New 10H perovskites Ba5Ln1−xMn4+yO15−δ with spin glass behaviour

Abstract

New 10H perovskite phases of composition Ba₅Ln_1−xMn_4+yO_15−δ (Ln = Sm–Lu) have been synthesised by solid-state reactions at 1300 °C. Their crystal structures have been investigated using X-ray and neutron diffraction. The 10H perovskite structure has an ordered arrangement of Ln and Mn ions on the corner-sharing octahedral centres and the face-sharing octahedral centres respectively. MnO₆ octahedral distortions and short Mn–Mn distances have been identified in these structures, and oxygen vacancies are found in the c-BaO₃ layers. Additionally, magnetic measurements and neutron diffraction identify spin glass transitions in these new materials. These transitions are related to the Mn ions on the corner sharing octahedral sites, which mediate magnetic interactions between tetramers of MnO₆ octahedra.