CoPtCr-SiO2/Ru longitudinal media with C underlayer for high-density flexible disk

A high-density magnetic recording flexible disk (FD) medium on polyethylene naphthalate (PEN) substrate film with an Ru underlayer and CoPtCr-SiO₂ magnetic layer was investigated. The Ru underlayer and magnetic layer were prepared at room temperature by a dc magnetron sputtering system using a roll-to-roll process. Media with and without an additional C underlayer were tested, and those with the C underlayer exhibited magnetostatic properties comparable to glass-substrate media (HD). Findings suggested that the C underlayer prevents outgassing from the PEN substrate film and improves the crystallinity of the Ru underlayer. The FD with C underlayer exhibited high-density magnetic recording properties.