The effect of manganese oxidation state on antiferromagnetic order in SrMn1−xSbxO3 (0 < x < 0.5) perovskite solid solutions

Abstract

The mixed-valence manganese (Mn³⁺/Mn⁴⁺) solid solution, SrMn_1−xSb_xO₃, was prepared for the first time. Two ranges of solid solutions were found: (1) SrMn_1−xSb_xO₃ (0.025 ≤ x ≤ 0.09) with monoclinically distorted 6H-SrMnO₃ polytype (sp. gr. C/2c) and (2) SrMn_1−xSb_xO₃ (0.17 ≤ x ≤ 0.50) with a tetragonal unit cell (sp. gr. I4/mcm). Crystal structure refinement using X-ray and neutron powder diffraction data showed that the structure of the monoclinic solid solution consists of corner-sharing octahedra around sites occupied by manganese and antimony ions and face-sharing octahedra around sites occupied by manganese ions only, while the tetragonal solid solution has a random distribution of B-site cations. The presence of long-range antiferromagnetic order with a Néel temperature of about 148 K for SrMn_0.80Sb_0.20O₃ and about 280 K for SrMn_0.925Sb_0.075O₃ was found from the results of DC and AC susceptibility and neutron diffraction experiments at 5 K and 80 K.