Perpendicular recording characteristics and microstructure for electroless plated CoNiReP flexible disks with a NiMoP underlayer

Two kinds of electroless-plated CoNiReP/NiMoP flexible disks were investigated from the viewpoint of forming a perpendicular recording medium containing an initial in-plane layer. A well-oriented HCP phase aligned with the c-axis normal to the film plane grew spontaneously in the perpendicularly anisotropic layer after deposition of the in-plane initial layer, which was composed of an FCC phase. In-plane coercivities of the in-plane anisotropic initial layers of 50 and 85 Oe were obtained by changing the bath factor of the NiSO₄ concentration to 0.10 and 0.06 mol.-dm^-3, respectively. Although the switching mechanism of the CoNiReP film had been clarified as a rotation, that of both in-plane anisotropic initial layers was dominated by wall motion. The reproduced voltage of the medium with the 50-Oe in-plane layer was higher than that of the medium with the 85-Oe in-plane layer. A medium with a quasi-soft magnetic in-plane anisotropic initial layer showed excellent recording characteristics when used with ring-type heads