Effect of oxidation process on grain-size reduction for longitudinal media using Ni-based amorphous seedlayer

Oxidation process using Ni-based amorphous seedlayer (NiNb, NiTa, and NiZr) has been studied to control the grain size of longitudinal media fabricated on glass substrate. The mechanism of the grain-size reduction was investigated using an in situ Auger electron spectroscopy technique. It is found that NiNb seedlayer is the most effective to reduce the media grain size. This is suggested to be due to the lowest affinity for oxygen for Nb as compared with Ta or Zr. The reduction of the grain size (GD_act) with using Ni-based seedlayer and oxygen process is inferred mainly due to uniform oxidation of the initial growth of the underlayer.