Thermal stability of granular-type FePt-MgO perpendicular recording media with soft underlayers

Thermal stability of written bits on [MgO xnm/FePt ynm]/sub 3//MgO4-nm/SiO/sub 2/ 4-nm/Fe-Ta-C 200-nm/Glass perpendicular media with two different structure having different stability factor has been investigated by magnetic force microscopy (MFM) equipped with in-situ sample heating system up to 200/spl deg/C. The disk with x= 2nm, and y= 2.5nm, shows no observable degradation even at 200/spl deg/C, indicating high thermal stability of this disk. On the other hand, for the disk with x= 4nm, and y= 3nm, some reversed domains are observed in the center area of 10kfci bits at 200/spl deg/C and some minor changes are found in the transition area of the higher frequency bits. The decay at a higher temperature is interpreted in terms of estimated thermal stability factor from MFM signal decay.