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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.

Composite multiferroic materials were prepared using the conventional ceramic double sintering process, with composition of Ґ BaTiO3/(1 − Ґ) Cu0.3Ni0.1Zn0.6Fe2O4, where Ґ represents the mass fraction of the ferroelectric phase ranging from 0.3 to 0.9. The behavior of the bulk composites under external dynamic magnetic and electric fields was studied as a function of the ferroelectric phase content. The objective of this work is to establish a relationship between the irreversibility process and magnetic and electrical losses in composite magnetoelectric materials. Experimental measurements were correlated with the entropy production of materials. The results allow us to infer that in the explored frequency range (from 1 MHz to 1.8 GHz), entropy production not only decreases as the ferroelectric phase content increases but is also related to the magnetic losses.

This paper reports the structural, dielectric, electrical, and multiferroic properties of Bi 2 FeNiO 6 (BFNO) double perovskite synthesised using a sol-gel modified combustion technique. Its calcination temperature, 873 K, was determined using the mass variation in the TGA curve. Structural characterisation was conducted with the X-ray diffraction technique and the perovskite was found to adopt a cubic structure with space group Fm 3 ¯ m (#225). Synchrotron-based powder angle dispersive X-ray diffraction (ADXRD) measurements were carried out to analyze the structural stability with temperature variation (RT-773 K). SEM studies revealed nearly cubic nanostructures with an average grain size of ~54 nm. EDS and XPS studies confirm the stoichiometric and electrical neutrality of the compound, respectively. The ε vs T curve shows the ferroelectric Curie temperature to be around 732 K, corroborating an exothermic peak observed in the DSC curve around the same temperature. The M-H curve and PE loop show the coexistence of ferroelectric and ferromagnetic properties in the as-prepared Bi 2 FeNiO 6 at room temperature. Graphical Abstract Highlights Citric acid-assisted Sol-gel modified combustion technique was implemented to synthesise Bi 2 FeNiO 6 double perovskite. Strong coupling between unpaired electrons of the t 2g and e g subshells in the Fe and Ni ions, respectively, is responsible for the magnetic phase transition shift to a higher temperature. The PE loop shows the sample is ferroelectric with remanent polarisation P r  = 1.6 μC/cm 2 . The ferroelectric transition was found at 733 K and is shown with a temperature-dependent dielectric constant curve. It exhibits room-temperature multiferroic properties with a semiconducting nature.

Magnetoelectric multiferroic materials have attracted great attention due to their intriguing properties and potential applications. In this paper, (1 − x) Co0.8Cu0.2Fe2O4-xBa0.6Sr0.4TiO3 (x = 0, 0.4, 0.45, 0.475, 0.5, 0.525, 0.55, 1) composites were prepared by the conventional solid-state method combining with a sol–gel process. The effect of x on the microstructure, dielectric and multiferroic properties has been systematically investigated and discussed. The results confirm pure bi-phase Co0.8Cu0.2Fe2O4 and Ba0.6Sr0.4TiO3 composites except for slight impurity phases, which are indexed as BaCuO2/BaFe12O19. All the samples show uniform and relatively smooth surfaces with the mean grain size of ∼ 1.5 μm which decreases slightly with the increase of x, demonstrating the moderating effect of the ferroelectric phase on the grain size. The dielectric constant shows intense dependence on the components and the highest value is obtained when x = 0.525. The ferroelectric loops demonstrate that the coercive field and remnant polarization of the sample x = 0.525 are higher than other samples except for the pure Ba0.6Sr0.4TiO3 specimen at room temperature. The Co0.8Cu0.2Fe2O4 shows better magnetic properties and the performance of magnetization decreases with the decrease of Ba0.6Sr0.4TiO3; meanwhile, the impurity phase and inhomogeneous structure have certain influences on the magnetic properties.

The structural, elastic, electronic and thermodynamic properties of multiferroic ternary sulfide perovskite YMnS 3 were predicted by using the density functional theory plus Hubbard correction through the full-potential linearized augmented plane-wave (PF-LAPW) method. The exchange–correlation potential was treated by using the generalized gradient approximation (GGA) for solids and (GGA + U). The study of the structural properties, thermodynamic stability and mechanical stability shows that the perovskite YMnS 3 is stable in cubic phase. The brittleness and ductility are also studied by the analysis of the elastic constants with the other mechanical parameters. As a result, the obtained findings show that the YMnS 3 is a ductile material. Moreover, the electronic band structure is strongly affected by the presence of the Hubbard correction where we have observed a phase transition from metallic character to half-metallic ferromagnetic character for a critical value of U  = 3 eV; for U greater than this value, the YMnS 3 material present a half-metallic ferromagnetic behavior with a total magnetic moment around 4.02 μ B . Besides, the half-metallic band gap is increased with rising the value of U . Finally, we investigated the influence of pressure and temperature on the lattice parameters, heat capacities, Debye temperatures and the entropies through the quasi-harmonic Debye model. Our results are based on the electronic and magnetic properties of YMnS 3 material, which indicate their potential for use in data storage and thermoelectric applications.

