MAGNETIC, RECORDING AND STRUCTURAL CHARACTERISTICS OF SPUTTERED CO-CR-PT FILMS FOR LONGITUDINAL RECORDING

Magnetic properties, recording performance, and microstructures of sputtered Co-Cr-Pt films used as longitudinal recording media are compared with those of Co-Ni-Pt and Co-Ni-Cr films. For the Co-Cr-Pt medium without any underlayer, as the Pt content is increased, the coercivity and the peak readout signal reach maximum values at 12 at% Pt, while the noise power continues to decrease. Consequently, the signal-to-noise ratio increases with increasing Pt content. The Co-Cr-Pt and Co-Ni-Pt media without underlayers exhibit a striped morphology without distinct grain boundaries, which lead to in high coercivities required for recording. In contrast, the low-coercivity Co-Ni-Cr medium without any underlayer exhibit a fine-grained morphology. Cr underlayers are required for enhanching media coercivities. In Cr films sputtered at 100 and 220°C, dominant crystallographic planes parallel to the substrate surface are {011} and {002}, respectively. A strong Cr {002} orientation may facilitate the growth of medium grains with a {1120} orientation, thereby increasing the coercivity. With 100 nm thick Cr underlayers, the Co-Cr-Pt medium has a signal-to-noise ratio higher than the Co-Ni-Pt and 100°C sputtered Co-Ni-Cr media, but lower than the Co-Ni-Cr medium sputtered at 220°C. © 1990.