Strong enhancement of spin ordering by A-site magnetic ions in the ferrimagnet CaCu3Fe2Os2O12

ABO(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 AA'3B2B'(2) O-12-type A-and B-site ordered ferrimagnet CaCu3Fe2Os2O12 with magnetic transition metals occupying three different atomic sites (A', B, and B' sites). This compound is synthesized by a special high-pressure annealing process. It possesses a much higher Curie temperature T-C of 580 K compared with that of the B-site-only ordered Ca2FeOsO6 (T-C = 320 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'-site Cu2+ and the B'-site Os5+, generating a strong Cu2+(up arrow)Fe3+(up arrow)Os5+(down arrow) ferrimagnetic spin coupling. This work opens up an alternative way for enhancing the spin ordering temperature by introducing A-site magnetic ions.