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Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories.

HighlightsThe development of bismuth ferrite as a multiferroic nanomaterial is summarized.The morphology, structures, and properties of bismuth ferrite and its potential applications in multiferroic devices with novel functions are presented and discussed.Some perspectives and issues needed to be solved are described.Multiferroic nanomaterials have attracted great interest due to simultaneous two or more properties such as ferroelectricity, ferromagnetism, and ferroelasticity, which can promise a broad application in multifunctional, low-power consumption, environmentally friendly devices. Bismuth ferrite (BiFeO3, BFO) exhibits both (anti)ferromagnetic and ferroelectric properties at room temperature. Thus, it has played an increasingly important role in multiferroic system. In this review, we systematically discussed the developments of BFO nanomaterials including morphology, structures, properties, and potential applications in multiferroic devices with novel functions. Even the opportunities and challenges were all analyzed and summarized. We hope this review can act as an updating and encourage more researchers to push on the development of BFO nanomaterials in the future.

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 CuCrP 2 S 6 with inherent antiferromagnetism and antiferroelectricity. Distinct from the homogeneous antiferroelectric bulk, thin-layer CuCrP 2 S 6 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 CrS 6 and P 2 S 6 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. Two-dimensional multiferroics with effective magnetoelectric coupling has not been realized. Here, the authors find a magnetoelectric coupling mechanism in two-dimensional CuCrP 2 S 6 interlocked with heterogeneous ferrielectric state.

Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO 3 system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO 3 dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high-resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial magnetoelectric coupling in the Fe/BaTiO 3 system. At this interface, an ultrathin oxidized iron layer exists, whose magnetization can be electrically and reversibly switched on and off at room temperature by reversing the BaTiO 3 polarization. The suppression/recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BaTiO 3 produces on the exchange coupling constants in the interfacial-oxidized Fe layer. The observed giant magnetoelectric response holds potential for optimizing interfacial magnetoelectric coupling in view of efficient, low-power spintronic devices. Interfacial magnetoelectric coupling could lead to a new generation of memory devices. Here, Bertacco and colleagues observe a large electric-field switchable magnetoelectric coupling effect in iron/barium titanate heterostructures, which is due to a thin oxidized iron layer.

Multiferroic (MF)-magnetoelectric (ME) composites, which integrate magnetic and ferroelectric materials, exhibit a higher operational temperature (above room temperature) and superior (several orders of magnitude) ME coupling when compared to single-phase multiferroic materials. Room temperature control and the switching of magnetic properties via an electric field and electrical properties by a magnetic field has motivated research towards the goal of realizing ultralow power and multifunctional nano (micro) electronic devices. Here, some of the leading applications for magnetoelectric composites are reviewed, and the mechanisms and nature of ME coupling in artificial composite systems are discussed. Ways to enhance the ME coupling and other physical properties are also demonstrated. Finally, emphasis is given to the important open questions and future directions in this field, where new breakthroughs could have a significant impact in transforming scientific discoveries to practical device applications, which can be well-controlled both magnetically and electrically.

The quest to realize new kinds of data storage devices has motivated recent studies in the field of magnetoelectric heterostructures. One of the most commonly investigated systems is Fe3O4/[Pb(Mg 1/3Nb2/3)O3]0.7–[PbTiO3]0.3 (PMN-PT), however, the interplay between different coupling mechanisms is not yet well understood. To disentangle the role of strain and polarisation influence in Fe3O4/PMN-PT, we report on magnetoelectric coupling measurements for different orientations of the applied magnetic field and for two different substrate cuts, PMN-PT(001) and PMN-PT(011). For Fe3O4/PMN-PT(011), having the sample aligned such that the magnetic field is parallel to the [011‾] easy axis leads to a remanent increase of the magnetisation for each electric field cycle. On the other hand, for the magnetic field along the [100] hard axis, the magnetisation follows a butterfly-like loop characteristic of strain coupling imparted by the substrate. For Fe3O4/PMN-PT(001), the magnetoelectric effect is a superposition of the observed behaviour of both in-plane directions in Fe3O4/PMN-PT(011). The magnetisation shows an initial remanent increase followed by a butterfly like loop. Polarised neutron reflectometry measurements on Fe3O4/PMN-PT(011) shows no difference between the behaviour at the interface and the bulk of the film and no decline of the interaction further away from the shared interface. Our results demonstrate the role of strain and polarisation on the magnetisation of the Fe3O4 layer and provide a clear step towards the design of future magnetoelectric systems.

