On the Relationship between Magnetic Viscosity and Coercivity of Perpendicular Media

The dependent and dc-demagnetization measurements were performed on two types of perpendicular thin film media, Co-Cr and Fe-alumite. From these the parameters for magnetic viscosity and irreversible susceptibility were derived. Their ratio, resulting in the fluctuation field, is shown to relate logarithmically to the coereivity. This so-called “Barbier plot for perpendicular media” is found to exhibit a slope of approximately one and a half instead of one, as is found for in-plane media. The activation volumes were also derived and related logarithmically to the coercivity. Here a slope of approximately minus one and a half was found, instead of minus 0.73 as is found for in-plane media.