A thin film magnetic disk (and a disk drive using the magnetic disk) with improved recording performance having a thin seed layer consisting of tantalum (Ta), a suitable underlayer and a CoPtCrB magnetic layer is described. The underlayer is preferably a Cr alloy with a grain size which is smaller than that of pure Cr. CrTi is suitable as an underlayer. An appropriate overcoat such as hydrogenated carbon can be applied.