Magnetic point groups and space groups

Abstract

We review the notion of magnetic symmetry of finite structures as well as infinite periodic and quasiperiodic crystals. We describe one of the most direct consequences of having magnetic symmetry in crystals which is the extinction of magnetic Bragg peaks in neutron diffraction patterns. We finish by mentioning the generalization of magnetic groups to spin groups and color groups.Comment: Written for the Encyclopedia of Condensed Matter Physics. Contains 2 color figures - gray scale version available from the author's website: http://www.tau.ac.il/~ronlif