Strong enhancement of spin ordering byA-site magnetic ions in the ferrimagnetCaCu3Fe2Os2O12

Abstract

$AB{\mathrm{O}}_{3}$ perovskite is a kind of very important functional material with versatile physical properties. Although $B$-site chemical substitution with various magnetic ions has been widely investigated, the $A$-site doping with magnetic transition metal is little known. Here we report $A{A}_{3}^{\ensuremath{'}}{B}_{2}{B}_{2}^{\ensuremath{'}}{\mathrm{O}}_{12}$-type $A$- and $B$-site ordered ferrimagnet $\mathrm{CaC}{\mathrm{u}}_{3}\mathrm{F}{\mathrm{e}}_{2}\mathrm{O}{\mathrm{s}}_{2}{\mathrm{O}}_{12}$ with magnetic transition metals occupying three different atomic sites (${A}^{\ensuremath{'}}, B$, and ${B}^{\ensuremath{'}}$ sites). This compound is synthesized by a special high-pressure annealing process. It possesses a much higher Curie temperature ${T}_{\mathrm{C}}$ of 580 K compared with that of the $B$-site-only ordered $\mathrm{C}{\mathrm{a}}_{2}\mathrm{FeOs}{\mathrm{O}}_{6}$ (${T}_{\mathrm{C}}=320\phantom{\rule{0.16em}{0ex}}\mathrm{K}$) without magnetic ion at the $A$ site. First-principles numerical calculations reveal that this enhancement primarily originates from the additional spin interaction between the ${A}^{\ensuremath{'}}$-site $\mathrm{C}{\mathrm{u}}^{2+}$ and the ${B}^{\ensuremath{'}}$-site $\mathrm{O}{\mathrm{s}}^{5+}$, generating a strong $\mathrm{C}{\mathrm{u}}^{2+}(\ensuremath{\uparrow})\mathrm{F}{\mathrm{e}}^{3+}(\ensuremath{\uparrow})\mathrm{O}{\mathrm{s}}^{5+}(\ensuremath{\downarrow})$ ferrimagnetic spin coupling. This work opens up an alternative way for enhancing the spin ordering temperature by introducing $A$-site magnetic ions.