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Sample records for frequency magnetoelectric coupling

  1. Strong magnetoelectric coupling at microwave frequencies in metallic magnetic film/lead zirconate titanate multiferroic composites

    NASA Astrophysics Data System (ADS)

    Pettiford, C.; Lou, J.; Russell, L.; Sun, N. X.

    2008-03-01

    Strong magnetoelectric coupling was observed at microwave frequencies in metallic magnetic film/lead zirconate titanate [Pb(Zr,Ti)O3] multiferroic composites, in which the magnetic films were either FeCoB or FeGaB with relatively high saturation magnetostriction constants between 40 and 70ppm and narrow ferromagnetic resonance linewidths of ˜20Oe at 10GHz. Large electrostatically induced ferromagnetic resonance frequency shifts of 50-110MHz at ˜2.3GHz were observed. These metallic magnetic film/Pb(Zr ,Ti)O3 multiferroic composites with large electrostatic tunability of the ferromagnetic resonance frequency provide great opportunities for integrated microwave multiferroic devices.

  2. Acoustic wave coupled magnetoelectric effect

    NASA Astrophysics Data System (ADS)

    Gao, J. S.; Zhang, N.

    2016-07-01

    Magnetoelectric (ME) coupling by acoustic waveguide was developed. Longitudinal and transversal ME effects of larger than 44 and 6 (V cm-1 Oe-1) were obtained with the waveguide-coupled ME device, respectively. Several resonant points were observed in the range of frequency lower than 47 kHz. Analysis showed that the standing waves in the waveguide were responsible for those resonances. The frequency and size dependence of the ME effects were investigated. A resonant condition about the geometrical size of the waveguide was obtained. Theory and experiments showed the resonant frequencies were closely influenced by the diameter and length of the waveguide. A series of double-peak curves of longitudinal magnetoelectric response were obtained, and their significance was discussed initially.

  3. 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.

  4. Magnetoelectric coupling by acoustic wave guide

    NASA Astrophysics Data System (ADS)

    Li, X. Y.; Liu, J.; Zhang, N.

    2016-04-01

    Magnetoelectric (ME) coupling by acoustic waveguide was developed. A very strong axial ME response was observed. The dependences of the sample size and the frequency of the ac field on the ME coupling were investigated. Several resonant points were observed in the frequency range applied (<50 kHz). Analysis shows that the standing waves transmitted in the waveguide were responsible for those resonances. And the resonant frequencies were closely influenced by the geometrical size of the waveguide. A resonant condition related to the size of the sample was obtained. The axial (or longitudinal) and transversal ME coefficients were observed to be up to 62 and 6 (V cm-1 Oe-1) at resonant points, respectively, indicating that the axial ME effect in this device was much higher than its transversal ones. A series of double-peak curves of axial ME coefficient versus magnetic field were observed. The significance of the double-peak curves was discussed.

  5. Thermally mediated mechanism to enhance magnetoelectric coupling in multiferroics.

    PubMed

    Chang, C-M; Mani, B K; Lisenkov, S; Ponomareva, I

    2015-05-01

    The main roadblock on the way to practical realization of magnetoelectric devices is the lack of multiferroics with strong magnetoelectric coupling. We propose an unusual route to dramatically enhance this coupling through a thermally mediated mechanism. Such a thermally mediated magnetoelectric effect is quantified by an isentropic rather than isothermal magnetoelectric response and is computed here from first principles. A robust enhancement of the magnetoelectric coupling is predicted for both naturally occurring and heterostructured materials. PMID:25978260

  6. Spin waves in a thin film with magnetoelectric coupling at the surfaces

    NASA Astrophysics Data System (ADS)

    Moore, T.; Camley, R. E.; Livesey, K. L.

    2014-12-01

    The standing spin waves in a thin ferromagnetic film are calculated when the surface magnetization is influenced by magnetoelectric coupling. At the interfaces, inversion symmetry is broken allowing for an energy term that is linear in the electric polarization in the film. For the two film surfaces, the magnetoelectric coupling is opposite in sign and therefore results in asymmetric pinning of the dynamic magnetization. The magnetoelectric pinning alters the spin wave frequencies and also the power absorbed by the material at these resonances.

  7. 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

  8. Synthetic magnetoelectric coupling in a nanocomposite multiferroic.

    PubMed

    Jain, P; Wang, Q; Roldan, M; Glavic, A; Lauter, V; Urban, C; Bi, Z; Ahmed, T; Zhu, J; Varela, M; Jia, Q X; Fitzsimmons, M R

    2015-01-01

    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, which 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. PMID:25766205

  9. Driving ferromagnetic resonance frequency of FeCoB/PZN-PT multiferroic heterostructures to Ku-band via two-step climbing: composition gradient sputtering and magnetoelectric coupling.

    PubMed

    Li, Shandong; Xue, Qian; Duh, Jenq-Gong; Du, Honglei; Xu, Jie; Wan, Yong; Li, Qiang; Lü, Yueguang

    2014-01-01

    RF/microwave soft magnetic films (SMFs) are key materials for miniaturization and multifunctionalization of monolithic microwave integrated circuits (MMICs) and their components, which demand that the SMFs should have higher self-bias ferromagnetic resonance frequency fFMR, and can be fabricated in an IC compatible process. However, self-biased metallic SMFs working at X-band or higher frequency were rarely reported, even though there are urgent demands. In this paper, we report an IC compatible process with two-step superposition to prepare SMFs, where the FeCoB SMFs were deposited on (011) lead zinc niobate-lead titanate substrates using a composition gradient sputtering method. As a result, a giant magnetic anisotropy field of 1498 Oe, 1-2 orders of magnitude larger than that by conventional magnetic annealing method, and an ultrahigh fFMR of up to 12.96 GHz reaching Ku-band, were obtained at zero magnetic bias field in the as-deposited films. These ultrahigh microwave performances can be attributed to the superposition of two effects: uniaxial stress induced by composition gradient and magnetoelectric coupling. This two-step superposition method paves a way for SMFs to surpass X-band by two-step or multi-step, where a variety of magnetic anisotropy field enhancing methods can be cumulated together to get higher ferromagnetic resonance frequency. PMID:25491374

  10. Driving ferromagnetic resonance frequency of FeCoB/PZN-PT multiferroic heterostructures to Ku-band via two-step climbing: composition gradient sputtering and magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Li, Shandong; Xue, Qian; Duh, Jenq-Gong; Du, Honglei; Xu, Jie; Wan, Yong; Li, Qiang; Lü, Yueguang

    2014-12-01

    RF/microwave soft magnetic films (SMFs) are key materials for miniaturization and multifunctionalization of monolithic microwave integrated circuits (MMICs) and their components, which demand that the SMFs should have higher self-bias ferromagnetic resonance frequency fFMR, and can be fabricated in an IC compatible process. However, self-biased metallic SMFs working at X-band or higher frequency were rarely reported, even though there are urgent demands. In this paper, we report an IC compatible process with two-step superposition to prepare SMFs, where the FeCoB SMFs were deposited on (011) lead zinc niobate-lead titanate substrates using a composition gradient sputtering method. As a result, a giant magnetic anisotropy field of 1498 Oe, 1-2 orders of magnitude larger than that by conventional magnetic annealing method, and an ultrahigh fFMR of up to 12.96 GHz reaching Ku-band, were obtained at zero magnetic bias field in the as-deposited films. These ultrahigh microwave performances can be attributed to the superposition of two effects: uniaxial stress induced by composition gradient and magnetoelectric coupling. This two-step superposition method paves a way for SMFs to surpass X-band by two-step or multi-step, where a variety of magnetic anisotropy field enhancing methods can be cumulated together to get higher ferromagnetic resonance frequency.

  11. 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

  12. Magnetoelectric Coupling in Composite Multiferroic Heterostructures

    NASA Astrophysics Data System (ADS)

    Hoffman, Jason

    In this work, we demonstrate a large charge-mediated magnetoelectric coupling in a PbZr0.2Ti0.8O3 / La0.8 Sr0.2MnO3 (PZT/LSMO) composite structure resulting from direct control of magnetism via charge carrier density. This approach has the advantage that its physical mechanism is transparent and the size of the effect can be quantified and understood qualitatively within the double-exchange model. Direct quantification of the charge-driven magnetic changes based on electronic, magnetic, and spectroscopic measurements show that both the spin state and spin configuration of LSMO are modulated. Using a combination of advanced physical vapor deposition techniques, we have grown epitaxial PZT/LSMO bilayer heterostructures on (001) SrTiO 3 substrates with excellent crystallinity, atomically smooth surfaces, low leakage current density, and abrupt interfaces. Magneto-optic Kerr effect (MOKE) magnetometry was used to directly interrogate the local magnetic state of the LSMO as a function of the PZT polarization state. We show direct control of magnetism via applied electric fields, including modulation of the magnetotransport behavior and magnetic-ordering temperature, on/off switching of magnetism, and hysteretic magnetization versus electric field (M-E) characteristics. The magnetoelectric coupling strength, which relates the change in magnetization to the applied electric field, is found to vary strongly with temperature, reaching a low temperature saturation value of +6 Oe cm / kV, much larger than observed in single-phase magnetoelectrics and too large to be explained by a simple band-filling model. To clarify the origin of the magnetoelectric coupling, we carried out near edge x-ray absorption measurements that revealed a well defined change in the position of the Mn absorption edge with the ferroelectric polarization, giving a direct measure of the change in Mn valency in LSMO. We explain these results in terms of an interfacial magnetic reconstruction, whereby the

  13. Magnetoelectric coupling effects in multiferroic complex oxide composite structures.

    PubMed

    Vaz, Carlos A F; Hoffman, Jason; Ahn, Charles H; Ramesh, Ramamoorthy

    2010-07-20

    The study of magnetoelectric materials has recently received renewed interest, in large part stimulated by breakthroughs in the controlled growth of complex materials and by the search for novel materials with functionalities suitable for next generation electronic devices. In this Progress Report, we present an overview of recent developments in the field, with emphasis on magnetoelectric coupling effects in complex oxide multiferroic composite materials. PMID:20414887

  14. 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.

  15. 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

  16. 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.

  17. Interface Magnetoelectric Coupling in Co/Pb(Zr,Ti)O3.

    PubMed

    Vlašín, Ondřej; Jarrier, Romain; Arras, Rémi; Calmels, Lionel; Warot-Fonrose, Bénédicte; Marcelot, Cécile; Jamet, Matthieu; Ohresser, Philippe; Scheurer, Fabrice; Hertel, Riccardo; Herranz, Gervasi; Cherifi-Hertel, Salia

    2016-03-23

    Magnetoelectric coupling at multiferroic interfaces is a promising route toward the nonvolatile electric-field control of magnetization. Here, we use optical measurements to study the static and dynamic variations of the interface magnetization induced by an electric field in Co/PbZr0.2Ti0.8O3 (Co/PZT) bilayers at room temperature. The measurements allow us to identify different coupling mechanisms. We further investigate the local electronic and magnetic structure of the interface by means of transmission electron microscopy, soft X-ray magnetic circular dichroism, and density functional theory to corroborate the coupling mechanism. The measurements demonstrate a mixed linear and quadratic optical response to the electric field, which results from a magneto-electro-optical effect. We propose a decomposition method of the optical signal to discriminate between different components involved in the electric field-induced polarization rotation of the reflected light. This allows us to extract a signal that we can ascribe to interface magnetoelectric coupling. The associated surface magnetization exhibits a clear hysteretic variation of odd symmetry with respect to the electric field and nonzero remanence. The interface coupling is remarkably stable over a wide frequency range (1-50 kHz), and the application of a bias magnetic field is not necessary for the coupling to occur. These results show the potential of exploiting interface coupling with the prospect of optimizing the performance of magnetoelectric memory devices in terms of stability, as well as fast and dissipationless operation. PMID:26939641

  18. Magnetoelectricity coupled exchange bias in BaMnF4.

    PubMed

    Zhou, Shuang; Wang, Ji; Chang, Xiaofeng; Wang, Shuangbao; Qian, Bin; Han, Zhida; Xu, Qingyu; Du, Jun; Wang, Peng; Dong, Shuai

    2015-01-01

    Multiferroic BaMnF4 powder was prepared by hydrothermal method. Hysteretic field dependent magnetization curve at 5 K confirms the weak ferromagnetism aroused from the canted antiferromagnetic spins by magnetoelectric coupling. The blocking temperature of 65 K for exchange bias coincides well with the peak at 65 K in the zero-field cooled temperature-dependent magnetization curve, which has been assigned to the onset temperature of two-dimensional antiferromagnetism. An upturn kink of exchange field and coercivity with decreasing temperature was observed from 40 K to 20 K, which is consistent with the two-dimensional to three-dimensional antiferromagnetic transition at Néel temperature (~26 K). In contrast to the conventional mechanism of magnetization pinned by interfacial exchange coupling in multiphases, the exchange bias in BaMnF4 is argued to be a bulk effect in single phase, due to the magnetization pinned by the polarization through magnetoelectric coupling. PMID:26671575

  19. Magnetoelectricity coupled exchange bias in BaMnF4

    PubMed Central

    Zhou, Shuang; Wang, Ji; Chang, Xiaofeng; Wang, Shuangbao; Qian, Bin; Han, Zhida; Xu, Qingyu; Du, Jun; Wang, Peng; Dong, Shuai

    2015-01-01

    Multiferroic BaMnF4 powder was prepared by hydrothermal method. Hysteretic field dependent magnetization curve at 5 K confirms the weak ferromagnetism aroused from the canted antiferromagnetic spins by magnetoelectric coupling. The blocking temperature of 65 K for exchange bias coincides well with the peak at 65 K in the zero-field cooled temperature-dependent magnetization curve, which has been assigned to the onset temperature of two-dimensional antiferromagnetism. An upturn kink of exchange field and coercivity with decreasing temperature was observed from 40 K to 20 K, which is consistent with the two-dimensional to three-dimensional antiferromagnetic transition at Néel temperature (~26 K). In contrast to the conventional mechanism of magnetization pinned by interfacial exchange coupling in multiphases, the exchange bias in BaMnF4 is argued to be a bulk effect in single phase, due to the magnetization pinned by the polarization through magnetoelectric coupling. PMID:26671575

  20. 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.

  1. 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.

  2. 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.

