Magnetic Properties of CoPt Alloy Films Sputtered on Pt Underlayers

CoPt alloy films have been sputtered on room-temperature glass slides. It has been found that effective perpendicular anisotropy K ⊥ depends on the film composition and reaches a maximum in films with M s∼850 emu/cm3, and that K ⊥ is greatly enhanced by the application of substrate bias and the deposition of a Pt underlayer. K ⊥ increases with increasing CoPt layer thickness d(CoPt), becoming almost constant beyond d(CoPt)=100 nm in films sputtered on 100-nm-thick Pt underlayers. It has also been found that sputtering at higher Ar gas pressure without substrate bias greatly enhances coercivity, though K ⊥ is somewhat reduced.