We have investigated the magnetic, dielectric, pyroelectric, and thermal expansion properties of a layered perovskite metal–organic framework, [NH_(4)Cl]_(2)[Ni(HCOO)_(2)(NH_(3))_(2)]. The material undergoes three ph...We have investigated the magnetic, dielectric, pyroelectric, and thermal expansion properties of a layered perovskite metal–organic framework, [NH_(4)Cl]_(2)[Ni(HCOO)_(2)(NH_(3))_(2)]. The material undergoes three phase transitions including a canted antiferromagnetic transition at ~36 K, and two successive structural transitions around 100 K and 110 K, respectively. The temperature dependence of dielectric permittivity and pyroelectric current suggests that the structural transitions induce weak ferroelectricity along the c-axis and antiferroelectricity in the ab plane. A negative thermal expansion along the c-axis is observed between two structural phase transitions, which is ascribed to the abnormal shrinkage of interlayer hydrogen bonding length. Moreover, the ferroelectric/antiferroelectric phase transition temperature shifts towards a higher temperature under a magnetic field, suggesting certain magnetoelectric coupling in the paramagnetic phase. Our study suggests that the layered metal–organic frameworks provide a unique playground for exploring exotic physical properties such as multiferroicity and abnormal thermal expansion.展开更多
The multiferroicity in the RMn_(2)O_(5)family remains unclear,and less attention has been paid to its dependence on high-temperature(high-T)polarized configuration.Moreover,no consensus on the high-T space group symme...The multiferroicity in the RMn_(2)O_(5)family remains unclear,and less attention has been paid to its dependence on high-temperature(high-T)polarized configuration.Moreover,no consensus on the high-T space group symmetry has been reached so far.In view of this consideration,one may argue that the multiferroicity of RMn_(2)O_(5)in the low-T range depends on the poling sequence starting far above the multiferroic ordering temperature.In this work,we investigate in detail the variation of magnetically induced electric polarization in GdMn_(2)O_(5)and its dependence on electric field poling routine in the high-T range.It is revealed that the multiferroicity does exhibit qualitatively different behaviors if the high-T poling routine changes,indicating the close correlation with the possible high-T polarized state.These emergent phenomena may be qualitatively explained by the co-existence of two low-T polarization components,a scenario that was proposed earlier.One is the component associated with the Mn^(3+)–Mn^(4+)–Mn^(3+)exchange striction that seems to be tightly clamped by the high-T polarized state,and the other is the component associated with the Gd Mn^(3+)–Mn^(4+)–Mn^(3+)exchange striction that is free of the clamping.The present findings may offer a different scheme for the electric control of the multiferroicity in RMn_(2)O_(5).展开更多
Multiferroic properties of short period perovskite type manganite superlattice((R_1MnO_3)n/(R_2MnO_3)n(n=1,2,3)) are considered within the framework of classical Heisenberg model using Monte Carlo simulation. Our resu...Multiferroic properties of short period perovskite type manganite superlattice((R_1MnO_3)n/(R_2MnO_3)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 noncoplanar spiral spin structure. These results are associated with the competition among exchange interaction, magnetic anisotropy, and Dzyaloshinskii–Moriya interaction.展开更多
Two-dimensional multiferroics,which simultaneously possess ferroelectricity and magnetism in a single phase,are well-known to possess great potential applications in nanoscale memories and spintronics.On the basis of ...Two-dimensional multiferroics,which simultaneously possess ferroelectricity and magnetism in a single phase,are well-known to possess great potential applications in nanoscale memories and spintronics.On the basis of first-principles calculations,a CrNCl_(2) monolayer is reported as an intrinsic multiferroic.The CrNCl_(2) has an antiferromagnetic ground state,with a N´eel temperature of about 88 K,and it exhibits an in-plane spontaneous polarization of 200 pC/m.The magnetic moments of CrNCl_(2) mainly come from the dxy orbital of the Cr cation,but the plane of the dxy orbital is perpendicular to the direction of the ferroelectric polarization,which hardly suppresses the occurrence of ferroelectricity.Therefore,the multiferroic exits in the CrNCl_(2).In addition,like CrNCl_(2),the CrNBr_(2) is an intrinsic multiferroic with antiferromagneticferroelectric ground state while CrNI_(2) is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state.These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.展开更多
Double perovskite manganite Y2MnCrO6 ceramic Novel multiferroic properties are displayed with respect is synthesized and its multiferroic properties are investigated. to other multiferroics, such as high ferroelectric...Double perovskite manganite Y2MnCrO6 ceramic Novel multiferroic properties are displayed with respect is synthesized and its multiferroic properties are investigated. to other multiferroics, such as high ferroelectric phase transi- tion 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 re- markable 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.展开更多
Two-dimensional planar pentagonal crystals,long pursued for their geometrically frustrated lattice configurations and emergent quantum phenomena,have remained challenging to realize due to the intrinsic incompatibilit...Two-dimensional planar pentagonal crystals,long pursued for their geometrically frustrated lattice configurations and emergent quantum phenomena,have remained challenging to realize due to the intrinsic incompatibility of regular pentagons with Euclidean tiling.Here,we unveil 37 dynamically stable binary planar pentagonal monolayers through high-throughput computational screening of 1470 stoichiometric candidates.These materials exhibit room-temperature magnetism,including ferromagnetic(Curie temperature(T_(C))up to 521 K),antiferromagnetic(Néel temperature(T_(N))up to 761 K),and altermagnetic(TN=984 K)ground states,alongside unprecedented electronic states:Dirac semimetals,Dirac half-metal,nodal-loop semimetal,nodal-loop half-metal,and altermagnetic semiconductors(Mn_(4)N_(2))with giant spin splitting(0.78 eV).The latter achieves pure spin-polarized transport windows(-0.04 to 0.36 eV)and strain-tunable valley splitting(18.2 meV under 4%uniaxial strain).Intrinsic type-Ⅱ multiferroicity emerges in Fe_(4)C_(2) and Mn_(4)C_(2),featuring in-plane electric polarization(1.4 and 1.6 pC/m),ferroelasticity(0.8%and 1.2%reversible strain),and reversal chirality.Topological band analysis identifies chiral edge states in Dirac semimetal pentagons,alongside a magnetic topological insulator with Chern number|C|=2 in Mo_(2)S_(4) and W_(2)Te_(4).Temperature-driven structural transitions in Os_(2)S_(4) and Tc_(2)S_(4) from pentagonal to Lieb lattices accompany topological state switching and metal-to-semiconductor transitions.This work establishes pentagonal lattices as a platform for symmetry-driven multifunctionality,bridging geometric frustration with applications in spintronics,nanoelectronics,and quantum devices.展开更多
