Remanence coercivity of dot arrays of hcp-CoPt perpendicular films

Abstract

The remanence coercivity, Hr, of hcp-CoPt dot arrays with various dot thicknesses, δ, (3 and 10 nm) and Pt content (20-30at%) were experimentally investigated as a function of the dot diameter, D(30-400 nm). All dot arrays showed a single domain state, even after removal of an applied field equal to Hr. The angular dependence of Hr for the dot arrays indicated coherent rotation of the magnetization during nucleation. Hr increased as Ddecreased in all series of dot arrays with various δ and Pt content. Assuming that the nucleation field of a dot is determined by the switching field of a grain having the smallest switching field, we calculated the value of nucleation field Hncal taking account of the c-axis distribution and the distribution of the demagnetizing field in the dot. The values of Hr obtained experimentally are in good agreement with those of Hncal, taking account of thermal agitation of magnetization. This result suggested that the reversal process of hcp-CoPt dot arrays starts from a nucleation at the center of the dot followed by a propagation process. © 2010 IOP Publishing Ltd.