end, thereby reducing the stress produced by applied magnetic fields and a reduction in MEVC. Estimates of MEVC are in good agreement with the data.

  7. Neutron powder diffraction study of nuclear and magnetic structures of multiferroic (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3: Evidence for isostructural phase transition and magnetoelastic and magnetoelectric couplings

    NASA Astrophysics Data System (ADS)

    Singh, Anar; Senyshyn, Anatoliy; Fuess, Hartmut; Chatterji, Tapan; Pandey, Dhananjai

    2011-02-01

    We report here the results of a high-resolution neutron powder diffraction study on the multiferroic solid solution system (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3 in the temperature range 4 to 700 K. Using irreducible representation theory to analyze the magnetic structure by Rietveld refinement, we show that the magnetic structure is collinear G-type antiferromagnetic. Further, we confirm the occurrence of an isostructural phase transition (IPT) accompanying the magnetic ordering around ˜625 K in (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3. It is shown that as a result of the IPT, the positions of all the atoms change significantly in the magnetically ordered phase, leading to an excess polarization which scales linearly with the sublattice magnetization obtained by Rietveld refinement of the magnetic structure. Structural evidence for magnetoelastic coupling for the magnetic transitions below room temperature is also presented.

  8. Analysis and experimental validation of the middle-frequency vibro-acoustic coupling property for aircraft structural model based on the wave coupling hybrid FE-SEA method

    NASA Astrophysics Data System (ADS)

    Yan, Yunju; Li, Pengbo; Lin, Huagang

    2016-06-01

    The finite element (FE) method is suitable for low frequency analysis and the statistical energy analysis (SEA) for high frequency analysis, but the vibro-acoustic coupling analysis at middle frequency, especially with a certain range of uncertainty system, requires some new methods. A hybrid FE-SEA method is proposed in this study and the Monte Carlo method is used to check the hybrid FE-SEA method through the energy response analysis of a beam-plate built-up structure with some uncertainty, and the results show that two kinds of calculation results match well consistently. Taking the advantage of the hybrid FE-SEA method, the structural vibration and the cabin noise field responses under the vibro-acoustic coupling for an aircraft model are numerically analyzed, and, also, the corresponding experiment is carried out to verify the simulated results. Results show that the structural vibration responses at low frequency accord well with the experiment, but the error at high frequency is greater. The error of sound pressure response level in cabin throughout the spectrum is less than 3 dB. The research proves the reliability of the method proposed in this paper. This indicates that the proposed method can overcome the strict limitations of the traditional method for a large complex structure with uncertainty factors, and it can also avoid the disadvantages of solving complex vibro-acoustic system using the finite element method or statistical energy analysis in the middle frequency.

  9. Time Circular Birefringence in Time-Dependent Magnetoelectric Media

    PubMed Central

    Zhang, Ruo-Yang; Zhai, Yan-Wang; Lin, Shi-Rong; Zhao, Qing; Wen, Weijia; Ge, Mo-Lin

    2015-01-01

    Light traveling in time-dependent media has many extraordinary properties which can be utilized to convert frequency, achieve temporal cloaking, and simulate cosmological phenomena. In this paper, we focus on time-dependent axion-type magnetoelectric (ME) media, and prove that light in these media always has two degenerate modes with opposite circular polarizations corresponding to one wave vector , and name this effect “time circular birefringence” (TCB). By interchanging the status of space and time, the pair of TCB modes can appear simultaneously via “time refraction” and “time reflection” of a linear polarized incident wave at a time interface of ME media. The superposition of the two TCB modes causes the “time Faraday effect”, namely the globally unified polarization axes rotate with time. A circularly polarized Gaussian pulse traversing a time interface is also studied. If the wave-vector spectrum of a pulse mainly concentrates in the non-traveling-wave band, the pulse will be trapped with nearly fixed center while its intensity will grow rapidly. In addition, we propose an experimental scheme of using molecular fluid with external time-varying electric and magnetic fields both parallel to the direction of light to realize these phenomena in practice. PMID:26329928

  10. Magnetoelectric effect in porous bulk ferromagnetic/piezoelectric composites

    NASA Astrophysics Data System (ADS)

    Bichurin, M. I.; Srinivasan, G.

    2005-03-01

    Bulk and layered composites of piezoelectric and magnetostrictive phases show magnetoelectric (ME) properties. Bulk composites are desirable over layered samples due to superior mechanical strength. Here we discuss a model that considers the influence of porosity on ME interactions in a bulk composite. The composite is assumed to consist of piezoelectric, magnetostrictive and void (pores) subsystems. We solved combined elastostatic, electrostatic and magnetostatic equations to obtain effective composite parameters (piezoelectric modules, magnetostriction factors, compliances, ME coefficients). Expressions for longitudinal and transverse low-frequency ME voltage coefficients have been obtained for 3- 0-0 and 0-3-0 connectivity types. The dependence for ME voltage coefficient on volume fractions of the two phases are shown to be dependent on connectivity type. The strength of ME interaction depends on porosity. The calculated ME coefficients are in good agreement with data in Ref.1. *G. Srinivasan, C. P. DeVreugd, C. S. Flattery, V. M. Laletsin and N. Paddubnaya. Appl. Phys. Lett., 85, 2550 (2004). - supported by grants from the Russian Ministry of Education (Å02-3.4-278), the Universities of Russia Foundation (UNR 01.01.026) and the National Science Foundation (DMR-0302254).

  11. Mitigating Oscillator Pulling Due To Magnetic Coupling in Monolithic Mixed-Signal Radio-Frequency Integrated Circuits

    SciTech Connect

    Sobering, Ian David

    2014-01-01

    An analysis of frequency pulling in a varactor-tuned LC VCO under coupling from an on-chip PA is presented. The large-signal behavior of the VCO's inversion-mode MOS varactors is outlined, and the susceptibility of the VCO to frequency pulling from PA aggressor signals with various modulation schemes is discussed. We show that if the aggressor signal is aperiodic, band-limited, or amplitude-modulated, the varactor-tuned LC VCO will experience frequency pulling due to time-modulation of the varactor capacitance. However, if the aggressor signal has constant-envelope phase modulation, VCO pulling can be eliminated, even in the presence of coupling, through careful choice of VCO frequency and divider ratio. Additional mitigation strategies, including new inductor topologies and system-level architectural choices, are also examined.

  12. Magnetoelectric thin film composites with interdigital electrodes

    NASA Astrophysics Data System (ADS)

    Piorra, A.; Jahns, R.; Teliban, I.; Gugat, J. L.; Gerken, M.; Knöchel, R.; Quandt, E.

    2013-07-01

    Magnetoelectric (ME) thin film composites on silicon cantilevers are fabricated using Pb(Zr0.52Ti0.45)O3 (PZT) films with interdigital transducer electrodes on the top side and FeCoSiB amorphous magnetostrictive thin films on the backside. These composites without any direct interface between the piezoelectric and magnetostrictive phase are superior to conventional plate capacitor-type thin film ME composites. A limit of detection of 2.6 pT/Hz1/2 at the mechanical resonance is determined which corresponds to an improvement of a factor of approximately 2.8 compared to the best plate type sensor using AlN as the piezoelectric phase and even a factor of approximately 4 for a PZT plate capacitor.

  13. Magnetoelectric effect in organic molecular solids

    PubMed Central

    Naka, Makoto; Ishihara, Sumio

    2016-01-01

    The Magnetoelectric (ME) effect in solids is a prominent cross correlation phenomenon, in which the electric field (E) controls the magnetization (M) and the magnetic field (H) controls the electric polarization (P). A rich variety of ME effects and their potential in practical applications have been investigated so far within the transition-metal compounds. Here, we report a possible way to realize the ME effect in organic molecular solids, in which two molecules build a dimer unit aligned on a lattice site. The linear ME effect is predicted in a long-range ordered state of spins and electric dipoles, as well as in a disordered state. One key of the ME effect is a hidden ferroic order of the spin-charge composite object. We provide a new guiding principle of the ME effect in materials without transition-metal elements, which may lead to flexible and lightweight multifunctional materials. PMID:26876424

  14. A model of magneto-electric multipoles

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Balcar, E.

    2015-03-01

    A long-known Hamiltonian of electrons with entangled spin and orbital degrees of freedom is re-examined as a model of magneto-electric multipoles (MEs). In the model, a magnetic charge and simple quantum rotator are tightly locked in action, some might say they are enslaved entities. It is shown that MEs almost perfectly accord with those inferred from an analysis of magnetic neutron diffraction data on a ceramic superconductor (YBCO) in the pseudo-gap phase. Nigh on perfection between Stone's model and inferred MEs is achieved by addition to the original model of a crystal-field potential appropriate for the magnetic space group used in the published data analysis. An impression of thermal properties of multipoles is sought from a molecular-field model.

  15. Modifications in the frustrated magnetism, oxidation state of Co and magnetoelectric coupling effects induced by a partial replacement of Ca by Gd in the spin-chain compound Ca3Co2O6

    NASA Astrophysics Data System (ADS)

    Basu, Tathamay; Singh, Kiran; Sampathkumaran, E. V.

    2013-12-01

    We have systematically investigated the influence of the gradual replacement of Ca by Gd on the magnetic and complex dielectric properties of the well-known geometrically frustrated spin-chain system Ca3Co2O6 (TN = 24 K with additional magnetic transitions below 12 K), by studying the series Ca3-xGdxCo2O6 (x ≤ 0.7), down to 1.8 K. Heat-capacity measurements establish that the reduction of TN with Gd substitution is much less compared to that by Y substitution. The magnetic moment data reveal that there are changes in the oxidation state of Co as well, unlike for Y substitution, beyond x = 0.2. Thus, despite being isovalent, both these substitutions interestingly differ in changing these magnetic properties in these oxides. We propose that the valence electrons of Y and those of R ions play different roles in deciding the magnetic characteristics of these mixed oxides. It is observed that a small amount (x = 0.3) of Gd substitution for Ca is enough to suppress glassy ac magnetic susceptibility behavior for the peak around 12 K. An additional low-temperature magnetic anomaly close to 5 K gets more prominent with increasing Gd concentration as revealed by heat-capacity data. Trends in temperature dependence of complex dielectric behavior were also tracked with varying composition and a frequency dependence is observed, not only for the transition in the region around 10 K (for some compositions), but also for the 5 K transition which is well resolved for a higher concentration of Gd. Thus, the Gd-substituted Ca3Co2O6 series is shown to reveal interesting magnetic and dielectric behaviors of this family of oxides.

  16. The influence of interlayer exchange coupling in giant-magnetoresistive devices on spin diode effect in wide frequency range

    SciTech Connect

    Ziętek, Sławomir Skowroński, Witold; Wiśniowski, Piotr; Czapkiewicz, Maciej; Stobiecki, Tomasz; Ogrodnik, Piotr; Barnaś, Józef

    2015-09-21

    Spin diode effect in a giant magnetoresistive strip is measured in a broad frequency range, including resonance and off-resonance frequencies. The off-resonance dc signal is relatively strong and also significantly dependent on the exchange coupling between magnetic films through the spacer layer. The measured dc signal is described theoretically by taking into account magnetic dynamics induced by Oersted field created by an ac current flowing through the system.

  17. Plasma dynamics in a discharge produced by a pulsed dual frequency inductively coupled plasma source

    SciTech Connect

    Mishra, Anurag; Lee, Sehan; Yeom, Geun Y.

    2014-11-01

    Using a Langmuir probe, time resolved measurements of plasma parameters were carried out in a discharge produced by a pulsed dual frequency inductively coupled plasma source. The discharge was sustained in an argon gas environment at a pressure of 10 mTorr. The low frequency (P{sub 2} {sub MHz}) was pulsed at 1 kHz and a duty ratio of 50%, while high frequency (P{sub 13.56} {sub MHz}) was maintained in the CW mode. All measurements were carried out at the center of the discharge and 20 mm above the substrate. The results show that, at a particular condition (P{sub 2} {sub MHz} = 200 W and P{sub 13.56} {sub MHz }= 600 W), plasma density increases with time and stabilizes at up to ∼200 μs after the initiation of P{sub 2} {sub MHz} pulse at a plasma density of (2 × 10{sup 17} m{sup −3}) for the remaining duration of pulse “on.” This stabilization time for plasma density increases with increasing P{sub 2} {sub MHz} and becomes ∼300 μs when P{sub 2} {sub MHz} is 600 W; however, the growth rate of plasma density is almost independent of P{sub 2} {sub MHz}. Interestingly, the plasma density sharply increases as the pulse is switched off and reaches a peak value in ∼10 μs, then decreases for the remaining pulse “off-time.” This phenomenon is thought to be due to the sheath modulation during the transition from “pulse on” to “pulse off” and partly due to RF noise during the transition period. The magnitude of peak plasma density in off time increases with increasing P{sub 2} {sub MHz}. The plasma potential and electron temperature decrease as the pulse develops and shows similar behavior to that of the plasma density when the pulse is switched off.

  18. Influence of nanoparticle formation on discharge properties in argon-acetylene capacitively coupled radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Wegner, Th.; Hinz, A. M.; Faupel, F.; Strunskus, T.; Kersten, H.; Meichsner, J.

    2016-02-01

    This contribution presents experimental results regarding the influence of nanoparticle formation in capacitively coupled radio frequency (13.56 MHz) argon-acetylene plasmas. The discharge is studied using non-invasive 160 GHz Gaussian beam microwave interferometry and optical emission spectroscopy. Particularly, the temporal behavior of the electron density from microwave interferometry is analyzed and compared with the changing plasma emission and self-bias voltage caused by nanoparticle formation. The periodic particle formation with a cycle duration between 30 s and 140 s starts with an electron density drop over more than one order of magnitude below the detection limit (8 × 1014 m-3). The electron density reduction is the result of electron attachment processes due to negative ions and nanoparticle formation. The onset time constant of nanoparticle formation is five times faster compared to the expulsion of the particles from the plasma due to multi-disperse size distribution. Moreover, the intensity of the argon transition lines increases and implies a rising effective electron temperature. The cycle duration of the particle formation is affected by the total gas flow rate and exhibits an inverse proportionality to the square of the total gas flow rate. The variation in the total gas flow rate influences the force balance, which determines the confinement time of the nanoparticles. As a further result, the cycle duration is dependent on the axial position of the powered electrode, which also corresponds to different distances relative to the fixed optical axis of the microwave interferometer.

  19. Suppression of dynamics and frequency synchronization in coupled slow and fast dynamical systems

    NASA Astrophysics Data System (ADS)

    Gupta, Kajari; Ambika, G.

    2016-06-01

    We present our study on the emergent states of two interacting nonlinear systems with differing dynamical time scales. We find that the inability of the interacting systems to fall in step leads to difference in phase as well as change in amplitude. If the mismatch is small, the systems settle to a frequency synchronized state with constant phase difference. But as mismatch in time scale increases, the systems have to compromise to a state of no oscillations. We illustrate this for standard nonlinear systems and identify the regions of quenched dynamics in the parameter plane. The transition curves to this state are studied analytically and confirmed by direct numerical simulations. As an important special case, we revisit the well-known model of coupled ocean-atmosphere system used in climate studies for the interactive dynamics of a fast oscillating atmosphere and slowly changing ocean. Our study in this context indicates occurrence of multi stable periodic states and steady states of convection coexisting in the system, with a complex basin structure.

  20. Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

    PubMed Central

    Balram, Krishna C.; Davanço, Marcelo I.; Song, Jin Dong; Srinivasan, Kartik

    2016-01-01

    Optomechanical cavities have been studied for applications ranging from sensing to quantum information science. Here, we develop a platform for nanoscale cavity optomechanical circuits in which optomechanical cavities supporting co-localized 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency (RF) field through the piezo-electric effect, which produces acoustic waves that are routed and coupled to the optomechanical cavity by phononic crystal waveguides, or optically through the strong photoelastic effect. Along with mechanical state preparation and sensitive readout, we use this to demonstrate an acoustic wave interference effect, similar to atomic coherent population trapping, in which RF-driven coherent mechanical motion is cancelled by optically-driven motion. Manipulating cavity optomechanical systems with equal facility through both photonic and phononic channels enables new architectures for signal transduction between the optical, electrical, and mechanical domains. PMID:27446234

  1. On the location of frequencies of maximum acoustic-to-seismic coupling

    SciTech Connect

    Sabatier, J.M.; Bass, H.E.; Elliott, G.R.

    1986-10-01

    Measurements of the acoustic-to-seismic transfer function (ratio of the normal soil particle velocity at a depth d to the acoustic pressure at the surface) for outdoor ground surfaces quite typically reveal a series of maxima and minima. In a publication (Sabatier et al., J. Acoust. Soc. Am. 80, 646--649 (1986)), the location and magnitude of these maxima are measured and predicted for several outdoor ground surfaces using a layered poroelastic model of the ground surface. In this paper, the seismic transfer function for a desert site is compared to the seismic transfer function for holes dug in the desert floor which were filled with pumice (volcanic rock). The hole geometry was rectangular and the hole depths varied from 0.25--2.0 m. The p- and s-wave speeds, densities, porosities, and flow resistivities for the desert floor and pumice were all measured. By varying the hole depth and the fill material, the maxima in the seismic transfer function can be shifted in frequency and the locations of the maxima compare reasonably with that of a hard-backed layer calculation. The area or extent of the acoustic-to-seismic coupling for pumice was determined to be less than 1 m/sup 2/.

  2. Measurement of Radiation Frequency of Gyrotron by GaAs Schottky Barrier Diodes Coupled with Thin-Film Slot Antenna

    NASA Astrophysics Data System (ADS)

    Hayashi, Kosuke; Furuya, Takashi; Tachiki, Takashi; Uchida, Takashi; Idehara, Toshitaka; Yasuoka, Yoshizumi

    2010-03-01

    Thin-film slot-antenna-coupled GaAs Schottky barrier diodes (SBDs) used at the 180 GHz band were fabricated by microfabrication techniques, and the radiation frequency of a gyrotron at the University of Fukui (Gyrotron FU CW IV) was measured. In second-harmonic mixing using a local oscillator (LO) wave of 88.0899 GHz, an intermediate frequency (IF) signal of 102.8 MHz was observed and the radiation frequency of the gyrotron was found to be 176.077 GHz.

  3. Single-photon frequency-comb generation in a one-dimensional waveguide coupled to two atomic arrays

    NASA Astrophysics Data System (ADS)

    Liao, Zeyang; Nha, Hyunchul; Zubairy, M. Suhail

    2016-03-01

    An atomic chain coupled to a one-dimensional (1D) photonic waveguide can become a very good atom mirror. This atom mirror can have a very high reflectivity for a single-photon pulse due to the collective interaction between the atoms. Two atom arrays coupled to a 1D waveguide can form a good cavity. When a single-photon pulse is incident from one side of the cavity, only a discrete subset of photon frequencies can transmit the cavity and the transmitted frequencies are almost equally spaced, which is similar to a frequency comb. The linewidth of the comb frequency can be reduced if we increase the atom number in the atomic arrays. More interestingly, if the photon pulse is initially inside the cavity, the photon spectrum after a long time of interaction is also discretized with the comb frequencies being significantly amplified while other frequencies being largely suppressed. This single-photon frequency comb may be useful for precision measurement.

