EFFECT OF HEAD GAP LENGTH ON PERPENDICULAR RECORDING PERFORMANCE OF ELECTROLESS CoNiReP/NiFeP DOUBLE-LAYERED MEDIA USING MIG HEADS

The perpendicular recording characteristics of electroless-plated CoNiReP/NiFeP double-layered media were examined in combination with the use of metal-in-gap (MIG) heads of various head gap length (GL), focusing upon the perpendicular layer thickness (δp) and underlayer coercivity (Hc(u)). It was necessary to adjust the value of δp to be in accordance with the value of GL in order to obtain a sufficient "phase synchronization (PS) effect" which enhances the reproduced voltage [1]. The combination of a GL=0.13 μm head with a δp=0.2 μm and the Hc(u)=160 Oe medium appeared to be optimum for demonstrating the PS effect. For high density recording, the combination of a small-GL head (0.08 μm) and thicker δp(0.3 μm) medium with lower Hc(u) (50 Oe) was optimum, because the improvement of head field permeation was performed by lower Hc(u) and better crystal orientation at the surface was obtained by thicker δp.