極薄高融点ＷＣｒシード層による薄膜磁気記録媒体の結晶粒微細化 高Ｈｋ｀ｇｒａｉｎ´媒体における低ノイズ化

Abstract

To reduce grain size while maintaining high coercive force in longitudinal thin-film media, we applied a combination of deposition of a very thin WCr seedlayer with a dry-etching process to a magnetic medium material with comparatively high magnetocrystalline anisotropy. As a result: (a) the deposition of a 0.5-nm WCr seedlayer reduced the grain size from 9.1 nm to 7.9 nm; (b) the SN ratio of the medium with 0.25-nm − 1.0-nm-thick WCr seedlayer increased by 1.5 dB due to a 20% decrease in medium noise compared with the standard medium without WCr seedlayer, caused mainly by reduction of the grain size; and (c) in the case of media with WCr seedlayer thickness less than 1.5 nm, high coercivity was maintained due to strong c-axis orientation and high thermal stability (νactKugrain/kBT > 80), enabling these media to maintain a high recording resolution. Consequently, application of this sputtering process to media with high magnetocrystalline anisotropy stability is very effective in improving SN ratio while maintaining recording resolution.