A Perovskite Containing Quadrivalent Iron as a Charge‐Disproportionated Ferrimagnet

Abstract

Ferri interesting: CaCuII3FeIV4O12, prepared at 15 GPa and 1300 K, undergoes a charge disproportionation (2 FeIV→FeIII+FeV) and electrical, magnetic, and structural changes at 210 K. The FeIIIO6 and FeVO6 octahedra are ordered in a rock-salt manner (see picture; Ca gray, O blue, Cu red), and the low-temperature phase has the ferrimagnetic structure CuII(S=1/2,↓)3FeIII(S=5/2,↑)2FeV(S=3/2,↑)2.