In recent years,the unique mechanism of sliding ferroelectricity with ultralow switching barriers has been experimentally verified in a series of 2-dimensional(2D)materials.However,its practical applications are hinde...In recent years,the unique mechanism of sliding ferroelectricity with ultralow switching barriers has been experimentally verified in a series of 2-dimensional(2D)materials.However,its practical applications are hindered by the low polarizations,the challenges in synthesis of ferroelectric phases limited in specific stacking configurations,and the low density for data storage since the switching process involves large-area simultaneous sliding of a whole layer.Herein,through first-principles calculations,we propose a type of semi-sliding ferroelectricity in the single metal porphyrin molecule intercalated in 2D bilayers.An enhanced vertical polarization can be formed independent on stacking configurations and switched via sliding of the molecule accompanied by the vertical displacements of its metal ion anchored from the upper layer to the lower layer.Such semi-sliding ferroelectricity enables each molecule to store 1 bit data independently,and the density for data storage can be greatly enhanced.When the bilayer exhibits intralayer ferromagnetism and interlayer antiferromagnetic coupling,a considerable difference in Curie temperature between 2 layers and a switchable net magnetization can be formed due to the vertical polarization.At a certain range of temperature,the exchange of paramagnetic-ferromagnetic phases between 2 layers is accompanied by ferroelectric switching,leading to a hitherto unreported type of multiferroic coupling that is long-sought for efficient"magnetic reading+electric writing".展开更多
Two 0.93(Na_(0.5)Bi_(0.5))TiO_(3)-0.07BaTiO_(3)ceramics were sintered for 2 h and 3 h,respectively,by a conventional solid reaction method.The ceramic sintered for 2h showed a normal ferroelectric hysteresis loop and ...Two 0.93(Na_(0.5)Bi_(0.5))TiO_(3)-0.07BaTiO_(3)ceramics were sintered for 2 h and 3 h,respectively,by a conventional solid reaction method.The ceramic sintered for 2h showed a normal ferroelectric hysteresis loop and paramagnetic behavior,while the ceramic sintered for 3 h showed a pinched ferroelectric hysteresis loop,weak ferromagnetism,and enhanced magnetoelectric coupling.The origins of the sintering time-related multiferroic properties are discussed in detail.The work offers a new way to induce multiferroicity in ceramics by tuning sintering time.展开更多
The RMn_(2)O_(5) manganite compounds represent one class of multiferroic family with magnetic origins,which has been receiving continuous attention in the past decade.So far,our understanding of the magnetic origins f...The RMn_(2)O_(5) manganite compounds represent one class of multiferroic family with magnetic origins,which has been receiving continuous attention in the past decade.So far,our understanding of the magnetic origins for ferroelectricity in RMn_(2)O_(5) is associated with the nearly collinear antiferromagnetic structure of Mn ions,while the exchange striction induced ionic displacements are the consequence of the spin frustration competitions.While this scenario may be applied to almost all RMn_(2)O_(5) members,its limitation is either clear:the temperature-dependent behaviors of electric polarization and its responses to external stimuli are seriously materials dependent.These inconsistences raise substantial concern with the state-of-the-art physics of ferroelectricity in RMn_(2)O_(5).In this mini-review,we present our recent experimental results on the roles of the 4f moments from R ions which are intimately coupled with the 3d moments from Mn ions.DyMn_(2)O_(5) is a golden figure for illustrating these roles.It is demonstrated that the spin structure accommodates two nearly collinear sublattices which generate respectively two ferroelectric(FE)sublattices,enabling DyMn_(2)O_(5) an emergent ferrielectric(FIE)system rarely identified in magnetically induced FEs.The evidence is presented from several aspects,including FIE-like phenomena and magnetoelectric responses,proposed structural model,and experimental check by nonmagnetic substitutions of the 3d and 4f moments.Additional perspectives regarding possible challenges in understanding the multiferroicity of RMn_(2)O_(5) as a generalized scenario are discussed.展开更多
Multiferroic tunnel junctions(MFTJs),which combine tunneling magnetoresistance(TMR)and electroresistance(TER)efects,have emerged as key candidates for data storage.Two-dimensional van der Waals(vdW)MFTJs,in particular...Multiferroic tunnel junctions(MFTJs),which combine tunneling magnetoresistance(TMR)and electroresistance(TER)efects,have emerged as key candidates for data storage.Two-dimensional van der Waals(vdW)MFTJs,in particular,are promising spintronic devices for the post-Moore era.However,these vdW MFTJs are typically based on multiferroics composed of ferromagnetic and ferroelectric materials or multilayer magnetic materials with sliding ferroelectricity,which increases device fabrication complexity.In this work,we design a vdW MFTJ using bilayer MoPtGe_(2)S_(6),a material with homologous multiferroicity in each monolayer,combined with symmetric PtTe_(2)electrodes.Using frst-principles calculations based on density functional theory and nonequilibrium Green's functions,we theoretically explore the spin-polarized electronic transport properties of this MFTJ.By controlling the ferroelectric and ferromagnetic polarization directions of bilayer MoPtGe_(2)S_(6),the MFTJ can exhibit six distinct non-volatile resistance states,with maximum TMR(137%)and TER(1943%)ratios.Under biaxial strain,TMR and TER can increase to 265%and 4210%,respectively.The TER ratio also increases to 2186%under a 0.1 V bias voltage.Remarkably,the MFTJ exhibits a pronounced spin-fltering and a signifcant negative diferential resistance efect.These fndings not only highlight the potential of monolayer multiferroic MoPtGe_(2)S_(6)for MFTJs but also ofer valuable theoretical insights for future experimental investigations.展开更多
