Coercivity enhancement of FePt thin films coated with a monolayer array of γ-Fe2O3 nanoparticles

We report on a two-dimensional magnetic nanocomposite material consisting of a monolayer of ~ 11 nm diameter colloidal γ-Fe2O3 nanoparticles arrayed by the Langmuir–Blodgett method over a ~ 3 nm thin film of FePt deposited on a glass slide substrate, thus exploiting the advantages of both thin film fabrication and chemical synthesis. The FePt film was obtained by magnetron sputtering of a FePt target, followed by vacuum annealing at 600 °C. FePt magnetic polarization perpendicular to the film plane was observed. The parallel to the plane hysteresis loops are dominated by the diamagnetic glass substrate. The perpendicular to the plane hysteresis loops are highly square with a coercivity of 4.87 × 106/4π (A/m), which upon deposition of the monolayer array of γ-Fe2O3 nanoparticles increases to 6.31 × 106/4π (A/m).