Magneto-Optical Properties and Thermal Expansion Anomaly in Fe-Tb Amorphous Alloys

In order to investigate the difference between the Curie temperature and the coercive force depending on the preparation conditions, thin amorphous films and bulk amorphous alloys of Fe-Tb have been prepared by rf and dc sputtering, respectively. The differential thermal analysis, the Kerr rotation angle and the thermal expansion have also been investigated because Fe-Tb amorphous alloys are considered suitable for magneto-optical recording media. In contrast to the data reported previously, there is no distinct difference in the concentration dependence of the Curie temperature and the coercive force depending on the different sputtering conditions. The exothermic curves in the thermal analysis exhibit an anomalous behavior below the crystallization peak. The concentration dependence of the Kerr rotation angle is not significant. A marked thermal expansion anomaly related to the magnetovolume effect is observed, and hence the difference in the thermal expansion between the amorphous alloys and the substrate should be taken into consideration because it causes stresses which are associated with poor stability of magneto-optical memory films