Phase separation in La2−x A x CoMnO6 (A=Ca and Sr) perovskites

Abstract

Magnetic and neutron-diffraction studies of La2CoMnO6 doped with strontium and calcium ions are carried out. Stoichiometric and calcium-containing samples are orthorhombically distorted, whereas the oxidation and doping with strontium ions stabilizes a rhombohedral structure. Neutron-diffraction studies show that La2CoMnO6 is a ferromagnet, whereas a Ca-substituted compound does not exhibit long-range magnetic order. The whole set of data suggest that these compounds are inhomogeneous magnets that consist of clusters in which Co2+ and Mn4+ ions are ordered similar to ions in NaCl and of regions in which there is no such ordering. These regions exhibit different magnetic properties. Phase separation is discussed in a model of solid solutions with intrinsic chemical inhomogeneity on the nanometer scale.