CoPtCr-SiO_2/Ru垂直磁気記録媒体における磁気特性のPt,Cr組成依存性(磁気記録)

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The magnetic properties and media noise performance of {(Co_<100-X>Cr_x)_<100-Y>Pt_Y}_<89>-{SiO_2}_<11>/Ru media were investigated as functions of the Pt and Cr contents. The magnetic anisotropy energy K_u shows a broad maximum at a Pt cont,ent around Y=20 at%, almost, irrespective of the Cr content. The anisotropy energy of the grains, K_u^g, calculated by taking account of the volume fraction, reaches nearly 8 x 10^6 erg/cm^3 even with a Cr content of X = 10 at%. The ratio of the magnetic anisotropy energy to the thermal energy, Ku V_<act>/kT, at this composition maintains a value of more than 100, even with 10 nm thickness and a grain size of 7.7 nm, indicating a high potential to resist thermal agitation. The high K_u causes a large remanence coercivity H_r and a loop squareness of 1 in the Pt content region around Y=20. The activation diameter D_<act> increases gradually as the Pt content increases, while an increase of the Cr contont reduces the D_<act>. The signal-to-media-noise ratio SNmR improvos as the Pt content decreases, which accords well with the reduction in D_<act>. It is likely that a Pt content of Y= 15-20 at% is an optimum composition to attain both low media noise and high thermal stability. There is a trade-off betwecn low noise performance and thermal stability as a function of the Cr content.
社団法人日本磁気学会の論文
2004-03-01