spin canting

File:Dzyloshinskii Moriya antisymmetric exchange.jpg

Some antiferromagnetic materials exhibit a non-zero magnetic moment at a temperature near absolute zero. This effect is ascribed to spin 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 exchange would align the spins exactly antiparallel, while antisymmetric exchange arising 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.{{Cite book |author=Richard Winpenny |title=Molecular Cluster Magnets |publisher=World Scientific |year=2011 |isbn=9789814322942 |page=119}}

This effect is observable in many materials such as hematite.{{Cite web |url=http://magician.ucsd.edu/essentials/webbookse18.html#x23-280079 |title=Ferromagnetism |publisher=University of California, San Diego |accessdate=2 January 2013 |archive-date=11 June 2016 |archive-url=https://web.archive.org/web/20160611194326/http://magician.ucsd.edu/essentials/WebBookse18.html#x23-280079 |url-status=dead }}