A CoPtCr-Si O2 film is a potential material for high-density perpendicular recording media due to their high magnetic anisotropy constant Ku. However, the value of Ku decreases in high levels of Pt content. In this study, this phenomenon was analyzed by synchrotron radiation grazing incidence x-ray diffraction and transmission electron microscopy techniques. Although the CoPtCr-Si O2 films contained almost no fcc phase at 20 at. % Pt or less, it increased remarkably at 30 at. % Pt. This result coincided with the variations of Ku with respect to the Pt content for the CoPtCr-Si O2 films. We consider that the fcc phase formation at Pt content levels in the vicinity of 30 at. % is an influential factor of the Ku reduction. Our techniques proved to be sensitive for the detection of fcc regions in the CoPtCr-Si O2 films.