Comparison of Experiment and Simulation Results of Interlayer Thickness Effect in Perpendicular Recording Media

The effect of interlayer thickness (t IL ) on recording performance of the media showing relatively close to coherent switching behavior is investigated. The range of t IL was widely controlled from 20 to 45 nm by inserting an amorphous CrTa filling layer between NiW(6 nm)/Ru(14 nm) and amorphous FeCoTaZr soft underlayer (SUL). Minor heating effects at a thicker CrTa on a glass substrate are detected, but the change in magnetic properties and microstructure even at t IL = 45 nm is small enough to study the head-to-SUL spacing effect. A thinner IL clearly improves both reverse overwrite (ROW) and signal-to-noise (SoNR 2T ) at 2 T, but it reduces resolution (RES). Less dependence of magnetic core width (MCW) on t IL is shown due to compensation of wider magnetic write width (MWW) and narrower erasure band (EB) at a thinner IL. According to simulation results, a thinner IL enhances field strength underneath the center of the writer and more field penetration into the media but the maximum effective field located near the gap changes very little. These field profiles improve writeability at low frequencies, but they do not affect much at mid-to-high frequencies. This situation can explain better ROW, lower RES, and wider MWW at a thinner IL. Higher crosstrack field gradient at a thinner IL corresponds to narrower EB. The improvement of SoNR 2T at a thinner IL is caused by the increase in signal at low frequency and the further decrease in dc noise. All the recording parameters with increasing t IL are qualitatively consistent with simulation results.