Formation of Magnetic Cluster and Remanence Coercivity in Granular-Type Perpendicular Media.

The magnetic cluster size D[subcluster] of perpendicular recording media, which is a main factor in media noise, is discussed in terms of demagnetizing field of magnetic clusters, remanence coercivity, and magnetization switching. It was shown that the values of remanence coercivity obtained by subtracting thermal agitation effect H[sub0] are ∼70% of those calculated using the Stoner-Wohlfarth model taking account of the c-axis distribution, H[supS-W][subr], even in CoPtCr-SiO[sub2] media with well segregated grains. Demagnetizing field of magnetic cluster H[subd] is calculated as a function of the ratio of D[subcluster] to film thickness, δ. An intrinsic remanence coercivity H[supint][sub0] was obtained by compensating the H[sub0] value by the H[subd](H[supint][sub0] = H[sub0] + H[subd]). The H[supint][sub0] values are very close to those of H[supS-W][subr] especially in media with well-segregated grains. This result means that the magnetization reversal of these media is mainly determined by coherent rotation of magnetization; however, the demagnetizing field of magnetic cluster, besides thermal agitation effect, reduces the value of H[sub0]. [ABSTRACT FROM AUTHOR]