Ambient pressure synthesis and properties of LaCu3Fe2TiSbO12: New A-site ordered ferrimagnetic quadruple perovskite

Abstract

A large number of quadruple perovskites are synthesized and reported under high pressure while ambient pressure synthesized quadruple perovskites are limited in number. Recently, ambient pressure synthesis of quadruple perovskites has gained much interest.1 The A-site ordered quadruple perovskite, LaCu3Fe2TiSbO12, reported for the first time, is synthesized by high-temperature solid-state reactions at ambient pressure. Rietveld structure refinement using P-XRD data reveal formation of LaCu3Fe2TiSbO12 in body centered cubic Im-3 space group with lattice parameter of 7.4465(7) Å. The compound shows complete 1:3 order of A-site La with A′-site Cu and B/B′-site disorder of Fe with Ti and Sb instead of both A- and B-site order in CaCu3Fe2Sb2O12 (Larregola et al., 2014; Chen et al., 2013) [1,2]. The magnetic transitions observed in the compound around 160 and 60 ​K are attributed to short-range orders. The static disorder at the B-sublattice introduced by non-magnetic Ti and Sb precludes the possibility of long-range magnetic order in the compound. Lower saturation magnetization presumably supports antiferromagnetic ordering of A-site Cu2+ and B-site Fe3+ spins interrupted by the B-site disorder restricting it to a short-range phenomenon. The ferrimagnetic quadruple perovskite also show reasonably high dielectric constant in the low-frequency region and a low dielectric loss at room temperature. The stabilization of LaCu3Fe2TiSbO12 under ambient pressure despite having a fairly large global instability index (GII, calculated with SPuDS) of 0.276 v.u. is interesting and may suggest accessibility of many new quadruple perovskites at atmospheric pressure.