Giant coercivity and spin clusters in high pressure polymorphs of Mn2LiReO6.

Abstract

We present Mn₂LiReO₆ synthesised at high pressure in two different polymorphs. They are the only A-site manganites with an ideal +/7+ charge distribution over the B/B′ sites. The lower pressure polymorph crystallises in a polar R3 ordered-ilmenite type structure (OIL) with a calculated 26.9 μC cm⁻² electrical polarisation. It shows a cluster spin glass behaviour due to Li/Mn anti-site mixing. The well-ordered higher-pressure double-perovskite polymorph (DPv, P2₁/n) develops weak-ferromagnetism with giant magnetic coercivity (H_C = 6.9 T at 2 K) due to magnetocrystalline anisotropy enhanced by symmetry-restricted exchange interactions but in the absence of spin–orbit coupling.