Theory of magnon-driven spin Seebeck effect

TL;DR

This paper presents a theoretical framework explaining the spin Seebeck effect as a result of magnon-driven spin pumping, linking it to interface conductance, magnetic coherence, and temperature differences between magnons and electrons.

Contribution

It introduces a comprehensive theory connecting magnon dynamics and spin pumping to the spin Seebeck effect, emphasizing the role of interface properties and temperature gradients.

Findings

The spin Seebeck effect arises from magnon-driven spin pumping.

The effect depends on interface spin-mixing conductance.

Temperature differences between magnons and electrons are crucial.

Abstract

The spin Seebeck effect is a spin-motive force generated by a temperature gradient in a ferromagnet that can be detected via normal metal contacts through the inverse spin Hall effect [K. Uchida {\it et al.}, Nature {\bf 455}, 778-781 (2008)]. We explain this effect by spin pumping at the contact that is proportional to the spin-mixing conductance of the interface, the inverse of a temperature-dependent magnetic coherence volume, and the difference between the magnon temperature in the ferromagnet and the electron temperature in the normal metal [D. J. Sanders and D. Walton, Phys. Rev. B {\bf 15}, 1489 (1977)].