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Sample records for multiferroic orthorhombic dymno3

  1. Large rotating magnetocaloric effect in the orthorhombic DyMnO3 single crystal

    NASA Astrophysics Data System (ADS)

    Balli, M.; Mansouri, S.; Jandl, S.; Fournier, P.; Dimitrov, D. Z.

    2016-07-01

    A large magnetocaloric effect can be obtained around TN, Dy ̴8 K simply by spinning the orthorhombic DyMnO3 single crystal within the cb-plane in a constant magnetic field, instead of the standard magnetization-demagnetization process. Under 7 T, the maximum rotating entropy change (-ΔSR, cb) and the associated adiabatic temperature change (ΔTad, cb) are 16.3 J/kg K and 11 K, respectively. The corresponding refrigerant capacity is 440 J/kg, with no thermal and field hysteresis losses. Our findings show that the orthorhombic DyMnO3 could be used as a good refrigerant in more compact and efficient cryomagnetocaloric refrigerators.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  4. Writing and reading chiral domains in multiferroic DyMnO3 using soft X-rays

    NASA Astrophysics Data System (ADS)

    Schierle, E.; Soltwisch, V.; Schmitz, D.; Feyerherm, R.; Maljuk, A.; Yokaichiya, F.; Argyriou, D. N.; Weschke, E.

    2010-03-01

    The structure and dynamics of domains and domain walls are at the heart of any device that utilizes the properties of a ferroic material. Multiferroics, materials that exhibit a strong coupling between ferroelectric and magnetic order, offer the possibility of rich and complex domain arrangement that can be exploited for spintronics and magneto-electric devices. However, due to the complex magnetic order that is found in multiferroics, imaging of domains of a composite ferroic nature is challenging. We report on soft X-ray studies of the multiferroic material DyMnO3, where regions of opposite ferroelectric polarization correspond to magnetic domains of opposite chirality due to the spin-driven nature of ferroelectricity. With local charging induced by the X-ray beam via the photoelectric effect we are able to imprint a pattern of chiral magnetic domains on the surface of a single crystal. We utilize the circular dichroism in magnetic X-ray diffraction caused by the cycloidal magnetic ordering of the Dy-4f moments to read out the chiral domains, taking further advantage of the large enhancement at the Dy-M5 resonance. The method we describe here suggests a novel approach to control and image domains and domain walls in multiferroic materials.

  5. Prominent role of oxygen in the multiferroicity of DyMnO3 and TbMnO3: A resonant soft x-ray scattering spectroscopy study

    NASA Astrophysics Data System (ADS)

    Huang, S. W.; Lee, J. M.; Jeng, Horng-Tay; Shao, YuCheng; Wray, L. Andrew; Chen, J. M.; Qiao, R.; Yang, W. L.; Cao, Y.; Lin, J.-Y.; Schoenlein, R. W.; Chuang, Y.-D.

    2016-07-01

    Oxygen is known to play an important role in the multiferroicity of rare earth manganites; however, how this role changes with rare earth elements is still not fully understood. To address this question, we have used resonant soft x-ray scattering spectroscopy to study the F -type (0 ,τ ,0 ) diffraction peak from the antiferromagnetic order in DyMnO3 and TbMnO3. We focus on the measurements at O K edge of these two manganites, supplemented by the results at Mn L2 and Dy M5 edge of DyMnO3. We show that the electronic states of different elements are coupled more strongly in DyMnO3 than in TbMnO3, presumably due to the stronger lattice distortion and the tendency to develop E-type antiferromagnetism in the ferroelectric state that promote the orbital hybridization. We also show that the anomaly in the correlation length of (0 ,τ ,0 ) peak in DyMnO3 signifies the exchange interaction between Mn and rare earth spins. Our findings reveal the prominent role of oxygen orbitals in the multiferroicity of rare earth manganites and the distinct energetics between them.

  6. The prominent role of oxygen in the multiferroicity of DyMnO3 and TbMnO3: a resonant soft x-ray scattering spectroscopy study

    DOE PAGES

    S. W. Huang; Lee, J. M.; Jeng, H. -T.; Shao, Y.; Wray, L. A.; Chen, J. M.; Qiao, R.; Yang, W. L.; Cao, Y.; Lin, J. -Y.; et al

    2016-07-21

    Oxygen is known to play an important role in the multiferroicity of rare earth manganites; however, how this role changes with rare earth elements is still not fully understood. To address this question, we have used resonant soft x-ray scattering spectroscopy to study the F-type (0; ; 0) diffraction peak from the antiferromagnetic order in DyMnO3 and TbMnO3. We focus on the measurements at O K-edge of these two manganites, supplemented by the results at Mn L2- and Dy M5-edge of DyMnO3. We show that the electronic states of di erent elements are coupled more strongly in DyMnO3 than inmore » TbMnO3, presumably due to the stronger lattice distortion and the tendency to develop E-type antiferromagnetism in the ferroelectric state that promote the orbital hybridization. We also show that the anomaly in the correlation length of (0; ; 0) peak in DyMnO3 signifies the exchange interaction between Mn and rare earth spins, which is absent in TbMnO3. Our findings reveal the prominent role of oxygen orbitals in the multiferroicity of rare earth manganites and the distinct energetics between them.« less

  7. Static and dynamic magnetic properties and interplay of Dy3+, Gd3+ and Mn3+ spins in orthorhombic DyMnO3 and GdMnO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Das, Raja; Jaiswal, Adhish; Poddar, Pankaj

    2013-01-01

    Single-phase orthorhombic DyMnO3 and GdMnO3 nanoparticles in the size range 60-70 and 35-45 nm, respectively, were synthesized using a modified hydrothermal method. The magnetic property measurements of DyMnO3 nanocrystals show anomalies around ˜43 K (antiferromagnetic (AFM) coupling between Mn3+ spins) and at 7 K in the form of a peak in the zero-field-cooled curve (AFM coupling between Dy3+ spins). Whereas, GdMnO3 undergoes a phase transition at ˜42 K from paramagnetic to an incommensurate-antiferromagnetic phase (ICAFM) followed by a second anomaly at ˜22 K, which could be associated with the transition from ICAFM into a canted A-type AFM ordering of the Mn3+ spins. This transition is followed by a long-range ordering of the Gd3+ moments at 6 K yielding the canting of the Gd3+ spins with a ferromagnetic (FM) component antiparallel to the FM moment of the canted Mn3+ spins. No anomaly near the Néel temperature of the Mn moments for both DyMnO3 and GdMnO3 nanoparticles was observed in ac magnetization which were observed in dc magnetization. The room temperature Raman spectra of DyMnO3 shows two most intense Raman modes at 480 and 609 cm-1 which can be assigned to an antisymmetric Jahn-Teller stretching mode and a symmetric or breathing stretching mode, respectively, involving Mn-O bond stretching.

  8. Implementing Room-Temperature Multiferroism by Exploiting Hexagonal-Orthorhombic Morphotropic Phase Coexistence in LuFeO3 Thin Films.

    PubMed

    Song, Seungwoo; Han, Hyeon; Jang, Hyun Myung; Kim, Young Tae; Lee, Nam-Suk; Park, Chan Gyung; Kim, Jeong Rae; Noh, Tae Won; Scott, James F

    2016-09-01

    Room-temperature multiferroism in LuFeO3 (LFO) films is demonstrated by exploiting the orthorhombic-hexagonal (o-h) morphotrophic phase coexistence. The LFO film further reveals a magnetoelectric coupling effect that is not shown in single-phase (h- or o-) LFO. The observed multiferroism is attributed to the combination of sufficient polarization from h-LFO and net magnetization from o-LFO.

  9. PREFACE: Multiferroics Multiferroics

    NASA Astrophysics Data System (ADS)

    Loidl, Alois; von Loehneysen, Hilbert; Kalvius, G. Michael

    2008-10-01

    This special issue deals with the simultaneous occurrence of at least two primary ferroic properties, namely of ferroelectricity, ferromagnetism, ferrotoroidicity or ferroelasticity in one single homogeneous phase. The question of how different ferroic states can coexist in a single-phase material is an important issue and is outlined in detail using symmetry arguments and Landau theory for continuous phase transitions, which shows that the spin structure alone can break spatial inversion symmetry leading to ferroelectric order. The main focus of this special issue lies on single-phase materials that are magnetic and ferroelectric. They promise control of electric properties by magnetic fields and the control of magnetic properties by electric fields. The magnetoelectric coupling will allow the design of materials with novel electronic properties and in selected cases bring them to application. Ferromagnetic ferroelectrics are scarce in nature. This is because the conventional mechanism for ferroelectricity, namely an off-centering of the cations, which can be achieved best in ions with empty d shells, contradicts the formation of magnetic order in materials with partly filled d shells [1, 2]. Ferroelectricity in specific cases is achieved via the stereochemical activity of lone pairs in magnetic oxides. But in these cases the coupling between ferroelectricty and magnetism is weak. There have been a number of studies on multiferroics, especially in the 1960s and 1970s, particularly in the former Soviet Union [3, 4], but these activities faded away, most probably due to the lack of materials with strong magnetoelectric coupling and high ordering temperature, although the enormous potential of multiferroics for technological important applications was recognized early on [5]. An intense revival and the return of multiferroicity to the forefront of condensed matter research has been triggered by the invention of a number of frustrated magnets, like manganite rare

  10. X-ray resonant magnetic scattering investigations of hexagonal multiferroics R-manganese oxide (R = dysprosium, holmium, erbium)

    NASA Astrophysics Data System (ADS)

    Nandi, Shibabrata

    This dissertation is concerned with the magnetic structure of hexagonal multiferroic compounds RMnO3 (R = Ho, Dy, Er) in both zero and applied electric field. Microscopic magnetic structures in zero field were studied using x-ray resonant magnetic scattering (XRMS). Magnetic structure in applied electric field was studied using bulk magnetization, x-ray resonant magnetic scattering (XRMS), and x-ray magnetic circular dichroism (XMCD). The magnetic structures of Ho, Dy, and Er members have been determined using high-quality single-crystal samples grown by optical floating zone technique. We have determined that the magnetic structure of Ho3+ in HoMnO 3 to be Gamma3 in the intermediate temperature magnetic phase ITP (between 40 K and 4.5 K). The magnetic Ho3+ moments are aligned along the c axis and, at 12 K, the ratio between the magnetic moments of the Ho(2a) and Ho(4b) Wyckoff site is ˜ -2. The moments at the Ho(2a) site are antiferromagnetically aligned to the moments at the Ho(4b) site in the a-b plane. We also conclude that there is a change of the magnetic structure of Ho3+ at 4.5 K. Below 4.5 K, the magnetic phase can be well described by the co-existence of the ITP (Gamma3) with a decreasing 'ordered moment' and a new magnetic phase LTP with magnetic representation Gamma1 with a rapidly increasing Ho (4b) moment for decreasing temperatures. We failed to observe resonant magnetic scattering from Mn K-edge due to the presence of non-magnetic anisotropic tensor scattering at the magnetic Bragg peaks. Therefore, existence of a c component of the Mn3+ moments, predicted by symmetry analysis, can not be tested. We have also determined the magnetic structures of Dy3+ and Er3+ moments in DyMnO3 and ErMnO3, respectively. Dy3+ moments order according to the magnetic representation Gamma3 in the intermediate temperature magnetic phase, ITP (between 68 K and 8 K). In the low temperature phase, LTP (below 8 K), XRMS together with magnetization measurements indicate that

  11. Topological multiferroics

    NASA Astrophysics Data System (ADS)

    Scarrozza, Marco; Maccioni, Maria Barbara; Lopez, Giorgia M.; Fiorentini, Vincenzo

    2015-10-01

    Based on first-principles calculations, we explore an unconventional type of multiferroicity obtained via magnetic doping of wide-gap layered-perovskite ferroelectrics of the family A?Ti?O?. Using the ? member La?Ti?O? as home base, we substitute 3d atoms for Ti. The highlights of our results are that (1) low-concentration substitution of Ti by V produces robust unidirectional ferromagnetic (FM) order, resulting in a small-gap proper multiferroic, which in addition has electrically switchable magnetization, and (2) the isovalent substitution of Mn for Ti produces multiferroicity with weak FM order due to canting of antiferromagnetic Mn spins, and larger-than-usual linear magnetoelectric coupling.

  12. The evolution of multiferroics

    NASA Astrophysics Data System (ADS)

    Fiebig, Manfred; Lottermoser, Thomas; Meier, Dennis; Trassin, Morgan

    2016-08-01

    Materials with a coexistence of magnetic and ferroelectric order — multiferroics — provide an efficient route for the control of magnetism by electric fields. The study of multiferroics dates back to the 1950s, but in recent years, key discoveries in theory, synthesis and characterization techniques have led to a new surge of interest in these materials. Different mechanisms, such as lone-pair, geometric, charge-ordering and spin-driven effects, can support multiferroicity. The general focus of the field is now shifting into neighbouring research areas, as we discuss in this Review. Multiferroic thin-film heterostructures, device architectures, and domain and interface effects are explored. The violation of spatial and inversion symmetry in multiferroic materials is a key feature because it determines their properties. Other aspects, such as the non-equilibrium dynamics of multiferroics, are underrated and should be included in the topics that will define the future of the field.

  13. Structural morphology of orthorhombic sulphur

    NASA Astrophysics Data System (ADS)

    Hartman, P.

    1984-10-01

    Using an interatomic potential function specific surface energies, attachment energies and slice energies have been calculated for 7 F faces and 18 S faces of orthorhombic sulphur. These energies are compared with statistical parameters ( P values) for the frequency of occurrence of these faces on natural sulphur. It is found that P values are not correlated with the specific surface energies, except for the most important F faces. There is a positive correlation ( r=0.881) with the surface energy per mol although this quantity has no physical meaning. It is supposed that an S face is due to alternating periods of dissolution (or evaporation) and growth, so that it occurs as a narrow face on the site of a previous edge. An excellent correlation ( r=0.951) is found between the P value of an S face and a quantity P 1 P 2ξ h, where P 1 and P 2 are the P values of neighbouring faces that constitute the S face, ξ is proportional to the slice energy and h a distance determined by the interfacial angles of the three faces. This process should hold for the morphological development of any mineral, provided that no face-specific adsorption of cosolutes occurs.

  14. Dissipationless Multiferroic Magnonics

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Sigrist, Manfred

    2015-04-01

    We propose that the magnetoelectric effect in multiferroic insulators with a coplanar antiferromagnetic spiral order, such as BiFeO3 , enables electrically controlled magnonics without the need of a magnetic field. Applying an oscillating electric field in these materials with a frequency as low as household frequency can activate Goldstone modes that manifest fast planar rotations of spin, whose motion is essentially unaffected by crystalline anisotropy. Combining with spin ejection mechanisms, such a fast planar rotation can deliver electricity at room temperature over a distance of the magnetic domain, which is free from energy loss due to Gilbert damping in an impurity-free sample.

  15. Multiferroic rhodium clusters.

    PubMed

    Ma, Lei; Moro, Ramiro; Bowlan, John; de Heer, Walt A; Kirilyuk, Andrei

    2014-10-10

    Simultaneous magnetic and electric deflection measurements of rhodium clusters (Rh(N), 6 ≤ N ≤ 40) reveal ferromagnetism and ferroelectricity at low temperatures, while neither property exists in the bulk metal. Temperature-independent magnetic moments (up to 1 μ(B) per atom) are observed, and superparamagnetic blocking temperatures up to 20 K. Ferroelectric dipole moments on the order of 1D with transition temperatures up to 30 K are observed. Ferromagnetism and ferroelectricity coexist in rhodium clusters in the measured size range, with size-dependent variations in the transition temperatures that tend to be anticorrelated in the range n = 6-25. Both effects diminish with size and essentially vanish at N = 40. The ferroelectric properties suggest a Jahn-Teller ground state. These experiments represent the first example of multiferroic behavior in pure metal clusters. PMID:25375737

  16. Engineering multiferroism in CaMnO3.

    PubMed

    Bhattacharjee, Satadeep; Bousquet, Eric; Ghosez, Philippe

    2009-03-20

    Structural instabilities of CaMnO3 are investigated from first principles. We point out that, on top of a strong antiferrodistortive instability responsible for its orthorhombic ground state, the cubic perovskite structure of CaMnO3 also exhibits a weak ferroelectric instability. Although ferroelectricity is suppressed by antiferrodistortive motions, we show that it can be favored using strain or chemical engineering in order to make CaMnO3 multiferroic. We finally highlight that the ferroelectric instability of CaMnO3 is Mn-dominated. This illustrates that, contrary to common belief, ferroelectricity and magnetism are not necessarily exclusive but can be driven by the same cation.

  17. Neutron scattering studies of multiferroics

    NASA Astrophysics Data System (ADS)

    Cabrera, Ivelisse M.

    Magnetoelectric multiferroics are systems that exhibit magnetic and ferroelectric order. In strongly coupled multiferroics, competing magnetic interactions can break spatial inversion symmetry and yield ferroelectricity through a magnetic phase transition. In this dissertation, I present original work on the multiferroic properties of Ni3V2O8 and critical phenomena in TbMnO3 and RbFe(MoO4)2. Ni3V2O8 is an insulating magnet where Ni-spins order in a longitudinal amplitude modulated pattern along the a axis in the high-temperature incommensurate (HTI) phase. Upon cooling to the low-temperature incommensurate phase, an additional spine site spin component along b results in a cycloidal structure that breaks spatial inversion symmetry, yielding ferroelectricity. Electric control of multiferroic domains is demonstrated quantitatively and qualitatively using polarized magnetic neutron diffraction. We show that magnetic and ferroelectric domains are strongly coupled in this system and that definite cycloid handedness is achieved by antisymmetric Dzyaloshinskii-Moriya interactions. Ni3 V2O8 displays a memory effect where the system reverts to the previous polarization state upon exiting and re-entering the multiferroic phase through a first order phase transition. Our results suggest that small multiferroic domains in the paraelectric, commensurate phase retain the polarization history and reestablish it upon re-entering the multiferroic phase. TbMnO3 is a frustrated magnet similar to Ni3V 2O8 which undergoes two magnetic phase transitions before becoming multiferroic. A temperature-dependent magnetic diffraction study near TN reveals that this system orders through a continuous phase transition. Further studies in the HTI phase are needed to clarify whether a novel, weak transition exists at around 39 K. Our results support the single irreducible representation model as the system enters the HTI phase. RbFe(MoO4)2 is a nearly 2D antiferromagnet that enters the

  18. Engineering charge ordering into multiferroicity

    NASA Astrophysics Data System (ADS)

    He, Xu; Jin, Kui-juan

    2016-04-01

    Multiferroic materials have attracted great interest but are rare in nature. In many transition-metal oxides, charge ordering and magnetic ordering coexist, so that a method of engineering charge-ordered materials into ferroelectric materials would lead to a large class of multiferroic materials. We propose a strategy for designing new ferroelectric or even multiferroic materials by inserting a spacing layer into each two layers of charge-ordered materials and artificially making a superlattice. One example of the model demonstrated here is the perovskite (LaFeO3)2/LaTiO3 (111) superlattice, in which the LaTiO3 layer acts as the donor and the spacing layer, and the LaFeO3 layer is half doped and performs charge ordering. The collaboration of the charge ordering and the spacing layer breaks the space inversion symmetry, resulting in a large ferroelectric polarization. As the charge ordering also leads to a ferrimagnetic structure, (LaFeO3)2/LaTiO3 is multiferroic. It is expected that this work can encourage the designing and experimental implementation of a large class of multiferroic structures with novel properties.

  19. Investigations on Flexible Multiferroic Composites

    NASA Astrophysics Data System (ADS)

    Roy, Subhasis; Biswas, Bulbul; Majumder, S. B.

    2008-10-01

    Multiferroic ceramics are one of the most attractive materials for the next generation computer memories, smart sensors, and high frequency microelectronic devices. As compared to single phase multiferroic, piezoelectric-magnetostrictive composite materials exhibit larger magnetoelectric coefficients and therefore better suited for practical applications. In the present paper, we have provided a brief introduction on the multiferroic electro-ceramics followed by the outline of recent research trends on these materials. The potentials of flexible polymer-magnetostrictive composite materials, synthesized by economic chemical based processing routes, has been outlined. To make flexible multiferroic composites, cobalt iron oxide (CoFe2O4) (CFO) spinel powders were synthesized by a polymer assisted decomposition route. The cation mixing in as prepared as well as calcined CFO powders were investigated by XRD Rietveld refinement. Guided by the structural refinement results the processing conditions of the powder synthesis were optimized to yield spinal CFO powder with improved magnetic properties. These powders were dispersed into ferroelectric polyvinyledene (PVDF) matrix and the polymer-spinal composite was cast using different weight fractions of the spinel component. The composites were characterized in terms of its structure and microstructure. Preliminary dielectric and magnetic properties of these CFO-polymer composites is reported.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  2. Multiferroic fluoride BaCoF4 Thin Films Grown Via Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Borisov, Pavel; Johnson, Trent; García-Castro, Camilo; Kc, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo; Lederman, David

    Multiferroic materials exhibit exciting physics related to the simultaneous presence of multiple long-range orders, in many cases consisting of antiferromagnetic (AF) and ferroelectric (FE) orderings. In order to provide a new, promising route for fluoride-based multiferroic material engineering, we grew multiferroic fluoride BaCoF4 in thin film form on Al2O3 (0001) substrates by molecular beam epitaxy. The films grow with the orthorhombic b-axis out-of-plane and with three in-plane structural twin domains along the polar c-axis directions. The FE ordering in thin films was verified by FE remanent hysteresis loops measurements at T = 14 K and by room temperature piezoresponse force microscopy (PFM). An AF behavior was found below Neel temperature TN ~ 80 K, which is in agreement with the bulk properties. At lower temperatures two additional magnetic phase transitions at 19 K and 41 K were found. First-principles calculations demonstrated that the growth strain applied to the bulk BaCoF4 indeed favors two canted spin orders, along the b- and a-axes, respectively, in addition to the main AF spin order along the c-axis. Supported by FAME (Contract 2013-MA-2382), WV Research Challenge Grant (HEPC.dsr.12.29), and DMREF-NSF 1434897.

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

    PubMed

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

    2016-01-01

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

  4. Functional domain walls in multiferroics

    NASA Astrophysics Data System (ADS)

    Meier, Dennis

    2015-11-01

    During the last decade a wide variety of novel and fascinating correlation phenomena has been discovered at domain walls in multiferroic bulk systems, ranging from unusual electronic conductance to inseparably entangled spin and charge degrees of freedom. The domain walls represent quasi-2D functional objects that can be induced, positioned, and erased on demand, bearing considerable technological potential for future nanoelectronics. Most of the challenges that remain to be solved before turning related device paradigms into reality, however, still fall in the field of fundamental condensed matter physics and materials science. In this topical review seminal experimental findings gained on electric and magnetic domain walls in multiferroic bulk materials are addressed. A special focus is put on the physical properties that emerge at so-called charged domain walls and the added functionality that arises from coexisting magnetic order. The research presented in this review highlights that we are just entering a whole new world of intriguing nanoscale physics that is yet to be explored in all its details. The goal is to draw attention to the persistent challenges and identify future key directions for the research on functional domain walls in multiferroics.

  5. Multiferroic oxide thin films and heterostructures

    NASA Astrophysics Data System (ADS)

    Lu, Chengliang; Hu, Weijin; Tian, Yufeng; Wu, Tom

    2015-06-01

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  6. Multiferroic oxide thin films and heterostructures

    SciTech Connect

    Lu, Chengliang E-mail: Tao.Wu@kaust.edu.sa; Hu, Weijin; Wu, Tom E-mail: Tao.Wu@kaust.edu.sa; Tian, Yufeng

    2015-06-15

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  7. Ferroelectricity and competing interactions in Ho-deficient non-stoichiometric orthorhombic HoMnO{sub 3}

    SciTech Connect

    Wang, J. X.; Yan, Z. B.; Xie, Y. L.; Zhou, X. H.; Liu, J.-M.

    2015-05-07

    We investigate the consequences of the Ho-deficient non-stoichiometry in orthorhombic HoMnO{sub 3} in terms of microscopic mechanisms for ferroelectricity modulation. It is suggested that the Ho-deficiency (then Mn excess) results in Ho-vacancies and then Mn occupation of the Ho-site with increasing non-stoichiometry. The Ho-deficiency enhances the Mn-Mn symmetric exchange striction by suppressing the independent Ho-Ho interaction, and thus benefits to the induced Ho spin ordering against the independent Ho spin ordering. The symmetric Ho-Mn exchange striction is thus enhanced by this induced Ho spin ordering, leading to remarkably enhanced ferroelectric polarization as observed. This work presents an alternative scheme to modulate the multiferroicity in rare-earth manganites of strong 4f-3d coupling.

  8. Room Temperature Multiferroicity of Charge Transfer Crystals.

    PubMed

    Qin, Wei; Chen, Xiaomin; Li, Huashan; Gong, Maogang; Yuan, Guoliang; Grossman, Jeffrey C; Wuttig, Manfred; Ren, Shenqiang

    2015-09-22

    Room temperature multiferroics has been a frontier research field by manipulating spin-driven ferroelectricity or charge-order-driven magnetism. Charge-transfer crystals based on electron donor and acceptor assembly, exhibiting simultaneous spin ordering, are drawing significant interests for the development of all-organic magnetoelectric multiferroics. Here, we report that a remarkable anisotropic magnetization and room temperature multiferroicity can be achieved through assembly of thiophene donor and fullerene acceptor. The crystal motif directs the dimensional and compositional control of charge-transfer networks that could switch magnetization under external stimuli, thereby opening up an attractive class of all-organic nanoferronics.

  9. Observation of Anomalous Phonons in Orthorhombic Rare-earth Manganites

    SciTech Connect

    P Gao; H Chen; T Tyson; Z Liu; J Bai; L Wang; Y Chio; S Cheong

    2011-12-31

    We observe the appearance of a phonon near the lock-in temperature in orthorhombic REMnO{sub 3} (RE denotes rare earth) (RE: Lu and Ho) and anomalous phonon hardening in orthorhombic LuMnO{sub 3}. The anomalous phonon occurs at the onset of spontaneous polarization. No such changes were found in incommensurate orthorhombic DyMnO{sub 3}. These observations directly reveal different electric polarization mechanisms in the E-type and incommensurate-type orthorhombic REMnO{sub 3}.

  10. Topological crystalline metal in orthorhombic perovskite iridates.

    PubMed

    Chen, Yige; Lu, Yuan-Ming; Kee, Hae-Young

    2015-03-16

    Since topological insulators were theoretically predicted and experimentally observed in semiconductors with strong spin-orbit coupling, increasing attention has been drawn to topological materials that host exotic surface states. These surface excitations are stable against perturbations since they are protected by global or spatial/lattice symmetries. Following the success in achieving various topological insulators, a tempting challenge now is to search for metallic materials with novel topological properties. Here we predict that orthorhombic perovskite iridates realize a new class of metals dubbed topological crystalline metals, which support zero-energy surface states protected by certain lattice symmetry. These surface states can be probed by photoemission and tunnelling experiments. Furthermore, we show that by applying magnetic fields, the topological crystalline metal can be driven into other topological metallic phases, with different topological properties and surface states.

  11. Conversion acoustic resonances in orthorhombic crystals

    NASA Astrophysics Data System (ADS)

    Lyubimov, V. N.; Bessonov, D. A.; Alshits, V. I.

    2016-05-01

    A classification of acoustic-beam reflection resonances in orthorhombic crystals under conditions where a proximity to conversion is implemented in the vicinity of total internal reflection is proposed. In this case, the energy from the incident pump beam falls almost entirely into a narrow intense reflected beam propagating at a small angle with respect to the surface. The crystal boundary is parallel to one of the elastic symmetry planes, and the excited beam propagates near one of axes 2 in this plane. Depending on the relations between the elastic moduli and the chosen propagation geometry, 18 types of resonances may occur, but no more than three in each crystal. The developed theory combines an approximate analytical description and accurate computer analysis. The relations between the elastic moduli providing minimum energy loss over the parasite reflected wave are determined. Some crystals with resonant excitation very close to conversion are revealed.

  12. Voltage control of magnetism in multiferroic heterostructures

    PubMed Central

    Liu, Ming; Sun, Nian X.

    2014-01-01

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories. PMID:24421373

  13. Voltage control of magnetism in multiferroic heterostructures.

    PubMed

    Liu, Ming; Sun, Nian X

    2014-02-28

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories.

  14. Niobia and tantala codoped orthorhombic zirconia ceramics

    SciTech Connect

    Hoeftberger, M.; Gritzner, G.

    1995-04-15

    During recent studies it was found that codoping of zirconia with niobia and tantala yielded very corrosion resistant, orthorhombic zirconia ceramics. The powders for those novel ceramics were made via the sol-gel technique by hydrolysis of the respective metal propoxides; a method which required dry-box techniques during the preparation of the alkoxides. In these studies the authors investigated the fabrication of precursor material from aqueous solutions. The preparation of aqueous solutions of salts of zirconium, niobium and tantalum is hampered by rapid hydrolysis. Premature hydrolysis of the chlorides and oxichlorides of niobium, tantalum and zirconium can be, however, prevented in aqueous solutions of oxalic acid. Thus the authors investigated the coprecipitation of hydroxides as precursors by reacting oxalic acid solutions of the respective cations with aqueous ammonia. In addition they studied the effects of calcination and of hydrothermal conversion of the hydroxides to oxides on the powder characteristics and on the mechanical properties of the niobia and tantala codoped zirconia ceramics.

  15. Multiferroicity in Perovskite Manganite Superlattice

    NASA Astrophysics Data System (ADS)

    Tao, Yong-Mei; Jiang, Xue-Fan; Liu, Jun-Ming

    2016-08-01

    Multiferroic properties of short period perovskite type manganite superlattice ((R1MnO3)n/(R2MnO3)n (n=1,2,3)) are considered within the framework of classical Heisenberg model using Monte Carlo simulation. Our result revealed the interesting behaviors in Mn spins structure in superlattice. Apart from simple plane spin cycloid structure which is shown in all manganites including bulk, film, and superlattice here in low temperature, a non-coplanar spiral spin structure is exhibited in a certain temperature range when n equals 1, 2 or 3. Specific heat, spin-helicity vector, spin correlation function, spin-helicity correlation function, and spin configuration are calculated to confirm this non-coplanar spiral spin structure. These results are associated with the competition among exchange interaction, magnetic anisotropy, and Dzyaloshinskii-Moriya interaction. Supported by the National Natural Science Foundation of China (NSFC) under Grant No. 11447136

  16. Novel multiferroicity in GdMnO3 thin films with self-assembled nano-twinned domains.

    PubMed

    Li, Xiang; Lu, Chengliang; Dai, Jiyan; Dong, Shuai; Chen, Yan; Hu, Ni; Wu, Guangheng; Liu, Meifeng; Yan, Zhibo; Liu, Jun-Ming

    2014-01-01

    There have been many interests in exploring multiferroic materials with superior ferroelectric and magnetic properties for the purpose of developing multifunctional devices. Fabrication of thin films plays an important role in achieving this purpose, since the multiferroicity can be tuned via strain, dimensionality, and size effect, without varying the chemical composition. Here, we report exotic multiferroic behaviors, including high-TC (~75 K) ferroelectric state, a large spontaneous polarization (~4900 μC/m(2)) and relatively strong ferromagnetism emerging at ~105 K, in orthorhombic GdMnO3/SrTiO3 (001) thin films with self-assembled nano-scale twin-like domains. We propose a possible ab-plane spiral-spin-order phase to be responsible for the large spontaneous polarization in the films, which can only be stabilized by relatively high magnetic field H > 6 T in the bulk crystals. It is suggested that the nano-scale twin-like domain structure is essential for the high temperature ferroelectricity and ferromagnetism of the thin films.

  17. Phase transformations in multiferroics Bi1- x Ca x Fe1- x Mn x O3

    NASA Astrophysics Data System (ADS)

    Troyanchuk, I. O.; Bushinsky, M. V.; Karpinsky, D. V.; Chobot, A. N.; Tereshko, N. V.; Franz, A.

    2016-09-01

    The crystal structure and the magnetic properties of multiferroics Bi1- x Ca x Fe1- x Mn x O3 ( x ≤ 0.22) have been studied. It has been found that the stoichiometric compositions undergo a crystal-structure transformation from the rhombohedral (space group R3 c) polar phase ( x ≤ 0.18) to the orthorhombic (space group Pnma) nonpolar phase ( x ≥ 0.20) via a two-phase structural state. The polar phase is antiferromagnetic at x < 0.10 and exhibits a metamagnetic behavior. The polar ( x ≥ 0.10) and nonpolar phases are weak ferromagnets at room temperature with a spontaneous magnetization close to 0.07 emu/g ( x = 0.18 and 0.22). A decrease in temperature leads to the transition to a state close to an antiferromagnetic one.

  18. Investigation of multiferroic behaviour of TbMnO{sub 3} nanoplates

    SciTech Connect

    Acharya, S.A. Khule, S.M.; Gaikwad, V.M.

    2015-07-15

    Highlights: • Hydrothermal synthesis of TbMnO{sub 3} nanoplate. • Morphology induced defects detected by Raman spectroscopy. • Magnetic and dielectric anomalies confirmed multiferroic behavior is retained in TbMnO{sub 3} nanoplates. - Abstract: In the present study, hydrothermally prepared TbMnO{sub 3} in plates-like morphology at nanoscale are investigated in multiferroic view point. X-ray diffraction study confirms the orthorhombic phase of as-synthesized TbMnO{sub 3}. Microstructural features studied by Scanning Electron Microscopy and Transmission Electron Microscopy show the plates-like morphology of as-synthesized TbMnO{sub 3} at nanoscale. Local distortions investigated by FT-Raman exhibits redshift in T mode by about 20 cm{sup −1} as compared to that of the single crystal. The redshift in T mode is mainly due to defect by tilting of octahedra and respective changes in bond angle of Mn–O(1)–Mn. This is assigned to the size-morphology induced defects. The temperature dependent zero-field-cooled and field-cooled magnetization are measured at H = 50 Oe and in the temperature range 2–300 K. The anomalies in magnetization are obtained at 8 and 42 K. Bifurcation of the ZFC and FC curves are observed very close to magnetic transition temperature 42 K. The 42 K anomaly is related to the sine wave ordering of Mn{sup 3+} moment; and 8 K anomaly is associated with magnetic ordering of the Tb{sup 3+}-sublattice propagation vector. The anomalies in the electric properties, ϵ′ (T), tan δ (T), which are noticed within the 28 K range, coincide with the temperature of incommensurate–commensurate (or lock-in) magnetic transition of TbMnO{sub 3.} This study confirms that multiferroic behavior is retained in TbMnO{sub 3} nanoplates.

  19. Multiferroic crossover in perovskite oxides

    NASA Astrophysics Data System (ADS)

    Weston, L.; Cui, X. Y.; Ringer, S. P.; Stampfl, C.

    2016-04-01

    The coexistence of ferroelectricity and magnetism in A B O3 perovskite oxides is rare, a phenomenon that has become known as the ferroelectric "d0 rule." Recently, the perovskite BiCoO3 has been shown experimentally to be isostructural with PbTiO3, while simultaneously the d6Co3 + ion has a high-spin ground state with C -type antiferromagnetic ordering. It has been suggested that the hybridization of Bi 6 s states with the O 2 p valence band stabilizes the polar phase, however, we have recently demonstrated that Co3 + ions in the perovskite structure can facilitate a ferroelectric distortion via the Co 3 d -O 2 p covalent interaction [L. Weston, et al., Phys. Rev. Lett. 114, 247601 (2015), 10.1103/PhysRevLett.114.247601]. In this paper, using accurate hybrid density functional calculations, we investigate the atomic, electronic, and magnetic structure of BiCoO3 to elucidate the origin of the multiferroic state. To begin with, we perform a more general first-principles investigation of the role of d electrons in affecting the tendency for perovskite materials to exhibit a ferroelectric distortion; this is achieved via a qualitative trend study in artificial cubic and tetragonal La B O3 perovskites. We choose La as the A cation so as to remove the effects of Bi 6 s hybridization. The lattice instability is identified by the softening of phonon modes in the cubic phase, as well as by the energy lowering associated with a ferroelectric distortion. For the La B O3 series, where B is a d0-d8 cation from the 3 d block, the trend study reveals that increasing the d orbital occupation initially removes the tendency for a polar distortion, as expected. However, for high-spin d5-d7 and d8 cations a strong ferroelectric instability is recovered. This effect is explained in terms of increased pseudo-Jahn-Teller (PJT) p -d vibronic coupling. The PJT effect is described by the competition between a stabilizing force (K0) that favors the cubic phase, and a vibronic term that

  20. Probing the evolution of antiferromagnetism in multiferroics

    SciTech Connect

    Holcomb, M.; Martin, L.; Scholl, A.; He, Q.; Yu, P.; Yang, C.-H.; Yang, S.; Glans, P.-A.; Valvidares, M.; Huijben, M.; Kortright, J.; Guo,, J.; Chu, Y.-H.; Ramesh, R.

    2010-06-09

    This study delineates the evolution of magnetic order in epitaxial films of the room-temperature multiferroic BiFeO3 system. Using angle- and temperature-dependent dichroic measurements and spectromicroscopy, we have observed that the antiferromagnetic order in the model multiferroic BiFeO3 evolves systematically as a function of thickness and strain. Lattice-mismatch-induced strain is found to break the easy-plane magnetic symmetry of the bulk and leads to an easy axis of magnetization which can be controlled through strain. Understanding the evolution of magnetic structure and how to manipulate the magnetism in this model multiferroic has significant implications for utilization of such magnetoelectric materials in future applications.

  1. Non-collinear magnetism in multiferroic perovskites.

    PubMed

    Bousquet, Eric; Cano, Andrés

    2016-03-31

    We present an overview of the current interest in non-collinear magnetism in multiferroic perovskite crystals. We first describe the different microscopic mechanisms giving rise to the non-collinearity of spins in this class of materials. We discuss, in particular, the interplay between non-collinear magnetism and ferroelectric and antiferrodistortive distortions of the perovskite structure, and how this can promote magnetoelectric responses. We then provide a literature survey on non-collinear multiferroic perovskites. We discuss numerous examples of spin cantings driving weak ferromagnetism in transition metal perovskites, and of spin-induced ferroelectricity as observed in the rare-earth based perovskites. These examples are chosen to best illustrate the fundamental role of non-collinear magnetism in the design of multiferroicity.

  2. Low energy consumption spintronics using multiferroic heterostructures.

    PubMed

    Trassin, Morgan

    2016-01-27

    We review the recent progress in the field of multiferroic magnetoelectric heterostructures. The lack of single phase multiferroic candidates exhibiting simultaneously strong and coupled magnetic and ferroelectric orders led to an increased effort into the development of artificial multiferroic heterostructures in which these orders are combined by assembling different materials. The magnetoelectric coupling emerging from the created interface between the ferroelectric and ferromagnetic layers can result in electrically tunable magnetic transition temperature, magnetic anisotropy or magnetization reversal. The full potential of low energy consumption magnetic based devices for spintronics lies in our understanding of the magnetoelectric coupling at the scale of the ferroic domains. Although the thin film synthesis progresses resulted into the complete control of ferroic domain ordering using epitaxial strain, the local observation of magnetoelectric coupling remains challenging. The ability to imprint ferroelectric domains into ferromagnets and to manipulate those solely using electric fields suggests new technological advances for spintronics such as magnetoelectric memories or memristors.

  3. Graphene-multiferroic interfaces for spintronics applications.

    PubMed

    Zanolli, Zeila

    2016-01-01

    Graphene and magnetoelectric multiferroics are promising materials for spintronic devices with high performance and low energy consumption. A very long spin diffusion length and high carrier mobility make graphene attractive for spintronics. The coupling between ferroelectricity and magnetism, which characterises magnetoelectrics, opens the way towards unique device architectures. In this work, we combine the features of both materials by investigating the interface between graphene and BaMnO3, a magnetoelectric multiferroic. We show that electron charge is transferred across the interface and magnetization is induced in the graphene sheet due to the strong interaction between C and Mn. Depending on the relative orientation of graphene and BaMnO3, a quasi-half-metal or a magnetic semiconductor can be obtained. A remarkably large proximity induced spin splitting of the Dirac cones (~300 meV) is achieved. We also show how doping with acceptors can make the high-mobility region of the electronic bands experimentally accessible. This suggests a series of possible applications in spintronics (e.g. spin filters, spin injectors) for hybrid organic-multiferroic materials and reveals hybrid organic-multiferroics as a new class of materials that may exhibit exotic phenomena such as the quantum anomalous Hall effect and a Rashba spin-orbit induced topological gap. PMID:27550389

  4. Graphene-multiferroic interfaces for spintronics applications

    PubMed Central

    Zanolli, Zeila

    2016-01-01

    Graphene and magnetoelectric multiferroics are promising materials for spintronic devices with high performance and low energy consumption. A very long spin diffusion length and high carrier mobility make graphene attractive for spintronics. The coupling between ferroelectricity and magnetism, which characterises magnetoelectrics, opens the way towards unique device architectures. In this work, we combine the features of both materials by investigating the interface between graphene and BaMnO3, a magnetoelectric multiferroic. We show that electron charge is transferred across the interface and magnetization is induced in the graphene sheet due to the strong interaction between C and Mn. Depending on the relative orientation of graphene and BaMnO3, a quasi-half-metal or a magnetic semiconductor can be obtained. A remarkably large proximity induced spin splitting of the Dirac cones (~300 meV) is achieved. We also show how doping with acceptors can make the high-mobility region of the electronic bands experimentally accessible. This suggests a series of possible applications in spintronics (e.g. spin filters, spin injectors) for hybrid organic-multiferroic materials and reveals hybrid organic-multiferroics as a new class of materials that may exhibit exotic phenomena such as the quantum anomalous Hall effect and a Rashba spin-orbit induced topological gap. PMID:27550389

  5. Graphene-multiferroic interfaces for spintronics applications.

    PubMed

    Zanolli, Zeila

    2016-08-23

    Graphene and magnetoelectric multiferroics are promising materials for spintronic devices with high performance and low energy consumption. A very long spin diffusion length and high carrier mobility make graphene attractive for spintronics. The coupling between ferroelectricity and magnetism, which characterises magnetoelectrics, opens the way towards unique device architectures. In this work, we combine the features of both materials by investigating the interface between graphene and BaMnO3, a magnetoelectric multiferroic. We show that electron charge is transferred across the interface and magnetization is induced in the graphene sheet due to the strong interaction between C and Mn. Depending on the relative orientation of graphene and BaMnO3, a quasi-half-metal or a magnetic semiconductor can be obtained. A remarkably large proximity induced spin splitting of the Dirac cones (~300 meV) is achieved. We also show how doping with acceptors can make the high-mobility region of the electronic bands experimentally accessible. This suggests a series of possible applications in spintronics (e.g. spin filters, spin injectors) for hybrid organic-multiferroic materials and reveals hybrid organic-multiferroics as a new class of materials that may exhibit exotic phenomena such as the quantum anomalous Hall effect and a Rashba spin-orbit induced topological gap.

  6. Graphene-multiferroic interfaces for spintronics applications

    NASA Astrophysics Data System (ADS)

    Zanolli, Zeila

    2016-08-01

    Graphene and magnetoelectric multiferroics are promising materials for spintronic devices with high performance and low energy consumption. A very long spin diffusion length and high carrier mobility make graphene attractive for spintronics. The coupling between ferroelectricity and magnetism, which characterises magnetoelectrics, opens the way towards unique device architectures. In this work, we combine the features of both materials by investigating the interface between graphene and BaMnO3, a magnetoelectric multiferroic. We show that electron charge is transferred across the interface and magnetization is induced in the graphene sheet due to the strong interaction between C and Mn. Depending on the relative orientation of graphene and BaMnO3, a quasi-half-metal or a magnetic semiconductor can be obtained. A remarkably large proximity induced spin splitting of the Dirac cones (~300 meV) is achieved. We also show how doping with acceptors can make the high-mobility region of the electronic bands experimentally accessible. This suggests a series of possible applications in spintronics (e.g. spin filters, spin injectors) for hybrid organic-multiferroic materials and reveals hybrid organic-multiferroics as a new class of materials that may exhibit exotic phenomena such as the quantum anomalous Hall effect and a Rashba spin-orbit induced topological gap.

  7. Structural, electrical and multiferroic properties of La-doped mullite Bi{sub 2}Fe{sub 4}O{sub 9} thin films

    SciTech Connect

    Raghavan, C.M.; Kim, J.W.; Kim, J.-W.; Kim, S.S.

    2015-10-15

    Highlights: • Chemical solution deposited La-doped Bi{sub 2}Fe{sub 4}O{sub 9} thin film. • Structural, electrical and multiferroic properties were investigated. • La-doped Bi{sub 2}Fe{sub 4}O{sub 9} exhibited enhanced electrical and multiferroic properties. - Abstract: Thin films of (Bi{sub 2−x}La{sub x})Fe{sub 4}O{sub 9} (x = 0 and x = 0.05) were prepared on Pt(1 1 1)/Ti/SiO{sub 2}/Si(1 0 0) substrates by using a chemical solution deposition method to investigate structural, microstructural, electrical and multiferroic properties. Both the thin films were crystallized in mullite type phases with orthorhombic structures containing no secondary and impurity phases, which was confirmed by X-ray diffraction and Raman spectroscopy studies. The (Bi{sub 1.95}La{sub 0.05})Fe{sub 4}O{sub 9} thin film exhibited improved electrical and multiferroic properties at room-temperature. The leakage current density of the (Bi{sub 1.95}La{sub 0.05})Fe{sub 4}O{sub 9} thin film was one order of magnitude lower than that of the Bi{sub 2}Fe{sub 4}O{sub 9} thin film. Furthermore, in the thin film form, (Bi{sub 2−x}La{sub x})Fe{sub 4}O{sub 9} exhibited better stability against electrical breakdowns and enhanced multiferroic properties.

  8. Sintering time effect on crystal structure and magnetic properties of Bi0.8La0.2FeO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Singh, Ompal; Agarwal, Ashish; Sanghi, Sujata; Singh, Jogender

    2016-05-01

    Effect of sintering time over the structure and magnetic properties has been studid in Bi0.8La0.2FeO3 multiferroic ceramics prepared by solid state reaction technique. The structure changes with the advent mixed phase rhombohedral and orthorhombic symmetry to immaculate orthorhombic structure with sintering time from 2 to 3 hour, as revealed by means of the simulation of XRD patterns via Rietveld analysis through FullProf software. The M - H plots depict decent enhancement in magnetization with values of remnant magnetization (Mr) from 0.01868emu/g to 0.09357emu/g while the sintering time is varied from 2 to 3 hour. The metamagnetic transition may be attributed to the crumpling of the modulated spin cycloid existing inherently in the pristine compound. The presented study may have considerable impact in commercial as well as advanced electronic applications.

  9. High pressure and Multiferroics materials. A happy marriage

    SciTech Connect

    Gilioli, Edmondo; Ehm, Lars

    2014-10-31

    We found that the community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. Moreover, the in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities.

  10. High pressure and multiferroics materials: a happy marriage.

    PubMed

    Gilioli, Edmondo; Ehm, Lars

    2014-11-01

    The community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. The in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities.

  11. High pressure and multiferroics materials: a happy marriage.

    PubMed

    Gilioli, Edmondo; Ehm, Lars

    2014-11-01

    The community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. The in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities. PMID:25485138

  12. First principles studies of multiferroic materials.

    PubMed

    Picozzi, Silvia; Ederer, Claude

    2009-07-29

    Multiferroics, materials where spontaneous long-range magnetic and dipolar orders coexist, represent an attractive class of compounds, which combine rich and fascinating fundamental physics with a technologically appealing potential for applications in the general area of spintronics. Ab initio calculations have significantly contributed to recent progress in this area, by elucidating different mechanisms for multiferroicity and providing essential information on various compounds where these effects are manifestly at play. In particular, here we present examples of density-functional theory investigations for two main classes of materials: (a) multiferroics where ferroelectricity is driven by hybridization or purely structural effects, with BiFeO(3) as the prototype material, and (b) multiferroics where ferroelectricity is driven by correlation effects and is strongly linked to electronic degrees of freedom such as spin-, charge-, or orbital-ordering, with rare-earth manganites as prototypes. As for the first class of multiferroics, first principles calculations are shown to provide an accurate qualitative and quantitative description of the physics in BiFeO(3), ranging from the prediction of large ferroelectric polarization and weak ferromagnetism, over the effect of epitaxial strain, to the identification of possible scenarios for coupling between ferroelectric and magnetic order. For the second class of multiferroics, ab initio calculations have shown that, in those cases where spin-ordering breaks inversion symmetry (e.g. in antiferromagnetic E-type HoMnO(3)), the magnetically induced ferroelectric polarization can be as large as a few µC cm(-2). The examples presented point the way to several possible avenues for future research: on the technological side, first principles simulations can contribute to a rational materials design, aimed at identifying spintronic materials that exhibit ferromagnetism and ferroelectricity at or above room temperature. On

  13. Nonlinear multiferroic phase shifters for microwave frequencies

    SciTech Connect

    Ustinov, Alexey B.; Kalinikos, Boris A.; Srinivasan, G.

    2014-02-03

    A nonlinear microwave phase shifter based on a planar multiferroic composite has been studied. The multiferroic structure is fabricated in the form of a bilayer consisting of yttrium iron garnet and barium strontium titanate. The principle of operation of the device is based on the linear and nonlinear control of the phase shift of the hybrid spin-electromagnetic waves propagating in the bilayer. The linear control is realized with magnetic and electric fields. The nonlinear control is provided by the input power of microwave signal. The device showed a nonlinear phase shift up to 250°, electric field induced phase shift up to 330°, and magnetic field induced phase shift of more than 180°.

  14. Nanoparticles induced multiferroicity in liquid crystal

    NASA Astrophysics Data System (ADS)

    Ganguly, Prasun; Kumar, Ajay; Muralidhar, K.; Biradar, A. M.

    2016-05-01

    Soft multiferroic character has been observed in a ferroelectric liquid crystal (FLC) dispersed with nickel nanoparticles (Ni NPs). A suitable amount of ferromagnetic Ni NPs has been added into FLC material, and the co-existence of ferroelectric and ferromagnetic ordering is examined using P-E and M-H hysteresis measurements. The magnitude of ferromagnetic order is found to depend strongly on the concentration of Ni NPs. Our theoretical approach indicated a strong dependence of helical pitch of FLC on the doping concentration of Ni NPs. We proposed that the intrinsic magnetic field of Ni NPs has been coupled with that of director field of the FLC molecules to result in the observed multiferroic behavior.

  15. Self-assembled Oniontype Multiferroic Nanostructures

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang; Briber, Robert M.; Wuttig, Manfred

    2009-03-01

    Spontaneously self-assembled oniontype multiferroic nanostructures based on block copolymers as templating materials are reported. Diblock copolymer containing two different magnetoelectric precursors separately segregated to the two microdomains have been shown to form well-ordered templated lamellar structures. Onion-type multilamellar ordered multiferroic (PZT/CoFe2O4) nanostructures have been induced by room temperature solvent annealing in a magnetic field oriented perpendicular to the plane of the film. The evolution of the onion-like microstructure has been characterized by AFM, MFM, and TEM. The structure retains lamellar periodicity observed at zero field. The onion structure is superparamagnetic above and antiferromagnetic below the blocking temperature. This templating process opens a route for nanometer-scale patterning of magnetic toroids by means of self-assembly on length scales that are difficult to obtain by standard lithography techniques.

  16. Phase transitions and domain structures in multiferroics

    NASA Astrophysics Data System (ADS)

    Vlahos, Eftihia

    2011-12-01

    Thin film ferroelectrics and multiferroics are two important classes of materials interesting both from a scientific and a technological prospective. The volatility of lead and bismuth as well as environmental issues regarding the toxicity of lead are two disadvantages of the most commonly used ferroelectric random access memory (FeRAM) materials such as Pb(Zr,Ti)O3 and SrBi2Ta2O9. Therefore lead-free thin film ferroelectrics are promising substitutes as long as (a) they can be grown on technologically important substrates such as silicon, and (b) their T c and Pr become comparable to that of well established ferroelectrics. On the other hand, the development of functional room temperature ferroelectric ferromagnetic multiferroics could lead to very interesting phenomena such as control of magnetism with electric fields and control of electrical polarization with magnetic fields. This thesis focuses on the understanding of material structure-property relations using nonlinear optical spectroscopy. Nonlinear spectroscopy is an excellent tool for probing the onset of ferroelectricity, and domain dynamics in strained ferroelectrics and multiferroics. Second harmonic generation was used to detect ferroelectricity and the antiferrodistortive phase transition in thin film SrTiO3. Incipient ferroelectric CaTiO3 has been shown to become ferroelectric when strained with a combination of SHG and dielectric measurements. The tensorial nature of the induced nonlinear polarization allows for probing of the BaTiO3 and SrTiO3 polarization contributions in nanoscale BaTiO3/SrTiO3 superlattices. In addition, nonlinear optics was used to demonstrate ferroelectricity in multiferroic EuTiO3. Finally, confocal SHG and Raman microscopy were utilized to visualize polar domains in incipient ferroelectric and ferroelastic CaTiO3.

  17. 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

  18. New design strategy for realizing multiferroic materials

    NASA Astrophysics Data System (ADS)

    Puggioni, Danilo; Giovannetti, Gianluca; Capone, Massimo; Rondinelli, James

    Ferroelectricity is a property that only insulating materials can exhibit. For this reason, nearly all searches for new multiferroic compounds, those simultaneously exhibiting ferroelectric and magnetic order, have focused on insulating magnetic oxides. Here, we propose a different approach: Start from a conducting oxide with broken inversion symmetry and search for routes to induce long-range magnetic order. Using density-functional and dynamical mean-field theories, we investigate the electronic properties of the polar metallic oxide LiOsO3. We show that a multiferroic state can be engineered by enclosing LiOsO3 between an insulating material, LiNbO3. We predict that the 1/1 superlattice of LiOsO3 and LiNbO3 exhibits strong coupling between magnetic and ferroelectric degrees of freedom with a ferroelectric polarization of 41.2 μCcm-2, Curie temperature of 927 K, and Néel temperature of 379 K. Our results show that one can start with polar metallic oxides to make multiferroics.

  19. Hybrid quasiparticles within the orthorhombic or hexagonal topology of RMO3 (R =Nd,Pr,Tm,Er; M =Mn,Cr) under strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Sopracase, R.; Holldack, K.; Del Campo, L.; Massa, N. E.; Martínez-Lope, M. J.; Alonso, J. A.

    2014-03-01

    We report on magnetoelectric quasiparticles that originate from electronic Coulomb and exchange correlations using a Bruker IFS125-HR interferometer at 0.5 cm-1 resolution in the THz beamline of the electron storage ring BESSYII in Berlin. Orthorhombic NdMnO3 and hexagonal TmMnO3 have quasiparticles at energies of zone center magnons. In both cases, increasing the applied field, the ~ 20 cm-1 line matching the lowest energy magnon, has its intensity reduced sharply while bands associated in TmMnO3 to magnon-acoustical phonon dispersion crossing and gap opening behave differently. The line at ~ 48 cm-1, the higher branch of the phonon gap, shows a Zeeman splitting-like behavior, while the lower branch at ~ 31 cm-1 has weak field dependences. The asymmetric envelope peaking at ~ 35 cm-1 in NdMnO3 weakens, softens, and evolves at 8 T into two unresolved bands suggesting field induced TA +magnon coupling materializing a condition for a multiferroic state. Metastable orthorhombic ErMnO3 has two bands at 5 K which resembles those of NdMnO3. A remarkable 35 cm-1 Zeeman splitting at 5 K in PrCrO3 is tentatively associated to Cr3+ electrons in a distorted polarizable p-d bond. ErCrO3 shows such a feature at 50 cm-1 as well additional zero field splitting at 8 and 9 cm-1 in the spin reorientation phase.

  20. Lattice dynamics and spin-phonon coupling in orthorhombic Eu1-xHoxMnO3 (x ≤0.3 ) studied by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Elsässer, S.; Geurts, J.; Mukhin, A. A.; Balbashov, A. M.

    2016-02-01

    Eu1-xHoxMnO3 with x <0.5 has an orthorhombic perovskite structure, where the partial substitution of europium by holmium increases the orthorhombic distortion and changes the low-temperature magnetic structure from canted antiferromagnetic to the multiferroic ground state with cycloidal spin arrangement for x >0.2 . We employ polarized, temperature-dependent Raman spectroscopy to study the lattice dynamics and spin-phonon coupling (SPC) effects for the two representative compositions x =0.1 and x =0.3 . We observe an enhancement of phonon frequencies by Ho3+ substitution and we use the Ag(4 ) mode as a measure to evaluate the orthorhombic distortion angle θ . SPC manifests itself as mode-specific softening for T <100 K, induced by the magnetic ordering of Mn3+ spins. Furthermore, we present evidence that the hitherto elusive Raman peak at ≈650 cm-1 is a phonon of B3 g symmetry and ascribe it to the B3 g(1 ) out-of-phase MnO6-breathing mode. We show that this mode has the strongest SPC effect of all observed phonon modes, a fact which we explain by the participation of the apical O(1) ions, modulating the Mn-O(1)-Mn bond whose SPC contribution was hitherto not accessible. Finally, we present a quantitative evaluation of the SPC contribution by the antiferromagnetic plane-to-plane coupling through the Mn-O(1)-Mn bonds and discriminate if from the in-plane ferromagnetic Mn-O(2)-Mn part.

  1. Specific features of nonvalent interactions in orthorhombic perovskites

    NASA Astrophysics Data System (ADS)

    Serezhkin, V. N.; Pushkin, D. V.; Serezhkina, L. B.

    2014-07-01

    It is established that isostructural orthorhombic perovskites ABO3 (sp. gr. Pnma in different systems, no. 62, Z = 4), depending on the specificity of nonvalent interactions (which determine the combinatorial-topological type of the Voronoi-Dirichlet polyhedra (VDPs) of four basis atoms), are divided into ten different stereotypes. It is shown by the example of 259 perovskites belonging to the DyCrO3 stereotype that VDP characteristics can be used to quantitatively estimate the distortion of BO6 octahedra, including that caused by the Jahn-Teller effect. It is found that one of the causes of the distortion of the coordination polyhedra of atoms in the structure of orthorhombic perovskites is heteroatomic metal-metal interactions, for which the interatomic distances are much shorter than the sum of the Slater radii of A and B atoms.

  2. Elastic constants in orthorhombic hen egg-white lysozyme crystals.

    PubMed

    Kitajima, N; Tsukashima, S; Fujii, D; Tachibana, M; Koizumi, H; Wako, K; Kojima, K

    2014-01-01

    The ultrasonic sound velocities of cross-linked orthorhombic hen egg-white lysozyme (HEWL) crystals, including a large amount of water in the crystal, were measured using an ultrasonic pulse-echo method. As a result, seven elastic constants of orthorhombic crystals were observed to be C11 = 5.24 GPa, C22 = 4.87 GPa, C12 = 4.02 GPa, C33 = 5.23 GPa, C44 = 0.30 GPa, C55 = 0.40 GPa, and C66 = 0.43 GPa, respectively. However, C13 and C23 could not be observed because the suitable crystal planes could not be cut from bulk crystals. We conclude that the observed elastic constants of the cross-linked crystals are coincident with those of the intrinsic crystals without cross-linking. Moreover, the characteristics of the elastic constants in orthorhombic HEWL crystals are due to the fact that the shear elastic constants, C44, C55, and C66, are softer than in tetragonal crystals. That is, the shear components, C44, C55, and C66, are one half of those of the tetragonal crystals.

  3. Giant orthorhombic distortions by Cu+ in ferrimagnetic spinel Mn334

    NASA Astrophysics Data System (ADS)

    Chung, Jae-Ho; Lee, Kee Hwan; Chang, Hun; Hwang, In Yong; Kang, Hyun Wook; Kim, Su Jae; Lee, Seongsu

    2015-03-01

    Mn3O4 is a tetragonal (c > a) spinel that exhibits noncollinear Yafet-Kittel ferrimagnetic ordering at low temperatures. We report large orthorhombic distortions in its ferrimagnetic phase stabilized by a few percent of Cu doping. The orthorhombic strains of the ferrimagnetic phases increased linearly to the doping and reached up to ɛ ~ 8 . 2 ×10-3 for x = 0.19, which is three times larger than the saturated value under external magnetic fields. For high doping (xagt 0 . 17), the distortions first appeared in the paramagnetic phases and underwent further enhancement simultaneously with the onset of the noncollinear ferrimagnetic ordering. We present the rich magnetostructural phase diagram of CuxMn3-xO4, and argue that the diluted t2 orbital degeneracy of Cu2+ under tetrahedral crystal field breaks the global symmetry and triggers the orthorhombic instability inherent in Mn3O4. This work was supported by the National Research Foundation of Korea through the ARCNEX (NRF-2011-0031933).

  4. Oxyhalides: A new class of high-TC multiferroic materials

    PubMed Central

    Zhao, Li; Fernández-Díaz, Maria Teresa; Tjeng, Liu Hao; Komarek, Alexander C.

    2016-01-01

    Magnetoelectric multiferroics have attracted enormous attention in the past years because of their high potential for applications in electronic devices, which arises from the intrinsic coupling between magnetic and ferroelectric ordering parameters. The initial finding in TbMnO3 has triggered the search for other multiferroics with higher ordering temperatures and strong magnetoelectric coupling for applications. To date, spin-driven multiferroicity is found mainly in oxides, as well as in a few halogenides. We report multiferroic properties for synthetic melanothallite Cu2OCl2, which is the first discovery of multiferroicity in a transition metal oxyhalide. Measurements of pyrocurrent and the dielectric constant in Cu2OCl2 reveal ferroelectricity below the Néel temperature of ~70 K. Thus, melanothallite belongs to a new class of multiferroic materials with an exceptionally high critical temperature. Powder neutron diffraction measurements reveal an incommensurate magnetic structure below TN, and all magnetic reflections can be indexed with a propagation vector [0.827(7), 0, 0], thus discarding the claimed pyrochlore-like “all-in–all-out” spin structure for Cu2OCl2, and indicating that this transition metal oxyhalide is, indeed, a spin-induced multiferroic material. PMID:27386552

  5. Spin dynamics in the multiferroic materials (invited)

    SciTech Connect

    Ye, Feng; Fishman, Randy Scott; Haraldsen, Jason T; Lorenz, Bernd; Chu, C. W.; Kimura, K.

    2012-01-01

    We report high resolution inelastic neutron scattering measurements and spin dynamics calculations in two multiferroic materials: the geometrically frustrated triangular lattice CuFeO2 and mineral Hu bnerite MnWO4. In un-doped CuFeO2 a low-T collinear spin structure is stabilized by long range magnetic interactions. When doped with a few percent of gallium, the spin order evolves into a complex noncollinear configuration and the system becomes multiferroic. Similarly, the ground state collinear spin order in pure MnWO4 results from delicate balance between competing magnetic interactions up to 11th nearest neighbors and can be tuned by substitution of Mn ions with magnetic or nonmagnetic impurities. The comprehensive investigation of spin dynamics in both systems help to understand the fundamental physical process and the interactions leading to the close interplay of magnetism and ferroelectricity in this type of materials. VC2012 American Institute of Physics. [doi:10.1063/1.3677863

  6. Reliable switching in MRAM and multiferroic logic

    NASA Astrophysics Data System (ADS)

    Munira, Kamaram; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha; Chen, Eugene; Ghosh, Avik W.

    2012-02-01

    Low reliable writing in spintronic devices limits their applicability in the automotive and defense industries. Coupling stochastic macromagnetic simulator with quantum transport, we show how greater reliable switching can be achieved in MRAM and multiferroic logic. Using a combination of spin-transfer torque and small applied perpendicular field in MRAM, the error rate can be considerably reduced for a given voltage pulse. In multiferroic logic, strain plays the role of the magnetic field. Information is passed along an array of nanomagnets (NM) (magnetostrictive + piezoelectric layers) through dipole coupling with neighboring NMs. A low voltage applied to the piezoelectric element causes the NM's magnetization to switch to its hard axis. Upon releasing the stress, the magnetization of the NM relaxes to the easy axis, with its final orientation determined by the dipolar coupling with the left NM, thus achieving a low power Bennett clocked computation. In the face of stagnation points along the potential energy landscape, the success rate of the straintronic switching can be controlled with by how fast the stress is removed from the NM. (Funding: DARPA, GRANDIS, NSF-NEB).

  7. Van vleck paramagnetism in orthorhombic TiO2 (Brookite)

    USGS Publications Warehouse

    Senftle, F.E.; Thorpe, A.N.