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

    PubMed

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

    2016-07-15

    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 BiFeO_{3} 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. PMID:27472140

  4. 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

  5. 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

  6. Interfacial Charge Induced Magnetoelectric Coupling at BiFeO₃/BaTiO₃ Bilayer Interface.

    PubMed

    Gupta, Rekha; Chaudhary, Sujeet; Kotnala, R K

    2015-04-29

    Bilayer thin films of BiFeO3-BaTiO3 at different thicknesses of BiFeO3 were prepared by RF-magnetron sputtering technique. A pure phase polycrystalline growth of thin films was confirmed from XRD results. Significantly improved ferroelectric polarization (2Pr ∼ 30 μC/cm(2)) and magnetic moment (Ms ∼ 33 emu/cc) were observed at room temperature. Effect of ferroelectric polarization on current conduction across the interface has been explored. Accumulation and depletion of charges at the bilayer interface were analyzed by current-voltage measurements which were further confirmed from hysteretic dynamic resistance and capacitance voltage profiles. Magnetoelectric coupling due to induced charges at grain boundaries of bilayer interface was further investigated by room temperature magnetocapacitance analysis. A room temperature magnetocapacitance was found to originate from induced charge at the bilayer interface which can be manipulated by varying the thickness of BFO to obtain higher ME coupling coefficient. Dynamic magnetoelectric coupling was investigated, and maximum longitudinal magnetoelectric coupling was observed to be 61 mV/cm·Oe at 50 nm thickness of BiFeO3. The observed magnetoelectric properties are potentially useful for novel room temperature magnetoelectric and spintronic device applications. PMID:25856737

  7. Electromagnetic wave propagation in time-dependent media with antisymmetric magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lin, Shi-Rong; Zhang, Ruo-Yang; Ma, Yi-Rong; Jia, Wei; Zhao, Qing

    2016-07-01

    This paper deals with electromagnetic wave propagation in time-dependent media with an antisymmetric magnetoelectric coupling and an isotropic time-dependent permittivity. We identify a new mechanism of linear birefringence, originated from the combined action of the time-dependent permittivity and the antisymmetric magnetoelectric coupling. Permittivity with linear and exponential temporal variations exemplifies the creation and control of these two distinct types of linear birefringent modes. As a novel nonlinear optical effect, a scheme utilizing optical Kerr effect in moving media is proposed for the realization of the predicted birefringence.

  8. 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

  9. Multiferroicity and Magnetoelectric Coupling in TbMnO3 Thin Films.

    PubMed

    Hu, Ni; Lu, Chengliang; Xia, Zhengcai; Xiong, Rui; Fang, Pengfei; Shi, Jing; Liu, Jun-Ming

    2015-12-01

    In this work, we report the growth and functional characterizations of multiferroic TbMnO3 thin films grown on Nb-doped SrTiO3 (001) substrates using pulsed laser deposition. By performing detailed magnetic and ferroelectric properties measurements, we demonstrate that the multiferroicity of spin origin known in the bulk crystals can be successfully transferred to TbMnO3 thin films. Meanwhile, anomalous magnetic transition and unusual magnetoelectric coupling related to Tb moments are observed, suggesting a modified magnetic configuration of Tb in the films as compared to the bulk counterpart. In addition, it is found that the magnetoelectric coupling enabled by Tb moments can even be seen far above the Tb spin ordering temperature, which provides a larger temperature range for the magnetoelectric control involving Tb moments. PMID:26573085

  10. Resonant magnetoelectric coupling in trilayers of ferromagnetic alloys and piezoelectric lead zirconate titanate: The influence of bias magnetic field

    NASA Astrophysics Data System (ADS)

    Srinivasan, G.; de Vreugd, C. P.; Laletin, V. M.; Paddubnaya, N.; Bichurin, M. I.; Petrov, V. M.; Filippov, D. A.

    2005-05-01

    We present the first data and theory for the bias magnetic field dependence of magnetoelectric coupling in the electromechanical resonance (EMR) region for ferromagnetic-piezoelectric heterostructures. Trilayers of Permendur, a Co-Fe-V alloy, and lead zirconate titanate were studied. Measurements of the magnetoelectric (ME) voltage coefficient αE indicate a strong ME coupling in the low-frequency range and a giant ME effect due to EMR at 200-300kHz for radial modes and at ˜2.7MHz for thickness modes. Data were obtained for the bias field H dependence of two key parameters, the EMR frequency fr and the ME coefficient αE,R at resonance. With increasing H , an increase in fr and a rapid rise and fall in αE,R are measured. In our model we consider two mechanisms for the magnetic field influence on ME interactions: (i) a shift in the EMR frequency due to changes in compliance coefficients ( ΔE effect) and (ii) variation in the piezomagnetic coefficient that manifests as a change in αE,R . Theoretical profiles of αE vs frequency and estimates of frequency shift based on the ΔE effect are in excellent agreement with the data.

  11. 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.

  12. Low Frequency Magnetoelectric Interactions in Single Crystal YIG/PMN-PT Bilayers

    NASA Astrophysics Data System (ADS)

    Devreugd, C. P.; Srinivasan, G.; Mantese, J. V.

    2004-03-01

    This work is concerned with magnetoelectric (ME) coupling in novel layered ferromagnetic-ferroelectric composites. The heterostructures are capable of electric-to-magnetic field conversion that is mediated by mechanical stress [1]. We recently developed a theoretical model for low frequency effects that predicts an order of magnitude enhancement in ME coupling in single crystals compared to polycrystalline samples [2]. Use of single crystals is critical for probing the influence of piezomagnetism, ac magnetostriction, and ferroelasticity of the magnetic component and similar parameters for the ferroelectric component. The studies are also important for the creation of an optimal interface to accomplish strong ME interactions. Bilayers were prepared by bonding epitaxial (100), (110), and (111) films of YIG and (001) single crystals of PMN-PT. Low frequency ME voltage coefficients were measured for transverse (dc magnetic field H and ac field in-plane) and longitudinal (magnetic fields out-of-plane) fields. Important results are as follows. (i) The ME voltage coupling is the largest for H along <111> of YIG and is the weakest for H along <100>. (ii) The voltage coefficient increases with increasing volume of YIG. (iii) The transverse coefficient is an order of magnitude higher than the longitudinal coefficient. (iv) Studies on bilayers with (111) YIG films reveal a significant influence of in-plane anisotropy on ME coupling. 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). This work was supported by a grant from the National Science Foundation (DMR-0322254)

  13. Parallel multilayer magnetoelectric composite based on (1-x)Pb(Mg1/3Nb2/3)-xPbTiO3 and Terfenol-D coupled with charge mode amplifier

    NASA Astrophysics Data System (ADS)

    Jiao, Jie; Li, Lingying; Ren, Bo; Guo, Hao; Deng, Hao; Di, Wenning; Zhao, Xiangyong; Jing, Weiping; Luo, Haosu

    2012-02-01

    In this paper, the sources and categories of noise regarding a charge mode magnetoelectric (ME) sensor are analyzed and simulated. A series of parallel multilayer magnetoelectric composites of Terfenol-D and (1-x)Pb(Mg1/3Nb2/3)-xPbTiO3 with different numbers of layers have been developed. The high magnetoelectric charge coefficients of these composites have been measured. By coupling different parallel multilayer magnetoelectric composites with a low noise-level charge amplifier, we found that the noise equivalent magnetic induction (NEB) of the ME sensor based on the charge mode is in accordance with the theoretical prediction, and multilayers can reduce the NEB at low frequency and hardly at high frequency. At last we have established a new method of using high g31 piezoelectric material that can effectively reduce the influence of the operational amplifier voltage noise component and enhance resolution.

  14. Magnetoelectric coupling and exchange bias effects in multiferroic NdCrO3.

    PubMed

    Indra, A; Dey, K; Midya, A; Mandal, P; Gutowski, O; Rütt, U; Majumdar, S; Giri, S

    2016-04-27

    We report ferroelectricity around  ∼88 K that appears well below T N (∼25 K), unlike other members of RCrO3 series. A synchrotron diffraction study suggests that the occurrence of ferroelectricity in NdCrO3 is coupled to the structural transformation from centrosymmetric Pnma to a non-centrosymmetric Pna21 space group. A strong magnetoelectric coupling is observed in the electric polarization [P(T)]. This coupling is significantly influenced by the magnetic field cooling effect, suggesting an exchange bias effect in P(T). This exchange bias effect is also revealed by the systematic shift of the magnetic hysteresis loops below T N. The rare occurrence of an exchange bias effect in both the magnetic and electric polarizations associated with a strong magnetoelectric coupling is of fundamental interest, as well as being attractive for technological applications close to liquid nitrogen temperature. PMID:27009362

  15. Magnetoelectric coupling and exchange bias effects in multiferroic NdCrO3

    NASA Astrophysics Data System (ADS)

    Indra, A.; Dey, K.; Midya, A.; Mandal, P.; Gutowski, O.; Rütt, U.; Majumdar, S.; Giri, S.

    2016-04-01

    We report ferroelectricity around  ∼88 K that appears well below T N (∼25 K), unlike other members of RCrO3 series. A synchrotron diffraction study suggests that the occurrence of ferroelectricity in NdCrO3 is coupled to the structural transformation from centrosymmetric Pnma to a non-centrosymmetric Pna21 space group. A strong magnetoelectric coupling is observed in the electric polarization [P(T)]. This coupling is significantly influenced by the magnetic field cooling effect, suggesting an exchange bias effect in P(T). This exchange bias effect is also revealed by the systematic shift of the magnetic hysteresis loops below T N. The rare occurrence of an exchange bias effect in both the magnetic and electric polarizations associated with a strong magnetoelectric coupling is of fundamental interest, as well as being attractive for technological applications close to liquid nitrogen temperature.

  16. Magnetoelectric coupling in the honeycomb antiferromagnet Co4Nb2O9

    NASA Astrophysics Data System (ADS)

    Khanh, N. D.; Abe, N.; Sagayama, H.; Nakao, A.; Hanashima, T.; Kiyanagi, R.; Tokunaga, Y.; Arima, T.

    2016-02-01

    The magnetic structure and magnetoelectric effect have been investigated for single crystals of the antiferromagnet Co4Nb2O9 . Single-crystal neutron diffraction and magnetic susceptibility measurement have revealed that the magnetic structure is different from a collinear arrangement with spin parallel to the trigonal axis as proposed previously. Co2 + magnetic moments are found to be almost lying in the basal plane, which lowers the magnetic symmetry to C 2 /c' with the propagation vector k =0 . Associated with the magnetic phase transition, a sharp anomaly in the dielectric constant and displacement current indicate the appearance of the magnetoelectric below Néel temperature TN with a large coupling constant up to 30 ps/m. The existence of off-diagonal components in a magnetoelectric tensor indicate the formation of ferrotoroidic order in Co4Nb2O9 . Such a magnetoelectric effect can be ascribed to the reduction of symmetry caused by simple antiferromagnetic order in a honeycomb network.

  17. Controlling magnetoelectric coupling by nanoscale phase transformation instrain engineered bismuth ferrite

    SciTech Connect

    Liu, Y. Y.; Vasudevan, Rama K; Pan, K.; Xie, S. H.; Liang, W. -I.; Kumar, Amit; Jesse, Stephen; Chen, Y. -C.; Chu, Y.-H.; Nagarajan, Valanoor; Kalinin, Sergei V; Li, J. Y.

    2012-01-01

    The magnetoelectric coupling in multiferroic materials is promising for a wide range of applications, yet manipulating magnetic ordering by electric field proves elusive to obtain and difficult to control. In this paper, we explore the prospect of controlling magnetic ordering in misfit strained bismuth ferrite (BiFeO3, BFO) films, combining theoretical analysis, numerical simulations, and experimental characterizations. Electric field induced transformation from a tetragonal phase to a distorted rhombohedral one in strain engineered BFO films has been identified by thermodynamic analysis, and realized by scanning probe microscopy (SPM) experiment. By breaking the rotational symmetry of a tip-induced electric field as suggested by phase field simulation, the morphology of distorted rhombohedral variants has been delicately controlled and regulated. Such capabilities enable nanoscale control of magnetoelectric coupling in strain engineered BFO films that is difficult to achieve otherwise, as demonstrated by phase field simulations.

  18. 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.

  19. Strong Magnetoelectric Coupling of Pb1-xSrx(Fe0.012Ti0.988)O3 Nanoparticles.

    PubMed

    Verma, Kuldeep Chand; Shah, Jyoti; Kotnala, R K

    2015-02-01

    Pb1-xSrx(Fe012Ti0.988)O3 (PSFT) nanoparticles were prepared by a chemical synthesis using polyvinyl alcohol as surfactant. X-ray diffraction pattern has been used to analyze the phase structure and average particles size. Transmission electron microscopy is used to confirm the nano size of the PSFT particles. The magnetoelectric (ME) coupling is observed at room temperature by measuring the ME coefficient (αE) as the function of applied dc magnetizing field under the influence of ac magnetic field of 2 Oe and frequency 800 Hz. The maximal value of αE is observed in PSFT3. The ME coupling is also studied by observing the variation of polarization hysteresis measured in the presence of zero and 0.2 T of external magnetic field. PMID:26353695

  20. Mesoporous bismuth ferrite with amplified magnetoelectric coupling and electric field-induced ferrimagnetism

    NASA Astrophysics Data System (ADS)

    Quickel, Thomas E.; Schelhas, Laura T.; Farrell, Richard A.; Petkov, Nikolay; Le, Van H.; Tolbert, Sarah H.

    2015-03-01

    Coupled ferromagnetic and ferroelectric materials, known as multiferroics, are an important class of materials that allow magnetism to be manipulated through the application of electric fields. Bismuth ferrite, BiFeO3, is the most-studied intrinsic magnetoelectric multiferroic because it maintains both ferroelectric and magnetic ordering to well above room temperature. Here we report the use of epitaxy-free wet chemical methods to create strained nanoporous BiFeO3. We find that the strained material shows large changes in saturation magnetization on application of an electric field, changing from 0.04 to 0.84 μb per Fe. For comparison, non-porous films produced using analogous methods change from just 0.002 to 0.01 μb per Fe on application of the same electric field. The results indicate that nanoscale architecture can complement strain-layer epitaxy as a tool to strain engineer magnetoelectric materials.

  1. Mesoporous bismuth ferrite with amplified magnetoelectric coupling and electric field-induced ferrimagnetism.

    PubMed

    Quickel, Thomas E; Schelhas, Laura T; Farrell, Richard A; Petkov, Nikolay; Le, Van H; Tolbert, Sarah H

    2015-01-01

    Coupled ferromagnetic and ferroelectric materials, known as multiferroics, are an important class of materials that allow magnetism to be manipulated through the application of electric fields. Bismuth ferrite, BiFeO3, is the most-studied intrinsic magnetoelectric multiferroic because it maintains both ferroelectric and magnetic ordering to well above room temperature. Here we report the use of epitaxy-free wet chemical methods to create strained nanoporous BiFeO3. We find that the strained material shows large changes in saturation magnetization on application of an electric field, changing from 0.04 to 0.84 μb per Fe. For comparison, non-porous films produced using analogous methods change from just 0.002 to 0.01 μb per Fe on application of the same electric field. The results indicate that nanoscale architecture can complement strain-layer epitaxy as a tool to strain engineer magnetoelectric materials. PMID:25754622

  2. 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.

