Effect of La substitution on structure and magnetic properties of sol-gel prepared BiFeO3

Detailed Rietveld analysis of the room temperature (RT) x-ray diffraction data of LaxBi1-xFeO3 (LBFO) ceramics (0 <= x <= 0.4) prepared by sol-gel route revealed that the system retains distorted rhombohedral R3c structure of parent compound BiFeO3 (BFO) for x <= 0.2 but transforms to orthorhombic Pbnm structure for x > 0.2. The fundamental 12 Raman modes of pure BFO (x = 0.0) are reduced to 10 modes for x = 0.2 and further reduced to 7 modes for x = 0.4, which is a clear indication of structural modification and symmetry changes brought about by La doping. The coercive field, H-C, increases remarkably with an increase in La doping and x = 0.4 exhibits the highest H-C (19.5 kOe at RT) 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, M-r, increase linearly with La doping content due to the gradual change in spin cycloid structure. M(T) curve shows an anomaly at 50 K, similar to that expected in a spin glass system. The Neel temperature (T-N) of the LBFO increases with x, approaching that of the LaFeO3. (c) 2013 AIP Publishing LLC