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Magnetic Control of Ferroelectric Polarization
Abstract
The magnetoelectric effect--the induction of magnetization by means of an electric field and induction of polarization by means of a magnetic field--was first presumed to exist by Pierre Curie, and subsequently attracted a great deal of interest in the 1960s and 1970s (refs 2-4). More recently, related studies on magnetic ferroelectrics have signalled a revival of interest in this phenomenon. From a technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate materials is limited and the effects are typically too small to be useful in applications. Here we report the discovery of ferroelectricity in a perovskite manganite, TbMnO3, where the effect of spin frustration causes sinusoidal antiferromagnetic ordering. The modulated magnetic structure is accompanied by a magnetoelastically induced lattice modulation, and with the emergence of a spontaneous polarization. In the magnetic ferroelectric TbMnO3, we found gigantic magnetoelectric and magnetocapacitance effects, which can be attributed to switching of the electric polarization induced by magnetic fields. Frustrated spin systems therefore provide a new area to search for magnetoelectric media.
... Magnetoelectric multiferroics offer a promising avenue for the terahertz BPVE by using magnetic excitations strongly coupled with the electronic states. The basic concept of contemporary multiferroics is parity breaking by long-range spin orders, resulting in the magnetically induced ferroelectricity and chirality [8][9][10] . In multiferroics, the Nature Communications | (2024) 15:4699 1 1234567890():,; 1234567890():,; ...
... Magnetoelectric multiferroics offer a promising avenue for the terahertz BPVE by using magnetic excitations strongly coupled with the electronic states. The basic concept of contemporary multiferroics is parity breaking by long-range spin orders, resulting in the magnetically induced ferroelectricity and chirality [8][9][10] . In multiferroics, the composite states of magnetic and ferroelectric orders exhibit versatile magnetoelectric phenomena beyond conventional ferroic materials 11,12 . ...
Direct conversion from terahertz photon to charge current is a key phenomenon for terahertz photonics. Quantum geometrical description of optical processes in crystalline solids predicts existence of field-unbiased dc photocurrent arising from terahertz-light generation of magnetic excitations in multiferroics, potentially leading to fast and energy-efficient terahertz devices. Here, we demonstrate the dc charge current generation from terahertz magnetic excitations in multiferroic perovskite manganites with spin-driven ferroelectricity, while keeping an insulating state with no free carrier. It is also revealed that electromagnon, which ranges sub-terahertz to 2 THz, as well as antiferromagnetic resonance shows the giant conversion efficiency. Polar asymmetry induced by the cycloidal spin order gives rise to this terahertz-photon-induced dc photocurrent, and no external magnetic and electric bias field are required for this conversion process. The observed phenomena are beyond the conventional photovoltaics in semi-classical regime and demonstrate the essential role of quantum geometrical aspect in low-energy optical processes. Our finding establishes a paradigm of terahertz photovoltaic phenomena, paving a way for terahertz photonic devices and energy harvesting.
... In fact, the typical electric polarization amplitude in multiferroics is three orders of magnitude smaller than that in ferroelectrics. Even for prototypical type II multiferroics such as TbMnO3 [2] the exact structure in the multiferroic state is not experimentally available, even though indirect experimental methods found some extremely small distortions [3]. As the build up of an electric polarization is hindered in conductive materials, it is not straightforward to test if such materials exhibit an intrinsic polarization. ...
... TbMnO3 where the spins rotate only along the wave vector q. [2] The scattering intensity from a single domain state of a cycloid will show circular dichroic contrast in the magnetic diffraction signal as observed in the cycloidal order of TbMnO3, [25], [26]. The dichroic contrast will be strongly dependent on the azimuthal angle defined by the angle between the ...
The interaction of magnetic order and ferroelectric polarization is a fundamental coupling with the prospect for the control of electronic properties and magnetism. The connection among magnetic order, charge localization and associated metal-insulator transition (MIT) is another cornerstone for materials control. Materials that combine both effects are therefore of great interest but so far not established. One of the classes of materials proposed to combine these functionalities is the family of RNiO 3 (R: lanthanide or Y), whose members show a clear MIT and an antiferromagnetic ground state, and for which an electric polarization has been predicted. Here, we show by resonant magnetic x-ray scattering with circular polarization that YNiO 3 does not only possess a magnetic structure containing domains of spin-rotations that are consistent with the occurrence of electric polarization, but also that there is a significant magnetoelectric interaction that allows manipulation of magnetic domains by an electric field. This shows that charge ordered RNiO 3 are magnetoelectric multiferroics with a MIT.
... Device applications require not only an understanding of the physical mechanisms behind material properties, but also the possibility of controlling or switching them. In the particular case of spintronics, which focuses on manipulating spin-related properties in materials, numerous mechanisms have been proposed to achieve spin polarization (SP) control [1][2][3][4] , including band topological effects 5,6 , magnetoelectric effects [7][8][9] , and spin-orbit coupling (SOC) [10][11][12][13][14][15] . One of the most studied SOC-driven phenomena is the SP induced by the breaking of the inversion symmetry, e.g., the Rashba effect in polar compounds [16][17][18] . ...
The control of the spin degree of freedom is at the heart of spintronics, which can potentially be achieved by spin-orbit coupling or band topological effects. In this paper, we explore another potential controlled mechanism under debate: the spin-deformation coupling (SDC) - the coupling between intrinsic or extrinsic geometrical deformations and the spin degree of freedom. We focus on polar-deformed thin films or two-dimensional compounds, where the Rashba spin-orbit coupling (SOC) is considered as an $SU(2)$ non-Abelian gauge field. We demonstrate that the dynamics between surface and normal electronic degrees of freedom can be properly decoupled using the thin-layer approach by performing a suitable gauge transformation, as introduced in the context of many-body correlated systems. Our work leads to three significant results: (i) gauge invariance implies that the spin is uncoupled from the surface's extrinsic geometry, challenging the common consensus; (ii) the Rashba SOC on a curved surface can be included as an $SU(2)$ non-Abelian gauge field in curvilinear coordinates; and (iii) we identify a previously unnoticed scalar geometrical potential dependent on the Rashba SOC strength. This scalar potential, independent of spin, represents the residual effect remaining after decoupling the normal component of the non-Abelian gauge field. The outcomes of our work open novel pathways for exploring the manipulation of spin degrees of freedom through the use of the SDC.
... The magnetic properties of rareearth doped perovskite and semi-metal nano-composite prepared by sol-gel technique have potential applications in memory and spintronic devices [3]. There are number of magnetoelectric multiferroic materials namely Cr 2 O 3 [6], TbMnO 3 [7], TbMn 2 O 5 [8], YMnO 3, HoMnO 3 [9], and BiFeO 3 [10] available as chemical compounds [5,11]. Unfortunately, most of these materials had shown ferroelectric and ferromagnetic properties at very low temperatures. ...
Lanthanum and cobalt-incorporated BiFeO3 (BFO) nanomaterials have been prepared and their structural, dielectric, and multiferroic properties have been reported here. Bi1-xLaxFe1-xCoxO3 (x = 0, 0.03, 0.06, 0.09, 0.12) nanomaterials have been synthesized successfully through a simple solvothermal technique. XRD and Rietveld refinement analysis using the FullProf Software confirms that all synthesized materials follow the rhombohedral perovskite crystal structure of the R3c space group. The variations of dielectric properties with frequency at room temperature and with temperature at different frequencies have been observed for the temperature range 35 °C to 360 °C. Impedance analysis has also been performed to indicate the contributions of grain, grain boundary, etc. of the samples in the electrical conduction process. The Nyquist plot gives information on the conduction mechanism of all synthesized samples, where grain, grain boundary, and electrode effects are present. The frequency-dependent AC conductivity behavior strongly follows Jonscher’s universal law. The enhancement of magnetic properties has been observed for the doped samples from the study of room temperature magnetic hysteresis loop using SQUID. The improvement in magnetoelectric coupling and energy storage efficiency has been observed for doped nanocompounds from the measurement of magneto-capacitance and P-E loop, respectively. The observed properties of the co-doped BFO nanomaterials are very useful for energy storage and spintronic devices.
... Since the early study in 1950s [29], various bulk multiferroic materials have been discovered [30,31], such as BiFeO 3 [32][33][34][35], BiMnO 3 [36], Pb(Fe 1/2 Nb 1/2 )O 3 [37,38] and TbMnO 3 [39][40][41][42]. While type-I multiferroic is commonly referred to the multiferroic materials with different ferroic orders disentangled from each other, the ferroelectric polarizations in type-II multiferroic are induced by specific magnetic textures through the inverse Dzyaloshinskii-Moriya (DM) mechanism [43,44], the spin-dependent p-d hybridization [45,46] or the exchange striction [47]. ...