  3. 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. PMID:24229099

  4. 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

  5. A generalized lumped-element equivalent circuit for tunable magnetoelectric microwave devices with multi-magnetoelectric laminates

    NASA Astrophysics Data System (ADS)

    Zhou, Hao-Miao; Lian, Jing

    2014-05-01

    According to the microwave transmission principle and the mechanism of ferromagnetic resonance, a generalized lumped element model for electrically and magnetically magnetoelectric tunable microwave devices with multi-magnetoelectric laminates is established. This model is introduced the RLC series resonant circuit and an ideal transformer model to characterize the ferromagnetic resonance effect and the coupling between microstrip line and the magnetoelectric laminates. Then, the model is degenerated to an existing microwave resonator, which contains only a single block magnetoelectric laminate, and transmission characteristics results predicted by the lumped element model are compared with the experimental results and the electromagnetic simulated results. It is found that the lumped circuit model can effectively predict the center frequency and bandwidth of the resonator. After that, the lumped element model is used to predict the band characteristics and the magnetic and electric tunability of the filter with multi-magnetoelectric laminates. The results show that the application of multi-magnetoelectric laminates in filters can not only broaden bandwidth, but also control the work frequency band by tuning the external electrostatic and magnetostatic field on the magnetoelectric laminates. Therefore, considering the practicality and versatility of microwave devices with multi-magnetoelectric laminates, the effective lumped element model can provide the theoretical basis for the design of novel magnetoelectric devices.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. Increased Sensitivity of Magnetoelectric Sensors at Low Frequencies Using Magnetic Field Modulation

    NASA Astrophysics Data System (ADS)

    Petrie, Jonathan; Viehland, Dwight; Gray, David; Mandal, Sanjay; Sreenivasulu, Gollapudi; Srinivasan, Gopalan; Edelstein, Alan

    2012-02-01

    Magnetoelectric (ME) laminate sensors are vector magnetometers that can detect pT magnetic fields at 1 kHz, although sensitivity may be reduced at lower frequencies. These passive sensors consist of alternating layers of magnetostrictive and piezoelectric materials. A magnetic field causes the magnetostrictive layer to strain the piezoelectric material and create measurable charge. We have shownootnotetextTo be published in Journal of Applied Physics. that since the strain response is a nonlinear function of the bias field, sweeping the magnetic bias on the magnetostrictive layer can modulate the ME response and increase the operating frequency of the sensor. This upward shift lowers the 1/f noise and increases the signal amplitude if the new operating frequency is near a mechanical resonance mode of the sensor. Using this modulation technique, the low frequency sensitivity has been improved by more than an order of magnitude and we have achieved a detectivity of 7 pT/Hz at1 Hz. In addition to increasing the magnetic signal frequency, we can use magnetic modulation to increase the operating frequency of acoustic signals detected by these sensors. This occurs because the ME sensors are nonlinear devices. In these cases using magnetic field modulation, the signal appears as sidebands around the modulation frequency.

  11. Study of room temperature magnetoelectric coupling in Ti substituted bismuth ferrite system

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Yadav, K. L.

    2006-10-01

    Dielectric, magnetic, and magnetoelectric properties of Ti substituted bismuth ferrite (BiFeO3) ceramic synthesized by solid state reaction are reported. Ti substitution for Fe in BiFeO3 increased the room temperature electrical resistivity by approximately six orders of magnitude and also increased the dielectric constant and reduced the loss tangent. The remanent polarization, coercive field, and maximum polarization were 0.081μC /cm2, 2.571kV/cm, and 0.658μC/cm2, respectively at 20kV/cm. An anomaly in the dielectric constant and loss tangent around Néel temperature was observed. The ferroelectric and magnetic hysteresis loops were measured which are not really saturated in BiFe0.75Ti0.25O3 compound and represented a partial reversal. The magnetoelectric coupling between electric dipoles and magnetic dipoles at room temperature was demonstrated by measuring the effect of magnetic poling on ferroelectric hysteresis loop and the change in the dielectric constant with the external magnetic field.

  12. Piezoelectric single crystal langatate and ferromagnetic composites: Studies on low-frequency and resonance magnetoelectric effects

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    Mechanical strain mediated magnetoelectric (ME) effects are studied in bilayers and trilayers of piezoelectric single-crystal lanthanum gallium tantalate (LGT) and magnetostrictive permendur (P). The ME voltage coefficient ranges from 2.3 V/cm Oe at 20 Hz to 720 V/cm Oe at bending resonance and is higher by an order of magnitude than in composites with ferroelectric lead zirconate titanate or lead magnesium niobate-lead titanate. The low-frequency magnetic noise for P-LGT-P is a factor of 2-10 smaller than for ferroelectrics based composites. Langatate is free of ferroelectric hysteresis, pyroelectric effects, and phase transitions up to 1450 °C and is of interest for ultrasensitive, high temperature magnetic sensors.

  13. 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

  14. 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.

  15. Direct and converse magneto-electric coupling in ferromagnetic shape memory alloys based thin film multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Singh, Kirandeep; Kaur, Davinder

    2015-12-01

    The ferromagnetic shape memory driven alterations in strain mediated direct and converse magnetoelectric coupling (DME & CME) was realized in sputtered deposited PZT/Ni-Mn-In multiferroic hetero-junctions. The ferroelectric (P-E loops), dielectric (ɛ vs frequency, ɛ-E), and voltage modulated magnetic anisotropy measurements (M-E curves) were executed in the plane (hard axis) and out of the plane (easy axis) of the functional magnetic material based PZT/Ni-Mn-In bilayer structure. A gain of ˜16 μC/cm2 in maximum polarization (Pmax) and ˜12% in tunability (nr) were observed along an easy magnetic axis of Ni-Mn-In. The butterfly shaped normalized magnetization (M/Ms) vs electric field (applied across the heterostructure) [M-E] plots evident the strain character of CME coupling. The co-action of (i) dissimilar carrier concentration between high symmetric austenitic cubic phase and low symmetry martensite phase of ferromagnetic shape memory alloys and (ii) martensitic transformation induced magnetization change in Ni-Mn-In cause an electrical field modulated hall resistivity; a change of ˜42% in hall resistivity was observed at 60 kV/cm electric field and 0.2 T magnetic field at 270 K. The reversible manipulation of remnant magnetization (Mr) with applied electric field was demonstrated as on/off switch using a square pulse of 60 kV/cm amplitude.

  16. 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.

  17. Proximate transition temperatures amplify linear magnetoelectric coupling in strain-disordered multiferroic BiMnO3

    NASA Astrophysics Data System (ADS)

    Mickel, Patrick R.; Jeen, Hyoungjeen; Kumar, Pradeep; Biswas, Amlan; Hebard, Arthur F.

    2016-04-01

    We report a giant linear magnetoelectric coupling in strained BiMnO3 thin films in which the disorder associated with an islanded morphology gives rise to extrinsic relaxor ferroelectricity that is not present in bulk centrosymmetric ferromagnetic crystalline BiMnO3. Strain associated with the disorder is treated as a local variable, which couples to the two ferroic order parameters, magnetization M ⃗ and polarization P ⃗. A straightforward "gas under a piston" thermodynamic treatment explains the observed correlated temperature dependencies of the product of susceptibilities and the magnetoelectric coefficient together with the enhancement of the coupling by the proximity of the ferroic transition temperatures close to the relaxor freezing temperature. Our interpretation is based on a trilinear coupling term in the free energy of the form L ⃗.(P ⃗×M ⃗) , where L ⃗ is a hidden antiferromagnetic order parameter, previously postulated by theory for BiMnO3. This phenomenological invariant not only preserves inversion and time-reversal symmetry of the strain-induced interactions but also explains the pronounced linear magnetoelectric coupling without using the more conventional higher order biquadratic interaction proportional to (P⃗.M ⃗) 2.

  18. Magneto-electric coupling in Ca3CoMnO6 thin films

    NASA Astrophysics Data System (ADS)

    Saha, J.; Sharma, G.; Kaushik, S. D.; Rani, V.; Sudesh; Siruguri, V.; Patnaik, S.

    2016-02-01

    We report on the growth and magneto-electric (ME) coupling of Ca3CoMnO6 thin films deposited by pulsed laser deposition technique. Ca3CoMnO6 is interesting because of its tunable inter-chain magnetic interactions that affect its ME coupling. An optical band gap of 1.73 eV was estimated by UV visible spectroscopy. The magnetic transition is surprisingly increased to 40 K, much above its bulk value (15 K). The increase in magnetic transition temperature is possibly due to stronger inter-chain interaction and strain caused by lattice mismatch. Due to canting the thin films show weak ferromagnetic like behavior at low temperature. The dielectric measurements show anomaly at 10 K and 40 K which are clearly visible at the first derivative of dielectric data. From direct polarization measurements we associate the 10 K transition to a magnetic structure driven ferroelectric phase. The magnetocapacitance data at 5 K shows substantial change in dielectric constant with magnetic field. The large ME coupling is also verified by polarization measurement, where a 5% change in polarization is observed on the application of 5 T external magnetic field.

  19. 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.

  20. Large magnetoelectric coupling in magnetically short-range ordered Bi5Ti3FeO15 film

    PubMed Central

    Zhao, Hongyang; Kimura, Hideo; Cheng, Zhenxiang; Osada, Minoru; Wang, Jianli; Wang, Xiaolin; Dou, Shixue; Liu, Yan; Yu, Jianding; Matsumoto, Takao; Tohei, Tetsuya; Shibata, Naoya; Ikuhara, Yuichi

    2014-01-01

    Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. However, single-phase materials with such cross-coupling properties at room temperature exist rarely in nature; new design of nano-engineered thin films with a strong magneto-electric coupling is a fundamental challenge. Here we demonstrate a robust room-temperature magneto-electric coupling in a bismuth-layer-structured ferroelectric Bi5Ti3FeO15 with high ferroelectric Curie temperature of ~1000 K. Bi5Ti3FeO15 thin films grown by pulsed laser deposition are single-phase layered perovskit with nearly (00l)-orientation. Room-temperature multiferroic behavior is demonstrated by a large modulation in magneto-polarization and magneto-dielectric responses. Local structural characterizations by transmission electron microscopy and Mössbauer spectroscopy reveal the existence of Fe-rich nanodomains, which cause a short-range magnetic ordering at ~620 K. In Bi5Ti3FeO15 with a stable ferroelectric order, the spin canting of magnetic-ion-based nanodomains via the Dzyaloshinskii-Moriya interaction might yield a robust magneto-electric coupling of ~400 mV/Oe·cm even at room temperature. PMID:24918357

  1. Reinterpreting the magnetoelectric coupling of polarizability tensors of infinite cylinders using symmetry: A simple TM/TE view

    NASA Astrophysics Data System (ADS)

    Chen, Parry Y.; Ben-Yakar, Jacob; Sivan, Yonatan

    2016-07-01

    Recently, Strickland et al. [Phys. Rev. B 91, 085104 (2015), 10.1103/PhysRevB.91.085104] retrieved dynamic polarizabilities of infinitely long wires at oblique incidence, reporting nonzero magnetoelectric coupling, seemingly defying existing theorems which forbid this in centrosymmetric scatterers. We reconcile this finding with existing symmetry restrictions on microscopic polarizabilities using a property of line dipoles. This motivates a reformulation of cylinder polarizability, yielding diagonal tensors that decompose the response into TM and TE contributions, simplifying subsequent treatment by homogenization theories. A transformation is derived between the formulation of Strickland et al. and our reformulation, allowing magnetoelectric coupling to be identified as the contrast between TM and TE responses, and enabling simple geometric insights into all its scaling and symmetry properties.

  2. Room temperature magnetoelectric coupling in BaTi1-xCrxO3 multiferroic thin films

    NASA Astrophysics Data System (ADS)

    Sundararaj, Anuraj; Chandrasekaran, Gopalakrishnan; Therese, Helen Annal; Annamalai, Karthigeyan

    2016-01-01

    We report on room temperature (RT) magnetoelectric coupling in tetragonal BaTi1-xCrxO3 thin film multiferroics (BTCO) sputter deposited on (100) SrTiO3 (where x = 0.005, 0.01, 0.02, and 0.03). As-deposited thin films are vacuum annealed by electron beam rapid thermal annealing technique. 50 nm thick BTCO with "x = 0.01" shows RT ferromagnetic and ferroelectric response with saturation magnetic moment of 1120 emu/cc and polarization of 14.7 microcoulomb/cm2. Piezoresponse/magnetic force microscope images shows RT magnetoelectric coupling in BTCO with "x = 0.01," which is confirmed using magnetocapacitance measurement where an increase in capacitance from 17.5 pF to 18.4 pF is observed with an applied magnetic field.

  3. Self-biased 215 MHz magnetoelectric NEMS resonator for ultra-sensitive DC magnetic field detection.

    PubMed

    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

  4. 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

  5. Phase transition and magneto-electric coupling of BiFeO3-YMnO3 multiferroic nanoceramics

    NASA Astrophysics Data System (ADS)

    Narayan Tripathy, Satya; Mishra, K. K.; Sen, S.; Mishra, B. G.; Pradhan, Dhiren K.; Palai, R.; Pradhan, Dillip K.

    2013-10-01

    We report the crystal structure, dielectric, magnetic, and magneto-electric properties of (1-x) BiFeO3-xYMnO3 (0.00 ≤ x ≤ 0.2) multiferroic nanoceramics prepared by auto-combustion technique. YMnO3 substitution is found to induce a structural phase transition from R3c to R3c+Pbnm after x ≈ 0.1 using Rietveld refinement technique. Field emission scanning electron micrographs show decrease in grain size with increase in YMnO3 content. The dielectric permittivity and loss tangent are found to be increased with composition x. The anomalies noticed from the temperature dependent dielectric analysis reveal the signature of magneto-electric coupling in the system. A decrease in magnetic ordering temperature as a function of composition is found from dielectric study. At room temperature, the dielectric permittivity of all the YMnO3 modified samples decrease with increasing magnetic field. The maximum value of magneto-electric coupling coefficient (ɛ(H)-ɛ(0))/ɛ(0) is found to be ˜ -5.5% at H = 2 T for x = 0.2. The behaviour of the magnetic hysteresis loop observed at room temperature suggests the suppression of space modulated spin structure.

  6. 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.

  7. 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.

  8. Magnetoelectric Heterostructures for Spintronics and Magnetic Sensing

    NASA Astrophysics Data System (ADS)

    Nan, Tianxiang

    Magnetoelectric heterostructures with coupled magnetization and electric polarization across their interfaces enable significantly improvement of performance of many devices such as magnetic sensors, microwave magnetic devices, and spintronics. I will first show that by utilizing a unique ferroelastic polarization switching pathway, one can achieve non-volatile electric-field-switching of magnetism in multiferroic heterostructures with different ferroelectric single crystals through a strain-mediated magnetoelectric coupling. In the same system, with atomically-thin ferromagnets, the interfacial charge-mediated should also be taken into account. The charge- and strain-mediated coupling mechanisms are demonstrated and precisely quantified by the electric-field-tuning of ferromagnetic resonance. With the same technique, magnetic relaxation including intrinsic and extrinsic damping has also been shown to be strongly correlated to the strain, which is attributed to the electric-field-modification of spin-orbit coupling. Moreover, I will also show the tuning of spin-orbit torques from the spin-Hall effect with applied voltage probed with spin-torque ferromagnetic resonance and show the possible application on voltage tunable spin-Hall nano-oscillators. In the second part of my thesis, I will show an ultra-miniaturized magnetoelectric nano-electromechanical system (NEMS) resonator based on an AlN/FeGaB magnetoelectric heterostructure for detecting wide band magnetic fields. With the high Quality factor and the ultra-high resonance frequency, a low DC magnetic field detection limit of 300 pT has been demonstrated.

