Current induced rotational torques in the skyrmion lattice phase of chiral magnets

TL;DR

This paper investigates how electric currents induce rotational torques in the skyrmion lattice phase of chiral magnets, revealing mechanisms involving lattice distortions and angular momentum transfer, with implications for magnetic control.

Contribution

It introduces a new mechanism for current-induced rotation of skyrmion lattices involving lattice distortions and angular momentum transfer, analyzed through adapted Landau-Lifshitz-Gilbert and Thiele equations.

Findings

Rotation angle depends on magnetic field orientation.

Lattice distortions contribute to angular momentum transfer.

Rotation varies with proximity to phase transition.

Abstract

In chiral magnets without inversion symmetry, the magnetic structure can form a lattice of magnetic whirl lines, a two-dimensional skyrmion lattice, stabilized by spin-orbit interactions in a small range of temperatures and magnetic fields. The twist of the magnetization within this phase gives rise to an efficient coupling of macroscopic magnetic domains to spin currents. We analyze the resulting spin-transfer effects, and, in particular, focus on the current induced rotation of the magnetic texture by an angle. Such a rotation can arise from macroscopic temperature gradients in the system as has recently been shown experimentally and theoretically. Here we investigate an alternative mechanism, where small distortions of the skyrmion lattice and the transfer of angular momentum to the underlying atomic lattice play the key role. We employ the Landau-Lifshitz-Gilbert equation and adapt the Thiele method to derive an effective equation of motion for the rotational degree of freedom. We discuss the dependence of the rotation angle on the orientation of the applied magnetic field and the distance to the phase transition.