Activation Volumes in CoPtCr-SiO{sub}2 Perpendicular Recording Media

摘要

CoPtCr-SiO{sub}2. perpendicular recording media with varying levels of SiO{sub}2 were examined by two different methods to determine the activation volume. The first is based on the sweep-rate dependence of the remanence coercivity using Sharrock's equation. The second is based OH the measurement of the fluctuation field from time-dependence data, determined using a magneto-optical Kerr effect (MOKE) magnetometer. The values of V{sub}(act) measured at the coercivity for both methods are almost the same, with the fluctuation field and activation volumes increasing with the SiO{sub}2 content. The difference between V{sub}(act) and the grain volume measured directly from bright-field TEM images decreases as the SiO{sub}2 content increases due to the reduction of intergranular exchange coupling. The experimental results indicate that values of V{sub}(act) obtained from single- and double-layered media are consistent. It was also found that the coercivity and normalized hysteresis loop slope at coercivity varied with SiO{sub}2 content, with the coercivity peaking at 8 at%SiO{sub}2 (nearly 26 vo!%SiO{sub}2).