Structural and multiferroic properties of La-modified BiFeO3 ceramics

The coexistence of the magnetic and the electrical properties in lanthanum (La)-modified bismuth ferrite (Bi1-xLaxFeO3, x=0.05, 0.1, 0.15, and 0.2) ceramics was studied and compared with those of bismuth ferrite (BiFeO3). The presence of a small secondary phase of BiFeO3 (arises due to excess Bi2O3) was removed on La substitution at the Bi site, as observed in x-ray diffraction (XRD). The effect of La substitution on dielectric constant, loss tangent, and remnant polarization of the samples was studied in a wide range of temperature (77-400 K) and frequency (1 kHz-1 MHz). The variation of magnetization, coercive field, and exchange bias with temperature (2-300 K) and La concentration were investigated. These changes in the magnetic parameters with La doping along with those of the electron magnetic resonance parameters measured at 300 K and 9.28 GHz are understood in terms of increase in the magnetic anisotropy and magnetization. These results also show that stabilization of crystal structure and nonuniformity in spin cycloid structure by La substitution enhances the multiferroic properties of BiFeO3. (c) 2007 American Institute of Physics.