Coercivity of TbFeCo/FePt Grain Composite Films

Abstract

We report the simulated results for coupled granular and continuous (CGC) films for the thermo assisted magnetic recoding, consisting of FePt particles under layers that act as domain pinning sites of TbFeCo layers. As domain size should be smaller to further increase the recording density, the number of FePt grains has to be decreased in the domain. The simulated results demonstrated that they could be formed in a domain as small as 18.3 nm in diameter, which corresponds to a recording density of 1.8 Tbit/inch 2. Here, three FePt grains were effective for pinning. We also estimated the effective wall coercivity, Hw, from the simulation varying the applied magnetic field until a domain had shrunk and disappeared. The Hw was over 12 [KOe] where there were only three grains for pinning. The Hw was a function of the radius of the curvature at the pinning point and also the inverse average wall length between the pinning points in the same composite films.