Bistability and relaxor ferrimagnetism in off-stoichiometric NiCrO3

NiCrO3 has been proposed as a likely candidate for antiferromagnetic half metallic behaviour. A sample prepared at high pressure adopts the corundum structure with Ni/Cr cation disorder, and is found to have off-stoichiometric composition Ni0.80Cr1.20O3. This material shows complex local magnetic ordering phenomena at temperatures below 120 K but without any long range spin order observed by neutron diffraction. The transition to local ferrimagnetism occurs at 50-100 K, with two distinct regimes at TC1 = 95 and TC2 = 53 K evidencing electronic phase separation driven by variations in local composition. At low temperature the system undergoes a further transition at TC3 = 22 K, assigned to potential freezing of a cluster glass-like state, that results in a substantial increase in magnetic anisotropy. Ni0.80Cr1.20O3 is a bistable relaxor ferrimagnet where magnetic properties are linked to the lattice strain manifold that is determined by the peculiarities in the local chemical composition.