Multiferroic Devices Research Articles

Magnetoelectric Tuning of 2D Ferromagnetism in 1T-CrTe2 through In2Se3 Substrate.

Electric field control of two-dimensional (2D) materials with optimized magnetic properties is not only of scientific interest but also of technological importance in terms of the functionality of various nanoscale devices. Here, we report the multiferroic control of the 2D ferromagnetism in 1T-CrTe2 monolayer through a ferroelectric In2Se3 sublayer. Our results reveal the effect of polarization switching on the electronic structures and magnetic properties of 1T-CrTe2/In2Se3 heterostructures, enabling effective manipulation of their magnetic anisotropy energy (MAE) and magnetization orientation. Additionally, we also demonstrate the strong dependence of their MAE and switching effect on the external strain and surface hydrogenation. Notably, polarization switching exhibits a reversal modification in the hydrogenated multiferroic structures. These tunable behaviors are primarily attributed to the alteration of p-orbitals near the Fermi level of the interfacial Te atoms due to magnetoelectric coupling. Our findings suggest the potential of 1T-CrTe2/In2Se3 heterojunctions for the practical application of 2D multiferroic spintronic devices.

Electronic and Transport Engineering of A-Type Antiferromagnets with Ferroelectric Sandwich Structure: Toward Multistate Nonvolatile Memory Applications.

Achieving higher-order multistates with mutual interstate switching at the nanoscale is essential for high-density storage devices; yet, it remains a significant challenge. Here, we demonstrate that integrating A-type antiferromagnetic semiconductors sandwiched between ferroelectric layers is an effective strategy to achieve high-performance multistate data storage. Taking the Sc2CO2/VSi2P4 bilayer (bi-VSi2P4)/Sc2CO2 van der Waals multiferroic heterostructure as an example, our first-principles calculations show that by switching the polarization direction of the upper and bottom ferroelectric Sc2CO2 layers, antiferromagnetic bi-VSi2P4 can exhibit four distinct states with different band structures. The intriguing band structure engineering stems from the polarization-field-induced band shift and interface charge transfer. Accordingly, the proposed Sc2CO2/bi-VSi2P4/Sc2CO2-based multiferroic device can achieve four different resistance states, accompanied by fully spin-polarized currents and giant tunneling electroresistance ratios. Our results propose a viable strategy for realizing nonvolatile electrical control of antiferromagnets at the nanoscale and provide insights into the development of advanced memories.

Voltage control of multiferroic magnon torque for reconfigurable logic-in-memory

Magnons, bosonic quasiparticles carrying angular momentum, can flow through insulators for information transmission with minimal power dissipation. However, it remains challenging to develop a magnon-based logic due to the lack of efficient electrical manipulation of magnon transport. Here we show the electric excitation and control of multiferroic magnon modes in a spin-source/multiferroic/ferromagnet structure. We demonstrate that the ferroelectric polarization can electrically modulate the magnon-mediated spin-orbit torque by controlling the non-collinear antiferromagnetic structure in multiferroic bismuth ferrite thin films with coupled antiferromagnetic and ferroelectric orders. In this multiferroic magnon torque device, magnon information is encoded to ferromagnetic bits by the magnon-mediated spin torque. By manipulating the two coupled non-volatile state variables—ferroelectric polarization and magnetization—we further present reconfigurable logic operations in a single device. Our findings highlight the potential of multiferroics for controlling magnon information transport and offer a pathway towards room-temperature voltage-controlled, low-power, scalable magnonics for in-memory computing.

