Effects of impurity gases on properties of Co-Cr perpendicular recording media in high-rate and continuous sputtering process

In a roll coater system based on dc-magnetron sputtering, the influence of impurity gas was studied in terms of magnetic properties of the Co-Cr perpendicular recording media. It was found that only water came out from the organic base film during sputtering. This deteriorates significantly the perpendicular anisotropy of the Co-Cr medium. To eliminate the influence of water, the base film needed to be degassed by heating the film before sputtering. Intentional addition of nitrogen, oxygen and hydrogen was examined to understand their individual effects. Although nitrogen is less reactive with the Co-Cr film than oxygen, a very small amount of nitrogen causes more severe degradation of the perpendicular anisotropy than oxygen does. On the other hand, hydrogen does not react with any film, Co-Cr nor Cu-Mo Permalloy, but its addition influences the coercive force of both films without any change of anisotropy nor crystal orientation.