CaCuMn$_6$O$_{12}$ vs. CaCu$_2$Mn$_5$O$_{12}$: a comparative study

The ferrimagnetic compounds Ca(Cu$_x$Mn$_{3-x}$)Mn$_4$O$_{12}$ of double distorted perovskites AC$_3$B$_4$O$_{12}$ family exhibit a rapid increase of the ferromagnetic component in magnetization at partial substitution of square coordinated (Mn$^{3+}$)$_C$ for (Cu$^{2+}$)$_C$. In transport properties this is seen in a change of semiconducting type of resistivity for the metallic one. The evolution in magnetic properties of Ca(Cu$_x$Mn$_{3-x}$)Mn$_4$O$_{12}$ is driven by strong antiferromagnetic exchange interaction of (Cu$^{2+}$)$_C$ with octahedra coordinated (Mn$^{3+}$/$^{4+}$)$_B$. The competing interactions of (Mn$^{3+}$)$_C$ with (Mn$^{3+}$/$^{4+}$)$_B$ lead to the formation of non-collinear magnetic structures which can be aligned by magnetic field.