Theory of the Spin Seebeck Effect

TL;DR

This paper presents a theoretical framework for understanding the spin Seebeck effect, where a temperature gradient in a ferromagnet generates spin currents that are converted into measurable voltages via the inverse spin Hall effect, highlighting the roles of magnons and phonons.

Contribution

It provides a comprehensive theoretical basis for the spin Seebeck effect and discusses the influence of magnon and phonon degrees of freedom in thermal spin phenomena.

Findings

Magnons and phonons are crucial in the spin Seebeck effect.

Theoretical understanding of spin voltage generation from temperature gradients.

Connection between spin currents and measurable voltages via inverse spin Hall effect.

Abstract

The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this article, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects.