Synthesis, magnetic properties, and neutron diffraction study of the complex perovskites R(Cu3−xMnx)Mn4O12 (R=Pr, Nd and x=1,2)

Abstract

The new complex perovskites of formula R(Cu3−xMnx)Mn4O12 (R=Pr, Nd and x=1,2) have been prepared. The partial replacement of Cu2+ by Mn3+ cations does not involve a change in symmetry from that of the parent compounds RCu3Mn4O12, presenting a cubic structure with space group Im3¯. The Mn3+ introduced at the square-planar 6b site promotes the valence mixing of Mn3+ and Mn4+ ions at the octahedral 8c site, leading to an increase in the bonding distances in the MnO6 octahedron and a slight decrease in the distances in the CuO4 polyhedron. All the compounds present a spontaneous increase in the magnetization below TC, typical of ferro- or ferrimagnetic materials. Due to the increasing content of Mn3+ at the 8c sites, some Mn–Mn exchange interactions switch from ferromagnetic (FM) to antiferromagnetic (AFM), weakening the overall FM exchange interactions and decreasing TC and MS. Neutron powder diffraction (NPD) data indicate that both sublattices (square-planar and octahedral) show a parallel arrangement of the magnetic moments.