    1968-01-01

    The magnetic susceptibility of the orthorhombic form of titanium dioxide has been measured from 5 to 300??K. After deducting the temperature-dependent component, which is probably due to defects or impurities, and the free-ion diamagnetic component, the Van Vleck paramagnetism was estimated to be 33??10-6 emu/mole. Comparison is made between this value and the Van Vleck paramagnetism of strontium titanate and the two tetragonal forms of titanium dioxide: rutile and anatase. ?? 1968 The American Physical Society.

  8. Magnetoelectric effects in multiferroic fibrous composite with imperfect interface

    SciTech Connect

    Wang, X.; Pan, E.

    2007-12-01

    This paper investigates the magnetoelectroelastic responses of multiferroic fibrous composites with imperfectly bonded interface under longitudinal shear. The proposed imperfect interface model is a natural generalization of the shear lag (or the spring layer) model. By virtue of the complex variable method, we first consider the case where an isolated circular multiferroic fiber is imperfectly bonded to an infinite multiferroic matrix. Very concise expressions for the complex field potentials characterizing the magnetoelectroelastic fields inside and outside the circular fiber are obtained when the matrix is subjected to the remote uniform magnetoelectroelastic loading. The Mori-Tanaka mean-field method is then employed to derive the effective moduli of the multiferroic fibrous composite made of randomly distributed fibers reinforced to the matrix. Particularly we demonstrate that the interfacial imperfection in elasticity, electricity, and magnetism will always cause a significant reduction in the magnetoelectric coefficient of the BaTiO{sub 3}-CoFe{sub 2}O{sub 4} fibrous composite.

  9. High pressure and Multiferroics materials. A happy marriage

    DOE PAGES

    Gilioli, Edmondo; Ehm, Lars

    2014-10-31

    We found that the community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. Moreover, the in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties andmore » the coupling to structural instabilities.« less

  10. Study of multiferroic properties of Bi2Fe2WO9 ceramic for device application

    NASA Astrophysics Data System (ADS)

    Rout, Jyoshna; Choudhary, R. N. P.

    2016-09-01

    The Bi2Fe2WO9 ceramic was prepared using a standard solid-state reaction technique. Preliminary analysis of X-ray diffraction pattern revealed the formation of single-phase compound with orthorhombic crystal symmetry. The surface morphology of the material captured using scanning electron microscope (SEM) exhibits formation of a densely packed microstructure. Comprehensive study of dielectric properties showed two anomalies at 200∘C and 450∘C: first one may be related to magnetic whereas second one may be related to ferroelectric phase transition. The field dependent magnetic study of the material shows the existence of small remnant magnetization (Mr) of 0.052emμ/g at room temperature. The existence of magneto-electric (ME) coupling coefficient along with above properties confirms multi-ferroic characteristics of the compound. Selected range temperature and frequency dependent electrical parameters (impedance, modulus, conductivity) of the compound shows that electric properties are correlated to its microstructure. Detailed studies of frequency dependence of ac conductivity suggest that the material obeys Jonscher’s universal power law.

  11. Multiferroicity and magnetoelectric effect in novel complex oxides

    NASA Astrophysics Data System (ADS)

    Choi, Young Jai

    Multiferroic materials, in which ferroelectric and magnetic ordering are simultaneously present, exhibit unprecedented physical properties due to the coupling between electric and magnetic order parameters. The significant cross-coupling effects in the newly found materials have invigorated research in multiferroics as they offer a new route toward fundamental understanding of how spin and lattice degrees of freedom interact and produce macroscopic phenomena. Furthermore, the emergence of multiple functional properties in such materials has stimulated the application in future generations of novel devices in which polarization can be controlled by a magnetic field or vice versa. Recently, the search for an enhanced coupling between dual order parameters has led to discoveries of new class of materials called magnetism-driven ferroelectrics. In such materials, ferroelectricity is induced by a fundamental new mechanism, by which magnetic orders with broken inversion symmetry result in ferroelectric distortions through exchange striction. The magnetic origin of their ferroelectricity engenders highly sensible ferroelectric properties to applied magnetic fields. Herein, we present discoveries of new multiferroics which reveal intriguing interplays between ferroelectricity and magnetism: (1) Thermal and magnetic reversal of electric polarization in the conical spiral multiferroic, CoCr 2O4, (2) Collinear-magnetism-induced ferroelectricity of the Ising chain magnet Ca3CoMnO6, and (3) Multiferroicity in the square-lattice antiferromagnet of Ba2CoGe2O 7. The rich physical phenomena among these new materials unveil a fascinating nature of multiferroicity.

  12. Polycrystalline ferroelectric or multiferroic oxide articles on biaxially textured substrates and methods for making same

    DOEpatents

    Goyal, Amit; Shin, Junsoo

    2015-03-31

    A polycrystalline ferroelectric and/or multiferroic oxide article includes a substrate having a biaxially textured surface; at least one biaxially textured buffer layer supported by the substrate; and a biaxially textured ferroelectric or multiferroic oxide layer supported by the buffer layer. Methods for making polycrystalline ferroelectric and/or multiferroic oxide articles are also disclosed.

  13. Synthetic magnetoelectric coupling in a nanocomposite multiferroic

    DOE PAGES

    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

  14. Landau model for the multiferroic delafossite antiferromagnets

    NASA Astrophysics Data System (ADS)

    Ribeiro, J. L.; Perez-Mato, J. M.; Vieira, L. G.

    2016-10-01

    A symmetry based framework is used to describe the complex phase diagrams observed in the multiferroic delafossite compounds. A free energy Landau functional is derived from the analysis of the transformation properties of the most general incommensurate magnetic spin order parameter. A principle of maximal symmetry is invoked and the stability of each of the different higher symmetry phases considered. The competition between different potential ground states is analysed within the scope of a simplified model, which emphasizes the role of the symmetry allowed phase dependent biquadratic couplings. The cross-over between the different competing states is also discussed. The results show that the diverse set of phase diagrams that are experimentally observed in this class of triangular lattice antiferromagnets and, in particular, the stabilization of magnetically induced ferroelectric states, can be well interpreted and described within this integrated phenomenological approximation.

  15. Spin dynamics in driven composite multiferroics

    NASA Astrophysics Data System (ADS)

    Wang, Zidong; Grimson, Malcolm J.

    2015-09-01

    A spin dynamics approach has been used to study the behavior of the magnetic spins and the electric pseudo-spins in a 1-D composite multiferroic chain with a linear magneto-electric coupling at the interface. The response is investigated with either external magnetic or electric fields driving the system. The spin dynamics is based on the Landau-Lifshitz-Gilbert equation. A Gaussian white noise is later added into the dynamic process to include the thermal effects. The interface requires a closer inspection of the magneto-electric effects. Thus, we construct a 2-D ladder model to describe the behavior of the magnetic spins and the electric pseudo-spins with different magneto-electric couplings.

  16. Spin dynamics in driven composite multiferroics

    SciTech Connect

    Wang, Zidong Grimson, Malcolm J.

    2015-09-28

    A spin dynamics approach has been used to study the behavior of the magnetic spins and the electric pseudo-spins in a 1-D composite multiferroic chain with a linear magneto-electric coupling at the interface. The response is investigated with either external magnetic or electric fields driving the system. The spin dynamics is based on the Landau-Lifshitz-Gilbert equation. A Gaussian white noise is later added into the dynamic process to include the thermal effects. The interface requires a closer inspection of the magneto-electric effects. Thus, we construct a 2-D ladder model to describe the behavior of the magnetic spins and the electric pseudo-spins with different magneto-electric couplings.

  17. Coupling Magnetism to Electricity in Multiferroic Heterostructures

    SciTech Connect

    Ramesh, R

    2012-02-15

    Complex perovskite oxides exhibit a rich spectrum of functional responses, including magnetism, ferroelectricity, highly correlated electron behavior, superconductivity, etc. The basic materials physics of such materials provide the ideal playground for interdisciplinary scientific exploration. Over the past decade we have been exploring the science of such materials (for example, colossal magnetoresistance, ferroelectricity, etc) in thin-film form by creating epitaxial heterostructures and nanostructures. Among the large number of materials systems, there exists a small set of materials which exhibit multiple order parameters; these are known as multiferroics. Using our work in the field of ferroelectric and ferromagnetic oxides as the background, we are now exploring such materials as epitaxial thin films, as well as nanostructures. Specifically, we are studying the role of thin-film growth, heteroepitaxy, and processing on the basic properties as well as the magnitude of the coupling between the order parameters. In our work we are exploring the switchability of the antiferromagnetic order using this coupling. What is the importance of this work? Antiferromagnets are pervasive in the recording industry. They are used as exchange biasing layers in magnetic tunnel junctions, etc. However, to date there has been no antiferomagnet that is electrically tunable. We believe that the multiferroic BiFeO3 is one compound where this can be observed at room temperature. The next step is to explore the coupling of a ferromagnet to this antiferromagnet through the exchange biasing concept. Ultimately, this will give us the opportunity to switch the magnetic state in a ferromagnet (and therefore the spin polarization direction) by simply applying an electric field to the underlying antiferromagnetic ferroelectric. In this talk, I will describe our progress to date on this exciting possibility.

  18. Prediction of Weyl semimetal in orthorhombic MoTe2

    NASA Astrophysics Data System (ADS)

    Sun, Yan; Wu, Shu-Chun; Ali, Mazhar N.; Felser, Claudia; Yan, Binghai

    2015-10-01

    We investigate the orthorhombic phase (Td) of the layered transition-metal dichalcogenide MoTe2 as a Weyl semimetal candidate. MoTe2 exhibits four pairs of Weyl points lying slightly above (˜6 meV ) the Fermi energy in the bulk band structure. Different from its cousin WTe2, which was recently predicted to be a type-II Weyl semimetal, the spacing between each pair of Weyl points is found to be as large as 4% of the reciprocal lattice in MoTe2 (six times larger than that of WTe2). When projected onto the surface, the Weyl points are connected by Fermi arcs, which can be easily accessed by angle-resolved photoemission spectroscopy due to the large Weyl point separation. In addition, we show that the correlation effect or strain can drive MoTe2 from a type-II to a type-I Weyl semimetal.

  19. Columnar epitaxy of hexagonal and orthorhombic silicides on Si(111)

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; Nieh, C. W.; Xiao, Q. F.; Hashimoto, Shin

    1990-01-01

    Columnar grains of PtSi and CrSi2 surrounded by high-quality epitaxial silicon are obtained by ultrahigh vacuum codeposition of Si and metal in an approximately 10:1 ratio on Si(111) substrates heated to 610-840 C. This result is similar to that found previously for CoSi2 (a nearly-lattice-matched cubic-fluorite crystal) on Si(111), in spite of the respective orthorhombic and hexagonal structures of PtSi and CrSi2. The PtSi grains are epitaxial and have one of three variants of the relation defined by PtSi(010)/Si(111), with PtSi 001 line/Si 110 line type.

  20. Structure-property relationships of multiferroic materials: A nano perspective

    NASA Astrophysics Data System (ADS)

    Bai, Feiming

    The integration of sensors, actuators, and control systems is an ongoing process in a wide range of applications covering automotive, medical, military, and consumer electronic markets. Four major families of ceramic and metallic actuators are under development: piezoelectrics, electrostrictors, magnetostrictors, and shape-memory alloys. All of these materials undergo at least two phase transformations with coupled thermodynamic order parameters. These transformations lead to complex domain wall behaviors, which are driven by electric fields (ferroelectrics), magnetic fields (ferromagnetics), or mechanical stress (ferroelastics) as they transform from nonferroic to ferroic states, contributing to the sensing and actuating capabilities. This research focuses on two multiferroic crystals, Pb(Mg1/3Nb 2/3)O3-PbTiO3 and Fe-Ga, which are characterized by the co-existence and coupling of ferroelectric polarization and ferroelastic strain, or ferro-magnetization and ferroelastic strain. These materials break the conventional boundary between piezoelectric and electrostrictors, or magnetostrictors and shape-memory alloys. Upon applying field or in a poled condition, they yield not only a large strain but also a large strain over field ratio, which is desired and much benefits for advanced actuator and sensor applications. In this thesis, particular attention has been given to understand the structure-property relationships of these two types of materials from atomic to the nano/macro scale. X-ray and neutron diffraction were used to obtain the lattice structure and phase transformation characteristics. Piezoresponse and magnetic force microscopy were performed to establish the dependence of domain configurations on composition, thermal history and applied fields. It has been found that polar nano regions (PNRs) make significant contributions to the enhanced electromechanical properties of PMN-x%PT crystals via assisting intermediate phase transformation. With increasing PT

  1. Multiferroic Vacancies at Ferroelectric PbTiO3 Surfaces

    NASA Astrophysics Data System (ADS)

    Shimada, Takahiro; Wang, Jie; Araki, Yasumitsu; Mrovec, Matous; Elsässer, Christian; Kitamura, Takayuki

    2015-09-01

    Multiferroics in nanoscale dimensions are promising for novel functional device paradigms, such as magnetoelectric memories, due to an intriguing cross-coupling between coexisting ferroelectric and (anti)ferromagnetic order parameters. However, the ferroic order is inevitably destroyed below the critical dimension of several nanometers. Here, we demonstrate a new path towards atomic-size multiferroics while resolving the controversial origin of dilute ferromagnetism that unexpectedly emerges in nanoparticles of nonmagnetic ferroelectric PbTiO3 . Systematic exploration using predictive quantum-mechanical calculations demonstrates that oxygen vacancies formed at surfaces induce ferromagnetism due to local nonstoichiometry and orbital symmetry breaking. The localized character of the emerged magnetization allows an individual oxygen vacancy to act as an atomic-scale multiferroic element with a nonlinear magnetoelectric effect that involves rich ferromagnetic-antiferromagnetic-nonmagnetic phase transitions in response to switching of the spontaneous polarization.

  2. Multiferroic Microwave and Millimeter Wave Devices

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gopalan

    2009-03-01

    Layered composites of ferrites and ferroelectrics are magneto-electric (ME) multiferroics and are of interest for studies on the physics of ME interactions and for novel signal processing devices. There are two types of interactions. (i) ME coupling in bound ferrite-piezoelectrics: An electric field E applied to the composite produces a mechanical deformation in the piezoelectric phase that in turn is coupled to the ferrite, resulting in a shift in the ferromagnetic resonance field. The strength of the interactions is measured from the FMR shifts. (ii) ME interactions in unbound ferrite-ferroelectrics: This is a proximity effect in which hybrid spin-electromagnetic waves are formed. An electric field applied to the ferroelectric will result in a change in the permittivity and a shift in the hybrid modes. We performed studies on the nature of ME interactions at 1-110 GHz in bilayers of epitaxial yttrium iron garnet (YIG) films, single crystal spinel ferrites or hexagonal ferrites and single crystal lead magnesium niobate-lead titanate (PMN-PT) or polycrystalline lead zirconium titanate (PZT). A stripline structure or a cavity resonator was used. Electric fields effects were investigated on magnetostatic waves, uniform precession modes or hybrid modes in the ferrite. We found evidence for strong microwave ME coupling. The coupling strength has been found to be dependent on magnetic field orientation, the nature of piezoelectric coupling and volume for both phases [1]. The high frequency ME effect is of importance for dual electric and magnetic field tunable ferrite-ferroelectric devices. We will discuss the design and characterization of ME resonators, phase shifters, delay lines and filters [2]. The work is supported by grants from the Army Research Office and the office of Naval Research. [4pt] [1] ``Multiferroic magnetoelectric composites: Historical perspective, status, and future direction,'' Ce-Wen Nan, M. I. Bichurin, S. Dong, D. Viehland, and G. Srinivasan, J

  3. Spin polarization of excitons in organic multiferroic composites

    NASA Astrophysics Data System (ADS)

    Han, Shixuan; Yang, Liu; Gao, Kun; Xie, Shijie; Qin, Wei; Ren, Shenqiang

    2016-06-01

    Recently, the discovery of room temperature magnetoelectricity in organic charge transfer complexes has reignited interest in the multiferroic field. The solution processed, large-area and low cost organic semiconductor materials offer new possibilities for the functional all organic multiferroic devices. Here we report the spin polarization of excitons and charge transfer states in organic charge transfer composites by using extended Su-Schrieffer-Heeger model including Coulomb interaction and spin-flip effect. With the consideration of spin polarization, we suggest a possible mechanism for the origin of excited ferromagnetism.

  4. Spin polarization of excitons in organic multiferroic composites

    PubMed Central

    Han, Shixuan; Yang, Liu; Gao, Kun; Xie, Shijie; Qin, Wei; Ren, Shenqiang

    2016-01-01

    Recently, the discovery of room temperature magnetoelectricity in organic charge transfer complexes has reignited interest in the multiferroic field. The solution processed, large-area and low cost organic semiconductor materials offer new possibilities for the functional all organic multiferroic devices. Here we report the spin polarization of excitons and charge transfer states in organic charge transfer composites by using extended Su-Schrieffer-Heeger model including Coulomb interaction and spin-flip effect. With the consideration of spin polarization, we suggest a possible mechanism for the origin of excited ferromagnetism. PMID:27334680

  5. Voltage impulse induced bistable magnetization switching in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Nan, T. X.; Zhou, Z. Y.; Lou, J.; Liu, M.; Yang, X.; Gao, Y.; Rand, S.; Sun, N. X.

    2012-03-01

    We report on voltage impulse induced reversible bistable magnetization switching in FeGaB/lead zirconate titanate (PZT) multiferroic heterostructures at room temperature. This was realized through strain-mediated magnetoelectric coupling between ferroelectric PZT and ferromagnetic FeGaB layer. Two reversible and stable voltage-impulse induced mechanical strain states were obtained in the PZT by applying an electric field impulse with its amplitude smaller than the electric coercive field, which led to reversible voltage impulse induced bistable magnetization switching. These voltage impulse induced bistable magnetization switching in multiferroic heterostructures provides a promising approach to power efficient bistable magnetization switching that is crucial for information storage.

  6. Orthorhombic Titanium Matrix Composite Subjected to Simulated Engine Mission Cycles

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.

    1997-01-01

    Titanium matrix composites (TMC's) are commonly made up of a titanium alloy matrix reinforced by silicon carbide fibers that are oriented parallel to the loading axis. These composites can provide high strength at lower densities than monolithic titanium alloys and superalloys in selected gas turbine engine applications. The use of TMC rings with unidirectional SiC fibers as reinforcing rings within compressor rotors could significantly reduce the weight of these components. In service, these TMC reinforcing rings would be subjected to complex service mission loading cycles, including fatigue and dwell excursions. Orthorhombic titanium aluminide alloys are of particular interest for such TMC applications because their tensile and creep strengths are high in comparison to those of other titanium alloys. The objective of this investigation was to assess, in simulated mission tests at the NASA Lewis Research Center, the durability of a SiC (SCS-6)/Ti-22Al-23Nb (at.%) TMC for compressor ring applications, in cooperation with the Allison Engine Company.

  7. Structural, Electrical, and Dielectric Properties of Multiferroic-Spinel Ferrite Composites

    NASA Astrophysics Data System (ADS)

    Nazir, Muhammad Aamir; Ul-Islam, Misbah; Ali, Irshad; Ali, Hassan; Ahmad, Bashir; Ramay, Shahid M.; Raza, Nadeem; Ehsan, Muhammad Fahad; Ashiq, Muhammad Naeem

    2016-02-01

    The present work reports development towards magnetoelectric ceramic composites, i.e., (1- x)Bi0.7Al0.3Mn0.3Fe0.7O3- xLi0.3Zn0.4Fe2.3O4 with x = 0.0, 0.25, 0.35, 0.45, and 1.0. Al- and Mn-doped bismuth multiferroic Bi0.7Al0.3Mn0.3Fe0.7O3 (AMBFO) and Zn-doped lithium ferrite Li0.3Zn0.4 Fe2.3O4 (LZF) were synthesized by the coprecipitation and sol-gel method, respectively. The composite system was synthesized by the conventional solid-state reaction technique followed by heat treatment at 700°C for 6 h. X-ray diffraction (XRD) analysis confirmed the formation of orthorhombic and face-centered cubic phase structure in AMBFO and LZF, respectively. The presence of peaks from both systems in the XRD pattern confirmed composite formation. The metal-to-semiconductor transition temperature decreased from 340 K to 330 K with increase in the LZF content, being mainly due to spin canting and phase structure conversion. The direct-current (DC) electrical resistivity was found to be highest for pure AMBFO and then started to decrease with increase in the Li-Zn ferrite (LZF) content in the composites. The dielectric constant decreased with increase in frequency for all samples, in accordance with Koop's phenomenological theory and the Debye relaxation model. However, the alternating-current (AC) conductivity increased with increase in frequency for all samples, which can be attributed to the conduction mechanism of polaron hopping. These composites open a new approach towards magnetoelectric applications, high-frequency devices, and semiconductor-based solar energy conversion systems.

  8. Magnetoelectric and magneto-dielectric effects in multiferroic manganites

    NASA Astrophysics Data System (ADS)

    Hur, Namjung

    2004-12-01

    Ferroelectric and magnetic materials have been a time-honored subject of study and have lead to some of the most important technological advances to date. Magnetic ordering is governed by the exchange interaction of the electron spins, while ferroelectric ordering is governed by the off-center structural distortions in the lattice. These two seemingly unrelated phenomena can actually coexist in certain unusual materials, termed multiferroics. The understanding of this remarkable occurrence remains a scientific challenge. Despite the possible coexistence of ferroelectricity and magnetism, any profound interplay between them has been rarely observed. This fact has largely prevented the realization of devices with a previously unavailable functionality, which these multiferroics could make possible. Herein, I have explored several multiferroic materials, which show astonishing interplays between ferroelectricity and magnetism during the course of my dissertation. A number of new discoveries have been made in the multiferroic manganites. Especially, polarization reversal by magnetic field and colossal magneto-capacitance effect have been observed in ThMn2O5 and DyMn2O5, respectively.

  9. Magnetoelectric imaging of multiferroic heterostructures (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ghidini, Massimo; Lesaine, Arnaud; Zhu, Bonan; Moya, Xavier; Yan, Wenjing; Crossley, Sam; Nair, Bhasi; Mansell, Rhodri; Cowburn, Russell P.; Barnes, Crispin H. W.; Kronast, Florian; Valencia, Sergio; Maccherozzi, Francesco; Dhesi, Sarnjeet S.; Mathur, Neil

    2015-09-01

    Electrical control of magnetism has been demonstrated in multiferroic compounds and ferromagnetic semiconductors, but electrical switching of a substantial net magnetization at room temperature has not been demonstrated in these materials. This goal has instead been achieved in heterostructures comprising ferromagnetic films in which electrically driven magnetic changes arise due to strain or exchange bias from ferroic substrates, or due to charge effects induced by a gate. However, previous work focused on electrical switching of an in-plane magnetization or involved the assistance of applied magnetic fields. In heterostructures made of juxtaposed ferroelectric and ferromagnetic layers, we have shown electrical control with no applied magnetic field of the perpendicular magnetization of small features [1] and of magnetic stripe domains patterns [2]. Here we investigate Ni81Fe19 films on ferroelectric substrates with and without buffer layers of Cu, whose presence precludes charge-mediated coupling. Ni81Fe19 has virtually zero magnetostriction, but sufficiently thin films show large magnetostriction, and thus, on increasing film thickness through the threshold for zero magnetostriction, we have seeked the crossover from charge- to strain-mediated coupling. We will then show that strain associated with the motion of 90°- ferroelectric domain walls in a BaTiO3 substrate, can switch the magnetization of an array of overlying single-domain Ni dots. [1] M. Ghidini, R. Pellicelli, J. L. Prieto, X. Moya, J. Soussi, J. Briscoe, S. Dunn and N. D. Mathur, Nature Communications 4 (2013) 1453. [2] M. Ghidini, F.Maccherozzi, X. Moya, L. C. Phillips, W.Yan, J. Soussi, N. Métallier, M.Vickers, , N. -J.Steinke, R. Mansell, C. H. W. Barnes, S. S. Dhesi, and N. D. Mathur, Adv. Mater.doi: 10.1002/adma.201404799 (2015).

  10. Bi deficiency-tuned functionality in multiferroic Bi1-δFe0.95Mn0.05O3 films

    NASA Astrophysics Data System (ADS)

    Chen, Jingyi; Wang, Yao; Wang, Hui; Zhang, Shuangmei; Deng, Yuan

    2016-01-01

    Structural evolution and ferroelectric (FE)-to-antiferroelectric (AFE) transition behaviors were observed in Bi1-δFe0.95Mn0.05O3 (100)-textured films with a carefully controlled Bi deficiency concentration δ. Raman spectra revealed an orthorhombic structural transition induced by Mn substitution. The polarization-electric field hysteresis loops and capacitance-voltage loops of Bi1-δFe0.95Mn0.05O3 films clearly demonstrated antiferroelectric behavior with increasing δ. The responses of the domain structure of the Bi1-δFe0.95Mn0.05O3 film under positive and negative applied voltages directly suggested the coexistence of FE and AFE phases. The existence of (100) superstructure reflections and antiparallel displacements of the Bi atoms along the [100] direction observed by transmission electron microscopy unambiguously reveal the AFE phase. The chemical substitution-induced orthorhombic structural transition in BiFe0.95Mn0.05O3 film implies that as the δ concentration increases, the changes in Bi-O bonding and the stereochemical activity of Bi 6s lone pair affect both the ferroelectric distortion and the antiferrodistortive rotation and therefore drive the Bi1-δFe0.95Mn0.05O3 crystal lattice to form a PbZrO3-type orthorhombic phase with an AFE order. A continuing increase in Bi deficiency creates defect dipole complexes which produce an internal field leading to a preferred direction of the ferroelectric domain. The Bi deficiency in multiferroic BiFeO3 provides a new route by which to tune functionality.

  11. Bi deficiency-tuned functionality in multiferroic Bi1-δFe0.95Mn0.05O3 films.

    PubMed

    Chen, Jingyi; Wang, Yao; Wang, Hui; Zhang, Shuangmei; Deng, Yuan

    2016-01-01

    Structural evolution and ferroelectric (FE)-to-antiferroelectric (AFE) transition behaviors were observed in Bi1-δFe0.95Mn0.05O3 (100)-textured films with a carefully controlled Bi deficiency concentration δ. Raman spectra revealed an orthorhombic structural transition induced by Mn substitution. The polarization-electric field hysteresis loops and capacitance-voltage loops of Bi1-δFe0.95Mn0.05O3 films clearly demonstrated antiferroelectric behavior with increasing δ. The responses of the domain structure of the Bi1-δFe0.95Mn0.05O3 film under positive and negative applied voltages directly suggested the coexistence of FE and AFE phases. The existence of (100) superstructure reflections and antiparallel displacements of the Bi atoms along the [100] direction observed by transmission electron microscopy unambiguously reveal the AFE phase. The chemical substitution-induced orthorhombic structural transition in BiFe0.95Mn0.05O3 film implies that as the δ concentration increases, the changes in Bi-O bonding and the stereochemical activity of Bi 6s lone pair affect both the ferroelectric distortion and the antiferrodistortive rotation and therefore drive the Bi1-δFe0.95Mn0.05O3 crystal lattice to form a PbZrO3-type orthorhombic phase with an AFE order. A continuing increase in Bi deficiency creates defect dipole complexes which produce an internal field leading to a preferred direction of the ferroelectric domain. The Bi deficiency in multiferroic BiFeO3 provides a new route by which to tune functionality. PMID:26775621

  12. Bi deficiency-tuned functionality in multiferroic Bi1-δFe0.95Mn0.05O3 films

    PubMed Central

    Chen, Jingyi; Wang, Yao; Wang, Hui; Zhang, Shuangmei; Deng, Yuan

    2016-01-01

    Structural evolution and ferroelectric (FE)-to-antiferroelectric (AFE) transition behaviors were observed in Bi1-δFe0.95Mn0.05O3 (100)-textured films with a carefully controlled Bi deficiency concentration δ. Raman spectra revealed an orthorhombic structural transition induced by Mn substitution. The polarization-electric field hysteresis loops and capacitance-voltage loops of Bi1-δFe0.95Mn0.05O3 films clearly demonstrated antiferroelectric behavior with increasing δ. The responses of the domain structure of the Bi1-δFe0.95Mn0.05O3 film under positive and negative applied voltages directly suggested the coexistence of FE and AFE phases. The existence of (100) superstructure reflections and antiparallel displacements of the Bi atoms along the [100] direction observed by transmission electron microscopy unambiguously reveal the AFE phase. The chemical substitution-induced orthorhombic structural transition in BiFe0.95Mn0.05O3 film implies that as the δ concentration increases, the changes in Bi-O bonding and the stereochemical activity of Bi 6s lone pair affect both the ferroelectric distortion and the antiferrodistortive rotation and therefore drive the Bi1-δFe0.95Mn0.05O3 crystal lattice to form a PbZrO3-type orthorhombic phase with an AFE order. A continuing increase in Bi deficiency creates defect dipole complexes which produce an internal field leading to a preferred direction of the ferroelectric domain. The Bi deficiency in multiferroic BiFeO3 provides a new route by which to tune functionality. PMID:26775621

  13. Enhancement of magnetic and ferroelectric behaviour in (Ca, Co) co-doped HoMnO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Rout, P. P.; Pradhan, S. K.; Das, S. K.; Samantaray, S.; Roul, B. K.

    2013-11-01

    The effect of sintering temperature on structural, electrical and magnetic behaviours of polycrystalline samples of Ho0.9Ca0.1Mn0.9Co0.1O3 prepared by the solid state reaction route sintered at three different temperature 1250 °C, 1350 °C, 1450 °C for 10 h are investigated. XRD, SEM, magnetization, dielectric and ferroelectric measurements were carried out. Experimental results showed the nucleation of orthorhombic phase as the sintering temperature increases from 1250 °C to 1450 °C. Ferroelectric (Tc) and antiferromagnetic transition temperature (TN) increases with increase in sintering temperature. Strong bifurcation of FC and ZFC curve in sample sintered at 1450 °C showed a clear onset of ferromagnetic state around 165 °K, which is confirmed from M to H graph at 165 °K. All the sample showed ferroelectric behaviour at room temperature which are leaky in nature. Sintering temperature along with Ca and Co doping in HoMnO3 ceramics plays an important role in phase transformation along with enhancement in multiferroic properties.

  14. Elastic anomaly and order-disorder nature of multiferroic barium sodium niobate studied by broadband brillouin scattering

    NASA Astrophysics Data System (ADS)

    Ota, Shiori; Matsumoto, Kazuya; Suzuki, Kohei; Kojima, Seiji

    2014-03-01

    The successive phase transitions of multiferroic barium sodium niobate, Ba2NaNb5O15 (BNN), were studied by Brillouin scattering. The LA, TA modes, and central peak were measured in a large temperature range from room temperature up to 750 °C. In the vicinity of a ferroelectric phase transition at about TC = 585 °C from the prototypic tetragonal 4/mmm to ferroelectric 4mm phases, elastic anomaly was observed for LA and TA modes. In addition, the order-disorder nature was observed by the temperature dependence of a central peak. For further cooling another elastic anomaly was also observed in the vicinity of a ferroelastic incommensurate phase transition at about TIC = 285 °C into orthorhombic 2mm phase with the appearance of incommensurate modulation. The large thermal hysteresis of elastic anomaly near TIC can be attributed the typical feature of the type III incommensurate phase transition predicted recently by Ishibashi and Iwata (2013 J. Phys. Soc. Jpn. 82 044703).

  15. The low-temperature crystal structure of the multiferroic melilite Ca2CoSi2O7.

    PubMed

    Sazonov, Andrew; Hutanu, Vladimir; Meven, Martin; Roth, Georg; Kézsmárki, István; Murakawa, Hiroshi; Tokura, Yoshinori; Náfrádi, Bálint

    2016-02-01

    In the antiferromagnetic ground state, below TN ≃ 5.7 K, Ca2CoSi2O7 exhibits strong magnetoelectric coupling. For a symmetry-consistent theoretical description of this multiferroic phase, precise knowledge of its crystal structure is a prerequisite. Here we report the results of single-crystal neutron diffraction on Ca2CoSi2O7 at temperatures between 10 and 250 K. The low-temperature structure at 10 K was refined assuming twinning in the orthorhombic space group P2(1)2(1)2 with a 3 × 3 × 1 supercell [a = 23.52 (1), b = 23.52 (1), c = 5.030 (3) Å] compared with the high-temperature normal state [tetragonal space group P42(1)m, a = b ≃ 7.86, c ≃ 5.03 Å]. The precise structural parameters of Ca2CoSi2O7 at 10 K are presented and compared with the literature X-ray diffraction results at 130 and 170 K (low-temperature commensurate phase), as well as at ∼ 500 K (high-temperature normal phase). PMID:26830804

  16. Magnetic properties of the orthorhombic NdPd

    NASA Astrophysics Data System (ADS)

    Dhar, Vijay; Provino, A.

    2016-09-01

    The equiatomic NdPd compound crystallizes in the orthorhombic CrB structure type (oS8, Cmcm, No. 63). The NdPd phase melts congruently at 1240 °C, as observed by differential thermal analysis; one further sharp thermal effect detected at 1040 °C is very likely due to a structural transition. We confirm the CrB prototype for the low-temperature form of NdPd. The lattice parameters of this compound are a=3.842(2) Å, b=10.776(7) Å, c=4.605(2) Å, as obtained from Guinier powder pattern; those for the corresponding iso-structural LaPd compound, prepared as non-magnetic reference, are a=3.947(2) Å, b=11.036(3) Å, c=4.663(2) Å. Despite the fact that NdPd has been known since long, its physical properties have not been investigated till date. Here we report the results of magnetization, heat capacity and electrical resistivity measurements performed on this compound. NdPd undergoes a single ferromagnetic transition close to 15 K, inferred from a sharp upturn in the magnetization at lower temperatures and from Arrott plots measured at selected temperatures between 1.9 and 18 K. The coercive field and remnant magnetization at 1.9 K are 320 Oe and 0.24 μB/f.u., which become negligible at 15 K. A sharp peak in the heat capacity at ≈15 K confirms the bulk magnetic transition. Isothermal magnetization at 2 K shows a tendency to saturation, reaching a value of 1.9 μB/f.u. at the maximum applied field of 70 kOe. The zero field resistivity shows an anomaly near 15 K, in correspondence with the magnetic and heat capacity data. A negative magnetoresistivity, typical of a ferromagnet, is observed in the magnetically ordered state in an applied magnetic field of 50 kOe. LaPd is a typical Pauli paramagnet with a Sommerfeld coefficient γ=3.9 mJ/mol K2.

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  18. Ultrafast optical pump-probe spectroscopy is used to reveal the coexistence of coupled antiferromagnetic (AFM)/ferroelectric (FE) and ferromagnetic (FM) orders in multiferroic TbMnO3 films, which can guide researchers in creating new kinds of multiferroic materials.

    SciTech Connect

    Qi, Jingbo; Zhu, Jianxin; Trugman, Stuart A.; Taylor, Antoinette; Jia, Quanxi; Prasankumar, Rohit

    2012-07-06

    Multiferroic materials have attracted much interest in the past decade, due not only to their novel device applications, but also their manifestations of coupling and interactions between different order parameters (particularly electric polarization and magnetic order). Recently, much attention has been focused on perovskite manganites, RMnO{sub 3} (R = rare earth ions), due to the discovery of a large magnetoelectric effect in these materials. The first member of this family to be discovered was TbMnO{sub 3} (TMO), which is now well established as a typical magnetoelectric multiferroic. Extensive experimental and theoretical studies have already been done on single crystal TMO (SC-TMO). In brief, SC-TMO, with a distorted orthorhombic perovskite structure, has an antiferromagnetic (AFM) phase transition at T{sub N} {approx}40 K with sinusoidally ordered Mn moments. Below T{sub FE} {approx} 28 K, ferroelectric (FE) order develops owing to the appearance of cycloidal spiral spin structure. In contrast, there are relatively few reports describing the properties of TMO thin films (typically grown on SrTiO{sub 3} (STO) substrates). In general, thin films can enable new functionality in materials, as their physical parameters can be changed by modifying their structure via strain imposed by the substrate. Strain in particular has the potential to directly couple FE and FM orders, which is very rare. This could benefit electronic device applications by providing low power consumption, high speed operation, and greater electric/magnetic field controllability. Previous investigations of magnetic properties in TMO films revealed an unexpected ferromagnetic (FM) order, in contrast to SC-TMO. However, several important questions regarding these films are still unanswered for instance: (1) What mechanism induces FM order? (2) Can FM, sinusoidal AFM and spiral AFM (or FE) orders coexist? (3) Can FM order be coupled to FE order? To fully understand these unique materials

  19. Topological Structures in Multiferroics - Domain Walls, Skyrmions and Vortices

    DOE PAGES

    Seidel, Jan; Vasudevan, Rama K.; Valanoor, Nagarajan

    2015-12-15

    Topological structures in multiferroic materials have recently received considerable attention because of their potential use as nanoscale functional elements. Their reduced size in conjunction with exotic arrangement of the ferroic order parameter and potential order parameter coupling allows for emergent and unexplored phenomena in condensed matter and functional materials systems. This will lead to exciting new fundamental discoveries as well as application concepts that exploit their response to external stimuli such as mechanical strain, electric and magnetic fields. In this review we capture the current development of this rapidly moving field with specific emphasis on key achievements that have castmore » light on how such topological structures in multiferroic materials systems can be exploited for use in complex oxide nanoelectronics and spintronics.« less

  20. Multiferroic materials based on organic transition-metal molecular nanowires.

    PubMed

    Wu, Menghao; Burton, J D; Tsymbal, Evgeny Y; Zeng, Xiao Cheng; Jena, Puru

    2012-09-01

    We report on the density functional theory aided design of a variety of organic ferroelectric and multiferroic materials by functionalizing crystallized transition-metal molecular sandwich nanowires with chemical groups such as -F, -Cl, -CN, -NO(2), ═O, and -OH. Such functionalized polar wires exhibit molecular reorientation in response to an electric field. Ferroelectric polarizations as large as 23.0 μC/cm(2) are predicted in crystals based on fully hydroxylized sandwich nanowires. Furthermore, we find that organic nanowires formed by sandwiching transition-metal atoms in croconic and rhodizonic acids, dihydroxybenzoquinone, dichloro-dihydroxy-p-benzoquinone, or benzene decorated by -COOH groups exhibit ordered magnetic moments, leading to a multiferroic organometallic crystal. When crystallized through hydrogen bonds, the microscopic molecular reorientation translates into a switchable polarization through proton transfer. A giant interface magnetoelectric response that is orders of magnitude greater than previously reported for conventional oxide heterostructure interfaces is predicted. PMID:22881120

  1. Study on multicaloric effect of CuO induced multiferroic

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Yadav, K. L.

    2014-08-01

    One of the induced multiferroic materials, CuO has the magnetic as well as ferroelectric phase transition at same temperature (TN1 ˜ 213 K, TC and TN2 ˜ 230 K). These type of materials can show two types of entropy; magnetic field induced entropy (Magnetocaloric Effect) as well as electeric field induced entropy (Electrocaloric Effect). The presence of both type of entropy may be called "Multicaloric Entropy" (M. Vopson, Solid State Commun. 152, 2067 (2012) and Meng et al., Phys. Lett. A 377, 567 (2013)). We observed that "Multicaloric Entropy" in the induced multiferroic materials also depends on the magnetoelectric interaction (γ). Therofore, this numerical attempt to calculate the entropy of CuO may be useful for the future "electro-magnetic" based refrigerator technology.

  2. Topological Structures in Multiferroics - Domain Walls, Skyrmions and Vortices

    SciTech Connect

    Seidel, Jan; Vasudevan, Rama K.; Valanoor, Nagarajan

    2015-12-15

    Topological structures in multiferroic materials have recently received considerable attention because of their potential use as nanoscale functional elements. Their reduced size in conjunction with exotic arrangement of the ferroic order parameter and potential order parameter coupling allows for emergent and unexplored phenomena in condensed matter and functional materials systems. This will lead to exciting new fundamental discoveries as well as application concepts that exploit their response to external stimuli such as mechanical strain, electric and magnetic fields. In this review we capture the current development of this rapidly moving field with specific emphasis on key achievements that have cast light on how such topological structures in multiferroic materials systems can be exploited for use in complex oxide nanoelectronics and spintronics.

  3. Modeling of efficient solid-state cooler on layered multiferroics.

    PubMed

    Starkov, Ivan; Starkov, Alexander

    2014-08-01

    We have developed theoretical foundations for the design and optimization of a solid-state cooler working through caloric and multicaloric effects. This approach is based on the careful consideration of the thermodynamics of a layered multiferroic system. The main section of the paper is devoted to the derivation and solution of the heat conduction equation for multiferroic materials. On the basis of the obtained results, we have performed the evaluation of the temperature distribution in the refrigerator under periodic external fields. A few practical examples are considered to illustrate the model. It is demonstrated that a 40-mm structure made of 20 ferroic layers is able to create a temperature difference of 25K. The presented work tries to address the whole hierarchy of physical phenomena to capture all of the essential aspects of solid-state cooling.

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

    DOEpatents

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

    2014-08-12

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

  5. Multiferroic properties of nanocrystalline BaTiO 3

    NASA Astrophysics Data System (ADS)

    Mangalam, R. V. K.; Ray, Nirat; Waghmare, Umesh V.; Sundaresan, A.; Rao, C. N. R.

    2009-01-01

    Some of the Multiferroics [H. Schmid, Ferroelectrics 162 (1994) 317] form a rare class of materials that exhibit magneto-electric coupling arising from the coexistence of ferromagnetism and ferroelectricity, with potential for many technological applications [J.F. Scott, Nat. Mater. 6 (2007) 256; N.A. Spaldin, M. Fiebig, Science 309 (2005) 391]. Over the last decade, an active research on multiferroics has resulted in the identification of a few routes that lead to multiferroicity in bulk materials [C. Ederer, N.A. Spaldin, Nat. Mater. 3 (2004) 849; D.V. Efremov, J. van den Brink, D.I. Khomskii, Nat. Mater. 3 (2004) 853; N. Hur, S. Park, P.A. Sharma, J.S. Ahn, S. Guha, S.W. Cheong, Nature 429 (2004) 392]. While ferroelectricity in a classic ferroelectric such as BaTiO 3 is expected to diminish with the reducing particle size, [C.H. Ahn, K.M. Rabe, J.M. Triscone, Science 303 (2004) 488; J. Junquera, P. Ghosez, Nature 422 (2003) 506] ferromagnetism cannot occur in its bulk form [N.A. Hill, J. Phys. Chem. B 104 (2000) 6694]. Here, we use a combination of experiment and first-principles simulations to demonstrate that multiferroic nature emerges in intermediate size nanocrystalline BaTiO 3, ferromagnetism arising from the oxygen vacancies at the surface and ferroelectricity from the core. A strong coupling between a surface polar phonon and spin is shown to result in a magnetocapacitance effect observed at room temperature, which can open up possibilities of new electro-magneto-mechanical devices at the nano-scale.

  6. Changing Dielectrics into Multiferroics---Alchemy Enabled by Strain

    NASA Astrophysics Data System (ADS)

    Schlom, Darrell

    2011-03-01

    Ferroelectric ferromagnets are exceedingly rare, fundamentally interesting multiferroic materials. The properties of what few compounds simultaneously exhibit these phenomena pale in comparison to useful ferroelectrics or ferromagnets: their spontaneous polarizations (Ps) or magnetizations (Ms) are smaller by a factor of 1000 or more. The same holds for (magnetic or electric) field-induced multiferroics. Recently, however, Fennie and Rabe proposed a new route to ferroelectric ferromagnets---transforming magnetically ordered insulators that are neither ferroelectric nor ferromagnetic, of which there are many, into ferroelectric ferromagnets using a single control parameter: strain. The system targeted, EuTi O3 , was predicted to simultaneously exhibit strong ferromagnetism (Ms ~ ~ ~7~μB /Eu) and strong ferroelectricity (Ps ~ ~ ~10~ μ C/cm2) under large biaxial compressive strain. These values are orders of magnitude higher than any known ferroelectric ferromagnet and rival the best materials that are solely ferroelectric or ferromagnetic. Hindered by the absence of an appropriate substrate to provide the desired compression, we show 3 both experimentally and theoretically the emergence of a multiferroic state under biaxial tension with the unexpected benefit that even lower misfits are required, thereby enabling higher quality crystalline films. The resulting genesis of a strong ferromagnetic ferroelectric points the way to high temperature manifestations of this spin-phonon coupling mechanism. Our work demonstrates that a single experimental parameter, strain, simultaneously controls multiple order parameters and is a viable alternative tuning parameter to composition for creating multiferroics. C.J. Fennie and K.M. Rabe, Phys. Rev. Lett. 97 (2006) 267602.

  7. Evidence of multiferroicity in NdMn2O5

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Balédent, V.; Damay, F.; Gukasov, A.; Moshopoulou, E.; Auban-Senzier, P.; Pasquier, C.; André, G.; Porcher, F.; Elkaim, E.; Doubrovsky, C.; Greenblatt, M.; Foury-Leylekian, P.

    2016-03-01

    Recently, R Mn2O5 (R =rare earth, Bi, Y) type multiferroics have drawn considerable attention, because of magnetically induced ferroelectricity along with an extremely large magnetoelectric coupling. Here, we present a detailed study on NdMn2O5 which is a crucial composition between the nonferroelectric PrMn2O5 and ferroelectric SmMn2O5 . We report the results of heat capacity, magnetization, dielectric permittivity, and electric polarization measurements along with an accurate description of the structural and microscopic magnetic properties obtained from high resolution x-ray and neutron diffraction studies. We show that NdMn2O5 is ferroelectric, although the magnitude of polarization is much weaker than that of the other multiferroic members. The direction of the polarization is along the crystallographic b axis and its magnitude can be tuned with the application of a magnetic field. Moreover, unlike the other multiferroic members of this series, ferroelectricity in NdMn2O5 emerges in an incommensurate magnetic state. The present study also provides evidence in support of the influence of the rare-earth size on the magnetoelectric phase diagram.

  8. Photocreating supercooled spiral-spin states in a multiferroic manganite

    NASA Astrophysics Data System (ADS)

    Sheu, Y. M.; Ogawa, N.; Kaneko, Y.; Tokura, Y.

    2016-08-01

    We demonstrate that the dynamics of the a b -spiral-spin order in a magnetoelectric multiferroic Eu0.55Y0.45MnO3 can be unambiguously probed through optical second harmonic signals, generated via spin-induced ferroelectric polarization. In the case of weak excitation, the ferroelectric and the spiral-spin order remains interlocked, both relaxing through spin-lattice relaxation in the nonequilibrium state. When the additional optical pulse illuminating the sample is intense enough to induce a local phase transition thermally, the system creates a metastable state of the b c -spiral-spin order (with the electric polarization P ∥c ) via supercooling across the first-order phase transition between the a b and b c spiral. The supercooled state of the b c -spiral spin is formed in the thermodynamical ground state of the a b spiral (P ∥a ), displaying a prolonged lifetime with strong dependence on the magnetic field along the a axis. The observed phenomena provide a different paradigm for photoswitching between the two distinct multiferroic states, motivating further research into a direct observation of the photocreated supercooled b c -spiral spin in multiferroic manganites.

  9. Ultra-low-energy analog straintronics using multiferroic composites

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    2014-03-01

    Multiferroic devices, i.e., a magnetostrictive nanomagnet strain-coupled with a piezoelectric layer, are promising as binary switches for ultra-low-energy digital computing in beyond Moore's law era [Roy, K. Appl. Phys. Lett. 103, 173110 (2013), Roy, K. et al. Appl. Phys. Lett. 99, 063108 (2011), Phys. Rev. B 83, 224412 (2011), Scientific Reports (Nature Publishing Group) 3, 3038 (2013), J. Appl. Phys. 112, 023914 (2012)]. We show here that such multiferroic devices, apart from performing digital computation, can be also utilized for analog computing purposes, e.g., voltage amplification, filter etc. The analog computing capability is conceived by considering that magnetization's mean orientation shifts gradually although nanomagnet's potential minima changes abruptly. Using tunneling magnetoresistance (TMR) measurement, a continuous output voltage while varying the input voltage can be produced. Stochastic Landau-Lifshitz-Gilbert (LLG) equation in the presence of room-temperature (300 K) thermal fluctuations is solved to demonstrate the analog computing capability of such multiferroic devices. This work was supported in part by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.

  10. Ultra-low-energy straintronics using multiferroic composites

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    2014-08-01

    The primary impediment to continued improvement of traditional charge-based electronic devices in accordance with Moore's law is the excessive energy dissipation that takes place in the devices during switching of bits. One very promising solution is to utilize strain-mediated multiferroic composites, i.e., a magnetostrictive nanomagnet strain-coupled to a piezoelectric layer, where the magnetization can be switched between its two stable states in sub-nanosecond delay while expending a minuscule amount of energy of ~1 attojoule at room-temperature. Apart from devising digital memory and logic, these multiferroic devices can be also utilized for analog signal processing, e.g., voltage amplifier. First, we briefly review the recent advances on multiferroic straintronic devices and then we show here that in a magnetostrictive nanomagnet, it is possible to achieve the so-called Landauer limit (or the ultimate limit) of energy dissipation of amount kT ln(2) compensating the entropy loss, thereby linking information and thermodynamics.

  11. Magnetic structures in potential multiferroic GdCrO3

    NASA Astrophysics Data System (ADS)

    Manuel, Pascal; Chapon, Laurent; Khalyavin, Dmitry; Xueyun, Wang; Cheong, Sang-Wook

    2015-03-01

    For the past decade, multiferroics materials have atracted a lot of attention in the condensed matter community because of potential applications for devices. A somewhat ambiguous addition to the multiferroics family was recently reported in the peroskite based GdCrO3 in both bulk and thin film samples. Indeed, ferroelectricity was evidenced by a strong enhancement of the capacitance in a field but significant leakage and no well developed P-E hysteresis blurred the picture. Our own measurements clearly indicate the existence of a polar phase below 2K. To complete the understanding of this material, the determination of the magnetic structure is required but is hampered by the fact Gd is a strong neutron absorber. We will present some neutron diffraction data collected on an isotopic 160GdCrO3 sample at the WISH diffractometer at ISIS which confirm the presence of three successive magnetic phases, previously only seen by magnetization, as a function of temperature. We will compare our determined structures against predictions based on group theoretical considerations and experimental work on other rare-earth ortho-chromates and discuss the mechanism for multiferroicity.

  12. Raman phonons in multiferroic FeVO4 crystals

    NASA Astrophysics Data System (ADS)

    Zhang, An-Min; Liu, Kai; Ji, Jian-Ting; He, Chang-Zhen; Tian, Yong; Jin, Feng; Zhang, Qing-Ming

    2015-12-01

    Multiferroic materials are promising candidates for next-generation multi-functional devices, because of the coexistence of multi-orders and the coupling between the orders. FeVO4 has been confirmed to be a multiferroic compound, since it exhibits both ferroelectricity and antiferromagnetic ordering at low temperatures. In this paper, we have performed careful Raman scattering measurements on high-quality FeVO4 single crystals. The compound has a very rich phonon structure due to its low crystal symmetry (P - 1) and at least 47 Raman-active phonon modes have been resolved in the low and hightemperature spectra. Most of the observed modes are well assigned with aid of first-principles calculations and symmetry analysis. The present study provides an experimental basis for exploring spin-lattice coupling and the mechanism of multiferroicity in FeVO4 Project supported by the National Basic Research Program of China (Grant No. 2012CB921701), the National Natural Science Foundation of China (Grant Nos. 11174367 and 11004243), the China Postdoctoral Science Foundation, the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (Grant Nos. 10XNI038, 14XNLF06, and 14XNLQ03).

  13. Growth of epitaxial orthorhombic YO1.5-substituted HfO2 thin film

    NASA Astrophysics Data System (ADS)

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Funakubo, Hiroshi

    2015-07-01

    YO1.5-substituted HfO2 thin films with various substitution amounts were grown on (100) YSZ substrates by the pulsed laser deposition method directly from the vapor phase. The epitaxial growth of film with different YO1.5 amounts was confirmed by the X-ray diffraction method. Wide-area reciprocal lattice mapping measurements were performed to clarify the crystal symmetry of films. The formed phases changed from low-symmetry monoclinic baddeleyite to high-symmetry tetragonal/cubic fluorite phases through an orthorhombic phase as the YO1.5 amount increased from 0 to 0.15. The additional annular bright-field scanning transmission electron microscopy indicates that the orthorhombic phase has polar structure. This means that the direct growth by vapor is of polar orthorhombic HfO2-based film. Moreover, high-temperature X-ray diffraction measurements showed that the film with a YO1.5 amount of 0.07 with orthorhombic structure at room temperature only exhibited a structural phase transition to tetragonal phase above 450 °C. This temperature is much higher than the reported maximum temperature of 200 °C to obtain ferroelectricity as well as the expected temperature for real device application. The growth of epitaxial orthorhombic HfO2-based film helps clarify the nature of ferroelectricity in HfO2-based films (186 words/200 words).

  14. The induced magnetic and electric fields' paradox leading to multicaloric effects in multiferroics

    NASA Astrophysics Data System (ADS)

    Vopson, Melvin M.

    2016-04-01

    Magneto-electric effect in multiferroics implies that an applied magnetic field induces an electric polarization change in a multiferroic solid and vice versa, an applied electric field modifies its magnetization. The magneto-electric effect is a powerful feature of multiferroics and has attracted huge interest due to potential technological applications. One such possible application is the multicaloric effect in multiferroics. However, a closer examination of this effect and its derivation leads to a paradox, in which the predicted changes in one of the order phase at a constant applied field are due to the excitation by the same field. Here this apparent paradox is first explained in detail and then solved. Understanding how electric and magnetic fields can be induced in multiferroic materials is an essential tool enabling their theoretical modeling as well as facilitating the introduction of future applications.

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  17. Dipole-field sums and Lorentz factors for orthorhombic lattices, and implications for polarizable molecules

    NASA Technical Reports Server (NTRS)

    Purvis, C. K.; Taylor, P. L.

    1982-01-01

    A method for computing the Lorentz tensor components in single crystals via rapidly convergent sums of Bessels functions is developed using the relationship between dipole-field sums and the tensor components. The Lorentz factors for simple, body-centered, and base-centered orthorhombic lattices are computed using this method, and the derivative Lorentz factors for simple orthorhombic lattices are also determined. Both the Lorentz factors and their derivatives are shown to be very sensitive to a lattice structure. The equivalent of the Clausius-Mossotti relation for general orthorhombic lattices is derived using the Lorentz-factor formalism, and the permanent molecular dipole moment is related to crystal polarization for the case of a ferroelectric of polarizable point dipoles. It is concluded that the polarization enhancement due to self-polarization familiar from classical theory may actually be a reduction in consequences of negative Lorentz factors in one or two lattice directions for noncubic crystals.

  18. Crystallization of the Focal Adhesion Kinase Targeting (FAT) Domain in a Primitive Orthorhombic Space Group

    SciTech Connect

    Magis,A.; Bailey, K.; Kurenova, E.; Hernandez Prada, J.; Cance, W.; Ostrov, D.

    2008-01-01

    X-ray diffraction data from the targeting (FAT) domain of focal adhesion kinase (FAK) were collected from a single crystal that diffracted to 1.99 Angstroms resolution and reduced to the primitive orthorhombic lattice. A single molecule was predicted to be present in the asymmetric unit based on the Matthews coefficient. The data were phased using molecular-replacement methods using an existing model of the FAK FAT domain. All structures of human focal adhesion kinase FAT domains solved to date have been solved in a C-centered orthorhombic space group.

  19. Oxyhalides: A new class of high-T C multiferroic materials.

    PubMed

    Zhao, Li; Fernández-Díaz, Maria Teresa; Tjeng, Liu Hao; Komarek, Alexander C

    2016-05-01

    Magnetoelectric multiferroics have attracted enormous attention in the past years because of their high potential for applications in electronic devices, which arises from the intrinsic coupling between magnetic and ferroelectric ordering parameters. The initial finding in TbMnO3 has triggered the search for other multiferroics with higher ordering temperatures and strong magnetoelectric coupling for applications. To date, spin-driven multiferroicity is found mainly in oxides, as well as in a few halogenides. We report multiferroic properties for synthetic melanothallite Cu2OCl2, which is the first discovery of multiferroicity in a transition metal oxyhalide. Measurements of pyrocurrent and the dielectric constant in Cu2OCl2 reveal ferroelectricity below the Néel temperature of ~70 K. Thus, melanothallite belongs to a new class of multiferroic materials with an exceptionally high critical temperature. Powder neutron diffraction measurements reveal an incommensurate magnetic structure below T N, and all magnetic reflections can be indexed with a propagation vector [0.827(7), 0, 0], thus discarding the claimed pyrochlore-like "all-in-all-out" spin structure for Cu2OCl2, and indicating that this transition metal oxyhalide is, indeed, a spin-induced multiferroic material. PMID:27386552

  20. Fabrication and characterization of electrospun orthorhombic InVO4 nanofibers

    NASA Astrophysics Data System (ADS)

    Song, Lingjun; Liu, Suwen; Lu, Qifang; Zhao, Gang

    2012-02-01

    The novel orthorhombic InVO4 nanofibers have been successfully synthesized by annealing electrospun precursor fibers. Citric acid was used as a ligand for it could react with metal salts to get a transparent homogeneous precursor solution and homogeneous precursor sol for electrospining. Polyvinyl pyrrolidone (PVP, K-30) was used as a binder and a structure guide reagent because it was one kind of water-soluble polymers. It is easy to gain one-dimensional materials while the viscosity of the citrate/PVP sol was suitable. The structure, morphology and photocatalytic properties of the nanofibers were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electron microscopy (SEM) analysis, UV-vis spectrophotometer and fluorescence spectrophotometer. The nanofibers calcined at 700 °C were orthorhombic InVO4 with a width in the range of 30-100 nm and length in micron-grade. This one-dimensional pure orthorhombic InVO4 had the higher photocatalytic activity under visible light irradiation. The photo-degradation rate of nitrobenzene aqueous solution under visible light reached 69% after 6 h. It is obvious that the orthorhombic InVO4 nanofibers have a potential application in wastewater-treatment.

  1. High-efficient thermoelectric materials: The case of orthorhombic IV-VI compounds.

    PubMed

    Ding, Guangqian; Gao, Guoying; Yao, Kailun

    2015-01-01

    Improving the thermoelectric efficiency is one of the greatest challenges in materials science. The recent discovery of excellent thermoelectric performance in simple orthorhombic SnSe crystal offers new promise in this prospect [Zhao et al. Nature 508, 373 (2014)]. By calculating the thermoelectric properties of orthorhombic IV-VI compounds GeS,GeSe,SnS, and SnSe based on the first-principles combined with the Boltzmann transport theory, we show that the Seebeck coefficient, electrical conductivity, and thermal conductivity of orthorhombic SnSe are in agreement with the recent experiment. Importantly, GeS, GeSe, and SnS exhibit comparative thermoelectric performance compared to SnSe. Especially, the Seebeck coefficients of GeS, GeSe, and SnS are even larger than that of SnSe under the studied carrier concentration and temperature region. We also use the Cahill's model to estimate the lattice thermal conductivities at the room temperature. The large Seebeck coefficients, high power factors, and low thermal conductivities make these four orthorhombic IV-VI compounds promising candidates for high-efficient thermoelectric materials.

  2. High-efficient thermoelectric materials: The case of orthorhombic IV-VI compounds

    PubMed Central

    Ding, Guangqian; Gao, Guoying; Yao, Kailun

    2015-01-01

    Improving the thermoelectric efficiency is one of the greatest challenges in materials science. The recent discovery of excellent thermoelectric performance in simple orthorhombic SnSe crystal offers new promise in this prospect [Zhao et al. Nature 508, 373 (2014)]. By calculating the thermoelectric properties of orthorhombic IV-VI compounds GeS,GeSe,SnS, and SnSe based on the first-principles combined with the Boltzmann transport theory, we show that the Seebeck coefficient, electrical conductivity, and thermal conductivity of orthorhombic SnSe are in agreement with the recent experiment. Importantly, GeS, GeSe, and SnS exhibit comparative thermoelectric performance compared to SnSe. Especially, the Seebeck coefficients of GeS, GeSe, and SnS are even larger than that of SnSe under the studied carrier concentration and temperature region. We also use the Cahill's model to estimate the lattice thermal conductivities at the room temperature. The large Seebeck coefficients, high power factors, and low thermal conductivities make these four orthorhombic IV-VI compounds promising candidates for high-efficient thermoelectric materials. PMID:26045338

  3. Antiferroelectric Materials, Applications and Recent Progress on Multiferroic Heterostructures

    NASA Astrophysics Data System (ADS)

    Zhou, Ziyao; Yang, Qu; Liu, Ming; Zhang, Zhiguo; Zhang, Xinyang; Sun, Dazhi; Nan, Tianxiang; Sun, Nianxiang; Chen, Xing

    2015-04-01

    Antiferroelectric (AFE) materials with adjacent dipoles oriented in antiparallel directions have a double polarization hysteresis loops. An electric field (E-field)-induced AFE-ferroelectric (FE) phase transition takes place in such materials, leading to a large lattice strain and energy change. The high dielectric constant and the distinct phase transition in AFE materials provide great opportunities for the realization of energy storage devices like super-capacitors and energy conversion devices such as AFE MEMS applications. Lots of work has been done in this field since 60-70 s. Recently, the strain tuning of the spin, charge and orbital orderings and their interactions in complex oxides and multiferroic heterostructures have received great attention. In these systems, a single control parameter of lattice strain is used to control lattice-spin, lattice-phonon, and lattice-charge interactions and tailor properties or create a transition between distinct magnetic/electronic phases. Due to the large strain/stress arising from the phase transition, AFE materials are great candidates for integrating with ferromagnetic (FM) materials to realize in situ manipulation of magnetism and lattice-ordered parameters by voltage. In this paper, we introduce the AFE material and it's applications shortly and then review the recent progress in AFEs based on multiferroic heterostructures. These new multiferroic materials could pave a new way towards next generation light, compact, fast and energy efficient voltage tunable RF/microwave, spintronic and memory devices promising approaches to in situ manipulation of lattice-coupled order parameters is to grow epitaxial oxide films on FE/ferroelastic substrates.

  4. Spin-driven multiferroics in BaYFeO{sub 4}

    SciTech Connect

    Cong, Jun-Zhuang; Shen, Shi-Peng; Chai, Yi-Sheng; Yan, Li-Qin; Shang, Da-Shan; Wang, Shou-Guo; Sun, Young

    2015-05-07

    We report on the spin-driven multiferroic property and magnetoelectric effect in the lately synthesized compound BaYFeO{sub 4}. Due to its peculiar crystal structure, the system exhibits complex magnetic phases with multiple transitions. The dielectric and pyroelectric measurements evidence a spin-driven multiferroic state raised by the cycloidal spin structure below T{sub 1} = 36 K. Strong magnetoelectric effect has also been observed in the multiferroic state. The origin of noncollinear cycloidal spin structure in BaYFeO{sub 4} is believed to arise from the interactions between low-dimensional magnetic columns.

  5. Striped Multiferroic Phase in Double-Exchange Model for Quarter-Doped Manganites

    SciTech Connect

    Dong, Shuai; Yu, Rong; Liu, J.-M.; Dagotto, Elbio R

    2009-01-01

    The phase diagram of quarter-hole-doped perovskite manganites is investigated using the doubleexchange model. An exotic striped type-II multiferroic phase, where 25% of the nearest-neighbor spin couplings are orthogonal to each other, is found in the narrow-bandwidth region. Comparing with the spiral-spin ordering phase of undoped manganites, the multiferroic Curie temperature of the new phase is estimated to be 4 times higher, while the ferroelectric polarization is similar in magnitude. Our study provides a path for noncollinear spin multiferroics based on electronic self-organization, different from the traditional approach based on superexchange frustration.

  6. Dynamic response in a finite size composite multiferroic thin film

    NASA Astrophysics Data System (ADS)

    Wang, Zidong; Grimson, Malcolm J.

    2016-03-01

    Composite multiferroics, heterostructures of ferromagnetic and ferroelectric materials, are characterized by a remarkable magnetoelectric effect at the interface. Previous work has supported the ferromagnetic structure with magnetic spins and the ferroelectric with pseudospins which act as electric dipoles in a microscopic model, coupled with a magnetoelectric interaction [Wang and Grimson, J. Appl. Phys. 118, 124109 (2015)]. In this work, by solving the stochastic Landau-Lifshitz-Gilbert equation, the electric-field-induced magnetization switching in a twisted boundary condition has been studied, and a behavior of domain wall in the ferromagnetic structure is discussed.

