Magnetic properties of laser annealed garnet films as determined by FMR and bubble statics

The effects of high power laser irradiation upon the magnetic properties of Ga-substituted garnet films were studied by ferromagnetic resonance (FMR) and bubble statics. FMR measurements showed that for a certain range of laser power, annealing changes the magnetic properties in a layer located at the free surface, the thickness of which increases with increasing laser power P. For a sufficiently high P the whole film is transformed, and for even higher P the film is melted in a thin surface layer. The change of collapse field and stripe width as a function of P is fairly well explained by this model. The modification of the magnetic properties can be well explained by a migration of about 3% of Ga
³⁺
from the tetra- to the octahedrical site, but surprisingly the amount of Ga migration is independent of the laser power.