Ferromagnetic resonance study of GdN thin films with bulk and extended lattice constants

Abstract

The magnetic properties of GdN thin films with bulk and 2.4% extended lattice parameters have been studied by x-band ferromagnetic resonance (FMR) spectroscopy. Simple, anisotropic, single line FMR spectra are observed in the $0\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}18\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}$ field range. Both films show an in-plane easy axis of magnetization due to the predominance of the shape related demagnetization fields. The films deposited on (100) Si substrates are strained with uniaxial anisotropy constants up to ${K}_{u}=+5\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.3em}{0ex}}\mathrm{erg}∕{\mathrm{cm}}^{3}$ at $T=4\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The lattice extension reduces the magnetization and decreases the Curie temperature from $69\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for the bulk films to $20\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for the films with extended lattice constants. Highly increased FMR linewidths are observed for the lattice extended films indicating large, local variations of the demagnetization fields.