The ferroelectric polarization in van der Waals multiferroic NiI2 is believed to be induced by the helimagnetic spin order. The formation of the helimagnetic ground spin configuration and the properties of its spin excitation are yet to be clarified. In the present work, we explore the proper magnetic ground states with well-defined magnon spectra in a single layer NiI2, by analyzing the role of different interactions. While the spin frustration due to the ferromagnetic and antiferromagnetic exchange terms stabilizes a helimagnetic phase, the anisotropic Kitaev interaction introduces a canting of the spin rotation plane. We find the modulation vector of the helimagnetic structure can be continuously oriented within the atomic plane by the competition between the Kitaev interaction and the third-nearest-neighbor exchange. The calculation of magnon spectrum reveals anomalous features with soft magnons at finite wave vectors, which is found to be related with the vibration of the canting plane. From the finite-temperature calculation of the magnon spectra, we predict a magnetic phase transition driven by soft magnons, which cause a spatial modulation of the canting plane. Furthermore, a sign change is predicted in the temperature dependence of the transverse magnon thermal conductivity. Our results provide a comprehensive understanding of the spin ground state and the soft magnons in the van der Waals NiI2.
... In magnetoelectric multiferroics, a magnetic order coexists and interacts with a ferroelectric one. Several microscopic scenarios of why such coexistence may occur and how the magnetic order can affect the electric polarization have been established [1][2][3][4][5] and the work is rapidly progressing in this direction. Understanding such interactions between the magnetic and electric degrees of freedom is of great importance from both the fundamental and practical points of view. ...
Magnetoelectric multiferroics are key materials for next-generation spintronic devices due to their entangled magnetic and ferroelectric properties. Spiral multiferroics possess ferroelectric polarization and are particularly promising for electric control of magnetism and magnetic control of ferroelectricity. In this work, we uncover long-period incommensurate states characterized by unique multiferroic kinks in corundum nickelate Ni 2 InSbO 6 , a member of a promising family of polar magnets. Utilizing a 2-orbital S = 1 model, we derive formulas for Heisenberg and anisotropic magnetic exchanges and magnetically-induced polarization, enabling their calculations from first principles. We use these parameters in Monte Carlo and Landau theory-based calculations to reproduce experimentally observed magnetic structures and polarization dependence on the magnetic field. We predict magnetic phase transitions between flat spiral, conical spiral, canted antiferromagnetic and ferromagnetic states under increasing magnetic fields. Kinks in the spiral phases repel each other through a Yukawa-like potential arising from exchange of massive magnons. We also find that suitably directed electric fields can be used to stabilize the ferromagnetic and spiral states. The findings open a new pathway to predictive first-principles modelling of multiferroics and will inspire experiments and technological applications based on multiferroic kinks.
... Several ways to circumvent the incompatibility between ferroelectricity and magnetism proved to be effective. The covalent bonding between magnetic and ligand ions can lead to a polar lattice distortion, if the competing lattice instabilities are suppressed by strains and chemical substitutions 54 , which explains ferroelectricity in Sr 1−x Ba x MnO 3 and Sr 1−x Ba x Mn 1−y Ti y O 3 55,56 strongly coupled to an antiferromagnetic ordering of Mn spins. Ferroelectricity and magnetism coexist in compounds with both magnetic and non-magnetic transition metal ions, such as BiFeO 3 57 , and improper ferroelectrics, e.g. ...
The simultaneous presence of ferroelectricity and magnetism in multiferroics breaks both spatial inversion and time reversal symmetries at the macroscopic scale, which opens the door to many interesting phenomena and resembles the violation of these symmetries in particle physics. The symmetry breaking in multiferroics occurs spontaneously at phase transitions rather than at the level of fundamental interactions, and thus can be controlled. Moreover, each crystal is a universe in itself with a unique set of symmetries, coupling constants and ordered patterns, which presents plenty of opportunities to find and design materials with strong magnetoelectric coupling.
... In recent years, thin films of the rare earth perovskite RMnO 3 exhibiting multiferroicity have gained significant attention among researchers due to their potential in memory storage, spintronics and sensors [1][2][3][4]. The term multiferroics refers to materials that exhibit any two or all three of the ferroic orders namely ferromagnetism, ferroelectricity and ferroelasticity within a single phase [5][6][7]. Depending on the atomic size of the rare earth ions RE (La -Dy)/ RE (Ho -Lu), Mn-based perovskites exhibit a structural dissimilarity of orthorhombic and hexagonal symmetries, respectively. Manipulating these compounds into thin film enables us to engineer their physio-chemical behaviour. ...
GdMnO3 (GMO) thin films were sputtered using an RF Magnetron unit on Quartz substrates. Films post-annealed for 12 h at 750 ℃ and 850 ℃ confirm the orthorhombic structure with pbnm symmetry. The increase in temperature of the films increases their crystallinity and grain size. Raman study substantiates the results of XRD. Annealing at higher temperatures shows a broadening in Raman peaks along with a right shift in the active modes. XPS anlaysis revelas the presense of Mn with Mn³⁺ and Mn⁴⁺ oxidation state. The AFM topography images show increased values in average roughness, root mean square roughness, Kurtosis, skewness and Shannon entropy as a function of rising temperature values. The second-order transition from the incommensurate antiferromagnetic phase to the canted A-type commensurate antiferromagnetic phase is observed. The magnetization value is found to be higher for the film annealed at 850 ℃, whereas the film annealed at 750 ℃ exhibits spin glass behaviour.
... One of the most prominent examples for this is the orthorhombic (Pbnm) perovskite TbMnO3 (TMO). 5 Spin frustration leads to a complex magnetic order that breaks inversion symmetry. 6 Below TN1 = 41K, the magnetic structure of TMO adopts a sinusoidal spin-density wave configuration, wherein all spins are aligned parallel to the b-axis. ...
The multiferroic properties of TbMnO3 demonstrate high versatility under applied pressure, making the material potentially suitable for use in flexible electronics. Here, we report on the preparation of elastic freestanding TbMnO3 membranes with dominant (001) or (010) crystallographic out-of-plane orientation. Membranes with thickness of 20 nm display orthorhombic bulk-like relaxed lattice parameters with strong suppression of twinning for the (010) oriented membranes. Strain in flexible membranes was tuned by using a commercial strain cell device and characterized by Raman spectroscopy. The B1g out-of-phase oxygen-stretching mode, representative for the Mn-O bond distance, systematically shifts to lower energy with increasing strain (epsilon{max} ~ 0.5 %). The flexibility and elastic properties of the membranes allow for specific manipulation of the multiferroic state by strain, whereas the choice of the crystallographic orientation gives possibility for an in- or out-of-plane electric polarization.
... [16][17][18][19][20][21] Among these, the representative of single-phase multiferroics is type-I multiferroics BiFeO 3 22-26 and type-II multiferroics TbMnO 3 . [27][28][29][30][31] In type-I multiferroic materials, the magnetoelectric coupling is weak due to the distinct origins of ferromagnetism and ferroelectricity. 22,32 On the other hand, in type-II multiferroics, the ferroelectricity originates from a super spin current formed by specific spin-ordered states along with spatial polarization resulting from charge order. ...
The emergence of multiferroic materials, which possess both ferromagnetic (FM) and ferroelectric (FE) properties, drive advancements in magnetoelectric applications and the next generation of spintronics. Based on first-principles calculations, we investigate an engineered two-dimensional multiferroic van der Waals heterostructures consisting of FM VSiSnN4 monolayer (ML) and fully hydrogenated FE AlN bilayer. We find that the magnetic anisotropy of VSiSnN4 ML is tunable between out-of-plane and in-plane, and a phase transition between semiconductor and metal is induced in VSiSnN4/AlN bilayer when the FE polarization direction of AlN bilayer is reversed. Surprisingly, when the FE polarization of AlN bilayer is upward, the Curie temperature of VSiSnN4/AlN bilayer can be significantly increased from 204 to 284 K. Such nonvolatile and tunable magnetic anisotropy, Curie temperature, and band alignment in VSiSnN4/AlN multiferroic heterostructure are highly promising for future low-current operation of data storage and logic devices.
... Magnetoelectric (ME) effects enable the manipulation of magnetic (electric) properties using electric (magnetic) fields, which is of interest in terms of both fundamental physics and potential spintronic applications [1,2]. ME manipulations can be achieved by multiferroic materials exhibiting magnetic and electric orders [3]. ...
A recent experiment reported type-II multiferroicity in monolayer (ML) NiI2 based on a presumed spiral magnetic configuration (spiral-B), which is, as we found here, under debate in the ML limit. Freestanding ML NiI2 breaks its C3 symmetry, as it prefers a striped antiferromagnetic order (AABB-AFM) along with an intralayer antiferroelectric (AFE) order. However, substrate confinement may preserve the C3 symmetry and/or apply tensile strain to the ML. This leads to another spiral magnetic order (spiral−IVX), while bilayer shows a different order (spiral−VX) and spiral-B dominates in thicker layers. Thus, three multiferroic phases, namely, spiral-B+FE, spiral−IVX+FE, spiral−VX+FE, and an antimultiferroic AABB-AFM+AFE one, show layer thickness dependence and geometry-dependent dominance, ascribed to competition among thickness-dependent Kitaev, biquadratic, and Heisenberg spin-exchange interactions and single-ion magnetic anisotropy. Our theoretical results clarify the debate on the multiferroicity of ML NiI2 and shed light on the role of layer stacking induced changes in noncollinear spin-exchange interactions and magnetic anisotropy in thickness-dependent magnetism.
