Single-phase multiferroic BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3（doped with rare earth ions La-（3＋） and Nd-（3＋）） films grown on（111）-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequen...Single-phase multiferroic BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3（doped with rare earth ions La-（3＋） and Nd-（3＋）） films grown on（111）-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric（ME） coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3 exhabited a rhombohedral structure with（111） preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO3 crystals, and it enhanced effectively the in-plane ME coupling（the ME coupling coefficient αE increased from 0.13 in the pure BiFeO3 to 0.21 in Bi（0.9）La（0.1）FeO3 and 0.34 V/（Oe·cm） in Bi（0.9）Nd（0.1）FeO3）. The mechanism of these phenomena was investigated systematically.展开更多
An effective regulation of the magnetism and interface of ferromagnetic materials is not only of great scientific significance,but also has an urgent need in modern industry.In this work,by using the first-principles ...An effective regulation of the magnetism and interface of ferromagnetic materials is not only of great scientific significance,but also has an urgent need in modern industry.In this work,by using the first-principles calculations,we demonstrate an effective approach to achieve non-volatile electrical control of ferromagnets,which proves this idea in multiferroic heterostructures of ferromagnetic La TiO_(3)and ferroelectric Bi FeO_(3).The results show that the magnetic properties and two-dimensional electron gas concentrations of La TiO_(3)films can be controlled by changing the polarization directions of Bi FeO_(3).The destroyed symmetry being introduced by ferroelectric polarization of the system leads to the transfer and reconstruction of the Ti-3 d electrons,which is the fundamental reason for the changing of magnetic properties.This multiferroic heterostructures will pave the way for non-volatile electrical control of ferromagnets and have potential applications.展开更多
In this study, we observe a strong inverse magnetoelectric coupling in Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure, which produces large electric field（E-field） tunability of microwave magnetic properties....In this study, we observe a strong inverse magnetoelectric coupling in Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure, which produces large electric field（E-field） tunability of microwave magnetic properties. With the increase of the E-field from 0 to 8 kV/cm, the magnetic anisotropy field Heffis dramatically enhanced from 169 to 600 Oe, which further leads to a significant enhancement of ferromagnetic resonance frequency from 4.57 to 8.73 GHz under zero bias magnetic field, and a simultaneous decrease of the damping constant α from 0.021 to 0.0186. These features demonstrate that this multiferroic composite is a promising candidate for fabricating E-field tunable microwave components.展开更多
The exploration of two-dimensional antiferrovalley materials as potential candidates for valleytronics offers intriguing prospects to investigate exotic valley physics and develop next-generation nano-electronic devic...The exploration of two-dimensional antiferrovalley materials as potential candidates for valleytronics offers intriguing prospects to investigate exotic valley physics and develop next-generation nano-electronic devices.Achieving efficient anomalous valley Hall effect(AVHE)switching in antiferrovalley materials constitutes an important step towards their application,yet such advancement has been scarcely reported so far.In this study,we demonstrate,through first-principles calculations and model analysis,that the experimentally synthesized MnSe monolayer is a hitherto unexplored but exceptional antiferrovalley material with spontaneous valley polarization.And more importantly,by constructing a multiferroic MnSe/In_(2)Se_(3) heterostructure,the desired nonvolatile on/off switching of the AVHE can be successfully realized through polarization reversal.This unique phenomenon,characterized by the emergence/annihilation of fully spin-polarized valley polarization,arises from the combined effect of strong magnetoelectric coupling-induced changes in magnetic anisotropy and PT symmetry breaking.Our findings provide a novel approach for achieving nonvolatile control of the AVHE in antiferrovalley materials,opening up significant opportunities for valleytronic applications.展开更多
Rare-earth orthoferrite SmFeO3 is an outstanding single-phase multiferroic material,holding great potential in novel low-power electronic devices.Nevertheless,simultaneous magnetic and ferroelectric orders as well as ...Rare-earth orthoferrite SmFeO3 is an outstanding single-phase multiferroic material,holding great potential in novel low-power electronic devices.Nevertheless,simultaneous magnetic and ferroelectric orders as well as magnetoelectric(ME)coupling effect at room temperature(RT)in this system have not been demonstrated yet.In this study,epitaxial SmFeO3 films were successfully prepared onto tensile-strain Nb-SrTiO3(Nb-STO)substrates by a pulsed laser deposition(PLD)method.Measurement results show that the films exhibit obvious ferromagnetic and ferroelectric orders at RT.Meanwhile,the magnetic anisotropy gradually changes from out-of-plane(OP)to in-plane(IP)direction with increasing film thickness,which is attributed to the variations of O 2p-Fe 3d hybridization intensity and Fe 3d-orbit occupancy caused by the strain-relaxed effect.Moreover,electrically driven reversible magnetic switching further proves that the SmFeO3 films exhibit the RT ME coupling effect,suggesting promising applications in new-generation electric-write magnetic-read data storage devices.展开更多
