Dynamic behavior of small bits written by laser irradiation on GdFe films

Abstract

Field nucleation and collapse of small bits have been investigated under a laser beam irradiation on an amorphous GdFe sputtered film by means of the photometric method. The writing process of a bit consists of the motion of the ’’head-on wall’’ along the film thickness and then the radial motion of the ’’side wall.’’ Small bits are stable at higher temperature during beam irradiation, but they collapse during cooling to room temperature near the compensation point after cutting off the laser beam, because the wall energy tension overcomes the coercive field near the compensation point. The conventional thermomagnetic writing was also carried out by pulse laser irradiation of non-coated and Ni-coated GdFe films. It was found that the small bits can be stabilized by coating a Ni-layer thicker than 200 Å.