Nonvolatile ferroelectric control of both magnetic anisotropy and half-metallicity in multiferroic heterostructures GdI2/Al2Te3

Nonvolatile all-electric spin manipulation is optimal for low-power and compact spintronic devices. Herein, using first-principles density functional theory, we propose a bilayer van der Waals (vdW) multiferroic heterostructure (HS) GdI2/Al2Te3 constructed of ferromagnetic electride GdI2 and ferroelectric (FE) semiconductor Al2Te3 to possess robust magnetoelectric coupling near room temperature. By reversing the electrical polarization states in Al2Te3, the magnetoelectric coupling not only allows the reversible switch of GdI2 from semiconductor to half-metal but also promotes the reversible transition of magnetocrystalline anisotropy from in-plane to out-of-plane. More importantly, the high Curie temperature (TC) of GdI2 and the unspoiled semiconducting nature of Al2Te3 in the HS predict the practical feasibility of this spin manipulation. Additionally, GdI2 exhibits substantial valley polarization when its magnetization direction changes to out-of-plane. These findings pave the way for achieving robust and efficient spin manipulation through all-electric control and also provide implications for multiferroic memory devices with highly efficient data reading and writing based on the HS.

Multiferroic neuromorphic computation devices

Neuromorphic computation is based on memristors, which function equivalently to neurons in brain structures. These memristors can be made more efficient and tailored to neuromorphic devices by using ferroelastic domain boundaries as fast diffusion paths for ionic conduction, such as of oxygen, sodium, or lithium. In this paper, we show that the local memristor generates a second, unexpected feature, namely, weak magnetic fields that emerge from moving ferroelastic needle domains and vortices. The vortices appear near ferroelastic “junctions” that are common when the external stimulus is a combination of electric fields and structural phase transitions. Many ferroelastic materials show such phase transitions near room temperatures so that device applications display a “multiferroic” scenario where the memristor is driven electrically and read magnetically. Our computer simulation study of an elastic spring model suggests magnetic fields in the order of 10−7 T, which opens the way for a fundamentally new way of running neuromorphic devices. The magnetism in such devices emerges entirely from intrinsic displacement currents and not from any intrinsic magnetism of the material.

Gas‐Induced Electrical and Magnetic Modulation of Two‐Dimensional Conductive Metal–Organic Framework

AbstractControlled modulation of electronic and magnetic properties in stimuli‐responsive materials provides valuable insights for the design of magnetoelectric or multiferroic devices. This paper demonstrates the modulation of electrical and magnetic properties of a semiconductive, paramagnetic metal−organic framework (MOF) Cu3(C6O6)2 with small gaseous molecules, NH3, H2S, and NO. This study merges chemiresistive and magnetic tests to reveal that the MOF undergoes simultaneous changes in electrical conductance and magnetization that are uniquely modulated by each gas. The features of response, including direction, magnitude, and kinetics, are modulated by the physicochemical properties of the gaseous molecules. This study advances the design of multifunctional materials capable of undergoing simultaneous changes in electrical and magnetic properties in response to chemical stimuli.

Gas-Induced Electrical and Magnetic Modulation of Two-Dimensional Conductive Metal-Organic Framework.

Controlled modulation of electronic and magnetic properties in stimuli-responsive materials provides valuable insights for the design of magnetoelectric or multiferroic devices. This paper demonstrates the modulation of electrical and magnetic properties of a semiconductive, paramagnetic metal-organic framework (MOF) Cu3(C6O6)2 with small gaseous molecules, NH3, H2S, and NO. This study merges chemiresistive and magnetic tests to reveal that the MOF undergoes simultaneous changes in electrical conductance and magnetization that are uniquely modulated by each gas. The features of response, including direction, magnitude, and kinetics, are modulated by the physicochemical properties of the gaseous molecules. This study advances the design of multifunctional materials capable of undergoing simultaneous changes in electrical and magnetic properties in response to chemical stimuli.

