New stabilized phases in the Sr/Ca–Mn–Co–O system: structural–magnetic properties relationship

Abstract

Polycrystalline Sr₃CaMn₂CoO₉ and (Sr_0.5Ca_0.5)₁₅Mn₇Co₄O₃₃ have been synthesized and characterised by X-ray and electron diffraction, high resolution electron microscopy and magnetic measurements. These oxides constitute the α = 3, β = 1 and α = 4, β = 1 terms of the homologous series (A₃B₂O₆)_α(A₃B₃O₉)_β, respectively. Isolated rows of polyhedra sharing faces along the c-axis are made up of units of two and one face-sharing octahedra (occupied by Mn) linked by one trigonal prism (occupied by Co) in an ordered way. The chains are separated by columns of Sr/Ca atoms. Magnetic measurements suggest antiferromagnetic correlations in the two new commensurate monodimensional oxides. The influence of the size of alkaline-earth atoms on the long-range magnetic interactions is discussed.