  9. Dynamic behavior of magnetoelectric coupling of CuFeO2 induced by a high magnetic field

    NASA Astrophysics Data System (ADS)

    Xia, Nianming; Shi, Liran; Xia, Zhengcai; Chen, Borong; Jin, Zhao; Wang, Yeshuai; Ouyang, Zhongwen; Zuo, Huakun; Shen, Yining

    2014-03-01

    Magnetoelectric effects and their dynamic behavior in a CuFeO2 single crystal grown by the floating zone technique are investigated at low temperature in pulsed high magnetic fields. Experimental results show that the magnetization, dielectric polarization, and magnetoelectric coupling are anisotropic. In the magnetization, a field-induced multi-step-like transition with hysteresis is observed, in which the critical magnetic fields are independent of the field sweep rate. In the dielectric polarization, the field-induced dielectric polarization with hysteresis (or partial irreversible) is only observed in the incommensurate-noncollinear phase. In particular, no obvious spontaneous dielectric polarization is observed in the lower magnetic field regime. Using a pulsed high magnetic field with various magnetic field strength and field sweep rates, the coupling behavior between the magnetic moment and the dielectric polarization is investigated. Experimental results show that the dielectric polarization is weakly related to the field sweep rate. In the field-decreasing branch, the magnetic field is higher, the magnetic field region of the dielectric polarization remains is lower, indicating that the pulsed high magnetic field has an effect on the enhancement of the spontaneous dielectric polarization.

  10. Charge mediated room temperature magnetoelectric coupling in Zn1-xSmxO/BaTiO3 bilayer thin film.

    PubMed

    Sundararaj, Anuraj; Chandrasekaran, Gopalakrishnan; Therese, Helen Annal; Annamalai, Karthigeyan

    2015-08-01

    We present a room-temperature magnetoelectrically coupled bilayer thin film multiferroic system (BTS) 'Zn1-xSmxO/BaTiO3 (where x = 0.02 and 0.04)' grown on a SrTiO3 (100) substrate. The thin film layers are polycrystalline and continuous with an average roughness of 3.2 nm. At room temperature, the BTSs with x = 0.02 (BTS2) and x = 0.04 (BTS4) are ferromagnetic with a saturation magnetic moment (Ms) of 5.1 memu and 8.6 memu respectively, while the latter shows a paramagnetic trace. Both BTS2 and BTS4 are ferroelectric at room temperature with a saturation polarization (Ps) of 12.51 μC cm(-2) and 6.75 μC cm(-2), respectively. The coercive (electric) field required to polarize BTSs increases as a function of x (25.2 kV cm(-1) for BTS2 and 62.3 kV cm(-1) for BTS4). The change in degree of polarization/magnetization (domain contrast of the piezoresponse/magnetic force microscopy images), permittivity and resistance, as a function of external magnetic/electric field, directly suggests that the Zn0.98Sm0.02O/BaTiO3 BTS is magnetoelectrically coupled at room temperature. PMID:26184425

  11. 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.

  12. 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.

  13. Zigzag-shaped piezoelectric based high performance magnetoelectric laminate composite

    NASA Astrophysics Data System (ADS)

    Cho, Kyung-Hoon; Yan, Yongke; Folgar, Christian; Priya, Shashank

    2014-06-01

    We demonstrate a 33-mode piezoelectric structure with zigzag shape for high sensitivity magnetoelectric laminates. In contrast to the 33-mode macro fiber composite (MFC), this zigzag shape piezoelectric layer excludes epoxy bonding layer between the electrode and piezoelectric materials, thereby, significantly improving the polarization degree, electromechanical coupling, and the stability of loss characteristics. The polarization degree was monitored from the change in phase angle near resonance, and the loss stability was determined from the changes in dielectric loss and rate of capacitance variation defined by (C - Cf)/Cf, where C is capacitance at a given frequency and Cf is capacitance at 100 Hz. Magnetoelectric composite with zigzag patterned piezoelectric layer was found to exhibit giant magnetoelectric response both in low frequency off-resonance region (6.75 V cm-1 Oe-1 at 1 kHz) and at anti-resonance frequency (357 V cm-1 Oe-1).

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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. PMID:26732894

  2. Determination of the magnetoelectric coupling coefficient from temperature dependences of the dielectric permittivity for multiferroic ceramics Bi{sub 5}Ti{sub 3}FeO{sub 15}

    SciTech Connect

    Bartkowska, J. A. Dercz, J.

    2013-11-15

    In the multiferroic materials, the dielectric and magnetic properties are closely correlated through the coupling interaction between the ferroelectric and magnetic order. We attempted to determine the magnetoelectric coupling coefficient from the temperature dependences of the dielectric permittivity for multiferroic Bi{sub 5}Ti{sub 3}FeO{sub 15}. Multiferroic ceramics Bi{sub 5}Ti{sub 3}FeO{sub 15} belong to materials of the Aurivillius-type structure. Multiferroic ceramics Bi{sub 5}Ti{sub 3}FeO{sub 15} was synthesized via sintering the Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} mixture and TiO{sub 2} oxides. The precursor material was ground in a high-energy attritorial mill for 5 hours. This material was obtained by a solid-state reaction process at T = 1313 K. We investigated the temperature dependences of the dielectric permittivity for the different frequencies. From the dielectric measurements, we determined the temperature of phase transition of the ferroelectric-to-paraelectric type at about 1013 K. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.

  3. Electrically modulated magnetoelectric sensors

    NASA Astrophysics Data System (ADS)

    Hayes, P.; Salzer, S.; Reermann, J.; Yarar, E.; Röbisch, V.; Piorra, A.; Meyners, D.; Höft, M.; Knöchel, R.; Schmidt, G.; Quandt, E.

    2016-05-01

    Magnetoelectric thin film composites have demonstrated their potential to detect sub-pT magnetic fields if mechanical resonances (typically few hundred Hz to a few kHz) are utilized. At low frequencies (1-100 Hz), magnetic field-induced frequency conversion has enabled wideband measurements with resonance-enhanced sensitivities by using the nonlinear characteristics of the magnetostriction curve. Nevertheless, the modulation with a magnetic field with a frequency close to the mechanical resonance results in a number of drawbacks, which are, e.g., size and energy consumption of the sensor as well as potential crosstalk in sensor arrays. In this work, we demonstrate the feasibility of an electric frequency conversion of a magnetoelectric sensor which would overcome the drawbacks of magnetic frequency conversion. This magnetoelectric sensor consists of three functional layers: an exchange biased magnetostrictive multilayer showing a high piezomagnetic coefficient without applying a magnetic bias field, a non-linear piezoelectric actuation layer and a linear piezoelectric sensing layer. In this approach, the low frequency magnetic signal is shifted into the mechanical resonance of the sensor, while the electric modulation frequency is chosen to be either the difference or the sum of the resonance and the signal frequency. Using this electric frequency conversion, a limit of detection in the low nT/Hz1/2 range was shown for signals of low frequency.

  4. 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.

  5. Magnetoelectric coupling in multiferroic heterostructure of rf-sputtered Ni-Mn-Ga thin film on PMN-PT

    NASA Astrophysics Data System (ADS)

    Teferi, M. Y.; Amaral, V. S.; Lounrenco, A. C.; Das, S.; Amaral, J. S.; Karpinsky, D. V.; Soares, N.; Sobolev, N. A.; Kholkin, A. L.; Tavares, P. B.

    2012-06-01

    In this paper, we report a preparation of multiferroic heterostructure from thin film of Ni-Mn-Ga (NMG) alloy and lead magnesium niobate-lead titanate (PMN-PT) with effective magnetoelectric (ME) coupling between the film as ferromagnetic material and PMN-PT as piezoelectric material. The heterostructure was prepared by relatively low temperature (400 °C) deposition of the film on single crystal of piezoelectric PMN-PT substrate using rf magnetron co-sputtering of Ni50Mn50 and Ni50Ga50 targets. Magnetic measurements by Superconducting Quantum Interference Design (SQIUD) Magnetometer and Vibrating Sample Magnetometer (VSM) on the film revealed that the film is in ferromagnetically ordered martensitic state at room temperature with saturation magnetization of ˜240 emu/cm3 and Curie temperature of ˜337 K. Piezoresponse force microscopy (PFM) measurement done at room temperature on the substrate showed the presence of expected hysteresis loop confirming the stability of the piezoelectric state of the substrate after deposition. Room temperature ME voltage coefficient (αME) of the heterostructure was measured as a function of applied bias dc magnetic field in Longitudinal-Transverse (L-T) ME coupling mode by lock-in technique. A maximum ME coefficient αME of 3.02 mV/cm Oe was measured for multiferroic NMG/PMN-PT heterostructure which demonstrates that there is ME coupling between the film as ferromagnetic material and PMN-PT as piezoelectric material.

  6. First principles prediction of interfacial magnetoelectric coupling in tetragonal La2/3Sr1/3MnO3/BiFeO3 multiferroic superlattices.

    PubMed

    Feng, Nan; Mi, Wenbo; Wang, Xiaocha

    2015-05-28

    The electronic structure and magnetic properties of the tetragonal La2/3Sr1/3MnO3/BiFeO3 multiferroic superlattices with different interfacial terminations have been studied by first-principles calculations. Our results for all the models of the tetragonal La2/3Sr1/3MnO3/BiFeO3 superlattices exhibit a metallic electronic structure. More importantly, we find that the magnetoelectric coupling can be realized in the tetragonal La2/3Sr1/3MnO3/BiFeO3 heterostructures by means of exchange bias, which can be attributed to the interfacial exchange coupling. These findings are useful for magnetoelectrically controlled spintronic devices. PMID:25940540

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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-) 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.

  13. 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.

  14. 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.

  15. 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

  16. Equivalent circuit model including magnetic and thermo sources for the thermo-magneto-electric coupling effect in magnetoelectric laminates

    NASA Astrophysics Data System (ADS)

    Cui, Xiao-Le; Zhou, Hao-Miao

    2015-07-01

    The nonlinear thermo-magneto-mechanical magnetostrictive constitutive and the linear thermo-mechanical-electric piezoelectric constitutive are adopted in this paper. The bias magnetic field and ambient temperature are equivalent to a magnetic source and a thermo source, respectively. An equivalent circuit, which contains a magnetic source and a thermo source at the input, for the thermo-magneto-electric coupling effect in magnetoelectric (ME) laminates, is established. The theoretical models of the output voltage and static ME coefficient for ME laminates can be derived from this equivalent circuit model. The predicted static ME coefficient versus temperature curves are in excellent agreement with the experimental data available both qualitatively and quantitatively. It confirms the validity of the proposed model. Then the models are adopted to predict variations in the output voltages and ME coefficients in the laminates under different ambient temperatures, bias magnetic fields, and the volume ratios of magnetostrictive phases. This shows that the output voltage increases with both increasing temperature and increasing volume ratio of magnetostrictive phases; the ME coefficient decreases with increasing temperature; the ME coefficient shows an initial sharp increase and then decreases slowly with the increase in the bias magnetic field, and there is an optimum volume ratio of magnetostrictive phases that maximize the ME coefficient. This paper can not only provide a new idea for the study of the thermo-magneto-electric coupling characteristics of ME laminates, but also provide a theoretical basis for the design and application of ME laminates, operating under different sensors. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

  17. 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.

  18. 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.

  19. Magnetoelectric effects in ferromagnetic films on ferroelectric substrates

    NASA Astrophysics Data System (ADS)

    Filippov, D. A.; Srinivasan, G.; Gupta, A.

    2008-10-01

    Theories for magnetoelectric (ME) effects in a bilayer consisting of magnetostrictive film on piezoelectric substrate are discussed. The ME coupling at low frequencies and at mechanical resonance due to acoustic modes have been estimated and applied to the specific case of a thin film of permendur or nickel ferrite on lead zirconate titanate (PZT). Both ideal and non-ideal interface coupling are considered. The theory predicts strong ME coupling for magnetic films on piezoelectric substrates. At low frequency, the ME coefficient is maximum when PZT is 2-4 times as thick as the magnetic film. The ME coefficient, for ideal coupling, shows resonance enhancement at a single frequency. For non-ideal interface coupling, enhancement is expected at two frequencies corresponding to coupled oscillations in magnetic and piezoelectric layers.

  20. 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.

  1. Coupled Resonance Laser Frequency Stabilization

    NASA Astrophysics Data System (ADS)

    Burd, Shaun; Uys, Hermann; MAQClab Team

    2013-05-01

    We have demonstrated simultaneous laser frequency stabilization of a UV and IR laser, to the same photodiode signal derived from the UV laser only. For trapping and cooling Yb+ ions, a frequency stabilized laser is required at 369.9 nm to drive the S1/2-P1/2 cooling cycle. Since that cycle is not closed, a repump beam is needed at 935.18 nm to drive the D3/2-D[ 3 / 2 ] transition, which rapidly decays back to the S1/2 state. Our 369 nm laser is locked using Doppler free polarization spectroscopy of Yb+ ions, generated in a hollow cathode discharge lamp. Without pumping, the metastable D3/2 level is only sparsely populated, making direct absorption of 935 nm light difficult to detect. A resonant 369 nm pump laser can populate the D3/2 state, and fast repumping to the S1/2 ground state by on resonant 935 nm light, can be detected via the change in absorption of the 369 nm laser. This is accomplished using lock-in detection on the same photodiode signal to which the 369 nm laser is locked. In this way, simultaneous locking of two frequencies in very different spectral regimes is accomplished, while exploiting only the photodiode signal from one of the lasers. A rate equation model gives good qualitative agreement with experimental observation. This work was partially funded by the South African National Research Foundation.

  2. 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.

  3. 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.

  4. Magnetoelectric spintronics

    NASA Astrophysics Data System (ADS)

    Kleemann, W.

    2013-07-01

    A promising way to overcome power and temperature issues in optimizing the performance of microelectronic devices will take advantage of purely electric field-controlled devices with a minimum amount of Joule heating. Multiphase multiferroic and magnetoelectric materials are most promising, since they can be tailored according to the technical needs. Here, we focus onto electric switching of the exchange bias effect in Cr2O3/(Pt/Co/Pt) heterostructures thus controlling the magnetic states of spintronic devices such as MERAM and MEXOR.