... This proposal shines a light on the construction of 2D multiferroics with 1 Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-sen University, Guangzhou 510275, China. 2 State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, 510275 Guangzhou, China. 3 Centre for Physical Mechanics and Biophysics, Sun Yat-Sen University, Guangzhou 510275, China. e-mail: luox77@mail.sysu.edu.cn a different coupling mechanism, which have been implemented in a range of materials including 2H-VS 2 22 , 1T-FeCl 2 23 , VSi 2 P 4 24 , MnBi 2 Te 4 25 , YI 2 26 and MnSe 27 . ...
The emergence of magnetic transition metal dichalcogenides has significantly advanced the development of valleytronics due to the spontaneous breaking of time-reversal symmetry and space-inversion symmetry. However, the lack of regulation methods has prevented researchers from exploring their potential applications. Herein, we propose to use strain engineering to control the spin-valley coupling in the sliding ferroelectric bilayer 2H-VX 2 (X = S, Se, Te). Four multiferroic states are constructed by combining the sliding ferroelectricity and antiferromagnetism in the R-stacking bilayer VX 2 , where the spin and valley polarizations are coupled together from the layer-dependent spin-polarized band structures. By applying a small external strain or pressure on the out-of-plane van der Waals direction, we predicted that there is an antiferromagnetic to magnetic transition in the bilayer VX 2 , leading to the interesting spin-polarized and chiral circularly polarized radiation at K + and K - valleys, similar to those found in the magnetic monolayer. To comprehend the coupling between various degrees of freedom in these multiferroic systems, we have developed an effective k·p model. This model unveils a linear relationship between the electric polarization generated by interlayer sliding and the energy difference of the valence band maximum at K + and K - valleys. Thus, providing an alternate method to measure the electric polarization in the sliding ferroelectrics. Based on the strong coupling between the strain, spin-valley, and electric polarization, it is likely to use the strain to control the interesting emerging properties of 2H-VX 2 such as the anomalous valley Hall effect.
... T. Kimura et al. verified that TbMnO 3 displays spherical spin order with a 10% MD ratio at -261 °C in a 6 T magnetic field. [7]. At room temperature, MF composites have a much better MD effect than single phase materials because the performance attributes of composites are those that each of their constituent components cannot accomplish on their own [8]. ...
In the present study, the effect of the composites made up of magnetostrictive Co0.9Ni0.1Fe2O4 (CNFO) and colossal magnetoresistive La0.67Sr0.33MnO3 (LSMO) ferrites with the ferroelectric solid solution of 0.5Ba0.7Ca0.3TiO3-0.5BaZr0.2Ti0.8O3 (0.5BCT-0.5BZT) on the multiferroic properties are studied comparatively. Here, the magnetodielectric (MD) composite of 0.5(CNFO)-0.5(0.5BCT-0.5BZT) and 0.175(LSMO)-0.825(0.5BCT-0.5BZT) investigated comparatively using various characterization techniques. The simple and low-cost hydroxide co-precipitation method was used for the synthesis of individual constituents of the ferroelectric 0.5BCT-0.5BZT and ferromagnetic CNFO and LSMO. Structural studies of composites verified the existence of ferrite and ferroelectric phases. The microstructure displays the LSMO and CNFO particles arranged in close proximity over the BCT-BZT ferroelectric phase. The dielectric constant and tangent loss (Quality factor) variation of the composites were investigated for 100 Hz to 1 MHz frequency from room temperature to higher temperatures upto 500 °C. The magnetic hysteresis plot can be used to study how the composite saturation magnetization increases with an increase in ferrite content. Magnetocapacitance measurements up to 1 Tesla magnetic field gives 7% and 2.5% MD coefficients for the both composite materials.
... Exploring quantum states of matter in extreme conditions, such as low temperatures, high magnetic fields, and high pressures, is one of the central topics in condensed matter physics. Among them, field-induced phases have been extensively investigated, for example, spin-lattice-coupled magnetization plateaus in frustrated spin systems [1][2][3][4], field-induced flop of the spin-driven electric polarization in multiferroics [5,6], and spin-nematic states in quantum spin systems [7,8]. Neutron scattering is one of the most powerful techniques to study these exotic phenomena because it can probe Fourier-transformed time-space correlation functions of atomic positions and magnetic moments; specifically crystal and magnetic structures are determined by the elastic scattering, and phonons and magnons are measured by the inelastic scatterings. ...
We present proof-of-principle experiments of stroboscopic time-of-flight (TOF) neutron diffraction in long pulsed magnetic fields. By utilizing electric double-layer capacitors, we developed a long pulsed magnet for neutron diffraction measurements, which generates pulsed magnetic fields with the full widths at half maximum of > 10 2 ms. The field variation is slow enough to be approximated as a steady field within the time scale of a polychromatic neutron pulse passing through a sample placed in a distance of the order of 10 1 m from the neutron source. This enables us to efficiently explore the reciprocal space using a wide range of neutron wavelength in high magnetic fields. We applied this technique to investigate field-induced magnetic phases in the triangular lattice antiferromagnets CuFe 1 − x Ga x O 2 ( x = 0 , 0.035 ).
Published by the American Physical Society 2024
... Usually, MF materials are a class of materials where at least two ferroic orders (ferroelectric, ferromagnetic/anti-ferromagnetic/ferrimagnetic, or ferroelastic) coexist, and subsequently, coupling happens between any two ferroic orders. [25][26][27] An MF material is typically divided into two categories: (i) single-phase MF material in which the ferroelectric (FE) and ferromagnetic (FM) phases naturally coexist and magnetoelectric (ME) coupling occurs directly between the FE and FM phases, 28,29 and (ii) double-phase MF material produced artificially by merging the FM and FE phases in the form of an FM/FE heterostructure system in which neither the FM nor the FE phase exhibits multiferroicity, but the system as a whole exhibit multiferroic property due to the ME coupling accomplished indirectly via induced strain. 30,31 In the FM/FE heterostructure, the application of an electric field across the thickness of the bottom FE layer produces electrostrictive strain in the FE film due to the converse piezoelectric effect (CPE). ...
We have fabricated the ZnFe2O4/ZnO (ZFO/ZnO) heterostructure on a silicon substrate by pulsed laser deposition technique and studied the magnetization switching by the electric field in the ZFO/ZnO heterostructure using an indigenously developed optical cantilever beam magnetometer setup. The magnetization (M) vs electric field (E) curve reveals that the magnetization of the ZFO film has been switched by an electric field applied along the thickness of the ZnO film. The saturation magnetization is found to be 28.77 MA/m from the M–E curve. The emergence of electric field-driven magnetization switching in the ZFO/ZnO heterostructure is attributed to the strain-mediated magnetoelectric coupling between the electric polarization of the ZnO film and the magnetization of the ZFO film as evidenced by the butterfly-type hysteresis behavior of magnetization with the applied electric field. However, the realization of electric field-controlled magnetization switching in the ZFO/ZnO heterostructure is regarded as a potential aspect for the fabrication of energy-efficient spintronic devices such as magnetoelectric random access memory cells, highly sensitive magnetic field sensors, magneto-logic devices, and neuromorphic devices.
... 7-11 ME laminates exhibit electrical polarization induced by transferred strain from the MS phase under magnetic stimulation and vice versa. [12][13][14][15] ME laminates are classified according to the type of materials used as the Electrostatically induced β-phase alignment in the PVDF/thermally annealed CoFe 2 O 4 /Ni magnetoelectric laminates PE phase. 16,17 Polymer-based ME laminates comprising PE polymers (e.g., poly(vinylidene fluoride) [PVDF] and its copolymers) have been actively investigated for the development of electronic devices because of their advantages such as flexibility, biocompatibility, easy and low-cost processing, and excellent electrical properties. ...
... Compounds of this family containing mag-netic ions in the В sublattice of perovskite, such as PCN, PNN, and PNT, received much less investigation. These compounds have attracted attention in the early 2000s after the discovery of multiferroics [6] and relaxor multiferroics, including the compound PbFe 1/2 Nb 1/2 O 3 [7]. It was assumed that the crystals of PCN, PNN, and some other relaxors of this family exhibit both magnetic and ferroelectric ordering. ...
