Effect of a Ti seed layer on the magnetic properties of CoCrTa double-layered perpendicular media

The effect of a Ti seed layer on the magnetic properties and microstructure of Co₇₇Cr₁₉Ta₄ was studied in Co₇₇Cr₁₉Ta₄/Ti/M (M=Co₉₁Zr₃Nb₆, Fe, Co) double-layered perpendicular recording media. A thin Ti film of ∼5 nm enhanced the c-axis alignment perpendicular to the film plane, resulting in a large perpendicular anisotropy K_u and the best magnetic properties under the present experimental conditions. The coercivity at this Ti thickness (3-3.7 kOe) was approximately half of the magnetocrystalline anisotropy field H_k estimated from the K_u value, even with the present thick 50 nm CoCrTa. The recording performance using a single-pole-type writing head showed that media with a 5 nm Ti layer had higher recording sensitivity compared to media without Ti layers, and a higher SN value at densities greater than 200 kFRPI. No significant loss of recording resolution due to the nonmagnetic Ti space between the CoCrTa and the back layers was observed by the use of the 5 nm Ti film. Moreover, the results for media with Fe back layers indicated that a thinner back layer with a high flux density can be used without any reduction of recording sensitivity and resolution.