We report experimental studies on enhancing the magnetoelectric （ME） coupling of Co4Nb2O9 by sub- stituting the non-magnetic metal Mg for Co. A series of single crystal Co4-xMgxNb2O9 （x = 0, 1, 2, 3） with a single...We report experimental studies on enhancing the magnetoelectric （ME） coupling of Co4Nb2O9 by sub- stituting the non-magnetic metal Mg for Co. A series of single crystal Co4-xMgxNb2O9 （x = 0, 1, 2, 3） with a single-phase corundum-type structure are synthesized using the optical floating zone method, and the good quality and crystallographic orientations of the synthesized samples are confirmed by the Laue spots and sharp XRD peaks. Although the Neel temperatures （TN） of the Mg substituted crystals decrease slightly from 27 K for pure C04Nb2O9 to 19 K and 11 K for Co3MgNb2O9 and Co2Mg2Nb2O9, respectively, the ME coupling is doubly enhanced by Mg substitution when x = 1. The ME coefficient OlMg of Co3MgNb2O9 required for the magnetic field （electric field） control of electric polarization （magnetization） is measured to be 12.8 ps/m （13.7 ps/m）. These results indicate that the Mg substituted Co4-xMgxNb2O9 （x = 1） could serve as a potential candidate material for applications in future logic spintronics and logic devices.展开更多
Multiferroic composite structures are widely used in sensing,driving and communication.The study of their magnetoelectric(ME)behavior under various excitations is crucial.This study investigates the nonlinear ME influ...Multiferroic composite structures are widely used in sensing,driving and communication.The study of their magnetoelectric(ME)behavior under various excitations is crucial.This study investigates the nonlinear ME influence of a multilayer composite ring structure consisting of Terfenol-D(TD)magnetostrictive and lead zirconate titanate(PZT)piezoelectric rings utilizing a multiphysics field modeling framework based on the fully coupled finite element method.The ME coupling coefficient of the PZT/TD concentric composite ring is predicted using the linear piezoelectric constitutive model and the nonlinear magnetostrictive constitutive model,which is congruent to the experimental data.The effect of the interface area of a trilayered structure on the coupling performance at the resonant frequency is investigated,considering the magnitude and frequency of the magnetic field and keeping the material ratio constant.The ME coupling coefficient of a trilayered structure is larger than that of a bilayered structure with the same material ratio,and the maximum ME coupling coefficient of a trilayered structure increases nonlinearly with the increase in the interface area.At the resonant frequency,the structure's ME coupling performance is considerably improved.An optimization technique based on structural geometric design and magnetic field control is presented to optimize the ME coupling coefficient.展开更多
Two-dimensional （2D） equations for multiferroic （MF） laminated plates with imperfect interfaces are established in this paper. The interface between two adjacent sublayers, which are not perfectly bonded together,...Two-dimensional （2D） equations for multiferroic （MF） laminated plates with imperfect interfaces are established in this paper. The interface between two adjacent sublayers, which are not perfectly bonded together, is modeled as a general spring-type layer. The mechanical displacements, and the electric and magnetic potentials of the two adjacent layers are assumed to be discontinuous at the interface. As an example, the influences of imperfect interfaces on the magnetoelectric （ME） coupling effects in an MF sandwich plate are investigated with the established 2D governing equations. Numerical results show that the imperfect interfaces have a significant impact on the ME coupling effects in MF laminated structures.展开更多
Because of the wide selectivity of ferromagnetic and ferroelectric(FE)components,electric-field(E-field)control of magnetism via strain mediation can be easily realized through composite multiferroic heterostructures....Because of the wide selectivity of ferromagnetic and ferroelectric(FE)components,electric-field(E-field)control of magnetism via strain mediation can be easily realized through composite multiferroic heterostructures.Here,an MgO-based magnetic tunnel junction(MTJ)is chosen rationally as the ferromagnetic constitution and a high-activity(001)-Pb(Mg_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)O_(3)(PMN-0.3PT)single crystal is selected as the FE component to create a multiferroic MTJ/FE hybrid structure.The shape of tunneling magnetoresistance(TMR)versus in situ E-fields imprints the butterfly loop of the piezo-strain of the FE without magnetic-field bias.The E-field-controlled change in the TMR ratio is up to-0.27%without magnetic-field bias.Moreover,when a typical magnetic field(~±10 Oe)is applied along the minor axis of the MTJ,the butterfly loop is changed significantly by the E-fields relative to that without magnetic-field bias.This suggests that the E-field-controlled junction resistance is spin-dependent and correlated with magnetization switching in the free layer of the MTJ.In addition,based on such a multiferroic heterostructure,a strain-gauge factor up to approximately 40 is achieved,which decreases further with a sign change from positive to negative with increasing magnetic fields.This multiferroic hybrid structure is a promising avenue to control TMR through E-fields in low-power-consumption spintronic and straintronic devices at room temperature.展开更多
A Monte-Carlo simulation on phase transitions in ferroelectromagnets (FEMs) in which a weak antiferromagnetic ordering occurs at the Neel point TN far below the ferroelectric ordering point TE was performed. It is rev...A Monte-Carlo simulation on phase transitions in ferroelectromagnets (FEMs) in which a weak antiferromagnetic ordering occurs at the Neel point TN far below the ferroelectric ordering point TE was performed. It is revealed that an intrinsic coupling between spins and electric-dipoles (mp-coupling) does result in a weak ferromagnetic transition from the paramagnetic state at a temperature far above TN, as long as the coupling is strong enough. The magnetoelectric properties as a function of temperature, mp-coupling strength and external electric and magnetic fields were investigated. A mean-field calculation based on the Heisenberg model was performed and a rough consistency between the simulated and calculated ferromagnetic transitions was shown.展开更多
