Date of this Version
Nanostructured FePt: M (M=C,Ag,Cu) perpendicular magnetic recording media are investigated by numerical simulations and model calculations. Both intra- and intergranular exchanges are considered, and it is assumed that the interaction through the matrix is mediated by conduction electrons. Several limits, including free-electron-like Ruderman-Kittel-Kasuya-Yosida interactions, are considered. The atomic modeling yields effective intergranular coupling strengths that depend on both cluster radius and distance, on the magnetic properties of the clusters, and on the electronic nature of the medium. In the simulations, the exchange is approximated by a thin shell with reduced exchange and zero anisotropy. The simulations show that intergranular exchange reduces the coercivity of the system, and the magnetization reversal proceeds in a regime between localized nucleation and discrete domain-wall pinning, depending on the intergranular exchange. Coercivity and loop-shape reduction also depend on the geometry of the particle system.