  7. Unfolding of Vortices into Topological Stripes in a Multiferroic Material

    NASA Astrophysics Data System (ADS)

    Wang, X.; Mostovoy, M.; Han, M. G.; Horibe, Y.; Aoki, T.; Zhu, Y.; Cheong, S.-W.

    2014-06-01

    Multiferroic hexagonal RMnO3 (R =rare earths) crystals exhibit dense networks of vortex lines at which six domain walls merge. While the domain walls can be readily moved with an applied electric field, the vortex cores so far have been impossible to control. Our experiments demonstrate that shear strain induces a Magnus-type force pulling vortices and antivortices in opposite directions and unfolding them into a topological stripe domain state. We discuss the analogy between this effect and the current-driven dynamics of vortices in superconductors and superfluids.

  8. Room-Temperature Multiferroic Hexagonal LuFeO3

    SciTech Connect

    Cheng, Xuemei; Balke, Nina; Chi, Miaofang; Gai, Zheng; Keavney, David; Lee, Ho Nyung; Shen, Jian; Snijders, Paul C; Wang, Wenbin; Ward, Thomas Z; Xu, Xiaoshan; Yi, Jieyu; Zhu, Leyi; Christen, Hans M; Zhao, Jun

    2013-01-01

    We observed the coexistence of ferroelectricity and weak ferromagnetism at room temperature in the hexagonal phase of LuFeO3 stabilized by epitaxial thin film growth. While the ferroelectricity in hexagonal LuFeO3 can be understood as arising from its polar structure, the observation of weak ferromagnetism at room temperature is remarkable considering the frustrated triangular spin structure. An explanation of the room temperature weak ferromagnetism is proposed in terms of a subtle lattice distortion revealed by the structural characterization. The combination of ferroelectricity and weak ferromagnetism in epitaxial films at room temperature offers great potential for the application of this novel multiferroic material in next generation devices.

  9. A neutron diffraction study of RMn2O5 multiferroics

    NASA Astrophysics Data System (ADS)

    Radaelli, P. G.; Chapon, L. C.

    2008-10-01

    The magnetic properties of RMn2O5 multiferroics as obtained by unpolarized and polarized neutron diffraction experiments are reviewed. We discuss the qualitative features of the magnetic phase diagram in both zero magnetic field and in field and analyze the commensurate magnetic structure and its coupling to an applied electric field. The origin of ferroelectricity is discussed based on calculations of the ferroelectric polarization predicted by different microscopic coupling mechanisms (exchange-striction and cycloidal spin-orbit models). A minimal model containing a small set of parameters is also presented in order to understand the propagation of the magnetic structure along the c-direction.

  10. Orthorhombic faults system at the onset of the Late Mesozoic-Cenozoic Barents Sea rifting

    NASA Astrophysics Data System (ADS)

    Collanega, Luca; Breda, Anna; Massironi, Matteo

    2016-04-01

    The structures of the Late Mesozoic/Cenozoic Barents Sea rifting have been investigated with multichannel 3D seismics, covering an area of 7700 sqKm in the Hoop Fault Complex, a transitional area between the platform and the marginal basins. The main structural lineaments have been mapped in a time domain 3D surface and their activity ranges have been constrained through the sin-sedimentary thickness variations detected in time-thickness maps. Two main fault systems have been identified: an orthorhombic fault system consisting of two fault sets trending almost perpendicularly one to the other (WNW-ESE and NNE-SSW) and a graben/half-graben system, elongated approximately N-S in the central part of the study area. While the graben/half-graben system can be explained through the theory of Anderson, this landmark theory fails to explain the simultaneous activity of the two fault sets of the orthorhombic system. So far, the models that can better explain orthorhombic fault arrangements are the slip model by Reches (Reches, 1978; Reches, 1983; Reches and Dieterich, 1983) and the odd-axis model by Krantz (Krantz, 1988). However, these models are not definitive and a strong quest to better understand polymodal faulting is actual (Healy et al., 2015). In the study area, the presence of both a classical Andersonian and an orthorhombic system indicates that these models are not alternative but are both effective and necessary to explain faulting in different circumstances. Indeed, the Andersonian plain strain and the orthorhombic deformation have affected different part of the succession during different phases of the rifting. In particular, the orthorhombic system has affected only the Late Mesozoic-Cenozoic interval of the succession and it was the main active system during the initial phase of the rifting. On the other hand, the graben/half-graben system has affected the whole sedimentary succession, with an increasing activity during the development of the rifting. It has

  11. Large magnetoelectric response in multiferroic polymer-based composites

    NASA Astrophysics Data System (ADS)

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

    2005-01-01

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

  12. Electric-field control of magnetism in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Zhao, Yonggang; Zhang, Sen; Li, Peisen; Chen, Aitian; Li, Dalai; Yang, Lifeng; Rizwan, S.; Liu, Y.; Xiao, Xia; Wu, Yizheng; Jin, Xiaofeng; Han, Xiufeng; Zhang, Huiyun; Zhu, Meihong

    2015-03-01

    We have studied electric-field control of magnetism in different multiferroic heterostructures, composed of ferromagnetic (FM) and ferroelectric (FE) materials such as Co40Fe40B20(CoFeB)/Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) and magnetic tunnel junctions (MTJ) on PMN-PT, etc. A giant electric-field control of magnetization as well as magnetic anisotropy was observed in a CoFeB/PMN-PT structure at room temperature with a maximum relative magnetization change up to 83 percent and a 90° rotation of the easy axis. In MTJ of CoFeB/AlOx/CoFeB grown on PMN-PT, we demonstrate a reversible, continuous magnetization rotation and manipulation of tunneling magnetoresistance at room temperature by electric fields without the assistance of a magnetic field. These results show the interesting new physics and potential applications of the FM/FE multiferroic heterostructures.

  13. One-way electromagnetic waveguide using multiferroic Fibonacci superlattices

    NASA Astrophysics Data System (ADS)

    Tang, Zhenghua; Lei, Dajun; Huang, Jianquan; Jin, Gui; Qiu, Feng; Yan, Wenyan

    2015-12-01

    The multiferroic Fibonacci superlattices (MFSs) are composed of single-phase multiferroic domains with polarization and magnetization according to the rule of Fibonacci sequence. We propose to construct a one-way electromagnetic waveguide by the MFSs. The forbidden band structures of the MFSs for the forward and backward electromagnetic waves are not completely overlapped, and an obvious translation between them occurs around the fixed point ω bar = 1 with broken time-reversal and space inversion symmetries (TRSIS), which indicates the existence of one-way electromagnetic modes in the MFSs. Transmission spectrum is utilized to present this property and to indicate further one-way electromagnetic modes lying within the polaritonic band gap. The maximum forbidden bandwidth (divided by midgap frequency) of 5.4% for the backward electromagnetic wave (BEW) is found, in which the forward electromagnetic wave (FEW) can pass. The functions of one-way propagation modes and polaritonic band gap integrated into the MFSs can miniaturize the one-way photonic devices. The properties can also be applied to construct compact microwave isolators.

  14. Photocatalytic water splitting for hydrogen generation on cubic, orthorhombic, and tetragonal KNbO3 microcubes

    NASA Astrophysics Data System (ADS)

    Zhang, Tingting; Zhao, Kun; Yu, Jiaguo; Jin, Jian; Qi, Yang; Li, Huiquan; Hou, Xinjuan; Liu, Gang

    2013-08-01

    Potassium niobate (KNbO3) microcubes with orthorhombic and tetragonal phases were hydrothermally prepared and characterized by powder X-ray diffraction, nitrogen adsorption-desorption, micro-Raman spectroscopy, Fourier transform infrared spectroscopy, diffuse reflectance UV-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The photoreactivity of the as-prepared KNbO3 samples was evaluated regarding the hydrogen evolution from aqueous methanol under UV, and the results were compared with that of cubic KNbO3 microcubes. The photocatalytic reactivity was shown to be phase-dependent, following the order cubic > orthorhombic > tetragonal. Insight into the phase-dependent photocatalytic properties was gained by first-principles density functional calculations. The best photocatalytic performance of cubic KNbO3 is ascribed to it having the highest symmetry in the bulk structure and associated unique electronic structure. Further, the surface electronic structure plays a key role leading to the discrepancy in photoreactivity between orthorhombic and tetragonal KNbO3. The results from this study are potentially applicable to a range of perovskite-type mixed metal oxides useful in water splitting as well as other areas of heterogeneous photocatalysis.Potassium niobate (KNbO3) microcubes with orthorhombic and tetragonal phases were hydrothermally prepared and characterized by powder X-ray diffraction, nitrogen adsorption-desorption, micro-Raman spectroscopy, Fourier transform infrared spectroscopy, diffuse reflectance UV-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The photoreactivity of the as-prepared KNbO3 samples was evaluated regarding the hydrogen evolution from aqueous methanol under UV, and the results were compared with that of cubic KNbO3 microcubes. The photocatalytic reactivity was

  15. CoFe2/Al2O3/PMNPT multiferroic heterostructures by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Zhou, Ziyao; Grocke, Garrett; Yanguas-Gil, Angel; Wang, Xinjun; Gao, Yuan; Sun, Nianxiang; Howe, Brandon; Chen, Xing

    2016-05-01

    Multiferroic materials and applications allow electric bias control of magnetism or magnetic bias control of polarization, enabling fast, compact, energy-efficient devices in RF/microwave communication systems such as filters, shifters, and antennas; electronics devices such as inductors and capacitors; and other magnetic material related applications including sensors and memories. In this manuscript, we utilize atomic layer deposition technology to grow magnetic CoFe metallic thin films onto PMNPT, with a ˜110 Oe electric field induced ferromagnetic resonance field shift in the CoFe/Al2O3/PMNPT multiferroic heterostructure. Our work demonstrates an atomic layer deposition fabricated multiferroic heterostructure with significant tunability and shows that the unique thin film growth mechanism will benefit integrated multiferroic application in near future.

  16. Thermodynamics of multicaloric effects in multiferroic materials: application to metamagnetic shape-memory alloys and ferrotoroidics.

    PubMed

    Planes, Antoni; Castán, Teresa; Saxena, Avadh

    2016-08-13

    We develop a general thermodynamic framework to investigate multicaloric effects in multiferroic materials. This is applied to the study of both magnetostructural and magnetoelectric multiferroics. Landau models with appropriate interplay between the corresponding ferroic properties (order parameters) are proposed for metamagnetic shape-memory and ferrotoroidic materials, which, respectively, belong to the two classes of multiferroics. For each ferroic property, caloric effects are quantified by the isothermal entropy change induced by the application of the corresponding thermodynamically conjugated field. The multicaloric effect is obtained as a function of the two relevant applied fields in each class of multiferroics. It is further shown that multicaloric effects comprise the corresponding contributions from caloric effects associated with each ferroic property and the cross-contribution arising from the interplay between these ferroic properties.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  17. Magnetic switching of ferroelectric domains at room temperature in multiferroic PZTFT

    PubMed Central

    Evans, D.M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Arredondo, M.; Katiyar, R.S.; Gregg, J.M.; Scott, J.F.

    2013-01-01

    Single-phase magnetoelectric multiferroics are ferroelectric materials that display some form of magnetism. In addition, magnetic and ferroelectric order parameters are not independent of one another. Thus, the application of either an electric or magnetic field simultaneously alters both the electrical dipole configuration and the magnetic state of the material. The technological possibilities that could arise from magnetoelectric multiferroics are considerable and a range of functional devices has already been envisioned. Realising these devices, however, requires coupling effects to be significant and to occur at room temperature. Although such characteristics can be created in piezoelectric-magnetostrictive composites, to date they have only been weakly evident in single-phase multiferroics. Here in a newly discovered room temperature multiferroic, we demonstrate significant room temperature coupling by monitoring changes in ferroelectric domain patterns induced by magnetic fields. An order of magnitude estimate of the effective coupling coefficient suggests a value of ~1 × 10−7 sm−1. PMID:23443562

  18. Multiferroic properties of stretchable BiFeO3 nano-composite film

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Cho, J. Y.; Park, S. Y.; Yoo, Y. J.; Yoo, P. S.; Lee, B. W.; Lee, Y. P.

    2015-02-01

    We present a simple drop-casting method for preparing multiferroic nano-composite film where BiFeO3 (BFO) nanoparticles (NPs) were evenly dispersed into polyvinyl alcohol (PVA) polymer. BFO NPs used in this work were synthesized by the conventional sol-gel method, having diameter of tens of nm and being in good crystallinity. The BFO NPs were loaded into a highly insulating PVA polymer solution as filler. The multiferroic properties of the film reveal ferromagnetic ordering due to the uncompensated spiral ordering and saturated ferroelectric curves due to the cut-off of current leakage. Moreover, the prepared films show high flexibility and their multiferroicities are preserved well even in a high curved condition, reflecting the possibility for fabricating wearable devices based on multiferroic materials.

  19. Designing room-temperature multiferroic materials in a single-phase solid-solution film

    NASA Astrophysics Data System (ADS)

    Mao, H. J.; Song, C.; Cui, B.; Peng, J. J.; Li, F.; Xiao, L. R.; Pan, F.

    2016-09-01

    The search for multiferroic materials with simultaneous ferroelectric and ferromagnetic properties in a single phase at room temperature continues to be fuelled from the perspective of developing multifunctional devices. Here we design a single-phase multiferroic La0.67Sr0.33MnO3-BaTiO3 film, which possesses epitaxial single-crystal and solid-solution structure, high magnetic Curie temperature (~640 K) as well as switchable ferroelectric polarization. Moreover, a notable strain-mediated magnetoelectric coupling at room temperature in the way of modulating the magnetism with an external applied voltage is also observed. The synthetic solid-solution multiferroic film may open an extraordinary avenue for exploring a series of room-temperature multiferroic materials.

  20. James C. McGroddy Prize for New Materials Talk: A theorist's-eye view of multiferroics

    NASA Astrophysics Data System (ADS)

    Spaldin, Nicola

    2010-03-01

    I will summarize the evolution of the field of multiferroics -- that is materials that show multiple simultaneous ferroic orderings -- since their ``renaissance'' in the late 1990s. In particular, I will illustrate how first-principles electronic structure calculations have contributed to progress in the field, and conversely, how fascinating questions in multiferroics have prompted the development of improved electronic structure methods. Finally I will share my ideas on the most exciting open problems and emerging directions in multiferroics and beyond.

  1. Mutual Ferromagnetic-Ferroelectric Coupling in Multiferroic Copper Doped ZnO

    SciTech Connect

    Herng, T.S.; Sanchez-Hanke, C.; Wong, M.F.; Qi, D.; Yi, J.; Kumar, A.; Huang, A.; Kartawidjaja, F.C.; Smadici, S.; Abbamonte, P.; Shannigraphi, S.; Xue, J.M.; Wang, J.; Feng, Y.P.; Rusydi, A.; Zeng, K.; Ding, J.

    2011-01-01

    A mutual ferromagnetic and ferroelectric coupling (multiferroic behavior) in Cu-doped ZnO is demonstrated via deterministic control of Cu doping and defect engineering. The coexistence of multivalence Cu ions and oxygen vacancies is important to multiferroic behaviors in ZnO:Cu. The samples show clear ferroelectric and ferromagnetic domain patterns. These domain structures may be written reversibly via electric and magnetic bias.

  2. Mueller matrix ellipsometry studies of the optical phonons and crystal field excitations in multiferroic orthoferrites RFeO3 (R=Tb,Dy)

    NASA Astrophysics Data System (ADS)

    Martinez, V. A.; Stanislavchuk, T. N.; Sirenko, A. A.; Litvinchuk, A. P.; Wang, Yazhong; Cheong, S. W.

    Optical properties of multiferroic orthoferrites RFeO3 (R=Tb,Dy) bulk crystals have been studied in the far-infrared range from 50 to 1000 cm-1 and temperatures from 7 K to 300 K. Mueller matrix and rotating analyzer ellipsometry measurements were carried out at the U4IR beamline of the National Synchrotron Light Source at Brookhaven National Lab. Optical phonon spectra and crystal field excitations were measured for all three orthorhombic axes of RFeO3. In the experimental temperature dependencies of the phonon frequencies we found non-Grüneisen behavior caused by the electron-phonon and spin-phonon interactions. We determined the symmetries and selection rules for the crystal field transitions in Tb3+ and Dy3+ ions. Magnetic field dependencies of the optical spectra allowed us to determine anisotropy of the crystal field g-factors for Tb3+ and Dy3+ ions. This Project is supported by collaborative DOE Grant DE-FG02-07ER46382 between Rutgers U. and NJIT. Use of NSLS-BNL was supported by DOE DE-AC02-98CH10886. V.A. Martinez was supported by NEU NSF-1343716.

  3. 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.

  4. 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.

  5. The Solubility of Orthorhombic Lysozyme Crystals Obtained at High pH

    SciTech Connect

    Aldabaibeh, Naser; Jones, Matthew J.; Myerson, Allan S.; Ulrich, Joachim

    2009-07-06

    The high pH region of the phase diagram of lysozyme with NaCl as a precipitant was determined. In this region of the phase diagram, lysozyme crystallizes in one of two different orthorhombic modifications, the low and high temperature orthorhombic modifications. The solubility of two modifications was measured at different temperatures, pH values, and NaCl concentrations. Both modifications show a similar dependence on the solution conditions where solubility increases with temperature and decreases with pH and NaCl concentration. The transition temperature between the two modifications was determined from the solubility curves and was shown to increase with pH and NaCl concentration. At pH values close to the isoelectric point (pH 11), the transition temperature becomes independent of NaCl concentration.

  6. On the relative stability of orthorhombic and hcp phases of beryllium at high pressures

    NASA Astrophysics Data System (ADS)

    Palanivel, B.; Rao, R. S.; Godwal, B. K.; Sikka, S. K.

    2000-10-01

    High-pressure electronic properties of Be have been investigated theoretically by means of ab initio electronic structure calculations. The calculations have been carried out by the semi-relativistic full-potential, linear muffin-tin orbital (FPLMTO) method, within the local density approximation. The crystal structure stability among the hcp, bcc and orthorhombic (distorted hcp) phases has been studied as a function of compression. The bcc structure is found to be energetically stable at pressures above 180 GPa. From the results of our calculations, the orthorhombic phase cannot occur as an intermediate phase between the ambient pressure hcp phase and the high-pressure bcc structure. Our work thus suggests the need for more accurate high-pressure x-ray data.

  7. Superconductivity in MgPtSi: An orthorhombic variant of MgB2

    NASA Astrophysics Data System (ADS)

    Kudo, Kazutaka; Fujimura, Kazunori; Onari, Seiichiro; Ota, Hiromi; Nohara, Minoru

    2015-05-01

    A ternary compound, MgPtSi, was synthesized by solid-state reaction. An examination of the compound by powder x-ray diffraction revealed that it crystallizes in the orthorhombic TiNiSi-type structure with the P n m a space group. The structure comprises alternately stacked layers of Mg and PtSi honeycomb network, which is reminiscent of MgB2, and the buckling of the honeycomb network causes orthorhombic distortion. Electrical and magnetic studies revealed that MgPtSi exhibited superconductivity with a transition temperature of 2.5 K. However, its isostructural compounds, namely, MgRhSi and MgIrSi, were not found to exhibit superconductivity.

  8. Spontaneous Ferroelectric Order in a Bent-Core Smectic Liquid Crystal of Fluid Orthorhombic Layers

    SciTech Connect

    R Reddy; C Zhu; R Shao; E Korblova; T Gong; Y Shen; M Glaser; J Maclennan; D Walba; N Clark

    2011-12-31

    Macroscopic polarization density, characteristic of ferroelectric phases, is stabilized by dipolar intermolecular interactions. These are weakened as materials become more fluid and of higher symmetry, limiting ferroelectricity to crystals and to smectic liquid crystal stackings of fluid layers. We report the SmAP{sub F}, the smectic of fluid polar orthorhombic layers that order into a three-dimensional ferroelectric state, the highest-symmetry layered ferroelectric possible and the highest-symmetry ferroelectric material found to date. Its bent-core molecular design employs a single flexible tail that stabilizes layers with untilted molecules and in-plane polar ordering, evident in monolayer-thick freely suspended films. Electro-optic response reveals the three-dimensional orthorhombic ferroelectric structure, stabilized by silane molecular terminations that promote parallel alignment of the molecular dipoles in adjacent layers.

  9. The variability residual stresses of thick superconductor films during orthorhombic to tetragonal transformation

    SciTech Connect

    Wu, W.; Danyluk, S.; Lanagan, M.T.; Poeppel, R.B.

    1992-04-01

    YBa{sub 2}Cu{sub 3}O{sub x} thick films have been deposited by spray pyrolysis of a sol-gel on 10 cm diameter polycrystalline MgO wafers. The film thickness was built up in layers of approximately 1 {mu}m thick. The in-plane residual stresses were measured by an optical interferometry (shadow moire) method as a function of film structure. In-plane residual stress maps over the area of the wafer have been obtained. The average stress of the 5 {mu}m orthorhombic phase was 0.84 GPa. As the film transforms from the orthorhombic to the tetragonal structure, the tensile stresses decreased by 0.5 GPa.

  10. The variability residual stresses of thick superconductor films during orthorhombic to tetragonal transformation

    SciTech Connect

    Wu, W.; Danyluk, S. . Dept. of Civil Engineering, Mechanics, and Metallurgy); Lanagan, M.T.; Poeppel, R.B. )

    1992-01-01

    YBa{sub 2}Cu{sub 3}O{sub x} thick films have been deposited by spray pyrolysis of a sol-gel on 10 cm diameter polycrystalline MgO wafers. The film thickness was built up in layers of approximately 1 {mu}m thick. The in-plane residual stresses were measured by an optical interferometry (shadow moire) method as a function of film structure. In-plane residual stress maps over the area of the wafer have been obtained. The average stress of the 5 {mu}m orthorhombic phase was 0.84 GPa. As the film transforms from the orthorhombic to the tetragonal structure, the tensile stresses decreased by 0.5 GPa.

  11. Lattice dynamics of proton conductor SrZrO{sub 3} in orthorhombic phase

    SciTech Connect

    Sharma, Anupam Deep; Sinha, M. M.

    2014-04-24

    In the this paper, we are presenting the results of our theoretical investigation on the zone centre phonon frequencies and phonon dispersion relation of SrZrO{sub 3} in its orthorhombic phase by using lattice dynamical simulation method based on short range force constant model to understand the role of phonon in this system. The calculations involves interatomic force constants upto third neighbour. The calculated zone centre phonon frequencies in Raman mode, agrees well with available existing results.

  12. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, M.M.; Peng, M.Y.; Ma, Y.; Visco, S.J.; DeJonghe, L.C.

    1996-09-24

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M{sub x}Z{sub y}Mn{sub (1{minus}y)}O{sub 2}, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell. 11 figs.

  13. Stabilization of orthorhombic phase in single-crystal ZnSnN2 films

    NASA Astrophysics Data System (ADS)

    Senabulya, Nancy; Feldberg, Nathaniel; Makin, Robert. A.; Yang, Yongsoo; Shi, Guangsha; Jones, Christina M.; Kioupakis, Emmanouil; Mathis, James; Clarke, Roy; Durbin, Steven M.

    2016-07-01

    We report on the crystal structure of epitaxial ZnSnN2 films synthesized via plasma-assisted vapor deposition on (111) yttria stabilized zirconia (YSZ) and (001) lithium gallate (LiGaO2) substrates. X-ray diffraction measurements performed on ZnSnN2 films deposited on LiGaO2 substrates show evidence of single-crystal, phase-pure orthorhombic structure in the Pn21a symmetry [space group (33)], with lattice parameters in good agreement with theoretically predicted values. This Pn21a symmetry is imposed on the ZnSnN2 films by the LiGaO2 substrate, which also has orthorhombic symmetry. A structural change from the wurtzite phase to the orthorhombic phase in films grown at high substrate temperatures ˜550°C and low values of nitrogen flux ˜10-5 Torr is observed in ZnSnN2 films deposited on YSZ characterized by lattice contraction in the basal plane and a 5.7% expansion of the out-of-plane lattice parameter.

  14. High temperature far-infrared dynamics of orthorhombic NdMnO3: emissivity and reflectivity.

    PubMed

    Massa, Néstor E; del Campo, Leire; Meneses, Domingos De Sousa; Echegut, Patrick; Martínez-Lope, María Jesús; Alonso, José Antonio

    2013-06-12

    We report on near normal far- and mid-infrared emission and reflectivity of NdMnO3 perovskite from room temperature to sample decomposition above 1800 K. At 300 K the number of infrared active phonons is in close agreement with the 25 calculated for the orthorhombic D(2h)(16)-Pbnm (Z = 4) space group. Their number gradually decreases as we approach the temperature of orbital disorder at ~1023 K where the orthorhombic O' lower temperature cooperative phase coexists with the cubic orthorhombic O. At above ~1200 K, the three infrared active phonons coincide with that expected for cubic Pm-3m (Z = 1) in the high temperature insulating regime. Heating samples in dry air triggers double exchange conductivity by Mn(3+) and Mn(4+) ions and a small polaron mid-infrared band. Fits to the optical conductivity single out the octahedral antisymmetric and symmetric vibrational modes as the main phonons in the electron-phonon interactions at 875 K. For 1745 K, it is enough to consider the symmetric stretching internal mode. An overdamped defect induced Drude component is clearly outlined at the highest temperatures. We conclude that rare earth manganite eg electrons are prone to spin, charge, orbital, and lattice couplings in an intrinsic orbital distorted perovskite lattice, favoring embryonic low energy collective excitations.

  15. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, Marca M.; Peng, Marcus Y.; Ma, Yanping; Visco, Steven J.; DeJonghe, Lutgard C.

    1996-01-01

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M.sub.x Z.sub.y Mn.sub.(1-y) O.sub.2, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell.

  16. Electrically Controllable Spontaneous Magnetism in Nanoscale Mixed Phase Multiferroics

    SciTech Connect

    He, Q.; Chu, Y. H.; Heron, J. T.; Yang, S. Y.; Wang, C. H.; Kuo, C. Y.; Lin, H. J.; Yu, P.; Liang, C. W.; Zeches, R. J.; Chen, C. T.; Arenholz, E.; Scholl, A.; Ramesh, R.

    2010-08-02

    The emergence of enhanced spontaneous magnetic moments in self-assembled, epitaxial nanostructures of tetragonal (T-phase) and rhombohedral phases (R-phase) of the multiferroic BiFeO{sub 3} system is demonstrated. X-ray magnetic circular dichroism based photoemission electron microscopy (PEEM) was applied to investigate the local nature of this magnetism. We find that the spontaneous magnetization of the R-phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent T-phase and the epitaxial constraint. Reversible electric field control and manipulation of this magnetic moment at room temperature is shown using a combination of piezoresponse force microscopy and PEEM studies.

  17. Separating read and write units in multiferroic devices

    PubMed Central

    Roy, Kuntal

    2015-01-01

    Strain-mediated multiferroic composites, i.e., piezoelectric-magnetostrictive heterostructures, hold profound promise for energy-efficient computing in beyond Moore’s law era. While reading a bit of information stored in the magnetostrictive nanomagnets using a magnetic tunnel junction (MTJ), a material selection issue crops up since magnetostrictive materials in general cannot be utilized as the free layer of the MTJ. This is an important issue since we need to achieve a high magnetoresistance for technological applications. We show here that magnetically coupling the magnetostrictive nanomagnet and the free layer e.g., utilizing the magnetic dipole coupling between them can circumvent this issue. By solving stochastic Landau-Lifshitz-Gilbert equation of magnetization dynamics in the presence of room-temperature thermal fluctuations, we show that such design can eventually lead to a superior energy-delay product. PMID:26086736

  18. Separating read and write units in multiferroic devices.

    PubMed

    Roy, Kuntal

    2015-01-01

    Strain-mediated multiferroic composites, i.e., piezoelectric-magnetostrictive heterostructures, hold profound promise for energy-efficient computing in beyond Moore's law era. While reading a bit of information stored in the magnetostrictive nanomagnets using a magnetic tunnel junction (MTJ), a material selection issue crops up since magnetostrictive materials in general cannot be utilized as the free layer of the MTJ. This is an important issue since we need to achieve a high magnetoresistance for technological applications. We show here that magnetically coupling the magnetostrictive nanomagnet and the free layer e.g., utilizing the magnetic dipole coupling between them can circumvent this issue. By solving stochastic Landau-Lifshitz-Gilbert equation of magnetization dynamics in the presence of room-temperature thermal fluctuations, we show that such design can eventually lead to a superior energy-delay product.

  19. High-temperature scintillation properties of orthorhombic Gd2Si2O7 aiming at well logging

    NASA Astrophysics Data System (ADS)

    Tsubota, Youichi; Kaneko, Junichi H.; Higuchi, Mikio; Nishiyama, Shusuke; Ishibashi, Hiroyuki

    2015-06-01

    Scintillation and luminescence properties of orthorhombic Gd2Si2O7:Ce (GPS:Ce) single-crystal scintillators were investigated for temperatures ranging from room temperature (RT) to 573 K. Orthorhombic GPS crystals were grown by using a top-seeded solution growth (TSSG) method. The scintillation light yield of the orthorhombic GPS at RT was ∼2.9 times higher than that of Gd2SiO5:Ce (GSO). The light yield values of the orthorhombic GPS (Ce = 2.5%) were almost unchanged for temperatures ranging from RT to 523 K, and at 523 K, were higher than twice the light yield of GSO at RT. These GPS scintillators are expected to contribute to oil exploration at greater depths.

  20. Thermal conductivity and multiferroics of electroactive polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Jin, Jiezhu

    Electronically conducting polymers and electromechanical polymers are the two important branches of the cutting-edge electroactive polymers. They have shown significant impact on many modern technologies such as flat panel display, energy transport, energy conversion, sensors and actuators. To utilize conducting polymers in microelectronics, optoelectronics and thermoelectrics, it is necessary to have a comprehensive study of their thermal conductivity since thermal conductivity is a fundamental materials property that is particularly important and sometimes a determining factor of the device performance. For electromechanical polymers, larger piezoelectric effect will contribute to the improvement of magnetoelectric (ME) coupling efficiency in their multiferroic composites. This dissertation is devoted to characterizing electronically conducting polymers for their electrical and thermal conductivity, and developing new classes of electromechanical polymers and strain-mediated electromechanical polymer-based multiferroic ME composites. Conducting polymers opened up new possibilities for devices combining novel electrical and thermal properties, but there has been limited understanding of the length-scale effect of the electrical and thermal conductivity, and the mechanism underlying the electricity and heat transport behavior. In this dissertation, the analytical model and experimental technique are presented to measure the in-plane thermal conductivity of polyaniline thin films. For camphorsulfonic acid doped polyaniline patterned on silicon oxide/silicon substrate using photolithography and reactive ion etching, the thermal conductivity of the film with thickness of 20 nm is measured to be 0.0406 W/m˙K, which significantly deviates from their bulk (> 0.26 W/m˙K). The size effect on thermal conductivity at this scale is attributed to the significant phonon boundary scattering. When the film goes up to 130 nm thick, the thermal conductivity increases to 0.166 W

  1. Observation of lattice defects in orthorhombic hen-egg white lysozyme crystals with laser scattering tomography

    NASA Astrophysics Data System (ADS)

    Sato, K.; Fukuba, Y.; Mitsuda, T.; Hirai, K.; Moriya, K.

    1992-08-01

    The effectivity of using laser scattering tomography (LST) as a nondestructive technique for finding lattice defects in protein crystals is demonstrated using an orthorhombic egg-white lysozyme crystal grown by a batch method. It was found that LST figures could be observed from the crystal portions where no defects were detectable by the naked eye or optical microscopy; the number of microdefects revealed in the LST patterns increased on approaching the crystal surface. Two types of defects were differentiated by polarization analysis: (1) point-type defects, assumed to be microdefects such as vacancies, precipitates, or impurities, and (2) bulk-type defects, assumed to correspond to inclusions.

  2. 93Nb Nuclear Quadrupole Resonance in Orthorhombic Phase of Niobium Pentabromide

    NASA Astrophysics Data System (ADS)

    Okubo, Noriaki; Abe, Yoshihito

    1982-05-01

    The 93Nb NQR has been investigated in one phase of NbBr5 which was identified to be orthorhombic by the X-ray analysis. The resonance frequencies have been measured between 4.2 K and 423 K, its melting point. The coupling constant showed a positive temperature dependence up to melting point. The temperature dependence of the coupling constant is compared between NbBr5 and NbCl5 from the view point of π-bond character.

  3. Temperature and Pressure Sensors Based on Spin-Allowed Broadband Luminescence of Doped Orthorhombic Perovskite Structures

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I. (Inventor); Chambers, Matthew D. (Inventor)

    2014-01-01

    Systems and methods that are capable of measuring pressure or temperature based on luminescence are discussed herein. These systems and methods are based on spin-allowed broadband luminescence of sensors with orthorhombic perovskite structures of rare earth aluminates doped with chromium or similar transition metals, such as chromium-doped gadolinium aluminate. Luminescence from these sensors can be measured to determine at least one of temperature or pressure, based on either the intense luminescence of these sensors, even at high temperatures, or low temperature techniques discussed herein.

  4. Room temperature multiferroic properties and magnetoelectric coupling in Sm and Ni substituted Bi{sub 4−x}Sm{sub x}Ti{sub 3−x}Ni{sub x}O{sub 12±δ} (x = 0, 0.02, 0.05, 0.07) ceramics

    SciTech Connect

    Paul, Joginder Bhardwaj, Sumit; Sharma, K. K.; Kotnala, R. K.; Kumar, Ravi

    2014-05-28

    Lead free multiferroic Bi{sub 4−x}Sm{sub x}Ti{sub 3−x}Ni{sub x}O{sub 12±δ} (x = 0.02, 0.05, and 0.07) samples have been synthesized by conventional solid state route. X-ray diffraction analysis reveals single phase up to x = 0.07, and a secondary phase appears at x > 0.07. Raman spectroscopy confirms the local distortions in the crystal. Field emission scanning electron microscopy shows plate like grains. Substitution has increased the orthorhombic distortion, grain size, and hence the ferroelectric transition temperature (T{sub c}). A significant reduction in the values of dielectric constant (ε′) and loss tangent (tan δ) has been observed with the increase of Sm and Ni ions. The increase in dc resistivity at room temperature has been found with substitution. Enhancement in the values of remnant polarization (2P{sub r}) and magnetization (2M{sub r}) is observed. Magnetoelectric coupling coefficient (α) values of 0.60 mV/cm/Oe are achieved in Bi{sub 4−x}Sm{sub x}Ti{sub 3−x}Ni{sub x}O{sub 12±δ} ceramic samples. Hence, we have successfully converted the ferroelectric Bi{sub 4}Ti{sub 3}O{sub 12} into a multiferroic, which is a new lead free multiferroic material, can be useful for future electromagnetic devices.

  5. Surface morphology of orthorhombic Mo2C catalyst and high coverage hydrogen adsorption

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Tian, Xinxin; Yang, Yong; Li, Yong-Wang; Wang, Jianguo; Beller, Matthias; Jiao, Haijun

    2016-09-01

    High coverage hydrogen adsorption on twenty two terminations of orthorhombic Mo2C has been systematically studied by using density functional theory and ab initio thermodynamics. Hydrogen stable coverage on the surfaces highly depends on temperatures and H2 partial pressure. The estimated hydrogen desorption temperatures under ultra-high vacuum condition on Mo2C are in reasonable agreement with the available temperature-programmed desorption data. Obviously, hydrogen adsorption can affect the surface stability and therefore modify the surface morphology of Mo2C. Upon increasing the chemical potential of hydrogen which can be achieved by increasing the H2 partial pressure and/or decreasing the temperature, the proportions of the (001), (010), (011) and (100) surfaces increase, while those of the (101), (110) and (111) surfaces decrease. Among these surfaces, the (100) surface is most sensitive upon hydrogen adsorption and the (111) surface is most exposed under a wide range of conditions. Our study clearly reveals the role of hydrogen on the morphology of orthorhombic Mo2C catalyst in conjugation with hydro-treating activity.

  6. Electron paramagnetic resonance identification of the orthorhombic iron-indium pair in silicon

    NASA Astrophysics Data System (ADS)

    Gehlhoff, W.; Emanuelsson, P.; Omling, P.; Grimmeiss, H. G.

    1990-04-01

    A different EPR spectrum (Lu4) in silicon doped with indium and iron is reported together with an EPR spectrum previously observed by Ludwig and Woodbury. The two spectra show orthorhombic symmetry and are found to originate from the same FeIn pair. They are explained as transitions within the two Kramers doublets of an S=3/2 system with a zero-field splitting which is very large compared with the microwave energy. The ratio between the orthorhombic and axial fine-structure parameters is determined to be E/D=0.052, and the g values of the defect were found to be gz=2.09, gy=2.05, and gx=2.07(z∥<100>, and x,y∥<110>). The temperature dependence of the intensities of both spectra shows that the lower doublet corresponds to Lu4 and the upper one to the previously observed spectrum. Contrary to what has hitherto been believed, this observation implies that the axial fine-structure parameter has the same sign for the iron-indium pair as for the iron-aluminum and iron-gallium pairs.

  7. Combining intra- and intermolecular charge-transfer: a new strategy towards molecular ferromagnets and multiferroics.

    PubMed

    Di Maiolo, Francesco; Sissa, Cristina; Painelli, Anna

    2016-01-21

    Organic ferroelectric materials are currently a hot research topic, with mixed stack charge transfer crystals playing a prominent role with their large, electronic-in-origin polarization and the possibility to tune the transition temperature down to the quantum limit and/or to drive the ferroelectric transition via an optical stimulus. By contrast, and in spite of an impressive research effort, organic ferromagnets are rare and characterized by very low transition temperatures. Coexisting magnetic and electric orders in multiferroics offer the possibility to control magnetic (electric) properties by an applied electric (magnetic) field with impressive technological potential. Only few examples of multiferroics are known today, based on inorganics materials. Here we demonstrate that, by decorating mixed stack charge transfer crystals with organic radicals, a new family of robust molecular ferromagnets can be designed, stable up to ambient temperature, and with a clear tendency towards multiferroic behaviour.

  8. Voltage control of the magnetic coercive field: Multiferroic coupling or artifact?

    NASA Astrophysics Data System (ADS)

    Vopsaroiu, M.; Cain, M. G.; Woolliams, P. D.; Weaver, P. M.; Stewart, M.; Wright, C. D.; Tran, Y.

    2011-03-01

    The ability to dynamically tune the coercive field of magnetic thin films is a powerful tool for applications, including in magnetic recording disk technologies. Recently, a number of papers have reported the electrical voltage control of the coercive field of various magnetic thin films in multiferroic composites. Theoretically, this is possible in magneto-electric (ME) multiferroics due to the piezoferroelectric component that can be electrically activated to dynamically modify the properties of the magnetic component of the composite via a direct or strain mediated ME coupling. In this paper we fabricated and examined such structures and we determined that the magnetic coercive field reduction is most likely due to a heating effect. We concluded that this effect is probably an artifact that cannot be attributed to a multiferroic coupling.

  9. Combining intra- and intermolecular charge-transfer: a new strategy towards molecular ferromagnets and multiferroics

    PubMed Central

    Di Maiolo, Francesco; Sissa, Cristina; Painelli, Anna

    2016-01-01

    Organic ferroelectric materials are currently a hot research topic, with mixed stack charge transfer crystals playing a prominent role with their large, electronic-in-origin polarization and the possibility to tune the transition temperature down to the quantum limit and/or to drive the ferroelectric transition via an optical stimulus. By contrast, and in spite of an impressive research effort, organic ferromagnets are rare and characterized by very low transition temperatures. Coexisting magnetic and electric orders in multiferroics offer the possibility to control magnetic (electric) properties by an applied electric (magnetic) field with impressive technological potential. Only few examples of multiferroics are known today, based on inorganics materials. Here we demonstrate that, by decorating mixed stack charge transfer crystals with organic radicals, a new family of robust molecular ferromagnets can be designed, stable up to ambient temperature, and with a clear tendency towards multiferroic behaviour. PMID:26790963

  10. Evidence for room temperature electric polarization in RMn(2)O(5) multiferroics.

    PubMed

    Balédent, V; Chattopadhyay, S; Fertey, P; Lepetit, M B; Greenblatt, M; Wanklyn, B; Saouma, F O; Jang, J I; Foury-Leylekian, P

    2015-03-20

    It is established that the multiferroics RMn(2)O(5) crystallize in the centrosymmetric Pbam space group and that the magnetically induced electric polarization appearing at low temperature is accompanied by a symmetry breaking. However, both our present x-ray study-performed on compounds with R=Pr,Nd,Gd,Tb, and Dy-and first-principles calculations unambiguously rule out this picture. Based on structural refinements, geometry optimization, and physical arguments, we demonstrate in this Letter that the actual space group is likely to be Pm. This turns out to be of crucial importance for RMn(2)O(5) multiferroics since Pm is not centrosymmetric. Ferroelectricity is thus already present at room temperature, and its enhancement at low temperature is a spin-enhanced process. This result is also supported by direct observation of optical second harmonic generation. This fundamental result calls into question the actual theoretical approaches that describe the magnetoelectric coupling in this multiferroic family.

  11. Phonon excitations and magnetoelectric coupling in multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  12. Electrical control of antiferromagnetic domains in multiferroicBiFeO3 film at room temperature

    SciTech Connect

    Zhao, T.; Scholl, A.; Zavaliche, F.; Lee, K.; Barry, M.; Doran,A.; Cruz, M.P.; Chu, Y.H.; Ederer, C.; Spaldin, N.A.; Das, R.R.; Kim,D.M.; Baek, S.H.; Eom, C.B.; Ramesh, R.

    2006-09-11

    Multiferroic materials, which offer the possibility ofmanipulating the magnetic state by an electric field or vice versa, areof great current interest. In this work, we demonstrate the firstobservation of electrical control of antiferromagnetic domain structurein a single-phase multiferroic material at room temperature.High-resolution images of both antiferromagnetic and ferroelectric domainstructures of (001)-oriented multiferroic BiFeO3 filmsrevealed a cleardomain correlation, indicating a strong coupling between the two types oforder. The ferroelectric structure was measured using piezo forcemicroscopy, whereas X-ray photoemission electron microscopy as well asits temperature dependence was used to detect the antiferromagneticconfiguration. Antiferromagnetic domainswitching induced by ferroelectricpolarization switching was observed, in agreement with theoreticalpredictions.

  13. Growth of epitaxial orthorhombic YO{sub 1.5}-substituted HfO{sub 2} thin film

    SciTech Connect

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Funakubo, Hiroshi

    2015-07-20

    YO{sub 1.5}-substituted HfO{sub 2} thin films with various substitution amounts were grown on (100) YSZ substrates by the pulsed laser deposition method directly from the vapor phase. The epitaxial growth of film with different YO{sub 1.5} amounts was confirmed by the X-ray diffraction method. Wide-area reciprocal lattice mapping measurements were performed to clarify the crystal symmetry of films. The formed phases changed from low-symmetry monoclinic baddeleyite to high-symmetry tetragonal/cubic fluorite phases through an orthorhombic phase as the YO{sub 1.5} amount increased from 0 to 0.15. The additional annular bright-field scanning transmission electron microscopy indicates that the orthorhombic phase has polar structure. This means that the direct growth by vapor is of polar orthorhombic HfO{sub 2}-based film. Moreover, high-temperature X-ray diffraction measurements showed that the film with a YO{sub 1.5} amount of 0.07 with orthorhombic structure at room temperature only exhibited a structural phase transition to tetragonal phase above 450 °C. This temperature is much higher than the reported maximum temperature of 200 °C to obtain ferroelectricity as well as the expected temperature for real device application. The growth of epitaxial orthorhombic HfO{sub 2}-based film helps clarify the nature of ferroelectricity in HfO{sub 2}-based films (186 words/200 words)

  14. Spin correlated dielectric memory and rejuvenation in multiferroic CuCrS{sub 2}

    SciTech Connect

    Karmakar, A.; Dey, K.; Majumdar, S.; Giri, S.; Chatterjee, S.

    2014-02-03

    We report a rare consequence of memory effect in dielectric response (ϵ) and magnetic field induced rejuvenation in a relaxor-type multiferroic chalcogenide, CuCrS{sub 2}. Despite reasonably high conductivity, we are able to detect significant spontaneous polarization using an improvised technique verifying ferroelectric (FE) order. Concomitant appearance of both FE and antiferromagnetic orders authenticates multiferroicity. A smeared out FE transition and strong frequency dependence of the broadened peak in ϵ obeying Dynamical scaling law signify relaxor properties. We discuss the role of geometrical frustration in the antiferromagnetically coupled layered triangular lattice and metal ligand hybridization for these unusual properties.

  15. 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.

  16. Simultaneous imaging of the ferromagnetic and ferroelectric structure in multiferroic heterostructures

    SciTech Connect

    Unguris, J. Pierce, D. T.; Bowden, S. R.; Trassin, M.; Ramesh, R.; Cheong, S.-W.; Fackler, S.; Takeuchi, I.

    2014-07-01

    By measuring the spin polarization of secondary electrons and the intensity of backscattered electrons generated in a scanning electron microscope, we are able to simultaneously image the ferromagnetic domain structure of a ferromagnetic thin film and the ferroelectric domain structure of the underlying ferroelectric substrate upon which it is grown. Simultaneous imaging allows straightforward, quantitative measurements of the correlations in these complex multiferroic systems. We have successfully imaged domains in CoFe/BFO and Fe/BTO, two systems with very different ferromagnet/ferroelectric coupling mechanisms, demonstrating how this technique provides a new local probe of magneto electric/strictive effects in multiferroic heterostructures.

  17. Unusual Mott transition in multiferroic PbCrO3

    PubMed Central

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-01-01

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. Turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by “bandwidth” control or “band filling.” However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. Here, we report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of ∼3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at ∼300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid–gas transition. The anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking. PMID:26604314

  18. Raman spectroscopy of multiferroic TbMnO3

    NASA Astrophysics Data System (ADS)

    Simpson, J. R.; Hight Walker, A. R.; Valdés Aguilar, R.; Sushkov, A. B.; Drew, H. D.; Park, S.; Choi, Y. J.; Zhang, C.; Cheong, S.-W.

    2008-03-01

    Coupling between the lattice and magnetic degrees of freedom in TbMnO3 has been observed to produce magnetic excitations with electric dipole activity, or electromagnons. Recent reports of electromagnons in other multiferroic (113)-orthomanganitesootnotetextR. Vald'es Aguilar et al., Phys. Rev. B 76, 060404 (2007). and related (125)-manganitesootnotetextA. B. Sushkov et al., Phys. Rev. Lett. 98, 027202 (2007). indicate a complementary Raman study may provide additional insight into the importance of spin-lattice coupling. We present Raman spectra of single-crystal and polycrystalline TbMnO3 using a triple-grating spectrometer in a collinear backscattering configuration as a function of temperature (4-300,K) and polarization along various crystallographic axes. The absence of any observable low-frequency modes (intensity <1000 times that of prominent Raman-active phonons) suggests a weak scattering cross-section for the electromagnon. Additionally, we discuss the temperature dependence of Raman-active phonons and compare with results from infrared measurements.

  19. Unusual Mott transition in multiferroic PbCrO 3

    DOE PAGES

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; et al

    2015-11-24

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. When turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. We report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of similar to 3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrentmore » with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at similar to 300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. Moreover, the anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking.« less

  20. Effect of periodicity on order parameters of multiferroic superlattices

    NASA Astrophysics Data System (ADS)

    Kumari, Shalini; Ortega, Nora; Kumar, Ashok; Katiyar, Ram

    2015-03-01

    Superlattice (SL) structures with alternating perovskite oxide layers have attracted enormous attention due to involved fascinating physics and technology. The half-metallic oxide La0.67Sr0.33MnO3(LSMO) and multiferroic Pb(Zr0.53Ti0.47)0.60 (Fe0.5Ta0.5)0.40 O3(PZTFT) materials have been chosen to fabricate SLs by pulsed laser deposition technique on cubic LSAT substrates with LSMO or LaNiO3 as bottom electrodes. X-ray diffraction studies revealed superlattice structure with satellite peaks modulated around main peaks. Atomic force microscopy studies disclosed a systematic decrease in grain size with decrease of modulation periodicity (Λ) in SLs. Piezo force microscopy studies of SL films confirmed ferroelectricity at a nanoscale level. XPS studies of SLs with Λ = 5 nm confirmed the existence of all elements in the films. A relatively small reduction in saturation magnetization from 28 to 20 emu/cm3at H =5 kOe, remanant polarization from 21 to 10 μC/cm2 and increase in dielectric constant from 530 to 743 were observed with decrease of Λ.The observed features will be explained in context of finite size, interfaces, stress, lattice distortion, and grain sizes effects. NSF Grant EPS-01002410

  1. An oxygen-deficiency modulated multiferroic: Cobalt-substituted perovskite

    NASA Astrophysics Data System (ADS)

    Florez, Juan Manuel

    In this work, we use density functional theory to model recently demonstrated room temperature ferromagnetism and ferroelectricity in polycrystalline and single crystal Cobalt-substituted SrTiO3 thin films (SrTi0.70Co0.30O3-d), deposited at different oxygen pressures to change their oxygen vacancy concentration. The modeling indicates an origin for both magnetism and electric polarization in the interactions between oxygen vacancies and the B-site cations. The magnetization saturation increases with the oxygen deficiency as a result of valence spin states changes, which depend on whether the oxygen octahedral of the respective local B-site cations are complete or not. On the other hand, a finite electric polarization appears as a result of a non-centrosymmetric distribution of different resulting local charges and such a polarization increases when the oxygen vacancies increase. Increasing of both order parameters, magnetic and ferroelectric, are analyzed respect to all possible Co-sites and O-vacancies distributions, showing that these results suggest a class of multiferroic materials with properties controlled by their oxygen stoichiometry. Agreement and discrepancies between experiments and modeling are discussed. 1J M Florez and P Vargas thank Fondecyt 1130950 and 11130128, all authors thank the MISTI MIT-Chile, and CAR thanks the (S3TEC) and DoE under DE-SC0001299.

  2. Unusual Mott transition in multiferroic PbCrO3.

    PubMed

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-12-15

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. Turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. Here, we report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of ∼3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at ∼300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. The anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking. PMID:26604314

  3. Multi-ferroic and magnetoelectric materials and interfaces.

    PubMed

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

    2011-08-13

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

  4. Lattice and Magnetic Effects on Multiferroic Transitions in Garnets

    NASA Astrophysics Data System (ADS)

    Louca, Despina; Kamazawa, K.; Proffen, T.

    2007-03-01

    The possible presence of ferroelectricity in a magnetically ordered state has attracted considerable attention particularly in ABO3 and AB2O5 systems with B = Mn. Evidence for strong coupling of the two order parameters has been provided in the so-called multiferroics, where the field-induced polarization leads to a giant magnetoelectric effect and a magneto-dielectric effect. It was recently shown that the ferrimagnetic garnet crystal of Tb3Fe5O12 exhibits a large magnetodielectric response as well when a very small magnetic field is applied (1). To understand the origin of the high sensitivity of the dielectric effect in garnets, we investigated the crystal and magnetic structures of Tb3(Fe/Ga)5O12 using pulsed neutron diffraction. The garnet crystal appears to be very close to a lattice instability and high-resolution diffraction showed that the lattice gradually changes symmetry from cubic to rhombohedral with cooling over a wide temperature range. At the same time, magnetic diffuse scattering is observed that goes away by 15 K. The role of the lattice and of local distortions in the magnetic polarization and the coupling of the magnetostriction to the dielectric effect will be discussed. (1) N. Hur et al, Appl. Phys. Lett. 87, 042901 (2005).

  5. Anomalous sound velocity in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Cao, Xian-Sheng; Ji, Gao-Feng; Jiang, Xing-Fang

    2016-11-01

    The sound velocity in multiferroic BiFeO3 (BFO) is studied with using Green's function technology on the basis of the magnetoelectric coupling, the spin-phonon interaction and the anharmonic phonon-phonon interaction. The Heisenberg-like model is employed to describe the magnetic subsystem, and the transverse Ising model is used to explain the ferroelectric subsystem. The reduced velocity is obtained in the limit of zero wave vectors. It is shown that the reduced velocity of sound in BiFeO3 exhibits a kink at the magnetic phase transition temperature TN. This anomaly in reduced velocity can be explained as an influence of vanishing magnetic ordering above TN and the ferroelectric subsystem can not be influenced by the magnetic subsystem above TN due to TN≪TC in the BFO. It is shown that the influence of the RM is only below TN in the phase where ferroelectric and magnetic properties exist together, whereas the RE influences the properties of the reduced velocity in the whole temperature region (T

  6. Magnetic and ferroelectric properties of multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Noda, Y.; Kimura, H.; Fukunaga, M.; Kobayashi, S.; Kagomiya, I.; Kohn, K.

    2008-10-01

    The magnetic and ferroelectric properties of multiferroic RMn2O5 (R = Y, Tb, Ho, Er, Tm) are reviewed based on recent neutron diffraction and dielectric measurements. Successive phase transitions of magnetic and dielectric ordering were found to occur simultaneously in this system. The characteristic magnetic ordering of the system exhibits an incommensurate-commensurate phase transition, and again transitions to an incommensurate phase. Special attention is given to the magnetic structure in order to discuss the mechanism for the introduction of ferroelectric polarization. For all the compounds examined, the spin configuration for Mn4+ and Mn3+ ions in the commensurate magnetic phase, where spontaneous electric polarization occurs, was determined to be a transverse spiral spin structure propagating along the c-axis. By contrast, the alignment of the induced 4f moment of R3+ ions showed variation, depending on the character of each of the elements. Corresponding responses to external fields such as a magnetic field, hydrostatic pressure etc at low temperature are strongly dependent on the rare earth element present in the RMn2O5 system. The so-called colossal magnetoelectric effect in this system can be easily interpreted by the phase transition from the magnetic incommensurate and weak ferroelectric phase to the commensurate and ferroelectric phase.

  7. Multicaloric effect in bi-layer multiferroic composites

    NASA Astrophysics Data System (ADS)

    Vopson, M. M.; Zhou, D.; Caruntu, G.

    2015-11-01

    The multicaloric effect was theoretically proposed in 2012 and, despite numerous follow up studies, the effect still awaits experimental confirmation. The main limitation is the fact that the multicaloric effect is only observed at a temperature equal to the transition temperature of the magnetic and electric phases coexisting within a multiferroic (MF) (i.e., T ≈ Tcm ≈ Tce). Such condition is hard to fulfill in single phase MFs and a solution is to develop suitable composite MF materials. Here, we examine the multicaloric effect in a bi-layer laminated composite MF in order to determine the optimal design parameters for best caloric response. We show that magnetically induced multicaloric effect requires magnetic component of heat capacity smaller than that of the electric phase, while the layer thickness of the magnetic phase must be at least 5 times the thickness of the electric phase. The electrically induced multicaloric effect requires the magnetic layer to be 10% of the electric phase thickness, while its heat capacity must be larger than that of the electric phase. These selection rules are generally applicable to bulk as well as thin film MF composites for optimal multicaloric effect.

  8. Multicaloric effect in bi-layer multiferroic composites

    SciTech Connect

    Vopson, M. M.; Zhou, D.; Caruntu, G.

    2015-11-02

    The multicaloric effect was theoretically proposed in 2012 and, despite numerous follow up studies, the effect still awaits experimental confirmation. The main limitation is the fact that the multicaloric effect is only observed at a temperature equal to the transition temperature of the magnetic and electric phases coexisting within a multiferroic (MF) (i.e., T ≈ T{sub c}{sup m} ≈ T{sub c}{sup e}). Such condition is hard to fulfill in single phase MFs and a solution is to develop suitable composite MF materials. Here, we examine the multicaloric effect in a bi-layer laminated composite MF in order to determine the optimal design parameters for best caloric response. We show that magnetically induced multicaloric effect requires magnetic component of heat capacity smaller than that of the electric phase, while the layer thickness of the magnetic phase must be at least 5 times the thickness of the electric phase. The electrically induced multicaloric effect requires the magnetic layer to be 10% of the electric phase thickness, while its heat capacity must be larger than that of the electric phase. These selection rules are generally applicable to bulk as well as thin film MF composites for optimal multicaloric effect.

  9. Magnetic and Ferroelectric Anisotropy in Multiferroic FeVO4

    NASA Astrophysics Data System (ADS)

    Abdelhamid, Ehab; Dixit, Ambesh; Kimura, Kenta; Kimura, Tsuyoshi; Jayakumar, Onattu; Naik, Vaman; Naik, Ratna; Lawes, Gavin; Nadgorny, Boris

    FeVO4 has been studied as a model system for understanding the magnetoelectric interaction mechanisms in low symmetry multiferroics. Triclinic FeVO4 is characterized by two antiferromagnetic phase transitions, occurring at TN 1 = 22 K and TN 2 = 15 K, with the latter transition signaling a break in the space inversion symmetry, accompanied by the development of a non-collinear magnetic order which induces ferroelectricity. Earlier measurements on polycrystalline FeVO4 doped with magnetic (Cr and Mn) as well as non magnetic (Zn) dopants indicate the stability of the two antiferromagnetic transition temperatures. In this work, single crystals of both undoped and doped FeVO4 were grown from flux. To track the changes in lattice parameters induced by changing the doping concentration (measured by EDAX), XRD and Raman spectra were obtained. By recording the magnetization along two different crystal orientations, we were able to confirm the easy magnetic axis in this structure. Finally, we obtain the crystal's ferroelectric polarization along two different directions in an attempt to further understand the mechanism responsible for the ferroelectric transition. This work is supported by the NSF under DMR-1306449.

  10. Diluted orbital degeneracy and large orthorhombic distortions in ferrimagnetic spinel CuxMn3 -xO4

    NASA Astrophysics Data System (ADS)

    Lee, Kee Hwan; Chang, Hun; Hwang, In Yong; Chung, Jae-Ho; Kang, Hyun Wook; Kim, Su Jae; Lee, Seongsu

    2015-02-01

    We report large orthorhombic distortions in the ferrimagnetic tetragonal (c >a ) spinel CuxMn3 -xO4 stabilized by a few percent of Cu doping. The orthorhombic strains of the ferrimagnetic phases increased linearly to the doping and reached up to ɛ ≈8.2 ×10-3 for x =0.19 , which is three times larger than the saturated value under external magnetic fields. For high doping (x ≳0.17 ), the distortions first appeared in the paramagnetic phases and underwent further enhancement simultaneously with the onset of the noncollinear ferrimagnetic ordering. We present the rich magnetostructural phase diagram of CuxMn3 -xO4 , and argue that the diluted t2 orbital degeneracy of Cu2 + under tetrahedral crystal field breaks the global symmetry and triggers the orthorhombic instability inherent in Mn3O4 .

  11. Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO2-based thin films

    NASA Astrophysics Data System (ADS)

    Katayama, Kiliha; Shimizu, Takao; Sakata, Osami; Shiraishi, Takahisa; Nakamura, Shogo; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Uchida, Hiroshi; Funakubo, Hiroshi

    2016-04-01

    Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO1.5-0.93HfO2 films grown by pulsed laser deposition was investigated. To achieve in-plane lattice matching, indium tin oxide (ITO) and yttria-stabilized zirconia (YSZ) were selected as underlying layers. We obtained (100)- and (001)/(010)-oriented films on ITO and YSZ, respectively. Ferroelastic domain formation was confirmed for both films by X-ray diffraction using the superlattice diffraction that appeared only for the orthorhombic symmetry. The formation of ferroelastic domains is believed to be induced by the tetragonal-orthorhombic phase transition upon cooling the films after deposition. The present results demonstrate that the orientation of HfO2-based ferroelectric films can be controlled in the same manner as that of ferroelectric films composed of conventional perovskite-type material such as Pb(Zr, Ti)O3 and BiFeO3.

  12. Colloidal nanocrystals of orthorhombic Cu2ZnGeS4: phase-controlled synthesis, formation mechanism and photocatalytic behavior

    NASA Astrophysics Data System (ADS)

    Fan, Cong-Min; Regulacio, Michelle D.; Ye, Chen; Lim, Suo Hon; Lua, Shun Kuang; Xu, Qing-Hua; Dong, Zhili; Xu, An-Wu; Han, Ming-Yong

    2015-02-01

    The orthorhombic polymorph of Cu2ZnGeS4 (CZGS) is a metastable wurtzite-derived phase that can only be prepared in the bulk form by extensive heating at high temperatures (>=790 °C) when using the conventional solid-state reaction route. By employing a facile solution-based synthetic strategy, we were able to obtain phase-pure orthorhombic CZGS in nanocrystalline form at a much lower reaction temperature. Prior to this work, the colloidal synthesis of single-phase orthorhombic CZGS on the nanoscale has never been reported. We find that the use of an appropriate combination of coordinating solvents and precursors is crucial to the sole formation of this metastable phase in solution. A possible formation mechanism is proposed on the basis of our experimental results. Because CZGS consists of environmentally benign metal components, it is regarded as a promising alternative material to the technologically useful yet toxic cadmium-containing semiconductors. The orthorhombic CZGS nanocrystals display strong photon absorption in the visible spectrum and are photocatalytically active in dye degradation under visible-light illumination.The orthorhombic polymorph of Cu2ZnGeS4 (CZGS) is a metastable wurtzite-derived phase that can only be prepared in the bulk form by extensive heating at high temperatures (>=790 °C) when using the conventional solid-state reaction route. By employing a facile solution-based synthetic strategy, we were able to obtain phase-pure orthorhombic CZGS in nanocrystalline form at a much lower reaction temperature. Prior to this work, the colloidal synthesis of single-phase orthorhombic CZGS on the nanoscale has never been reported. We find that the use of an appropriate combination of coordinating solvents and precursors is crucial to the sole formation of this metastable phase in solution. A possible formation mechanism is proposed on the basis of our experimental results. Because CZGS consists of environmentally benign metal components, it is

  13. Intrinsic metastability of orthorhombic HfTiO{sub 4} in thin film hafnia-titania

    SciTech Connect

    Cisneros-Morales, Massiel Cristina; Aita, Carolyn Rubin

    2011-01-31

    Orthorhombic (o) HfTiO{sub 4} is crystallized when sputter deposited hafnia-titania nanolaminates with ultrathin layers and bilayer (HfO{sub 2}){sub 0.5}(TiO{sub 2}){sub 0.5} composition are annealed between 573 and 1173 K. However, o-HfTiO{sub 4} demixes after annealing at 1273 K, a result not predicted from bulk thermodynamics. X-ray diffraction and Raman microscopy are used here to study structural changes as o-HfTiO{sub 4} demixes upon long-term annealing at 1273 K into Ti-doped monoclinic HfO{sub 2} and Hf-doped rutile TiO{sub 2}. We conclude that o-HfTiO{sub 4} crystallized at low temperature is intrinsically metastable. A space group symmetry analysis shows that demixing can be accomplished by a continuous phase transition chain.

  14. Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates.

    PubMed

    Shafaei, Shahram; Van Opdenbosch, Daniel; Fey, Tobias; Koch, Marcus; Kraus, Tobias; Guggenbichler, Josef Peter; Zollfrank, Cordt

    2016-01-01

    The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3 × 2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25 °C to 600 °C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300 °C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area.

  15. Quasi-one-dimensional electronic structure in orthorhombic RbC[sub 60

    SciTech Connect

    Chauvet, O.; Oszlanyi, G.; Forro, L. ); Stephens, P.W. ); Tegze, M.; Faigel, G.; Janossy, A. )

    1994-04-25

    X-ray diffraction studies show that the stable phase of the alkali fullerene RbC[sub 60] is orthorhombic ([ital o]-RbC[sub 60]) below 350 K. C[sub 60] molecules form chains along [bold a] with an unusually short spacing of 9.12 A and magnetic properties suggest that [ital o]-RbC[sub 60] is a quasi-1D metal with a transition to a spin density wave ground state at 50 K. The high temperature fcc phase of RbC[sub 60] may be stabilized below 300 K by quenching from 500 K; it is paramagnetic above 300 K and transforms into a nonmagnetic ground state beween 300 and 250 K.