This paper investigates the frictional adhesive contact of a rigid,electrically/magnetically conductive spherical indenter sliding past a multiferroic coating deposed onto a rigid substrate,based on the hybrid element...This paper investigates the frictional adhesive contact of a rigid,electrically/magnetically conductive spherical indenter sliding past a multiferroic coating deposed onto a rigid substrate,based on the hybrid element method.The adhesion behavior is described based on the Maugis-Dugdale model.The adhesion-driven conjugate gradient method is employed to calculate the distribution of unknown pressures,while the discrete convolution-fast Fourier transform is utilized to compute the deformations,surface electric and magnetic potentials as well as the subsurface stresses,electric displacements,and magnetic inductions.The goal of this study is to investigate the influences of adhesion parameter,friction coefficient,coating thickness,and surface electric and magnetic charge densities on contact behaviors,such as contact area and pressures,electric and magnetic potentials,and subsurface stresses.展开更多
Ferromagnetic materials play an important role in memory materials,but conventional control methods are often limited by issues such as high power consumption and volatility.Multiferroic heterostructures provide a pro...Ferromagnetic materials play an important role in memory materials,but conventional control methods are often limited by issues such as high power consumption and volatility.Multiferroic heterostructures provide a promising alternative to achieve low power consumption and nonvolatile electric control of magnetic properties.In this paper,a two-dimensional multiferroic van der Waals heterostructure OsCl_(2)/Sc_(2)CO_(2),which is composed of ferromagnetic monolayer OsCl_(2)and ferroelectric monolayer Sc_(2)CO_(2),is studied by first-principles density functional theory.The results show that by reversing the direction of the electric polarization of Sc_(2)CO_(2),OsCl_(2)can be transformed from a semiconductor to a half-metal,demonstrating a nonvolatile electrical manipulation of the heterostructure through ferroelectric polarization.The underlying physical mechanism is explained by band alignments and charge density differences.Furthermore,based on the heterostructure,we construct a multiferroic tunnel junction with a tunnel electroresistance ratio of 3.38×10^(14)%and a tunnel magnetoresistance ratio of 5.04×10^(6)%,allowing control of conduction states via instantaneous electric or magnetic fields.The findings provide a feasible strategy for designing advanced nanodevices based on the giant tunnel electroresistance and tunnel magnetoresistance effects.展开更多
The adhesion enhancing effect induced by electro-magnetic loading and the adhesion weakening effect resulting from interfacial shear stress have been observed and widely reported in open literature.However,the adhesio...The adhesion enhancing effect induced by electro-magnetic loading and the adhesion weakening effect resulting from interfacial shear stress have been observed and widely reported in open literature.However,the adhesion behavior of multiferroic composites in the simultaneous presence of these two effects and the competitive mechanism between them are still unclear.In this paper,the non-slipping adhesive contact problem between a multiferroic half-space and a perfectly conducting rigid cylinder subject to multi-field loading is studied.The stated problem is reduced to a system of coupled singular integral equations,which are analytically solved with the analytical function theory.The closed-form solutions of the generalized stress fields including the contact stress,normal electric displacement,and magnetic induction are obtained.The stable equilibrium state of the adhesion system is determined with the Griffith energy balance criterion.The adhesion behavior subject to mechanical-electro-magnetic loading and a mismatch strain is discussed in detail.Numerical results indicate that exerting electro-magnetic loading can enhance the adhesion effect for both two types of multiferroic composites,namely,κ-class(non-oscillatory singularity)andε-class,which is different from the case of piezoelectric materials.It is found that the contact size finally decreases in the simultaneous presence of the electro-magnetic enhancing and shear-stress weakening effects.The results derived from this work not only are helpful to understand the contact behavior of multiferroic composites at micro/nano scale,but also have potential application value in achieving switchable adhesion.展开更多
The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic si...The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic simulations, we investigate recently synthesized ultrathin perovskite bismuth ferrite(BFO) films. Our numerical results reveal that, at the monolayer limit, the ferroelectricity of BFO is missing because the octahedral distortions are constrained. However, the monolayer bismuth ferrite is a topological antiferromagnetic metal with tunable bimeron magnetic structure. The dual topologically non-trivial characteristics make monolayer bismuth ferrite a multifunctional building block in future spintronic devices.展开更多
Besides equilibrium behavior,exploring the spin–phonon coupling in multiferroic materials under non-equilibrium conditions is crucial for a deep understanding of the mechanisms as well as their high-frequency applica...Besides equilibrium behavior,exploring the spin–phonon coupling in multiferroic materials under non-equilibrium conditions is crucial for a deep understanding of the mechanisms as well as their high-frequency applications.Here,by utilizing time-resolved refectance spectroscopy,we demonstrate ultrafast spin–phonon coupling dynamics in multiferroic 0.58BiFeO_(3)-0.42Bi_(0.5)K_(0.5)TiO_(3)(BF-BKT)single crystals.With ultrafast laser pumping,coherent acoustic phonons with low damping are created in BF-BKT.Temperature-dependent results indicate that both the frequency and amplitude of laser-induced coherent phonons are sensitive to the emergence of antiferromagnetic order.Moreover,the spin state change driven by external magnetic felds can enhance the oscillation amplitude of the coherent acoustic phonons even above the magnetic Néel temperature.These fndings experimentally confrm that spin–phonon coupling in multiferroic materials exists not only in the spin-ordered state but also in the spin-disordered state,and not only in the equilibrium state but also in the non-equilibrium state excited by ultrafast lasers,suggesting their promising applications in high-frequency devices.展开更多
