Phase transition of chemically synthesized FePt nanoparticles under high pressure

We present the results of a study related to phase transformation of chemically synthesized FePt nanoparticlesunder high pressure from face-centered cubic into face-centered tetragonal structure. As-synthesized nanoparticles arearound 4.5 nm and show superparamagnetic behavior at 300 K. After annealing under 60 bar pressure of hydrogen at400 ◦ C for 2 h, nanoparticles exhibit strong ferromagnetic behavior with 5391 Oe coercivity. Results show that highpressure annealing lowers the decomposition temperature of the surfactants surrounding nanoparticles and partiallyhinders agglomeration arising from heat treatment. The promising ferromagnetic properties of the FePt nanoparticlesafter annealing under high pressure make them suitable for ultrahigh-density memory devices.

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