  16. Failure development around a borehole in an orthorhombic thermo-elastoplastic rock medium

    NASA Astrophysics Data System (ADS)

    Piłacik, Alicja; Dąbrowski, Marcin

    2016-04-01

    The elastic anisotropy of a rock medium is one of the main factors affecting stress distribution around the borehole. It governs the initiation and propagation of the technologically induced compressive and tensile failure zones, and reopening of natural mechanical discontinuities. We conducted a two-dimensional analysis of failure around a pressurized horizontal borehole in an orthorhombic elastic rock medium subject to variable far-field loads. The analytical solution to the thermoelastic problem was derived. An elastoplastic finite element method code was developed using MILAMIN platform (milamin.org) and implemented in MATLAB. Various yield functions were used, including von Mises, Mohr-Coulomb, Drucker-Prager and Hoek-Brown failure criteria. The analysis was augmented by introducing rock heterogeneities and discrete mechanical discontinuities in the vicinity of the borehole.

  17. Body-Centered Orthorhombic C16 : A Novel Topological Node-Line Semimetal

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Tao; Weng, Hongming; Nie, Simin; Fang, Zhong; Kawazoe, Yoshiyuki; Chen, Changfeng

    2016-05-01

    We identify by ab initio calculations a novel topological semimetal carbon phase in all-s p2 bonding networks with a 16-atom body-centered orthorhombic unit cell, termed bco-C16. Total-energy calculations show that bco-C16 is comparable to solid fcc-C60 in energetic stability, and phonon and molecular dynamics simulations confirm its dynamical stability. This all-s p2 carbon allotrope can be regarded as a three-dimensional modification of graphite, and its simulated x-ray diffraction (XRD) pattern matches well a previously unexplained diffraction peak in measured XRD spectra of detonation and chimney soot, indicating its presence in the specimen. Electronic band structure calculations reveal that bco-C16 is a topological node-line semimetal with a single nodal ring. These findings establish a novel carbon phase with intriguing structural and electronic properties of fundamental significance and practical interest.

  18. Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates.

    PubMed

    Shafaei, Shahram; Van Opdenbosch, Daniel; Fey, Tobias; Koch, Marcus; Kraus, Tobias; Guggenbichler, Josef Peter; Zollfrank, Cordt

    2016-01-01

    The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3 × 2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25 °C to 600 °C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300 °C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area. PMID:26478404

  19. Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO3

    NASA Astrophysics Data System (ADS)

    Dixon, Charlotte A. L.; Kavanagh, Christopher M.; Knight, Kevin S.; Kockelmann, Winfried; Morrison, Finlay D.; Lightfoot, Philip

    2015-10-01

    The thermal evolution of the crystal structure of the prototypical orthorhombic perovskite LaFeO3 has been studied in detail by powder neutron diffraction in the temperature range 25

  20. Body-Centered Orthorhombic C_{16}: A Novel Topological Node-Line Semimetal.

    PubMed

    Wang, Jian-Tao; Weng, Hongming; Nie, Simin; Fang, Zhong; Kawazoe, Yoshiyuki; Chen, Changfeng

    2016-05-13

    We identify by ab initio calculations a novel topological semimetal carbon phase in all-sp^{2} bonding networks with a 16-atom body-centered orthorhombic unit cell, termed bco-C_{16}. Total-energy calculations show that bco-C_{16} is comparable to solid fcc-C_{60} in energetic stability, and phonon and molecular dynamics simulations confirm its dynamical stability. This all-sp^{2} carbon allotrope can be regarded as a three-dimensional modification of graphite, and its simulated x-ray diffraction (XRD) pattern matches well a previously unexplained diffraction peak in measured XRD spectra of detonation and chimney soot, indicating its presence in the specimen. Electronic band structure calculations reveal that bco-C_{16} is a topological node-line semimetal with a single nodal ring. These findings establish a novel carbon phase with intriguing structural and electronic properties of fundamental significance and practical interest. PMID:27232027

  1. The scattering potential of partial derivative wavefields in 3D elastic orthorhombic media: An inversion prospective

    NASA Astrophysics Data System (ADS)

    Oh, Ju-Won; Alkhalifah, Tariq

    2016-07-01

    Multi-parameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multi component sensors, the potential for tradeoff between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C11, C22 and C33 are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C33 while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C11 and C22 if we have large enough offsets. The elastic coefficients C13, C23 and C12 suffer from strong trade-offs with C55, C44 and C66, respectively. The trade-offs between C13 and C55, as well as C23 and C44, can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C12 and C66, we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.

  2. The scattering potential of partial derivative wavefields in 3-D elastic orthorhombic media: an inversion prospective

    NASA Astrophysics Data System (ADS)

    Oh, Ju-Won; Alkhalifah, Tariq

    2016-09-01

    Multiparameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multicomponent sensors, the potential for trade-off between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C11, C22, and C33 are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C33 while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C11 and C22 if we have large enough offsets. The elastic coefficients C13, C23, and C12 suffer from strong trade-offs with C55, C44, and C66, respectively. The trade-offs between C13 and C55, as well as C23 and C44, can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C12 and C66, we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.

  3. A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

    NASA Astrophysics Data System (ADS)

    Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey

    2016-09-01

    There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3-BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3-BiMnO3-PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.

  4. 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.

  5. Effects of Nickel Doping on the Multiferroic and Magnetic Phases of MnWO 4

    DOE PAGES

    Poudel, N.; Lorenz, B.; Lv, B.; Wang, Y. Q.; Ye, F.; Wang, Jinchen; Fernandez-baca, J. A.; Chu, C. W.

    2015-12-15

    There are various orders in multiferroic materials with a frustrated spiral spin modulation inducing a ferroelectric state are extremely sensitive to small perturbations such as magnetic and electric fields, external pressure, or chemical substitutions. A classical multiferroic, the mineral Hubnerite with chemical formula MnWO4, shows three different magnetic phases at low temperature. The intermediate phase between 7.5K < T < 12.7K is multiferroic and ferroelectricity is induced by an inversion symmetry breaking spiral Mn-spin order and strong spin-lattice interactions. Furthermore, the substitution of Ni2+ (spin 1) for Mn2+ (spin 5/2) in MnWO4 and its effects on the magnetic and multiferroicmore » phases are studied. The ferroelectric phase is stabilized for low Ni content (up to 10%). Upon further Ni doping, the polarization in the ferroelectric phase is quickly suppressed while a collinear and commensurate magnetic phase, characteristic of the magnetic structure in NiWO4, appears first at higher temperature, gradually extends to lower temperature, and becomes the ground state above 30% doping. Between 10% and 30%, the multiferroic phase coexists with the collinear commensurate phase. In this concentration region, the spin spiral plane is close to the a-b plane which explains the drop of the ferroelectric polarization. Finally, the phase diagram of Mn1-xNixWO4 is derived by a combination of magnetic susceptibility, specific heat, electric polarization, and neutron scattering measurements.« less

  6. A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

    PubMed Central

    Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey

    2016-01-01

    There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3–BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3–BiMnO3–PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses. PMID:27677353

  7. Perovskite solid solutions with multiferroic morphotropic phase boundaries and property enhancement

    NASA Astrophysics Data System (ADS)

    Algueró, M.; Amorín, H.; Fernández-Posada, C. M.; Peña, O.; Ramos, P.; Vila, E.; Castro, A.

    2016-05-01

    Recently, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of phases in the BiFeO3-BiCoO3 perovskite binary system, associated with the existence of a discontinuous morphotropic phase boundary (MPB) between multiferroic polymorphs of rhombohedral and tetragonal symmetries. This might be a general property of multiferroic phase instabilities, and a novel promising approach for room temperature magnetoelectricity. We review here our current investigations on the identification and study of additional material systems, alternative to BiFeO3-BiCoO3 that has only been obtained by high pressure synthesis. Three systems, whose phase diagrams were, in principle, liable to show multiferroic MPBs have been addressed: the BiMnO3-PbTiO3 and BiFeO3-PbTiO3 binary systems, and the BiFeO3-BiMnO3-PbTiO3 ternary one. A comprehensive study of multiferroism across different solid solutions was carried out based on electrical and magnetic characterizations, complemented with mechanical and electromechanical measurements. An in-depth structural analysis was also accomplished when necessary.

  8. The formation mechanism of a time order in the activated BiFeO3 multiferroic

    NASA Astrophysics Data System (ADS)

    Godovikov, S. K.; Nikitin, S. M.

    2015-10-01

    It was established experimentally that internal local pressure is the physical cause of the previously observed phenomenon of self-organization of atomic displacements in multiferroics of BiFeO3 type, activated by an external impulse action. Mössbauer spectroscopy on nuclei 57Fe was used as the main research method.

  9. Hydrodynamics of domain walls in ferroelectrics and multiferroics: Impact on memory devices

    NASA Astrophysics Data System (ADS)

    Scott, J. F.; Evans, D. M.; Gregg, J. M.; Gruverman, A.

    2016-07-01

    The standard "Kittel Law" for the thickness and shape of ferroelectric, ferroelastic, or ferromagnet domains assumes mechanical equilibrium. The present paper shows that such domains may be highly nonequilibrium, with unusual thicknesses and shapes. In lead germanate and multiferroic lead zirconate titanate iron tantalate domain wall instabilities resemble hydrodynamics (Richtmyer-Meshkov and Helfrich-Hurault, respectively).

  10. Multiferroic phase of doped delafossite CuFeO2 identified using inelastic neutron scattering

    SciTech Connect

    Haraldsen, Jason T; Ye, Feng; Fishman, Randy Scott; Fernandez-Baca, Jaime A; Yamaguchi, Y.; Kimura, K.; Kimura, T.

    2010-01-01

    Multiferroic materials allow the electric polarization to be controlled by switching the direction of magnetic ordering and consequently offer prospects for many new technological applications [1 4]. Because multiferroic behavior has been found in materials that exhibit complex (non-collinear and incommensurate) magnetic order, it is essential to know the spin arrangement of the ground states in these materials [4 9]. In many cases, elastic neutron scattering measurements alone are not sufficient to distinguish among several potential complex magnetic states. We report inelastic neutron scattering (INS) measurements that provide a distinct dynamical fingerprint for the multiferroic ground state of 3.5% Ga-doped CuFeO2. The complex ground state is stabilized by the displacement of the oxygen atoms [10], which are also responsible for the multiferroic coupling predicted by Arima [8]. By comparing the observed and calculated spectrum of spin excitations, we conclude that the magnetic ground state is a distorted screwtype spin configuration. The exchange interactions that stabilize this structure are consistent with those obtained from inelastic measurements [11, 12] on undoped CuFeO2.

  11. Colloidal nanocrystals of orthorhombic Cu2ZnGeS4: phase-controlled synthesis, formation mechanism and photocatalytic behavior.

    PubMed

    Fan, Cong-Min; Regulacio, Michelle D; Ye, Chen; Lim, Suo Hon; Lua, Shun Kuang; Xu, Qing-Hua; Dong, Zhili; Xu, An-Wu; Han, Ming-Yong

    2015-02-21

    The orthorhombic polymorph of Cu2ZnGeS4 (CZGS) is a metastable wurtzite-derived phase that can only be prepared in the bulk form by extensive heating at high temperatures (≥790 °C) when using the conventional solid-state reaction route. By employing a facile solution-based synthetic strategy, we were able to obtain phase-pure orthorhombic CZGS in nanocrystalline form at a much lower reaction temperature. Prior to this work, the colloidal synthesis of single-phase orthorhombic CZGS on the nanoscale has never been reported. We find that the use of an appropriate combination of coordinating solvents and precursors is crucial to the sole formation of this metastable phase in solution. A possible formation mechanism is proposed on the basis of our experimental results. Because CZGS consists of environmentally benign metal components, it is regarded as a promising alternative material to the technologically useful yet toxic cadmium-containing semiconductors. The orthorhombic CZGS nanocrystals display strong photon absorption in the visible spectrum and are photocatalytically active in dye degradation under visible-light illumination.

  12. Pressure-induced amorphization in orthorhombic Ta{sub 2}O{sub 5}: An intrinsic character of crystal

    SciTech Connect

    Li, Quanjun; Zhang, Huafang; Cheng, Benyuan; Liu, Ran; Liu, Bo; Zou, Bo; Cui, Tian; Liu, Bingbing; Liu, Jing; Chen, Zhiqiang

    2014-05-21

    The phase transition of orthorhombic Ta{sub 2}O{sub 5} was investigated by in situ synchrotron X-ray diffraction and Raman spectroscopy. The orthorhombic phase transforms into an amorphous form completely at 24.7 GPa. A bulk modulus B{sub 0} = 139 (9) GPa for the orthorhombic Ta{sub 2}O{sub 5} is derived from the P-V data. We suggest that the pressure-induced amorphization (PIA) in Ta{sub 2}O{sub 5} can be attributed to the unstability of the a axis under high pressure leads to the connections of polyhedral breaking down and even triggers disorder of the whole crystal frame. These results demonstrate that the PIA is an intrinsic character of Ta{sub 2}O{sub 5} which depends on its orthorhombic crystal structure rather than nanosize effects. This study provides a new kind of bulk material for investigating PIA in metal oxides.

  13. Complexity of High-Pressure Orthorhombic Iron Oxides, the Characterization of Fe5O6

    NASA Astrophysics Data System (ADS)

    Lavina, B.; Meng, Y.

    2014-12-01

    Occurring as accessory minerals in most rocks and forming large deposits of considerable economical importance, iron oxides have a major petrological importance. Their role as oxygen buffers, in differentiation processes and as magnetic phases summarize the critical importance of iron oxides in most petrological contexts, independently of their abundance.The discovery of a new compound in the Fe-O system, Fe4O5[1], reshaped our assumptions on the behavior of iron oxides in the Earth's deep interior, where phases of FeO and Fe3O4 were considered the sole plausible players. Further studies found that Fe4O5 is stable in a wide compositional range[2] and can accept a wide extent of isomorphic substitutions[3].We used laser heating synthesis in diamond anvil cell and microdiffraction mapping with high brilliance synchrotron x-ray[4] to explore the complexity of the Fe-O system at high pressure and temperature. We found coexistence of two to three oxides in most of the samples we investigated. By means of a careful exploration of diffraction effects in the reciprocal space, we singled-out the diffraction peaks of a few grains in multiphase diffraction patterns. These allowed a reliable characterization of yet a new iron oxide, Fe5O6. This compound, synthesized between 10 and 20 GPa, is also orthorhombic and can be described with the same building blocks of the other known orthorhombic iron oxides. A comparison of compressibility and lattice parameters of the latest iron oxides will be presented. [1] Lavina, B. et al. Discovery of the recoverable high-pressure iron oxide Fe4O5. Proc Natl Acad Sci U S A 108, 17281-5 (2011).[2] Woodland, A. B., Frost, D. J., Trots, D. M., Klimm, K. & Mezouar, M. In situ observation of the breakdown of magnetite (Fe3O4) to Fe4O5 and hematite at high pressures and temperatures. Am Mineral 97, 1808-1811 (2012).[3] Woodland, A. B. et al. Fe4O5 and its solid solutions in several simple systems. Cotrib Mineral Petrol 166, 1677-1686 (2013

  14. Double-exchange theory of ferroelectric polarization in orthorhombic manganites with twofold periodic magnetic texture

    NASA Astrophysics Data System (ADS)

    Solovyev, I. V.; Nikolaev, S. A.

    2013-04-01

    We argue that many aspects of improper ferroelectric (FE) activity in orthorhombic manganites can be rationalized by considering the limit of infinite intra-atomic splitting between majority- and minority-spin states (or the double-exchange limit), which reduces the problem to the analysis of a spinless double-exchange (DE) Hamiltonian. We apply this strategy to the low-energy model, derived from the first-principles electronic-structure calculations, and combine it with the Berry-phase theory of electric polarization. We start with the analysis of the simplest two-orbital model, describing the behavior of the eg bands, and apply it to the E-type antiferromagnetic (AFM) phase, which in the DE limit effectively breaks up into one-dimensional zigzag chains. We derive an analytical expression for the electronic polarization (Pel) and explain how it depends on the orbital ordering and the energy splitting Δ between eg states. Then, we evaluate parameters of this model for the series of manganites. For these purposes, we start from a more general five-orbital model for all Mn 3d bands and construct a new downfolded model for the eg bands. From the analysis of these parameters, we conclude that the behavior of Pel in realistic manganites always corresponds to the limit of large Δ. This property holds for all considered compounds even in the local-density approximation, which typically underestimates Δ. We further utilize this property in order to derive an analytical expression for Pel in a general twofold periodic magnetic texture, based on the five-orbital model and the perturbation-theory expansion for the Wannier functions in the first order of 1/Δ. This expression explains the functional dependence of Pel on the relative directions of spins. Furthermore, it suggests that Pel is related to the asymmetry of transfer integrals, which should have simultaneously symmetric and antisymmetric components in the crystal-field representation. The main contribution to this

  15. High-Pressure Orthorhombic Ferromagnesite as a Potential Deep-Mantle Carbon Carrier

    PubMed Central

    Liu, Jin; Lin, Jung-Fu; Prakapenka, Vitali B.

    2015-01-01

    Knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth. PMID:25560542

  16. Silver-decorated orthorhombic nanotubes of lithium vanadium oxide: an impeder of bacterial growth and biofilm.

    PubMed

    Diggikar, Rahul S; Patil, Rajendra H; Kale, Sheetal B; Thombre, Dipalee K; Gade, Wasudeo N; Kulkarni, Milind V; Kale, Bharat B

    2013-09-01

    Reoccurrence of infectious diseases and ability of pathogens to resist antibacterial action has raised enormous challenges which may possibly be confronted by nanotechnology routes. In the present study, uniformly embedded silver nanoparticles in orthorhombic nanotubes of lithium vanadium oxide (LiV2O5/Ag) were explored as an impeder of bacterial growth and biofilm. The LiV2O5/Ag nanocomposites have impeded growth of Gram-positive Bacillus subtilis NCIM 2063 and Gram-negative Escherichia coli NCIM 2931 at 60 to 120 μg/mL. It also impeded the biofilm in Pseudomonas aeruginosa NCIM 2948 at 12.5 to 25 μg/mL. Impedance in the growth and biofilm occurs primarily by direct action of the nanocomposites on the cell surfaces of test organisms as revealed by surface perturbation in scanning electron microscopy. As the metabolic growth and biofilm formation phenomena of pathogens play a central role in progression of pathogenesis, LiV2O5/Ag nanocomposite-based approach is likely to curb the menace of reoccurrence of infectious diseases. Thus, LiV2O5/Ag nanocomposites can be viewed as a promising candidate in biofabrication of biomedical materials.

  17. Search for half-metallic ferromagnetism in orthorhombic Ce(Fe/Cr)O3 perovskites

    NASA Astrophysics Data System (ADS)

    Abbad, A.; Benstaali, W.; Bentounes, H. A.; Bentata, S.; Benmalem, Y.

    2016-02-01

    The full-potential linearized augmented plane wave (FPLAPW) method based on the density functional theory within the GGA and GGA+U, is used to investigate the structural, magnetic and half-metallic properties of the Pnma orthorhombic Cerium orthoferrite (CeFeO3) and Cerium orthochromite (CeCrO3). The calculated densities of states presented in this study identify the metallic behavior CeFeO3 when we use the GGA scheme, whereas when we use the GGA+U, we see that its exhibits half-metallic character with an integer magnetic moment of 24 μB per formula unit at its equilibrium volume. CeCrO3 is half-metallic for both approaches and of n type conductivity for GGA but p type conductivity for GGA+U. It is found that the majority of the magnetic moments of both compounds originate from the cerium sites since the f states of Ce are spin polarized. From the band structure and the densities of states analysis, we find that CeCrO3 and CeFeO3 are strong candidates for spintronic applications.

  18. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier.

    PubMed

    Liu, Jin; Lin, Jung-Fu; Prakapenka, Vitali B

    2015-01-01

    Knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO₃] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO₃ system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO₂, the occurrence of the tetrahedrally-coordinated carbonates based on CO₄ structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO₃ carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO₃ phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth. PMID:25560542

  19. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier

    DOE PAGES

    Liu, Jin; Lin, Jung -Fu; Prakapenka, Vitali B.

    2015-01-06

    In this study, knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions ofmore » approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth.« less

  20. The compressibility of cubic white, orthorhombic black and rhombohedral black phosphorus

    SciTech Connect

    Clark, S; Zaug, J M

    2009-06-05

    The effect of pressure on the crystal structure of white phosphorus has been studied up to 22.4 GPa. The {alpha} phase was found to transform into the {alpha}' phase at 0.87 {+-} 0.04 GPa with a volume change of 0.1 {+-} 0.3 cc/mol. A fit of a second order Birch-Murghanan equation to the data gave Vo = 16.94 {+-} 0.08 cc/mol and K{sub o} = 6.7 {+-} 0.5 GPa for the {alpha} phase and Vo = 16.4 {+-} 0.1 cc/mol and K{sub o} = 9.1 {+-} 0.3 GPa for the {alpha}' phase. The {alpha}' phase was found to transform to the A17 phase of black phosphorus at 2.68 {+-} 0.34 GPa and then with increasing pressure to the A7 and then simple cubic phase of black phosphorus. A fit of a second order Birch-Murnaghan equation to our orthorhombic and rhombohedral black phosphorus data gave Vo = 11.43 {+-} 0.02 cc/mol and K{sub o} = 34.7 {+-} 0.5 GPa for the A17 phase and Vo = 9.62 {+-} 0.01 cc/mol and K{sub o} = 65.0 {+-} 0.6 GPa for the A7 phase.

  1. Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO{sub 3}

    SciTech Connect

    Dixon, Charlotte A.L.; Kavanagh, Christopher M.; Knight, Kevin S.; Kockelmann, Winfried; Morrison, Finlay D.; Lightfoot, Philip

    2015-10-15

    The thermal evolution of the crystal structure of the prototypical orthorhombic perovskite LaFeO{sub 3} has been studied in detail by powder neutron diffraction in the temperature range 25

  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. Direct observation of multiferroic vortex domains in YMnO3.

    PubMed

    Zhang, Qinghua; Tan, Guotai; Gu, Lin; Yao, Yuan; Jin, Changqing; Wang, Yanguo; Duan, Xiaofeng; Yu, Richeng

    2013-01-01

    Topological vortices with swirling ferroelectric, magnetic and structural anti-phase relationship in hexagonal RMnO3 (R = Ho to Lu, Y, and Sc) have attracted much attention because of their intriguing behaviors. Herein, we report the structure of multiferroic vortex domains in YMnO3 at atomic scale using state-of-the-art aberration-corrected scanning transmission electron microscopy (STEM). Two types of displacements were identified among six domain walls (DWs); six translation-ferroelectric domains denoted by α+, γ-, β+, α-, γ+ and β-, respectively, were recognized, demonstrating the interlocking nature of the anti-vortex domain. We found that the anti-vortex core is about four unit cells wide. In addition, we reconstructed the vortex model with three swirling pairs of DWs along the [001] direction. These results are very critical for the understanding of topological behaviors and unusual properties of the multiferroic vortex.

  4. Phase transition of BiMnO3 multiferroic thin film by Landau-Ginzburg theory

    NASA Astrophysics Data System (ADS)

    Alrub, Ahmad Musleh; Ong, Lye-Hock; Chew, K.-H.; Khoshman, J. M.; Al Shabaan, Ghadeer N.; Abu Hilaleh, Rawa'Ah

    2016-05-01

    Magnetoelectric (ME) multiferroic bismuth manganite (BiMnO3) has ferroelectric (FE) and ferromagnetic order parameters that coupled biquadratically. Landau free energy expression in these order parameters is proposed to investigate the phase transition and thermodynamic properties of a BiMnO3 film. The surface energy term is included in the free energy. We find that the ME coupling enhances the magnetic transition temperature. The magnetization and polarization order parameters are both increased strongly below the new magnetic transition temperature. The curves for magnetization and polarization versus temperature show that the phase transition is second-order. The entropy, free energy, and specific heat of the BiMnO3 multiferroic are calculated. Thickness-driven phase transitions for magnetization and polarization of BiMnO3 thin film are clearly indicated.

  5. Chemically modulated multiferroicity in Dy-doped Gd2Ti2O7

    NASA Astrophysics Data System (ADS)

    Lin, L.; Zhao, Z. Y.; Liu, D.; Xie, Y. L.; Dong, S.; Yan, Z. B.; Liu, J.-M.

    2013-05-01

    The ferroelectricity and magnetoelectric coupling of Gd2Ti2O7 and Gd2-xDyxTi2O7 with Dy3+ substitution of Gd3+ are investigated. For Gd2Ti2O7, a ferroelectric polarization emerges at ˜30 K and is only ˜1.80 μC/m2 at 2 K, while the magnetoelectric response is quite weak. The Dy3+ substitution in Gd2-xDyxTi2O7, however, results in significant enhancement of polarization with remarkable magnetoelectric response up to 35% at 2 K under a magnetic field of 9 T, suggesting the multiferroicity of Gd2-xDyxTi2O7. It is understood that the chemical modulation of the multiferroicity is basically related to the extreme sensitivity of the spin-spin interactions in this highly frustrated system.

  6. Film size-dependent voltage-modulated magnetism in multiferroic heterostructures

    PubMed Central

    Hu, J.-M.; Shu, L.; Li, Z.; Gao, Y.; Shen, Y.; Lin, Y. H.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    The electric-voltage-modulated magnetism in multiferroic heterostructures, also known as the converse magnetoelectric (ME) coupling, has drawn increasing research interest recently owing to its great potential applications in future low-power, high-speed electronic and/or spintronic devices, such as magnetic memory and computer logic. In this article, based on combined theoretical analysis and experimental demonstration, we investigate the film size dependence of such converse ME coupling in multiferroic magnetic/ferroelectric heterostructures, as well as exploring the interaction between two relating coupling mechanisms that are the interfacial strain and possibly the charge effects. We also briefly discuss some issues for the next step and describe new device prototypes that can be enabled by this technology. PMID:24421375

  7. Simultaneous occurrence of multiferroism and short-range magnetic order in DyFeO3

    DOE PAGES

    Wang, Jinchen; Liu, Juanjuan; Sheng, Jieming; Luo, Wei; Ye, Feng; Zhao, Zhiying; Sun, Xuefeng; Danilkin, Sergey A.; Deng, Guochu; Bao, Wei

    2016-04-06

    In this paper, we present a combined neutron scattering and magnetization study on the multiferroic DyFeO3, which shows a very strong magnetoelectric effect. Applying magnetic field along the c axis, the weak ferromagnetic order of the Fe ions is quickly recovered from a spin reorientation transition, and the long-range antiferromagnetic order of Dy becomes a short-range one. We found that the short-range order concurs with the multiferroic phase and is responsible for its sizable hysteresis. In conclusion, our H-T phase diagram suggests that the strong magnetoelectric effect in DyFeO3 has to be understood with not only the weak ferromagnetism ofmore » Fe but also the short-range antiferromagnetic order of Dy.« less

  8. Enhanced multiferroic characteristics in Fe-doped BiTiO ceramics

    NASA Astrophysics Data System (ADS)

    Chen, X. Q.; Yang, F. J.; Cao, W. Q.; Wang, H.; Yang, C. P.; Wang, D. Y.; Chen, K.

    2010-07-01

    Modification of Bi 4Ti 3O 12 multiferroic ceramics prepared by a conventional solid state reaction method were investigated by substituting Ti partly with Fe. The introduction of Fe does not change the layered perovskite structure of Bi 4Ti 3O 12. Upon increasing Fe content, the remnant polarization of the samples is enhanced. The magnetism of the ceramics at room temperature develops from diamagnetism to weak ferromagnetism with increasing Fe doping. The largest variations of 15% and 6% in remnant polarization and magnetization, achieved in a Bi 4Ti 1Fe 2O 12-δ sample after poling it in a magnetic field at 1 T and a DC electric field at 30 kV/cm for 10 min, are evidence of magnetoelectric coupling between the electric dipoles and magnetic dipoles at room temperature. The present results suggest a new candidate for a room temperature multiferroic material with enhanced properties.

  9. Multiferroicity in vanadium-doped La2Ti2O7: insights from first principles

    NASA Astrophysics Data System (ADS)

    Scarrozza, Marco; Filippetti, Alessio; Fiorentini, Vincenzo

    2013-04-01

    We explore an unconventional route in the search for multiferroicity investigating the magnetic doping of La2Ti2O7 (LTO), a ferroelectric layered perovskite, by density functional calculations. We find that substitution of Ti (in the 3 d 0 configuration) by V (3 d 1) produces: (i) robust ferromagnetic (FM) order, achieving multiferroicity; (ii) structural and magnetic anisotropy, as the dopants cluster in magnetic chains. Moreover, the FM V-chains possess antiferro orbital ordering. We show that the origin of the strong FM coupling lies in the fruitful host-dopant combination: the layered structure of the host prewires the orbitals t 2 g with d xy and d xz lower in energy, the V dopants provide the full occupancy of the bonding levels. We further address the stability of chains vs. temperature and the role of oxygen vacancies in undoped as well as Sc-doped and V-doped LTO.

  10. Temperature dependences of the electric polarization and wave number of incommensurate structures in multiferroics

    NASA Astrophysics Data System (ADS)

    Pikin, S. A.

    2016-05-01

    It is shown that the electric polarization and wave number of incommensurate modulations, proportional to each other, increase according to the Landau law in spin multiferroic cycloids near the Néel temperature. In this case, the constant magnetization component (including the one for a conical spiral) is oriented perpendicular to the spin incommensurability wave vector. A similar temperature behavior should manifest itself for spin helicoids, the axes of which are oriented parallel to the polarization vector but their spin rotation planes are oriented perpendicular to the antiferromagnetic order plane. When the directions of axes of the magnetization helicoid and polarization vector coincide, the latter is quadratic with respect to magnetization and linearly depends on temperature, whereas the incommensurate-modulation wave number barely depends on temperature. Structural distortions of unit cells for multiferroics of different types determine their axial behavior.

  11. Effects of transition metal doping on multiferroic ordering in nickel vanadate and iron orthovanadate

    NASA Astrophysics Data System (ADS)

    Kumarasiri, Akila

    We have studied the effects of doping both non-magnetic and magnetic ions on the phase transitions and multiferroic ordering in two multiferroic oxides; Ni3V2O8 and FeVO4. Magnetic, dielectric, specific heat, polarization and AC susceptibility measurements were used to track changes in phase transition temperatures. We found that the two higher temperature magnetic transitions in Ni3V2O 8; TH = 9.1 K and TL = 6.3 K are suppressed to lower temperatures with all transition metal dopants. For Zn doping, the rates of the suppression of both TH and TL with dopant fraction are consistent with simple site dilution for two-dimensional spin systems, with the suppression of TH consistent with Ising spins and the suppression of TL consistent with Heisenberg spins. However, samples remain multiferroic at least up to 15% Zn doping. Conversely, spin-1/2 Cu doping strongly suppresses both transitions, for which the multiferroic magnetic structure is completely suppressed at only 10% Cu doping. However, below 10% Cu doping, the samples show enhanced ferroelectric polarization, and a sizable net magnetization also develops. With spin-3/2 Co doping, suppression is very small, with the multiferroic transition persisting even at 30% doping and the material showing Ni 3V2O8 magnetic characteristics up to 80% doping. On the Co rich side of the composition, we find that the magnetic ordering temperatures for Co3V2O8 are suppressed rapidly with Ni doping. With higher spin dopants (e.g. spin-2 Fe and spin-5/2 Mn), suppression remains fairly low. We also present phase diagrams for (Ni 1-xMx)3V2O8 (M = Zn, Cu, Co, Fe and Mn). These studies suggest that the spin structures in Ni3V 2O8 responsible for the development of ferroelectric order are relatively robust against perturbations produced by both magnetic and non-magnetic dopants, with the most significant disruption of the magnetic structure developing for Cu doping. In the case of FeVO4, we find that the magnetoelectric coupling in FeVO4

  12. Multiferroicity in ZnO nanodumbbell/BiFeO3 nanoparticle heterostructures

    NASA Astrophysics Data System (ADS)

    Mahesh, Dabbugalla; Mandal, Swapan K.

    2016-04-01

    We report here on the multiferroic properties of ZnO-BiFeO3 (BiFeO3 referred hereinafter as BFO) nanocomposite structures obtained by using a facile solution-based synthesis route. ZnO is found to grow in the form of well-crystallized and self-assembled dumbbell-like structures. BFO nanoparticles (NPs) are deposited onto ZnO nanodumbbells (NDs) to obtain ZnO-BFO heterostructures. The nanocomposites show prominent ferroelectric polarization hysteresis loop along with enhanced magnetization in comparison to pure BFO NPs. The ordered alignment of spins along with the suppression of Fe-O-Fe antiferromagnetic super-exchange interactions at the ZnO/BFO interface plausibly gives rise to observed multiferroic properties.

  13. Theory of magnetic-field-induced polarization flop in spin-spiral multiferroics

    NASA Astrophysics Data System (ADS)

    Mochizuki, Masahito

    2015-12-01

    The magnetic-field-induced 90∘ flop of ferroelectric polarization P in a spin-spiral multiferroic material TbMnO3 is theoretically studied based on a microscopic spin model. I find that the direction of the P flop or the choice of +Pa or -Pa after the flop is governed by magnetic torques produced by the applied magnetic field H acting on the Mn spins and thus is selected in a deterministic way, in contradistinction to the naively anticipated probabilistic flop. This mechanism resolves a puzzle of the previously reported memory effect in the P direction depending on the history of the magnetic-field sweep, and enables controlled switching of multiferroic domains by externally applied magnetic fields. My Monte-Carlo analysis also uncovers that the magnetic structure in the P ∥a phase under H ∥b is not a previously anticipated simple a b -plane spin cycloid but a conical spin structure.

  14. Gigantic directional asymmetry of luminescence in multiferroic CuB 2O 4

    NASA Astrophysics Data System (ADS)

    Toyoda, S.; Abe, N.; Arima, T.

    2016-05-01

    In multiferroic materials, luminescence intensities can be direction dependent, i.e., different between the opposite propagating directions of emitted light. However, the effect has not been thought to be used for technological applications, since only small directional asymmetry has been reported so far. Here we show that the effect is robust in multiferroic CuB2O4 . The luminescence intensity changes by about 70 % between the opposite directions of the emission, which is about 100 times larger than the previously reported values. We demonstrate that such a gigantic directional asymmetry of luminescence can be applied to the imaging of canted antiferromagnetic domains. The observation of the effect and its application to magnetic domain imaging are important for a deeper understanding of light-matter interactions as well as technological applications such as optical reading techniques for magnetic memory devices.

  15. Low-field Switching Four-state Nonvolatile Memory Based on Multiferroic Tunnel Junctions

    PubMed Central

    Yau, H. M.; Yan, Z. B.; Chan, N. Y.; Au, K.; Wong, C. M.; Leung, C. W.; Zhang, F.Y.; Gao, X. S.; Dai, J. Y.

    2015-01-01

    Multiferroic tunneling junction based four-state non-volatile memories are very promising for future memory industry since this kind of memories hold the advantages of not only the higher density by scaling down memory cell but also the function of magnetically written and electrically reading. In this work, we demonstrate a success of this four-state memory in a material system of NiFe/BaTiO3/La0.7Sr0.3MnO3 with improved memory characteristics such as lower switching field and larger tunneling magnetoresistance (TMR). Ferroelectric switching induced resistive change memory with OFF/ON ratio of 16 and 0.3% TMR effect have been achieved in this multiferroic tunneling structure. PMID:26239505

  16. Multiferroic behavior in elemental selenium below 40 K: effect of electronic topology.

    PubMed

    Pal, Anirban; Shirodkar, Sharmila N; Gohil, Smita; Ghosh, Shankar; Waghmare, Umesh V; Ayyub, Pushan

    2013-01-01

    The quasi-one-dimensional, chiral crystal structure of Selenium has fascinating implications: we report simultaneous magnetic and ferroelectric order in single crystalline Se microtubes below ≈40 K. This is accompanied by a structural transition involving a partial fragmentation of the infinite chains without losing overall crystalline order. Raman spectral data indicate a coupling of magnons with phonons and electric field, while the dielectric constant shows a strong dependence on magnetic field. Our first-principles theoretical analysis reveals that this unexpected multiferroic behavior originates from Selenium being a weak topological insulator. It thus exhibits stable electronic states at its surface, and magnetism emerges from their spin polarization. Consequently, the broken two-fold rotational symmetry permits switchable polarization along its helical axis. We explain the observed magnetoelectric couplings using a Landau theory based on the coupling of phonons with spin and electric field. Our work opens up a new class of topological surface-multiferroics with chiral bulk structure.

  17. Effect of uniaxial strain on the structural, electronic and elastic properties of orthorhombic BiMnO3

    NASA Astrophysics Data System (ADS)

    Yang, Pei; Haibin, Wu

    2015-03-01

    We study the elastic constants and electronic properties of orthorhombic BiMnO3 under uniaxial strain along the c-axis using the first-principles method. It is found that, beyond the range -0.025 < ɛ < 0.055, the predicted stiffness constants cij cannot demand the Born stability criteria and the compliance constant s44 shows abrupt changes, which accompany phase transition. In addition, the results for magnetism moments and polycrystalline properties are also reported. Additionally, under compressive strain, a band gap transition from the indirect to the direct occurs within -0.019 < ɛ < -0.018. Furthermore, the response of the band gap of orthorhombic BiMnO3 to uniaxial strain is studied.

  18. Negative phase velocity and negative refraction in orthorhombic dielectric-magnetic lossy media with polarization along one of principal axes

    NASA Astrophysics Data System (ADS)

    Potisook, Chanin; Natenapit, Mayuree

    2014-05-01

    The characteristics of the TE plane wave propagations in orthorhombic dielectric-magnetic lossy media are investigated. The special case for the electric field being parallel to one principal axis and the wave vector lying wholly in the plane formed by the other two principal axes is considered. The dissipation is taken into account by letting the elements of the permittivity and the permeability tensors to be complex. The general condition on the negative phase velocity for uniform TE plane waves is provided in terms of material parameters and the propagation angle. The numerical calculations for the angles between the average Poynting vector and the phase velocity are performed in order to justify the theoretical analysis. In addition, the TE refraction between the free space and the orthorhombic dielectric-magnetic lossy media are also considered and the general condition on the negative refraction is derived.

  19. Ultrafast structural dynamics of the orthorhombic distortion in the Fe-pnictide parent compound BaFe2As2

    PubMed Central

    Rettig, L.; Mariager, S. O.; Ferrer, A.; Grübel, S.; Johnson, J. A.; Rittmann, J.; Wolf, T.; Johnson, S. L.; Ingold, G.; Beaud, P.; Staub, U.

    2016-01-01

    Using femtosecond time-resolved hard x-ray diffraction, we investigate the structural dynamics of the orthorhombic distortion in the Fe-pnictide parent compound BaFe2As2. The orthorhombic distortion analyzed by the transient splitting of the (1 0 3) Bragg reflection is suppressed on an initial timescale of 35 ps, which is much slower than the suppression of magnetic and nematic order. This observation demonstrates a transient state with persistent structural distortion and suppressed magnetic/nematic order which are strongly linked in thermal equilibrium. We suggest a way of quantifying the coupling between structural and nematic degrees of freedom based on the dynamics of the respective order parameters. PMID:27158636

  20. Influence of downsizing of zeolite crystals on the orthorhombic ↔ monoclinic phase transition in pure silica MFI-type

    NASA Astrophysics Data System (ADS)

    Kabalan, Ihab; Michelin, Laure; Rigolet, Séverinne; Marichal, Claire; Daou, T. Jean; Lebeau, Bénédicte; Paillaud, Jean-Louis

    2016-08-01

    The impact of crystal size on the transition orthorhombic ↔ monoclinic phase in MFI-type purely silica zeolites is investigated between 293 and 473 K using 29Si MAS NMR and powder X-ray diffraction. Three silicalite-1 zeolites are synthesized: a material constituted of micron-sized crystals, pseudospherical nanometer-sized crystals and hierarchical porous zeolites with a mesoporous network created by the use of a gemini-type diquaternary ammonium surfactant giving nanosheet zeolites. Our results show for the first time that the orthorhombic ↔ monoclinic phase transition already known for micron-sized particles also occurs in nanometer-sized zeolite crystals whereas our data suggest that the extreme downsizing of the zeolite crystal to one unit cell in thickness leads to an extinction of the phase transition.

  1. One-step hydrothermal synthesis, characterization and magnetic properties of orthorhombic PrCrO{sub 3} cubic particles

    SciTech Connect

    Zhang, Youjin Yao, Chengpeng; Fan, Yun; Zhou, Maozhong

    2014-11-15

    Highlights: • Orthorhombic PrCrO{sub 3} cubic particles were prepared by a simple and facile one-step hydrothermal method. • The possible formation mechanism of PrCrO{sub 3} cubic particles was proposed. • The as-synthesized PrCrO{sub 3} exhibited behaviors of magnetic transition and negative magnetization. - Abstract: Orthorhombic PrCrO{sub 3} cubic particles were synthesized by a simple and facile one-step hydrothermal method of processing temperature 280 °C for 7 days. The products prepared in this paper have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM). The magnetic properties of the final sample are also studied. The XRD pattern shows the pure orthorhombic phase for PrCrO{sub 3} particles, the XPS and FTIR results further demonstrate the purity and composition of the product. FESEM images show cubic morphology for the PrCrO{sub 3} particles. The possible growth mechanism for PrCrO{sub 3} cubic particles is proposed. Through the investigation of magnetic properties, it can be seen that the orthorhombic PrCrO{sub 3} cubic particles exhibit behaviors of magnetic transition and negative magnetization. The Néel temperature is about 232 K and the magnetic hysteresis loop under 4 K shows that the coercivity (H{sub C}) and remanence (M{sub r}) is about 1728 Oe and 4.88 emu/g, respectively.

  2. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic.

    PubMed

    Mundy, Julia A; Brooks, Charles M; Holtz, Megan E; Moyer, Jarrett A; Das, Hena; Rébola, Alejandro F; Heron, John T; Clarkson, James D; Disseler, Steven M; Liu, Zhiqi; Farhan, Alan; Held, Rainer; Hovden, Robert; Padgett, Elliot; Mao, Qingyun; Paik, Hanjong; Misra, Rajiv; Kourkoutis, Lena F; Arenholz, Elke; Scholl, Andreas; Borchers, Julie A; Ratcliff, William D; Ramesh, Ramamoorthy; Fennie, Craig J; Schiffer, Peter; Muller, David A; Schlom, Darrell G

    2016-01-01

    Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3-the geometric ferroelectric with the greatest known planar rumpling-we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially-from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering. PMID:27652564

  3. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic

    NASA Astrophysics Data System (ADS)

    Mundy, Julia A.; Brooks, Charles M.; Holtz, Megan E.; Moyer, Jarrett A.; Das, Hena; Rébola, Alejandro F.; Heron, John T.; Clarkson, James D.; Disseler, Steven M.; Liu, Zhiqi; Farhan, Alan; Held, Rainer; Hovden, Robert; Padgett, Elliot; Mao, Qingyun; Paik, Hanjong; Misra, Rajiv; Kourkoutis, Lena F.; Arenholz, Elke; Scholl, Andreas; Borchers, Julie A.; Ratcliff, William D.; Ramesh, Ramamoorthy; Fennie, Craig J.; Schiffer, Peter; Muller, David A.; Schlom, Darrell G.

    2016-09-01

    Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3—the geometric ferroelectric with the greatest known planar rumpling—we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially—from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.

  4. Order Parameters and Phase Diagram of Multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Harris, A. B.; Aharony, Amnon; Entin-Wohlman, Ora

    2008-05-01

    The generic magnetic phase diagram of multiferroic RMn2O5 (with R=Y, Ho, Tb, Er, Tm), which allows different sequences of ordered magnetic structures for different R’s and different control parameters, is described using order parameters which explicitly incorporate the magnetic symmetry. A phenomenological magnetoelectric coupling is used to explain why some of these magnetic phases are also ferroelectric. Several new experiments, which can test this theory, are proposed.

  5. Lattice dynamics and spin-phonon interactions in multiferroic RMn2O5: Shell model calculations

    NASA Astrophysics Data System (ADS)

    Litvinchuk, A. P.

    2009-08-01

    The results of the shell model lattice dynamics calculations of multiferroic RMn2O5 materials (space group Pbam) are reported. Theoretical even-parity eigenmode frequencies are compared with those obtained experimentally in polarized Raman scattering experiments for R=Ho,Dy. Analysis of displacement patterns allows to identify vibrational modes which facilitate spin-phonon coupling by modulating the Mn-Mn exchange interaction and provides explanation of the observed anomalous temperature behavior of phonons.

  6. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

    DOE PAGES

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud’ko, Sergey L.; Canfield, Paul C.

    2015-07-28

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). The properties of the HT MnBi, which is stable between 613 and 719 K, have notmore » been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625–xRhxBi [x=0.02(1)] adopts a new superstructure of the NiAs/Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3μB/f.u. at low temperatures. Thus, while this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.« less

  7. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier

    SciTech Connect

    Liu, Jin; Lin, Jung -Fu; Prakapenka, Vitali B.

    2015-01-06

    In this study, knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth.

  8. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

    SciTech Connect

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud’ko, Sergey L.; Canfield, Paul C.

    2015-07-28

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). The properties of the HT MnBi, which is stable between 613 and 719 K, have not been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625–xRhxBi [x=0.02(1)] adopts a new superstructure of the NiAs/Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3μB/f.u. at low temperatures. Thus, while this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.

  9. Dynamic and structural properties of orthorhombic rare-earth manganites under high pressure

    NASA Astrophysics Data System (ADS)

    Mota, D. A.; Almeida, A.; Rodrigues, V. H.; Costa, M. M. R.; Tavares, P.; Bouvier, P.; Guennou, M.; Kreisel, J.; Moreira, J. Agostinho

    2014-08-01

    We report a high-pressure study of orthorhombic rare-earth manganites AMnO3 using Raman scattering (for A=Pr, Nd, Sm, Eu, Tb, and Dy) and synchrotron x-ray diffraction (XRD), for A = Pr, Sm, Eu, and Dy. In all cases, a phase transition was evidenced by the disappearance of the Raman signal at a critical pressure that depends on the A cation. For the compounds with A=Pr, Sm, and Dy, XRD confirms the presence of a corresponding structural transition to a noncubic phase, so that the disappearance of the Raman spectrum can be interpreted as an insulator-to-metal transition. We analyze the compression mechanisms at work in the different manganites via the pressure dependence of the lattice parameters, the shear strain in the ac plane, and the Raman bands associated with out-of-phase MnO6 rotations and in-plane O2 symmetric stretching modes. Our data show a crossover across the rare-earth series between two different kinds of behavior. For the smaller A cations considered in this study (Dy and Tb), the compression is nearly isotropic in the ac plane, with only small evolutions of the tilt angles and cooperative Jahn-Teller distortion. As the radius of the A cation increases, the pressure-induced reduction of Jahn-Teller distortion becomes more pronounced and increasingly significant as a compression mechanism, while the pressure-induced tilting of octahedra chains becomes conversely less pronounced. We finally discuss our results in light of the notion of chemical pressure and show that the analogy with hydrostatic pressure works quite well for manganites with the smaller A cations considered in this paper but can be misleading with large A cations.

  10. Orthorhombic 11C pyrrhotite from Michałkowa, Góry Sowie Block, The Sudetes, Poland - preliminary report

    NASA Astrophysics Data System (ADS)

    Rybicki, Maciej; Krzykawski, Tomasz

    2014-09-01

    This study provides the preliminary report about first occurrence of orthorhombic 11C pyrrhotite (Fe(1-x)S) from the Sudetes, Poland. Samples of pyrrhotite-containing two-pyroxene gabbro were found in a classic pegmatite locality in Michałkowa near Walim in the Góry Sowie Block. Based on microscopic methods, pyrrhotite is associated with pentlandite, chalcopyrite, chromite, ilmenite, gersdorffite, magnetite, biotite, magnesiohornblende, clinochlore, lizardite and talc. X-Ray diffraction (XRD) indicate that pyrrhotite has orthorhombic 11C structure and it is characterized by: a = 3.433(9) Å, b = 5.99(2) Å, c = 5.7432(5) Å, β = 90º and d102 = 2.06906 Å. Mössbauer studies confirmed the XRD data. Pyrrhotite has three sextets with hyperfine parameter values 30.8 T for sextet A, 27.9 T and 25.8 T for sextets B and C respectively, indicating orthorhombic structure, the composition near Fe10S11 and x = 0.0909

  11. Orthorhombic 11C Pyrrhotite from Michałkowa, Góry Sowie Block, The Sudetes, Poland - Preliminary Report

    NASA Astrophysics Data System (ADS)

    Rybicki, Maciej; Krzykawski, Tomasz

    2014-09-01

    This study provides the preliminary report about first occurrence of orthorhombic 11C pyrrhotite (Fe(i-x)S) from the Sudetes, Poland. Samples of pyrrhotite-containing two-pyroxene gabbro were found in a classic pegmatite locality in Michałkowa near Walim in the Góry Sowie Block. Based on microscopic methods, pyrrhotite is associated with pentlandite, chalcopyrite, chromite, ilmenite, gersdorffite, magnetite, biotite, magnesiohornblende, clinochlore, lizardite and talc. X-Ray diffraction (XRD) indicate that pyrrhotite has orthorhombic 11C structure and it is characterized by: a = 3.433(9) Å, b = 5.99(2) Å, c = 5.7432(5) Å, ß = 90° and d 102 = 2.06906 Å. Mössbauer studies confirmed the XRD data. Pyrrhotite has three sextets with hyperfine parameter values 30.8 T for sextet A, 27.9 T and 25.8 T for sextets B and C respectively, indicating orthorhombic structure, the composition near Fe10S11 and x = 0.0909.

  12. Facile Route to the Controlled Synthesis of Tetragonal and Orthorhombic SnO2 Films by Mist Chemical Vapor Deposition.

    PubMed

    Bae, Jae-Yoon; Park, Jozeph; Kim, Hyun You; Kim, Hyun-Suk; Park, Jin-Seong

    2015-06-10

    Two types of tin dioxide (SnO2) films were grown by mist chemical vapor deposition (Mist-CVD), and their electrical properties were studied. A tetragonal phase is obtained when methanol is used as the solvent, while an orthorhombic structure is formed with acetone. The two phases of SnO2 exhibit different electrical properties. Tetragonal SnO2 behaves as a semiconductor, and thin-film transistors (TFTs) incorporating this material as the active layer exhibit n-type characteristics with typical field-effect mobility (μ(FE)) values of approximately 3-4 cm(2)/(V s). On the other hand, orthorhombic SnO2 is found to behave as a metal-like transparent conductive oxide. Density functional theory calculations reveal that orthorhombic SnO2 is more stable under oxygen-rich conditions, which correlates well with the experimentally observed solvent effects. The present study paves the way for the controlled synthesis of functional materials by atmospheric pressure growth techniques. PMID:25984757

  13. Bounds and self-consistent estimates for elastic constants of granular polycrystals composed of orthorhombics or crystal with higher symmetries

    SciTech Connect

    Berryman, J. G.

    2011-02-01

    Methods for computing Hashin-Shtrikman bounds and related self-consistent estimates of elastic constants for polycrystals composed of crystals having orthorhombic symmetry have been known for about three decades. However, these methods are underutilized, perhaps because of some perceived difficulties with implementing the necessary computational procedures. Several simplifications of these techniques are introduced, thereby reducing the overall computational burden, as well as the complications inherent in mapping out the Hashin-Shtrikman bounding curves. The self-consistent estimates of the effective elastic constants are very robust, involving a quickly converging iteration procedure. Once these self-consistent values are known, they may then be used to speed up the computations of the Hashin-Shtrikman bounds themselves. It is shown furthermore that the resulting orthorhombic polycrystal code can be used as well to compute both bounds and self-consistent estimates for polycrystals of higher-symmetry tetragonal, hexagonal, and cubic (but not trigonal) materials. The self-consistent results found this way are shown to be the same as those obtained using the earlier methods, specifically those methods designed specially for each individual symmetry type. But the Hashin-Shtrikman bounds found using the orthorhombic code are either the same or (more typically) tighter than those found previously for these special cases (i.e., tetragonal, hexagonal, and cubic). The improvement in the Hashin-Shtrikman bounds is presumably due to the additional degrees of freedom introduced into the available search space.

  14. Photo-enhanced salt-water splitting using orthorhombic Ag8SnS6 photoelectrodes in photoelectrochemical cells

    NASA Astrophysics Data System (ADS)

    Cheng, Kong-Wei; Tsai, Wei-Tseng; Wu, Yu-Hsuan

    2016-06-01

    Orthorhombic Ag8SnS6 photoelectrodes are prepared on various substrates via reactive sulfurization using the radio-frequency magnetron sputtering of silver-tin metal precursors. Evaluations of the photoelectrochemical performances of Ag8SnS6 photoelectrodes with various levels of silver content are carried out in various aqueous solutions. X-ray diffraction patterns and Hall measurements of samples after a three-stage sulfurization process show that all samples are the pure orthorhombic Ag8SnS6 phase with n-type conductivity. The energy band gaps, carrier concentrations, and mobilities of samples on glass substrates are 1.31-1.33 eV, 7.07 × 1011-8.52 × 1012 cm-3, and 74.9-368 cm2 V-1 s-1, respectively, depending on the [Ag]/[Ag+Sn] molar ratio in samples. The highest photoelectrochemical performances of orthorhombic Ag8SnS6 photoelectrodes in aqueous 0.35 M Na2S + 0.25 M K2SO3 and 0.5 M NaCl solutions are respectively 2.09 and 2.5 mA cm-2 at an applied voltages of 0.9 and 1.23 V vs. a reversible hydrogen electrode under light irradiation with a light intensity of 100 mW cm-2 from a 300-W Xe lamp.

  15. Polar-graded multiferroic SrMnO3 thin films

    DOE PAGES

    Lupini, Andrew R.; Guzman, Roger; Maurel, Laura; Langenberg, Eric; Algarabel, Pedro A.; Pardo, Jose A.; Magen, Cesar

    2016-03-21

    Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization with atomic resolution, both far from and near the domainmore » walls, and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Furthermore, we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity.« less

  16. Polar-Graded Multiferroic SrMnO3 Thin Films.

    PubMed

    Guzmán, Roger; Maurel, Laura; Langenberg, Eric; Lupini, Andrew R; Algarabel, Pedro A; Pardo, José A; Magén, César

    2016-04-13

    Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization with atomic resolution, both far from and near the domain walls, and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Herein we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity. PMID:26999643

  17. Reversible electric control of exchange bias in a multiferroic field-effect device.

    PubMed

    Wu, S M; Cybart, Shane A; Yu, P; Rossell, M D; Zhang, J X; Ramesh, R; Dynes, R C

    2010-09-01

    Electric-field control of magnetization has many potential applications in magnetic memory storage, sensors and spintronics. One approach to obtain this control is through multiferroic materials. Instead of using direct coupling between ferroelectric and ferromagnetic order parameters in a single-phase multiferroic material, which only shows a weak magnetoelectric effect, a unique method using indirect coupling through an intermediate antiferromagnetic order parameter can be used. In this article, we demonstrate electrical control of exchange bias using a field-effect device employing multiferroic (ferroelectric/antiferromagnetic) BiFeO(3) as the dielectric and ferromagnetic La(0.7)Sr(0.3)MnO(3) as the conducting channel; we can reversibly switch between two distinct exchange-bias states by switching the ferroelectric polarization of BiFeO(3). This is an important step towards controlling magnetization with electric fields, which may enable a new class of electrically controllable spintronic devices and provide a new basis for producing electrically controllable spin-polarized currents.

  18. The search for new multiferroic ABF4 fluorides via first-principles structure maps

    NASA Astrophysics Data System (ADS)

    Abbett, Brian; Krishnapriyan, Aditi; Fennie, Craig J.

    2013-03-01

    Transition metal ABF4 fluorides are observed in a wide variety of different structure types. One, the BaMnF4 structure, is an interesting family of polar (possibly ferroelectric) materials that display canted-antiferromagnetism, which has been predicted (Ederer and Spaldin) to reverse when the polarization reverses. This strong coupling between magnetism and polarization has motivated us to explore additional ABF4 structure types. In this talk we will discuss our search for new multiferroic ABF4 fluorides by creating structure maps from first principles. As a first step we categorize the ABF4 compounds found in the ICSD. We focus on structures for which the B-site is octahedrally coordinated; these can be fitted into one of four categories: BaMF4, Dion-Jacobson, and the so-called slip (100) or slip (110) structures. These four categories represent high symmetry structures which allow distortions to lower symmetry structures. Note that most of the known multiferroic ABF4 compounds form in the BaMF4 structure. We elucidate a simple descriptor that helps to build the chemical and physical intuition as to why a compound forms in this structure type needed for the rational design of new multiferroic ABF4 fluorides. 2012 CCMR-NSF REU Student

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  20. Polar-Graded Multiferroic SrMnO3 Thin Films.

    PubMed

    Guzmán, Roger; Maurel, Laura; Langenberg, Eric; Lupini, Andrew R; Algarabel, Pedro A; Pardo, José A; Magén, César

    2016-04-13

    Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization with atomic resolution, both far from and near the domain walls, and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Herein we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  2. Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

    SciTech Connect

    Sadovnikov, A. V. Nikitov, S. A.; Beginin, E. N.; Bublikov, K. V.; Grishin, S. V.; Sheshukova, S. E.; Sharaevskii, Yu. P.

    2015-11-28

    Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.

  3. Application of a generalized matrix averaging method for the calculation of the effective properties of thin multiferroic layers

    SciTech Connect

    Starkov, A. S.; Starkov, I. A.

    2014-11-15

    It is proposed to use a generalized matrix averaging (GMA) method for calculating the parameters of an effective medium with physical properties equivalent to those of a set of thin multiferroic layers. This approach obviates the need to solve a complex system of magnetoelectroelasticity equations. The required effective characteristics of a system of multiferroic layers are obtained using only operations with matrices, which significantly simplifies calculations and allows multilayer systems to be described. The proposed approach is applicable to thin-layer systems, in which the total thickness is much less than the system length, radius of curvature, and wavelengths of waves that can propagate in the system (long-wave approximation). Using the GMA method, it is also possible to obtain the effective characteristics of a periodic structure with each period comprising a number of thin multiferroic layers.

  4. Electric-field control of electromagnon propagation and spin-wave injection in a spiral multiferroic/ferromagnet composite

    SciTech Connect

    Chen, Hong-Bo; Li, You-Quan; Berakdar, Jamal

    2015-01-28

    We consider theoretically a composite chain consisting of a multiferroic helimagnet coupled to a conventional ferromagnet and inspect the conversion of electromagnon excitation into spin waves and vice versa. We demonstrate an electric-field control of spin-wave injection realized by electrically exciting an electromagnon that propagates with an intrinsic frequency larger than the gap of the spin wave in the ferromagnet. The efficiency of the conversion of the electromagnon into spin waves depends strongly on the strength of the magnetoelectric coupling at the interface and the intrinsic frequency of the multiferroic helimagnets. The phenomena predicted here suggest that a multiferroic/ferromagnet composite offers new opportunities for spin-wave injection, conversion, and control using electric field.

  5. Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

    NASA Astrophysics Data System (ADS)

    Sadovnikov, A. V.; Beginin, E. N.; Bublikov, K. V.; Grishin, S. V.; Sheshukova, S. E.; Sharaevskii, Yu. P.; Nikitov, S. A.

    2015-11-01

    Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.

  6. X-band frequency response and electromagnetic interference shielding in multiferroic BiFeO3 nanomaterials

    NASA Astrophysics Data System (ADS)

    Reshi, Hilal Ahmad; Singh, Avanish Pratap; Pillai, Shreeja; Para, Touseef Ahmad; Dhawan, S. K.; Shelke, Vilas

    2016-10-01

    The presence of electric dipoles, magnetic dipoles and mobile charges is a prerequisite for electromagnetic interference (EMI) shielding materials. Here, we demonstrate that multiferroic compound with incipient ensemble of electric and magnetic dipoles can perform as an EMI shielding material. We synthesized single phase BiFeO3 nanomaterial and studied complex electromagnetic properties in an X-band frequency region. A shielding effectiveness up to 11 dB with a major contribution from absorption was observed in the BiFeO3 nanomaterials. An auxiliary functionality of radiation shielding is revealed in the multiferroic BiFeO3 compound.

  7. All-thin-film multilayered multiferroic structures with a slot-line for spin-electromagnetic wave devices

    SciTech Connect

    Nikitin, Andrey A.; Ustinov, Alexey B.; Semenov, Alexander A.; Kalinikos, Boris A.; Lähderanta, E.

    2014-03-03

    Spin-electromagnetic waves propagating in thin-film multilayered multiferroic structures containing a slot transmission line have been investigated both experimentally and theoretically. The thin-film structure was composed of a ferrite film, a ferroelectric film, and a slot-line. It was shown that the spectrum of the spin-electromagnetic wave was formed as a result of hybridization of the spin wave in the ferrite film with the electromagnetic wave in the slot-line and was electrically and magnetically tunable. For the experimental investigations, a microwave phase shifter based on the multiferroic structure has been fabricated. Performance characteristics are presented.

  8. Uniaxial-stress control of spin-driven ferroelectricity in multiferroic Ba(2)CoGe(2)O(7).

    PubMed

    Nakajima, Taro; Tokunaga, Yusuke; Kocsis, Vilmos; Taguchi, Yasujiro; Tokura, Yoshinori; Arima, Taka-Hisa

    2015-02-13

    We have demonstrated that spin-driven ferroelectricity in a tetragonal multiferroic Ba(2)CoGe(2)O(7) is controlled by applying uniaxial stress. We found that the application of compressive stress along the [110] direction leads to a 45° or 135° rotation of the sublattice magnetization of the staggered antiferromagnetic order in this system. This allows the spontaneous electric polarization to appear along the c axis. The present study suggests that an application of anisotropic stress, which is the simplest way to control symmetry of matter, can induce a variety of cross-correlated phenomena in spin-driven multiferroics.

  9. Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites

    NASA Astrophysics Data System (ADS)

    Smith, P. R.; Graves, J. A.; Rhodes, Cg.

    1994-06-01

    The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti3Al ( α 2) + disordered beta (β), while the Ti-21 Al-22Nb matrix contained three phases: α2, ordered beta ( β 0), and ordered orthorhombic (O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products (i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in the α 2 + β matrix composite were much more rapid than in the O + β 0 + α 2 matrix composite. Additionally, interfacial reaction in the α 2 + β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in the O + β 0+ α 2 matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α2+ β alloy in all of these mechanical behavioral areas, on both an absolute and a specific (i.e., density corrected) basis.

  10. An orthorhombic crystal form of cyclohexaicosaose, CA26.32.59 H(2)O: comparison with the triclinic form.

    PubMed

    Nimz, O; Gessler, K; Usón, I; Saenger, W

    2001-11-01

    Cycloamylose containing 26 glucose residues (cyclohexaicosaose, CA26) crystallized from water and 30% (v/v) polyethyleneglycol 400 in the orthorhombic space group P2(1)2(1)2(1) in the highly hydrated form CA26.32.59 H(2)O. X-ray analysis of the crystals at 0.85 A resolution shows that the macrocycle of CA26 is folded into two short left-handed V-amylose helices in antiparallel arrangement and related by a twofold rotational pseudosymmetry as reported recently for the (CA26)(2).76.75 H(2)O triclinic crystal form [Gessler, K. et al. Proc. Natl. Acad. Sci. USA 1999, 96, 4246-4251]. In the orthorhombic crystal form, CA26 molecules are packed in motifs reminiscent of V-amylose in hydrated and anhydrous forms. The intramolecular interface between the V-helices in CA26 is dictated by formation of an extended network of interhelical C-H...O hydrogen bonds; a comparable molecular arrangement is also evident for the intermolecular packing, suggesting that it is a characteristic feature of V-amylose interaction. The hydrophobic channels of CA26 are filled with disordered water molecules arranged in chains and held in position by multiple C-H...O hydrogen bonds. In the orthorhombic and triclinic crystal forms, the structures of CA26 molecules are equivalent but the positions of the individual water molecules are different, suggesting that the patterns of water chains are perturbed even by small structural changes associated with differences in packing arrangements in the two crystal lattices rather than with differences in the CA26 geometry.

  11. Strain effect on electronic structure and thermoelectric properties of orthorhombic SnSe: A first principles study

    SciTech Connect

    Cuong, Do Duc; Rhim, S. H. Hong, Soon Cheol; Lee, Joo-Hyong

    2015-11-15

    Strain effect on thermoelectricity of orthorhombic SnSe is studied using density function theory. The Seebeck coefficients are obtained by solving Boltzmann Transport equation (BTE) with interpolated band energies. As expected from the crystal structure, calculated Seebeck coefficients are highly anisotropic, and agree well with experiment. Changes in the Seebeck coefficients are presented, when strain is applied along b and c direction with strength from -3% to +3%, where influence by band gaps and band dispersions are significant. Moreover, for compressive strains, the sign change of Seebeck coefficients at particular direction suggests that the bipolar transport is possible for SnSe.

