Anisotropic low temperature thermal resistance in polycrystalline magnetic thin films

The scattering of spin waves and the thermal resistance due to this scattering are calculated for polycrystalline magnetic thin films with a small overall uniaxial anisotropy. The scattering is caused by the random orientation of crystallites, and also by the magnetization ripple, which is likewise produced by this random orientation. The wavelength spectra of the ripple and of the spin waves at low energy are essentially influenced by the magnetostatic interaction, which is taken into account within Harte's linearized thin film approximation, and for comparison also within Hoffmann's approximation. Due to the anisotropy of the spectra, the contribution of the spin waves to the thermal resistance of permalloy films should be highly anisotropic at temperatures of 2 K and below.