Three Perovskite Phases with Different Cation Orders in Sm 2 MnMn(Mn 4-x Sb x )O 12 .

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 5+ in Sm 2 MnMn(Mn 4-x Sb x )O 12 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 2 /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 2 /n; the x=1.8 sample has a B-site rock-salt-ordered and A-site-disordered structure with space group P2 1 /n. All the samples show one ferrimagnetic transition: T C increases from 35 K to 73 K for 0.5≤x≤1.0, T C =81 K for x=1.5 and 1.6, and T C =53 K for x=1.8.