  5. 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

  6. Multiferroic CoFe2O4-Pb(Zr(0.52)Ti(0.48))O3 core-shell nanofibers and their magnetoelectric coupling.

    PubMed

    Xie, Shuhong; Ma, Feiyue; Liu, Yuanming; Li, Jiangyu

    2011-08-01

    Multiferroic CoFe(2)O(4)-Pb(Zr(0.52)Ti(0.48))O(3) core-shell nanofibers have been synthesized by coaxial electrospinning in combination with a sol-gel process. The core-shell configuration of nanofibers has been verified by scanning electron microscopy and transmission electron microscopy, and the spinel structure of CoFe(2)O(4) and perovskite structure of Pb(Zr(0.52)Ti(0.48))O(3) have been confirmed by X-ray diffraction and selected area electron diffraction. The multiferroic properties of core-shell nanofibers have been demonstrated by magnetic hysteresis and piezoresponse force microscopy, and their magnetoelectric coupling has been confirmed by evolution of piezoresponse under an external magnetic field, showing magnetically induced ferroelectric domain switching and changes in switching characteristics. The lateral magnetoelectric coefficient is estimated to be 2.95 × 10(4) mV/cmOe, two orders of magnitude higher than multiferroic thin films of similar composition. PMID:21643573

  7. The magnetoelectric coupling in rhombohedral-tetragonal phases coexisted Bi0.84Ba0.20FeO3

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Xuan, Haicheng; Wang, Liaoyu; Zhang, Yan; Shen, Kai; Wang, Dunhui; Qiu, Teng; Xu, Qingyu

    2012-06-01

    Ba doped Bi1.04-xBaxFeO3 ceramics with x up to 0.30 have been prepared by the tartaric acid modified sol-gel method. The X ray diffraction patterns show that the structure transforms from rhombohedral to tetragonal with increasing the Ba substitution concentration from 10% to 30% and the coexistence of distorted rhombohedral and tetragonal phases in 20% Ba substituted BiFeO3, which was further confirmed by the Raman spectra. Bi0.84Ba0.20FeO3 exhibits the highest magnetization (1.6 emu/g under magnetic field of 12 kOe) compared with the other samples of different Ba substitution concentration. Significant enhancement of the ferroelectricity has been observed in 20% and 30% Ba substituted BiFeO3 with saturate polarization close to 6.6 μC/cm2 for Bi0.74Ba0.30FeO3. The magnetoelectric coupling of Bi0.84Ba0.20FeO3 has been measured and the maximum decrease of magnetization under magnetic field of 9.8 kOe was about 0.06 emu/g with increasing applied electric field to 11 kV/cm, and the magnetoelectric coefficient is 1.5×10-12 s/m.

  8. 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.

  9. 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.

  10. Effect of thickness on the stress and magnetoelectric coupling in bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4 films

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Li, Zheng; Wang, Jianjun; He, Hongcai; Nan, Cewen

    2015-01-01

    Magnetoelectric bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4(PZT-CFO) films with different PZT thicknesses were grown on (111)Pt/Ti/SiO2/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 A1(TO1) 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Substrate clamping effect onto magnetoelectric coupling in multiferroic BaTiO3-CoFe2O4 core-shell nanofibers via coaxial electrospinning

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    We report large lateral magnetoelectric (ME) coupling coefficients α 31 of 1.2×104 \\text{mV} \\text{cm}-1 \\text{Oe}-1 and 3.5× 104 \\text{mV} \\text{cm}-1 \\text{Oe}-1 in substrate bonded and free-standing multiferroic BaTiO3-CoFe2O4 (BTO-CFO) core-shell nanofibers (NFs) with and without substrate clamping effect, respectively. The BTO-CFO core-shell NFs were synthesised by a sol-gel coaxial electrospinning technique, and their ME coupling was directly observed by demonstrating the evolution of piezoelectric coefficient (d 33), ferroelectric domain, and phase contrast induced by an external magnetic field. These impressed α 31 coefficients originated from the nanoconfinement of the interphase elastic interaction between the ferromagnetic core fiber and the ferroelectric shell interlayer, as well as the strain transformation at the one-dimensional (1D) fiber boundary. This means that the decreasing substrate clamping effect results in an enhanced ME coupling in multiferroic NFs, which is similar to that of thin films. These findings make people understand the substrate clamping effect and enable nanoscale ME device applications.

  17. Design and fabrication of a microscale magnetoelectric surgical tool

    NASA Astrophysics Data System (ADS)

    Clarke, Joshua; Sundaresan, Vishnu Baba

    2011-04-01

    Magnetoelectric materials made from magnetostrictive and piezoelectric constituents are best suited for selfsensing actuators. The relationship between applied magnetic field (force), tip displacement (deflection) and current output (sensing signal) is necessary for the development of self-sensing actuator systems. The dynamic behavior of the constituent magnetostrictive materials and piezoelectric materials independent of each other are well-understood. The coupled dynamic force-strain-sensing behavior of magnetoelectric materials as selfsensing actuators is largely unexplored and provides the motivation for our work in this area. This paper presents theoretical and experimental analysis of the dynamic behavior of a Metglas/PVDF magnetoelectric laminate composite. Experimental results for the mechanical and electrical behavior of a 15mm × 30mm × 75μm Metglas/PVDF cantilever beam across the frequency spectrum are compared to those predicted by an equation of motion developed using the principle of virtual work and Hamiltonian principle. The theoretically developed model predicts the observed displacement and sensing current within 35% and 20% respectively. A parametric analysis is presented to determine the optimum design parameters of the composite for self-sensing actuation.

  18. 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.

  19. 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.

  20. 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.

  1. Inductive coupled radio frequency plasma bridge neutralizer.

    PubMed

    Scholze, F; Tartz, M; Neumann, H

    2008-02-01

    A 13.56 MHz radio frequency plasma bridge neutralizer (rf-PBN) for ion thruster applications as well as ion beam surface processing of insulating materials is presented. The energy for the plasma excitation is inductively coupled into the plasma chamber. Because no components are located inside the plasma, the lifetime of the rf-PBN is expected to be very long. A compact tuning system adapts the input power to the plasma impedance. The electron current may be controlled over a wide range by the rf input power. An electron current of up to 1.6 A has been extracted. PMID:18315215

  2. 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.

  3. 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.

  4. Mode coupling of Schwarzschild perturbations: Ringdown frequencies

    SciTech Connect

    Pazos, Enrique; Brizuela, David; Martin-Garcia, Jose M.; Tiglio, Manuel

    2010-11-15

    Within linearized perturbation theory, black holes decay to their final stationary state through the well-known spectrum of quasinormal modes. Here we numerically study whether nonlinearities change this picture. For that purpose we study the ringdown frequencies of gauge-invariant second-order gravitational perturbations induced by self-coupling of linearized perturbations of Schwarzschild black holes. We do so through high-accuracy simulations in the time domain of first and second-order Regge-Wheeler-Zerilli type equations, for a variety of initial data sets. We consider first-order even-parity (l=2, m={+-}2) perturbations and odd-parity (l=2, m=0) ones, and all the multipoles that they generate through self-coupling. For all of them and all the initial data sets considered we find that--in contrast to previous predictions in the literature--the numerical decay frequencies of second-order perturbations are the same ones of linearized theory, and we explain the observed behavior. This would indicate, in particular, that when modeling or searching for ringdown gravitational waves, appropriately including the standard quasinormal modes already takes into account nonlinear effects.

  5. CoFe{sub 2}O{sub 4}/Pb(Zr{sub 052}Ti{sub 0.48})O{sub 3} disk-ring magnetoelectric composite structures

    SciTech Connect

    Li Lei; Lin Yiqi; Chen Xiangming

    2007-09-15

    Magnetoelectric composite structures of CFO (CoFe{sub 2}O{sub 4})-disk/PZT (Pb(Zr{sub 052}Ti{sub 0.48})O{sub 3})-ring and PZT-disk/CFO-ring were prepared and evaluated, where the magnetostrictive and piezoelectric phases were coupled through normal stresses. Under bias magnetic fields around 3400 Oe, the peak magnetoelectric coefficients reached 18.1 and 102.6 mV cm{sup -1} Oe{sup -1} at 1 kHz for CFO-disk/PZT-ring and PZT-disk/CFO-ring structures, respectively, which were much higher than that of the corresponding layered composite. Prediction for magnetoelectric coefficients at low frequency was conducted, and the improved interfacial mechanical coupling through normal stresses was responsible for the enhanced magnetoelectric properties of the present composite structures. Moreover, the frequency dependence of the magnetoelectric coefficient was investigated, and the resonant magnetoelectric coefficients were up to 4120 and 6430 mV cm{sup -1} Oe{sup -1} for CFO-disk/PZT-ring and PZT-disk/CFO-ring composite structures, respectively.

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

    PubMed

    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 [Formula: see text] (LSMO) and [Formula: see text] (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. PMID:27494690

  7. 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.

  8. 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

  9. Magnetoelectric effects via pentalinear interactions

    NASA Astrophysics Data System (ADS)

    Zhao, Hong Jian; Grisolia, M. N.; Yang, Yurong; Íñiguez, Jorge; Bibes, M.; Chen, Xiang Ming; Bellaiche, L.

    2015-12-01

    Magnetoelectric multiferroic materials, particularly with the perovskite structure, are receiving a lot of attention because of their inherent coupling between electrical polarization and magnetic ordering. However, very few types of direct coupling between polarization and magnetization are known, and it is unclear whether they can be useful to the design of spintronic devices exploiting the control of magnetization by electric fields. For instance, the typical biquadratic coupling only allows changing the magnitude of the magnetization by an electric field, but it does not permit an electric-field-induced switching of the magnetization. Similarly, the so-called Lifshitz invariants allow an electric-field control of complicated magnetic orderings, but not of the magnetization. Here, we report on original direct couplings between polarization and magnetization in epitaxial perovskite films, via the use of first-principles methods and the development of an original Landau-type phenomenological theory. Our results feature pentalinear interactions involving the ferromagnetic and antiferromagnetic vectors as well as the polar distortions and oxygen octahedral tilting, and permit a number of striking effects. Examples include a continuous electric-field control of the magnetization magnitude and sign, and the discrete switching of the magnetization magnitude. Thus, the high-order, pentalinear couplings demonstrated in this work may open paths towards specific magnetoelectric effects, as well as spintronic and magnonic devices.

  10. 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.

  11. Magnetoelectric interactions in layered composites of piezoelectric quartz and magnetostrictive alloys

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, G.; Petrov, V. M.; Fetisov, L. Y.; Fetisov, Y. K.; Srinivasan, G.

    2012-12-01

    Mechanical strain mediated magnetoelectric effects are studied in bilayers and trilayers of piezoelectric quartz and magnetostrictive permendur (P), an alloy of Fe-Co-V. It is shown that the magnetoelectric voltage coefficient (MEVC), proportional to the ratio of the piezoelectric coupling coefficient to the permittivity, is higher in quartz-based composites than for traditional ferroelectrics-based ME composites. In bilayers of X-cut single crystal quartz and permendur, the MEVC varies from 1.5 V/cm Oe at 20 Hz to ˜185 V/cm Oe at bending resonance or electromechanical resonance corresponding to longitudinal acoustic modes. In symmetric X-cut quartz-P trilayers, the MEVC ˜4.8 V/cm Oe at 20 Hz and ˜175 V/cm Oe at longitudinal acoustic resonance. Trilayers of Y-cut quartz and permendur show ME coupling under a shear strain with an MEVC that is an order of magnitude smaller than for longitudinal strain in samples with X-cut quartz. A model for low-frequency and resonance ME effects which allows for explicit expressions of MEVC and resonance frequencies is provided and calculated. MEVCs are in general agreement with measured values. Magnetoelectric composites with quartz have the desired characteristics such as the absence of ferroelectric hysteresis and pyroelectric losses and could potentially replace ferroelectrics in composite-based magnetic sensors, transducers, and high-frequency devices.

  12. Resonance magnetoelectric effects in magnetostrictive-piezoelectric three-layer structures

    NASA Astrophysics Data System (ADS)

    Filippov, D. A.; Laletsin, U.; Srinivasan, G.

    2007-11-01

    A theory is discussed for magnetoelectric (ME) interactions at electromechanical resonance in a heterogeneous ferromagnetic-piezoelectric three-layer structure. An expression has been obtained for the transverse ME coefficients αE ,T as a function of interface coupling β between the layers. For 0<β<1, the theory predicts resonance enhancement of αE ,T at two interrelated radial modes. As β is increased from 0, the low-frequency resonance occurs at progressively increasing frequency until it merges with the high-frequency mode when β =1. These predictions are in general agreement with representative data for a permendur-PZT-permendur trilayer composite.

  13. The nature of magnetoelectric coupling in Pb(Zr,Ti)O3 -Pb(Fe,Ta)O3.

    PubMed

    Evans, Donald M; Alexe, Marin; Schilling, Alina; Kumar, Ashok; Sanchez, Dilsom; Ortega, Nora; Katiyar, Ram S; Scott, James F; Gregg, J Marty

    2015-10-21

    The coupling between magnetization and polarization in a room temperature multiferroic (Pb(Zr,Ti)O3 -Pb(Fe,Ta)O3 ) is explored by monitoring the changes in capacitance that occur when a magnetic field is applied in each of three orthogonal directions. Magnetocapacitance effects, consistent with P(2) M(2) coupling, are strongest when fields are applied in the plane of the single crystal sheet investigated. PMID:26351267

  14. 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.

  15. 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).

  16. 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.

  17. Nonlinear magnetoelectric effect in composite multiferroics

    NASA Astrophysics Data System (ADS)

    Filippov, D. A.; Laletin, V. M.; Firsova, T. O.

    2014-05-01

    The theoretical and experimental studies of the nonlinear magnetoelectric effect in composite multiferroics in the low-frequency spectral region and in the electromechanical resonance region have been performed. It has been shown that such structures demonstrate a nonlinear magnetoelectric effect, which is quadratic in ac magnetic field strength at weak magnetic fields. In the region of the electromechanical resonance, the resonance excitation of an electric field occurs by means of ac magnetic field at a frequency lower than the resonance frequency by a factor of two. In the low-frequency spectral region, there is a difference of amplitude values of two neighboring voltage maxima due to the superposition of signals from the linear and nonlinear effects, and the difference is proportional to the dc magnetic field strength in weak fields. The results of the experimental study of the two-layer permendur-lead zirconate titanate structure are presented.

  18. 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.

  19. 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.

  20. 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

  1. Magnetoelectric coupling tuned by competing single iron anisotropies in Mn1-xNixTiO3

    DOE PAGESBeta

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

    2014-01-01

    A flop of electric polarization from Pc to Pa is observed in MnTiO3 as a spin flop transtion is triggered by a c-axis magnetic field, Hc=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 rotationmore » 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

  2. 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

  3. Quantification of size effects in the magnetoelectric response of metallic glass/PVDF laminates

    NASA Astrophysics Data System (ADS)

    Lasheras, A.; Gutiérrez, J.; Barandiarán, J. M.

    2016-05-01

    Metallic glass/polyvinylidene fluoride three-layered magnetoelectric laminated composites have been studied. Size effects in the magnetoelectric response arisen both from the reduction of the length of the laminate and from the increase of the operating frequency have been quantified for the lengths ranging from 3 cm down to 0.5 cm. It has been concluded that the decrease in this magnetoelectric response arises mainly from the demagnetizing effects, with reductions of 86% for the longest laminate that increase up to 99% for the shortest one. From these values, an intrinsic magnetoelectric coefficient of 325 V/cm Oe has been obtained.

  4. 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.

  5. Magnetoelectric resonance engine

    SciTech Connect

    Moscrip, W.M.

    1992-09-15

    This patent describes a magnetoelectric resonance thermal machine. It comprises a reciprocating, multiple-piston, Alpha-type Stirling-cycle mechanical assembly; an electronic quadrature phase-lock circuit; an ancillary external energy and mass transfer subsystem; and a master microcomputer control system.

  6. 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

  7. Magnetoelectric Effect in Ceramics Based on Bismuth Ferrite

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  8. 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.

