Transmission electron microscopy of amorphous Fe-Tb thin films irradiated by pulsed laser beam

Amorphous Tb-Fe films were prepared on thin carbon films and glass substrates by r.f. sputtering method. They were irradiated by pulsed laser beams, the energy range of which was that commonly adopted for thermo-magnetic recording. Thermal effects were studied mainly by transmission electron microscopy. Structure of the irradiated areas changed from amorphous to crystalline, while magnetization of the corresponding area turned from perpendicular to in-plane orientation. Degree and diameter of a thermally influenced area depended largely on the film thickness over the range from 200 to 2000 Å. In a 500 Å Tb30Fe70film on a thin carbon substrate a circular area of 0.8 μm in diameter was crystallized by one 1 μs pulse of 2 mW. The damage was more evident in thinner films.