Write/Erase Cyclability of Pt/Co Magneto-Optical Disks

The write/erase cyclability of Co-rich Pt/Co disks was studied, along with factors limiting the cyclability. Annealing experiments suggested that a decrease in CNR results from degradation of the perpendicular magnetic anisotropy in a Pt/Co film heated by an erasing laser beam. The main mechanism of degradation is atomic intermixing at the interface in Pt/Co multilayers. In the case of a Pt/Co film exposed to air, Co might be oxidized during erase cycles. The higher peak temperature of Pt/Co films accelerates the intermixing. Therefore, the number of cycles was increased by adding a heat-diffusive layer to the Pt/Co film in order to lower the peak temperature. For example, Au-coated Pt/Co disks were capable of 10⁵ cycles as a result of a lower peak temperature (430°C), whereas SiN-coated Pt/Co disks, with a peak temperature of 770°C, were capable of only 10² cycles.