A medium formation technique for fabricating high purity Co
90Pt
10 magnetic thin film with uniform grain size was developed, whereby the signal-to-medium-noise ratio (S/Nm) can be improved. In this technique, a Co
90Pt
10 (CP) island layer is deposited as a nucleation site layer (NSL) on SiO
2/Si disk substrate with adherent gas. After the deposition, a heat treatment is sequentially carried out in order to remove the adherent gas. High purity films can be produced by the removal of adherent gas. A Cr film and a Co
90Pt
10 magnetic film are successively deposited after the heat treatment (HT). In the deposition of Cr film, the fabricated Co
90Pt
10 island forces nucleation of Cr grain to start from the Co
90Pt
10 island and thus eliminates simultaneous nucleation from many points on the region without the Co
90Pt
10 island. The resulting Cr film as a underlayer is composed of a monolayer of closely packed Cr grains with uniform grain size. In this medium formation, nucleation of Co
90Pt
10 grain to magnetic layer to start from the Cr grain to underlayer is created. Therefore, Co
90Pt
10 magnetic thin film with uniform grain size is produced. The fabrication of high purity Co
90Pt
10 magnetic film with uniform grain size has been achieved by the deposition of NSL and removal of adherent gas. As a result, it is indicated that the use of this technique results in increase of S/Nm at 304.4 kFCI of 25%.
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