It was demonstrated that SrCoO3−δ could be stabilised into phase-pure perovskite forms by introducing small amounts (~5%) of rare earth ions (Sm3+ to Yb3+). At the same doping levels, La3+ and Pr3+ crystallised in the same isostructural trigonal structure as Sr6Co5O15. The Nd3+ composition exhibited a mixture of both structure-types. Powder X-ray diffraction revealed only a simple cubic perovskite structure. However, a combination of electron and neutron diffraction revealed a tetragonal (P4/mmm) ap x ap x 2ap superstructure. Here, Sr and the rare-earth ions were disordered over a single site while the O vacancies were localised on apical O2 sites. Magnetisation measurements showed that these materials underwent transitions to a spin-glass state at below 150K, and that significant coupling occurred between the rare-earth ions and the mixed Co3+/4+ ions. Magnetisation measurements, as a function of applied field, revealed that - below the transition temperature - ferromagnetic ordering took place at relatively large fields.

Oxygen Vacancy Ordering and Magnetism in the Rare Earth Stabilised Perovskite Form of SrCoO3-δ. M.James, D.Cassidy, K.F.Wilson, J.Horvat, R.L.Withers: Solid State Sciences, 2004, 6[7], 655-62