Heat-assisted magnetic probe recording onto a thin film with perpendicular magnetic anisotropy

The possibility of magnetic probe recording into a continuous perpendicular medium is discussed. By applying a current from the tip to the medium, a very localized area can be heated and bits as small as 80 nm in diameter could be written. This value is close to the calculated minimum diameter of reversed cylindrical domains in our perpendicular medium. A current can be injected directly from the tip to the medium by means of a current source, or one can use capacitive currents. We prefer the first method, since the current, and therefore the heating process, can be controlled more precisely. The energy required to write a bit is in the order of 1 nJ. Calculations show that most of the heat is dissipated at the tip end. Demagnetizing fields of the surrounding material play an important role and are so strong that bits can be written without applying an external field. By decreasing the film thickness, the demagnetizing fields are reduced, and selective overwriting of previously written bits could be demonstrated