Magnon instability driven by heat current in magnetic bilayers

TL;DR

This paper theoretically shows that a temperature bias in a ferromagnet/paramagnet bilayer can induce magnon instability and microwave emission by affecting magnon lifetime and scattering processes.

Contribution

It introduces a novel mechanism where heat current drives magnon instability, revealing the interplay between spin and heat currents in magnetic bilayers.

Findings

Magnon instability can be induced by temperature bias.

Microwave emission occurs due to suppression of Umklapp scattering.

Heat current influences magnon lifetime and stability.

Abstract

We theoretically demonstrate that, in a ferromagnet/paramagnet bilayer, a magnon instability accompanied by a gigahertz microwave emission can be driven simply by means of a temperature bias. Employing many-body theory for investigating the effects of a phonon heat current on the magnon lifetime, we show that the magnon instability occurs upon the suppression of the Umklapp scattering at low temperatures, leading to microwave emission. The present finding provides crucial information about the interplay of spin current and heat current.