Thermal instability in a ferrimagnetic resonator strongly coupled to a loop-gap microwave cavity

TL;DR

This paper investigates the nonlinear thermal response of a ferrimagnetic resonator coupled to a microwave cavity, revealing conditions for instability and self-sustained power modulation due to heating effects.

Contribution

It provides the first measurement of the Kerr coefficient and damping rate of a ferrimagnetic sphere in a strongly coupled microwave system, highlighting thermal instability mechanisms.

Findings

Identification of a parameter range causing system instability

Observation of self-sustained power modulation

Attribution of instability to heating above Curie temperature

Abstract

We study nonlinear response of a ferrimagnetic sphere resonator (FSR) strongly coupled to a microwave loop gap resonator (LGR). The measured response in the regime of weak nonlinearity allows the extraction of the FSR Kerr coefficient and its cubic damping rate. We find that there is a certain range of driving parameters in which the system exhibits instability. In that range, self-sustained modulation of the reflected power off the system is generated. The instability is attributed to absorption-induced heating of the FSR above its Curie temperature.