Effect of microstructural features on media noise in longitudinal recording media

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Abstract
High‐resolution transmission‐electron microscopy (HRTEM) has been used to analyze CoCrTa, CoCrPt, and CoNiCrPt alloy thin films deposited under similar conditions onto NiP plated Al substrates with a Cr underlayer. Apparent ∼50 nm Co alloy grains observed by bright field TEM are found to be clusters of smaller 10–20 nm grains with a common growth orientation. Subtle differences have also been observed in the stacking fault density, Co alloy fcc phase concentration, lattice mismatch, and grain separation in the films. In particular, HRTEM shows that the CoCrTa film has clear physical separation between the 10 and 20 nm grains, which is not observed in the other media. Despite similar hysteresis loop properties, the signal‐to‐noise ratio of CoCrTa is 2.3 dB higher than CoCrPt and 4.6 dB higher than CoNiCrPt. Small isolated grains have been shown to improve media noise, as is observed in CoCrTa media.