An attempt to observe the basal plane anisotropy of hematite

Abstract

THE weak ferromagnetism of hematite is confined to the basal plane at room temperature. On the basis of thermomagnetic observations by Pauthenet, NBel (1953) concluded that the antiferromagnetic spin alignment had complete freedom of orientation within this plane, from which it must be concluded that hematite is magnetically isotropic within the plane. However, in order to explain the fact that hematite can have a very stable remanence, Wohlfarth (1955) assumed a, basal plane anisotropy of triaxial (sin 38) symmetry. Dzyaloshinski (1958), whose explanation of the weak ferromagnetism of hematite in terms of slightly canted anti-ferromagnetic spins is now generally accepted, required a hexagonal anisotropy, with a possible smaller triaxial term. Either would explain the magnetic hardness of hematite.