Magnetism and Crystal Symmetry of α-Mn

A systematic method of magnetic structure analysis is developed and applied to the case of α-Mn. Scalar, vector, and tensor quantities in a phenomenological thermodynamical potential are expanded in complete sets of basis functions which form irreducible representations of the space group, and on this basis, a possible magnetic structure for α-Mn is discussed. A non-collinear magnetic structure containing thirteen parameters is proposed. The magnetic point group is isomorphic with either D 2 d of C 3 v depending on whether the principal axis is along either a <100> or a <111>, respectively. Possible modes of magnetostrictive atom-displacement are also discussed.