Spectra of coupled magnetoelastic waves of a biaxial strongly anisotropic ferromagnet with biquadratic interaction

Abstract

The spectra of coupled magnetoelastic waves in a biaxial ferromagnet with biquadratic interaction are investigated. The phase diagrams of the system under investigation are constructed as functions of biquadratic exchange. It is shown that for a strong Heisenberg exchange (exceeding the biquadratic interaction), phase transitions in the system occur only through a decrease in the magnitude of the magnetization vector. For a strong biquadratic exchange (exceeding the Heisenberg interaction), orientational phase transitions are possible, which are reduced to a reorientation of the principal axis of the tensor of quadrupole magnetic moments.

Phase Transition in Temperature ?Quadrupolar Phase-Disordered Phase? in a Two-Dimensional Non-Heisenberg Ferromagnet

“…which describe the transition of the magnetic ion from state M 0 to state M. The spin operators are related to the Hubbard operators by the expressions [2,3,9] …”

“…This interaction should be replaced by a more complicated one, comprising the biquadratic coupling as well [1]. The influence of biquadratic exchange on phase states of magnetically ordered 3D systems is well studied [1][2][3][4][5][6]. It is shown, that the amount of this interaction leads (at some relation between material constants) to the appearance of a phase with tensorial order parameter, the so called quadrupolar phase.…”