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Sample records for multiferroic orthorhombic dymno3

  1. Phase transitions and rare-earth magnetism in hexagonal and orthorhombic DyMnO(3) single crystals.

    PubMed

    Harikrishnan, S; Rößler, S; Naveen Kumar, C M; Bhat, H L; Rößler, U K; Wirth, S; Steglich, F; Elizabeth, Suja

    2009-03-04

    The floating-zone method with different growth ambiences has been used to selectively obtain hexagonal or orthorhombic DyMnO(3) single crystals. The crystals were characterized by x-ray powder diffraction of ground specimens and a structure refinement as well as electron diffraction. We report magnetic susceptibility, magnetization and specific heat studies of this multiferroic compound in both the hexagonal and the orthorhombic structure. The hexagonal DyMnO(3) shows magnetic ordering of Mn(3+) (S = 2) spins on a triangular Mn lattice at T(N)(Mn) = 57 K characterized by a cusp in the specific heat. This transition is not apparent in the magnetic susceptibility due to the frustration on the Mn triangular lattice and the dominating paramagnetic susceptibility of the Dy(3+) (S = 9/2) spins. At T(N)(Dy) = 3 K, a partial antiferromagnetic order of Dy moments has been observed. In comparison, the magnetic data for orthorhombic DyMnO(3) display three transitions. The data broadly agree with results from earlier neutron diffraction experiments, which allows for the following assignment: a transition from an incommensurate antiferromagnetic ordering of Mn(3+) spins at T(N)(Mn) = 39 K, a lock-in transition at T(lock-in) = 16 K and a second antiferromagnetic transition at T(N)(Dy) = 5 K due to the ordering of Dy moments. Both the hexagonal and the orthorhombic crystals show magnetic anisotropy and complex magnetic properties due to 4f-4f and 4f-3d couplings.

  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. The crucial role of Mn spiral spin order in stabilizing the Dy-Mn exchange striction in multiferroic DyMnO3.

    PubMed

    Wang, H W; Li, C L; Yuan, S L; Wang, J F; Lu, C L; Liu, J-M

    2017-02-01

    DyMnO3 hosts the less addressed duality of multiferroicity, owing to the Dy-Mn exchange striction and inverse Dzyaloshinskii-Moriya interaction between Mn spin pairs. Although the duality in DyMnO3 has been discussed earlier, there remains a question whether the Mn magnetic sublattice is necessarily multiferroic for generating the Dy-Mn exchange striction. In this work, we investigate the multiferroicity of Dy(Mn1-xFex)O3 (0 ≤ x ≤ 0.1) through detailed magnetic and ferroelectric characterization. It is found that Fe-doping continuously suppresses the independent Dy spin order but instead promotes the Dy-Mn(Fe) coupling. This coupling benefits the Dy-Mn(Fe) exchange striction which remarkably enhances the ferroelectric polarization at a low doping level (x ≤ 0.015), beyond which the Mn spiral spin order breaks down leading to collapse of the macroscopic polarization at x ≥ 0.05. This work discloses the crucial role of Mn spiral spin order in stabilizing the Dy-Mn exchange striction and thus highlights the duality of multiferroicity in DyMnO3.

  5. 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.; ...

    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

  6. Phase transition and phase separation in multiferroic orthorhombic Dy1−xHoxMnO3 (0 ≤ x ≤ 1)

    PubMed Central

    Zhang, Na; Dong, Shuai; Fu, Zhaoming; Yan, Zhibo; Chang, Fanggao; Liu, Junming

    2014-01-01

    We report on structural, magnetic, ferroelectric, and thermodynamic properties of polycrystalline orthorhombic manganites Dy1−xHoxMnO3 for Ho substitution levels 0 ≤ x ≤ 1. This system offers a possibility to systemically modulate the multiferroicity of RMnO3 via tuning the A-site ionic radii as well as the A-site magnetism. The successive transition of the multiferroic ground state is traced from the bc-cycloidal (DyMnO3) to the E-type antiferromagnetic phase (HoMnO3). In the middle substitution range 0.4 < x < 0.5, the phase separation is prominent, which's residual may survive in an even wider range. Accompanied with the phase transition and phase separation, obvious enhancement of both the polarization and magnetoelectric response is observed. Our experimental study also confirmed that the rare earth (Dy/Ho)-Mn exchange striction is a crucial role in deciding the multiferroicity of manganites. PMID:25266322

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

    SciTech Connect

    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.; Schoenlein, R. W.; Chuang, Y. -D.

    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 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; ; 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.

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

    SciTech Connect

    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.; Schoenlein, R. W.; Chuang, Y. -D.

    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 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; ; 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.

  9. Observation of anomalous phonons in orthorhombic rare-earth manganites

    NASA Astrophysics Data System (ADS)

    Gao, P.; Chen, H. Y.; Tyson, T. A.; Liu, Z. X.; Bai, J. M.; Wang, L. P.; Choi, Y. J.; Cheong, S.-W.

    2010-12-01

    We observe the appearance of a phonon near the lock-in temperature in orthorhombic REMnO3 (RE denotes rare earth) (RE: Lu and Ho) and anomalous phonon hardening in orthorhombic LuMnO3. The anomalous phonon occurs at the onset of spontaneous polarization. No such changes were found in incommensurate orthorhombic DyMnO3. These observations directly reveal different electric polarization mechanisms in the E-type and incommensurate-type orthorhombic REMnO3.

  10. 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.

  11. Size dependences of crystal structure and magnetic properties of DyMnO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Tajiri, T.; Terashita, N.; Hamamoto, K.; Deguchi, H.; Mito, M.; Morimoto, Y.; Konishi, K.; Kohno, A.

    2013-11-01

    We synthesized DyMnO3 nanoparticles with particle sizes of about 7.5-15.3 nm in the pores of mesoporous silica and investigated their crystal structure and magnetic properties. As the particle size decreased, the lattice constants of the DyMnO3 nanoparticles deviated from those of the bulk crystal, and the Jahn-Teller distortion in the nanoparticle systems decreased. In addition, the estimated lattice strain increased with decreasing particle size. The DyMnO3 nanoparticles showed superparamagnetic behavior. The blocking temperature and the coercive field increased with decreasing particle size, and this behavior was contrary to the usual magnetic size effects. It is deduced that these unique size dependences of the magnetic properties for the DyMnO3 nanoparticles were derived from the changes in lattice constants and lattice strain. The anisotropic lattice deformation in the crystal structure of the nanoparticles induces an enhancement of the magnetic anisotropy, which results in the increase in blocking temperature and coercive field with decreasing particle size.

  12. Synthesis and magnetic properties of DyMnO3 nanoparticles in mesoporous silica

    NASA Astrophysics Data System (ADS)

    Tajiri, Takayuki; Kohno, Atsushi; Hamamoto, Kenta; Ando, Yuhki; Deguchi, Hiroyuki; Mito, Masaki

    2013-08-01

    We synthesized nanoparticles of the perovskite manganite DyMnO3 in pores of mesoporous silica SBA-15 and investigated their magnetic properties. X-ray diffraction patterns of the nanoparticles indicated successful synthesis of the DyMnO3 nanoparticles with a particle size of about 10 nm in the pores of SBA-15. The temperature dependence of the DC magnetic susceptibility for the DyMnO3 nanoparticles exhibited a pronounced magnetic irreversibility between the field-cooling and the zero-field-cooling susceptibility due to the blocking phenomena and indicated a change of the magnetic exchange interactions from those for the bulk crystal. The in-phase susceptibility χ' and the out-of-phase susceptibility χ″ of the AC susceptibility for the nanoparticles exhibited a peak at the blocking temperature, and that peak shifted toward higher temperature with increasing frequency. Magnetization curves for the nanoparticles were reproduced by using a Langevin function and exhibited a hysteresis loop at temperatures below the blocking temperature. Magnetic size effects and superparamagnetic behaviors were observed in the DyMnO3 nanoparticles.

  13. Polarization enhancement and ferroelectric switching enabled by interacting magnetic structures in DyMnO3 thin films

    PubMed Central

    Lu, Chengliang; Dong, Shuai; Xia, Zhengcai; Luo, Hui; Yan, Zhibo; Wang, Haowen; Tian, Zhaoming; Yuan, Songliu; Wu, Tao; Liu, Junming

    2013-01-01

    The mutual controls of ferroelectricity and magnetism are stepping towards practical applications proposed for quite a few promising devices in which multiferroic thin films are involved. Although ferroelectricity stemming from specific spiral spin ordering has been reported in highly distorted bulk perovskite manganites, the existence of magnetically induced ferroelectricity in the corresponding thin films remains an unresolved issue, which unfortunately halts this step. In this work, we report magnetically induced electric polarization and its remarkable response to magnetic field (an enhancement of ~800% upon a field of 2 Tesla at 2 K) in DyMnO3 thin films grown on Nb-SrTiO3 substrates. Accompanying with the large polarization enhancement, the ferroelectric coercivity corresponding to the magnetic chirality switching field is significantly increased. A picture based on coupled multicomponent magnetic structures is proposed to understand these features. Moreover, different magnetic anisotropy related to strain-suppressed GdFeO3-type distortion and Jahn-Teller effect is identified in the films. PMID:24291803

  14. Low Temperature Phonon Properties of Orthorhombic REMnO3

    NASA Astrophysics Data System (ADS)

    Liu, Zhenxian; Gao, Peng; Chen, Haiyan; Tyson, Trevor A.

    2010-03-01

    We present the temperature dependent phonon spectra of orthorhombic-LuMnO3 and DyMnO3. The temperature dependent phonon spectra results are compared with the XAFS measurement results to probe for structural changes in the low temperature region which may coincide with ferroelectric behavior.

  15. Large magneto (thermo) dielectric effect in multiferroic orthorhombic LuMnO3

    NASA Astrophysics Data System (ADS)

    Wang, L. J.; Chai, Y. S.; Feng, S. M.; Zhu, J. L.; Manivannan, N.; Jin, C. Q.; Gong, Z. Z.; Wang, X. H.; Li, L. T.

    2012-06-01

    We have investigated the relation between ferroelectric and magnetic orders of orthorhombic (o-) LuMnO3 ceramics. The increase of dielectric constant ɛ exceeds 82% near incommensurate to commensurate E-type antiferromagnetic (AFM) spin ordering transition temperature TL, reflecting a large magneto (thermo) dielectric response. Meanwhile, distinct anomalies and thermal hysteresis behavior are observed near this temperature in both temperature dependence of ɛ and specific heat Cp, indicating a strong coupling between FE and magnetic orders in o-LuMnO3. Comparing to o-HoMnO3, TmMnO3, and YbMnO3 with similar E-type AFM ground state, o-LuMnO3 has the largest magneto (thermo) dielectric effect

  16. Crystal-Orientation-Modulated Exchange Bias in Orthorhombic-YMnO3/La0.6Sr0.4MnO3 Multiferroic Heterostructures.

    PubMed

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

    2015-07-15

    The magnetic properties of the all-oxide multiferroic heterostructures composed of orthorhombic YMnO3 (YMO) with E-type antiferromagnetic and double-exchange ferromagnetic (FM) La0.6Sr0.4MnO3 (LSMO) were studied. An orientation-modulated exchange bias effect, which is related to the interfacial Mn-O-Mn bond angle, was discovered. Because of the large bond angle in YMO/LSMO(100) heterostructures, a strong exchange coupling at the interface is formed. This strong exchange coupling sustains an FM phase in YMO at the interface region. The FM phase with strong magnetocrystalline anisotropy contributes to the vertical shift and exchange bias effect in (100) orientation heterostructures. When LSMO (110) and (111) were layered with YMO, the Mn-O-Mn bond angle was reduced, leading to a weakened exchange coupling at the interface, and only a relatively small exchange bias at low temperatures was visible.

  17. Magnetic transition anisotropies in orthorhombic LuMnO3 and HoMnO3 multiferroic thin films

    NASA Astrophysics Data System (ADS)

    Tsai, T. Y.; Lin, T. H.; Slowry, S.; Luo, C. W.; Wu, K. H.; Lin, J.-Y.; Uen, T. M.; Juang, J. Y.

    2010-01-01

    We have successfully prepared the b-axis-oriented orthorhombic LuMnO3 (LuMO) and HoMnO3 (HMO) thin films by pulsed laser deposition on (110)-LaAlO3 substrates. The nearly perfect alignment between the film growth orientation and the substrate allows us to study the magnetic transitions along the respective crystal orientation, which has displayed marked anisotropic behaviours. In particular, with the largest ionic size difference between Lu and Ho for the family of RMnO3 displaying the E-type AFM, the effects of lattice distortion on the magnetic transition are compared.

  18. Electric field control of terahertz polarization in a multiferroic manganite with electromagnons.

    PubMed

    Shuvaev, A; Dziom, V; Pimenov, Anna; Schiebl, M; Mukhin, A A; Komarek, A C; Finger, T; Braden, M; Pimenov, A

    2013-11-27

    All-electrical control of a dynamic magnetoelectric effect is demonstrated in a classical multiferroic manganite DyMnO3, a material containing coupled antiferromagnetic and ferroelectric orders. Because of intrinsic magnetoelectric coupling with electromagnons a linearly polarized terahertz light rotates upon passing through the sample. The amplitude and the direction of the polarization rotation are defined by the orientation of ferroelectric domains and can be switched by static voltage. These experiments allow the terahertz polarization to be tuned using the dynamic magnetoelectric effect.

  19. Preparation, Structural, Optical, Electrical, and Magnetic Characterisation of Orthorhombic GdCr0.3Mn0.7O3 Multiferroic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Singh, Deepa; Bamzai, K. K.

    2017-01-01

    In this article, chromium-doped gadolinium manganate (GdCr0.3Mn0.7O3) nanoparticles has been prepared by wet-chemical route in order to investigate their structural, optical, electrical, and room temperature magnetic properties. Microstructural and compositional analyses have been carried out by X-ray diffraction and scanning electron microscopy (SEM). Synthesised material is found to be in orthorhombic crystal structure with Pbnm space group. The spherical morphology of the nanoparticles has been examined from the SEM images. Functional groups have been identified using Fourier transform infrared spectroscopy. Dielectric constant, dielectric loss, AC conductivity (σac), and activation energy in the range of 1 kHz-1 MHz from room temperature to high temperature (400°C) have been investigated. The frequency dependence of AC conductivity obeys the universal power law. The value of activation energy depends on increase in frequency. Room temperature magnetic behaviour suggests the material to be paramagnetic in nature.

  20. 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

  1. Magnetic Order and Ferroelectricity in RMnO3 Multiferroic Manganites: Coupline Between R- and Mn-spins

    SciTech Connect

    Aliouane, N.; Prokhnenko, O; Feyerherm, R; Mostovoy, M; Strempfer, J; Habicht, K; Rule, K; Dudzik, E; Wolter, A; et. al.

    2008-01-01

    Combining polarized and unpolarized neutron scattering techniques with x-ray resonant magnetic scattering we have studied the coupling between the Mn- and R-spin-ordering in the multiferroic RMnO3, R = Tb and Dy. Polarized neutron diffraction reveals the moment orientation associated with the various modes describing the complex magnetic ordering observed in TbMnO3, while neutron diffraction in high magnetic fields allows the identification of the origin (Mn versus Tb) of the various modes. In this way we identify significant Cx and Fz contributions from Tb arising from the coupling of Tb moments to the Mn cycloidal ordering. The x-ray studies give further insight into this coupling. In the ferroelectric phase, both TbMnO3 and DyMnO3 show an induced ordering of the R-ion with a propagation vector clamped to the Mn ordering. While in TbMnO3 this clamping leads to a ground state in which the two propagation vectors tTb and tMn obey the relation 3tTb-tMn = 1, in DyMnO3 the ferroelectric polarization is effectively enhanced. The theoretical analysis of these effects not only explains the observed behavior for R = Tb and Dy but can also be applied to understand the Mn-R interaction in the related compounds with R = Gd and Ho. Finally we show both experimentally and theoretically how the Mn-R coupling can enhance the ferroelectric polarization in this manganite's multiferroics.

  2. Single orthorhombic b axis orientation and antiferromagnetic ordering type in multiferroic CaMnO3 thin film with La0.67Ca0.33MnO3 buffer layer

    NASA Astrophysics Data System (ADS)

    Wang, F.; Dong, B. J.; Zhang, Y. Q.; Liu, W.; Zhang, H. R.; Bai, Y.; Li, S. K.; Yang, T.; Sun, J. R.; Wang, Z. J.; Zhang, Z. D.

    2017-09-01

    The detailed crystal structure and antiferromagnetic properties of a 42 nm thick CaMnO3 film grown on a LaAlO3 substrate with a 9 nm La0.67Ca0.33MnO3 buffer layer have been investigated. Compared with a CaMnO3 film directly grown on a LaAlO3 substrate, only one kind of orthorhombic b axis orientation along the [100] axis of the substrate is observed in the CaMnO3 film with a La0.67Ca0.33MnO3 buffer layer. To determine the antiferromagnetic ordering type of our CaMnO3 film with a buffer layer, the first-principles calculations were carried out with the results, indicating that the CaMnO3 film, even under a tensile strain of 1.9%, is still a compensated G-type antiferromagnetic order, the same as the bulk. Moreover, the exchange bias effect is observed at the interface of the CaMnO3/La0.67Ca0.33MnO3 film, further confirming the antiferromagnetic ordering of the CaMnO3 film with a buffer layer. In addition, it is concluded that the exchange bias effect originates from the spin glass state at the La0.67Ca0.33MnO3/CaMnO3 interface, which arises from a competition between the double-exchange ferromagnetic La0.67Ca0.33MnO3 and super-exchange antiferromagnetic CaMnO3 below the spin glass freezing temperature.

  3. Dynamical multiferroicity

    NASA Astrophysics Data System (ADS)

    Juraschek, Dominik M.; Fechner, Michael; Balatsky, Alexander V.; Spaldin, Nicola A.

    2017-06-01

    An appealing mechanism for inducing multiferroicity in materials is the generation of electric polarization by a spatially varying magnetization that is coupled to the lattice through the spin-orbit interaction. Here we describe the reciprocal effect, in which a time-dependent electric polarization induces magnetization even in materials with no existing spin structure. We develop a formalism for this dynamical multiferroic effect in the case for which the polarization derives from optical phonons, and compute the strength of the phonon Zeeman effect, which is the solid-state equivalent of the well-established vibrational Zeeman effect in molecules, using density functional theory. We further show that a recently observed behavior—the resonant excitation of a magnon by optically driven phonons—is described by the formalism. Finally, we discuss examples of scenarios that are not driven by lattice dynamics and interpret the excitation of Dzyaloshinskii-Moriya-type electromagnons and the inverse Faraday effect from the viewpoint of dynamical multiferroicity.

  4. Compression behavior of orthorhombic paracetamol.

    PubMed

    Joiris, E; Di Martino, P; Berneron, C; Guyot-Hermann, A M; Guyot, J C

    1998-07-01

    Orthorhombic crystals of paracetamol exhibit good technological properties during compression. The purpose of this study was to investigate the compression behavior of this substance and to compare it to that of monoclinic paracetamol. From the crystal structure, it could be hypothesized that sliding planes are present in the orthorhombic form, and could be responsible for an increase in crystal plasticity. Compression of pure orthorhombic or monoclinic paracetamol tablets was carried out on a fully instrumented single punch machine. Data was used to establish Heckel's profiles. Images of compressed crystals were obtained by scanning electron microscopy. Tabletability of the orthorhombic crystals was far better than that of the monoclinic ones, and capping was not observed even at high compression pressure. Compared to the monoclinic form, orthorhombic paracetamol exhibited greater fragmentation at low pressure, increased plastic deformation at higher pressure, and lower elastic recovery during decompression. Plastic behavior was confirmed by SEM - micrographs showing that crystals folded under pressure. A compactibility study showed that the nature of interparticle bonds was similar for both polymorphs, the number of bonds being greater for orthorhombic paracetamol. Unlike the monoclinic form, orthorhombic paracetamol is suitable for the direct compression process. The crystalline structure accounts for its better compression behavior, because of the presence of sliding planes.

  5. Multiferroic RMnO3 thin films

    NASA Astrophysics Data System (ADS)

    Fontcuberta, Josep

    2015-03-01

    Multiferroic materials have received an astonishing attention in the last decades due to expectations that potential coupling between distinct ferroic orders could inspire new applications and new device concepts. As a result, a new knowledge on coupling mechanisms and materials science has dramatically emerged. Multiferroic RMnO3 perovskites are central to this progress, providing a suitable platform to tailor spin-spin and spin-lattice interactions. With views towards applications, the development of thin films of multiferroic materials have also progressed enormously and nowadays thin-film manganites are available, with properties mimicking those of bulk compounds. Here we review achievements on the growth of hexagonal and orthorhombic RMnO3 epitaxial thin films and the characterization of their magnetic and ferroelectric properties, we discuss some challenging issues, and we suggest some guidelines for future research and developments. En ce qui concerne les applications, le développement de films minces de matériaux multiferroïques a aussi énormément progressé, et de nos jours des films minces de manganites avec des propriétés similaires à celles des matériaux massifs existent. Nous passons en revue ici les résultats obtenus dans le domaine de la croissance de couches minces épitaxiés de RMnO3 hexagonal et orthorhombique et de la caractérisation de leurs propriétés magnétiques et ferroélectriques. Nous discutons certains enjeux et proposons quelques idées pour des recherches et développements futurs.

  6. Multiferroic BaCoF4 in Thin Film Form: Ferroelectricity, Magnetic Ordering, and Strain.

    PubMed

    Borisov, Pavel; Johnson, Trent A; García-Castro, Andrés Camilo; KC, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo H; Lederman, David

    2016-02-03

    Multiferroic materials have simultaneous magnetic and ferroelectric long-range orders and can be potentially useful for a wide range of applications. Conventional ferroelectricity in oxide perovskites favors nonmagnetic electronic configurations of transition metal ions, thus limiting the number of intrinsic multiferroic materials. On the other hand, this is not necessarily true for multiferroic fluorides. Using molecular beam epitaxy, we demonstrate for the first time that the multiferroic orthorhombic fluoride BaCoF4 can be synthesized in thin film form. Ferroelectric hysteresis measurements and piezoresponse force microscopy show that the films are indeed ferroelectric. From structural information, magnetic measurements, and first-principles calculations, a modified magnetic ground state is identified which can be represented as a combination of bulk collinear antiferromagnetism with two additional canted spin orders oriented along orthogonal axes of the BaCoF4 unit cell. The calculations indicate that an anisotropic epitaxial strain is responsible for this unusual magnetic ground state.

  7. Multiferroics of spin origin.

    PubMed

    Tokura, Yoshinori; Seki, Shinichiro; Nagaosa, Naoto

    2014-07-01

    Multiferroics, compounds with both magnetic and ferroelectric orders, are believed to be a key material system to achieve cross-control between magnetism and electricity in a solid with minute energy dissipation. Such a colossal magnetoelectric (ME) effect has been an issue of keen interest for a long time in condensed matter physics as well as a most desired function in the emerging spin-related electronics. Here we begin with the basic mechanisms to realize multiferroicity or spin-driven ferroelectricity in magnetic materials, which have recently been clarified and proved both theoretically and experimentally. According to the proposed mechanisms, many families of multiferroics have been explored, found (re-discovered), and newly developed, realizing a variety of colossal ME controls. We overview versatile multiferroics from the viewpoints of their multiferroicity mechanisms and their fundamental ME characteristics on the basis of the recent advances in exploratory materials. One of the new directions in multiferroic science is the dynamical ME effect, namely the dynamical and/or fast cross-control between electric and magnetic dipoles in a solid. We argue here that the dynamics of multiferroic domain walls significantly contributes to the amplification of ME response, which has been revealed through the dielectric spectroscopy. Another related issue is the electric-dipole-active magnetic resonance, called electromagnons. The electromagnons can provide a new stage of ME optics via resonant coupling with the external electromagnetic wave (light). Finally, we give concluding remarks on multiferroics physics in the light of a broader perspective from the emergent electromagnetism in a solid as well as from the possible application toward future dissipationless electronics.

  8. Multiferroics of spin origin

    NASA Astrophysics Data System (ADS)

    Tokura, Yoshinori; Seki, Shinichiro; Nagaosa, Naoto

    2014-07-01

    Multiferroics, compounds with both magnetic and ferroelectric orders, are believed to be a key material system to achieve cross-control between magnetism and electricity in a solid with minute energy dissipation. Such a colossal magnetoelectric (ME) effect has been an issue of keen interest for a long time in condensed matter physics as well as a most desired function in the emerging spin-related electronics. Here we begin with the basic mechanisms to realize multiferroicity or spin-driven ferroelectricity in magnetic materials, which have recently been clarified and proved both theoretically and experimentally. According to the proposed mechanisms, many families of multiferroics have been explored, found (re-discovered), and newly developed, realizing a variety of colossal ME controls. We overview versatile multiferroics from the viewpoints of their multiferroicity mechanisms and their fundamental ME characteristics on the basis of the recent advances in exploratory materials. One of the new directions in multiferroic science is the dynamical ME effect, namely the dynamical and/or fast cross-control between electric and magnetic dipoles in a solid. We argue here that the dynamics of multiferroic domain walls significantly contributes to the amplification of ME response, which has been revealed through the dielectric spectroscopy. Another related issue is the electric-dipole-active magnetic resonance, called electromagnons. The electromagnons can provide a new stage of ME optics via resonant coupling with the external electromagnetic wave (light). Finally, we give concluding remarks on multiferroics physics in the light of a broader perspective from the emergent electromagnetism in a solid as well as from the possible application toward future dissipationless electronics.

  9. Multiferroic and Magnetoelectric Materials

    NASA Astrophysics Data System (ADS)

    Kleemann, Wolfgang; Binek, Christian

    Magnetoelectric (ME) materials are of utmost interest in view of both fundamental understanding and novel desirable applications. Despite its smallness the linear ME effect has been shown to control spintronic devices very efficiently, e.g. by using the classic ME antiferromagnet Cr2O 3. An electric field can switch its ferromagnetic surface magnetization and thus control exchange bias based spin valve devices. Similar nano-engineering concepts exist also for type-I multiferroic single phase materials like BiFeO3 and BiMnO3. ME response has been realized in stress-strain coupled multiphase magnetoelectric composites like BaTiO_3/Fe and—record high—in PZT/ FeBSiC, just right for sensorics applications. In type-II multiferroics, whose ferroelectricity is due to modulated magnetic ordering, the ME coupling is of fundamental interest. Higher order ME response characterizes disordered type-III multiferroics and extends the conventional multiferroic scenario toward ME multiglass (e.g. Sr1-xMnxTiO3) or relaxor spin glass (e.g. PbFe0.5Nb0.5O3).

  10. Symmetry in Multiferroics

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook

    2008-03-01

    Symmetries govern Nature ubiquitously from the beauty of human faces to the local gauge invariance of quantum field theory. Magnetic order in frustrated magnets can occur without space inversion symmetry. When it relaxes to the magnetically-ordered configuration through exchange-striction, lattice can also loose inversion symmetry, leading to the presence of ferroelectric polarization. In these magnetically-driven ferroelectrics, dielectric properties turn out to be highly susceptible to applied magnetic fields. Both symmetric and antisymmetric exchange coupling can be involved in the exchange-striction. One form of symmetry often broken in Nature is the symmetry between left- and right-handedness. For example, the manner in which light propagates naturally selects one handedness, and is customarily described by a right-handed rule, depicting the relationship among the oscillating electric field, magnetic field and propagation vector of light. Chiral molecules also have a definite handedness, and given the preponderance of chiral molecules, it is not surprising that most complex proteins as well as their constituent amino acids are chiral. What is remarkable however, is that most of naturally occurring amino acids share the same chirality; only left-handedness. Such handedness, or chirality, appears to be a characteristic signature of life. In the multiferroic spinel CoCr2O4, conical magnetic order accompanies ferroelectric polarization as well as ferromagnetic moment. The relevant handedness and chirality in the multiferroic state will be also discussed.

  11. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  12. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  13. 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

  14. Structure transition of multiferroic hexagonal TmMnO3 compound under high pressure

    NASA Astrophysics Data System (ADS)

    Wang, L. J.; Feng, S. M.; Zhu, J. L.; Liu, Q. Q.; Li, Y. C.; Li, X. D.; Liu, J.; Jin, C. Q.

    2010-06-01

    The high-pressure-induced structure transition in multiferroic hexagonal TmMnO3 (h-TmMnO3) has been investigated using an in situ angle-dispersive synchrotron X-ray diffraction technique in a diamond anvil cell. The experimental results show that the phase transition from ambient hexagonal to orthorhombic structure with space group Pbnm begins around 10.2 GPa. The Rietveld refinement method was used to determine the lattice parameters and lattice compressibility of the h-TmMnO3 compound from 0.8 to 28.6 GPa. The pressure evolution of average bond distances and bond angles between the Mn and O atoms in the ab-plane was obtained. The magnetic properties under different pressures as well as their effect on multiferroic properties are discussed using extrapolations from the empirical relation of magnetic order versus rare-earth ionic radius.

  15. Pressure Dependence of Structure Stability of Multiferroic Hexagonal-RMnO3

    NASA Astrophysics Data System (ADS)

    Chen, Zhiqiang; Gao, Peng; Tyson, Trevor. A.; Liu, Zhenxian; Hu, Jinzhu; Zhang, Chenglin; Kim, Sung-Baek; Cheong, Sang-Wook

    2009-03-01

    We present high pressure IR and X-ray diffraction measurements of the hexagonal multiferroic systems HoMnO3, YMnO3 and LuMnO3. Measurements were conducted over the pressure range ambient to ˜20 GPa. No phase changes were observed over this broad range of hydrostatic pressures. These suggest that the hexagonal structure is stable at higher pressures. The thermal treatment is necessary to overcome the barrier (breaking and reconnection of bonds) to achieve the hexagonal to orthorhombic phase change. A discussion of the effect of hydrostatic pressure on the ferroelectric properties of these systems will be given based on comparisons with density functional calculations.

  16. Multiferroic Properties of o-LuMnO3 Controlled by b-Axis Strain

    NASA Astrophysics Data System (ADS)

    Windsor, Y. W.; Huang, S. W.; Hu, Y.; Rettig, L.; Alberca, A.; Shimamoto, K.; Scagnoli, V.; Lippert, T.; Schneider, C. W.; Staub, U.

    2014-10-01

    Strain is a leading candidate for controlling magnetoelectric coupling in multiferroics. Here, we use x-ray diffraction to study the coupling between magnetic order and structural distortion in epitaxial films of the orthorhombic (o-) perovskite LuMnO3. An antiferromagnetic spin canting in the E-type magnetic structure is shown to be related to the ferroelectrically induced structural distortion and to a change in the magnetic propagation vector. By comparing films of different orientations and thicknesses, these quantities are found to be controlled by b-axis strain. It is shown that compressive strain destabilizes the commensurate E-type structure and reduces its accompanying ferroelectric distortion.

  17. Multiferroic properties of o-LuMnO3 controlled by b-axis strain.

    PubMed

    Windsor, Y W; Huang, S W; Hu, Y; Rettig, L; Alberca, A; Shimamoto, K; Scagnoli, V; Lippert, T; Schneider, C W; Staub, U

    2014-10-17

    Strain is a leading candidate for controlling magnetoelectric coupling in multiferroics. Here, we use x-ray diffraction to study the coupling between magnetic order and structural distortion in epitaxial films of the orthorhombic (o-) perovskite LuMnO(3). An antiferromagnetic spin canting in the E-type magnetic structure is shown to be related to the ferroelectrically induced structural distortion and to a change in the magnetic propagation vector. By comparing films of different orientations and thicknesses, these quantities are found to be controlled by b-axis strain. It is shown that compressive strain destabilizes the commensurate E-type structure and reduces its accompanying ferroelectric distortion.

  18. 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.

  19. Dispersion analysis of arbitrarily cut orthorhombic crystals.

    PubMed

    Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G

    2017-06-05

    We developed a measurement and evaluation scheme to perform dispersion analysis on arbitrarily cut orthorhombic crystals based on the schemes developed for triclinic and uniaxial crystals. As byproduct of dispersion analysis the orientations of the crystal axes are found. In contrast to the spectra of arbitrarily cut uniaxial crystals, where the fit routine has to separate two independent principal spectra, the spectra of arbitrarily cut orthorhombic crystals are a combination of three independent spectra and the evaluation scheme gets more complex. Dispersion analysis is exemplary performed on two different crystals, which show different spectral features and different levels of difficulties to evaluate. Neodymium gallate (NdGaO3) has broad overlapping reflections bands while topaz (Al2SiO4 [F, OH]2) has a quite high total number of infrared active bands. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Tunnel junctions with multiferroic barriers.

    PubMed

    Gajek, Martin; Bibes, Manuel; Fusil, Stéphane; Bouzehouane, Karim; Fontcuberta, Josep; Barthélémy, Agnès; Fert, Albert

    2007-04-01

    Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La(0.1)Bi(0.9)MnO(3) (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2 nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.

  1. Functional domain walls in multiferroics.

    PubMed

    Meier, Dennis

    2015-11-25

    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.

  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 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

  4. 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.

  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. Experimental and ab initio investigations of the x-ray absorption near edge structure of orthorhombic LuMnO3

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Borca, C. N.; Kleymenov, E.; Nachtegaal, M.; Delley, B.; Janousch, M.; Dönni, A.; Tachibana, M.; Kitazawa, H.; Takayama-Muromachi, E.; Kenzelmann, M.; Niedermayer, C.; Lippert, T.; Wokaun, A.; Schneider, C. W.

    2012-06-01

    X-ray near edge absorption spectroscopy was used to probe the electronic structure of multiferroic orthorhombic LuMnO3 polycrystalline samples and strained, twin-free orthorhombic (1-10) LuMnO3 films grown by pulsed laser deposition on (1-10) YAlO3 substrates. For all o-LuMnO3 samples x-ray near edge absorption spectroscopy spectra reveal that the pre-edge structure is influenced by the increase in MnO6 distortion as a result of the smaller Re-ion or film strain. Furthermore there is clear evidence of anisotropic Mn-O bonding and Mn orbital ordering along the c- and [110] direction. The experimental film and bulk data are in agreement with ab initio simulations.

  8. An orthorhombic polymorph of mulinic acid.

    PubMed

    Brito, Iván; Bórquez, Jorge; Loyola, Luis Alberto; López-Rodríguez, Matías; Cárdenas, Alejandro

    2010-01-09

    THE TITLE COMPOUND [SYSTEMATIC NAME: (3S,3aS,10bR)-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,10,10a,10b-deca-hydro-endo-epidioxy-cyclo-hepta-[e]indene-3a(1H)-carboxylic acid], C(20)H(30)O(4), is a polymorphic form of a previously reported structure [Loyola et al. (1990 ▶). Tetra-hedron, 46, 5413-5420]. The newly found ortho-rhom-bic polymorph crystallizes in P2(1)2(1)2(1) with two mol-ecules in the asymmetric unit. The mol-ecules are linked into discrete D(2) chains by simple O-H⋯O inter-actions. There are only slight variations in the mol-ecular geometry and supra-molecular organization in the crystal structures of the two polymorphs. The densities are 1.145 (monoclinic, P2(1)) and 1.155 Mg m(-3) (ortho-rhom-bic, P2(1)2(1)2(1)).

  9. 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.

  10. Ferroelectricity and competing interactions in Ho-deficient non-stoichiometric orthorhombic HoMnO3

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    We investigate the consequences of the Ho-deficient non-stoichiometry in orthorhombic HoMnO3 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.

  11. 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}.

  12. 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.

  13. 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

  14. Measurement Techniques of the Magneto-Electric Coupling in Multiferroics

    PubMed Central

    Fetisov, Y. K.; Caruntu, G.; Srinivasan, G.

    2017-01-01

    The current surge of interest in multiferroic materials demands specialized measurement techniques to support multiferroics research. In this review article we detail well-established measurement techniques of the magneto-electric coupling coefficient in multiferroic materials, together with newly proposed ones. This work is intended to serve as a reference document for anyone willing to develop experimental measurement techniques of multiferroic materials. PMID:28817089

  15. β phase and γ-β metal-insulator transition in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Palai, R.; Katiyar, R. S.; Schmid, H.; Tissot, P.; Clark, S. J.; Robertson, J.; Redfern, S. A. T.; Catalan, G.; Scott, J. F.

    2008-01-01

    We report on extensive experimental studies on thin film, single crystal, and ceramics of multiferroic bismuth ferrite BiFeO3 using differential thermal analysis, high-temperature polarized light microscopy, high-temperature and polarized Raman spectroscopy, high-temperature x-ray diffraction, dc conductivity, optical absorption and reflectivity, and domain imaging, and show that epitaxial (001) thin films of BiFeO3 are clearly monoclinic at room temperature, in agreement with recent synchrotron studies but in disagreement with all other earlier reported results. We report an orthorhombic order-disorder β phase between 820 and 925 (±5)°C , and establish the existence range of the cubic γ phase between 925 (±5) and 933 (±5)°C , contrary to all recent reports. We also report the refined Bi2O3-Fe2O3 phase diagram. The phase transition sequence rhombohedral-orthorhombic-cubic in bulk [monoclinic-orthorhombic-cubic in (001)BiFeO3 thin film] differs distinctly from that of BaTiO3 . The transition to the cubic γ phase causes an abrupt collapse of the band gap toward zero (insulator-metal transition) at the orthorhombic-cubic β-γ transition around 930°C . Our band structure models, high-temperature dc resistivity, and light absorption and reflectivity measurements are consistent with this metal-insulator transition.

  16. 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

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

    PubMed Central

    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/m2) 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. PMID:25387445

  18. 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.

  19. Simulations of twisted bilayer orthorhombic black phosphorus

    NASA Astrophysics Data System (ADS)

    Pan, Douxing; Wang, Tzu-Chiang; Xiao, Wende; Hu, Dongmei; Yao, Yugui

    2017-07-01

    We identified, by means of coincidence site lattice theory, an evaluative stacking phase with a wavelike Moiré pattern, denoted as 2 O -t α P , from all potentially twisted bilayer orthorhombic black phosphorus. Such a twisted stacking comes with a low formation energy of -162.8 meV , very close to existing AB stacking, according to first-principles calculations. Particularly, classic molecular dynamic simulations verified that the stacking can be directly obtained in an in situ cleavage. The stability of 2 O -t α P stacking can be directly attributed to the corrugated configuration of black phosphorus leading to the van der Waals constraining forces, where the top layer can get stuck to the bottom when one layer rotates in plane relative to the other by ˜70 .5∘ . Tribological analysis further revealed that the interlayer friction of 2 O -t α P stacking reaches up to 1.3 nN, playing a key role in the origin of 2 O -t α P .

  20. Symmetry conditions for type II multiferroicity in commensurate magnetic structures.

    PubMed

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

    2016-07-20

    Type II multiferroics are magnetically ordered phases that exhibit ferroelectricity as a magnetic induced effect. We show that in single-k magnetic phases the presence in the paramagnetic phase of non-symmorphic symmetry combined with some specific type of magnetic propagation vector can be sufficient for the occurrence of this type of multiferroic behaviour. Other symmetry scenarios especially favourable for spin driven multiferroicity are also presented. We review and classify known type II multiferroics under this viewpoint. In addition, some other magnetic phases which due to their symmetry properties can exhibit type II multiferroicity are pointed out.

  1. 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.

  2. 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

  3. Coupled Magnetic Cycloids in Multiferroic TbMnO3 and Eu3/4Y1/4MnO3

    SciTech Connect

    H Jang; J Lee; K Ko; W Noh; T Koo; J Kim; K Lee; J Park; C Zhang; S Kim

    2011-12-31

    Based on the detailed Mn L{sub 2,3}-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple A-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on F-type canting from the A type, and the ordering type becomes the off-phase synchronized bc cycloid in TbMnO{sub 3} or the tilted antiphase ab cycloid in Eu{sub 3/4}Y{sub 1/4}MnO{sub 3}. The F-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.

  4. 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.

  5. 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.

  6. Giant thermal Hall effect in multiferroics

    NASA Astrophysics Data System (ADS)

    Ideue, T.; Kurumaji, T.; Ishiwata, S.; Tokura, Y.

    2017-08-01

    Multiferroics, in which dielectric and magnetic orders coexist and couple with each other, attract renewed interest for their cross-correlated phenomena, offering a fundamental platform for novel functionalities. Elementary excitations in such systems are strongly affected by the lattice-spin interaction, as exemplified by the electromagnons and the magneto-thermal transport. Here we report an unprecedented coupling between magnetism and phonons in multiferroics, namely, the giant thermal Hall effect. The thermal transport of insulating polar magnets (ZnxFe1-x)2Mo3O8 is dominated by phonons, yet extremely sensitive to the magnetic structure. In particular, large thermal Hall conductivities are observed in the ferrimagnetic phase, indicating unconventional lattice-spin interactions and a new mechanism for the Hall effect in insulators. Our results show that the thermal Hall effect in multiferroic materials can be an effective probe for strong lattice-spin interactions and provide a new tool for magnetic control of thermal currents.

  7. 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.

  8. 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

  9. Multiferroics: Making a point of control

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei V.

    2017-02-01

    The coexistence of spin order and disorder at a critical point in the phase diagram of multiferroic materials may be exploited to locally control magnetoelectric coupling -- as is now shown for doped BiFeO3 by means of scanning probe microscopy.

  10. E -type noncollinear magnetic ordering in multiferroic o -LuMnO3

    NASA Astrophysics Data System (ADS)

    Mukherjee, Saumya; Dönni, Andreas; Nakajima, Taro; Mitsuda, Setsuo; Tachibana, Makoto; Kitazawa, Hideaki; Pomjakushin, Vladimir; Keller, Lukas; Niedermayer, Christof; Scaramucci, Andrea; Kenzelmann, Michel

    2017-03-01

    Multiferroic orthorhombic o -LuMnO3 exhibits large ferroelectric polarization induced by an E -type magnetic order. Recently, the E -type magnetic phase in LuMnO3 was proposed to feature magnetic moments tilted away from the collinear ordering. We employed neutron diffraction to determine the symmetry of the magnetic order in o -LuMnO3 . We observed that below TN=39 K, the Mn3 + spins order into an incommensurate amplitude-modulated phase that obeys the Pbnm crystal symmetry and is paraelectric. The incommensurate phase locks into a commensurate phase at TC=35.5 K described by a fully antiferromagnetic and noncollinear E -type order. This noncollinear E -type ordering breaks the spatial inversion symmetry and induces a spontaneous polarization at TC. At T =2 K, an appreciably large electric polarization was observed similar to that of other orthorhombic manganites featuring E -type magnetic order. We also present a Pbnm symmetry-allowed Dzyaloshinskii-Moriya interaction that explains the noncollinear E -type order in the commensurate phase. These results are in qualitative agreement with the type of distortions from collinear E -type antiferromagnetic order found using Monte Carlo simulation for rare-earth manganites [M. Mochizuki et al., Phys. Rev. B 84, 144409 (2011), 10.1103/PhysRevB.84.144409].

