# Experimental investigation of the temperature-dependent magnon density and its influence on studies of spin-transfer-torque-driven systems

## TL;DR

This study investigates how thermal magnon density in ferromagnetic layers varies with temperature and impacts spin-transfer-torque systems, revealing a linear relationship and limits for magnon suppression at finite currents.

## Contribution

It provides the first detailed experimental analysis of temperature-dependent magnon density and its effect on spin-transfer-torque-driven systems.

## Key findings

- Magnon density increases linearly with temperature.
- Lowering of spin-wave frequency occurs with rising temperature.
- Maximum magnon suppression is limited at finite current.

## Abstract

We present the temperature dependence of the thermal magnon density in a thin ferromagnetic layer. By employing Brillouin light scattering and varying the temperature, an increase of the magnon density accompanied by a lowering of the spin-wave frequency is observed with increasing temperature. The magnon density follows the temperature according to the Bose-Einstein distribution function which leads to an approximately linear dependency. In addition, the influence of this effect in spin-transfer-torque-driven systems is presented. In particular, the increase in the magnon density with temperature sets the limit for a suppression of magnons in charge current-driven systems. Hence, the maximum possible suppression of thermal magnons occurs at a finite current.