Magnetics of ultrathin FePt nanoparticle films

A clear dependence of the magnetic behavior of annealed assemblies of FePt nanoparticles on sample thickness was observed. This was a result with potentially significant technological consequences. While it was possible that this thickness dependence could result either from the upper layers of nanoparticles becoming oxidized or the lower layers forming a silicide structure, neither of these possibilities were consistent with x-ray diffraction measurements, which show no evidence for either iron oxides or silicides following an anneal at 580°C.