The ultraclean sputtering process (UC-process) was newly introduced in the fabrication of Co62.5Ni30Cr7.5 and Co85.5Cr10.5Ta4 thin film media to establish a new concept in controlling microstructure. UC-process enables the realization of high coercive force Hc up to 2.7-3 kOe in both CoNiCr and CoCrTa media (15/50 nm magnetic/Cr thicknesses) without the decrement of saturation magnetization. The purification of the atmosphere during sputtering and the removal of the adsorbed oxygen impurity on the substrate surface play important roles in obtaining high Hc by applying the UC-process. This high Hc is mainly due to the realization of large magnetocrystalline anisotropy field of grains Hkgrain and low intergranular exchange coupling. UC-process realizes the adequate separation of grains by segregated grain boundaries even in media with thin Cr thickness of 2.5 nm, and enables grain size reduction without the remarkable increment in intergranular exchange coupling. In these media, the reduction of the grain size is most effective for the improvement of readback signal to media noise ratio S/Nm. In the media with grains sufficiently separated by segregated grain boundaries fabricated by the UC-process, control of grain size reduction and further increase in Hc/Hkgrain value through the decrement in intergranular magnetostatic coupling are required to obtain higher S/Nm value.
|Number of pages
|IEICE Transactions on Electronics
|Published - 1995 Nov