Electromagnetic soliton propagation in a spin torque helimagnet

Abstract

We study the nonlinear dynamics of the electromagnetic wave propagation in a spin-torque driven helimagnet which accounts for the fundamental magnetic interactions. The dynamical Landau–Lifshitz equation includes the magnetic spin exchange, anisotropy, helimagnetic spin coupling through the anti-symmetric Dzyaloshinskii–Moriya interaction driven by the applied electric current density. The electromagnetic wave propagation is governed by the Maxwell equation with the induced current density factor. On the basis of the reductive perturbation method, we present a higher order nonlinear Schrödinger (NLS) equation as a reduction of the Maxwell–Landau model. Through the direct ansatz method, we derive a set of solutions for the NLS equation. These solutions include bright, dark and kink or front soliton solutions for certain specific conditions imposed on the spin-torque helimagnet.