~(57)Fe Hyperfine Parameters in Bi_(1-x)La_xFeO_3 (x = 0 -1)

摘要

~(57)Fe Moessbauer study of the Bi_(1-x)La_xFeO_3 (x=0, 0.1, 0.2, 0.61, 0.9, 1.0) perovskites has been performed at room temperature (RT) to analyze influence of the space spin-modulated magnetic structure (SSMMS) on parameters of hyperfine interactions, the valence and magnetic states of iron ions. SSMMS in perovskites BiFeO_3 and Bi_(0.9)La_(0.1)FeO_3 leads to a specific distribution of hyperfine fields P(H) with two peaks. Substitution La for Bi more than x = 0.2 destroys SSMMS and P(H) corresponds to a distribution for a homogeneous spin structure. Concentration dependences of hyperfine fields (H), isomer (δ) and quadrupole (ε) shifts were measured. Due to the isomer shift values the iron ions are in the trivalent state. The local magnetic moments μ(Fe) on Fe~(+3) ions were determined in these perovskites.