  11. 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.

  12. Sintering time effect on crystal structure and magnetic properties of Bi{sub 0.8}La{sub 0.2}FeO{sub 3} multiferroics

    SciTech Connect

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

    2016-05-06

    Effect of sintering time over the structure and magnetic properties has been studied in Bi{sub 0.8}La{sub 0.2}FeO{sub 3} 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.

  13. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    DTIC Science & Technology

    2016-06-15

    AFRL-AFOSR-JP-TR-2016-0061 Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials Sylvie Begin-Colin UNIVERSITE DE...TITLE AND SUBTITLE Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-12-1...Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials AOARD 124014 Final Report – S. Begin – IPCMS Strasbourg France

  14. 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.

  15. High pressure and multiferroics materials: a happy marriage

    PubMed Central

    Gilioli, Edmondo; Ehm, Lars

    2014-01-01

    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

  16. Bottom-up multiferroic nanostructures

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang

    Multiferroic and especially magnetoelectric (ME) nanocomposites have received extensive attention due to their potential applications in spintronics, information storage and logic devices. The extrinsic ME coupling in composites is strain mediated via the interface between the piezoelectric and magnetostrictive components. However, the design and synthesis of controlled nanostructures with engineering enhanced coupling remain a significant challenge. The purpose of this thesis is to create nanostructures with very large interface densities and unique connectivities of the two phases in a controlled manner. Using inorganic solid state phase transformations and organic block copolymer self assembly methodologies, we present novel self assembly "bottom-up" techniques as a general protocol for the nanofabrication of multifunctional devices. First, Lead-Zirconium-Titanate/Nickel-Ferrite (PZT/NFO) vertical multilamellar nanostructures have been produced by crystallizing and decomposing a gel in a magnetic field below the Curie temperature of NFO. The ensuing microstructure is nanoscopically periodic and anisotropic. The wavelength of the PZT/NFO alternation, 25 nm, agrees within a factor of two with the theoretically estimated value. The macroscopic ferromagnetic and magnetoelectric responses correspond qualitatively and semi-quantitatively to the features of the nanostructure. The maximum of the field dependent magnetoelectric susceptibility equals 1.8 V/cm Oe. Second, a magnetoelectric composite with controlled nanostructures is synthesized using co-assembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite (CFO) nano-cylinders within a matrix of ferroelectric Lead-Zirconium-Titanate (PZT). The initial magnetic permeability of the self-assembled CFO/PZT nanocomposite changes by a factor of 5 through the application of 2.5 V. This work may have significant impact on the

  17. Nonreciprocal Multiferroic Superlattices with Broken Parity Symmetry

    NASA Astrophysics Data System (ADS)

    Tang, Zhenghua; Zhang, Weiyi

    Multiferroic materials are characterized by the coexistence of ferroelectric and ferromagnetic (or antiferromagnetic) orders, the coupling to lattice vibration can be invoked either through piezoelectric or piezomagnetic effects. In this paper, the polaritonic band structures of multiferroic superlattices composed of oppositely polarized domains are investigated using the generalized transfer matrix method. For the primitive cell with broken parity symmetry, the polaritonic band structure is asymmetrical with respect to the forward and backward propagation directions (nonreciprocality). In particular, the band extreme points move away from the Brillouin zone center. This asymmetry in band-gap positions and widths can be used to design compact one-way optical isolators, while the extremely slow light velocities near the asymmetrical upper edges of lower bands includes the essential ingredients for designing slow light devices.

  18. 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°.

  19. 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.

  20. Bandgap tuning of multiferroic oxide solar cells

    NASA Astrophysics Data System (ADS)

    Nechache, R.; Harnagea, C.; Li, S.; Cardenas, L.; Huang, W.; Chakrabartty, J.; Rosei, F.

    2015-01-01

    Multiferroic films are increasingly being studied for applications in solar energy conversion because of their efficient ferroelectric polarization-driven carrier separation and above-bandgap generated photovoltages, which in principle can lead to energy conversion efficiencies beyond the maximum value (˜34%) reported in traditional silicon-based bipolar heterojunction solar cells. However, the efficiency reported so far is still too low (<2%) to be considered for commercialization. Here, we demonstrate a new approach to effectively tune the bandgap of double perovskite multiferroic oxides by engineering the cationic ordering for the case of Bi2FeCrO6. Using this approach, we report a power conversion efficiency of 8.1% under AM 1.5 G irradiation (100 mW cm-2) for Bi2FeCrO6 thin-film solar cells in a multilayer configuration.

  1. Collective magnetism at multiferroic vortex domain walls.

    PubMed

    Geng, Yanan; Lee, N; Choi, Y J; Cheong, S-W; Wu, Weida

    2012-12-12

    Cross-coupled phenomena of multiferroic domains and domain walls are of fundamental scientific and technological interest. Using cryogenic magnetic force microscopy, we find alternating net magnetic moments at ferroelectric domain walls around vortex cores in multiferroic hexagonal ErMnO(3), which correlate with each other throughout the entire vortex network. This collective nature of domain wall magnetism originates from the uncompensated Er(3+) moments at domain walls and the self-organization of the vortex network. Our results demonstrate that the collective domain wall magnetism can be controlled by external magnetic fields and represent a major advancement in the manipulation of local magnetic moments by harnessing cross-coupled domain walls.

  2. Thermodynamics of Multicaloric Effects in Multiferroics

    NASA Astrophysics Data System (ADS)

    Planes, Antoni; Castan, Teresa; Saxena, Avadh

    2014-03-01

    Ferroic and multiferoic materials thermally respond to externally driven changes of ferroic properties. Usually these changes are induced by application or removal of the field thermodynamically conjugated to a specific property. The isothermal change of entropy and the adiabatic change of temperature are commonly used in order to quantify the caloric response of a given material. From this perspective we provide a general thermodynamic framework to study multicaloric effects in multiferroic materials. This is applied to the case of a magnetoelectric multiferroic, which is described by means of a Landau free energy with a biquadratic coupling between polarization and magnetization. We obtain a phase diagram, the isothermal entropy change and the adiabatic temperature change across different continuous and first order transitions as the applied electric and magnetic fields are varied. The obtained multicaloric effects are suitably decomposed into the corresponding electrocaloric and magnetocaloric contributions.

  3. Ultra-Low Straintronics Using Multiferroic Composites

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    2013-08-01

    This paper reviews the recent developments on building nanoelectronics for our future information processing paradigm using multiferroic composites. With appropriate choice of materials, when a tiny voltage of few tens of millivolts is applied across a multiferroic composite, i.e., a piezoelectric layer stain-coupled with a magnetostrictive layer, the piezoelectric layer gets strained and the generated stress in the magnetostrictive layer switches the magnetization direction between its two stable states. We particularly review the switching dynamics of magnetization and calculation of associated metrics like switching delay and energy dissipation. Such voltage-induced magnetization switching mechanism dissipates a minuscule amount of energy of only 1 attojoule in sub-nanosecond switching delay at room-temperature. The performance metrics for such nonvolatile straintronic devices make them very attractive for building not only memory devices but also building logic, so that they can be deemed suitable for computational purposes. Hence, multiferroic straintronics has profound promise of contributing to beyond Moore's law technology, i.e., of being possible replacement of conventional charge-based electronics, which is reaching its performance limit specifically due to excessive energy dissipation.

  4. Impedance spectroscopy and ferromagnetic properties of Bi0.8Gd0.2FeO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Tian, Yahui; Xue, Fei; Fu, Qiuyun; Zhou, Dongxiang; Hu, Yunxiang; Zhou, Ling; Zheng, Zhiping; Xin, Zengnian

    2017-08-01

    Multiferroic Bi0.8Gd0.2FeO3 (BGFO) ceramics were prepared by a rapid-liquid phase sintering process. BGFO ceramics can be sintered at a sintering temperature range of 875 °C-940 °C and shown a pure orthorhombic (space group, Pnma) structure. The crystal symmetry and lattice parameters were determined from the Rietveld analysis for the experimental data. BGFO ceramics sintered at 900 °C exhibited high theoretical relative density (∼98%), strong ferroelectricity and good magnetism. BGFO ceramics exhibited the similar dielectric relaxation properties to the typical relaxor ferroelectrics. The role of oxygen vacancies at high temperature in dielectric and ac conductivity behavior was also discussed. The diffusing of structure defects between the grain and grain boundary was established using Impedance Spectroscopy (IS).

  5. Effects of holmium substitution on multiferroic properties in Tb0.67Ho0.33MnO3

    NASA Astrophysics Data System (ADS)

    Staruch, M.; Lawes, G.; Kumarasiri, A.; Cotica, L. F.; Jain, M.

    2013-02-01

    In this work, the structural, electrical, and magnetic properties of orthorhombic TbMnO3 and Tb0.67Ho0.33MnO3 ceramics are presented. The lattice parameters and the Mn-O-Mn bond angle were found to decrease with Ho-substitution as evidenced by Rietveld refinement of the X-ray diffraction data and Raman spectroscopy measurements. A weak ferromagnetic moment was observed in both dc and ac magnetic measurements of the Ho-substituted sample possibly due to spin canting in the antiferromagnetic phase. Tb0.67Ho0.33MnO3 was confirmed to be multiferroic with appearance of spontaneous polarization below 25 K and an additional increase in polarization ˜15.5 K associated with the ordering of the Ho3+ moments.

  6. Structural, electrical, and multiferroic properties of Aurivillius (Bi7- x La x )Fe3Ti3O21 thin films

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The effects of La3+- ion doping on the structural, electrical, and multiferroic properties of the six-layered Aurivillius-phase Bi7Fe3Ti3O21 thin film were investigated. A chemical solution deposition method was used to deposit the (Bi7- x La x )Fe3Ti3O21 ( x = 0 and 0.6) thin films on Pt(111)/Ti/SiO2/Si(100) substrates. The formation of Aurivillius orthorhombic structures was confirmed by using X-ray diffraction and Raman spectroscopy studies. The (Bi6.4La0.6)Fe3Ti3O21 thin film exhibited a low leakage current density (1.84 × 10-6 A/cm2 at an applied electric field of 100 kV/cm) and a large remnant polarization (20.20 μC/cm2 at an applied electric field of 318 kV/cm) as compared to the Bi7Fe3Ti3O21 thin film. The enhanced electrical and multiferroic properties are ascribed to a reduced oxygen concentration and a structural distortion. Both thin films were weakly ferromagnetic at room temperature.

  7. 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

  8. 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.

  9. Materials Data on DyMnO3 (SG:185) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-22

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  10. Materials Data on DyMnO3 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-22

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  11. Physical properties of multidimensional and multiferroic composites

    NASA Astrophysics Data System (ADS)

    Mori, Kiyotaka

    The properties of multidimensional and multiferroic composite systems consisting of smart materials are investigated for the intended use in microelectromechanical systems (MEMS) sensor and actuator applications. A multidimensional composite system combines within it different dimensionalities such as 1-D, 2-D, and 3-D constituents. A multiferroic composite system, meanwhile, consists of different ferroics such as ferroelastic, ferromagnetic and ferroelectric materials. We demonstrate effects of dimensionality on thermoelastic properties of NiTi/Si cantilevers for MEMS actuators. The stress state of the bimorph cantilevers is controlled by the dimensionality of the Si cantilever surface (2-D or 1-D corrugated) or the NiTi thin film (2-D or 1-D patterned). Compared to single dimensional NiTi/Si cantilevers the multidimensional device features an improved actuation performance, that is, it combines a small thermoelastic with a large martensitic transformational deflection. We also demonstrate magnetoelectric effects as examples of multiferroic composite systems for novel sensor applications. An example is the magnetic field induced magnetoelectric effect, MEH, in a ferroelectric/ferromagnetic composite PVDF/Terfenol-D. Here, an applied magnetic field induces a piezomagnetic strain in Terfenol-D, which couples to PVDF and induces a piezoelectric charge or voltage. We obtained a MEH coefficient of 1.43 V/cm Oe in agreement with an analytical calculation. The magnetoelastic coupling coefficient of the PVDF/Terfenol-D composite is estimated as 11%. Further, we demonstrate an electrical field induced magnetoelectric effect, MEE, in the ferromagnetic/ferroelectric composites CoB/PZT and PZT/Metglas/PZT. In this case the application of an electric field induces a piezoelectric strain in the PZT ceramic. The strain couples to piezomagnetic CoB or Metglas. Hence, the magnetization of the ferromagnetic materials changes with the electrical field applied to the ferroelectric

  12. Multiferroic vortices: arrested Kosterlitz-Thouless order

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook

    2012-02-01

    The fascinating concept of topological defects permeates ubiquitously our understanding of the early-stage universe, hurricanes, quantum matters such as superfluids and superconductors, and also technological materials such as liquid crystals and magnets. Large-scale spatial configurations of these topological defects have been investigated only in a limited degree. Exceptions include the cases of supercurrent vortices or liquid crystals, but they tend to exhibit either trivial or rather-irregular configurations. Hexagonal REMnO3 (RE= rare earths) with RE=Ho-Lu, Y, and Sc, is an improper ferroelectric where the size mismatch between RE and Mn induces a trimerization-type structural phase transition, and this structural transition leads to three structural domains, each of which can support two directions of ferroelectric polarization. We reported that domains in h-REMnO3 meet in cloverleaf arrangements that cycle through all six domain configurations, Occurring in pairs, the cloverleafs can be viewed as vortices and antivortices, in which the cycle of domain configurations is reversed. Vortices and antivortices are topological defects: even in a strong electric field they won't annihilate. These ferroelectric vortices/antivortices are found to be associated with intriguing magnetism. The seemingly-irregular configurations of a zoo of multiferroic vortices and antivortices in h-REMnO3 can be neatly analyzed in terms of graph theory and this graph theoretical analysis reflects the nature of self-organized criticality in complexity phenomena as well as the condensation and eventual annihilation processes of topological vortex-antivortex pairs. Furthermore, these numerous multiferroic vortices/antivortices can be understood as an arrested Kosterlitz-Thouless phase. [4pt] [1] Insulating Interlocked Ferroelectric and Structural Antiphase Domain Walls in Multiferroic YMnO3, T. Choi, - - -, S-W. Cheong, Nature Materials 9, 253 (2010). [0pt] [2] Self

  13. Electronic and magnetic properties of orthorhombic iron selenide

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.

    2016-02-01

    Iron orbitals in orthorhombic iron selenide (FeSe) can produce chargelike multipoles that are polar (parity-odd). Orbitals in question include Fe (3 d ), Fe (4 p ), and p -type ligands that participate in transport properties and bonding. The polar multipoles may contribute weak, space-group forbidden Bragg spots to diffraction patterns collected with x rays tuned in energy to a Fe atomic resonance (Templeton & Templeton scattering). Ordering of conventional, axial magnetic dipoles does not accompany the tetragonal-orthorhombic structural phase transition in FeSe, unlike other known iron-based superconductors. We initiate a new line of inquiry for this puzzling property of orthorhombic FeSe, using a hidden magnetic order that belongs to the m'm'm' magnetic crystal class. It is epitomized by the absence of ferromagnetism and axial magnetic dipoles and the appearance of magnetic monopoles and magnetoelectric quadrupoles. A similar magnetic order occurs in cuprate superconductors, yttrium barium copper oxide and Hg1201, where it was unveiled with the Kerr effect and in Bragg diffraction patterns revealed by polarized neutrons.

  14. Multiferroic behavior at a spin state transition

    NASA Astrophysics Data System (ADS)

    Zapf, Vivien; Chikara, Shalinee; Singleton, John; Lin, Shizeng; Batista, Cristian; Scott, Brian; Smythe, Nathan

    Traditionally, multiferroic behavior is studied in materials with coexisting long-range orders, such as ferromagnetism and ferroelectricity. Here we present multiferroic behavior at a spin-state transition (SST). SSTs, for example, the S = 1 to S = 2 transition in Mn3+ can become cooperative magneto-structural phase transitions due to structural coupling between ions. SSTs are accompanied by change in the orbital occupation and hence, strongly coupled to the lattice and charge degrees of freedom. They are a dominant functionality in metal-organic materials, persisting up to room temperature in some compounds. We demonstrate that a magnetic SST can induce ferroelectricity. We study a Mn-based metal-organic system in which a three-fold degenerate dynamic Jahn-Teller effect at high temperatures vanishes when the temperature is lowered, and the system drops into a lower spin state. Application of a magnetic field restores the high spin Jahn-Teller-active state and allows the Jahn Teller distortions to order cooperatively, creating a dielectric constant change and a net electric polarization. We use high magnetic fields at the NHMFL to study the magnetic and electric behavior of this system across a significant fraction of its T-H phase space, and compare to theoretical modeling.

  15. 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

  16. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    DTIC Science & Technology

    2016-05-23

    AFRL-AFOSR-JP-TR-2016-0056 Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials Yuanzhe Piao SEOUL NATIONAL UNIVERSITY...Mar 2015 4. TITLE AND SUBTITLE Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER... polymer composites consisting of magnetic nanoparticles that possess high , and low tan and polymer matrix with high dielectric constant and

  17. Enhancing magnetoelectric effect in multiferroic composite bilayers via flexoelectricity

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  18. Multiferroic, magnetoelectric and optical properties of Mn doped BiFeO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Chauhan, Sunil; Kumar, Manoj; Chhoker, Sandeep; Katyal, S. C.; Singh, Hemant; Jewariya, Mukesh; Yadav, K. L.

    2012-03-01

    Mn doped BiFeO3 (5, 10 and 15 mol%) nanoparticles were synthesized using sol-gel technique. The influence of Mn doping on structural, dielectric, magnetic, magnetoelectric and optical properties of BiFeO3 was studied. Rietveld refinement of XRD patterns showed rhombohedral to orthorhombic phase transition for 15 mol% Mn doped BiFeO3 sample. Magnetic measurements revealed the enhancement of ferromagnetic property with increasing Mn doping in BiFeO3. The characteristic dielectric anomaly, expected in the vicinity of antiferromagnetic transition temperature TN (Neel temperature) was found in all Mn doped BiFeO3 samples. The magnetoelectric coupling was evidenced by the change in capacitance with the change in the applied magnetic field. On increasing Mn concentration from 5 to 15 mol% in BiFeO3, a change in magnetocapacitance from 1.46% to 2.6% showed the improvement of multiferroic properties. In order to explore the optical properties of Mn doped BiFeO3 nanoparticles, their photoluminescent properties were also investigated.

  19. 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.

  20. 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.

  1. Universal Octahedral-Site Distortion in Orthorhombic Perovskite Oxides

    NASA Astrophysics Data System (ADS)

    Zhou, J.-S.; Goodenough, J. B.

    2005-02-01

    Lattice parameters of the orthorhombic perovskites RMO3 ( R=rare earth, M=Ti, V, …, Ni, and Ga) have been simulated based on the ionic M-O bond length and rigid MO6/2 octahedra. Comparison with experimental data shows that the long-standing lattice-parameter anomaly generally found for the larger R3+ ions in these families is caused by a structural feature that is not revealed by the geometric tolerance factor widely used for the perovskites.

  2. 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.

  3. Magnetodielectric coupling in multiferroic holmium iron garnets

    NASA Astrophysics Data System (ADS)

    Malar Selvi, M.; Chakraborty, Deepannita; Venkateswaran, C.

    2017-02-01

    Single phase magneto-electric multiferroics require a large magnetic or electric field for producing magneto-electric (ME) and magnetodielectric (MD) effects. For utilizing these effects in devices investigations on the room temperature and low field MD studies are necessary. Recently, efforts have been largely devoted to the investigation of rare earth iron garnets. In the physical method, the preparation of rare earth iron garnet requires high sintering temperature and processing time. To solve these problems, ball milling assisted microwave sintering technique is used to prepare nanocrystalline holmium iron garnets (Ho3Fe5O12). Magnetic and dielectric properties of the prepared sample are investigated. These properties get enhanced in nanocrystalline form when compared to the bulk. The MD coupling of the prepared sample is evident from the anomaly in the temperature dependent dielectric constant plot and the ME coupling susceptibility is derived from the room temperature MD measurements.

  4. 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.

  5. Synthetic magnetoelectric coupling in a nanocomposite multiferroic

    DOE PAGES

    Jain, P.; Wang, Q.; Roldan, M.; ...

    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. Finally, 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

  6. Synthetic magnetoelectric coupling in a nanocomposite multiferroic

    PubMed Central

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

    2015-01-01

    Given the paucity of single phase multiferroic materials (with large ferromagnetic moment), composite systems seem an attractive solution to realize magnetoelectric coupling between ferromagnetic and ferroelectric order parameters. Despite having antiferromagnetic order, BiFeO3 (BFO) has nevertheless been a key material due to excellent ferroelectric properties at room temperature. We studied a superlattice composed of 8 repetitions of 6 unit cells of La0.7Sr0.3MnO3 (LSMO) grown on 5 unit cells of BFO. Significant net uncompensated magnetization in BFO, an insulating superlattice, is demonstrated using polarized neutron reflectometry. Remarkably, the magnetization enables magnetic field to change the dielectric properties of the superlattice, which we cite as an example of synthetic magnetoelectric coupling. Importantly, controlled creation of magnetic moment in BFO is a much needed path toward design and implementation of integrated oxide devices for next generation magnetoelectric data storage platforms. PMID:25766205

  7. Study a compound orthorhombic lattice pattern in dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Dong, Lifang; Gao, Xing; Liu, Weibo; Wei, Lingyan; Pan, Yuyang

    2016-12-01

    The compound orthorhombic lattice pattern which is composed of the bright spot and the dim spot is observed for the first time in a dielectric barrier discharge system. It is found that the dim spot is located at the gravity center of the surrounding three bright spots. The discharge bifurcates from a square lattice, hexagon pattern to compound orthorhombic lattice pattern and finally changes to an irregular pattern. The phase diagram of the pattern types as a function of the applied voltage and the argon concentration is given. The spatio-temporal dynamics of the pattern is studied by the time correlation measurement and the high speed video camera images. Results show that the dim spot is formed by both volume discharge and surface discharge induced by the bright spot. The differences of plasma parameters between the bright spots and the dim spots obtained by optical emission spectroscopy verify that the dim spot is formed by both volume discharge and surface discharge. To better understand the mechanism of firing of the dim spots for the same conditions as in the first phase diagram, the phase diagram of the mechanism of firing of the dim spots as a function of the gas pressure and the argon concentration is given. The simulation of the electric fields of wall charges accumulated by bright spots further verifies that the bright spot has an effect on the formation of dim spot.

  8. Multiferroic Phases and Transitions in Ferroelectric Lead Titanate Nanodots

    PubMed Central

    Xu, Tao; Shimada, Takahiro; Uratani, Yoshitaka; Wang, Xiaoyuan; Wang, Jie; Kitamura, Takayuki

    2017-01-01

    Discovery of novel phases and their associated transitions in low-dimensional nanoscale systems is of central interest as the origin of emergent phenomena and new device paradigms. Although typical ferroelectrics such as PbTiO3 exhibit diverse phase transition sequences, the conventional incompatible mechanisms of ferroelectricity and magnetism keep them as simply nonmagnetic phases, despite the immense practical prospective of multiferroics in novel functional devices. Here, we demonstrate using density function theory that PbTiO3 nanodots exhibit unconventional multiferroic phase transitions. The nanosize and nonstoichiometric effects intrinsic to nanodots bring about the coexistence of ferromagnetism with the host electric polarization, mediated by the termination and surface morphology. We also predict the key features of the size-dependent phase diagram of nanodots that involve a rich sequence of ferroelectric-multiferroic-ferromagnetic/nonmagnetic (FE-MF-FM/NM) multiferroic phase transitions. The present work thus provides an avenue to realizing multiferroics and multifunctional oxides in low-dimensional systems. PMID:28367955

  9. Epitaxial thin films of novel multiferroic double perovskites.

    NASA Astrophysics Data System (ADS)

    Venimadhav, A.; Li, Qi

    2006-03-01

    Recently multiferroic materials have attracted great interest. However, relatively a few pure multiferroic compounds are currently known. Here we show the exploration of design of multiferroic properties in double perovskites by combining the ferrolectrisity driven by the Bi lone pairs and selectively choosing the 3d transition metals following Goodenough-Kanamori's rules to bring in ferromagnetism. We present growth issues in stabilizing the single phase, epitaxial thin films of new double perovskite multiferroic systems such as Bi2NiMnO6, Bi2FeCrO6 and La2NiMnO6 by pulsed laser deposition. Targets of these compositions were synthesized by solid state method with 15% of excess Bi in the composition to compensate the volatility of Bi during the deposition. We also present the synthesis of Bi2FeCrO6 by growing a superlattice structures from individual targets of Bi FeO3 and BiCrO3. In the cubic double perovskites, cations show rock salt kind of ordering in the (111) direction and hence growing these films on STO (111) substrates has an advantage. We present the growth, structural and multiferroic properties in these double perovskite thin films..

  10. 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

  11. Orthorhombic C32: a novel superhard sp3 carbon allotrope.

    PubMed

    Zhang, Miao; Liu, Hanyu; Du, Yonghui; Zhang, Xinxin; Wang, Yanchao; Li, Quan

    2013-09-07

    Using a recently developed 'Crystal structure AnaLYsis by Particle Swarm Optimization' (CALYPSO) algorithm on a structural search, we predicted a novel sp(3) carbon allotrope possessing an orthorhombic lattice with the space group Cmmm (oC32). The calculated elastic constants and the simulated hardness revealed that oC32 simultaneously possesses ultra-incompressible and superhard properties with a high bulk modulus of 457 GPa and a high Vickers hardness of 96.2 GPa. This oC32 phase is dynamically stable and energetically more preferable than the experientially observed cold-compressed carbon, thus oC32 is expected to be experimentally synthesizable under extreme conditions. These results further expand the list of meta-stable carbon allotropes and superhard materials under atmospheric and extreme conditions.

  12. 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.

  13. 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.

  14. Novel superhard carbon: C-centered orthorhombic C8.

    PubMed

    Zhao, Zhisheng; Xu, Bo; Zhou, Xiang-Feng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan; Wang, Hui-Tian; Tian, Yongjun

    2011-11-18

    A novel carbon allotrope of C-centered orthorhombic C(8) (Cco-C(8)) is predicted by using a recently developed particle-swarm optimization method on structural search. Cco-C(8) adopts a sp(3) three-dimensional bonding network that can be viewed as interconnected (2,2) carbon nanotubes through 4- and 6-member rings and is energetically more favorable than earlier proposed carbon polymorphs (e.g., M carbon, bct-C(4), W carbon, and chiral C(6)) over a wide range of pressures studied (0-100 GPa). The simulated x-ray diffraction pattern, density, and bulk modulus of Cco-C(8) are in good accordance with the experimental data on structurally undetermined superhard carbon recovered from cold compression of carbon nanotube bundles. The simulated hardness of Cco-C(8) can reach a remarkably high value of 95.1 GPa, such that it is capable of cracking diamond.

  15. Nuclear quadrupole resonance studies of amorphous, orthorhombic, and rhombohedral arsenic

    SciTech Connect

    Jellison, G.E. Jr.; Petersen, G.L.; Taylor, P.C.

    1980-10-15

    Pulsed nuclear quadrupole resonance (NQR) experiments have been performed on three forms of elemental arsenic: amorphous (a), rhombohedral (rh), and orthorhombic (or). The temperature dependence of the spin-lattice relaxation time (T/sub 1/) provides evidence for the existence of disorder (tunneling) modes in a-As. It is found that the NQR line shape of a-As is highly asymmetric, and this asymmetry is attributed to a distribution of dihedral angles in a-As. The observed NQR frequencies indicate that the amount of bonding s admixture is different in each material (rh-As:3%, or-As:7%, a-As:10%). Simple calculations in comparison with x-ray results indicate that the bonding configurations in these three forms of arsenic do not necessarily correspond to maximum overlap of bonding orbitals on adjacent atoms.

  16. Electronically-driven orthorhombic distortion in FeSe

    NASA Astrophysics Data System (ADS)

    Watson, Matthew; Davies, Nathaniel; Haghighirad, Amir; Narayanan, Arjun; Kim, Timur; Hoersch, Moritz; Blake, Samuel; Coldea, Amalia

    2015-03-01

    FeSe is structurally the simplest of Fe-based superconductors, and exhibits a tetragonal-to-orthorhombic structural transition at ~ 90 K, but no long-range magnetism at any temperature. We report measurements of the resistivity anisotropy in FeSe above Ts finding a large and divergent response to an applied strain, with a comparable magnitude and temperature-dependence to measurements in Ba(Fe1-xCox)2As2, but opposite sign. We compare this data with literature reports on NMR and our own ARPES data, which taken together indicate that the structural transition is electronically-driven with orbital degrees of freedom playing a central role. This work was supported by EPSRC, UK (EP/I004475/1) and Diamond Light Source.

  17. Solute transport in orthorhombic lysozyme crystals: a molecular simulation study.

    PubMed

    Malek, Kourosh

    2007-12-01

    Long-time equilibrium molecular dynamics simulations were performed to study the passage of a substrate, L: -arabinose, through nanopores of orthorhombic hen egg white lysozyme crystals. Cross-linked protein crystals (CLPC), as novel biological nanoporous media, consist of an extensive regular matrix of chiral solvent-filled nanopores via which ions and solutes, e.g. sugars and amino acids, travel in and out. We studied the diffusive motion of arabinose inside protein channels. The computed diffusion coefficients within the crystal were orders of magnitudes lower relative to the diffusion coefficient of the solute in water. This study is valuable for understanding the nature of solute-protein interactions and transport phenomena in CLPCs and provides an understanding of biocatalytic and bioseparation processes using CLPC.

  18. Te vacancy-driven superconductivity in orthorhombic molybdenum ditelluride

    NASA Astrophysics Data System (ADS)

    Cho, Suyeon; Kang, Se Hwang; Yu, Ho Sung; Kim, Hyo Won; Ko, Wonhee; Hwang, Sung Woo; Han, Woo Hyun; Choe, Duk-Hyun; Jung, Young Hwa; Chang, Kee Joo; Lee, Young Hee; Yang, Heejun; Wng Kim, Sung

    2017-06-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have received great attentions because of diverse quantum electronic states such as topological insulating (TI), Weyl semimetallic (WSM) and superconducting states. Recently, the superconducting states emerged in pressurized semimetallic TMDs such as MoTe2 and WTe2 have become one of the central issues due to their predicted WSM states. However, the difficulty in synthetic control of chalcogen vacancies and the ambiguous magneto transport properties have hindered the rigorous study on superconducting and WSM states. Here, we report the emergence of superconductivity at 2.1 K in Te-deficient orthorhombic T d-MoTe2-x with an intrinsic electron-doping, while stoichiometric monoclinic 1T‧-MoTe2 shows no superconducting state down to 10 mK, but exhibits a large magnetoresistance of 32 000% at 2 K in a magnetic field of 14 T originating from nearly perfect compensation of electron and hole carriers. Scanning tunnelling spectroscopy and synchrotron x-ray diffraction combined with theoretical calculations clarify that Te vacancies trigger superconductivity via intrinsic electron doping and the evolution of the T d phase from the 1T‧ phase below 200 K. Unlike the pressure-induced superconducting state of monoclinic MoTe2, this Te vacancy-induced superconductivity is emerged in orthorhombic MoTe2, which is predicted as Weyl semimetal, via electron-doping. This chalcogen vacancy induced-superconductivity provides a new route for cultivating superconducting state together with WSM state in 2D van der Waals materials.

  19. Cautions to predicate multiferroic by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Liu, Chen; Ma, Jing; Ma, Ji; Zhang, Yujun; Chen, Jiahui; Nan, Ce-Wen

    2017-05-01

    With the ever-increasing research activities in multiferroic driven by its profound physics and enormous potential for application, magnetic force microscopy (MFM), as a variety of atomic force microscope (AFM), has been brought to investigate the magnetic properties and the voltage controlled magnetism, especially in thin films and heterostructures. Here by taking a representative multiferroic system BiFeO3/La0.67Sr0.33MnO3 heterostructure and a ferroelectric PMN-PT single crystal for examples, we demonstrated that the MFM image is prone to be seriously interfered by the electrostatic interaction between the tip and sample surface, and misleads the predication of multiferroic. Assisted by the scanning Kelvin probe microscopy (SKPM), the origin and mechanism were discussed and an effective solution was proposed.

  20. Anisotropic symmetric exchange as a new mechanism for multiferroicity

    NASA Astrophysics Data System (ADS)

    Feng, J. S.; Xiang, H. J.

    2016-05-01

    Discovering new magnetoelectric multiferroics is an exciting research area. Very recently, a collinear antiferromagnetic spin order was found to induce a ferroelectric polarization in a highly symmetric cubic perovskite LaMn3Cr4O12 . This spin-driven ferroelectricity could not be explained by any of the existing multiferroic models. Here, we put forward a new model, i.e., anisotropic symmetric exchange, to understand this phenomenon, which was confirmed by density functional calculations and tight-binding simulations. Furthermore, our perturbation analysis shows that the anisotropic symmetric exchange term can be even stronger than the conventional contributions in some 5 d systems. Our multiferroic model can not only explain the experimental results, but also may open a new avenue for exploring exotic magnetoelectric coupling effects.

  1. Ultrafast spectroscopy of semiconducting and multiferroic materials

    NASA Astrophysics Data System (ADS)

    Lou, Shitao

    In this thesis, we have used ultrafast spectroscopy to study the optical properties of two semiconductors, GaAs and Ge, and one hexagonal multiferroic material, LuMnO3. Both semiconductor and multiferroic materials are of great importance technologically and economically. By using ultrafast spectroscopy, we obtained time resolved electron and phonon dynamics directly, which is unavailable by conventional optical methods. Electron-hole pairs, coherent phonon oscillations and an optical coherence response are excited when femtosecond laser pulses interact with either GaAs or Ge crystals. The coherent phonon mode excited in GaAs/Ge is of T 2/T2g symmetry as determined by probe beam polarization analysis. The pump polarization dependence of the phonon oscillation is consistent with the transient stimulated Raman scattering (TSRS) mechanism. From the pump polarization dependence of the phonon oscillation, we have identified two excitation mechanisms contributing to the coherent phonon in GaAs, one is consistent with TSRS, and the other is consistent with screening effect of photoexcited electrons. The femtosecond laser pulse, with 800 nm center wavelength and polarized perpendicular to the c axis of LuMnO3, excites a narrow intra-atomic dxy, x2--y2 to d3z2--r2 transition in Mn. This excitation results in a transient reflectivity change for light of the same wavelength and polarization, by partial saturation of the transition. The relaxation time of this electronic excitation is about 1 ps. Furthermore, the electronic excitation resonantly excites a coherent optical phonon with A1 symmetry (TO: 118 cm--1 and LO: 120 cm --1), involving Lu ions motion along the c-axis, which is identified to be the soft mode driving the ferroelectric transition. A remarkable reversal of the sign of the oscillation amplitude (pi phase shift) of the reflectivity curve was observed upon comparing longitudinal optical (LO) with transverse optical (TO) mode geometries. The phase reversal is

  2. Persistent multiferroicity without magnetoelectric effects in CuO

    NASA Astrophysics Data System (ADS)

    Wang, Fen; Zou, Tao; Liu, Yi; Yan, Li-Qin; Sun, Young

    2011-09-01

    Multiferroicity and magnetoelectric effects in CuO have been investigated by measurements of magnetization, dielectric constant, and electric polarization with and without magnetic fields. Dielectric anomalies which indicate ferroelectric transitions were observed at two magnetic transition temperatures. Ferroelectric polarization was well detected in the incommensurate spiral phase. However, both dielectric constant and polarization have little changes in a 7 T magnetic field. Our study suggests that although with a high multiferroic temperature, the spiral spin structure in CuO is very stable and the induced ferroelectricity sustains even in a high magnetic field, which results in little magnetoelectric effects.

  3. 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

  4. Spin polarization of excitons in organic multiferroic composites.

    PubMed

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

    2016-06-23

    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.

  5. Theory of giant-caloric effects in multiferroic materials

    NASA Astrophysics Data System (ADS)

    Vopson, Melvin M.

    2013-08-01

    A generalized thermodynamic theory of giant-caloric effects in coupled multiferroic solids is introduced. The generalized theory allows analytical derivation of any caloric effect in solids displaying any type of cross coupling. In the particular cases of the non-coupled ferroic materials, the theory reproduces the well-known formulae describing magnetocaloric, electrocaloric or elastocaloric effects. This work facilitates adequate modeling tools and analytical relations capable of predicting caloric effects in complex coupled multiferroic materials, which is very beneficial to future developments in solid-state cooling technologies.

  6. Multiferroic properties of Indian natural ilmenite

    NASA Astrophysics Data System (ADS)

    Acharya, Truptimayee; Choudhary, R. N. P.

    2017-03-01

    In this communication, the main results and analysis of extensive studies of electric and magnetic characteristics (relative dielectric constant, tangent loss, electric polarization, electric transport, impedance, magnetic polarization and magneto-electric coupling coefficient) of Indian natural ilmenite (NI) have been presented. Preliminary structural analysis was studied by Rietveld refinement of room temperature XRD data, which suggests the rhombohedral crystal system of NI. Maxwell-Wagner mechanism was used to explain the nature of the frequency dependence of the relative dielectric constant. The impedance analysis reveals that below 270 °C, only the bulk contributes, whereas at higher temperature, both grain boundary and the bulk contribute to the resistive characteristics of the material. The magnitude of the depression angles of the semicircles in the Nyquist plot has been estimated. The correlated barrier hopping model has been used to explain the frequency dependence of ac conductivity of the material. The activation energy of the compound has been estimated using the temperature dependence of dc conductivity plot. The obtained polarization hysteresis loops manifest improper ferroelectric behavior of NI. The existence M-H hysteresis loop supports anti-ferromagnetism in the studied material. The magneto-electric voltage coupling coefficient is found to be 0.7 mV/cm Oe. Hence, other than dielectric constant, electric polarization, magnetization and magneto-electric studies support the existence of multiferroic properties in NI.

  7. Facile strategy and mechanism for orthorhombic SnO2 thin films

    NASA Astrophysics Data System (ADS)

    Chen, Zhiwen; Lai, Joseph K. L.; Shek, Chan-Hung

    2006-12-01

    Orthorhombic phase SnO2 is a material with unknown optical, electrical, and gas-sensing properties. It was found previously only at high pressures and temperatures. A facile strategy for the synthesis of orthorhombic SnO2 is of fundamental importance. Using pulsed-laser deposition, the authors report a kind of experimental realization of a pure orthorhombic SnO2 thin film under low pressure and temperature that are much lower than those of traditional methods. The optical properties of an orthorhombic SnO2 thin film were measured by spectrophotometric transmittance. The oxygen exchange reaction mechanism at the grain interfaces was proposed to explain the formation and optical properties of this orthorhombic phase.

  8. Microscopic evidence of magnetic and structure phase transition in multiferroic spinel FeV2O4

    NASA Astrophysics Data System (ADS)

    Myoung, Bo Ra; Kim, Sam Jin; Lim, Jung Tae; Kouh, Taejoon; Kim, Chul Sung

    2017-05-01

    We report the microscopic evidence for magnetic and structural phase transitions in multiferroic spinel FeV2O4 from the hyperfine magnetic interaction. FeV2O4 sample shows three different crystal structures with the phase transitions from tetragonal to orthorhombic structure around 70 K, from orthorhombic to tetragonal structure around 109 K, and from tetragonal to cubic structure around 140 K. Mössbauer spectra of FeV2O4, obtained at various temperatures, were analyzed with severely distorted 8-line below TC, and doublet at TC. Also, the Mössbauer spectra change from doublet to singlet around TJT ≅ 140 K due to the reduction of Jahn-Teller effect. The value of electric quadrupole splitting (Δ EQ ) is 3.05 mm/s at 4.2 K, indicating the noncollinear spin structure with strong polarization from the gap energy of 5T2g band, Δ1 ≅ 0. Whereas, there is collinear spin structure between TS ≅ 70 K < T < TC ≅ 109 K, since Δ1 in this temperature range increases from the value when T < TS due to the non-degenerate energy state with commensuration in the collinear state. Also, we have found that large polar angle θ for T < TS suggests the spin of the Fe2+ cations aligns along c-axis with the distortion in the a-b plane, while the small azimuthal angle θ suggest the direction of the spin is within ab-plane for TS < T < TC.

  9. Two ortho-rhom-bic polymorphs of hydro-morphone.

    PubMed

    Mazurek, Jaroslaw; Hoffmann, Marcel; Fernandez Casares, Ana; Cox, D Phillip; Minardi, Mathew D; Sasine, Josh

    2016-05-01

    Conditions to obtain two polymorphic forms by crystallization from solution were determined for the analgesic drug hydro-morphone [C17H19NO3; systematic name: (4R,4aR,7aR,12bS)-9-hy-droxy-3-methyl-1,2,4,4a,5,6,7a,13-octa-hydro-4,12-methano-benzofuro[3,2-e]iso-quinolin-7-one]. These two crystalline forms, designated as I and II, belong to the P212121 ortho-rhom-bic space group. In both polymorphs, the hydro-morphone mol-ecules adopt very similar conformations with some small differences observed only in the N-methyl amine part of the mol-ecule. The crystal structures of both polymorphs feature chains of mol-ecules connected by hydrogen bonds; however, in form I this inter-action occurs between the hydroxyl group and the tertiary amine N atom whereas in form II the hydroxyl group acts as a donor of a hydrogen bond to the O atom from the cyclic ether part.