The purpose of the present study was to learn the morphological, structural, ferroelectric, dielectric, electromechanical, magnetoelectric, and magnetic properties, and DC conductivity of BaTiO3-Ni0.64Zn0.36Fe2O4 (BT-F) multiferroic composites compacted via the free sintering method. The influence of the ferrite content in ceramic composite materials on the functional properties is investigated and discussed. X-ray diffraction studies confirmed the presence of two main phases of the composite, with strong reflections originating from BaTiO3 and weak peaks originating from nickel-zinc ferrite. BT-F ceramic composites have been shown to exhibit multiferroism at room temperature. All studied compositions have high permittivity values and low dielectric loss, while the ferroelectric properties of the BT component are maintained at a high level. On the other hand, magnetic properties depend on the amount of the ferrite phase and are the strongest for the composition with 15 wt.% of F (magnetization at RT is 4.12 emu/g). The magnetoelectric coupling between BT and F phases confirmed by the lock-in technique is the largest for 15 wt.% ferrite. In the present work, the process conditions of the free sintering method for obtaining BT-F multiferroic composite with good electrical and magnetic properties (in one material) were optimized. An improved set of multifunctional properties allows the expansion of the possibilities of using multiferroic composites in microelectronics.

The Chern insulator manifests itself via the surface quantized Hall current and magnetoelectric effect. The manipulation of surface magnetizations enables a control of the dissipationless chiral transport and thus allows for potential applications of topological magnetoelectric devices with low-energy consumption. Here, we present experimental studies of bias-modulated switching the magnetic states utilizing the magnetoelectric coupling in a Chern insulator. This is achieved via applying a d.c. bias across the source and drain at various magnetic states, during which an effective magnetic field is developed to switch the quantum anomalous Hall state towards its opposite. Comprehensive transport studies show that the switch efficiency is proportional to the amplitude and applying time of the bias, depends on the initial magnetic state, but is insensitive to the electric polarity. Our results provide an efficient scheme to manipulate the Chern insulator and understanding on the electric breakdown of chiral edge states.

We report experimental studies on enhancing the magnetoelectric (ME) coupling of Co 4Nb 2O 9 by substituting the non-magnetic metal Mg for Co. A series of single crystal Co 4−xMg xNb 2O 9 ( x = 0, 1, 2, 3) with a single-phase corundum-type structure are synthesized using the optical floating zone method, and the good quality and crystallographic orientations of the synthesized samples are confirmed by the Laue spots and sharp XRD peaks. Although the Néel temperatures ( T N ) of the Mg substituted crystals decrease slightly from 27 K for pure Co 4Nb 2O 9 to 19 K and 11 K for Co 3MgNb 2O 9 and Co 2Mg 2Nb 2O 9, respectively, the ME coupling is doubly enhanced by Mg substitution when x = 1. The ME coefficient α ME of Co 3MgNb 2O 9 required for the magnetic field (electric field) control of electric polarization (magnetization) is measured to be 12.8 ps/m (13.7 ps/m). These results indicate that the Mg substituted Co 4−xMg xNb 2O 9 ( x = 1) could serve as a potential candidate material for applications in future logic spintronics and logic devices.

Altermagnets, a recently identified class of collinear magnets, exhibit unique properties such as zero net magnetization and spin polarization dictated by lattice symmetry, making them a subject of intense research. In contrast to conventional strategies for inducing altermagnetism in antiferromagnets that rely on manipulating real‐space symmetry, this work introduces a novel and general approach to achieving altermagnetism by modulating spin‐space symmetry. Through a combination of tight‐binding models and first‐principles calculations, the microscopic origin of altermagnetism driven by spin‐space symmetry is uncovered, and the mechanism underlying enhanced spin splitting is identified. Furthermore, it is demonstrated that this spin‐space modulation can synergistically interact with ferroelectricity, enabling a spin symmetry‐dependent magnetoelectric coupling mechanism that is distinct from conventional multiferroics. This unique coupling is validated by the magneto‐optical Kerr effect, providing a robust theoretical foundation for the development of next‐generation spintronic devices that harness the potential of altermagnetism. Antiferromagnets can be induced into altermagnets by changing the real‐space symmetry, increasing their potential for use in spintronic devices. Here, a novel and general approach is proposed: transforming antiferromagnets into altermagnets by modulating spin‐space symmetry, rather than real‐space symmetry. This mechanism can further synergistically interact with ferroelectricity to establish a spin‐symmetry‐dependent magnetoelectric coupling framework, distinct from conventional multiferroics.