The structure of the relaxor ferroelectrics PbNi1/3Ta2/3O3 (PNT) was studied by powder X-ray diffraction. The measurements were performed at 313.5 ± 1 K using a powder, which was prepared by grinding PNT single crystals grown by the spontaneous crystallization. The structure refinement and the fitting of the simulated diffraction pattern to the experimental data were performed by the Rietveld method. It was demonstrated that the grown crystals of PNT have a perovskite structure (sp. gr. Pm3m (221), a = 4.02679(2) Å). Polarized Raman spectra of PNT were recorded at room temperature. The main modes of the light scattering spectra were assigned to the Е1 and А1 components of the transverse optical phonon (ТО1) and the А1 component of the longitudinal optical phonon (LO3). The temperature dependence of the dielectric susceptibility shows a broad frequency-dependent anomaly with a maximum at 89 К at a frequency of 1 kHz.
... To date, the type I multiferroic BiFeO3 is the only known room-temperature singlephase multiferroic material. Alternatively, the helical magnetic orders break the spatial inversion symmetry and simultaneously lead to electric orders 7,8 , giving rise to type-II multiferroics. The quest for a new single-phase multiferroic remains an open challenge. ...
Multiferroic materials with a coexistence of ferroelectric and magnetic order have been intensively pursued to achieve the mutual control of electric and magnetic properties toward energy-efficient memory and logic devices. The breakthrough progress of 2D van der Waals magnet and ferroelectric encourages the exploration of low dimensional multiferroics, which holds the promise to understand inscrutable magnetoelectric coupling and invent advanced spintronic devices. However, confirming ferroelectricity with optical techniques is challenging on 2D materials, particularly in conjunction with antiferromagnetic orders in a single-layer multiferroic. The prerequisite of ferroelectric is the electrically switchable spontaneous electric polarizations, which must be proven through reliable and direct electrical measurements. Here we report the discovery of 2D vdW multiferroic with out-of-plane ferroelectric polarization in trilayer NiI2 device, as revealed by scanning reflective magnetic circular dichroism microscopy and ferroelectric hysteresis loop. The evolutions of between ferroelectric and antiferroelectric phase have been unambiguously observed. Moreover, the magnetoelectric interaction is directly probed by external electromagnetic field control of the multiferroic domains switching. This work opens up opportunities for exploring new multiferroic orders and multiferroic physics at the limit of single or few atomic layers, and for creating advanced magnetoelectronic devices.
... In this spirit, multiferroics are potentially of great interest, since they display broken inversion symmetry and a ferroelectric polarization that can be switched by the application of an electric field, which in turn allows for control of the magnetism and, potentially, the magnons. The idea that multiferroics could be promising candidates for magnonic manipulation has been considered for some time 6,20 , but despite this early interest, observation and manipulation of magnon transport in multiferroics-that is, the capability to manipulate spin transport via ferroelectric polarization reversal and resultant DMI switching-remain elusive. ...
A magnon is a collective excitation of the spin structure in a magnetic insulator and can transmit spin angular momentum with negligible dissipation. This quantum of a spin wave has always been manipulated through magnetic dipoles (that is, by breaking time-reversal symmetry). Here we report the experimental observation of chiral spin transport in multiferroic BiFeO3 and its control by reversing the ferroelectric polarization (that is, by breaking spatial inversion symmetry). The ferroelectrically controlled magnons show up to 18% modulation at room temperature. The spin torque that the magnons in BiFeO3 carry can be used to efficiently switch the magnetization of adjacent magnets, with a spin–torque efficiency comparable to the spin Hall effect in heavy metals. Utilizing such controllable magnon generation and transmission in BiFeO3, an all-oxide, energy-scalable logic is demonstrated composed of spin–orbit injection, detection and magnetoelectric control. Our observations open a new chapter of multiferroic magnons and pave another path towards low-dissipation nanoelectronics.
... Multiferroics are characterized by the coexistence and/or coupling of ferromagnetic, ferroelectric and ferroelastic (spin, polarization and phonon) ordering in a single phase material [1,2]. The modification of magnetic ordering by electric field or electric ordering by magnetic field in magnetoelectric multiferroics has dragged a great deal of attention among the researchers to study not only it's fascinating properties but also to use in various potential applications such as memory devices, sensors, spin valve etc. [3][4][5]. In this class of materials, perovskites are extensively investigated as it shows a better functionality than other similar materials. ...
... Despite the tremendous success in classifying and revealing multiferroic mechanisms in paradigmatic bulk systems, viz. type-I multiferroics with nearly independent magnetism and ferroelectricity 2 and type-II multiferroics originated from Dzyaloshinskii-Moriya interaction and other types of magnetic orderings such as collinear magnetic structures [3][4][5] , the quest for a room-temperature multiferroic with efficient coupling between magnetism and ferroelectricity remains as the holy grail of the resurgent field. Recent studies on magnetism and ferroelectricity in two-dimensional (2D) van der Waals (vdW) crystals open unparalleled opportunities for multiferroic research [6][7][8][9][10] , considering that abundant choices of ferroic atomic layers with single-crystal quality can be readily tuned by electrostatic field, strain, interfaces and spin-lattice interactions [11][12][13][14] . ...
The discovery of various primary ferroic phases in atomically-thin van der Waals crystals have created a new two-dimensional wonderland for exploring and manipulating exotic quantum phases. It may also bring technical breakthroughs in device applications, as evident by prototypical functionalities of giant tunneling magnetoresistance, gate-tunable ferromagnetism and non-volatile ferroelectric memory etc. However, two-dimensional multiferroics with effective magnetoelectric coupling, which ultimately decides the future of multiferroic-based information technology, has not been realized yet. Here, we show that an unconventional magnetoelectric coupling mechanism interlocked with heterogeneous ferrielectric transitions emerges at the two-dimensional limit in van der Waals multiferroic CuCrP2S6 with inherent antiferromagnetism and antiferroelectricity. Distinct from the homogeneous antiferroelectric bulk, thin-layer CuCrP2S6 under external electric field makes layer-dependent heterogeneous ferrielectric transitions, minimizing the depolarization effect introduced by the rearrangements of Cu⁺ ions within the ferromagnetic van der Waals cages of CrS6 and P2S6 octahedrons. The resulting ferrielectric phases are characterized by substantially reduced interlayer magnetic coupling energy of nearly 50% with a moderate electric field of 0.3 V nm⁻¹, producing widely-tunable magnetoelectric coupling which can be further engineered by asymmetrical electrode work functions.
... The spontaneous polarization is a consequence of the crystal structure of the material, which is typically asymmetric. 30 The external electric field must be greater than a certain threshold value in order to reverse the polarization. 31 The P-E hysteresis loop is a consequence of the ferroelectric domain structure. ...
This study investigates the magnetoelectric coupling effect in dual‐phase multiferroic composites prepared using a solid‐state reaction method. The composites were fabricated with the formula (1− x )Ba₀.₇₇Ca₀.₂₃TiO₃(BCT) + x Ni₀.₆Zn₀.₂₅La₀.₁₅Fe₂O₄(NZLFO), where x varied from 0% to 100% in 10% increments. Ca‐doped BaTiO₃ served as the ferroelectric phase, while La‐doped Ni–Zn ferrite acted as the ferromagnetic phase. The effects of varying ferrite content ( x ) on structural, optical, ferroelectric, electrical, and magnetoelectric properties were comprehensively analyzed. X‐ray diffraction (XRD) with Rietveld refinement revealed a spinel cubic structure for the ferrite phases and a tetragonal structure for the perovskite phases. The study observed a moderate influence of ferrite concentration on the lattice parameters of BCT and an opposing effect on the lattice parameters of NZLFO. Optical measurements indicated higher light absorption in the visible range compared to the UV region and wide optical bandgap. Magnetic properties, characterized by saturation magnetization, exhibited a dependence on temperature, with a Curie temperature ( T c) of 700 K. Electrical resistivity displayed a maximum at x = 50% and remained constant at high frequencies. The study also confirmed the presence of electric polarization induced by a magnetic field, with the highest magnetoelectric coefficient observed at x = 10%. These findings demonstrate the successful fabrication of dual‐phase multiferroic composites with tunable properties through controlled ferrite content. The observed magnetoelectric coupling suggests potential applications in multifunctional devices.
... Such behavior is rarely reported in 2D materials. The presence of such linear and cubic coupling terms in spin polarization without the inclusion of spin-orbit coupling indicates a strong magnetoelectric coupling, which is in great contrast to that found in conventional multiferroic materials such as BiFeO 3 , TbMnO 3 and in known 2D multiferroics 20,22,23,32,34,44,45 . Note that the deviation from the fitting line at the end points is likely due to the instability of Stoner magnetism (see Supplementary Fig. 8), which is another manifestation of strong magnetoelectric coupling. ...
