Magnetic Properties and Microstructure of Electroless-Plated CoNiP Perpendicular Magnetic Recording Media

The correlation between the magnetic properties and micro-structure of electroless-plated CoNiP perpendicular magnetic recording media was investigated. By adjusting the plating bath factors, the perpendicular coercivity, H
_c⊥
, of the film can be controlled to up to 1500 Oe without changing the saturation magnetization M
_s
and the shapes of the M-H loops. Reflection high-energy electron diffraction (RHEED) analysis showed that these films consist of mixtures of ≪002≫ perpendicularly oriented hep structure regions, and fcc regions without an obvious crystal orientation. The increase in the proportion of the ≪002≫ oriented hep region in such films results in higher H
_c
values; film with the maximum H
_c
of 1500 Oe consisted almost entirely of ≪002≫ oriented hep crystal region. Transmission electron microscope observations revealed that the grain size increases to about 0.03 μm with an increase in H
_c⊥
, up to 1500 Oe. It was also clarified that in the initial growth stage, these films show a low H
_c
, and consist of fine crystallites with low crystal orientation.