Weak antiferromagnetic ordering and pure magnetic reflections induced by Dzyaloshinskii-Moriya interaction in MnSi-type crystals

Abstract

Symmetry analysis of the Dzyaloshinskii-Moriya (DM) interaction in MnSi-type cubic crystals demonstrates that the magnetic moments are tilted periodically, producing a weak antiferromagnetic pattern, when the helix is unwound by magnetic field. The tilt angles of four Mn sublattices are determined by a component of the DM vector perpendicular to that one responsible for helical spiraling; both components have been evaluated using a simple model. It is shown that the tilting should induce pure magnetic reflections 00l, l=2n+1 in neutron or x-ray magnetic scattering, and the structure factors of these "forbidden" reflections are calculated for arbitrary field orientations.