Modulating the electronic and optical properties of CrI3/In2Se3 van der Waals heterostructures by external fields

The van der Waals heterostructures (vdWH) composed of two-dimensional (2D) magnetic materials and non-magnetic atomic layers provide promising candidates for innovative device design. Here, we construct the CrI3/α-In2Se3 vdWH and regulate its band structure, magnetism and optical absorption through external fields. The intrinsic vdWH possesses type-Ⅱ band alignment with 0.38 eV band gap. As a result of proximity effects and superexchange interaction, magnetism is induced in the α-In2Se3 layer. The Curie temperature of the vdWH with FM coupling has increased to 99.3 K. Interestingly, with the increasing of the applied electric field, the band alignment exhibits a transition from type-Ⅱ to type-Ⅰ and then back to type-Ⅱ. When the electric field is −4.31 V/nm, the vdWH convert from semiconductor to half-metal. Moreover, the applying biaxial and vertical strain can influence the energy level of hybridization, and transferred charges. For example, the increased magnetic moment of the CrI3 monolayer increased by four times when the distance gap is decreased by 0.5 Å. These properties can offer novel strategies for engineering band structure and regulating magnetic properties, thereby enabling researchers to design tunable multiferroic vdWH devices.

Concomitant Light-Reversible Magnetic Response in Multiferroic Oxide Heterostructures for Multiphysics Applications.

The concept of multiphysics, where materials respond to diverse external stimuli, such as magnetic fields, electric fields, light irradiation, stress, heat, and chemical reactions, plays a fundamental role in the development of innovative devices. Nanomanufacturing, especially in low-dimensional systems, enhances the synergistic interactions taking place on the nanoscale. Light-matter interaction, rather than electric fields, holds great promise for achieving low-power, wireless control over magnetism, solving two major technological problems: the feasibility of electrical contacts at smaller scales and the undesired heating of the devices. Here, we shed light on the remarkable reversible modulation of magnetism using visible light in epitaxial Fe3O4/BaTiO3 heterostructure. This achievement is underpinned by the convergence of two distinct mechanisms. First, the magnetoelastic effect, triggered by ferroelectric domain switching, induces a proportional change in coercivity and remanence upon laser illumination. Second, light-matter interaction induces charged ferroelectric domain walls' electrostatic decompensations, acting intimately on the magnetization of the epitaxial Fe3O4 film by magnetoelectric coupling. Crucially, our experimental results vividly illustrate the capability to manipulate magnetic properties using visible light. This concomitant mechanism provides a promising avenue for low-intensity visible-light manipulation of magnetism, offering potential applications in multiferroic devices.

Two-dimensional 1T′ α -VXY (X = S, Se, Te; Y = Cl, Br, I): A multifunctional vanadium chalcohalide family with room-temperature ferromagnetism and sliding ferroelectricity

Two-dimensional (2D) ferromagnetic materials with Curie temperature (Tc) above room temperature have great potential ranging from spintronics to information processing and storage. Here, we computationally design a series of 1T′α-VXY (X = S, Se, Te; Y = Cl, Br, I) monolayers with the X and Y atoms arranged alternately in the 2D plane. VXY monolayers are ferromagnetic semiconductors with Tc much higher than room temperature. Furthermore, the symmetry breaking of VXY bilayers leads to sliding ferroelectricity with large reversible out-of-plane electric polarization and moderate interlayer sliding barriers. We further show that half-metal-to-semiconductor nonvolatile field-effect switching can be achieved in multiferroic van der Waals heterostructures composed of VXY and In2S3 ferroelectric substrates due to the synergistic effect between the polarization field-induced band edge shifting and the selective charge transfer at the interface. These findings reveal a promising role of 2D Janus 1T′α-VXY in spintronics, ferroelectric, and multiferroic device applications.

Coexisting Magnetism, Ferroelectric, and Ferrovalley Multiferroic in Stacking-Dependent Two-Dimensional Materials.

Two-dimensional (2D) multiferroic materials have widespread application prospects in facilitating the integration and miniaturization of nanodevices. However, the magnetic, ferroelectric, and ferrovalley properties in one 2D material are rarely coupled. Here, we propose a mechanism for manipulating magnetism, ferroelectric, and valley polarization by interlayer sliding in a 2D bilayer material. Monolayer GdI2 is a ferromagnetic semiconductor with a valley polarization of up to 155.5 meV. More interestingly, the magnetism and valley polarization of bilayer GdI2 can be strongly coupled by sliding ferroelectricity, making these tunable and reversible. In addition, we uncover the microscopic mechanism of the magnetic phase transition by a spin Hamiltonian and electron hopping between layers. Our findings offer a new direction for investigating 2D multiferroic devices with implications for next-generation electronic, valleytronic, and spintronic devices.

