EFFECT OF GRAIN ISOLATION ON MEDIA NOISE IN THIN-FILM LONGITUDINAL MEDIA

Particulate media exhibit low media noise as compared to thin-film longitudinal media. The main source of media noise in thin-film longitudinal media is the zig-zag transitions which occur due to a strong magnetic coupling between neighboring grains. Thus if the grains in thin-film longitudinal media can be isolated, the media noise should be decreased. In order to alter the magnetic coupling across grain boundaries, CoNiCr/Cr films of different microstructure were prepared by changing the Cr underlayer microstructure [1], [2]. SEM analysis indicates that the grain structure of these media ranged from continuous to isolated grains. VSM results show that both S and S* decrease as the grain isolation increases. The media noise of the disk with continuous grains increases linearly with frequency, reaches a maximum, and eventually decreases and has been explained by Belk et al. [3]. However, the media noise for isolated grain media is weakly dependent on the recording frequency—more like a particulate media. The interrelation between microstructure, magnetic, and recording results are discussed. © 1990 IEEE