Oxidation of an amorphous iron-terbium alloy.

The magnetic properties of amorphous iron-terbium alloy thin films, which are being investigated for use as high density mass memory storage media in magneto-optic devices, are degraded by exposure to air. Therefore, we have studied the mechanism of the air oxidation of an amorphous Fe(0.74)Tb(0.26) alloy at 200C by Auger electron spectroscopy with depth profiling by argon ion sputtering. Initially the alloy undergoes internal oxidation of Tb, the kinetics obeying a parabolic rate law. After the alloy has been internally oxidized, two oxide films form on its surface. There is an outer film of gamma-Fe(2)O (3) and an inner film of TbO(x)(1.51.8). The growth of the gamma-Fe(2)O(3) film follows parabolic kinetics(1) while the growth of the TBO(x) film obeys a near linear rate law.