Spectral characteristics of time resolved magnonic spin Seebeck effect

TL;DR

This paper investigates the spectral features of the time-resolved magnonic spin Seebeck effect in YIG, revealing that small wave-vector exchange magnons significantly contribute to the spin current, advancing understanding of spin caloritronics.

Contribution

It introduces a comprehensive model combining LLG dynamics with thermal effects to clarify the spectral contributions in the spin Seebeck effect, highlighting the role of subthermal exchange magnons.

Findings

Small wave-vector exchange magnons dominate the spin current.

The model aligns with recent experimental observations.

Thermal gradient formation is described self-consistently.

Abstract

Spin Seebeck effect (SSE) holds promise for new spintronic devices with low-energy consumption. The underlying physics, essential for a further progress, is yet to be fully clarified. This study of the time resolved longitudinal SSE in the magnetic insulator yttrium iron garnet (YIG) concludes that a substantial contribution to the spin current stems from small wave-vector subthermal exchange magnons. Our finding is in line with the recent experiment by S. R. Boona and J. P. Heremans, Phys. Rev. B 90, 064421 (2014). Technically, the spin-current dynamics is treated based on the Landau-Lifshitz-Gilbert (LLG) equation also including magnons back-action on thermal bath, while the formation of the time dependent thermal gradient is described self-consistently via the heat equation coupled to the magnetization dynamics