Nonequilibrium interacting electrons in a ferromagnet

TL;DR

This paper investigates how interactions among transport electrons influence the magnetization dynamics in ferromagnets, especially in the presence of inhomogeneities like domain walls, revealing conditions under which traditional equations are modified or preserved.

Contribution

It introduces a framework for understanding the effects of electron interactions on magnetization dynamics, extending the noninteracting models to include inhomogeneities and fluctuations.

Findings

Inhomogeneities affect the equations of motion for magnetization.

In the uniform or wide domain wall limit, equations retain their noninteracting form with renormalized parameters.

Strong ferromagnetic fluctuations extend the noninteracting limit to narrower domain walls.

Abstract

Dynamics of the magnetization in ferromagnets is examined in the presence of transport electrons allowing the latter to interact. It is found that the existence of inhomogeneities such as domain wall (DW) structures, leads to changes that affect the dynamical structure of the equations of motion for the magnetization. Only in the limit of uniform magnetizations or sufficiently wide DW's, the equations of motion maintain the form they have in the noninteracting case. In this limit, results like the spin torques, the Gilbert parameter, and the DW velocities become renormalized. However the length scale that defines such a limit depends on the strength of the interaction. It is shown that if large ferromagnetic fluctuations exist in the metallic band then the range for which conformity with the noninteracting case holds extends to the limit of arbitrarily narrow DW's.