Strong magnetoelectric effects in single-phase two-dimensional (2D) materials are extremely rare in nature. Here by first-principles calculations, we find a strong magnetoelectric coupling in polar stacking bilayer Hf 2 S that allows the reversal of net magnetic moments with the reversal of electric dipoles. Further analysis shows that such strong magnetoelectric effects benefit from the Stoner instability of surface Hf atoms triggered by polar stacking. Moreover, an unexpectedly large out-of-plane electric polarization (which is at least two times larger than that of bilayer BN) survives in the material, despite its metallicity. The large electric polarization is ascribed to the delocalized interlayer electrons which generally present in layered electride materials. It is quite interesting that large electric polarization, metallicity and magnetism coexist in one single-phase material. Our findings reveal rich physical phenomena to be explored in 2D stacking multiferroics and suggest an alternative way of searching for strong magnetoelectric materials with ultrathin thickness.
Parity-time-reversal symmetry ( PT symmetry), a symmetry for the combined operations of space inversion ( P ) and time reversal ( T ), is a fundamental concept of physics and characterizes the functionality of materials as well as P and T symmetries. In particular, the PT -symmetric systems can be found in the centrosymmetric crystals undergoing the parity-violating magnetic order which we call the odd-parity magnetic multipole order. While this spontaneous order leaves PT symmetry intact, the simultaneous violation of P and T symmetries gives rise to various emergent responses that are qualitatively different from those allowed by the nonmagnetic P -symmetry breaking or by the ferromagnetic order. In this review, we introduce candidates hosting the intriguing spontaneous order and overview the characteristic physical responses. Various off-diagonal and/or nonreciprocal responses are identified, which are closely related to the unusual electronic structures such as hidden spin-momentum locking and asymmetric band dispersion.
Spin‐orbit coupling refers to the relativistic interaction between the spin and orbital motions of electrons. This interaction leads to numerous intriguing phenomena, including spin‐orbit torques, spin–momentum locking, topological spin textures, etc., that have recently gained prominence in the field of spin‐orbitronics. In particular, the emerging ferroelectric control is recognized and validated as an effective means to enhance energy efficiency across a broad spectrum of spin‐orbitronic devices. Here, cutting‐edge research on ferroelectric control of spin‐orbitronics (FECSO) by means of spontaneous polarization, reversible ferroelectric switching, and multiferroic coupling, are comprehensively reviewed. Two fascinating topics are mainly discussed: topological spin texture and spin‐charge interconversion. The classification of control mechanisms for different interactions in FECSO is summarized first. Then, from the perspective of material classification, the ferroelectric‐controlled spin‐orbit coupling with tunable topological spin texture in oxide systems, magnetic metal multilayers, and 2D van der Waals materials is reviewed. Subsequently, the ferroelectric‐tunable spin‐charge interconversion on heavy metal layers, oxide interfaces, and ferroelectric Rashba semiconductors is highlighted. In the end, the challenges and forthcoming prospects of FECSO are discussed. This work may provide pertinent and forward‐thinking guidance to accelerate the ongoing advancement of this field.
This review summarizes recent developments in quadruple perovskite oxides, including their preparation strategies, structural characterization, physical properties, and potential applications across diverse technological and scientific domains.
The compound Ba3HoRu2O9 magnetically orders at 50 K (TN1), followed by another complex magnetic ordering at 10.2 K (TN2). The second magnetic phase transition was characterized by the coexistence of two competing magnetic ground states associated with two different magnetic wave vectors (K1=0.500 and K2=0.250.250). The multiferroicity and magnetoelectric coupling were predicted below TN2 in these 4d-based materials. Here, we have discussed the origin of spin-driven ferroelectricity, which is not known yet, and the nature of magnetoelectric domains. We have investigated the compound through time-of-flight neutron diffraction, synchrotron x-ray diffraction (XRD), ac susceptibility, frequency-dependent complex dielectric spectroscopy, and dc magnetization under external pressure. We have demonstrated that the noncollinear structure involving two different magnetic ions, Ru (4d) and Ho (4f), breaks the spatial inversion symmetry via inverse Dzyaloshinskii-Moriya (DM) interaction through strong 4d-4f magnetic correlation, which shifts the oxygen atoms and results in nonzero polarization. Such an observation of inverse DM interaction from two different magnetic ions which cause ferroelectricity is rarely observed. The stronger spin-orbit coupling of 4d orbital might play a major role in creating DM interaction of noncollinear spins. We have systematically studied the spin and dipolar dynamics, which exhibit intriguing behavior with shorter coherence lengths of second magnetic phase associated with the k2 wave vector. The results manifest the development of finite-size magnetoelectric domains instead of true long-range ordering, which justifies the experimentally obtained low value of ferroelectric polarization. The lattice parameters and volume show a sharp anomaly at TN2 obtained by analyzing the temperature-dependence XRD, which is consistent with the ferroelectric transition, predicting a noncentrosymmetric space group, P6¯2c, for this compound. Furthermore, we have investigated the effect of external pressure on this complex magnetism. The result reveals an enhancement of ordering temperature by the application of external pressure (∼1.6 K/GPa). The external pressure might favor stabilizing the magnetic ground state associated with second magnetic phase. Our study shows an unconventional mechanism of spin-driven ferroelectricity involving inverse DM interaction between Ru (4d) and Ho (4f) magnetic ions due to strong 4d−4f cross coupling.
The coupling of ferromagnetic and ferroelectric materials has sparked great interest in the field of spintronics due to nonvolatile electrical magnetic control. In this work, we propose two-dimensional multiferroic MnSe2/In2Se3 van der Waals (vdW) heterostructure to investigate the magnetoelectric coupling. The electronic structure, magnetic anisotropy, magnetic phase transition, and transport properties were investigated by employing the first-principles calculations in combination with the nonequilibrium Green’s function method. The results reveal that polarization reversal not only can effectively tune the Schottky-to-Ohmic contact but also reorients the magnetic easy axis. In addition, Curie temperature (Tc) was predicted based on the Heisenberg model and Monte Carlo simulations, and the competition between interfacial charge injection and lattice mismatch determines the Tc of MnSe2/In2Se3 heterostructure. Furthermore, we constructed the vdW MnSe2/In2Se3-based magnetic-tunnel-junction and ferroelectric-tunnel-junction nanodevice, which exhibits high tunneling magnetoresistance of up to 1.805×103% and a spin-filter efficiency of up to 98.5%. Our findings demonstrate the significant potentials of multiferroic MnSe2/In2Se3 vdW heterostructures in designing a next-generation spintronic and nonvolatile memory device.
We investigate emergent conductive phenomena triggered by collinear antiferromagnetic orderings. We show that an up-down-zero spin configuration in a triangle cluster leads to linear and nonlinear spin conductivities even without the relativistic spin–orbit coupling; the linear spin conductivity is characterized by the Drude-type one, while the nonlinear spin conductivity is characterized by the Hall-type one. We demonstrate the emergence of both spin conductivities in the breathing kagome system consisting of a triangle cluster. The nonlinear spin conductivity becomes larger than the linear one when the Fermi level lies near the region where a small partial band gap opens. Our results indicate that collinear antiferromagnets with the triangle geometry give rise to rich spin conductive phenomena.
The composition-dependent spin exchange interaction in a perovskite-structured Pb(Fe0.5−xNix)Nb1/2O3 system has been studied to understand its multiferroicity at room-temperature. Special emphasis was paid to the magnetic behavior in terms of magnetic moment, interatomic distance, and atomic ordering because they play a key role in the modulation of magnetic multiferroic behavior. We observed that 10 mol. % Ni incorporation led to multiferroic behavior with considerable ferrimagnetic properties (saturation magnetization of 0.6 emu/g and a coercive field of 20 Oe) coupled with the inherent properties of displacive ferroelectricity (spontaneous polarization of 20 μC/cm2). A subsequent increase in the Ni substitution degree degraded the ferroelectricity due to a phase transition from a non-centrosymmetric rhombohedral to a centrosymmetric cubic system. We have shown that magnetic spins with a pronounced magnetic moment along the [001] direction are ferrimagnetically arranged when the interatomic distance between the magnetic transition metals at the octahedral site is less than 4 Å, resulting in significant magnetic properties The objective of this study is to provide a general methodology for modulating magnetic orders in ferroelectric perovskite oxides.
Topological magnon insulators support chiral edge excitations, whose lack of electric charge makes them notoriously difficult to detect experimentally. We show that relativistic magnetoelectric coupling universally renders chiral edge magnons electrically active, thereby facilitating electrical probes of magnon topology. Considering a two-dimensional out-of-plane magnetized topological magnon insulator, we predict a fluctuation-activated electric polarization perpendicular to the sample edges. Furthermore, the chiral topological electromagnons give rise to a unique in-gap signal in electrical absorption experiments. These results suggest THz spectroscopy as a promising probe for topological magnons.
