Effects of nitrogen addition to the CoCr recording layer of a double layered perpendicular rigid disk

Increase of the coercive force (H-c) and narrowing of the coercive force distribution (Delta H-c) was observed on double layered perpendicular rigid disks which were prepared by adding a small quantity of N-2 during CoCr layer sputtering deposition. The effects of the N-2 addition gave rise to an increase of output signal and D-50. This change of recording property with N-2 addition is due to narrow dispersion and reduction of CoCr grain diameter as measured by atomic force microscopy (AFM). But medium noise which was caused by magnetic inhomogeneity was also enhanced. Furthermore expansion of the domain size was found at the dc-erased state by magnetic force microscopy (MFM).