  9. Induced ferromagnetism and magnetoelectric coupling in ion-beam synthesized BiFeO3–CoFe2O4 nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Modarresi, H.; Lazenka, V.; Menéndez, E.; Lorenz, M.; Bisht, M.; Volodin, A.; Van Haesendonck, C.; Grundmann, M.; Van Bael, M. J.; Temst, K.; Vantomme, A.

    2016-08-01

    Ferrimagnetic CoFe2O4 (cobalt ferrite) is formed within an epitaxial BiFeO3 (bismuth ferrite) thin film matrix by Co channeled ion implantation and subsequent annealing. The presence of nanoscale CoFe2O4 crystals in the matrix is confirmed by x-ray diffraction using synchrotron radiation. The significantly increased magnetic moment and the low-temperature coercive field of the composite system evidence the formation of ferrimagnetic cobalt ferrite and its nanoscale character, respectively. The results demonstrate that ion beam synthesis is an appropriate method to controllably transform a planar system into a granular one, increasing the interface area between cobalt ferrite and bismuth ferrite. The ferroelectric nature of the BiFeO3–CoFe2O4 composite is confirmed by several scanning probe microscopy techniques. At room temperature, the composite exhibits a magnetoelectric voltage coefficient of α ME  =  17.5 V (cm · Oe)‑1, while a single-phase BiFeO3 thin film shows a α ME value of 4.2 V (cm · Oe)‑1. The high magnetoelectric voltage coefficient is interpreted to be the result of the interfacial interaction between the ferrimagnetic CoFe2O4 nanocrystallites and the multiferroic BiFeO3 matrix.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Mechanisms of transcription-repair coupling and mutation frequency decline.

    PubMed Central

    Selby, C P; Sancar, A

    1994-01-01

    Mutation frequency decline is the rapid and irreversible decline in the suppressor mutation frequency of Escherichia coli cells if the cells are kept in nongrowth media immediately following the mutagenic treatment. The gene mfd, which is necessary for mutation frequency decline, encodes a protein of 130 kDa which couples transcription to excision repair by binding to RNA polymerase and to UvrA, which is the damage recognition subunit of the excision repair enzyme. Although current evidence suggests that transcription-repair coupling is the cause of the preferential repair of the transcribed strand of mRNA encoding genes as well as of suppressor tRNA genes, the decline occurs under stringent response conditions in which the tRNA genes are not efficiently transcribed. Thus, the mechanism of strand-specific repair is well understood, but some questions remain regarding the precise mechanism of mutation frequency decline. PMID:7968917

  15. Novel microwave magnetic and magnetoelectric composite materials and devices

    NASA Astrophysics Data System (ADS)

    Pettiford, Carl I.

    Bulk microwave magnetic materials and devices have been widely used in different RF/microwave devices such as inductors, filters, circulars, isolators, and phase shifters. With the even increasing level of integration of RFIC and MMIC, there is an urgent need for new microwave magnetic thin film materials and new integrated RF/microwave magnetic devices. In this thesis, we have addressed these needs in three different areas: (1) exchange biased ferromagnetic/anti-ferromagnetic multilayer thin films with enhanced anisotropy fields, (2) magneto-electric heterostructures and devices, and (3) metamaterial multilayers for FMR enhancement, tunability, and plane wave absorption. Metallic soft magnetic thin films have been demonstrated to have high saturation magnetization, large permeability and relatively high self-biased ferromagnetic resonance (FMR) frequencies, showing great promise for applications in integrated RF and microwave magnetic devices. One problem for these metallic magnetic films is however their relatively low anisotropy fields that are typically in the range of 10˜30 Oe, which severely limit their application frequency range. In this work, we investigated the exchange coupled ferromagnetic/anti-ferromagnetic/ferromagnetic CoFe/PtMn/CoFe multilayer films. These CoFe/PtMn/CoFe multilayer films showed a significantly enhanced anisotropy field of 160 Oe, which was 5˜10 times of that of the FeCo films. In addition, a narrow FMR linewidth of 45 Oe at X-band was achieved in the CoFe/PtMn/CoFe trilayer. The exchange coupling in the ferromagnetic/anti-ferromagnetic/ferromagnetic trilayers leads to a significantly enhanced anisotropy field that is crucial for the application of metallic magnetic films in integrated magnetic RF/microwave devices. The magnetoelectric coupling of novel YIG/PZT, FeCoB/PZT and FeGaB/PZT multiferroic heterostructures were investigated at DC and at microwave frequencies. An electrostatically tunable band-reject filter device was

  16. 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

  17. Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory

    NASA Astrophysics Data System (ADS)

    Elnaggar, Sameh Y.; Tervo, Richard; Mattar, Saba M.

    2014-01-01

    Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance.

  18. Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory.

    PubMed

    Elnaggar, Sameh Y; Tervo, Richard; Mattar, Saba M

    2014-01-01

    Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance. PMID:24246950

  19. 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.

  20. 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.

  1. 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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. 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. PMID:26651632

  5. 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.

  6. 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.

  7. 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.

  8. Linear magnetoelectric effect by orbital magnetism.

    PubMed

    Scaramucci, A; Bousquet, E; Fechner, M; Mostovoy, M; Spaldin, N A

    2012-11-01

    We use symmetry analysis and first-principles calculations to show that the linear magnetoelectric effect can originate from the response of orbital magnetic moments to the polar distortions induced by an applied electric field. Using LiFePO(4) as a model compound we show that spin-orbit coupling partially lifts the quenching of the 3d orbitals and causes small orbital magnetic moments (μ((L)) ≈ 0.3 μ(B)) parallel to the spins of the Fe(2+) ions. An applied electric field E modifies the size of these orbital magnetic moments inducing a net magnetization linear in E. PMID:23215421

  9. 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.

  10. Synchronization of phase oscillators with frequency-weighted coupling

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  11. Synchronization of phase oscillators with frequency-weighted coupling.

    PubMed

    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 heterogeneous couplings. PMID:26903110

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Carrier-mediated magnetoelectricity in complex oxide heterostructures.

    PubMed

    Rondinelli, James M; Stengel, Massimiliano; Spaldin, Nicola A

    2008-01-01

    Increasing demands for high-density, stable nanoscale memory elements, as well as fundamental discoveries in the field of spintronics, have led to renewed interest in exploring the coupling between magnetism and electric fields. Although conventional magnetoelectric routes often result in weak responses, there is considerable current research activity focused on identifying new mechanisms for magnetoelectric coupling. Here we demonstrate a linear magnetoelectric effect that arises from a carrier-mediated mechanism, and is a universal feature of the interface between a dielectric and a spin-polarized metal. Using first-principles density functional calculations, we illustrate this effect at the SrRuO3/SrTiO3 interface and describe its origin. To formally quantify the magnetic response of such an interface to an applied electric field, we introduce and define the concept of spin capacitance. In addition to its magnetoelectric and spin capacitive behaviour, the interface displays a spatial coexistence of magnetism and dielectric polarization, suggesting a route to a new type of interfacial multiferroic. PMID:18654450

  19. Coupling measurements on intelligent missiles at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Braun, Ch.; Guidi, P.; Schmidt, H. U.

    1995-03-01

    This paper describes our low power microwave coupling measurements on terminally guided missiles in the frequency range between 100 and 8000 MHz. The plane wave excitation experiments have been carried out in our field coupling facility, which consists of an asymmetric triplate transmission line with maximum field levels of about 40 V/m in the working volume. As test objects we examined five (semi) autonomous guided missiles. Three of them, former experimental studies from the Diehl company (GE), are presented in this paper. The test objects were positioned in the simulator in three orthogonal orientation with respect to the external field and were not connected to a power supply (inactive condition). In order to be able to systematically analyze the interaction of the external electromagnetic fields with the avionics and its wiring, we had to divide the investigations into three independent phases, namely, external interaction with the fuselage, mode of penetration to the interior of the missile and excitation of the electrical systems and the cabling. The coupling paths depend very much on the design principles of the airframe. The main threat identified was back door coupling via those wings and fins, which are not attached galvanically to the outer surface of the hull. Because of flight guidance, these parts are fastened through slots to the bearings of the motor drives inside the missile. The dominant cable resonances sometimes can be traced back to the resonances of the wings and/or fins and the type of cabling. Another threat was coupling via the long slots required for the folding wings. These shafts penetrate the whole body and enable the external fields to couple into the interior. The peak amplitudes at the ends of the cables were found to be between 50 to 500 (micro A/(V/m)), depending on the test object.

  20. 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.

  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. Giant magnetoelectric effect in negative magnetostrictive/piezoelectric/positive magnetostrictive semiring structure

    NASA Astrophysics Data System (ADS)

    Zeng, Lingyu; Zhou, Minhong; Bi, Ke; Lei, Ming

    2016-01-01

    Magnetoelectric (ME) Ni/PZT/TbFe2 and TbFe2/PZT composites with two semiring structures are prepared. The dependence between ME coupling and magnetostrictive property of the composite is discussed. Because Ni possesses negative magnetostrictive property and TbFe2 shows positive magnetostrictive property, the ME voltage coefficient of Ni/PZT/TbFe2 semiring structure is much larger than that of TbFe2/PZT. In these composites, the ME voltage coefficient increases and the resonance frequency gradually decreases with the increase of the semiring radius, showing that structural parameters are key factors to the composite properties. Due to the strong ME coupling effect, a giant ME voltage coefficient αE = 44.8 V cm-1 Oe-1 is obtained. This approach opens a way for the design of ME composites with giant ME voltage coefficient.

  3. Electromagnetic coupling in frequency domain induced polarisation data

    NASA Astrophysics Data System (ADS)

    Routh, Partha Sarathi

    2000-11-01

    Frequency domain induced polarization (IP) surveys are commonly carried out to provide information about the chargeability structure of the earth. The goals might be as diverse as trying to delineate a mineralized and/or alteration zone for mineral exploration, or to find a region of contaminants for an environmental problem. Unfortunately, the measured responses can have contributions from inductive and galvanic effects of the ground. The inductive components are called EM coupling effects. They are considered to be ``noise'' and much of this thesis is devoted towards either removing these effects, or reformulating the inverse problem so that inductive effects are part of the ``signal''. If the forward modeling is based on galvanic responses only, then the inductive responses must first be removed from the data. The motivation for attacking the problem in this manner is that it is easier to solve D.C. resistivity equation than the full Maxwell's equation. The separation of the inductive response from the total response is derived by expressing the total electric field as a product of an IP response function, and an electric field which depends on EM coupling response. This enables me to generate formulae to obtain IP amplitude (PFE) and phase response from the raw data. The data can then be inverted, using a galvanic forward modeling. I illustrate this with 1D and 3D synthetic examples. To handle field data sets, I have developed an approximate method for estimating the EM coupling effects based upon the assumption that the earth is locally 1D. The 1D conductivity is obtained from a 2D inversion of the low frequency DC resistivity data. Application of this method to a field data set has shown encouraging results. I also examine the EM coupling problem in terms of complex conductivity. I show that if the forward modeling is carried out with full Maxwell's equation, then there is no need to remove EM coupling. I illustrate this with 1D synthetic example. In summary

  4. 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.

  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. 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.

  7. High-frequency search for mass-coupled mesoscopic forces

    NASA Astrophysics Data System (ADS)

    Yan, Haiyang; Otto, Hans; Weisman, Evan; Khatiwada, Rakshya; Long, Josh

    2014-03-01

    The possible existence of unobserved interactions of nature with ranges of mesoscopic scale (microns to millimeters) and very weak couplings to matter has attracted a great deal of scientific attention. We report on an experimental search for exotic mass-coupled in this range. Our technique uses a planar, double-torsional tungsten oscillator as a test mass, a similar oscillator as a source mass, and a stiff conducting shield in between them to suppress backgrounds. This method affords operation at the limit of instrumental thermal noise, which we have we have recently demonstrated with a measurement of the noise kinetic energy of a detector prototype in thermal equilibrium at room temperature. The fluctuations of the oscillator in a high-Q torsional mode with a resonant frequency near 1 kHz are detected with capacitive transducers coupled to a sensitive differential amplifier. The apparatus is calibrated by means of a known electrostatic force and input from a finite-element model of the selected mode. The measured kinetic energy is in agreement with the expected value of 1/2 kT.

  8. Hot-Pressed Ferrite-Lead Zirconate Titanate Magnetoelectric Composites

    NASA Astrophysics Data System (ADS)

    Devreugd, C. P.; Srinivasan, G.; Micheli, A. L.; Mantese, J. V.

    2004-03-01

    The electromagnetic coupling in magnetostrictive/piezoelectric is mediated by mechanical stress: magnetostriction induced mechanical deformation and piezoelectric effect induced electric fields. Composites studied so far include ferrite-lead zirconate titanate (PZT) and manganite-PZT [1-3]. Bulk or layered composites are usually synthesized by conventional sintering of mixture of powders or laminated thick films. This study is concerned with the fabrication of novel ferromagnetic-ferroelectric bulk and thin film layered composites by hot pressing together with studies on the nature of magnetoelectric interactions. The objective is to obtain defect free samples with good interface coupling. Systems studied includes Ni-Zn, Co-Zn and Co-Ni ferrites that are predicted to show high piezomagnetic and magnetomechanical couplings and PZT. Samples were prepared using aluminum oxide or high temperature alloy dies. Sintering was done at 1300 K at a pressure of 5000-7000 psi. Measurements of transverse and longitudinal ME coefficients are performed at low frequencies (10 Hz-1kHz), and at electromechanical resonance (100-300 kHz). Important results of our studies are follows. (1) Hot-pressed samples show an order of magnitude improvement in ME voltage coefficient compared to samples processed by conventional sintering. The enhancement is attributed to an increase in density, sample resistivity, and interface coupling. (2) The longitudinal coupling is stronger than the transverse effect. (3) There is a significant increase in ME interactions at electromechanical resonance. (4) Samples with Ni-Zn ferrites show the highest ME coefficients. The results are analysed using our model for a bulk composite. - supported by a grant from the National Science Foundation (DMR-0322254) 1. G. Srinivasan, E. T. Rasmussen, J. Gallegos, Yu. I. Bokhan, and V. M. Laletin, Phys. Rev. B, 64, 214408 (2001). 2. G. Srinivasan, E. T. Rasmussen, B. J. Levin, and R. Hayes, Phys. Rev. B 65, 134402 (2002). 3

  9. Charge-transfer magnetoelectrics of polymeric multiferroics.

    PubMed

    Qin, Wei; Jasion, Daniel; Chen, Xiaomin; Wuttig, Manfred; Ren, Shenqiang

    2014-04-22

    The renaissance of multiferroics has yielded a deeper understanding of magneto-electric coupling of inorganic single-phase multiferroics and composites. Here, we report charge-transfer polymeric multiferroics, which exhibit external field-controlled magnetic, ferroelectric, and microwave response, as well as magneto-dielectric coupling. The charge-transfer-controlled ferroic properties result from the magnetic field-tunable triplet exciton which has been validated by the dynamic polaron-bipolaron transition model. In addition, the temperature-dependent dielectric discontinuity and electric-field-dependent polarization confirms room temperature ferroelectricity of crystalline charge-transfer polymeric multiferroics due to the triplet exciton, which allows the tunability of polarization by the photoexcitation. PMID:24654686

  10. Abnormal cross-frequency coupling in the tinnitus network

    PubMed Central

    Adamchic, Ilya; Langguth, Berthold; Hauptmann, Christian; Tass, Peter A.