In recent decades, there has been a notable surge in interest surrounding multiferroic perovskite nanoparticle-based materials. These materials have garnered attention due to their unique structural characteristics, which allow for multiple ferroic order parameters simultaneously coexisting within a specific temperature range. This feature promises to enable intriguing interactions between these ferroic order parameters. The appeal of these materials lies in their capacity to efficiently separate carriers through ferroelectric polarization and generate photo-voltages above the bandgap, paving the way for the creation of innovative multifunctional devices for green energy applications. One significant challenge that has emerged is the quest to reduce the bandgap of these materials to photon energies in the visible range while preserving at least one of the ferroic order parameters. We propose an approach involving elemental composition engineering of multiferroic perovskite nanoparticles to tackle this challenge. Specifically, we suggest the substitutional doping of these nanoparticles with suitable transition metal cations to fine-tune the characteristics of the transition metal−oxygen bond. In this chapter, efforts have been made to summarize the diverse effects of nanoparticle doping, shedding light on how they can modify the properties of multiferroic nanoparticle-based perovskites to make them suitable for green energy applications. We will also provide a concise overview of comprehensive modification procedures, offering insight into alternative methods for tuning the properties of perovskite materials. The behavior of BiFeO3 and transition-metal-doped BiFeO3 is discussed as a representative case of perovskite materials.
The emergence of multiferroic materials, which possess both ferromagnetic (FM) and ferroelectric (FE) properties, drive advancements in magnetoelectric applications and the next generation of spintronics. Based on first-principles calculations, we investigate an engineered two-dimensional multiferroic van der Waals heterostructures consisting of FM VSiSnN4 monolayer (ML) and fully hydrogenated FE AlN bilayer. We find that the magnetic anisotropy of VSiSnN4 ML is tunable between out-of-plane and in-plane and a phase transition between semiconductor and metal is induced in VSiSnN4/AlN bilayer when the FE polarization direction of AlN bilayer is reversed. Surprisingly, when the FE polarization of AlN bilayer is upward, the Curie temperature of VSiSnN4/AlN bilayer can be significantly increased from 204K to 284K. Such non-volatile and tunable magnetic anisotropy, Curie temperature and band alignment in VSiSnN4/AlN multiferroic heterostructure are highly promising for future low-current operation of data storage and logic devices.
Photoelectronic devices that utilize ferroelectric polarization offer significant advantages in terms of dipole-modulated charge separation and energy band gap. In this paper, we investigate the unusual photoresponse characteristics of a two-dimensional CuInP2S6 crystal with cation order-disorder mediated phases, namely, paraelectricity, ferroelectricity, and dipolar glass. Notably, the photocurrent demonstrates a clear anisotropic photoresponse in the ferroelectric state, whereas it becomes isotropic with significantly reduced values in the dipolar glass state. This anisotropy-isotropy change can be attributed to ferroelectric frustration within the dipolar glass phase. In addition, the Cu cation ordering at low temperature results in a larger band gap and suppressed photocurrent compared with the paraelectric and ferroelectric phases. This discovery offers valuable insights into understanding the impact of order-disorder phase transitions on the photodetective performance of ferroelectric materials.
Giant spin-induced ferroelectric polarization has been observed in the multiferroic CaMn7O12, the origin of which remains controversial. Various theoretical models have been proposed in this regard, some of which put the preformed orbital order as a prerequisite factor, while others attribute it to the combination of Dzyaloshinskii-Moriya interactions and exchange striction. In this paper, we resolve this issue by replacing Ca with disordered Bi3+/Ag+ ions through high-pressure and high-temperature methods, leading to the successful synthesis of single-phase isostructural (Bi0.5Ag0.5)Mn7O12. No orbital order is observed down to 30 K, while a giant electric polarization of ∼1900µCm−2 is realized below TN≈80 K when the system enters an antiferromagnetically ordered state. The low-temperature spin structure adopts the magnetic point group of 31′, the same as CaMn7O12. Our results strongly indicate that the giant ferroelectric polarization is primarily caused by exchange striction instead of orbital order.
We have investigated the magnetoelectric effect of a series of Y-type hexaferrite Ba0.8Sr1.2Co2Fe11.1−xAl0.9CrxO22 (x ≤ 0.4) at room temperature. Although the magnetoelectric voltage coefficient αE of these multiferroic hexaferrites is not high, it changes rapidly with an applied DC magnetic field, a phenomenon known as the giant magnetotranstance (GMT) effect. It is found that the GMT effect is enhanced with increasing content of Cr and reaches the maximum for x = 0.2. Specifically, the magnetotranstance ratio in the x = 0.2 sample is as high as −96% at 2000 Oe and −84% at 500 Oe. Further addition of Cr content causes a decay of the GMT effect. This kind of room-temperature GMT effect in Y-type hexaferrites opens up a route toward practical applications for the single-phase multiferroics.
Ferroelectricity, which has diverse important applications such as memory elements, capacitors, and sensors, was first discovered in a molecular compound, Rochelle salt, in 1920 by Valasek. Owing to their superiorities of lightweight, biocompatibility, structural tunability, mechanical flexibility, etc., the past decade has witnessed the renaissance of molecular ferroelectrics as promising complementary materials to commercial inorganic ferroelectrics. Thus, on the 100th anniversary of ferroelectricity, it is an opportune time to look into the future, specifically into how to push the boundaries of material design in molecular ferroelectric systems and finally overcome the hurdles to their commercialization. Herein, we present a comprehensive and accessible review of the appealing development of molecular ferroelectrics over the past 10 years, with an emphasis on their structural diversity, chemical design, exceptional properties, and potential applications. We believe that it will inspire intense, combined research efforts to enrich the family of high-performance molecular ferroelectrics and attract widespread interest from physicists and chemists to better understand the structure-function relationships governing improved applied functional device engineering.
Although BiFeO3 is one of the most studied multiferroic materials, recent magnetization and neutron scattering studies have revealed a new magnetic phase in this compound—the transverse conical phase. To study the collective spin excitations of this phase, we performed terahertz spectroscopy in magnetic fields up to 17 T at and above room temperature. We observed five spin-wave branches in the magnetic phase with long-wavelength conical modulation. Using a numerical spin dynamics model, we found two kinds of excitations with magnetic moments oscillating either along or perpendicular to the static fields. Remarkably, we detected strong directional dichroism, an optical manifestation of the magnetoelectric effect, for one spin-wave mode of the conical phase. According to our experiments, the stability of the conical state is sensitive to the magnetic-field history, and it can become (meta)stable at or close to zero magnetic field, which may allow exploiting its magnetoelectric properties at room temperature.
With the discovery of two-dimensional (2D) ferroelectricity and ferromagnetism in van der Waals (vdW) materials, there has been significant interest in 2D multiferroics. Herein, we report the occurrence of weak ferromagnetism and magnetoelectricity in vdW antiferromagnet MnPSe3 single crystals. Our results demonstrate that MnPSe3 undergoes an antiferromagnetic transition at the Néel temperature TN = 70 K with weak ferromagnetism along the [1–10] direction. Detailed magnetoelectric (ME) data show that MnPSe3 exhibits a linear ME tensor αij with nine nonzero components. Additionally, a magnetically induced electric polarization as large as 98.5 μC/m2 is observed along the [110] direction, with a ME coefficient of 13.5 ps/m at 10 K for a magnetic field of 9 T applied along the [110] direction. Importantly, we discuss our experiments based on symmetry and microscopic analysis, thereby suggesting that the spin-dependent p-d hybridization mechanism plays an important role in the emergence of magnetic-field-induced ferroelectricity. Hence, our findings provide insights for exploring the ME coupling in vdW materials.
Recent studies identified spin-order-driven phenomena such as spin-charge interconversion without relying on the relativistic spin-orbit interaction. Those physical properties can be prominent in systems containing light magnetic atoms due to sizable exchange splitting and may pave the way for realization of giant responses correlated with the spin degree of freedom. In this paper, we present a systematic symmetry analysis based on the spin crystallographic groups and identify the physical property of a vast number of magnetic materials up to 1500 in total. By decoupling the spin and orbital degrees of freedom, our analysis enables us to take a closer look into the relation between the dimensionality of spin structures and the resultant physical properties and to identify the spin and orbital contributions separately. In stark contrast to the established analysis with magnetic space groups, the spin crystallographic group manifests richer symmetry including spin-translation symmetry and leads to emergent responses. For representative examples, we discuss the geometrical nature of the anomalous Hall effect and magnetoelectric effect and classify the spin Hall effect arising from the nonrelativistic spin-charge coupling. Using the power of computational analysis, we apply our symmetry analysis to a wide range of magnets, encompassing complex magnets such as those with noncoplanar spin structures as well as collinear and coplanar magnets. We identify emergent multipoles relevant to physical responses and argue that our method provides a systematic tool for exploring sizable electromagnetic responses driven by spin order.
