Temperature-dependent Brillouin light scattering spectra of magnons in yttrium iron garnet and permalloy

Abstract

In the field of spin caloritronics, knowledge of the magnon temperature is crucial. We investigate the temperature sensing capabilities of Brillouin light scattering (BLS), a technique which is commonly used in studying magnons. The magnon BLS spectra are characterized by three parameters: peak frequency, linewidth, and integrated intensity, each of which can be used for temperature sensing. The BLS spectra of magnons in both an insulator (yttrium iron garnet or YIG) and a metal (permalloy $\mathrm{N}{\mathrm{i}}_{80}\mathrm{F}{\mathrm{e}}_{20}$ or Py) are measured at different temperatures as the sample is uniformly heated. Unexpectedly, we find the temperature dependence of the BLS integrated intensity is opposite between YIG and Py. The mechanisms contributing to the temperature dependence of the three BLS spectra parameters are discussed and the temperature precision of each parameter is determined.