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Multi - iron material refers to materials which contain both two and more than two of iron (such as ferroelectricity, iron elastic , ferromagnetic , etc.) , it is more important is having magnetic and electric coupling response , while such material may be the microelectronic technology compatible , has a broad application prospects in the driver , sensing , storage and intelligent systems , making multiferroic materials has become a new research focus of materials Science . As a typical single phase multiferroic materials , BiFeO 3 (BFO) is found only at room temperature ferroelectricity and magnetic ordering materials . In this thesis, leakage current of BFO materials for large magnetoelectric effect of weak insufficient study the BFO 's preparation process , as well as sintering of micro- structure and performance of the BFO La doping and magnetic fields . The main contents are as follows : the first chapter introduces the history and status of the studies of multiferroic materials , focus on the single-phase multiferroic material BiFeO 3 < / sub> structure , performance, and study the present situation and problems . Chapter II , for the BFO of Bi characteristics likely to be volatile , solid-phase reaction method , preparation of the different Bi : Fe molar ratio of the polycrystalline BFO its doped compounds La ( the Bi 1 - x La < sub> x FeO 3 , x = 0,0.05,0.1,0.15,0.2), and its structure and physical properties were studied to obtain optimal BI excess parameter (Bi : Fe molar ratio = 1.02) and the amount of La-doped ( x = 0.1 ) . Chapter sintering conditions in the absence of magnetic field and the external magnetic field (0.5T) Preparation of Bi , La , 0.9 0.1 < / sub > FeO 3 < / sub > ( BLFO ) more crystal bulk material , the research found that the magnetic field grain refinement can play a role and improve the material density , making BLFO electrode performance significantly improved . Chapter IV , respectively, in the presence or absence of a magnetic field under the conditions of sintering Bi 0.9 La 0.1 FeO 3 and cobalt Ferrite (CoFe by 2 O 4 , CFO) composite samples magnetic and ferroelectric studies show that the composites prepared under a magnetic field of its magnetic properties and have significantly improved the performance of the electric polarization . Chapter V , the paper summarizes briefly on the next phase of work outlook .
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