Preparation And Characterization Of Multiferroic Materials

Multiferroic materials coexisting of ferroelectricity, ferroelasticity or ferromagn-etism have become one of the hottest topics of condensed matter physics and materials science in recent years, especially their potential for applications as multifunctional devices such as magneto-mechanical-electric exchanger, transducers, and data-storage. In this paper, the synthesis technologies, structural characterization and multiferroic properties of both the composties and single phase multiferroic materials were investigated. The mian contents are as follows:1. Magnetoelectric composites PbZr0.52Ti0.48O3-NiFe2O4were prepared by a conventional ceramic method, in which PbZr0.52Ti0.48O3is the piezoelectric phase and NiFe2O4is the ferrite phase. Our studies show that:reaction between PbZr0.52Ti0.48O3and NiFe2O4is not clear; but weak reaction existence reveales from the decrease of saturation magnetization in the ceramic composites; the magnetostriction strongly depends on the mole fraction of PbZr0.52Ti0.48O3; a model of the magnetostriction consisting of strain and polarization in the composites is proposed, under the model, the contribution of the magnetoelectric effect to magnetostriction is discussed quantitatively, the value is (-2.63-2.2x); moreover, the maximum magnetoe-lectric coefficient of17.6mV/cm Oe for the composite with PbZr0.52Ti0.48O3mole fraction of0.7is obtained; the frequency of microwave absorption decreases with an increase of PbZr0.52Ti0.48O3content in the composites. Study of this system is of great significance for the application of multiferr-oic materials in the devices.2. Room temperature ferromagnetism is observed in BaTiO3nanoparticles and microparticles synthesized using hydrothermal method and sol-gel method, respectively. The room temperature ferromagnetism of BaTiO3nanoparticles is related to the distortion of lattice, which is proved by the results of changing the post-annealing conditions and of the X-ray diffraction Rietveld of the sample synthesized at140℃. The same conclusion can be obtained in BaTiO3microparticles. In addition, the ferromagnetism didn’t vanish quickly. What is more, BaTiO3still had high ferroelectricity property and low leakage current. But the source of the ferromagnetism in the samples needs to be further in-depth studied.