Achieving polarization switching in wurtzite(wz)crystals has long been hindered by substantial energy barriers and high coercive electric fields.Here,we demonstrate that an in-plane ferroelectric(FE)switch can be trig...Achieving polarization switching in wurtzite(wz)crystals has long been hindered by substantial energy barriers and high coercive electric fields.Here,we demonstrate that an in-plane ferroelectric(FE)switch can be triggered within the(0001)crystallographic plane,through the discovery of hiddenAbm2 and Pmc2_(1)monolayer phases.The structural self-reconstruction,induced by lattice expansion,converts interfacial covalent bonds into van der Waals interactions,enabling facile exfoliation of wz monolayers.These monolayers exhibit multiferroic order and diverse electronic functionalities,including giant spin splittings(~540 meV),transition between half-metal and semiconductor,and wide band gaps(0–4.57 eV).Importantly,the FE transition can be finely tuned via a transient state,leading to significant reductions in the barrier energy(<~3 meV/atom)and coercive field(~0.6–1.0 MV/cm),and yielding fully electric control of 100%spin polarization.Our study provides in-depth insights into the inplane FE mechanism in wz systems,opening new avenues for the design and discovery of wz-based FE devices,as well as the rich physics in tetrahedral semiconductors.展开更多
The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently d...The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.展开更多
Ferromagnetic transition has generally been considered to involve only an ordering of magnetic moment with no change in the host crystal structure or symmetry, as evidenced by a wealth of crystal structure data from c...Ferromagnetic transition has generally been considered to involve only an ordering of magnetic moment with no change in the host crystal structure or symmetry, as evidenced by a wealth of crystal structure data from conventional X-ray diffractometry （XRD）. However, the existence of magnetostriction in all known ferromagnetic systems indicates that the magnetic moment is coupled to the crystal lattice; hence there is a possibility that magnetic ordering may cause a change in crystal structure. With the development of high-resolution synchrotron XRD, more and more magnetic transitions have been found to be accompanied by simultaneous structural changes. In this article, we review our recent progress in understand- ing the structural change at a ferromagnetic transition, including synchrotron XRD evidence of structural changes at the ferromagnetic transition, a phenomenological theory of crystal structure changes accompanying ferromagnetic transitions, new insight into magnetic morphotropic phase boundaries （MPB） and so on. Two intriguing implications of non-centric symmetry in the ferromagnetic phase and the first-order nature of ferromagnetic transition are also discussed here. In short, this review is intended to give a self-consistent and logical account of structural change occurring simultaneously with a ferromagnetic transition, which may provide new insight for developing highly magneto-responsive materials.展开更多
Two-dimensional(2D)intrinsic multiferroics have attracted considerable attention for the next generation of advanced information technologies.Herein,we report that bilayer Janus FeSCl,a novel 2D system designed by sub...Two-dimensional(2D)intrinsic multiferroics have attracted considerable attention for the next generation of advanced information technologies.Herein,we report that bilayer Janus FeSCl,a novel 2D system designed by substituting sulfur in monolayer 1T-FeCl_(2),exhibits a giant spontaneous valley polarization and intrinsic magnetoelectric coupling.This Janus structure exhibits a ground-state bilayer structure that breaks space-inversion symmetry,enabling sliding ferroelectricity.Each monolayer displays robust intralayer ferromagnetic ordering,while the bilayer hosts interlayer antiferromagnetic alignment with opposing magnetic moments.Crucially,ferrovalley-mediated coupling links ferroelectric polarization and antiferromagnetic order,allowing electric-field-driven magnetic reversal.Notably,the direction of the net magnetic moment can be reversed through ferroelectric polarization switching,enabling nonvolatile control of the magnetism.The elucidated mechanisms are generalizable to diverse 2D material families,offering a universal framework for designing atomic-scale multiferroics.This work not only establishes foundational insights into 2D multiferroics but also advances the understanding of coupled charge-spin-valley physics in low-dimensional systems.展开更多
Bi1-xYbxFeO3（0〈x〈0.2） powders have been synthesized using a sol-gel method. The X- ray diffraction data show a structural transition from the rhombohedral R3c phase to the orthorhombic Pnma phase between x=0.1 and...Bi1-xYbxFeO3（0〈x〈0.2） powders have been synthesized using a sol-gel method. The X- ray diffraction data show a structural transition from the rhombohedral R3c phase to the orthorhombic Pnma phase between x=0.1 and 0.125, which should induce a ferroelectric- paraelectric transformation. The phase transition is also proven by the Raman spectroscopy. A moderate signal on magnetization appears to illustrate the enhancement of magnetization at the transformation boundary, which is suggested to be the destruction of the spin cycloid structure at low concentration. The appearance of antiferromagnetic ordering is proposed to account for the afterward reduction of the magnetization at high concentration.展开更多
基金Project supported by the National Key Research and Development Program of China (Grant No. 2021YFA1400303)the National Natural Science Foundation of China (Grant No. 12227806)。
文摘We have investigated the magnetic, dielectric, pyroelectric, and thermal expansion properties of a layered perovskite metal–organic framework, [NH_(4)Cl]_(2)[Ni(HCOO)_(2)(NH_(3))_(2)]. The material undergoes three phase transitions including a canted antiferromagnetic transition at ~36 K, and two successive structural transitions around 100 K and 110 K, respectively. The temperature dependence of dielectric permittivity and pyroelectric current suggests that the structural transitions induce weak ferroelectricity along the c-axis and antiferroelectricity in the ab plane. A negative thermal expansion along the c-axis is observed between two structural phase transitions, which is ascribed to the abnormal shrinkage of interlayer hydrogen bonding length. Moreover, the ferroelectric/antiferroelectric phase transition temperature shifts towards a higher temperature under a magnetic field, suggesting certain magnetoelectric coupling in the paramagnetic phase. Our study suggests that the layered metal–organic frameworks provide a unique playground for exploring exotic physical properties such as multiferroicity and abnormal thermal expansion.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11804088,11234005,11374147,51431006,and 11704109)the National Key Research Program of China(Grant No.2016YFA0300101)the Research Project of Hubei Provincial Department of Education,China(Grant No.B2018146)