    2014-01-01

    Neuroimaging studies have identified networks of brain areas and oscillations associated with tinnitus perception. However, how these regions relate to perceptual characteristics of tinnitus, and how oscillations in various frequency bands are associated with communications within the tinnitus network is still incompletely understood. Recent evidence suggests that apart from changes of the tinnitus severity the changes of tinnitus dominant pitch also have modulating effect on the underlying neuronal activity in a number of brain areas within the tinnitus network. Therefore, in a re-analysis of an existing dataset, we sought to determine how the oscillations in the tinnitus network in the various frequency bands interact. We also investigate how changes of tinnitus loudness, annoyance and pitch affect cross-frequency interaction both within and between nodes of the tinnitus network. Results of this study provide, to our knowledge, the first evidence that in tinnitus patients, aside from the previously described changes of oscillatory activity, there are also changes of cross-frequency coupling (CFC); phase-amplitude CFC was increased in tinnitus patients within the auditory cortex and the dorsolateral prefrontal regions between the phase of delta-theta and the amplitude of gamma oscillations (Modulation Index [MI] 0.17 in tinnitus patients vs. 0.08 in tinnitus free controls). Moreover, theta phase in the anterior cingulate region modulated gamma in the auditory (MI 0.1) and dorsolateral prefrontal regions (MI 0.19). Reduction of tinnitus severity after acoustic coordinated reset therapy led to a partial normalization of abnormal CFC. Also treatment induced changes in tinnitus pitch significantly modulated changes in CFC. Thus, tinnitus perception is associated with a more pronounced CFC within and between nodes of the tinnitus network. CFC can coordinate tinnitus-relevant activity in the tinnitus network providing a mechanism for effective communication between

  11. 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

  12. Laminated magneto-electric structures for tunable contactless magnetic sensing and energy harvesting

    NASA Astrophysics Data System (ADS)

    Finkel, Peter

    2010-03-01

    Multiferroic materials attracted increasingly high attention due to their potential in various multifunction sensing, filtering and energy transduction applications. In this work we investigated the magnetoelectric laminated multiferroic structure exhibiting a strong magneto-electric (ME) effect. We report here the magnetetoelctric coupling properties of the magnetoelastic/piezoelectric laminated FeNi42%/ polyvinylidene fluoride (PVDF) clamped composite structure as a function of stress and magnetic field. The magnetically and elastically tunable, flexural resonant mode was probed using Doppler laser spectroscopy. Most commercially available methods of magnetic sensing involve electrical current or voltage measurements requiring electrical wiring or similar contact connections to measure an electric signal correlated with a magnetic field; and therefore are not immune to EMI and shot-noise. Our solution could overcome this shortcoming is to implement a completely remote contactless, i.e. optical, measurement approach. Here we demonstrate that this bimorph structure can be used for low-frequency contactless detection of magnetic field fluctuation and magnetic field monitoring for non-contact resonant optical magnetic field sensing and energy harvesting.

  13. 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.

  14. Ferroelastic switching for nanoscale non-volatile magnetoelectric devices

    SciTech Connect

    Baek, S. H.; Jang, H. W.; Folkman, C. M.; Li, Yulan; Winchester, B.; Zhang, J. X.; He, Q.; Chu, Y. H.; Nelson, C. T.; Rzchowski, M. S.; Pan, X. Q.; Ramesh, R.; Chen , L.Q.; Eom, C.B.

    2010-04-01

    Multiferroics, where (anti-) ferromagnetic, ferroelectric, and ferroelastic order parameters coexist [1-5], enables manipulation of magnetic ordering by electric field through switching of the electric polarization [6-9]. It has been shown that realization of magnetoelectric coupling in single-phase multiferroic such as BiFeO3 requires ferroelastic (71o, 109o) rather than ferroelectric (180o) domain switching [6]. However, the control of such ferroleastic switching in a singlephase system has been a significant challenge as elastic interactions tend to destabilize small switched volumes, resulting in subsequent ferroelastic backswitching at zero electric field, thus disappearance of nonvolatile information storage [10, 11]. Guided by our phase-field simulations, we here report an approach to stabilize ferroelastic switching by eliminating the stress-induced instability responsible for back-switching using isolated monodomain BiFeO3islands. This work demonstrates a critical step to control and utilize nonvolatile magnetoelectric coupling at the nanoscale. Beyond magnetoelectric coupling, it provides a framework for exploring a route to control multiple order parameters coupled to ferroelastic order in other low-symmetry materials.

  15. The electrical asymmetry effect in multi-frequency capacitively coupled radio frequency discharges

    NASA Astrophysics Data System (ADS)

    Schulze, J.; Schüngel, E.; Donkó, Z.; Czarnetzki, U.

    2011-02-01

    The electrical asymmetry effect (EAE) in geometrically symmetric capacitively coupled radio frequency discharges operated at multiple consecutive harmonics is investigated by a particle-in-cell (PIC) simulation and an analytical model. The model is based on the original EAE model, which is extended by taking into account the floating potentials, the voltage drop across the plasma bulk, and the symmetry parameter resulting from the PIC simulation. Compared with electrically asymmetric dual-frequency discharges we find that (i) a significantly stronger dc self-bias can be generated electrically and that (ii) the mean ion energies at the electrodes can be controlled separately from the ion flux over a broader range by tuning the phase shifts between the individual voltage harmonics. A recipe for the optimization of the applied voltage waveform to generate the strongest possible dc self-bias electrically and to obtain maximum control of the ion energy via the EAE is presented.

  16. Charge dynamics in capacitively coupled radio frequency discharges

    NASA Astrophysics Data System (ADS)

    Schulze, J.; Schüngel, E.; Donkó, Z.; Czarnetzki, U.

    2010-06-01

    In a capacitively coupled radio frequency (CCRF) discharge the number of positive and negative charges lost to each electrode must balance within one RF period to ensure a constant total uncompensated charge in the discharge, Qtot, on time average. This balance is the result of a compensation of electron and ion fluxes at each electrode within one RF period. Although Qtot is constant on temporal average, it is time dependent on time scales shorter than one RF period, since it results from a balance of the typically constant ion flux and the strongly time dependent electron flux at each electrode. Nevertheless, Qtot is assumed to be constant in various models. Here the dynamics of Qtot is investigated in a geometrically symmetric CCRF discharge operated in argon at 13.56 and 27.12 MHz with variable phase shift θ between the driving voltages by a PIC simulation and an analytical model. Via the electrical asymmetry effect (EAE) a variable dc self-bias is generated as a function of θ. It is found that Qtot is not temporally constant within the low frequency period, but fluctuates by about 10% around its time average value. This modulation is understood by an analytical model. It is demonstrated that this charge dynamics leads to a phase shift of the dc self-bias not captured by models neglecting the charge dynamics. This dynamics is not restricted to dual frequency discharges. It is a general phenomenon in all CCRF discharges and can generally be described by the model introduced here. Finally, Qtot is split into the uncompensated charges in each sheath. The sheath charge dynamics and the self-excitation of non-linear plasma series resonance oscillations of the RF current via the EAE at low pressures of a few pascals are discussed.

  17. Magnetoelectric domain control in multiferroic TbMnO3

    NASA Astrophysics Data System (ADS)

    Matsubara, Masakazu; Manz, Sebastian; Mochizuki, Masahito; Kubacka, Teresa; Iyama, Ayato; Aliouane, Nadir; Kimura, Tsuyoshi; Johnson, Steven L.; Meier, Dennis; Fiebig, Manfred

    2015-06-01

    The manipulation of domains by external fields in ferroic materials is of major interest for applications. In multiferroics with strongly coupled magnetic and electric order, however, the magnetoelectric coupling on the level of the domains is largely unexplored. We investigated the field-induced domain dynamics of TbMnO3 in the multiferroic ground state and across a first-order spin-flop transition. In spite of the discontinuous nature of this transition, the reorientation of the order parameters is deterministic and preserves the multiferroic domain pattern. Landau-Lifshitz-Gilbert simulations reveal that this behavior is intrinsic. Such magnetoelectric correlations in spin-driven ferroelectrics may lead to domain wall-based nanoelectronics devices.

  18. Multiferroics. Magnetoelectric domain control in multiferroic TbMnO₃.

    PubMed

    Matsubara, Masakazu; Manz, Sebastian; Mochizuki, Masahito; Kubacka, Teresa; Iyama, Ayato; Aliouane, Nadir; Kimura, Tsuyoshi; Johnson, Steven L; Meier, Dennis; Fiebig, Manfred

    2015-06-01

    The manipulation of domains by external fields in ferroic materials is of major interest for applications. In multiferroics with strongly coupled magnetic and electric order, however, the magnetoelectric coupling on the level of the domains is largely unexplored. We investigated the field-induced domain dynamics of TbMnO3 in the multiferroic ground state and across a first-order spin-flop transition. In spite of the discontinuous nature of this transition, the reorientation of the order parameters is deterministic and preserves the multiferroic domain pattern. Landau-Lifshitz-Gilbert simulations reveal that this behavior is intrinsic. Such magnetoelectric correlations in spin-driven ferroelectrics may lead to domain wall-based nanoelectronics devices. PMID:26045431

  19. Highly sensitive tube-topology magnetoelectric magnetic sensors

    NASA Astrophysics Data System (ADS)

    Gillette, Scott Matthew

    Magnetoelectric (ME) composites have drawn increasing interest in recent years due to advancements in the technology resulting in enhanced ME coupling coefficients, stable room-temperature operation, sub-nanoTesla noise floor, low- and zero-biased operation, and fabrication of compact, miniaturized devices. Now, more than ever, practical use of ME devices in commercial magnetometry applications is feasible, while continued development of numerous other applications, such as voltage-tunable magnetic field generators, voltage-tunable inductors, and magnetically-tunable capacitors, bolster the overall usefulness of ME composites as a valuable technology. This dissertation focuses on development and characterization of tube-topology ME composites as magnetic field sensors. The novel topology is most notable for demonstrating high zero-external-bias sensitivity, low noise floor, low-frequency bandwidth, and self-powered, stable room temperature operation. Numerous characterization studies are included in this work where several devices are analyzed as a function of test-field, DC-bias field, geometry, material choice, and more. The overall conclusions drawn upon these results indicate strongly that the tube-topology ME magnetic field sensor holds promise to compete with existing hall-effect and flux-gate magnetometers. ME composites are at the tipping point of commercialization for use in magnetometry applications and are emerging as a valuable technology for use in numerous creative ways.

  20. 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.

  1. Enhancing magnetoelectric effect in multiferroic composite bilayers via flexoelectricity

    NASA Astrophysics Data System (ADS)

    Zhang, Chunli; Zhang, Lingli; Shen, Xudong; Chen, Weiqiu

    2016-04-01

    We employ the flexoelectricity to enhance the magnetoelectric (ME) (coupling) effect in multiferroic (MF) composites and structures. An analytical model is presented to predict the ME effect in a MF composite bilayer consisting of piezomagnetic and piezoelectric layers. The flexoelectric effect in the piezoelectric layer is taken into account. The static ME effect in the MF composite bilayer with free boundary conditions is investigated. The results indicate that flexoelectricity can dramatically enhance the ME effect in multiferroic composites and structures.

  2. 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.

  3. 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.

  4. 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.

  5. 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. PMID:25832285

  6. 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

  7. Micromagnetism and topological defects in magnetoelectric media

    NASA Astrophysics Data System (ADS)

    Pyatakov, A. P.; Sergeev, A. S.; Nikolaeva, E. P.; Kosykh, T. B.; Nikolaev, A. V.; Zvezdin, K. A.; Zvezdin, A. K.

    2015-10-01

    This paper briefly reviews research of the magnetoelectric materials and multiferroics as domain-structured media. The review is focused on magnetoelectric phenomena in epitaxial iron garnet films (electrically induced displacement and tilting of domain boundaries) as a striking example of magnetoelectricity in micromagnetism. The paper also considers the effect of an electric field on other topological defects in magnetically ordered media, including Bloch lines and Bloch points at domain boundaries, magnetic vortices, and skyrmions.

  8. 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.

  9. Modular networks with delayed coupling: Synchronization and frequency control

    NASA Astrophysics Data System (ADS)

    Maslennikov, Oleg V.; Nekorkin, Vladimir I.

    2014-07-01

    We study the collective dynamics of modular networks consisting of map-based neurons which generate irregular spike sequences. Three types of intramodule topology are considered: a random Erdös-Rényi network, a small-world Watts-Strogatz network, and a scale-free Barabási-Albert network. The interaction between the neurons of different modules is organized by relatively sparse connections with time delay. For all the types of the network topology considered, we found that with increasing delay two regimes of module synchronization alternate with each other: inphase and antiphase. At the same time, the average rate of collective oscillations decreases within each of the time-delay intervals corresponding to a particular synchronization regime. A dual role of the time delay is thus established: controlling a synchronization mode and degree and controlling an average network frequency. Furthermore, we investigate the influence on the modular synchronization by other parameters: the strength of intermodule coupling and the individual firing rate.

  10. 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.

  11. Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal-Organic Framework.

    PubMed

    Tian, Ying; Shen, Shipeng; Cong, Junzhuang; Yan, Liqin; Wang, Shouguo; Sun, Young

    2016-01-27

    A resonant quantum magnetoelectric coupling effect has been demonstrated in the multiferroic metal-organic framework of [(CH3)2NH2]Fe(HCOO)3. This material shows a coexistence of a spin-canted antiferromagnetic order and ferroelectricity as well as clear magnetoelectric coupling below TN ≈ 19 K. In addition, a component of single-ion quantum magnets develops below ∼ 8 K because of an intrinsic magnetic phase separation. The stair-shaped magnetic hysteresis loop at 2 K signals resonant quantum tunneling of magnetization. Meanwhile, the magnetic field dependence of dielectric permittivity exhibits sharp peaks just at the critical tunneling fields, evidencing the occurrence of resonant quantum magnetoelectric coupling effect. This resonant effect enables a simple electrical detection of quantum tunneling of magnetization. PMID:26743039

  12. 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.

  13. 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.

  14. 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.

  15. 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; University of Chinese Academy of Sciences, Beijing 100049

    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%.

  16. 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.

  17. Magnetoelectric Effects in hexagonal ferrite-PZT bilayers

    NASA Astrophysics Data System (ADS)

    Mathe, V. M.; Srinivasan, G.

    2008-03-01

    Magnetoelectric (ME) bilayers consisting of magnetostrictive and a piezoelectric layer are of interest for studies on the nature of ME interactions and useful technologies. Co2Z and Zn2Y are well known hexagonal ferrites with easy plane or uniaxial anisotropy. PZT has high piezoelectric coefficient. This study is on samples with Co2Z or Zn2Y as a magnetostrictive layer and PZT as a piezoelectric layer to form magnetoelectric bilayers. Low frequency (100 Hz) ME coefficient was measured over 0-17 kOe for various orientations of bilayers in a plane parallel to ac and bias magnetic fields. We measured a strong dependence of the ME voltage coefficients on magneitude and orientation of the bias field. The data are compared with theory. VLM gratefully acknowledge the award of a BOYSCAST fellowship and a FAST TRACK fellowship by DST, India. The research was supported by NSF grants.

