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Multiferroic materials have garnered significant attention in recent years due to their unique magnetoelectric coupling effect. However, it is difficult to directly switch the magnetization/polarization directions of conventional solid multiferroic materials under the action of an applied electric/magnetic field, limiting the enhancement of the magnetoelectric coupling coefficient. In this study, CoFe2O4 (CFO) nanoparticles with an average size of 52.27 nm were prepared using the chemical co-precipitation method, and Ba0.8Sr0.2TiO3 (BST) nanoparticles with an average size of 66.10 nm were prepared via the sol–gel method. On this basis, CFO–BST multiferroic fluids were created through ball milling, and the effect of viscosity on the magnetoelectric properties was investigated. It was found that viscosity is positively correlated with the settling stability of the fluids. With increasing viscous resistance and stability, the magnetic dielectric response of the multiferroic fluids increases at first and then decreases. The highest magnetic dielectric response (3.9%) was observed for fluids with a viscosity of 1000 mPa s. Furthermore, it was discovered that the multiferroic fluids exhibited an obvious switching effect when subjected to a discontinuous magnetic field. Additionally, the polarization intensity of the multiferroic fluids was found to increase initially before decreasing with increasing viscosity. The multiferroic fluids with a viscosity of 1000 mPa s achieved a magnetoelectric coupling coefficient of 89.8 V (cm Oe)−1 when subjected to an applied magnetic field of 91 Oe due to their good stability and suitable viscosity. This investigation implies that multiferroic liquids may have potential application in information storage and new capacitors. [ABSTRACT FROM AUTHOR]

Multiferroic materials have attracted much attention because of their magnetoelectric coupling effect. In this paper, MnFe2O4 (MFO) magnetic particles and PbZr0.52Ti0.48O3 (PZT) ferroelectric particles were prepared by hydrothermal method and sol–gel method, respectively. PZT particles with different sizes were produced by tuning the sintering temperature, and on this basis, MFO-PZT multiferroic liquid was prepared by using monoamino ethoxy-coupling agent as the surfactants and dimethyl silicone oil as the carrier liquid. The effect of PZT particle size on magnetoelectric properties was studied. XRD and SEM show that the PZT particle and the MFO particle have no secondary phase, the size of MFO particle is 52 nm, and the PZT particle sizes are 0.38 μm, 1.07 μm, 1.68 μm, and 1.79 μm, respectively. When the particle size of PZT is 0.38 μm, a large dielectric constant of 8.39 of the multiferroic liquid was observed at low frequency (250 Hz). When the size of PZT is 1.79 μm, the liquid has the maximum saturation polarization intensity Ps ~ 0.0191 μC/cm2 and the maximum residual polarization intensity Pr ~ 0.0063 μC/cm2 was obtained. When a magnetic field is applied, the value of both Pr and Ps increases. When the size of PZT is 1.07 μm, the maximum magnetoelectric coupling coefficient of the liquid is 54.82 V/(cm·Oe). Compared with the same series of magnetoelectric materials, the magnetoelectric composite multiferroic liquid has a potential application prospect. [ABSTRACT FROM AUTHOR]

BaFe12O19 (BaM) powders and their corresponding ceramics were prepared by the sol–gel method at different solution concentrations (0.195–0.325 mol/L). The effects of solution concentration on microstructure, surface morphology, electrical properties, and magnetic properties of BaM powder BaM ceramics were systematically studied. XRD results show that the powders are pure BaM phase. SEM results show that with the increase in solution concentration, the grain size of ceramic increases, and the grain size of hexagonal sheet structure decreases gradually. At room temperature, when the solution concentration is 0.195 mol/L, ceramics' saturation polarization intensity and residual polarization intensity reach the maximum, which are 0.528 μC/cm2 and 0.297 μC/cm2, respectively. When the solution concentration is 0.325 mol/L, the ferroelectric properties of ceramic deteriorate due to the influence of leakage current. The ferroelectric hysteresis loop and magnetic hysteresis loop of ceramics show the multiferroic properties of ceramics at room temperature, which provides a new choice for single-phase multiferroic materials and lays a foundation for the multi-functionalization of BaM devices. [ABSTRACT FROM AUTHOR]