文摘The multiferroicity in the RMn_(2)O_(5)family remains unclear,and less attention has been paid to its dependence on high-temperature(high-T)polarized configuration.Moreover,no consensus on the high-T space group symmetry has been reached so far.In view of this consideration,one may argue that the multiferroicity of RMn_(2)O_(5)in the low-T range depends on the poling sequence starting far above the multiferroic ordering temperature.In this work,we investigate in detail the variation of magnetically induced electric polarization in GdMn_(2)O_(5)and its dependence on electric field poling routine in the high-T range.It is revealed that the multiferroicity does exhibit qualitatively different behaviors if the high-T poling routine changes,indicating the close correlation with the possible high-T polarized state.These emergent phenomena may be qualitatively explained by the co-existence of two low-T polarization components,a scenario that was proposed earlier.One is the component associated with the Mn^(3+)–Mn^(4+)–Mn^(3+)exchange striction that seems to be tightly clamped by the high-T polarized state,and the other is the component associated with the Gd Mn^(3+)–Mn^(4+)–Mn^(3+)exchange striction that is free of the clamping.The present findings may offer a different scheme for the electric control of the multiferroicity in RMn_(2)O_(5).
基金Supported by the National Natural Science Foundation of China(NSFC) under Grant No.11447136
文摘Multiferroic properties of short period perovskite type manganite superlattice((R_1MnO_3)n/(R_2MnO_3)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 noncoplanar spiral spin structure. These results are associated with the competition among exchange interaction, magnetic anisotropy, and Dzyaloshinskii–Moriya interaction.
基金Project supported by the National Key R&D Program of China(Grant No.2019YFB1704600)the International Cooperation Research Project of Shenzhen(Grant No.GJHZ20180413182004161)+2 种基金the Hubei Provincial Natural Science Foundation of China(Grant No.2020CFA032)the National Natural Science Foundation of China(Grant No.51805395)the China Scholarship Council(Grant No.201906270142).
文摘Two-dimensional multiferroics,which simultaneously possess ferroelectricity and magnetism in a single phase,are well-known to possess great potential applications in nanoscale memories and spintronics.On the basis of first-principles calculations,a CrNCl_(2) monolayer is reported as an intrinsic multiferroic.The CrNCl_(2) has an antiferromagnetic ground state,with a N´eel temperature of about 88 K,and it exhibits an in-plane spontaneous polarization of 200 pC/m.The magnetic moments of CrNCl_(2) mainly come from the dxy orbital of the Cr cation,but the plane of the dxy orbital is perpendicular to the direction of the ferroelectric polarization,which hardly suppresses the occurrence of ferroelectricity.Therefore,the multiferroic exits in the CrNCl_(2).In addition,like CrNCl_(2),the CrNBr_(2) is an intrinsic multiferroic with antiferromagneticferroelectric ground state while CrNI_(2) is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state.These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.
基金supported by the National Basic Research Program of China(Grant No.2009CB929501)the National High Technology Research and Development Program of China(Grant No.2014AA032904)the National Natural Science Foundation of China(Grant Nos.11174130 and U1232210)
文摘Double perovskite manganite Y2MnCrO6 ceramic Novel multiferroic properties are displayed with respect is synthesized and its multiferroic properties are investigated. to other multiferroics, such as high ferroelectric phase transi- tion 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 re- markable 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.
基金supported by the National Natural Science Foundation of China (22225301, 22303092)the Anhui Provincial Natural Science Foundation (2308085QB51)+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0450101)the Fundamental Research Funds for the Central Universities (WK9990000153)the Innovation Program for Quantum Science and Technology (2021ZD0303302)the Supercomputing Centers of both the University of Science and Technology of China (USTCSCC)the Chinese Academy of Sciences (SCCAS)。
文摘Two-dimensional planar pentagonal crystals,long pursued for their geometrically frustrated lattice configurations and emergent quantum phenomena,have remained challenging to realize due to the intrinsic incompatibility of regular pentagons with Euclidean tiling.Here,we unveil 37 dynamically stable binary planar pentagonal monolayers through high-throughput computational screening of 1470 stoichiometric candidates.These materials exhibit room-temperature magnetism,including ferromagnetic(Curie temperature(T_(C))up to 521 K),antiferromagnetic(Néel temperature(T_(N))up to 761 K),and altermagnetic(TN=984 K)ground states,alongside unprecedented electronic states:Dirac semimetals,Dirac half-metal,nodal-loop semimetal,nodal-loop half-metal,and altermagnetic semiconductors(Mn_(4)N_(2))with giant spin splitting(0.78 eV).The latter achieves pure spin-polarized transport windows(-0.04 to 0.36 eV)and strain-tunable valley splitting(18.2 meV under 4%uniaxial strain).Intrinsic type-Ⅱ multiferroicity emerges in Fe_(4)C_(2) and Mn_(4)C_(2),featuring in-plane electric polarization(1.4 and 1.6 pC/m),ferroelasticity(0.8%and 1.2%reversible strain),and reversal chirality.Topological band analysis identifies chiral edge states in Dirac semimetal pentagons,alongside a magnetic topological insulator with Chern number|C|=2 in Mo_(2)S_(4) and W_(2)Te_(4).Temperature-driven structural transitions in Os_(2)S_(4) and Tc_(2)S_(4) from pentagonal to Lieb lattices accompany topological state switching and metal-to-semiconductor transitions.This work establishes pentagonal lattices as a platform for symmetry-driven multifunctionality,bridging geometric frustration with applications in spintronics,nanoelectronics,and quantum devices.
