MAGNETIC-PROPERTIES AND CRYSTAL-STRUCTURE OF COCRTAPT THIN-FILM FOR LONGITUDINAL RECORDING MEDIA

Magnetic properties and crystal structure of sputtered CoCrTaPt/Cr and CoCrTa/Cr thin films were studied as a function of Pt content and the substrate temperature. It was observed that the coercivity increased with Pt content or the substrate temperature, and that the coercivity was saturated with a small amount of Pt at high substrate temperature compared to at low substrate temperature. X-ray diffraction study showed that at high substrate temperature, Co (11.0) grew epitaxially on Cr(200). That indicates c axis of hexagonal-close-packed Co phase lies in the film plane. It was also shown that diffraction angles of Co planes shifted lower with the addition of Pt. These shifts are attributed to the diffusion of Pt into the Co lattice, and the shifts are promoted by the increase of the substrate temperature. The addition of Pt led to the increase of crystalline magnetic anisotropy constant (Ku), and the increase of Ku was also promoted by the increase of the substrate temperature. The increase of the coercivity by the addition of Pt is considered to be caused by the increment of in-plane crystalline magnetic anisotropy which is due to the diffusion of Pt into the Co lattice. The increase of the coercivity by the increase of the substrate temperature is attributed to the increment of the in-plane component of the c axis.