Changes of Magnetic Anisotropy of CoPtCr Perpendicular Films Due to Ru Intermediate Layer Under High Gas Pressure

The uniaxial magnetic anisotropy K_u of CoPtCr-SiO₂ granular perpendicular recording media increases when they are deposited on a Ru intermediate layer with high Ar gas pressure. In order to clarify the reason for the increase in K_u , we investigated the correlation between K_u of continuous CoPtCr film and the Ar gas pressure of the Ru layer. Six kinds of CoPtCr films with the compositions close to practical CoPtCr-SiO₂ recording media were deposited on the Ru layer with the Ar gas pressure varying from 0.6 to 8.0 Pa. The increase in K_u of continuous CoPtCr films was confirmed. Through the investigation on microstructure using X-ray diffraction, we found that the stacking faults or the fraction of face center cubic (FCC) phase of CoPtCr grains were independent on the gas pressure of Ru while the ratio of hexagonal close packed (HCP) crystal constant c/a monotonously decreased with increasing gas pressure. We conclude that the increase in K_u of CoPtCr continuous film is mostly related to the decease of c/a due to high gas pressure of Ru layer.