Nonvolatile manipulation of transport and magnetic properties by external electric field is significant for information storage. In this study, we investigate the electric field control of resistance and magnetization...Nonvolatile manipulation of transport and magnetic properties by external electric field is significant for information storage. In this study, we investigate the electric field control of resistance and magnetization in a magnetoelectric heterostructure comprising an electronic phase-separated La0.325Pr0.3Ca0.375MnO3（LPCMO） thin film and a ferroelectric（011）-oriented 0.7Pb（Mg1/3Nb2/3）O3-0.3PbTiO3（PMN-PT） substrate. In a room-temperature poled sample, the metal-toinsulator transition temperature of an LPCMO film increases and the resistance decreases with variation in the effect of the remnant strain. Meanwhile, the increase in the magnetization of the sample is observed as well. This effect would be beneficial for the development of novel storage devices with low power consumption.展开更多
In this paper, multiferroics and magnetocapacitive effect of triangular-lattice antiferromagnet Ag Al0.02Cr0.98S2 are investigated by magnetic, ferroelectric, pyroelectric current and dielectric measurement. We find t...In this paper, multiferroics and magnetocapacitive effect of triangular-lattice antiferromagnet Ag Al0.02Cr0.98S2 are investigated by magnetic, ferroelectric, pyroelectric current and dielectric measurement. We find that it is a multiferroic material and the magnetocapacitive effect reaches a factor of up to 90 in an external field of 7 T. The results imply the further possibility of synthesizing the magnetocapacitive materials by modifying the frustrated spin structure in terms of a few B-site doping nonmagnetic ions.展开更多
NiFe204 （NFO）/ZnO composite nanoparticles with different ZnO components were investigated, which were pre- pared by a simple wet chemical route method. The magnetoelectric coupling between magnetostriction from NFO ...NiFe204 （NFO）/ZnO composite nanoparticles with different ZnO components were investigated, which were pre- pared by a simple wet chemical route method. The magnetoelectric coupling between magnetostriction from NFO and piezoelectricity from ZnO was induced by the surface coating NFO nanoparticles of ZnO layer, NFO/ZnO composite showed ferroelectric properties and the remanent electric polarization reached 0.08 μC/cm. Moreover, the changes of resistance at different room temperatures reached about 2% under 3 T magnetic fields comparing with that of zero mag- netic fields. Furthermore, multiferroic NFO/ZnO resulted in enhancement of microwave absorption due to magnetoelectric coupling.展开更多
In this paper,magnetic and dielectric properties of the quasi-two-dimensional triangular-lattice system CuCrS2 and its B-site-diluted analogs CuAl1-xCrxS2（x = 0.01 and x = 0.02） are investigated.Antiferromagnetic ph...In this paper,magnetic and dielectric properties of the quasi-two-dimensional triangular-lattice system CuCrS2 and its B-site-diluted analogs CuAl1-xCrxS2（x = 0.01 and x = 0.02） are investigated.Antiferromagnetic phase transition is observed at about 38.5 K by magnetization measurement without shift induced by a small amount of doping Al.Magnetodielectric effect is found near TN in each of the three compounds.The dielectric constant decreases and the magnetocapacitance increases with the increase of substitution of nonmagnetic Al3＋ ions for the magnetic Cr^3＋ ions.The negative magnetocapacitive effect reaches ～ 13% for CuAl0.02Cr0.98S2.展开更多
Recent progress in the electrical control of magnetism in oxides,with profound physics and enormous potential applications,is reviewed and illustrated.In the first part,we provide a comprehensive summary of the electr...Recent progress in the electrical control of magnetism in oxides,with profound physics and enormous potential applications,is reviewed and illustrated.In the first part,we provide a comprehensive summary of the electrical control of magnetism in the classic multiferroic heterostructures and clarify the various mechanisms lying behind them.The second part focuses on the novel technique of electric double layer gating for driving a significant electronic phase transition in magnetic oxides by a small voltage.In the third part,electric field applied on ordinary dielectric oxide is used to control the magnetic phenomenon originating from charge transfer and orbital reconstruction at the interface between dissimilar correlated oxides.At the end,we analyze the challenges in electrical control of magnetism in oxides,both the mechanisms and practical applications,which will inspire more in-depth research and advance the development in this field.展开更多
Voltage control magnetism has been widely studied due to its potential applications in the next generation of information technology.PMN-PT,as a single crystal ferroelectric substrate,has been widely used in the study...Voltage control magnetism has been widely studied due to its potential applications in the next generation of information technology.PMN-PT,as a single crystal ferroelectric substrate,has been widely used in the study of voltage control magnetism because of its excellent piezoelectric properties.However,most of the research based on PMN-PT only studies the influence of a single tensile(or compressive)stress on the magnetic properties due to the asymmetry of strain.In this work,we show the effect of different strains on the magnetic anisotropy of an Fe_(19)Ni_(81)/(011)PMN-PT heterojunction.More importantly,the(011)cut PMN-PT generates non-volatile strain,which provides an advantage when investigating the voltage manipulation of RF/microwave magnetic devices.As a result,a ferromagnetic resonance field tunability of 70 Oe is induced in our sample by the non-volatile strain.Our results provide new possibilities for novel voltage adjustable RF/microwave magnetic devices and spintronic devices.展开更多
