Perovskites Bi0.8La0.2FeO3 and Bi0.8La0.2Fe0.95Cr0.05O3: Crystal structure and magnetic and charge states of iron ions

Perovskites of the Bi_0.8La_0.2Fe_{1 ? x} Cr _x O₃ system (x = 0, 0.05) were investigated by Mössbauer spectroscopy in the temperature range of 298–800 K. The samples were fabricated by solid-state synthesis and had a rhombic structure. Iron ions in Bi_0.8La_0.2FeO₃ and Bi_0.8La_0.2Fe_0.95Cr_0.05O₃ are situated in trivalent states. The magnetic transition temperatures (the Néel temperatures T _N ) T _N = 677.5 ± 2.5 K for Bi_0.8La_0.2FeO₃ and T _N = 647.6 ± 2.5 K for Bi_0.8La_0.2Fe_0.95Cr_0.05O₃ are measured. The substitution of trivalent iron ions from trivalent chromium ions in the amount x = 0.05 in Bi_0.8La_0.2Fe_0.95Cr_0.05O₃ perovskite decreases the hyperfine magnetic field at nuclei ⁵⁷Fe in Fe⁺³-O-Cr⁺³ chains by 30 kOe.