Perpendicular Magnetic Recording Media with Double-Recording-Layer having Different Coercivities

A new recording layer construction for double-layer perpendicular recording media is proposed. The recording layer is composed of two strata, with a high-H_c (⊥) stratum on the surface side and a low-H_c (⊥) stratum on the soft magnetic layer side. As a result, the recording sensitivity is improved without decreasing the reproduced voltage. The total thickness of the recording layer was set at 0.3 μm, and the coercivities of the high- and low-H_c (⊥) strata were set at 650 Oe and 350 Oe, respectively. The satisfactory results are explained by the strong dependence of the reproduced voltage on the coercivity of the recording layer near the surface, but not near the soft magnetic layer; the recording sensitivity then mostly depends on the average coercivity of the recording layer. This new recording layer construction is useful for alleviating the degradation of the recording and overwrite sensitivities which accompany thinner main poles in recording heads. The double-stratum recording layer medium reported here is also useful for raising the reproduced voltage, since the recording sensitivity is raised without decreasing the total thickness of the recording layer.