  10. Covalent dependence of octahedral rotations in orthorhombic perovskite oxides.

    PubMed

    Cammarata, Antonio; Rondinelli, James M

    2014-09-21

    The compositional dependence of metal-oxygen BO6 octahedral distortions, including bond elongations and rotations, is frequently discussed in the ABO3 perovskite literature; structural distortions alleviate internal stresses driven by under- or over-coordinated bond environments. Here we identify the dependence of octahedral rotations from changes in metal-oxygen bond covalency in orthorhombic perovskites. Using density functional theory we formulate a covalency metric, which captures both the real and k-space interactions between the magnitude and sense, i.e., in-phase or out-of-phase, octahedral rotations, to explore the link between the ionic-covalent Fe-O bond and the interoctahedral Fe-O-Fe bond angles in Pbnm ferrates. Our survey finds that the covalency of the metal-oxygen bond is correlated with the rotation amplitude: We find the more covalent the Fe-O bond, the less distorted is the structure and the more important the long-range inter-octahedral (Fe-O-Fe bond angle) interactions. Finally, we show how to indirectly tune the B-O bond covalency by A-cation induced BO6 rotations independent of ionic size, facilitating design of targeted bonding interactions in complex perovskites.

  11. Theoretical Study of Orthorhombic Distortions in High-Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Schnyder, Andreas; Manske, Dirk; Mudry, Christopher; Sigrist, Manfred

    2006-03-01

    Using a Fermi-liquid-based theory we calculate the response function for various spectroscopic probes in hole-doped high-TC superconductors, and determine the effects of orthorhombic distortions in the crystal lattice and asymmetry in the superconducting gap function. Employing the two-dimensional one-band Hubbard model and a generalized RPA-type theory we consider anisotropic hopping parameters (txty) and a mixing of d- and s-wave symmetry of the superconducting order parameter. Within this model, both the electronic Raman spectra and the dynamical magnetic susceptibility [1] are studied in detail. The relevance of these calculations to electronic Raman scattering measurements and inelastic neutron scattering experiments [2] on untwinned YBa2Cu3O6+x are discussed. [1] A. P. Schnyder, D. Manske, C. Mudry, and M. Sigrist, cond-mat/0510790. [2] V. Hinkov, S. Pailhes, P. Bourges, Y. Sidis, A. Ivanov, A. Kulakov, C. T. Lin, D. P. Chen, C. Bernhard, and B. Keimer, Nature 430, 650 (2004).

  12. Directed Growth of Orthorhombic Crystals in a Micropillar Array.

    PubMed

    Holzner, Gregor; Binder, Claudia; Kriel, Frederik H; Priest, Craig

    2017-02-14

    We report directed growth of orthorhombic crystals of potassium permanganate in spatial confinement of a micropillar array. The solution is introduced by spontaneous wicking to give a well-defined film (thickness 10-15 μm; volume ∼600 nL) and is connected to a reservoir (several microliters) that continuously "feeds" the evaporating film. When the film is supersaturated, crystals nucleate and preferentially grow in specific directions guided by one of several possible linear paths through the pillar lattice. Crystals that do not initially conform are stopped at an obstructing pillar, branch into another permitted direction, or spontaneously rotate to align with a path and continue to grow. Microspectroscopy is able to track the concentration of solute in a small region of interest (70 × 100 μm(2)) near to growing crystals, revealing that the solute concentration initially increases linearly beyond the solubility limit. Crystal growth near the region of interest resulted in a sharp decrease in the local solute concentration (which rapidly returns the concentration to the solubility limit), consistent with estimated diffusion time scales (<1 s for a 50 μm length scale). The ability to simultaneously track solute concentration and control crystal orientation in nanoliter samples will provide new insight into microscale dynamics of microscale crystallization.

  13. 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.

  14. Water in hydrated orthorhombic lysozyme crystal: Insight from atomistic simulations.

    PubMed

    Hu, Zhongqiao; Jiang, Jianwen; Sandler, Stanley I

    2008-08-21

    Biologically important water in orthorhombic lysozyme crystal is investigated using atomistic simulations. A distinct hydration shell surrounding lysozyme molecules is found from the number distribution of water molecules. While the number of water molecules in the hydration shell increases, the percentage decreases as the hydration level rises. Adsorption of water in the lysozyme crystal shows type-IV behavior. At low hydration levels, water molecules primarily intercalate the minor pores and cavity in the crystal due to the strong affinity between protein and water. At high hydration levels, the major pores are filled with liquidlike water as capillary condensation occurs. A type-H4 hysteresis loop is observed in the adsorption and desorption isotherms. The locations of the water molecules identified from simulation match fairly well with the experimentally determined crystallographic hydration sites. As observed in experiment, water exhibits anomalous subdiffusion because of the geometric restrictions and interactions of protein. With increasing hydration level, this anomaly is reduced and the diffusion of water tends to progressively approach normal Brownian diffusion. The flexibility of protein framework slightly enhances water mobility, but this enhancement decreases with increasing hydration level.

  15. Water in hydrated orthorhombic lysozyme crystal: Insight from atomistic simulations

    NASA Astrophysics Data System (ADS)

    Hu, Zhongqiao; Jiang, Jianwen; Sandler, Stanley I.

    2008-08-01

    Biologically important water in orthorhombic lysozyme crystal is investigated using atomistic simulations. A distinct hydration shell surrounding lysozyme molecules is found from the number distribution of water molecules. While the number of water molecules in the hydration shell increases, the percentage decreases as the hydration level rises. Adsorption of water in the lysozyme crystal shows type-IV behavior. At low hydration levels, water molecules primarily intercalate the minor pores and cavity in the crystal due to the strong affinity between protein and water. At high hydration levels, the major pores are filled with liquidlike water as capillary condensation occurs. A type-H4 hysteresis loop is observed in the adsorption and desorption isotherms. The locations of the water molecules identified from simulation match fairly well with the experimentally determined crystallographic hydration sites. As observed in experiment, water exhibits anomalous subdiffusion because of the geometric restrictions and interactions of protein. With increasing hydration level, this anomaly is reduced and the diffusion of water tends to progressively approach normal Brownian diffusion. The flexibility of protein framework slightly enhances water mobility, but this enhancement decreases with increasing hydration level.

  16. Thermal Decomposition Characteristics of Orthorhombic Ammonium Perchlorate (o-AP)

    SciTech Connect

    Behrens, R.; Minier, L.

    1999-03-01

    Preliminary STMBMS and SEM results of the thermal decomposition of AP in the orthorhombic phase are presented. The overall decomposition is shown to be complex and controlled by both physical and chemical processes. The data show that the physical and chemical processes can be probed and characterized utilizing SEM and STMBMS. The overall decomposition is characterized by three distinguishing features: an induction period, and accelerator period and a deceleratory period. The major decomposition event occurs in the subsurface of the AP particles and propagates towards the center of the particle with time. The amount of total decomposition is dependent upon particle size and increases from 23% for {approximately}50{micro}m-diameter AP to 33% for {approximately}200{micro}m-diameter AP. A conceptual model of the physical processes is presented. Insight into the chemical processes is provided by the gas formation rates that are measured for the gaseous products. To our knowledge, this is the first presentation of data showing that the chemical and physical decomposition processes can be identified from one another, probed and characterized at the level that is required to better understand the thermal decomposition behavior of AP. Future work is planned with the goal of obtaining data that can be used to develop a mathematical description for the thermal decomposition of o-AP.

  17. Two-dimensional multiferroics in monolayer group IV monochalcogenides

    NASA Astrophysics Data System (ADS)

    Wang, Hua; Qian, Xiaofeng

    2017-03-01

    Low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. Here, using first-principles theory we predict that two-dimensional (2D) monolayer group IV monochalcogenides including GeS, GeSe, SnS, and SnSe are a class of 2D semiconducting multiferroics with giant strongly-coupled in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. Their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. More importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their great potentials for tunable multiferroic functional devices by manipulating external electrical, mechanical, and optical field to control the internal responses, and enable the development of four device concepts including 2D ferroelectric memory, 2D ferroelastic memory, and 2D ferroelastoelectric nonvolatile photonic memory as well as 2D ferroelectric excitonic photovoltaics.

  18. Static and Dynamic Magnetoelectric Effects in Multiferroic Hexaferrites

    NASA Astrophysics Data System (ADS)

    Chun, Sae Hwan

    2014-03-01

    Multiferroics, wherein magnetism and ferroelectricity coexist, are of great interest for the prospect of new multifunctional devices by utilizing cross-coupling between the electric and magnetic properties. In most multiferroics currently known, however, the magnetoelectric (ME) coupling does not reach the level enough for the practical applications and the cross control of electric polarization by magnetic field or magnetization by electric field has been realized only at low temperature. Hence, for use in the ME devices, it is essential to increase both the ME sensitivity and the operating temperature. From investigation of multiferroic hexaferrites, we discover a chemical route to effectively tailor the critical magnetic field inducing electric polarization in (Ba,Sr)2Zn2 Fe12O22 (Zn2Y-type) by Al-substitution, yielding a giant magnetoelectric susceptibility. In (Ba,Sr)3Co2Fe24O41 (Co2Z-type) hexaferrite single crystals, we realize the control of magnetization by electric field at room temperature. In addition to those static ME properties, a dynamic ME effect, electric-dipole-active magnon resonance in THz frequency range, is also found in the Co2Z-type hexaferrite, exhibiting the spectral weight even at room temperature. The unprecedented supreme static and dynamic ME phenomena in the hexaferrites may provide a pathway to overcome the challenge in application of multiferroics for the real devices. Currently at Materials Science Division, Argonne National Laboratory, Argonne, IL 60439.

  19. Electrically driven magnetic antenna based on multiferroic composites

    NASA Astrophysics Data System (ADS)

    Wang, X.-G.; Sukhov, A.; Chotorlishvili, L.; Jia, C.-L.; Guo, G.-H.; Berakdar, J.

    2017-03-01

    We suggest and demonstrate via large scale numerical simulations an electrically operated spin-wave inducer based on composite multiferroic junctions. Specifically, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.

  20. 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.

  1. Electrically driven magnetic antenna based on multiferroic composites.

    PubMed

    Wang, X-G; Sukhov, A; Chotorlishvili, L; Jia, C-L; Guo, G-H; Berakdar, J

    2017-03-08

    We suggest and demonstrate via large scale numerical simulations an electrically operated spin-wave inducer based on composite multiferroic junctions. Specifically, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.

  2. Multiferroic and magnetoelectric nanocomposites for data processing

    NASA Astrophysics Data System (ADS)

    Kleemann, Wolfgang

    2017-06-01

    Recent progress in preparing and understanding composite magnetoelectrics is highlighted. Apart from optimized standard solutions novel methods of switching magnetism with electric fields and vice versa with focus on magnetoelectric (ME) data processing in multiferroic and magnetoelectric nanocomposites deserve particular interest. First, we report on the patented MERAM, which uses the electric field control of exchange bias in a layered composite via an epitaxial magnetoelectric Cr2O3 layer exchange coupled to a Pt/Co/Pt trilayer. It promises to crucially reduce Joule energy losses in RAM devices. Second, magnetic switching of the electric polarization by a transverse magnetic field in a composite of CoFe2O4 nanopillars embedded in a vertically poled BaTiO3 thick film produces a regular surface polarization pattern with rectangular local symmetry. Its possible use for data processing is discussed. Third, in the relaxor ferroelectric single-phase compound (BiFe0.9Co0.1O3)0.4-(Bi1/2K1/2TiO3)0.6 polar nanoregions emerging from ferrimagnetic Bi(Fe,Co)O3 regions embedded in a Bi1/2K1/2TiO3 relaxor component transform into ferroelectric clusters and simultaneously enable congruent magnetic clusters. The local polarization and magnetization couple with record-high direct and converse magnetoelectric coupling coefficients, α  ≈  1.0  ×  10-5 s m-1. These ‘multiferroic’ clusters are promising for applications in data storage or processing devices.

  3. 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).

  4. Electric-Field-Induced Magnetization Reversal in a Ferromagnet-Multiferroic Heterostructure

    DTIC Science & Technology

    2011-11-14

    system. The effect is reversible and mediated by an interfacial magnetic coupling dictated by the multiferroic. Such electric-field control of a...system. The effect is reversible and mediated by an interfacial magnetic coupling dictated by the multiferroic. Such electric-field control of a...by an interfacial magnetic coupling dictated by the multiferroic. Such electric-field control of a magnetoelectric device demonstrates an avenue for

  5. Multiferroicity in B-site ordered double perovskite Y2MnCrO6

    NASA Astrophysics Data System (ADS)

    Fang, Yong; Yan, Shi-Ming; Qiao, Wen; Wang, Wei; Wang, Dun-Hui; Du, You-Wei

    2014-11-01

    Double perovskite manganite Y2MnCrO6 ceramic is synthesized and its multiferroic properties are investigated. Novel multiferroic properties are displayed with respect to other multiferroics, such as high ferroelectric phase transition temperature, and the coexistence of ferrimagnetism and ferroelectricity. Moreover, the ferroelectric polarization of Y2MnCrO6 below the magnetic phase temperature can be effectively tuned by an external magnetic field, showing a remarkable magnetoelectric effect. These results open an effective avenue to explore magnetic multiferroics with spontaneous magnetization and ferroelectricity, as well as a high ferroelectric transition temperature.

  6. 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).

  7. 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

  8. 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.

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

    PubMed

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

    2016-01-18

    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.

  10. Nanoscale structural modulation and enhanced room-temperature multiferroic properties

    NASA Astrophysics Data System (ADS)

    Sun, Shujie; Huang, Yan; Wang, Guopeng; Wang, Jianlin; Fu, Zhengping; Peng, Ranran; Knize, Randy J.; Lu, Yalin

    2014-10-01

    Availability of a single-phase multiferroic material functional at room temperature poses a big challenge, although it is very important to both fundamental physics and application development. Recently, layered Aurivillius oxide materials, one of the most promising candidates, have attracted considerable interest. In this work, we investigated the nanoscale structural evolution of the six-layer Bi7Fe3-xCoxTi3O21 when substituting excessive Co. Nanoscale structural modulation (NSM) occurred at the boundaries when changing the material gradually from the originally designed six-layer nanoscale architecture down to five and then four, when increasing the Co content, inducing a previously unidentified analogous morphotropic transformation (AMT) effect. The AMT's net contribution to the enhanced intrinsic multiferroic properties at room temperature was confirmed by quantifying and deducting the contribution from the existing impurity phase using derivative thermo-magneto-gravimetry measurements (DTMG). Significantly, this new AMT effect may be caused by a possible coupling contribution from co-existing NSM phases, indicating a potential method for realizing multiferroic materials that function at room temperature.Availability of a single-phase multiferroic material functional at room temperature poses a big challenge, although it is very important to both fundamental physics and application development. Recently, layered Aurivillius oxide materials, one of the most promising candidates, have attracted considerable interest. In this work, we investigated the nanoscale structural evolution of the six-layer Bi7Fe3-xCoxTi3O21 when substituting excessive Co. Nanoscale structural modulation (NSM) occurred at the boundaries when changing the material gradually from the originally designed six-layer nanoscale architecture down to five and then four, when increasing the Co content, inducing a previously unidentified analogous morphotropic transformation (AMT) effect. The AMT

  11. Pressure-induced amorphization in orthorhombic Ta2O5: An intrinsic character of crystal

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The phase transition of orthorhombic Ta2O5 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 B0 = 139 (9) GPa for the orthorhombic Ta2O5 is derived from the P-V data. We suggest that the pressure-induced amorphization (PIA) in Ta2O5 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 Ta2O5 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.

  12. 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.

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

    SciTech Connect

    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.

  14. Magnetoelectrical control of nonreciprocal microwave response in a multiferroic helimagnet

    NASA Astrophysics Data System (ADS)

    Iguchi, Y.; Nii, Y.; Onose, Y.

    2017-05-01

    The control of physical properties by external fields is essential in many contemporary technologies. For example, conductance can be controlled by a gate electric field in a field effect transistor, which is a main component of integrated circuits. Optical phenomena induced by an electric field such as electroluminescence and electrochromism are useful for display and other technologies. Control of microwave propagation is also important for future wireless communication technology. Microwave properties in solids are dominated mostly by magnetic excitations, which cannot be easily controlled by an electric field. One solution to this problem is to use magnetically induced ferroelectrics (multiferroics). Here we show that microwave nonreciprocity, that is, different refractive indices for microwaves propagating in opposite directions, could be reversed by an external electric field in a multiferroic helimagnet Ba2Mg2Fe12O22. This approach offers an avenue for the electrical control of microwave properties.

  15. Deterministic control of ferroelastic switching in multiferroic materials.

    PubMed

    Balke, N; Choudhury, S; Jesse, S; Huijben, M; Chu, Y H; Baddorf, A P; Chen, L Q; Ramesh, R; Kalinin, S V

    2009-12-01

    Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.

  16. 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

  17. 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.

  18. Electrically controllable spontaneous magnetism in nanoscale mixed phase multiferroics.

    PubMed

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

    2011-01-01

    Magnetoelectrics and multiferroics present exciting opportunities for electric-field control of magnetism. However, there are few room-temperature ferromagnetic-ferroelectrics. Among the various types of multiferroics the bismuth ferrite system has received much attention primarily because both the ferroelectric and the antiferromagnetic orders are quite robust at room temperature. Here we demonstrate the emergence of an enhanced spontaneous magnetization in a strain-driven rhombohedral and super-tetragonal mixed phase of BiFeO₃. Using X-ray magnetic circular dichroism-based photoemission electron microscopy coupled with macroscopic magnetic measurements, we find that the spontaneous magnetization of the rhombohedral phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent tetragonal-like phase and the epitaxial constraint. Reversible electric-field control and manipulation of this magnetic moment at room temperature is also shown.

  19. 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.

  20. Multiferroic behavior in Lu2MnCoO6

    NASA Astrophysics Data System (ADS)

    Zapf, Vivien; Mun, E.-D.; Ueland, B. G.; Thompson, J. D.; Singleton, J.; Gardner, J.; Yáñez-Vilar, S.; Sánchez-Anduacute; jar; , M.; Señaris-Rodriguez, M. A.; Mira, J.; Biskup, N.; Batista, C. D.

    2012-02-01

    Lu2MnCoO6 is a new member of the multiferroics with coupling between net magnetization and net electric polarization. Similar to Ca3MnCoO6, an up-up-down-down order of the magnetic spins is found that breaks spatial-inversion symmetry and creates an electric polarization. Unlike Ca3MnCoO6, the Co and Mn ions are both in a S = 3/2 state, the ordering temperature is 42 K, and the magnetic field needed to suppress electric polarization is 2 T. We present an experimental study of the multiferroic properties and spin structure including neutron diffraction, electric polarization, magnetization, dielectric constant, and specific heat measurements.

  1. Spin model of magnetostrictions in multiferroic Mn perovskites.

    PubMed

    Mochizuki, Masahito; Furukawa, Nobuo; Nagaosa, Naoto

    2010-07-16

    We theoretically study origins of the ferroelectricity in the multiferroic phases of the rare-earth (R) Mn perovskites, RMnO(3), by constructing a realistic spin model including the spin-phonon coupling, which reproduces the entire experimental phase diagram in the plane of temperature and Mn-O-Mn bond angle for the first time. Surprisingly we reveal a significant contribution of the symmetric (S·S)-type magnetostriction to the ferroelectricity even in a spin-spiral-based multiferroic phase, which can be larger than the usually expected antisymmetric (S×S)-type contribution. This explains well the nontrivial behavior of the electric polarization. We also predict the noncollinear deformation of the E-type spin structure and a wide coexisting regime of the E and spiral states, which resolve several experimental puzzles.

  2. Engineering Ferroic and Multiferroic Materials for Active Cooling Applications

    DTIC Science & Technology

    2014-02-11

    also demonstrated. KEYWORDS: CVD graphene , ferroelectrics, PbZr0.2Ti0.8O3, polarization reversal, interface The rich two-dimensional physics in a...Research Laboratory Central Facilities, University of Illinois. Author contributions R.X. and L.W.M. designed the experiments ; L.W.M. supervised the project...SECURITY CLASSIFICATION OF: The objectives of this program are to design , synthesize, and characterize multiferroic materials and heterostructures and

  3. 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.

  4. Giant Optical Second Harmonic Generation in Two-Dimensional Multiferroics.

    PubMed

    Wang, Hua; Qian, Xiaofeng

    2017-08-09

    Nonlinear optical properties of materials such as second and higher order harmonic generation and electro-optic effect play pivotal roles in lasers, frequency conversion, electro-optic modulators, switches, and so forth. The strength of nonlinear optical responses highly depends on intrinsic crystal symmetry, transition dipole moments, specific optical excitation, and local environment. Using first-principles electronic structure theory, here we predict giant second harmonic generation (SHG) in recently discovered two-dimensional (2D) ferroelectric-ferroelastic multiferroics-group IV monochalcogenides (i.e., GeSe, GeS, SnSe, and SnS). Remarkably, the strength of SHG susceptibility in GeSe and SnSe monolayers is more than 1 order of magnitude higher than that in monolayer MoS2, and 2 orders of magnitude higher than that in monolayer hexagonal BN. Their extraordinary SHG is dominated by the large residual of two opposite intraband contributions in the SHG susceptibility. More importantly, the SHG polarization anisotropy is strongly correlated with the intrinsic ferroelastic and ferroelectric orders in group IV monochalcogenide monolayers. Our present findings provide a microscopic understanding of the large SHG susceptibility in 2D group IV monochalcogenide multiferroics from first-principles theory and open up a variety of new avenues for 2D ferroelectrics, multiferroics, and nonlinear optoelectronics, for example, realizing active electrical/optical/mechanical switching of ferroic orders in 2D multiferroics and in situ ultrafast optical characterization of local atomistic and electronic structures using noncontact noninvasive optical SHG techniques.

  5. Size effects on magnetoelectric response of multiferroic composite with inhomogeneities

    NASA Astrophysics Data System (ADS)

    Yue, Y. M.; Xu, K. Y.; Chen, T.; Aifantis, E. C.

    2015-12-01

    This paper investigates the influence of size effects on the magnetoelectric performance of multiferroic composite with inhomogeneities. Based on a simple model of gradient elasticity for multiferroic materials, the governing equations and boundary conditions are obtained from an energy variational principle. The general formulation is applied to consider an anti-plane problem of multiferroic composites with inhomogeneities. This problem is solved analytically and the effective magnetoelectric coefficient is obtained. The influence of the internal length (grain size or particle size) on the effective magnetoelectric coefficients of piezoelectric/piezomagnetic nanoscale fibrous composite is numerically evaluated and analyzed. The results suggest that with the increase of the internal length of piezoelectric matrix (PZT and BaTiO3), the magnetoelectric coefficient increases, but the rate of increase is ratcheting downwards. If the internal length of piezoelectric matrix remains unchanged, the magnetoelectric coefficient will decrease with the increase of internal length scale of piezomagnetic nonfiber (CoFe2O3). In a composite consisiting of a piezomagnetic matrix (CoFe2O3) reinforced with piezoelectric nanofibers (BaTiO3), an increase of the internal length in the piezomagnetic matrix, results to a decrease of the magnetoelectric coefficient, with the rate of decrease diminishing.

  6. 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.

  7. 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.

  8. Electric Field Control of Ferromagnetism and Magnetic Devices Using Multiferroics

    NASA Astrophysics Data System (ADS)

    Heron, John Thomas

    This dissertation presents a study of a heterostructure composed of room temperature magnetoelectric multiferroic BiFeO3 and ferromagnetic Co.90Fe.10, with specific interest in understanding the interfacial coupling mechanisms in this system and establishing the electric field control of a magnetization and spintronic devices. The field of spintronics has been plagued with the problem of a large energy dissipation as a consequence of the resistive losses that come during the writing of the magnetic state (i.e. reversing the magnetization direction). The primary aim of the work presented here is to investigate and understand a novel heterostructure and materials interface that can be demonstrated as a pathway to low energy spintronics. In this dissertation, I will address the specific aspects of multiferroicity, magnetoelectricity, and interface coupling that must be addressed in order to reverse a magnetization with an electric field. Furthermore, I will demonstrate the reversal of a magnetization with an electric field in single and multilayer magnetic devices. The primary advances made as a result of the work described herein are the use of epitaxial constraints to control the nanoscale domain structure of a multiferroic which is then correlated to the domain structure of the exchange coupled ferromagnet. Additionally, the magnetization direction of the ferromagnetic layer is controlled with only an applied electric field at both macroscopic and microscopic scales. Lastly, using this electric field control of ferromagnetism, the first demonstration of a magnetoelectric memory bit is presented.

  9. Multiferroic properties of nanostructured barium doped bismuth ferrite

    NASA Astrophysics Data System (ADS)

    El-Desoky, M. M.; Ayoua, M. S.; Mostafa, M. M.; Ahmed, M. A.

    2016-04-01

    Multiferroic nanoparticles of Bi1-xBaxFeO3 (x=0.10, 0.15, 0.20, 0.25 mol%) samples were prepared using conventional solid-state method. The nanostructural, multiferroic properties of the prepared samples was investigated. X-ray diffraction (XRD) patterns show the formation of BiBaFeO3 with single-phase rhombohedral-hexagonal structure. Spin canting or impurity phase could be a probable reason for the origin of ferromagnetism. At room temperature, remnant magnetization increased 18 times more than its initial value. A change in the magnetization is observed around 742-833 K. Néel temperature (TN) registers an increase of 30 times of Ba-doped BiFeO3 in comparison with undoped BiFeO3. The dielectric properties were affected by the properties of the substitutional ions as well as the crystalline structure of the present samples. Substitution with Ba2+ ions also improved the ferroelectric polarization with remanent polarization of 89 μC/cm2. The simultaneous occurrence of ferromagnetism and ferroelectric hysteresis loops in BiBaFeO3 multiferroic nanoparticles system at room temperature makes it a potential candidate for information storage and spintronics.

  10. Magneto-electric Coupling in Domain Engineered Multiferroic Thin Film Heterostructures

    DTIC Science & Technology

    2014-11-09

    SECURITY CLASSIFICATION OF: Epitaxial BiFeO3 (BFO) thin films have potential for designing novel magneto -electric devices if their unrivaled room...Aug-2013 Approved for Public Release; Distribution Unlimited Final Report: Magneto -electric Coupling in Domain Engineered Multiferroic Thin Film...53715 -1218 ABSTRACT Final Report: Magneto -electric Coupling in Domain Engineered Multiferroic Thin Film Heterostructures Report Title Epitaxial

  11. Exchange-biased hybrid ferromagnetic-multiferroic core-shell nanostructures.

    PubMed

    Shi, Da-Wei; Javed, Khalid; Ali, Syed Shahbaz; Chen, Jun-Yang; Li, Pei-Sen; Zhao, Yong-Gang; Han, Xiu-Feng

    2014-07-07

    Artificial exchange-biased two-phase core-shell nanostructures consisting of ferromagnetic (Ni) and multiferroic (BiFeO3) materials were manufactured by a two-step method. An exchange bias effect was observed and studied, which indicates that it is possible to fabricate ferromagnetic-multiferroic nanostructures to utilize the combined ferroelectric and antiferromagnetic functionalities of bismuth ferrite.

  12. Cross coupling between electric and magnetic orders in a multiferroic metal-organic framework

    PubMed Central

    Tian, Ying; Stroppa, Alessandro; Chai, Yisheng; Yan, Liqin; Wang, Shouguo; Barone, Paolo; Picozzi, Silvia; Sun, Young

    2014-01-01

    The coexistence of both electric and magnetic orders in some metal-organic frameworks (MOFs) has yielded a new class of multiferroics beyond inorganic materials. However, the coupling between two orders in multiferroic MOFs has not been convincingly verified yet. Here we present clear experimental evidences of cross coupling between electric and magnetic orders in a multiferroic MOF [(CH3)2NH2]Fe(HCOO)3 with a perovskite structure. The dielelectric constant exhibit a hump just at the magnetic ordering temperature TN. Moreover, both the direct (magnetic field control of dielectric properties) and converse (electric field control of magnetization) magnetoelectric effects have been observed in the multiferroic state. This work opens up new insights on the origin of ferroelectricity in MOFs and highlights their promise as magnetoelectric multiferroics. PMID:25317819

  13. 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

  14. 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).

  15. 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.

  16. Theoretical research on general Hosford yield function of cubic orthorhombic sheets metals

    NASA Astrophysics Data System (ADS)

    Yang, Feng; Liu, Jun; Zhou, Hui

    2017-04-01

    Most of rolled sheet metals belong to orthorhombic aggregates of cubic crystallites. The texture coefficients, characterized by the preferred orientation of the crystallites, are important to set up the yield function. Although Hosford yield function is more suitable for describing both yield and plastic deformation of orthorhombic material than Hill, it suffers from the restriction that the three principal stresses have to be coaxial with the orthotropy of materials. Hence, this paper proposes a new Hosford yield function of cubic orthorhombic metal sheet at any stress states by introducing orientation-dependent functions. As well, the new yield function which covers 3 material parameters and 3 texture coefficients is more general than Hosford yield function. The plastic anisotropy of the q-value and yield stress under any stress states is obtained from the new yield function. This yield function lay a theoretical foundation for analyzing the mechanical properties of metal materials.

  17. 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.

  18. Structural and transport properties of orthorhombic GdMnO3

    NASA Astrophysics Data System (ADS)

    Modi, Anchit; Thakur, Rajesh K.; Thakur, Rasna; Gaur, N. K.; Kaurav, N.; Okram, G. S.

    2013-06-01

    We report structural and transport properties of the polycrystalline orthorhombic GdMnO3 compound synthesized by using conventional solid state reaction method. The XRD pattern reveals the single phase formation of the reported compound in orthorhombic crystal structure with space group Pbnm (JCPDS: 25-0337). The temperature dependent resistivity study indicates the highly resistive nature of the compound especially in the low temperature region. The effect of low temperature magnetic ordering can be clearly understood from the resistivity versus temperature plot. The calculated activation energy by using Arrhenius equation fitting are found slightly lesser than the reported value which indicates the lesser dense nature of the prepared compound.

  19. Ferroelectric control of anisotropic damping in multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Zhang, Ning; Berakdar, Jamal; Jia, Chenglong

    2015-10-01

    The magnetoelectric effect on nonlocal magnetization dynamics is theoretically investigated in normal-metal/ferroelectric-insulator/ferromagnetic tunnel junctions. In addition to the Rashba spin-orbit interaction (SOI) originating from loss of parity symmetry at the interfaces, the topology of interfacial spiral spins triggered by ferroelectric polarization acts with an effective SOI that is electrically controllable. These spin-dependent interactions result in an anisotropic Gilbert damping with C2 v symmetry. The findings are of a direct relevance for the utilization of composite multiferroics for devices that rely on electrically controlled magnetic switching.

  20. Unfolding of vortices into topological stripes in a multiferroic material.

    PubMed

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

    2014-06-20

    Multiferroic hexagonal RMnO(3) (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.

  1. Thickness-dependent voltage-modulated magnetism in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Shu, Li; Li, Zheng; Ma, Jing; Gao, Ya; Gu, Lin; Shen, Yang; Lin, Yuanhua; Nan, C. W.

    2012-01-01

    The voltage-modulated magnetic behavior in multiferroic Ni/BaTiO3 heterostructures grown on SrTiO3 single crystal substrate was observed by the magneto-optical Kerr effect measurement in an AC modulation technique with synchronizing the frequency of the Kerr signal detector to the low-frequency AC actuation voltage. The results showed coexistence at room-temperature of two magnetoelectric (ME) mechanisms, i.e., strain- and interface charge-mediated couplings. The interaction between the different ME couplings leads to a remarkable thickness-dependent voltage modulation of the magnetic behavior.

  2. Ion doping effects in multiferroic MnWO4

    NASA Astrophysics Data System (ADS)

    Bahoosh, Safa Golrokh; Wesselinowa, J. M.

    2012-04-01

    We have studied the ion doping effects in multiferroic MnWO4 proposing a microscopic model. It is shown that the exchange interaction constants can be changed due to the different ion doping radii. This leads to reduction of the magnetic phase transition temperature TN by doping with non-magnetic ions, such as Zn, Mg, whereas TN is enhanced by doping with transition metal ions, such as Fe, Co. The different behavior of the temperature T1 (where up-up-down-down collinear spin structure appears) by Fe and Co doping could be explained taking into account the single-ion anisotropy.

  3. Neutron, X-ray, and optical studies of multiferroic materials

    NASA Astrophysics Data System (ADS)

    Hearmon, Alexander J.

    Developing a greater understanding of multiferroic materials, particularly those in which a strong coupling is exhibited between magnetic and electrical orderings, is of great importance if potential applications are to be realised. This thesis reports new experimental findings on several multiferroics using the techniques of X-ray and neutron diffraction together with nonlinear optical experiments. Spherical neutron polarimetry measurements on RbFe(MoOmultiferroicity in this proper screw system. The charge ordering in YbFe2O4 is examined by a detailed imaging of reciprocal space measured by elastic X-ray diffraction. Continuous helices of scattering are observed above the three-dimensional ordering transition temperature, whereas the intensity is concentrated onto separated maxima below this. The low temperature data are modelled using a simple oxygen displacement pattern, generalised to an incommensurate structure. The observed incommensurability implies that YbFe2O4 cannot be truly ferroelectric. The low field magnetic structures of a Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22 are observed in a resonant soft X-ray diffraction study. In zero field the system is helimagnetic, and with small applied fields peaks corresponding to a new phase appear. Energy calculations are used to suggest a suitable magnetic structure for the new phase and to show how this relates to the known commensurate phases that are present in low fields. Finally, an experimental setup designed to measure second harmonic generation from non-centrosymmetric crystals is presented, along with static measurements on the multiferroic system MnWO4. An optical

  4. Spin-electromagnetic waves in planar multiferroic multilayers

    NASA Astrophysics Data System (ADS)

    Nikitin, Andrey A.; Ustinov, Alexey B.; Vitko, Vitalii V.; Nikitin, Alexey A.; Kondrahov, Alexandr V.; Pirro, P.; Lähderanta, E.; Kalinikos, Boris A.; Hillebrands, B.

    2017-07-01

    A general electrodynamic theory is developed for dispersion characteristics of spin-electromagnetic waves (SEWs) propagating in multiferroic multilayers. The derivation is based on the full set of Maxwell's equations taking into account retardation effects. The multilayers are considered to be composed of an infinite number of ferrite and ferroelectric layers having arbitrary thicknesses, as well as arbitrary magnetic and electric parameters. As an example, spectra of SEWs are calculated and analyzed for a heterostructure containing two thin ferrite films separated by a thin ferroelectric film. An electric field tunability of the SEW dispersion characteristics at gigahertz frequencies is shown, providing an efficient control of SEW wave-numbers important for applications.

  5. 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.

  6. Synthesis and characterization of multiferroic Sm-doped BiFeO3 nanopowders and their bulk dielectric properties

    NASA Astrophysics Data System (ADS)

    Yotburut, Benjaporn; Thongbai, Prasit; Yamwong, Teerapon; Maensiri, Santi

    2017-09-01

    Multiferroic Bi1-xSmxFeO3 (x = 0, 0.05, 0.1, 0.2, and 0.3) nanopowders with particle sizes of 69-22.6 nm were prepared by a simple co-precipitation method. The structure and morphology of the samples were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns confirmed the phase transition from rhombohedral to orthorhombic phases. The results of X-ray absorption spectroscopy (XAS) data indicate that the oxidation state of Fe in the sample was Fe3+. The results of magnetic properties revealed the enhancement of weak ferromagnetic property with increasing Sm doping in BFO nanopowders. SEM images revealed that the average grain size decreased with an increase in Sm concentration. Undoped BFO ceramics exhibited a high dielectric constant ε‧ ∼1.1 × 104 and a low loss tangent of tan δ ∼0.5 at room temperature for 1 kHz. The room temperature dielectric constant decreased with increasing concentration of Sm doping and the dielectric relaxation peaks were observed at x ≤ 0.1. The dielectric relaxation peaks which were observed at all frequency ranges were x ≤ 0.1 samples which were attributed to Maxwell-Wagner relaxation. As the temperature increased, great increases in dielectric permittivity were observed in all the Bi1-xSmxFeO3 samples. The effects of grain boundaries on the dielectric properties of Sm-doped BFO ceramics were investigated by measuring the dielectric responds in the frequencies of 100 Hz-1 MHz at room temperature under applied dc bias of 0-20 V. It was found that, with an increase in applied dc bias voltage from 0 to 20 V, the dielectric constant decreases at frequencies below 104 Hz. However, the dielectric properties in the high-frequency region remained unchanged.

  7. Is an orthorhombic lateral packing and a proper lamellar organization important for the skin barrier function?

    PubMed

    Groen, Daniël; Poole, Dana S; Gooris, Gert S; Bouwstra, Joke A

    2011-06-01

    The lipid organization in the stratum corneum (SC), plays an important role in the barrier function of the skin. SC lipids form two lamellar phases with a predominantly orthorhombic packing. In previous publications a lipid model was presented, referred to as the stratum corneum substitute (SCS), that closely mimics the SC lipid organization and barrier function. Therefore, the SCS serves as a unique tool to relate lipid organization with barrier function. In the present study we examined the effect of the orthorhombic to hexagonal phase transition on the barrier function of human SC and SCS. In addition, the SCS was modified by changing the free fatty acid composition, resulting in a hexagonal packing and perturbed lamellar organization. By measuring the permeability to benzoic acid as function of temperature, Arrhenius plots were constructed from which activation energies were calculated. The results suggest that the change from orthorhombic to hexagonal packing in human SC and SCS, does not have an effect on the permeability. However, the modified SCS revealed an increased permeability to benzoic acid, which we related to its perturbed lamellar organization. Thus, a proper lamellar organization is more crucial for a competent barrier function than the presence of an orthorhombic lateral packing. Copyright © 2010 Elsevier B.V. All rights reserved.

  8. 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

  9. Invariant elastic constants and eigentensors of orthorhombic, tetragonal, hexagonal and cubic crystalline media

    PubMed

    Theocaris; Sokolis

    2000-07-01

    The purpose of this paper is to present a simple and direct way of determining the eigenvalues and eigentensors, as well as their orientations, for all crystals of the orthorhombic, tetragonal, hexagonal and cubic symmetries, a procedure based on the spectral decomposition of the compliance and stiffness fourth-rank tensors. First, both the eigenvalues and the idempotent fourth-rank tensors are derived for the orthorhombic and tetragonal-7 symmetries. The latter decompose, respectively, the second-rank symmetric tensor spaces of orthorhombic and tetragonal-7 media into orthogonal subspaces, consisting of the stress and strain eigentensors, and split the elastic potential into distinct noninteracting strain-energy parts. Accordingly, the spectrum of the compliance tensor of the tetragonal-6 symmetry is evaluated, by reduction of the eigenvalues and eigentensors of either the orthorhombic or tetragonal-7 symmetry. These results are, then, applied in turn to each of the hexagonal and cubic crystal systems. In each case, the eigenvalues, the idempotent tensors and the stress and strain eigentensors are easily derived as particular cases of the results obtained for the tetragonal-6 symmetry. Furthermore, it is noted that the positivity of the eigenvalues for each symmetry is equivalent to the positive definiteness of the elastic potential and, thus, necessary and sufficient conditions are acquired, in terms of the compliance-tensor components, characteristic of each symmetry.

  10. Anisotropic electronic structure of orthorhombic RbC60: A high-field ESR investigation

    NASA Astrophysics Data System (ADS)

    Rahmer, J.; Grupp, A.; Mehring, M.; Hone, J.; Zettl, A.

    2001-02-01

    The full anisotropy of the electronic g tensor of a RbC60 single crystal was determined by applying high-field ESR. The principal values of the g tensor gxx=2.0014, gyy=2.0012, and gzz=2.0019 reflect the orthorhombic symmetry and 3D nature of this polymeric phase.

  11. 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.

  12. Lead palladium titanate: A room-temperature multiferroic

    NASA Astrophysics Data System (ADS)

    Gradauskaite, Elzbieta; Gardner, Jonathan; Smith, Rebecca M.; Morrison, Finlay D.; Lee, Stephen L.; Katiyar, Ram S.; Scott, James F.

    2017-09-01

    There have been a large number of papers on bismuth ferrite (BiFe O3 ) over the past few years, trying to exploit its room-temperature magnetoelectric multiferroic properties. Although these are attractive, BiFe O3 is not the ideal multiferroic due to weak magnetization and the difficulty in limiting leakage currents. Thus there is an ongoing search for alternatives, including such materials as gallium ferrite (GaFe O3 ). In the present work we report a comprehensive study of the perovskite PbT i1 -xP dxO3 with 0

  13. 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.

  14. Multiferroic properties of artificially designed Perovskite-Spinel Heterostructures

    NASA Astrophysics Data System (ADS)

    Dussan, Sandra; Singh, Manoj K.; Katiyar, Ram S.

    2009-03-01

    Multiferroics materials are a class of functional material that combines two or more ordered parameters i.e. ferromagnetic, ferroelectric and ferroelastic. The recent finding of multiferroic composite material with the coexistence of these properties has attracted the attention of various researchers due to its potential applications in highly sensitive sensors and actuators as well as multistate memory devices. We synthesized and characterizatied CoFe2O4-BiFeO3 (CFO-BFO) heterostructure thin films grown on SrTiO3 (111), (100) substrates using Pulsed laser deposition. The XRD patterns of CFO-BFO multilayered films evidenced that all picks correspond to CFO and BFO structure also confirmed by their respective Raman spectra. We observed three peaks at 136, 168, and 215 cm-1 that can be assigned to A1(TO) modes of the BFO pure phase and at 468 and 695 cm-1 correspond to CFO. Room temperature M-H exhibited well-shaped magnetization hysteresis loops, good saturation and high coercivity. Preliminary results evidenced the existence of ferroelectricity and magnetic properties in heterostructure.

  15. Optical coupling to spin waves in multiferroic materials

    NASA Astrophysics Data System (ADS)

    de Sousa, Rogerio

    2009-05-01

    The coexistence of ferroelectricity and magnetism in multiferroic materials leads to several interesting effects related to the interplay of light with complex electric and magnetic order. One notable example is bismuth ferrite (BiFeO3), a room temperature multiferroic that exhibits a large ferroelectric moment coexisting with a spiral antiferromagnetic phase in the form of a cycloid. I will describe a theory of bulk BiFeO3, which predicts the appearance of several magnon branches related to magnetic fluctuations at integer multiples of the cycloid wavevector. These magnons get admixed with optical phonons at zero wavevector, giving rise to two series of electromagnon resonances in the far infrared spectrum [1], which were recently observed using Raman spectroscopy [2]. I will show that these results are helpful in designing low loss electronic devices based on spin-wave propagation [3]. [4pt] [1] R. de Sousa and J.E. Moore, Phys. Rev. B. 77, 012406 (2008). [0pt] [2] M. Cazayous, Y. Gallais, A. Sacuto, R. de Sousa, D. Lebeugle, and D. Colson, Phys. Rev. Lett. 101, 037601 (2008). [0pt] [3] R. de Sousa and J.E. Moore, Appl. Phys. Lett. 92, 022514 (2008).