Multiferroic nanoparticles of manganese doped bismuth ferrite with the chemical formula, Bi 1- x Mn x FeO 3 , with x values of 0, 0.025, 0.05, 0.075 and 0.1, were synthesized by sol–gel autocombustion method. X-ray diffraction measurements and Rietveld structural refinements were performed on the samples to ensure the formation of rhombohedrally distorted perovskite phase for all the samples. Dielectric measurements of the samples have been carried out in a wide range of frequencies from 1 to 40 MHz and at different temperatures in the range from 30° to 450 °C. Temperature-dependent dielectric anomalies were observed and the same were attributed to structural inhomogeneities at around 150°–270 °C, and to typical free charge carrier hopping mechanisms and anomalies at around 270°–420 °C. Impedance analysis of the samples provides indirect support for the reasons discussed in the dielectric properties and the corresponding electrical conductivity behaviour in these samples. Magnetic measurements were carried out to understand the influence of Mn ions on the magnetic behaviour of the studied multiferroics. The results of all these measurements are well discussed, and they indicate a considerable enhancement in the magnetic order with Mn doping and also a decrease in the dielectric loss with an evidence magnetoelectric coupling and thus making them useful for device applications.

The manipulation of magnetic properties by an electric field in magnetoelectric multiferroic materials has driven significant research activity, with the goal of realizing their transformative technological potential. Here, we review progress in the fundamental understanding and design of new multiferroic materials, advances in characterization and modelling tools to describe them, and the exploration of devices and applications. Focusing on the translation of the many scientific breakthroughs into technological innovations, we identify the key open questions in the field where targeted research activities could have maximum impact in transitioning scientific discoveries into real applications.Magnetoelectric multiferroics, where magnetic properties are manipulated by electric field and vice versa, could lead to improved electronic devices. Here, advances in materials, characterisation and modelling, and usage in applications are reviewed.

Multiferroic materials have attracted wide interest because of their exceptional static 1 – 3 and dynamical 4 – 6 magnetoelectric properties. In particular, type-II multiferroics exhibit an inversion-symmetry-breaking magnetic order that directly induces ferroelectric polarization through various mechanisms, such as the spin-current or the inverse Dzyaloshinskii–Moriya effect 3 , 7 . This intrinsic coupling between the magnetic and dipolar order parameters results in high-strength magnetoelectric effects 3 , 8 . Two-dimensional materials possessing such intrinsic multiferroic properties have been long sought for to enable the harnessing of magnetoelectric coupling in nanoelectronic devices 1 , 9 , 10 . Here we report the discovery of type-II multiferroic order in a single atomic layer of the transition-metal-based van der Waals material NiI 2 . The multiferroic state of NiI 2 is characterized by a proper-screw spin helix with given handedness, which couples to the charge degrees of freedom to produce a chirality-controlled electrical polarization. We use circular dichroic Raman measurements to directly probe the magneto-chiral ground state and its electromagnon modes originating from dynamic magnetoelectric coupling. Combining birefringence and second-harmonic-generation measurements with theoretical modelling and simulations, we detect a highly anisotropic electronic state that simultaneously breaks three-fold rotational and inversion symmetry, and supports polar order. The evolution of the optical signatures as a function of temperature and layer number surprisingly reveals an ordered magnetic polar state that persists down to the ultrathin limit of monolayer NiI 2 . These observations establish NiI 2 and transition metal dihalides as a new platform for studying emergent multiferroic phenomena, chiral magnetic textures and ferroelectricity in the two-dimensional limit. Multiple complementary optical signatures confirm the persistence of ferroelectricity and inversion-symmetry-breaking magnetic order down to monolayer NiI 2 , introducing the physics of type-II multiferroics into the area of van der Waals materials.

A multiferroic material Pb(Ni1/3Mn1/3W1/3)O3 with ferroelectric and ferromagnetic properties at room temperature is designed for multifunctional applications. A orthorhombic perovskite crystal structure has been assigned for the present perovskite according to the X-ray diffraction patterns. At 1 kHz, dielectric constant (ɛr) increases from 1655 at 298 K to its first maximum 3514 at 457 K referred as magnetic transition. The high values of ɛr in the low frequency range show better dispersion, and with the increase in frequency, a gradual decrease in the ɛr values was observed. The contribution of grain and/or electrode/interface effects in the resistive/capacitive properties was ascertained by the Nyquist plots. An equivalent circuit has been suggested consisting of resistive and capacitive components (R, C, Q) estimates the bulk (grain) and grain boundary resistance and capacitance. The activation energy was found to be greater than 0.2 eV, supporting the conduction mechanism due to hopping of charge carriers.

Materials that are simultaneously ferromagnetic and ferroelectric – multiferroics – promise the control of disparate ferroic orders, leading to technological advances in microwave magnetoelectric applications and next generation of spintronics. Single-phase multiferroics are challenged by the opposite d -orbital occupations imposed by the two ferroics, and heterogeneous nanocomposite multiferroics demand ingredients’ structural compatibility with the resultant multiferroicity exclusively at inter-materials boundaries. Here we propose the two-dimensional heterostructure multiferroics by stacking up atomic layers of ferromagnetic Cr 2 Ge 2 Te 6 and ferroelectric In 2 Se 3 , thereby leading to all-atomic multiferroicity. Through first-principles density functional theory calculations, we find as In 2 Se 3 reverses its polarization, the magnetism of Cr 2 Ge 2 Te 6 is switched, and correspondingly In 2 Se 3 becomes a switchable magnetic semiconductor due to proximity effect. This unprecedented multiferroic duality (i.e., switchable ferromagnet and switchable magnetic semiconductor) enables both layers for logic applications. Van der Waals heterostructure multiferroics open the door for exploring the low-dimensional magnetoelectric physics and spintronic applications based on artificial superlattices. Low dimensional multiferroic materials promise the technological advances in next generation spintronic and microwave magnetoelectric devices. Here the authors propose the multiferroicity in the atomically thin ferromagnetic Cr2Ge2Te6/ferroelectric In2Se3 van der Waals heterostructure due to the crosslayer magnetoelectric coupling.