  4. Multi-cavity coupling acoustic metamaterials with low-frequency broad band gaps based on negative mass density

    NASA Astrophysics Data System (ADS)

    Yang, Chuanhui; Wu, Jiu Hui; Cao, Songhua; Jing, Li

    2016-08-01

    This paper studies a novel kind of low-frequency broadband acoustic metamaterials with small size based on the mechanisms of negative mass density and multi-cavity coupling. The structure consists of a closed resonant cavity and an open resonant cavity, which can be equivalent to a homogeneous medium with effective negative mass density in a certain frequency range by using the parameter inversion method. The negative mass density makes the anti-resonance area increased, which results in broadened band gaps greatly. Owing to the multi-cavity coupling mechanism, the local resonances of the lower frequency mainly occur in the closed cavity, while the local resonances of the higher frequency mainly in the open cavity. Upon the interaction between the negative mass density and the multi-cavity coupling, there exists two broad band gaps in the range of 0-1800 Hz, i.e. the first-order band gap from 195 Hz to 660 Hz with the bandwidth of 465 Hz and the second-order band gap from 1157 Hz to 1663 Hz with the bandwidth of 506 Hz. The acoustic metamaterials with small size presented in this paper could provide a new approach to reduce the low-frequency broadband noises.

  5. Spatial Noise in Coupling Strength and Natural Frequency within a Pacemaker Network; Consequences for Development of Intestinal Motor Patterns According to a Weakly Coupled Phase Oscillator Model.

    PubMed

    Parsons, Sean P; Huizinga, Jan D

    2016-01-01

    Pacemaker activities generated by networks of interstitial cells of Cajal (ICC), in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP) in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude) was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave) activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e., spatial noise) with a long-tailed distribution, plateau steps occurred at pointsof low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency. PMID:26869875

  6. Spatial Noise in Coupling Strength and Natural Frequency within a Pacemaker Network; Consequences for Development of Intestinal Motor Patterns According to a Weakly Coupled Phase Oscillator Model

    PubMed Central

    Parsons, Sean P.; Huizinga, Jan D.

    2016-01-01

    Pacemaker activities generated by networks of interstitial cells of Cajal (ICC), in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP) in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude) was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave) activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e., spatial noise) with a long-tailed distribution, plateau steps occurred at pointsof low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency. PMID:26869875

  7. 3-D Surface Depression Profiling Using High Frequency Focused Air-Coupled Ultrasonic Pulses

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Kautz, Harold E.; Abel, Phillip B.; Whalen, Mike F.; Hendricks, J. Lynne; Bodis, James R.

    1999-01-01

    Surface topography is an important variable in the performance of many industrial components and is normally measured with diamond-tip profilometry over a small area or using optical scattering methods for larger area measurement. This article shows quantitative surface topography profiles as obtained using only high-frequency focused air-coupled ultrasonic pulses. The profiles were obtained using a profiling system developed by NASA Glenn Research Center and Sonix, Inc (via a formal cooperative agreement). (The air transducers are available as off-the-shelf items from several companies.) The method is simple and reproducible because it relies mainly on knowledge and constancy of the sound velocity through the air. The air transducer is scanned across the surface and sends pulses to the sample surface where they are reflected back from the surface along the same path as the incident wave. Time-of-flight images of the sample surface are acquired and converted to depth/surface profile images using the simple relation (d = V*t/2) between distance (d), time-of-flight (t), and the velocity of sound in air (V). The system has the ability to resolve surface depression variations as small as 25 microns, is useable over a 1.4 mm vertical depth range, and can profile large areas only limited by the scan limits of the particular ultrasonic system. (Best-case depth resolution is 0.25 microns which may be achievable with improved isolation from vibration and air currents.) The method using an optimized configuration is reasonably rapid and has all quantitative analysis facilities on-line including 2-D and 3-D visualization capability, extreme value filtering (for faulty data), and leveling capability. Air-coupled surface profilometry is applicable to plate-like and curved samples. In this article, results are shown for several proof-of-concept samples, plastic samples burned in microgravity on the STS-54 space shuttle mission, and a partially-coated cylindrical ceramic

  8. Defining regions of interest using cross-frequency coupling in extratemporal lobe epilepsy patients

    NASA Astrophysics Data System (ADS)

    Guirgis, Mirna; Chinvarun, Yotin; del Campo, Martin; Carlen, Peter L.; Bardakjian, Berj L.

    2015-04-01

    Objective. Clinicians identify seizure onset zones (SOZs) for resection in an attempt to localize the epileptogenic zone (EZ), which is the cortical tissue that is indispensible for seizure generation. An automated system is proposed to objectively localize this EZ by identifying regions of interest (ROIs). Methods. Intracranial electroencephalogram recordings were obtained from seven patients presenting with extratemporal lobe epilepsy and the interaction between neuronal rhythms in the form of phase-amplitude coupling was investigated. Modulation of the amplitude of high frequency oscillations (HFOs) by the phase of low frequency oscillations was measured by computing the modulation index (MI). Delta- (0.5-4 Hz) and theta- (4-8 Hz) modulation of HFOs (30-450 Hz) were examined across the channels of a 64-electrode subdural grid. Surrogate analysis was performed and false discovery rates were computed to determine the significance of the modulation observed. Mean MI values were subjected to eigenvalue decomposition (EVD) and channels defining the ROIs were selected based on the components of the eigenvector corresponding to the largest eigenvalue. ROIs were compared to the SOZs identified by two independent neurologists. Global coherence values were also computed. Main results. MI was found to capture the seizure in time for six of seven patients and identified ROIs in all seven. Patients were found to have a poorer post-surgical outcome when the number of EVD-selected channels that were not resected increased. Moreover, in patients who experienced a seizure-free outcome (i.e., Engel Class I) all EVD-selected channels were found to be within the resected tissue or immediately adjacent to it. In these Engel Class I patients, delta-modulated HFOs were found to identify more of the channels in the resected tissue compared to theta-modulated HFOs. However, for the Engel Class IV patient, the delta-modulated HFOs did not identify any of the channels in the resected

  9. Resonance magnetoelectric interactions in an asymmetric ferromagnetic-ferroelectric layered structure

    NASA Astrophysics Data System (ADS)

    Fetisov, L. Y.; Perov, N. S.; Fetisov, Y. K.; Srinivasan, G.; Petrov, V. M.

    2011-03-01

    Strain mediated magnetoelectric (ME) interactions have been investigated in a sample consisting of oppositely poled lead zirconate titanate (PZT) and asymmetric magnetostrictive layers. A thin layer of Ni with negative magnetostriction and amorphous ferromagnetic Metglas with positive magnetostriction are bonded to the PZT layers. It is shown that the magnetic layers facilitate effective excitation of bending oscillations in the structure, whereas the use of oppositely poled PZT layers results in an increase in the ME voltage at the bending resonance frequency, suppression of the voltage at the longitudinal electromechanical resonance frequency, and cancellation of thermal fluctuation in the voltage. The ME voltage coefficient at resonance is 18 V/(cm Oe); that is an order of magnitude higher than the value measured for a Ni-PZT bilayer of similar dimensions. Theoretical estimates of the ME voltage and resonance frequency are in good agreement with the data.

  10. Effect of source frequency and pulsing on the SiO2 etching characteristics of dual-frequency capacitive coupled plasma

    NASA Astrophysics Data System (ADS)

    Kim, Hoe Jun; Jeon, Min Hwan; Mishra, Anurag Kumar; Kim, In Jun; Sin, Tae Ho; Yeom, Geun Young

    2015-01-01

    A SiO2 layer masked with an amorphous carbon layer (ACL) has been etched in an Ar/C4F8 gas mixture with dual frequency capacitively coupled plasmas under variable frequency (13.56-60 MHz)/pulsed rf source power and 2 MHz continuous wave (CW) rf bias power, the effects of the frequency and pulsing of the source rf power on the SiO2 etch characteristics were investigated. By pulsing the rf power, an increased SiO2 etch selectivity was observed with decreasing SiO2 etch rate. However, when the rf power frequency was increased, not only a higher SiO2 etch rate but also higher SiO2 etch selectivity was observed for both CW and pulse modes. A higher CF2/F ratio and lower electron temperature were observed for both a higher source frequency mode and a pulsed plasma mode. Therefore, when the C 1s binding states of the etched SiO2 surfaces were investigated using X-ray photoelectron spectroscopy (XPS), the increase of C-Fx bonding on the SiO2 surface was observed for a higher source frequency operation similar to a pulsed plasma condition indicating the increase of SiO2 etch selectivity over the ACL. The increase of the SiO2 etch rate with increasing etch selectivity for the higher source frequency operation appears to be related to the increase of the total plasma density with increasing CF2/F ratio in the plasma. The SiO2 etch profile was also improved not only by using the pulsed plasma but also by increasing the source frequency.

  11. Trench and hole patterning with EUV resists using dual frequency capacitively coupled plasma (CCP)

    NASA Astrophysics Data System (ADS)

    Feurprier, Yannick; Lutker-Lee, Katie; Rastogi, Vinayak; Matsumoto, Hiroie; Chiba, Yuki; Metz, Andrew; Kumar, Kaushik; Beique, Genevieve; Labonte, Andre; Labelle, Cathy; Mignot, Yann; Hamieh, Bassem; Arnold, John

    2015-03-01

    Patterning at 10 nm and sub-10 nm technology nodes is one of the key challenges for the semiconductor industry. Several patterning techniques are under investigation to enable the aggressive pitch requirements demanded by the logic technologies. EUV based patterning is being considered as a serious candidate for the sub-10nm nodes. As has been widely published, a new technology like EUV has its share of challenges. One of the main concerns with EUV resists is that it tends to have a lower etch selectivity and worse LER/LWR than traditional 193nm resists. Consequently the characteristics of the dry etching process play an increasingly important role in defining the outcome of the patterning process. In this paper, we will demonstrate the role of the dual-frequency Capacitively Coupled Plasma (CCP) in the EUV patterning process with regards to improving LER/LWR, resist selectivity and CD tunability for holes and line patterns. One of the key knobs utilized here to improve LER and LWR, involves superimposing a negative DC voltage in RF plasma at one of the electrodes. The emission of ballistic electrons, in concert with the plasma chemistry, has shown to improve LER and LWR. Results from this study along with traditional plasma curing methods will be presented. In addition to this challenge, it is important to understand the parameters needed to influence CD tunability and improve resist selectivity. Data will be presented from a systematic study that shows the role of various plasma etch parameters that influence the key patterning metrics of CD, resist selectivity and LER/LWR. This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities.

  12. Control of synchronization and spiking regularity by heterogenous aperiodic high-frequency signal in coupled excitable systems

    NASA Astrophysics Data System (ADS)

    Qin, Ying-Mei; Wang, Jiang; Men, Cong; Chan, Wai-Lok; Wei, Xi-Le; Deng, Bin

    2013-10-01

    This paper investigates the synchronization and spiking regularity induced by heterogenous aperiodic (HA) signal in coupled excitable FitzHugh-Nagumo systems. We found new nontrivial effects of couplings and HA signals on the firing regularity and synchronization in coupled excitable systems without a periodic external driving. The phenomenon is similar to array enhanced coherence resonance (AECR), and it is shown that AECR-type behavior is not limited to systems driven by noises. It implies that the HA signal may be beneficial for the brain function, which is similar to the role of noise. Furthermore, it is also found that the mean frequencies, the amplitudes and the heterogeneity of HA stimuli can serve as control parameters in modulating spiking regularity and synchronization in coupled excitable systems. These results may be significant for the control of the synchronized firing of the brain in neural diseases like epilepsy.

  13. The external Q factor of a dual-feed coupling for superconducting radio frequency cavities: theoretical and experimental studies.

    PubMed

    Dai, J; Belomestnykh, S; Ben-Zvi, I; Xu, Wencan

    2013-11-01

    We propose a theoretical model based on network analysis to study the external quality factor (Q factor) of dual-feed coupling for superconducting radio-frequency (SRF) cavities. Specifically, we apply our model to the dual-feed 704 MHz half-cell SRF gun for Brookhaven National Laboratory's prototype Energy Recovery Linac (ERL). The calculations show that the external Q factor of this dual-feed system is adjustable from 10(4) to 10(9) provided that the adjustment range of a phase shifter covers 0°-360°. With a period of 360°, the external Q factor of the coupling system changes periodically with the phase difference between the two coupling arms. When the RF phase of both coupling arms is adjusted simultaneously in the same direction, the external Q factor of the system also changes periodically, but with a period of 180°.

  14. Effect of Air-Sea coupling on the Frequency Distribution of Intense Tropical Cyclones over the Northwestern Pacific

    NASA Astrophysics Data System (ADS)

    Ogata, Tomomichi; Mizuta, Ryo; Adachi, Yukimasa; Murakami, Hiroyuki; Ose, Tomomaki

    2016-04-01

    Effect of air-sea coupling on the frequency distribution of intense tropical cyclones (TCs) over the northwestern Pacific (NWP) region is investigated using an atmosphere and ocean coupled general circulation model (AOGCM). Monthly varying flux adjustment enables AOGCM to simulate both subseasonal air-sea interaction and realistic seasonal to interannual SST variability. The maximum of intense TC distribution around 20-30°N in the AGCM shifts equatorward in the AOGCM due to the air-sea coupling. Hence AOGCM reduces northward intense TC distribution bias seen in AGCM. Over the NWP, AOGCM-simulated SST variability is large around 20-30°N where the warm mixed layer becomes shallower rapidly. Active entrainment from subsurface water over this region causes stronger SST cooling and hence TC intensity decreases. These results suggest that air-sea coupling characterized by subsurface oceanic condition causes more realistic distribution of intense TCs over the NWP.

  15. Effect of air-sea coupling on the frequency distribution of intense tropical cyclones over the northwestern Pacific

    NASA Astrophysics Data System (ADS)

    Ogata, Tomomichi; Mizuta, Ryo; Adachi, Yukimasa; Murakami, Hiroyuki; Ose, Tomoaki

    2015-12-01

    Effect of air-sea coupling on the frequency distribution of intense tropical cyclones (TCs) over the northwestern Pacific (NWP) region is investigated using an atmosphere and ocean coupled general circulation model (AOGCM). Monthly varying flux adjustment enables AOGCM to simulate both subseasonal air-sea interaction and realistic seasonal to interannual sea surface temperature (SST) variability. The maximum of intense TC distribution around 20-30°N in the AGCM shifts equatorward in the AOGCM due to the air-sea coupling. Hence, AOGCM reduces northward intense TC distribution bias seen in AGCM. Over the NWP, AOGCM-simulated SST variability is large around 20-30°N where the warm mixed layer becomes shallower rapidly. Active entrainment from subsurface water over this region causes stronger SST cooling, and hence, TC intensity decreases. These results suggest that air-sea coupling characterized by subsurface oceanic condition causes more realistic distribution of intense TCs over the NWP.

  16. Control of low-frequency noise for piping systems via the design of coupled band gap of acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Li, Yanfei; Shen, Huijie; Zhang, Linke; Su, Yongsheng; Yu, Dianlong

    2016-07-01

    Acoustic wave propagation and sound transmission in a metamaterial-based piping system with Helmholtz resonator (HR) attached periodically are studied. A transfer matrix method is developed to conduct the investigation. Calculational results show that the introduction of periodic HRs in the piping system could generate a band gap (BG) near the resonant frequency of the HR, such that the bandwidth and the attenuation effect of HR improved notably. Bragg type gaps are also exist in the system due to the systematic periodicity. By plotting the BG as functions of HR parameters, the effect of resonator parameters on the BG behavior, including bandwidth, location and attenuation performance, etc., is examined. It is found that Bragg-type gap would interplay with the resonant-type gap under some special situations, thereby giving rise to a super-wide coupled gap. Further, explicit formulation for BG exact coupling is extracted and some key parameters on modulating the width and the attenuation coefficient of coupled gaps are investigated. The coupled gap can be located to any frequency range as one concerned, thus rendering the low-frequency noise control feasible in a broad band range.

  17. Phase and amplitude dynamics in large systems of coupled oscillators: growth heterogeneity, nonlinear frequency shifts, and cluster states.

    PubMed

    Lee, Wai Shing; Ott, Edward; Antonsen, Thomas M

    2013-09-01

    This paper addresses the behavior of large systems of heterogeneous, globally coupled oscillators each of which is described by the generic Landau-Stuart equation, which incorporates both phase and amplitude dynamics of individual oscillators. One goal of our paper is to investigate the effect of a spread in the amplitude growth parameter of the oscillators and of the effect of a homogeneous nonlinear frequency shift. Both of these effects are of potential relevance to recently reported experiments. Our second goal is to gain further understanding of the macroscopic system dynamics at large coupling strength, and its dependence on the nonlinear frequency shift parameter. It is proven that at large coupling strength, if the nonlinear frequency shift parameter is below a certain value, then there is a unique attractor for which the oscillators all clump at a single amplitude and uniformly rotating phase (we call this a single-cluster "locked state"). Using a combination of analytical and numerical methods, we show that at higher values of the nonlinear frequency shift parameter, the single-cluster locked state attractor continues to exist, but other types of coexisting attractors emerge. These include two-cluster locked states, periodic orbits, chaotic orbits, and quasiperiodic orbits.

  18. Magnetoelectric Effects in Local Light-Matter Interactions

    NASA Astrophysics Data System (ADS)

    Bliokh, Konstantin Y.; Kivshar, Yuri S.; Nori, Franco

    2014-07-01

    We study the generic dipole interaction of a monochromatic free-space electromagnetic field with a bi-isotropic nanoparticle or a molecule. Contributions associated with the breaking of dual, P, and T symmetries are responsible for electric-magnetic asymmetry, chirality, and the nonreciprocal magnetoelectric effect, respectively. We calculate absorption rates, radiation forces, and radiation torques for the nanoparticle and introduce novel field characteristics quantifying the transfer of energy, momentum, and angular momentum due to the three symmetry-breaking effects. In particular, we put forward a concept of "magnetoelectric energy density," quantifying the local PT symmetry of the field. Akin to the "superchiral" light suggested recently for local probing of molecular chirality, here we suggest employing complex fields for a sensitive probing of the nonreciprocal magnetoelectric effect in nanoparticles or molecules.

  19. A magnetoelectric composite based microwave phase shifter

    NASA Astrophysics Data System (ADS)

    Bichurin, M. I.; Petrov, V. M.; Srinivasan, G.

    2008-03-01

    Magnetoelectric (ME) properties of ferrite-ferroelectric composites arise from their response to elastic and electromagnetic force fields. The unique combination of magnetic, electrical, and ME interactions opens up the possibility of electric field tunable ferromagnetic resonance (FMR) based devices [1]. Here we discuss an ME phase shifter operating in the FMR region at 9.3 GHz. A slot line on a yttrium iron garnet film bonded to lead zirconate titanate (PZT) provides a basis for the phase shifter. The circularly polarized microwave magnetic field of the slot line interacts with the ferrite and causes variation of phase velocity with the controlling magnetic and electric fields. Electrical tuning is realized with the application of a control voltage due to PZT. The estimated phase shift per unit length and unit voltage is to 20 deg/cm kV for a PZT thickness of 0.5 mm. 1 S. Shastry and G. Srinivasan, M.I. Bichurin, V.M. Petrov, A.S. Tatarenko. Phys. Rev. B, 70 064416 (2004). - supported by grants from the Office of Naval Research and the Russian Foundation for Basic Research.

