Effect of heating and cooling rates in annealing for preparation of L1₀-FePt nanoparticles on Si substrate

In order to obtain highly ordered L1₀-FePt nanoparticles for hard disk drive applications, the L1₀-phase transformation of chemically synthesized FePt nanoparticles deposited on a naturally oxidized Si substrate was investigated using rapid thermal annealing. The heating and cooling rates during annealing were changed logarithmically with a constant annealing temperature (800°C) and holding time (10 min). Almost completely ordered L1₀-FePt nanoparticles were confirmed by grazing incidence X-ray diffraction measurements, irrespective of the heating and cooling rates, and the amount of the silicide changed in response to both. Nearly pure L1₀-FePt was obtained when rapid heating (more than 780 K/min) and rapid cooling (more than 290 K/min) were applied. L1₀-FePt degraded into Fe₃Si and PtSi when the cooling rate was lower than 7.8 K/min. Rapid heating as well as rapid cooling of FePt nanoparticles can provide a facile route for the high-throughput production of L1₀-FePt-based high-density magnetic recording media.