基金supported by the National Natural Science Foundation of China under contract nos.1210040567 and 22073034the Fundamental Research Funds of Zhejiang Sci-Tech University under contract no.20062320-Y.
文摘In recent years,the unique mechanism of sliding ferroelectricity with ultralow switching barriers has been experimentally verified in a series of 2-dimensional(2D)materials.However,its practical applications are hindered by the low polarizations,the challenges in synthesis of ferroelectric phases limited in specific stacking configurations,and the low density for data storage since the switching process involves large-area simultaneous sliding of a whole layer.Herein,through first-principles calculations,we propose a type of semi-sliding ferroelectricity in the single metal porphyrin molecule intercalated in 2D bilayers.An enhanced vertical polarization can be formed independent on stacking configurations and switched via sliding of the molecule accompanied by the vertical displacements of its metal ion anchored from the upper layer to the lower layer.Such semi-sliding ferroelectricity enables each molecule to store 1 bit data independently,and the density for data storage can be greatly enhanced.When the bilayer exhibits intralayer ferromagnetism and interlayer antiferromagnetic coupling,a considerable difference in Curie temperature between 2 layers and a switchable net magnetization can be formed due to the vertical polarization.At a certain range of temperature,the exchange of paramagnetic-ferromagnetic phases between 2 layers is accompanied by ferroelectric switching,leading to a hitherto unreported type of multiferroic coupling that is long-sought for efficient"magnetic reading+electric writing".
基金supported by the National Natural Science Foundation of China(Grant No.11704242)the Natural Science Foundation of Shanghai,China(Grant No.17ZR1447200).
文摘Two 0.93(Na_(0.5)Bi_(0.5))TiO_(3)-0.07BaTiO_(3)ceramics were sintered for 2 h and 3 h,respectively,by a conventional solid reaction method.The ceramic sintered for 2h showed a normal ferroelectric hysteresis loop and paramagnetic behavior,while the ceramic sintered for 3 h showed a pinched ferroelectric hysteresis loop,weak ferromagnetism,and enhanced magnetoelectric coupling.The origins of the sintering time-related multiferroic properties are discussed in detail.The work offers a new way to induce multiferroicity in ceramics by tuning sintering time.
基金supported by the Natural Science Foundation of China(Grant Nos.11234005 and 51431006)the National 973 Projects of China(Grant No.2011CB922101).
文摘The RMn_(2)O_(5) manganite compounds represent one class of multiferroic family with magnetic origins,which has been receiving continuous attention in the past decade.So far,our understanding of the magnetic origins for ferroelectricity in RMn_(2)O_(5) is associated with the nearly collinear antiferromagnetic structure of Mn ions,while the exchange striction induced ionic displacements are the consequence of the spin frustration competitions.While this scenario may be applied to almost all RMn_(2)O_(5) members,its limitation is either clear:the temperature-dependent behaviors of electric polarization and its responses to external stimuli are seriously materials dependent.These inconsistences raise substantial concern with the state-of-the-art physics of ferroelectricity in RMn_(2)O_(5).In this mini-review,we present our recent experimental results on the roles of the 4f moments from R ions which are intimately coupled with the 3d moments from Mn ions.DyMn_(2)O_(5) is a golden figure for illustrating these roles.It is demonstrated that the spin structure accommodates two nearly collinear sublattices which generate respectively two ferroelectric(FE)sublattices,enabling DyMn_(2)O_(5) an emergent ferrielectric(FIE)system rarely identified in magnetically induced FEs.The evidence is presented from several aspects,including FIE-like phenomena and magnetoelectric responses,proposed structural model,and experimental check by nonmagnetic substitutions of the 3d and 4f moments.Additional perspectives regarding possible challenges in understanding the multiferroicity of RMn_(2)O_(5) as a generalized scenario are discussed.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3505301)the National Key R&D Program of Shanxi Province(Grant No.202302050201014)+1 种基金the National Natural Science Foundation of China(Grant No.12304148)the Natural Science Basic Research Program of Shanxi Province(Grant No.202203021222219)。
文摘Multiferroic tunnel junctions(MFTJs),which combine tunneling magnetoresistance(TMR)and electroresistance(TER)efects,have emerged as key candidates for data storage.Two-dimensional van der Waals(vdW)MFTJs,in particular,are promising spintronic devices for the post-Moore era.However,these vdW MFTJs are typically based on multiferroics composed of ferromagnetic and ferroelectric materials or multilayer magnetic materials with sliding ferroelectricity,which increases device fabrication complexity.In this work,we design a vdW MFTJ using bilayer MoPtGe_(2)S_(6),a material with homologous multiferroicity in each monolayer,combined with symmetric PtTe_(2)electrodes.Using frst-principles calculations based on density functional theory and nonequilibrium Green's functions,we theoretically explore the spin-polarized electronic transport properties of this MFTJ.By controlling the ferroelectric and ferromagnetic polarization directions of bilayer MoPtGe_(2)S_(6),the MFTJ can exhibit six distinct non-volatile resistance states,with maximum TMR(137%)and TER(1943%)ratios.Under biaxial strain,TMR and TER can increase to 265%and 4210%,respectively.The TER ratio also increases to 2186%under a 0.1 V bias voltage.Remarkably,the MFTJ exhibits a pronounced spin-fltering and a signifcant negative diferential resistance efect.These fndings not only highlight the potential of monolayer multiferroic MoPtGe_(2)S_(6)for MFTJs but also ofer valuable theoretical insights for future experimental investigations.
