Investigation of particle formation and superstructure development in FePt nanoparticles and their effect on magnetic properties

FePt nanoparticles with perpendicular magnetic anisotropy embedded in non-magnetic matrices M (M=Ag, C) have been fabricated by sputtering FePt/M multilayer films onto single crystal MgO [0 0 1] at temperatures above 300 °C. Particles with controlled particle size down to a few nanometers and tailored microstructure and magnetic properties can be obtained by varying the bilayer thicknesses, the substrate temperature, the type of substrate material and the post-annealing conditions. Ordered FePt nanoparticles have also been prepared directly by gas phase condensation techniques (cluster gun).The cluster gun allows a better control of particle size and distribution, and enables an in situ heat treatment of the particles to transform their structure into the desired phase before they are deposited onto the substrate, thus avoiding the undesirable effects of alloying and oxidation.