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

    SciTech Connect

    Planes, Antoni; Castán, Teresa; Saxena, Avadh

    2016-07-11

    In this paper, 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. Finally, this article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

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

    DOE PAGES

    Planes, Antoni; Castán, Teresa; Saxena, Avadh

    2016-07-11

    In this paper, 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. Itmore » 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. Finally, this article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.« less

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

    PubMed Central

    Castán, Teresa; Saxena, Avadh

    2016-01-01

    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’. PMID:27402925

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

    SciTech Connect

    Planes, Antoni; Castán, Teresa; Saxena, Avadh

    2016-07-11

    In this paper, 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. Finally, this article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

  20. 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.

  1. 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

  2. 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.

  3. Electronic structure, linear, and nonlinear optical responses in magnetoelectric multiferroic material BiFeO(3).

    PubMed

    Ju, Sheng; Cai, Tian-Yi; Guo, Guang-Yu

    2009-06-07

    BiFeO(3) has attracted great interest for its multiferroic property. The spontaneous electric polarization, multiferroism, and static magnetoelectric coupling have been widely studied both experimentally and theoretically. Here, in this paper, we report on the effects of magnetic ordering, spin fluctuation, and external magnetic field on the linear dielectric function and second-harmonic generation (SHG) in multiferroic BiFeO(3). First, our generalized gradient approximation plus Hubbard U calculations reproduce very well experimental data of linear dielectric function. In the mean time, it is revealed that SHG susceptibilities differ dramatically between antiferromagnetic configuration and ferromagnetic one, which is due to the enhanced contrast in the double-photon resonance absorption. Further Monte Carlo simulation of the coupling between electric order and spin-pair correlation function is presented for the spin fluctuation dependence of SHG. The significant nonlinear optical magnetoelectric effect around the Neel temperature provides novel route to enhancing magnetoelectric coupling in multiferroic materials.

  4. 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'. © 2016 The Author(s).

  5. 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.

  6. Research Update: Electrical manipulation of magnetism through strain-mediated magnetoelectric coupling in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Chen, A. T.; Zhao, Y. G.

    2016-03-01

    Electrical manipulation of magnetism has been a long sought-after goal to realize energy-efficient spintronics. During the past decade, multiferroic materials combining (anti)ferromagnetic and ferroelectric properties are now drawing much attention and many reports have focused on magnetoelectric coupling effect through strain, charge, or exchange bias. This paper gives an overview of recent progress on electrical manipulation of magnetism through strain-mediated magnetoelectric coupling in multiferroic heterostructures.

  7. Nanoscale Engineering of Multiferroic Hybrid Composites for Micro- and Nano-scale Devices

    DTIC Science & Technology

    2012-09-14

    multiferroic composites resulted in a discovery of a new biomedical application of multiferroic nanoparticles. This concept was a subject of UNO Technology...potential between the electrode and the film [4], pinning of the domain walls by defects [3] or the presence of an internal electric field inside the...Nanocomposites," Acs Nano, vol. 4, pp. 1099-1107, Feb. [2] A. Gruverman, et al., "Nanoscale observation of photoinduced domain pinning and investigation

  8. Structural, dielectric and impedance characteristics of (Sm0.5Li0.5)(Fe0.5V0.5)O3 multiferroics

    NASA Astrophysics Data System (ADS)

    Nath, Susmita; Barik, Subrat Kumar; Choudhary, R. N. P.; Barik, Sujit Kumar

    2017-07-01

    A single phase multiferroic magnetoelectric compound, (Sm0.5Li0.5)(Fe0.5V0.5)O3, is found at room temperature. This sample is fabricated using solid state reaction route. Analysis of the structural properties of the sample by X-ray diffraction method confirmed the fabrication of the desired compound with orthorhombic unit cell structure. Morphological property of the sample is recorded by field emission scanning electron microscopy (FE-SEM). Impedance spectroscopy is employed to determine the various electrical parameters such as dielectric constant, loss tangent, impedance, electric modulus, etc. at different temperature (RT-400 °C) within a frequency range of (1 kHz-1 MHz). Furthermore, the bulk resistance as function of temperature and J-E characteristic showed the semiconducting behavior of sample with negative temperature coefficient of resistance (NTCR) type nature of the compound. The M-H loop of this sample indicates the ferromagnetic nature with very low coercive field. A dedicated magnetoelectric set up is used to measure the ME coefficient as a function of magnetic field and found a significant ME coefficient of 2.99 mV Cm-1 Oe-1 at room temperature.

  9. 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.

  10. 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.

  11. Investigation of crystal structure, dielectric and magnetic properties in La and Nd co-doped BiFeO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Singh, Ompal; Agarwal, Ashish; Sanghi, Sujata; Das, Amitabh; Anju

    2017-03-01

    For the investigation of the crystal structure, dielectric properties and magnetic properties of La and Nd co-doped BiFeO3 multiferroics; Bi0.8La0.2-xNdxFeO3 (x=0.075, 0.1, 0.125) samples were prepared through solid state reaction method. Rietveld refinement of the obtained XRD patterns shows that there is change in crystal structure in these samples. At higher concentration of La (at x=0.075), the crystal structure was found to have mixed symmetry with rhombohedral and triclinic phases, while with equal concentration of both the dopants (at x=0.1), the structure changes to mixed symmetry having rhombohedral and orthorhombic phases. At higher concentration of Nd (at x=0.125), again mixed symmetry was established having both phases of the previous composition but approximately in reverse fraction. In dielectric analysis, x=0.1 sample showed the highest values of dielectric constant (ε‧) and dielectric loss (tan δ). For x=0.125 sample, it was observed that the dielectric constant and dielectric loss response are improved. The magnetic characterization (M-H loops) indicates the significant enhancement in magnetisation with increasing concentration of Nd. Nd doping leads to the destruction of spiral modulation, forming the antiferromagnets, and visualisation of improved magnetisation via canting of spins.

  12. 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.

  13. 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

  14. 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.

  15. Compressibility of orthorhombic perovskites. The effect of transition metal ions (TMI)

    NASA Astrophysics Data System (ADS)

    Ardit, Matteo

    2015-12-01

    Interest in perovskites evenly spans Materials Science and Geophysics. Due to their inimitably lattice flexibility enabling small as well as large ions to be accommodated, perovskites have become a base structure for new technological applications. Understanding the mechanisms governing their evolution at non-ambient conditions (such as high-pressure and high-temperature) is fundamentally important both for devising functional materials and in order to provide the most reliable possible deep-Earth model. With particular attention being paid to the chemical nature of the constituent ions, a suite of orthorhombic perovskites has been selected and contrasted using several parameterizations and models. A new perspective on the pressure-induced distortion of orthorhombic perovskite structures has enabled their compressional behaviour to be redefined.

  16. Ab initio structural, electronic and optical properties of orthorhombic CaGeO{sub 3}

    SciTech Connect

    Henriques, J.M.; Caetano, E.W.S. Freire, V.N.; Costa, J.A.P. da; Albuquerque, E.L.

    2007-03-15

    Orthorhombic CaGeO{sub 3} is studied using density-functional theory (DFT) considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The electronic band structure, density of states, dielectric function and optical absorption are calculated. Two very close indirect (S->{gamma}) and direct ({gamma}->{gamma}) band gap energies of 1.68eV (2.31eV) and 1.75eV (2.41eV) were obtained within the GGA (LDA) approximation, as well as the effective masses for electrons and holes. Comparing with orthorhombic CaCO{sub 3} (aragonite), the substitution of carbon by germanium changes the localization of the valence band maximum of the indirect transition, and decreases by almost 2.0eV the Kohn-Sham band gap energies.

  17. 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.

  18. 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.

  19. Angular dependences of spin-wave resonance spectra of inhomogeneous films with orthorhombic anisotropy

    NASA Astrophysics Data System (ADS)

    Zyuzin, A. M.; Bakulin, M. A.; Radaikin, V. V.; Yantsen, N. V.

    2017-02-01

    Zero spin-wave mode in inhomogeneous magnetic films with orthorhombic anisotropy has been found to exhibit a change of its localization region in two of three typical angular dependences of resonance fields of high-intensity modes. It has been shown that the anisotropy fields on both sides of the film can be determined from the resonance fields of the zero and uppermost high-intensity spin-wave modes of spin-wave resonance spectra.

  20. Finite-Difference Algorithm for 3D Orthorhombic Elastic Wave Propagation

    NASA Astrophysics Data System (ADS)

    Jensen, R.; Preston, L. A.; Aldridge, D. F.

    2016-12-01

    Many geophysicists concur that an orthorhombic elastic medium, characterized by three mutually orthogonal symmetry planes, constitutes a realistic representation of seismic anisotropy in shallow crustal rocks. This symmetry condition typically arises via a dense system of vertically-aligned microfractures superimposed on a finely-layered horizontal geology. Mathematically, the elastic stress-strain constitutive relations for an orthorhombic body contain nine independent moduli. In turn, these moduli can be determined by observing (or prescribing) nine independent P-wave and S-wave phase speeds along different propagation directions. We are developing an explicit time-domain finite-difference (FD) algorithm for simulating 3D elastic wave propagation in a heterogeneous orthorhombic medium. The components of the particle velocity vector and the stress tensor are governed by a set of nine, coupled, first-order, linear, partial differential equations (PDEs) called the velocity-stress system. All time and space derivatives are discretized with centered and staggered FD operators possessing second- and fourth-order numerical accuracy, respectively. Simplified FD updating formulae (with significantly reduced operation counts) for stress components are obtained by restricting the principle axes of the modulus tensor to be parallel to the global rectangular coordinate axes. Moreover, restriction to a piecewise homogeneous earth model reduces computational memory demand for storing the ten (including mass density) model parameters. These restrictions will be relaxed in the future. Novel perfectly matched layer (PML) absorbing boundary conditions, specifically designed for orthorhombic media, effectively suppress grid boundary reflections. Initial modeling results reveal the well-established anisotropic seismic phenomena of complex wavefront shapes, split (fast and slow) S-waves, and shear waves generated by a spherically-symmetric explosion in a homogeneous body.

  1. 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.

  2. Magnetoelectric excitations in multiferroic N i3Te O6

    NASA Astrophysics Data System (ADS)

    Skiadopoulou, Stella; Borodavka, Fedir; Kadlec, Christelle; Kadlec, Filip; Retuerto, Maria; Deng, Zheng; Greenblatt, Martha; Kamba, Stanislav

    2017-05-01

    The spin-order-induced ferroelectric antiferromagnet N i3Te O6 transcends the magnetoelectric performance of all other single-phase multiferroics because it exhibits nonhysteretic colossal magnetoelectric coupling [Y. S. Oh, S. Artyukhin, J. J. Yang, V. Zapf, J. W. Kim, D. Vanderbilt, and S.-W. Cheong, Nat Commun. 5, 3201 (2014), 10.1038/ncomms4201]. We investigated spin and lattice excitations in N i3Te O6 by a combination of infrared, Raman, and THz spectroscopies. Two spin excitations (near 13 and 35 c m-1 ) were observed simultaneously in Raman and time-domain THz spectra below the Néel temperature TN=53 K . We propose to assign them to electromagnons, which are activated by the dynamic magnetoelectric coupling. A third magnon is seen only in the Raman spectra near 206 c m-1 .

  3. 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

  4. Palladium-based ferroelectrics and multiferroics: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Kumari, Shalini; Pradhan, Dhiren K.; Ortega, Nora; Pradhan, Kallol; DeVreugd, Christopher; Srinivasan, Gopalan; Kumar, Ashok; Paudel, Tula R.; Tsymbal, Evgeny Y.; Bumstead, Alice M.; Scott, J. F.; Katiyar, Ram S.

    2017-06-01

    Palladium normally does not easily substitute for Ti or Zr in perovskite oxides. Moreover, Pd is not normally magnetic (but becomes ferromagnetic under applied uniaxial stress or electric fields). Despite these two great obstacles, we have succeeded in fabricating lead zirconate titanate with 30% Pd substitution. For 20:80 Zr:Ti, the ceramics are generally single-phase perovskites (>99%) but sometimes exhibit 1% PdO, which is magnetic at room temperature. The resulting material is multiferroic (ferroelectric-ferromagnetic) at room temperature. The processing is slightly unusual (>8 h in high-energy ball-milling in Zr balls), and the density functional theory provided shows that it occurs because of P d+4 in the oversized P b+2 site; if all P d+4 were to go into the T i+4 perovskite B site, only a small moment of 0.1 Bohr magnetons would result.

  5. 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.

  6. Stabilization of orthorhombic phase in single-crystal ZnSnN{sub 2} films

    SciTech Connect

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

    2016-07-15

    We report on the crystal structure of epitaxial ZnSnN{sub 2} films synthesized via plasma-assisted vapor deposition on (111) yttria stabilized zirconia (YSZ) and (001) lithium gallate (LiGaO{sub 2}) substrates. X-ray diffraction measurements performed on ZnSnN{sub 2} films deposited on LiGaO{sub 2} substrates show evidence of single-crystal, phase-pure orthorhombic structure in the Pn2{sub 1}a symmetry [space group (33)], with lattice parameters in good agreement with theoretically predicted values. This Pn2{sub 1}a symmetry is imposed on the ZnSnN{sub 2} films by the LiGaO{sub 2} 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{sup −5} Torr is observed in ZnSnN{sub 2} films deposited on YSZ characterized by lattice contraction in the basal plane and a 5.7% expansion of the out-of-plane lattice parameter.

  7. 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.

  8. 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.

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

    DOE PAGES

    Senabulya, Nancy; Feldberg, Nathaniel; Makin, Robert. A.; ...

    2016-09-22

    Here, 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°Cmore » 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.« less

  10. 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.

  11. Comparative compressibility and equation of state of orthorhombic and tetragonal edingtonite

    NASA Astrophysics Data System (ADS)

    Gatta, G. D.; Ballaran, T. Boffa; Comodi, P.; Zanazzi, P. F.

    The high-pressure (HP) behaviour of a natural orthorhombic and tetragonal edingtonite from Ice River, Canada, has been investigated using in situ single-crystal X-ray diffraction. The two isothermal equations of state up to 6.74(5) GPa were determined. V0, KT0 and K' refined with a third-order Birch-Murnaghan equation of state (BM-EoS) are: V0 = 598.70(7) Å3, KT0 = 59(1) GPa and K'=3.9(4) for orthorhombic edingtonite and V0 = 600.9(2) Å3, KT0 = 59(1) GPa and K'=4.2(5) for tetragonal edingtonite. The experiments were conducted with nominally hydrous pressure penetrating transmitting medium. No overhydration effect was observed within the pressure range investigated. At high-pressures the main deformation mechanism is represented by cooperative rotation of the secondary building unit (SBU).Si/Al distribution slightly influences the elastic behaviour of the tetrahedral framework: the SBU bulk moduli are 125(8) GPa and 111(4) GPa for orthorhombic and tetragonal edingtonite, respectively. Extra-framework contents of both zeolites show an interesting behaviour under HP conditions: the split Ba2 site at P >2.85 GPa is completely empty; only the position Ba1 is occupied. Electronic Supplementary Material. Supplementary material to this paper (Observed and calculated structure factors) is available in electronic form at http://dx.doi.org/10.1007/s00269-004-0394-y.

  12. Oxidation protection of Ti-aluminide orthorhombic alloys: An engineered multilayer approach

    SciTech Connect

    Warrier, S.G.; Krishnamurthy, S.; Smith, P.R.

    1998-04-01

    The lack of high-temperature environmental resistance is a major issue in the application of orthorhombic-based titanium aluminide alloys (O alloys) and their composites. Improvement in environmental capability can be achieved by applying diffusion barrier coatings to the surface of the orthorhombic matrix alloy. However, since thin coatings are prone to foreign-object damage, an approach based on thicker multilayer materials may be more prudent for fracture-critical applications. In the present study, foils of the orthorhombic alloy were diffusion bonded on either side with a {gamma} alloy, the latter used in an attempt to provide environmental protection. Mechanical tests suggested that the {gamma} alloy was successful in preventing degradation of the O alloy due to oxidation and interstitial embrittlement under thermal cycling conditions. Processing below the {beta} transus of the O alloy provided an improvement in the stress and strain to failure of the joined material compared to materials processed above the transus. However, in either case, the strengths of the joined materials were significantly lower than that of the uncoated O alloy with similar microstructures. Results suggest that the low strength of the joined materials may be due to cracking of the {gamma} alloy, resulting in premature failure of the O alloy. Finite element analysis (FEA) was performed to understand the stress distribution in the joined material and to investigate approaches for reducing the residual stress. Several approaches for improving the stress and strain to failure of the joined material are presented.

  13. Tape cast second generation orthorhombic-based titanium aluminide alloys for MMC applications. [Metal Matrix Composites

    SciTech Connect

    Smith, P.R.; Rosenberger, A.H. . Materials and Mfg. Directorate); Shepard, M.J. )

    1999-06-18

    Titanium metal matrix composites (TMCs) utilizing continuous SiC fiber reinforcement are considered important, if not, enabling materials for advanced Air Force propulsion systems, wherein combinations of high specific strength and elevated temperature capability are prerequisites to obtain desired increases in thrust-to-weight ratios and decreased specific fuel consumption. One such class of TMCs being assessed for use in rotating engine components are those based upon the orthorhombic titanium aluminide phase, Ti[sub 2]AlNb. These orthorhombic titanium matrix composites (O TMCs) are being examined for sustained use at temperatures up to 700 C. Previous studies have primarily focused on O TMCs made using the foil-fiber-foil fabrication process. More recently the Materials and Manufacturing Directorate of the Air Force Research Laboratory has been focusing attention on an alternative powder metallurgy approach for fabrication of O TMCs via tape casting. This latter approach has the potential to produce significant cost reduction (<$70/lb) for the matrix input material (powder). Unfortunately, little work has been done to understand the effects of powder microstructures and the tape casting process itself on the mechanical performance of O TMCs. Therefore, the first objective of this study is to examine the microstructural evolution and mechanical performance (with and without heat treatment) of three unreinforced heat orthorhombic-based titanium aluminide matrices made via tape casting. A second objective is to assess the viability of powder metallurgy processing for the fabrication of O TMCs.

  14. Multiferroic Applications of Nanoarchitectured, Solution-Processed Materials

    NASA Astrophysics Data System (ADS)

    Buditama, Abraham Nataniel

    This dissertation compiles work on sol-gel syntheses of multiferroic materials and applications thereof. Multiferroics, or materials that simultaneously exhibit multiple order parameters such as ferromagnetism, ferroelectricity, or ferroelasticity, may be fabricated by solution processing techniques. Specifically, these techniques may be used to control both the atomic and the nanoscale structures of piezoelectric lead zirconate titanate (PbZrxTi 1-xO3 or PZT) and magnetostrictive cobalt ferrite (CoFe 2O4 or CFO). The first part of this work focuses on strain-coupling PZT and CFO into a magnetoelectric composite. A mesoporous CFO framework was synthesized using block copolymer templating, which was subsequently conformally filled by PZT by atomic layer deposition (ALD). The final porosity of the film is controlled by the ALD PZT layer, and we show that this porosity influences the magnetoelectric coupling of the composite. An ex situ external electric field is applied to the composite, and samples with the greatest porosity, and thus greatest mechanical flexibility, were able to accommodate strain transfer to the CFO, resulting in a greater reduction of the sample saturation magnetization. The second part of this work focuses on using solution processing to control domain-level contributions to the material's ferroic properties. An iterative spin coating process can be used to create PZT films of arbitrary thickness. Electric domains are generally pinned in nanoscale PZT thin films, but models of PZT films on the mesoscale must consider domain reorientation. As for CFO, solution processing may be used to control the CFO grain size, which in turn limits the size of its magnetic domains, and subsequently its static magnetic properties.

  15. Characteristics and controllability of vortices in ferromagnetics, ferroelectrics, and multiferroics

    NASA Astrophysics Data System (ADS)

    Zheng, Yue; Chen, W. J.

    2017-08-01

    Topological defects in condensed matter are attracting e significant attention due to their important role in phase transition and their fascinating characteristics. Among the various types of matter, ferroics which possess a switchable physical characteristic and form domain structure are ideal systems to form topological defects. In particular, a special class of topological defects—vortices—have been found to commonly exist in ferroics. They often manifest themselves as singular regions where domains merge in large systems, or stabilize as novel order states instead of forming domain structures in small enough systems. Understanding the characteristics and controllability of vortices in ferroics can provide us with deeper insight into the phase transition of condensed matter and also exciting opportunities in designing novel functional devices such as nano-memories, sensors, and transducers based on topological defects. In this review, we summarize the recent experimental and theoretical progress in ferroic vortices, with emphasis on those spin/dipole vortices formed in nanoscale ferromagnetics and ferroelectrics, and those structural domain vortices formed in multiferroic hexagonal manganites. We begin with an overview of this field. The fundamental concepts of ferroic vortices, followed by the theoretical simulation and experimental methods to explore ferroic vortices, are then introduced. The various characteristics of vortices (e.g. formation mechanisms, static/dynamic features, and electronic properties) and their controllability (e.g. by size, geometry, external thermal, electrical, magnetic, or mechanical fields) in ferromagnetics, ferroelectrics, and multiferroics are discussed in detail in individual sections. Finally, we conclude this review with an outlook on this rapidly developing field.

  16. 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

  17. High - pressure synchrotron x-ray diffraction study of RMnO3 (R = Eu, Gd, Tb and Dy) upto 50 GPa

    NASA Astrophysics Data System (ADS)

    Muthu, D. V. S.; Midgley, A. E.; Scott, P. R.; Kruger, M. B.; Sahu, J. R.; Sood, A. K.; Rao, C. N. R.

    2012-07-01

    We have carried out synchrotron based high-pressure x-ray diffraction study of orthorhombic EuMnO3, GdMnO3, TbMnO3 and DyMnO3 up to 54.4, 41.6, 47.0 and 50.2 GPa, respectively. The diffraction peaks of all the four manganites shift monotonically to higher diffraction angles and the crystals retain the orthorhombic structure till the highest pressure. We have fitted the observed volume versus pressure data with the Birch-Murnaghan equation of state and determined the bulk modulus to be 185 ± 6 GPa, 190 ± 16 GPa, 188 ± 9 GPa and 192 ± 8 GPa for EuMnO3, GdMnO3, TbMnO3 and DyMnO3, respectively. The bulk modulus of EuMnO3 is comparable to other manganites, in contrast to theoretical predictions.

  18. Magnetic properties of multiferroics Bi1 - x Sm x FeO3 synthesized under high pressure

    NASA Astrophysics Data System (ADS)

    Makoed, I. I.; Ravinski, A. F.; Lazenka, V. V.; Galyas, A. I.; Demidenko, O. F.; Zhivul'ko, A. M.; Yanushkevich, K. I.; Moshchalkov, V. V.

    2017-08-01

    The magnetic properties of the multiferroics obtained upon isovalent substitution of samarium cations for bismuth cations in BiFeO3. The samples have been synthesized by solid-phase reactions under conditions of a cold pressing at high (4 GPa) pressure. The correlation between the structure and the magnetic properties of the multiferroics has been found based on analyzing the experimental data.

  19. Structural, electronic and optical properties of orthorhombic CdGeO{sub 3} from first principles calculations

    SciTech Connect

    Barboza, C.A.; Henriques, J.M.; Albuquerque, E.L.; Caetano, E.W.S.; Freire, V.N.; Costa, J.A.P. da

    2010-02-15

    Orthorhombic perovskite CdGeO{sub 3} was studied using the density-functional theory (DFT) formalism. The electronic band structure, density of states, effective masses, dielectric function and optical absorption were obtained. Comparing with orthorhombic CaGeO{sub 3}, which is an indirect S->GAMMA gap material, the substitution of calcium by cadmium changes the valence band maximum from the S point to the GAMMA point in reciprocal space, and decreases the Kohn-Sham band gap energy. Our results suggest that orthorhombic CdGeO{sub 3} has features of a semiconductor and is potentially useful for optoelectronic applications. - Abstract: Graphical Abstract Legend (TOC Figure): Different views of the unit cell of orthorhombic CdGeO{sub 3} (left, top). The electronic band structure near the main gap and the partial density of states (PDOS) are shown also (right), as well as the optical absorption for different polarizations of incident light (left, bottom).

  20. Tuning the multiferroic mechanisms of TbMnO3 by epitaxial strain

    NASA Astrophysics Data System (ADS)

    Shimamoto, Kenta; Mukherjee, Saumya; Manz, Sebastian; White, Jonathan S.; Trassin, Morgan; Kenzelmann, Michel; Chapon, Laurent; Lippert, Thomas; Fiebig, Manfred; Schneider, Christof W.; Niedermayer, Christof

    2017-03-01

    A current challenge in the field of magnetoelectric multiferroics is to identify systems that allow a controlled tuning of states displaying distinct magnetoelectric responses. Here we show that the multiferroic ground state of the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial strain. Neutron diffraction reveals that in highly strained films the magnetic order changes from the bulk-like incommensurate bc-cycloidal structure to commensurate magnetic order. Concomitant with the modification of the magnetic ground state, optical second-harmonic generation (SHG) and electric measurements show an enormous increase of the ferroelectric polarization, and a change in its direction from along the c- to the a-axis. Our results suggest that the drastic change of multiferroic properties results from a switch of the spin-current magnetoelectric coupling in bulk TbMnO3 to symmetric magnetostriction in epitaxially-strained TbMnO3. These findings experimentally demonstrate that epitaxial strain can be used to control single-phase spin-driven multiferroic states.

  1. Synthesis and induced multiferroicity of perovskite PbTiO3; a review

    NASA Astrophysics Data System (ADS)

    Bhatti, Humaira Safdar; Hussain, Syed Tajammul; Khan, Feroz Alam; Hussain, Shahzad

    2016-03-01

    Multiferroics are multifunctional materials possessing particularly two significant ferroic orders i.e. ferroelectricity and ferromagnetism. Owing to the technological importance of the multiferroics in a variety of electromagnetic appliances, intensive research has been focused on exploring co-existence and coupling of ferroelectricity and magnetism at room temperature and above. PbTiO3 is a ferroelectric material with the highest spontaneous polarization Ps among all the ferroelectric perovskites. Due to scarcity of multiferroic materials, PbTiO3 is being extensively studied for induction of magnetism. This review deals with the synthesis and study of induced multiferroic behavior in ferroelectric PbTiO3. A variety of synthesis techniques have been discussed for PbTiO3 powders and films which can be modified to tune the electric and magnetic properties in the material. A detailed discussion is presented on the induction and enhancement of multiferroicity in PbTiO3 by substitution of suitable transition-metal dopants and tailoring the size and morphologies. Device applications of the material have been briefly discussed to illustrate its technological importance. Finally the review has been concluded with future perspectives.

  2. Tuning the multiferroic mechanisms of TbMnO3 by epitaxial strain

    PubMed Central

    Shimamoto, Kenta; Mukherjee, Saumya; Manz, Sebastian; White, Jonathan S.; Trassin, Morgan; Kenzelmann, Michel; Chapon, Laurent; Lippert, Thomas; Fiebig, Manfred; Schneider, Christof W.; Niedermayer, Christof

    2017-01-01

    A current challenge in the field of magnetoelectric multiferroics is to identify systems that allow a controlled tuning of states displaying distinct magnetoelectric responses. Here we show that the multiferroic ground state of the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial strain. Neutron diffraction reveals that in highly strained films the magnetic order changes from the bulk-like incommensurate bc-cycloidal structure to commensurate magnetic order. Concomitant with the modification of the magnetic ground state, optical second-harmonic generation (SHG) and electric measurements show an enormous increase of the ferroelectric polarization, and a change in its direction from along the c- to the a-axis. Our results suggest that the drastic change of multiferroic properties results from a switch of the spin-current magnetoelectric coupling in bulk TbMnO3 to symmetric magnetostriction in epitaxially-strained TbMnO3. These findings experimentally demonstrate that epitaxial strain can be used to control single-phase spin-driven multiferroic states. PMID:28317838

  3. Surface relaxation and tilting in SrHfO 3 orthorhombic perovskite: Hybrid HF-DFT LCAO calculations

    NASA Astrophysics Data System (ADS)

    Evarestov, R. A.; Bandura, A. V.; Blokhin, E. N.

    2008-12-01

    HF-DFT LCAO hybrid simulations on (0 0 1) and (1 1 0) surfaces of orthorhombic and (0 0 1) surface of cubic SrHfO 3 perovskite are performed using a single slab model framework. PBE0 exchange-correlation functional is used for this study. The energy and crystal structure of bulk cubic and orthorhombic phases are calculated and compared. It is found that orthorhombic modification is more stable than cubic one by 24 kJ mol -1 per formula unit. Calculated average surface energies and relaxation energies proved to be similar for all orthorhombic surfaces. Atomic displacements along the direction normal to the surface are primarily determined by the type of termination and weakly depend on the surface indices. Without symmetry constraining, cubic surfaces are unstable with respect to reconstruction to corresponding orthorhombic surfaces at T = 0 K. While the upright displacements of the topmost atoms are mainly due to additional distortions of the surface octahedra, the lateral atomic displacements are closely related to changing in surface group tilting. The approach for the analysis of surface octahedron tilting is proposed and applied to the relaxed orthorhombic surfaces of SrHfO 3 perovskites. It is shown that the HfO 5 group on the HfO 2-termianted surfaces undergoes a considerable turn upon relaxation, resulting in alignment of Hf-O-Hf bonds to corresponding pseudo-cubic directions.

  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. Orthorhombic MoO3 nanobelts based NO2 gas sensor

    NASA Astrophysics Data System (ADS)

    Mane, A. A.; Moholkar, A. V.

    2017-05-01

    Molybdenum trioxide (MoO3) nanobelts have been deposited onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD patterns reveal that films are polycrystalline having an orthorhombic crystal structure. Raman spectra confirm that the films are orthorhombic in phase. The XPS study shows the presence of two well resolved spectral lines of Mo-3d core levels appearing at the binding energy values of 232.82 eV and 235.95 eV corresponding to Mo-3d5/2 and Mo-3d3/2, respectively. These binding energy values are assigned to Mo6+ oxidation state of fully oxidized MoO3. The FE-SEM micrographs show the formation of nanobelts-like morphology. The AFM micrographs reveal that the RMS surface roughness increases from 16.5 nm to 17.5 nm with increase in film thickness from 470 nm to 612 nm and then decreases to 16 nm for 633 nm film thickness. The band gap energy is found to be decreased from 3.40 eV to 3.38 eV. To understand the electronic transport phenomenon in MoO3 thin films, dielectric properties are studied. For 612 nm film thickness, the highest NO2 gas response of 68% is obtained at an operating temperature of 200 °C for 100 ppm concentration with response and recovery times of 15 s and 150 s, respectively. The lower detection limit is found to be 10 ppm which is half of the immediately dangerous to life or health (IDLH) value of 20 ppm. Finally, NO2 gas sensing mechanism in an orthorhombic MoO3 crystal structure is discussed in detail.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. The magnetic and multiferroic properties in BiMnO3

    NASA Astrophysics Data System (ADS)

    Zhai, Liang-Jun; Wang, Huai-Yu

    2017-03-01

    In this paper, the magnetic and multiferroic properties in the multiferroic material BiMnO3 are studied. A Heisenberg type Hamiltonian for BiMnO3 is proposed, in which the nearest and farther neighbors are considered. Thermodynamic quantities such as magnetization and magnetic susceptibility for different magnetic orderings under high pressure or magnetic field are calculated, and the simulation results fit the experimental results. Farther neighboring exchanges can result in the coexistence of the ferromagnetic ordering and certain antiferromagnetic ordering with no centrosymmetry. Our study demonstrates that the BiMnO3 should be the type-II multiferroic, and the ferromagnetic and ferroelectric orderings could coexist. The magnetic field control of ferroelectric polarization is also studied. The ferroelectric polarization is always suppressed by the external magnetic field.

  8. 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

  9. Microfluidic synthesis of multiferroic Janus particles with disk-like compartments

    NASA Astrophysics Data System (ADS)

    Yu, Xiaolei; Zhang, Cancan; You, Sujian; Liu, Huiqin; Zhang, Lingling; Liu, Wei; Guo, Shi-Shang; Zhao, Xing-Zhong

    2016-02-01

    Aiming to synthesize multiferroic materials in microscale, a microfluidic device capable of generating multiferroic Janus microparticles is demonstrated. Through bonding two polydimethylsiloxane (PDMS) layers "face to face," laminar flow containing an upper layer and a lower layer can be realized. Accordingly, poly(vinylidene fluoride-trifluoroethylene) ferroelectric polymers and Fe3O4 ferromagnetic particles are separately encapsulated in the two layers of a single droplet. Numerical simulation enables the analysis of cross-mixing between the two counterparts and helps to find an optimized location for adding subsequent ultraviolet treatment, which will polymerize the droplets into Janus particles without any side effect. By modulation of the flow rate, the size of the Janus particles can be precisely tuned. Finally, the ferroelectricity and magnetism of the Janus particles are verified by the magnetization and polarization measurements, indicating the multiferroic nature.

  10. Ferroelectric polymer-based nanocomposites: Towards multiferroic materials

    NASA Astrophysics Data System (ADS)

    Andrew, Jennifer S.

    This dissertation describes new routes towards magnetic-ferroelectric materials, leading to new materials for multiferroic applications. Multiferroic materials exhibit both ferromagnetic and ferroelectric properties, which tend to be mutually exclusive in single-phase materials. Therefore, composite materials are the obvious approach to realizing a material with both a high electric permittivity and high magnetic permeability. In composite systems the magnetoelectric effect arises from a mechanical coupling between a magnetostrictive and a piezoelectric phase. In order to enhance this coupling the interfacial area between the two phases should be maximized. This can be accomplished with nanoparticles, which have a large surface to volume ratio. This work begins with the synthesis of ferrimagnetic (MFe2O 4, M=Ni, Ni0.5Zn0.5, Co) and ferroelectric (BaTiO 3) nanoparticles. Aqueous coprecipitation routes produced superparamagnetic ferrite nanoparticles with an average diameter of 8-10 nanometers. Nanometer sized particles of barium titanate were also produced, but they were cubic and therefore do not exhibit ferroelectric behavior. We then developed routes to form nanoparticle-nanoparticle composites by controlling their stability in solution and therefore their final assembly into magnetic-dielectric nanocomposites. We also developed novel magnetic-ferroelectric composites by filling a ferroelectric polymer with magnetic and dielectric nanoparticles. Polyvinylidene difluoride (PVDF) fibers as well as fibers with continuously dispersed ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions and nanoparticle loading on the fiber morphology, crystallinity, and the crystalline structure of PVDF were examined. Magnetic and dielectric measurements were also performed. Electrospinning provides a simple technique to form PVDF in the ferroelectric beta

  11. Stability of the ordered orthorhombic phase in Ti-24Al-11Nb

    NASA Technical Reports Server (NTRS)

    Hsiung, L. M.; Wadley, H. N. G.

    1992-01-01

    The ordered orthorhombic 'O' phase in the Ti-Al-Nb ordered alloy system emerges either through slow cooling from above 1200 C or through isothermal aging after quenching from that temperature regime. An experimental investigation is presently conducted of the structural relationship between the O and alpha(2) phases, in order to clarify the mechanism of transition between the two. The transition occurs with the formation of a platelike alpha(2) phase within the O matrix, and may be characterized as due to a shape-deformation mechanism associated with diffusion of excess Nb away from the O/alpha(2) interface.

  12. 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.

  13. Strain tuned magnetoelectric coupling in orthorhombic YMnO3 thin films

    NASA Astrophysics Data System (ADS)

    Marti, X.; Fina, I.; Skumryev, V.; Ferrater, C.; Varela, M.; Fábrega, L.; Sánchez, F.; Fontcuberta, J.

    2009-10-01

    Orthorhombic YMnO3 epitaxial thin films were grown on Nb(0.5%)-doped SrTiO3(001) substrates. Film's thickness was varied to tune the epitaxial strain. Structural and magnetic properties are well correlated, presenting a more pronounced ferromagnetic behavior as the unit cell becomes more distorted. Dielectric properties were investigated as a function of the temperature and magnetic field. The dielectric peak occurring at temperatures below the antiferromagnetic ordering is proved to be magnetoelectric and its amplitude is dependent on the unit cell distortion. These findings allow tailoring ferromagnetic and magnetoelectric properties via epitaxial strain.

  14. Incommensurate magnetic structure in the orthorhombic perovskite ErMnO3

    NASA Astrophysics Data System (ADS)

    Ye, F.; Lorenz, B.; Huang, Q.; Wang, Y. Q.; Sun, Y. Y.; Chu, C. W.; Fernandez-Baca, J. A.; Dai, Pengcheng; Mook, H. A.

    2007-08-01

    By combining dielectric, specific heat, and magnetization measurements and high-resolution neutron powder diffraction, we have investigated the thermodynamic and magnetic and structural properties of the metastable orthorhombic perovskite ErMnO3 prepared by high-pressure synthesis. The system becomes antiferromagnetically correlated below 42K and undergoes a lock-in transition at 28K with propagation wave vector (0,kb,0) , which remains incommensurate at low temperature. The intercorrelation between the magnetic structure and electric properties and the role of the rare earth moment are discussed.

  15. On the orthorhombic phase in ZrO2-based alloys

    NASA Technical Reports Server (NTRS)

    Heuer, A. H.; Lanteri, V.; Chaim, R.; Lee, R.-R.; Farmer, S. C.

    1989-01-01

    During TEM observation, a tetragonal (t) to orthorhombic (o) phase transformation often occurs in thin portions of ZrO2-containing foils. This transformation is stress-induced and in some senses artifactual, in that the reaction product is actually a high-pressure phase, relative to monoclinic (m) ZrO2, that can form from metastable t-ZrO2 in the TEM because its density is intermediate between t- and m-ZrO2. Examples of the formation of o-ZrO2 in a number of different systems are given.

  16. [Effect of crystallization and branch on fine structure of orthorhombic in polyethylene].

    PubMed

    Kang, N; Xu, Y; Weng, S; Wu, J; Xu, D

    2001-02-01

    The CH2 rocking bands are used as a probe to monitor the crystalline behavior of polyethylene segments in a series of poly (ethylene-octene) copolymers. High resolution and cryogenic FTIR spectra reveal that different composition and/or crystalline condition of the copolymers result in significant variation on the CH2 rocking bands including the change in peak position, band width and A730/A720. We conclude that side chain in the copolymer can influence the structure of the orthorhombic polyethylene crystallite although they can not enter the crystal lattice.

  17. Structure of the welding zone between titanium and orthorhombic titanium aluminide for explosion welding: I. Interface

    NASA Astrophysics Data System (ADS)

    Rybin, V. V.; Grinberg, B. A.; Ivanov, M. A.; Kuz'min, S. V.; Lysak, V. I.; Elkina, O. A.; Patselov, A. M.; Inozemtsev, A. V.; Antonova, O. V.; Kozhevnikov, V. E.

    2011-10-01

    The structures of the interfaces and transition zones of bimetallic metal-intermetallide joints produced by explosion welding under various conditions have been studied. The welded materials were commercial-purity titanium and orthorhombic titanium aluminide of two alloying schemes. The specific features of the structure and substructure of the zones under study are discussed. Wave formation and formation of isolated vortex zones, as well as tracks of particles related to the transfer of particles of one metal into the other one, were observed. A possible scenario of formation of interfaces, depending on the composition of titanium aluminide and welding conditions, is proposed.

  18. Minimum strain rate and primary transient creep analysis of a fine structure orthorhombic titanium aluminide

    SciTech Connect

    Hayes, R.W.

    1996-03-15

    The purpose of the present paper is to present a preliminary analysis of the primary transient creep behavior of an orthorhombic titanium aluminide having a very fine microstructure. In order to analyze and understand the creep behavior within the primary transient regime it is necessary to understand the mechanisms controlling deformation within the minimum strain rate region. Therefore an analysis of the minimum strain rate behavior is also presented. It will be shown that the primary transient creep behavior is dependent upon whether creep in the minimum strain rate region is controlled by a viscous flow mechanism or a dislocation mechanism.

  19. Influence of a 60° domain structure on the orthorhombic niobate-based piezoelectric property

    NASA Astrophysics Data System (ADS)

    Tsuchida, Kohei; Kakimoto, Ken-ichi; Kagomiya, Isao

    2013-04-01

    The present work investigated the dependence of domain switching (90° and 60° domains) on the piezoelectric property due to an applied electric field in Mn-doped Na0.55K0.45NbO3 (Mn-NKN) ceramic samples. In addition, the electric-field-induced strain and temperature-dependent planar extensional electromechanical coupling factor k p were studied. The results indicate that the piezoelectric properties for the orthorhombic phase due to 60° domain switching are stable over a wide range of temperatures.

  20. Antiferroelectric Topological Insulators in Orthorhombic A MgBi Compounds (A =Li , Na, K)

    NASA Astrophysics Data System (ADS)

    Monserrat, Bartomeu; Bennett, Joseph W.; Rabe, Karin M.; Vanderbilt, David

    2017-07-01

    We introduce antiferroelectric topological insulators as a new class of functional materials in which an electric field can be used to control topological order and induce topological phase transitions. Using first principles methods, we predict that several alkali-MgBi orthorhombic members of an A B C family of compounds are antiferroelectric topological insulators. We also show that epitaxial strain and hydrostatic pressure can be used to tune the topological order and the band gap of these A B C compounds. Antiferroelectric topological insulators could enable precise control of topology using electric fields, enhancing the applicability of topological materials in electronics and spintronics.