Fully Electrically Controlled van der Waals Multiferroic Tunnel Junctions.

The fully electrical control of the magnetic states in magnetic tunnel junctions is highly pursued for the development of the next generation of low-power and high-density information technology. However, achieving this functionality remains a formidable challenge at present. Here we propose an effective strategy by constructing a trilayer van der Waals multiferroic structure, consisting of CrI3-AgBiPSe6 and Cr2Ge2Te6-In2Se3, to achieve full-electrical control of multiferroic tunnel junctions. Within this structure, two different magnetic states of the magnetic bilayers (CrI3/Cr2Ge2Te6) can be modulated and switched in response to the polarization direction of the adjacent ferroelectric materials (AgBiPSe6/In2Se3). The intriguing magnetization reversal is mainly attributed to the polarization-field-induced band structure shift and interfacial charge transfer. On this basis, we further design two multiferroic tunnel junction devices, namely, graphene/CrI3-AgBiPSe6/graphene and graphene/Cr2Ge2Te6-In2Se3/graphene. In these devices, good interfacial Ohmic contacts are successfully obtained between the graphene electrode and the heterojunction, leading to an ultimate tunneling magnetoresistance of 9.3 × 106%. This study not only proposes a feasible strategy and identifies a promising candidate for achieving fully electrically controlled multiferroic tunnel junctions but also provides insights for designing other advanced spintronic devices.

Orientation dependent magnetocapacitance tuning in epitaxial (La,Sr)MnO3/(K,Na)NbO3-based heterostructures

We fabricated multiferroic heterostructures composed of La0.67Sr0.33MnO3 (LSMO) and (K0.48Na0.48Li0.04) (Nb0.81Ta0.15Sb0.04)O3 (KNN-LTS) on (001)-, (110)-, and (111)-oriented SrTiO3 substrates using pulsed laser deposition technique. X-ray diffraction confirmed the coherent growth of LSMO layers, while KNN-LTS layers exhibited partial relaxation in the heterostructures, with relaxation increasing from (001) to (111) orientations. Notably, the (111)-oriented LSMO, which displayed the highest out-of-plane lattice relaxation, exhibited superior magnetic properties. On the other hand, (001)-oriented sample showcased the maximum ferroelectric and piezoelectric properties due to its high elastic deformation, whereas (111)-oriented sample, characterized by higher intrinsic lattice deformation, demonstrated better dielectric properties. Our elemental analysis confirmed interface charge transfer, indicating the presence of magnetoelectric coupling within the heterostructures. Then, the magnetocapacitance effect was attributed to a combination of interface magnetoelectric coupling and magnetoresistance in LSMO. The (111)-oriented sample displayed a remarkable MC value of approximately 62% near the transition temperature (around 352 K) of LSMO, while the (110)-oriented sample reached the highest MC of approximately 65% at 300 K. These findings suggest that engineered ferroelectric/ferromagnetic heterostructures hold promise for high MC performance at room temperature and offer opportunities for modulation with crystallographic orientation, making them potentially valuable for applications in multiferroic devices.