The low-dimensional frustrated antiferromagnet system has been an appealing playground for investigating the exotic magnetic ground states. The S=1/2 skew chain Co2V2O7 attracted considerable interest for its magnetization plateau and the emergent ferroelectricity under high magnetic fields. In this work, we report the comprehensive angular studies of the magnetization plateau and the ferroelectric polarization in Co2V2O7 under high fields up to 30 T. The magnetization was studied in detail with the applied field rotated within the bc and ab planes. We find that the 1/2 magnetization plateau is enhanced with the field rotating within the bc plane and becomes most pronounced when the field is titled 30∘ away from the b axis (denoted as the b* axis). The temperature dependence of ferroelectric polarization was also studied along the a, c, and b* axes, respectively. Based on these polarization measurements, the magnetic field temperature phase diagrams have been constructed for the three axes. We propose a model which considers the decoupling of the two inequivalent Co spins to explain the exotic polarization flop and the phase diagrams. This decoupling is considered to be enhanced by the dimerization effect, and that the non-negligible interchain interaction J3 plays a crucial role.
Magnetoelectric hexaferrites are the promising candidate materials for low-consumption magnetic memory device application, due to the existence of room-temperature magnetoelectric effect and the tunable magnetic structure. In this work, we studied the Ni doping effect on a rare room-temperature multiferroic BaSrCo2Fe11AlO22. With the comprehensive study of magnetism, magnetoelectricity, and ferroelectric properties, magnetoelectric phase diagrams of BaSrCo2-xNixFe11AlO22 were established. Generally, Ni doping has two important effects on magnetic and magnetoelectric properties. One is to strengthen superexchange interactions, greatly enhancing magnetic order temperature. Another effect is to destabilize the noncollinear magnetic structure at high temperature, causing the absence of ME effect at room temperature. In addition, the converse ME effects have been studied, revealing that converse ME coupling strength become weakened with the increase in Ni concentration. Our systematic studies provide important clues for synthesizing high performance magnetoelectric hexaferrites.
Weyl semimetals resulting from either inversion ( P ) or time-reversal ( T ) symmetry breaking have been revealed to show the record-breaking large optical response due to intense Berry curvature of Weyl-node pairs. Different classes of Weyl semimetals with both P and T symmetry breaking potentially exhibit optical magnetoelectric (ME) responses, which are essentially distinct from the previously observed optical responses in conventional Weyl semimetals, leading to the versatile functions such as directional dependence for light propagation and gyrotropic effects. However, such optical ME phenomena of (semi)metallic systems have remained elusive so far. Here, we show the large nonlinear optical ME response in noncentrosymmetric magnetic Weyl semimetal PrAlGe, in which the polar structural asymmetry and ferromagnetic ordering break P and T symmetry. We observe the giant second harmonic generation (SHG) arising from the P symmetry breaking in the paramagnetic phase, being comparable to the largest SHG response reported in Weyl semimetal TaAs. In the ferromagnetically ordered phase, it is found that interference between this nonmagnetic SHG and the magnetically induced SHG emerging due to both P and T symmetry breaking results in the magnetic field switching of SHG intensity. Furthermore, such an interference effect critically depends on the light-propagating direction. The corresponding magnetically induced nonlinear susceptibility is significantly larger than the prototypical ME material, manifesting the existence of the strong nonlinear dynamical ME coupling. The present findings establish the unique optical functionality of P - and T -symmetry broken ME topological semimetals.
Single crystals of hexagonal RMnO3 (R=Y, Yb, and Lu), where Mn ions form the triangular lattice, were investigated, focusing on their dielectric/magnetic anomalies as well as geometrical spin frustration. It is found that the ratio of a Weiss temperature to TN is ∼10 in RMnO3, indicating the dominant role of strong geometrical frustration. The effect of geometrical frustration also appears in specific heat, which shows a presence of a substantial amount of residual magnetic contribution below TN, indicating that a part of the spins are still fluctuating at T≪TN. It is also found that the dielectric anomaly at TN is strongly anisotropic, suggesting a unique correlation between magnetism and dielectric properties in these compounds.
It was observed that a ferroelectric domain boundary (DB) is always accompanied
by an antiferromagnetic DB in hexagonal YMnO3, by means of interference
effects of the second-harmonic signal. The clamping of these two order
parameters at the ferroelectric DB is shown theoretically to originate
from Dzyaloshinski–Moriya interaction. This interaction favouring a right
angle between the neighbouring spins is found to be operative within the
DB and to reverse the direction of the spins across the ferroelectric DB.
We review the results of X-ray scattering studies of the rare earth metals and present related new results for superlattices and thin slabs. In rare earth crystals we have observed weak structural modulations which accompany the magnetic ordering. The wave length of this modulation can be derived from a spin-slip model in accordance with symmetry considerations. X-ray scattering of both the charge and magnetization density modulations allow for highly accurate determination of the magnetic wave vector. The physical basis of our discussion is given in the context of lattice modulations. The implications of these results for the understanding of magnetic structure of rare earth superlattices are also discussed in the light of recent neutron diffraction studies of holmium-yttrium superlattices. The effect of the finite size of the magnetic block in a superlattice is considered and it is shown that significantly different behavior than in bulk is expected. In particular it is found that for thin slabs the ferromagnetic phase has the lowest energy.
Ferroelectromagnets are an interesting group of compounds that complement purely (anti-)ferroelectric or (anti-)ferromagnetic materials--they display simultaneous electric and magnetic order. With this coexistence they supplement materials in which magnetization can be induced by an electric field and electrical polarization by a magnetic field, a property which is termed the magnetoelectric effect. Aside from its fundamental importance, the mutual control of electric and magnetic properties is of significant interest for applications in magnetic storage media and 'spintronics'. The coupled electric and magnetic ordering in ferroelectromagnets is accompanied by the formation of domains and domain walls. However, such a cross-correlation between magnetic and electric domains has so far not been observed. Here we report spatial maps of coupled antiferromagnetic and ferroelectric domains in YMnO3, obtained by imaging with optical second harmonic generation. The coupling originates from an interaction between magnetic and electric domain walls, which leads to a configuration that is dominated by the ferroelectromagnetic product of the order parameters.
Enhancement of polarization and related properties in heteroepitaxially constrained thin films of the ferroelectromagnet,
BiFeO3, is reported. Structure analysis indicates that the crystal structure of film is monoclinic in contrast to bulk, which is
rhombohedral. The films display a room-temperature spontaneous polarization (50 to 60 microcoulombs per square centimeter)
almost an order of magnitude higher than that of the bulk (6.1 microcoulombs per square centimeter). The observed enhancement
is corroborated by first-principles calculations and found to originate from a high sensitivity of the polarization to small
changes in lattice parameters. The films also exhibit enhanced thickness-dependent magnetism compared with the bulk. These
enhanced and combined functional responses in thin film form present an opportunity to create and implement thin film devices
that actively couple the magnetic and ferroelectric order parameters.
The results are presented of the theoretical and experimental studies of ferroelectromagnets—crystals with magnetic and ferroelectric ordering. Considerable attention is paid to reviewing the results of the phenomenological analysis of the influence of the magnetoelectric interaction on the thermodynamic properties of ferroelectromagnets, their reaction to constant and variable electric and magnetic fields, the spectrum of spin waves and ferroelectric oscillations and the methods of exciting them. A table is presented of the expected magnetoelectric effects. The existing experimental studies of magnetoelectric interactions are described and the possible applications of ferroelectromagnets are discussed. A table is given of the known ferroelectromagnetic compounds.
Improper ferroelectrics are considered in the review from a unified point of view on the basis of the phenomenological Landau theory of phase transitions. In such ferroelectrics, in contrast to the ordinary ones, the order parameter of the phase transition is not the polarization but another physical quantitiy whose transformation properties are different from those of the polarization. Spontaneous polarization arises in the phase transition as a secondary effect. Therefore, the dielectric anomalies in the improper ferroelectrics are significantly different from the dielectric anomalies in the ordinary ferroelectrics. In particular, the temperature dependence of the permittivity does not obey the Curie-Weiss law, an electric field does not suppress the phase transition, etc. The dielectric anomalies are derived by analyzing a definite form of the thermodynamic potential with a two-component order parameter. Such an analysis turns out to be sufficient for the discussion of the available experimental data. The domain structure of the improper ferroelectrics also possesses specific properties: In particular, there exist domains which do not differ in their polarizations. Since the loss of stability in an improper ferroelectric phase transition occurs not with respect to polarization, the soft mode in the nonpolar phase is inactive in the infrared spectrum. Other distinctive features of the phonon spectrum in the phase-transition region are also considered. The experimental data on improper ferroelectrics are discussed. For the rare-earth molybdates, the theory is in quantitative agreeement with experiment. In certain other improper ferroelectrics the phase transitions are of first order and nowhere near to being of second order. The quantitative description of such transitions requires additional experimental data and further development of the theory.
DOI:https://doi.org/10.1103/PhysRev.82.113
Rb2ZnBr4 has been found to show phase transitions at about -86 and 18°C, respectively and to be ferroelectric in the a direction below -86°C.
