Noise characteristics of compositionally separated Co-Cr media

Media noise reduction is one of the keys to realizing high density recording. It is believed that longitudinal thin film media have the potential to achieve ultra high density recording with a dependence of noise characteristics on recording density similar to those of particulate media. We studied the source of thin film media noise by changing substrate temperature (Ts) during sputtering. A Co-Cr medium sputtered at 300°C showed a reduction in noise with increased recording density similar to particulate media. Furthermore, the magnitude of DC-erased noise depends on the Ts and is higher in high Ts films. From noise analysis, it was found that the maximum noise frequency of noisy media shifts to low frequency in DC-erased mode. Results obtained from TEM observations and NMR studies confirmed that the low noise media exhibit strong in-grain compositional separation.