  20. Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4

    SciTech Connect

    Toft-Petersen, Rasmus; Reehuis, Manfred; Jensen, Thomas B. S.; Andersen, Niels H.; Li, Jiying; Le, Manh Duc; Laver, Mark; Niedermayer, Christof; Klemke, Bastian; Lefmann, Kim; Vaknin, David

    2015-07-06

    We report significant details of the magnetic structure and spin dynamics of LiFePO4 obtained by single-crystal neutron scattering. Our results confirm a previously reported collinear rotation of the spins away from the principal b axis, and they determine that the rotation is toward the a axis. In addition, we find a significant spin-canting component along c. Furthermore, the possible causes of these components are discussed, and their significance for the magnetoelectric effect is analyzed. Inelastic neutron scattering along the three principal directions reveals a highly anisotropic hard plane consistent with earlier susceptibility measurements. While using a spin Hamiltonian, we show that the spin dimensionality is intermediate between XY- and Ising-like, with an easy b axis and a hard c axis. As a result, it is shown that both next-nearest neighbor exchange couplings in the bc plane are in competition with the strongest nearest neighbor coupling.

  1. Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4

    NASA Astrophysics Data System (ADS)

    Toft-Petersen, Rasmus; Reehuis, Manfred; Jensen, Thomas B. S.; Andersen, Niels H.; Li, Jiying; Le, Manh Duc; Laver, Mark; Niedermayer, Christof; Klemke, Bastian; Lefmann, Kim; Vaknin, David

    2015-07-01

    We report significant details of the magnetic structure and spin dynamics of LiFePO4 obtained by single-crystal neutron scattering. Our results confirm a previously reported collinear rotation of the spins away from the principal b axis, and they determine that the rotation is toward the a axis. In addition, we find a significant spin-canting component along c . The possible causes of these components are discussed, and their significance for the magnetoelectric effect is analyzed. Inelastic neutron scattering along the three principal directions reveals a highly anisotropic hard plane consistent with earlier susceptibility measurements. Using a spin Hamiltonian, we show that the spin dimensionality is intermediate between X Y - and Ising-like, with an easy b axis and a hard c axis. It is shown that both next-nearest neighbor exchange couplings in the b c plane are in competition with the strongest nearest neighbor coupling.

  2. Artworks characterization at THz frequencies: preliminary results via the Fiber-Coupled Terahertz Time Domain System

    NASA Astrophysics Data System (ADS)

    Catapano, Ilaria; Soldovieri, Francesco

    2015-04-01

    In the research field of art and archaeology, scientific observation and analysis are hugely demanded to gather as more information as possible on the materials and techniques used to create artworks as well as in previous restoration actions. In this frame, diagnostic tools exploiting electromagnetic waves deserve massive interest tanks to their ability to provide non-invasive and possibly contactless characterization of the investigated objects. Among the electromagnetic diagnostic technologies, those working at frequencies belonging to the 0.1-10 THz range are currently deserving an increased attention since THz waves are capable of penetrating into optically opaque materials (up to the preparation layers), without direct contact and by involving sufficiently low energy to be considered as perfectly non-invasive in practice [1,2]. Moreover, being THz non-ionizing radiations, a moderate exposure to them implies minor long term risks to the molecular stability of the historical artifact and humans. Finally, recent developments of THz technology have allowed the commercialization of compact, flexible and portable systems. One of them is the Fiber-Coupled Terahertz Time Domain System (FICO) developed by Z-Omega, acquired by the Institute of Electromagnetic Sensing of the Environment (IREA) in 2013. This system works in the range from 60GHz to 3THz with a waveform acquisition speed up to 500Hz, it is equipped with fiber optic coupled transmitting and receiving probes and, few months ago, has been potentiated by means of an automatic positioning system enabling to scan a 150mm x 150mm area. In the frame of the IREA research activities regarding cultural heritage, the FICO system is currently adopted to perform both spectroscopy and imaging, which are the two kind of analysis wherein THz technology can be profitably explored [3]. In particular, THz spectroscopy is used to distinguish different artists materials by exploiting their peculiar fingerprint in the absorption

  3. Colossal magnetoelectric effect in Co3TeO6 family of compounds

    NASA Astrophysics Data System (ADS)

    Artyukhin, Sergey; Oh, Yoon Seok; Yang, Jun Jie; Zapf, Vivien; Kim, Jae Wook; Cheong, Sang-Wook; Vanderbilt, David

    2014-03-01

    Multiferroic Co3TeO6 and related materials attracted much attention recently due to their rich phase diagrams, magnetic field - driven electric polarization and incommensurate spin structures. We model the interacting magnetic and ferroelectric degrees of freedom in these compounds with Landau-type theory and calculate the phase diagram. Comparison of our results with experiment reveals that a particular magnetic anisotropy in some of the compounds results in a second-order spin-flop transition, associated with a large change of polarization. In the vicinity of the transition the spin-flopped phase can be stabilized by a small external magnetic field, which gives rise to a colossal magnetoelectric effect, recently demostrated experimentally. Furthermore, we analyze the types of domain walls that can occur in these materials, and study their interactions. The clamping of domain walls of different types enables the cross-control of ferroic orderings, although they may not be coupled in the bulk. We corraborate our results with ab-initio computations of the polarization, piezoelectric response and optical properties. Our results could pave the way to the design of a new generation of magnetoelectric devices. The work at Rutgers University was supported by the NSF under Grant NSF-DMREF-1233349.

  4. Domain wall in a quantum anomalous Hall insulator as a magnetoelectric piston

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Pramey; Tserkovnyak, Yaroslav

    2016-07-01

    We theoretically study the magnetoelectric coupling in a quantum anomalous Hall insulator state induced by interfacing a dynamic magnetization texture to a topological insulator. In particular, we propose that the quantum anomalous Hall insulator with a magnetic configuration of a domain wall, when contacted by electrical reservoirs, acts as a magnetoelectric piston. A moving domain wall pumps charge current between electrical leads in a closed circuit, while applying an electrical bias induces reciprocal domain-wall motion. This pistonlike action is enabled by a finite reflection of charge carriers via chiral modes imprinted by the domain wall. Moreover, we find that, when compared with the recently discovered spin-orbit torque-induced domain-wall motion in heavy metals, the reflection coefficient plays the role of an effective spin-Hall angle governing the efficiency of the proposed electrical control of domain walls. Quantitatively, this effective spin-Hall angle is found to approach a universal value of 2, providing an efficient scheme to reconfigure the domain-wall chiral interconnects for possible memory and logic applications.

  5. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic.

    PubMed

    Mundy, Julia A; Brooks, Charles M; Holtz, Megan E; Moyer, Jarrett A; Das, Hena; Rébola, Alejandro F; Heron, John T; Clarkson, James D; Disseler, Steven M; Liu, Zhiqi; Farhan, Alan; Held, Rainer; Hovden, Robert; Padgett, Elliot; Mao, Qingyun; Paik, Hanjong; Misra, Rajiv; Kourkoutis, Lena F; Arenholz, Elke; Scholl, Andreas; Borchers, Julie A; Ratcliff, William D; Ramesh, Ramamoorthy; Fennie, Craig J; Schiffer, Peter; Muller, David A; Schlom, Darrell G

    2016-01-01

    Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3-the geometric ferroelectric with the greatest known planar rumpling-we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially-from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering. PMID:27652564

  6. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic

    NASA Astrophysics Data System (ADS)

    Mundy, Julia A.; Brooks, Charles M.; Holtz, Megan E.; Moyer, Jarrett A.; Das, Hena; Rébola, Alejandro F.; Heron, John T.; Clarkson, James D.; Disseler, Steven M.; Liu, Zhiqi; Farhan, Alan; Held, Rainer; Hovden, Robert; Padgett, Elliot; Mao, Qingyun; Paik, Hanjong; Misra, Rajiv; Kourkoutis, Lena F.; Arenholz, Elke; Scholl, Andreas; Borchers, Julie A.; Ratcliff, William D.; Ramesh, Ramamoorthy; Fennie, Craig J.; Schiffer, Peter; Muller, David A.; Schlom, Darrell G.

    2016-09-01

    Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3—the geometric ferroelectric with the greatest known planar rumpling—we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially—from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.

  7. Ion-beam sputtering deposition and magnetoelectric properties of layered heterostructures (FM/PZT/FM)n, where FM - Co or Ni78Fe22

    NASA Astrophysics Data System (ADS)

    Stognij, Alexander; Novitskii, Nikolai; Sazanovich, Andrei; Poddubnaya, Nadezhda; Sharko, Sergei; Mikhailov, Vladimir; Nizhankovski, Viktor; Dyakonov, Vladimir; Szymczak, Henryk

    2013-08-01

    Magnetoelectric properties of layered heterostructures (FM/PZT/FM)n (n≤ 3) obtained by ion-beam sputtering deposition of ferromagnetic metal (FM), where FM is the cobalt (Co) or permalloy Ni78Fe22, onto ferroelectric ceramic based on lead zirconate titanate (PZT) have been studied. The polished ferroelectric plates in thickness from 400 to 20 μm were subjected to finished treatment by ion-beam sputtering. After plasma activation they were covered by the ferromagnetic films from 1 to 6 μm in thickness. Enhanced characteristics of these structures were reached by means of both the thickness optimization of ferroelectric and ferromagnetic layers and obtaining of ferromagnetic/ferroelectric interfaces being free from defects and foreign impurities. Assuming on the basis of analysis of elastic stresses in the ferromagnetic film that the magnetoelectric effect forms within ferromagnetic/ferroelectric interface, the structures with 2-3 ferromagnetic layers were obtained. In layered heterostructure (Py/PZT/Py)3, the optimal thickness of ferromagnetic film was 2 μm, and outer and inner ferroelectric layers had 20 μm and 80 μm in thickness, respectively. For such structure the maximal magnetoelectric voltage coefficient of 250 mV/(cm Oe) was reached at a frequency 100 Hz in magnetic field of 0.25 T at room temperature. The structures studied can serve as energy-independent elements detecting the change of magnetic or electric fields in electronic devices based on magnetoelectric effect.

  8. Microwave magnetoelectric effect via skyrmion resonance modes in a helimagnetic multiferroic.

    PubMed

    Okamura, Y; Kagawa, F; Mochizuki, M; Kubota, M; Seki, S; Ishiwata, S; Kawasaki, M; Onose, Y; Tokura, Y

    2013-01-01

    Magnetic skyrmion, a topologically stable spin-swirling object, can host emergent electromagnetism, as exemplified by the topological Hall effect and electric-current-driven skyrmion motion. To achieve efficient manipulation of nano-sized functional spin textures, it is imperative to exploit the resonant motion of skyrmions, analogously to the role of the ferromagnetic resonance in spintronics. The magnetic resonance of skyrmions has recently been detected with oscillating magnetic fields at 1-2 GHz, launching a search for new skyrmion functionality operating at microwave frequencies. Here we show a microwave magnetoelectric effect in resonant skyrmion dynamics. Through microwave transmittance spectroscopy on the skyrmion-hosting multiferroic crystal Cu₂OSeO₃ combined with theoretical simulations, we reveal nonreciprocal directional dichroism (NDD) at the resonant mode, that is, oppositely propagating microwaves exhibit different absorption. The microscopic mechanism of the present NDD is not associated with the conventional Faraday effect but with the skyrmion magnetoelectric resonance instead, suggesting a conceptually new microwave functionality.

  9. Percolation Model of Magnetoelectric Effects in Ferrite/Piezoelectric Bulk Composite

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Bichurin, M. I.; Tuskov, D. S.; Srinivasan, G.

    2006-03-01

    A bulk composite consisting of ferrite-ferroelectric phases shows magnetoelectric (ME) effects that are product properties of the magnetostrictive deformation and piezoelectric charge generation. Bulk composites with strong ME effects are desirable over layered samples due to superior mechanical strength. Here we discuss a percolation approach for modeling the ME effect in bulk composite [1]. We calculated percolation threshold corresponding to structural phase transition of bulk composites from the state with ME interactions to a state with no ME interactions.Expressions for longitudinal and transverse low-frequency ME voltage coefficients have been obtained. Volume fractions corresponding to peak ME voltage coefficients are given. We obtained a piezoelectric volume fraction of 0.45 for maximum ME effect in bulk samples of lead zirconate titanate and nickel-cobalt ferrite. These estimates are in excellent agreement with data. supported by a grant from the NSF. [1] V. M. Petrov, M. I. Bichurin, V. M. Laletin, N. Paddubnaya, and G. Srinivasan, Magnetoelectric Interaction Phenomena in Crystals-NATO Science Series II. Vol. 164, Eds. M. Fiebig, V. V. Eremenko, and I. E. Chupis (Kluwer Academic Publishers, London, 2004), p.65-70.

  10. Enhanced Broadband Vibration Energy Harvesting Using a Multimodal Nonlinear Magnetoelectric Converter

    NASA Astrophysics Data System (ADS)

    Lin, Zhiming; Yang, Jin; Zhao, Jiangxin; Zhao, Nian; Liu, Jun; Wen, Yumei; Li, Ping

    2016-07-01

    In this work, we present a multimodal wideband vibration energy harvester designed to scavenge energy from ambient vibrations over a wide frequency range. The harvester consists of a folded cantilever, three magnetoelectric (ME) transducers, and two magnetic circuits. The folded cantilever enables multi-resonant response formed by bending of each stage, and the nonlinear magnetic forces acting on the folded cantilever beam allow further broadening of the frequency response. We also investigate the effects of the position of the ME transducer on the electrical output in order to achieve optimal performance. The experimental results show that the vibration energy harvester exhibited three resonance peaks in a range of 5 Hz to 30 Hz, a wider working bandwidth of 10.1 Hz, and a maximum average power value of 31.58 μW at an acceleration of 0.6 g (with g = 9.8 m/s2).

  11. Tunable coupling between fixed-frequency superconducting transmon qubits, Part II: Implementing a two-qubit XX-90 gate

    NASA Astrophysics Data System (ADS)

    McKay, David C.; Filipp, Stefan; Mezzacapo, Antonio; Magesan, Easwar; Chow, Jerry M.; Gambetta, Jay M.

    In this talk we will present a two-qubit gate implemented in a tunable coupling architecture which consists of a flux-tunable qubit (``coupler'') coupling two fixed-frequency transmons (``qubits''). In this architecture, a resonant SWAP (XX+YY) interaction is generated between the qubits when the coupler is modulated at the qubit frequency difference, typically a few hundred MHz. This interaction has a number of advantages, in particular, it only requires AC flux control and can resonantly address individual qubit pairs. Here we present a protocol which realizes the XX-90 gate based on this interaction. This gate has the specific characteristic that it takes any of the four basis states (| 00 > , | 10 > , | 01 > , | 11 >) to Bell states. We demonstrate gate fidelities greater than 96% characterized by state tomography and randomized benchmarking. Looking forward, this gate is a prime candidate for implementing the surface code because it can couple highly coherent qubits which are spaced far apart in frequency thereby minimizing crosstalk and collisions. This work is supported by ARO under Contract W911NF-14-1-0124.

  12. Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen

    SciTech Connect

    Zaka-ul-Islam, M.; Niemi, K.; Gans, T.; O'Connell, D.

    2011-07-25

    Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

  13. Cavity piezomechanical strong coupling and frequency conversion on an aluminum nitride chip

    NASA Astrophysics Data System (ADS)

    Zou, Chang-Ling; Han, Xu; Jiang, Liang; Tang, Hong X.

    2016-07-01

    Schemes to achieve strong coupling between mechanical modes of aluminum nitride microstructures and microwave cavity modes due to the piezoelectric effect are proposed. We show that the strong-coupling regime is feasible for an on-chip aluminum nitride device that is either enclosed by a three-dimensional microwave cavity or integrated with a superconducting coplanar resonator. Combining with optomechanics, the piezomechanical strong coupling permits coherent conversion between microwave and optical modes with high efficiency. Hence, the piezomechanical system will be an efficient transducer for applications in hybrid quantum systems.

  14. Beta-coupled high-frequency activity and beta-locked neuronal spiking in the subthalamic nucleus of Parkinson's disease.

    PubMed

    Yang, Andrew I; Vanegas, Nora; Lungu, Codrin; Zaghloul, Kareem A

    2014-09-17

    Beta frequency (13-30 Hz) oscillatory activity in the subthalamic nucleus (STN) of Parkinson's disease (PD) has been shown to influence the temporal dynamics of high-frequency oscillations (HFOs; 200-500 Hz) and single neurons, potentially compromising the functional flexibility of the motor circuit. We examined these interactions by simultaneously recording both local field potential and single-unit activity from the basal ganglia of 15 patients with PD during deep brain stimulation (DBS) surgery of the bilateral STN. Phase-amplitude coupling (PAC) in the STN was specific to beta phase and HFO amplitude, and this coupling was strongest at the dorsal STN border. We found higher beta-HFO PAC near DBS lead contacts that were clinically effective compared with the remaining non-effective contacts, indicating that PAC may be predictive of response to STN DBS. Neuronal spiking was locked to the phase of 8-30 Hz oscillations, and the spatial topography of spike-phase locking (SPL) was similar to that of PAC. Comparisons of PAC and SPL showed a lack of spatiotemporal correlations. Beta-coupled HFOs and field-locked neurons had different preferred phase angles and did not co-occur within the same cycle of the modulating oscillation. Our findings provide additional support that beta-HFO PAC may be central to the pathophysiology of PD and suggest that field-locked neurons alone are not sufficient for the emergence of beta-coupled HFOs. PMID:25232117

  15. Magnetic field directed assembly of superstructures of ferrite-ferroelectric core-shell nanoparticles and studies on magneto-electric interactions

    SciTech Connect

    Srinivasan, G. Sreenivasulu, G.; Benoit, Crystal; Petrov, V. M.; Chavez, F.

