Spin canting

Antisymmetric exchange would align spins perpendicular to each other

Someantiferromagneticmaterials exhibit a non-zeromagnetic momentat a temperature nearabsolute zero.This effect is ascribed tospin canting,a phenomenon through which spins are tilted by a small angle about their axis rather than being exactly co-parallel.

Spin canting is due to two factors contrasting each other:isotropic exchangewould align the spins exactly antiparallel, whileantisymmetric exchangearising from relativistic effects (spin–orbit coupling) would align the spins at 90° to each other. The net result is a small perturbation, the extent of which depends on the relative strength of these effects.

This effect is observable in many materials such ashematite.