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 microstructures were prepared by changing the Cr underlayer microstructure. 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 N.R. Belk et al. (see ibid., vol.MAG-21, no.5, p.1350-5, Sept. 1985). However, the media noise for isolated grain media is weakly dependent on the recording frequency-more like particulate media. The interrelations between microstructure, magnetic, and recording results are discussed