The ferromagnetic interlayer exchange coupling Jinter for stacked perpendicular recording media with a granular layer (GL)/interlayer (IL)/alloy capping layer (CL) structure was quantitatively evaluated by Q-band ferromagnetic resonance (FMR). Two resonances with acoustic and optical precession modes were observed in the FMR signals from the stacked media. Fitting using the Landau-Lifshitz-Gilbert (LLG) equation indicated that J inter increased from 0.55 to 1.83 erg/cm2 when the Pt IL thickness was reduced from 2.0 to 1.0 nm for media based on Co 82Cr10Pt8-CL (4 nm) and Co74Pt 16Cr10-8 mol (SiO2)-GL (16 nm). The optimum Pt IL thickness at which the switching field distribution was minimized due to a large reduction in the saturation field of the stacked media was found to correspond to the boundary condition between antiparallel and parallel precession of the magnetic moments of the GL and CL in FMR.
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