The voltage control of magnetism has attracted intensive attention owing to the abundant physical phenomena associated with magnetoelectric coupling. More importantly, the techniques to electrically manipulate spin dy...The voltage control of magnetism has attracted intensive attention owing to the abundant physical phenomena associated with magnetoelectric coupling. More importantly, the techniques to electrically manipulate spin dynamics, such as magnetic anisotropy and ferromagnetic resonance, are of great significance because of their potential applications in high-density memory devices, microwave signal processors, and magnetic sensors. Recently, voltage control of spin waves has also been demonstrated in several multiferroic heterostructures. This development provides new platforms for energyefficient, tunable magnonic devices. In this review, we focus on the most recent advances in voltage control of ferromagnetic resonance and spin waves in magnetoelectric materials and discuss the physical mechanisms and prospects for practical device applications.展开更多
Altermagnets,with spin splitting and vanishing magnetization,have been attributed to many fascinating phenomena and potential applications.In particular,integrating ferroelectricity with altermagnetism to enable magne...Altermagnets,with spin splitting and vanishing magnetization,have been attributed to many fascinating phenomena and potential applications.In particular,integrating ferroelectricity with altermagnetism to enable magnetoelectric coupling and electric control of spin has drawn significant attention.However,its experimental realization and precise spin manipulation remain elusive.Here,by focusing on molecular ferroelectrics,the first discovered ferroelectrics renowned for their highly controllable molecular polarizations and structural flexibility,we reveal that these obstacles can be removed by an emergent multiferroic altermagnet with tunable spin polarization in a large class of fabricated organic materials.Using a symmetry-based design and a tight-binding model,we uncover the underlying mechanism of such molecular ferroelectric altermagnets and demonstrate how noncollinear molecular polarization can switch the spin polarization on and off and even reverse its sign,as detectable by the magneto-optical Kerr effect.From the first-principles calculations,we verify the feasibility of these materials in a series of well-established hybrid organic-inorganic perovskites and metal-organic frameworks.Our findings bridge molecular ferroelectrics and altermagnetic spintronics,highlighting an unexplored potential of multifunctional organic multiferroics.展开更多
Realizing robust magnetoelectric(ME)coupling effect near room temperature is still a long-standing challenge for the application of multiferroic materials in next-generation low-power spintronic and memory devices.Her...Realizing robust magnetoelectric(ME)coupling effect near room temperature is still a long-standing challenge for the application of multiferroic materials in next-generation low-power spintronic and memory devices.Here we report a systematic study on the magnetic,dielectric,and ME coupling properties of Y-type hexaferrite Ba_(0.5)Sr_(1.5)Co_(2)Fe_(12-x)Al_(x)O_(22)(x=0.0,0.5,1.0)single crystals.The Al doping can induce the shifting of the alternating longitudinal conical(ALC)-proper screw(PS)magnetic phase transition temperature from 200 K for x?0e365 K for x-1.0.The most interesting feature is that the Ba_(0.5)Sr_(1.5)Co_(2)Fe_(11)AlO_(22) single crystal displays a direct and converse ME coupling coefficient with aH~3,100 ps/m and aE~3,900 ps/m at 250 K,respectively,due to the Al-doped enhanced stability of ALC phase.Moreover,the exchange bias also verifies the strong coupling of electric and magnetic orders.These results provide a valuable insight on the modulation of ALC structure and the mechanism of ME effect in Y-type hexaferrites.展开更多
Single-phase multiferroics(MFs)exhibiting ferroelectricity and ferromagnetism and the strong magnetoelectric(ME)coupling effect at room temperature are seen as key to the development of the next-generation of spintron...Single-phase multiferroics(MFs)exhibiting ferroelectricity and ferromagnetism and the strong magnetoelectric(ME)coupling effect at room temperature are seen as key to the development of the next-generation of spintronic devices,multi-state memories,logic devices and sensors.Herein,the single-tetragonal phase(1ex)(Sr_(0.3)Bi_(0.35)Na_(0.329)Li_(0.021))TiO_(3-x)BiFeO_(3)(x=0.2 or 0.4)system was designed to study the intrinsic ME coupling effect at room temperature and high frequencies.The polarization arises from the cooperative displacement of both Fe3t and Ti4t relative to the oxygen sublattice in the tetragonally distorted perovskite structure,and the magnetization stems from indirect exchange magnetic interaction between adjacent iron ions.A switchable voltage-controlled magnetization was confirmed by a change of the coercive magnetic field,Hc,and remnant magnetization,Mr,in the x=0.4 component subjected to an external electric field at room temperature and was possibly attributed to a strain-mediated ME coupling effect.In addition,resonance behaviours of the complex magnetic permeability and complex dielectric permittivity in the GHz band indicate that this ME effect is intrinsic in nature and could broaden the applications of multiferroics to devices operating at microwave frequencies.展开更多
基金Project supported by National Natural Science Foundation of China(51462003)Science Research Fund of Guizhou Province,China(2015-4006,2014-001,2014-7612)+1 种基金the Introduced Talents Funds of Guizhou University(2014-30)Master’s Innovation Funds of Guizhou University(2016065)
文摘Single-phase multiferroic BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3（doped with rare earth ions La-（3＋） and Nd-（3＋）） films grown on（111）-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric（ME） coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3 exhabited a rhombohedral structure with（111） preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO3 crystals, and it enhanced effectively the in-plane ME coupling（the ME coupling coefficient αE increased from 0.13 in the pure BiFeO3 to 0.21 in Bi（0.9）La（0.1）FeO3 and 0.34 V/（Oe·cm） in Bi（0.9）Nd（0.1）FeO3）. The mechanism of these phenomena was investigated systematically.
