In developing magnetic recording disks based on gamma ferrite (Fe2O3) thin film media and having very low level noise and high corrosion resistance, it is necessary to oxidize magnetite (Fe3O4) to gamma ferrite by heat treatment at temperature of 300°C or higher.
This requires a new underlayer that is non-magnetically stable under such severe conditions.
Based on a report by Osamu Takano on Ni-Cu-P, experiments were conducted to vary the [Ni2+]/[Cu2+] ratio in the Ni-Cu-P bath to determine how heat treatment affect non-magnetic characteristics.
It was found that by varying the [Ni2+]/[Cu2+] ratio deposits with a wide range of Ni or Cu contents could be plated. Films containing less than 60% Ni showed non-magnetically stable characteristics even after severe heat treatment.
It was concluded that electroless Ni-Cu-P opened the way to development of high quality magnetic recording disks.
