Spin canting and spin-flop transition in antiferromagnetic Cr2O3 nanocrystals

Abstract

The structure and magnetic properties of Cr2O3 and Cr nanoparticles have been investigated. The as-prepared Cr nanoparticles show a core/shell structure, consisting of a Cr core and a thin Cr oxide shell with a thickness of 1.5–2.5 nm. Annealing the Cr nanoparticles in air leads to the formation of Cr2O3 nanoparticles with spherical morphology. The temperature dependence of the magnetization indicates that these Cr2O3 nanocrystals are antiferromagnetic below their Néel temperature of 320 K and undergo an antiferromagnetic to weak-ferromagnetic transition below about 140 K due to spin canting at disordered surfaces. Below 100 K, a spin-flop transition is induced by an external field with a critical field lower than about 7 T.