基金support from the National Natural Science Foundation of China(12102085)the Postdoctoral Science Foundation of China(2023M730504)+2 种基金the Sichuan Province Regional Innovation and Cooperation Project(2024YFHZ0210)supported by the European Union-NextGenerationEU through the Italian Ministry of University and Research under the following programs:(NM)PRIN2022(Projects of Relevant National Interest)grant no.2022SJ8HTC-Electroactive Gripper for Micro-Object Manipulation(ELFIN)(NM)PRIN2022 PNRR(Projects of Relevant National Interest)grant no.P2022MAZHX-Tribological Modeling for Sustainable Design of Industrial Frictional Interfaces(TRIBOSCORE).
文摘This paper investigates the frictional adhesive contact of a rigid,electrically/magnetically conductive spherical indenter sliding past a multiferroic coating deposed onto a rigid substrate,based on the hybrid element method.The adhesion behavior is described based on the Maugis-Dugdale model.The adhesion-driven conjugate gradient method is employed to calculate the distribution of unknown pressures,while the discrete convolution-fast Fourier transform is utilized to compute the deformations,surface electric and magnetic potentials as well as the subsurface stresses,electric displacements,and magnetic inductions.The goal of this study is to investigate the influences of adhesion parameter,friction coefficient,coating thickness,and surface electric and magnetic charge densities on contact behaviors,such as contact area and pressures,electric and magnetic potentials,and subsurface stresses.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074213,11574108,and 12104253)the National Key R&D Program of China(Grant No.2022YFA1403103)+2 种基金the Major Basic Program of the Natural Science Foundation of Shandong Province(Grant No.ZR2021ZD01)the Natural Science Foundation of Shandong Provincial(Grant No.ZR2023MA082)the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province。
文摘Ferromagnetic materials play an important role in memory materials,but conventional control methods are often limited by issues such as high power consumption and volatility.Multiferroic heterostructures provide a promising alternative to achieve low power consumption and nonvolatile electric control of magnetic properties.In this paper,a two-dimensional multiferroic van der Waals heterostructure OsCl_(2)/Sc_(2)CO_(2),which is composed of ferromagnetic monolayer OsCl_(2)and ferroelectric monolayer Sc_(2)CO_(2),is studied by first-principles density functional theory.The results show that by reversing the direction of the electric polarization of Sc_(2)CO_(2),OsCl_(2)can be transformed from a semiconductor to a half-metal,demonstrating a nonvolatile electrical manipulation of the heterostructure through ferroelectric polarization.The underlying physical mechanism is explained by band alignments and charge density differences.Furthermore,based on the heterostructure,we construct a multiferroic tunnel junction with a tunnel electroresistance ratio of 3.38×10^(14)%and a tunnel magnetoresistance ratio of 5.04×10^(6)%,allowing control of conduction states via instantaneous electric or magnetic fields.The findings provide a feasible strategy for designing advanced nanodevices based on the giant tunnel electroresistance and tunnel magnetoresistance effects.
基金Project supported by the National Natural Science Foundation of China(Nos.12272269,11972257,and 11472193)the Shanghai Pilot Program for Basic Researchthe Shanghai Gaofeng Project for University Academic Program Development。
文摘The adhesion enhancing effect induced by electro-magnetic loading and the adhesion weakening effect resulting from interfacial shear stress have been observed and widely reported in open literature.However,the adhesion behavior of multiferroic composites in the simultaneous presence of these two effects and the competitive mechanism between them are still unclear.In this paper,the non-slipping adhesive contact problem between a multiferroic half-space and a perfectly conducting rigid cylinder subject to multi-field loading is studied.The stated problem is reduced to a system of coupled singular integral equations,which are analytically solved with the analytical function theory.The closed-form solutions of the generalized stress fields including the contact stress,normal electric displacement,and magnetic induction are obtained.The stable equilibrium state of the adhesion system is determined with the Griffith energy balance criterion.The adhesion behavior subject to mechanical-electro-magnetic loading and a mismatch strain is discussed in detail.Numerical results indicate that exerting electro-magnetic loading can enhance the adhesion effect for both two types of multiferroic composites,namely,κ-class(non-oscillatory singularity)andε-class,which is different from the case of piezoelectric materials.It is found that the contact size finally decreases in the simultaneous presence of the electro-magnetic enhancing and shear-stress weakening effects.The results derived from this work not only are helpful to understand the contact behavior of multiferroic composites at micro/nano scale,but also have potential application value in achieving switchable adhesion.
基金supported by the National Natural Science Foundation of China (Grant No. 12174382)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDB0460000 and XDB28000000)the Innovation Program for Quantum Science and Technology (Grant Nos. 2024ZD0300104 and 2021ZD0302600)。
文摘The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic simulations, we investigate recently synthesized ultrathin perovskite bismuth ferrite(BFO) films. Our numerical results reveal that, at the monolayer limit, the ferroelectricity of BFO is missing because the octahedral distortions are constrained. However, the monolayer bismuth ferrite is a topological antiferromagnetic metal with tunable bimeron magnetic structure. The dual topologically non-trivial characteristics make monolayer bismuth ferrite a multifunctional building block in future spintronic devices.
