Electronic states of self stabilized L10 FePt alloy nanoparticles

The ligand capped bimetallic FePt alloys were prepared by using the chemical coreduction method in the presence of oleic acid and oleylamine. An X-ray photoelectron spectroscopy (XPS) study on the as prepared and annealed samples reveals the degradation of hydrocarbon capping with annealing temperature along with a phase transformation to a L1₀ phase. This degradation of organic capping results in formation of capping layer over FePt which has been observed using High Resolution Transmission electron microscopy (HRTEM). This capping layer over the FePt nanoparticles was further investigated with Raman studies confirming the presence of the graphitic carbon. The presence of the graphitic layer enhances the stability of FePt nanoparticles by protecting the surface against oxidation. This was confirmed by the magnetic measurements which show a high coercivity of 11.8 kOe, retained over a period of one year.