The reliability of rare earth-transition metal (RE-TM) alloy films with a multilayer structure which attains a high signal to noise ratio is discussed. In order to study the stability of the multi-layer magneto-optic (M-O) medium which consists of the GdTbFe layer sandwiched between nitride layers, heating tests (380∼480°C) have been conducted. Magneto-optic properties are evaluated by Kerr hysteresis loop.
In a high temperature environmemt (400°C), the coercive force (Hc) is found to increase and the the Curie temperature (Tc) is found to decrease. It seems that the change of Hc and Tc results from the decrease of effective RE component. However the sample using SUS-304 as a reflector exhibits less change of Hc than that using Al at 4OO°C, and the sample heated in the vaccum (2×10-6 torr) exhibits a small change in Hc. From these results, it is felt that the phenomenon in a high temperature environment is caused by selective oxidation of RE atoms.
There is little change of magneto-optic properties at 380°C. Therefore the multilayer M-O medium using AIN is promising as a high stability material for thermo-magnetic recording.