  1. Antiferroelectric Topological Insulators in Orthorhombic AMgBi Compounds (A=Li, Na, K).

    PubMed

    Monserrat, Bartomeu; Bennett, Joseph W; Rabe, Karin M; Vanderbilt, David

    2017-07-21

    We introduce antiferroelectric topological insulators as a new class of functional materials in which an electric field can be used to control topological order and induce topological phase transitions. Using first principles methods, we predict that several alkali-MgBi orthorhombic members of an ABC family of compounds are antiferroelectric topological insulators. We also show that epitaxial strain and hydrostatic pressure can be used to tune the topological order and the band gap of these ABC compounds. Antiferroelectric topological insulators could enable precise control of topology using electric fields, enhancing the applicability of topological materials in electronics and spintronics.

  2. Multiferroicity in TTF-CA Organic Molecular Crystals Predicted through Ab Initio Calculations

    NASA Astrophysics Data System (ADS)

    Giovannetti, Gianluca; Kumar, Sanjeev; Stroppa, Alessandro; van den Brink, Jeroen; Picozzi, Silvia

    2009-12-01

    We show by means of ab initio calculations that the organic molecular crystal TTF-CA is multiferroic: it has an instability to develop spontaneously both ferroelectric and magnetic ordering. Ferroelectricity is driven by a Peierls transition of the TTF-CA in its ionic state. Subsequent antiferromagnetic ordering strongly enhances the opposing electronic contribution to the polarization. It is so large that it switches the direction of the total ferroelectric moment. Within an extended Hubbard model, we capture the essence of the electronic interactions in TTF-CA, confirm the presence of a multiferroic groundstate, and clarify how this state develops microscopically.

  3. 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.

  4. A new class of room-temperature multiferroic thin films with bismuth-based supercell structure.

    PubMed

    Chen, Aiping; Zhou, Honghui; Bi, Zhenxing; Zhu, Yuanyuan; Luo, Zhiping; Bayraktaroglu, Adrian; Phillips, Jamie; Choi, Eun-Mi; Macmanus-Driscoll, Judith L; Pennycook, Stephen J; Narayan, Jagdish; Jia, Quanxi; Zhang, Xinghang; Wang, Haiyan

    2013-02-20

    Intergrowth of two partially miscible phases of BiFeO(3) and BiMnO(3) gives a new class of room-temperature multiferroic phase, Bi(3) Fe(2) Mn(2) O(10+δ) , which has a unique supercell (SC) structure. The SC heterostructures exhibit simultaneously room-temperature ferrimagnetism and remanent polarization. These results open up a new avenue for exploring room-temperature single-phase multiferroic thin films by controlling the phase mixing of two perovskite BiRO(3) (R = Cr, Mn, Fe, Co, Ni) materials.

  5. Phonon anomalies and the ferroelectric phase transition in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Haumont, R.; Kreisel, J.; Bouvier, P.; Hippert, F.

    2006-04-01

    We report a temperature-dependent Raman scattering investigation of the multiferroic material bismuth ferrite BiFeO3 (BFO). The observed loss of the Raman spectrum at the ferroelectric Curie temperature TC should be in agreement with a cubic Pm3¯m structure of the high-temperature paraelectric phase. Surprisingly, the ferroelectric-to-paraelectric phase transition is not soft-mode driven, indicating a nonconventional ferroelectric. Furthermore, our results reveal pronounced phonon anomalies around the magnetic Néel temperature TN . We tentatively attribute these anomalies to the multiferroic character of BFO.

  6. 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.

  7. Combined caloric effects in a multiferroic Ni-Mn-Ga alloy with broad refrigeration temperature region

    NASA Astrophysics Data System (ADS)

    Hu, Yong; Li, Zongbin; Yang, Bo; Qian, Suxin; Gan, Weimin; Gong, Yuanyuan; Li, Yang; Zhao, Dewei; Liu, Jian; Zhao, Xiang; Zuo, Liang; Wang, Dunhui; Du, Youwei

    2017-04-01

    Solid-state refrigeration based on the caloric effects is promising to replace the traditional vapor-compressing refrigeration technology due to environmental protection and high efficiency. However, the narrow working temperature region has hindered the application of these refrigeration technologies. In this paper, we propose a method of combined caloric, through which a broad refrigeration region can be realized in a multiferroic alloy, Ni-Mn-Ga, by combining its elastocaloric and magnetocaloric effects. Moreover, the materials' efficiency of elastocaloric effect has been greatly improved in our sample. These results illuminate a promising way to use multiferroic alloys for refrigeration with a broad refrigeration temperature region.

  8. 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).

  9. 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.

  10. Inversion symmetry controlled multiferroic response in an Ising Chain Magnet

    NASA Astrophysics Data System (ADS)

    Jo, Younjung; Lee, Seongsu; Yi, Heetaek; Cheong, Sangwook; Balicas, Luis

    2008-03-01

    Recently, Choi et al. [1] discovered that ferroelectricity in the Ising chain magnet results from inversion symmetry breaking due to the formation of an alternating ionic order of two different ions leading to an up-up-down-down spin configuration. Here we report the observation of drastic changes in the multiferroic character as a function of magnetic field in the Ising chain magnet. Application of a magnetic field up to 33 T, leads to two abrupt changes in the dielectric constant, respectively at H1 = 5 T and at H2=20T, with the first one leading to a fast suppression of the dielectric polarization. The saturation values of the magnetic moment observed by using a vibrating sample magnetometer and a cantilever beam magnetometer suggest that the one ionic moments align along the field for fields above 5 T followed by the subsequent alignment of the other ionic moments above 20 T. [1] Y.J. Choi et al. Physical Review Lett. submitted

  11. Superadiabatic quantum heat engine with a multiferroic working medium.

    PubMed

    Chotorlishvili, L; Azimi, M; Stagraczyński, S; Toklikishvili, Z; Schüler, M; Berakdar, J

    2016-09-01

    A quantum thermodynamic cycle with a chiral multiferroic working substance such as LiCu_{2}O_{2} is presented. Shortcuts to adiabaticity are employed to achieve an efficient, finite-time quantum thermodynamic cycle, which is found to depend on the spin ordering. The emergent electric polarization associated with the chiral spin order, i.e., the magnetoelectric coupling, renders possible steering of the spin order by an external electric field and hence renders possible an electric-field control of the cycle. Due to the intrinsic coupling between the spin and the electric polarization, the cycle performs an electromagnetic work. We determine this work's mean-square fluctuations, the irreversible work, and the output power of the cycle. We observe that the work mean-square fluctuations are increased with the duration of the adiabatic strokes, while the irreversible work and the output power of the cycle show a nonmonotonic behavior. In particular, the irreversible work vanishes at the end of the quantum adiabatic strokes. This fact confirms that the cycle is reversible. Our theoretical findings evidence the existence of a system inherent maximal output power. By implementing a Lindblad master equation we quantify the role of thermal relaxations on the cycle efficiency. We also discuss the role of entanglement encoded in the noncollinear spin order as a resource to affect the quantum thermodynamic cycle.

  12. 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.

  13. Stress magnetization model for magnetostriction in multiferroic composite

    NASA Astrophysics Data System (ADS)

    Gualdi, A. J.; Zabotto, F. L.; Garcia, D.; de Oliveira, A. J. A.

    2013-08-01

    An alternative to obtain multiferroic materials is the production of composite materials that combine ferroelectric and magnetic materials. In particular, the use of magnetostrictive materials as ferromagnetic phase in composites is very important because the mechanical stress applied in ferroelectric phase induces the appearance of magnetoelectric effect. In this work, we have proposed a generalized model for the magnetostriction dependence with the magnetization of the 0-3 type composite magnetoelectric materials. Including both piezomagnetic and stress dependence in the magnetostriction, a relevant improvement was reached as compared to the ordinary square magnetization model. Based on the Gibbs free energy expansion, the magnetostriction behavior of the composite (1-x)Pb(Mg1/3Nb2/3)-xPbTiO3/CoFe2O4 at 300 K and 5 K is described. Furthermore, using the piezomagnetic correction, the magnetostriction data for the pure CoFe2O4 is fitted showing that this ferrite presents a relevant piezomagnetic effect.

  14. 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

  15. Superadiabatic quantum heat engine with a multiferroic working medium

    NASA Astrophysics Data System (ADS)

    Chotorlishvili, L.; Azimi, M.; Stagraczyński, S.; Toklikishvili, Z.; Schüler, M.; Berakdar, J.

    2016-09-01

    A quantum thermodynamic cycle with a chiral multiferroic working substance such as LiCu2O2 is presented. Shortcuts to adiabaticity are employed to achieve an efficient, finite-time quantum thermodynamic cycle, which is found to depend on the spin ordering. The emergent electric polarization associated with the chiral spin order, i.e., the magnetoelectric coupling, renders possible steering of the spin order by an external electric field and hence renders possible an electric-field control of the cycle. Due to the intrinsic coupling between the spin and the electric polarization, the cycle performs an electromagnetic work. We determine this work's mean-square fluctuations, the irreversible work, and the output power of the cycle. We observe that the work mean-square fluctuations are increased with the duration of the adiabatic strokes, while the irreversible work and the output power of the cycle show a nonmonotonic behavior. In particular, the irreversible work vanishes at the end of the quantum adiabatic strokes. This fact confirms that the cycle is reversible. Our theoretical findings evidence the existence of a system inherent maximal output power. By implementing a Lindblad master equation we quantify the role of thermal relaxations on the cycle efficiency. We also discuss the role of entanglement encoded in the noncollinear spin order as a resource to affect the quantum thermodynamic cycle.

  16. 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

  17. Heat-Assisted Multiferroic Solid-State Memory

    PubMed Central

    2017-01-01

    A heat-assisted multiferroic solid-state memory design is proposed and analysed, based on a PbNbZrSnTiO3 antiferroelectric layer and Ni81Fe19 magnetic free layer. Information is stored as magnetisation direction in the free layer of a magnetic tunnel junction element. The bit writing process is contactless and relies on triggering thermally activated magnetisation switching of the free layer towards a strain-induced anisotropy easy axis. A stress is generated using the antiferroelectric layer by voltage-induced antiferroelectric to ferroelectric phase change, and this is transmitted to the magnetic free layer by strain-mediated coupling. The thermally activated strain-induced magnetisation switching is analysed here using a three-dimensional, temperature-dependent magnetisation dynamics model, based on simultaneous evaluation of the stochastic Landau-Lifshitz-Bloch equation and heat flow equation, together with stochastic thermal fields and magnetoelastic contributions. The magnetisation switching probability is calculated as a function of stress magnitude and maximum heat pulse temperature. An operating region is identified, where magnetisation switching always occurs, with stress values ranging from 80 to 180 MPa, and maximum temperatures normalised to the Curie temperature ranging from 0.65 to 0.99. PMID:28841185

  18. Heat-Assisted Multiferroic Solid-State Memory.

    PubMed

    Lepadatu, Serban; Vopson, Melvin M

    2017-08-25

    A heat-assisted multiferroic solid-state memory design is proposed and analysed, based on a PbNbZrSnTiO₃ antiferroelectric layer and Ni81Fe19 magnetic free layer. Information is stored as magnetisation direction in the free layer of a magnetic tunnel junction element. The bit writing process is contactless and relies on triggering thermally activated magnetisation switching of the free layer towards a strain-induced anisotropy easy axis. A stress is generated using the antiferroelectric layer by voltage-induced antiferroelectric to ferroelectric phase change, and this is transmitted to the magnetic free layer by strain-mediated coupling. The thermally activated strain-induced magnetisation switching is analysed here using a three-dimensional, temperature-dependent magnetisation dynamics model, based on simultaneous evaluation of the stochastic Landau-Lifshitz-Bloch equation and heat flow equation, together with stochastic thermal fields and magnetoelastic contributions. The magnetisation switching probability is calculated as a function of stress magnitude and maximum heat pulse temperature. An operating region is identified, where magnetisation switching always occurs, with stress values ranging from 80 to 180 MPa, and maximum temperatures normalised to the Curie temperature ranging from 0.65 to 0.99.

  19. 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.

  20. 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

  1. Unusual Mott transition in multiferroic PbCrO 3

    DOE PAGES

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; ...

    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

  2. The Facile Hydrothermal Preparation of Orthorhombic WO3 With (001) Facet and Its Photocatalytic Performance.

    PubMed

    Deng, Xiaoyan; Dou, Jinbiao; Li, Fenfen; Gao, Hongtao; Liu, Guangjun

    2015-12-01

    The orthorhombic WO3 nanoplates with (001) facet were fabricated via a facile hydrothermal process, using HBF4 as the acid source. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffused reflectance spectroscopy (DRS), respectively. It indicated that the obtained product was orthorhombic WO3 (JCPDS No. 20-1324). And the energy gap was estimated to be 2.52 eV by the intersection point of the tangent of the absorption edge and the baseline. It was affirmed that WO3 crystalline grew along the (001) direction, indicating the product was exposed with (001) facet. The photocatalytic activity of (001) WO3 nanoplates was investigated on the degradation of Rhodamine B (RhB). It demonstrated that photocatalysts exhibited obvious photocatalytic performance under visible light irradiation. The degradation rate of RhB with the typical product reached 95% after being irradiated for 5 h. It indicated that the photocatalytic efficiency of WO3 could be improved by controlling the crystal growth and its morphology.

  3. 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.

  4. Formation of vortices during explosion welding (titanium-orthorhombic titanium aluminide)

    NASA Astrophysics Data System (ADS)

    Rybin, V. V.; Greenberg, B. A.; Antonova, O. V.; Elkina, O. A.; Ivanov, M. A.; Inozemtsev, A. V.; Patselov, A. M.; Sidorov, I. I.

    2009-10-01

    The possibility of cladding commercially pure titanium by a plate of orthorhombic titanium aluminide has been investigated. The bimetallic joints of orthorhombic titanium aluminide (Ti-30Al-16Nb-1Zr-1Mo) with commercially pure titanium have been obtained by explosion welding. It has been found that the weld joint investigated had a multilayer structure consisting of a zone of continuous deformation observed in both materials, a zone of titanium recrystallization, and a transition zone near the interface. Wave formation and formation of isolated vortex zones have been observed. It has been found that upon explosion welding the bonding of the surfaces is effected via melting and subsequent mixing (in the zone of vortices) and the transfer of particles of one metal into another with the formation of particle tracks (outside the zone of vortices). A possible scenario of the formation of the vortex zone in the melt with a subsequent eutectic decomposition is proposed. The structure of the vortex zones was found to consist of an ultrafine mixture of α and β grains (both phases are disordered) with the grain size changing in the limits of 50-300 nm. The regions of transition from the vortex zone to the region of continuous deformation of the aluminide and to the recrystallized zone of titanium have been investigated.

  5. 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)

  6. In situ study of electric field-induced magnetization in multiferroic BiFeO(3) nanowires.

    PubMed

    Prashanthi, K; Thundat, T

    2014-01-01

    In this work, we have studied electric field-induced magnetization effect of multiferroic BiFeO3 (BFO) nanowires in situ using magnetic force microscopy (MFM). Changes in magnetic domain contrast have been observed in the MFM phase images under applied electric potential, which indicate local magnetoelectric (ME) coupling in the nanowires. The values of saturation and magnetization at different applied electric fields were evaluated. These results suggest that one-dimensional multiferroic BFO nanowires are potential candidates for realizing multiferroic devices at nanoscale with unique functionalities. © 2013 Wiley Periodicals, Inc.

  7. Effect of Pr- and Nd- doping on structural, dielectric, and magnetic properties of multiferroic Bi0.8La0.2Fe0.9Mn0.1O3

    NASA Astrophysics Data System (ADS)

    Singh, Rahul; Dwivedi, G. D.; Shahi, P.; Kumar, D.; Prakash, Om; Ghosh, A. K.; Chatterjee, Sandip

    2014-04-01

    Bi0.8La0.15RE0.05Fe0.9Mn0.1O3 (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 A1-3 and weak E-2 modes in Bi0.8La0.15Nd0.05Fe0.9Mn0.1O3 indicate the presence of chemically more active Bi-O covalent bonds (which favors stereochemical activity of Bi lone pair electrons) in comparison to Bi0.8La0.15Pr0.05Fe0.9Mn0.1O3. Moreover, Bi0.8La0.15Nd0.05Fe0.9Mn0.1O3 system shows higher dielectric constant, low dielectric loss, and higher magnetization value in comparison to Bi0.8La0.15Pr0.05Fe0.9Mn0.1O3 system. Ferroelectric transition temperature decreases to 460 °C for both systems in comparison to 710 °C of Bi0.8La0.2Fe0.9Mn0.1O3. The improved dielectric and magnetic response suggests Bi0.8La0.15Nd0.05Fe0.9Mn0.1O3 a better multiferroic system than Bi0.8La0.15Pr0.05Fe0.9Mn0.1O3.

  8. 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.

  9. 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.

  10. 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.

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

    PubMed

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

    2016-09-28

    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.

  12. 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.

  13. 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

  14. Ultra-Low-Energy Electric Field-Induced Magnetization Switching in Multiferroic Heterostructures

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    2016-10-01

    Electric field-induced magnetization switching in multiferroics is intriguing for both fundamental studies and potential technological applications. Here, we review the recent developments on electric field-induced magnetization switching in multiferroic heterostructures. Particularly, we study the dynamics of magnetization switching between the two stable states in a shape-anisotropic single-domain nanomagnet using stochastic Landau-Lifshitz-Gilbert (LLG) equation in the presence of thermal fluctuations. For magnetostrictive nanomagnets in strain-coupled multiferroic composites, such study of magnetization dynamics, contrary to steady-state scenario, revealed intriguing new phenomena on binary switching mechanism. While the traditional method of binary switching requires to tilt the potential profile to the desired state of switching, we show that no such tilting is necessary to switch successfully since the magnetization’s excursion out of magnet’s plane can generate a built-in asymmetry during switching. We also study the switching dynamics in multiferroic heterostructures having magnetoelectric coupling at the interface and magnetic exchange coupling that can facilitate to maintain the direction of switching with the polarity of the applied electric field. We calculate the performance metrics like switching delay and energy dissipation during switching while simulating LLG dynamics. The performance metrics turn out to be very encouraging for potential technological applications.

  15. Toward pressure-induced multiferroicity in PrMn2O5

    NASA Astrophysics Data System (ADS)

    Peng, W.; Balédent, V.; Chattopadhyay, S.; Lepetit, M.-B.; Yahia, G.; Colin, C. V.; Gooch, M. J.; Pasquier, C. R.; Auban-Senzier, P.; Greenblatt, M.; Foury-Leylekian, P.

    2017-08-01

    The series of multiferroics R Mn2O5 is extensively studied for its quasicollinear spin arrangement, which results in an electrical polarization according to the exchange-striction model. Variations of the interatomic distances modified by the external pressure can strongly influence the multiferroic properties. Understanding this influence is of great importance, especially for the future realization of multiferroic devices. As PrMn2O5 is paraelectric at ambient pressure, it is the most suitable candidate to search for pressure induced multiferroicity. In this paper, we report the emergence of a new pressure induced magnetic phase in PrMn2O5 determined by powder neutron diffraction under pressure. This new magnetic phase presenting at relatively low pressure becomes completely exclusive at 8 GPa. The determination of its magnetic structure has thus been possible for the first time. More importantly, the magnetic structure stabilized under pressure should induce a strong spontaneous electric polarization due to the nearly perfect collinearity of the Mn3 + and Mn4 + spins.

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

    DOE PAGES

    Poudel, N.; Lorenz, B.; Lv, B.; ...

    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

  17. Light-controlled resistive switching memory of multiferroic BiMnO3 nanowire arrays.

    PubMed

    Sun, Bai; Li, Chang Ming

    2015-03-14

    A multiferroic BiMnO3 nanowire array was prepared using a hydrothermal process and its resistive switching memory behaviors were further investigated. The prominent ferroelectricity can be well controlled by white-light illumination, thus offering an excellent light-controlled resistive switching memory device using a Ag/BiMnO3/Ti structure at room temperature.

  18. 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.

  19. 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.

  20. 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.

  1. Solution-phase synthesis of rubidium lead iodide orthorhombic perovskite nanowires

    NASA Astrophysics Data System (ADS)

    Lim, Da-Hye; Ramasamy, Parthiban; Kwak, Do-Hyun; Lee, Jong-Soo

    2017-06-01

    Recently, metal halide perovskite nanocrystals have demonstrated outstanding properties in various optoelectronic applications. Cesium lead halides (CsPbX3) are the most studied perovskites in nanoscale dimensions. However, halide perovskite nanocrystals with other cations have rarely been reported. It is important to develop new perovskite compositions to further expand their application in various fields. In this paper, we first report the synthesis of colloidal rubidium lead iodide (RbPbI3) nanowires (NWs). RbPbI3 NWs have an orthorhombic crystal structure and are single-crystalline in nature. The diameter of the NWs is around 32 nm with lengths up to several tens of micrometers. RbPbI3 NWs absorb strongly below 450 nm. RbPbI3 devices exhibited good photoresponsive behavior, suggesting a potential use in optoelectronics.

  2. Locked octahedral tilting in orthorhombic perovskites: At the boundary of the general rule predicting phase transitions

    NASA Astrophysics Data System (ADS)

    Ardit, M.; Dondi, M.; Cruciani, G.

    2017-01-01

    Mainly ruled by oxygen octahedral rotations, perovskite oxides can exhibit zone boundary transitions (ZBTs) either with d Tc/d P >0 or d Tc/d P <0 . Synchrotron structural investigations at high pressure conditions place YA l0.25C r0.75O3 orthorhombic perovskite at the boundary of ZBTs. The absence of changes in the octahedral tilting and a volume reduction with pressure exclusively controlled by an isotropic polyhedral compression set YA l0.25C r0.75O3 as the first finding of a possible asymptote at the Clapeyron relation for predicting ZBTs in perovskites. Furthermore, the discovery of a "locked-tilt perovskite" can pave the way to a new class of functional materials.

  3. Structural transition of PETN-I to ferroelastic orthorhombic phase PETN-III at elevated pressures.

    PubMed

    Tschauner, O; Kiefer, B; Lee, Y; Pravica, M; Nicol, M; Kim, E

    2007-09-07

    Using powder x-ray diffraction and first-principles calculations, we provide evidence for a structural transition of PETN-I below 6 GPa to an orthorhombic phase of space group P2(1)2(1)2. The transition can be rationalized as shear-stress induced and ferroelastic, which involves a slight static displacement of the molecules that breaks the fourfold symmetry of PETN-I. Previously reported changes in the optical spectra reflect a lifting of the twofold degeneracy of modes in tetragonal PETN-I. The observed transition is expected to induce soft shear compliances along specific directions in PETN crystallites that may relate to the observed dependence of detonation pressure on crystal orientation.

  4. Structural Transition of PETN-I to Ferroelastic Orthorhombic Phase PETN-III at Elevated Pressures

    SciTech Connect

    Tschauner,O.; Kiefer, B.; Lee, Y.; Pravica, M.; Nicol, M.; Kim, E.

    2007-01-01

    Using powder x-ray diffraction and first-principles calculations, we provide evidence for a structural transition of PETN-I below 6 GPa to an orthorhombic phase of space group P2{sub 1}2{sub 1}2. The transition can be rationalized as shear-stress induced and ferroelastic, which involves a slight static displacement of the molecules that breaks the fourfold symmetry of PETN-I. Previously reported changes in the optical spectra reflect a lifting of the twofold degeneracy of modes in tetragonal PETN-I. The observed transition is expected to induce soft shear compliances along specific directions in PETN crystallites that may relate to the observed dependence of detonation pressure on crystal orientation.

  5. Determination of the resistivity anisotropy of orthorhombic materials via transverse resistivity measurements

    DOE PAGES

    Walmsley, P.; Fisher, I. R.

    2017-04-05

    Measurements of the resistivity anisotropy can provide crucial information about the electronic structure and scattering processes in anisotropic and low-dimensional materials, but quantitative measurements by conventional means often suffer very significant systematic errors. Here we describe a novel approach to measuring the resistivity anisotropy of orthorhombic materials, using a single crystal and a single measurement that is derived from a π/4 rotation of the measurement frame relative to the crystallographic axes. In this new basis, the transverse resistivity gives a direct measurement of the resistivity anisotropy, which combined with the longitudinal resistivity also gives the in-plane elements of the conventionalmore » resistivity tensor via a 5-point contact geometry. In conclusion, this is demonstrated through application to the charge-density wave compound ErTe3, and it is concluded that this method presents a significant improvement on existing techniques, particularly when measuring small anisotropies.« less

  6. Anomalous Phonon Behavior in Orthorhombic LuMnO3 at Low Temperature

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Chen, Haiyan; Tyson, Trevor A.; Liu, Zhenxian; Bai, Jianming; Wang, Liping; Choi, Youngjai; Cheong, Sang-Wook

    2011-03-01

    We present the pressure dependent phonon spectra of orthorhombic-LuMnO3 which are conducted in the low temperature region (below TN and TL) . A temperature dependent anomalous phonon coincides with the ferroelectric behavior at low pressure condition. At ~ 10 GPa, this anomalous phonon exhibits an unusual softening trend which will be suppressed at higher pressure. This work is supported by DOE Grant DE-FG02-07ER46402 (NJIT), by DE-FG02-07ER46402 (Rutgers), by COMPRES (U2A beam line at NSLS), the Consortium for Materials Properties Research in Earth Sciences under NSF Cooperative Agreement EAR01-35554, U.S. Department of Energy (DOE-BES and NNSA/CDAC) and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886 (use of NSLS at Brookhaven National Laboratory).

  7. Body-centered orthorhombic C16: A novel topological node-line semimetal

    DOE PAGES

    Wang, Jian -Tao; Weng, Hongming; Nie, Simin; ...

    2016-05-11

    We identify by ab initio calculations a novel topological semimetal carbon phase in all-sp2 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-sp2 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 topologicalmore » node-line semimetal with a single nodal ring. Lastly, these findings establish a novel carbon phase with intriguing structural and electronic properties of fundamental significance and practical interest.« less

  8. Electron-phonon scattering effects on electronic and optical properties of orthorhombic GeS

    NASA Astrophysics Data System (ADS)

    Villegas, Cesar E. P.; Rocha, A. R.; Marini, Andrea

    2016-10-01

    Group-VI monochalcogenides are attracting a great deal of attention due to their peculiar anisotropic properties. Very recently, it has been suggested that GeS could act as a promissory absorbing material with high input-output ratios, which are relevant features for designing prospective optoelectronic devices. In this work, we use the ab initio many-body perturbation theory to study the role of electron-phonon coupling on orthorhombic GeS. We identify the vibrational modes that efficiently couple with the electronic states responsible for giving rise to the first and second excitonic state. We also study finite-temperature optical absorption, and we show that even at T →0 K , the role of the electron-phonon interaction is crucial to properly describe the position and width of the main experimental excitation peaks. Our results suggest that the electron-phonon coupling is essential to properly describe the optical properties of the monochalcogenides family.

  9. Orthorhombic boron oxide under pressure: In situ study by X-ray diffraction and Raman scattering

    NASA Astrophysics Data System (ADS)

    Cherednichenko, Kirill A.; Le Godec, Yann; Kalinko, Aleksandr; Mezouar, Mohamed; Solozhenko, Vladimir L.

    2016-11-01

    High-pressure phase of boron oxide, orthorhombic β-B2O3, has been studied in situ by synchrotron X-ray diffraction to 22 GPa and Raman scattering to 46 GPa at room temperature. The bulk modulus of β-B2O3 has been found to be 169(3) GPa that is in good agreement with our ab initio calculations. Raman and IR spectra of β-B2O3 have been measured at ambient pressure; all experimentally observed bands have been attributed to the theoretically calculated ones, and the mode assignment has been performed. Based on the data on Raman shift as a function of pressure, combined with equation-of-state data, the Grüneisen parameters of all experimentally observed Raman bands have been calculated. β-B2O3 enriched by 10B isotope has been synthesized, and the effect of boron isotopic substitution on Raman spectra has been studied.

  10. Thermoelectric properties of orthorhombic group IV-VI monolayers from the first-principles calculations

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong; Wang, Yue-Hua

    2017-01-01

    Two-dimensional (2D) materials may have potential applications in thermoelectric devices. In this work, the thermoelectric properties of orthorhombic group IV-VI monolayers AB (A = Ge and Sn; B = S and Se) are systematically investigated by the first-principles calculations and semiclassical Boltzmann transport theory. The spin-orbit coupling (SOC) is considered for their electron part, which produces observable effects on the power factor, especially for n-type doping. According to the calculated ZT, the four monolayers exhibit diverse anisotropic thermoelectric properties although they have a similar hinge-like crystal structure. The GeS along zigzag and armchair directions shows the strongest anisotropy, while SnS and SnSe show mostly isotropic efficiency of thermoelectric conversion. This can be explained by the strength of anisotropy of their respective power factor and electronic and lattice thermal conductivities. The calculated results show that the ZT between n- and p-type doping has little difference for GeS, SnS, and SnSe. It is found that GeSe, SnS, and SnSe show better thermoelectric performance compared to GeS in n-type doping and that SnS and SnSe exhibit higher efficiency of thermoelectric conversion in p-type doping. Compared to other many 2D materials, orthorhombic group IV-VI monolayers AB (A = Ge and Sn; B = S and Se) may possess better thermoelectric performance due to lower lattice thermal conductivities. Our work would be beneficial to stimulate further theoretical and experimental works.

  11. 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.

  12. CoFe{sub 2}/Al{sub 2}O{sub 3}/PMNPT multiferroic heterostructures by atomic layer deposition

    SciTech Connect

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

    2016-05-02

    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/Al{sub 2}O{sub 3}/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.

  13. Phase transformations in multiferroic Bi{sub 1−x}La{sub x}Fe{sub 1−y}Ti{sub y}O{sub 3} ceramics probed by temperature dependent Raman scattering

    SciTech Connect

    Xu, L. P.; Zhang, X. L.; Zhang, J. Z.; Hu, Z. G. Chu, J. H.; Zhang, L. L.; Yu, J.

    2014-10-28

    Optical phonons and phase transitions of Bi{sub 1−x}La{sub x}Fe{sub 1−y}Ti{sub y}O{sub 3} (BLFTO, 0.02 ≤ x ≤ 0.12, 0.01 ≤ y ≤ 0.08) ceramics have been investigated by Raman scattering in the temperature range from 80 to 680 K. Four phase transitions around 140, 205, 570, and 640 K can be observed. The Raman modes are sensitive to the spin reorientation around 140 and 205 K, owing to the strong magnon-phonon coupling. The transformation around 570 K is a structural transition from rhombohedral to orthorhombic phase due to an external pressure induced by the chemical substitution. The anomalies of the phonon frequencies near Néel temperature T{sub N} have been discussed in the light of the multiferroicity. Moreover, it was found that the structural transition temperature and T{sub N} of BLFTO ceramics decrease towards room temperature with increasing doping composition as a result of size mismatch between substitution and host cations.

  14. Low-dimensional magnetic properties of orthorhombic MnV2O6 : A nonstandard structure stabilized at high pressure

    NASA Astrophysics Data System (ADS)

    Hneda, M. L.; da Cunha, J. B. M.; Gusmão, M. A.; Neto, S. R. Oliveira; Rodríguez-Carvajal, J.; Isnard, O.

    2017-01-01

    This paper presents the physical properties of a nonstandard orthorhombic form of MnV2O6 , including a comparison with the isostructural orthorhombic niobate MnNb2O6 , and with the usual MnV2O6 monoclinic polymorph. Orthorhombic (P b c n ) MnV2O6 is obtained under extreme conditions of high pressure (6.7 GPa) and high temperature (800 ∘C ). A negative Curie-Weiss temperature θCW is observed, implying dominant antiferromagnetic interactions at high temperatures, in contrast to the positive θCW of the monoclinic form. Specific-heat measurements are reported down to 1.8 K for all three compounds, and corroborate the magnetic-transition temperatures obtained from susceptibility data. Orthorhombic MnV2O6 presents a transition to an ordered antiferromagnetic state at TN=4.7 K. Its magnetic structure, determined by neutron diffraction, is unique among the columbite compounds, being characterized by a commensurate propagation vector k =(0 ,0 ,1/2 ) . It presents antiferromagnetic chains running along the c axis, but with a different spin pattern in comparison to the chains observed in MnNb2O6 . By a comparative discussion of our observations in this three compounds, we are able to highlight the interplay between competing interactions and dimensionality that yield their magnetic properties.

  15. Cubic and orthorhombic structures of aluminum hydride Al H3 predicted by a first-principles study

    NASA Astrophysics Data System (ADS)

    Ke, Xuezhi; Kuwabara, Akihide; Tanaka, Isao

    2005-05-01

    The most stable structure of aluminum hydride AlH3 is believed to be a hexagonal symmetry. However, using the density functional theory, we have identified two more stable structures for the AlH3 with the cubic and orthorhombic symmetries. Based on the quasiharmonic approximation, the cubic and orthorhombic AlH3 are almost degenerate when the zero-point energies are included. The geometric and electronic structures, the phonon, and the thermodynamic properties for the hexagonal, cubic, and orthorhombic AlH3 have been studied by means of density functional theory and direct ab initio force constant approach. The calculated electronic structures, phonon density of states, and thermodynamic functions [including S(T) and H(T)-H(0) ] for the three hydrides are similar. The results show that these three hydrides have negative enthalpies of formation, but positive free energies of formation. This conclusion is the same as that made by Wolverton for the hexagonal AlH3 [Phys. Rev. B 69, 144109 (2004)]. The thermodynamic properties indicate that the orthorhombic and cubic AlH3 should be more difficult to dissociate than the hexagonal AlH3 .

  16. Structural, optoelectronic, infrared and Raman spectra of orthorhombic SrSnO{sub 3} from DFT calculations

    SciTech Connect

    Moreira, E.; Henriques, J.M.; Azevedo, D.L.; Caetano, E.W.S.; Freire, V.N.; Albuquerque, E.L.

    2011-04-15

    Orthorhombic SrSnO{sub 3} was investigated using density functional theory (DFT) considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The electronic band structure, density of states, complex dielectric function, optical absorption, and the infrared and Raman spectra were computed. Calculated lattice parameters are close to the experimental measurements, and an indirect band gap E(S{yields}{Gamma})=1.97eV (2.27 eV) was obtained within the GGA (LDA) level of calculation. Effective masses for holes and electrons were estimated, being very anisotropic in comparison with similar results for orthorhombic CaSnO{sub 3}. The complex dielectric function and the optical absorption of SrSnO{sub 3} were shown to be sensitive to the plane of polarization of the incident light. The infrared spectrum between 100 and 600 cm{sup -1} was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum of orthorhombic SrSnO{sub 3} was achieved. -- Graphical abstract: Orthorhombic SrSnO{sub 3}: a view of the unit cell (left) and plots showing the calculated and experimental Raman spectra (right). Display Omitted Research highlights: {yields} We have performed DFT calculations on orthorhombic SrSnO{sub 3} crystals, obtaining their structural, electronical and optical properties. {yields} An indirect band gap was obtained, and anisotropic effective masses were found for both electrons and holes. {yields} The complex dielectric function and the optical absorption of SrSnO{sub 3} were shown to be very sensitive to the plane of polarization of the incident light. {yields} The infrared spectrum between 100 and 600 cm{sup -1} was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum was achieved.

  17. 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

  18. The nature of Mn4+ luminescence in the orthorhombic perovskite, GdAlO3

    NASA Astrophysics Data System (ADS)

    Srivastava, A. M.; Brik, M. G.

    2017-01-01

    In this paper we report on the spectroscopic properties of Mn4+ (3d3) ion in the orthorhombic perovskite, GdAlO3 and calculate the energy levels using the exchange charge model of crystal-field theory. The calculated Mn4+ energy levels are in good agreement with the experimental data. The results of our calculations yield the crystal-field splitting and Racah parameters of Dq = 2083 cm-1, B = 780 cm-1 and C = 2864 cm-1, with C/B = 3.67. The emission spectrum is composed of the zero phonon line (2Eg → 4A2g transition) with dominating intensity and its vibrational sidebands. We have also calculated Mulliken atomic charges and bond populations for three isostructural perovskites (GdAlO3, LaGaO3 and CaZrO3) to seek correlation between the energy position of the Mn4+2E level and the covalence of Mn4+sbnd O2- chemical bonding.

  19. Ferroelectric BaTiO3 phase of orthorhombic crystal structure contained in nanoparticles

    NASA Astrophysics Data System (ADS)

    Ram, S.; Jana, A.; Kundu, T. K.

    2007-09-01

    Ferroelectric BaTiO3 phase of a Pnma orthorhombic crystal structure is synthesized from a chemical method using a polymer complex of Ba2+ and Ti4+ with polyvinyl alcohol (PVA). After burning out the polymer at temperature as high as 550 °C in air for 2 h results in an average 15 nm crystallite BaTiO3 size, with lattice parameters a =0.6435 nm, b =0.5306 nm, c =0.8854 nm, and density 5.124 g/cm3. The relationship between dielectric constant ɛr and temperature showed a single Curie transition temperature TC=131 °C, with as large a ɛr value as 263 at TC. A low value of dissipation factor tan δ, as small as 0.033 at room temperature (frequency f =1 kHz), with good insulating properties made the sample promising for use in uncooled infrared detectors and thermal imaging applications. The ɛr value is nearly independent of f value up to 100 kHz. A spectrum of sharp EPR signals of g values 2.21 to 1.88 characterizes three major kinds of VBa-, VTi3-, and Ti3+-Vo2+ paramagnetic species present in the imperfections.

  20. 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

  1. 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.

  2. Molecular Structure and Dynamics in the Low Temperature (Orthorhombic) Phase of NH3BH3

    SciTech Connect

    Cho, Herman M.; Shaw, Wendy J.; Parvanov, Venci M.; Schenter, Gregory K.; Karkamkar, Abhijeet J.; Hess, Nancy J.; Mundy, Christopher J.; Kathmann, Shawn M.; Sears, Jesse A.; Lipton, Andrew S.; Ellis, Paul D.; Autrey, Thomas

    2008-05-08

    Variable temperature 2H NMR experiments on the orthorhombic phase of selectively deuterated NH3BH3 spanning the static to fast exchange limits of the borane and amine motions are reported. New values of the electric field gradient (EFG) tensor parameters have been obtained from the static 2H spectra of Vzz = 5.509(±0.275)×1014 statvolt/cm2 and ! = 0.00±0.05 for the borane hydrogens and Vzz = 9.615(±0.481)×1014 statvolt/cm2 and ! = 0.00±0.05 for the amine hydrogens. The molecular symmetry inferred from the observation of equal EFG tensors for both the boron and amine hydrogens is in sharp contrast with the Cs symmetry derived from diffraction studies. The origin of the apparent discrepancy has been investigated using molecular dynamics methods in combination with electronic structure calculations of NMR parameters, bond lengths, and bond angles. The computation of parameters from a statistical ensemble rather than from a single set of atomic Cartesian coordinates gives values that are in close quantitative agreement with the 2H NMR electric field gradient tensor measurements and are more consistent with the molecular symmetry revealed by the NMR spectra. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  3. Superconductivity at 3.1 K in the orthorhombic ternary silicide ScRuSi

    NASA Astrophysics Data System (ADS)

    Ruan, Bin-Bin; Wang, Xiao-Chuan; Yu, Jia; Pan, Bo-Jin; Mu, Qing-Ge; Liu, Tong; Chen, Gen-Fu; Ren, Zhi-An

    2017-02-01

    We report the synthesis, crystal structure, superconductivity and physical property characterizations of the ternary equiatomic compound ScRuSi. Polycrystalline samples of ScRuSi were prepared by an arc-melting method. The as-prepared samples were identified as the orthorhombic Co2P-type o-ScRuSi by powder x-ray diffraction analysis. Electrical resistivity measurements show o-ScRuSi to be a metal which superconducts below a T c of 3.1 K; the upper critical field μ 0 H c2(0) is estimated to be 0.87 T. The magnetization and specific heat measurements confirm the bulk type-II superconductivity in o-ScRuSi, with a specific heat jump within the BCS weak coupling limit. o-ScRuSi is the first Co2P-type superconductor to contain scandium. After annealing at 1273 K for a week, o-ScRuSi transforms into hexagonal Fe2P-type h-ScRuSi, which is a Pauli-paramagnetic metal with no superconductivity observed above 1.8 K.

  4. 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

  5. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Photo-thermoelectric properties of SnS nanocrystals with orthorhombic layered structure

    NASA Astrophysics Data System (ADS)

    Hyun, Cheol-Min; Choi, Jeong-Hun; Lee, Myoung-Jae; Ahn, Ji-Hoon

    2017-07-01

    The photo-thermoelectric properties of SnS nanocrystals, two-dimensional materials with an orthorhombic symmetry, were investigated using a focused laser scanning method. The SnS nanocrystals were synthesized by a vapor transport method, and their fundamental material and electrical properties were investigated. Upon shining a laser onto the SnS channel region under a positive source-drain bias, a positive photocurrent was observed due to photo-excited electron-hole pairs. On the other hand, when this external electric field was not applied, a strong photocurrent was observed within the metal electrode region rather than at the metal-semiconductor interface, which indicated that the major mechanism for the photocurrent under zero external bias was a photo-induced thermoelectric effect rather than a photovoltaic effect. Moreover, the Seebeck coefficient of the SnS nanocrystal device was approximately 1735 μV/K, which is 3.5 times larger than that of its bulk counterpart.

  7. Ferromagnetism in orthorhombic RAgAl3 (R = Ce and Pr) compounds

    NASA Astrophysics Data System (ADS)

    Nallamuthu, S.; Dzubinska, Andrea; Reiffers, Marian; Fernandez, Jesus Rodriguez; Nagalakshmi, R.

    2017-09-01

    We present a detailed study on magnetic, thermodynamic and transport properties of polycrystalline RAgAl3(R = Ce and Pr) compounds. Both compounds crystallize in orthorhombic structure, which is distorted from the tetragonal BaAl4 structure with the space group Cmcm. Heat capacity measurement indicates the bulk magnetic ordering of the compounds. CeAgAl3 and PrAgAl3 order ferromagnetically at TC=3.8 K and 5.8 K, respectively as it was confirmed from magnetic measurements. CeAgAl3 exhibits heavy fermion behaviour. The Schottky behaviour in heat capacity data was observed in both compounds. The crystalline electric field (CEF) analysis of the magnetic parts of heat capacity of CeAgAl3 and PrAgAl3 yielded to a CEF level scheme with three doublets and nine singlets and with an overall splitting of 51 K and 180 K, respectively. Fit yielded a magnetic doublet state for CeAgAl3, whereas for PrAgAl3 a pseudo-doublet ground-state with an energy difference of 15 K has been obtained. The resistivity measurements display a low temperature drop at the magnetic ordering temperature of the compounds. Negative magnetoresistance (MR) due to the ferromagnetic ordering has been observed for both Ce and Pr compounds.

