Thermal stability of the magnetization following thermomagnetic writing in perpendicular media

Abstract

The thermal decay of the magnetization in granular thin films with high perpendicular anisotropy following thermomagnetic writing is investigated using a semianalytical and a numerical mean-field self-consistent model. We study the effects of cooling rate, dispersions in grain volumes and anisotropy fields, damping, and intergranular interactions. Two distinct contributions to the thermal decay arise from cooling and storage, respectively. The magnetization freezes during cooling as a result of the increase in anisotropy and the net thermal decay for slow cooling is logarithmically dependent on the time before the magnetization is frozen. The areal density advantage of heat-assisted, over conventional magnetic recording increases sharply when the thermal decay starts close to the Curie temperature. The maximum benefits of heat-assisted recording using FePt media are derived by heating above the Curie temperature.