Control of Coercivity in Exchange-Coupled Graded (001) $\hbox {FePt}:\hbox {SiO}_{2}$ Nanocomposite Films

We fabricated exchange-coupled composite films with perpendicular anisotropy using nanograms of L1₀ FePt as a magnetically hard base layer and FePt : SiO₂ as a relatively soft phase. The degree of anisotropy and nanostructure in the soft layer was controlled by varying the deposition temperature. Growth of the low-anisotropy layer followed the particulate structure of the base layer at deposition temperatures of 390°C or greater. Perpendicular coercivities were strongly dependent on both the anisotropy and thickness of the softer layer.