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 (MS) 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 MS values of recording layer and underlayer. Moreover, the D50 value of 172 kFRPI was attained by the highest SQR(¿) medium of the double layer evaluated with a 0.20¿m 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.