  8. High-temperature deformation and failure of an orthorhombic titanium aluminide sheet material

    SciTech Connect

    Nicolaou, P.D.; Semiatin, S.L.

    1996-11-01

    The high-temperature deformation and failure behavior of an orthorhombic titanium aluminide sheet alloy (fabricated by diffusion bonding of six thin foils) was established by conducting uniaxial tension and plane-strain compression tests at 980 C and strain rates between 10{sup {minus}4} and 10{sup {minus}2} s{sup {minus}1}. The stress-strain response was characterized by a peak stress at low strains followed by moderate flow softening. Values of the strain-rate sensitivity index (m) were between 0.10 and 0.32, and the plastic anisotropy parameter (R) was of the order of 0.6 to 1.0. Cavity nucleation and growth were observed during tensile deformation at strain rates of 10{sup {minus}3} s{sup {minus}1} and higher. However, the combined effects of low m, low cavity growth rate {eta}, and flow softening were deduced to be the source of failure controlled by necking and flow localization rather than cavitation-induced fracture prior to necking.

  9. Magnetic performance of orthorhombic Mn35Ge35Te30 nanocrystals

    NASA Astrophysics Data System (ADS)

    Mahdy, Iman A.

    2017-01-01

    Nanocrystalline antiferromagnetic Mn35Ge35Te30 diluted magnetic semiconductors powder syntheses by the conventional direct reaction of pure metals. Nanocrystalline nature of the prepared sample confirmed using various techniques, where x-Ray diffraction (XRD) and atomic force microscope (AFM) measurements shows ~96 nm particle size, while transmission electron microscope (TEM) shows 92 nm particle size. XRD analysis show orthorhombic symmetry with lattice parameters a=7.386611±(0.0066) Å, b=8.962502±(0.0090) Å and c=7.027349±(0.0040) Å. Electron Spin resonance (ESR) show a broad asymmetric line whereas the remnant Mn2+ six-hyperfine lines are broadened within |+1/2>→|-1/2> line according to high anisotropy; calculated Landé g-factor is 2.047. Vibrating sample magnetometer (VSM) analysis, field-moment characteristics revealed a hysteresis loop with small coercive field indicating that Mn35Ge35Te30 is a soft magnetic material. Moreover, hysteresis measurements at different temperatures show increasing magnetization with increasing temperature up to 150 K followed by decreased with increasing temperature up to 300 K. This behavior indicated to the antiferromagnetic nature of the prepared nanocrystalline materials. Magnetic moment - temperature measurements show Néel temperature TN=172.6 K. Magnetic force microscope revealed magnetic domains as a result of interaction between magnetic dipole moments of magnetic cantilever and pressed powder.

  10. 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

  11. Electronic structure and thermoelectric properties of orthorhombic SrLiAs

    SciTech Connect

    Guo, Li Bin; Wang, Yuan Xu Yan, Yu Li; Yang, Gui; Yang, Jue Ming; Feng, Zhen Zhen

    2014-07-21

    The electronic structure and the transport properties of orthorhombic SrLiAs were investigated using first-principles calculations and the semiclassical Boltzmann theory. It is found that the electrical conductivity along the y-direction is higher than those along other two directions, which is most likely originated from the covalent ladder-like structure formed by the Li and As atoms. Moreover, the transport properties of n-type SrLiAs are better than those of p-type one, due to the large band dispersion along the y-direction near the Fermi level. Further, the value of power factor with respect to relaxation time achieves 9.2 × 10{sup 11} W K{sup −2} m{sup −1} s{sup −1} for n-type SrLiAs along the y-direction at 1000 K with an optimal carrier concentration of 6.5 × 10{sup 20 }cm{sup −3}. The obtained minimum lattice thermal conductivity is comparable to those of other Zintl phase compounds.

  12. Intrinsic ferroelectric polarization of orthorhombic manganites with E-type spin order

    NASA Astrophysics Data System (ADS)

    Chai, Y. S.; Oh, Y. S.; Wang, L. J.; Manivannan, N.; Feng, S. M.; Yang, Y. S.; Yan, L. Q.; Jin, C. Q.; Kim, Kee Hoon

    2012-05-01

    By directly measuring electrical hysteresis loops using the Positive-Up Negative-Down (PUND) method, we determined accurately the remanent ferroelectric polarization Pr of orthorhombic RMnO3 (R = Ho, Tm, Yb, and Lu) compounds below their E-type spin ordering temperatures. We found that LuMnO3 has the largest Pr of 0.17 μC/cm2 at 6 K in the series, the value of which allows us to predict that its single-crystal form can produce a Pr of at least 0.6 μC/cm2 at 0 K. Furthermore, at a fixed temperature, Pr decreases systematically with increasing rare earth ion radius from R = Lu to Ho, exhibiting a strong correlation with the variation of the in-plane Mn-O-Mn bond angle and Mn-O distances. Our experimental results suggest that the contribution of the Mn t2g orbitals may dominate the ferroelectric polarization.

  13. Thermal-expansion anisotropy of orthorhombic martensite in the two-phase (α + β) titanium alloy

    NASA Astrophysics Data System (ADS)

    Demakov, S. L.; Stepanov, S. I.; Illarionov, A. G.; Ryzhkov, M. A.

    2017-03-01

    Anisotropy of the thermal expansion coefficient (TEC) has been revealed along the axes of the crystal lattice of the α″ titanium martensite in the two-phase (α + β) titanium alloy of grade VT16 (Ti-3Al-5V-4.5Mo, wt %). It has been established by the method of in situ X-ray diffraction analysis that the lattice parameter b of the orthorhombic martensite obtained by quenching from different temperatures decreases upon heating. The TECs along the axes of the crystal lattice of the martensite obtained by quenching from different temperatures have been calculated. It has been shown that the uniaxial extension of bars of the VT16 alloy quenched for the metastable β phase with relative deformations of 0.7, 1, 2, 3, 4, 5, 6, and 8% leads to the formation of the deformation-induced martensite with an axial texture along the b direction of the martensite lattice. In the course of dilatometric studies of the deformed bars, it has been established that there are two temperature intervals (from-100 to +70°C and from 150 to 300°C) with a low TEC. In the first interval, the value of the TEC varies from-2 × 10-6 to +8 × 10-6 K-1 and is determined by the volume fraction of the oriented α″ martensite. This Invar effect is one-dimensional and is manifested along the b axis of the martensite.

  14. An unusual case of pseudo-merohedral twinning in orthorhombic crystals of Dicer.

    PubMed

    MacRae, Ian J; Doudna, Jennifer A

    2007-09-01

    The crystal structure of the enzyme Dicer from Giardia intestinalis was solved to 3.3 A resolution by MAD using crystals belonging to space group P2(1)2(1)2 [Macrae et al. (2006), Science, 311, 195-198]. These crystals were derived from crystals that diffracted X-rays to 3.0 A resolution but were refractory to structure determination because they were twinned. It is shown here that the original Dicer crystals represent an unusual case of perfect pseudo-merohedral twinning of orthorhombic crystals. Before the twinning problem was overcome, it was possible to calculate a low-resolution electron-density map in space group P4(1) that was used to build a partial molecular model. Experimental phases were sufficient to identify heavy-atom sites that indicated space-group inconsistency, leading to identification of the true space group. This information guided the search for different crystallization conditions that yielded untwinned crystals and ultimately a fully interpretable electron-density map.

  15. 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.

  16. Ambient stable tetragonal and orthorhombic phases in penta-twinned bipyramidal au microcrystals.

    PubMed

    Mettela, Gangaiah; Bhogra, Meha; Waghmare, Umesh V; Kulkarni, Giridhar U

    2015-03-04

    Face-centered cubic (fcc) lattice is the only known crystal structure of bulk gold. In the present work, we report the presence of body-centered tetragonal (bct) and body-centered orthorhombic (bco) phases in bipyramidal Au microcrystals with penta-twinned tips. These microcrystals have been obtained by thermolysis of (AuCl4)(-) stabilized with tetraoctylammonium bromide (ToABr) in air at about 220 °C for 30 min. Using a laboratory monochromatic X-ray source, the non-fcc phases could be readily detected. The remarkable occurrence of non-fcc phases of Au grown in the temperature window of 200-250 °C results from the geometrically induced strains in the bipyramids. Having derived first-principles theoretical support for the temperature-dependent stability of non-fcc Au structures under stress, we identify its origin in soft modes. Annealing at high temperatures relieves the stress, thus destabilizing the non-fcc phases.

  17. Ultra-low-energy non-volatile straintronic computing using single multiferroic composites

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    2013-10-01

    The primary impediment to continued downscaling of traditional charge-based electronic devices in accordance with Moore's law is the excessive energy dissipation that takes place in the device during switching of bits. One very promising solution is to utilize multiferroic heterostructures, comprised of a single-domain magnetostrictive nanomagnet strain-coupled to a piezoelectric layer, in which the magnetization can be switched between its two stable states while dissipating minuscule amount of energy. However, no efficient and viable means of computing is proposed so far. Here we show that such single multiferroic composites can act as universal logic gates for computing purposes, which we demonstrate by solving the stochastic Landau-Lifshitz-Gilbert equation of magnetization dynamics in the presence of room-temperature thermal fluctuations. The proposed concept can overwhelmingly simplify the design of large-scale circuits and portend a highly dense yet an ultra-low-energy computing paradigm for our future information processing systems.

  18. An experimental approach for synthesis of Fe-Al-O multiferroic fibrous material

    NASA Astrophysics Data System (ADS)

    Starbov, N.; Starbova, K.; Vanderbemden, Ph; Simeonova, P.; Lovchinov, V.

    2012-12-01

    Basic principles of the electro-hydrodynamics are applied for synthesis of solid state Fe-Al-O multi-ferroic fibrous material. For that purpose stable blend spinning solutions comprised of a high molecular assisting organic polymer and salts of iron and aluminum are developed. These solutions are tested under electrospinning conditions and synthesis of homogeneous as spun non-woven mats characterized by fibre mean diameters in the micro-and nano-size range is successfully demonstrated. Multi-step thermal procedure is applied for the consecutive solvent evaporation, polymer pyrolisis and final fibre calcination. Electron-optical imaging technique and XRD are applied for revealing the sample morphology and the phase composition correspondingly. The results obtained outline the wide possibilities for fabrication of multi-ferroics fibrous nano-materials on the basis of Fe-Al-O.

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

    NASA Astrophysics Data System (ADS)

    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.

    2015-08-01

    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.

  20. Magnetoelectric coupling in the type-I multiferroic ScFeO3

    NASA Astrophysics Data System (ADS)

    Giovannetti, G.; Puggioni, D.; Barone, P.; Picozzi, S.; Rondinelli, J. M.; Capone, M.

    2016-11-01

    We investigate the electronic structure and the ferroelectric properties of the recently discovered multiferroic ScFeO3 by means of ab initio calculations. The 3 d manifold of Fe in the half-filled configuration naturally favors an antiferromagnetic ordering, with a theoretical estimate of the antiferromagnetic Néel temperature in good agreement with the experimental values. We find that the inversion symmetry breaking is driven by the off-centering of Sc atoms, which results in a large ferroelectric polarization of ˜105 μ C /cm2. Surprisingly the ferroelectric polarization is sensitive to the local magnetization of the Fe atoms resulting in a large negative magnetoelectric interaction. This behavior is unexpected in type-I multiferroic materials because the magnetic and ferroelectric orders are of different origins.

  1. Flux growth of multiferroic Cu3Nb2O8 single crystals

    NASA Astrophysics Data System (ADS)

    Chen, R.; Shi, M. M.; Liu, Y. J.; Liu, C. B.; Zhu, H. P.; Dong, C.; Liu, Y.; Shi, J.; Xia, Z. C.; Ouyang, Z. W.; Wang, J. F.

    2017-10-01

    Cu3Nb2O8 belongs to a new multiferroic family with coexisting structure and magnetic chiralities. In this work, we report on the flux growth of Cu3Nb2O8 single crystals using a V2O5-K2MoO4 mixture as the flux with a 5:1 ratio. The obtained crystals have an average size of 3 × 3 × 2 mm3 and high quality determined from X-ray diffraction, specific heat and susceptibility measurements. The experimental results on the single crystals reveal robust anomalies at 26.2 K and 24.5 K in specific heat and magnetic anisotropy along different crystallographic axes, which provide a better understanding of this fascinating multiferroic compound.

  2. Multiferroic Behavior in Elemental Selenium below 40 K: Effect of Electronic Topology

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  3. Magnetoelectric and multiferroic properties of ternary copper chalcogenides Cu2MIIMIVS4

    NASA Astrophysics Data System (ADS)

    Nénert, G.; Palstra, T. T. M.

    2009-04-01

    We investigate theoretically the ternary copper chalcogenides with the general formula Cu2MIIMIVS4. This family of compounds can crystallize in two different non-centrosymmetric structures, I\\bar {4}2m or Pnm 21. We show that all the reported members of Cu2MIIMIVS4 having the Pnm 21 symmetry exhibit a large spontaneous polarization. This result suggests that several of these materials are likely to be multiferroics since they order magnetically at low temperature. We discuss in detail in the framework of Landau theory the members Cu2MnSnS4 and Cu2MnGeS4 which should present both a linear magnetoelectric effect and multiferroic behavior.

  4. Multiferroicity and Magnetoelectric Coupling in TbMnO3 Thin Films.

    PubMed

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

    2015-12-09

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

  5. 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

  6. Synthesis, characterization, properties, and applications of nanosized ferroelectric, ferromagnetic, or multiferroic materials

    DOE PAGES

    Dhak, Debasis; Hong, Seungbum; Das, Soma; ...

    2015-01-01

    Recently, there has been an enormous increase in research activity in the field of ferroelectrics and ferromagnetics especially in multiferroic materials which possess both ferroelectric and ferromagnetic properties simultaneously. However, the ferroelectric, ferromagnetic, and multiferroic properties should be further improved from the utilitarian and commercial viewpoints. Nanostructural materials are central to the evolution of future electronics and information technologies. Ferroelectrics and ferromagnetics have already been established as a dominant branch in electronics sector because of their diverse applications. The ongoing dimensional downscaling of materials to allow packing of increased numbers of components into integrated circuits provides the momentum for evolutionmore » of nanostructural devices. Nanoscaling of the above materials can result in a modification of their functionality. Furthermore, nanoscaling can be used to form high density arrays of nanodomain nanostructures, which is desirable for miniaturization of devices.« less

  7. 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.

  8. First-principles approach to investigate toroidal property of magnetoelectric multiferroic GaFeO3

    NASA Astrophysics Data System (ADS)

    Nie, Yung-mau

    2016-01-01

    A first-principles approach incorporating the concept of toroidal moments as a measure of the spin vortex is proposed and applied to simulate the toroidization of magnetoelectric multiferroic GaFeO3. The nature of space-inversion and time-reversal violations of ferrotoroidics is reproduced in the simulated magnetic structure of GaFeO3. For undoped GaFeO3, a toroidal moment of -22.38 μB Å per unit cell was obtained, which is the best theoretical estimate till date. Guided by the spin vortex free-energy minimization perturbed by an externally applied field, it was discovered that the minority spin markedly biases the whole toroidization. In summary, this approach not only calculates the toroidal moment but provides a way to understand the toroidal nature of magnetoelectric multiferroics.

  9. Perspectives of voltage control for magnetic exchange bias in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Zhou, Z.; Sun, N. X.; Liu, M.

    2017-04-01

    Exchange bias, as an internal magnetic bias induced by a ferromagnetic-antiferromagnetic exchange coupling, is extremely important in many magnetic applications such as memories, sensors and other devices. Voltage control of exchange bias in multiferroics provides an energy-efficient way to achieve a rapidly 180° deterministic switching of magnetization, which has been considered as a key challenge in realizing next generation of fast, compact and ultra-low power magnetoelectric memories and sensors. Additionally, exchange bias can enhance dynamic magnetoelectric coupling strength in an external-field-free manner. In this paper, we provide a perspective on voltage control of exchange bias in different multiferroic heterostructures. Brief mechanization and related experiments are discussed as well as future trend and challenges that can be overcome by electrically tuning of exchange bias in state-of-the-art magnetoelectric devices.

  10. Multiferroic domain boundaries as active memory devices: trajectories towards domain boundary engineering.

    PubMed

    Salje, Ekhard K H

    2010-04-06

    Twin boundaries in ferroelastics and curved interfaces between crystalline and amorphous zircon can, in principle, act as multiferroic structural elements and lead the way to the discovery of novel multiferroic devices which are based on structurally heterogeneous materials. While this paradigm has not yet been explored in full, this review shows that physical and chemical properties can vary dramatically inside twin boundaries and interfaces. Properties that have been already been explored include electric dipoles in a non-polar matrix, the appearance of superconductivity in twin boundaries and the catalytic reaction of hydrous species in interfaces of radiation damaged material. Some of the fundamental physical and chemical properties of twin boundaries and related interfaces are described and possible applications are outlined.

  11. 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.

  12. 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

    2014-04-29

    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.

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

    DOE PAGES

    Wang, Jinchen; Liu, Juanjuan; Sheng, Jieming; ...

    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

  14. {sup 57}Fe NMR study of multiferroic BiFeO{sub 3}

    SciTech Connect

    Pokatilov, V. S. Sigov, A. S.

    2010-03-15

    The effects of the {sup 57}Fe isotope content and high-frequency magnetic field amplitude h{sub 1} on the shape of the NMR spectrum of multiferroic BiFeO{sub 3} at T = 4.2 K are studied by pulsed nuclear magnetic resonance. The NMR spectrum shape and transverse relaxation time T{sub 2} are found to depend strongly on the {sup 57}Fe isotope content and h{sub 1} in multiferroic BiFeO{sub 3} in the presence of a spatial spin-modulated structure of a cycloid type. In a sample with a high {sup 57}Fe isotope content, the Suhl-Nakamura interaction contributes substantially to T{sub 2}. When these dynamic effects are taken into account for analysis of the NMR spectrum shape, an undisturbed (without an anharmonicity effect) spatial spin-modulated structure of a cycloid type is shown to exist in BiFeO{sub 3}.

  15. Neutron scattering studies of BiFeO(3) multiferroics: a review for microscopists.

    PubMed

    Sosnowska, I M

    2009-11-01

    Application of the neutron scattering technique in the study of crystal and magnetic properties of multiferroic BiFeO(3) is presented. The crucial role of the neutron scattering technique, complementary to X-ray diffraction method and transmission electron microscopy, is shown. Especially the ultra high-resolution time-of-flight (TOF) neutron diffraction technique used by Sosnowska et al. to detect the magnetic cycloid ordering and its role in studies of physical properties of BiFeO(3) and its alloys are reviewed. The first inelastic neutron scattering patterns of magnetic excitations in BiFeO(3) are also presented. Applications of different microscopy techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), field emission TEM and SEM (FESEM and FETEM), magnetic force microscope (MFM) and polarization force microscopy (PFM) bring insight on the fundamental problem of ferroelectricity and confirm the potential of BiFeO(3) multiferroic material for nanoscale devices.

  16. Investigation of spin-electromagnetic wave envelope solitons in a multiferroic layered structure

    NASA Astrophysics Data System (ADS)

    Ustinov, A. B.; Kondrashov, A. V.; Nikitin, A. A.; Cherkasskii, M. A.; Kalinikos, B. A.

    2015-12-01

    Hybrid spin-electromagnetic wave (SEW) envelope solitons have been studied both experimentally and theoretically. The solitons were formed during auto-generation of SEWs in an active ring resonator for which the role of the nonlinear dispersive waveguide media was played by a multiferroic layered ferrite-ferroelectric structure. It is demonstrated that the dielectric constant of the structure affects the nonlinear properties of SEWs.

  17. 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.

  18. 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

    2016-09-22

    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.

  19. Theoretical Investigation of Dual Tuning of Solitonic Processes in Multiferroic Structures

    NASA Astrophysics Data System (ADS)

    Cherkasskii, M. A.; Nikitin, A. A.; Ustinov, A. B.; Stashkevich, A.; Kalinikos, B. A.

    2016-11-01

    . The solitonic wave processes in a multiferroic structure based on ferroelectric and ferrite layers are studied. The influence of external electric and magnetic fields on frequency and wave-number ranges, where bright and dark solitons can exist, are analysed. The investigation was carried out with the nonlinear Schrodinger equation. Results show that an increase of the electric field shifts the boundary between bright and dark solitons to long-wave region. An increase in magnetic field results in the opposite effect.

  20. Polar-graded multiferroic SrMnO3 thin films

    SciTech Connect

    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 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. 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.

  1. Polar-graded multiferroic SrMnO3 thin films

    DOE PAGES

    Lupini, Andrew R.; Guzman, Roger; Maurel, Laura; ...

    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

  2. Theoretical study of electronic transport properties in pillar-embedded multiferroic transition-metal oxides

    NASA Astrophysics Data System (ADS)

    Tai, Yuan-Yen; Zhu, Jian-Xin

    2015-03-01

    Multiferroics show great potential in novel application to nanotechnologies based on well-established experimental techniques. Recently, vertically aligned nanocomposite (VAN) multiferroic thin films have demonstrated a significant amount of research interest owing to their promising results to give more delicate device, such as a larger interfacial area and intrinsic heteroepitaxy in this 3D structure. In order to understand the basic influence of the nano-pillar structure to the bulk multiferroics, we apply scaling theory to study the quasiparticle localization/delocalization effects of this novel nanostructure. Within an effective tight-binding model, we apply the transfer matrix method to calculate the wave function behavior throughout its transverse direction. We will show that how the critical behavior varies with various disordered nano-pillar patterns. We will also give a qualitative connection of our results to the transport experiments. Work at the LANL was performed under the auspices of the U.S. DOE Contract No. DEAC52- 06NA25396 through the LANL-LDRD program.

  3. Evidence for Room Temperature Electric Polarization in RM n 2O5 Multiferroics

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    It is established that the multiferroics R Mn2O5 crystallize in the centrosymmetric P b a m 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 P m . This turns out to be of crucial importance for R Mn2O5 multiferroics since P m 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.

  4. Experimental observation of ferrielectricity in multiferroic DyMn2O5

    PubMed Central

    Zhao, Z. Y.; Liu, M. F.; Li, X.; Lin, L.; Yan, Z. B.; Dong, S.; Liu, J. -M.

    2014-01-01

    One of the major breakthroughs associated with multiferroicity in recent years is the discovery of ferroelectricity generated by specific magnetic structures in some magnetic insulating oxides such as rare-earth manganites RMnO3 and RMn2O5. An unresolved issue is the small electric polarization. Relatively large electric polarization and strong magnetoelectric coupling have been found in those manganites of double magnetic ions: magnetic rare-earth R ion and Mn ion, due to the strong R-Mn (4f-3d) interactions. DyMn2O5 is a representative example. We unveil in this work the ferrielectric nature of DyMn2O5, in which the two ferroelectric sublattices with opposite electric polarizations constitute the ferrielectric state. One sublattice has its polarization generated by the symmetric exchange striction from the Mn-Mn interactions, while the polarization of the other sublattice is attributed to the symmetric exchange striction from the Dy-Mn interactions. We present detailed measurements on the electric polarization as a function of temperature, magnetic field, and measuring paths. The present experiments may be helpful for clarifying the puzzling issues on the multiferroicity in DyMn2O5 and other RMn2O5 multiferroics. PMID:24496324

  5. First-principles exploration of multiferroic oxides with double-perovskite structure

    NASA Astrophysics Data System (ADS)

    Oguchi, Tamio; Shishidou, Tatsuya; Uratani, Yoshitaka

    2006-03-01

    Multiferroics have attracted much attention recently because of their novel properties. There are a few known as ferromagnetic and ferroelectric materials, particularly with perovskite-type crystal structure. Ferroelectrics should be insulating and likely ionic. Furthermore, it is widely recognized that covalent bonds between the cation and anion orbitals are crucial to realize atomic displacements to a noncentrosymmetric structure. As for magnetism, most of magnetic perovskite oxides usually have an antiferromagnetic order (mostly frustrating) due to a superexchange coupling. According to the Kanamori-Goodenough rule for the superexchange coupling, certain combinations of the transition-metals ions (d^3-d^5 and d^3-d^8 configurations) may possibly give a ferromagnetic coupling by the 180^o superexchange mechanism. In this study, we explore possible co-existence of spontaneous electric polarization and ferromagnetic ordering from first principles, by focusing bismuth double-perovskite oxides Bi2BB'O6 (B, B' = 3d ions) as target materials. Ferromagnetic and ferrimagnetic solutions are obtained for cubic Bi2MnNiO6, Bi2CrFeO6 and Bi2CrCuO6 with nearly gapped electronic structure. Quite recently, Bi2MnNiO6 has been successfully synthesized by a high-pressure technique and revealed multiferroic properties. Possible multiferroic properties of Bi2MnNiO6 with the observed monoclinic structure are investigated in detail.

  6. 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.

  7. Chemically Functionalized Phosphorene: Two-Dimensional Multiferroics with Vertical Polarization and Mobile Magnetism.

    PubMed

    Yang, Qing; Xiong, Wei; Zhu, Lin; Gao, Guoying; Wu, Menghao

    2017-08-23

    In future nanocircuits based on two-dimensional (2D) materials, the ideal nonvolatile memories (NVMs) would be based on 2D multiferroic materials that can combine both efficient ferroelectric writing and ferromagnetic reading, which remain hitherto unreported. Here we show first-principles evidence that a halogen-intercalated phosphorene bilayer can be multiferroic with most long-sought advantages: its "mobile" magnetism can be controlled by ferroelectric switching upon application of an external electric field, exhibiting either an "on" state with spin-selective and highly p-doped channels, or an "off" state, insulating against both spin and electron transport, which renders efficient electrical writing and magnetic reading. Vertical polarization can be maintained against a depolarizing field, rendering high-density data storage possible. Moreover, all those functions in the halogenated regions can be directly integrated into a 2D phosphorene wafer, similar to n/p channels formed by doping in a silicon wafer. Such formation of multiferroics with vertical polarization robust against a depolarizing field can be attributed to the unique properties of covalently bonded ferroelectrics, distinct from ionic-bonded ferroelectrics, which may be extended to other van der Waals bilayers for the design of NVM in future 2D wafers. Every intercalated adatom can be used to store one bit of data: "0" when binding to the upper layer and "1" when binding to the down layer, giving rise to a possible approach of realizing single atom memory for high-density data storage.

  8. Atomic Mechanism of Hybridization-Dependent Surface Reconstruction with Tailored Functionality in Hexagonal Multiferroics.

    PubMed

    Deng, Shiqing; Cheng, Shaobo; Xu, Changsong; Ge, Binghui; Sun, Xuefeng; Yu, Rong; Duan, Wenhui; Zhu, Jing

    2017-08-16

    The broken symmetry along with anomalous defect structures and charging conditions at multiferroics surface can alter both crystal structures and electronic configurations, bringing in emergent physical properties. Extraordinary surface states are induced into original mutually coupled order parameters in such strongly correlated oxides, which flourish in diverse properties but remain less explored. Here, we report the peculiar surface ferroelectric states and reconfigurable functionalities driven by the relaxation of surface and consequent changes in O 2p and Y 4d orbital (p-d) hybridization within a representative hexagonal multiferroics, YMnO3. An unprecedented surface reconstruction is achieved by tailored p-d hybridization coupling with in-plane oxygen vacancies, which is atomically revealed on the basis of the advantages of state-of-the-art aberration-corrected (scanning) transmission electron microscopy. Further ab initio density functional theory calculations verify the key roles of in-plane oxygen vacancies in modulating polarization properties and electronic structure, which should be regarded as the atomic multiferroic element. This surface configuration is found to induce tunable functionalities, such as surface ferromagnetism and conductivity. Meanwhile, the controversial origin of improper ferroelectricity that is unexpectedly free from critical size has also been atomically unraveled. Our findings provide new insights into the design and implementation of surface chemistry devices by simply controlling the oxygen stoichiometry, greatly advance our understandings of surface science in strongly correlated oxides, and enable exciting innovations and new technological functionality paradigms.

  9. Many-body localization phase in a spin-driven chiral multiferroic chain

    NASA Astrophysics Data System (ADS)

    Stagraczyński, S.; Chotorlishvili, L.; Schüler, M.; Mierzejewski, M.; Berakdar, J.

    2017-08-01

    Many-body localization (MBL) is an emergent phase in correlated quantum systems with promising applications, particularly in quantum information. Here, we unveil the existence and analyze this phase in a chiral multiferroic model system. Conventionally, MBL occurrence is traced via level statistics by implementing a standard finite-size scaling procedure. Here, we present an approach based on the full distribution of the ratio of adjacent energy spacings. We find a strong broadening of the histograms of counts of these level spacings directly at the transition point from MBL to the ergodic phase. The broadening signals reliably the transition point without relying on an averaging procedure. The fast convergence of the histograms even for relatively small systems allows monitoring the MBL dynamics with much less computational effort. Numerical results are presented for a chiral spin chain with a dynamical Dzyaloshinskii-Moriya interaction, an established model to describe the spin excitations in a single-phase spin-driven multiferroic system. The multiferroic MBL phase is uncovered and it is shown how to steer it via electric fields.

  10. Polarized-neutron-scattering studies on the chiral magnetism in multiferroic MnWO4

    NASA Astrophysics Data System (ADS)

    Finger, T.; Senff, D.; Schmalzl, K.; Schmidt, W.; Regnault, L. P.; Becker, P.; Bohatý, L.; Braden, M.

    2010-02-01

    Neutron diffraction with spherical polarization analysis is a powerful tool for studying the multiferroic materials where the ferroelectric polarization arises from a complex magnetic structure. Analyzing the off-diagonal terms in the polarization matrix one may directly detect the chiral contributions even in a multidomain arrangement. In MnWO4 one can control the chiral magnetism by varying an electric field at constant temperature. The analysis of multiferroic hysteresis cycles at four equivalent magnetic Bragg peaks fully agrees with a nearly monodomain chiral arrangement controlled by the electric field. A pronounced asymmetry of the hysteresis cycles and memory effects point to strong pinning of the chiral magnetism in MnWO4. We find a second-order harmonic modulation which exhibits both magnetic and structural character and which may be related with the domain pinning. The observed interference between the nuclear and the magnetic modulation is another manifestation of the coupling between the crystal structure and the magnetism in the multiferroic oxides.

  11. A second ferroelectric transition induced by pressure in multiferroic GdMn2O5

    NASA Astrophysics Data System (ADS)

    Lorenz, Bernd; Poudel, Narayan; Gooch, Melissa; Chu, Ching-Wu; Cheong, Sang-Wook

    2015-03-01

    In multiferroic materials different magnetic and ferroelectric states compete for the ground state and are usually close in energy. This results in a high sensitivity of the multiferroic state to external perturbations, such as magnetic fields or pressure, which has been demonstrated, e.g. in Ni3V2O8,MnWO4,andRMn2O5 (R = Tb, Ho, Dy, Y). Here we report the results of a high-pressure study of the multiferroic and ferroelectric properties of GdMn2O5,theRMn2O5 compound with the highest value of the polarization. The ferroelectric polarization below 29 K is enhanced upon application of pressure. Above a critical pressure, a second ferroelectric transition at even higher temperature is detected through a sizable increase of the polarization and a second peak of the dielectric constant. The ferroelectric polarization at high pressures exhibits two step-like increases upon decreasing temperature. This work was supported by the US AFOSR, the T.L.L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through TCSUH.

  12. Electronic transitions and multiferroicity in transition metal oxides

    NASA Astrophysics Data System (ADS)

    Zhou, Haidong

    Four systems have been studied for the localized-itinerant electronic transition in transition-metal oxides: (i) In CaV1- xTixO3, substitution of Ti(IV) introduces Anderson-localized states below a mobility edge mu c that increases with x, crossing epsilon F in the range 0.2 < x< 0.4 and also transforms the strong-correlation fluctuations to localized V(IV): t1e0 configurations for x ≥ 0.1. (ii) The properties of LaTiO3+delta reveal that a hole-poor, strongly correlated electronic phase coexists with a hole-rich, itinerant-electron phase. With delta ≥ 0.03, the hole-rich phase exists as a minority phase of isolated, mobile itinerant-electron clusters embedded in the hole-poor phase. With delta ≥ 0.08, isolated hole-poor clusters are embedded in an itinerant-electron matrix. As delta > 0.08 increases, the hole-poor clusters become smaller and more isolated until they are reduced to super-paramagnetic strong-correlation fluctuations by delta = 0.12. (iii) The data of Y1-xLaxTiO 3 appears to distinguish an itinerant-electron antiferromagnetic phase in the La-rich samples from a localized-electron ferromagnetic phase with a cooperative Jahn-Teller distortion in the Y-rich phase. (iv) The transition at Tt in Mg[Ti2]O4 is a semiconductor-semiconductor transition associated with Ti-Ti dimerization instabilities. The dimerization is caused by lattice instabilities resulting from a double-well Ti-Ti bond potential at a crossover from localized to itinerant electronic behavior. RMn1-xGaxO 3 (R = Ho, Y) and Ho1-xY xMnO3 have been studied for the multiferroicity of RMnO3. Ga doping raises the ferrielectric Curie temperature TC and the Mn-spin reorientation temperature TSR while lowering TN of the Mn spins and the Ho magnetic ordering temperature T 2. The data show an important coupling between the Mn3+-ion and HO3+-ion spins as well as a TSR that is driven by a cooperative MnO5 site rotation and R 3+-ion displacements that modify the c lattice parameter. The data also

  13. 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

  14. 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.

  15. Continuously controllable optical band gap in orthorhombic ferroelectric KNbO3-BiFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pascual-Gonzalez, Cristina; Schileo, Giorgio; Murakami, Shunsuke; Khesro, Amir; Wang, Dawei; Reaney, Ian M.; Feteira, Antonio

    2017-04-01

    The optical bandgap of orthorhombic ferroelectric KNbO3 is shown to be continuously controllable via Bi and Fe co-substitution according to a K1-xBixNb1-xFexO3 doping mechanism. The room temperature X-ray diffraction data combined with Raman spectroscopy analysis show the polar orthorhombic crystal structure to persist up to x = 0.25, while the bandgap narrows monotonically by 1 eV (˜33%). In-situ Raman spectroscopy corroborates the polar nature of all compositions in the temperature range of -100 to 200 °C. The ability to control the bandgap while maintaining the spontaneous polarisation makes the K1-xBixNb1-xFexO3 system interesting for photoinduced processes in a wide temperature range.

  16. Multiferroic nature of intrinsic point defects in BiFeO3: A hybrid Hartree-Fock density functional study

    NASA Astrophysics Data System (ADS)

    Shimada, Takahiro; Matsui, Takahiro; Xu, Tao; Arisue, Kou; Zhang, Yajun; Wang, Jie; Kitamura, Takayuki

    2016-05-01

    To achieve a fundamental understanding of the multiferroic behavior and electronic properties of intrinsic vacancies in BiFe O3 , here we performed first-principles calculations based on hybrid Hartree-Fock density functional theories, which can accurately describe defect electronic structures. Oxygen vacancies, which behave as deep donors with high concentrations under oxygen-poor conditions, reduce the magnetic moments at neighboring Fe ions in the neutral state, while charged oxygen vacancies induce additional ferroelectric polarizations. Cation vacancies, on the other hand, are likely to form under oxygen-rich conditions and result in multiferroic properties distinct from those induced by oxygen vacancies. Bi vacancies act as triple-shallow acceptors and strongly suppress spontaneous polarization regardless of charge states, while Fe vacancies locally interfere with both electric and spin polarization and are thus regarded as multiferroic singular points in BiFe O3 . A rich variety of the multiferroic behavior of vacancies can be systematically understood from the localized/delocalized features of defect states, and the different formation conditions for vacancies provide a strategy to tailor the multiferroic properties of BiFe O3 through control of the concentration and charge states of vacancies.

  17. 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.

  18. High pressure Raman investigations of multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Bai, L. G.; Zhu, K.; Liu, Y. L.; Jiang, S.; Liu, J.; Chen, J.; Xing, X. R.

    2009-09-01

    We have reported a Raman scattering investigation of bismuth ferrite (BiFeO3) under high pressure up to 50 GPa. Distinct changes in the Raman spectra show evidence for three pressure-induced structural transitions. The abrupt frequency redshifts of the Raman modes near 300 cm-1 at around 3 GPa are attributed to the modulation of the FeO6 octahedral tilts. The disappearance of the modes below 250 cm-1 at 8.6 GPa, together with the enhancement of the two modes in the range of 300-400 cm-1, indicate the phase transition from the rhombohedral to orthorhombic symmetry. Afterward, the E-3 and E-4 modes disappear at 44.6 GPa, pointing to the occurrence of the orthorhombic-cubic phase transition, which is consistent with the previous postulate that an orthorhombic-cubic transition takes place across the metal-insulator transition at high pressures.

  19. External and internal magnetic-field effects on ferroelectricity in orthorhombic rare-earth manganites

    NASA Astrophysics Data System (ADS)

    Kuwahara, H.; Noda, K.; Akaki, M.

    2006-03-01

    We report the dielectric and magnetic properties of the perovskite (Eu,Y)MnO3 crystal without the presence of the 4f magnetic moments of the rare earth ions. The subject compound, (Eu,Y)MnO3, was controlled the average ionic radius of the A site so that it was the same as that of TbMnO3 in which the intriguing magnetoelectric effect has been recently discovered. The (Eu,Y)MnO3 crystal was found to have two distinct ferroelectric phases with polarization along the a (Pa, T<=23K) and c (Pc, 23K<=T<=25K) axes in the orthorhombic Pbnm setting in a zero magnetic field. In addition, we have demonstrated a magnetic-field-induced switching between these ferroelectric phases: Pa changed to Pc by the application of magnetic fields parallel to the a axis (Ha). In analogy to the case of Pc in TbMnO3, this result is possibly interpreted as follows. In the case of (Eu,Y)MnO3, Mn 3d spins rotate in the ab plane and Pa would emerge in a zero field. In the Ha, the field will force the spins to rotate in the bc plane, in which Pc would be stabilized. Magnetization measurements supported this interpretation: We confirmed the change of the spin rotation axis of the helix from the c axis to the a axis induced by application of the Ha because there is no 4f moments acting as an internal magnetic field and interacting with the 3d spins. Results obtained with other rare-earth manganites such as (Gd,Tb)MnO3 and (Eu,Ho)MnO3 will be presented.

  20. New structure of high-pressure body-centered orthorhombic Fe2SiO4

    DOE PAGES

    Yamanaka, Takamitsu; Kyono, Atsushi; Nakamoto, Yuki; ...

    2015-08-01

    Here, a structural change in Fe2SiO4 spinel and the structure of a new high pressure phase are determined by Rietveld 26 profile fitting of x-ray diffraction data up to 64 GPa at ambient temperature. The compression curve of the spinel is discontinuous at approximately 20 GPa. Fe Kβ x-ray emission measurements at high pressure show that the transition from a high spin (HS) to an intermediate spin (IS) state begins at 17 GPa in the spinel phase. The IS electronic state is gradually enhanced with pressure, which results in an isostructural phase transition. A transition from the cubic spinel structure to a body centered orthorhombic phase (I-Fe2SiO4) with space group Imma and Z=4 was observed at approximately 34 GPa. The structure of I-Fe2SiO4 has two crystallographically distinct FeO6 octahedra, which are arranged in layers parallel to (101) and (011) and are very similar to the layers of FeO6 octahedra that constitute the spinel structure. Silicon also exists in six-fold coordination in I-Fe2SiO4. The transformation to the new high-pressure phase is reversible under decompression at ambient temperature. A Martensitic transformation of each slab of the spinel structure with translation vector [more » $$\\vec{1/8}$$ $$\\vec{1/8}$$ $$\\vec{1/8}$$] generates the I-Fe2SiO4 structure. Laser heating of I-Fe2SiO4 at 1500 K results in a decomposition of the material to rhombohedral FeO and SiO2 stishovite.« less

  1. 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.

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

    DOE PAGES

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; ...

    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

  3. Structural and Ferromagnetic Properties of an Orthorhombic Phase of MnBi Stabilized with Rh Additions

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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). To date, 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 -xRhx Bi [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 3 μB/f .u . at low temperatures. 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.

  4. Crystallization kinetics of orthorhombic paracetamol from supercooled melts studied by non-isothermal DSC.

    PubMed

    Nikolakakis, Ioannis; Kachrimanis, Kyriakos

    2017-02-01

    A simple and highly reproducible procedure was established for the study of orthorhombic paracetamol crystallization kinetics, comprising melting, quench-cooling of the melt and scanning the formed glass by DSC at different heating rates. Results were analyzed on the basis of the mean as well as local values of the Avrami exponent, n, the energy of activation, as well as the Šesták-Berggren two-parameter autocatalytic kinetic model. The mean value of the Avrami kinetic exponent, n, ranged between 3 and 5, indicating deviation from the nucleation and growth mechanism underlying the Johnson-Mehl, Avrami-Kolmogorov (JMAK) model. To verify the extent of the deviation, local values of the Avrami exponent as a function of the volume fraction transformed were calculated. Inspection of the local exponent values indicates that the crystallization mechanism changes over time, possibly reflecting the uncertainty of crystallization onset, instability of nucleation due to an autocatalytic effect of the crystalline phase, and growth anisotropy due to impingement of spherulites in the last stages of crystallization. The apparent energy of activation, Ea, has a rather low mean value, close to 81 kJ/mol, which is in agreement with the observed instability of glassy-state paracetamol. Isoconversional methods revealed that Ea tends to decrease with the volume fraction transformed, possibly because of the different energy demands of nucleation and growth. The exponents of the Šesták-Berggren two-parameter model showed that the crystallized fraction influences the process, confirming the complexity of the crystallization mechanism.

  5. Microstructure and properties of a titanium alloy-orthorhombic titanium aluminide layered composite

    NASA Astrophysics Data System (ADS)

    Galeev, R. M.; Valiakhmetov, O. R.; Safiullin, R. V.; Imaev, V. M.; Imaev, R. M.

