Thermoelastic enhancement of the magnonic spin Seebeck effect in thin films and bulk samples

TL;DR

This paper develops a self-consistent theoretical framework incorporating magneto-elastic effects to understand how thermoelastic deformations influence the magnonic spin Seebeck effect in thin films and bulk samples, revealing potential control mechanisms.

Contribution

It provides analytical expressions for coupled magneto-elastic modes and explores how thermoelastic effects modify the spin Seebeck effect, a novel integration of elastic and magnetic phenomena.

Findings

Deformation and displacement decay rates differ between bulk and thin films.

Thermoelastic steady states can enhance or reduce the magnonic gap.

Gap reduction increases magnon contribution to the spin Seebeck effect.

Abstract

A non-uniform temperature profile may generate a pure spin current in magnetic films, as observed for instance in the spin Seebeck effect. In addition, thermally induced elastic deformations may set in that could affect the spin current. A self-consistent theory of the magnonic spin Seebeck effect including thermally activated magneto-elastic effects is presented and analytical expressions for the thermally activated deformation tensor and dispersion relations for coupled magneto-elastic modes are obtained. We derived analytical results for bulk (3D) systems and thin magnetic (2D) films. We observed that the displacement vector and the deformation tensor in bulk systems decay asymptotically as $u\sim1/R^{2}$ and $\varepsilon\sim1/R^{3}$, respectively, while the decays in thin magnetic films proceed slower following $u\sim1/R$ and $\varepsilon\sim1/R^{2}$. The dispersion relations evidence a strong anisotropy in the magnetic excitations. We observed that a thermoelastic steady state deformation may lead to both an enchantment or a reduction of the gap in the magnonic spectrum. The reduction of the gap increases the number of magnons contributing to the spin Seebeck effect and offers new possibilities for the thermoelastic control of the Spin Seebeck effect.