Order–disorder and magnetic clusters in some mixed-metal perovskites

Abstract

The temperature dependence of the ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectra and the zero-field-cooled and field-cooled magnetic susceptibilities of SrLaFeSnO₆, SrEuFeSnO₆, BaLaFeSnO₆ and CaLaFeSnO₆ show the existence of unusual magnetic relaxation behaviour. In the case of CaLaFeSnO₆ there is evidence for a non-random distribution of the Fe and Sn, although the other compounds are fully disordered. It is proposed that competition between the first- and second-nearest-neighbour superexchange interactions leads to the formation of magnetic clusters which can grow with decrease in temperature until long-range antiferromagnetic order is achieved.