Photovoltaic energy conversion in multiferroic perovskite absorber-based devices via experiment and theoretical calculations

Initially, La and Ti-doped BiFeO3 (BLFTO) was prepared through the solid-state method, and the formation of perovskite structure was confirmed through powder X-ray diffraction (XRD) analysis. SEM-EDX analysis confirms the merging of grains for the increasing concentration of Ti ion doping and the presence of all elements in the samples. The bandgap tuning in BLFTO (2.05 eV–2.11 eV) was analyzed through UV–vis spectroscopy and confirming the change in bandgap for Ti-doped BLFO samples. The observed energy bandgap range of the doped BFO absorber suggested its potential applications in solar cell devices. Therefore, we have designed lead-free FTO/TiO2/absorber/Spiro-OMeTAD/Au heterostructure device and achieved a power conversion efficiency (PCE) of ∼5.61% with an open-circuit voltage (VOC) of ∼0.91 V, fill factor (FF) of 55.55%, and current density (JSC) of 10.87 mA/cm2 for lead-free doped Bi0.80La0.20Fe1−xTixO3 (x = 0.0) based perovskite solar cells with proper optimization of thickness of absorber and operating temperature.

Simultaneous existence of magnetic and ferroelectric orders in bi-phase composites for multiferroic applications

Multiferroic materials has brought evolutionary impact in multifunctional devices that are exclusively based on magnetoelectric coupling. In this work, a bi-phasic composite series of the form; (1–x)[Bi0.8La0.2FeO3] + x[Zn0.5Co0.5Fe2O4] was prepared using sol–gel auto–combustion. The X-ray diffraction analysis confirmed the rhombohedrally distorted cubic structure of BiFeO3 and normal spinel cubic structure of Zn0.5Co0.5Fe2O4 having R3c and Fd-3 m space group symmetry, respectively. A reduction in average crystallite size was observed by gradually enhancing the substituent spinel contents (x). Energy dispersive X-ray confirmed the presence of all the constituent elements in accordance with stoichiometrically calculated values. Mostly the particles having spherical shapes were observed via micro-graphical analysis. At x = 0.2, the composite sample showed the highest value of recoverable energy density as 7.2 × 10-2 mJ/cm3 with the highest value of % efficiency ∼ 88.83 %. A clear enhancement in saturation magnetization was observed from 0.16 to 19.87 emu/g. The remanent magnetization also increased from 0.018 to 6.363 emu/g by enhancing the spinel phase contents. Furthermore, coercivity also increased significantly from 672.98 Oe to 841.89 Oe in the composite samples. The highest squareness ratio Mr:Ms was observed at x = 0.3. These distinctive properties of the nanocomposites lead toward potential applications in multiferroic and spintronic devices.

Spontaneous Chiral Resolution of a MnIII Spin-Crossover Complex with High Temperature 80 K Hysteresis.

Non-centrosymmetric spin-switchable systems are of interest for their prospective applications as magnetically active non-linear optical materials and in multiferroic devices. Chiral resolution of simple spin-crossover chelate complexes into the Δ and Λ forms offers a facile route to homochiral magnetic switches, which could be easily enantiomerically enriched. Here, we report the spontaneous resolution of a new hysteretic spin-crossover complex, [MnIII (sal2 323)]SCN ⋅ EtOH (1), into Δ and Λ forms, without the use of chiral reagents, where sal2 323 is a Schiff base resulting from condensation of 1,2-bis(3-aminopropylamino)ethane with 2-hydroxybenzaldehyde. The enantiopurity of the Δ and Λ isomers was confirmed by single crystal X-ray diffraction and circular dichroism. Quantum chemistry calculations were used to investigate the electronic structure. The opening of a wide 80 K thermal hysteresis window at high temperature highlights the potential for good magneto-optical function at ambient temperature for materials of this type.

Solution-Processed Multiferroic Thin-Films with Large Magnetoelectric Coupling at Room-Temperature.

