Structure, ferroelectric properties, and magnetic properties of the La-doped bismuth ferrite

Bi1-x Lax Fe O3 ceramics with x=0, 0.1, 0.2, and 0.3 have been synthesized by solid state reaction, starting from metal oxides. A series of structure transformations is found to depend upon the doping level. Below 10% La doping, Bi1-x Lax Fe O3 maintains the rhombohedral structure of BiFe O3. However, for Bi0.8 La0.2 Fe O3 and Bi0.7 La0.3 Fe O3, the structures change to the orthorhombic and tetragonal, respectively. La doping significantly reduces electric leakage and leads to successful observation of electrical polarization hysteresis loops. Doping with La also enhances the ferromagnetic moment, due to the broken cycloid spin structure caused by the changes in the crystalline structure.