Recording Characteristics of Electroless-plated CoNiReP/NiWP Double Layers

Electroless-plated CoNiReP/NiWP double layer films were investigated for perpendicular magnetic recording media as flexible disks. The magnetic properties of a CoNiReP recording layer, such as a saturation magnetization (M
_S
) value and squareness ratio of perpendicular hysteresis loops (SQR (⊥)), were changed by NiWP underlayers. The reproduced output voltage of CoNiReP/NiWP flexible disks at low recording density with a ring-type head increased with M
_S
values of recording layer and underlayer. Moreover, the D
₅₀
value of 172 kFRPI was attained by the highest SQR(⊥) medium of the double layer evaluated with a 0.20μm gap length sendust ring-type head. This may be mainly due to large perpendicular anisotropy of the top region of recording layer which is improved by the underlayer addition.