Observation of A -site antiferromagnetic and B -site ferrimagnetic orderings in the quadruple perovskite oxide CaCu3Co2Re2O12

Abstract

A quadruple perovskite oxide $\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Co}}_{2}{\mathrm{Re}}_{2}{\mathrm{O}}_{12}$ was synthesized by high-pressure annealing. This compound crystallizes in an $A$- and $B$-site ordered quadruple perovskite structure with space group $Pn\text{\ensuremath{-}}3$. The charge combination is determined to be $\mathrm{Ca}{{\mathrm{Cu}}^{2+}}_{3}{{\mathrm{Co}}^{2+}}_{2}{{\mathrm{Re}}^{6+}}_{2}{\mathrm{O}}_{12}$ by bond valence sum analysis and x-ray absorption spectroscopy. In contrast to other isostructural $A{\mathrm{Cu}}_{3}{B}_{2}{B}_{2}^{\ensuremath{'}}{O}_{12}$ compounds with a single magnetic transition, a long-range antiferromagnetic phase transition originating from the ${A}^{\ensuremath{'}}$-site ${\mathrm{Cu}}^{2+}$ sublattice is found to occur at ${T}_{N}\ensuremath{\approx}28\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Subsequently, the spin coupling between the $B$-site ${\mathrm{Co}}^{2+}$ and ${B}^{\ensuremath{'}}$-site ${\mathrm{Re}}^{6+}$ ions contributes to a ferrimagnetic transition around ${T}_{\mathrm{C}}\ensuremath{\approx}20\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Strong electrical insulating behavior is identified by optical measurement with an energy gap of approximately 3.75 eV. The mechanisms of the spin interactions are discussed in detail.