Low-temperature sputter deposition of high-coercivity Co-Cr films for perpendicular recording

Abstract

A low-temperature magnetron sputter-deposition method for Co-Cr medium has been developed. Films of 17 wt % Cr-Co were deposited to a thickness of 100–200 nm onto glass substrates over an extremely wide range of Ar gas pressures at room temperature. A high hcp c-axis orientation to the film normal (Δθ50<6°) could be obtained even at pressures over 50 Pa (375 mTorr) when the films were deposited onto a well-oriented c-axis Ti underlayer. Co-Cr films with a perpendicular coercivity as high as 1000 Oe with an anisotropy field of 5 kOe were obtained at extremely high Ar pressures; e.g., 70 Pa (525 mTorr). Scanning electron microscopy observations showed that the films had a fine columnar structure with distinct grain boundaries and the grain size was dramatically reduced with the introduction of the Ti underlayer. It was determined that the large anisotropy field for the Co-Cr films is attributed to crystalline anisotropy. The mechanism of magnetization reversal in the films is suggested to be rotational.