The effects of an intermediate layer of carbon on the structural and magnetic properties of a CoCrPtTa recording layer were investigated in double-layered perpendicular magnetic recording media with either amorphous CoTaZr or crystalline FeAlSi as soft magnetic backlayers. Introducing a thin layer of carbon enhanced the perpendicular magnetic anisotropy with both soft magnetic backlayers. This result suggests that the introduction of a non-magnetic intermediate layer is useful in improving the basic magnetic properties of the CoCr-alloy recording layer even when an amorphous soft magnetic backlayers is used.

The effect of NiP as a seed layer for the [Co/Pd]n multilayer perpendicular recording media was studied. It was found that a thin layer of 2 nm NiP inserted between the FeCoC soft magnetic underlayer and the [Co/Pd]n recording layer improved the magnetic properties such as coercivity, squareness and nucleation field. These improvements may be due to the enhanced grain isolation promoted by the NiP seed layer, as well as the lower surface roughness of the NiP seed layer. Read/write test using Guzik spin stand with a ring-type head showed a D50 value 220 kFCI in the roll-off curve. The magnetic transitions recorded up to 390 kFCI for [Co/Pd]n media with the NiP seed layer can be observed clearly with MFM.

Time decay of magnetic properties in perpendicular magnetic recording media was studied. It was suggested that magnetization in media with a low energy ratio, KV/kT, of 50 is thermally stable in the absence of a demagnetizing field while coercivity exhibits a large time dependence. Magnetization in perpendicular recording media exhibited an appreciable time decay even for films with a large energy ratio of 300. The decay is attributed to the small perpendicular squareness due to a large perpendicular demagnetizing field acting in the media. The recording density dependence of the time decay in the output was explained in terms of the change in the demagnetizing field with the density. It is concluded that the use of media with large squareness as well as large energy ratio effectively reduces time decay in the output.