Dissipation due to pure spin-current generated by spin pumping

TL;DR

This paper develops a generalized theory of Joule heating that includes dissipation due to pure spin currents generated by spin pumping, highlighting the role of spin-dependent scatterings and interface effects.

Contribution

It introduces a new theoretical framework for understanding dissipation from spin currents, extending traditional Joule heating to include spin-related entropy changes.

Findings

Dissipation from spin currents is linked to spin-dependent scatterings.

Spin pumping causes additional dissipation at interfaces.

Dissipation correlates with increased Gilbert damping.

Abstract

Based on spin-dependent transport theory and thermodynamics, we develop a generalized theory of the Joule heating in the presence of a spin current. Along with the conventional Joule heating consisting of an electric current and electrochemical potential, it is found that the spin current and spin accumulation give an additional dissipation because the spin-dependent scatterings inside bulk and ferromagnetic/nonmagnetic interface lead to a change of entropy. The theory is applied to investigate the dissipation due to pure spin-current generated by spin pumping across a ferromagnetic/nonmagnetic/ferromagnetic multilayer. The dissipation arises from an interface because the spin pumping is a transfer of both the spin angular momentum and the energy from the ferromagnet to conduction electrons near the interface. It is found that the dissipation is proportional to the enhancement of the Gilbert damping constant by spin pumping.