High pressure synthesis of polar and non-polar cation-ordered polymorphs of Mn2ScSbO6

Abstract

Two new cation-ordered polymorphs of Mn₂ScSbO₆ have been synthesised at high-pressure. At 5.5 GPa and 1523 K Mn₂ScSbO₆ crystallizes in the Ni₃TeO₆-type structure with the polar R3 space group and cell parameters a = 5.3419 (5) Å and c = 14.0603 (2) Å. Below T_C = 42.0 K it exhibits ferrimagnetic order with a net magnetization of 0.6μ_B arising from unusual site-selective Mn/Sc disorder and is thus a potential multiferroic material. A double perovskite phase obtained at 12 GPa and 1473 K crystallizes in the non-polar P2₁/n monoclinic space group with cell parameters a = 5.2909 (3) Å, b = 5.4698 (3) Å, c = 7.7349 (5) Å and β = 90.165 (6) °. Magnetization and neutron diffraction experiments reveal antiferromagnetic order below T_N = 22.3 K with the spins lying in the ac plane.