    2015-05-07

    Composites of ferromagnetic and ferroelectric are of interest for studies on mechanical strain mediated magneto-electric (ME) interactions and for useful technologies. Here, we report on magnetic-field-assisted-assembly of barium titanate (BTO)-nickel ferrite (NFO) core-shell particles into linear chains and 2D/3D arrays and measurements of ME effects in such assemblies. First, we synthesized the core-shell nano-particles with 50–600 nm BTO and 10–200 nm NFO by chemical self-assembly by coating the ferroic particles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst via the “click” reaction. The core-shell structure was confirmed with electron microscopy and scanning probe microscopy. We obtained superstructure of the core-shell particles by subjecting them to a magnetic field gradient that exerts an attractive force on the particles and align them toward the regions of high field strengths. At low particle concentration, linear chains were formed and they evolved into 2D and 3D arrays at high particle concentrations. Magnetoelectric characterization on unassembled films and assembled arrays has been performed through measurements of low-frequency ME voltage coefficient (MEVC) by subjecting the sample to a bias magnetic field and an ac magnetic field. The MEVC is higher for field-assembled samples than for unassembled films and is found to be sensitive to field orientation with a higher MEVC for magnetic fields parallel to the array direction than for magnetic fields perpendicular to the array. A maximum MEVC of 20 mV/cm Oe, one of the highest reported for any bulk nanocomposite, is measured across the array thickness. A model is provided for ME coupling in the superstructures of BTO-NFO particulate composites. First, we estimated the MEVC for a free-standing BTO-NFO core-shell particle and then extended the model to include an array of linear chains of the particles. The theoretical estimates are in

  16. Multisensory representation of frequency across audition and touch: high density electrical mapping reveals early sensory-perceptual coupling.

    PubMed

    Butler, John S; Foxe, John J; Fiebelkorn, Ian C; Mercier, Manuel R; Molholm, Sophie

    2012-10-31

    The frequency of environmental vibrations is sampled by two of the major sensory systems, audition and touch, notwithstanding that these signals are transduced through very different physical media and entirely separate sensory epithelia. Psychophysical studies have shown that manipulating frequency in audition or touch can have a significant cross-sensory impact on perceived frequency in the other sensory system, pointing to intimate links between these senses during computation of frequency. In this regard, the frequency of a vibratory event can be thought of as a multisensory perceptual construct. In turn, electrophysiological studies point to temporally early multisensory interactions that occur in hierarchically early sensory regions where convergent inputs from the auditory and somatosensory systems are to be found. A key question pertains to the level of processing at which the multisensory integration of featural information, such as frequency, occurs. Do the sensory systems calculate frequency independently before this information is combined, or is this feature calculated in an integrated fashion during preattentive sensory processing? The well characterized mismatch negativity, an electrophysiological response that indexes preattentive detection of a change within the context of a regular pattern of stimulation, served as our dependent measure. High-density electrophysiological recordings were made in humans while they were presented with separate blocks of somatosensory, auditory, and audio-somatosensory "standards" and "deviants," where the deviant differed in frequency. Multisensory effects were identified beginning at ∼200 ms, with the multisensory mismatch negativity (MMN) significantly different from the sum of the unisensory MMNs. This provides compelling evidence for preattentive coupling between the somatosensory and auditory channels in the cortical representation of frequency.

  17. Multisensory representation of frequency across audition and touch: high density electrical mapping reveals early sensory-perceptual coupling.

    PubMed

    Butler, John S; Foxe, John J; Fiebelkorn, Ian C; Mercier, Manuel R; Molholm, Sophie

    2012-10-31

    The frequency of environmental vibrations is sampled by two of the major sensory systems, audition and touch, notwithstanding that these signals are transduced through very different physical media and entirely separate sensory epithelia. Psychophysical studies have shown that manipulating frequency in audition or touch can have a significant cross-sensory impact on perceived frequency in the other sensory system, pointing to intimate links between these senses during computation of frequency. In this regard, the frequency of a vibratory event can be thought of as a multisensory perceptual construct. In turn, electrophysiological studies point to temporally early multisensory interactions that occur in hierarchically early sensory regions where convergent inputs from the auditory and somatosensory systems are to be found. A key question pertains to the level of processing at which the multisensory integration of featural information, such as frequency, occurs. Do the sensory systems calculate frequency independently before this information is combined, or is this feature calculated in an integrated fashion during preattentive sensory processing? The well characterized mismatch negativity, an electrophysiological response that indexes preattentive detection of a change within the context of a regular pattern of stimulation, served as our dependent measure. High-density electrophysiological recordings were made in humans while they were presented with separate blocks of somatosensory, auditory, and audio-somatosensory "standards" and "deviants," where the deviant differed in frequency. Multisensory effects were identified beginning at ∼200 ms, with the multisensory mismatch negativity (MMN) significantly different from the sum of the unisensory MMNs. This provides compelling evidence for preattentive coupling between the somatosensory and auditory channels in the cortical representation of frequency. PMID:23115172

  18. On the (Frequency) Modulation of Coupled Oscillator Arrays in Phased Array Beam Control

    NASA Technical Reports Server (NTRS)

    Pogorzelski, R.; Acorn, J.; Zawadzki, M.

    2000-01-01

    It has been shown that arrays of voltage controlled oscillators coupled to nearest neighbors can be used to produce useful aperture phase distributions for phased array antennas. However, placing information of the transmitted signal requires that the oscillations be modulated.

  19. Comparison of air-launched and ground-coupled configurations of SFCW GPR in time, frequency and wavelet domain

    NASA Astrophysics Data System (ADS)

    Van De Vijver, Ellen; De Pue, Jan; Cornelis, Wim; Van Meirvenne, Marc

    2015-04-01

    A stepped frequency continuous wave (SFCW) ground penetrating radar (GPR) system produces waveforms consisting of a sequence of sine waves with linearly increasing frequency. By adopting a wide frequency bandwidth, SFCW GPR systems offer an optimal resolution at each achievable measurement depth. Furthermore, these systems anticipate an improved penetration depth and signal-to-noise ratio (SNR) as compared to time-domain impulse GPRs, because energy is focused in one single frequency at a time and the phase and amplitude of the reflected signal is recorded for each discrete frequency step. However, the search for the optimal practical implementation of SFCW GPR technology to fulfil these theoretical advantages is still ongoing. In this study we compare the performance of a SFCW GPR system for air-launched and ground-coupled antenna configurations. The first is represented by a 3d-Radar Geoscope GS3F system operated with a V1213 antenna array. This array contains 7 transmitting and 7 receiving antennae resulting in 13 measurement channels at a spacing of 0.075 m and providing a total scan width of 0.975 m. The ground-coupled configuration is represented by 3d-Radar's latest-generation SFCW system, GeoScope Mk IV, operated with a DXG1212 antenna array. With 6 transmitting and 5 receiving antennae this array provides 12 measurement channels and an effective scan width of 0.9 m. Both systems were tested on several sites representative of various application environments, including a test site with different road specimens (Belgian Road Research Centre) and two test areas in different agricultural fields in Flanders, Belgium. For each test, data acquisition was performed using the full available frequency bandwidth of the systems (50 to 3000 MHz). Other acquisition parameters such as the frequency step and dwell time were varied in different tests. Analyzing the data of the different tests in time, frequency and wavelet domain allows to evaluate different performance

  20. Inhibitory and excitatory pulse coupling of two frequency-different chemical oscillators with time delay.

    PubMed

    Proskurkin, Ivan S; Lavrova, Anastasia I; Vanag, Vladimir K

    2015-06-01

    Dynamical regimes of two pulse coupled non-identical Belousov-Zhabotinsky oscillators have been studied experimentally as well as theoretically with the aid of ordinary differential equations and phase response curves both for pure inhibitory and pure excitatory coupling. Time delay τ between a spike in one oscillator and perturbing pulse in the other oscillator plays a significant role for the phase relations of synchronous regimes of the 1:1 and 1:2 resonances. Birhythmicity between anti-phase and in-phase oscillations for inhibitory pulse coupling as well as between 1:2 and 1:1 resonances for excitatory pulse coupling have also been found. Depending on the ratio of native periods of oscillations T2/T1, coupling strength, and time delay τ, such resonances as 1:1 (with different phase locking), 2:3, 1:2, 2:5, 1:3, 1:4, as well as complex oscillations and oscillatory death are observed.

  1. Power coupling and electrical characterization of a radio-frequency micro atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Marinov, D.; Braithwaite, N. St. J.

    2014-12-01

    We propose an efficient RF power coupling scheme for a micro atmospheric pressure plasma jet operating in helium. The discharge gap is used as a resonant element in a series LC circuit. In resonance, the voltage across the discharge gap is amplified and the ignition of the plasma is enabled with the input RF power as low as 0.5 W. High power coupling efficiency and simplicity of the circuit allow accurate electrical characterization of the discharge. Systematic measurements of the dissipated power as a function of the applied voltage are reported for the discharge operating in helium with molecular admixtures of N2 and O2.

  2. Effects of relationship duration, cohabitation, and marriage on the frequency of intercourse in couples: Findings from German panel data.

    PubMed

    Schröder, Jette; Schmiedeberg, Claudia

    2015-07-01

    Research into the changes in the frequency of sexual intercourse is (with few exceptions) limited to cross-sectional analyses of marital duration. We investigate the frequency of intercourse while taking into account relationship duration as well as the duration of cohabitation and marriage, effects of parenthood, and relationship quality. For the analysis we apply fixed effects regression models using data from the German Family Panel (pairfam), a nationwide randomly sampled German panel survey. Our findings imply that the drop in sex frequency occurs early in the relationship, whereas neither cohabitation nor marriage affects the frequency of intercourse to a significant extent. Sex frequency is reduced during pregnancy and as long as the couple has small children, but becomes revived later on. Relationship quality is found to play a role as well. These results are contrary to the honeymoon effect found in earlier research, but indicate that in times of postponed marriage an analogous effect may be at work in the initial period of the relationship.

  3. Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGaxFe2-xO4/BaTiO3 composite

    NASA Astrophysics Data System (ADS)

    Ni, Yan; Zhang, Zhen; Nlebedim, Cajetan I.; Jiles, David C.

    2015-05-01

    Multiferroic materials exhibit magnetoelectric (ME) coupling and promise new device applications including magnetic sensors, generators, and filters. An effective method for developing ME materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, the electrical and magnetic properties of Ga doped magnetoelectric CoGaxFe2-xO4/BaTiO3 composite are studied systematically. It is found that Ga doping improves the sensitivity of magnetoelastic response and stabilizes the magnetic phase of the composites. More importantly, Ga doping reduces the electrical conductivity of composite, as well as the dielectric loss. An enhancement of the electrostrain with doping Ga is also observed. Quantitative estimation indicates that magnetoelectric coupling is enhanced for Ga-doped CoGaxFe2-xO4/BaTiO3 composites. Thus, the present work is beneficial to the practical application of composite CoFe2O4/BaTiO3-based multiferroic materials.

  4. Twisted MoSe2 bilayers with variable local stacking and interlayer coupling revealed by low-frequency Raman spectroscopy

    DOE PAGESBeta

    Puretzky, Alexander A.; Liang, Liangbo; Li, Xufan; Xiao, Kai; Sumpter, Bobby G.; Meunier, Vincent; Geohegan, David B.

    2016-01-14

    Unique twisted bilayers of MoSe2 with multiple stacking orientations and interlayer couplings in the narrow range of twist angles, 60 ± 3°, are revealed by low-frequency Raman spectroscopy and theoretical analysis. The slight deviation from 60 allows the concomitant presence of patches featuring all three high-symmetry stacking configurations (2H or AA', AB', A'B) in one unique bilayer system. In this case, the periodic arrangement of the patches and their size strongly depend on the twist angle. Ab initio modeling predicts significant changes in frequencies and intensities of low-frequency modes versus stacking and twist angle. Experimentally, the variable stacking and couplingmore » across the interface is revealed by the appearance of two breathing modes corresponding to the mixture of the high-symmetry stacking configurations and unaligned regions of monolayers. Only one breathing mode is observed outside the narrow range of twist angles. This indicates a stacking transition to unaligned monolayers with mismatched atom registry without the in-plane restoring force required to generate a shear mode. As a result, the variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide a new platform for optoelectronic applications of these materials.« less

  5. Application of coupled analysis methods for prediction of blast-induced dominant vibration frequency

    NASA Astrophysics Data System (ADS)

    Li, Haibo; Li, Xiaofeng; Li, Jianchun; Xia, Xiang; Wang, Xiaowei

    2016-03-01

    Blast-induced dominant vibration frequency (DVF) involves a complex, nonlinear and small sample system considering rock properties, blasting parameters and topography. In this study, a combination of grey relational analysis and dimensional analysis procedures for prediction of dominant vibration frequency are presented. Six factors are selected from extensive effect factor sequences based on grey relational analysis, and then a novel blast-induced dominant vibration frequency prediction is obtained by dimensional analysis. In addition, the prediction is simplified by sensitivity analysis with 195 experimental blast records. Validation is carried out for the proposed formula based on the site test database of the firstperiod blasting excavation in the Guangdong Lufeng Nuclear Power Plant (GLNPP). The results show the proposed approach has a higher fitting degree and smaller mean error when compared with traditional predictions.

  6. Colossal magnetodielectric effect and spin flop in magnetoelectric Co4Nb2O9 crystal

    NASA Astrophysics Data System (ADS)

    Yin, L. H.; Zou, Y. M.; Yang, J.; Dai, J. M.; Song, W. H.; Zhu, X. B.; Sun, Y. P.

    2016-07-01

    We have investigated the detailed magnetic, magnetoelectric (ME), magnetodielectric (MD) and thermal expansion properties in Co4Nb2O9 crystal. A magnetic-field-induced spin flop was observed below antiferromagnetic (AFM) transition temperature TN. Dielectric constant at applied magnetic field nearly diverges around the AFM transition, giving rise to a colossal MD effect as high as ˜138% around TN. Theoretical analysis of the ME and MD data revealed a major contribution of critical spin fluctuation to the colossal MD effect in Co4Nb2O9. These results suggest that linear ME materials with large ME coupling might be potentially used to realize large MD effect for future application.

  7. Switchable voltage control of the magnetic coercive field via magnetoelectric effect

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Ma, Jing; Li, Zheng; Shen, Yang; Lin, Yuanhua; Nan, C. W.

    2011-08-01

    Switchable voltage modulation of the magnetic properties is reported in different multiferroic bilayers with magnetic films grown on pre-poled ferroelectric substrates, based on the magneto-optical Kerr effect observations. The dynamic voltage control of the magnetic coercive field (Hc) is dependent not only on the materials properties of each ferroic layer, but also on the bias voltage history. The Hc versus electric field behaviors essentially track the dependence of the piezostrains of the substrates on the bias voltage. The observations demonstrate that Hc in such multiferroic bilayers can be controlled by voltage via strain-mediated magnetoelectric coupling and that the Hc change is not an artifact due to a heating effect.

  8. Stress-mediated magnetoelectric control of ferromagnetic domain wall position in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Mathurin, Théo; Giordano, Stefano; Dusch, Yannick; Tiercelin, Nicolas; Pernod, Philippe; Preobrazhensky, Vladimir

    2016-02-01

    The motion of a ferromagnetic domain wall in nanodevices is usually induced by means of external magnetic fields or polarized currents. Here, we demonstrate the possibility to reversibly control the position of a Néel domain wall in a ferromagnetic nanostripe through a uniform mechanical stress. The latter is generated by an electro-active substrate combined with the nanostripe in a multiferroic heterostructure. We develop a model describing the magnetization distribution in the ferromagnetic material, properly taking into account the magnetoelectric coupling. Through its numerical implementation, we obtain the relationship between the electric field applied to the piezoelectric substrate and the position of the magnetic domain wall in the nanostripe. As an example, we analyze a structure composed of a PMN-PT substrate and a TbCo2/FeCo composite nanostripe.

  9. Differential-mode vibrational noise cancellation structure for Metglas/Pb(Zr,Ti)O₃ fiber magnetoelectric laminates.

    PubMed

    Gao, Junqi; Zhai, Junyi; Shen, Ying; Shen, Liangguo; Gray, David; Li, Jiefang; Finkel, Peter; Viehland, D

    2011-08-01

    A differential structure which has the ability to reject external vibrational noise for Metglas/Pb(Zr,Ti)O(3) (PZT) fiber-based magnetoelectric (ME) heterostructures has been studied. This type of ME structure functions better than conventional sensors as a magnetic sensor when used in an environment in which vibrational isolation is impractical. Sensors fabricated with this differential mode structure can attenuate external vibrational noise by about 10 to 20 dB at different frequencies, while simultaneously having a doubled ME voltage coefficient. Interestingly, in addition to offering a means of mitigating vibrational noise, this ME structure offers the potential to be a hybrid sensor, separating magnetic and acoustical signals.

  10. PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES: CHF3 Dual-Frequency Capacitively Coupled Plasma by Optical Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, Yi-Jun; Ye, Chao; Huang, Xiao-Jiang; Yuan, Jing; Xing, Zhen-Yu; Ning, Zhao-Yuan

    2008-08-01

    We investigate the intermediate gas phase in the CHF3 13.56 MHz/2 MHz dual-frequency capacitively couple plasma (CCP) for the SiCOH low dielectric constant (low-k) film etching, and the effect of 2 MHz power on radicals concentration. The major dissociation reactions of CHF3 in 13.56MHz CCP are the low dissociation bond energy reactions, which lead to the low F and high CF2 concentrations. The addition of 2 MHz power can raise the probability of high dissociation bond energy reactions and lead to the increase of F concentration while keeping the CF2 concentration almost a constant, which is of advantage to the SiCOH low-k films etching. The radical spatial uniformity is dependent on the power coupling of two sources. The increase of 2 MHz power leads to a poor uniformity, however, the uniformity can be improved by increasing 13.56 MHz power.

  11. Collective excitations of strongly coupled bilayer charged Bose liquids in the third-frequency-moment sum rule

    NASA Astrophysics Data System (ADS)

    Tas, Murat; Tanatar, B.

    2008-09-01

    We calculate the collective excitation modes of strongly coupled bilayer charged Bose systems. We employ the dielectric matrix formulation to study the correlation effects within the random-phase approximation (RPA), the self consistent field approximation Singwi, Tosi, Land, and Sjölander (STLS), and the quasilocalized charge approximation (QLCA), which satisfies the third-frequency-moment (⟨ω3⟩) sum rule. We find that the QLCA predicts a long-wavelength correlation-induced energy gap in the out-of-phase plasmon mode, similar to the situation in electronic bilayer systems. The energy gap and the plasmon density of states are studied as a function of interlayer separation and coupling parameter rs . The results should be helpful for experimental investigations.

  12. Using neutron scattering to explore new magnetoelectric phenomena in both thin films and skyrmion lattices

    NASA Astrophysics Data System (ADS)

    White, Jonathan

    2014-03-01

    Neutron scattering continues to be an invaluable tool for exploring the microscopic magnetic properties of magnetoelectric (ME) and multiferroic materials. Here I will present studies where neutron scattering techniques less commonly used for studying MEs have provided pivotal insight into new ME coupling phenomena. Firstly, we have used polarized neutron reflectometry (PNR) in a study of multiferroic and strained orthorhombic (o-) LuMnO3 thin films. Unlike bulk o-LuMnO3 which is a commensurate antiferromagnet, the films display drastically different properties and are simultaneously incommensurately antiferromagnetic and ferromagnetic at low temperature. The pivotal PNR experiments allowed us to measure the spatial distribution of the ferromagnetic magnetization in the films, and show that the ferromagnetism is most pronounced close to the film-substrate interface which is highly strained due to the lattice mismatch. We could further show the ferromagnetism and antiferromagnetism in the film to be directly coupled, and so demonstrate the promising functional properties of these films. Secondly, we have used small-angle neutron scattering (SANS) to study the topologically protected magnetic spin vortices, or skyrmions, in the chiral-lattice ME insulator Cu2OSeO3. Until 2012, skyrmions had been observed only in (semi)conducting B20 compounds where it is known that they can be manipulated by conduction electrons. From our SANS experiments on Cu2OSeO3, we show that applied electric fields can control the skyrmion lattice orientation in insulators, and in an essentially lossless manner that is dependent on both the size and sign of the electric field. These results provide the first evidence for a the electric field control of topologically protected magnetism in bulk magnetoelectrics.

