Thermal stability and media noise performance of the CoPrTb/CoCrTa composite perpendicular media are discussed. Angular dependence of remanance coercivity and the ΔM plot indicate that magnetization reversal in the CoPrTb/CoCrTa composite media is mainly proceeded by local switching of magnetization, while the magnetization loop of the composite media show very steep slope and large squareness M r/M s compared to those of CoCrTa media. Recording performance of (CoPrTb/CoCrTa)/Ti/CoZrNb double-layered perpendicular media was examined using a single-pole-type write head and a GMR read head. The recording resolution, D 50, of a CoPrTb(10 nm)/CoCrTa(20 nm) composite medium is about 50 kfrpi higher than that of CoCrTa medium, and the signal to medium noise ratio, S/N m, was about 10 dB higher than that of the CoCrTa medium (at 300 kfrpi). The CoPrTb/CoCrTa composite media show very high thermal stability of read back signals even at low recording density, although the value of M r/M s is smaller than 0.9. The continuous CoPrTb layer is assumed to prevent the thermal reversal of individual grains of the CoCrTa layer by the interfacial exchange coupling.
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