Properties and stability of thin films for magneto optic recording

CoGdTb films have been prepared by rf sputtering over a range of bias voltages containing either Ar or Kr and protected with either SiO
2
or Si
3
N
4
. Annealing has been carried out in air as well as in pure Ar. The stability of various parameters on annealing has been studied as a function of preparation conditions. The parameters studied were the perpendicular anisotropy, the coercivity, the compensation temperature, the gas content and the elemental depth profiles. These results are compared to the stability of the perpendicular anisotropy of samples of FeGd and FeTb obtained from outside our laboratory. Three of the samples had equivalent and excellent stability; the FeGd-Al
2
O
3
-SiO
2
, CoGdTbAr-SiO
2
and FeTb-SiO
2
all annealed in air. The three samples with the poorest stability were the CoGdTbKr-SiO
2
, CoGdTbAr-SiN both annealed in air and the CoGdTbAr-SiO
2
annealed in pure argon. The results are discussed in terms of the mechanisms responsible for the changes. Much of the instability is clearly due to structural rearrangement of the film independent of oxidation.