  13. Microstrip superconducting quantum interference device radio-frequency amplifier: Scattering parameters and input coupling

    SciTech Connect

    Kinion, D; Clarke, J

    2008-01-24

    The scattering parameters of an amplifier based on a dc Superconducting QUantum Interference Device (SQUID) are directly measured at 4.2 K. The results can be described using an equivalent circuit model of the fundamental resonance of the microstrip resonator which forms the input of the amplifier. The circuit model is used to determine the series capacitance required for critical coupling of the microstrip to the input circuit.

  14. The discharge mode transition and O(5p1) production mechanism of pulsed radio frequency capacitively coupled plasma

    NASA Astrophysics Data System (ADS)

    Liu, X. Y.; Hu, J. T.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Shi, J. J.

    2012-07-01

    The discharge mode transition from uniform plasma across the gas gap to the α mode happens at the rising phase of the pulsed radio frequency capacitively coupled plasma (PRF CCP). This transition is attributed to the fast increasing stochastic heating at the edge of sheath. In the second stage with the stable current and voltage amplitude, the consistency between experimental and numerical spatial-temporal 777 nm emission profile suggests that He* and He2* dominate the production of O(5p1) through dissociation and excitation of O2. Finally, the sterilization efficiency of PRF CCP is found to be higher than that of plasma jet.

  15. A two-dimensional broadband vibration energy harvester using magnetoelectric transducer

    SciTech Connect

    Yang, Jin Wen, Yumei; Li, Ping; Yue, Xihai; Yu, Qiangmo; Bai, Xiaoling

    2013-12-09

    In this study, a magnetoelectric vibration energy harvester was demonstrated, which aims at addressing the limitations of the existing approaches in single dimensional operation with narrow working bandwidth. A circular cross-section cantilever rod, not a conventional thin cantilever beam, was adopted to extract vibration energy in arbitrary in-plane motion directions. The magnetic interaction not only resulted in a nonlinear motion of the rod with increased frequency bandwidth, but also contributed to a multi-mode motion to exhibit double power peaks. In energy harvesting with in-plane directions, it showed a maximum bandwidth of 4.4 Hz and power of 0.59 mW, with acceleration of 0.6 g (with g = 9.8 m s{sup −2})

  16. Magnetoelectric composite ceramics of nickel ferrite and lead zirconate titanate via in situ processing

    NASA Astrophysics Data System (ADS)

    Wu, Dandan; Gong, Weihua; Deng, Haijin; Li, Ming

    2007-08-01

    Magnetoelectric (ME) composite ceramics of NiFe2O4 (NFO) and lead zirconate titanate (PZT) were synthesized by a simple in situ processing based on a sol-gel method followed by a conventional sintering. X-ray diffraction patterns and scanning electron microscopy images revealed that this processing can produce two pure phases simultaneously. The in situ grown magnetic NiFe2O4 grains were well dispersed in the PZT matrix. The results demonstrated an attractive ME response of about 28.5 V cm-1 Oe-1 in the 0.35 NiFe2O4/0.65PZT at a resonance frequency of around 287 kHz.

  17. Giant magnetodielectric effect in Terfenol-D/PZT magnetoelectric laminate composite

    NASA Astrophysics Data System (ADS)

    Yao, Y. P.; Hou, Y.; Dong, S. N.; Li, X. G.

    2011-07-01

    The magnetic field dependence of the dielectric permittivity of Terfenol-D/PbZrxTi1-xO3 magnetoelectric composites in the temperature range from 200 K to 340 K was investigated systematically. It was found that there is a large magnetodielectric effect up to 15% around the electromechanical resonance frequency in a magnetic field of 5 kOe at room temperature. Nonmonotonic variations of dielectric permittivity with magnetic fields are associated with the mechanical energy loss due to magnetic domain wall motion in the magnetostrictive layer Terfenol-D. A numerical modeling is proposed and agrees well with the experimental data. The results are of significance in the development of magnetic-field-tuned electronic devices at room temperature.

  18. Note: high sensitivity self-bias magnetoelectric sensor with two different magnetostrictive materials.

    PubMed

    Chen, Lei; Li, Ping; Wen, Yumei; Zhu, Yong

    2013-06-01

    The self-bias magnetoelectric (ME) sensor is designed, fabricated, and characterized for detecting weak ac magnetic-field. The two different magnetostrictive materials produce the gradient of magnetization, resulting in an internal magnetic field and a strong ME response. At zero-biased dc magnetic field, a low-frequency ME voltage coefficient (dVME∕dHac) of 22.11 mV∕Oe is achieved, which is 17.69 times higher than that of the previous magnets∕0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) sensor. Furthermore, the ME voltage coefficient reaches 2.73 V∕Oe at resonance. The induced ME voltage shows an excellent linear relationship to ac magnetic field when field amplitude varies from ~10(-7) Oe to 1 Oe. PMID:23822388

  19. FEM Modeling of a Magnetoelectric Transducer for Autonomous Micro Sensors in Medical Application

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Talleb, Hakeim; Gensbittel, Aurélie; Ren, Zhuoxiang

    2015-11-01

    In the context of wireless and autonomous sensors, this paper presents the multiphysics modeling of an energy transducer based on magnetoelectric (ME) composite for biomedical applications. The study considers the power requirement of an implanted sensor, the communication distance, the size limit of the device for minimal invasive insertion as well as the electromagnetic exposure restriction of the human body. To minimize the electromagnetic absorption by the human body, the energy source is provided by an external reader emitting low frequency magnetic field. The modeling is carried out with the finite element method by solving simultaneously the multiple physics problems including the electric load of the conditioning circuit. The simulation results show that with the T-L mode of a trilayer laminated ME composite, the transducer can deliver the required energy in respecting different constraints.

  20. Electroless Deposition of Nickel on Lead Zirconium Titanate Ceramics: Preparation, Magnetic and Magnetoelectric Properties

    NASA Astrophysics Data System (ADS)

    Bi, K.; Hong, H.; Wu, W.; Wang, Y. G.

    2012-12-01

    The Ni layers with good soft magnetic properties have been successfully electroless deposited on PZT layers. To study the thermodynamics and kinetics of electroless Ni-deposition, the effect of bath parameters such as pH and temperature has been discussed. The structural, magnetic and magnetostrictive properties of Ni layers deposited at various pH and temperature are characterized by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer and standard strain-gauge technique. The grain size, deposition rate, magnetic properties and magnetostrictive properties of Ni layers and magnetoelectric effect of Ni/PZT/Ni trilayers depend strongly on the thermodynamics and kinetics of electroless deposition processes. A maximum ME voltage coefficient of αE,31 = 5.8 V cm-1 Oe-1 is obtained at a frequency of about 101 kHz. These trilayers exhibit a promising potential in actuators, transducers and sensors.

  1. Magnetoelectric coupling in Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 thin films deposited on Pt/TiO2/SiO2/Si substrate

    NASA Astrophysics Data System (ADS)

    Cibert, C.; Zhu, J.; Poullain, G.; Bouregba, R.; More-Chevalier, J.; Pautrat, A.

    2013-01-01

    Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) thin films were sputtered on Pt/TiO2/SiO2/Si substrate. PZT and Terfenol-D layers were chosen for their large piezoelectric and magnetostrictive coefficients, respectively. 4%-5% magnetocapacitance has been measured on a Terfenol-D/Pt/PZT stack at room temperature. A magnetoelectric (ME) voltage coefficient of 150 mV/cm Oe was obtained at low dc magnetic field out of mechanical resonance. This work demonstrates the possibility to achieve ME effect in integrated devices involving Terfenol-D and PZT thin films providing that the diffusion, which may occur between both active layers is reduced using an intermediate layer.

  2. COUPLING

    DOEpatents

    Frisch, E.; Johnson, C.G.

    1962-05-15

    A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)

  3. Quantum frequency conversion and strong coupling of photonic modes using four-wave mixing in integrated microresonators

    NASA Astrophysics Data System (ADS)

    Vernon, Z.; Liscidini, M.; Sipe, J. E.

    2016-08-01

    Single-photon-level quantum frequency conversion has recently been demonstrated using silicon nitride microring resonators. The resonance enhancement offered by such systems enables high-efficiency translation of quantum states of light across wide frequency ranges at subwatt pump powers. We present a detailed theoretical analysis of the conversion dynamics in these systems and show that they are capable of converting single- and multiphoton quantum states. Analytic formulas for the conversion efficiency, spectral conversion probability density, and pump-power requirements are derived which are in good agreement with previous theoretical and experimental results. We show that with only modest improvement to the state of the art, efficiencies exceeding 95% are achievable using less than 100 mW of pump power. At the critical driving strength that yields maximum conversion efficiency, the spectral conversion probability density is shown to exhibit a flat-topped peak, indicating a range of insensitivity to the spectrum of a single-photon input. Two alternate theoretical approaches are presented to study the conversion dynamics: a dressed-mode approach that yields a better intuitive picture of the conversion process, and a study of the temporal dynamics of the participating modes in the resonator, which uncovers a regime of Rabi-like coherent oscillations of single photons between two different frequency modes. This oscillatory regime arises from the strong coupling of distinct frequency modes mediated by coherent pumps.

  4. Study on high coupling efficiency Er-doped fiber laser for femtosecond optical frequency comb

    NASA Astrophysics Data System (ADS)

    Pang, Lihui; Liu, Wenjun; Han, Hainian; Wei, Zhiyi

    2016-09-01

    The femtosecond laser is crucial to the operation of the femtosecond optical frequency comb. In this paper, a passively mode-locked erbium-doped fiber laser is presented with 91.4 fs pulse width and 100.8 MHz repetition rate, making use of the nonlinear polarized evolution effect. Using a 976 nm pump laser diode, the average output power is 16 mW from the coupler and 27 mW from the polarization beam splitter at the pump power of 700 mW. The proposed fiber laser can offer excellent temporal purity in generated pulses with high power, and provide a robust source for fiber-based frequency combs and supercontinuum generation well suited for industrial applications.

  5. Modulations of the plasma uniformity by low frequency sources in a large-area dual frequency inductively coupled plasma based on fluid simulations

    SciTech Connect

    Sun, Xiao-Yan; Zhang, Yu-Ru; Li, Xue-Chun; Wang, You-Nian

    2015-05-15

    As the wafer size increases, dual frequency (DF) inductively coupled plasma (ICP) sources have been proposed as an effective method to achieve large-area uniform plasma processing. A two-dimensional (2D) self-consistent fluid model, combined with an electromagnetic module, has been employed to investigate the influence of the low frequency (LF) source on the plasma radial uniformity in an argon DF discharge. When the DF antenna current is fixed at 10 A, the bulk plasma density decreases significantly with the LF due to the less efficient heating, and the best radial uniformity is obtained at 3.39 MHz. As the LF decreases to 2.26 MHz, the plasma density is characterized by an edge-high profile, and meanwhile the maximum of the electron temperature appears below the outer two-turn coil. Moreover, the axial ion flux at 3.39 MHz is rather uniform in the center region except at the radial edge of the substrate, where a higher ion flux is observed. When the inner five-turn coil frequency is fixed at 2.26 MHz, the plasma density profiles shift from edge-high over uniform to center-high as the LF coil current increases from 6 A to 18 A, and the best plasma uniformity is obtained at 14 A. In addition, the maximum of the electron temperature becomes lower with a second peak appears at the radial position of r = 9 cm at 18 A.

  6. Calculation of the plasma frequency of a stack of coupled Josephson junctions irradiated with electromagnetic waves

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Rahmonov, I. R.; Gaafar, M. A.

    2012-11-01

    We perform a precise numerical study of phase dynamics in high-temperature superconductors under electromagnetic radiation. We observe the charging of superconducting layers in the bias current interval corresponding to the Shapiro step. A remarkable change in the longitudinal plasma wavelength at parametric resonance is shown. Double resonance of the Josephson oscillations with radiation and plasma frequencies leads to additional parametric resonances and the non-Bessel Shapiro step.

  7. Kinetic interpretation of resonance phenomena in low pressure capacitively coupled radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Wilczek, Sebastian; Trieschmann, Jan; Eremin, Denis; Brinkmann, Ralf Peter; Schulze, Julian; Schuengel, Edmund; Derzsi, Aranka; Korolov, Ihor; Hartmann, Peter; Donkó, Zoltán; Mussenbrock, Thomas

    2016-06-01

    Low pressure capacitive radio frequency (RF) plasmas are often described by equivalent circuit models based on fluid approaches that predict the self-excitation of resonances, e.g., high frequency oscillations of the total current in asymmetric discharges, but do not provide a kinetic interpretation of these effects. In fact, they leave important questions open: How is current continuity ensured in the presence of energetic electron beams generated by the expanding sheaths that lead to a local enhancement of the conduction current propagating through the bulk? How do the beam electrons interact with cold bulk electrons? What is the kinetic origin of resonance phenomena? Based on kinetic simulations, we find that the energetic beam electrons interact with cold bulk electrons (modulated on a timescale of the inverse local electron plasma frequency) via a time dependent electric field outside the sheaths. This electric field is caused by the electron beam itself, which leaves behind a positive space charge, that attracts cold bulk electrons towards the expanding sheath. The resulting displacement current ensures current continuity by locally compensating the enhancement of the conduction current. The backflow of cold electrons and their interaction with the nonlinear plasma sheath cause the generation of multiple electron beams during one phase of sheath expansion and contribute to a strongly non-sinusoidal RF current. These kinetic mechanisms are the basis for a fundamental understanding of the electron power absorption dynamics and resonance phenomena in such plasmas, which are found to occur in discharges of different symmetries including perfectly symmetric plasmas.

  8. Dynamic gamma frequency feedback coupling between higher and lower order visual cortices underlies perceptual completion in humans.

    PubMed

    Moratti, S; Méndez-Bértolo, C; Del-Pozo, F; Strange, B A

    2014-02-01

    To perceive a coherent environment, incomplete or overlapping visual forms must be integrated into meaningful coherent percepts, a process referred to as "Gestalt" formation or perceptual completion. Increasing evidence suggests that this process engages oscillatory neuronal activity in a distributed neuronal assembly. A separate line of evidence suggests that Gestalt formation requires top-down feedback from higher order brain regions to early visual cortex. Here we combine magnetoencephalography (MEG) and effective connectivity analysis in the frequency domain to specifically address the effective coupling between sources of oscillatory brain activity during Gestalt formation. We demonstrate that perceptual completion of two-tone "Mooney" faces induces increased gamma frequency band power (55-71Hz) in human early visual, fusiform and parietal cortices. Within this distributed neuronal assembly fusiform and parietal gamma oscillators are coupled by forward and backward connectivity during Mooney face perception, indicating reciprocal influences of gamma activity between these higher order visual brain regions. Critically, gamma band oscillations in early visual cortex are modulated by top-down feedback connectivity from both fusiform and parietal cortices. Thus, we provide a mechanistic account of Gestalt perception in which gamma oscillations in feature sensitive and spatial attention-relevant brain regions reciprocally drive one another and convey global stimulus aspects to local processing units at low levels of the sensory hierarchy by top-down feedback. Our data therefore support the notion of inverse hierarchical processing within the visual system underlying awareness of coherent percepts.

  9. Experimental Observation and Computational Analysis of Striations in Electronegative Capacitively Coupled Radio-Frequency Plasmas

    NASA Astrophysics Data System (ADS)

    Liu, Yong-Xin; Schüngel, Edmund; Korolov, Ihor; Donkó, Zoltán; Wang, You-Nian; Schulze, Julian

    2016-06-01

    Self-organized spatial structures in the light emission from the ion-ion capacitive rf plasma of a strongly electronegative gas (CF4 ) are observed experimentally for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These "striations" are found to be generated by the resonance between the driving radio frequency and the eigenfrequency of the ion-ion plasma (derived from an analytical model) that establishes a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma. The growth of the instability is followed by the numerical simulations.

  10. Experimental Observation and Computational Analysis of Striations in Electronegative Capacitively Coupled Radio-Frequency Plasmas.

    PubMed

    Liu, Yong-Xin; Schüngel, Edmund; Korolov, Ihor; Donkó, Zoltán; Wang, You-Nian; Schulze, Julian

    2016-06-24

    Self-organized spatial structures in the light emission from the ion-ion capacitive rf plasma of a strongly electronegative gas (CF_{4}) are observed experimentally for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These "striations" are found to be generated by the resonance between the driving radio frequency and the eigenfrequency of the ion-ion plasma (derived from an analytical model) that establishes a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma. The growth of the instability is followed by the numerical simulations. PMID:27391730

  11. Analysis of the acoustoelectric behavior of microwave frequency, temperature-compensated AlN-based multilayer coupling configurations

    NASA Astrophysics Data System (ADS)

    Caliendo, Cinzia

    2008-11-01

    Piezoelectric AlN films, 1.3-6.2 μm thick, have been grown on bare and metallized Al2O3(0001) substrates by reactive radio-frequency-sputtering technique at 180 °C. The films were uniform, stress-free, highly c-axis oriented normal to the surface, and extremely adhesive to the substrates. Surface acoustic wave (SAW) delay lines, showing harmonic modes with operating frequencies up to about 2.44 GHz, were obtained just using conventional optical lithography at 7.5 μm linewidth resolution. Four interdigital transducer (IDT)/counter electrode configurations were obtained locating the IDTs either on the AlN free surface or at the Al2O3/AlN interface, with and without an Al thin metal film opposite the IDTs. The temperature induced shift of the fundamental and harmonic operating frequencies of the four configurations was measured at different temperatures in the range from -25 to 70 °C. The first order temperature coefficient of delay (TCD) of the four structures was experimentally evaluated for different film thickness values and for SAWs propagating along and normal the Al2O3 a-axis. Eight AlN thicknesses, i.e., the temperature-compensated points (TCPs), were experimentally estimated at which the TCD is equal to 0 ppm/°C. These TCPs were found to be in good agreement with those theoretically evaluated. The SAW propagation along the four coupling structures was investigated in terms of phase and group velocity, electromechanical coupling coefficient, electrical potential, and IDT capacitance and radiation resistance for different film thickness values and SAW propagation directions. The numerical simulation of the mechanical and electrical behaviors of the coupling structures showed how the electroacoustic transduction efficiency, the IDT directivity, and bandwidth can benefit from having different electrical boundary conditions. The obtained results confirm the AlN feasibility to the implementation of SAW devices for application to gigahertz range, good

  12. Coupled molecular and cantilever dynamics model for frequency-modulated atomic force microscopy.

    PubMed

    Klocke, Michael; Wolf, Dietrich E

    2016-01-01

    A molecular dynamics model is presented, which adds harmonic potentials to the atomic interactions to mimic the elastic properties of an AFM cantilever. It gives new insight into the correlation between the experimentally monitored frequency shift and cantilever damping due to the interaction between tip atoms and scanned surface. Applying the model to ionic crystals with rock salt structure two damping mechanisms are investigated, which occur separately or simultaneously depending on the tip position. These mechanisms are adhesion hysteresis on the one hand and lateral excitations of the cantilever on the other. We find that the short range Lennard-Jones part of the atomic interaction alone is sufficient for changing the predominant mechanism. When the long range ionic interaction is switched off, the two damping mechanisms occur with a completely different pattern, which is explained by the energy landscape for the apex atom of the tip. In this case the adhesion hysteresis is always associated with a distinct lateral displacement of the tip. It is shown how this may lead to a systematic shift between the periodic patterns obtained from the frequency and from the damping signal, respectively. PMID:27335760

  13. Coupled molecular and cantilever dynamics model for frequency-modulated atomic force microscopy.

    PubMed

    Klocke, Michael; Wolf, Dietrich E

    2016-01-01

    A molecular dynamics model is presented, which adds harmonic potentials to the atomic interactions to mimic the elastic properties of an AFM cantilever. It gives new insight into the correlation between the experimentally monitored frequency shift and cantilever damping due to the interaction between tip atoms and scanned surface. Applying the model to ionic crystals with rock salt structure two damping mechanisms are investigated, which occur separately or simultaneously depending on the tip position. These mechanisms are adhesion hysteresis on the one hand and lateral excitations of the cantilever on the other. We find that the short range Lennard-Jones part of the atomic interaction alone is sufficient for changing the predominant mechanism. When the long range ionic interaction is switched off, the two damping mechanisms occur with a completely different pattern, which is explained by the energy landscape for the apex atom of the tip. In this case the adhesion hysteresis is always associated with a distinct lateral displacement of the tip. It is shown how this may lead to a systematic shift between the periodic patterns obtained from the frequency and from the damping signal, respectively.