Magnetoelectric composites have attracted much attention due to their strong magnetoelectric coupling effect. In this paper, PbTiO3-NiFe2O4 (PTO/NFO) composite ceramics were prepared by sol-gel method. Effect of sintering temperatures on the structure, dielectric properties and multiferroic properties were studied. XRD results show that PTO/NFO ceramics have been successfully prepared. When the sintering temperature is 1050 °C, the secondary phase PbO2 exists in the ceramics. SEM results show that there were two kinds of grains with different sizes. EDS analysis suggested that the large particles are NFO and the small particles are PTO. The sintering temperature has a great influence on the dielectric and ferroelectric properties of the prepared ceramics. When the sintering temperature is 950 °C, the ceramics show the maximum dielectric constant at low frequency. When the sintering temperature is 1150 °C, the maximum residual polarization is 1.236 μC/cm2. The conductive mechanism of ceramics is dominated by Space Charge – Limited Conduction. The remanent magnetization and coercive field decrease with increasing the sintering temperature. The magnetoelectric coupling coefficient shows that ceramics have strong magnetoelectric coupling performance (5.7 V/cm·Oe). [ABSTRACT FROM AUTHOR]

Ca 3 (Ti 1- x Co x) 2 O 7 ceramics were prepared by a tartaric acid sol-gel method and sintered in an oxygen atmosphere. The introduction of Co2+/Co3+ as acceptor dopants leads to the formation of more oxygen vacancies and defect dipoles in Ca 3 (Ti 1- x Co x) 2 O 7 ceramics. Oxygen vacancy and defect dipoles lead to the transition of dielectric, leakage, and ferroelectric behaviors of Ca 3 (Ti 1- x Co x) 2 O 7 ceramics. The coexistence of hybrid improper ferroelectricity and ferromagnetism at room temperature in Ca 3 (Ti 1- x Co x) 2 O 7 ceramics has been successfully realized through the superexchange interaction of Co–O–Co. Ca 3 (Ti 1- x Co x) 2 O 7 ceramics exhibit superior ferroelectricity (the remnant polarization is 3.29 μC/cm2) and enhanced ferromagnetism (the remnant magnetization reaches 6.4×10−3 emu/g). This strategy based on the introduction of transition metal ions with unfilled 3d shells at B sites is an important approach to realize novel room-temperature single-phase multiferroic materials for Ca 3 Ti 2 O 7 -based materials. [ABSTRACT FROM AUTHOR]

With the development of electronic information technology, the miniaturization of lightweight devices and their integration have increased the requirements for materials, and two-dimensional composite multiferroic materials have become a major research hotspot in recent years. However, it is difficult for traditional solid multiferroic material to directly switch the magnetic/polarization direction under the action of an applied electric/magnetic field, limiting the improvement of the magnetoelectric coupling coefficient. In this study, a series of BiFeO 3 (BFO)/CoFe 2 O 4 (CFO) composite film multiferroic materials were prepared by changing the annealing routes and annealing atmosphere, the microstructure, ferroelectric properties, dielectric properties, photovoltaic properties, magnetic properties, and magnetoelectric coupling properties of composite films were routeatically studied. The results showed that under the slow annealing route, the composite film has obvious ellipsoidal grains with distinct grain boundaries and better crystallinity. Moreover, the performance of the film after annealing in different atmospheres of the slow annealing route was improved compared with that of the rapid annealing route after annealing in different atmospheres. Simultaneously, by changing the annealing atmosphere of the composite film, the film exhibited better magnetic optical properties and coupling properties after annealing in oxygen. In addition, this study showed that the dielectric constant and residual polarization value of the film increase under the action of magnetic field and illumination, and the maximum photomagnetic dielectric response (3.19%) and photomagnetic response (1.58%) are observed in the annealed film under the oxygen atmosphere of the slow annealing regime, indicating that the magnetoelectric coupling effect of the film is improved under the action of applied light. • Under the slow annealing system, the composite films have grain boundaries and better crystallinity. • The properties of the films annealed under the slow annealing regime are good under different atmospheres. • Films show better magnetic, optical and coupling properties after annealing in oxygen. • The dielectric constant and residual polarization of the film increase under the action of magnetic field and illumination. • Large photomagneto-dielectric responses (3.19%) and photomagneto-electric responses (1.58%) were observed. [ABSTRACT FROM AUTHOR]

