Magnetic and structural properties of CoCrTaNiPt longitudinal thin-film media

The effects of Ni addition on magnetic and structural properties of CoCrTaNiPt/Cr longitudinal media fabricated under the UC process have been investigated. It is found that the addition of Ni up to 13 at. % increases the magnetocrystalline anisotropy field of grain Hkgrain by 10%, and decreases the saturation magnetization Ms by 20%. As a result, coercivity Hc increases by 10%–15% and the ratio of the saturation flux density to anisotropy field 4πMs/Hkgrain decreases by 30%. Further addition of Ni from 13 to 19 at. % results in a decrease of Hc by 7% and a decrease of Hc/Hkgrain from 0.38 to 0.36. This is due to the degraded grain-boundary structure and the increase of the stacking fault density. The addition of Ni up to 13 at. % is effective in increasing Hkgrain and decreasing 4πMs/Hkgrain, while retaining a high Hc/Hkgrain value of about 0.38. As a result, Hc as high as 3.2 kOe is obtained even when using an isotropic NiP/Al substrate.