  14. Coupled molecular and cantilever dynamics model for frequency-modulated atomic force microscopy

    PubMed Central

    Klocke, Michael

    2016-01-01

    Summary A molecular dynamics model is presented, which adds harmonic potentials to the atomic interactions to mimic the elastic properties of an AFM cantilever. It gives new insight into the correlation between the experimentally monitored frequency shift and cantilever damping due to the interaction between tip atoms and scanned surface. Applying the model to ionic crystals with rock salt structure two damping mechanisms are investigated, which occur separately or simultaneously depending on the tip position. These mechanisms are adhesion hysteresis on the one hand and lateral excitations of the cantilever on the other. We find that the short range Lennard-Jones part of the atomic interaction alone is sufficient for changing the predominant mechanism. When the long range ionic interaction is switched off, the two damping mechanisms occur with a completely different pattern, which is explained by the energy landscape for the apex atom of the tip. In this case the adhesion hysteresis is always associated with a distinct lateral displacement of the tip. It is shown how this may lead to a systematic shift between the periodic patterns obtained from the frequency and from the damping signal, respectively. PMID:27335760

  15. Phase and frequency entrainment in locally coupled phase oscillators with repulsive interactions

    NASA Astrophysics Data System (ADS)

    Giver, Michael; Jabeen, Zahera; Chakraborty, Bulbul

    2011-03-01

    Recent experiments in one and two-dimensional microfluidic arrays of droplets containing Belousov - Zhabotinsky reactants show a rich variety of spatial patterns [J. Phys. Chem. Lett. 1, 1241-1246 (2010)]. These experiments provide the first steps towards creating easily reproducible model active emulsion systems. Motivated by this experimental system, we study repulsively coupled Kuramoto oscillators with nearest neighbor interactions on a linear chain as well as a ring in one dimension. We show using linear stability analysis as well as numerical study, that the stable phase patterns depend on the geometry of the lattice and that a transition to the ordered state does not exist in the thermodynamic limit. We will also present results comparing our Kuramoto model with finite element simulations of the Brusselator model in geometries similar to those of the experiment.

  16. The theoretical ultimate magnetoelectric coefficients of magnetoelectric composites by optimization design

    SciTech Connect

    Wang, H.-L.; Liu, B.

    2014-03-21

    This paper investigates what is the largest magnetoelectric (ME) coefficient of ME composites, and how to realize it. From the standpoint of energy conservation, a theoretical analysis is carried out on an imaginary lever structure consisting of a magnetostrictive phase, a piezoelectric phase, and a rigid lever. This structure is a generalization of various composite layouts for optimization on ME effect. The predicted theoretical ultimate ME coefficient plays a similar role as the efficiency of ideal heat engine in thermodynamics, and is used to evaluate the existing typical ME layouts, such as the parallel sandwiched layout and the serial layout. These two typical layouts exhibit ME coefficient much lower than the theoretical largest values, because in the general analysis the stress amplification ratio and the volume ratio can be optimized independently and freely, but in typical layouts they are dependent or fixed. To overcome this shortcoming and achieve the theoretical largest ME coefficient, a new design is presented. In addition, it is found that the most commonly used electric field ME coefficient can be designed to be infinitely large. We doubt the validity of this coefficient as a reasonable ME effect index and consider three more ME coefficients, namely the electric charge ME coefficient, the voltage ME coefficient, and the static electric energy ME coefficient. We note that the theoretical ultimate value of the static electric energy ME coefficient is finite and might be a more proper measure of ME effect.

  17. Magnetoelectric Effects and Related Phenomena in Spin-spiral Hexaferrites

    NASA Astrophysics Data System (ADS)

    Kimura, Tsuyoshi

    2012-02-01

    Among various multiferroics, extensive studies of ferroelectrics originating from magnetic orders, i.e., magnetically-induced ferroelectrics in which the inversion simmetry breaking and resultant ferroelectricity are induced by complex magnetic orders, have been triggered almost a decade ago by the discovery of multiferroic nature in a perovskite-type rare-earh manganites TbMnO3. The magnetically-induced ferroelectrics often show giant magnetoelectric effects, remarkable changes in electric polarization in response to a magnetic field, since the origin of their ferroelectricity is driven by magnetism which sensitively responds to an applied magnetic field. Though a large number of new magnetically-induced ferroelectrics have been reported in the past decade, so far there has been no practical application employing the magnetoelectric effect of the magnetically-induced ferroelectrics. This is partly because none of the existing magnetically-induced ferroelectrics have combined large and robust electric and magnetic polarizations at room temperature until quite recently. The situation is changed by the discoveries of magnetoelectricity in hexagonal ferrites (hexaferrites) with spin-spiral structures.ootnotetextT. Kimura, G. Lawes, and A. P. Ramirez, Phys. Rev. Lett. 94, 137201 (2005).^,ootnotetextY. Kitagawa et al., Nature Mater. 9, 797 (2010).^,ootnotetextK. Okumura et al., Appl. Phys. Lett. 98, 212504 (2011). In this presentation, I show our recent studies on magnetoelectric effects and related phenomena in the new series of magnetically-induced ferroelectrics which are promising candidates for multiferroics operating at room temperature and low fields. This work has been done in collaboration with Y. Hiraoka, T. Ishikura, K. Okumura, Y. Kitagawa, H. Nakamura, Y. Wakabayashi, M. Soda, T. Asaka, and Y. Tanaka.

  18. A shear horizontal surface wave in magnetoelectric materials.

    PubMed

    Liu, Jinxi; Fang, Daining; Liu, Xiangling

    2007-07-01

    We show that a semi-infinite magnetoelectric (ME) material adjoining a vacuum sustains the propagation of a shear horizontal wave accompanied by electromagnetic waves. The ME material is assumed to possess hexagonal (6 mm) symmetry. The expression for the phase velocity of this wave is obtained explicitly. The result is helpful for applications of piezoelectric-piezomagnetic composites to acoustic wave and microwave devices.

  19. Coupling and Stacking Order of ReS2 Atomic Layers Revealed by Ultralow-Frequency Raman Spectroscopy.

    PubMed

    He, Rui; Yan, Jia-An; Yin, Zongyou; Ye, Zhipeng; Ye, Gaihua; Cheng, Jason; Li, Ju; Lui, C H

    2016-02-10

    We investigate the ultralow-frequency Raman response of atomically thin ReS2, a special type of two-dimensional (2D) semiconductors with unique distorted 1T structure. Bilayer and few-layer ReS2 exhibit rich Raman spectra at frequencies below 50 cm(-1), where a panoply of interlayer shear and breathing modes are observed. The emergence of these interlayer phonon modes indicate that the ReS2 layers are coupled and orderly stacked. Whereas the interlayer breathing modes behave similarly to those in other 2D layered crystals, the shear modes exhibit distinctive behavior due to the in-plane lattice distortion. In particular, the two shear modes in bilayer ReS2 are nondegenerate and clearly resolved in the Raman spectrum, in contrast to the doubly degenerate shear modes in other 2D materials. By carrying out comprehensive first-principles calculations, we can account for the frequency and Raman intensity of the interlayer modes and determine the stacking order in bilayer ReS2.

  20. Experimental and numerical investigations of electron density in low-pressure dual-frequency capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Wen, De-Qi; Liu, Yong-Xin; Gao, Fei; Lu, Wen-Qi; Wang, You-Nian

    2013-11-15

    The electron density is measured in low-pressure dual-frequency (2/60 MHz) capacitively coupled oxygen discharges by utilizing a floating hairpin probe. The dependence of electron density at the discharge center on the high frequency (HF) power, low frequency (LF) power, and gas pressure are investigated in detail. A (1D) particle-in-cell/Monte Carlo method is developed to calculate the time-averaged electron density at the discharge center and the simulation results are compared with the experimental ones, and general agreements are achieved. With increasing HF power, the electron density linearly increases. The electron density exhibits different changes with the LF power at different HF powers. At low HF powers (e.g., 30 W in our experiment), the electron density increases with increasing LF power while the electron density decreases with increasing LF power at relatively high HF powers (e.g., 120 W in our experiment). With increasing gas pressure the electron density first increases rapidly to reach a maximum value and then decreases slowly due to the combined effect of the production process by the ionization and the loss processes including the surface and volume losses.

  1. Coupled microwave ECR and radio-frequency plasma source for plasma processing

    DOEpatents

    Tsai, C.C.; Haselton, H.H.

    1994-03-08

    In a dual plasma device, the first plasma is a microwave discharge having its own means of plasma initiation and control. The microwave discharge operates at electron cyclotron resonance (ECR), and generates a uniform plasma over a large area of about 1000 cm[sup 2] at low pressures below 0.1 mtorr. The ECR microwave plasma initiates the second plasma, a radio frequency (RF) plasma maintained between parallel plates. The ECR microwave plasma acts as a source of charged particles, supplying copious amounts of a desired charged excited species in uniform manner to the RF plasma. The parallel plate portion of the apparatus includes a magnetic filter with static magnetic field structure that aids the formation of ECR zones in the two plasma regions, and also assists in the RF plasma also operating at electron cyclotron resonance. 4 figures.

  2. Coupled microwave ECR and radio-frequency plasma source for plasma processing

    DOEpatents

    Tsai, Chin-Chi; Haselton, Halsey H.

    1994-01-01

    In a dual plasma device, the first plasma is a microwave discharge having its own means of plasma initiation and control. The microwave discharge operates at electron cyclotron resonance (ECR), and generates a uniform plasma over a large area of about 1000 cm.sup.2 at low pressures below 0.1 mtorr. The ECR microwave plasma initiates the second plasma, a radio frequency (RF) plasma maintained between parallel plates. The ECR microwave plasma acts as a source of charged particles, supplying copious amounts of a desired charged excited species in uniform manner to the RF plasma. The parallel plate portion of the apparatus includes a magnetic filter with static magnetic field structure that aids the formation of ECR zones in the two plasma regions, and also assists in the RF plasma also operating at electron cyclotron resonance.

  3. Occurrence of magnetoelectric effect correlated to the Dy order in Dy2NiMnO6 double perovskite

    NASA Astrophysics Data System (ADS)

    Masud, Md G.; Dey, K.; Ghosh, A.; Majumdar, S.; Giri, S.

    2015-08-01

    Magnetic, dielectric, and ac conductivity as well as room temperature structural and Raman studies are performed on double perovskite Dy2NiMnO6. The crystal structure of the compound adopts monoclinic P21/n space group, where alternate Mn and Ni distorted octahedral are arranged in anti-phase a- a- b+ order in Glazer notation. Magnetization studies show two magnetic transitions around 100 K and 20 K which are related to the ordering of transition and rare earth cations moment, respectively. Temperature dependent dielectric permittivity shows Havriliak-Negami type thermally activated dielectric relaxation. The ac conductivity at different temperature is found to follow Jonscher power law behavior. Time-temperature scaling of the conductivity spectra reveals that the charge transport dynamics is independent of temperature. Intriguingly, an anomaly in the dielectric constant is observed close to the order of Dy moment which indicates intrinsic magnetoelectric coupling. The hybridization between Dy and Ni/Mn is suggested to be correlated with the magnetoelectric coupling.

  4. Effect of driving voltages in dual capacitively coupled radio frequency plasma: A study by nonlinear global model

    SciTech Connect

    Bora, B.

    2015-10-15

    On the basis of nonlinear global model, a dual frequency capacitively coupled radio frequency plasma driven by 13.56 MHz and 27.12 MHz has been studied to investigate the influences of driving voltages on the generation of dc self-bias and plasma heating. Fluid equations for the ions inside the plasma sheath have been considered to determine the voltage-charge relations of the plasma sheath. Geometrically symmetric as well as asymmetric cases with finite geometrical asymmetry of 1.2 (ratio of electrodes area) have been considered to make the study more reasonable to experiment. The electrical asymmetry effect (EAE) and finite geometrical asymmetry is found to work differently in controlling the dc self-bias. The amount of EAE has been primarily controlled by the phase angle between the two consecutive harmonics waveforms. The incorporation of the finite geometrical asymmetry in the calculations shift the dc self-bias towards negative polarity direction while increasing the amount of EAE is found to increase the dc self-bias in either direction. For phase angle between the two waveforms ϕ = 0 and ϕ = π/2, the amount of EAE increases significantly with increasing the low frequency voltage, whereas no such increase in the amount of EAE is found with increasing high frequency voltage. In contrast to the geometrically symmetric case, where the variation of the dc self-bias with driving voltages for phase angle ϕ = 0 and π/2 are just opposite in polarity, the variation for the geometrically asymmetric case is different for ϕ = 0 and π/2. In asymmetric case, for ϕ = 0, the dc self-bias increases towards the negative direction with increasing both the low and high frequency voltages, but for the ϕ = π/2, the dc-self bias is increased towards positive direction with increasing low frequency voltage while dc self-bias increases towards negative direction with increasing high frequency voltage.

  5. Magnetoelectrical stimulation of motor cortex in children with motor disturbances.

    PubMed

    Müller, K; Hömberg, V; Aulich, A; Lenard, H G

    1992-04-01

    Transcranial magnetoelectrical stimulation (TMS) is now widely used as a diagnostic tool in adults. In this study we report our experiences with this technique in children with central motor disturbances. We used a Cadwell MES10 magnetoelectrical stimulator with a maximal magnetic field of 2 tesla. The stimulation procedure followed a standardized protocol, with the patients being as relaxed as possible in order to avoid contamination of parameters with different preinnervational levels. Stimulation data were compared to a data base obtained in 58 normal children. The first group of patients consisted of 20 children aged from 7 months to 16 years with hemiparesis of different etiologies. Neuroimaging data were correlated with the results of magnetoelectrical stimulation. In 13 patients a pathological pattern of TMS could be detected, and in 7 of these a corresponding lesion of the cortico-spinal tract was found in CT or MRI scans. In 7 children TMS was normal, in spite of a clear-cut lesion of the cortico-spinal tract in CT or MRI scans in 4 of them. The second group of patients consisted of 16 children with extrapyramidal disease, mostly of hereditary origin, such as DOPA-responsive dystonia or benign hereditary chorea. TMS showed a normal response pattern in this group. We discuss problems and possible pitfalls in TMS in childhood in evaluating the diagnostic value of TMS. At the moment the diagnostic usefulness of TMS in children with motor disturbances appears limited and calls for careful interpretation. PMID:1373370

  6. Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal

    SciTech Connect

    Prokhorenko, S.; Kohlstedt, H.; Pertsev, N. A.

    2014-09-21

    Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr₀.₅Ti₀.₅)O₃-FeGaB and BaTiO₃-FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.

  7. Magnetoelectricity in CoFe2O4 nanocrystal-P(VDF-HFP) thin films

    PubMed Central

    2013-01-01

    Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature (Tc > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 μm. We describe the synthesis and structural characterization of the nanocrystals and composite films by XRD, TEM, HRTEM, STEM, and SEM, as well as dielectric and magnetic properties, in order to identify evidence of cooperative interactions between the two phases. The CoFe2O4 polymer nanocomposite thin films exhibit composition-dependent effective permittivity, loss tangent, and specific saturation magnetization (Ms). An enhancement of the effective permittivity and saturation magnetization of the CoFe2O4-P(VDF-HFP) films was observed and directly compared with CoFe2O4-polyvinylpyrrolidone, a non-ferroelectric polymer-based nanocomposite prepared by the same method. The comparison provided evidence for the observation of a magnetoelectric effect in the case of CoFe2O4-P(VDF-HFP), attributed to a magnetostrictive/piezoelectric interaction. An enhancement of Ms up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe2O4-P(VDF-HFP) sample. PMID:24004499

  8. Modeling the coupled return-spread high frequency dynamics of large tick assets

    NASA Astrophysics Data System (ADS)

    Curato, Gianbiagio; Lillo, Fabrizio

    2015-01-01

    Large tick assets, i.e. assets where one tick movement is a significant fraction of the price and bid-ask spread is almost always equal to one tick, display a dynamics in which price changes and spread are strongly coupled. We present an approach based on the hidden Markov model, also known in econometrics as the Markov switching model, for the dynamics of price changes, where the latent Markov process is described by the transitions between spreads. We then use a finite Markov mixture of logit regressions on past squared price changes to describe temporal dependencies in the dynamics of price changes. The model can thus be seen as a double chain Markov model. We show that the model describes the shape of the price change distribution at different time scales, volatility clustering, and the anomalous decrease of kurtosis. We calibrate our models based on Nasdaq stocks and we show that this model reproduces remarkably well the statistical properties of real data.

  9. Capacitively-Coupled Resistivity measurements to determine frequency dependent electrical parameters in periglacial environment - theoretical considerations and first field tests.

    NASA Astrophysics Data System (ADS)

    Przyklenk, A.; Hördt, A.; Radić, T.

