1: 1 Ca2+:Cu2+ A-site Order in a Ferrimagnetic Double Double Perovskite

Cation ordering in ABX(3) perovskites is important to structural, physical and chemical properties. Here we report discovery of CaCuFeReO6 with the tetragonal AA ' BB ' O-6 double double perovskite structure that was previously only reported for A '=Mn compositions. CaCuFeReO6 occurs in the same phase field as CaCu3Fe2Re2O12 demonstrating that different A-cation ordered peroskites may be obtained in the same chemical system. CaCuFeReO6 has ferrimagnetic order of Fe, Re and Cu spins below T-C=567 K, in contrast to Mn analogues where the Mn spins order separately at much lower temperatures. The magnetoresistance of CaCuFeReO6 displays low-field butterfly hysteresis with an unusual change from negative to positive values as field increases. Many more AA ' BB ' O-6 double double perovskites may be accessible for A '=Cu and other divalent transition metals at high pressure, so the presently known phases likely represent only the tip of the iceberg for this family.

Automated summary

The cation ordering in ABX(3) perovskites plays a crucial role in determining the structural, physical, and chemical properties of materials. The discovery of CaCuFeReO6 with a unique structure and magnetic properties suggests that there may be many more undiscovered materials in this family.