Magnetization Process of the Screw Spin Structure with Orthorhombic Anisotropy Energy

Abstract

Modifications of the screw spin structure due to external magnetic field and orthorhombic anisotropy energy at absolute zero are studied based on the model offered by Nagamiya, Nagata and Kitano. External magnetic field is applied along the easy axis of the in-plane anisotropy energy. When the anisotropy constant in the plane perpendicular to the screw axis is not zero, a ferrimagnetic Ising state, in which spins on one sublattice are down and those on two sublattices are up, becomes stable near cos q 0 =-1/2 in intermediate field, where q 0 is the turn angle of the screw. A ferrimagnetic fan state, which is a modification of the ferrimagnetic Ising state, is stable near cos q 0 =-3/4 in slightly lower field. Near cos q 0 =-1/2 two kinds of triangular state are seen to be stable. It is also shown that a four sublattice state such as \(\upuparrows\downdownarrows\) and a hexa-angular arrangement of spins are stable near cos q 0 =0 and 1/2, respectively, for weak field.