  12. Ferromagnetic state in ultrathin orthorhombic CrAs films: Thickness, lattice distortion, and half-metallic contributions

    NASA Astrophysics Data System (ADS)

    Araújo, Alexandre A.; Laks, Bernardo; de Camargo, P. C.

    2006-11-01

    Orthorhombic CrAs thin films were investigated using first-principles spin-polarized calculations in the full-potential linearized augmented plane-wave method. Our results consider two different geometry optimization processes and show that the ferromagnetic state is favored by b -axis expansion, being more stable than the antiferromagnetic state for film thickness below approximately 24Å . The calculated maximum magnetic moment per formula unit is near 3μB and decreases with increasing film thickness, in good agreement with the observed saturation magnetization. The electronic structure of very thin films with expanded b axis suggests a half-metallic behavior.

  13. Part III. The tensile behavior of Ti-Al-Nb O+Bcc orthorhombic alloys

    NASA Astrophysics Data System (ADS)

    Boehlert, C. J.

    2001-08-01

    The tensile behavior of Ti-Al-Nb alloys with Al concentrations between 12 and 26 at. pct and Nb concentrations between 22 and 38 at. pct has been investigated for temperatures between 25 °C and 650 °C. Several microstructural features were evaluated in an attempt to identify microstructure-property relationships. In particular, the effects of the phase volume fraction, composition, morphology, and grain size were examined. In addition, the constitutive properties were evaluated using single-phase microstructures, and the results provided insight into the microstructure-property relationships of the two-phase orthorhombic (O)+body-centered-cubic (bcc) microstructures. The disordered fully-bcc ( β) Ti-12Al-38Nb microstructure, produced through heat treatment above the β-transus, exhibited a room-temperature (RT) elongation of more than 27 pct and the lowest yield strength (YS-553 MPa) of all the alloys studied. The ordered fully-bcc (B2) microstructures, produced through supertransus heat treatment of near-Ti2AlNb alloys, exhibited fracture strengths up to 672 MPa and low elongations-to-failure ( ɛ f≤0.6 pct). Thus, increasing the Al content, which favors ordering of the bcc structure, significantly reduces the ductility of the bcc phase. Similar to the ordered B2 microstructure, the ordered fully-O Ti2AlNb microstructures exhibited intermediate RT strength (≤704 MPa) and ɛ f (≤1 pct). The O+bcc microstructures tended to exhibit strengths greater than both the fully-O and fully-bcc microstructures, and this was attributed to the finer grain sizes in the two-phase microstructures compared to their single-phase counterparts. A RT of 1125 MPa was measured for the finest-grained two-phase microstructure. The O+bcc microstructures containing greater bcc-phase volume fractions tended to exhibit greater elongations yet poorer elevated-temperature strengths. A higher Al content typically resulted in larger elevated-temperature strengths. For the Ti-12Al-38Nb bcc

  14. Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites.

    PubMed

    Sreenivasulu, Gollapudi; Qu, Peng; Petrov, Vladimir; Qu, Hongwei; Srinivasan, Gopalan

    2016-02-20

    Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data.

  15. A Local Approach to Solid State Problems: Pseudo Jahn-Teller origin of Ferroelectricity and Multiferroicity

    NASA Astrophysics Data System (ADS)

    Bersuker, I. B.

    2013-04-01

    This is a partially review paper in which, in continuation of previous work, it is shown that in perovskite crystals of ABO3 type the spontaneous polarization is triggered by local vibronic interactions, the pseudo Jahn-Teller effect (PJTE). The driving force of the latter is added covalency by distortion, which is essentially of local (chemical) origin. The local origin of polar instability in crystals is confirmed by the theorem of structural instability proved earlier. For crystals of BaTiO3 type local PJT interactions of the metal ion with the oxygen environment results in a peculiar adiabatic potential energy surface (APES) which has eight trigonal [111] type minima, twelve [110] type saddle points between them, six higher in energy [100] type saddle points at the top of the barrier connecting four minima, and a maximum at the cubic symmetry. The temperature dependence of the free energy with this potential explains the origin of all the four phases in such crystals; only the lowest rhombohedral phase is fully ordered, the other two ones at higher temperatures are partially disordered, and the paraelectric phase is fully (three-dimensionally) disordered. For BaTiO3 this picture is confirmed by numerical estimates and ab initio DFT calculations. An important further development of this theory was reached recently by showing that not only B ions with electronic d0 configurations are subject to the PJTE instability to produce ferroelectricity in perovskite crystals ("the d0 mystery"), but some other specific dn configurations with unpaired electrons may be dipolar active too, the crystal being thus both magnetic and ferroelectric (multiferroic), and the necessary conditions for such multiferroicity are formulated for the whole d0-dn variety of perovskites. Moreover, the condition of multiferroicity was shown to depend also on the spin state, high-spin or low-spin, which in conditions of spin crossover leads to a magnetic-ferroelectric crossover that can be

  16. Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites

    PubMed Central

    Sreenivasulu, Gollapudi; Qu, Peng; Petrov, Vladimir; Qu, Hongwei; Srinivasan, Gopalan

    2016-01-01

    Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data. PMID:26907290

  17. Three-dimensional magnetic correlations in multiferroic LuFe2O4

    SciTech Connect

    Christianson, Andrew D; Lumsden, Mark D; Angst, Manuel; Yamani, Z.; Tian, Wei; Jin, Rongying; Payzant, E Andrew; Nagler, Stephen E; Sales, Brian C; Mandrus, David

    2008-01-01

    We present single crystal neutron diffraction measurements on multiferroic LuFe{sub 2}O{sub 4}. Magnetic reflections are observed below transitions at 240 and 175 K indicating that the magnetic interactions in LuFe{sub 2}O{sub 4} are three-dimensional in character. The magnetic structure is refined as a ferrimagnetic spin configuration below the 240 K transition. Below 175 K a significant broadening of the magnetic peaks is observed along with the buildup of a diffuse component to the magnetic scattering.

  18. Electric-field control of exchange bias in multiferroic epitaxial heterostructures.

    PubMed

    Laukhin, V; Skumryev, V; Martí, X; Hrabovsky, D; Sánchez, F; García-Cuenca, M V; Ferrater, C; Varela, M; Lüders, U; Bobo, J F; Fontcuberta, J

    2006-12-01

    The magnetic exchange between epitaxial thin films of the multiferroic (antiferromagnetic and ferroelectric) hexagonal YMnO3 oxide and a soft ferromagnetic (FM) layer is used to couple the magnetic response of the FM layer to the magnetic state of the antiferromagnetic one. We will show that biasing the ferroelectric YMnO3 layer by an electric field allows control of the magnetic exchange bias and subsequently the magnetotransport properties of the FM layer. This finding may contribute to paving the way towards a new generation of electric-field controlled spintronic devices.

  19. Ferroelectric phase transitions in multiferroic Ge1 -xMnxTe driven by local lattice distortions

    NASA Astrophysics Data System (ADS)

    Kriegner, Dominik; Furthmüller, Jürgen; Kirchschlager, Raimund; Endres, Jan; Horak, Lukas; Cejpek, Petr; Reichlova, Helena; Marti, Xavier; Primetzhofer, Daniel; Ney, Andreas; Bauer, Günther; Bechstedt, Friedhelm; Holy, Vaclav; Springholz, Gunther

    2016-08-01

    The evolution of local ferroelectric lattice distortions in multiferroic Ge1 -xMnxTe is studied by x-ray diffraction, x-ray absorption spectroscopy, and density functional theory. We show that the anion/cation displacements smoothly decrease with increasing Mn content, thereby reducing the ferroelectric transition from 700 to 100 K at x =0.5 , where the ferromagnetic Curie temperature reaches its maximum. First principles calculations explain this quenching by different local bond contributions of the Mn 3 d shell compared to the Ge 4 s shell in excellent quantitative agreement with the experiments.

  20. Spectral origin of the colossal magnetodielectric effect in multiferroic DyMn2O5

    NASA Astrophysics Data System (ADS)

    Sushkov, A. B.; Kant, Ch.; Schiebl, M.; Shuvaev, A. M.; Pimenov, Anna; Pimenov, Andrei; Lorenz, Bernd; Park, S.; Cheong, S.-W.; Mostovoy, Maxim; Drew, H. D.

    2014-08-01

    The origin of the colossal magnetodielectric (CMD) effect in DyMn2O5 [N. Hur et al., Phys. Rev. Lett. 93, 107207 (2004), 10.1103/PhysRevLett.93.107207] has been an outstanding question in multiferroics. Here, we report the activation of the electric dipole mode at 4-5 cm-1 in an applied magnetic field, which fully accounts for the CMD effect. We examine two alternative explanations of this mode: an electromagnon and transitions between f-electron levels of Dy3+ ions. The experimental and theoretical evidence supports an electromagnon origin of the CMD effect.

  1. Magnetic exchange interaction between rare-earth and Mn ions in multiferroic hexagonal manganites

    SciTech Connect

    Talbayev, Diyar; Trugman, Stuart A; Taylor, Antoinette J; Averitt, Richard D; Namjung, Hur; Andrew, Laforge D; Dimitri, Basov N

    2008-01-01

    The authors report a study of magnetic dynamics in multiferroic hexagonal manganite HoMnO{sub 3} by far-infrared spectroscopy. Low-temperature magnetic excitation spectrum of HoMnO{sub 3} consists of magnetic-dipole transitions of Ho ions within the crystal-field split J = 8 manifold and of the triangular antiferromagnetic resonance of Mn ions. They determine the effective spin Hamiltonian for the Ho ion ground state. The magnetic-field splitting of the Mn antiferromagnetic resonance allows us to measure the magnetic exchange coupling between the rare-earth and Mn ions.

  2. Electronic Correlations Decimate the Ferroelectric Polarization of Multiferroic HoMn2O5

    NASA Astrophysics Data System (ADS)

    Giovannetti, Gianluca; van den Brink, Jeroen

    2008-06-01

    We show that electronic correlations decimate the intrinsic ferroelectric polarization of multiferroic manganites RMn2O5, where R is a rare earth element. Such is manifest from ab initio band structure computations that account for the Coulomb interactions between the manganese 3d electrons—the root of magnetism in RMn2O5. Including these leads to an amplitude and direction of polarization of HoMn2O5 that agree with experiment. The decimation is caused by a near cancellation of the ionic polarization induced by the lattice and the electronic one due to valence charge redistributions.

  3. Theory of antisymmetric spin-pair-dependent electric polarization in multiferroics

    NASA Astrophysics Data System (ADS)

    Miyahara, S.; Furukawa, N.

    2016-01-01

    We investigate magnetoelectric couplings between an electric polarization and an antisymmetric spin pair, Si×Sj , in a multiorbital Hubbard model on a distorted lattice. We microscopically derive a generic form of the electric polarization, pAS=d ̂(Si×Sj) , with a tensor, d ̂, which includes the electric polarization induced by the Katsura-Nagaosa-Balatsky formula as a subset. The origin and nature of these magnetoelectric couplings are clarified in a unified way; the results indicate that various noncollinear magnetic structures, such as canted antiferromagnetic, proper screw, and 120∘ spin structures, show multiferroic behaviors owing to non-Katsura-Nagaosa-Balatsky coupling.

  4. Exchange bias effect modified asymmetric magnetization reversal in Ni/YMnO3 multiferroic bilayers

    NASA Astrophysics Data System (ADS)

    Gong, Junlu; Zheng, Dongxing; Li, Dong; Jin, Chao; Li, Peng; Feng, Liefeng; Bai, Haili

    2016-04-01

    Exchange bias (EB) effect modified asymmetric magnetization reversal in Ni/YMnO3 multiferroic bilayers was investigated by combining anisotropic magnetoresistance (AMR) with free energy methods. The promotion and inhibition effects of EB field on magnetization rotation result in the asymmetry of magnetization reversal. The AMR curves exhibit shape transition from arc-like to sin2θH-dependence with increasing external fields due to the competition between Zeeman energy and interfacial coupling energy. The phase shift and asymmetric behaviors become weak as the EB field decreases. Our work suggests that controlling the EB effect can be an alternative way to manipulate the magnetization reversal in exchange biased systems.

  5. THz generation via optical rectification from multiferroic BiFeO3

    SciTech Connect

    Talbayev, Diyar; Taylor, Antoinette J

    2008-01-01

    We detected broadband coherent terahertz (THz) emission from multiferroic BiFeO{sub 3} after illuminating a high-quality bulk single ferroelectric domain crystal with a {approx}100 fs optical pulse. The dependence of the emitted THz waveform on the energy and polarization of the optical pulse is consistent with the optical rectification mechanism of THz emission. The THz emission provides a sensitive probe of the electric polarization state of BiFeO{sub 3}, enabling applications in ferroelectric memories and ferroelectric domain imaging. We also report room-temperature THz optical constants of BiFeO{sub 3}.

  6. Optical properties of integrated multiferroic BiFeO3 thin films for microwave applications

    NASA Astrophysics Data System (ADS)

    Allibe, J.; Bougot-Robin, K.; Jacquet, E.; Infante, I. C.; Fusil, S.; Carrétéro, C.; Reverchon, J.-L.; Marcilhac, B.; Creté, D.; Mage, J.-C.; Barthélémy, A.; Bibes, M.

    2010-05-01

    BiFeO3 is the prototypical multiferroic and one of the few with both (anti)ferroic ordering temperatures above 300 K. While its magnetic and ferroelectric properties and their coupling have been investigated intensely, offering opportunities in spintronics, little is known concerning its optical properties and their coupling to the ferroic orders. For applications in the microwave range, we report on the integration of BiFeO3 onto low permittivity substrates. Such integrated films show good ferroelectric and optical properties consistent with those of films grown on SrTiO3 substrates. Prospects for the use of BiFeO3 in optical applications are discussed.

  7. Phase stability, mechanical and thermodynamic properties of orthorhombic and trigonal MgSiN2: an ab initio study

    NASA Astrophysics Data System (ADS)

    Arab, Fahima; Sahraoui, F. Ali; Haddadi, Khelifa; Bouhemadou, Abdelmadjid; Louail, Layachi

    2016-05-01

    Structural stability and mechanical and thermodynamic properties of the orthorhombic and trigonal MgSiN2 polymorphs (or-MgSiN2 and tr-MgSiN2) were investigated through density functional theory and quasi-harmonic Debye model (QHDM). Our calculations show that or-MgSiN2 is energetically the stable polymorph at low pressure, in agreement with previous experimental and theoretical study. Under pressure, a crystallographic transition from the orthorhombic structure to the trigonal one occurs around 25, 17.45 and 19.05 GPa as obtained from the generalized gradient approximation of Perdew-Wang (GGA-PW91), the generalized gradient approximation parameterized recently by Perdew et al (GGA-PBEsol) and the local density approximation developed by Ceperley and Alder and parameterized by Perdew and Zunger (LDA-CAPZ), respectively. Single-crystalline and polycrystalline elastic constants and related properties, namely Vickers hardness, acoustic Grüneisen parameter, minimum thermal conductivity, isotropic sound velocities and Debye temperature, were numerically estimated for both or-MgSiN2 and tr-MgSiN2. We have showed that the hardness of tr-MgSiN2 is comparable to that of the harder materials like c-BN and B6O. Temperature and pressure dependencies of volume, bulk modulus, thermal expansion, Grüneisen parameter, heat capacities and Debye temperature were investigated using QHDM.

  8. First-principles calculations of properties of orthorhombic iron carbide Fe7C3 at the Earth's core conditions

    NASA Astrophysics Data System (ADS)

    Raza, Zamaan; Shulumba, Nina; Caffrey, Nuala M.; Dubrovinsky, Leonid; Abrikosov, Igor A.

    2015-06-01

    A recently discovered phase of orthorhombic iron carbide o-Fe7C3 [Prescher et al., Nat. Geosci. 8, 220 (2015), 10.1038/ngeo2370] is assessed as a potentially important phase for interpretation of the properties of the Earth's core. In this paper, we carry out first-principles calculations on o-Fe7C3 , finding properties to be in broad agreement with recent experiments, including a high Poisson's ratio (0.38). Our enthalpy calculations suggest that o-Fe7C3 is more stable than Eckstrom-Adcock hexagonal iron carbide (h-Fe7C3 ) below approximately 100 GPa. However, at 150 GPa, the two phases are essentially degenerate in terms of Gibbs free energy, and further increasing the pressure towards Earth's core conditions stabilizes h-Fe7C3 with respect to the orthorhombic phase. Increasing the temperature tends to stabilize the hexagonal phase at 360 GPa, but this trend may change beyond the limit of the quasiharmonic approximation.

  9. Electrochemical characterization of orthorhombic Na{sub x}MnO{sub 2} for alkali metal polymer batteries

    SciTech Connect

    Doeff, M.M.; Ding, Lie; DeJonghe, L.C.

    1995-04-01

    Electrochemical potential spectroscopy (ECPS) has been used successfully to observe and explain ordering transitions in orthorhombic Na{sub x}MnO{sub 2} as it is discharged in a sodium/polymer cell. Features can be assigned on the basis of sequential filling of sites in the small and then the large tunnels of the structure as the reduction progresses. Intercalation of lithium into Na{sub x}MnO{sub 2} may be less straightforward than that of sodium, and is worthy of investigation by ECPS. Li/Na{sub x}MnO{sub 2} cells have a greater discharge capacity than Na/Na{sub x}MnO{sub 2} cells, suggesting that more than four lithiums per large tunnel can be inserted. (It is also possible, but less likely that more than one lithium can be placed inside the small tunnels.) This implies that the sites for lithium occupancy might be somewhat different than that for sodium. Further investigation into the properties of orthorhombic Na{sub x}MnO{sub 2} and its utility as a positive electrode for rechargeable sodium and lithium cells is presently underway in this laboratory.

  10. Effect of Al{sup 3+} substitution on the structural, magnetic, and electric properties in multiferroic Bi{sub 2}Fe{sub 4}O{sub 9} ceramics

    SciTech Connect

    Huang, S.; Shi, L.R.; Tian, Z.M.; Yuan, S.L.; Zhu, C.M.; Gong, G.S.; Qiu, Y.

    2015-07-15

    Structural, magnetic, and electric properties have been investigated in polycrystalline Bi{sub 2}(Fe{sub 1−x}Al{sub x}){sub 4}O{sub 9} (0≤x≤0.25) ceramics synthesized by a modified Pechini method. Structural analysis reveals that Al{sup 3+} doped Bi{sub 2}Fe{sub 4}O{sub 9} crystallizes in orthorhombic structure with Pbnm space group. Surface morphology of the end products is examined by scanning electron microscopy and the grain size has a tendency to decrease with increase in Al{sup 3+} doping level. Compared with pure Bi{sub 2}Fe{sub 4}O{sub 9}, room temperature coexistent multiferroic-like behavior is observed in Al{sup 3+} doped Bi{sub 2}Fe{sub 4}O{sub 9}. By analyzing magnetic properties, the Néel temperature monotonously shifts to low temperatures from ~260 K (x=0) to ~35 K (x=0.25). Moreover, the spin dynamic measured by the shift in ac magnetic susceptibility as a function of frequency provides a possibility of spin-glass-like behavior, which is further confirmed by fitting the critical slowing down power law and memory effect. - Graphical abstract: Compared with pure Bi{sub 2}Fe{sub 4}O{sub 9}, room temperature weak ferromagnetic property and enhanced ferroelectric-like behavior can be achieved simultaneously with proper Al{sup 3+} doping. - Highlights: • Bi{sub 2}(Fe{sub 1−x}Al{sub x}){sub 4}O{sub 9} (0≤x≤0.25) ceramics are fabricated via a Pechini method. • Weak ferromagnetic and ferroelectric behaviors can be achieved simultaneously. • Spin-glass-like behavior is detected with proper Al{sup 3+} doping. • The memory and aging effects are observed with proper Al{sup 3+} doping.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  12. Orbital Reconstruction Enhanced Exchange Bias in La0.6Sr0.4MnO3/Orthorhombic YMnO3 Heterostructures

    PubMed Central

    Zheng, Dongxing; Jin, Chao; Li, Peng; Wang, Liyan; Feng, Liefeng; Mi, Wenbo; Bai, Haili

    2016-01-01

    The exchange bias in ferromagnetic/multiferroic heterostructures is usually considered to originate from interfacial coupling. In this work, an orbital reconstruction enhanced exchange bias was discovered. As La0.6Sr0.4MnO3 (LSMO) grown on YMnO3 (YMO) suffers a tensile strain (a > c), the doubly degenerate eg orbital splits into high energy 3z2 − r2 and low energy x2 − y2 orbitals, which makes electrons occupy the localized x2 − y2 orbital and leads to the formation of antiferromagnetic phase in LSMO. The orbital reconstruction induced antiferromagnetic phase enhances the exchange bias in the LSMO/YMO heterostructures, lightening an effective way for electric-field modulated magnetic moments in multiferroic magnetoelectric devices. PMID:27090614

  13. Orbital Reconstruction Enhanced Exchange Bias in La0.6Sr0.4MnO3/Orthorhombic YMnO3 Heterostructures

    NASA Astrophysics Data System (ADS)

    Zheng, Dongxing; Jin, Chao; Li, Peng; Wang, Liyan; Feng, Liefeng; Mi, Wenbo; Bai, Haili

    2016-04-01

    The exchange bias in ferromagnetic/multiferroic heterostructures is usually considered to originate from interfacial coupling. In this work, an orbital reconstruction enhanced exchange bias was discovered. As La0.6Sr0.4MnO3 (LSMO) grown on YMnO3 (YMO) suffers a tensile strain (a > c), the doubly degenerate eg orbital splits into high energy 3z2 ‑ r2 and low energy x2 ‑ y2 orbitals, which makes electrons occupy the localized x2 ‑ y2 orbital and leads to the formation of antiferromagnetic phase in LSMO. The orbital reconstruction induced antiferromagnetic phase enhances the exchange bias in the LSMO/YMO heterostructures, lightening an effective way for electric-field modulated magnetic moments in multiferroic magnetoelectric devices.

  14. Hexagonal phase stabilization and magnetic orders of multiferroic L u1 -xS cxFe O3

    NASA Astrophysics Data System (ADS)

    Lin, L.; Zhang, H. M.; Liu, M. F.; Shen, Shoudong; Zhou, S.; Li, D.; Wang, X.; Yan, Z. B.; Zhang, Z. D.; Zhao, Jun; Dong, Shuai; Liu, J.-M.

    2016-02-01

    Hexagonal LuFe O3 has drawn a lot of research attention due to its contentious room-temperature multiferroicity. Due to the instability of hexagonal phase in the bulk form, most experimental studies focused on LuFe O3 thin films which can be stabilized by strain using proper substrates. Here we report on the hexagonal phase stabilization, magnetism, and magnetoelectric coupling of bulk LuFe O3 by partial Sc substitution of Lu. First, our first-principles calculations show that the hexagonal structure can be stabilized by partial Sc substitution, while the multiferroic properties, including the noncollinear magnetic order and geometric ferroelectricity, remain robustly unaffected. Therefore, L u1 -xS cxFe O3 can act as a platform to check the multiferroicity of LuFe O3 and related materials in the bulk form. Second, the magnetic characterizations on bulk L u1 -xS cxFe O3 demonstrate a magnetic anomaly (probable antiferromagnetic ordering) above room temperature, ˜425-445 K, followed by magnetic transitions in low temperatures (˜167-172 K). In addition, a magnetoelectric response is observed in the low-temperature region. Our study provides useful information on the multiferroic physics of hexagonal R Fe O3 and related systems.

  15. 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.

  16. Entanglement and manipulation of the magnetic and spin–orbit order in multiferroic Rashba semiconductors

    PubMed Central

    Krempaský, J.; Muff, S.; Bisti, F.; Fanciulli, M.; Volfová, H.; Weber, A. P.; Pilet, N.; Warnicke, P.; Ebert, H.; Braun, J.; Bertran, F.; Volobuev, V. V.; Minár, J.; Springholz, G.; Dil, J. H.; Strocov, V. N.

    2016-01-01

    Entanglement of the spin–orbit and magnetic order in multiferroic materials bears a strong potential for engineering novel electronic and spintronic devices. Here, we explore the electron and spin structure of ferroelectric α-GeTe thin films doped with ferromagnetic Mn impurities to achieve its multiferroic functionality. We use bulk-sensitive soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to follow hybridization of the GeTe valence band with the Mn dopants. We observe a gradual opening of the Zeeman gap in the bulk Rashba bands around the Dirac point with increase of the Mn concentration, indicative of the ferromagnetic order, at persistent Rashba splitting. Furthermore, subtle details regarding the spin–orbit and magnetic order entanglement are deduced from spin-resolved ARPES measurements. We identify antiparallel orientation of the ferroelectric and ferromagnetic polarization, and altering of the Rashba-type spin helicity by magnetic switching. Our experimental results are supported by first-principles calculations of the electron and spin structure. PMID:27767052

  17. Oxygen vacancy assisted multiferroic property of Cu doped ZnO films.

    PubMed

    Liu, Hongyan; Wang, Yonglin; Wu, Jianhua; Zhang, Guanli; Yan, Yue

    2015-04-14

    Exploring multi-functional properties in a single material is the focus for future material design and applications. In this work, we investigated the multiferroic property of Cu doped ZnO films using a combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), classical magnetometry and electric measurements. The results show that the texture of Cu doped ZnO films is deteriorated with an increase in Cu contents, whereas the dielectric property is improved due to the introduction of Cu ions. The XAS result reveals that the Cu atoms occupy the substitutional Zn sites in the ZnO host, and thus induce local electric dipoles owing to the displacement of the Cu-O bond. The presence of oxygen vacancies together with Cu ions facilitates the movement of the ferroelectric domain boundary, and contributes to the ferromagnetism due to the indirect exchange between Cu atoms and large-sized vacancy orbitals. The Cu doped ZnO film is a feasible promising candidate for applications in multiferroic devices.

  18. Shining light on CuO for exploring high-Tc multiferroics

    NASA Astrophysics Data System (ADS)

    Stucky, A.; Ubaldini, A.; Levallois, J.; Tran, M. K.; van der Marel, D.; Giannini, E.

    2014-12-01

    Searching for a 3D multiferroic material with a strong magnetoelectric coupling and high critical temperature is a major challenge in modern condensed matter research. CuO is the building block of high-temperature superconductors and triggered a new interest when it was established as potential high temperature multiferroic. We have succeeded in growing high quality single crystals of CuO with two different methods, namely the floating zone under high oxygen pressure and the chemical vapor transport growth. The fact that we are able to grow crystals of the same compound by different techniques makes it possible to study the effect of slightly different chemical compositions, various kinds of defects and variable strain on the final properties of the compound. Optical spectroscopy has been deployed to study the optical response of cupric oxide. Thereby we achieved a deeper insight of the optical, electronic and structural properties by measuring the infrared reflectivity under a magnetic field and the Raman shift under hydrostatic high pressure.

  19. Pronounced multiferroicity in oleic acid stabilized BiFeO3 nanocrystals at room temperature.

    PubMed

    Mahesh, Dabbugalla; Mandal, Swapan K; Mahato, Bipul K; Rana, Bivas; Barman, Anjan

    2013-06-01

    We report on the experimental observation of pronounced multiferroicity in BiFeO3 nanocrystals (size approximately 40 nm) at room temperature. Large scale BiFeO3 nanocrystals are synthesized using a low temperature chemical route and further stabilized with oleic acid. The nanocrystals exhibit a significant distortion in lattice parameter c compared to the bulk. Oleic acid plays an important role in reducing oxygen vacancies and Fe2+ ions at the nanocrystal surface giving rise to a high resistivity (approximately 10(10) omega-cm at 300 K) of the sample. The direct band gap of nanocrystals is measured to be approximately 4.2 eV (about 1.5 times the bulk value) suggesting a strong quantum confinement effect. The nanocrystals show a remarkably high spontaneous saturation magnetization approximately 4.39 emu/g along with a prominent ferroelectric hysteresis loop at room temperature. Particle size effect leading to the appearance of large number of uncompensated spins and suppression of modulated spin structure have resulted a strong spontaneous magnetization in such nanoscale multiferroic materials. PMID:23862453

  20. IR phonons induced by the helical magnetic order in multiferroic TbMn2O5

    NASA Astrophysics Data System (ADS)

    Valdes Aguilar, Rolando; Sushkov, A.; Drew, H. D.; Cheong, S. W.

    2006-03-01

    The interplay between magnetic order and the lattice in multiferroic crystals has produced such interesting phenomena as polarization reversal and change of dielectric properties with magnetic fields . Ferroelectricity in the multiferroic materials REMn2O5 (RE = rare earth) is thought to originate from a helical antiferromagnetic order. In order to study this possiblity we have made an infrared study of TbMn2O5. We find that several IR phonons show correlations with the distinct magnetic and dielectric phase transitions. Of special interest is the phonon spectrum for light polarization along the b axis where a mode at ˜ 706 cm-1 exists only in the commensurate magnetic phase with k = (1/2,0,1/4) in the temperature range of 24-33 K. Possible scenarios for this phonon are: (1) the appearance of zone-folded modes; (2) the activation of previously silent modes due to the reduction of crystal symmetry. These scenarios are discussed in terms of the spin-lattice coupling in this class of materials. Hur, N et al. Nature 429 (2004) 392.

  1. Understanding the spin-driven polarizations in Bi MO3 (M = 3 d transition metals) multiferroics

    NASA Astrophysics Data System (ADS)

    Kc, Santosh; Lee, Jun Hee; Cooper, Valentino R.

    Bismuth ferrite (BiFeO3) , a promising multiferroic, stabilizes in a perovskite type rhombohedral crystal structure (space group R3c) at room temperature. Recently, it has been reported that in its ground state it possess a huge spin-driven polarization. To probe the underlying mechanism of this large spin-phonon response, we examine these couplings within other Bi based 3 d transition metal oxides Bi MO3 (M = Ti, V, Cr, Mn, Fe, Co, Ni) using density functional theory. Our results demonstrate that this large spin-driven polarization is a consequence of symmetry breaking due to competition between ferroelectric distortions and anti-ferrodistortive octahedral rotations. Furthermore, we find a strong dependence of these enhanced spin-driven polarizations on the crystal structure; with the rhombohedral phase having the largest spin-induced atomic distortions along [111]. These results give us significant insights into the magneto-electric coupling in these materials which is essential to the magnetic and electric field control of electric polarization and magnetization in multiferroic based devices. Research is supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division and the Office of Science Early Career Research Program (V.R.C) and used computational resources at NERSC.

  2. Magnetization dynamics and frustration in the multiferroic double perovskite Lu2MnCoO6

    DOE PAGES

    Zapf, Vivien S.; Ueland, B. G.; Laver, Mark; Lonsky, Martin; Pohlit, Merlin; Muller, Jens; Lancaster, Tom; Moller, Johannes S.; Blundell, Stephen J.; Singleton, John; et al

    2016-04-29

    Here, we investigate the magnetic ordering and the magnetization dynamics (from kHz to THz time scales) of the double perovskite Lu2MnCoO6 using elastic neutron diffraction, muon spin relaxation, and micro-Hall magnetization measurements. This compound is known to be a type II multiferroic with the interesting feature that a ferromagneticlike magnetization hysteresis loop couples to an equally hysteretic electric polarization in the bulk of the material despite a zero-field magnetic ordering of the type ↑↑↓↓ along Co-Mn spin chains. Here we explore the unusual dynamics of this compound and find extremely strong fluctuations, consistent with the axial next-nearest-neighbor Ising (ANNNI) modelmore » for frustrated spin chains. We identify three temperature scales in Lu2MnCoO6 corresponding to the onset of highly fluctuating long-range order below TN = 50±3 K identified from neutron scattering, the onset of magnetic and electric hysteresis, with change in kHz magnetic and electric dynamics below a 30 K temperature scale, and partial freezing of ~MHz spin fluctuations in the muon spin relaxation data below 12 ± 3 K. Our results provide a framework for understanding the multiferroic behavior of this compound and its hysteresis and dynamics.« less

  3. Electric-field-induced spin wave generation using multiferroic magnetoelectric cells

    SciTech Connect

    Cherepov, Sergiy; Khalili Amiri, Pedram; Alzate, Juan G.; Wong, Kin; Lewis, Mark; Upadhyaya, Pramey; Nath, Jayshankar; Bao, Mingqiang; Wang, Kang L.; Bur, Alexandre; Wu, Tao; Carman, Gregory P.; Khitun, Alexander

    2014-02-24

    In this work, we report on the demonstration of voltage-driven spin wave excitation, where spin waves are generated by multiferroic magnetoelectric (ME) cell transducers driven by an alternating voltage, rather than an electric current. A multiferroic element consisting of a magnetostrictive Ni film and a piezoelectric [Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}]{sub (1−x)}–[PbTiO{sub 3}]{sub x} substrate was used for this purpose. By applying an AC voltage to the piezoelectric, an oscillating electric field is created within the piezoelectric material, which results in an alternating strain-induced magnetic anisotropy in the magnetostrictive Ni layer. The resulting anisotropy-driven magnetization oscillations propagate in the form of spin waves along a 5 μm wide Ni/NiFe waveguide. Control experiments confirm the strain-mediated origin of the spin wave excitation. The voltage-driven spin wave excitation, demonstrated in this work, can potentially be used for low-dissipation spin wave-based logic and memory elements.

  4. One-dimensional multiferroic bismuth ferrite fibers obtained by electrospinning techniques.

    PubMed

    Baji, Avinash; Mai, Yiu-Wing; Li, Qian; Wong, Shing-Chung; Liu, Yun; Yao, Q W

    2011-06-10

    We report the fabrication of novel multiferroic nanostructured bismuth ferrite (BiFeO(3)) fibers using the sol-gel based electrospinning technique. Phase pure BiFeO(3) fibers were prepared by thermally annealing the electrospun BiFeO(3)/polyvinylpyrrolidone composite fibers in air for 1 h at 600 °C. The x-ray diffraction pattern of the fibers (BiFeO(3)) obtained showed that their crystalline structures were rhombohedral perovskite structures. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the BiFeO(3) fibers were composed of fine grained microstructures. The grains were self-assembled and self-organized to yield dense and continuous fibrous structures. The magnetic hysteresis loops of these nanostructured fibers displayed the expected ferromagnetic behavior, whereby a coercivity of ∼ 250 Oe and a saturation magnetization of ∼ 1.34 emu g(-1) were obtained. The ferroelectricity and ferroelectric domain structures of the fibers were confirmed using piezoresponse force microscopy (PFM). The piezoelectric hysteresis loops and polar domain switching behavior of the fibers were examined. Such multiferroic fibers are significant for electroactive applications and nano-scale devices.

  5. Synthesis of magnetic and multiferroic materials from polyvinyl alcohol-based gels

    NASA Astrophysics Data System (ADS)

    Lisnevskaya, I. V.; Bobrova, I. A.; Lupeiko, T. G.

    2016-01-01

    This review article summarizes results on the synthesis of the magnetic materials including modified nickel ferrite (Ni0.9Co0.1Cu0.1Fe1.9O4-δ), yttrium iron garnet (Y3Fe5O12), lanthanum-containing manganites (MxLa1-xMnO3 (M=Pb, Ba or Sr; x=0.3-0.35)), and multiferroics (BiFeO3 and BiFe0.5Mn0.5O3) from polyvinyl alcohol-based gels. It is shown that the ammonium nitrate accelerates destruction of organic components of xerogels and thus Ni0.9Co0.1Cu0.1Fe1.9O4-δ and BiFeO3 can be prepared at record low temperatures (100 and 250 °C, respectively) which are 200-300 °C lower compared to the process where air is used as an oxidizing agent. As for the synthesis of Y3Fe5O12, MxLa1-xMnO3 and BiFe0.5Mn0.5O3, the presence of NH4NO3 favors formation of foreign phases, which ultimately complicate reaction mechanisms and lead to the higher temperature to synthesize target products. Developed methods provide nanoscale magnetic and multiferroic materials with an average particle size of ∼20-50 nm.

  6. Superior electro-optic response in multiferroic bismuth ferrite nanoparticle doped nematic liquid crystal device

    PubMed Central

    Nayek, Prasenjit; Li, Guoqiang

    2015-01-01

    A superior electro-optic (E-O) response has been achieved when multiferroic bismuth ferrite (BiFeO3/BFO) nanoparticles (NPs) were doped in nematic liquid crystal (NLC) host E7 and the LC device was addressed in the large signal regime by an amplitude modulated square wave signal at the frequency of 100 Hz. The optimized concentration of BFO is 0.15 wt%, and the corresponding total optical response time (rise time + decay time) for a 5 μm-thick cell is 2.5 ms for ~7 Vrms. This might be exploited for the construction of adaptive lenses, modulators, displays, and other E-O devices. The possible reason behind the fast response time could be the visco-elastic constant and restoring force imparted by the locally ordered LCs induced by the multiferroic nanoparticles (MNPs). Polarized optical microscopic textural observation shows that the macroscopic dislocation-free excellent contrast have significant impact on improving the image quality and performance of the devices. PMID:26041701

  7. Thermally assisted electric field control of magnetism in flexible multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Liu, Yiwei; Zhan, Qingfeng; Dai, Guohong; Zhang, Xiaoshan; Wang, Baomin; Liu, Gang; Zuo, Zhenghu; Rong, Xin; Yang, Huali; Zhu, Xiaojian; Xie, Yali; Chen, Bin; Li, Run-Wei

    2014-11-01

    Thermal and electrical control of magnetic anisotropy were investigated in flexible Fe81Ga19 (FeGa)/Polyvinylidene fluoride (PVDF) multiferroic heterostructures. Due to the large anisotropic thermal deformation of PVDF (α1 = -13 × 10-6 K-1 and α2 = -145 × 10-6 K-1), the in-plane uniaxial magnetic anisotropy (UMA) of FeGa can be reoriented 90° by changing the temperature across 295 K where the films are magnetically isotropic. Thus, the magnetization of FeGa can be reversed by the thermal cycling between 280 and 320 K under a constant magnetic field lower than coercivity. Moreover, under the assistance of thermal deformation with slightly heating the samples to the critical temperature, the electric field of +/- 267 kV cm-1 can well align the UMA along the two orthogonal directions. The new route of combining thermal and electrical control of magnetic properties realized in PVDF-based flexible multiferroic materials shows good prospects in application of flexible thermal spintronic devices and flexible microwave magnetic materials.

  8. A concept for a magnetic field detector underpinned by the nonlinear dynamics of coupled multiferroic devices

    SciTech Connect

    Beninato, A.; Baglio, S.; Andò, B.; Emery, T.; Bulsara, A. R.; Jenkins, C.; Palkar, V.

    2013-12-09

    Multiferroic (MF) composites, in which magnetic and ferroelectric orders coexist, represent a very attractive class of materials with promising applications in areas, such as spintronics, memories, and sensors. One of the most important multiferroics is the perovskite phase of bismuth ferrite, which exhibits weak magnetoelectric properties at room temperature; its properties can be enhanced by doping with other elements such as dysprosium. A recent paper has demonstrated that a thin film of Bi{sub 0.7}Dy{sub 0.3}FeO{sub 3} shows good magnetoelectric coupling. In separate work it has been shown that a carefully crafted ring connection of N (N odd and N ≥ 3) ferroelectric capacitors yields, past a critical point, nonlinear oscillations that can be exploited for electric (E) field sensing. These two results represent the starting point of our work. In this paper the (electrical) hysteresis, experimentally measured in the MF material Bi{sub 0.7}Dy{sub 0.3}FeO{sub 3}, is characterized with the applied magnetic field (B) taken as a control parameter. This yields a “blueprint” for a magnetic (B) field sensor: a ring-oscillator coupling of N = 3 Sawyer-Tower circuits each underpinned by a mutliferroic element. In this configuration, the changes induced in the ferroelectric behavior by the external or “target” B-field are quantified, thus providing a pathway for very low power and high sensitivity B-field sensing.

  9. Control of the multiferroic transition in Ni3V2O8 by transition metal doping

    NASA Astrophysics Data System (ADS)

    Kumarasiri, A.; Lawes, G.

    2011-08-01

    We have studied the effects of doping magnetic ions on the phase transitions in polycrystalline Ni3V2O8 samples using magnetic, dielectric, and specific heat measurements. Substituting spin-1/2 Cu results in a larger suppression of the transition temperatures than observed on doping with spin-3/2 Co. The multiferroic-ordering transition persists at small concentrations for both Co and Cu dopants, with this phase still developing at concentrations of almost 30 at% Co. However, the multiferroic-magnetic structure is completely suppressed at only 10 at% Cu. On the Co-rich side of the composition, we find that the magnetic-ordering temperatures for Co3V2O8 are suppressed rapidly with Ni doping. We present phase diagrams for (Ni1-xMx)3V2O8 (M = Cu and Co). These studies suggest that the spin structures in Ni3V2O8 responsible for the development of ferroelectric order are relatively robust against perturbations produced by magnetic dopants, with the most significant disruption of the magnetic structure developing for Cu doping.

  10. Synthesis of multiferroic Er-Fe-O thin films by atomic layer and chemical vapor deposition

    SciTech Connect

    Mantovan, R. Vangelista, S.; Wiemer, C.; Lamperti, A.; Tallarida, G.; Chikoidze, E.; Dumont, Y.; Fanciulli, M.

    2014-05-07

    R-Fe-O (R = rare earth) compounds have recently attracted high interest as potential new multiferroic materials. Here, we report a method based on the solid-state reaction between Er{sub 2}O{sub 3} and Fe layers, respectively grown by atomic layer deposition and chemical vapor deposition, to synthesize Er-Fe-O thin films. The reaction is induced by thermal annealing and evolution of the formed phases is followed by in situ grazing incidence X-ray diffraction. Dominant ErFeO{sub 3} and ErFe{sub 2}O{sub 4} phases develop following subsequent thermal annealing processes at 850 °C in air and N{sub 2}. Structural, chemical, and morphological characterization of the layers are conducted through X-ray diffraction and reflectivity, time-of-flight secondary ion-mass spectrometry, and atomic force microscopy. Magnetic properties are evaluated by magnetic force microscopy, conversion electron Mössbauer spectroscopy, and vibrating sample magnetometer, being consistent with the presence of the phases identified by X-ray diffraction. Our results constitute a first step toward the use of cost-effective chemical methods for the synthesis of this class of multiferroic thin films.

  11. Thermally assisted electric field control of magnetism in flexible multiferroic heterostructures

    PubMed Central

    Liu, Yiwei; Zhan, Qingfeng; Dai, Guohong; Zhang, Xiaoshan; Wang, Baomin; Liu, Gang; Zuo, Zhenghu; Rong, Xin; Yang, Huali; Zhu, Xiaojian; Xie, Yali; Chen, Bin; Li, Run-Wei

    2014-01-01

    Thermal and electrical control of magnetic anisotropy were investigated in flexible Fe81Ga19 (FeGa)/Polyvinylidene fluoride (PVDF) multiferroic heterostructures. Due to the large anisotropic thermal deformation of PVDF (α1 = −13 × 10−6 K−1 and α2 = −145 × 10−6 K−1), the in-plane uniaxial magnetic anisotropy (UMA) of FeGa can be reoriented 90° by changing the temperature across 295 K where the films are magnetically isotropic. Thus, the magnetization of FeGa can be reversed by the thermal cycling between 280 and 320 K under a constant magnetic field lower than coercivity. Moreover, under the assistance of thermal deformation with slightly heating the samples to the critical temperature, the electric field of ± 267 kV cm−1 can well align the UMA along the two orthogonal directions. The new route of combining thermal and electrical control of magnetic properties realized in PVDF-based flexible multiferroic materials shows good prospects in application of flexible thermal spintronic devices and flexible microwave magnetic materials. PMID:25370605

  12. Muon-Spin Rotation in Multiferroic Cu3Mo2O9 under Electric Fields

    NASA Astrophysics Data System (ADS)

    Kuroe, Haruhiko; Kuwahara, Hideki; Sekine, Tomoyuki; Watanabe, Isao; Raselli, Andrea-Raeto; Elender, Matthias; Biswas, Pabitra Kumar; Hase, Masashi; Oka, Kunihiko; Ito, Toshimitsu; Eisaki, Hiroshi

    It has been demonstrated that the muon spin rotation measurements under electric field give helpful information about the electrically induced magnetism, e.g., the cross correlation effects in multiferroic materials. We have developed an electric-field application system up to 500V for the Dolly spectrometer at the Paul Scherrer Institute. We report the electric-field effects on the μSR spectrum in the multiferroic material Cu3Mo2O9, where a slightly canted antiferromagnetic long-range order appears together with the ferroelectricity below 8K. In the muon-spin rotation spectrum at 1.5K, two kinds of the internal magnetic fields are clearly observed as a beating oscillation. The muon-spin spectrum depends on the electric fields along the c axis of the crystal along which the spontaneous electric polarization appears. From the fitting of the spectra in time and frequency domains, it is shown that the observation of the electric-field dependence on the muon-spin spectra clearly indicates a change of the internal magnetic fields induced by the application of the external electric fields. We propose a model with one muon-stopping site which explains the observed spectra qualitatively. This model is based on the magnetic excitations in Cu3Mo2O9 obtained from the inelastic neutron-scattering experiments.

  13. High-temperature electromagnons in the magnetically induced multiferroic cupric oxide driven by intersublattice exchange.

    PubMed

    Jones, S P P; Gaw, S M; Doig, K I; Prabhakaran, D; Hétroy Wheeler, E M; Boothroyd, A T; Lloyd-Hughes, J

    2014-01-01

    Magnetically induced ferroelectric multiferroics present an exciting new paradigm in the design of multifunctional materials, by intimately coupling magnetic and polar order. Magnetoelectricity creates a novel quasiparticle excitation--the electromagnon--at terahertz frequencies, with spectral signatures that unveil important spin interactions. To date, electromagnons have been discovered at low temperature (<70 K) and predominantly in rare-earth compounds such as RMnO3. Here we demonstrate using terahertz time-domain spectroscopy that intersublattice exchange in the improper multiferroic cupric oxide (CuO) creates electromagnons at substantially elevated temperatures (213-230 K). Dynamic magnetoelectric coupling can therefore be achieved in materials, such as CuO, that exhibit minimal static cross-coupling. The electromagnon strength and energy track the static polarization, highlighting the importance of the underlying cycloidal spin structure. Polarized neutron scattering and terahertz spectroscopy identify a magnon in the antiferromagnetic ground state, with a temperature dependence that suggests a significant role for biquadratic exchange. PMID:24777198

  14. Tunneling magnetoresistance and electroresistance in Fe/PbTiO3/Fe multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Dai, Jian-Qing

    2016-08-01

    We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO3/Fe multiferroic tunnel junction with asymmetric TiO2- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6pz orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing to the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.

  15. Effects of Nickel Doping on the Multiferroic and Magnetic Phases of MnWO 4

    SciTech Connect

    Poudel, N.; Lorenz, B.; Lv, B.; Wang, Y. Q.; Ye, F.; Wang, Jinchen; Fernandez-baca, J. A.; Chu, C. W.

    2015-12-15

    There are various orders in multiferroic materials with a frustrated spiral spin modulation inducing a ferroelectric state are extremely sensitive to small perturbations such as magnetic and electric fields, external pressure, or chemical substitutions. A classical multiferroic, the mineral Hubnerite with chemical formula MnWO4, shows three different magnetic phases at low temperature. The intermediate phase between 7.5K < T < 12.7K is multiferroic and ferroelectricity is induced by an inversion symmetry breaking spiral Mn-spin order and strong spin-lattice interactions. Furthermore, the substitution of Ni2+ (spin 1) for Mn2+ (spin 5/2) in MnWO4 and its effects on the magnetic and multiferroic phases are studied. The ferroelectric phase is stabilized for low Ni content (up to 10%). Upon further Ni doping, the polarization in the ferroelectric phase is quickly suppressed while a collinear and commensurate magnetic phase, characteristic of the magnetic structure in NiWO4, appears first at higher temperature, gradually extends to lower temperature, and becomes the ground state above 30% doping. Between 10% and 30%, the multiferroic phase coexists with the collinear commensurate phase. In this concentration region, the spin spiral plane is close to the a-b plane which explains the drop of the ferroelectric polarization. Finally, the phase diagram of Mn1-xNixWO4 is derived by a combination of magnetic susceptibility, specific heat, electric polarization, and neutron scattering measurements.

  16. Optical spectroscopic study of multiferroic BiFeO3 and LuFe2O4

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoshan

    2010-03-01

    Iron-based multiferroics such as BiFeO3 and LuFe2O4 exhibit the highest magnetic and ferroelectric ordering temperatures among known multiferroics. LuFe2O4 is a frustrated system with several phase transitions that result in electronically driven multiferroicity. To understand how this peculiar multiferroic mechanism correlates with magnetism, we studied electronic excitations by optical spectroscopy and other complementary techniques. We show that the charge order, which determines the dielectric properties, is due to the ``order by fluctuation'' mechanism, evidenced by the onset of charge fluctuation well below the charge ordering transition. We also find a low temperature monoclinic distortion driven by both temperature and magnetic field, indicating strong coupling between structure, magnetism and charge order. BiFeO3 is the only known single phase multiferroics with room temperature magnetism and ferroelectricity. To investigate the spin-charge coupling, we measured the optical properties of BiFeO3. We find that the absorption onset occurs due to on-site Fe^3+ excitations at 1.41 and 1.90 eV. Temperature and magnetic-field-induced spectral changes reveal complex interactions between on-site crystal-field and magnetic excitations in the form of magnon sidebands. The sensitivity of the magnon sidebands allows us to map out the magnetic-field temperature phase diagram which demonstrates optical evidence for spin spiral quenching above 20 T and suggests a spin domain reorientation near 10 T. Work done in collaboration with T.V. Brinzari, R.C. Rai, M. Angst, R.P. Hermann, A.D. Christianson, J.-W. Kim, Z. Islam, B.C. Sales, D. Mandrus, S. Lee, Y.H. Chu, L. W. Martin, A. Kumar, R. Ramesh, S.W. Cheong, S. McGill, and J.L. Musfeldt.

  17. Scattering of an electromagnetic plane wave by a homogeneous sphere made of an orthorhombic dielectric-magnetic material.

    PubMed

    Ulfat Jafri, A D; Lakhtakia, Akhlesh

    2014-01-01

    An exact transition matrix was formulated for electromagnetic scattering by an orthorhombic dielectric-magnetic sphere whose permeability dyadic is a scalar multiple of its permittivity dyadic. Calculations were made for plane waves incident on the sphere. As the size parameter increases, the role of anisotropy evolves; multiple lobes appear in the plots of the differential scattering efficiency in any scattering plane; the total scattering, extinction, and forward-scattering efficiencies exhibit a prominent maximum each; and the absorption efficiency generally increases with weak undulations. Certain orientations of the sphere with respect to the directions of propagation and the electric field of the incident plane wave make it highly susceptible to detection in a monostatic configuration, whereas other orientations make it much less vulnerable to detection. Impedance match to the ambient free space decreases backscattering efficiency significantly, although anisotropy prevents null backscattering. PMID:24561944

  18. Lithium insertion processes of orthorhombic Na{sub x}MnO{sub 2}-based electrode materials

    SciTech Connect

    Doeff, M.M.; Richardson, T.J.; Kepley, L.

    1996-08-01

    Electrochemical, thermal, and structural characterization of lithium insertion processes into orthorhombic Na{sub x}MnO{sub 2}-based materials is presented. Chimie douce oxidation, reduction, and/or exchange reactions of the precursor Na{sub 0.44}MnO{sub 2} can be used to prepare high capacity (180 mAh/g), high potential compounds for use in secondary lithium batteries. Lithiated Na{sub x}MnO{sub 2} is quite stable; formation of spinel phases occurs only under conditions of prolonged severe abuse during cycling in electrochemical cells, or upon heating to 500 C. The lithium-ion intercalation process is considerably more complex than that for sodium ions; features are seen in the electrochemical potential-step experiments that may be attributed to several phase transitions. These results are interpreted in terms of the unusual structure, and implications for future use of these materials in lithium batteries are discussed.

  19. Scattering of an electromagnetic plane wave by a homogeneous sphere made of an orthorhombic dielectric-magnetic material.

    PubMed

    Ulfat Jafri, A D; Lakhtakia, Akhlesh

    2014-01-01

    An exact transition matrix was formulated for electromagnetic scattering by an orthorhombic dielectric-magnetic sphere whose permeability dyadic is a scalar multiple of its permittivity dyadic. Calculations were made for plane waves incident on the sphere. As the size parameter increases, the role of anisotropy evolves; multiple lobes appear in the plots of the differential scattering efficiency in any scattering plane; the total scattering, extinction, and forward-scattering efficiencies exhibit a prominent maximum each; and the absorption efficiency generally increases with weak undulations. Certain orientations of the sphere with respect to the directions of propagation and the electric field of the incident plane wave make it highly susceptible to detection in a monostatic configuration, whereas other orientations make it much less vulnerable to detection. Impedance match to the ambient free space decreases backscattering efficiency significantly, although anisotropy prevents null backscattering.

  20. Theoretical investigations of the optical and EPR spectra for trivalent cerium and ytterbium ions in orthorhombic YF3 crystal

    NASA Astrophysics Data System (ADS)

    Liu, Hong-Gang; Zheng, Wen-Chen

    2016-09-01

    The optical spectra and electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants A) for trivalent cerium and ytterbium ions in YF3 crystal with orthorhombic structure are investigated together by the complete diagonalization (of energy matrix) method (CDM). The obtained results are in reasonable agreement with the experimental ones. More importantly, two magnetically nonequivalent centers in YF3 crystal observed in EPR experiments are confirmed and ascribed to their specific positions in a unit cell by our calculations based on superposition model (SPM) analysis. Such identification of local sites with different magnetic properties would help us to understand not only the EPR spectra and magnetic susceptibility of other lanthanide ions doped in crystals with the same structure as YF3 but also the energy transfer scheme between two lanthanide ions occupying such two sites. All results are discussed carefully.

  1. Magnetic excitations and anomalous spin-wave broadening in multiferroic FeV2O4

    SciTech Connect

    Zhang, Qiang; Ramazanoglu, Mehmet; Chi, Songxue; Liu, Yong; Lograsso, Thomas A.; Vaknin, David

    2014-06-01

    We report on the different roles of two orbital-active Fe2+ at the A site and V3+ at the B site in the magnetic excitations and on the anomalous spin-wave broadening in FeV2O4. FeV2O4 exhibits three structural transitions and successive paramagnetic (PM)–collinear ferrimagnetic (CFI)–noncollinear ferrimagnetic (NCFI)/ferroelectric transitions. The high-temperature tetragonal/PM–orthorhombic/CFI transition is accompanied by the appearance of a large energy gap in the magnetic excitations due to strong spin-orbit-coupling-induced anisotropy at the Fe2+ site. While there is no measurable increase in the energy gap from the orbital ordering of V3+ at the orthorhombic/CFI–tetragonal/NCFI transition, anomalous spin-wave broadening is observed in the orthorhombic/CFI state due to V3+ spin fluctuations at the B site. The spin-wave broadening is also observed at the zone boundary without softening in the NCFI/ferroelectric phase, which is discussed in terms of magnon-phonon coupling. Our study also indicates that the Fe2+ spins without the frustration at the A site may not play an important role in inducing ferroelectricity in the tetragonal/NCFI phase of FeV2O4.

  2. Formation of (111) orientation-controlled ferroelectric orthorhombic HfO2 thin films from solid phase via annealing

    NASA Astrophysics Data System (ADS)

    Mimura, Takanori; Katayama, Kiliha; Shimizu, Takao; Uchida, Hiroshi; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-08-01

    0.07YO1.5-0.93HfO2 (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt. % Sn-doped In2O3(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiOx/SiO2/(001)Si substrates, and (111)ITO/(111)Pt/TiOx/SiO2/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including θ-2θ measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111)ITO//(111)yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111)ITO/(111)Pt/TiOx/SiO2/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111)Pt/TiOx/SiO2/(001)Si substrate, which does not contain ITO. Polarization-hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (Pr) of 9.6 and 10.8 μC/cm2 and coercive fields (Ec) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature.

  3. Photo-and pressure-induced transformations in the linear orthorhombic polymer of C{sub 60}

    SciTech Connect

    Meletov, K. P. Davydov, V. A.; Arvanitidis, J.; Christofilos, D.; Andrikopoulos, K. S.; Kourouklis, G. A.

    2008-10-15

    Stability of the linear orthorhombic polymer of C{sub 60} under pressure and laser irradiation is studied by Raman scattering and X-ray diffraction measurements. The Raman spectrum at ambient pressure remains unchanged, in the time scale of the experiment, up to an intensity of 3200 W/cm{sup 2} of the 514.5 nm line of an Ar{sup +} laser, but irreversible changes are observed at higher intensities. The Raman spectra recorded at increased pressure show similar irreversible changes even at the laser intensity as low as 470 W/cm{sup 2}. The X-ray diffraction and Raman measurements of the pressure-treated samples, performed after pressure release, show that the nonirradiated material does not exhibit any changes in the crystal structure and phonon spectra. This behavior indicates a pressure-enhanced photo-induced transformation to a new polymeric phase characterized by a Raman spectrum that differs from those of the other known polymeric phases of C{sub 60}. The Raman spectra of the phototransformed linear orthorhombic polymer of C{sub 60} were measured at a pressure of up to 29 GPa. The pressure dependence of the Raman mode frequencies show singularities near 4 GPa and 15 GPa, respectively, related to a reversible phase transition and an irreversible transformation to a metastable disordered phase. The diffuse Raman spectrum of the disordered phase does not exhibit substantial changes with an increase in pressure up to 29 GPa. The high-pressure phase transforms to a mixture of pristine and dimerized C{sub 60}, after pressure release and exposure to ambient conditions for 30 h.

  4. Theory of magnetic switching of ferroelectricity in spiral magnets.

    PubMed

    Mochizuki, Masahito; Furukawa, Nobuo

    2010-10-29

    We propose a microscopic theory for magnetic switching of electric polarization (P) in the spin-spiral multiferroics by taking TbMnO3 and DyMnO3 as examples. We reproduce their phase diagrams under a magnetic field Hex by Monte Carlo simulation of an accurate spin model and reveal that competition among the Dzyaloshinskii-Moriya interaction, spin anisotropy, and spin exchange is controlled by the applied Hex, resulting in magnetic transitions accompanied by reorientation or vanishing of P. We also discuss the relevance of the proposed mechanisms to many other multiferroics such as LiCu2O2, MnWO4, and Ni3V2O4. PMID:21231137

  5. Synthesis and Characterization of Ferroic and Multiferroic Nanostructures by Liquid Phase Deposition

    NASA Astrophysics Data System (ADS)

    Yourdkhani, Amin

    Magnetoelectric multiferroics have garnered an increasing interest in the past decade due to their unique properties and relevant applications in data storage, sensing and spintronics. A key requirement for the enhancement of the magnetoelectric effect at room temperature is the optimization of the interface between the constituting phases by designing nanocomposites with selectable topologies and variable chemical composition. In this research, the rational design of two-phase spinel-perovskite ceramic nanocomposites with two different geometries: coaxial nanostructures (1-D) and bilayered nanostructures (2-D), by a soft solution chemistry approach will be described. The liquid phase deposition (LPD) method is a simple and versatile route for the deposition of highly uniform spinel ferrite (MFe2O4) and/or titanium-based perovskite (BaTiO3, PbTiO3) by the controlled hydrolysis of metal fluoro-complexes at temperatures as low as 40°C. By designing a sequential deposition process, 1-D and 2-D magnetoelectric nanostructures were fabricated by filling perovskite nanotubes with the ferrite phase or depositing a ferrite layer on top of a perovskite thin film, respectively. The compositional and morphological characteristics of these highly uniform metal oxide nanostructures were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning probe microscopy (SPM) and electron microscopy (FE-SEM and TEM). The direct evidence of the stress mediated magnetoelectric coupling between the spinel and perovskite of the bilayered nanostructures was qualitatively studied by Raman spectroscopy. Additionally, the direct magnetoelectric effect in these 1-D and bilayered multiferroic nanocomposites was evaluated both quantitatively and qualitatively by using a novel magnetic field-assisted piezoelectric force microscopy (M-PFM) technique. The quantitative estimation of the magnetoelectric coupling coefficients was performed by tracking the changes in the phase and -amplitude

  6. Layered-structural monoclinic–orthorhombic perovskite La{sub 2}Ti{sub 2}O{sub 7} to orthorhombic LaTiO{sub 3} phase transition and their microstructure characterization

    SciTech Connect

    Herrera, G.; Jiménez-Mier, J.; Chavira, E.

    2014-03-01

    The layered-structural ceramics, such as lanthanum titanate (La{sub 2}Ti{sub 2}O{sub 7}), have been known for their good temperature and low dielectric loss at microwave frequencies that make them good candidate materials for high frequency applications. However, few studies have been conducted on the synthesis optimization by sol gel reaction, in particular by acrylamide polymerization route. The interest in La{sub 2}Ti{sub 2}O{sub 7} ceramic has been greatly increased recently due to the effect of oriented grains. This anisotropy of the microstructure leads to anisotropy in dielectric, electrical and mechanical properties. In this study, grain oriented lanthanum titanate was produced by the sol–gel acrylamide polymerization route. The characterizations of the samples were achieved by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). X-ray diffraction indicates that the formation of monoclinic perovskite La{sub 2}Ti{sub 2}O{sub 7} nanocrystals is a necessary first step to obtain orthorhombic LaTiO{sub 3} nanocomposites (with space group Pbnm). In this work we identified that the monoclinic perovskite La{sub 2}Ti{sub 2}O{sub 7} with space group P2{sub 1} transforms its structure into one with the orthorhombic space group Cmc2{sub 1} at approximately 1073 K. The microstructure associated consisted of flaky monoclinic La{sub 2}Ti{sub 2}O{sub 7} nanocomposites in comparison with round-shaped LaTiO{sub 3} nanocomposites. - Highlights: • The flaky-like La{sub 2}Ti{sub 2}O{sub 7} compound was synthesized by sol–gel acrylamide route. • Simultaneous monitoring of the DTA and XRD with temperature was performed. • Phase transformation characterization of La{sub 2}Ti{sub 2}O{sub 7} has been carried out. • The variation of the La{sub 2}Ti{sub 2}O{sub 7} and LaTiO{sub 3} grain morphology has been compared.

  7. 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.

  8. Dispersion characteristics of spin-electromagnetic waves in planar multiferroic structures

    SciTech Connect

    Nikitin, Andrey A.; Ustinov, Alexey B.; Vitko, Vitaliy V.; Semenov, Alexander A.; Mironenko, Igor G.; Belyavskiy, Pavel Yu.; Kalinikos, Boris A.; Stashkevich, Andrey A.; Lähderanta, E.

    2015-11-14

    A method of approximate boundary conditions is used to derive dispersion relations for spin-electromagnetic waves (SEWs) propagating in thin ferrite films and in multiferroic layered structures. A high accuracy of this method is proven. It was shown that the spin-electromagnetic wave propagating in the structure composed of a thin ferrite film, a thin ferroelectric film, and a slot transmission line is formed as a result of hybridization of the surface spin wave in the ferrite film and the electromagnetic wave in the slot-line. The structure demonstrates dual electric and magnetic field tunability of the SEW spectrum. The electric field tunability is provided by the thin ferroelectric film. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the slot-line gap width. The theory is confirmed by experimental data.

  9. Strain-mediated multiferroic control of spontaneous exchange bias in Ni-NiO heterostructures

    NASA Astrophysics Data System (ADS)

    Domann, John P.; Sun, Wei-Yang; Schelhas, Laura T.; Carman, Greg P.

    2016-10-01

    This paper presents the measurement of strain-mediated multiferroic control of spontaneous exchange bias (SEB) in magnetostrictive nickel/nickel oxide (Ni/NiO) bilayers on ferroelectric lead magnesium niobate-lead titanate (PMN-PT). Electric field control of a positive to negative exchange bias shift was measured, with an overall shift of 40.5 Oe, corresponding to a 325% change. Observed changes in coercivity are also reported and provide insight into the role of competing anisotropies in these structures. The findings in this paper provide evidence that magnetoelastic anisotropy can be utilized to control spontaneous exchange bias (SEB). This control of SEB is accomplished by modifying a bulk anisotropy (magnetoelasticity) that adjusts the mobility of interfacial anti-ferromagnetic spins and, therefore, the magnitude of the exchange bias. The demonstrated magnetoelastic control of exchange bias provides a useful tool in the creation of future magnetoelectric devices.

