Three Perovskite Phases with Different Cation Orders in SmMnMn(MnSb)O.

Cation order, which can be controlled by synthesis conditions and stoichiometry, plays an important role in properties of perovskite materials. Here we show that aliovalent doping by Sb in SmMnMn(MnSb)O quadruple perovskite solid solutions can control cation orders in both A and B sites. Samples with 0.4≤x≤2 were synthesized by a high-pressure, high-temperature method at 6 GPa and 1770 K. Three regions with different cation orders were found at 0.5≤x≤1.0, x=1.5-1.6, and x=1.8. The 0.5≤x≤1.0 compositions have a B-site-disordered and A-site columnar-ordered structure with space group P4/nmc; the x=1.5 and 1.6 samples have a B-site rock-salt-ordered and A-site columnar-ordered structure with space group P4/n; the x=1.8 sample has a B-site rock-salt-ordered and A-site-disordered structure with space group P2/n. All the samples show one ferrimagnetic transition: T increases from 35 K to 73 K for 0.5≤x≤1.0, T=81 K for x=1.5 and 1.6, and T=53 K for x=1.8.