基金supported by the National Key R&D Program of China(Grant No.2021YFA1600200)the National Natural Science Foundation of China(Grant Nos.U2032218 and 12111530283)。
文摘Besides equilibrium behavior,exploring the spin–phonon coupling in multiferroic materials under non-equilibrium conditions is crucial for a deep understanding of the mechanisms as well as their high-frequency applications.Here,by utilizing time-resolved refectance spectroscopy,we demonstrate ultrafast spin–phonon coupling dynamics in multiferroic 0.58BiFeO_(3)-0.42Bi_(0.5)K_(0.5)TiO_(3)(BF-BKT)single crystals.With ultrafast laser pumping,coherent acoustic phonons with low damping are created in BF-BKT.Temperature-dependent results indicate that both the frequency and amplitude of laser-induced coherent phonons are sensitive to the emergence of antiferromagnetic order.Moreover,the spin state change driven by external magnetic felds can enhance the oscillation amplitude of the coherent acoustic phonons even above the magnetic Néel temperature.These fndings experimentally confrm that spin–phonon coupling in multiferroic materials exists not only in the spin-ordered state but also in the spin-disordered state,and not only in the equilibrium state but also in the non-equilibrium state excited by ultrafast lasers,suggesting their promising applications in high-frequency devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.12574067,61827815)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515030086)+1 种基金Shenzhen Science and Technology Innovation Commission(Grant Nos.JCYJ20250529085144002,JCYJ20220531102601004,KOTD20180412181422399)Shenzhen University 2035 Program for Excellent Research(Grant No.2023C010).
文摘Achieving polarization switching in wurtzite(wz)crystals has long been hindered by substantial energy barriers and high coercive electric fields.Here,we demonstrate that an in-plane ferroelectric(FE)switch can be triggered within the(0001)crystallographic plane,through the discovery of hiddenAbm2 and Pmc2_(1)monolayer phases.The structural self-reconstruction,induced by lattice expansion,converts interfacial covalent bonds into van der Waals interactions,enabling facile exfoliation of wz monolayers.These monolayers exhibit multiferroic order and diverse electronic functionalities,including giant spin splittings(~540 meV),transition between half-metal and semiconductor,and wide band gaps(0–4.57 eV).Importantly,the FE transition can be finely tuned via a transient state,leading to significant reductions in the barrier energy(<~3 meV/atom)and coercive field(~0.6–1.0 MV/cm),and yielding fully electric control of 100%spin polarization.Our study provides in-depth insights into the inplane FE mechanism in wz systems,opening new avenues for the design and discovery of wz-based FE devices,as well as the rich physics in tetrahedral semiconductors.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB921500)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07030300)the National Natural Science Foundation of China(Grant No.11574378)
文摘The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.
基金Project supported by the National Basic Research Program of China (Grant No. 2012CB619401)the National Natural Science Foundation of China (Grant Nos. 51222104 and 51071117)the Fundamental Research Funds for Central Universities
文摘Ferromagnetic transition has generally been considered to involve only an ordering of magnetic moment with no change in the host crystal structure or symmetry, as evidenced by a wealth of crystal structure data from conventional X-ray diffractometry （XRD）. However, the existence of magnetostriction in all known ferromagnetic systems indicates that the magnetic moment is coupled to the crystal lattice; hence there is a possibility that magnetic ordering may cause a change in crystal structure. With the development of high-resolution synchrotron XRD, more and more magnetic transitions have been found to be accompanied by simultaneous structural changes. In this article, we review our recent progress in understand- ing the structural change at a ferromagnetic transition, including synchrotron XRD evidence of structural changes at the ferromagnetic transition, a phenomenological theory of crystal structure changes accompanying ferromagnetic transitions, new insight into magnetic morphotropic phase boundaries （MPB） and so on. Two intriguing implications of non-centric symmetry in the ferromagnetic phase and the first-order nature of ferromagnetic transition are also discussed here. In short, this review is intended to give a self-consistent and logical account of structural change occurring simultaneously with a ferromagnetic transition, which may provide new insight for developing highly magneto-responsive materials.
基金support fromthe National Natural Science Foundation of China(Grants No.12404267,No.12404048,No.12404104).
文摘Two-dimensional(2D)intrinsic multiferroics have attracted considerable attention for the next generation of advanced information technologies.Herein,we report that bilayer Janus FeSCl,a novel 2D system designed by substituting sulfur in monolayer 1T-FeCl_(2),exhibits a giant spontaneous valley polarization and intrinsic magnetoelectric coupling.This Janus structure exhibits a ground-state bilayer structure that breaks space-inversion symmetry,enabling sliding ferroelectricity.Each monolayer displays robust intralayer ferromagnetic ordering,while the bilayer hosts interlayer antiferromagnetic alignment with opposing magnetic moments.Crucially,ferrovalley-mediated coupling links ferroelectric polarization and antiferromagnetic order,allowing electric-field-driven magnetic reversal.Notably,the direction of the net magnetic moment can be reversed through ferroelectric polarization switching,enabling nonvolatile control of the magnetism.The elucidated mechanisms are generalizable to diverse 2D material families,offering a universal framework for designing atomic-scale multiferroics.This work not only establishes foundational insights into 2D multiferroics but also advances the understanding of coupled charge-spin-valley physics in low-dimensional systems.
基金This work was supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project, the Ministry of Education of China （No.708070）, the National Natural Science Foundation of China （No.10874046 and No.11104081）, and the Fundamental Research Funds for the Central Universities （No.2012zz0078）.
文摘Bi1-xYbxFeO3（0〈x〈0.2） powders have been synthesized using a sol-gel method. The X- ray diffraction data show a structural transition from the rhombohedral R3c phase to the orthorhombic Pnma phase between x=0.1 and 0.125, which should induce a ferroelectric- paraelectric transformation. The phase transition is also proven by the Raman spectroscopy. A moderate signal on magnetization appears to illustrate the enhancement of magnetization at the transformation boundary, which is suggested to be the destruction of the spin cycloid structure at low concentration. The appearance of antiferromagnetic ordering is proposed to account for the afterward reduction of the magnetization at high concentration.