  18. 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.

  19. High efficiency coupling of radio frequency beams from the dual frequency gyrotron with a corrugated waveguide transmission system.

    PubMed

    Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Mitsunaka, Yoshika; Sakamoto, Keishi

    2013-01-01

    High efficiency coupling of the millimeter-wave output of the dual-frequency gyrotron with the transmission line was demonstrated. The dual-frequency gyrotron was design to produce similar beam profiles for two operation frequencies (170 GHz and 137 GHz). Using two RF beam reflecting mirrors in a matching optics unit (MOU), which are designed to transform the beam profile of the gyrotron output to the fundamental waveguide mode (HE(11) mode) at 170 GHz, high efficiency coupling was demonstrated for two frequencies. The measured mode purity of HE(11) mode was 96% at 170 GHz and 94% at 137 GHz operations with the identical mirrors at the fixed mirror position and angle. The results indicate that the significantly simple dual frequency system is realized by the gyrotron designed to output the similar beam profiles at different frequency operation. PMID:23387644

  20. Magnetoelectric effect in piezoelectric/magnetostrictive multilayer (2-2) composites

    SciTech Connect

    Avellaneda, M.; Harshe, G.

    1994-07-01

    We consider the magnetoelectric effect arising in a multilayer composite consisting of bonded layers of a piezoelectric ceramic and a magnetostrictive material operating in the linear regime. Magnetoelectric coupling arises from the mechanical contacts between layers and the electric/mechanical and magnetic/mechanical coupling in each phase. Calculations of the magnetoelectric coefficient alpha * as well as of the figures of merit k(sub me) and k(sub me,cl) are presented. These calculations fully take into account the electric, magnetic and mechanical mismatch in the material properties, as well as the volume-fractions of both materials. We derive the optimal volume fraction f(sub 1)(sup crit) of piezoelectric material needed to maximize the figure of merit k(sub fme) or k(sub me,cl) for the composite and give criteria for optimizing the magnetoelectric effect in terms of the choice of the individual constituents. We computed the figures of merit of a variety of piezoelectric /magnetostrictive combinations. The combinations CoFe2O4/PZT5H (k(sub me) = 14%), Terfenol D/PZT5A (k(sub me) = 22%) and Terfenol D/PZT4 (k(sub me) = 30%) show reasonable energy transfer to be useful as magnetoelectric transducers. 11 refs.

  1. 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

  2. Linear magnetoelectricity at room temperature in perovskite superlattices by design

    NASA Astrophysics Data System (ADS)

    Ghosh, Saurabh; Das, Hena; Fennie, Craig J.

    2015-11-01

    Discovering materials that display a linear magnetoelectric (ME) effect at room temperature is a challenge. Such materials could facilitate devices based on the electric field control of magnetism. Here we present simple, chemically intuitive design rules to identify a class of bulk magnetoelectric materials based on the "bicolor" layering of P b n m ferrite perovskites, e.g., LaFeO3/LnFeO3 superlattices, Ln = lanthanide cation. We use first-principles density functional theory calculations to confirm these ideas. We elucidate the origin of this effect and show it is a general consequence of the layering of any bicolor P b n m perovskite superlattice in which the number of constituent layers are odd (leading to a form of hybrid improper ferroelectricity). Our calculations suggest that the ME effect in these superlattices is larger than that observed in the prototypical magnetoelectric materials Cr2O3 and BiFeO3. Furthermore, in these proposed materials, the strength of the linear ME coupling increases with the magnitude of the induced spontaneous polarization which is controlled by the La/Ln cation radius mismatch. We use a simple mean field model to show that the proposed materials order magnetically above room temperature.

  3. 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).

  4. Colossal magnetoelectric effect induced by parametric amplification

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Onuta, Tiberiu-Dan; Long, Christian J.; Geng, Yunlong; Takeuchi, Ichiro

    2015-11-01

    We describe the use of parametric amplification to substantially increase the magnetoelectric (ME) coefficient of multiferroic cantilevers. Parametric amplification has been widely used in sensors and actuators based on optical, electronic, and mechanical resonators to increase transducer gain. In our system, a microfabricated mechanical cantilever with a magnetostrictive layer is driven at its fundamental resonance frequency by an AC magnetic field. The resulting actuation of the cantilever at the resonance frequency is detected by measuring the voltage across a piezoelectric layer in the same cantilever. Concurrently, the spring constant of the cantilever is modulated at twice the resonance frequency by applying an AC voltage across the piezoelectric layer. The spring constant modulation results in parametric amplification of the motion of the cantilever, yielding a gain in the ME coefficient. Using this method, the ME coefficient was amplified from 33 V/(cm Oe) to 2.0 MV/(cm Oe), an increase of over 4 orders of magnitude. This boost in the ME coefficient directly resulted in an enhancement of the magnetic field sensitivity of the device from 6.0 nT /√{Hz } to 1.0 nT /√{Hz } . The enhancement in the ME coefficient and magnetic field sensitivity demonstrated here may be beneficial for a variety actuators and sensors based on resonant multiferroic devices.

  5. Origin of ferromagnetism and oxygen-vacancy ordering induced cross-controlled magnetoelectric effects at room temperature

    NASA Astrophysics Data System (ADS)

    Wei, X. K.; Zou, T.; Wang, F.; Zhang, Q. H.; Sun, Y.; Gu, L.; Hirata, A.; Chen, M. W.; Yao, Y.; Jin, C. Q.; Yu, R. C.

    2012-04-01

    In dilute magnetic oxide hexagonal Ba(Ti0.9Fe0.1)O2.81 bulk ceramic, we report on combined ferromagnetism and improper ferroelectricity as well as cross-controlled magnetoelectric effects at room temperature. The annular-bright-field (ABF) imaging technique in scanning transmission electron microscopy (STEM) demonstrates an oxygen vacancy ordering in the hexagonal closest-packed Ba1-O1 layers and severe distortion of the octahedra and pyramids. Strong dependencies of the susceptibility on temperature and magnetic field as well as the frequency dependence of magnetization under an ac electric field reveal that the intrinsic ferromagnetism of the highly insulating system dynamically evolves from a paramagnetic ground state, and dynamic exchanges of trapped electrons in the ordered polarons are attributed to the ferromagnetic interaction. Accordingly, aided by the motion of oxygen vacancies, responses of the trapped electrons to the ac magnetic field result in the reversal of magnetically induced voltages between high and low states. Our results not only expand our understanding on the magnetoelectric coupling mechanism, but also provide a grand opportunity toward designing novel multiferroic materials through introducing ordered point defects into a centrosymmetric matrix.

  6. 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

  7. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, X. Z.; Xiang, H. J.

    2014-09-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the "asymmetric multiferroic." In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  8. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, Xuezeng; Xiang, Hongjun; Rondinelli, James; Materials Theory; Design Group Team

    2015-03-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the ``asymmetric multiferroic.'' In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Resonance Assisted Synchronization of Coupled Oscillators: Frequency Locking without Phase Locking

    NASA Astrophysics Data System (ADS)

    Thévenin, J.; Romanelli, M.; Vallet, M.; Brunel, M.; Erneux, T.

    2011-09-01

    Frequency locking without phase locking of two coupled nonlinear oscillators is experimentally demonstrated. This synchronization regime is found for two coupled laser modes, beyond the phase-locking range fixed by Adler’s equation, because of a resonance mechanism. Specifically, we show that the amplitudes of the two modes exhibit strong fluctuations that produce average frequency synchronization, even if the instantaneous phases are unlocked. The experimental results are in good agreement with a theoretical model.

  15. Estimation of Electron Temperature and Frequency Components in a Dual Frequency Capacitively-Coupled Plasma Processing Reactor

    NASA Astrophysics Data System (ADS)

    Ito, Toru; Mo, Yun; Masahiro, Horigome

    2008-10-01

    The measurement of electron temperature in RF plasma sources with Langmuir probes is difficult because of the influence of rf noise. We attempted to estimate the electron temperature in a capacitively-coupled plasma processing reactor with a Surface Wave Probe [1] which employs microwaves. We also estimated the frequency spectrum with the sensitive PAP [1, 2]. We measured the harmonics which appeared in the bulk plasma for various experimental conditions in the dual-frequency [60 MHz and 2MHz] capacitively-coupled plasma processing reactor. We estimated RF power spectra for several experimental conditions like RF power [500-2000W], gas pressure [3-20Pa], and gas species [Ar, CF4]. The measurement results suggest the existence of energy transport among several frequency spectrum. [1ex] [1] K. Nakamura, M. Ohata, and H. Sugai: J. Vac. Sci. Technol. A 21, 325 (2003). [0pt] [2] T. Shirakawa and H. Sugai : Jpn. J. Appl. Phys. 32, 5129 (1993).

  16. 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.

  17. Theory of magnetoelectric effect for bending modes in magnetostrictive-piezoelectric bilayers

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Srinivasan, G.; Bichurin, M. I.; Galkina, T. A.

    2009-03-01

    In a magnetostrictive-piezoelectric bilayer the interaction between the magnetic and electric subsystems occurs through mechanical deformation. A model is discussed here for the resonance enhancement of such magnetoelectric (ME) interactions at frequencies corresponding to bending oscillations. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account so that the bending deformations could be considered in an applied magnetic or electric field. The frequency dependence for longitudinal and transverse ME voltage coefficients have obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to bilayers that are free to vibrate at both ends, or simply supported at both ends, or fixed at one end. It is shown that the bending resonance and consequent enhancement in ME coupling occurs at the lowest frequency for a bilayer that is fixed at one end and free at the other end. The model is applied to a specific case of permendur-lead zinconate titanate bilayer. The theory is in very good agreement with representative data.

  18. Examining Low Frequency Molecular Modulations from the High Frequency Vantage Point: Anharmonically-Coupled Low Frequency Modes in PCET Model Systems

    NASA Astrophysics Data System (ADS)

    Reynolds, Anthony

    Proton-coupled electron transfer model systems (PCET) are examined using polarization selective femtosecond infrared pump-probe spectroscopy to determine how the structural modes are coupled to the OH/OD stretching vibrational mode by monitoring low frequency oscillations in the OH/OD vibrational mode using pump-probe techniques. For all of the systems discussed in this dissertation, low frequency modes are anharmonically coupled to the OH/OD stretching vibration. The OH/OD stretching vibration discussed in this dissertation have complex and broad lineshapes in the infrared region (IR) that are difficult to decipher. A broadband IR (BBIR) source, when used as part of a third order nonlinear infrared pump-probe spectroscopy, gains access into the electronic ground state potential energy surface. This information reveals the molecular dynamics that give rise to the complex structure in an IR spectra. The BBIR used for these experiments is generated by focusing 800 nm/400 nm pulses into compressed air and is tunable from 2 -- 5 microns with a FWHM greater than 1200 wavenumbers. The BBIR is a crucial mid-IR source in subsequent chapters for examining the broad lineshapes of the OH/OD stretching mode, which often exceeds 200 wavenumbers. The coupling of low frequency structural modulations to hydrogen bonding dynamics in PCET systems is explored by using the OH/OD stretching vibration in CCl4 or CHCl3. Third order nonlinear ultrafast infrared pump-probe spectroscopy is used to gather information on the high frequency OH/OD stretching vibrational modes in the ground state such as vibrational relaxation time and anharmonic vibrational coupling to low frequency structural modulations. At least one anharmonically coupled low frequency mode between 120 and 250 wavenumbers has been observed in all systems. To better understand and visualize how the low frequency mode may contribute to the PCET chemistry, we calculated the fundamental frequencies and third order coupling

  19. A study and classification of non-linear high frequency ionospheric instabilities by coupled mode theory.

    NASA Technical Reports Server (NTRS)

    Harker, K. J.

    1972-01-01

    Two basic high-frequency ionospheric instabilities are discussed - i.e., the three-wave parametric interaction, and the oscillating two-stream instability. In the parametric instability, the ion-acoustic wave has a complex frequency, whereas in the oscillating two-stream instability the ion-acoustic frequency is purely imaginary. The parametric instability is shown to be the only one whose threshold depends on the ion collision frequency. A coupled-mode theory is proposed which permits study and classification of high-frequency instabilities on a unified basis.

  20. 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.

  1. Tunable features of magnetoelectric transformers.

    PubMed

    Dong, Shuxiang; Zhai, Junyi; Priya, Shashank; Li, Jie-Fang; Viehland, Dwight

    2009-06-01

    We have found that magnetostrictive FeBSiC alloy ribbons laminated with piezoelectric Pb(Zr,Ti)O(3) fiber can act as a tunable transformer when driven under resonant conditions. These composites were also found to exhibit the strongest resonant magnetoelectric voltage coefficient of 750 V/cm-Oe. The tunable features were achieved by applying small dc magnetic biases of -5

  2. 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.

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

    PubMed

    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. PMID:27078339

  4. 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.

  5. 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%.

  6. Prediction of a novel magnetoelectric switching mechanism in multiferroics.

    PubMed

    Yang, Yurong; Iñiguez, Jorge; Mao, Ai-Jie; Bellaiche, L

    2014-02-01

    We report a first-principles study of the recently predicted Pmc21 phase of the multiferroic BiFeO3 material, revealing a novel magnetoelectric effect that makes it possible to control magnetism with an electric field. The effect can be viewed as a two-step process: Switching the polarization first results in the change of the sense of the rotation of the oxygen octahedra, which in turn induces the switching of the secondary magnetic order parameter. The first step is governed by an original trilinear-coupling energy between polarization, octahedral tilting, and an antiferroelectric distortion. The second step is controlled by another trilinear coupling, this one involving the predominant and secondary magnetic orders as well as the oxygen octahedral tilting. In contrast with other trilinear-coupling effects in the literature, the present ones occur in a simple ABO3 perovskite and involve a large polarization. PMID:24580626

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

    SciTech Connect

    Rockway, J D; Champagne, N J; Sharpe, R M; Fasenfest, B

    2004-01-14

    Frequency domain techniques are popular for analyzing electromagnetics (EM) and coupled circuit-EM problems. These techniques, such as the method of moments (MoM) and the finite element method (FEM), are used to determine the response of the EM portion of the problem at a single frequency. Since only one frequency is solved at a time, it may take a long time to calculate the parameters for wideband devices. In this paper, a fast frequency sweep based on the Asymptotic Wave Expansion (AWE) method is developed and applied to generalized mixed circuit-EM problems. The AWE method, which was originally developed for lumped-load circuit simulations, has recently been shown to be effective at quasi-static and low frequency full-wave simulations. Here it is applied to a full-wave MoM solver, capable of solving for metals, dielectrics, and coupled circuit-EM problems.

  8. 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.

  9. Nonlinear magnetoelectric response of planar ferromagnetic-piezoelectric structures to sub-millisecond magnetic pulses.

    PubMed

    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

  10. 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