Influence of La-doping on structure and magnetic behaviors in BiFeO3

The series of polycrystalline Bi1−xLaxFeO3 (0 ⩽ x ⩽ 0.50) ceramic powders was successfully synthesized by sol-gel method in this paper. X-ray diffraction and Rietveld crystal structure refinement software (FULLPROF) were used as complementary method to study structure and hyperfine interactions of the samples. It was a clear indication of structural modification and symmetry changes brought about by La doping. The BFO is crystallized in rhombohedrally distorted perovskite structure with space group R3c for x ⩽ 0.10. With an increase of La content, within the range x = 0.10-0.20 a structural phase evolutes from rhombohedral to cubic Pm3¯m structure, and then transits to orthorhombic Pbnm structure on further increasing the La-doping to x = 0.50. The magnetization of La-doped samples is improved with the increase of La content. The coercive field (Hc) increases remarkably with an increase in La doping and x = 0.50 exhibits the highest Hc (20.2 kOe at room temperature) reported so far in any rare earth doped BFO, which will have a great potential for practical application in non-volatile memory devices. Moreover, high-field magnetization and remanence (Mr) increase with La doping content due to the gradual change in spin cycloid structure.