基金the National Natural Science Foundation of China(Grant No.12047517)the International Cooperation Project of Science and Technology of Henan Province,China(Grant No.182102410096)+1 种基金the Natural Science Foundation of Henan Province,China(Grant No.202300410069)the China Postdoctoral Science Foundation(Grant Nos.2020M682274 and 2020TQ0089)。
文摘An effective regulation of the magnetism and interface of ferromagnetic materials is not only of great scientific significance,but also has an urgent need in modern industry.In this work,by using the first-principles calculations,we demonstrate an effective approach to achieve non-volatile electrical control of ferromagnets,which proves this idea in multiferroic heterostructures of ferromagnetic La TiO_(3)and ferroelectric Bi FeO_(3).The results show that the magnetic properties and two-dimensional electron gas concentrations of La TiO_(3)films can be controlled by changing the polarization directions of Bi FeO_(3).The destroyed symmetry being introduced by ferroelectric polarization of the system leads to the transfer and reconstruction of the Ti-3 d electrons,which is the fundamental reason for the changing of magnetic properties.This multiferroic heterostructures will pave the way for non-volatile electrical control of ferromagnets and have potential applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674187)
文摘In this study, we observe a strong inverse magnetoelectric coupling in Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure, which produces large electric field（E-field） tunability of microwave magnetic properties. With the increase of the E-field from 0 to 8 kV/cm, the magnetic anisotropy field Heffis dramatically enhanced from 169 to 600 Oe, which further leads to a significant enhancement of ferromagnetic resonance frequency from 4.57 to 8.73 GHz under zero bias magnetic field, and a simultaneous decrease of the damping constant α from 0.021 to 0.0186. These features demonstrate that this multiferroic composite is a promising candidate for fabricating E-field tunable microwave components.
基金supported by the National Natural Science Foundation of China(Grant No.12004137)the Taishan Scholar Program of Shandong Province(Grant No.ts20190939)+1 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2020QA052)the Qilu Young Scholar of Shandong University.
文摘The exploration of two-dimensional antiferrovalley materials as potential candidates for valleytronics offers intriguing prospects to investigate exotic valley physics and develop next-generation nano-electronic devices.Achieving efficient anomalous valley Hall effect(AVHE)switching in antiferrovalley materials constitutes an important step towards their application,yet such advancement has been scarcely reported so far.In this study,we demonstrate,through first-principles calculations and model analysis,that the experimentally synthesized MnSe monolayer is a hitherto unexplored but exceptional antiferrovalley material with spontaneous valley polarization.And more importantly,by constructing a multiferroic MnSe/In_(2)Se_(3) heterostructure,the desired nonvolatile on/off switching of the AVHE can be successfully realized through polarization reversal.This unique phenomenon,characterized by the emergence/annihilation of fully spin-polarized valley polarization,arises from the combined effect of strong magnetoelectric coupling-induced changes in magnetic anisotropy and PT symmetry breaking.Our findings provide a novel approach for achieving nonvolatile control of the AVHE in antiferrovalley materials,opening up significant opportunities for valleytronic applications.
基金This work was supported by the National Natural Science Foundation of China(51871137,51901118,51571136 and 61904099).The authors acknowledge Shanghai Synchrotron Radiation Facility at the Beamline BL08U1A and the National Synchrotron Radiation Laboratory at the Beamline BL12-a for the XAS measurements.
文摘Rare-earth orthoferrite SmFeO3 is an outstanding single-phase multiferroic material,holding great potential in novel low-power electronic devices.Nevertheless,simultaneous magnetic and ferroelectric orders as well as magnetoelectric(ME)coupling effect at room temperature(RT)in this system have not been demonstrated yet.In this study,epitaxial SmFeO3 films were successfully prepared onto tensile-strain Nb-SrTiO3(Nb-STO)substrates by a pulsed laser deposition(PLD)method.Measurement results show that the films exhibit obvious ferromagnetic and ferroelectric orders at RT.Meanwhile,the magnetic anisotropy gradually changes from out-of-plane(OP)to in-plane(IP)direction with increasing film thickness,which is attributed to the variations of O 2p-Fe 3d hybridization intensity and Fe 3d-orbit occupancy caused by the strain-relaxed effect.Moreover,electrically driven reversible magnetic switching further proves that the SmFeO3 films exhibit the RT ME coupling effect,suggesting promising applications in new-generation electric-write magnetic-read data storage devices.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 11774217 and 11574194） and the Project for Applied Basic Research Programs of Yunnan Province （No. 2017FD142）.