    2009-03-01

    The microstructure and tensile properties of a layered composite material fabricated by solid-state bonding of its components using pressure welding are studied at room and elevated temperatures. The components are made of a high-temperature VT25U titanium alloy and an intermetallic alloy ( O alloy) based on orthorhombic titanium aluminide of the composition Ti-23Al-22.7Nb-1.1V-0.6Zr-0.2Si-0.3C (at %). The study of the microstructure and chemical composition of the composite by scanning electron microscopy and energy dispersive X-ray analysis demonstrates that this method of producing a layered composite provides high-quality poreless bonding of materials of different types. The solid-state bonding zone has an intermediate chemical composition. Mechanical tests demonstrate that the room-temperature strength of the composite is comparable with that of the O alloy and is higher than that of the titanium alloy; as the fraction of the titanium alloy in the composite decreases, this strength increases. The relative elongation of the layered composite is found to be higher than that of the O alloy and lower than that of the titanium alloy. In the temperature range 500-700°C, the strength of the composite material is 25% higher than that of the titanium alloy, and its plasticity is lower than that of the titanium alloy. Our method is shown to be promising for producing layered composite materials that have high mechanical properties over a wide temperature range.

  6. 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.

  7. 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.

  8. Optical phonon characteristics of an orthorhombic-transformed polymorph of CaTa2O6 single crystal fibre

    NASA Astrophysics Data System (ADS)

    Almeida, R. M.; Andreeta, M. R. B.; Hernandes, A. C.; Dias, A.; Moreira, R. L.

    2014-03-01

    Infrared-reflectivity spectroscopy and micro-Raman scattering were used to determine the optical phonon features of orthorhombic calcium tantalite (CaTa2O6) single crystal fibres. The fibres, obtained by the Laser-Heated Pedestal Growth method, grew into an ordered cubic structure \\left( Pm\\bar{3} \\right). Long-time annealing was used to induce a polymorphic transformation to an aeschynite orthorhombic structure (Pnma space group). The phase transformation led to the appearance of structural domains and micro-cracks, responsible for diffuse scattering and depolarization of the scattered light in the visible range, but not in the infrared region. Thus, polarized infrared spectroscopy could be performed within oriented single domains, with an appropriate microscope, allowing us to determine all relevant polar phonons of the orthorhombic CaTa2O6. The obtained phononic dielectric response, {{\\epsilon }_{r}} = 22.4 and = 86 × 103 GHz, shows the appropriateness of the material for microwave applications. Totally symmetric Raman modes could be resolved by polarization, after re-polishing the cracked sample surface.

  9. Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO{sub 2}-based thin films

    SciTech Connect

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

    2016-04-07

    Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO{sub 1.5}-0.93HfO{sub 2} 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 HfO{sub 2}-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)O{sub 3} and BiFeO{sub 3}.

  10. Estimation of effective geostress parameters driven by anisotropic stress and rock-physics models with orthorhombic symmetry

    NASA Astrophysics Data System (ADS)

    Pan, Xinpeng; Zhang, Guangzhi; Yin, Xingyao

    2017-10-01

    Estimation of effective geostress parameters is fundamental to the trajectory design and hydraulic fracturing in shale-gas reservoirs. Considering the shale characteristics of excellent stratification, well-developed cracks or fractures and small-scale pores, an effective or suitable shale anisotropic rock-physics model contributes to achieving the accurate prediction of effective geostress parameters in shale-gas reservoirs. In this paper, we first built a shale anisotropic rock-physics model with orthorhombic symmetry, which helps to calculate the anisotropic and geomechanical parameters under the orthorhombic assumption. Then, we introduced an anisotropic stress model with orthorhombic symmetry compared with an isotropic stress model and a transversely isotropic stress model. Combining the effective estimation of the pore pressure and the vertical stress parameters, we finally obtained the effective geostress parameters including the minimum and maximum horizontal stress parameters, providing a useful guide for the exploration and development in shale-gas reservoirs. Of course, ultimately the optimal choice of the hydraulic-fracturing area may also take into consideration other multi-factors such as the rock brittleness, cracks or fractures, and hydrocarbon distribution.

  11. Effect of orthorhombic-tetragonal phase transition on structure and piezoelectric properties of KNN-based lead-free ceramics.

    PubMed

    Zhang, Yang; Li, Lingyu; Shen, Bo; Zhai, Jiwei

    2015-05-07

    (1 - x)(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3-xSrZrO3 ((1 - x)KNLNS-xSZ) lead free piezoelectric ceramics have been prepared by the conventional solid state reaction method, via adjusting the orthorhombic-tetragonal phase transition temperature to near room temperature with doping SrZrO3, and the effects of SrZrO3 content on polymorphic phase transition have been investigated. These results show that the phase structure of the ceramics was changed from orthorhombic to tetragonal at x ≥ 0.02 mol, and the orthorhombic-tetragonal phase transition temperature was modified to around room temperature with increasing SrZrO3. Remarkable piezoelectric and ferroelectric properties has been obtained in (1 - x)KNLNS-xSZ system with x = 0.02, which showed a piezoelectric parameter of d33 = 256 pC N(-1), Curie temperature Tc = 270 °C, strain levels of 0.16% at 50 kV cm(-1), remnant polarization Pr = 24.9 μC cm(-2) and coercive field Ec = 10.6 kV cm(-1).

  12. 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.

  13. Twinning induced by the rhombohedral to orthorhombic phase transition in lanthanum gallate (LaGaO3)

    NASA Astrophysics Data System (ADS)

    Wang, W. L.; Lu, H. Y.

    2006-10-01

    Phase-transformation-induced twins in pressureless-sintered lanthanum gallate (LaGaO3) ceramics have been analysed using the transmission electron microscopy (TEM). Twins are induced by solid state phase transformation upon cooling from the rhombohedral (r, Rbar{3}c) to orthorhombic ( o, Pnma) symmetry at ˜145°C. Three types of transformation twins {101} o , {121} o , and {123} o were found in grains containing multiple domains that represent orientation variants. Three orthorhombic orientation variants were distinguished from the transformation domains converged into a triple junction. These twins are the reflection type as confirmed by tilting experiment in the microscope. Although not related by group-subgroup relation, the transformation twins generated by phase transition from rhombohedral to orthorhombic are consistent with those derived from taking cubic Pm {bar {3}}m aristotype of the lowest common supergroup symmetry as an intermediate metastable structure. The r→ o phase transition of first order in nature may have occurred by a diffusionless, martensitic-type or discontinuous nucleation and growth mechanism.

  14. An orthorhombic representation of a heterogeneous medium for the finite-difference modelling of seismic wave propagation

    NASA Astrophysics Data System (ADS)

    Kristek, Jozef; Moczo, Peter; Chaljub, Emmanuel; Kristekova, Miriam

    2017-02-01

    The possibility of applying one explicit finite-difference (FD) scheme to all interior grid points (points not lying on a grid border) no matter what their positions are with respect to the material interface is one of the key factors of the computational efficiency of the FD modelling. Smooth or discontinuous heterogeneity of the medium is accounted for only by values of the effective grid moduli and densities. Accuracy of modelling thus very much depends on how these effective grid parameters are evaluated. We present an orthorhombic representation of a heterogeneous medium for the FD modelling. We numerically demonstrate its superior accuracy. Compared to the harmonic-averaging representation the orthorhombic representation is more accurate mainly in the case of strong surface waves that are especially important in local surface sedimentary basins. The orthorhombic representation is applicable to modelling seismic wave propagation and earthquake motion in isotropic models with material interfaces and smooth heterogeneities using velocity-stress, displacement-stress and displacement FD schemes on staggered, partly staggered, Lebedev and collocated grids.

  15. First-principles study of structural and elastic properties of monoclinic and orthorhombic BiMnO3.

    PubMed

    Mei, Zhi-Gang; Shang, Shun-Li; Wang, Yi; Liu, Zi-Kui

    2010-07-28

    The structural and elastic properties of BiMnO(3) with monoclinic (C 2/c) and orthorhombic (Pnma) ferromagnetic (FM) structures have been studied by first-principles calculations within LDA + U and GGA + U approaches. The equilibrium volumes and bulk moduli of BiMnO(3) phases are evaluated by equation of state (EOS) fittings, and the bulk properties predicted by LDA + U calculations are in better agreement with experiment. The orthorhombic phase is found to be more stable than the monoclinic phase at ambient pressure. A monoclinic to monoclinic phase transition is predicted to occur at a pressure of about 10 GPa, which is ascribed to magnetism versus volume instability of monoclinic BiMnO(3). The single-crystal elastic stiffness constants c(ij)s of the monoclinic and orthorhombic phases are investigated using the stress-strain method. The c(46) of the monoclinic phase is predicted to be negative. In addition, the polycrystalline elastic properties including bulk modulus, shear modulus, Young's modulus, bulk modulus-shear modulus ratio, Poisson's ratio, and elastic anisotropy ratio are determined based on the calculated elastic constants. The presently predicted phase transition and elastic properties open new directions for investigation of the phase transitions in BiMnO(3), and provide helpful guidance for the future elastic constant measurements.

  16. Large low-field magnetodielectric response in multiferroic Bi2NiMnO6 thin film

    NASA Astrophysics Data System (ADS)

    Rathi, A.; Anshul, Avneesh; Gupta, Anurag; Rout, P. K.; Maurya, K. K.; Kotnala, R. K.; Pant, R. P.; Basheed, G. A.

    2017-04-01

    Single-phase multiferroics exhibiting a large low-field magnetodielectric effect (MDE) are of great interest for the practical realization of multifunctional devices, as existing multiferroics demand large magnetic fields to cause any significant MDE. Here, we report remarkably large MDE \\equiv Δ {{\\varepsilon}\\prime} /{{\\varepsilon}\\prime}∼ 6 % at very low fields (H≤slant 5 kOe) near T C in multiferroic Bi2NiMnO6 thin film. More importantly, the insensitivity of {{\\varepsilon}\\prime} to temperature and frequency variations, and pronounced change in {{\\varepsilon}\\prime} near T C in zero magnetic field attribute the observed large MDE to the inherent exchange magnetoelectric interactions.

  17. 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.

  18. 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.

  19. 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.

  20. Identification of the ferroelectric switching process and dopant-dependent switching properties in orthorhombic HfO2: A first principles insight

    NASA Astrophysics Data System (ADS)

    Clima, S.; Wouters, D. J.; Adelmann, C.; Schenk, T.; Schroeder, U.; Jurczak, M.; Pourtois, G.

    2014-03-01

    The origin of the ferroelectric polarization switching in orthorhombic HfO2 has been investigated by first principles calculations. The phenomenon can be regarded as being the coordinated displacement of four O ions in the orthorhombic unit cell, which can lead to a saturated polarization as high as 53 μC/cm2. We show the correlation between the computed polarization reversal barrier and the experimental coercive fields.

  1. Synthesis and Characterization of Novel Ferromagnetic, Ferroelectric, Single Phase and Composite Multiferroic Mesoporous Materials

    NASA Astrophysics Data System (ADS)

    Quickel, Thomas Eugene

    Mesoporous nanostructures offer facile routes to novel materials with interesting and often unparalleled properties. Ferrimagnetic, ferroelectric and multiferroic phases, the latter comprising materials that simultaneously possess multiple order parameters, are of great technological importance. Developments in our knowledge of and ability to produce new materials exploiting their properties could have fundamental impacts. Employing versatile solution phase chemistry techniques utilizing co-assembly between organic block co-polymers and inorganic metal precursors, we are able to produce 3-dimensional porous nano-structures in thin film format. Mesoporous frameworks comprising various magnetic ferrites are explored in chapters 2, 3 & 4. The crystal structure and nanoscale architecture for each material is thoroughly examined, and the effects of mesoporosity on the magnetic characteristics of the individual ferrites are determined. The ferrites investigated (MFe2O4,M=Co, Zn, Ni, Mg) are magnetostrictive as their magnet moments are subject to change upon straining of the crystal lattice. It was observed that the nano-scale architecture imparts novel strain states on to the polycrystalline phases and spin re-orientation of their magnetic moment results, emulating results that, previous to the finding in this study, were exclusive to epitaxial growth techniques. Furthermore, the presence of high surface area, resulting from mesoporosity, increases surface spin states drastically altering the magnetic functionality of porous ferrites versus their bulk counterparts. The effects of mesoporosity on piezoelectric materials was also investigated. Piezoelectrics comprise a fascinating class of materials that exhibit internal creation of charge upon the action of mechanical strain, the reverse of which is also true. Mesoporous piezoelectric phases were successfully prepared, and the effects of porosity on the ferroelectric order paramter were established. The presence of pores

  2. On the effect of polarization direction on the converse magnetoelectric response of multiferroic composite rings

    NASA Astrophysics Data System (ADS)

    Youssef, George; Lopez, Mario; Newacheck, Scott

    2017-03-01

    The application domain of composite multiferroic materials with magnetoelectric coupling has been widening on the nano-, micro- and macro-scales. Generally, a composite multiferroic material consists of two, or more, layers of a piezoelectric material and a magnetostrictive material. In turn, the proliferation of multiferroics in more applications is accompanied by a keen focus on understanding the effect of material phases, geometry, bonding interface and arrangement of phases by performing theoretical, numerical and experimental studies to fundamentally elucidate the response. In this experimental study, a focus is given to exploit the effect of the polarization direction of the piezoelectric phase on the overall converse magnetoelectric (CME) response of a composite concentric PZT/Terfenol-D structure. Specifically, radially and axially polarized PZT rings were concentrically bonded to the outer surface of two Terfenol-D rings, respectively. It was found that the maximum, near resonance, CME coefficient of the axially-poled configuration is 443 mG V‑1 when tested at 34 kHz, 80 kV m‑1 electric field and 784 Oe bias magnetic field. On the other hand, the near resonance CME value for the radially-poled configuration remained nearly constant at 281.9 ± 5.3 mG V‑1 between bias magnetic fields of 532 Oe and 1524 Oe at AC electric field of 80 kV m‑1 with a frequency of 36 kHz. Interestingly, the CME coefficient of radially-poled composite structure exhibits a saturation behavior, while the CME coefficient for axially-poled structure is distinguished by a single peak. The difference in the response is attributed to the amount strain transduction due to the polarization direction.

  3. Fabrication of self-assembled epitaxial nanostructures consisting of multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Stern, Ilan

    As the field of epitaxial, self-assembled, thin film nanostructures continues to evolve, we have seen the emergence of novel growth techniques, exciting new multiferroic heterostructures and the increase in strain control engineering. The interest in such heterostructures ranges from high speed computing and storage devices, to smart sensors and actuators. Magnetic tunneling junctions and the development of highly efficient composites in the use of photovoltaics is certainly a direction of the future of thin film physics. Through the method of pulsed laser deposition (PLD), we have developed and engineered complex multiferroic transition metal oxides. By examining the structural and physical characterization of BiFeO3-CoFe2O4 epitaxially grown on spinel MgAl2O4 (001) by way of HR-XRD, AFM, TEM SEM, SQUID, and VSM, we have added additional growth parameters, i.e., the role of substrate structure, which can be used in the control of the structural formation of spinel and perovskite multiferroic heterostructures. This additional growth parameter is a critical step in the advancement in structural control and growth morphology. Additionally, control engineering of ferromagnetic vertically aligned nanostructures (VAN's), embedded in a ferroelectric matrix was accomplished using a 1:1 molar ratio of ferromagnetic NiCO2O4 and ferroelectric BaTiO3, which is to be used in the study of electrical transport, and 3-dimensional strain control. Finally, a conducting bottom electrode (Nb-STO) was developed to allow for the out-of-plane transport measurements on the NCO-BTO heterocomposite.

  4. Recognition of exchange striction as the origin of magnetoelectric coupling in multiferroics

    NASA Astrophysics Data System (ADS)

    Yahia, G.; Damay, F.; Chattopadhyay, S.; Balédent, V.; Peng, W.; Elkaim, E.; Whitaker, M.; Greenblatt, M.; Lepetit, M.-B.; Foury-Leylekian, P.

    2017-05-01

    The magnetoelectric coupling, a phenomenon inducing magnetic (electric) polarization by application of an external electric (magnetic) field and first conjectured by Curie in 1894, is observed in most of the multiferroics and used for many applications in various fields such as data storage or sensing. However, its microscopic origin is a long-standing controversy in the scientific community. An intense revival of interest developed in the beginning of the 21st century due to the emergence of multiferroic frustrated magnets in which the ferroelectricity is magnetically induced and which present an inherent strong magnetoelectric coupling. The Dzyaloshinskii-Moriya interaction (DMI) well accounts for such ferroelectricity in systems with a noncollinear magnetic order such as the RMnO3 manganites. The DMI effect is, however, inadequate for systems presenting ferroelectricity induced by quasicollinear spin arrangements such as the prominent RMn2O5 manganites. Among different microscopic mechanisms proposed to resolve this incompatibility, the exchange-striction model stands as the most invoked candidate. In this scenario, the polar atomic displacements originate from the release of a frustration caused by the magnetic order. Despite its theoretical description 15 years ago, this mechanism had yet to be unambiguously validated experimentally. The breakthrough finally comes from SmMn2O5 presenting a unique magnetic order revealed by powder neutron diffraction. The unique orientation of its magnetic moment establishes the missing element that definitely validates the exchange striction as the effective mechanism for the spin-induced ferroelectricity in this series. More generally, this is a proof of concept that validates this model on actual systems, facilitating the development of a new generation of multiferroics with unrivaled magnetoelectric properties.

  5. 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

  6. 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

  7. Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo2 Laves phases.

    PubMed

    Driver, S L; Herrero-Albillos, J; Bonilla, C M; Bartolomé, F; García, L M; Howard, C J; Carpenter, M A

    2014-02-05

    Magnetic phase transitions in RCo2 Laves phases with R as a rare earth element are accompanied by changes in crystallographic space group. For purely structural transitions they would be described as improper ferroelastic and therefore fulfil the condition for multiferroic phase transitions in combining two out of three properties, ferro/antiferromagnetism, ferroelectricity and ferroelasticity. Here lattice parameter data from the literature and new measurements of elastic and anelastic properties, by resonant ultrasound spectroscopy, for NdCo2 and ErCo2 have been analysed from this perspective. The temperature dependence of symmetry-breaking shear strains is consistent with the cubic ↔ tetragonal transition in NdCo2 being close to tricritical in character and the cubic ↔ rhombohedral transition in ErCo2 being first order. Elastic softening and acoustic loss within the stability ranges of the ferroelastic phases can be understood in terms of a combination of intrinsic softening due to strain/order parameter coupling and ferroelastic twin-wall motion. Softening ahead of the transitions does not fit with standard macroscopic descriptions of dynamic effects from other systems but, rather, in the case of NdCo2, might be attributed to the involvement of a second zone centre order parameter related to a separate instability driven by cooperative Jahn-Teller distortions. In ErCo2, acoustic loss in the temperature interval above the transition point is discussed in terms of a possible tweed microstructure associated with strain coupling to local magnetic ordering. The overall multiferroic behaviour can be understood in terms of a single magnetic order parameter (irrep mΓ+4 of magnetic space group Fd3m1') which couples with a structural order parameter (irrep Γ+3 or Γ+5). The coupling is linear/quadratic which, in the case of two separate instabilities, causes them to combine in a single multiferroic phase transition.

  8. 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.

  9. 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.

  10. Multiferroicity in the Spin-1/2 Quantum Matter of LiCu2O2

    SciTech Connect

    Rusydi,A.; Mahns, I.; Mueller, S.; Ruebhausen, M.; Park, S.; Choi, Y.; Zhang, C.; Cheong, S.; Smadici, S.; et al. .

    2008-01-01

    Multiferroicity in LiCu2O2 single crystals is studied using resonant soft x-ray magnetic scattering, hard x-ray diffraction, heat capacity, magnetic susceptibility, and electrical polarization. Two magnetic transitions are found at 24.6 K (T1) and 23.2 K (T2). Our data are consistent with a sinusoidal spin structure at T2

  11. 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.

  12. Theory of magneto-optical effects in helical multiferroic materials via toroidal magnon excitation

    NASA Astrophysics Data System (ADS)

    Miyahara, S.; Furukawa, N.

    2014-05-01

    We investigate dynamical magnetoelectric effect owing to Nambu-Goldstone magnon resonance in helical multiferroic materials. Using the spin wave expansion, we analyzed magneto- and electroactive modes in the J1-J2 Heisenberg model through the spin-current mechanism. Under external magnetic field, the Nambu-Goldstone magnons accompany dynamical toroidal moments, i.e., toroidal magnons, and their resonant absorption shows anomalous features such as nonreciprocal directional dichroism and natural circular dichroism. The estimation indicates that such effects are gigantic in helical magnets.

  13. Analysis of the multiferroicity in the hexagonal manganite YMnO3.

    PubMed

    Singh, Kiran; Lepetit, Marie-Bernadette; Simon, Charles; Bellido, Natalia; Pailhès, Stéphane; Varignon, Julien; De Muer, Albin

    2013-10-16

    We performed magnetic and ferroelectric measurements, associated with Landau theory and symmetry analysis, in order to clarify the situation of the YMnO3 system, a classical example of type I multiferroics. We found that the only magnetic group compatible with all experimental data (neutron scattering, magnetization, polarization, dielectric constant, second harmonic generation) is the P6'(3) group. In this group a small ferromagnetic component along c is induced by the Dzyaloshinskii-Moriya interaction, and observed here in magnetization measurements. We found that the ferromagnetic and antiferromagnetic components can only be switched simultaneously, while the magnetic orders are functions of the polarization square and therefore insensitive to its sign.

  14. 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.

  15. Realization of anomalous multiferroicity in free-standing graphene with magnetic adatoms

    NASA Astrophysics Data System (ADS)

    Marques, Y.; Ricco, L. S.; Dessotti, F. A.; Machado, R. S.; Shelykh, I. A.; de Souza, M.; Seridonio, A. C.

    2016-11-01

    It is generally believed that free-standing graphene does not demonstrate any ferroic properties. In the present work we revise this statement and show that a single graphene sheet with a pair of magnetic adatoms can be driven into ferroelectric (FE) and multiferroic (MF) phases by tuning the Dirac cones slope. The transition into the FE phase occurs gradually, but an anomalous MF phase appears abruptly by means of a quantum phase transition. Our findings suggest that such features should exist in graphene recently investigated by scanning tunneling microscopy [H. González-Herrero et al., Science 352, 437 (2016), 10.1126/science.aad8038].

  16. A first order reversal curve investigation of pressure hysteresis in multiferroics spin transition compound

    NASA Astrophysics Data System (ADS)

    Tanasa, Radu; Stancu, Alexandru; Codjovi, Epiphane; Linares, Jorge; Varret, François; Létard, Jean-François

    2008-04-01

    Spin crossover multiferroic [Fe(PM-BiA)2(NCS)2] is investigated for the first time with the first order reversal curve (FORC) diagram method for its hysteretic pressure behavior. The experimental setup allows the measurements of the high spin fraction as the function of temperature, light intensity, and pressure. The experimental FORC diagrams obtained in compression and releasing modes show significant differences which are in disagreement with the classical Preisach model. Also, stronger kinetic effects are evidenced in the compression mode and possible explanations of this effect considering the viscoelastic behavior are provided.

  17. Self-organization, condensation, and annihilation of topological vortices and antivortices in a multiferroic

    PubMed Central

    Chae, S. C.; Horibe, Y.; Jeong, D. Y.; Rodan, S.; Lee, N.; Cheong, S.-W.

    2010-01-01

    The interaction among topological defects can induce novel phenomena such as disclination pairs in liquid crystals and superconducting vortex lattices. Nanoscale topological vortices with swirling ferroelectric, magnetic, and structural antiphase relationships were found in multiferroic h-YMnO3. Herein, we report the discovery of intriguing, but seemingly irregular configurations of a zoo of topological vortices and antivortices. These configurations can be neatly analyzed in terms of graph theory and reflect the nature of self-organized criticality in complexity phenomena. External stimuli such as chemistry-driven or electric poling can induce the condensation and eventual annihilation of topological vortex–antivortex pairs. PMID:21115846

  18. Identifying the spectroscopic modes of multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Fishman, Randy S.; Furukawa, Nobuo; Haraldsen, Jason T.; Matsuda, Masaaki; Miyahara, Shin

    2012-12-01

    We have identified the modes of multiferroic BiFeO3 measured by THz and Raman spectroscopies. Excellent agreement with the observed peaks is obtained by including the effects of easy-axis anisotropy along the direction of the electric polarization. By distorting the cycloidal spin state, anisotropy splits the Ψ±1 mode into peaks at 20 and 21.5 cm-1 and activates the lower Φ±2 mode at 27 cm-1 (T=200 K). An electromagnon is identified with the upper Ψ±1 mode at 21.5 cm-1. Our results also explain recent inelastic neutron-scattering measurements.

  19. Polarized micro Raman spectroscopy of multiferroic BiFeO3 single crystals

    NASA Astrophysics Data System (ADS)

    Beekman, C.; Cheong, Sang-Wook; Burch, Kenneth

    2011-03-01

    In Bismuth ferrite (BiFe O3) antiferromagnetic and ferroelectric order parameters coexist at room temperature, making this material an excellent candidate for new functionalities, such as electrical control of ferromagnetism. Despite extensive reports on Raman scattering experiments on single crystals and thin films, controversy still remains in the observation and assignment of the phonon modes. However, proper Raman mode assignment to describe the phonons critical for the multiferroic behavior is necessary. We present polarized micro Raman spectroscopy of single crystals with uniform ferroelectric polarization. Careful examination of the Raman spectra upon crystal rotation enables us to unambiguously assign several (A1 , Ex and Ey) modes.

  20. Ferroelectric size effects in multiferroic BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Chu, Y. H.; Zhao, T.; Cruz, M. P.; Zhan, Q.; Yang, P. L.; Martin, L. W.; Huijben, M.; Yang, C. H.; Zavaliche, F.; Zheng, H.; Ramesh, R.

    2007-06-01

    Ferroelectric size effects in multiferroic BiFeO3 have been studied using a host of complementary measurements. The structure of such epitaxial films has been investigated using atomic force microscopy, transmission electron microscopy, and x-ray diffraction. The crystal structure of the films has been identified as a monoclinic phase, which suggests that the polarization direction is close to ⟨111⟩. Such behavior has also been confirmed by piezoforce microscopy measurements. That also reveals that the ferroelectricity is down to at least 2nm.

  1. Magnetic Exchange Interaction between Rare-Earth and Mn Ions in Multiferroic Hexagonal Manganites

    NASA Astrophysics Data System (ADS)

    Talbayev, D.; Laforge, A. D.; Trugman, S. A.; Hur, N.; Taylor, A. J.; Averitt, R. D.; Basov, D. N.

    2008-12-01

    We report a study of magnetic dynamics in multiferroic hexagonal manganite HoMnO3 by far-infrared spectroscopy. The low-temperature magnetic excitation spectrum of HoMnO3 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. We 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. Effect of Y doping on thermal properties of multiferroic BiCrO{sub 3}

    SciTech Connect

    Parey, Vanshree Shukla, Aarti; Parveen, Atahar; Gaur, N. K.

    2016-05-06

    The effect of Yttrium doping (0.01 ≤ x ≤ 0.5) on elastic and thermal properties of multiferroic BiCrO{sub 3} has been investigated using the Modified Rigid Ion Model (MRIM). We have computed the specific heat and volume thermal expansion coefficient for pure and doped BiCrO{sub 3} as a function of temperature (1K ≤ T ≤ 300K). The specific heat results are in good agreement with the available experimental data. A check on thermal stability of the pure and doped compounds is made by computing other properties like Debye temperature, cohesive energy and bulk modulus.

  3. Mechanical loss in multiferroic materials at high frequencies: friction and the evolution of ferroelastic microstructures.

    PubMed

    Zhao, Z; Ding, X; Lookman, T; Sun, J; Salje, E K H

    2013-06-18

    Energy absorption in multiferroic materials stems typically from strain relaxation which can be strong even when no extrinsic defects exist in the material. Computer simulations of a simple two-dimensional model on a generic, proper ferroelastic material identify the dissipative mechanisms associated with the dynamical motion as: a) advance and retraction of needle-shaped twin domains and, b) movement of kinks inside twin boundaries. Both movements involve friction losses. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Investigation of multiferroic behavior on flakes-like BiFeO{sub 3}

    SciTech Connect

    Sheikh, Javed R.; Gaikwad, Vishwajit M.; Acharya, Smita A.

    2016-05-23

    In present work, multiferroic BiFeO{sub 3} was synthesized by hydrothermal route. The rhombohedral structure was confirmed X-ray diffraction pattern and data fitted with Reitveld refinement using Full-Prof software suite. SEM micrograph shows flake like morphology. Frequency and temperature dependence of dielectric constant and dielectric loss were studied and detected enhancement in dielectric constant. The magnetic measurement indicates antiferromagnetic nature of BFO. P-E curve shows ferroelectic hysteresis loop with remanent polarization (2Pr) 0.3518 µC/cm{sup 2}. The dielectric anomaly observed near T{sub N} can be assigned to magnetoelectric coupling which is useful in device application.

  5. Polarity-tunable spin transport in all-oxide multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Soni, Rohit; Petraru, Adrian; Nair, Harikrishnan S.; Vavra, Ondrej; Ziegler, Martin; Kim, Seong Keun; Jeong, Doo Seok; Kohlstedt, Hermann

    2016-05-01

    A multiferroic tunnel junction (MFTJ) promisingly offers multinary memory states in response to electric- and magnetic-fields, referring to tunneling electroresistance (TER) and tunneling magnetoresistance (TMR), respectively. In spite of recent progress, a substantial number of questions concerning the understanding of these two intertwined phenomena still remain open, e.g. the role of microstructural/chemical asymmetry at the interfaces of the junction and the effect of an electrode material on the MFTJ properties. In this regard, we look into the multiferroic effect of all-complex-oxide MFTJ (La0.7Sr0.3MnO3/Pb(Zr0.3Ti0.7)O3/La0.7Sr0.3MnO3). The results reveal apparent TER-TMR interplay--captured by the reversible electric-field control of the TMR effect. Finally, microscopy analysis on the MFTJ revealed that the observed TER-TMR interplay is perhaps mediated by microstructural and chemical asymmetry in our nominally symmetric MFTJ.A multiferroic tunnel junction (MFTJ) promisingly offers multinary memory states in response to electric- and magnetic-fields, referring to tunneling electroresistance (TER) and tunneling magnetoresistance (TMR), respectively. In spite of recent progress, a substantial number of questions concerning the understanding of these two intertwined phenomena still remain open, e.g. the role of microstructural/chemical asymmetry at the interfaces of the junction and the effect of an electrode material on the MFTJ properties. In this regard, we look into the multiferroic effect of all-complex-oxide MFTJ (La0.7Sr0.3MnO3/Pb(Zr0.3Ti0.7)O3/La0.7Sr0.3MnO3). The results reveal apparent TER-TMR interplay--captured by the reversible electric-field control of the TMR effect. Finally, microscopy analysis on the MFTJ revealed that the observed TER-TMR interplay is perhaps mediated by microstructural and chemical asymmetry in our nominally symmetric MFTJ. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01277a

  6. Intertwining of Frustration with Magneto-Elastic Coupling in the Multiferroic LuMnO3

    NASA Astrophysics Data System (ADS)

    Yano, Shin-ichiro; Louca, Despina; Chi, Songxue; Matsuda, Masaaki; Qiu, Yiming; Copley, John R. D.; Cheong, Sang-Wook

    2014-02-01

    Residual magnetic frustration in the multiferroic LuMnO3 may be key towards understanding magneto-elastic coupling in hexagonal manganites. Critical magnetic scattering present well above the magnetic ordering temperature TN persists below, as observed by inelastic neutron scattering. The magnetic fluctuations are confined in two dimensions implied by the characteristic wavevector dependence of the magnetic structure factor that changes from symmetric to asymmetric across TN. The low dimensionality of the magnetic structure is also evident in the temperature dependence of the commensurate antiferromagnetic intensity which follows a mean field exponent of β ˜ 0.2.

  7. Magnetic excitations in multiferroic LuMnO3 studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Lewtas, H. J.; Boothroyd, A. T.; Rotter, M.; Prabhakaran, D.; Müller, H.; Le, M. D.; Roessli, B.; Gavilano, J.; Bourges, P.

    2010-11-01

    We present data on the magnetic and magnetoelastic coupling in the hexagonal multiferroic manganite LuMnO3 from inelastic neutron scattering, magnetization, and thermal-expansion measurements. We measured the magnon dispersion along the main symmetry directions and used this data to determine the principal exchange parameters from a spin-wave model. An analysis of the magnetic anisotropy in terms of the crystal field acting on the Mn is presented. We compare the results for LuMnO3 with data on other hexagonal RMnO3 compounds.

  8. Enhanced multiferroic properties of (Nd, Cr) co-doped BiFeO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Shu, Huazhong; Wang, Zhongcao; Mao, Weiwei; Ma, Yuhui; Chu, Liang; Wang, Xingfu; Chen, Wei; Zhang, Jian; Yang, Jianping; Song, Rongfang; Li, Xing'ao

    2017-05-01

    Pure BiFeO3 (BFO) and doped Bi1- x Nd x Fe0.975Cr0.025O3 ( x = 0.025, 0.05, and 0.075) nanoparticles were prepared by a sol-gel method. The doping effects were systematically investigated on the structural, morphological, magnetic, and ferroelectric properties. The dopant results in forming nanoparticles, and the (Nd, Cr) co-doped BFO nanoparticles show excellent ferromagnetic and ferroelectric properties. The proposed mechanism for the co-doped BFO provides an alternative strategy to form nanoparticles with enhanced multiferroic properties.

  9. Study of epitaxial multiferroic BiFeO{sub 3} films

    SciTech Connect

    Kothari, Deepti; Reddy, V. Raghavendra; Gupta, Ajay

    2010-12-01

    Multiferroic BiFeO{sub 3} epitaxial thin films are prepared using pulsed laser deposition method on single crystal SrTiO{sub 3}(001) substrates. The prepared films are characterized by [001] growth and the in-plane {phi}-scans haven shown that the films are characterized by ''cube-on-cube'' epitaxial growth. The photoelectron spectroscopy results confirm the presence of Fe{sup 3+} only. Better magnetic properties are observed in the case of less thickness BiFeO{sub 3} film as compared to higher thickness, which could be due to the in-plane strain effect.

  10. Ultrathin limit of exchange bias coupling at oxide multiferroic/ferromagnetic interfaces.

    PubMed

    Huijben, M; Yu, P; Martin, L W; Molegraaf, H J A; Chu, Y-H; Holcomb, M B; Balke, N; Rijnders, G; Ramesh, R

    2013-09-14

    Exchange bias coupling at the multiferroic- ferromagnetic interface in BiFeO₃ /La₀.₇ Sr₀.₃ MnO₃ heterostructures exhibits a critical thickness for ultrathin BiFeO₃ layers of 5 unit cells (2 nm). Linear dichroism measurements demonstrate the dependence on the BiFeO₃ layer thickness with a strong reduction for ultrathin layers, indicating diminished antiferromagnetic ordering that prevents interfacial exchange bias coupling. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. 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

    2001-11-08

    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.

  12. Tetragonal-to-Orthorhombic Structural Phase Transition at 90Kin the Superconductor Fe1:01Se

    SciTech Connect

    McQueen, T.M.; Tao, J.; Williams, A.J.; Stephens, P.W.; Zhu, Y.; Ksenofontov, V.; Casper, F.; 4 C.; Cava, R.J.

    2009-07-30

    In this Letter we show that superconducting Fe{sub 1.01}Se undergoes a structural transition at 90 K from a tetragonal to an orthorhombic phase but that nonsuperconducting Fe{sub 1.03}Se does not. High resolution electron microscopy at low temperatures further reveals an unexpected additional modulation of the crystal structure of the superconducting phase that involves displacements of the Fe atoms, and that the nonsuperconducting composition shows a different, complex nanometer-scale structural modulation. Finally, we show that magnetism is not the driving force for the phase transition in the superconducting phase.

  13. Orthorhombic polar Nd-doped BiFeO3 thin film on MgO substrate.

    PubMed

    Leontyev, I N; Yuzyuk, Yu I; Janolin, P-E; El-Marssi, M; Chernyshov, D; Dmitriev, V; Golovko, Yu I; Mukhortov, V M; Dkhil, B

    2011-08-24

    A Nd-doped BiFeO(3) thin film deposited on MgO substrate was studied by synchrotron diffraction. The ferroelectric nature of the film is proven by in-plane remanent polarization measurement. The highest possible symmetry of the film is determined to be orthorhombic, within the Fm2m space group. Such a structure is rotated by 45° with respect to the substrate and is consistent with tilts of oxygen octahedra doubling the unit cell. This polar structure presents a rather unusual strain-accommodation mechanism.

  14. 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.

  15. Effect of hydrogen on the structure of quenched orthorhombic titanium aluminide-based alloy and phase transformations during subsequent heating

    NASA Astrophysics Data System (ADS)

    Khadzhieva, O. G.; Illarionov, A. G.; Popov, A. A.; Grib, S. V.

    2013-06-01

    The effect of hydrogen on structure formation and changes in the volume fractions of phases in an alloy based on orthorhombic titanium aluminide ( O phase) alloy upon its quenching is studied. X-ray diffraction analysis is used to determine the lattice parameters of phases. It has been shown that hydrogen is dissolved mainly in the β0 phase. Differential thermal analysis is used to determine stages and temperature ranges of phase transformations during heating; it was found that introduced hydrogen shifts the β0 → O and reverse O → β0 transformations into the low-temperature range; the enthalpies of transformation are calculated.

  16. Ground state of orthorhombic RbC60: A high-field electron-spin-resonance investigation

    NASA Astrophysics Data System (ADS)

    Bennati, M.; Griffin, R. G.; Knorr, S.; Grupp, A.; Mehring, M.

    1998-12-01

    We report on electron paramagnetic resonance in the low-temperature phase of orthorhombic RbC60 at 94 and 140 GHz microwave frequencies. Below about 25-30 K characteristic features that could be related to antiferromagnetic resonance (AFMR) or alternatively to spin clusters are clearly distinguished from the conduction-electron spin resonance signal above 50 K. The different scenarios, AFMR vs spin glass or spin clusters, are discussed. If the experimental data are interpreted within the AFMR scenario the corresponding spin-flop field can be estimated to be about 0.34 T.

  17. 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.

  18. Dispersive SH waves in a cylindrical multiferroic composite with interfacial irregularity: Approximate analysis on coordinate-dependent phase velocity

    NASA Astrophysics Data System (ADS)

    Li, Yong-Dong; Liu, Shi-Lun; Jin, Ying; Wei, Hong-Xing; Guan, Yong

    2017-09-01

    Irregular interfaces may be formed between the neighboring ferromagnetic and ferroelectric layers of multiferroic composites during the hot-pressing process. They undoubtedly affects the mechanical behavior of multiferroic composites and this is a scientific problem deserving studying. In addition, phase velocity will be a function of coordinate if the interface is irregular, and this makes the governing equation so complicated that direct analytical solution is unobtainable. The present article proposes an approximate approach for analyzing SH waves in a cylindrical multiferroic composite with interfacial irregularity. The dispersion equation is analytically derived and numerically solved. After the validity range of the approximate treatment is clarified, parametric studies reveals that interfacial corrugations can give rise to an oscillatory distribution of phase velocity along the propagation direction. Because such oscillation can lead to unstable signal transmission, it should be avoided in engineering. Further discussion suggests three possible ways for suppressing the oscillation of phase velocity. The research results can provide references for optimizing the design, manufacture and application of multiferroic devices.

  19. Introducing Barium in Transition Metal Oxide Frameworks: Impact upon Superconductivity, Magnetism, Multiferroism and Oxygen Diffusion and Storage.

    PubMed

    Raveau, Bernard

    2017-06-01

    The role of barium in the structural chemistry of some transition metal oxides of the series "Cu, Mn, Fe,Co" is reviewed, based on its size effect and its particular chemical bonding. Its impact upon various properties, superconductivity, magnetism, multiferroism, oxygen storage is emphasized. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Ultrafast IR spectroscopic study of coherent phonons and dynamic spin-lattice coupling in multiferroic LuMnO3

    NASA Astrophysics Data System (ADS)

    Jang, Kyeong-Jin; Lim, Jongseok; Ahn, Jaewook; Kim, Ji-Hee; Yee, Ki-Ju; Ahn, Jai Seok; Cheong, Sang-Wook

    2010-02-01

    The concurrent existence of ferroelectricity and magnetism within a single crystalline system characterizes the multiferroic materials discovered in recent years. To understand and develop the multiferroic phenomenon, we need to investigate the unusual coupling between spin and lattice degrees of freedom. Spins in multiferroics are expected to be elastically coupled to phonons. Therefore, the time-dependent study can be a crucial factor in understanding the coupled dynamics. Here, we report the observations of strong dynamic spin-lattice coupling in multiferroic LuMnO3. A coherent optical phonon of 3.6 THz and its temperature dependence is measured for the first time from our femtosecond IR pump and probe spectroscopy. Also, we observed a coherent acoustic phonon of 47 GHz similar to a previous report (Lim et al 2003 Appl. Phys. Lett. 83 4800). Temperature-dependent measurements show that both optical and acoustic phonons become significantly underdamped as temperature decreases to TN, and they disappear below TN. These observations reveal that phonons are coupled to spins by magneto-elastic coupling, and the disappearance of phonon modes at TN is consistent with the isostructural coupling scheme suggested by Lee et al (2008 Nature 451 805).

  1. 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

  2. Orthorhombic phases with large unit cells coexisting with the decagonal quasicrystal in an AlCoNiTb alloy

    SciTech Connect

    Yu, R.C. . Beijing Lab. of Electron Microscopy Jilin Univ., Changchun . Dept. of Physics); Li, X.Z.; Zhang, Z.; Kuo, K.H. . Beijing Lab. of Electron Microscopy); Xu, D.P.; Su, W.H. . Dept. of Physics)

    1994-11-15

    Elser and Henley suggested that if the irrational golden number [tau] = (1 + [radical]5)/2 associated with the three mutually orthogonal, equivalent twofold axes in an IQC (icosahedral quasicrystal) is approximated by a rational ratio of two consecutive Fibonacci numbers (0, 1, 1, 2, 3, 5, 8, [hor ellipsis], F[sub 0] = 0, F[sub 1] = 1, and F[sub n+1] = F[sub n] + F[sub n[minus]1]), such as F[sub n+1]/F[sub n] = 1/0, 1/1, 2/1, 3/2, 5/3, 8/5, [hor ellipsis], then a cubic crystalline phase generally called an approximant will result. Such an analysis has been extended later to 2-dimensional decagonal quasicrystals (DQCs). If the irradiation [tau] along two mutually orthogonal, non-equivalent, quasiperiodic twofold directions perpendicular to the periodic tenfold axis of a DQC is replaced by rational ratios F[sub n+1]/F[sub n], an orthorhombic approximant with a large unit cell will form. This not only explains the existing orthorhombic Al-TM (transitional metals) phases with large unit cells, such as Al[sub 60]Mn[sub 11]Ni[sub 4] and Al[sub 3]Mn, but also predicts many new approximants with even larger unit cells some of which have been found experimentally afterwards.