    2016-05-01

    Capacitively-Coupled Resistivity (CCR) is conventionally used to emulate DC resistivity measurements and may provide important information about the ice content of material in periglacial areas. The application of CCR theoretically enables the determination of both electrical parameters, i.e. the resistivity and the electrical permittivity, by analyzing magnitude and phase shift spectra. The electrical permittivity may dominate the impedance, especially in periglacial areas or regions of hydrogeological interest. However, previous theoretical work suggested that the phase shift may strongly depend on electrode height above ground, implying that electrode height must be known with great accuracy to determine electrical permittivity. Here, we demonstrate with laboratory test measurements, theoretical modelling and by analysing the Jacobian matrix of the inversion, that the sensitivity towards electrode height is drastically reduced if the electrical permittivity is frequency dependent in a way that is typical for ice. For the fist time, we used a novel broadband CCR device "Chameleon" for a field test located in one of the ridge galleries beneath the crest of Mount Zugspitze. A permanently ice covered bottom of a tunnel was examined. For the inversion of the measured spectra, the frequency dependance of the electrical parameters was parameterized in 3 different ways. A Debye Model for pure ices, a Cole-Cole Model for pure ices and a dual Cole-Cole Model including interfacial water additionally. The frequency-dependent resistivity and permittivity spectra obtained from the inversion, including low and high frequency limits, agree reasonably well with laboratory and field measurements reported in the literature.

  10. Broadband high-sensitivity current-sensing device utilizing nonlinear magnetoelectric medium and nanocrystalline flux concentrator

    NASA Astrophysics Data System (ADS)

    Zhang, Jitao; He, Wei; Zhang, Ming; Zhao, Hongmei; Yang, Qian; Guo, Shuting; Wang, Xiaolei; Zheng, Xiaowan; Cao, Lingzhi

    2015-09-01

    A broadband current-sensing device with frequency-conversion mechanism consisting of Terfenol-D/Pb(Zr.Ti)O3 (PZT)/Terfenol-D magnetoelectric laminate and Fe73.5Cu1Nb3Si13.5B9 nanocrystalline flux concentrator is fabricated and characterized. For the purpose of acquiring resonance-enhanced sensitivity within broad bandwidth, a frequency-modulation mechanism is introduced into the presented device through the nonlinearity of field-dependence giant magnetostrictive materials. The presented configuration provides a solution to monitor the weak currents and achieves resonance-enhanced sensitivity of 178.4 mV/A at power-line frequency, which exhibits ˜3.86 times higher than that of direct output at power-line frequency of 50 Hz. Experimental results demonstrate that a weak step-change input current of 1 mA can be clearly distinguished by the output amplitude or phase. This miniature current-sensing device provides a promising application in power-line weak current measurement.

  11. Broadband high-sensitivity current-sensing device utilizing nonlinear magnetoelectric medium and nanocrystalline flux concentrator.

    PubMed

    Zhang, Jitao; He, Wei; Zhang, Ming; Zhao, Hongmei; Yang, Qian; Guo, Shuting; Wang, Xiaolei; Zheng, Xiaowan; Cao, Lingzhi

    2015-09-01

    A broadband current-sensing device with frequency-conversion mechanism consisting of Terfenol-D/Pb(Zr.Ti)O3 (PZT)/Terfenol-D magnetoelectric laminate and Fe73.5Cu1Nb3Si13.5B9 nanocrystalline flux concentrator is fabricated and characterized. For the purpose of acquiring resonance-enhanced sensitivity within broad bandwidth, a frequency-modulation mechanism is introduced into the presented device through the nonlinearity of field-dependence giant magnetostrictive materials. The presented configuration provides a solution to monitor the weak currents and achieves resonance-enhanced sensitivity of 178.4 mV/A at power-line frequency, which exhibits ∼3.86 times higher than that of direct output at power-line frequency of 50 Hz. Experimental results demonstrate that a weak step-change input current of 1 mA can be clearly distinguished by the output amplitude or phase. This miniature current-sensing device provides a promising application in power-line weak current measurement.

  12. Extracted ion current density in close-coupling multi-antenna type radio frequency driven ion source: CC-MATIS

    SciTech Connect

    Oka, Y. E-mail: oka@LHD.nifs.ac.jp; Shoji, T.

    2014-02-15

    Positive ions are extracted by using a small extractor from the Close-Coupling Multi-Antenna Type radio frequency driven Ion Source. Two types of RF antenna are used. The maximum extracted ion current density reaches 0.106 A/cm{sup 2}. The RF net power efficiency of the extracted ion current density under standard condition is 11.6 mA/cm{sup 2}/kW. The efficiency corresponds to the level of previous beam experiments on elementary designs of multi-antenna sources, and also to the efficiency level of a plasma driven by a filament in the same chamber. The multi-antenna type RF plasma source is promising for all metal high density ion sources in a large volume chamber.

  13. A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit.

    PubMed

    Huang, Yongxian; Tian, Xiubo; Yang, Shiqin; Chu, Paul K

    2007-10-01

    A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984) x 10(16) at.cm(2) s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.

  14. Ultrafast direct modulation of transverse-mode coupled-cavity VCSELs far beyond the relaxation oscillation frequency

    NASA Astrophysics Data System (ADS)

    Dalir, Hamed; Koyama, Fumio

    2014-02-01

    A novel approach for bandwidth augmentation for direct modulation of VCSELs using transverse-coupled-cavity (TCC) scheme is raised, which enables us to tailor the modulation-transfer function. The base structure is similar to that of 3QW VCSELs with 980 nm wavelength operation. While the bandwidth of conventional VCSELs was limited by 9-10 GHz, the 3-dB bandwidth of TCC VCSEL with aperture diameters of 8.5×8.5μm2 and 3×3μm2 are increased by a factor of 3 far beyond the relaxation-oscillation frequency. Our current bandwidth achievement on the larger aperture size is 29 GHz which is limited by the used photo-detector. To the best of our knowledge this is the fastest 980 nm VCSEL.

  15. Coupled cluster evaluation of the frequency dispersion of the first and second hyperpolarizabilities of water, methanol, and dimethyl ether

    NASA Astrophysics Data System (ADS)

    Beaujean, Pierre; Champagne, Benoît

    2016-07-01

    The static and dynamic first (β‖) and second (γ‖) hyperpolarizabilities of water, methanol, and dimethyl ether have been evaluated within the response function approach using a hierarchy of coupled cluster levels of approximation and doubly augmented correlation consistent atomic basis sets. For the three compounds, the electronic β‖ and γ‖ values calculated at the CCSD and CC3 levels are in good agreement with gas phase electric field-induced second harmonic generation (EFISHG) measurements. In addition, for dimethyl ether, the frequency dispersion of both properties follows closely recent experimental values [V. W. Couling and D. P. Shelton, J. Chem. Phys. 143, 224307 (2015)] demonstrating the reliability of these methods and levels of approximation. This also suggests that the vibrational contributions to the EFISHG responses of these molecules are small.

  16. The deposition of chromium by the use of an inductively-coupled radio-frequency plasma torch

    SciTech Connect

    Carson, L.; Chumbley, L.S.

    1997-11-15

    This paper discusses attempts to deposit a layer of hard Cr metal, with properties similar to those of layers currently obtained by electrolytic methods, onto a metallic substrate using an inductively-coupled, radio-frequency plasma torch (ICP-RF) torch. Preliminary studies indicated that it might be possible to produce a suitable layer using a number of chromium-based compounds. For this study, Cr powders and a chromium precursor were injected into the high temperature region of the plasma plume, where thermal decomposition of the feed material produced Cr atoms that deposited onto the surface of metal substrates placed below the plasma torch. The films produced were examined to determine thickness, chemical compositions, and adherence. Since the goal of the project was to develop a coating method that was not only industrially suitable but also environmentally safe, care was taken to monitor the emissions produced by the system during deposition.

  17. Strong ionization asymmetry in a geometrically symmetric radio frequency capacitively coupled plasma induced by sawtooth voltage waveforms.

    PubMed

    Bruneau, Bastien; Gans, Timo; O'Connell, Deborah; Greb, Arthur; Johnson, Erik V; Booth, Jean-Paul

    2015-03-27

    The ionization dynamics in geometrically symmetric parallel plate capacitively coupled plasmas driven by radio frequency tailored voltage waveforms is investigated using phase resolved optical emission spectroscopy (PROES) and particle-in-cell (PIC) simulations. Temporally asymmetric waveforms induce spatial asymmetries and offer control of the spatiotemporal dynamics of electron heating and associated ionization structures. Sawtooth waveforms with different rise and fall rates are employed using truncated Fourier series approximations of an ideal sawtooth. Experimental PROES results obtained in argon plasmas are compared with PIC simulations, showing excellent agreement. With waveforms comprising a fast voltage drop followed by a slower rise, the faster sheath expansion in front of the powered electrode causes strongly enhanced ionization in this region. The complementary waveform causes an analogous effect in front of the grounded electrode. PMID:25860749

  18. A novel biomarker of amnestic MCI based on dynamic cross-frequency coupling patterns during cognitive brain responses.

    PubMed

    Dimitriadis, Stavros I; Laskaris, Nikolaos A; Bitzidou, Malamati P; Tarnanas, Ioannis; Tsolaki, Magda N

    2015-01-01

    The detection of mild cognitive impairment (MCI), the transitional stage between normal cognitive changes of aging and the cognitive decline caused by AD, is of paramount clinical importance, since MCI patients are at increased risk of progressing into AD. Electroencephalographic (EEG) alterations in the spectral content of brainwaves and connectivity at resting state have been associated with early-stage AD. Recently, cognitive event-related potentials (ERPs) have entered into the picture as an easy to perform screening test. Motivated by the recent findings about the role of cross-frequency coupling (CFC) in cognition, we introduce a relevant methodological approach for detecting MCI based on cognitive responses from a standard auditory oddball paradigm. By using the single trial signals recorded at Pz sensor and comparing the responses to target and non-target stimuli, we first demonstrate that increased CFC is associated with the cognitive task. Then, considering the dynamic character of CFC, we identify instances during which the coupling between particular pairs of brainwave frequencies carries sufficient information for discriminating between normal subjects and patients with MCI. In this way, we form a multiparametric signature of impaired cognition. The new composite biomarker was tested using data from a cohort that consists of 25 amnestic MCI patients and 15 age-matched controls. Standard machine-learning algorithms were employed so as to implement the binary classification task. Based on leave-one-out cross-validation, the measured classification rate was found reaching very high levels (95%). Our approach compares favorably with the traditional alternative of using the morphology of averaged ERP response to make the diagnosis and the usage of features from spectro-temporal analysis of single-trial responses. This further indicates that task-related CFC measurements can provide invaluable analytics in AD diagnosis and prognosis. PMID:26539070

  19. A novel biomarker of amnestic MCI based on dynamic cross-frequency coupling patterns during cognitive brain responses.

    PubMed

    Dimitriadis, Stavros I; Laskaris, Nikolaos A; Bitzidou, Malamati P; Tarnanas, Ioannis; Tsolaki, Magda N

    2015-01-01

    The detection of mild cognitive impairment (MCI), the transitional stage between normal cognitive changes of aging and the cognitive decline caused by AD, is of paramount clinical importance, since MCI patients are at increased risk of progressing into AD. Electroencephalographic (EEG) alterations in the spectral content of brainwaves and connectivity at resting state have been associated with early-stage AD. Recently, cognitive event-related potentials (ERPs) have entered into the picture as an easy to perform screening test. Motivated by the recent findings about the role of cross-frequency coupling (CFC) in cognition, we introduce a relevant methodological approach for detecting MCI based on cognitive responses from a standard auditory oddball paradigm. By using the single trial signals recorded at Pz sensor and comparing the responses to target and non-target stimuli, we first demonstrate that increased CFC is associated with the cognitive task. Then, considering the dynamic character of CFC, we identify instances during which the coupling between particular pairs of brainwave frequencies carries sufficient information for discriminating between normal subjects and patients with MCI. In this way, we form a multiparametric signature of impaired cognition. The new composite biomarker was tested using data from a cohort that consists of 25 amnestic MCI patients and 15 age-matched controls. Standard machine-learning algorithms were employed so as to implement the binary classification task. Based on leave-one-out cross-validation, the measured classification rate was found reaching very high levels (95%). Our approach compares favorably with the traditional alternative of using the morphology of averaged ERP response to make the diagnosis and the usage of features from spectro-temporal analysis of single-trial responses. This further indicates that task-related CFC measurements can provide invaluable analytics in AD diagnosis and prognosis.

  20. A novel biomarker of amnestic MCI based on dynamic cross-frequency coupling patterns during cognitive brain responses

    PubMed Central

    Dimitriadis, Stavros I.; Laskaris, Nikolaos A.; Bitzidou, Malamati P.; Tarnanas, Ioannis; Tsolaki, Magda N.

    2015-01-01

    The detection of mild cognitive impairment (MCI), the transitional stage between normal cognitive changes of aging and the cognitive decline caused by AD, is of paramount clinical importance, since MCI patients are at increased risk of progressing into AD. Electroencephalographic (EEG) alterations in the spectral content of brainwaves and connectivity at resting state have been associated with early-stage AD. Recently, cognitive event-related potentials (ERPs) have entered into the picture as an easy to perform screening test. Motivated by the recent findings about the role of cross-frequency coupling (CFC) in cognition, we introduce a relevant methodological approach for detecting MCI based on cognitive responses from a standard auditory oddball paradigm. By using the single trial signals recorded at Pz sensor and comparing the responses to target and non-target stimuli, we first demonstrate that increased CFC is associated with the cognitive task. Then, considering the dynamic character of CFC, we identify instances during which the coupling between particular pairs of brainwave frequencies carries sufficient information for discriminating between normal subjects and patients with MCI. In this way, we form a multiparametric signature of impaired cognition. The new composite biomarker was tested using data from a cohort that consists of 25 amnestic MCI patients and 15 age-matched controls. Standard machine-learning algorithms were employed so as to implement the binary classification task. Based on leave-one-out cross-validation, the measured classification rate was found reaching very high levels (95%). Our approach compares favorably with the traditional alternative of using the morphology of averaged ERP response to make the diagnosis and the usage of features from spectro-temporal analysis of single-trial responses. This further indicates that task-related CFC measurements can provide invaluable analytics in AD diagnosis and prognosis. PMID:26539070

  1. Coupling effect and control strategies of the maglev dual-stage inertially stabilization system based on frequency-domain analysis.

    PubMed

    Lin, Zhuchong; Liu, Kun; Zhang, Li; Zeng, Delin

    2016-09-01

    Maglev dual-stage inertially stabilization (MDIS) system is a newly proposed system which combines a conventional two-axis gimbal assembly and a 5-DOF (degree of freedom) magnetic bearing with vernier tilting capacity to perform dual-stage stabilization for the LOS of the suspended optical instrument. Compared with traditional dual-stage system, maglev dual-stage system exhibits different characteristics due to the negative position stiffness of the magnetic forces, which introduces additional coupling in the dual stage control system. In this paper, the coupling effect on the system performance is addressed based on frequency-domain analysis, including disturbance rejection, fine stage saturation and coarse stage structural resonance suppression. The difference between various control strategies is also discussed, including pile-up(PU), stabilize-follow (SF) and stabilize-compensate (SC). A number of principles for the design of a maglev dual stage system are proposed. A general process is also suggested, which leads to a cost-effective design striking a balance between high performance and complexity. At last, a simulation example is presented to illustrate the arguments in the paper.

  2. A hybrid model of radio frequency biased inductively coupled plasma discharges: description of model and experimental validation in argon

    NASA Astrophysics Data System (ADS)

    Wen, De-Qi; Liu, Wei; Gao, Fei; Lieberman, M. A.; Wang, You-Nian

    2016-08-01

    A hybrid model, i.e. a global model coupled bidirectionally with a parallel Monte-Carlo collision (MCC) sheath model, is developed to investigate an inductively coupled discharge with a bias source. This hybrid model can self-consistently reveal the interaction between the bulk plasma and the radio frequency (rf) bias sheath. More specifically, the plasma parameters affecting characteristics of rf bias sheath (sheath length and self-bias) are calculated by a global model and the effect of the rf bias sheath on the bulk plasma is determined by the voltage drop of the rf bias sheath. Moreover, specific numbers of ions are tracked in the rf bias sheath and ultimately the ion energy distribution function (IEDF) incident on the bias electrode is obtained. To validate this model, both bulk plasma density and IEDF on the bias electrode in an argon discharge are compared with experimental measurements, and a good agreement is obtained. The advantage of this model is that it can quickly calculate the bulk plasma density and IEDF on the bias electrode, which are of practical interest in industrial plasma processing, and the model could be easily extended to serve for industrial gases.

  3. [INVITED] Coupling of polarisation of high frequency electric field and electronic heat conduction in laser created plasma

    NASA Astrophysics Data System (ADS)

    Gamaly, Eugene G.; Rode, Andrei V.

    2016-08-01

    Powerful short laser pulse focused on a surface swiftly transforms the solid into the thermally and electrically inhomogeneous conductive plasma with the large temperature and dielectric permeability gradients across the focal spot. The laser-affected spot becomes thermally inhomogeneous with where temperature has maximum in the centre and gradually decreasing to the boundaries of the spot in accord to the spatial intensity distribution of the Gaussian pulse. Here we study the influence of laser polarisation on ionization and absorption of laser radiation in the focal spot. In this paper we would like to discuss new effect in thermally inhomogeneous plasma under the action of imposed high frequency electric field. We demonstrate that high-frequency (HF) electric field is coupled with the temperature gradient generating the additional contribution to the conventional electronic heat flow. The additional heat flow strongly depends on the polarisation of the external field. It appears that effect has maximum when the imposed electric field is collinear to the thermal gradient directed along the radius of a circular focal spot. Therefore, the linear polarised field converts the circular laser affected spot into an oval with the larger oval's axis parallel to the field direction. We compare the developed theory to the available experiments, discuss the results and future directions.

  4. Characteristics of dual-frequency capacitively coupled SF6/O2 plasma and plasma texturing of multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Xu, Dong-Sheng; Zou, Shuai; Xin, Yu; Su, Xiao-Dong; Wang, Xu-Sheng

    2014-06-01

    Due to it being environmentally friendly, much attention has been paid to the dry plasma texturing technique serving as an alternative candidate for multicrystalline silicon (mc-Si) surface texturing. In this paper, capacitively coupled plasma (CCP) driven by a dual frequency (DF) of 40.68 MHz and 13.56 MHz is first used for plasma texturing of mc-Si with SF6/O2 gas mixture. Using a hairpin resonant probe and optical emission techniques, DF-CCP characteristics and their influence on mc-silicon surface plasma texturing are investigated at different flow rate ratios, pressures, and radio-frequency (RF) input powers. Experimental results show that suitable plasma texturing of mc-silicon occurs only in a narrow range of plasma parameters, where electron density ne must be larger than 6.3 × 109 cm-3 and the spectral intensity ratio of the F atom to that of the O atom ([F]/[O]) in the plasma must be between 0.8 and 0.3. Out of this range, no cone-like structure is formed on the mc-silicon surface. In our experiments, the lowest reflectance of about 7.3% for mc-silicon surface texturing is obtained at an [F]/[O] of 0.5 and ne of 6.9 × 109 cm-3.