The evolution of spin- and orbital-ordered states has been investigated for a series of insulating perovskites RMnO3 (R=La,Pr,Nd,...). RMnO3 with a large GdFeO3-type distortion is regarded as a frustrated spin system having ferromagnetic nearest-neighbor and antiferromagnetic (AF) next-nearest-neighbor (NNN) interactions within a MnO2 plane. The staggered orbital order associated with the GdFeO3-type distortion induces the anisotropic NNN interaction, and yields unique sinusoidal and up-up-down-down AF ordered states in the distorted perovskites with e1g configuration.
We have investigated the structural, magnetic, and electric properties of ferromagnetic BiMnO3 with a highly distorted perovskite structure. At TE=750 770 K, a centrosymmetric to non-centrosymmetric structural transition takes place, which describes of the ferroelectricity in the system. The changes in the dielectric constant were induced by the magnetic ordering (TM≈100 K) as well as by the application of magnetic fields near TM. These features are attributed to the inherent coupling between the ferroelectric and ferromagnetic orders in the multiferroic system.
Anomalies in the dielectric constant and loss tangent have been observed in the ferroelectromagnet YMnO3 near its Néel temperature of ∼80 K and below its ferroelectric Curie temperature of ∼914 K. These anomalies are indicative of coupling between the ferroelectric and antiferromagnetic orders in this compound. A small but distinct magnetoelectric effect and a magnetoresistive effect up to ∼15% were also detected in a magnetic field at 5 T. The results will be contrasted with previous theoretical predictions.
The dielectric constant, and the ferroelectric, pyroelectric, and piezoelectric properties of thiourea crystals have been measured in the temperature range 90°K to 300°K. At least three dielectric anomalies are found at 169°K, 177°K, and 202°K, the lowest of these corresponding to a pronounced discontinuity. The crystals are ferroelectric in two regions, below 169°K and between 176°K and 180°K. Substitution of deuterium for hydrogen causes the anomalies to move upwards in temperature by 16°, 16°, and 11°, respectively. The crystal structure has been determined in detail at 120°K in the lower ferroelectric region. The transition from the antiferroelectric room temperature structure to the ferroelectric state is accomplished by small rotations of the molecules such that two of the molecules in the crystal unit cell have tilts to the ferroelectric b axis appreciably different from the other two, and the resultant of the molecular dipoles along [010] is no longer zero. The ferroelectric reversal is thus easily accomplished by interchanging the tilts of the two pairs of molecules.
A general magneto-electric medium is one in which there is a linear, reciprocal relationship between the magnetic field and the electric polarization, and between the electric field and the magnetic polarization, as well as the more familiar linear relationship between the magnetic field and the magnetic polarization and between the electric field and electric polarization. In this paper the relationship between the fields and polarizations is expressed by means of a single tensor equation relating the field and polarization tensors in the medium. The properties of the rank four susceptibility tensor, required to establish this relationship, are investigated. A general tensor wave equation is obtained for a homogeneous anisotropic medium. The equation to the wave vector surface is obtained as a six by six determinant, which must vanish, and which gives well-known results when applied to simple anisotropic dielectric, or magnetic, crystals. When this equation is applied to an ideal magneto-electric medium, in which the magnetic and electric susceptibilities may be neglected, the conclusion is reached that waves of constant amplitude cannot propagate in a magneto-electric medium. If propagation takes place at all the waves will have either positive or negative damping due to an exchange of energy between waves having perpendicular planes of polarization.
Investigation of polycrystalline samples synthesized at high pressures as well as thin films deposited by nebulized spray pyrolysis suggest that BiMnO3 is ferromagnetic with a TC of 105 K and ferroelectric with a Curie temperature of around 450 K. It remains ferroelectric down to low temperatures through the ferromagnetic transition.
Results of first-principles electronic structure calculations on the low-temperature monoclinic phase of the ferromagnetic perovskite BiMnO3 [Atou et al. J. Solid State Chem. 1999, 145, 639] are presented. In agreement with experiments, the calculations obtain an insulating ferromagnetic ground state for this material. The role of Bi 6s “lone pairs” in stabilizing the highly distorted perovskite structure is examined using real-space visualization of the electronic structure. Comparisons are drawn with the electronic structures of hypothetical cubic BiMnO3 and with the electronic structure of the prototypical perovskite manganite, LaMnO3. The exploitation of s electron lone pairs in the design of new ferroic materials is suggested.
We study the coupling mechanism between antiferromagnetic and ferroelectric ordering that coexist spontaneously at low temperatures. According to the results of experiment and previous theoretical considerations, we propose a possible coupling form related to a combination of electric polar and spin correlation and use it to calculate the thermodynamic properties of a ferroelectromagnetic system, including its magnetization m, polarization p, magnetization susceptibility χm, magnetoelectric susceptibility χme and polarization susceptibility χp, in the case of magnetization m perpendicular to polarization p. It is found that the relationship between m, χm and χme is in agreement with that of phenomenological theory, and polarization induced by magnetic coupling leads to an anomaly of χp at low temperature, which is consistent qualitatively with experimental results.
Magnetic and neutron diffraction experiments on TbMnO3 powder and single crystals are reported. Below 40 K a sine-wave ordering of the Mn3+ moments is found with the wave-vector along the b-axis kMn = (0 0.28 0). Below 7 K a short-range ordering of the Tb3+ moments takes place with a different wave-vector kTb = (0 0.415 0).
The low temperature magnetic properties of terbium orthoferrite have been studied by means of magnetization measurements performed on various samples between 1 K and 10 K. The curves obtained for the x and y crystallographic directions enable characteristic parameters of the Tb3+ ions to be determined. Although these values are the same, measurements along the z axis clearly show up two kinds of samples with different behaviour as a function of temperature. This discrepancy is accounted for by shape effects which arise from the possibility of domain wall motion. These shape effects are due to dipolar interactions and are consistent with the predictions of the theoretical phase diagram published previously. Les propriétés magnétiques de l'orthoferrite de terbium à basse température sont étudiées à partir de mesures d'aimantation réalisées entre 1 K et 10 K sur divers échantillons. Les courbes obtenues suivant les axes cristallographiques x et y permettent la détermination des paramètres physiques de l'ion Tb3+. Bien que les valeurs trouvées pour ces paramètres soient les mêmes, des mesures effectuées dans la direction z font apparaître clairement deux types d'échantillons caractérisés par un comportement différent en fonction de la température. L'explication qui en est donnée, basée sur des différences de cinétique des domaines, utilise les prédictions relatives aux effets de forme dipolaires, qui sont contenues dans un diagramme de phase théorique publié antérieurement.
Les propriétés magnétiques de TbFeO3 à basse température sont étudiées en fonction d'un champ appliqué suivant les directions cristallographiques x et y. Les mesures de susceptibilité différentielle effectuées suivant x en fonction de la température permettent de construire le diagramme de phase des deux types d'échantillons qui se distinguent par l'existence ou non d'une phase intermédiaire ferromagnétique avant l'apparition de l'ordre antiferromagnétique vers 3 K. Un traitement théorique tenant compte de la possibilité d'une rotation progressive du système des Fe dans le plan xOz, a été développé et a permis d'interpréter quantitativement les résultats expérimentaux en utilisant les valeurs des paramètres d'échange Fe-Tb et Tb-Tb déterminées par ailleurs. Les mesures d'aimantation suivant la direction y montrent deux transitions successives à 1,1 K pour des valeurs du champ très différentes. Une explication qualitative de l'existence de cette double transition peut être donnée en introduisant une structure coopérative intermédiaire de type Fx Fy associée à une rotation du système des Fe de Gx Fz à G z Fx.
X-ray diffraction has been applied to investigate the magnetic structure of thulium. Magnetic scattering was observed at the magnetic modulation wave vector q, and charge scattering at 2q and 4q. A high-resolution study of the temperature dependence of the modulation at 2q showed two regimes: one incommensurate and the other commensurate. An analysis of the charge scattering at 2q shows that the ordering transition is continuous or almost continuous. The magnetic states of thulium were also probed by a resonance study of the magnetic scattering at the fundamental wave vector. Near the LIII absorption edge, an enhancement of the magnetic scattering of approximately 50 was observed. The results of polarization analysis of the magnetic scattering agreed with simple one-electron multipole scattering.
IT has been shown that slight deformations occur in the crystal structures of various oxides of the iron group. B. Ruhemann1 has found that there is a very slight change in the crystal structure of MnO near 120° K. Rooksby2 and Tombs and Rooksby3 have reported that the face-centred, cubic arrangements in MnO, FeO, CoO and NiO show changes to tetragonal or rhombohedral symmetry upon cooling through a transition temperature.
Evidenceforthelikelyoccurrenceofmagnetoferroelectricityinthesimple perovskite, BiMnO3
- A Moreiradossantos
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Magnetoelectric Interaction Phenomena in Crystals
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