  10. Magnetic excitations in multiferroic TbMnO3: evidence for a hybridized soft mode.

    PubMed

    Senff, D; Link, P; Hradil, K; Hiess, A; Regnault, L P; Sidis, Y; Aliouane, N; Argyriou, D N; Braden, M

    2007-03-30

    The magnetic excitations in multiferroic TbMnO3 have been studied by inelastic neutron scattering in the spiral and sinusoidally ordered phases. At the incommensurate magnetic zone center of the spiral phase, we find three low-lying magnons whose character has been fully determined using neutron-polarization analysis. The excitation at the lowest energy is the sliding mode of the spiral, and two modes at 1.1 and 2.5 meV correspond to rotations of the spiral rotation plane. These latter modes are expected to couple to the electric polarization. The 2.5 meV mode is in perfect agreement with recent infrared-spectroscopy data giving strong support to its interpretation as a hybridized phonon-magnon excitation.

  11. Electric field control of magnon-induced magnetization dynamics in multiferroics

    NASA Astrophysics Data System (ADS)

    Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

    2016-08-01

    We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves.

  12. Magnetic biasing of a ferroelectric hysteresis loop in a multiferroic orthoferrite.

    PubMed

    Tokunaga, Y; Taguchi, Y; Arima, T; Tokura, Y

    2014-01-24

    In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign. PMID:24484164

  13. Resonant Soft X-ray Scattering Studies of Multiferroic YMn2O5

    SciTech Connect

    Partzsch, S.; Wilkins, S.B.; Schierle, E.; Soltwisch, V.; Hill, J.P.; Weschke, E.; Souptel, D.; Buchner, B.; Geck, J.

    2011-06-17

    We performed soft x-ray resonant scattering at the MnL{sub 2,3}- and OK edges of YMn{sub 2}O{sub 5}. While the resonant intensity at the MnL{sub 2,3} edges represent the magnetic order parameter, the resonant scattering at the OK edge is found to be directly related to the macroscopic ferroelectric polarization. The latter observation reveals the important role of the spin-dependent Mn-O hybridization for the multiferroicity of YMn{sub 2}O{sub 5}. We present details about how to obtain correct energy dependent lineshapes and discuss the origin of the resonant intensity at the OK edge.

  14. Microstructural, dielectric and magnetic properties of multiferroic composite system barium strontium titanate – nickel cobalt ferrite

    SciTech Connect

    Pahuja, Poonam Tandon, R. P.

    2015-05-15

    Multiferroic composites (1-x) Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3} + (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4} (where x = 0.1, 0.2, 0.3, 0.4) has been prepared by solid state reaction method. X-ray diffraction analysis of the composite samples confirmed the presence of both barium strontium titanate (BST) and nickel cobalt ferrite (NCF) phases. FESEM images indicated the well dispersion of NCF grains among BST grains. Dielectric constant and loss of the composite samples decreases with increase in frequency following Maxwell-Wagner relaxation mechanism. Composite sample with highest ferrite content possesses highest values of remanent and saturation magnetization.

  15. Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4

    NASA Astrophysics Data System (ADS)

    Kremer, Reinhard K.; Law, J. M.; Reuvekamp, P.; Glaum, R.; Lee, C.; Kang, J.; Whangbo, M.-H.

    2012-02-01

    The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO4, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, EPR and dielectric capacitance measurements and density functional evaluations of the intra- and interchain spin exchange interactions. We found type-II multiferroicity below the N'eel temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor (Jnn) and next-nearest-neighbor (Jnnn) intra-chain spin exchange interactions. Experimental and theoretical results indicate that the ratio Jnn/Jnnn is close to 2, putting CuCrO4 in the vicinity of the Majumdar-Ghosh point. First low-temperature neutron powder diffraction data are consistent with a canted magnetic structure below ˜8 K.

  16. Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4

    NASA Astrophysics Data System (ADS)

    Law, J. M.; Reuvekamp, P.; Glaum, R.; Lee, C.; Kang, J.; Whangbo, M.-H.; Kremer, R. K.

    2011-07-01

    The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO4, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, electron paramagnetic resonance and dielectric capacitance measurements, and density functional evaluations of the intrachain and interchain spin-exchange interactions. We found type-II multiferroicity below the Néel temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor (Jnn) and next-nearest-neighbor (Jnnn) intrachain spin-exchange interactions. Experimental and theoretical results indicate that the ratio Jnn/Jnnn is close to 2, putting CuCrO4 in the vicinity of the Majumdar-Ghosh point.

  17. Electric field control of magnon-induced magnetization dynamics in multiferroics.

    PubMed

    Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

    2016-01-01

    We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves. PMID:27554064

  18. Electric-field-driven magnetization reversal in square-shaped nanomagnet-based multiferroic heterostructure

    SciTech Connect

    Peng, Ren-Ci; Nan, Ce-Wen E-mail: cwnan@tsinghua.edu.cn; Wang, J. J. E-mail: cwnan@tsinghua.edu.cn; Chen, Long-Qing; Hu, Jia-Mian

    2015-04-06

    Based on phase field modeling and thermodynamic analysis, purely electric-field-driven magnetization reversal was shown to be possible in a multiferroic heterostructure of a square-shaped amorphous Co{sub 40}Fe{sub 40}B{sub 20} nanomagnet on top of a ferroelectric layer through electrostrain. The reversal is made possible by engineering the mutual interactions among the built-in uniaxial magnetic anisotropy, the geometry-dependent magnetic configuration anisotropy, and the magnetoelastic anisotropy. Particularly, the incorporation of the built-in uniaxial anisotropy made it possible to reverse magnetization with one single unipolar electrostrain pulse, which is simpler than previous designs involving the use of bipolar electrostrains and may alleviate ferroelectric fatigue. Critical conditions for triggering the magnetization reversal are identified.

  19. Dynamic in situ visualization of voltage-driven magnetic domain evolution in multiferroic heterostructures.

    PubMed

    Gao, Ya; Hu, Jia-Mian; Wu, Liang; Nan, C W

    2015-12-23

    Voltage control of magnetism in multiferroic heterostructures provides a promising solution to the excessive heating in spintronic devices. Direct observation of voltage-modulated magnetic domain evolution dynamics is desirable for studying the mechanism of the voltage control of magnetism at mesoscale, but has remained challenging. Here we explored a characterization method for the dynamic in situ evolution of pure voltage modulated magnetic domains in the heterostructures by employing the scanning Kerr microscopy function in the magneto optic Kerr effect system. The local magnetization reorientation of a Ni/PMN-PT heterostructure were characterized under sweeping applied voltage on the PMN-PT single crystal, and the results show that the magnetization rotation angle in the local regions is much greater than that obtained from macroscopic magnetization hysteresis loops.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  1. Electric field control of magnon-induced magnetization dynamics in multiferroics

    PubMed Central

    Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

    2016-01-01

    We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves. PMID:27554064

  2. A study of the dielectric and magnetic properties of multiferroic materials using the Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Sosa, A.; Almodovar, N. S.; Portelles, J.; Heiras, J.; Siqueiros, J. M.

    2012-03-01

    A study of the dielectric and magnetic properties of multiferroic materials using the Monte Carlo (MC) method is presented. Two different systems are considered: the first, ferroelectric-antiferromagnetic (FE-AFM) recently studied by X. S. Gaoand J. M. Liu and the second antiferroelectric-ferromagnetic (AFE-FM). Based on the DIFFOUR-Ising hybrid microscopic model developed by Janssen, a Hamiltonian that takes into account the magnetoelectric coupling in both ferroic phases is proposed. The obtained results show that the existence of such coupling modifies the ferroelectric and magnetic ordering in both phases. Additionally, it is shown that the presence of a magnetic or an electric field influences the electric polarization and the magnetization, respectively, making evident the magnetoelectric effect.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  4. An effective model of magnetoelectricity in multiferroics RMn2O5

    NASA Astrophysics Data System (ADS)

    Fang, Chen; Hu, Jiangping

    2008-06-01

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

  5. Spiral Spin Structure in the Commensurate Magnetic Phase of Multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Kimura, Hiroyuki; Kobayashi, Satoru; Fukuda, Yoshikazu; Osawa, Toshihiro; Kamada, Youichi; Noda, Yukio; Kagomiya, Isao; Kohn, Kay

    2007-07-01

    Crystal and magnetic structure analyses have been performed for single crystals of multiferroic materials RMn2O5 (R = Y, Ho, Er) using the neutron diffraction technique. For all the compounds, the magnetic structure in the commensurate magnetic phase, where spontaneous electric polarization occurs, was determined to be a transverse spiral spin structure propagating along the c-axis. The results demonstrate that the spin configuration for Mn4+ and Mn3+ ions is essentially the same in all three materials, suggesting that the ferroelectricity of the commensurate magnetic phase originates from the spin configurations of Mn ions. By contrast, the alignment of the induced 4 f-moment of Ho3+ ions is quite different from that of Er3+ ions, which might give a rich variety of magnetic field response for magnetic and dielectric properties in the RMn2O5 system.

  6. Measurement of complicated temperature-dependent polarization of multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Fukunaga, Mamoru; Noda, Yukio

    2011-09-01

    We have measured the temperature-dependent electric polarization P(T) of multiferroic rare-earth (R) manganese oxides RMn2O5 using both typical pyroelectric measurements and hysteresis loops with the double-wave method (DWM), and revealed the complicated behavior of the P(T). RMn2O5 single crystal samples often exhibit a tendency to macroscopically polarize without applying an external electric field. We have found that the tendency appeared in P(T) by the pyroelectric measurement can be measured by the DWM loops. The tendency to polarize is equivalent to asymmetric non-hystersis loops obtained by the DWM. We clarify the relationship between P(T) by pyroelectric measurement and that by the DWM loops, which can warrant the measured P(T).

  7. Electromagnons in multiferroic RMn2O5 compounds and their microscopic origin

    NASA Astrophysics Data System (ADS)

    Sushkov, A. B.; Mostovoy, M.; Valdés Aguilar, R.; Cheong, S.-W.; Drew, H. D.

    2008-10-01

    We summarize the existing experimental data on electromagnons in multiferroic RMn2O5 compounds, where R denotes a rare earth ion, Y or Bi, and discuss a realistic microscopic model of these materials based on the assumption that the microscopic mechanism of magnetically induced ferroelectricity and electromagnon absorption relies entirely on the isotropic Heisenberg exchange and magnetostrictive coupling of spins to a polar lattice mode and does not involve relativistic effects. This model explains many magnetic and optical properties of RMn2O5 manganites, such as the spin re-orientation transition, magnetically induced polarization, appearance of the electromagnon peak in the non-collinear spin state and the polarization of light for which this peak is observed. We compare experimental and theoretical results on electromagnons in RMn2O5 and RMnO3 compounds.

  8. Magnetic domains in multiferroic YMn$2O5 probed by Spherical Neutron Polarimetry under electric field

    NASA Astrophysics Data System (ADS)

    Vecchini, Carlo; Chapon, Laurent; Radaelli, Paolo; Daoud-Aladine, Aziz; Brown, Jane; Chatterji, Tapan; Park, Soonyong; Cheong, Sang-Wook

    2008-03-01

    Precise determination of the magnetic structures in multiferroics RMn2O5 (R: Y, Ho, Bi) have been obtained by single crystal neutron diffraction. The analysis shows the presence of zig-zag antiferromagnetic chains in the ab-plane. An additional weak magnetic component parallel to the c-axis was detected which is modulated in phase quadrature with the a-b components. The nature and population of the coexisting antiferromagnetic domains in YMn2O5 have been determined by Spherical Neutron Polarimetry under an external electric field. We have proved that reversing the electrical polarity results in the inversion of the population of two types of antiferromagnetic domains, with opposite in-plane spin components. This analysis strongly supports theories in which the coupling of the magnetic configuration to the ferroelectric polarisation is due to magnetic exchange striction and likely not related to the small cycloidal modulation in the bc-plane.

  9. Spin chirality and electric polarization in multiferroic compounds RMn2O5 ( R=Ho, Er)

    NASA Astrophysics Data System (ADS)

    Wakimoto, Shuichi; Kimura, Hiroyuki; Fukunaga, Mamoru; Nishihata, Keisuke; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio; Tokura, Yoshinori

    2009-09-01

    Polarized neutron diffraction experiments have been performed on multiferroic materials RMn2O5 ( R=Ho, Er) under electric fields in the ferroelectric commensurate (CM) and the low-temperature incommensurate (LT-ICM) phases, where the former has the highest electric polarization and the latter has reduced polarization. It is found that, after cooling in electric fields down to the CM phase, the magnetic chirality is proportional to the electric polarization. Also we confirmed that the magnetic chirality can be switched by the polarity of the electric polarization in both the CM and LT-ICM phases. These facts suggest an intimate coupling between the magnetic chirality and the electric polarization. However, upon the transition from the CM to LT-ICM phase, the reduction of the electric polarization is not accompanied by any reduction of the magnetic chirality, implying that the CM and LT-ICM phases contain different mechanisms of the magnetoelectric coupling.

  10. Investigation of Magnetic and Electrical Properties of Multiferroic CZFO-PZT Nanocomposites

    NASA Astrophysics Data System (ADS)

    Mandal, P. R.; Nath, T. K.

    2011-11-01

    The room temperature multiferroic nanocomposite materials of ferrite-ferroelectric ceramics viz. cobalt-zinc ferrite (i.e. Co0.65Zn0.35Fe2O4) and lead zirconate titanate (i.e. PbZr0.52Ti0.48O3) sintered at three different temperatures were prepared by sol-gel technique. Magnetization versus magnetic field measurements show typical hysteresis loops, attesting room temperature ferrimagnetic behavior of the composites. The ferrimagnetic Curie temperature is nearly 230 °C which is slightly decreased from pure Co-Zn ferrite. The dielectric constant increases with increasing particle size. The ferroelectric Tc decreases gradually but the transition becomes increasingly diffuse with decrease in particle size. The polarization versus electric field (P-E) measurement exhibits a clear saturating nature of hysteresis loop which proves the excellent ferroelectricity of the nanocomposite.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  12. Stress-mediated magnetoelectric control of ferromagnetic domain wall position in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Mathurin, Théo; Giordano, Stefano; Dusch, Yannick; Tiercelin, Nicolas; Pernod, Philippe; Preobrazhensky, Vladimir

    2016-02-01

    The motion of a ferromagnetic domain wall in nanodevices is usually induced by means of external magnetic fields or polarized currents. Here, we demonstrate the possibility to reversibly control the position of a Néel domain wall in a ferromagnetic nanostripe through a uniform mechanical stress. The latter is generated by an electro-active substrate combined with the nanostripe in a multiferroic heterostructure. We develop a model describing the magnetization distribution in the ferromagnetic material, properly taking into account the magnetoelectric coupling. Through its numerical implementation, we obtain the relationship between the electric field applied to the piezoelectric substrate and the position of the magnetic domain wall in the nanostripe. As an example, we analyze a structure composed of a PMN-PT substrate and a TbCo2/FeCo composite nanostripe.

  13. Dynamic in situ visualization of voltage-driven magnetic domain evolution in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Gao, Ya; Hu, Jia-Mian; Wu, Liang; Nan, C. W.

    2015-12-01

    Voltage control of magnetism in multiferroic heterostructures provides a promising solution to the excessive heating in spintronic devices. Direct observation of voltage-modulated magnetic domain evolution dynamics is desirable for studying the mechanism of the voltage control of magnetism at mesoscale, but has remained challenging. Here we explored a characterization method for the dynamic in situ evolution of pure voltage modulated magnetic domains in the heterostructures by employing the scanning Kerr microscopy function in the magneto optic Kerr effect system. The local magnetization reorientation of a Ni/PMN-PT heterostructure were characterized under sweeping applied voltage on the PMN-PT single crystal, and the results show that the magnetization rotation angle in the local regions is much greater than that obtained from macroscopic magnetization hysteresis loops.

  14. Dynamic in situ visualization of voltage-driven magnetic domain evolution in multiferroic heterostructures.

    PubMed

    Gao, Ya; Hu, Jia-Mian; Wu, Liang; Nan, C W

    2015-12-23

    Voltage control of magnetism in multiferroic heterostructures provides a promising solution to the excessive heating in spintronic devices. Direct observation of voltage-modulated magnetic domain evolution dynamics is desirable for studying the mechanism of the voltage control of magnetism at mesoscale, but has remained challenging. Here we explored a characterization method for the dynamic in situ evolution of pure voltage modulated magnetic domains in the heterostructures by employing the scanning Kerr microscopy function in the magneto optic Kerr effect system. The local magnetization reorientation of a Ni/PMN-PT heterostructure were characterized under sweeping applied voltage on the PMN-PT single crystal, and the results show that the magnetization rotation angle in the local regions is much greater than that obtained from macroscopic magnetization hysteresis loops. PMID:26613293

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

    NASA Astrophysics Data System (ADS)

    Wang, Zidong; Grimson, Malcolm J.

    2015-06-01

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

  16. Visualization of weak ferromagnetic domains in multiferroic hexagonal ferrite thin film

    NASA Astrophysics Data System (ADS)

    Wu, Weida; Wang, Wenbo; Moyer, Jarrett A.; Schiffer, Peter; Mundy, Julia A.; Muller, David A.; Schlom, Darrell G.

    Hexagonal h-LuFeO3 thin film has been reported to be a room-temperature multiferroic. Extensive studies on high quality MBE thin films revealed a magnetoelectric phase with weak ferromagnetism emerges below TN ~ 147 K. However, the direct observation of weak ferromagnetic domain structures is still lacking. Here we report cryogenic magnetic force microscopy (MFM) results on 200 nm thick h-LuFeO3 film grown by molecular-beam epitaxy (MBE) on (111)-oriented yttria-stablized cubic zirconia (YSZ) substrates. Labyrinth-like weak ferromagnetic domain structures were observed with a domain size ~ 1 μm and domain wall width ~ 0 . 4 μm . Field-dependent MFM data indicates the coercive field is ~ 2 . 66 T at 50 K and ~ 3 . 15 T at 6 K. This work is supported by DOE BES under Award # DE-SC0008147.

  17. Spin-state crossover in multiferroic Ca3Co2-xMnxO6

    NASA Astrophysics Data System (ADS)

    Flint, R.; Yi, H.-T.; Chandra, P.; Cheong, S.-W.; Kiryukhin, V.

    2010-03-01

    Ca3Co2-xMnxO6 (x˜0.96) is a multiferroic with spin-chains of alternating Co2+ and Mn4+ ions. The spin state of Co2+ remains unresolved due to a discrepancy between high-temperature x-ray absorption (S=(3)/(2)) and low-temperature neutron (S=(1)/(2)) measurements. Using a combination of magnetic modeling and crystal-field analysis, we show that the existing low temperature data cannot be reconciled within a high spin scenario by invoking spin-orbit or Jahn-Teller distortions. To unify the experimental results, we propose a spin-state crossover with specific experimental predictions.

  18. Multiferroic properties of NiS nanoplates grown within Na-4 mica

    NASA Astrophysics Data System (ADS)

    Mandal, Amrita; Bose, Anindita; Mitra, Sreemanta; Datta, Anindya; Banerjee, Sourish; Chakravorty, Dipankar

    2012-09-01

    Nanoplates of NiS with thickness 0.6 nm were grown within the crystal channels of Na-4 mica. The thickness of the nanoplates is confirmed by atomic force microscopy. The nanocomposites exhibited multiferroic (both ferromagnetic and ferroelectric) behavior at room temperature. Ferromagnetism was adduced to an increase of surface defects as a result of the two-dimensional configuration of the sample. Ferroelectric behavior was explained as arising due to a small distortion in the crystal structure of NiS grown within the Na-4 mica channels. This was substantiated by the refined values of lattice constants as determined by profile matching of X-ray data by a computer program. A magnetodielectric effect was also observed in this nanocomposite with a change of 0.77% in the dielectric constant for a magnetic field of 0.6 T.

  19. Hyperfine and crystal field interactions in multiferroic HoCrO3

    NASA Astrophysics Data System (ADS)

    Kumar, C. M. N.; Xiao, Y.; Nair, H. S.; Voigt, J.; Schmitz, B.; Chatterji, T.; Jalarvo, N. H.; Brückel, Th

    2016-11-01

    We report a comprehensive specific heat and inelastic neutron scattering study to explore the possible origin of multiferroicity in HoCrO3. We have performed specific heat measurements in the temperature range 100 mK-290 K and inelastic neutron scattering measurements were performed in the temperature range 1.5-200 K. From the specific heat data we determined hyperfine splitting at 22.5(2) μeV and crystal field transitions at 1.379(5) meV, 10.37(4) meV, 15.49(9) meV and 23.44(9) meV, indicating the existence of strong hyperfine and crystal field interactions in HoCrO3. Further, an effective hyperfine field is determined to be 600(3) T. The quasielastic scattering observed in the inelastic scattering data and a large linear term γ =6.3(8) mJ mol-1  K-2 in the specific heat is attributed to the presence of short range exchange interactions, which is understood to be contributing to the observed ferroelectricity. Further the nuclear and magnetic entropies were computed to be, ˜17.2 Jmol-1 K-1 and  ˜34 Jmol-1 K-1, respectively. The entropy values are in excellent agreement with the limiting theoretical values. An anomaly is observed in the peak position of the temperature dependent crystal field spectra around 60 K, at the same temperature an anomaly in the pyroelectric current is reported. From this we could elucidate a direct correlation between the crystal electric field excitations of Ho3+ and ferroelectricity in HoCrO3. Our present study, along with recent reports, confirm that HoCrO3, and RCrO3 (R  =  rare earth) in general, possess more than one driving force for the ferroelectricity and multiferroicity.

  20. The shape factor influence on the control process of multiferroic nanoparticle configurations in GHz range

    NASA Astrophysics Data System (ADS)

    Ionescu, D.; Kovaci, M.

    2015-11-01

    Materials with piezoelectric properties associated with the ferroic phases generate multiferroic structures at microscopic level. Multiferroic core-shell nanoparticles with different configurations were considered: nanospheres versus nanotubes - spherical (magnetostrictive core / piezoelectric shell), respectively cylindrical (magnetostrictive rod / piezoelectric cylindrical coating) The external sphere diameter / cylinder lengths were of 80 - 100 nm to 360 nm, while the inner sphere / rod diameters were of 20 to 60 nm. The influence of the constituents shape on their control process realized by an applied magnetic field, H0 (100 - 270 Oe) was investigated. The nanoparticles were simulated using the HFSS 13.0 program, at frequencies in microwave range (16 - 28 GHz), considering the nanostructures with hexaferrites as magnetic phase (AFe12O19 M-type hexaferrites, with A an alkali earth metal) and the Bi2NiMnO6 perovskite like piezoelectric. The particle configurations response is function of their geometrical shape, modified by the core diameter and the shell thickness. The magnetoelectric (ME) coefficient tensor has been determined using a physical algorithm based on the near-filed values in the particles vicinity, generated by the HFSS, and also the ME voltage coefficient (obtained of tens of mV/cmOe). Performance of the two shapes composite nanoparticles to generate a strong ME response was discussed comparatively and the influence of the shape factor was illustrated on graphs. Each composite configuration presents specific advantages in respect with the control process by the H0 field, considering that the effect of dipolar field generated as response by the electric phase is strongly anisotropic. These features can be elegant illustrated by simulations (non destructive, applied at nanoscale) which help us to decide to the proper nanoparticles shape and the optimal intensity of the applied fields for the desired strength of the ME effect in a defined microscopic

  1. Multiferroicity and skyrmions carrying electric polarization in GaV4S8

    PubMed Central

    Ruff, Eugen; Widmann, Sebastian; Lunkenheimer, Peter; Tsurkan, Vladimir; Bordács, Sandor; Kézsmárki, Istvan; Loidl, Alois

    2015-01-01

    Skyrmions are whirl-like topological spin objects with high potential for future magnetic data storage. A fundamental question that is relevant to both basic research and application is whether ferroelectric (FE) polarization can be associated with skyrmions’ magnetic texture and whether these objects can be manipulated by electric fields. We study the interplay between magnetism and electric polarization in the lacunar spinel GaV4S8, which undergoes a structural transition associated with orbital ordering at 44 K and reveals a complex magnetic phase diagram below 13 K, including ferromagnetic, cycloidal, and Néel-type skyrmion lattice (SkL) phases. We found that the orbitally ordered phase of GaV4S8 is FE with a sizable polarization of ~1 μC/cm2. Moreover, we observed spin-driven excess polarizations in all magnetic phases; hence, GaV4S8 hosts three different multiferroic phases with coexisting polar and magnetic order. These include the SkL phase, where we predict a strong spatial modulation of FE polarization close to the skyrmion cores. By taking into account the crystal symmetry and spin patterns of the magnetically ordered phases, we identify exchange striction as the main microscopic mechanism behind the spin-driven FE polarization in each multiferroic phase. Because GaV4S8 is unique among known SkL host materials owing to its polar crystal structure and the observed strong magnetoelectric effect, this study is an important step toward the nondissipative electric field control of skyrmions. PMID:26702441

  2. Hyperfine and crystal field interactions in multiferroic HoCrO3.

    PubMed

    Kumar, C M N; Xiao, Y; Nair, H S; Voigt, J; Schmitz, B; Chatterji, T; Jalarvo, N H; Brückel, Th

    2016-11-30

    We report a comprehensive specific heat and inelastic neutron scattering study to explore the possible origin of multiferroicity in HoCrO3. We have performed specific heat measurements in the temperature range 100 mK-290 K and inelastic neutron scattering measurements were performed in the temperature range 1.5-200 K. From the specific heat data we determined hyperfine splitting at 22.5(2) μeV and crystal field transitions at 1.379(5) meV, 10.37(4) meV, 15.49(9) meV and 23.44(9) meV, indicating the existence of strong hyperfine and crystal field interactions in HoCrO3. Further, an effective hyperfine field is determined to be 600(3) T. The quasielastic scattering observed in the inelastic scattering data and a large linear term [Formula: see text] mJ mol(-1)  K(-2) in the specific heat is attributed to the presence of short range exchange interactions, which is understood to be contributing to the observed ferroelectricity. Further the nuclear and magnetic entropies were computed to be, ∼17.2 Jmol(-1) K(-1) and  ∼34 Jmol(-1) K(-1), respectively. The entropy values are in excellent agreement with the limiting theoretical values. An anomaly is observed in the peak position of the temperature dependent crystal field spectra around 60 K, at the same temperature an anomaly in the pyroelectric current is reported. From this we could elucidate a direct correlation between the crystal electric field excitations of Ho(3+) and ferroelectricity in HoCrO3. Our present study, along with recent reports, confirm that HoCrO3, and RCrO3 (R  =  rare earth) in general, possess more than one driving force for the ferroelectricity and multiferroicity. PMID:27633731

  3. Magnetoelectic multiferroic superlattices and interfaces: Designing spintronic materials from first principles

    NASA Astrophysics Data System (ADS)

    Zanolli, Zeila

    2015-03-01

    The research challenges of the near and far future in electronics focus on the quest for new materials and novel device concepts to achieve low energy consumption, increased reliability and high device density. These can be obtained by designing active elements and interconnects whose operating principle is not (only) based on the electron charge but on the spin degree of freedom of the electron. The nanoscopic size of the materials calls for atomistic and parameter free (ab initio) simulations, which have proven to be crucial in achieving the necessary accuracy and predictive power. Materials which present a coupling between ferroelectricity and magnetism, i.e. magnetoelectric (ME) multiferroics, have been proposed as fundamental building blocks for spintronic devices. However ferroelectricity and magnetism are often exclusive or weakly coupled in bulk. In this talk, we will discuss how superlattices of perovskites can be designed from first principles to achieve strongly coupled ME and, hence, achieve control the weak magnetization via an electric field. Most important, advanced epitaxial techniques allow one to actually grow such magnetoelectric superlattices. Another route to optimize spintronic devices is to exploit the unique electronic and transport properties of Carbon-based nanomaterials. The latter present spin diffusion lengths up to 100 μm and high electron velocity. However, a large spin diffusion length comes at the price of small Spin Orbit coupling, which limits the possibility of manipulating electrons via an external applied field. Further, to achieve graphene-based devices one also needs to open its vanishing electronic gap. We use first principle techniques to show that placing graphene on a ME substrate can overcome these limitations by inducing magnetism and opening an electronic band-gap in the hybrid organic-multiferroic material. Z.Z. acknowledges EC support under the Marie-Curie IEF (PIEF-Ga-2011-300036), computational resources from the

  4. 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

  5. Robustness of magnetic and electric domains against charge carrier doping in multiferroic hexagonal ErMnO3

    NASA Astrophysics Data System (ADS)

    Hassanpour, E.; Wegmayr, V.; Schaab, J.; Yan, Z.; Bourret, E.; Lottermoser, Th; Fiebig, M.; Meier, D.

    2016-04-01

    We investigate the effect of chemical doping on the electric and magnetic domain pattern in multiferroic hexagonal ErMnO3. Hole- and electron doping are achieved through the growth of Er1‑x Ca x MnO3 and Er1‑x Zr x MnO3 single crystals, which allows for a controlled introduction of divalent and tetravalent ions, respectively. Using conductance measurements, piezoresponse force microscopy and nonlinear optics we study doping-related variations in the electronic transport and image the corrsponding ferroelectric and antiferromagnetic domains. We find that moderate doping levels allow for adjusting the electronic conduction properties of ErMnO3 without destroying its characteristic domain patterns. Our findings demonstrate the feasibility of chemical doping for non-perturbative property-engineering of intrinsic domain states in this important class of multiferroics.

  6. Optical diode effect at spin-wave excitations in the room-temperature multiferroic BiFeO3.

    DOE PAGES

    Kezsmarki, I.; Nagel, U.; Bordacs, S.; Fishman, Randy Scott; Lee, Jun Hee; Yi, Hee Taek; Cheong, Sang-Wook; Room, T.

    2015-09-15

    The ability to read and write a magnetic state current-free by an electric voltage would provide a huge technological advantage. Dynamic or optical ME effects are equally interesting, because they give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. This phenomenon, if realized at room temperature, would allow the development of optical diodes which transmit unpolarized light in one, but not in the opposite, direction. Here, we report strong unidirectional transmission in the room-temperature multiferroic BiFeO3 over the gigahertz-terahertz frequency range. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. Our findingsmore » are an important step toward the realization of optical diodes, supplemented by the ability to switch the transmission direction with a magnetic or electric field.« less

  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

    2016-02-05

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

  8. 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.

  9. 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

  10. Exchange-striction induced giant ferroelectric polarization in copper-based multiferroic material α -Cu2V2O7

    NASA Astrophysics Data System (ADS)

    Sannigrahi, J.; Bhowal, S.; Giri, S.; Majumdar, S.; Dasgupta, I.

    2015-06-01

    We report α -Cu2V2O7 to be an improper multiferroic with the simultaneous development of electric polarization and magnetization below TC=35 K . The observed spontaneous polarization of 0.55 μ C cm-2 magnitude is highest among copper-based improper multiferroic materials. Our study demonstrates a sizable amount of magnetoelectric coupling below TC, even with a low magnetic field. The theoretical calculations based on density functional theory indicate magnetism in α -Cu2V2O7 is a consequence of ferro-orbital ordering driven by a polar lattice distortion due to the unique pyramidal (CuO5) environment of Cu. Spin-orbit coupling further stabilizes orbital ordering and is crucial for magnetism. The calculations indicate that the origin of the giant ferroelectric polarization is primarily due to the symmetric exchange-striction mechanism and is corroborated by temperature-dependent x-ray studies.

  11. Phase composition, microstructure, and thermophysical and dielectric properties of multiferroic Bi1- x Dy x FeO3

    NASA Astrophysics Data System (ADS)

    Khasbulatov, S. V.; Pavelko, A. A.; Shilkina, L. A.; Reznichenko, L. A.; Gadjiev, G. G.; Bakmaev, A. G.; Magomedov, M.-R. M.; Omarov, Z. M.; Aleshin, V. A.

    2016-05-01

    An extensive study was performed to establish correlations between the crystal structure, the grain composition, and the dielectric and thermophysical properties of high-temperature multiferroics of the Bi1- x Dyx FeO3 type ( x = = 0.05-0.20). It is shown that a trade-off between the macroresponses in the materials is achieved at x = 0.10; this circumstance permits recommendation of the materials for practical use.

  12. James C. McGroddy Prize for New Materials Talk: What is new in multiferroicity?: Mott ferroelectrics!

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook

    2010-03-01

    Multiferroicity is an old topic. For example, linear magnetoelectric effect in materials such as Cr2O3 with broken time reversal and space inversion symmetry has been known since 1960's. However, giant cross-coupling effects such as flipping polarization or enormous change of dielectric constant by applied magnetic fields have been recently observed in systems such as Tb(Dy)MnO3 and Tb(Dy)Mn2O5 [1-3]. The important ingredient for these giant magnetoelectric effects turns out to be associated with the presence of non-zero d electrons and their mutual interactions, leading to the Mott-insulator-type charge gap, magnetism, and collective phase transitions. Particularly, the collective nature of simultaneous magnetic-ferroelectric phase transitions results in the giant magnetoelectric effects. In addition, fascinating charge transport properties such as a switchable photovoltaic effect and characteristic conduction properties at domain walls stem from the (carrier-doped) Mott insulating nature of compounds such as BiFeO3 and hexagonal YMnO3 [4,5]. [4pt] [1] Kimura, T. et al. Magnetic control of ferroelectric polarization. Nature 426, 55--58 (2003).[0pt] [2] Hur, N. et al. Electric polarization reversal and memory in a multiferroic material induced by magnetic fields. Nature 429, 392--395 (2004).[0pt] [3] Cheong, S.-W. & Mostovoy, M. Multiferroics: a magnetic twist for ferroelectricity. Nature Mater. 6, 13--20 (2007).[0pt] [4] Seidel, J. et al. Conduction at domain walls in oxide multiferroics. Nature Mater. 8, 229--234 (2009).[0pt] [5] Choi, T., Lee, S., Choi, Y.J., Kiryukhin, V. & Cheong, S.-W. Switchable ferroelectric diode and photovoltaic effect in BiFeO3. Science 324, 63--66 (2009)

  13. Investigations of surface structural, dynamical, and magnetic properties of systems exhibiting multiferroicity, and topological phases by helium scattering spectroscopies

    SciTech Connect

    El-Batanouny, Maged

    2015-08-03

    We propose to investigate the surface structural, dynamics and magnetic properties of the novel class of topological insulator crystals, as well as crystals that exhibit multiferroicity, magnetoelectricity and thermoelectricity. Topological insulators (TIs) are a new class of insulators in which a bulk gap for electronic excitations is generated because of the strong spin-orbit coupling inherent to these systems. These materials are distinguished from ordinary insulators by the presence of gapless metallic surface states, resembling chiral edge modes in quantum Hall systems, but with unconventional spin textures. These exotic metallic states are formed by topological conditions that also render the electrons travelling on such surfaces insensitive to scattering by impurities. The electronic quasi-particles populating the topological surface state are Dirac fermions; they have a linear dispersion and thus are massless just like photons. We propose to investigate the interaction of these massless Dirac fermions with the massive lattice in the newly discovered crystals, Bi2Se3, Bi2Te3 and Sb2Te3. We shall use inelastic helium beam scattering from surfaces to search for related signatures in surface phonon dispersions mappings that cover the entire surface Brillouin zone of these materials. Our recent investigations of the (001) surface of the multiferroic crystals (Li/Na)Cu2O2 revealed an anomalous surface structural behavior where surface Cu$^{2+}$ row rise above the surface plane as the crystal was cooled. Subsequent worming revealed the onset of a thermally activated incommensurate surface phase, driven by the elevated rows. We are currently investigating the structure of the magnetic phases in these quasi-one-dimensional magnetic rows. Multiferroics are excellent candidates for large magnetoelectric response. We propose to extend this investigation to the class of delafossites which are also multiferroics and have been investigated as good candidates for

  14. Electronic and multiferroic properties of Zn{sub 0.85}Mg{sub 0.15}O thin film

    SciTech Connect

    Devi, Vanita Joshi, B. C.; Kumar, Manish; Wadikar, A. D.; Choudhary, R. J.; Phase, D. M.

    2015-06-24

    Thin film sample of Zn{sub 0.85}Mg{sub 0.15}O was prepared on Si (100) substrate by pulsed laser deposition and its structural, electronic, magnetic and ferroelectric properties were investigated. The Zn{sub 0.85}Mg{sub 0.15}O thin film sample is found to show room temperature multiferroic properties; suitable for device fabrication.

  15. Conduction and magnetization improvement of BiFeO{sub 3} multiferroic nanoparticles by Ag{sup +} doping

    SciTech Connect

    Ahmed, M.A.; Mansour, S.F.; El-Dek, S.I.; Abu-Abdeen, M.

    2014-01-01

    Graphical abstract: HRTEM micrographs of the samples BiFeO{sub 3}. - Highlights: • Flash auto combustion method was successful in the preparation of Ag doped BiFeO{sub 3} in nanosize. • Ag doping results in hexagonal platelet shapes up to x = 0.10, at x ≥ 0.15 needle shape predominates. • Mixed conduction is obtained in Ag doped samples. • This nanometric multiferroic could be recommended as attractive cathode for solid oxide fuel cell. - Abstract: Nanometric multiferroic namely Ag doped (BiFeO{sub 3}) was synthesized using flash auto combustion technique and glycine as a fuel. Single phase rhombohedral–hexagonal perovskite structure was obtained by annealing at 550 °C, as determined from XRD. High resolution transmission electron microscope (HRTEM) clarifies the hexagonal platelet shape with size 17.9 nm. Maximum room temperature AC conductivity was obtained at Ag content of x = 0.10. The results of this study promote the use of such multiferroic in solid oxide fuel cell applications.

  16. Ultra low-power straintronics with multiferroic nanomagnets: magnetization dynamics, universal logic gates and associated energy dissipation

    NASA Astrophysics Data System (ADS)

    Salehi-Fashami, Mohammad; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2012-02-01

    Stress induced magnetization dynamics of dipole coupled multiferroic nanomagnet arrays is modeled by solving the Landau-Lifshitz-Gilbert (LLG) equation. We show that in such multiferroic nanomagnets, consisting of magnetostrictive layers elastically coupled to piezoelectric layers, the single domain magnetization can be rotated by a large angle (˜ 90^o) in ˜ 1 ns if a tiny voltage of a few tens of millivolts is applied across the piezoelectric layer [Nanotechnology, 22, 155201, 2011, Appl. Phys. Lett. 99, 063108, 2011]. Arrays of such multiferroic nanomagnets can be laid out in specific geometric patterns to implement combinational and sequential logic circuits by exploiting inter-magnet dipole coupling and Bennett clocked with specific stress cycles to propagate logic bits and implement dynamic logic. In this work, we theoretically demonstrate logic propagation in and fan-out characteristics of a universal NAND gate and discuss energy dissipation in the magnet and in the external clock. We show that this energy dissipation can be 3 orders of magnitude more energy-efficient than current CMOS technology for a reasonable clock speed of 1 GHz. This work is supported by the NSF under grant ECCS-1124714.

  17. Optical Diode Effect at Spin-Wave Excitations of the Room-Temperature Multiferroic BiFeO_{3}.

    PubMed

    Kézsmárki, I; Nagel, U; Bordács, S; Fishman, R S; Lee, J H; Yi, Hee Taek; Cheong, S-W; Rõõm, T

    2015-09-18

    Multiferroics permit the magnetic control of the electric polarization and the electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to read and write a magnetic state current-free by an electric voltage would provide a huge technological advantage. Dynamic or optical ME effects are equally interesting, because they give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. This phenomenon, if realized at room temperature, would allow the development of optical diodes which transmit unpolarized light in one, but not in the opposite, direction. Here, we report strong unidirectional transmission in the room-temperature multiferroic BiFeO_{3} over the gigahertz-terahertz frequency range. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. These findings are an important step toward the realization of optical diodes, supplemented by the ability to switch the transmission direction with a magnetic or electric field.

  18. Optical Diode Effect at Spin-Wave Excitations of the Room-Temperature Multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Kézsmárki, I.; Nagel, U.; Bordács, S.; Fishman, R. S.; Lee, J. H.; Yi, Hee Taek; Cheong, S.-W.; Rõõm, T.

    2015-09-01

    Multiferroics permit the magnetic control of the electric polarization and the electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to read and write a magnetic state current-free by an electric voltage would provide a huge technological advantage. Dynamic or optical ME effects are equally interesting, because they give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. This phenomenon, if realized at room temperature, would allow the development of optical diodes which transmit unpolarized light in one, but not in the opposite, direction. Here, we report strong unidirectional transmission in the room-temperature multiferroic BiFeO3 over the gigahertz-terahertz frequency range. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. These findings are an important step toward the realization of optical diodes, supplemented by the ability to switch the transmission direction with a magnetic or electric field.

  19. Symmetries and multiferroic properties of novel room-temperature magnetoelectrics: Lead iron tantalate – lead zirconate titanate (PFT/PZT)

    DOE PAGES

    Sanchez, Dilsom A.; Ortega, N.; Kumar, Ashok; Roque-Malherbe, R.; Polanco, R.; Scott, J. F.; Katiyar, Ram S.

    2011-12-01

    Mixing 60-70% lead zirconate titanate with 40-30% lead iron tantalate produces a single-phase, low-loss, room-temperature multiferroic with magnetoelectric coupling: (PbZr₀.₅₃Ti₀.₄₇O₃) (1-x)- (PbFe₀.₅Ta₀.₅O₃)x. The present study combines x-ray scattering, magnetic and polarization hysteresis in both phases, plus a second-order dielectric divergence (to epsilon = 6000 at 475 K for 0.4 PFT; to 4000 at 520 K for 0.3 PFT) for an unambiguous assignment as a C2v-C4v (Pmm2-P4mm) transition. The material exhibits square saturated magnetic hysteresis loops with 0.1 emu/g at 295 K and saturation polarization Pr = 25 μC/cm², which actually increases (to 40 μC/cm²) in the high-T tetragonal phase, representingmore » an exciting new room temperature oxide multiferroic to compete with BiFeO₃. Additional transitions at high temperatures (cubic at T>1300 K) and low temperatures (rhombohedral or monoclinic at T<250 K) are found. These are the lowest-loss room-temperature multiferroics known, which is a great advantage for magnetoelectric devices.« less

  20. Structural, magnetic and electrical properties of samarium substituted multiferroic bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Gowrishankar, M.; Babu, D. Rajan; Madeswaran, S.

    2016-05-01

    Polycrystalline Bi0.8Sm0.2FeO3 was synthesized by a simple co - precipitation route. Single phase of the prepared sample was confirmed by X-ray diffraction analysis which further reveals that it crystalizes as mixed crystal structure of rhombohedral with R3c space group and orthorhombic with Pnma space group. A considerable increase in magnetization was observed at room temperature VSM analysis and temperature dependent dielectric analysis shows an anomaly at the vicinity of Neel temperature (TN). Room temperature ferroelectric study explicitly authenticates the formation of a better loop due to the reduced leakage current and the suppression of oxygen deficiencies.

  1. Deep inelastic neutron scattering from orthorhombic ordered HCl: Short-time proton dynamics and anomalous neutron cross sections

    SciTech Connect

    Senesi, R.; Colognesi, D.; Pietropaolo, A.; Abdul-Redah, T.

    2005-08-01

    Deep inelastic neutron scattering measurements from orthorhombic ordered HCl are presented and analyzed in order to clarify the problem of an anomalous deficit in the neutron-proton cross section found in previous experiments on various materials. A reliable model for the HCl short-time single-particle dynamics, including atomic vibrational anisotropies and deviations from the impulsive approximation, is set up. The model HCl response function is transformed into simulated time-of-flight spectra, taking carefully into account the effects of instrumental resolution and the filter absorption profile used for neutron energy analysis. Finally, the experimental values of the anomalous reduction factor for the neutron-proton cross section are extracted by comparing simulated and experimental data. Results show a 34% reduction of the H cross section, varying with the scattering angle in a range centered at 53 deg. In addition, the same approximate procedure used in earlier studies is also employed, providing results in reasonable agreement with the more rigorous ones, and confirming the substantial reliability of the past work on this subject.

  2. Crystal structure and partial Ising-like magnetic ordering of orthorhombic D y2Ti O5

    NASA Astrophysics Data System (ADS)

    Shamblin, Jacob; Calder, Stuart; Dun, Zhiling; Lee, Minseong; Choi, Eun Sang; Neuefeind, Joerg; Zhou, Haidong; Lang, Maik

    2016-07-01

    The structure and magnetic properties of orthorhombic D y2Ti O5 have been investigated using x-ray diffraction, neutron diffraction, and alternating current (ac)/direct current (dc) magnetic susceptibility measurements. We report a continuous structural distortion below 100 K characterized by negative thermal expansion in the [0 1 0] direction. Neutron diffraction and magnetic susceptibility measurements revealed that two-dimensional (2D) magnetic ordering begins at 3.1 K, which is followed by a three-dimensional magnetic transition at 1.7 K. The magnetic structure has been solved through a representational analysis approach and can be indexed with the propagation vector k =[0 1 /2 0 ] . The spin structure corresponds to a coplanar model of interwoven 2D "sheets" extending in the [0 1 0] direction. The local crystal field is different for each D y3 + ion (Dy1 and Dy2), one of which possesses strong uniaxial symmetry indicative of Ising-like magnetic ordering. Consequently, two succeeding transitions under magnetic field are observed in the ac susceptibility, which are associated with flipping each D y3 + spin independently.

  3. Native defects and Pr impurities in orthorhombic CaTiO3 by first-principles calculations

    NASA Astrophysics Data System (ADS)

    Zhu, Ailing; Wang, Jianchuan; Zhao, Dongdong; Du, Yong

    2011-07-01

    Formation energies of native defects and Pr impurities in orthorhombic CaTiO3 are explored using the first-principles calculations. The Ca vacancy (VCa), Ti vacancy (VTi) and Ca antisite (CaTi) are found to be energetically preferable. The Ti antisite (TiCa) and O vacancy (VO) are not energetically favorable in the wide range of Fermi level. In Pr-doped CaTiO3, Pr substituting for Ca (PrCa) is likely to form under condition A in which CaTiO3 is in equilibrium with CaO and O2. Under condition B (TiO2, CaTiO3 and O2 are in equilibrium), PrTi defect is energetically preferable depending on the Fermi levels. Several native defects and the two sites of Pr impurities in CaTiO3 are coincided with several different defects in Pr-doped CaTiO3 reported in the literature. Based on the present calculations, we can elucidate that the Ca deficiency design of the traditional formula Ca1-xVCa(x/2)PrxTiO3 is not the best for efficient red photoluminescence, which is realized via the experimental measurements.

  4. Crystal Field Splitting is Limiting the Stability and Strength of Ultra-incompressible Orthorhombic Transition Metal Tetraborides

    PubMed Central

    Zhang, R. F.; Wen, X. D.; Legut, D.; Fu, Z. H.; Veprek, S.; Zurek, E.; Mao, H. K.

    2016-01-01

    The lattice stability and mechanical strengths of the supposedly superhard transition metal tetraborides (TmB4, Tm = Cr, Mn and Fe) evoked recently much attention from the scientific community due to the potential applications of these materials, as well as because of general scientific interests. In the present study, we show that the surprising stabilization of these compounds from a high symmetry to a low symmetry structure is accomplished by an in-plane rotation of the boron network, which maximizes the in-plane hybridization by crystal field splitting between d orbitals of Tm and p orbitals of B. Studies of mechanical and electronic properties of TmB4 suggest that these tetraborides cannot be intrinsically superhard. The mechanical instability is facilitated by a unique in-plane or out-of-plane weakening of the three-dimensional covalent bond network of boron along different shear deformation paths. These results shed a novel view on the origin of the stability and strength of orthorhombic TmB4, highlighting the importance of combinational analysis of a variety of parameters related to plastic deformation of the crystalline materials when attempting to design new ultra-incompressible, and potentially strong and hard solids. PMID:26976479

  5. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    DOE PAGES

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G.; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2014-12-19

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms,more » which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.« less

  6. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    SciTech Connect

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G.; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2014-12-19

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms, which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.

  7. Pseudotetragonal and orthorhombic ordered structures in substoichiometric YBa2Cu3O6+x oxides at x<0.4

    NASA Astrophysics Data System (ADS)

    Semenovskaya, S.; Khachaturyan, A. G.

    1995-04-01

    The previous analysis [S. Semenovskaya and A.G. Khachaturyan, Phys. Rev. B 46, 6511 (1992); Physica D 66, 205 (1993)] of the structural transformations in nonstoichiometric YBa2Cu3O6+x oxides is extended to a ``tetragonal'' stoichiometry region, x<0.4. Available diffraction data [Th. Zeiske, D. Hohlwein, R. Sonntag, F. Kubanek, and G. Collin, Z. Phys. B 86, 11 (1992); Tan Kemin, Hu Meisheng, and W. Yening, J. Phys. Condens. Matter 1, 1049 (1989)] (on the √2 a0×2 √2 a0 structures formed at small x<0.4) are analyzed by the concentration-wave method and computer-simulation technique. It is found that at small x<0.4, oxygen ordering results in a sequence of transformations different from those observed at x>0.5. It produces the pseudotetragonal and orthorhombic \\{1/4 1) / 4 0\\} phases formed by the (1/21/20) and \\{1/4 1) / 4 0\\} concentration waves. These phases form a family of [110] oxygen-atom chain structures, which are different from the [010] Cu(1)-O chain structures formed at x>0.5. These differences can be explained only if a significant change in oxygen-oxygen (O-O) potential near x~0.4 (where the superconductivity disappears) is assumed. The O-O interaction potential at x<0.4 was estimated and used to perform computer simulations of oxygen ordering kinetics at x=0.25.

  8. Stimulated Raman scattering spectroscopy and χ(3)-nonlinear lasing effects in single crystals of aragonite (orthorhombic CaCO3)

    NASA Astrophysics Data System (ADS)

    Kaminskii, A. A.; Rhee, H.; Lux, O.; Eichler, H. J.; Koltashev, V. V.; Kleinschrodt, R.; Bohatý, L.; Becker, P.

    2012-04-01

    The present work gives a brief review of the nonlinear χ(2)- and χ(3)-lasing properties of SRS-active natural crystals (minerals) known so far. This compilation complements new results of a detailed investigation of Raman induced χ(3)-effects in aragonite single crystals (orthorhombic CaCO3) under single- and dual-wavelength picosecond excitation in the UV, visible and near-IR spectral ranges. The studied effects at room and cryogenic temperatures comprise Stokes and anti-Stokes combs of almost two octaves bandwidth, THG, SFG, as well as cascaded and cross-cascaded χ(3) leftrightarrow χ(3) interactions. All recorded lasing χ(3)-components were identified and attributed to three observed SRS-promoting vibration modes ωSRS1 ≈ 1087 cm-1, ωSRS2 ≈ 152 cm-1, and ωSRS3 ≈ 205 cm-1 (at room temperature) of aragonite. Stimulated Raman scattering (SRS) investigations of minerals so far enrich the arsenal of SRS-active crystals, which can be applied to solve fundamental and applied tasks of modern laser physics and nonlinear optics.

  9. Mott Multiferroics and Ferroelectric Metals from Dynamical Mean-Field Theory combined with Density-Functional Theory

    NASA Astrophysics Data System (ADS)

    Capone, Massimo

    2015-03-01

    Multiferroic materials, in which ferroelectricity and long-range magnetic ordering coexist, are natural candidates for applications. In this perspective, the most promising compounds are those in which the two phenomena do not simply coexist, but they influence each other through a magnetoelectric coupling. We present different applications of Density Functional Theory combined with Dynamical Mean-Field Theory in which electron-electron correlation effects are crucial in the stabilization of multiferroic behavior and in the magnetoelectric coupling. Within this wide family we can distinguish different cases. In Sr0.5Ba0.5MnO3 the multiferroic behavior is associated with a Mott insulating state in which the Mn half-filled t2g orbitals are responsible of the magnetic properties and the value of the polarization is strongly affected by the magnetic state. LiOsO3 shares the same electronic configuration with half-filled Os t2g orbitals. Despite this configuration enhances the effect of electron-electron interactions, the material remains metallic and represents a peculiar ferroelectric metal. We propose however how to turn this non-magnetic polar metal into a multiferroic through the design of a superlattice, which increases the degree of correlation, leading to Mott localization of the Os orbitals. In completely different systems, such as organic crystals like (TMTTF)2-X, strong correlations can lead to multiferroicity in organic crystals such as (TMTTF)2-X, where charge ordering promotes a polarization which is favored by an antiferromagnetic ordering. We finally discuss how strong correlations can play a major role away from half-filling when the Hund's coupling is sizable in compounds with a nominal valence of, e.g., two electrons in the three t2g orbitals. Such ``Hund's metals'' are correlated despite being far from Mott localization. This physical regime can be a fertile ground to obtain other ferroelectric metals. This work is supported by ERC/FP7 through the

  10. Uniaxial strain-induced magnetic order transition from E-type to A-type in orthorhombic YMnO{sub 3} from first-principles

    SciTech Connect

    Lin, S. X.; Fang, X. G.; Zhang, A. H.; Lu, X. B.; Gao, J. W.; Gao, X. S.; Zeng, M.; Liu, J.-M.

    2014-10-28

    The spin ordering magnetic structures of orthorhombic YMnO{sub 3} subjected to uniaxial strain have been investigated using first-principles calculations based on density functional theory. On applying compressive uniaxial strain of −0.8% along the b orientation, the spin ordering magnetic structure is predicted to change from E-type to A-type antiferromagnetic orderings. The structure analysis also reveals that the uniaxial strain has a dramatic influence on the Mn-O bond lengths and Mn-O-Mn bond angles, allowing the gradual suppression of the alternation of the long and short Mn-O-Mn bonds in the ab plane. These changes present very interesting possibilities for engineering the spin ordering along with ferroelectric property in orthorhombic YMnO{sub 3}.

  11. Orthorhombic fault fracture patterns and non-plane strain in a synthetic transfer zone during rifting: Lennard shelf, Canning basin, Western Australia

    NASA Astrophysics Data System (ADS)

    Miller, John McL.; Nelson, E. P.; Hitzman, M.; Muccilli, P.; Hall, W. D. M.

    2007-06-01

    A complex series of faults occur within transfer zones normal to the WNW-trending rifted northern margin of the Canning basin (Western Australia). These zones controlled basinal fluid flow and the formation of some carbonate-hosted Mississippi Valley-type Zn-Pb deposits along the basin margin during Devonian to Carboniferous rifting. The study area has a regional fault geometry similar to a synthetic overlapping transfer zone. Surface and underground mapping in this transfer zone, combined with 3D modelling, indicate the faults and related extension fractures have an orthorhombic geometry. The orthorhombic fault-fracture mesh developed in response to three-dimensional non-plane strain in which the intermediate finite extension magnitude was non-zero. Pre-mineralisation marine calcite fill in the fault-fracture mesh indicates that it formed early in the deformation history. Later deformation that overprints the Zn-Pb mineralisation and fault-fracture mesh, was associated with a different maximum extension direction and this modified and reactivated the faults with both dip-slip and oblique-slip movement and tilting of earlier structures. The orthorhombic geometry is not observed at a regional scale (>10 × 10 km), indicating probable scale-dependant behaviour. This study indicates that this transfer zone developed either by (1) strain partitioning with synchronous strike-slip structures and adjacent zones of non-plane extension, or (2) by a component of non-plane extension sub-parallel to the basin margin followed by subsequent transtensional overprint of the system (preferred model). Synthetic overlapping transfer zones are inferred to be key regions where orthorhombic fault geometries may develop.

  12. Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

    NASA Astrophysics Data System (ADS)

    Abdel-Hafiez, M.; Pu, Y. J.; Brisbois, J.; Peng, R.; Feng, D. L.; Chareev, D. A.; Silhanek, A. V.; Krellner, C.; Vasiliev, A. N.; Chen, Xiao-Jia

    2016-06-01

    A comprehensive study of the doping dependence of the phase diagram of FeSe-based superconductors is still required due to the lack of a clean and systematic means of doping control. Here, we report on the magneto-optical imaging, thermodynamic and transport properties, as well as in situ angle-resolved photoemission spectroscopy (ARPES) studies of impurity scattering in stoichiometric FeSe single crystals. Co doping at the Fe site is found to decrease the superconducting transition temperature (Tc). The upper critical field and specific heat all indicate a possible multiband superconductivity with strong coupling in the Co-doped system. A remarkable feature in FeSe is that its temperature dependent resistivity exhibits a wide hump at high temperatures, a signature of a crossover from a semiconductinglike behavior to metallic behavior. A structural tetragonal-to-orthorhombic phase transition (Ts) (a consequence of the electronic nematicity) is suppressed by either physical or chemical pressures. Due to the reconstruction of the Fermi surface at Ts, specific heat anomalies at Ts present Δ Cp/Ts≈γn , being γn the Sommerfield coefficient at low temperature. This reflect an additional electronic instability in the FeSe1 -xSx system. ARPES data between 180 and 282 K indicates the existence of a chemical potential shift with increasing thermal excitations, resulting in a change of the Fermi-surface topology and exhibiting a semimetal behavior. We found that the temperature-induced Lifshitz transition is much higher than the temperature for the nematic order.

  13. Multiferroic nanomagnetic logic: Hybrid spintronics-straintronic paradigm for ultra-low energy computing

    NASA Astrophysics Data System (ADS)

    Salehi Fashami, Mohammad

    Excessive energy dissipation in CMOS devices during switching is the primary threat to continued downscaling of computing devices in accordance with Moore's law. In the quest for alternatives to traditional transistor based electronics, nanomagnet-based computing [1, 2] is emerging as an attractive alternative since: (i) nanomagnets are intrinsically more energy-efficient than transistors due to the correlated switching of spins [3], and (ii) unlike transistors, magnets have no leakage and hence have no standby power dissipation. However, large energy dissipation in the clocking circuit appears to be a barrier to the realization of ultra low power logic devices with such nanomagnets. To alleviate this issue, we propose the use of a hybrid spintronics-straintronics or straintronic nanomagnetic logic (SML) paradigm. This uses a piezoelectric layer elastically coupled to an elliptically shaped magnetostrictive nanomagnetic layer for both logic [4-6] and memory [7-8] and other information processing [9-10] applications that could potentially be 2-3 orders of magnitude more energy efficient than current CMOS based devices. This dissertation focuses on studying the feasibility, performance and reliability of such nanomagnetic logic circuits by simulating the nanoscale magnetization dynamics of dipole coupled nanomagnets clocked by stress. Specifically, the topics addressed are: 1. Theoretical study of multiferroic nanomagnetic arrays laid out in specific geometric patterns to implement a "logic wire" for unidirectional information propagation and a universal logic gate [4-6]. 2. Monte Carlo simulations of the magnetization trajectories in a simple system of dipole coupled nanomagnets and NAND gate described by the Landau-Lifshitz-Gilbert (LLG) equations simulated in the presence of random thermal noise to understand the dynamics switching error [11, 12] in such devices. 3. Arriving at a lower bound for energy dissipation as a function of switching error [13] for a

  14. Application of orthorhombic standardization in magnetic susceptibility studies of localized spin models with S=1, 3/2, 2, 5/2

    NASA Astrophysics Data System (ADS)

    Pełka, Robert; Rudowicz, Czesław

    2016-09-01

    The standardization idea is nowadays tacitly accepted in EMR area, however, its usefulness in magnetism studies has not been fully recognized as yet. This idea arises due to intrinsic features of orthorhombic Hamiltonians of any physical nature, including the crystal (ligand) field (CF/LF) Hamiltonians or the zero-field splitting (ZFS) ones. Standardization limits the ratio of the orthorhombic parameter to the axial one to a fixed range between 0 and a specific value that depends on the notation used. For the ZFS parameters expressed in the conventional spin Hamiltonian (SH) notation the ratio λ=E/D can always be limited to the range (0, ±1/3) by appropriate choice of coordinate system. Implications of standardization of orthorhombic spin Hamiltonians for interpretation of experimental magnetic susceptibility data are considered. Using a numerical example, we show the existence of alternative solutions for ZFS parameters potentially obtainable from fitting experimental magnetic data and discuss their importance. For the first time algebraic applications of the standardization to the expressions for magnetic susceptibility tensor derived earlier for localized spin models with S=1, 3/2, 2, 5/2 and with rhombic anisotropy are explored. The numerical and algebraic results allow us to formulate an 'invariance principle'. These considerations facilitate interpretation of experimental magnetic data and provide an additional check of correctness of analytical magnetic susceptibility expressions.

  15. Intrinsic Ferroelasticity and/or Multiferroicity in Two-Dimensional Phosphorene and Phosphorene Analogues.

    PubMed

    Wu, Menghao; Zeng, Xiao Cheng

    2016-05-11

    Phosphorene and phosphorene analogues such as SnS and SnSe monolayers are promising nanoelectronic materials with desired bandgap, high carrier mobility, and anisotropic structures. Here, we show first-principles calculation evidence that these monolayers are potentially the long-sought two-dimensional (2D) materials that can combine electronic transistor characteristic with nonvolatile memory readable/writeable capability at ambient condition. Specifically, phosphorene is predicted to be a 2D intrinsic ferroelastic material with ultrahigh reversible strain, whereas SnS, SnSe, GeS, and GeSe monolayers are multiferroic with coupled ferroelectricity and ferroelasticity. Moreover, their low-switching barriers render room-temperature nonvolatile memory accessible, and their notable structural anisotropy enables ferroelastic or ferroelectric switching readily readable via electrical, thermal, optical, mechanical, or even spintronic detection upon the swapping of the zigzag and armchair direction. In addition, it is predicted that the GeS and GeSe monolayers as well as bulk SnS and SnSe can maintain their ferroelasticity and ferroelectricity (anti-ferroelectricity) beyond the room temperature, suggesting high potential for practical device application. PMID:27096689

  16. Ultrafast near-infrared nonlinear absorption in a multiferroic single crystal of bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Matsubara, Eiichi; Mochizuki, Takeshi; Nagai, Masaya; Ito, Toshimitsu; Ashida, Masaaki

    2015-09-01

    We studied the ultrafast third-order optical nonlinearity in a single crystal of multiferroic bismuth ferrite (BiFeO3) in the near-infrared range of 0.5-1.0 eV, where the material is fundamentally transparent, at room temperature. With pump pulses at 1.55 eV, which is off-resonant to the strong inter-band charge transfer (CT) transition, we observed instantaneous transient absorption with a pencil-like temporal profile originating from the two-photon CT transition from the oxygen 2p to the iron 3d levels. In contrast, under pumping with 3.10 eV photons, the pencil-like absorption change was not observed but decay profiles showed longer time constants. Although the two-photon absorption coefficient estimated to be 1.5 cm/GW is 10 (100) times smaller than that of two (one)-dimensional cuprates, it is larger than those of common semiconductors such as ZnSe at the optical communication wavelength.

  17. Intrinsic Ferroelasticity and/or Multiferroicity in Two-Dimensional Phosphorene and Phosphorene Analogues.

    PubMed

    Wu, Menghao; Zeng, Xiao Cheng

    2016-05-11

    Phosphorene and phosphorene analogues such as SnS and SnSe monolayers are promising nanoelectronic materials with desired bandgap, high carrier mobility, and anisotropic structures. Here, we show first-principles calculation evidence that these monolayers are potentially the long-sought two-dimensional (2D) materials that can combine electronic transistor characteristic with nonvolatile memory readable/writeable capability at ambient condition. Specifically, phosphorene is predicted to be a 2D intrinsic ferroelastic material with ultrahigh reversible strain, whereas SnS, SnSe, GeS, and GeSe monolayers are multiferroic with coupled ferroelectricity and ferroelasticity. Moreover, their low-switching barriers render room-temperature nonvolatile memory accessible, and their notable structural anisotropy enables ferroelastic or ferroelectric switching readily readable via electrical, thermal, optical, mechanical, or even spintronic detection upon the swapping of the zigzag and armchair direction. In addition, it is predicted that the GeS and GeSe monolayers as well as bulk SnS and SnSe can maintain their ferroelasticity and ferroelectricity (anti-ferroelectricity) beyond the room temperature, suggesting high potential for practical device application.

