Effect of low-frequency AC magnetic susceptibility of Ru/Co^sub 60^Fe^sub 20^V^sub 20^ and Ta/Co^sub 60^Fe^sub 20^V^sub 20^ films

In this study, the maximum alternating current (AC) magnetic susceptibility (χac) and optimal resonance frequency (fres) of (a) glass/Ru (X nm)/Co60Fe20V20(5 nm) and (b) glass/Ta(Y nm)/Co60Fe20V20(5 nm) films at room temperature (RT) were investigated through low-frequency AC magnetic susceptibility (χac) measurement, where X and Y each ranged from 5 to 10 nm. The variation of the highest χac at the optimal resonance frequency (fres), at which the spin sensitivity is maximal, was examined using an experiment. The results indicated that χac decreased as the frequency was increased. The maximum χac of glass/Ru(9 nm)/Co60Fe20V20(5 nm) and glass/Ta(8 nm)/Co60Fe20V20(5 nm) was 20.6 × 10−3 and 15.5 × 10−3 at fres 100 Hz and 1000 Hz, respectively. The maximum χac of glass/Ru(9 nm)/Co60Fe20V20(5 nm) was 1.3 times larger than that of glass/Ta(8 nm)/Co60Fe20V20(5 nm). This indicated that the effect of the Ru seed layer is apparently suitable for low-frequency magnetic recording applications.