Co(-B)/Pd人工格子垂直磁気記録媒体の磁気異方性と磁化の熱擾乱 : 垂直磁気記録媒体

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Magnetic properties and recording performance are discussed for [Co/Pd (1 nm)]_9 and [(Co-27 at% B) /Pd (1 nm)]_9 superlattice perpendicular recording media as a function of the Co or Co-B layer thickness, δ_<Co> or δ_<CoB>. The perpendicular magnetic anisotropy K_u of these media shows maximum values of 5.7 x 10^6 erg/cm^3 (Co/Pd) and 3.2 x 10^6 erg/cm^3 at δ_<Co> or δ_<CoB> of around 0.2-0.3 nm. The KuV/kT (V; the activation volume, k; the Boltzmann constant, T; the absolute temperature) of the Co/Pd medium has large values of more than 200 (δ_<Co>>0.3nm), while the Ku V/kT in both media significantly decreases as the thickness decreases, which is not coincident with the thickness dependence of K_u. The value of K_u/2πM_s^2 (M_s ; the saturation magnetization) in both media increases monotonically as the thickness decreases, and is 〜10 at δ_<Co> or δ_<CoB> of around 0.2-0.1 nm. The signal-to-medium-noise ratio SN_mR of the Co-B/Pd media is higher than that of the Co/Pd media, and increases as δ_<CoB> decreases. TEM images and magnetic characterization revealed that these differences in SN_mR are mainly due to the differences in the strength of intergranular exchange coupling.
2002-04-01