Understanding magnetic properties of arrays of small FePt dots with perpendicular anisotropy

► FePt dot arrays with dot size down to 15 nm are fabricated. ► Post-annealing leads to enhancements in the magnetic properties of the dot arrays. ► Micromagnetic simulations reveal the microstructure features of the small FePt dots. ► Effective anisotropy and the SFD are dominated by the induced defects in the dots.