文摘We report experimental studies on enhancing the magnetoelectric （ME） coupling of Co4Nb2O9 by sub- stituting the non-magnetic metal Mg for Co. A series of single crystal Co4-xMgxNb2O9 （x = 0, 1, 2, 3） with a single-phase corundum-type structure are synthesized using the optical floating zone method, and the good quality and crystallographic orientations of the synthesized samples are confirmed by the Laue spots and sharp XRD peaks. Although the Neel temperatures （TN） of the Mg substituted crystals decrease slightly from 27 K for pure C04Nb2O9 to 19 K and 11 K for Co3MgNb2O9 and Co2Mg2Nb2O9, respectively, the ME coupling is doubly enhanced by Mg substitution when x = 1. The ME coefficient OlMg of Co3MgNb2O9 required for the magnetic field （electric field） control of electric polarization （magnetization） is measured to be 12.8 ps/m （13.7 ps/m）. These results indicate that the Mg substituted Co4-xMgxNb2O9 （x = 1） could serve as a potential candidate material for applications in future logic spintronics and logic devices.
基金supported by the National Key Research and Development Program of China(2018YFB0703500)the Natural Science Foundation of Beijing(3202001).
文摘Multiferroic composite structures are widely used in sensing,driving and communication.The study of their magnetoelectric(ME)behavior under various excitations is crucial.This study investigates the nonlinear ME influence of a multilayer composite ring structure consisting of Terfenol-D(TD)magnetostrictive and lead zirconate titanate(PZT)piezoelectric rings utilizing a multiphysics field modeling framework based on the fully coupled finite element method.The ME coupling coefficient of the PZT/TD concentric composite ring is predicted using the linear piezoelectric constitutive model and the nonlinear magnetostrictive constitutive model,which is congruent to the experimental data.The effect of the interface area of a trilayered structure on the coupling performance at the resonant frequency is investigated,considering the magnitude and frequency of the magnetic field and keeping the material ratio constant.The ME coupling coefficient of a trilayered structure is larger than that of a bilayered structure with the same material ratio,and the maximum ME coupling coefficient of a trilayered structure increases nonlinearly with the increase in the interface area.At the resonant frequency,the structure's ME coupling performance is considerably improved.An optimization technique based on structural geometric design and magnetic field control is presented to optimize the ME coupling coefficient.
基金supported by the National Natural Science Foundation of China(11672265,11202182,11272281,11621062,and 11321202)the Fundamental Research Funds for the Central Universities(2016QNA4026 and 2016XZZX001-05)the open foundation of Zhejiang Provincial Top Key Discipline of Mechanical Engineering
文摘Two-dimensional （2D） equations for multiferroic （MF） laminated plates with imperfect interfaces are established in this paper. The interface between two adjacent sublayers, which are not perfectly bonded together, is modeled as a general spring-type layer. The mechanical displacements, and the electric and magnetic potentials of the two adjacent layers are assumed to be discontinuous at the interface. As an example, the influences of imperfect interfaces on the magnetoelectric （ME） coupling effects in an MF sandwich plate are investigated with the established 2D governing equations. Numerical results show that the imperfect interfaces have a significant impact on the ME coupling effects in MF laminated structures.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52072102 and 11775224)It was also partially funded through the Open Foundation of the Hefei National Laboratory for Physical Sciences at the Microscale(Grant No.KF2020002).
文摘Because of the wide selectivity of ferromagnetic and ferroelectric(FE)components,electric-field(E-field)control of magnetism via strain mediation can be easily realized through composite multiferroic heterostructures.Here,an MgO-based magnetic tunnel junction(MTJ)is chosen rationally as the ferromagnetic constitution and a high-activity(001)-Pb(Mg_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)O_(3)(PMN-0.3PT)single crystal is selected as the FE component to create a multiferroic MTJ/FE hybrid structure.The shape of tunneling magnetoresistance(TMR)versus in situ E-fields imprints the butterfly loop of the piezo-strain of the FE without magnetic-field bias.The E-field-controlled change in the TMR ratio is up to-0.27%without magnetic-field bias.Moreover,when a typical magnetic field(~±10 Oe)is applied along the minor axis of the MTJ,the butterfly loop is changed significantly by the E-fields relative to that without magnetic-field bias.This suggests that the E-field-controlled junction resistance is spin-dependent and correlated with magnetization switching in the free layer of the MTJ.In addition,based on such a multiferroic heterostructure,a strain-gauge factor up to approximately 40 is achieved,which decreases further with a sign change from positive to negative with increasing magnetic fields.This multiferroic hybrid structure is a promising avenue to control TMR through E-fields in low-power-consumption spintronic and straintronic devices at room temperature.
基金This project was financially supported by the National Natural Science Foundation of China (Nos. 50332020, 10021001, 10474039) and the National Key Project for Basic Researches of China (No. 2002CB613303).
文摘A Monte-Carlo simulation on phase transitions in ferroelectromagnets (FEMs) in which a weak antiferromagnetic ordering occurs at the Neel point TN far below the ferroelectric ordering point TE was performed. It is revealed that an intrinsic coupling between spins and electric-dipoles (mp-coupling) does result in a weak ferromagnetic transition from the paramagnetic state at a temperature far above TN, as long as the coupling is strong enough. The magnetoelectric properties as a function of temperature, mp-coupling strength and external electric and magnetic fields were investigated. A mean-field calculation based on the Heisenberg model was performed and a rough consistency between the simulated and calculated ferromagnetic transitions was shown.
