Ferri- and ferro-magnetism in CaMnMReO6 double double perovskites of late transition metals M = Co and Ni

Abstract

Two new double double perovskites of ideal compositions CaMnMReO₆ (M = Co, Ni) are reported. The M = Co material has refined composition CaMn_0.7Co_1.3ReO₆ and orders ferrimagnetically below T_C = 188 K with a relatively large saturated magnetisation of 4.5 μ_B. The M = Ni product, CaMn_1.2Ni_0.8ReO₆, is a remarkable example of a ferromagnetic oxide with four distinct spin sublattices all collinearly ordered below T_C = 152 K.