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 H^grain_k by 10%, and decreases the saturation magnetization M_s by 20%. As a result, coercivity H_c increases by 10%-15% and the ratio of the saturation flux density to anisotropy field 4 πM_s/H^grain_k decreases by 30%. Further addition of Ni from 13 to 19 at. % results in a decrease of H_c by 7% and a decrease of H_c/H^grain_k 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 H_graink and decreasing 4 πM_s/H^grain_k, while retaining a high H_c/H^grain_k value of about 0.38. As a result, H_c as high as 3.2 kOe is obtained even when using an isotropic NiP/Al substrate.