Magnetic properties of ferrites-cobaltites Bi1 − x La x Fe1 − x Co x O3 (1.0 ≥ x ≥ 0.7) with a perovskite structure

Abstract

The molar magnetic susceptibility (χmol) of Bi1 − xLaxFe1 − xCoxO3 solid solutions (x = 1.0, 0.9, 0.8, or 0.7) with a crystal structure of rhombohedrally distorted perovskite (R\(\bar 3\)c) has been investigated in the temperature range of 5–300 K in a 0.86 T magnetic field. In the temperature range where χmol depends on temperature T according to the Curie-Weiss law, the resulting effective magnetic moments of Fe3+ and Co3+ ions (\(\mu _{eff,Fe^{3 + } ,Co^{3 + } ,} \mu _{eff,Fe^{3 + } } \) and \(\mu _{eff,Co^{3 + } } \)) have been determined for the solid solutions under study. Fe3+ ions in the solid solutions have been found to be in the mixed intermediate spin (IS) and high spin (HS) states (\(\mu _{eff,Fe^{3 + } } \) is 4.26μB and 4.68μB for the temperature range of 5–100 and 150–300 K, respectively). It is shown that 8% Co3+ ions in LaCoO3 at 5–19 K are in the paramagnetic IS state and they determine to a great extent the magnetic susceptibility. It is established that only 9% and 18% Co3+ ions in Bi1 − xLaxFe1 − xCoxO3 solid solutions (x = 0.9 or 0.8) are in the paramagnetic IS state in the temperature ranges of 5–30 and 5–110 K, respectively, while the other ions are diamagnetic.