基金Project supported by the National Natural Science Foundation of China(Grant No.51571108)
文摘Nonvolatile manipulation of transport and magnetic properties by external electric field is significant for information storage. In this study, we investigate the electric field control of resistance and magnetization in a magnetoelectric heterostructure comprising an electronic phase-separated La0.325Pr0.3Ca0.375MnO3（LPCMO） thin film and a ferroelectric（011）-oriented 0.7Pb（Mg1/3Nb2/3）O3-0.3PbTiO3（PMN-PT） substrate. In a room-temperature poled sample, the metal-toinsulator transition temperature of an LPCMO film increases and the resistance decreases with variation in the effect of the remnant strain. Meanwhile, the increase in the magnetization of the sample is observed as well. This effect would be beneficial for the development of novel storage devices with low power consumption.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB833102)the National Natural Science Foundation of China(Grant Nos.10974244+1 种基金11274369and 11104337)
文摘In this paper, multiferroics and magnetocapacitive effect of triangular-lattice antiferromagnet Ag Al0.02Cr0.98S2 are investigated by magnetic, ferroelectric, pyroelectric current and dielectric measurement. We find that it is a multiferroic material and the magnetocapacitive effect reaches a factor of up to 90 in an external field of 7 T. The results imply the further possibility of synthesizing the magnetocapacitive materials by modifying the frustrated spin structure in terms of a few B-site doping nonmagnetic ions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51671099,11374131,and 51501081)
文摘NiFe204 （NFO）/ZnO composite nanoparticles with different ZnO components were investigated, which were pre- pared by a simple wet chemical route method. The magnetoelectric coupling between magnetostriction from NFO and piezoelectricity from ZnO was induced by the surface coating NFO nanoparticles of ZnO layer, NFO/ZnO composite showed ferroelectric properties and the remanent electric polarization reached 0.08 μC/cm. Moreover, the changes of resistance at different room temperatures reached about 2% under 3 T magnetic fields comparing with that of zero mag- netic fields. Furthermore, multiferroic NFO/ZnO resulted in enhancement of microwave absorption due to magnetoelectric coupling.
基金Project supported by the National Basic Research Program of China (Grant No. 2010CB833102)the National Natural Science Foundation of China (Grant No. 10974244)
文摘In this paper,magnetic and dielectric properties of the quasi-two-dimensional triangular-lattice system CuCrS2 and its B-site-diluted analogs CuAl1-xCrxS2（x = 0.01 and x = 0.02） are investigated.Antiferromagnetic phase transition is observed at about 38.5 K by magnetization measurement without shift induced by a small amount of doping Al.Magnetodielectric effect is found near TN in each of the three compounds.The dielectric constant decreases and the magnetocapacitance increases with the increase of substitution of nonmagnetic Al3＋ ions for the magnetic Cr^3＋ ions.The negative magnetocapacitive effect reaches ～ 13% for CuAl0.02Cr0.98S2.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51322101,51202125,and 51231004)the National Hi-tech Research and Development Project of China(Grant Nos.2014AA032904 and 2014AA032901)
文摘Recent progress in the electrical control of magnetism in oxides,with profound physics and enormous potential applications,is reviewed and illustrated.In the first part,we provide a comprehensive summary of the electrical control of magnetism in the classic multiferroic heterostructures and clarify the various mechanisms lying behind them.The second part focuses on the novel technique of electric double layer gating for driving a significant electronic phase transition in magnetic oxides by a small voltage.In the third part,electric field applied on ordinary dielectric oxide is used to control the magnetic phenomenon originating from charge transfer and orbital reconstruction at the interface between dissimilar correlated oxides.At the end,we analyze the challenges in electrical control of magnetism in oxides,both the mechanisms and practical applications,which will inspire more in-depth research and advance the development in this field.
文摘Voltage control magnetism has been widely studied due to its potential applications in the next generation of information technology.PMN-PT,as a single crystal ferroelectric substrate,has been widely used in the study of voltage control magnetism because of its excellent piezoelectric properties.However,most of the research based on PMN-PT only studies the influence of a single tensile(or compressive)stress on the magnetic properties due to the asymmetry of strain.In this work,we show the effect of different strains on the magnetic anisotropy of an Fe_(19)Ni_(81)/(011)PMN-PT heterojunction.More importantly,the(011)cut PMN-PT generates non-volatile strain,which provides an advantage when investigating the voltage manipulation of RF/microwave magnetic devices.As a result,a ferromagnetic resonance field tunability of 70 Oe is induced in our sample by the non-volatile strain.Our results provide new possibilities for novel voltage adjustable RF/microwave magnetic devices and spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.51602244)the National 111 Project of China(Grant No.B14040)the Fundamental Research Funds for the Central Universities,China(Grant No.xjj2018207)
文摘The voltage control of magnetism has attracted intensive attention owing to the abundant physical phenomena associated with magnetoelectric coupling. More importantly, the techniques to electrically manipulate spin dynamics, such as magnetic anisotropy and ferromagnetic resonance, are of great significance because of their potential applications in high-density memory devices, microwave signal processors, and magnetic sensors. Recently, voltage control of spin waves has also been demonstrated in several multiferroic heterostructures. This development provides new platforms for energyefficient, tunable magnonic devices. In this review, we focus on the most recent advances in voltage control of ferromagnetic resonance and spin waves in magnetoelectric materials and discuss the physical mechanisms and prospects for practical device applications.
