Preparation And Magnetoelectricity Properties Of Single-phase Multiferroic Materials

Multiferroic materials are materials which exhibit both magnetic order and ferroelectricity in the same phase, and exhibit magnetoelectric (ME) effect between two phases. Magnetoelectric multiferroics are expected to have broad prospect of application for informated storage,spintronic device,magnetic sensor,capacitance-inductance integration device and microwave technology area. But the magnetic phase-transition temperature in single-phase multiferroic is very low, most of the multiferoic ME effect occurs at low temperature. This thesis is trying to explore the new multiferroic candidates based on the latest status of the research, and make it realize strong multiferroic property at room temperature in order to narrow the gap between the theory and practice. On one hand, the single-phase multiferroics is synthesized by the technical innovation based on the lastest achievements of the international research, and its multiferroic properties are characterised by the new research methods; On the other hand, the doped multiferroics is synthesized and its multiferroic properties are characterized. The three kinds of the single-phase multiferroic materials and a kind of doped multiferroic material were found through the study, and they have very good multiferroic properties at room temperature. The research contents and results of the multiferroic materials include:1. Preparation and characterization of single-phase multiferroic PbFe12O19ceramicPbFe12O19ceramic has been successfully synthesized by the polymer precursor method using glycerin as a solvent sintering at1000℃. The ferroelectric test indicates that it has an intrinsic ferroelectric characterization. The research of the crystal structure model of PbFe12O19pushes us to propose that the ferroelectric might arise from Fe cation shifts away from the center along b axis, while O2and O4shifts off their original positions of octahedron along opposite directions of a-axis, which leads to the distortion of O5-Fe-O6bond away from straight line. 2. Preparation and characterization of doped PbFe12O19ceramicFirst, the magnetic-phase PbFe12O19powder has been successfully synthesized by polymer precursor method using glycerin and benzene as a solvent. Then the doped PbFe12O19ceramic is prepared by the method of mechanical miaxing and the content of doped SiO2is0.4percent. The ferroelectric test and the magnetic test prove the doped PbFe12O19ceramic is a multiferroic material at room temperature.3. Preparation and characterization of single-phase multiferroic BaFe12O19ceramicBaFe12O19ceramic has been successfully synthesized by the polymer precursor method sintering at1000℃. The ferroelectric test indicates that it has an intrinsic ferroelectric characterization. The research of the crystal structure model of BaFe12O19pushes us to propose that the ferroelectric might arise from Fe cation shifts away from the center along b axis, while O2and O4shifts off their original positions of octahedron along opposite directions of a-axis, which leads to the distortion of O1-Fe-O6bond away from straight line. BaFe12O19ceramic is tranditional magnetic material and the magnetic test proves that BaFe12O19ceramic has strong ferromagnetic feature at the room temperture though.4. Preparation and characterization of single-phase multiferroic SrFe12O19ceramicSrFe12O19ceramic has been successfully synthesized by the polymer precursor method sintering at1100℃. The ferroelectric test indicates that it has a large ferroelectricity. SrFe12O19ceramic is a tranditional magnetic material and the magnetic test proves that SrFe12O19ceramic is a strong ferromagnetic material too at room temperature.