Spin pumping by a field-driven domain wall

TL;DR

This paper derives a general expression for charge current induced by a time-varying magnetization in ferromagnets, focusing on a field-driven domain wall, and suggests a way to experimentally determine key spin transfer parameters.

Contribution

It provides a universal formula for charge current related to magnetization dynamics, applicable to various microscopic details, and evaluates it specifically for a field-driven domain wall.

Findings

Charge current depends on conductivities and non-adiabatic torque parameter β.

The current's behavior is strongly influenced by the ratio of β to Gilbert damping.

Results suggest an experimental method to measure the β parameter.

Abstract

We calculate the charge current in a metallic ferromagnet to first order in the time derivative of the magnetization direction. Irrespective of the microscopic details, the result can be expressed in terms of the conductivities of the majority and minority electrons and the non-adiabatic spin transfer torque parameter $\beta$. The general expression is evaluated for the specific case of a field-driven domain wall and for that case depends strongly on the ratio of $\beta$ and the Gilbert damping constant. These results may provide an experimental method to determine this ratio, which plays a crucial role for current-driven domain-wall motion.