Experimental realization of thin films with a significant room-temperature magnetoelectric coupling coefficient, αME, in the absence of an external DC magnetic field, has been thus far elusive. Here, a large coupling coefficient of 750 ± 30 mV Oe-1 cm-1 is reported for multiferroic polymer nanocomposites (MPCs) thin-films in the absence of an external DC magnetic field. The MPCs are based on PMMA-grafted cobalt-ferrite nanoparticles uniformly dispersed in the piezoelectric polymer poly(vinylidene fluoride-co-trifluoroethylene, P(VDF-TrFE). It is shown that nanoparticle agglomeration plays a detrimental role and significantly reduces αME. Surface functionalization of the nanoparticles by grafting a layer of poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization (ATRP) renders the nanoparticle miscible with P(VDF-TRFE) matrix, thus enabling their uniform dispersion in the matrix even in submicrometer thin films. Uniform dispersion yields maximized interfacial interactions between the ferromagnetic nanoparticles and the piezoelectric polymer matrix leading to the experimental demonstration of large αME values in solution-processed thin films, which can be exploited in flexible and printable multiferroic electronic devices for sensing and memory applications.

The annealing temperature dependence of the RRAM effect and the oxygen vacancy mechanism for double perovskite Bi2FeCrO6 film

Resistive random access memory (RRAM) is the most potentially nonvolatile memory of the next generation. In this paper, the double perovskite Bi2FeCrO6 (BFCO) thin films were prepared on FTO/glass using the sol-gel method. And, the resistive switching (RS) phenomena were observed in the Au/BFCO/FTO/glass device annealed at different temperatures. Moreover, the RS behaviors and the mechanism of the Au/BFCO/FTO device were analyzed and discussed, and the RS behaviors could be due to the interaction between the interfacial barrier and oxygen vacancies, and the change of RRAM performance under the annealing temperatures can be attributed to the crystallinity and oxygen vacancy defect content in double perovskite BFCO films, so that, the largest and most stable switching ratios of more than 102 for the BFCO film is achieved annealed at 700 °C. These findings will help us design and fabricate the multiferroic BFCO-based resistive switching memory devices.

Tuneable physical properties of ReI3 through ferroelectric polarization switching in 2D van der Waals multiferroic heterostructures

Ferroelectric switching of atom-thick van der Waals (vdW) magnets is desirable for the future advancement of multiferroic nanodevices. In this work, we systematically investigated the physical properties of a ReI3 layer in contact with an In2Se3 ferroelectric substrate using first-principles calculations. We demonstrated that a phase transition from ferromagnetic to antiferromagnetic occurs in the ReI3 layer under the polarization electric field of the In2Se3 layer, and the magnetocrystalline anisotropy energy is sharply reduced by 54% and 63% for upward and downward polarization directions, respectively. A semiconductor-to-metal transition occurs in the ReI3 layer as the electric polarization of the ferroelectric layer is switched. We further demonstrate that the electric polarization of the In2Se3 substrate breaks the inversion symmetry of the ReI3 layer and generates appreciable Dzyaloshinskii-Moriya (DM) interactions between the magnetic moments of Re3+ ions. Furthermore, the DM interactions can be well controlled by the ferroelectric polarization of the In2Se3 layer, which enables nonvolatile electric control of AFM skyrmions in the ReI3/In2Se3 heterostructure. These results suggest a new strategy to tune the physical properties of ReI3 and may have potential application in future multiferroic devices.

Electric field tuning of ferromagnetic resonance field and linewidth in epitaxial LiFe5O8/PMN-PT (0 1 1) heterostructure

Here a typical ME heterostructure is prepared by growing epitaxial LiFe5O8 (LFO) thin films on Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) (011) substrates by pulse laser deposition (PLD). Ferromagnetic resonance (FMR) test results at in situ voltage show that the tunability of FMR field (Hr) and linewidth (ΔH) have strong angular dependences with external magnetic field. It is inferred that the change of the orientation of equilibrium magnetization contributes to the abnormal enhancement of ME coupling at certain angles. The theoretical fitting reveals that the Gilbert damping (ΔHGilb), two-magnon scattering (ΔHTMS) and inhomogeneous broadening (ΔHinhom) play the different roles for the increase of linewidth of LFO film at various magnetic field directions. Additionally, the ME coupling in LFO/PMN-PT (011) heterostructure shows well temperature stability at range of 100–300 K. Those discoveries enrich the understanding of the ME phenomenon and provide guidance to the development of novel multiferroic materials and devices.