• Mn 0.5 Zn 0.5 Fe 2 O 4 -PbZr y Ti 1-y O 3 multiferroic fluids were prepared by the ball milling method. • The polarization intensity of PbZr y Ti 1- y O 3 particles reaches its maximum of 2.55 μC cm−2. • Aa high dielectric constant of 4.6 and a saturation polarization intensity of 15.69 nC cm-2 were obtained. • All specimens present obvious magnetodielectric response. • The maximum longitudinal magnetoelectric coupling coefficient α E33 is 11.49 V cm−1 Oe-1. The Mn 0.5 Zn 0.5 Fe 2 O 4 -PbZr y Ti 1-y O 3 multiferroic fluids were prepared by the ball milling method, and the polarization intensities of PbZr y Ti 1-y O 3 particles on the magnetoelectric coupling (ME) effect were investigated. X-ray diffraction analysis (XRD) results indicate that the pure phase Mn 0.5 Zn 0.5 Fe 2 O 4 and PbZr y Ti 1-y O 3 particles (y = 0, 0.25, 0.5, 0.75, and 1) were successfully prepared. When y = 0.5, the polarization intensity of PbZr y Ti 1- y O 3 particles reaches its maximum of 2.55 μC cm−2. At this time, the Mn 0.5 Zn 0.5 Fe 2 O 4 -PbZr y Ti 1-y O 3 multiferroic fluids possess a high dielectric constant of 4.6 and a saturation polarization intensity of 15.69 nC cm−2. After applying the magnetic field, it shows a better magnetodielectric response (56.12 %), while the ferroelectric properties are also significantly improved. When the polarization intensity reaches its maximum value, the maximum longitudinal magnetoelectric coupling coefficient α E33 is 11.49 V cm−1 Oe-1. It provides a new approach to achieving the strong magnetoelectric coupling effect in multiferroic fluids. [ABSTRACT FROM AUTHOR]

• The effect of pH value of precursor solution on the microstructure and magnetoelectric properties of BaFe 12 O 19 nanoparticles and ceramics were studied. • The change of pH value of precursor solution causes large distortion of hexagonal flake grains of ceramics, which reflects the deformation of hexagonal cells in BaFe 12 O 19 crystal and leads to the asymmetry of local lattice. • The ferroelectric hysteresis loop and hysteresis loop indicate the multiferroic properties of the prepared ceramics at room temperature. The effect of ceramics leakage current on ferroelectric property were further studied. In this paper, BaFe 12 O 19 (BaM) ceramics at different pH values were prepared by sol–gel method. Effects of pH value on the microstructure, electrical as well as magnetic properties were systematically studied. XRD indicate that the ceramics were mainly BaM. However, with the pH value increasing further, the BaFe 2 O 4 impurity phase appears gradually in both powders and ceramics due to the degree of complexation between citric acid and metal cations and other reasons. SEM results show that the grain size of ceramics decreases from 2.28 μm to 1.35 μm with the pH value increase from 4 to 8. It is found that room temperature dielectric constant, residual polarization, and saturation magnetization of the ceramics is the largest when the pH value of the solution is 4, which are 0.108 μC/cm2 and 32.829 emu/g, respectively. The dielectric constant and residual polarization of ceramics decrease with the increase of pH value. The ferroelectric and magnetic hysteresis loops have confirmed room-temperature multiferroic properties of the prepared ceramics. It laid the foundation for the further development of new room temperature single-phase multi-iron materials. [ABSTRACT FROM AUTHOR]