Challenge of Media Noise Suppression With Oxidation Control in Granular Structure for CoPtCr-Based Sputtered Tape Toward 400 Gb/in²

A sputtered tape that uses a CoPtCr-based granular recording layer consisting of magnetic grains and grain boundary oxides was developed for practical applications in next-generation large-capacity magnetic tapes. The role of oxides in CoPtCr-oxide composite targets in forming nanostructures for the granular layer was investigated under the distinctive conditions of a roll-to-roll sputtering system. It was confirmed that: 1) increasing the amount of Co3O4 in the CoPtCr-SiO2-Co3O4 composite target improved the magnetic isolation between magnetic grains and the magnetic anisotropy of the granular recording layer due to diffusion of Si and Cr from within magnetic grains to oxide grain boundaries by oxidation; 2) this magnetic isolation led to 3.6 dB improvement in the broadband signal-to-noise ratio (BB-SNR) at a linear density of 353 kfci through suppression of noise; and 3) overlaying CoPtCrB alloy layer to this sample as a cap layer brought the higher BB-SNR of 2.3 dB than that for the sample reported by us in TMRC2017. Applying the latest track-following technology, this SNR improvement was estimated to have the potential to achieve an areal density of 375 Gb/in(2).