Silicide formation and particle size growth in high-temperature-annealed, self-assembled FePt nanoparticles

L10 FePt nanoparticle assemblies consisting of a few layers of 4-nm-diameter particles, are a potential data storage medium beyond 1 Tbit/in2. However, annealing at temperatures >500 °C is required to form the high anisotropy L10 phase. Recent studies have shown a substantial drop in magnetization for Tanneal>650 °C. We show that this reduction in magnetization is due to silicide formation as a result of a chemical reaction with the native oxide or Si substrate. We also show that full L10 ordering is established only after annealing at 725 °C for 60 min and note that particle agglomeration occurs under these conditions.