  3. 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.

  4. Luminescence of Bi3+ in the orthorhombic perovskites, SrB4+O3 (B4+=Zr, Sn)

    NASA Astrophysics Data System (ADS)

    Srivastava, Alok M.

    2017-10-01

    This paper examines the optical properties of Bi3+ in the orthorhombic perovskites SrB4+O3 [B4+=Sn, Zr]. The luminescence of SrZrO3 is associated with emission from the D-state that corresponds with the Bi3+ (6s2) -Zr4+ (4d0) charge transfer transition. The emission spectrum as a function of temperature was monitored for SrSnO3:Bi3+. At low temperatures, the localized 3P0,1 → 1S0 transition dominates the emission spectrum. With increasing temperature, the localized emission quenches in favor of emission from the D-state. A comparative study of the Bi3+ luminescence in the orthorhombic perovskites CaZrO3, CaSnO3, SrZrO3 and SrSnO3 shows that D-state emission occurs when the fundamental absorption band of the perovskite host lattice is less than about 6 eV.

  5. Field Induced Phase Transition with Quadrupole Fluctuation in HoFe2Al10 with Orthorhombic Symmetry

    NASA Astrophysics Data System (ADS)

    Kamikawa, Shuhei; Ishii, Isao; Takezawa, Kohki; Sakami, Tatsuhiro; Nakagawa, Fumiya; Tanida, Hiroshi; Sera, Masafumi; Suzuki, Takashi

    2017-04-01

    To explore phase transitions in HoFe2Al10 with an orthorhombic structure, we performed ultrasonic measurements on transverse elastic moduli C55 and C66 under magnetic fields H. At zero magnetic field, C55 and C66 show an elastic softening down to 0.5 K without a clear anomaly, suggesting that no phase transition exists at zero magnetic field. However, in H along the a- and c-axes, the softening of C55 under 0.6 (0.4) T stops at TQ = 0.8 (0.75) K for H || a (c). Below TQ, C55 shows an elastic hardening. With further increasing H, we observed a remarkable softening of C55 toward TQ. C66 also shows a kink anomaly at TQ in H || a and c. From the results, we clarified the field induced phase transition for H || a and c in HoFe2Al10. The minimum point of C55 at TQ suggests that the field induced phase transition results from a quadrupolar ordering with the order parameter of quadrupole Ozx despite a singlet ground state under an orthorhombic crystal electric field in HoFe2Al10.

  6. Orthorhombic fulleride (CH3NH2)K3C60 close to Mott-Hubbard instability: Ab initio study

    NASA Astrophysics Data System (ADS)

    Potočnik, Anton; Manini, Nicola; Komelj, Matej; Tosatti, Erio; Arčon, Denis

    2012-08-01

    We study the electronic structure and magnetic interactions in methylamine-intercalated orthorhombic alkali-doped fullerene (CH3NH2)K3C60 within the density functional theory. As in the simpler ammonia intercalated compound (NH3)K3C60, the orthorhombic crystal-field anisotropy Δ lifts the t1u triple degeneracy at the Γ point and drives the system deep into the Mott-insulating phase. However, the computed Δ and conduction electron bandwidth W cannot alone account for the abnormally low experimental Néel temperature, TN=11 K, of the methylamine compound, compared to the much higher value TN=40 K of the ammonia one. Significant interactions between CH3NH2 and C603- are responsible for the stabilization of particular fullerene-cage distortions and the ensuing low-spin S=1/2 state. These interactions also seem to affect the magnetic properties, as interfullerene exchange interactions depend on the relative orientation of deformations of neighboring C603- molecules. For the ferro-orientational order of CH3NH2-K+ groups we find an apparent reduced dimensionality in magnetic exchange interactions, which may explain the suppressed Néel temperature. The disorder in exchange interactions caused by orientational disorder of CH3NH2-K+ groups could further contribute to this suppression.

  7. 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.

  8. 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.

  9. Absence of Evidence ≠ Evidence of Absence: Statistical Analysis of Inclusions in Multiferroic Thin Films

    PubMed Central

    Schmidt, Michael; Amann, Andreas; Keeney, Lynette; Pemble, Martyn E.; Holmes, Justin D.; Petkov, Nikolay; Whatmore, Roger W.

    2014-01-01

    Assertions that a new material may offer particularly advantageous properties should always be subjected to careful critical evaluation, especially when those properties can be affected by the presence of inclusions at trace level. This is particularly important for claims relating to new multiferroic compounds, which can easily be confounded by unobserved second phase magnetic inclusions. We demonstrate an original methodology for the detection, localization and quantification of second phase inclusions in thin Aurivillius type films. Additionally, we develop a dedicated statistical model and demonstrate its application to the analysis of Bi6Ti2.8Fe1.52Mn0.68O18 (B6TFMO) thin films, that makes it possible to put a high, defined confidence level (e.g. 99.5%) to the statement of ‘new single phase multiferroic materials’. While our methodology has been specifically developed for magnetic inclusions, it can easily be adapted to any other material system that can be affected by low level inclusions. PMID:25026969

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    We report the fabrication of novel multiferroic nanostructured bismuth ferrite (BiFeO3) fibers using the sol-gel based electrospinning technique. Phase pure BiFeO3 fibers were prepared by thermally annealing the electrospun BiFeO3/polyvinylpyrrolidone composite fibers in air for 1 h at 600 °C. The x-ray diffraction pattern of the fibers (BiFeO3) obtained showed that their crystalline structures were rhombohedral perovskite structures. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the BiFeO3 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.

  12. 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.

  13. Modulation of spin dynamics via voltage control of spin-lattice coupling in multiferroics

    DOE PAGES

    Zhu, Mingmin; Zhou, Ziyao; Peng, Bin; ...

    2017-02-03

    Our work aims at magnonics manipulation by the magnetoelectric coupling effect and is motivated by the most recent progresses in both magnonics (spin dynamics) and multiferroics fields. Here, voltage control of magnonics, particularly the surface spin waves, is achieved in La0.7Sr0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 multiferroic heterostructures. With the electron spin resonance method, a large 135 Oe shift of surface spin wave resonance (≈7 times greater than conventional voltage-induced ferromagnetic resonance shift of 20 Oe) is determined. A model of the spin-lattice coupling effect, i.e., varying exchange stiffness due to voltage-induced anisotropic lattice changes, has been established to explain experiment results with good agreement.more » In addition, an “on” and “off” spin wave state switch near the critical angle upon applying a voltage is created. The modulation of spin dynamics by spin-lattice coupling effect provides a platform for realizing energy-efficient, tunable magnonics devices.« less

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 Bi0.7Dy0.3FeO3 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 Bi0.7Dy0.3FeO3, 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.

  15. Giant multiferroic effects in topological GeTe-Sb2Te3 superlattices

    PubMed Central

    Tominaga, Junji; Kolobov, Alexander V; Fons, Paul J; Wang, Xiaomin; Saito, Yuta; Nakano, Takashi; Hase, Muneaki; Murakami, Shuichi; Herfort, Jens; Takagaki, Yukihiko

    2015-01-01

    Multiferroics, materials in which both magnetic and electric fields can induce each other, resulting in a magnetoelectric response, have been attracting increasing attention, although the induced magnetic susceptibility and dielectric constant are usually small and have typically been reported for low temperatures. The magnetoelectric response usually depends on d-electrons of transition metals. Here we report that in [(GeTe)2(Sb2Te3)l]m superlattice films (where l and m are integers) with topological phase transition, strong magnetoelectric response may be induced at temperatures above room temperature when the external fields are applied normal to the film surface. By ab initio computer simulations, it is revealed that the multiferroic properties are induced due to the breaking of spatial inversion symmetry when the p-electrons of Ge atoms change their bonding geometry from octahedral to tetrahedral. Finally, we demonstrate the existence in such structures of spin memory, which paves the way for a future hybrid device combining nonvolatile phase-change memory and magnetic spin memory. PMID:27877740

  16. Nanoscale Skyrmions in a Nonchiral Metallic Multiferroic: Ni2MnGa

    DOE PAGES

    Phatak, Charudatta; Heinonen, Olle; De Graef, Marc; ...

    2016-05-17

    Magnetic skyrmions belong to a set of topologically nontrivial spin textures at the nanoscale that have received increased attention due to their emergent behavior and novel potential spintronic applications. Discovering materials systems that can host skyrmions at room temperature in the absence of external magnetic field is of crucial importance not only from a fundamental aspect, but also from a technological point of view. So far, the observations of skyrmions in bulk metallic ferromagnets have been limited to low temperatures and to materials that exhibit strong chiral interactions. In this paper, we show the formation of nanoscale skyrmions in amore » nonchiral multiferroic material, which is ferromagnetic and ferroelastic, Ni2MnGa at room temperature without the presence of external magnetic fields. By using Lorentz transmission electron microscopy in combination with micromagnetic simulations, we elucidate their formation, behavior, and stability under applied magnetic fields at room temperature. Finally, the formation of skyrmions in a multiferroic material with no broken inversion symmetry presents new exciting opportunities for the exploration of the fundamental physics of topologically nontrivial spin textures.« less

  17. Nanoscale Skyrmions in a Nonchiral Metallic Multiferroic: Ni2MnGa

    SciTech Connect

    Phatak, Charudatta; Heinonen, Olle; De Graef, Marc; Petford-Long, Amanda

    2016-05-17

    Magnetic skyrmions belong to a set of topologically nontrivial spin textures at the nanoscale that have received increased attention due to their emergent behavior and novel potential spintronic applications. Discovering materials systems that can host skyrmions at room temperature in the absence of external magnetic field is of crucial importance not only from a fundamental aspect, but also from a technological point of view. So far, the observations of skyrmions in bulk metallic ferromagnets have been limited to low temperatures and to materials that exhibit strong chiral interactions. In this paper, we show the formation of nanoscale skyrmions in a nonchiral multiferroic material, which is ferromagnetic and ferroelastic, Ni2MnGa at room temperature without the presence of external magnetic fields. By using Lorentz transmission electron microscopy in combination with micromagnetic simulations, we elucidate their formation, behavior, and stability under applied magnetic fields at room temperature. Finally, the formation of skyrmions in a multiferroic material with no broken inversion symmetry presents new exciting opportunities for the exploration of the fundamental physics of topologically nontrivial spin textures.

  18. 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.

  19. 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.

  20. Long-wavelength magnetic excitations in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Talbayev, D.; Gigax, J. G.; Taylor, A. J.; Lee, Seongsu; Cheong, S.-W.

    2009-03-01

    Magnetic and lattice vibrations play a central role in the properties of multiferroics. This low-energy electrodynamics can help unravel the fundamental interactions between magnetic and lattice degrees of freedom. BiFeO3 is a multiferroic material with robust room temperature ferroelectricity and antiferromagnetism and promising technological potential. The interaction between the ferroelectric and antiferromagnetic order parameters leads to the modification of the isotropic Heisenberg-antiferromagnet ground state that becomes an incommensurate cycloid with a very long period. The cycloidal magnetic structure results in a complex spectrum of zero-wavevector magnetic excitations; these magnetic modes were detected using Raman scattering. Here, we report a far-infrared spectroscopic study of a BiFeO3 single crystal. We detected magnetic resonances at energies close to those reported in the Raman spectroscopy studies. The magnetic character of these excitations is supported by their characteristic temperature dependence. We will discuss our results in the context of possible electric-dipole activity of the observed resonances.

  1. Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions

    SciTech Connect

    Dai, Jian-Qing

    2016-08-21

    We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction with asymmetric TiO{sub 2}- 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 6p{sub z} 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.

  2. Large magnetoelectric effect in organic ferroelectric copolymer-based multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Subedi, Ram Chandra; Geng, Rugang; Luong, Hoang Mai; Huang, Weichuan; Li, Xiaoguang; Hornak, Lawrence A.; Nguyen, Tho Duc

    2017-01-01

    We report electrically controlled interfacial spin polarization, or the magnetoelectric effect in multiferroic tunnel junctions by employing organic ferroelectric copolymers, poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFE)), as a tunneling barrier. First, we show that the ferroelectric domains and spontaneous ferroelectric polarization of the P(VDF-TrFE) films can be formed in a thin interlayer. Next, we demonstrate that the tunneling magnetoresistance in the unpolarized multiferroic tunnel junction severely quenches from 21% at 20 K to 0.7% at 296 K. Remarkably, we find that the interfacial spin polarization of the device, dubbed spinterface, can be gradually tuned by controlling the ferroelectric polarization with an applied electric field. Specifically, the tunneling electromagnetoresistance can reach around 1000% while the tunneling electroresistance reaches about 30% at 200 K. We speculate that the interface might act as a polarization-dependent spin filter causing the large spinterface effect. The result suggests that organic magnetoelectric-based information storage with four-state bits is feasible at room temperature.

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

    DOE PAGES

    Zapf, Vivien S.; Ueland, B. G.; Laver, Mark; ...

    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

  4. 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

  5. Entanglement and manipulation of the magnetic and spin-orbit order in multiferroic Rashba semiconductors

    NASA Astrophysics Data System (ADS)

    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.

    2016-10-01

    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.

  6. 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.

  7. 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

  8. Antiferromagnetic Resonance in Multiferroic YMnO3 and LuMnO3

    NASA Astrophysics Data System (ADS)

    Zvyagin, Sergei

    2009-03-01

    Multiferroic rare-earth manganites have attracted much attention because of the coexistence of ferroelectric and magnetic orders. Combining conventional far-infrared Fourier-transform and THz-range free electron laser electron spin resonance (ESR) spectroscopy techniques, magnetic excitations in hexagonal multiferroic YMnO3 and LuMnO3 in the antiferromagnetically (AFM) ordered phase have been studied. The gap in the excitation spectrum (˜42 and ˜48 cm-1 for YMnO3 and LuMnO3, respectively) was observed directly. Similar slope of the frequency-field dependences of AFM resonance modes, ˜ 0.5 cm-1/T, was revealed for both compounds. A fine structure of AFM resonance absorption has been revealed by means of high-resolution ESR techniques, which can be explained taking into account a finite interaction between the neighboring Mn^3+ layers. The work was done in collaboration with M. Ozerov, D. Kamensky, E. Cizm'ar, J. Wosnitza, A.K. Kolezhuk, D. Smirnov, H.D. Zhou, and C.R. Wiebe.

  9. Structural and multiferroic properties of barium substituted bismuth ferrite nanocrystallites prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Anju; Agarwal, Ashish; Aghamkar, Praveen; Lal, Bhajan

    2017-03-01

    Nanocrystalline Bi1-xBaxFeO3 (0≤x≤0.3) multiferroics were efficiently obtained by sol-gel method after sintering at 800 °C for one hour. The Ba substitution in BiFeO3 (BFO) strongly modifies its structural and multiferroic properties. XRD studies revealed the structural transition from distorted rhombohedral (R3c) to pseudo-cubic (Pm3m) crystal symmetry. The magnetization increases appreciably for x=0.1, which is due to spin canting of magnetic moments at the nanoparticle surfaces and decreases afterward. From the temperature dependent magnetization studies, it is found that magnetic transition temperature (TN) is 620 K for x=0 and 640 K for x=0.1. Besides, the maximum polarisation value decreases with increasing Ba content. SEM micrographs revealed the formation of cubic nanocrystallites with increased porosity on Ba substitution. FTIR analysis of the samples also supports the structural change towards increased crystal symmetry.

  10. Magnetic and dielectric properties of Ce-Co substituted BiFeO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Sharma, Jyoti; Bhat, Bilal Hamid; Kumar, Arun; Kumar, Sachin; Kaur, Talwinder; Want, Basharat; Srivastava, A. K.

    2017-03-01

    The present investigation shows the significant improvement in the structural, magnetic and dielectric properties of Bi1-x Ce x Fe1-x Co x O3 (x  =  0, 0.01, 0.03, 0.05) multiferroic materials, synthesized via an auto-combustion method. The synthesized materials are found to have structural distortion in the rhombohedral R3c structure as observed by x-ray diffraction. The high dielectric constant (~1850 at 2.5 MHz) was found for x  =  0.05 multiferroic material from dielectric analysis. The presence of a weak doublet along with a sextet pattern in the Mossbauer spectra indicates the secondary phase. M-H loops of these materials demonstrate that Ce-Co doping in BiFeO3 enhances retentivity, coercivity, and saturation magnetization. Improvement in the magnetic and dielectric properties in Ce-Co doped BiFeO3 leads to multifunctional device application.

  11. 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.

  12. Eu doping in multiferroic BiFeO3 ceramics studied by Mossbauer and EXAFS spectroscopy.

    PubMed

    Kothari, Deepti; Raghavendra Reddy, V; Gupta, Ajay; Meneghini, Carlo; Aquilanti, Giuliana

    2010-09-08

    Bismuth ferrite ceramics (BiFeO(3)) are multifunctional materials classified as multiferroics for their special magnetic and electric properties that can be modified by substitutional doping at the Bi and/or Fe sites. Understanding the relation between magnetoelectric response and structural/electronic modification upon doping is a relevant issue. In this work, the structure of Eu-doped multiferroic systems (Bi(1-x)Eu(x)FeO(3), x = 0, 0.5, 0.1, 0.15) as well as the valence state of Fe and Eu ions have been investigated combining Mossbauer and x-ray absorption fine structure (XAFS) spectroscopy techniques. The Eu(3+) doping at the Bi site results in better magnetic properties. High temperature (57)Fe Mossbauer data and Fe K-edge XAFS results show that FeO(6) octahedron distortions reduce with Eu(3+) doping. It is conclusively shown that the observed magnetic properties in BiFeO(3) with chemical substitution (Eu) are mainly due to the structural distortions and not due to Fe multiple valence. (151)Eu Mossbauer measurements show that the Eu(3+)(Bi(3+)) site is magnetically inactive in BiFeO(3).

  13. 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

  14. 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.

  15. 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.

  16. Growth and Development of Meta-Multiferroic Systems using Pulsed Electron Deposition

    NASA Astrophysics Data System (ADS)

    Kirkwood, David

    Meta-multiferroic systems exhibit unique properties and hold the potential for novel device functionality due to the simultaneous showing of ferroelectric and magnetic ordering in these materials. The direct or indirect coupling of these order parameters only adds to their usefulness and scientific intrigue. Recent advances in thin film deposition technology along with collaborative efforts between experimentalists and theoreticians have led to a renewed interest in these materials in the past decade. A novel deposition technique called Pulsed Electron Deposition (PED) has recently been developed which may provide researchers with a new means of producing films of equal or better quality to more conventional methods such as Pulsed Laser Deposition, Sputtering, and MBE currently used to study multiferroic materials. Pulsed electron deposition utilizes a channel spark process to generate short pulses of high energy electrons which are directed into a target, causing rapid heating and ejection of the target material which can then be captured by an appropriately placed growth template to produce thin films. PED has been used to grow a number of materials such as the superconducting oxides like YBCO, glassy materials like borosilicate, polymers (PTFE) and even metals with a low heat conductivity coefficient (Sn, Zn, Fe, Ti, and their alloys), though the technique is still in its infancy. In this dissertation, a PED tool equipped with two electron gun sources was used to experimentally explore the capabilities of this tool to grow high quality thin films of oxide materials of significant importance to the study of meta-multiferroic systems. Thin films of the multiferroic oxide Bismuth Ferrite (BiFeO3), the ferrimagnetic oxide Magnetite (Fe3O 4), and the conducting oxide Strontium Ruthenate (SrRuO3) were grown by PED. The influences of deposition parameters on the electrical, magnetic, structural, chemical and morphological properties of the films were characterized

  17. Structure-Controllable Synthesis of Multiferroic YFeO3 Nanopowders and Their Optical and Magnetic Properties

    PubMed Central

    Wang, Meng; Wang, Ting; Song, Shenhua; Tan, Manlin

    2017-01-01

    Phase-pure hexagonal and orthorhombic YFeO3 nanopowders are synthesized by low-temperature solid-state reaction along with Zr doping. The obtained powders are characterized by X-ray diffraction, field emission scanning electron microscopy, and physical property measurements. The hexagonal YFeO3 exhibits a narrower optical band gap in comparison to the orthorhombic one, while the orthorhombic YFeO3 presents better magnetic properties. The formation of hexagonal or orthorhombic phase can be effectively controlled by Zr doping. The temperature range of synthesizing the hexagonal YFeO3 nanopowders is increased by ~200 °C due to Zr doping so that they can be easily synthesized, which possesses a finer particle size and a smaller optical band gap, making it favorable for optical applications. PMID:28772985

  18. High pressure Raman investigations of multiferroic BiFeO(3).

    PubMed

    Yang, Y; Bai, L G; Zhu, K; Liu, Y L; Jiang, S; Liu, J; Chen, J; Xing, X R

    2009-09-23

    We have reported a Raman scattering investigation of bismuth ferrite (BiFeO(3)) under high pressure up to 50 GPa. Distinct changes in the Raman spectra show evidence for three pressure-induced structural transitions. The abrupt frequency redshifts of the Raman modes near 300 cm(-1) at around 3 GPa are attributed to the modulation of the FeO(6) octahedral tilts. The disappearance of the modes below 250 cm(-1) at 8.6 GPa, together with the enhancement of the two modes in the range of 300-400 cm(-1), indicate the phase transition from the rhombohedral to orthorhombic symmetry. Afterward, the E-3 and E-4 modes disappear at 44.6 GPa, pointing to the occurrence of the orthorhombic-cubic phase transition, which is consistent with the previous postulate that an orthorhombic-cubic transition takes place across the metal-insulator transition at high pressures.

  19. First-principles study of the photovoltaic properties of orthorhombic Ca2Si1-xPx (0

    NASA Astrophysics Data System (ADS)

    Cen, Weifu; Yang, Yinye; Fan, Menghui

    2017-06-01

    Electronic structure and optical properties of simple orthorhombic Ca2Si1-xPx have been calcu-lated by the first-principles methods. The result shown that the band gap of the simple ortho-rhombic Ca2Si1-xPx was still a direct semiconductor and the band gap was increased with the concentration of P impurity increased. The dielectric constant and refractive index were in-creased with the concentration of P impurity increased. The extinction coefficient, the reflectivi-ty, the absorption and the conductivity have significant changed in the energy range of 0eV∼1eV. Therefore, Transmission property of energy band structure and optical properties of simple or- thorhombic Ca2Si1-xPx were changed by changing the impurity concentration. It is a useful method for modulating photoelectric transmission property of the simple orthorhombic Ca2Si1-xPx.

  20. AFM observation of the surface morphology and impurity effects on orthorhombic hen egg-white lysozyme crystals

    NASA Astrophysics Data System (ADS)

    Matsuzuki, Y.; Kubota, T.; Liu, X. Y.; Ataka, M.; Takano, K. J.

    2002-07-01

    Cation-exchange high performance liquid chromatography at pH 6, developed originally to purify human lysozyme, was applied to hen egg-white lysozyme. We could remove at least three kinds of impurities from the commercial product. The impurities were considered to be modified lysozyme molecules, mostly based on N-terminal amino acid analyses. Atomic force microscopic observation was made on the crystals both from the purified and non-purified solutions. The (1 1 0) faces of the orthorhombic crystals grown at 40°C from the purified solution contained linear steps, while most of the linear edges became round and rugged on the crystals from non-purified solutions. A similar change in step morphology is known to occur on insulin crystals when two amino acids were mutated from the wild type. On the (0 1 0) face, elongated, round steps became rugged when crystals grew from non-purified solutions.

  1. Spectacular switching from ferrimagnetism to antiferromagnetism by zinc doping in "114" orthorhombic CaBaCo4O7

    NASA Astrophysics Data System (ADS)

    Sarkar, Tapati; Motin Seikh, Md.; Pralong, V.; Caignaert, V.; Raveau, B.

    2012-06-01

    We report a spectacular switching from ferrimagnetism to antiferromagnetism in orthorhombic "114" CaBaCo4O7 by doping with a diamagnetic cation, Zn2+. Magnetic hysteresis loops, together with M(T) and χ'(T) curves at various frequencies, show that ferrimagnetism is abruptly converted to antiferromagnetism below T ˜ 80 K for less than 3% Zn doping, with the simultaneous appearance of local magnetic frustration. A model is proposed based on the ordered doping of Zn2+ at Co2+ sites in the ferromagnetic zig-zag chains of CaBaCo4O7, leading, by domino effect, to ferrimagnetic domains distributed at random and ordered at 180°. The boundaries of the junction of these domains contain Zn2+ and are magnetically frustrated. The crucial role of such ferromagnetic zig-zag chains for designing and tuning magnetic properties in oxides with a triangular metallic lattice is emphasized.

  2. Mapping of second-nearest-neighbor fluoride ions of orthorhombic Gd 3+-Ag + complexes in CaF 2

    NASA Astrophysics Data System (ADS)

    Nakata, R.; Den Hartog, H. W.

    The ENDOR technique is applied to determine the positions of 24 second-nearest-neighbor F - ions around an orthorhombic Gd 3+-Ag + complex in CaF 2 crystals. Experimental ENDOR data of the second-nearest-neighbor F - ions are analyzed by using the usual spin Hamiltonian and a least-squares fitting method. The best fits of the experimental results give superhyperfine (shf) constants and the F - directions ( K, L, M) with respect to the Gd 3+ ion, from which the distance between the second-nearest-neighbor F - ion and the Gd 3+ ion is determined by assuming that the hyperfine interaction is due to the classical dipole-dipole interaction. The displacements of the F - ions are estimated and compared with the theoretical values calculated by Bijvank and den Hartog on the basis of a polarizable point charge model.

  3. The ultraviolet and visible luminescence of Bi3+ in the orthorhombic perovskite, GdAlO3

    NASA Astrophysics Data System (ADS)

    Srivastava, A. M.; Comanzo, H. A.

    2017-01-01

    The spectroscopic properties of the Bi3+ ion as a function of its concentration is examined to clarify the nature of optical transitions that are responsible for the ultraviolet (333 nm) and visible emission of GdAlO3:Bi3+. The UV band which is characterized by small Stokes shift (0.52 eV) is ascribed to emission from isolated Bi3+ ions (3P0,1 → 1S0 transition). The peak emission wavelength and the width of the visible band depend on the Bi3+ concentration. This emission is ascribed to pairs or cluster of Bi3+ ions in the perovskite lattice. The spectroscopic properties of the pair emission in GdAlO3 are contrasted with the impurity trapped excitonic emission in CaSnO3. A comparative study of the behavior of Bi3+ luminescence in a series of materials with the orthorhombic perovskite structure is presented.

  4. Magnetic structure and properties of orthorhombic Li2Ni(SO4)2: A possible magnetoelectric material

    NASA Astrophysics Data System (ADS)

    Reynaud, Marine; Rodríguez-Carvajal, Juan; Chotard, Jean-Noël; Tarascon, Jean-Marie; Rousse, Gwenaëlle

    2014-03-01

    In this paper, we report on the structural and magnetic properties, as deduced from susceptibility measurements and neutron powder diffraction experiments, of an orthorhombic nickel disulfate, Li2Ni(SO4)2. This phase presents NiO6 octahedra linked via SO4 groups only, leading to an antiferromagnetic behavior resulting from super-super-exchange interactions. Magnetic moments order below TN = 28 K and the observed magnetic structure can be explained using two antiferromagnetic and one ferromagnetic exchange interactions, which are discussed in relation with the Goodenough-Kanamori-Anderson rules. The magnetic structure, with k = (0, 0, 0), has the symmetry Pb' c'a' that has the inversion center associated with time inversion, so the compound should be a linear magnetoelectric.

  5. Synthesis, photoluminescence and Judd-Ofelt parameters of LiNa3P2O7:Eu3+ orthorhombic microstructures

    NASA Astrophysics Data System (ADS)

    Munirathnam, K.; Dillip, G. R.; Raju, B. Deva Prasad; Joo, S. W.; Dhoble, S. J.; Nagabhushana, B. M.; Hari Krishna, R.; Ramesh, K. P.; Varadharaj Perumal, S.; Prakashbabu, D.

    2015-09-01

    We report, for the first time, the photoluminescence properties of Eu3+-doped LiNa3P2O7 phosphor, synthesized by a facile solid-state reaction method in air atmosphere. The crystal structure and phase purity of the phosphors were analyzed by X-ray diffraction analysis. Orthorhombic structural morphology was identified by scanning electron microscopy. The phosphate groups in the phosphor were confirmed by Fourier transform infrared analysis. Bandgap of the phosphor was calculated from the diffuse reflectance spectra data using Kubelka-Munk function. Under 395-nm UV excitation, the phosphors show signs of emitting red color due to the 5D0 → 7F2 transition. In accordance with Judd-Ofelt theory, spectroscopic parameters such as oscillator intensity parameter Ω t ( t = 2), spontaneous emission probabilities, fluorescence branching ratios and radiative lifetimes were calculated and analyzed for the first time in this system.

  6. Interface-controlled fatigue cracking of SCS-6/Ti-22Al-23Nb orthorhombic titanium aluminide composite

    SciTech Connect

    Her, Y.C.; Wang, P.C.; Yang, J.M.

    1998-11-01

    The effect of aging at elevated temperature on interfacial stability and fatigue behavior of a SCS-6/Ti-22Al-23Nb orthorhombic (O) titanium aluminide composite is investigated. The composite was heat treated in vacuum at 900 C for up to 250 hours to change the microstructural characteristics. The stability of the matrix alloy and interfacial reaction zone after extended thermal exposure was analyzed. The effect of interface on fatigue behavior, including stiffness degradation, evolution of fatigue damage, and crack growth rates, was characterized. Finally, a modified shear-lag model was used to predict the saturated matrix crack spacing in the composite under fatigue loading. The results demonstrate that aging at elevated temperature affects the stability of the interfacial reaction zone, which, in turn, degrades the fatigue properties of the composite. However, fatigue crack will not developed from the ruptured interfacial reaction layer until the thickness of the reaction zone or the maximum applied stress exceeds a critical value.

  7. Structure of the welding zone between titanium and orthorhombic titanium aluminide for explosion welding: II. Local melting zones

    NASA Astrophysics Data System (ADS)

    Grinberg, B. A.; Ivanov, M. A.; Rybin, V. V.; Kuz'min, S. V.; Lysak, V. I.; Elkina, O. A.; Patselov, A. M.; Antonova, O. V.; Inozemtsev, A. V.

    2011-10-01

    The structure and chemical composition of the local melting zones that form during explosion welding of orthorhombic titanium aluminide with commercial-purity titanium near a wavy interface between them are studied. The Rayleigh number is estimated to propose a possible mechanism for the formation of a concentric structure in these zones. Titanium aluminide fragments are detected near the zone boundaries. It is assumed that the fragmentation in the transition zone is caused by the division of a material into loosely coupled microvolumes under the action of a strong external action in a time comparable with the explosion time. Outside the transition zone, fragmentation occurs via a traditional way beginning from dislocation accumulation. Both processes occur in titanium aluminide and only one process (banded structure formation) takes place in titanium.

  8. The electrocaloric effect around the orthorhombic- tetragonal first-order phase transition in BaTiO3

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Ding, Kai; Zheng, Guang-Ping; Shi, San-Qiang; Cao, Jiang-Li; Qiao, Lijie

    2012-06-01

    This paper demonstrates the electrocaloric effect (ECE) around BaTiO3's orthorhombic-tetragonal first-order phase transition. By manipulating a field-induced transition of a metastable phase in the thermal hysteresis zone, a huge exothermic or endothermic peak appears after first applying or removing electric fields because of the energy change of lattice structure. A large ECE of ΔT/E = 1.4K.m/MV, equaling to latent heat, is achieved under 10kV/cm at 10°C. The entropy change for polarization ordering alone induces an ECE two orders of magnitude lower under the same condition. It confirms the dominant factor to ECE of the energy flow due to the structural phase transition.

  9. Non-planar Dzyaloshinskii spirals and magnetic domain walls in non-centrosymmetric systems with orthorhombic anisotropy.

    PubMed

    Heide, Marcus; Bihlmayer, Gustav; Blügel, Stefan

    2011-04-01

    The basic micromagnetic models of Landau, Lifshitz, and Dzyaloshinskii, are extended by an anisotropy term with two independent parameters. The resulting ground states of the magnetic domains and the domain-wall profiles are discussed for crystal lattices with orthorhombic unit cells. In these simple geometries, the magnetization is not confined to a single plane. Depending on the relations between the spin-stiffness, anisotropy, and Dzyaloshinskii-Moriya interaction several different zero-temperature phases of the magnetic structure are found. The corresponding phase diagrams are obtained numerically. Analytical results are given for some special cases. The studied model is of particular relevance for magnetic wires, nanostripes and ultrathin magnetic films deposited on non-magnetic surfaces.

  10. 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.

  11. Formation of (111) orientation-controlled ferroelectric orthorhombic HfO{sub 2} thin films from solid phase via annealing

    SciTech Connect

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

    2016-08-01

    0.07YO{sub 1.5}-0.93HfO{sub 2} (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 In{sub 2}O{sub 3}(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates, and (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(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/TiO{sub x}/SiO{sub 2}/(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/TiO{sub x}/SiO{sub 2}/(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 (P{sub r}) of 9.6 and 10.8 μC/cm{sup 2} and coercive fields (E{sub c}) 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.

  12. Studies of the EPR g factors and the local structures for the orthorhombic Er 3+ centers in garnets

    NASA Astrophysics Data System (ADS)

    Wu, Shao-Yi; Dong, Hui-Ning

    2005-05-01

    The perturbation formulas of the EPR g factors gx, gy and gz for a 4f11 ion in orthorhombic symmetry are established. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various states are taken into account. The above formulas are applied to the orthorhombic Er3+ centers in YAG, YGG and LuGG garnets. By analyzing their g factors, we find that the polar angles θj‧ of the impurity-ligand bonds related to the Z axis of the crystals in these Er3+ centers are smaller than the host angles θj in pure crystals, whereas the azimuthal angles ϕj ‧ related to the X axis in the impurity centers are larger than the corresponding ϕj in the hosts. The g factors and their anisotropies Δg [= gz - (gx + gy)/2] and δg (= gx - gy) for Er3+ in the garnets based on the above local structural parameters are in good agreement with the observed values. In addition, the angular distortions Δθ (=θj‧ -θj) or Δϕ (=ϕj‧ -ϕj) obtained by analyzing the EPR data in this work are different from Δθ2 or Δϕ2 (for only the second set of ligands, i.e., j = 2) based on the superposition model crystal-field analysis in the previous work. The validity of the results is discussed.

  13. Structure, bonding and physical properties of tetragonal and orthorhombic SiS{sub 2} from (hybrid) DFT calculations

    SciTech Connect

    Zwijnenburg, Martijn A. Bell, Robert G.; Cora, Furio

    2008-09-15

    The energetics, structure and physical properties of tetragonal and orthorhombic SiS{sub 2} were calculated by periodic density functional theory (DFT) calculations, using both localized orbital and projected augmented wave basis-sets. All methods applied agree upon the relative energies of the different polymorphs but show differences in the predicted geometries, which are minimized upon improving the basis-set quality. The hybrid PBE0 functional was found to give the best match between experimental and calculated structures. When comparing SiS{sub 2} with its much better studied oxide analog silica, we observe that upon substituting sulphur for oxygen, the energy landscape changes dramatically. Other effects of changing S for O are found to be smaller Si-X-Si angles, a broader distribution of X-Si-X angles, a more flexible framework and a significantly reduced band gap. The latter is in line with the experimental observation of photoluminescence in related GaGeS{sub 2} compounds and suggests that SiS{sub 2} might find application in UV light emitting diodes. Finally, a comparison of the maximally localized Wannier functions demonstrates that the Si-S bonds in SiS{sub 2} have a considerably more covalent character than the Si-O bonds in silica. - Graphical abstract: Periodic DFT calculations were employed to study the (physical) properties of tetragonal and orthorhombic SiS{sub 2}. The results obtained were compared with those for SiS{sub 2} better studied oxide analog silica and demonstrate large changes in the materials' energy landscape, nature of bonding, flexibility and band gap, upon substitution of sulphur for oxygen.

  14. A new phase in the system lithium-aluminum: Characterization of orthorhombic Li{sub 2}Al

    SciTech Connect

    Puhakainen, Kati; Bostroem, Magnus; Groy, Thomas L.; Haeussermann, Ulrich

    2010-11-15

    Investigation of the Li rich part of the binary Li-Al system revealed the existence of a new phase, orthorhombic Li{sub 2}Al, which is isostructural to Li{sub 2}Ga and Li{sub 2}In. The crystal structure was determined from single crystal X-ray diffraction data (Cmcm, a=4.658(2) A, b=9.767(4) A, c=4.490(2) A, Z=4). Refinement of atomic position site occupancies yielded a composition Li{sub 1.92}Al{sub 1.08} (64 at% Li) indicating a small homogeneity range, Li{sub 2-x}Al{sub 1+x}. Li{sub 2}Al is the peritectic decomposition product of the stoichiometric compound Li{sub 9}Al{sub 4}, which is stable below 270{+-}2 {sup o}C. Li{sub 2}Al itself decomposes peritectically to Li{sub 3}Al{sub 2} and Li rich melt at 335{+-}2 {sup o}C. The discovery of Li{sub 2}Al (Li{sub 2-x}Al{sub 1+x}) settles a long standing inconsistency in the Li-Al phase diagram which was based on the assumption that Li{sub 9}Al{sub 4} possesses a high temperature modification. - Graphical abstract: A new phase, Li{sub 2}Al, has been discovered in the binary Li-Al system. The structure of orthorhombic Li{sub 2}Al is closely related to that of the established monoclinic phase Li{sub 9}Al{sub 4}.

  15. 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.

  16. Numerical Simulation of Spin-Chirality Switching in Multiferroics via Intense Electromagnon Excitations

    NASA Astrophysics Data System (ADS)

    Mochizuki, Masahito; Nagaosa, Naoto

    2011-09-01

    Chirality, i.e., the right- and left-handedness of structure, is one of the key concepts in many fields of science including biology, chemistry and physics, and its manipulation is an issue of vital importance. The electron spins in solids can form chiral configurations. In perovskite manganites RMnO3 (R = Tb, Dy,...etc), the Mn-spins form a cycloidal structure, which induces ferroelectric polarization (P) through the relativistic spin-orbit interaction. This magnetism-induced ferroelectricity (multiferroics) and associated infrared-active spin waves (electromagnons) open a promising route to control the spins by purely electric means in a very short time. In this paper, we show theoretically with an accurate spin Hamiltonian for TbMnO3 that a picosecond optical pulse can switch the spin chirality by intensely exciting the electromagnons with a terahertz frequency.

  17. Long-Range Magnetic Interactions in the Multiferroic Antiferromagnet MnWO4

    SciTech Connect

    Ye, Feng; Fishman, Randy Scott; Fernandez-Baca, Jaime A; Podlesnyak, Andrey A; Ehlers, Georg; Mook Jr, Herbert A; Wang, Y.-Q.; Lorenz, Bernd; Chu, C. W.

    2011-01-01

    The spin-wave excitations of the multiferroic MnWO4 have been measured in its low-temperature collinear commensurate phase using high-resolution inelastic neutron scattering. These excitations can be well described by a Heisenberg model with competing long-range exchange interactions and a single-ion anisotropy term. We find that the magnetic interactions are strongly frustrated within the zigzag spin chain along c-axis and between chains along the a-axis, while the coupling between spin along the b-axis is much weaker. We argue that the balance of these interactions results in the noncollinear incommensurate spin structure associated with the magnetoelectric effect, and the perturbation of the magnetic interactions leads to the observed rich phase diagrams of the chemically-doped materials. This delicate balance can also be tuned by the application of external electric or magnetic fields to achieve practical magnetoelectric control of this type of materials.

  18. 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.

  19. Magnetic inhomogeneity in a multiferroic EuTiO3 thin film

    NASA Astrophysics Data System (ADS)

    Geng, Yanan; Lee, J. H.; Schlom, D. G.; Freeland, J. W.; Wu, Weida

    2013-03-01

    We report on variable temperature magnetic force microscopy studies of a strain-enabled multiferroic EuTiO3 film epitaxially grown on a (110)-oriented DyScO3 substrate. Our temperature- and magnetic-field-dependent studies clearly reveal an inhomogeneous magnetic state with the coexistence of ferromagnetic and nonferromagnetic states at low magnetic fields, which provides a microscopic origin of the anomalous missing moment in previous studies [Lee , Nature (London)0028-083610.1038/nature09331 466, 954 (2010)]. The spins of the nonferromagnetic phase can be aligned by modest magnetic fields (>1.5 T). The observed magnetic inhomogeneity probably originates from the coexistence of nearly degenerate magnetic ground states.

  20. High-resolution characterization of multiferroic heterojunction using aberration-corrected scanning transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Yuan, Zhoushen; Ruan, Jieji; Xie, Lin; Pan, Xiaoqing; Wu, Di; Wang, Peng

    2017-04-01

    Multiferroic tunnel junctions have been considered as potential candidates for nonvolatile memory devices. Understanding the atomic structure at the interface is crucial for optimizing the performances in such oxide electronics. Spatially resolved electron energy loss spectroscopy (EELS) combined with aberration-corrected scanning transmission electron microscopy is employed to measure the compositional profiles across the interfaces of different layers with atomic resolution. Two-dimensional elemental imaging with atomic resolution is demonstrated, and the influences of the interface sharpness, the terminal layer, and cation intermixing are investigated. An asymmetric sublattice intermixing at the Pr0.8Ca0.2MnO3/BaTiO3/La0.7Sr0.3MnO3 interface is observed, which can affect the local Mn valence and coupling. The reduction in the Mn valence at the interface is further studied using EELS near-edge fine structures.