基金supported by the National Natural Science Foundation of China(12474155,12447163,and 11904250)the Zhejiang Provincial Natural Science Foundation of China(LR25A040001)+1 种基金the China Postdoctoral Science Foundation(2025M773440)the U.S.DOE,Office of Science BES,Award No.DE-SC0004890(Y.L,I.Z.).
文摘Altermagnets,with spin splitting and vanishing magnetization,have been attributed to many fascinating phenomena and potential applications.In particular,integrating ferroelectricity with altermagnetism to enable magnetoelectric coupling and electric control of spin has drawn significant attention.However,its experimental realization and precise spin manipulation remain elusive.Here,by focusing on molecular ferroelectrics,the first discovered ferroelectrics renowned for their highly controllable molecular polarizations and structural flexibility,we reveal that these obstacles can be removed by an emergent multiferroic altermagnet with tunable spin polarization in a large class of fabricated organic materials.Using a symmetry-based design and a tight-binding model,we uncover the underlying mechanism of such molecular ferroelectric altermagnets and demonstrate how noncollinear molecular polarization can switch the spin polarization on and off and even reverse its sign,as detectable by the magneto-optical Kerr effect.From the first-principles calculations,we verify the feasibility of these materials in a series of well-established hybrid organic-inorganic perovskites and metal-organic frameworks.Our findings bridge molecular ferroelectrics and altermagnetic spintronics,highlighting an unexplored potential of multifunctional organic multiferroics.
基金supported by the National Key Research Program of China(2022YFB3807603)the Science and Technology Projects in Guangzhou(202201000008)+2 种基金the Guangdong Provincial Key Laboratory(2020B1212060066)the National Natural Science Foundation of China(Grants Nos.52272108,and 52002134)the Hubei Provincial Natural Science Foundation of China(2023AFA105).
文摘Realizing robust magnetoelectric(ME)coupling effect near room temperature is still a long-standing challenge for the application of multiferroic materials in next-generation low-power spintronic and memory devices.Here we report a systematic study on the magnetic,dielectric,and ME coupling properties of Y-type hexaferrite Ba_(0.5)Sr_(1.5)Co_(2)Fe_(12-x)Al_(x)O_(22)(x=0.0,0.5,1.0)single crystals.The Al doping can induce the shifting of the alternating longitudinal conical(ALC)-proper screw(PS)magnetic phase transition temperature from 200 K for x?0e365 K for x-1.0.The most interesting feature is that the Ba_(0.5)Sr_(1.5)Co_(2)Fe_(11)AlO_(22) single crystal displays a direct and converse ME coupling coefficient with aH~3,100 ps/m and aE~3,900 ps/m at 250 K,respectively,due to the Al-doped enhanced stability of ALC phase.Moreover,the exchange bias also verifies the strong coupling of electric and magnetic orders.These results provide a valuable insight on the modulation of ALC structure and the mechanism of ME effect in Y-type hexaferrites.
基金support by the National Natural Science Foundation of China(Grant No.51972322)Z.H.would like to acknowledge the financial support by the Postdoctoral Fellowship Program of CPSF(No.GZC20232832)+5 种基金Queen Mary University of London and the China Scholarship Council(No.201806370199)for a joint Ph.D.scholarship.V.K.thanks the Grant Agency of the Slovak Academy of Sciences for support through Grant No.2/0034/23.H.Y.the financial support from the Royal Society a Newton Advanced Fellowship award(No.NAF\R1\201126)C.J.thanks the finacial support by the National Natural Science Foundation of China(No.12174164)the 111 Project under Grant No.B20063the Key R&D Project of Gansu Province(No.22YF7WA014).
文摘Single-phase multiferroics(MFs)exhibiting ferroelectricity and ferromagnetism and the strong magnetoelectric(ME)coupling effect at room temperature are seen as key to the development of the next-generation of spintronic devices,multi-state memories,logic devices and sensors.Herein,the single-tetragonal phase(1ex)(Sr_(0.3)Bi_(0.35)Na_(0.329)Li_(0.021))TiO_(3-x)BiFeO_(3)(x=0.2 or 0.4)system was designed to study the intrinsic ME coupling effect at room temperature and high frequencies.The polarization arises from the cooperative displacement of both Fe3t and Ti4t relative to the oxygen sublattice in the tetragonally distorted perovskite structure,and the magnetization stems from indirect exchange magnetic interaction between adjacent iron ions.A switchable voltage-controlled magnetization was confirmed by a change of the coercive magnetic field,Hc,and remnant magnetization,Mr,in the x=0.4 component subjected to an external electric field at room temperature and was possibly attributed to a strain-mediated ME coupling effect.In addition,resonance behaviours of the complex magnetic permeability and complex dielectric permittivity in the GHz band indicate that this ME effect is intrinsic in nature and could broaden the applications of multiferroics to devices operating at microwave frequencies.
