Complex Ferrimagnetism and Magnetoresistance Switching in Ca-Based Double Double and Triple Double Perovskites

Cation ordering in ABO 3 perovskites can lead to interesting and useful phenomena such as ferrimagnetism and high magnetoresistance by spin polarized conduction in Sr 2 FeMoO 6 . We used high pressures and temperatures to synthesize the cation ordered AA′BB′O 6 perovskites CaMnFeReO 6, CaMnMnReO 6, and Ca(Mn 0.5 Cu 0.5 )FeReO 6 . These have columnar A/A′ and rocksalt B/B′ cation orders, as found in the recently discovered double double perovskite MnNdMnSbO 6, and partial Mn/Cu order over tetrahedral and square planar A′ sites in Ca(Mn 0.5 Cu 0.5 )FeReO 6 demonstrates that triple double cation order is possible. Neutron diffraction reveals complex ferrimagnetic orders in all three materials; CaMnFeReO 6 and Ca(Mn 0.5 Cu 0.5 )FeReO 6 have large room temperature magnetizations with low temperature switching of magnetoresistance in the latter material, and CaMnMnReO 6 displays a high coercivity of 1.3 T at low temperatures.