Preparation under high pressures and neutron diffraction study of new ferromagnetic RCu₃Mn₄O₁₂ (R = Pr, Sm, Eu, Gd, Dy, Ho, Tm, Yb) perovskites

We report on the study of some new derivatives of the complex perovskite CaCu₃Mn₄O₁₂. Ca²⁺ cations can be replaced by rare earths in the RCu₃Mn₄O₁₂ (R = rare earths) family, implying an electron doping effect that dramatically affects the magnetic properties. These compounds must be prepared under high pressure conditions. We have synthesized for the first time, at 2 GPa in a piston–cylinder press, some new members of the family, with R = Pr, Sm, Eu, Gd, Dy, Ho, Tm and Yb, for which we describe structural and magnetization data. The materials with non-absorbing rare earths have been studied by means of neutron powder diffraction, allowing us to determine the subtle structural features which are related to the observed physical properties. In fact, for most of the R cations, the ferromagnetic T_C increases remarkably up to 400 K.