  18. Fast 180° magnetization switching in a strain-mediated multiferroic heterostructure driven by a voltage.

    PubMed

    Peng, Ren-Ci; Hu, Jia-Mian; Momeni, Kasra; Wang, Jian-Jun; Chen, Long-Qing; Nan, Ce-Wen

    2016-01-01

    Voltage-driven 180° magnetization switching provides a low-power alternative to current-driven magnetization switching widely used in spintronic devices. Here we computationally demonstrate a promising route to achieve voltage-driven in-plane 180° magnetization switching in a strain-mediated multiferroic heterostructure (e.g., a heterostructure consisting of an amorphous, slightly elliptical Co40Fe40B20 nanomagnet on top of a Pb(Zr,Ti)O3 film as an example). This 180° switching follows a unique precessional path all in the film plane, and is enabled by manipulating magnetization dynamics with fast, local piezostrains (rise/release time <0.1 ns) on the Pb(Zr,Ti)O3 film surface. Our analyses predict ultralow area energy consumption per switching (~0.03 J/m(2)), approximately three orders of magnitude smaller than that dissipated by current-driven magnetization switching. A fast overall switching time of about 2.3 ns is also demonstrated. Further reduction of energy consumption and switching time can be achieved by optimizing the structure and material selection. The present design provides an additional viable route to realizing low-power and high-speed spintronics. PMID:27272678

  19. Fast 180° magnetization switching in a strain-mediated multiferroic heterostructure driven by a voltage

    NASA Astrophysics Data System (ADS)

    Peng, Ren-Ci; Hu, Jia-Mian; Momeni, Kasra; Wang, Jian-Jun; Chen, Long-Qing; Nan, Ce-Wen

    2016-06-01

    Voltage-driven 180° magnetization switching provides a low-power alternative to current-driven magnetization switching widely used in spintronic devices. Here we computationally demonstrate a promising route to achieve voltage-driven in-plane 180° magnetization switching in a strain-mediated multiferroic heterostructure (e.g., a heterostructure consisting of an amorphous, slightly elliptical Co40Fe40B20 nanomagnet on top of a Pb(Zr,Ti)O3 film as an example). This 180° switching follows a unique precessional path all in the film plane, and is enabled by manipulating magnetization dynamics with fast, local piezostrains (rise/release time <0.1 ns) on the Pb(Zr,Ti)O3 film surface. Our analyses predict ultralow area energy consumption per switching (~0.03 J/m2), approximately three orders of magnitude smaller than that dissipated by current-driven magnetization switching. A fast overall switching time of about 2.3 ns is also demonstrated. Further reduction of energy consumption and switching time can be achieved by optimizing the structure and material selection. The present design provides an additional viable route to realizing low-power and high-speed spintronics.

  20. Material Designs and Combinational Growth Techniques to Enable Novel Multiferroic Devices

    NASA Astrophysics Data System (ADS)

    Cole, Melanie; Ngo, Eric; Ivill, Mathew; Hirsch, S.; Hubbard, Cliff; Toonen, Ryan; Sarney, Wendy; Integrated Electromagnetic Materials Research Group Collaboration

    2013-03-01

    Voltage control of magnetism in magnetic/ferroelectric bilayers has been most recently demonstrated in ultrathin metallic magnetic films through an electric field induced spin polarized charge screening effect. Voltage-controlled magnetism in magnetic/ferroelectric multilayers would provide a unique opportunity for integrating voltage-tunable RF/microwave magnetic devices on integrated circuits. It has been theoretically predicted that the voltage-control of magnetism in ferromagnetic/ferroelectric heterostructures can be significantly enhanced by utilizing high-K dielectrics. The critical challenge is how to enhance the permittivity of the ferroelectric film while maintaining low loss and low leakage characteristics and accomplishing this in an affordable manner by employing industry standard processing methods and large area low cost substrates. In this work we demonstrate the achievement of high-k, low loss and low leakage BST films utilizing optimized sputtered SrTiO3 buffer layers combined with a MOSD grown Mg-doped Ba0.60Sr0.40TiO3 overgrowth film on affordable large area substrates. Results of this research serves to promote enhanced EM coupling to enable a new class of charge mediated integratable voltage control multiferroic devices exploiting the converse ME effect.

  1. Giant Controllable Magnetization Changes Induced by Structural Phase Transitions in a Metamagnetic Artificial Multiferroic

    DOE PAGES

    Bennett, S. P.; Wong, A. T.; Glavic, A.; Herklotz, A.; Urban, C.; Valmianski, I.; Biegalski, M. D.; Christen, H. M.; Ward, T. Z.; Lauter, V.

    2016-03-04

    We realize that a controllable metamagnetic transition from AFM to FM ordering would open the door to a plethora of new spintronics based devices that, rather than reorienting spins in a ferromagnet, harness direct control of a materials intrinsic magnetic ordering. In this study FeRh films with drastically reduced transition temperatures and a large magneto-thermal hysteresis were produced for magnetocaloric and spintronics applications. Remarkably, giant controllable magnetization changes (measured to be as high has ~25%) are realized and by manipulating the strain transfer from the external lattice when subjected to two structural phase transitions of BaTiO3 (001) single crystal substrate.more » These magnetization changes are the largest seen to date to be controllably induced in the FeRh system. Using polarized neutron reflectometry we reveal how just a slight in plane surface strain change at ~290C results in a massive magnetic transformation in the bottom half of the film clearly demonstrating a strong lattice-spin coupling in FeRh. By means of these substrate induced strain changes we show a way to reproducibly explore the effects of temperature and strain on the relative stabilities of the FM and AFM phases in multi-domain metamagnetic systems. In our study also demonstrates for the first time the depth dependent nature of a controllable magnetic order using strain in an artificial multiferroic heterostructure.« less

  2. Large elasto-optic effect and reversible electrochromism in multiferroic BiFeO3

    PubMed Central

    Sando, D.; Yang, Yurong; Bousquet, E.; Carrétéro, C.; Garcia, V.; Fusil, S.; Dolfi, D.; Barthélémy, A.; Ghosez, Ph.; Bellaiche, L.; Bibes, M.

    2016-01-01

    The control of optical fields is usually achieved through the electro-optic or acousto-optic effect in single-crystal ferroelectric or polar compounds such as LiNbO3 or quartz. In recent years, tremendous progress has been made in ferroelectric oxide thin film technology—a field which is now a strong driving force in areas such as electronics, spintronics and photovoltaics. Here, we apply epitaxial strain engineering to tune the optical response of BiFeO3 thin films, and find a very large variation of the optical index with strain, corresponding to an effective elasto-optic coefficient larger than that of quartz. We observe a concomitant strain-driven variation in light absorption—reminiscent of piezochromism—which we show can be manipulated by an electric field. This constitutes an electrochromic effect that is reversible, remanent and not driven by defects. These findings broaden the potential of multiferroics towards photonics and thin film acousto-optic devices, and suggest exciting device opportunities arising from the coupling of ferroic, piezoelectric and optical responses. PMID:26923332

  3. Calcination temperature influenced multiferroic properties of Ca-doped BiFeO{sub 3} nanoparticles

    SciTech Connect

    Dhir, Gitanjali Uniyal, Poonam; Verma, N. K.

    2015-06-24

    The influence of Ca-doping and particle size on structural, morphological and magnetic properties of BiFeO{sub 3} nanoparticles has been studied. A sol-gel method was employed for the synthesis of nanoparticles and their particle size was tailored by varying the calcination temperature. Structural analysis revealed a rhombohedral distortion induced by Ca-substitution. The broadening of diffraction peaks with decreasing calcination temperature was indicative of reduction in crystallite size. The morphological analysis revealed the formation of agglomerated nanoparticles having average particle size ranging from 10-15 and 50-55 nm for C4 and C6, respectively. The agglomeration is attributed to high surface energy of nanoparticles. Ferromagnetism has been displayed by all the synthesized nanoparticles. Enhancement of saturation magnetization with Ca-substitution is attributed to suppression of spin cycloid structure by the reduction in size, lattice distortion and creation of oxygen vacancies by the substitution of divalent ion at trivalent site. Further, this value increases as a function of decreasing particle size. Strong particle size effects on magnetic properties of the synthesized nanoparticles are owed to increasing surface to volume ratio. All these observations are indicative of strong dependence of multiferroism on particle size.

  4. Electric polarization observed in single crystals of multiferroic Lu2MnCoO6

    NASA Astrophysics Data System (ADS)

    Chikara, S.; Singleton, J.; Bowlan, J.; Yarotski, D. A.; Lee, N.; Choi, H. Y.; Choi, Y. J.; Zapf, V. S.

    2016-05-01

    We report electric polarization and magnetization measurements in single crystals of double perovskite Lu2Mn Co O6 using pulsed magnetic fields and optical second harmonic generation in dc magnetic fields. We observe well-resolved magnetic field-induced changes in the electric polarization in single crystals and thereby resolve the question about whether multiferroic behavior is intrinsic to these materials or is an extrinsic feature of polycrystals. We find electric polarization along the crystalline b axis, that is suppressed by applying a magnetic fields along the c axis, and advance a model for the origin of magnetoelectric coupling. We furthermore map the phase diagram using both capacitance and electric polarization to identify regions of ordering and regions of magnetoelectric hysteresis. This compound is a rare example of coupled hysteretic behavior in the magnetic and electric properties. The ferromagneticlike magnetic hysteresis loop that couples to hysteretic electric polarization can be attributed not to ordinary ferromagnetic domains, but to the rich physics of magnetic frustration of Ising-like spins in the axial next-nearest-neighbor interaction model.

  5. Understanding the multiferroicity in TmMn2O5 by a magnetically induced ferrielectric model

    PubMed Central

    Yang, L.; Li, X.; Liu, M. F.; Li, P. L.; Yan, Z. B.; Zeng, M.; Qin, M. H.; Gao, X. S.; Liu, J.-M.

    2016-01-01

    The magnetically induced electric polarization behaviors in multiferroic TmMn2O5 in response to varying temperature and magnetic field are carefully investigated by means of a series of characterizations including the high precision pyroelectric current technique. Here polycrystalline rather than single crystal samples are used for avoiding the strong electrically self-polarized effect in single crystals, and various parallel experiments on excluding the thermally excited current contributions are performed. The temperature-dependent electric polarization flop as a major character is identified for different measuring paths. The magneto-current measurements indicate that the electric polarization in the low temperature magnetic phase region has different origin from that in the high temperature magnetic phase. It is suggested that the electric polarization does have multiple components which align along different orientations, including the Mn3+-Mn4+-Mn3+ exchange striction induced polarization PMM, the Tm3+-Mn4+-Tm3+ exchange striction induced polarization PTM, and the low temperature polarization PLT probably associated with the Tm3+ commensurate phase. The observed electric polarization flop can be reasonably explained by the ferrielectric model proposed earlier for DyMn2O5, where PMM and PTM are the two antiparallel components both along the b-axis and PLT may align along the a-axis. Finally, several issues on the unusual temperature dependence of ferroelectric polarizations are discussed. PMID:27713482

  6. Inelastic Neutron Scattering on Multiferroics NdFe3(BO3)4

    NASA Astrophysics Data System (ADS)

    Hayashida, Shohei; Soda, Minoru; Itoh, Shinichi; Yokoo, Tetsuya; Ohgushi, Kenya; Kawana, Daichi; Masuda, Takatsugu

    Inelastic neutron scattering experiment is performed on single crystals of multiferroics NdFe3(11BO3)4 to explore the magnetic excitations. Fe-centered dispersive excitation with the band width of 5 meV is observed along the crystallographic c∗ direction and that of 3 meV is along the a∗ direction. The energy gap of 0.57 meV due to an axial-type anisotropy is ob- served at the AF zone center. The energy of Nd-centered flat excitation is 1 meV. Furthermore, anticrossing of the Fe- and Nd-centered excitations is observed, meaning the existence of the f -d coupling, i.e., the interaction between the Nd3+ and Fe3+ moments. Spin-wave analysis on the observed neutron spectrum revealed the underlying magnetic Hamiltonian in NdFe3(11BO3)4. Discussion on the axial-type anisotropy in the ab - plane based on the magnetic model leads to the conclusion that the anisotropy of the Nd3+ ion plays a main role in the determination of the structures of both magnetic moment and electric polarization in NdFe3(BO3)4.

  7. Microwave magnetoelectric effect via skyrmion resonance modes in a helimagnetic multiferroic.

    PubMed

    Okamura, Y; Kagawa, F; Mochizuki, M; Kubota, M; Seki, S; Ishiwata, S; Kawasaki, M; Onose, Y; Tokura, Y

    2013-01-01

    Magnetic skyrmion, a topologically stable spin-swirling object, can host emergent electromagnetism, as exemplified by the topological Hall effect and electric-current-driven skyrmion motion. To achieve efficient manipulation of nano-sized functional spin textures, it is imperative to exploit the resonant motion of skyrmions, analogously to the role of the ferromagnetic resonance in spintronics. The magnetic resonance of skyrmions has recently been detected with oscillating magnetic fields at 1-2 GHz, launching a search for new skyrmion functionality operating at microwave frequencies. Here we show a microwave magnetoelectric effect in resonant skyrmion dynamics. Through microwave transmittance spectroscopy on the skyrmion-hosting multiferroic crystal Cu₂OSeO₃ combined with theoretical simulations, we reveal nonreciprocal directional dichroism (NDD) at the resonant mode, that is, oppositely propagating microwaves exhibit different absorption. The microscopic mechanism of the present NDD is not associated with the conventional Faraday effect but with the skyrmion magnetoelectric resonance instead, suggesting a conceptually new microwave functionality.

  8. Calcination temperature influenced multiferroic properties of Ca-doped BiFeO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Dhir, Gitanjali; Uniyal, Poonam; Verma, N. K.

    2015-06-01

    The influence of Ca-doping and particle size on structural, morphological and magnetic properties of BiFeO3 nanoparticles has been studied. A sol-gel method was employed for the synthesis of nanoparticles and their particle size was tailored by varying the calcination temperature. Structural analysis revealed a rhombohedral distortion induced by Ca-substitution. The broadening of diffraction peaks with decreasing calcination temperature was indicative of reduction in crystallite size. The morphological analysis revealed the formation of agglomerated nanoparticles having average particle size ranging from 10-15 and 50-55 nm for C4 and C6, respectively. The agglomeration is attributed to high surface energy of nanoparticles. Ferromagnetism has been displayed by all the synthesized nanoparticles. Enhancement of saturation magnetization with Ca-substitution is attributed to suppression of spin cycloid structure by the reduction in size, lattice distortion and creation of oxygen vacancies by the substitution of divalent ion at trivalent site. Further, this value increases as a function of decreasing particle size. Strong particle size effects on magnetic properties of the synthesized nanoparticles are owed to increasing surface to volume ratio. All these observations are indicative of strong dependence of multiferroism on particle size.

  9. The structural and magnetic properties of Sr-doped multiferroic CaMn7O12

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Guang; Ma, Xiao-Chen; Xie, Liang

    2015-10-01

    The structural and magnetic properties of Sr-doped multiferroic CaMn7O12 were investigated by X-ray diffraction (XRD), Raman spectra, X-ray absorption spectroscopy and temperature dependence of magnetization. The XRD indicates that the samples are rhombohedral lattice (space group R3¯) with small additional phase Mn3O4. The refined lattice parameters of the main phase increases by the Sr doping. The Raman spectra demonstrate the phonon vibration direction is affected, which is probably due to the rotation of MnO6 octahedral. However, as the valence state of Sr and Ca is same at +2, the samples with doping show nonvariation of peak position at Mn 2p X-ray absorption spectra, indicating that the ratio of Mn3+ and Mn4+ ions is unchanged. And the magnetic transition temperature both at T1 = 90K and T2 = 42K is also not tunable because the amount of magnetic interaction between Mn3+ and Mn4+ is not influenced by doping Sr ion. Only the enhancement of the magnetization at low temperature is observed, which is the same as the effect caused by external magnetic fields. An unsaturated wasp-waist type hysteresis loop is observed, indicating the competition between ferromagnetic-like and antiferromagnetic order.

  10. Thermal, magnetic and electrical properties of Tb1-xDyxMnO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Pavan Kumar, N.; Jitender, Thakur; Laxmi, Vijaya; Venugopal Reddy, P.

    2016-03-01

    A series of multiferroic materials with the compositional formula, Tb1-xDyxMnO3 (where x=0, 0.1, 0.2, 0.3 and 0.4) were prepared by the sol gel method. After characterizing the samples structurally, a systematic investigation of specific heat, magnetization and dielectric properties over the temperature range, 4-300 K, was undertaken. Based on these studies, it was found that all the samples exhibit a transition at 40 K and the observed behavior may be attributed to the ordering of Mn3+ ions. Further, all the five samples are found to exhibit a ferroelectric transition in the temperature range 20-24 K. Finally, yet another transition was also exhibited by all the samples at temperatures below 10 K and is attributed to the antiferromagnetic (AF) ordering of rare-earth ionic moments. The magnetic entropy of all the samples was also computed with the help of their heat capacity data.

  11. Understanding the multiferroicity in TmMn2O5 by a magnetically induced ferrielectric model

    NASA Astrophysics Data System (ADS)

    Yang, L.; Li, X.; Liu, M. F.; Li, P. L.; Yan, Z. B.; Zeng, M.; Qin, M. H.; Gao, X. S.; Liu, J.-M.

    2016-10-01

    The magnetically induced electric polarization behaviors in multiferroic TmMn2O5 in response to varying temperature and magnetic field are carefully investigated by means of a series of characterizations including the high precision pyroelectric current technique. Here polycrystalline rather than single crystal samples are used for avoiding the strong electrically self-polarized effect in single crystals, and various parallel experiments on excluding the thermally excited current contributions are performed. The temperature-dependent electric polarization flop as a major character is identified for different measuring paths. The magneto-current measurements indicate that the electric polarization in the low temperature magnetic phase region has different origin from that in the high temperature magnetic phase. It is suggested that the electric polarization does have multiple components which align along different orientations, including the Mn3+-Mn4+-Mn3+ exchange striction induced polarization PMM, the Tm3+-Mn4+-Tm3+ exchange striction induced polarization PTM, and the low temperature polarization PLT probably associated with the Tm3+ commensurate phase. The observed electric polarization flop can be reasonably explained by the ferrielectric model proposed earlier for DyMn2O5, where PMM and PTM are the two antiparallel components both along the b-axis and PLT may align along the a-axis. Finally, several issues on the unusual temperature dependence of ferroelectric polarizations are discussed.

  12. High-field magneto-thermo-mechanical testing system for characterizing multiferroic bulk alloys.

    PubMed

    Bruno, Nickolaus M; Karaman, Ibrahim; Ross, Joseph H; Chumlyakov, Yuriy I

    2015-11-01

    Multiferroic meta-magnetic shape memory alloys are well known for exhibiting large magnetic field induced actuation strains, giant magnetocaloric effects, magneto-resistance, and structural and magnetic glassy behaviors. Thus, they are candidates for improving modern day sensing, actuation, magneto-resistance, and solid-state refrigeration processes. Until now, however, experimental apparatuses have typically been able to probe a limited ferroic parameter space in these materials, i.e., only concurrent thermal and mechanical responses, or magnetic and thermal responses. To overcome this barrier and better understand the coupling of multiple fields on materials behavior, a magneto-thermo-mechanical characterization device has been designed and implemented. This device is capable of compressing a specimen at load levels up to 5300 N collinearly with applied fields up to 9 T between temperatures of -100 °C and 120 °C. Uniaxial stress, strain, temperature, magnetic field, and the volumetric average magnetization have been simultaneously measured under mixed loading conditions on a NiCoMnIn meta-magnetic shape memory alloy and a few selected results are presented here. PMID:26628146

  13. Large elasto-optic effect and reversible electrochromism in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Sando, D.; Yang, Yurong; Bousquet, E.; Carrétéro, C.; Garcia, V.; Fusil, S.; Dolfi, D.; Barthélémy, A.; Ghosez, Ph.; Bellaiche, L.; Bibes, M.

    2016-02-01

    The control of optical fields is usually achieved through the electro-optic or acousto-optic effect in single-crystal ferroelectric or polar compounds such as LiNbO3 or quartz. In recent years, tremendous progress has been made in ferroelectric oxide thin film technology--a field which is now a strong driving force in areas such as electronics, spintronics and photovoltaics. Here, we apply epitaxial strain engineering to tune the optical response of BiFeO3 thin films, and find a very large variation of the optical index with strain, corresponding to an effective elasto-optic coefficient larger than that of quartz. We observe a concomitant strain-driven variation in light absorption--reminiscent of piezochromism--which we show can be manipulated by an electric field. This constitutes an electrochromic effect that is reversible, remanent and not driven by defects. These findings broaden the potential of multiferroics towards photonics and thin film acousto-optic devices, and suggest exciting device opportunities arising from the coupling of ferroic, piezoelectric and optical responses.

  14. Exploring Strain Induced Magnetization Effects in Metamagnetic Artificial Multiferroics using Polarized Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Bennett, Steven; Herklotz, Andreas; Wong, Anthony; Ward, Thomas; Lauter, Valeria

    There is currently a strong drive to realize a controllable magnetic ordering transition for use in next generation spintronic based memory and computation devices. One proposed method to gain such control is the use of a changing strain in a thin film metamagnetic artificial multiferroic system. While basic concepts using electric field actuated piezoelectric strain have been recently demonstrated1, there is very little understanding of the details of strains effect on such magnetic phase transitions. Using the depth sensitive method of polarized neutron reflectometry we have been able to probe the fine details of strains contribution to the metamagnetic transition in thin films of metamagnetic FeRh2. Here we explore the effects of changing lattice strain as a function of depth using both a barium titanate substrate's structural phase transitions3 and He ion implantation. These studies have discovered a remarkably large coupling between the systems strain state and the switching behavior across the magnetostructural metamagnetic transition. 1 Cherifi, R. O. et al. Nat. Mater. 31, 345-351 (2014), 2 Bennett, S. P. et al. Sci. Rep. 5, 9142 (2015), 3 Bennett, S. P. et al. submitted (2015)

  15. Strain mediated coupling in magnetron sputtered multiferroic PZT/Ni-Mn-In/Si thin film heterostructure

    SciTech Connect

    Singh, Kirandeep; Kaur, Davinder; Singh, Sushil Kumar

    2014-09-21

    The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of P{sub sat}~55 μC/cm² obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290 K (structural transition region of Ni-Mn-In) in these heterostructures. I-V measurements taken at different temperatures indicated that ohmic conduction was the main conduction mechanism over a large electric field range in these heterostructures. Magnetic measurement revealed that heterostructure was ferromagnetic at room temperature with a saturation magnetization of ~123 emu/cm³. Such multiferroic heterostructures exhibits promising applications in various microelectromechanical systems.

  16. Partial glass isosymmetry transition in multiferroic hexagonal ErMn O3

    NASA Astrophysics Data System (ADS)

    Barbour, A.; Alatas, A.; Liu, Y.; Zhu, C.; Leu, B. M.; Zhang, X.; Sandy, A.; Pierce, M. S.; Wang, X.; Cheong, S.-W.; You, H.

    2016-02-01

    Ferroelectric transitions of a hexagonal multiferroic, ErMn O3 , are studied by x-ray scattering techniques. An isosymmetry transition, similar to that previously observed for YMn O3 , approximately 300 K below the well-known ferroic transition temperature, is investigated. The partially glassy behavior of the isosymmetry transition is identified by the appearance of quasielastic scattering lines in high-energy-resolution scans. The glassy behavior is further supported by the increased interlayer decorrelation of (√{3 }×√{3 }) R 30∘ ordering below the isosymmetry transition. The transition behavior is considered for possible hidden sluggish modes and two-step phase transitions theoretically predicted for the stacked triangular antiferromagnets. The in-plane azimuthal (orientational) ordering behaviors were also compared to the theoretical predictions. Coherent x-ray speckle measurements show unambiguously that the domain sizes decrease anomalously near both the isosymmetry and ferroic transitions. However, domain boundary fluctuations increase monotonically with an Arrhenius form with an activation energy of 0.54(5) eV through both transitions.

  17. High-field magneto-thermo-mechanical testing system for characterizing multiferroic bulk alloys.

    PubMed

    Bruno, Nickolaus M; Karaman, Ibrahim; Ross, Joseph H; Chumlyakov, Yuriy I

    2015-11-01

    Multiferroic meta-magnetic shape memory alloys are well known for exhibiting large magnetic field induced actuation strains, giant magnetocaloric effects, magneto-resistance, and structural and magnetic glassy behaviors. Thus, they are candidates for improving modern day sensing, actuation, magneto-resistance, and solid-state refrigeration processes. Until now, however, experimental apparatuses have typically been able to probe a limited ferroic parameter space in these materials, i.e., only concurrent thermal and mechanical responses, or magnetic and thermal responses. To overcome this barrier and better understand the coupling of multiple fields on materials behavior, a magneto-thermo-mechanical characterization device has been designed and implemented. This device is capable of compressing a specimen at load levels up to 5300 N collinearly with applied fields up to 9 T between temperatures of -100 °C and 120 °C. Uniaxial stress, strain, temperature, magnetic field, and the volumetric average magnetization have been simultaneously measured under mixed loading conditions on a NiCoMnIn meta-magnetic shape memory alloy and a few selected results are presented here.

  18. High-field magneto-thermo-mechanical testing system for characterizing multiferroic bulk alloys

    NASA Astrophysics Data System (ADS)

    Bruno, Nickolaus M.; Karaman, Ibrahim; Ross, Joseph H.; Chumlyakov, Yuriy I.

    2015-11-01

    Multiferroic meta-magnetic shape memory alloys are well known for exhibiting large magnetic field induced actuation strains, giant magnetocaloric effects, magneto-resistance, and structural and magnetic glassy behaviors. Thus, they are candidates for improving modern day sensing, actuation, magneto-resistance, and solid-state refrigeration processes. Until now, however, experimental apparatuses have typically been able to probe a limited ferroic parameter space in these materials, i.e., only concurrent thermal and mechanical responses, or magnetic and thermal responses. To overcome this barrier and better understand the coupling of multiple fields on materials behavior, a magneto-thermo-mechanical characterization device has been designed and implemented. This device is capable of compressing a specimen at load levels up to 5300 N collinearly with applied fields up to 9 T between temperatures of -100 °C and 120 °C. Uniaxial stress, strain, temperature, magnetic field, and the volumetric average magnetization have been simultaneously measured under mixed loading conditions on a NiCoMnIn meta-magnetic shape memory alloy and a few selected results are presented here.

  19. The origin of photovoltaic responses in BiFeO3 multiferroic ceramics.

    PubMed

    Tu, C-S; Hung, C-M; Schmidt, V H; Chien, R R; Jiang, M-D; Anthoninappen, J

    2012-12-12

    Multiferroic BiFeO(3) (BFO) ceramics with electrodes of indium tin oxide (ITO) and Au thin films exhibit significant photovoltaic effects under near-ultraviolet illumination (λ = 405 nm) and show strong dependences on light wavelength, illumination intensity, and sample thickness. The correlation between photovoltaic responses and illumination intensity can be attributed to photo-excited and thermally generated charge carriers in the interface depletion region between BFO ceramic and ITO thin film. A theoretical model is developed to describe the open-circuit photovoltage and short-circuit photocurrent density as a function of illumination intensity. This model can be applied to the photovoltaic effects in p-n junction type BFO thin films and other systems. The BFO ceramic exhibits stronger photovoltaic responses than the ferroelectric Pb(1-x)La(x)(Zr(y)Ti(1-y))(1-x/4)O(3) (PLZT) ceramics under near-ultraviolet illumination. Comparisons are made with other systems and models for the photovoltaic effect.

  20. Nature of unusual spontaneous and field-induced phase transitions in multiferroics RMn 2O 5

    NASA Astrophysics Data System (ADS)

    Pyatakov, A. P.; Kadomtseva, A. M.; Vorob'ev, G. P.; Popov, Yu. F.; Krotov, S. S.; Zvezdin, A. K.; Lukina, M. M.

    2009-04-01

    Complex magnetic, magnetoelectric and magnetoelastic studies of spontaneous and field-induced phase transitions in TmMn 2O 5 were carried out. In the vicinity of spontaneous phase transition temperatures (35 and 25 K) the magnetoelectric and magnetoelastic dependences demonstrated the jumps of polarization and magnetostriction induced by the field ˜150 kOe. These anomalies can be attributed to the influence of magnetic field on the conditions of incommensurate-commensurate phase transition at 35 K and the reverse one at 25 K. In b-axis dependences the magnetic field-induced spin-reorientation phase transition was also observed below 20 K. Finally the magnetoelectric anomaly associated with metamagnetic transition is observed below the temperature of rare-earth subsystem ordering at relatively small critical fields of 5 kOe. This variety of spontaneous and induced phase transitions in RMn 2O 5 stems from the interplay of three magnetic subsystems: Mn 3+, Mn 4+, R 3+. The comparison with YMn 2O 5 highlights the role of rare earth in low-temperature region (metamagnetic and spin-reorientation phase transitions), while the phase transition at higher temperatures between incommensurate and commensurate phases should be ascribed to the different temperature dependences of Mn 3+ and Mn 4+ ions. The strong correlation of magnetoelastic and magnetoelectric properties observed in the whole class of RMn 2O 5 highlights their multiferroic nature.

  1. Spin-driven ferroelectricity in the multiferroic compounds of RMn2O5

    NASA Astrophysics Data System (ADS)

    Kimura, H.; Noda, Y.; Kohn, K.

    2009-04-01

    Neutron diffraction studies under magnetic field as well as under hydrostatic pressure for microscopic magnetism on multiferroic RMn2O5 ( R=rare-earth, Bi, and Y) are reviewed to discuss about the relevance between the magnetic property and dielectric property in detail. Without any external fields, a series of RMn2O5 shows successive magnetic phase transitions of incommensurate-commensurate-incommensurate as temperature decreases, in which the dielectric phase transitions concomitantly occur. At the lowest temperature phase of HoMn2O5, the magnetic transition from the incommensurate phase to the commensurate one is induced by applying both magnetic field and hydrostatic pressure. At this field-induced magnetic transition, a spontaneous electric polarization simultaneously induced, indicating that the ferroelectricity in this material is magnetically controlled. Competition of multiple magnetic ground states due to intensional magnetic frustration in this system can be easily tuned by applying external fields, which give rise to the rich variety of spin-driven dielectric transitions.

  2. Magnetic structure and physical properties of the multiferroic compound PrMn2O5

    NASA Astrophysics Data System (ADS)

    Doubrovsky, C.; André, G.; Bouquet, F.; Elkaim, E.; Li, M.; Greenblatt, M.; Foury-Leylekian, P.

    2012-06-01

    RMn2O5 (R=lanthanide, Bi, Y) multiferroic compounds are intensively studied for their potential application in the spintronic field. In these systems, the key issue is to understand the origin of the strong coupling between the ferroelectric and magnetic orders and to investigate the influence of the nature of the R ions in this coupling. While the phase diagram of RMn2O5 compounds with small R size is well established, this of large R size compounds is missing due to the lack of samples originating with difficulties of synthesis. We present in this paper the first investigation of the thermodynamic, structural and magnetic properties of high quality polycrystalline PrMn2O5 samples. Our work shows that PrMn2O5 presents two magnetic transitions corresponding to commensurate magnetic orderings. We also evidence a weak lattice effect coupled to the magnetic order. Our results point out that the physical properties of PrMn2O5 differ from those of the parent compounds with magnetic R ions.

  3. Magnetic structure and electric field effects in multiferroic YMn2O5

    NASA Astrophysics Data System (ADS)

    de Souza, R. A.; Staub, U.; Scagnoli, V.; Garganourakis, M.; Bodenthin, Y.; Huang, S.-W.; García-Fernández, M.; Ji, S.; Lee, S.-H.; Park, S.; Cheong, S.-W.

    2011-09-01

    The magnetic structure of multiferroic RMn2O5 (R = Y, Er) has been investigated by means of resonant soft x-ray diffraction. Energy, temperature, and azimuthal angle scans were performed in addition to reciprocal space maps on the magnetic reflection in the different magnetic phases of YMn2O5. We also investigated the orbital magnetic moment at the oxygen K-edge for RMn2O5 with both, R = Y and R = Er compositions. These moments reflect the strong hybridization between Mn 3d and oxygen 2p states. Experiments with applied electric fields are additionally presented, showing that the helical component of the magnetic structure in the CM phase of YMn2O5 can be reversed by the application of an electric field. However, the incommensurate magnetic reflection in the high-temperature phase is unaffected. Interestingly, this is observed only in the presence of a small electrical current, indicative of a current-induced/-enhanced switching of magnetic domains.

  4. Thermodynamic and neutron diffraction studies on multiferroic NdMn2O5

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Balédent, V.; Auban-Senzier, P.; Pasquier, C.; Doubrovsky, C.; Greenblatt, M.; Foury-Leylekian, P.

    2015-03-01

    Magnetically frustrated RMn2O5 oxides have attracted considerable attention in recent years, because most of the members of this family show spin ordering induced dielectric polarization along with strong magneto-electric coupling. Although the true origin of the ferroelectricity is still a matter of debate, it has been observed that the magneto-electric phase diagram can be substantially tuned with the variation of rare earth elements. In this work, we have chosen NdMn2O5 as the compound of our interest since it lies exactly in between the ferroelectric and non-ferroelectric members of this family and also, because there are few investigations performed on RMn2O5 systems with large rare earth atoms . With the combination of heat capacity, magnetic susceptibility, dielectric permittivity, powder X-ray diffraction, and powder neutron diffraction measurements, it has been found that NdMn2O5 undergoes an incommensurate magnetic ordering around 30 K followed by a possible ferroelectric-like transition at ∼26 K. Another lock-in kind of magnetic transition appears when the temperature is decreased to ∼15 K. With further lowering of temperature, an antiferromagnetic ordering, which is presumably associated with the Nd3+, is achieved near 4 K. This study thus sheds light on a new compound of the RMn2O5 series presenting different multiferroic properties.

  5. Classification and Interpretation of the Polarization of Multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Fukunaga, Mamoru; Noda, Yukio

    2010-05-01

    We have collected and compared temperature-dependent polarization data of multiferroic RMn2O5 for 11 kinds of rare earths (R) from the literature and our own measurements. Although the reported data are inconsistent, it was found that the maximum polarization values for R=Y, Dy, Ho, Er, and Tm are almost equal above 30 K except for the phase transition temperature where the polarization disappears. The findings suggest a standard polarization value for RMn2O5 of 100-120 nC/cm2 at 30 K in a commensurate magnetic (CM) phase. We discuss the nature and issues of the measured polarization of RMn2O5 from the data and our detailed measurement results for YMn2O5. Temperature-dependent ferroelectric hysteresis loops of YMn2O5 by the double-wave method reveal that an antiferroelectric-like high-temperature incommensurate magnetic (ICM) phase and a ferroelectric low-temperature ICM phase, while the intermediate CM phase is ferrielectric.

  6. Local structure studies of multiferroic RMn2O5 (R=Bi, Pr, Gd)

    NASA Astrophysics Data System (ADS)

    Fabbris, G.; Massa, N. E.; Granado, E.; Maciel, G. A.; Souza, J. A.; Alonso, J. A.; Martinez, M. J.; Azevedo, G. M.

    2009-03-01

    EXAFS measurements from 20 K to 300K were used to investigate the local structure of multiferroic RMn2O5 (R = Bi, Pr, Gd, TM TC 40K) in transmission mode at the Mn K- and R L3- edges in the XAFS2-LNLS beamline and analyzed using the IFEFFIT and FEFF codes. For BiMn2O5, Mn K-edge reveals very small temperature dependence of the Debye-Waller factor (DWF) and an Einstein temperature (ET) from Mn-O bonds of 675±22 K, suggesting that MnO polyhedra are rigid. We find structural distortions in the first coordination shell at the Bi L3-edge associated to vibrational anomalies in the Bi-O bonds. The quantitative analysis relates the origin of such distortions to two very distinct values of DWT and ET (294±7K and 462±28K) for these bonds on first shell. Similar behavior is observed for PrMn2O5, and GdMn2O5.

  7. Pressure effect on ferroelectric properties of multiferroics RMn2O5, (R = Gd, Tm)

    NASA Astrophysics Data System (ADS)

    Poudel, Narayan; Gooch, Melissa; Lorenz, Bernd; Chu, Ching-Wu; Kim, Jaewook; Cheong, Sang-Wook

    The pressure effect on the ferroelectric properties of the multiferroics GdMn2O5 and TmMn2O5 is studied up to 18.2 kbar. Unlike in RMn2O5 (R= Tb, Ho, Y), no significant change in polarization is observed in TmMn2O5 up to 16.6 kbar . However, a new ferroelectric phase is observed in GdMn2O5 above a critical pressure, Pc = 10 kbar at higher temperature. Our result indicates that pressure decouples the Gd moment from the Mn spin system and splits the ferroelectric phase. Thermal expansion data shows a large increase of the c axis at the ambient-pressure ferroelectric transition. The pressure-induced contraction of the c lattice parameter is found to be the cause for splitting of ferroelectric phase by decoupling of two spin systems above Pc. The pressure-temperature phase diagram is derived based on dielectric and ferroelectric properties.

  8. Modified Heisenberg model for the zig-zag structure in multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    The class of RMn2O5 (R = Ho, Tb, Y, Eu) compounds offers multiferroic properties where the refined magnetic zig-zag order breaks the inversion symmetry. Varying the temperature, the system undergoes a magnetic and a subsequent ferroelectric phase transition where the ferroelectricity is magnetically induced. We propose a modified anisotropic Heisenberg model that can be used as a tractable analytical model studying the properties of those antiferromagnetic zig-zag spin chains. Based on a finite temperature Green's function method, it is shown that the polarization is induced solely by different exchange couplings of the two different Mn4+ and Mn3+ magnetic ions. We calculate the excitation energy of the spin system for finite temperatures, which for its part determines the temperature dependent magnetization and polarization. The ferroelectric phase transition is manifested as a kink in the excitation energy. The variation of the polarization by an external magnetic field depends strongly on the direction of that field. Whereas, the polarization in b-direction increases with an external magnetic field as well in b-direction it can be switched for strong fields in a-direction. The results based on that modified Heisenberg model are in qualitative agreement with experimental data.

  9. Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic

    NASA Astrophysics Data System (ADS)

    Kim, Jae Wook; Khim, Seunghyun; Chun, Sae Hwan; Jo, Y.; Balicas, L.; Yi, H. T.; Cheong, S.-W.; Harrison, N.; Batista, C. D.; Hoon Han, Jung; Hoon Kim, Kee

    2014-07-01

    Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba2CoGe2O7, where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field (H), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field Hc=37.1 T due to enhanced AF quantum fluctuations. When H>Hc, the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter.

  10. Pulse and quench induced dynamical phase transition in a chiral multiferroic spin chain

    NASA Astrophysics Data System (ADS)

    Azimi, M.; Sekania, M.; Mishra, S. K.; Chotorlishvili, L.; Toklikishvili, Z.; Berakdar, J.

    2016-08-01

    Quantum dynamics of magnetic order in a chiral multiferroic chain is studied. We consider two different scenarios: ultrashort terahertz excitations or a sudden electric field quench. Performing analytical and numerical exact diagonalization calculations, we trace the pulse induced spin dynamics and extract quantities that are relevant to quantum information processing. In particular, we analyze the dynamics of the system chirality, the von Neumann entropy, and the pairwise and many-body entanglement. If the characteristic frequencies of the generated states are noncommensurate, then a partial loss of pair concurrence occurs. Increasing the system size, this effect becomes even more pronounced. Many-particle entanglement and chirality are robust and persist in the incommensurate phase. To analyze the dynamical quantum transitions for the quenched and pulsed dynamics we combined the Weierstrass factorization technique for entire functions and the Lanczos exact diagonalization method. For a small system we obtained analytical results including the rate function of the Loschmidt echo. Exact numerical calculations for a system up to 40 spins confirm phase transition. Quench-induced dynamical transitions have been extensively studied recently. Here we show that related dynamical transitions can be achieved and controlled by appropriate electric field pulses.

  11. Large elasto-optic effect and reversible electrochromism in multiferroic BiFeO3.

    PubMed

    Sando, D; Yang, Yurong; Bousquet, E; Carrétéro, C; Garcia, V; Fusil, S; Dolfi, D; Barthélémy, A; Ghosez, Ph; Bellaiche, L; Bibes, M

    2016-01-01

    The control of optical fields is usually achieved through the electro-optic or acousto-optic effect in single-crystal ferroelectric or polar compounds such as LiNbO3 or quartz. In recent years, tremendous progress has been made in ferroelectric oxide thin film technology-a field which is now a strong driving force in areas such as electronics, spintronics and photovoltaics. Here, we apply epitaxial strain engineering to tune the optical response of BiFeO3 thin films, and find a very large variation of the optical index with strain, corresponding to an effective elasto-optic coefficient larger than that of quartz. We observe a concomitant strain-driven variation in light absorption--reminiscent of piezochromism--which we show can be manipulated by an electric field. This constitutes an electrochromic effect that is reversible, remanent and not driven by defects. These findings broaden the potential of multiferroics towards photonics and thin film acousto-optic devices, and suggest exciting device opportunities arising from the coupling of ferroic, piezoelectric and optical responses. PMID:26923332

  12. Giant Controllable Magnetization Changes Induced by Structural Phase Transitions in a Metamagnetic Artificial Multiferroic.

    PubMed

    Bennett, S P; Wong, A T; Glavic, A; Herklotz, A; Urban, C; Valmianski, I; Biegalski, M D; Christen, H M; Ward, T Z; Lauter, V

    2016-01-01

    The realization of a controllable metamagnetic transition from AFM to FM ordering would open the door to a plethora of new spintronics based devices that, rather than reorienting spins in a ferromagnet, harness direct control of a materials intrinsic magnetic ordering. In this study FeRh films with drastically reduced transition temperatures and a large magneto-thermal hysteresis were produced for magnetocaloric and spintronics applications. Remarkably, giant controllable magnetization changes (measured to be as high has ~25%) are realized by manipulating the strain transfer from the external lattice when subjected to two structural phase transitions of BaTiO3 (001) single crystal substrate. These magnetization changes are the largest seen to date to be controllably induced in the FeRh system. Using polarized neutron reflectometry we reveal how just a slight in plane surface strain change at ~290C results in a massive magnetic transformation in the bottom half of the film clearly demonstrating a strong lattice-spin coupling in FeRh. By means of these substrate induced strain changes we show a way to reproducibly explore the effects of temperature and strain on the relative stabilities of the FM and AFM phases in multi-domain metamagnetic systems. This study also demonstrates for the first time the depth dependent nature of a controllable magnetic order using strain in an artificial multiferroic heterostructure. PMID:26940159

  13. Multiferroicity and spiral magnetism in FeVO{sub 4} with quenched Fe orbital moments

    SciTech Connect

    Daoud-Aladine, A.; Chapon, L. C.; Kundys, B.; Martin, C.; Simon, C.; Radaelli, P. G.; Brown, P. J.

    2009-12-01

    FeVO{sub 4} has been studied by heat capacity, magnetic susceptibility, electric polarization and single-crystal neutron-diffraction experiments. The triclinic crystal structure is made of S-shaped clusters of six Fe{sup 3+} ions, linked by VO{sub 4}{sup 3-} groups. Two long-range magnetic ordering transitions occur at T{sub N1}=22 K and T{sub N2}=15 K. Both magnetic structures are incommensurate and below T{sub N2}, FeVO{sub 4} becomes weakly ferroelectric coincidentally with the loss of the collinearity of the magnetic structure in a very similar fashion than in the classical TbMnO{sub 3} multiferroic material. However we argue that the symmetry considerations and the mechanisms invoked to explain these properties in TbMnO{sub 3} do not straightforwardly apply to FeVO{sub 4}. First, the magnetic structures, even the collinear structure, are all acentric so that ferroelectricity in FeVO{sub 4} is not correlated with the fact magnetic ordering is breaking inversion symmetry. Regarding the mechanism, FeVO{sub 4} has quenched orbital moments that questions the exact role of the spin-orbit interactions.

  14. Frustration and multiferroic behavior in Ca3CoMnO6

    SciTech Connect

    Zapf, Vivien

    2012-06-01

    Lu{sub 2}MnCoO{sub 6} and Ca{sub 3}MnCoO{sub 6} satisfy one of the primary goals of multiferroics research, namely ferromagnetic-like magnetization coupled to ferroelectric-like polarization. Thus the mechanism for magnetoelectric coupling in these materials deserves careful study. New data shows that the physics of these compound may be related to the classic 'ANNNI' model. Frustration between ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions between Ising spins creates an 'up up down down' magnetic structure in zero magnetic field, along c-axis chains that consist of alternating Co and Mn ions. In applied magnetic fields 'up up down,' 'up up up down' and other metastable variations can evolve, yielding hysteretic ferromagnetic-like magnetization. The key is that the phase slips between regions of 'up' and 'down' carries an electric polarization due to broken spatial inversion symmetry. Thus these phase slips can be manipulated with both electric and magnetic fields. The result is a profusion of magnetic and electric states that are closely-spaced in temperature, electric, and magnetic field. We present experimental studies of the magnetic, electric, and structural properties of these two compounds. We include very new data up to 100 Ton Ca{sub 3}CoMnO{sub 6} that resolves a key controversy of over the magnetic structure and the size of the moments.

  15. Unusual Mott transition in multiferroic PbCrO 3

    SciTech Connect

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-11-24

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. When turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. We report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of similar to 3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at similar to 300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. Moreover, the anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking.

  16. Fast 180° magnetization switching in a strain-mediated multiferroic heterostructure driven by a voltage

    PubMed Central

    Peng, Ren-Ci; Hu, Jia-Mian; Momeni, Kasra; Wang, Jian-Jun; Chen, Long-Qing; Nan, Ce-Wen

    2016-01-01

    Voltage-driven 180° magnetization switching provides a low-power alternative to current-driven magnetization switching widely used in spintronic devices. Here we computationally demonstrate a promising route to achieve voltage-driven in-plane 180° magnetization switching in a strain-mediated multiferroic heterostructure (e.g., a heterostructure consisting of an amorphous, slightly elliptical Co40Fe40B20 nanomagnet on top of a Pb(Zr,Ti)O3 film as an example). This 180° switching follows a unique precessional path all in the film plane, and is enabled by manipulating magnetization dynamics with fast, local piezostrains (rise/release time <0.1 ns) on the Pb(Zr,Ti)O3 film surface. Our analyses predict ultralow area energy consumption per switching (~0.03 J/m2), approximately three orders of magnitude smaller than that dissipated by current-driven magnetization switching. A fast overall switching time of about 2.3 ns is also demonstrated. Further reduction of energy consumption and switching time can be achieved by optimizing the structure and material selection. The present design provides an additional viable route to realizing low-power and high-speed spintronics. PMID:27272678

  17. Giant Controllable Magnetization Changes Induced by Structural Phase Transitions in a Metamagnetic Artificial Multiferroic

    PubMed Central

    Bennett, S. P.; Wong, A. T.; Glavic, A.; Herklotz, A.; Urban, C.; Valmianski, I.; Biegalski, M. D.; Christen, H. M.; Ward, T. Z.; Lauter, V.

    2016-01-01

    The realization of a controllable metamagnetic transition from AFM to FM ordering would open the door to a plethora of new spintronics based devices that, rather than reorienting spins in a ferromagnet, harness direct control of a materials intrinsic magnetic ordering. In this study FeRh films with drastically reduced transition temperatures and a large magneto-thermal hysteresis were produced for magnetocaloric and spintronics applications. Remarkably, giant controllable magnetization changes (measured to be as high has ~25%) are realized by manipulating the strain transfer from the external lattice when subjected to two structural phase transitions of BaTiO3 (001) single crystal substrate. These magnetization changes are the largest seen to date to be controllably induced in the FeRh system. Using polarized neutron reflectometry we reveal how just a slight in plane surface strain change at ~290C results in a massive magnetic transformation in the bottom half of the film clearly demonstrating a strong lattice-spin coupling in FeRh. By means of these substrate induced strain changes we show a way to reproducibly explore the effects of temperature and strain on the relative stabilities of the FM and AFM phases in multi-domain metamagnetic systems. This study also demonstrates for the first time the depth dependent nature of a controllable magnetic order using strain in an artificial multiferroic heterostructure. PMID:26940159

  18. 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.

  19. Effect of Pr- and Nd- doping on structural, dielectric, and magnetic properties of multiferroic Bi{sub 0.8}La{sub 0.2}Fe{sub 0.9}Mn{sub 0.1}O{sub 3}

    SciTech Connect

    Singh, Rahul; Shahi, P.; Chatterjee, Sandip; Dwivedi, G. D.; Ghosh, A. K.; Kumar, D.; Prakash, Om

    2014-04-07

    Bi{sub 0.8}La{sub 0.15}RE{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3} (where RE = Pr and Nd) have been prepared via conventional solid state route. The Rietveld refinement of X-ray diffraction patterns shows that both systems crystallize in orthorhombic Pnma space group. Raman modes observed for these two systems indicate that both systems are very close to orthorhombic Pnma structure. Appearance of prominent A{sub 1}-3 and weak E-2 modes in Bi{sub 0.8}La{sub 0.15}Nd{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3} indicate the presence of chemically more active Bi-O covalent bonds (which favors stereochemical activity of Bi lone pair electrons) in comparison to Bi{sub 0.8}La{sub 0.15}Pr{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3}. Moreover, Bi{sub 0.8}La{sub 0.15}Nd{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3} system shows higher dielectric constant, low dielectric loss, and higher magnetization value in comparison to Bi{sub 0.8}La{sub 0.15}Pr{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3} system. Ferroelectric transition temperature decreases to 460 °C for both systems in comparison to 710 °C of Bi{sub 0.8}La{sub 0.2}Fe{sub 0.9}Mn{sub 0.1}O{sub 3}. The improved dielectric and magnetic response suggests Bi{sub 0.8}La{sub 0.15}Nd{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3} a better multiferroic system than Bi{sub 0.8}La{sub 0.15}Pr{sub 0.05}Fe{sub 0.9}Mn{sub 0.1}O{sub 3}.

  20. Multiferroicity in Mn-deficient Ca3CoMnO6: The consequence of Fe substitution

    NASA Astrophysics Data System (ADS)

    Lin, L.; Xie, Y. L.; Liu, M. F.; Guo, Y. J.; Yan, Z. B.; Liu, J.-M.

    2013-07-01

    We present careful experiments on the multiferroicity in Ca3CoMn0.92O6 by Fe substitution of Mn. It is revealed that a proper Fe substitution modulates the Co/Mn spin order, favoring the ferroelectricity. The multifold interactions between the intra-chain spins and inter-chain spins are analyzed. It is suggested that the Mn deficiency and Fe substitution can break the inter-chain interactions to some extent, resulting in the delicate competition between these mutual interactions. The modulation of the ionic (charge) disorder and spin frustration order is the core physics for improving the ferroelectric performance.

  1. Nanostructured multiferroic PbFe0.5Nb0.5O3 and its physical properties

    NASA Astrophysics Data System (ADS)

    Ubushaeva, E. N.; Abdulvakhidov, K. G.; Mardasova, I. V.; Abdulvakhidov, B. K.; Vitchenko, M. A.; Amirov, A. A.; Batdalov, A. B.; Gamzatov, A. G.

    2010-11-01

    Polycrystalline multiferroic PbFe0.5Nb0.5O3 (PFN) fabricated by a solid-phase method is studied. Before sintering, a synthesized PFN powder is processed in Bridgman anvils via a force action in combination with shear deformation (FASD) at room temperature. The electrophysical properties and structural parameters of processed samples and a reference sample are compared. Point defects are shown to play a key role in the formation of the physical properties beginning from an FASD of 200 MPa.

  2. Dielectric and phonon properties of the multiferroic ferrimagnet Cu{sub 2}OSeO{sub 3}

    SciTech Connect

    Apostolova, I. N.

    2014-02-14

    We propose a microscopic model in order to study the multiferroic properties of Cu{sub 2}OSeO{sub 3} taking into account the ferrimagnetic interaction, frustration, linear magnetoelectric (ME) coupling, and anharmonic spin-phonon interaction. We have shown that the dielectric constant and the phonon energy and damping have a kink near the magnetic phase transition T{sub C} = 58 K which disappears with increasing of an external magnetic field. This behavior is an evidence for a strong ME coupling and in qualitative agreement with the experimental data.

  3. Two orthorhombic crystal structures of a galactose-specific lectin from Artocarpus hirsuta in complex with methyl-alpha-D-galactose.

    PubMed

    Rao, K N; Suresh, C G; Katre, U V; Gaikwad, S M; Khan, M I

    2004-08-01

    Based on their carbohydrate specificity, the jacalin family of lectins can be divided into two groups: galactose-specific and mannose-specific. The former are cytoplasmic proteins, whereas the latter are localized in the storage vacuoles of cells. It has been proposed that the post-translational modification in some of the lectins that splits their polypeptide chains into two may be crucial for galactose specificity. The mannose-specific members of the family are single-chain proteins that lack the above modification. Although the galactose-specific and the mannose-specific jacalin-type lectins differ in their sequences, they share a common fold: the beta-prism I fold, which is characteristic of Moraceae plant lectins. Here, two crystal structures of a jacalin-related lectin from Artocarpus hirsuta, which is specific for galactose, in complex with methyl-alpha-D-galactose are reported. The lectin crystallized in two orthorhombic forms and one hexagonal form under similar conditions. The crystals had an unusually high solvent content. The structure was solved using the molecular-replacement method using the jacalin structure as a search model. The two orthorhombic forms were refined using data to 2.5 and 3.0 A resolution, respectively. The structures of the A. hirsuta lectin and jacalin are identical. In orthorhombic form I the crystal packing provides three different micro-environments for sugar binding in the same crystal. The observed difference in the specificity for oligosaccharides between the A. hirsuta lectin and jacalin could only be explained based on differences in the molecular associations in the packing and variation of the C-terminal length of the beta-chain. The observed insecticidal activity of A. hirsuta lectin may arise from its similar fold to domain II of the unrelated delta-endotoxin from Bacillus thuringiensis.

  4. 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.

  5. Multiferroic tunnel junctions and ferroelectric control of magnetic state at interface (invited)

    SciTech Connect

    Yin, Y. W.; Raju, M.; Li, Qi; Hu, W. J.; Burton, J. D.; Gruverman, A.; Tsymbal, E. Y.; Kim, Y.-M.; Borisevich, A. Y.; Pennycook, S. J.; Yang, S. M.; Noh, T. W.; Li, X. G.; Zhang, Z. D.

    2015-05-07

    As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed in manganite/(Ba, Sr)TiO{sub 3}/manganite MFTJs at low temperatures and room temperature four-resistance state devices were also obtained. To enhance the TER for potential logic operation with a magnetic memory, La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/BaTiO{sub 3}/La{sub 0.5}Ca{sub 0.5}MnO{sub 3} /La{sub 0.7}Sr{sub 0.3}MnO{sub 3} MFTJs were designed by utilizing a bilayer tunneling barrier in which BaTiO{sub 3} is ferroelectric and La{sub 0.5}Ca{sub 0.5}MnO{sub 3} is close to ferromagnetic metal to antiferromagnetic insulator phase transition. The phase transition occurs when the ferroelectric polarization is reversed, resulting in an increase of TER by two orders of magnitude. Tunneling magnetoresistance can also be controlled by the ferroelectric polarization reversal, indicating strong magnetoelectric coupling at the interface.

  6. Reducing error rates in straintronic multiferroic nanomagnetic logic by pulse shaping

    NASA Astrophysics Data System (ADS)

    Munira, Kamaram; Xie, Yunkun; Nadri, Souheil; Forgues, Mark B.; Salehi Fashami, Mohammad; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo; Ghosh, Avik W.

    2015-06-01

    Dipole-coupled nanomagnetic logic (NML), where nanomagnets (NMs) with bistable magnetization states act as binary switches and information is transferred between them via dipole-coupling and Bennett clocking, is a potential replacement for conventional transistor logic since magnets dissipate less energy than transistors when they switch in a logic circuit. Magnets are also ‘non-volatile’ and hence can store the results of a computation after the computation is over, thereby doubling as both logic and memory—a feat that transistors cannot achieve. However, dipole-coupled NML is much more error-prone than transistor logic at room temperature (\\gt 1%) because thermal noise can easily disrupt magnetization dynamics. Here, we study a particularly energy-efficient version of dipole-coupled NML known as straintronic multiferroic logic (SML) where magnets are clocked/switched with electrically generated mechanical strain. By appropriately ‘shaping’ the voltage pulse that generates strain, we show that the error rate in SML can be reduced to tolerable limits. We describe the error probabilities associated with various stress pulse shapes and discuss the trade-off between error rate and switching speed in SML.The lowest error probability is obtained when a ‘shaped’ high voltage pulse is applied to strain the output NM followed by a low voltage pulse. The high voltage pulse quickly rotates the output magnet’s magnetization by 90° and aligns it roughly along the minor (or hard) axis of the NM. Next, the low voltage pulse produces the critical strain to overcome the shape anisotropy energy barrier in the NM and produce a monostable potential energy profile in the presence of dipole coupling from the neighboring NM. The magnetization of the output NM then migrates to the global energy minimum in this monostable profile and completes a 180° rotation (magnetization flip) with high likelihood.

  7. Electrochemical supercapacitor based on multiferroic BiMn2O5

    NASA Astrophysics Data System (ADS)

    Liu, Yangshuai; Zhitomirsky, Igor

    2015-06-01

    Submicrometre particles of multiferroic BiMn2O5 are prepared by a hydrothermal method. We demonstrate for the first time that BiMn2O5-multiwalled carbon nanotube (MWCNT) composite can be used as a new active material for positive electrodes of electrochemical supercapacitors (ES). The possibility of fabrication of BiMn2O5-MWCNT composites from colloidal suspensions using Celestine blue dye as a co-dispersant for BiMn2O5 and MWCNT is demonstrated. The composite BiMn2O5-MWCNT electrodes with high mass loading and high active material to current collector mass ratio show a capacitance of 6.0 F cm-2 (540 F cm-3) at a scan rate of 2 mV s-1 and capacitance retention of 75 and 58% at scan rates of 100 and 200 mV s-1, respectively. The new findings pave the way to the fabrication of efficient asymmetric devices, containing BiMn2O5-MWCNT positive electrodes and activated carbon-carbon black (AC-CB) negative electrodes. The asymmetric device shows good capacitive behavior and good cyclic stability in a voltage window of 1.8 V. The analysis of power-energy characteristics indicates that maximum energy density of 13.0 W h L-1 (9.0 W h kg-1) and maximum power density of 3.6 kW L-1 (2.5 kW kg-1) can be achieved.

  8. Spin-Driven Multiferroic Properties of PbMn7O12 Perovskite.

    PubMed

    Belik, Alexei A; Glazkova, Yana S; Terada, Noriki; Matsushita, Yoshitaka; Sobolev, Alexey V; Presniakov, Igor A; Tsujii, Naohito; Nimori, Shigeki; Takehana, Kanji; Imanaka, Yasutaka

    2016-06-20

    We synthesize PbMn7O12 perovskite under high-pressure (6 GPa) and high-temperature (1373 K) conditions and investigate its structural, magnetic, dielectric, and ferroelectric properties. We find that PbMn7O12 exhibits rich physical properties from interplay among charge, orbital, and spin degrees of freedom and rich structural properties. PbMn7O12 crystallizes in space group R3̅ near room temperature and shows a structural phase transition at TCO = 397 K to a cubic structure in space group Im3̅; the Im3̅-to-R3̅ transition is associated with charge ordering. Below TOO = 294 K, a structural modulation transition associated with orbital ordering takes place. There are two magnetic transitions with Néel temperatures of TN1 = 83 K and TN2 = 77 K and probably a lock-in transition at TN3 = 43 K (on cooling). There is huge hysteresis on specific heat (between ∼37 and 65 K at 0 Oe), dielectric constant (between ∼20 and 70 K at 0 Oe), and dc and ac magnetic susceptibilities around the lock-in transition. Sharp dielectric constant, dielectric loss, and pyroelectric current anomalies are observed at TN2, indicating that electric polarization is developed at this magnetic transition, and PbMn7O12 perovskite is a spin-driven multiferroic. Polarization of PbMn7O12 is measured to be ∼4 μC/m(2). Field-induced transitions are detected at ∼63 and ∼170 kOe at 1.6-2 K; similar high-magnetic field properties are also found for CdMn7O12, CaMn7O12, and SrMn7O12. PbMn7O12 exhibits a quite small magnetodielectric effect, reaching approximately -1.3 to -1.7% at 10 K and 90 kOe. PMID:27229299

  9. The magnetic structures and transitions of a potential multiferroic orthoferrite ErFeO{sub 3}

    SciTech Connect

    Deng, Guochu Maynard-Casely, Helen E.; Avdeev, Maxim; McIntyre, Garry J.; Guo, Peiyin; Ren, Wei; Cao, Shixun

    2015-04-28

    Rare-earth orthoferrites are very interesting due to their appealing optical and multiferroic properties. In this study, the magnetic structures and transitions of a typical rare-earth orthoferrite, ErFeO{sub 3}, have been reinvestigated in detail. The spin-reorientation transition of the Fe{sup 3+} magnetic phase and the low-temperature magnetic ordering of Er{sup 3+} were observed by neutron powder diffraction. The corresponding magnetic structures have been solved anew by symmetry analysis and refinement of the diffraction results. The magnetic moments of Fe{sup 3+} align in an antiferromagnetic way along the c axis with a weak ferromagnetic component along the b axis below the Néel temperature and above the spin-reorientation transition. Below the spin-reorientation transition, the Fe{sup 3+} moments rotate into an antiferromagnetic ordering state along the b axis with weak ferromagnetic alignment along the c axis. The spin-reorientation takes place in the bc plane. The Er{sup 3+} moments align antiferromagnetically with a C{sub y} mode below 4.5 K. For the Fe{sup 3+} moments, an additional C{sub x} mode is induced by the ordering of the Er{sup 3+} moments. Namely, they change from G{sub y}F{sub z} mode into C{sub x}G{sub y}F{sub z} mode in the Pnma space-group setting. This study resolves the long-lasting dispute about the magnetic structure of ErFeO{sub 3} at low temperature.

  10. Orthorhombic-tetragonal phase coexistence and enhanced piezo-response at room temperature in Zr, Sn, and Hf modified BaTiO{sub 3}

    SciTech Connect

    Kalyani, Ajay Kumar; Brajesh, Kumar; Ranjan, Rajeev; Senyshyn, Anatoliy

    2014-06-23

    The effect of Zr, Hf, and Sn in BaTiO{sub 3} has been investigated at close composition intervals in the dilute concentration limit. Detailed structural analysis by x-ray and neutron powder diffraction revealed that merely 2 mol. % of Zr, Sn, and Hf stabilizes a coexistence of orthorhombic (Amm2) and tetragonal (P4mm) phases at room temperature. As a consequence, all the three systems show substantial enhancement in the longitudinal piezoelectric coefficient (d{sub 33}), with Sn modification exhibiting the highest value ∼425 pC/N.

  11. Effect of lattice constant on pseudo Jahn-Teller polar distortion: Application to search for new multiferroic compounds

    NASA Astrophysics Data System (ADS)

    Song, Guang; Zhang, Weiyi

    2016-08-01

    By analog to Maxwell construction for the first-order phase transition, the pseudo Jahn-Teller polar distortion arises naturally once the local bond length of transition-metal oxygen octahedra is enhanced beyond the inflexion point of pair potential into the concave-down dominated region. This concept is applied to search for the new multiferroic compounds for which we specifically choose the (BaMnO3)1/(BaFeO3)1 superlattice as a candidate. The large Ba radius favors the polar distortion in a BaMnO3 layer, while the orbital-ordering-induced superexchange ferromagnetic coupling among Fe-Fe and double-exchange mediated ferromagnetic coupling among Fe-Mn ions stabilize the overall ferromagnetic insulator. A large magnetic moment of 7 μB per unit cell and electric polarization of 14.4 μ Ccm -2 are obtained. Our study offers an important insight for designing robust multiferroic compounds in the future.