  5. Compression effects in inductively coupled, high-power radio-frequency discharges for negative hydrogen ion production

    NASA Astrophysics Data System (ADS)

    Wilhelm, Rolf

    2003-02-01

    In the paper we present a simplified model description of inductively coupled plasma discharges operating at a rather high radio-frequency (rf) power. In this case the induced high plasma currents can cause periodic compressions over a substantial radial distance. Such conditions are obviously given in rf driven 1 MHz/150 kW plasma sources developed at the Institute for Plasma Physics Garching for negative (hydrogen) ion production in future neutral beam injection (NBI) systems for nuclear fusion research, such as the 1 MeV/50 MW NBI system for the International Thermonuclear Experimental Reactor [T. Inoue, R. Hemsworth, V. Kulygin, and Y. Okumura, Fusion Eng. Design 55, 291 (2001)]. The given model describes quite well the compression and other features of the discharge. The results include the Ohmic power input (i.e., electron heating), the resulting density build-up, and—as a new feature—periodical plasma compressions, leading to a direct energy input also into the plasma ions. The model also explains the strange effect of small argon admixtures, which improve the negative ion yield in rf sources by a factor of up to 2-3 (but which have no effect in conventional dc arc sources). With the calculated dependencies from external parameters (e.g., rf-power and frequency, gas pressure, ion mass or the specific geometry), the modeling may help for the further optimization of the rf source.

  6. Multi-Objective Optimization of Vehicle Sound Package in Middle Frequency Using Gray Relational Analysis Coupled with Principal Component Analysis

    NASA Astrophysics Data System (ADS)

    Chen, Shuming; Wang, Dengfeng; Shi, Tianze; Chen, Jing

    2015-12-01

    This research studies optimization design of the thickness of sound packages for a passenger car. The major characteristics indexes for performance determined to evaluate the process are sound pressure level of the interior middle frequency noise and weight of the sound package. Three kinds of materials of sound packages are selected for the optimization process. The corresponding parameters of the sound packages are the thickness of the insulation plate for outer side of the firewall, thickness of the sound absorbing wool for inner side of the firewall, thickness of PU foam for the front floor, and thickness of PU foam for the rear floor, respectively. In this paper, the optimization procedure is a multi-objective optimization. Therefore, gray relational analysis (GRA) is applied to decide the optimal combination of sound package parameters. Furthermore, the principal component analysis (PCA) is used to calculate the weighting values which are corresponding to multiple performance characteristics. Then, the results of the confirmation tests uncover that GRA coupled with principal analysis methods can effectively be applied to find the optimal combination of the thickness of the sound packages at different positions for a passenger car. Thus, the proposed method can be a useful tool to improve the automotive interior middle frequency noise and lower the weight of the sound packages. Additionally, it will also be useful for automotive manufactures and designers in other fields.

  7. Biochemical Frequency Control by Synchronisation of Coupled Repressilators: An In Silico Study of Modules for Circadian Clock Systems

    PubMed Central

    Hinze, Thomas; Schumann, Mathias; Bodenstein, Christian; Heiland, Ines; Schuster, Stefan

    2011-01-01

    Exploration of chronobiological systems emerges as a growing research field within bioinformatics focusing on various applications in medicine, agriculture, and material sciences. From a systems biological perspective, the question arises whether biological control systems for regulation of oscillatory signals and their technical counterparts utilise similar mechanisms. If so, modelling approaches and parameterisation adopted from building blocks can help to identify general components for frequency control in circadian clocks along with gaining insight into mechanisms of clock synchronisation to external stimuli like the daily rhythm of sunlight and darkness. Phase-locked loops could be an interesting candidate in this context. Both, biology and engineering, can benefit from a unified view resulting from systems modularisation. In a first experimental study, we analyse a model of coupled repressilators. We demonstrate its ability to synchronise clock signals in a monofrequential manner. Several oscillators initially deviate in phase difference and frequency with respect to explicit reaction and diffusion rates. Accordingly, the duration of the synchronisation process depends on dedicated reaction and diffusion parameters whose settings still lack to be sufficiently captured analytically. PMID:22046179

  8. Direct magnetoelectric effect in two-layer composite structures Tb0.12Dy0.2Fe0.68-PbZr0.53Ti0.47O3 at bending and longitudinal vibrations

    NASA Astrophysics Data System (ADS)

    Kalgin, A. V.; Gridnev, S. A.; Gribe, Z. H.

    2014-11-01

    The direct magnetoelectric effect has been studied in samples of two-layer composites containing 8 × 6 × 0.3-mm layers of the piezoelectric material PbZr0.53Ti0.47O3 and 6 × 6 × A-mm layers ( A = 0.3, 0.6, 0.9, 1.2, and 1.5) of the ferromagnet Tb0.12Dy0.2Fe0.68 and epoxy adhesive in the frequency range of 10-253 kHz at room temperature. It has been found that the magnetoelectric effect significantly increases at resonance frequencies (13.2-61.1 kHz) of the first harmonic of bending vibrations along the sample length, at resonance frequencies (39.5-90.7 kHz) of the first harmonic of bending vibrations along the sample width, and at resonance frequencies (123.3-141.0 kHz) of the first harmonic of longitudinal vibrations along the sample length. The magnetoelectric effect magnitudes at the resonance frequencies of the bending vibrations is found to be greater than that at the resonance frequencies of the longitudinal vibrations of the sample.

  9. Short range ferromagnetic, magneto-electric, and magneto-dielectric effect in ceramic Co3TeO6

    NASA Astrophysics Data System (ADS)

    Singh, Harishchandra; Ghosh, Haranath; Chandrasekhar Rao, T. V.; Sharma, G.; Saha, J.; Patnaik, S.

    2016-01-01

    We report observation of magneto-electric and magneto-dielectric couplings along with short range ferromagnetic order in ceramic Cobalt Tellurate (Co3TeO6, CTO) using magnetic, structural, dielectric, pyroelectric, and polarization studies. DC magnetization along with dielectric constant measurements indicate a coupling between magnetic order and electrical polarization. A strong anomaly in the dielectric constant at ˜17.4 K in zero magnetic field indicates spontaneous electric polarization, consistent with a recent neutron diffraction study. Observation of weak short range ferromagnetic order at lower temperatures is attributed to the Griffiths-like ferromagnetism. Furthermore, magnetic field dependence of the ferroelectric transition follows earlier theoretical predictions, applicable to single crystal CTO. Finally, combined dielectric, pyroelectric, and polarization measurements suggest that the ground state of CTO may possess spontaneous symmetry breaking in the absence of magnetic field.

  10. A nonlinear model for magnetocapacitance effect in PZT-ring/Terfenol-D-strip magnetoelectric composites

    NASA Astrophysics Data System (ADS)

    Zhang, Juanjuan; Wen, Jianbiao; Gao, Yuanwen

    2016-06-01

    In previous works, most of them employ a linear constitutive model to describe magnetocapacitance (MC) effect in magnetoelectric (ME) composites, which lead to deficiency in their theoretical results. In view of this, based on a nonlinear magnetostrictive constitutive relation and a linear piezoelectric constitutive relation, we establish a nonlinear model for MC effect in PZT-ring/Terfenol-D-strip ME composites. The numerical results in this paper coincide better with experimental data than that of a linear model, thus, it's essential to utilize a nonlinear constitutive model for predicting MC effect in ME composites. Then the influences of external magnetic fields, pre-stresses, frequencies, and geometric sizes on the MC effect are discussed, respectively. The results show that the external magnetic field is responsible for the resonance frequency shift. And the resonance frequency is sensitive to the ratio of outer and inner radius of the PZT ring. Moreover, some other piezoelectric materials are employed in this model and the corresponding MC effects are calculated, and we find that different type of piezoelectric materials affect the MC effect obviously. The proposed model is more accurate for multifunction devices designing.

  11. Symmetries and multiferroic properties of novel room-temperature magnetoelectrics: Lead iron tantalate – lead zirconate titanate (PFT/PZT)

    DOE PAGESBeta

    Sanchez, Dilsom A.; Ortega, N.; Kumar, Ashok; Roque-Malherbe, R.; Polanco, R.; Scott, J. F.; Katiyar, Ram S.

    2011-12-01

    Mixing 60-70% lead zirconate titanate with 40-30% lead iron tantalate produces a single-phase, low-loss, room-temperature multiferroic with magnetoelectric coupling: (PbZr₀.₅₃Ti₀.₄₇O₃) (1-x)- (PbFe₀.₅Ta₀.₅O₃)x. The present study combines x-ray scattering, magnetic and polarization hysteresis in both phases, plus a second-order dielectric divergence (to epsilon = 6000 at 475 K for 0.4 PFT; to 4000 at 520 K for 0.3 PFT) for an unambiguous assignment as a C2v-C4v (Pmm2-P4mm) transition. The material exhibits square saturated magnetic hysteresis loops with 0.1 emu/g at 295 K and saturation polarization Pr = 25 μC/cm², which actually increases (to 40 μC/cm²) in the high-T tetragonal phase, representingmore » an exciting new room temperature oxide multiferroic to compete with BiFeO₃. Additional transitions at high temperatures (cubic at T>1300 K) and low temperatures (rhombohedral or monoclinic at T<250 K) are found. These are the lowest-loss room-temperature multiferroics known, which is a great advantage for magnetoelectric devices.« less

  12. Successive Magnetic-Field-Induced Transitions and Colossal Magnetoelectric Effect in Ni3TeO6

    DOE PAGESBeta

    Kim, Jae Wook; Artyukhin, Sergei; Mun, Eun Deok; Jaime, Marcelo; Harrison, Neil; Hansen, Anders; Yang, J. J.; Oh, Yoon Seok; Vanderbilt, David; Zapf, Vivien S.; et al

    2015-09-24

    In this paper, we report the discovery of a metamagnetic phase transition in a polar antiferromagnet Ni3TeO6 that occurs at 52 T. The new phase transition accompanies a colossal magnetoelectric effect, with a magnetic-field-induced polarization change of 0.3 μC/cm2, a value that is 4 times larger than for the spin-flop transition at 9 T in the same material, and also comparable to the largest magnetically induced polarization changes observed to date. Via density-functional calculations we construct a full microscopic model that describes the data. We model the spin structures in all fields and clarify the physics behind the 52 Tmore » transition. The high-field transition involves a competition between multiple different exchange interactions which drives the polarization change through the exchange-striction mechanism. Finally, the resultant spin structure is rather counterintuitive and complex, thus providing new insights on design principles for materials with strong magnetoelectric coupling.« less

  13. Frequency-Tunable Multigigawatt Sub-Half-Cycle Light Pulses from Coupled-State Dynamics of Optical Solitons and Impulsively Driven Molecular Vibrations

    NASA Astrophysics Data System (ADS)

    Zheltikov, A. M.; Voronin, A. A.; Kienberger, R.; Krausz, F.; Korn, G.

    2010-09-01

    Coupling ultrashort optical field waveforms to ultrafast molecular vibrations in an impulsively excited Raman medium is shown to enable the generation of frequency-tunable sub-half-cycle multigigawatt light pulses. In a gas-filled hollow waveguide, this coupled-state dynamics is strongly assisted by soliton effects, which help to suppress temporal stretching of subcycle optical pulses, providing efficient Raman-type impulsive excitation of ultrafast molecular vibrations over large propagation paths.

  14. Modeling of the nanoparticle coagulation in pulsed radio-frequency capacitively coupled C2H2 discharges

    NASA Astrophysics Data System (ADS)

    Liu, Xiang-Mei; Li, Qi-Nan; Li, Rui

    2015-07-01

    The role of pulse parameters on nanoparticle property is investigated self-consistently based on a couple of fluid model and aerosol dynamics model in a capacitively coupled parallel-plate acetylene (C2H2) discharge. In this model, the mass continuity equation, momentum balance equation, and energy balance equation for neutral gas are taken into account. Thus, the thermophoretic force arises when a gas temperature gradient exists. The typical results of this model are positive and negative ion densities, electron impact collisions rates, nanoparticle density, and charge distributions. The simulation is performed for duty ratio 0.4/0.7/1.0, as well as pulse modulation frequency from 40 kHz to 2.7 MHz for pure C2H2 discharges at a pressure of 500 mTorr. We find that the pulse parameters, especially the duty ratio, have a great affect on the dissociative attachment coefficient and the negative density. More importantly, by decreasing the duty ratio, nanoparticles start to diffuse to the wall. Under the action of gas flow, nanoparticle density peak is created in front of the pulse electrode, where the gas temperature is smaller. Project supported by the Natural Science Foundation of Heilongjiang Province, China (Grant Nos. A2015011 and A2015010), the Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province, China (Grant No. LBH-Q14159), the National Natural Science Foundation of China (Grant No. 11404180), and the Program for Young Teachers Scientific Research in Qiqihar University, China (Grant No. 2014k-Z11).

  15. Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4

    DOE PAGESBeta

    Toft-Petersen, Rasmus; Reehuis, Manfred; Jensen, Thomas B. S.; Andersen, Niels H.; Li, Jiying; Le, Manh Duc; Laver, Mark; Niedermayer, Christof; Klemke, Bastian; Lefmann, Kim; et al

    2015-07-06

    We report significant details of the magnetic structure and spin dynamics of LiFePO4 obtained by single-crystal neutron scattering. Our results confirm a previously reported collinear rotation of the spins away from the principal b axis, and they determine that the rotation is toward the a axis. In addition, we find a significant spin-canting component along c. Furthermore, the possible causes of these components are discussed, and their significance for the magnetoelectric effect is analyzed. Inelastic neutron scattering along the three principal directions reveals a highly anisotropic hard plane consistent with earlier susceptibility measurements. While using a spin Hamiltonian, we showmore » that the spin dimensionality is intermediate between XY- and Ising-like, with an easy b axis and a hard c axis. As a result, it is shown that both next-nearest neighbor exchange couplings in the bc plane are in competition with the strongest nearest neighbor coupling.« less

  16. Microwave magnetoelectric fields and their role in the matter-field interaction.

    PubMed

    Kamenetskii, E O; Joffe, R; Shavit, R

    2013-02-01

    We show that in a source-free subwavelength region of microwave fields, there can exist field structures with a local coupling between the time-varying electric and magnetic fields differing from the electric-magnetic coupling in regular-propagating free-space electromagnetic waves. To distinguish such field structures from regular electromagnetic (EM) field structures, we term them as magnetoelectric (ME) fields. We study a structure and conservation laws of microwave ME near fields. We show that there exist sources of microwave ME near fields-the ME particles. These particles are represented by small quasi-two-dimensional ferrite disks with magnetic-dipolar-oscillation spectra. The near fields originating from such particles are characterized by topologically distinctive power-flow vortices, nonzero helicity, and a torsion degree of freedom. The paper consists of two main parts. In the first one, we give a theoretical background of properties of the electric and magnetic fields inside and outside of a ferrite particle with magnetic-dipolar-oscillation spectra resulting in the appearance of microwave ME near fields. In the second main part, we represent numerical and experimental studies of the microwave ME near fields and their interactions with matter. Based on the obtained properties of the ME near fields, we discuss possibilities for effective microwave sensing of natural and artificial chiral structures.

  17. Magnetoelectrics in disordered topological insulator Josephson junctions

    NASA Astrophysics Data System (ADS)

    Bobkova, I. V.; Bobkov, A. M.; Zyuzin, Alexander A.; Alidoust, Mohammad

    2016-10-01

    We study theoretically the coupling of electric charge and spin polarization in an equilibrium and nonequilibrium electric transport across a two-dimensional Josephson configuration comprised of disordered surface channels of a three-dimensional topological insulator. In the equilibrium state of the system, we predict the Edelstein effect, which is much more pronounced than its counterpart in conventional spin-orbit coupled materials. Employing a quasiclassical Keldysh technique, we demonstrate that the ground state of the system can be shifted experimentally into arbitrary macroscopic superconducting phase differences other than the standard "0" or "π ," constituting a ϕ0 junction, solely by modulating a quasiparticle flow injection into the junction. We propose a feasible experiment in which the quasiparticles are injected into the topological insulator surface by means of a normal electrode and voltage gradient so that oppositely oriented stationary spin densities can be developed along the interfaces and allow for direct use of the spin-momentum locking nature of Dirac fermions in the surface channels. The ϕ0 state is proportional to the voltage difference applied between the injector electrode and superconducting terminals that calibrates the injection rate of particles and, therefore, the ϕ0 shift.

  18. Thickness dependence of magnetoelectric response for composites of Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} films on CoFe{sub 2}O{sub 4} ceramic substrates

    SciTech Connect

    Wang, Jing Zhu, Kongjun; Wu, Xia; Deng, Chaoyong; Peng, Renci; Wang, Jianjun

    2014-08-15

    Using chemical solution spin-coating we grew Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} films of different thicknesses on highly dense CoFe{sub 2}O{sub 4} ceramics. X-ray diffraction revealed no other phases except Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} and CoFe{sub 2}O{sub 4}. In many of these samples we observed typical ferroelectric hysteresis loops, butterfly-shaped piezoelectric strains, and the magnetic-field-dependent magnetostriction. These behaviors caused appreciable magnetoelectric responses based on magnetic-mechanical-electric coupling. Our results indicated that the thickness of the Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} film was important in obtaining strong magnetoelectric coupling.

  19. Radio frequency measurements of tunnel couplings and singlet-triplet spin states in Si:P quantum dots

    NASA Astrophysics Data System (ADS)

    House, M. G.; Kobayashi, T.; Weber, B.; Hile, S. J.; Watson, T. F.; van der Heijden, J.; Rogge, S.; Simmons, M. Y.

    2015-11-01

    Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet-triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20 μeV to 8 meV. We measure dot-lead tunnel rates by analysis of the reflected signal and show that they change from 100 MHz to 22 GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon.

  20. Red-shifted cyanide stretching frequencies in cyanide-bridged transition metal donor-acceptor complexes. Support for vibronic coupling

    SciTech Connect

    Watzky, M.A.; Endicott, J.F.; Song, X.

    1996-06-05

    Patterns in the cyanide stretching frequencies have been examined in several series of monometal- and CN{sup {minus}} bridged transition metal complexes. Metal-to-cyanide back-bonding can be identified as a major factor contributing to red shifts of v{sub CN} in monometal complexes. This effect is complicated in cyanide-bridged complexes in two ways: (a) when both metals can back-bond to cyanide, the net interaction is repulsive and results in a blue shift of v{sub CN}: and (b) when a donor and acceptor are bridged, V{sub CN} undergoes a substantial red shift (sometimes more than 60 cm{sup {minus}1} lower in energy than the parent monometal complex). These effects can be described by simple perturbational models for the electronic interactions. Monometal cyanide complexes and CN{sup {minus}}-bridged backbonding metals can be treated in terms of their perturbations of the CN{sup {minus}} {pi} and {pi}* orbitals by using a simple, Hueckel-like, three-center perturbational treatment of electronic interactions. However, bridged donor-acceptor pairs are best described by a vibronic model in which it is assumed that the extent of electronic delocalization is in equilibrium with variations of some nuclear coordinates. Consistent with this approach, it is found that (a) the oscillator strength of the donor-acceptor charge transfer (DACT) absorption is roughly proportional to the red shift of v{sub CN} and (b) there are strong symmetry constraints on the coupling.