Spin-Transfer Torque in Helical Spin-Density Waves

TL;DR

This paper investigates the current-driven dynamics of helical spin-density waves, providing first-principles calculations of spin-transfer torque in materials like Er and Fe, revealing how torque influences spin spiral rotation.

Contribution

It introduces a method to compute spin-transfer torque from first principles for helical spin-density waves, linking torque to wave vector and Fermi surface polarization.

Findings

Torque induces rigid rotation of the spin spiral

Torque depends on wave vector and Fermi surface polarization

Dynamics of spin spiral are characterized by these torques

Abstract

The current driven magnetisation dynamics of a helical spin-density wave is investigated. Expressions for calculating the spin-transfer torque of real systems from first principles density functional theory are presented. These expressions are used for calculating the spin-transfer torque for the spin spirals of Er and fcc Fe at two different lattice volumes. It is shown that the calculated torque induces a rigid rotation of the order parameter with respect to the spin spiral axis. The torque is found to depend on the wave vector of the spin spiral and the spin-polarisation of the Fermi surface states. The resulting dynamics of the spin spiral is also discussed.