  12. Spin-Induced Polarizations and Nonreciprocal Directional Dichroism of the Room-Temperature Multiferroic BiFeO3

    DOE PAGES

    Fishman, Randy Scott; Lee, Jun Hee; Bordacs, Sandor; Kezsmarki, Istvan; Nagel, Urmas; Room, Toomas

    2015-09-14

    A microscopic model for the room-temperature multiferroic BiFeO3 that includes two Dzyaloshinskii-Moriya interactions and single-ion anisotropy along the ferroelectric polarization predicts both the zero-field spectroscopic modes as well as their splitting and evolution in a magnetic field. Due to simultaneously broken time-reversal and spatial-inversion symmetries, the absorption of light changes as the magnetic field or the direction of light propagation is reversed. We discuss three physical mechanisms that may contribute to this absorption asymmetry known as directional dichroism: the spin current, magnetostriction, and single-ion anisotropy. We conclude that the directional dichroism in BiFeO3 is dominated by the spin-current polarization andmore » is insensitive to the magnetostriction and easy-axis anisotropy. With three independent spin-current parameters, our model accurately describes the directional dichroism observed for magnetic field along [1, -1, 0]. Since some modes are almost transparent to light traveling in one direction but opaque for light traveling in the opposite direction, BiFeO3 can be used as a room-temperature optical diode at certain frequencies in the GHz to THz range. This work demonstrates that an analysis of the directional dichroism spectra based on an effective spin model supplemented by first-principles calculations can produce a quantitative microscopic theory of the magnetoelectric couplings in multiferroic materials.« less

  13. Magnetism and multiferroicity of an isosceles triangular lattice antiferromagnet Sr3NiNb2O9.

    PubMed

    Lee, M; Choi, E S; Ma, J; Sinclair, R; Dela Cruz, C R; Zhou, H D

    2016-11-30

    Various experimental measurements were performed to complete the phase diagram of a weakly distorted triangular lattice system, Sr3NiNb2O9 with Ni(2+) , spin-1 magnetic ions. This compound possesses an isosceles triangular lattice with two shorter bonds and one longer bond. It shows a two-step magnetic phase transition at [Formula: see text] K and [Formula: see text] K at zero magnetic field, characteristic of an easy-axis anisotropy. In the magnetization curves, a series of magnetic phase transitions was observed such as an up-up-down phase at [Formula: see text] T with 1/3 of the saturation magnetization (M sat) and an oblique phase at [Formula: see text] T with [Formula: see text]/3 M sat. Intriguingly, the magnetic phase transition below T N2 is in tandem with the ferroelectricity, which demonstrates multiferroic behaviors. Moreover, the multiferroic phase persists in all magnetically ordered phases regardless of the spin structure. The comparison between the phase diagrams of Sr3NiNb2O9 and its sister compound with an equilateral triangular lattice antiferromagnet Ba3NiNb2O9 (Hwang et al 2012 Phys. Rev. Lett. 109 257205), illustrates how a small imbalance among exchange interactions change the magnetic ground states of the TLAFs. PMID:27661860

  14. Crystalline and spin chiralities in multiferroics with langasite-type structure and Fe1- x Co x Si crystals

    NASA Astrophysics Data System (ADS)

    Pikin, S. A.; Lyubutin, I. S.; Dudka, A. P.

    2015-09-01

    It is shown that, when magnetic ordering occurs in layered iron-containing langasites (sp. gr. P321), one of the reasons for spin chiralities of different signs is the presence of structural chirality (the existence of inversion twins), which, in turn, is due to the nonsymmetricity of these crystals. Spin helicoids arise in these multiferroics at split sites of Fe3+ ions below the Néel point. The direction of electric polarization vectors coincides with the direction of the magnetic helicoid axes because of the piezoelectric properties of these materials. Due to the magnetostriction effects, structural chirality wave vector k z exceeds the magnetic helicoid wave vector by a factor of 2: k z = 2 q z. The temperatures of transitions to the chiral structural and chiral magnetic states may differ. In particular, if the structural transition initial temperature exceeds the magnetic transition temperature ( Т U > Т М ), structural displacements may arise in the absence of magnetism at Т М < Т < Т U . In noncentrosymmetric Fe1- x Co x Si crystals (sp. gr. P213), which are not multiferroics, magnetic chirality is due to the Dzyaloshinski-Moriya interaction. The dependence of the moduli of incommensurate wave number of the corresponding helicoid on the atomic composition of the crystals under consideration is nonmonotonic.

  15. Magnetism and multiferroicity of an isosceles triangular lattice antiferromagnet Sr3NiNb2O9.

    PubMed

    Lee, M; Choi, E S; Ma, J; Sinclair, R; Dela Cruz, C R; Zhou, H D

    2016-11-30

    Various experimental measurements were performed to complete the phase diagram of a weakly distorted triangular lattice system, Sr3NiNb2O9 with Ni(2+) , spin-1 magnetic ions. This compound possesses an isosceles triangular lattice with two shorter bonds and one longer bond. It shows a two-step magnetic phase transition at [Formula: see text] K and [Formula: see text] K at zero magnetic field, characteristic of an easy-axis anisotropy. In the magnetization curves, a series of magnetic phase transitions was observed such as an up-up-down phase at [Formula: see text] T with 1/3 of the saturation magnetization (M sat) and an oblique phase at [Formula: see text] T with [Formula: see text]/3 M sat. Intriguingly, the magnetic phase transition below T N2 is in tandem with the ferroelectricity, which demonstrates multiferroic behaviors. Moreover, the multiferroic phase persists in all magnetically ordered phases regardless of the spin structure. The comparison between the phase diagrams of Sr3NiNb2O9 and its sister compound with an equilateral triangular lattice antiferromagnet Ba3NiNb2O9 (Hwang et al 2012 Phys. Rev. Lett. 109 257205), illustrates how a small imbalance among exchange interactions change the magnetic ground states of the TLAFs.

  16. Magnetoelectric relaxor and reentrant behaviours in multiferroic Pb(Fe2/3W1/3)O3 crystal

    NASA Astrophysics Data System (ADS)

    Chen, Ling; Bokov, Alexei A.; Zhu, Weimin; Wu, Hua; Zhuang, Jian; Zhang, Nan; Tailor, Hamel N.; Ren, Wei; Ye, Zuo-Guang

    2016-03-01

    Significant quenched disorder in crystal structure can break ferroic (magnetic or electric) long-range order, resulting in the development of ferroic glassy states at low temperatures such as magnetic spin glasses, electric dipolar glasses, relaxor ferroelectrics, etc. These states have been widely studied due to novel physical phenomena they reveal. Much less known are the effects of quenched disorder in multiferroics, i.e. the materials where magnetic and electric correlations coexist. Here we report an unusual behaviour in complex perovskite Pb(Fe2/3W1/3)O3 (PFW) crystals: the coexistence of electric relaxor, magnetic relaxor and antiferromagnetic (AFM) states. The most striking finding is the transformation of the AFM phase into a new reentrant-type magnetic glassy phase below Tg ≅ 10 K. We show that the behaviour at this transformation contrasts the typical behaviour of canonical spin glasses and is similar to the behaviour of relaxor ferroelectrics. Magnetoelectric effect is also observed in the AFM phase in the temperature range of the transition into electric relaxor phase at Tf ≅ 200. The mechanism of magnetic relaxor behaviour is supposed to arise from the frustrated interactions among the spins located at the AFM domain walls. Our results should inspire further studies of multirelaxor behaviour in other multiferroic systems.

  17. Magnetoelectric relaxor and reentrant behaviours in multiferroic Pb(Fe2/3W1/3)O3 crystal

    PubMed Central

    Chen, Ling; Bokov, Alexei A.; Zhu, Weimin; Wu, Hua; Zhuang, Jian; Zhang, Nan; Tailor, Hamel N.; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Significant quenched disorder in crystal structure can break ferroic (magnetic or electric) long-range order, resulting in the development of ferroic glassy states at low temperatures such as magnetic spin glasses, electric dipolar glasses, relaxor ferroelectrics, etc. These states have been widely studied due to novel physical phenomena they reveal. Much less known are the effects of quenched disorder in multiferroics, i.e. the materials where magnetic and electric correlations coexist. Here we report an unusual behaviour in complex perovskite Pb(Fe2/3W1/3)O3 (PFW) crystals: the coexistence of electric relaxor, magnetic relaxor and antiferromagnetic (AFM) states. The most striking finding is the transformation of the AFM phase into a new reentrant-type magnetic glassy phase below Tg ≅ 10 K. We show that the behaviour at this transformation contrasts the typical behaviour of canonical spin glasses and is similar to the behaviour of relaxor ferroelectrics. Magnetoelectric effect is also observed in the AFM phase in the temperature range of the transition into electric relaxor phase at Tf ≅ 200. The mechanism of magnetic relaxor behaviour is supposed to arise from the frustrated interactions among the spins located at the AFM domain walls. Our results should inspire further studies of multirelaxor behaviour in other multiferroic systems. PMID:26936414

  18. Magnetic ordering-induced multiferroic behavior in [CH3NH3][Co(HCOO)3] metal-organic framework.

    DOE PAGES

    Gomez-Aguirre, Lilian Claudia; Zapf, Vivien S.; Pato-Doldan, Breogan; Mira, Jorge; Castro-Garcia, Socorro; Senaris-Rodriguez, Maria Antonia; Sanchez-Andujara, Manuel; Singleton, John

    2015-12-30

    Here, we present the first example of magnetic ordering-induced multiferroic behavior in a metal–organic framework magnet. This compound is [CH3NH3][Co(HCOO)3] with a perovskite-like structure. The A-site [CH3NH3]+ cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur. This material is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic component attributable to Dzyaloshinskii–Moriya (DM) interactions and experiences a discontinuous hysteretic magnetic-field-induced switching along [010] and a more continuous hysteresis along [101]. Coupling between the magnetic and electric order is resolved when the field is applied along this [101]: a spin rearrangementmore » occurs at a critical magnetic field in the ac plane that induces a change in the electric polarization along [101] and [10-1]. The electric polarization exhibits an unusual memory effect, as it remembers the direction of the previous two magnetic-field pulses applied. The data are consistent with an inverse-DM mechanism for multiferroic behavior.« less

  19. Magnetization Reversal by Out-of-plane Voltage in BiFeO3-based Multiferroic Heterostructures

    PubMed Central

    Wang, J. J.; Hu, J.M.; Peng, Ren-Ci; Gao, Y.; Shen, Y.; Chen, L. Q.; Nan, C. W.

    2015-01-01

    Voltage controlled 180° magnetization reversal has been achieved in BiFeO3-based multiferroic heterostructures, which is promising for the future development of low-power spintronic devices. However, all existing reports involve the use of an in-plane voltage that is unfavorable for practical device applications. Here, we investigate, using phase-field simulations, the out-of-plane (i.e., perpendicular to heterostructures) voltage controlled magnetism in heterostructures consisting of CoFe nanodots and (110) BiFeO3 thin film or island. It is predicted that the in-plane component of the canted magnetic moment at the CoFe/BiFeO3 interface can be reversed repeatedly by applying a perpendicular voltage across the bottom (110) BiFeO3 thin film, which further leads to an in-plane magnetization reversal in the overlaying CoFe nanodot. The non-volatility of such perpendicular voltage controlled magnetization reversal can be achieved by etching the continuous BiFeO3 film into isolated nanoislands with the same in-plane sizes as the CoFe nanodot. The findings would provide general guidelines for future experimental and engineering efforts on developing the electric-field controlled spintronic devices with BiFeO3-based multiferroic heterostructures. PMID:25995062

  20. Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3

    PubMed Central

    Dixit, Hemant; Hee Lee, Jun; Krogel, Jaron T.; Okamoto, Satoshi; Cooper, Valentino R.

    2015-01-01

    Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. However, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses. We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [–110]) under compressive and tensile strains. A direct coupling between the anisotropic antiferrodistortive rotations and the Dzyaloshinskii-Moria interactions drives the stabilization of the weak ferromagnetism. Furthermore, energetically competing C- and G-type magnetic orderings are observed at high compressive strains, suggesting that it may be possible to switch the weak ferromagnetism “on” and “off” under the application of strain. These findings emphasize the importance of strain and antiferrodistortive rotations as routes to enhancing induced weak ferromagnetism in multiferroic oxides. PMID:26246030

  1. Non-Volatile Ferroelectric Switching of Ferromagnetic Resonance in NiFe/PLZT Multiferroic Thin Film Heterostructures

    PubMed Central

    Hu, Zhongqiang; Wang, Xinjun; Nan, Tianxiang; Zhou, Ziyao; Ma, Beihai; Chen, Xiaoqin; Jones, John G.; Howe, Brandon M.; Brown, Gail J.; Gao, Yuan; Lin, Hwaider; Wang, Zhiguang; Guo, Rongdi; Chen, Shuiyuan; Shi, Xiaoling; Shi, Wei; Sun, Hongzhi; Budil, David; Liu, Ming; Sun, Nian X.

    2016-01-01

    Magnetoelectric effect, arising from the interfacial coupling between magnetic and electrical order parameters, has recently emerged as a robust means to electrically manipulate the magnetic properties in multiferroic heterostructures. Challenge remains as finding an energy efficient way to modify the distinct magnetic states in a reliable, reversible, and non-volatile manner. Here we report ferroelectric switching of ferromagnetic resonance in multiferroic bilayers consisting of ultrathin ferromagnetic NiFe and ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films, where the magnetic anisotropy of NiFe can be electrically modified by low voltages. Ferromagnetic resonance measurements confirm that the interfacial charge-mediated magnetoelectric effect is dominant in NiFe/PLZT heterostructures. Non-volatile modification of ferromagnetic resonance field is demonstrated by applying voltage pulses. The ferroelectric switching of magnetic anisotropy exhibits extensive applications in energy-efficient electronic devices such as magnetoelectric random access memories, magnetic field sensors, and tunable radio frequency (RF)/microwave devices. PMID:27581071

  2. Magnetism and multiferroicity of an isosceles triangular lattice antiferromagnet Sr3NiNb2O9

    NASA Astrophysics Data System (ADS)

    Lee, M.; Choi, E. S.; Ma, J.; Sinclair, R.; Dela Cruz, C. R.; Zhou, H. D.

    2016-11-01

    Various experimental measurements were performed to complete the phase diagram of a weakly distorted triangular lattice system, Sr3NiNb2O9 with Ni2+ , spin-1 magnetic ions. This compound possesses an isosceles triangular lattice with two shorter bonds and one longer bond. It shows a two-step magnetic phase transition at {{T}\\text{N1}}∼ 5.1 K and {{T}\\text{N2}}∼ 5.5 K at zero magnetic field, characteristic of an easy-axis anisotropy. In the magnetization curves, a series of magnetic phase transitions was observed such as an up-up-down phase at {μ0}{{H}c1}∼ 10.5 T with 1/3 of the saturation magnetization (M sat) and an oblique phase at {μ0}{{H}c2}∼ 16 T with \\sqrt{3} /3 M sat. Intriguingly, the magnetic phase transition below T N2 is in tandem with the ferroelectricity, which demonstrates multiferroic behaviors. Moreover, the multiferroic phase persists in all magnetically ordered phases regardless of the spin structure. The comparison between the phase diagrams of Sr3NiNb2O9 and its sister compound with an equilateral triangular lattice antiferromagnet Ba3NiNb2O9 (Hwang et al 2012 Phys. Rev. Lett. 109 257205), illustrates how a small imbalance among exchange interactions change the magnetic ground states of the TLAFs.

  3. Transversal spin freezing and re-entrant spin glass phases in chemically disordered Fe-containing perovskite multiferroics.

    PubMed

    Stephanovich, V A; Laguta, V V

    2016-03-14

    We propose experimental verification and theoretical explanation of magnetic anomalies in the complex Fe-containing perovskite multiferroics like PbFe1/2Nb1/2O3 and PbFe1/2Ta1/2O3. The theoretical part is based on our model of coexistence of the long-range magnetic order and spin glass in the above compounds. In our model, the exchange interaction is anisotropic, coupling antiferromagnetically z spin components of Fe(3+) ions. At the same time, the xy components are coupled by much weaker exchange interaction of ferromagnetic sign. In the system with spatial disorder (half of the corresponding lattice sites are occupied by spinless Nb(5+) ions) such frustrating interaction results in the fact that the antiferromagnetic order is formed by the z projection of the spins, while their xy components contribute to spin glass behaviour. Our theoretical findings are supported by the experimental evidence of such a coexistence of antiferromagnetic and spin glass phases in chemically disordered Fe-containing complex perovskite multiferroics. PMID:26890550

  4. James C. McGroddy Prize Talk: Controlling and Manipulating Ferromagnetism with an Electric Field Using Multiferroic Oxide Heterostructures

    NASA Astrophysics Data System (ADS)

    Ramesh, R.

    2010-03-01

    Complex perovskite oxides exhibit a rich spectrum of functional responses, including magnetism, ferroelectricity, highly correlated electron behavior, superconductivity, etc. The basic materials physics of such materials provide the ideal playground for interdisciplinary scientific exploration. Over the past decade we have been exploring the science of such materials (for example, colossal magnetoresistance, ferroelectricity, etc) in thin film form by creating epitaxial heterostructures and nanostructures. Among the large number of materials systems, there exists a small set of materials which exhibit multiple order parameters; these are known as multiferroics. Using our work in the field of ferroelectric and ferromagnetic oxides as the background, we are now exploring such materials, as epitaxial thin films as well as nanostructures. A particularly interesting problem is that related to electric field control and manipulation of ferromagnetism. In this talk I will describe to you some aspects of such materials as well as the scientific and technological excitement in this field. Finally I will share my ideas on the most exciting open problems and emerging directions in multiferroics and beyond.

  5. Non-Volatile Ferroelectric Switching of Ferromagnetic Resonance in NiFe/PLZT Multiferroic Thin Film Heterostructures

    NASA Astrophysics Data System (ADS)

    Hu, Zhongqiang; Wang, Xinjun; Nan, Tianxiang; Zhou, Ziyao; Ma, Beihai; Chen, Xiaoqin; Jones, John G.; Howe, Brandon M.; Brown, Gail J.; Gao, Yuan; Lin, Hwaider; Wang, Zhiguang; Guo, Rongdi; Chen, Shuiyuan; Shi, Xiaoling; Shi, Wei; Sun, Hongzhi; Budil, David; Liu, Ming; Sun, Nian X.

    2016-09-01

    Magnetoelectric effect, arising from the interfacial coupling between magnetic and electrical order parameters, has recently emerged as a robust means to electrically manipulate the magnetic properties in multiferroic heterostructures. Challenge remains as finding an energy efficient way to modify the distinct magnetic states in a reliable, reversible, and non-volatile manner. Here we report ferroelectric switching of ferromagnetic resonance in multiferroic bilayers consisting of ultrathin ferromagnetic NiFe and ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films, where the magnetic anisotropy of NiFe can be electrically modified by low voltages. Ferromagnetic resonance measurements confirm that the interfacial charge-mediated magnetoelectric effect is dominant in NiFe/PLZT heterostructures. Non-volatile modification of ferromagnetic resonance field is demonstrated by applying voltage pulses. The ferroelectric switching of magnetic anisotropy exhibits extensive applications in energy-efficient electronic devices such as magnetoelectric random access memories, magnetic field sensors, and tunable radio frequency (RF)/microwave devices.

  6. Non-Volatile Ferroelectric Switching of Ferromagnetic Resonance in NiFe/PLZT Multiferroic Thin Film Heterostructures.

    PubMed

    Hu, Zhongqiang; Wang, Xinjun; Nan, Tianxiang; Zhou, Ziyao; Ma, Beihai; Chen, Xiaoqin; Jones, John G; Howe, Brandon M; Brown, Gail J; Gao, Yuan; Lin, Hwaider; Wang, Zhiguang; Guo, Rongdi; Chen, Shuiyuan; Shi, Xiaoling; Shi, Wei; Sun, Hongzhi; Budil, David; Liu, Ming; Sun, Nian X

    2016-01-01

    Magnetoelectric effect, arising from the interfacial coupling between magnetic and electrical order parameters, has recently emerged as a robust means to electrically manipulate the magnetic properties in multiferroic heterostructures. Challenge remains as finding an energy efficient way to modify the distinct magnetic states in a reliable, reversible, and non-volatile manner. Here we report ferroelectric switching of ferromagnetic resonance in multiferroic bilayers consisting of ultrathin ferromagnetic NiFe and ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films, where the magnetic anisotropy of NiFe can be electrically modified by low voltages. Ferromagnetic resonance measurements confirm that the interfacial charge-mediated magnetoelectric effect is dominant in NiFe/PLZT heterostructures. Non-volatile modification of ferromagnetic resonance field is demonstrated by applying voltage pulses. The ferroelectric switching of magnetic anisotropy exhibits extensive applications in energy-efficient electronic devices such as magnetoelectric random access memories, magnetic field sensors, and tunable radio frequency (RF)/microwave devices. PMID:27581071

  7. Reversing ferroelectric polarization in multiferroic DyMn2O5 by nonmagnetic Al substitution of Mn

    NASA Astrophysics Data System (ADS)

    Zhao, Z. Y.; Liu, M. F.; Li, X.; Wang, J. X.; Yan, Z. B.; Wang, K. F.; Liu, J.-M.

    2014-08-01

    The multiferroic RMn2O5 family, where R is rare-earth ion or Y, exhibits rich physics of multiferroicity which has not yet well understood. DyMn2O5 is a representative member of this family. The ferroelectric polarization of DyMn2O5 is claimed to be magnetically relevant and have more than one component. Therefore, the polarization reversal upon the sequent magnetic transitions is expected. We investigate the evolution of the ferroelectric polarization upon a partial substitution of Mn3+ by nonmagnetic Al3+ in order to tailor the Mn3+-Mn4+ interactions and then to modulate the polarization in DyMn2-x/2Alx/2O5. It is revealed that the polarization can be successfully reversed by Al-substitution via substantially suppressing the Mn3+-Mn4+ interactions, while the Dy3+-Mn4+ interactions can sustain against the substitution until a level as high as x = 0.2. In addition, the independent Dy spin ordering is shifted remarkably down to an extremely low temperature due to the Al3+ substitution. The present work unveils the possibility of tailoring the Mn3+-Mn4+ and Dy3+-Mn4+ interactions independently, and thus reversing the ferroelectric polarization.

  8. Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3

    DOE PAGES

    Cooper, Valentino R.; Lee, Jun Hee; Krogel, Jaron T.; Okamoto, Satoshi; Dixit, Hemant M.

    2015-08-06

    Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. Thus, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses. We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains. A direct coupling between the anisotropic antiferrodistortive rotations and Dzyaloshinskii-Moria interactions drives the stabilization of weak ferromagnetism. Furthermore, energeticallymore » competing C- and G-type magnetic orderings are observed at high compressive strains, suggesting that it may be possible to switch the weak ferromagnetism on and off under application of strain. These findings emphasize the importance of strain and antiferrodistortive rotations as routes to enhancing induced weak ferromagnetism in multiferroic oxides.« less

  9. Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3

    SciTech Connect

    Cooper, Valentino R.; Lee, Jun Hee; Krogel, Jaron T.; Okamoto, Satoshi; Dixit, Hemant M.

    2015-08-06

    Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. Thus, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses. We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains. A direct coupling between the anisotropic antiferrodistortive rotations and Dzyaloshinskii-Moria interactions drives the stabilization of weak ferromagnetism. Furthermore, energetically competing C- and G-type magnetic orderings are observed at high compressive strains, suggesting that it may be possible to switch the weak ferromagnetism on and off under application of strain. These findings emphasize the importance of strain and antiferrodistortive rotations as routes to enhancing induced weak ferromagnetism in multiferroic oxides.

  10. Electrically driven magnetic domain wall rotation in multiferroic heterostructures to manipulate suspended on-chip magnetic particles.

    PubMed

    Sohn, Hyunmin; Nowakowski, Mark E; Liang, Cheng-yen; Hockel, Joshua L; Wetzlar, Kyle; Keller, Scott; McLellan, Brenda M; Marcus, Matthew A; Doran, Andrew; Young, Anthony; Kläui, Mathias; Carman, Gregory P; Bokor, Jeffrey; Candler, Robert N

    2015-05-26

    In this work, we experimentally demonstrate deterministic electrically driven, strain-mediated domain wall (DW) rotation in ferromagnetic Ni rings fabricated on piezoelectric [Pb(Mg1/3Nb2/3)O3]0.66-[PbTiO3]0.34 (PMN-PT) substrates. While simultaneously imaging the Ni rings with X-ray magnetic circular dichroism photoemission electron microscopy, an electric field is applied across the PMN-PT substrate that induces strain in the ring structures, driving DW rotation around the ring toward the dominant PMN-PT strain axis by the inverse magnetostriction effect. The DW rotation we observe is analytically predicted using a fully coupled micromagnetic/elastodynamic multiphysics simulation, which verifies that the experimental behavior is caused by the electrically generated strain in this multiferroic system. Finally, this DW rotation is used to capture and manipulate micrometer-scale magnetic beads in a fluidic environment to demonstrate a proof-of-concept energy-efficient pathway for multiferroic-based lab-on-a-chip applications. PMID:25906195

  11. High Pressure Experimental Studies on CuO: Indication of Re-entrant Multiferroicity at Room Temperature

    PubMed Central

    Jana, Rajesh; Saha, Pinku; Pareek, Vivek; Basu, Abhisek; Kapri, Sutanu; Bhattacharyya, Sayan; Mukherjee, Goutam Dev

    2016-01-01

    We have carried out detailed experimental investigations on polycrystalline CuO using dielectric constant, dc resistance, Raman spectroscopy and X-ray diffraction measurements at high pressures. Observation of anomalous changes both in dielectric constant and dielectric loss in the pressure range 3.7–4.4 GPa and reversal of piezoelectric current with reversal of poling field direction indicate to a change in ferroelectric order in CuO at high pressures. A sudden jump in Raman integrated intensity of Ag mode at 3.4 GPa and observation of Curie-Weiss type behaviour in dielectric constant below 3.7 GPa lends credibility to above ferroelectric transition. A slope change in the linear behaviour of the Ag mode and a minimum in the FWHM of the same indicate indirectly to a change in magnetic ordering. Since all the previous studies show a strong spin-lattice interaction in CuO, observed change in ferroic behaviour at high pressures can be related to a reentrant multiferroic ordering in the range 3.4 to 4.4 GPa, much earlier than predicted by theoretical studies. We argue that enhancement of spin frustration due to anisotropic compression that leads to change in internal lattice strain brings the multiferroic ordering to room temperature at high pressures. PMID:27530329

  12. Atomic and electronic structure of the BaTiO3/Fe interface in multiferroic tunnel junctions.

    PubMed

    Bocher, Laura; Gloter, Alexandre; Crassous, Arnaud; Garcia, Vincent; March, Katia; Zobelli, Alberto; Valencia, Sergio; Enouz-Vedrenne, Shaïma; Moya, Xavier; Mathur, Neil D; Marthur, Neil D; Deranlot, Cyrile; Fusil, Stéphane; Bouzehouane, Karim; Bibes, Manuel; Barthélémy, Agnès; Colliex, Christian; Stéphan, Odile

    2012-01-11

    Artificial multiferroic tunnel junctions combining a ferroelectric tunnel barrier of BaTiO(3) with magnetic electrodes display a tunnel magnetoresistance whose intensity can be controlled by the ferroelectric polarization of the barrier. This effect, called tunnel electromagnetoresistance (TEMR), and the corollary magnetoelectric coupling mechanisms at the BaTiO(3)/Fe interface were recently reported through macroscopic techniques. Here, we use advanced spectromicroscopy techniques by means of aberration-corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) to probe locally the nanoscale structural and electronic modifications at the ferroelectric/ferromagnetic interface. Atomically resolved real-space spectroscopic techniques reveal the presence of a single FeO layer between BaTiO(3) and Fe. Based on this accurate description of the studied interface, we propose an atomistic model of the ferroelectric/ferromagnetic interface further validated by comparing experimental and simulated STEM images with atomic resolution. Density functional theory calculations allow us to interpret the electronic and magnetic properties of these interfaces and to understand better their key role in the physics of multiferroics nanostructures. PMID:22191458

  13. High Pressure Experimental Studies on CuO: Indication of Re-entrant Multiferroicity at Room Temperature

    NASA Astrophysics Data System (ADS)

    Jana, Rajesh; Saha, Pinku; Pareek, Vivek; Basu, Abhisek; Kapri, Sutanu; Bhattacharyya, Sayan; Mukherjee, Goutam Dev

    2016-08-01

    We have carried out detailed experimental investigations on polycrystalline CuO using dielectric constant, dc resistance, Raman spectroscopy and X-ray diffraction measurements at high pressures. Observation of anomalous changes both in dielectric constant and dielectric loss in the pressure range 3.7–4.4 GPa and reversal of piezoelectric current with reversal of poling field direction indicate to a change in ferroelectric order in CuO at high pressures. A sudden jump in Raman integrated intensity of Ag mode at 3.4 GPa and observation of Curie-Weiss type behaviour in dielectric constant below 3.7 GPa lends credibility to above ferroelectric transition. A slope change in the linear behaviour of the Ag mode and a minimum in the FWHM of the same indicate indirectly to a change in magnetic ordering. Since all the previous studies show a strong spin-lattice interaction in CuO, observed change in ferroic behaviour at high pressures can be related to a reentrant multiferroic ordering in the range 3.4 to 4.4 GPa, much earlier than predicted by theoretical studies. We argue that enhancement of spin frustration due to anisotropic compression that leads to change in internal lattice strain brings the multiferroic ordering to room temperature at high pressures.

  14. High Pressure Experimental Studies on CuO: Indication of Re-entrant Multiferroicity at Room Temperature.

    PubMed

    Jana, Rajesh; Saha, Pinku; Pareek, Vivek; Basu, Abhisek; Kapri, Sutanu; Bhattacharyya, Sayan; Mukherjee, Goutam Dev

    2016-01-01

    We have carried out detailed experimental investigations on polycrystalline CuO using dielectric constant, dc resistance, Raman spectroscopy and X-ray diffraction measurements at high pressures. Observation of anomalous changes both in dielectric constant and dielectric loss in the pressure range 3.7-4.4 GPa and reversal of piezoelectric current with reversal of poling field direction indicate to a change in ferroelectric order in CuO at high pressures. A sudden jump in Raman integrated intensity of Ag mode at 3.4 GPa and observation of Curie-Weiss type behaviour in dielectric constant below 3.7 GPa lends credibility to above ferroelectric transition. A slope change in the linear behaviour of the Ag mode and a minimum in the FWHM of the same indicate indirectly to a change in magnetic ordering. Since all the previous studies show a strong spin-lattice interaction in CuO, observed change in ferroic behaviour at high pressures can be related to a reentrant multiferroic ordering in the range 3.4 to 4.4 GPa, much earlier than predicted by theoretical studies. We argue that enhancement of spin frustration due to anisotropic compression that leads to change in internal lattice strain brings the multiferroic ordering to room temperature at high pressures. PMID:27530329

  15. Microwave tunability in a GaAs-based multiferroic heterostructure: MnAl/GaAs/Co2PMN-PT

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Gao, J.; Lou, J.; Liu, M.; Yoon, S. D.; Geiler, A. L.; Nedoroscik, M.; Heiman, D.; Sun, N. X.; Vittoria, C.; Harris, V. G.

    2009-04-01

    A strong magnetoelectric (ME) interaction is presented in a magnetostrictive-semiconductor-piezoelectric heterostructure that consists of the Huesler alloy, Co2MnAl, GaAs, and lead magnesium niobate-lead titanate (PMN-PT). The laminated Co2MnAl/GaAs/PMN-PT structure, having a thickness of 19 nm/180 μm/500 μm, demonstrates a ferromagnetic resonance (FMR) field shift of 28 Oe with an external electric field of 200 V across the PMN-PT substrate. This corresponds to a resonance frequency shift of ˜125 MHz at X-band. It yields a large ME coupling (7 Oe cm/kV) and microwave tunability (˜32 MHz/kV cm-1), compared to other trilayer multiferroic composite structures. In addition, static magnetization measurement indicates a reduction in the remanence magnetization while applying the electric field, which corroborates the ME interactions mediated by the translation of magnetoelastic forces in this structure. This work explores the potential of multiferroic heterostrucuture transducers for use in FMR microwave devices tuned by electric fields.

  16. Reversible electrically-driven magnetic domain wall rotation in multiferroic heterostructures to manipulate suspended on-chip magnetic particles

    NASA Astrophysics Data System (ADS)

    Nowakowski, Mark; Sohn, Hyunmin; Liang, Cheng-Yen; Hockel, Joshua; Wetzlar, Kyle; Keller, Scott; McLellan, Brenda; Marcus, Matthew; Doran, Andrew; Young, Anthony; Kläui, Mathias; Carman, Gregory; Bokor, Jeffrey; Candler, Robert

    2015-03-01

    We experimentally demonstrate reversible electrically-driven, strain-mediated domain wall (DW) rotation in Ni rings fabricated on piezoelectric [Pb(Mg1/3Nb2/3) O3]0.66-[PbTiO3]0.34 (PMN-PT) substrates. An electric field applied across the PMN-PT substrate induces a strain in the Ni rings producing DW rotation around the ring toward the dominant PMN-PT strain axis by inverse magnetostriction. We observe DWs reversibly cycled between their initial and rotated state as a function of the applied electric field with x-ray magnetic circular dichroism photo-emission electron microscopy. The DW rotation is analytically predicted using a fully coupled micromagnetic/elastodyanmic multi-physics simulation to verify that the experimental behavior is caused by the electrically-generated strain in this multiferroic system. Finally, this DW rotation is used to capture and manipulate magnetic particles in a fluidic environment to demonstrate a proof-of-concept energy-efficient pathway for multiferroic-based lab-on-a-chip applications. Supported by TANMS (NSF 11-537), E3S, US Dept of Energy (DE-AC02-05CH11231), EU, and DFG.

  17. Investigation on multiferroic, optical and photoluminescence properties of CoFe2O4/(Pb1-xSrx)TiO3 nanostructured composite thin films

    NASA Astrophysics Data System (ADS)

    Bala, Kanchan; Sharma, Pankaj; Negi, N. S.

    2016-11-01

    Multiferroic nanostructured composite thin films consisting of CoFe2O4 (CFO) and Pb1-xSrxTiO3 (PST; x = 0.1, 0.2, 0.3, 0.4 and 0.5) layers have been deposited on Pt/TiO2/SiO2/Si and quartz substrates by using metallo-organic decomposition process and spin coating. The effect of Sr content on the multiferroic and optical properties have been investigated. The phase purity such as spinel structure of CFO and perovskite structure of PST has been verified by X-ray diffraction. Cross-sectional scanning electron microscopy images revealed clear interface between CFO and PST layers without any noticeable diffusion. The multiferroic properties of CFO/PST composite films have been confirmed by magnetic and ferroelectric hysteresis loops with low leakage current density. The residual strain sensitivity of multiferroic and optical properties has been observed in the composite films. The decrease in saturation magnetization and saturation polarization with increase in Sr content has been observed which could be attributed to the decrease in residual strain of CFO/PST composite films. The magnetic phase transition temperature of the CFO/PST composite films is also reduced. The optical refractive index decreases with increase of amount of Sr content. The photoluminescence spectra of the CFO/PST composite films possess a blue shift which can be attributed to the Pb and oxygen vacancies as localized sensitizing centers. We show that the multiferroic and optical properties of the CFO/PST composite films are highly sensitive to the heterostructure strains which can be controlled by Sr content.

  18. Difference in the luminescence properties of orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5}:Ln (Ln = Tb{sup 3+} and Dy{sup 3+})

    SciTech Connect

    Tyagi, Adish; Shah, Alpa; Sudarsan, V. Vatsa, R.K.; Jain, V.K.

    2015-04-15

    Highlights: • Improved emission colour purity with orthorhombic form of Y{sub 2}GeO{sub 5}. • Non-stationary quenching exists in orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5}:Tb. • Ion pair formation and cross relaxation quenching operating for Y{sub 2}GeO{sub 5}:Dy samples. - Abstract: The luminescence properties of Tb{sup 3+} and Dy{sup 3+} doped orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5} are significantly different. Orthorhombic Y{sub 2}GeO{sub 5} doped with Tb{sup 3+} and Dy{sup 3+} ions gives bright green and blue emission upon UV light excitation with CIE coordinates (0.25, 0.46) and (0.25, 0.24), respectively. The monoclinic Y{sub 2}GeO{sub 5} doped with these ions exhibits light green and yellowish white emissions, respectively. This has been attributed to the differences in crystallographic environments around Y{sup 3+} ions in orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5}. Quantum yield of emission for orthorhombic Y{sub 2}GeO{sub 5}:Tb (∼29%) is significantly higher than that of the monoclinic Y{sub 2}GeO{sub 5}:Tb (∼14%). Lifetime values corresponding to {sup 4}F{sub 9/2} level of Dy{sup 3+} ions in both monoclinic and orthorhombic forms of Y{sub 2}GeO{sub 5} follow an opposite trend with respect to {sup 5}D{sub 4} level of Tb{sup 3+} ions. This is attributed to difference in the concentration quenching mechanism operating for Tb{sup 3+} and Dy{sup 3+} ions.

  19. Deterministic Two-Dimensional Polymorphism Growth of Hexagonal n-Type SnS₂ and Orthorhombic p-Type SnS Crystals.

    PubMed

    Ahn, Ji-Hoon; Lee, Myoung-Jae; Heo, Hoseok; Sung, Ji Ho; Kim, Kyungwook; Hwang, Hyein; Jo, Moon-Ho

    2015-06-10

    van der Waals layered materials have large crystal anisotropy and crystallize spontaneously into two-dimensional (2D) morphologies. Two-dimensional materials with hexagonal lattices are emerging 2D confined electronic systems at the limit of one or three atom thickness. Often these 2D lattices also form orthorhombic symmetries, but these materials have not been extensively investigated, mainly due to thermodynamic instability during crystal growth. Here, we show controlled polymorphic growth of 2D tin-sulfide crystals of either hexagonal SnS2 or orthorhombic SnS. Addition of H2 during the growth reaction enables selective determination of either n-type SnS2 or p-type SnS 2D crystal of dissimilar energy band gap of 2.77 eV (SnS2) or 1.26 eV (SnS) as a final product. Based on this synthetic 2D polymorphism of p-n crystals, we also demonstrate p-n heterojunctions for rectifiers and photovoltaic cells, and complementary inverters.

  20. Structural studies of the rhombohedral and orthorhombic monouranates: CaUO4, α-SrUO4, β-SrUO4 and BaUO4

    NASA Astrophysics Data System (ADS)

    Murphy, Gabriel; Kennedy, Brendan J.; Johannessen, Bernt; Kimpton, Justin A.; Avdeev, Maxim; Griffith, Christopher S.; Thorogood, Gordon J.; Zhang, Zhaoming

    2016-05-01

    The structures of some AUO4 (A=Ca, Sr, or Ba) oxides have been determined using a combination of neutron and synchrotron X-ray diffraction, supported by X-ray absorption spectroscopic measurements at the U L3-edge. The smaller Ca cation favours a rhombohedral AUO4 structure with 8-coordinate UO8 moieties whilst an orthorhombic structure based on UO6 groups is found for BaUO4. Both the rhombohedral and orthorhombic structures can be stabilised for SrUO4. The structural studies suggest that the bonding requirements of the A site cation play a significant role in determining which structure is favoured. In the rhombohedral structure, Bond Valence Sums demonstrate the A site is invariably overbonded, which, in the case of rhombohedral α-SrUO4, is compensated for by the formation of vacancies in the oxygen sub-lattice. The uranium cation, with its flexible oxidation state, is able to accommodate this by inducing vacancies along its equatorial coordination site as demonstrated by neutron powder diffraction.

  1. Synthesis of Tetragonal and Orthorhombic Polymorphs of Hf3N4 by High-Pressure Annealing of a Prestructured Nanocrystalline Precursor

    PubMed Central

    2013-01-01

    Hf3N4 in nanocrystalline form is produced by solution phase reaction of Hf(NEtMe)4 with ammonia followed by low-temperature pyrolysis in ammonia. Understanding of phase behavior in these systems is important because early transition-metal nitrides with the metal in maximum oxidation state are potential visible light photocatalysts. A combination of synchrotron powder X-ray diffraction and pair distribution function studies has been used to show this phase to have a tetragonally distorted fluorite structure with 1/3 vacancies on the anion sites. Laser heating nanocrystalline Hf3N4 at 12 GPa and 1500 K in a diamond anvil cell results in its crystallization with the same structure type, an interesting example of prestructuring of the phase during preparation of the precursor compound. This metastable pathway could provide a route to other new polymorphs of metal nitrides and to nitrogen-rich phases where they do not currently exist. Importantly it leads to bulk formation of the material rather than surface conversion as often occurs in elemental combination reactions at high pressure. Laser heating at 2000 K at a higher pressure of 19 GPa results in a further new polymorph of Hf3N4 that adopts an anion deficient cottunite-type (orthorhombic) structure. The orthorhombic Hf3N4 phase is recoverable to ambient pressure and the tetragonal phase is at least partially recoverable. PMID:23721167

  2. Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

    PubMed Central

    Kobayashi, S.; Tokuda, Y.; Mizoguchi, T.; Shibata, N.; Sato, Y.; Ikuhara, Y.; Yamamoto, T.

    2010-01-01

    The oxidation state of Mn in cubic SrMnO3 and orthorhombic SrMnO2.5 was investigated by electron energy loss (EEL) spectroscopy. Change in the oxidation state of Mn produced some spectral changes in the O-K edge as well as in the Mn-L2,3 edge EEL spectra. This study demonstrated that the oxidation state of Mn and the amount of oxygen vacancies in cubic SrMnO3 and orthorhombic SrMnO2.5 could be quantified by analyzing the features of the O-K edge spectrum and the Mn L3∕L2 ratio in the Mn-L2,3 edge spectrum. Our quantitative analysis showed that the spectral changes in the Mn-L2,3 edge were mainly caused by the oxidation state of Mn, whereas those in the O-K edge could be sensitive to both the oxidation state of Mn and to lattice distortions. PMID:21245943

  3. Polar octahedral rotations, cation displacement and ferroelectricity in multiferroic SmCrO3

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Dey, K.; Chakraborty, M.; Majumdar, S.; Giri, S.

    2014-08-01

    Our thorough synchrotron diffraction studies provide a clue on the origin of ferroelectricity in SmCrO3. Careful observation demonstrates that polar order develops in the paramagnetic state. Rietveld refinement of the diffraction data confirms that emergence of polar order is correlated with the structural transformation from centrosymmetric Pbnm to non-centrosymmetric Pna21 space group of the distorted orthorhombic structure. Rotations of polar CrO6 octahedra and Sm displacement are proposed to be correlated with the emergence of polar order, which is extended over a wide temperature range and increases gradually with decreasing temperature. This is consistent with the relaxor behavior as evident from the frequency-dependent dielectric response satisfying the Vogel-Fulcher law. A non-collinear to collinear spin transformation is suggested well below the spin reorientation transition. Appearance of ferroelectricity without any correlation to the antiferromagnetic order in SmCrO3 suggests a new class of ferroelectricity. All-electron full-potential first-principles calculation demonstrates significant Sm-Cr hybridization near the Fermi level, which substantiates the experimental findings.

  4. Temperature dependent x-ray diffraction and dielectric studies of multiferroic GaFeO3

    NASA Astrophysics Data System (ADS)

    Kumar, Rajeev; Mall, Ashish Kumar; Gupta, Rajeev

    2016-05-01

    Polycrystalline GaFeO3 (GFO) samples were synthesized by sol-gel method. The structural and dielectric properties of GaFeO3 ceramic have been investigated by a combination of XRD and permittivity measurement. The X-ray diffraction spectra shows single phase orthorhombically distorted perovskite structure with Pc21n symmetry over a wide range of temperature 300K to 600K, with no evidence of any phase transition. Refined lattice parameters (a, b, c and V) increases with increasing temperature. Temperature dependent dielectric properties were investigated in the frequency range from 100Hz-5MHz. Impedance spectroscopy study on the sample showed that the dielectric constant and ac conductivity with frequency increases on increasing the temperature. Cole-Cole plots suggest that the response from grain is dominant at low temperature whereas grain boundary response overcomes as temperature increases. The relaxation activation energy (calculated from Cole-Cole plots) value is found to be 0.32 eV for the grain boundary. We believe that the oxygen ion vacancies play an important role in conduction processes at higher temperatures.

  5. Size effect on multiferroic TbMn{sub 2}O{sub 5} nanorods

    SciTech Connect

    Yang, Chun-Chuen Tung, Yung-Hsiang; Hsu, Ting-Wei; You, Pang-Yen; Chen, Yi-Jung; Chan, Ting-Shan; Chen, Yang-Yuan

    2015-05-07

    The effect of the size of TbMn{sub 2}O{sub 5} on their magnetoelectric properties is studied using a field emission transmission electron microscope, ac magnetic susceptibility, relative dielectric constant, specific heat capacity, and x-ray diffraction at various temperatures. A bulk sample and nanorods with two axial lengths, 〈L{sub C}〉, are investigated. Nanorods with 〈L{sub C}〉 of 216 nm and 64 nm crystallize with orthorhombic Pbam symmetry as the bulk material. The axial direction of the two sizes of nanorod is parallel to the c axis of the crystal. No particular radial direction is observed. The critical size for the magnetic ordering of TbMn{sub 2}O{sub 5} is found to be between 〈L{sub C}〉 = 64 nm and 216 nm. Experiments on specific heat capacity verified these results. No similar phenomenon concerning the ferroelectric property is observed. At T = 30 K and 35 K, the 〈L{sub C}〉 = 216 nm sample yields a charge-ordering-like x-ray diffraction peak, which may be associated with the magnetically induced charge ordering superlattice.

  6. Strain coupling and dynamic relaxation dynamics associated with ferroic and multiferroic phase transition

    NASA Astrophysics Data System (ADS)

    Carpenter, Michael

    Almost any change that occurs in a crystal structure results in some lattice strain and it is inevitable that this will appear also as a change in elastic properties. It follows that one of the most characteristic features of phase transitions, whether driven by structural, magnetic or electronic effects, will be variations of elastic constants. In addition, transformation microstructures such as ferroelastic twins may be mobile under some conditions of temperature and stress and will give characteristic patterns of acoustic loss when measured by dynamical methods. Thanks substantially to the pioneering work of Dr Albert Migliori in developing the technique of Resonant Ultrasound Spectroscopy (RUS), it has been possible to follow the elastic and anelastic behaviour associated with phase transitions quantitatively as a function of temperature through the interval 2-1600 K. It is also possible to add magnetic and electric fields. The frequency window 0.1-2 MHz and inherently small strains of RUS appear to be particularly sensitive for observing the consequences of strain coupling and microstructure relaxation dynamics. Recent collaborative work carried out using the RUS facilities in Cambridge will be presented, relating to phase transitions in multiferroic perovskites, such as PbZr0.53Ti0.47O3-PbFe0.5Nb0.5O3 and Sr2FeMoO6, the ferroelectric/improper ferroelastic transition in GeTe, and magnetoelastic behaviour of EuTiO3. A common feature of these is softening of the shear modulus ahead of the transition that is not expected on the basis of linear/quadratic coupling between strain and the driving order parameter (improper ferroelastic). This appears to be due to coupling of acoustic modes with unseen central modes which are related to collective motions of domains with short range order. In some cases the ferroelastic twin walls have a well defined freezing interval (GeTe) whereas anelastic loss and stiffening over a wide temperature interval appears to be diagnostic

  7. Quantification of charge-to-strain mediated interface coupling transfiguration in FE/FSMA multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Singh, Kirandeep; Kaur, Davinder

    2016-01-01

    Thickness modulated direct, local measurement of magnetoelectric (ME) coupling was executed in a high quality sputter deposited PZT/Ni-Mn-In bilayer system grown on Si(1 0 0) substrate. The additive temperature and magnetic-field-driven shape-memory behavior of bottom ferromagnetic (FM) Ni-Mn-In layer, which vanish at ultra-low regime (8 nm), induce fluctuations in the dielectric and ferroelectric (FE) characteristic of PZT. The prominent magnetic-field-modulated P-E loops registered at room temperature in  ±400 kV cm-1 electric field range illustrate the presence of giant strain-mediated direct ME coupling in bilayers. This giant strain-mediated direct ME coupling in bilayers can be imputed to magnetic-field-actuated shape-memory behavior of Ni-Mn-In film. The I-V characteristic depicts that the PZT/Ni-Mn-In bilayer endures transition from Ohmic conduction (dominant at low field) to interface-limited Fowler-Nordheim (FN) tunneling prevailing at high electric field. Magnetic measurements of the bilayer revealed that voltage-attuned magnetic anisotropy variation was strongly dependent on the thickness of the bilayer. The normalized magnetization (M/M s) versus electric field (ME) plots was sketched to cognize the origin of interfacial converse ME coupling. The occurrence of butterfly-shaped ME loops showed the dominance of strain-mediated coupling in the (200 nm/220 nm) bilayer, in contrast to (40 nm/8 nm) heterostructure coupling which was purely charge mediated. The co-existence of charge- and strain-mediated ME coupling in (80 nm/30 nm) structure was evident from quite asymmetric features of ME curves. In 80 nm/30 nm multiferroic heterostructure two reversible and stable magnetic field states of Ni-Mn-In were observed at zero electric field. Such a non-volatile switching of magnetization accomplished by reversing the electric field could prove useful in future MERAM devices.

  8. Phase-field crystal approach for modeling the role of microstructure in multiferroic composite materials

    NASA Astrophysics Data System (ADS)

    Seymour, Matthew; Sanches, F.; Elder, Ken; Provatas, Nikolas

    2015-11-01

    This paper introduces a phase-field crystal (PFC) approach that couples the atomic-scale PFC density field to order parameters describing ferromagnetic and ferroelectric ordering, as well to a solute impurity field. This model extends the magnetic PFC model introduced by Faghihi et al. [N. Faghihi, Ph.D. Thesis, The University of Western Ontario, 2012; N. Faghihi, N. Provatas, K. R. Elder, M. Grant, and M. Karttunen, Phys. Rev. E 88, 032407 (2013), 10.1103/PhysRevE.88.032407] to incorporate polarization and concentration fields, as well as anisotropic ordering of the magnetization and polarization fields as determined by the local crystalline orientation. Magnetoelectric coupling is incorporated through the elastic coupling. Analytic calculations for a body centered-cubic (BCC) system are presented to illustrate that the model reduces to the standard multiferroic phase-field models when only a single crystal is considered. Two special cases of the model are then studied, the first focusing on magnetocrystalline interactions in a system described by the two-point correlation function of the XPFC model developed by Greenwood et al. [M. Greenwood, N. Provatas, and J. Rottler, Phys. Rev. Lett. 105, 045702 (2010), 10.1103/PhysRevLett.105.045702; M. Greenwood, J. Rottler, and N. Provatas, Phys. Rev. E 83, 031601 (2011), 10.1103/PhysRevE.83.031601], and the second focusing on electrocrystalline interactions in a system described by the original PFC kernel developed by Elder et al. K. R. Elder, M. Katakowski, M. Haataja, and M. Grant, Phys. Rev. Lett. 88, 245701 (2002), 10.1103/PhysRevLett.88.245701; K. R. Elder and M. Grant, Phys. Rev. E 70, 051605 (2004), 10.1103/PhysRevE.70.051605]. We examine the small deformation properties of these two realizations of the model . Numerical simulations are performed to illustrate how magnetocrystalline coupling can be exploited to design a preferential grain texture and how defects and grain boundaries influence the ferroelectric

  9. Theory of domain wall motion mediated magnetoelectric effects in a multiferroic composite

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Srinivasan, G.

    2014-10-01

    A model is discussed for magnetoelectric (ME) interactions originating from the motion of magnetic domain walls (DWs) in a multiferroic composite of orthoferrites RFeO3 (RFO) with magnetic stripe domains and a piezoelectric such as lead magnesium niobate-lead titanate (PMN-PT). The DWs in RFO can be set in motion with an ac magnetic field up to a critical speed of 20 km/s, the highest for any magnetic system, leading to the excitation of bulk and shear magnetoacoustic waves. Thus, the ME coupling will arise from flexural deformation associated with DW motion (rather than the Joule magnetostriction mediated coupling under a static or quasistatic condition). A c plane orthoferrite with a single Néel-type DW in the bc plane and an ac magnetic field H along the c axis is assumed. The deflection in the bilayer due to DW motion is obtained when the DW velocity is a linear function H and the resulting induced voltage across PMN-PT is estimated. It is shown that a combination of spatial and time harmonics of the bending deformation leads to (i) a linear ME coefficient defined by αE=E/H and (ii) a quadratic ME coefficient αEQ=E/H2. The model is applied to yttrium orthoferrites (YFO) and a PMN-PT bilayer since YFO has one of the highest DW mobility amongst the orthoferrites. The coefficient αE is dependent on the DW position, and it is maximum when the DW equilibrium position is at the center of the sample. In YFO/PMN-PT the estimated low-frequency αE ˜ 30 mV/cm Oe and resonance value is 1.5 V/(cm Oe). Since orthoferrites (and PMN-PT) are transparent in the visible region and have a large Faraday rotation, the DW dynamics and the ME coupling could be studied simultaneously. The theory discussed here is of interest for studies on ME coupling and for applications such as magnetically controlled electro-optic devices.

  10. Numerical adiabatic potentials of orthorhombic Jahn-Teller effects retrieved from ultrasound attenuation experiments. Application to the SrF2:Cr crystal

    NASA Astrophysics Data System (ADS)

    Zhevstovskikh, I. V.; Bersuker, I. B.; Gudkov, V. V.; Averkiev, N. S.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.

    2016-06-01

    A methodology is worked out to retrieve the numerical values of all the main parameters of the six-dimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter anomalies when the direction of propagation and polarization of its wave of strain coincides with the characteristic directions of symmetry breaking in the JTE. For the SrF2:Cr crystal, employed as a basic example, we observed anomaly peaks in the temperature dependence of attenuation of ultrasound at frequencies of 50-160 MHz in the temperature interval of 40-60 K for the wave propagating along the [110] direction, for both the longitudinal and the shear modes, the latter with two polarizations along the [001] and [1 1 ¯ 0 ] axes, respectively. We show that these anomalies are due to the ultrasound relaxation by the system of non-interacting Cr2+ JT centers with orthorhombic local distortions. The interpretation of the experimental findings is based on the T2 g⊗(eg+t2 g) JTE problem including the linear and the quadratic terms of vibronic interactions in the Hamiltonian and the same-symmetry modes reduced to one interaction mode. Combining the experimental results with a theoretical analysis, we show that on the complicated six-dimensional APES of this system with three tetragonal, four trigonal, and six orthorhombic extrema points, the latter are global minima, while the former are saddle points, and we estimate numerically all the main parameters of this surface, including the linear and quadratic vibronic coupling constants, the primary force constants, the coordinates of all the extrema points and their energies, the energy barrier between the orthorhombic minima, and the tunneling splitting of the ground vibrational states. To our knowledge, such a based-on-experimental-data numerical reconstruction of the APES

  11. An investigation on the defect structures and spin Hamiltonian parameters for the two orthorhombic Ti3+ centers in ZnWO4

    NASA Astrophysics Data System (ADS)

    Ding, Chang-Chun; Wu, Shao-Yi; Zhu, Qing-Sheng; Zhang, Zhi-Hong; Teng, Bao-Hua; Wu, Ming-He

    2015-11-01

    By employing the perturbation formulae of the spin Hamiltonian parameters (SHPs) (g factors gxx, gyy, gzz, hyperfine structure constants Axx, Ayy, Azz and superhyperfine parameters Axx', Ayy', Azz') for a 3d1 ion in orthorhombically elongated octahedra and tetrahedra, the defect structures and the experimental EPR spectra are theoretically and systematically investigated for the two orthorhombic Ti3+ centers C1 and C2 in ZnWO4. Center C1 is ascribed to the impurity Ti3+ at host W6+ site associated with two nearest neighbor oxygen vacancies due to charge compensation. The resultant tetrahedral [TiO4]5- cluster is determined to undergo the local orthorhombic elongation distortion, characterized by the axial distortion angle Δθ (=θ-θ0≈-6.84°) of the local impurity-ligand bond angle θ related to θ0 (≈54.74°) and the perpendicular distortion angle Δε (=ε-ε0≈2.5°) related to ε0 (≈45°) of an ideal tetrahedron because of the Jahn-Teller effect. Center C2 is attributed to Ti3+ on Zn2+ site, and this octahedral [TiO6]9- cluster may experience the local axial elongation ΔZ (≈0.001 Ǻ) and the planar bond angle variation Δφ (≈9.1°) due to the Jahn-Teller effect, resulting in a more regular oxygen octahedron. All the calculated SHPs (i.e., g factors for both centers, the hyperfine structure constants for center C2 and superhyperfine parameters of next nearest neighbor ligand W for center C1) show good agreement with the observed values. However, the theoretical results based on the previous assignment of center C1 as Ti3+ on W6+ site with only one nearest planar oxygen vacancy (i.e., five-fold coordinated octahedral [TiO5]7- cluster) show much worse agreement with the experimental data. The defect structures and the SHPs (especially the g anisotropies) are discussed for both centers. The present studies on the superhyperfine parameters of ligand W6+ for center C1 would be helpful to further investigations on the superhyperfine interactions of

  12. Intrinsically incompatible crystal (ligand) field parameter sets for transition ions at orthorhombic and lower symmetry sites in crystals and their implications

    NASA Astrophysics Data System (ADS)

    Rudowicz, C.; Gnutek, P.

    2010-01-01

    Central quantities in spectroscopy and magnetism of transition ions in crystals are crystal (ligand) field parameters (CFPs). For orthorhombic, monoclinic, and triclinic site symmetry CF analysis is prone to misinterpretations due to large number of CFPs and existence of correlated sets of alternative CFPs. In this review, we elucidate the intrinsic features of orthorhombic and lower symmetry CFPs and their implications. The alternative CFP sets, which yield identical energy levels, belong to different regions of CF parameter space and hence are intrinsically incompatible. Only their ‘images’ representing CFP sets expressed in the same region of CF parameter space may be directly compared. Implications of these features for fitting procedures and meaning of fitted CFPs are categorized into negative: pitfalls and positive: blessings. As a case study, the CFP sets for Tm 3+ ions in KLu(WO 4) 2 are analysed and shown to be intrinsically incompatible. Inadvertent, so meaningless, comparisons of incompatible CFP sets result in various pitfalls, e.g., controversial claims about the values of CFPs obtained by other researchers as well as incorrect structural conclusions or faulty systematics of CF parameters across rare-earth ion series based on relative magnitudes of incompatible CFPs. Such pitfalls bear on interpretation of, e.g., optical spectroscopy, inelastic neutron scattering, and magnetic susceptibility data. An extensive survey of pertinent literature was carried out to assess recognition of compatibility problems. Great portion of available orthorhombic and lower symmetry CFP sets are found intrinsically incompatible, yet these problems and their implications appear barely recognized. The considerable extent and consequences of pitfalls revealed by our survey call for concerted remedial actions of researchers. A general approach based on the rhombicity ratio standardization may solve compatibility problems. Wider utilization of alternative CFP sets in the

  13. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3

    SciTech Connect

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; Gehring, P. M.; Stock, C.; Matsuda, Masaaki; Winn, Barry L.; Gu, Genda; Shapiro, Stephen M.; Birgeneau, R. J.; Ushiyama, T.; Yanagisawa, Y.; Tomioka, Y.; Ito, T.; Xu, Guangyong

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in this multiferroic material are coupled.

  14. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3

    DOE PAGES

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; Gehring, P. M.; Stock, C.; Matsuda, Masaaki; Winn, Barry L.; Gu, Genda; Shapiro, Stephen M.; Birgeneau, R. J.; et al

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in thismore » multiferroic material are coupled.« less

  15. Magnetic switching and phase competition in the multiferroic antiferromagnet Mn1−xFexWO4

    SciTech Connect

    Ye, Feng; Ren, Y.; Fernandez-Baca, Jaime A; Mook Jr, Herbert A; Lynn, J. W.; Chaudhury, R. P.; Wang, Y. Q.; Lorenz, Bernd; Chu, C. W.

    2008-01-01

    Elastic neutron scattering is used to study the spin correlations in the multiferroic Mn1−xFexWO4 with x=0.035, 0.05, and 0.10. The noncollinear incommensurate ICM magnetic structure associated with the ferroelectric FE phase in pure MnWO4 is suppressed at x=0.035 and completely absent at x=0.10. The ICM spin order and FE phase can be restored by applying a magnetic field along the spin easy axis. The low-T commensurate magnetic structure extends in both H/T with increasing Fe concentration. The systematic evolution of the magnetic and electric properties indicates that the noncollinear ICM spin order results from competing magnetic interactions and its stabilization can be tuned by the internal x or external magnetic-field perturbations.

  16. Stability of multiferroicity against Dy/Mn off-stoichiometry in DyMnO{sub 3}

    SciTech Connect

    Wang, J. X.; Liu, M. F.; Zhao, Z. Y.; Yan, Z. B.; Liu, J.-M.

    2014-05-07

    We investigate the effects of slight Dy/Mn off-stoichiometry on the multiferroic behaviors of DyMnO{sub 3} (Dy{sub 1−x}Mn{sub 1+x}O{sub 3}). It is revealed that the distorted lattice structure and ferroelectric property exhibit higher stability against the Mn deficiency than the Dy deficiency. Since the electric polarization includes the contributions from the Mn-Mn and Dy-Mn interactions, the measured polarization exhibits different dependence on the Mn deficiency from that on the Dy deficiency. The present work suggests that the Dy/Mn off-stoichiometry is detrimental to the ferroelectricity, owing to the modulated spin interactions and reshuffled spin frustration.

  17. Electronic structure of multiferroic BiFeO3 by resonant soft-x-ray emission spectroscopy

    SciTech Connect

    Higuchi, Tohru; Higuchi, T.; Liu, Y.-S.; Yao, P.; Glans, P.-A.; Guo, Jinghua; Chang, C.; Wu, Z.; Sakamoto, W.; Itoh, N.; Shimura, T.; Yogo, T.; Hattori, T.

    2008-07-11

    The electronic structure of multiferroic BiFeO{sub 3} has been studied using soft-X-ray emission spectroscopy. The fluorescence spectra exhibit that the valence band is mainly composed of O 2p state hybridized with Fe 3d state. The band gap corresponding to the energy separation between the top of the O 2p valence band and the bottom of the Fe 3d conduction band is 1.3 eV. The soft-X-ray Raman scattering reflects the features due to charge transfer transition from O 2p valence band to Fe 3d conduction band. These findings are similar to the result of electronic structure calculation by density functional theory within the local spin-density approximation that included the effect of Coulomb repulsion between localized d states.

  18. High temperature extended x-ray absorption fine structure study of multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Raghavendra Reddy, V.; Meneghini, Carlo; Kothari, Deepti; Gupta, Ajay; Aquilanti, Giuliana

    2012-08-01

    Local atomic structure modifications around Fe atoms in polycrystalline multiferroic BiFeO3 are studied by Fe K edge x-ray absorption spectroscopy as a function of temperature across the Néel temperature (TN = 643 K) in order to reveal local structure modifications related to the magnetic transition. This work demonstrates that on crossing TN the local structure around Fe shows peculiar changes: the Fe-O bond lengths get shorter, the ligand symmetry increases and the Fe-O bond length disorder (σ2) deviates from Debye behaviour. These results suggest that the structural transition at the ferroelectric Curie temperature (TC = 1103 K) is anticipated by early local rearrangement of the structure starting already at TN.

  19. Thermal evolution of the full three-dimensional magnetic excitations in the multiferroic BiFeO3

    SciTech Connect

    Xu, Zhijun; Wen, Jinsheng; Berlijn, Tom; Gehring, Peter M; Stock, Christopher K; Stone, Matthew B; Gu, G. D.; Shapiro, S. M.; Birgeneau, R J; Xu, Guangyong

    2012-01-01

    We present neutron inelastic scattering measurements of the full three-dimensional spin-wave dispersion in the multiferroic material BiFeO3 for temperatures from 5K to 700K. Despite the presence of strong electromagnetic coupling, the magnetic excitations behave like conventional magnons over all parts of the Brillouin zone. At low temperature the spin-waves are well-defined coherent modes, described by a classical model for a G-type antiferromagnet. A softening of the spin-wave velocity and broadening in energy is already present at room temperature, which is well below the N eel temperature TN 640K, and increases on heating. In addition, a strong hybridization of the Fe 3d and O 2p states is found to modify the distribution of the spin-wave spectral weight significantly, which implies that the spins are not restricted to the Fe atomic sites as previously believed.

  20. Axisymmetric thermo-elastic field in an annular plate of functionally graded multiferroic composites subjected to uniform thermal loadings

    NASA Astrophysics Data System (ADS)

    Shi, T. F.; Wang, C. J.; Liu, C.; Liu, Y.; Dong, Y. H.; Li, X. Y.

    2016-03-01

    This paper presents the thermo-magneto-electro-elastic (thermo-MEE) field in an annular plate of heterogeneous multiferroic composite medium subjected to thermal loadings uniformly distributed on the main boundaries. As a prior, the temperature distribution is determined by solving the thermo-conduction equation. Then, the direct displacement method is employed to derive the coupling thermo-MEE field. Finally, numerical calculations are performed to validate the present analysis and to investigate the influence of the material heterogeneity and the multi-field coupling. The present solutions can be readily reduced to those for circular plate upon letting the inner radius tend to zero. The obtained solutions may serve as a benchmark to various numerical codes and simplified analyzes, since no ad hoc hypothesis is adopted in the present work.