Damping of parametrically excited magnons in the presence of the longitudinal spin Seebeck effect

TL;DR

This study investigates the influence of the longitudinal spin Seebeck effect on magnon damping in YIG films, finding that LSSE's effect is weak, but temperature gradients significantly alter damping.

Contribution

It provides a detailed measurement of magnon damping under LSSE conditions using single magnon mode excitation to avoid multimode interference.

Findings

LSSE-related damping modification is too weak to detect.

Temperature gradients significantly affect magnon damping.

Single magnon mode measurement clarifies damping behavior.

Abstract

The impact of the longitudinal spin Seebeck effect (LSSE) on the magnon damping in magnetic-insulator/nonmagnetic-metal bilayers was recently discussed in several reports. However, results of those experiments can be blurred by multimode excitation within the measured linewidth. In order to avoid possible intermodal interference, we investigated the damping of a single magnon group in a platinum covered Yttrium Iron Garnet (YIG) film by measurement of the threshold of its parametric excitation. Both dipolar and exchange spin-wave branches were probed. It turned out that the LSSE-related modification of spin-wave damping in a micrometer-thick YIG film is too weak to be observed in the entire range of experimentally accessible wavevectors. At the same time, the change in the mean temperature of the YIG layer, which can appear by applying a temperature gradient, strongly modifies the damping value.