Co-PrTb/Co-Cr-Ta複合型垂直磁気記録媒体の熱安定性と記録再生特性 : 垂直磁気記録媒体

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The thermal stability and medium noise performance of Co_<100-X>(PrTb)_X/Co-Cr-Ta (X = 21-31.7 at%) composite perpendicular media are discussed. The perpendicular magnetic anisotropy K_u shows a maximum at X = 〜25, although the saturation magnetization decreases gradually as X increases. The ratio of "intrinsic" remanence coercivity obtained by subtracting the thermal agitation to the anisotropy field, H_0/H_k, increases as X increases, indicating a reduction of the exchange coupling of magnetization. The medium noise of the composite media, which have CoZrNb soft back-layers, decreases gradually as X increases and as the Co-PrTb thickness decreases, resulting in a higher signal-to-medium-noise ratio SN_mR. The SN_mR of a Co_<76.5>(PrTb)_<23.5> (5 nm) / Co_<77>Cr_<19>Ta_4 (25nm) composite medium is about 8 dB higher than that of a Co_<77>Cr_<19>Ta_4 (30 nm) medium at 300 kFRPI. The composite media show high thermal stability of read-back signals even at low recording density. However, the thermal signal-decay increases gradually as the Co-PrTb thickness decreases, and also as X increases, indicating that the thermal stability has a trade-off relation with the medium noise performance.
2002-04-01