Magnetic singularities in helimagnetic crystals

Abstract

Singularities of the spin structure in helimagnets are studied on the basis of the description of disclinations already made for cholesteric mesophases. The main differences arise from the possibility of two chiralities in helimagnets (i.e. two directions of rotation about the helical axis) and from the strong coupling between the spin and the lattice, which favours χ disclinations. It is shown that regions of opposite chiralities may be separated by ‘twin’ boundaries and χ ‘twin disclinations’ which can move by a process similar to the classical Cottrell and Bilby's process for solid lattices. Other types of singularities are briefly described and discussed.