Thermal stability study for anisotropic and isotropic hard disk media

Thermal stability of anisotropic and isotropic Co alloy thin-film media is investigated. The orientation ratio of CoCrTa(Pt)/Cr media was controlled b y the mechanical texture of the NiP/Al substrates. Bulk magnetic properties , delta M curves and time decay of magnetization in the circumferential and radial directions were measured. The maximum magnetic viscosity coefficien t calculated from the time decay of magnetization in the circumferential di rection was higher than that in the radial direction for a mechanically tex tured sample, while it was similar in both directions for a non-textured sa mple. The magnetic viscosity coefficient in the circumferential direction i s smaller than that in the radial direction when the reverse field is in th e range of the demagnetization field for thin-film recording media. This im plies that an anisotropic sample (namely, a sample with a high orientation ratio) will be more thermally stable when it is not exposed to a large exte rnal magnetic field.