Hydrogen-induced crystal structural transformation of FePt nanoparticles at low temperature

The hydrogen-induced crystal structural transformation of FePt nanoparticles from a chemically disordered face-centered-cubic (fee) structure to a chemically ordered L₁₀ structure was first demonstrated at around 300°C. The hydrogen treatment at low temperature led to not complete but considerable suppression of the nanoparticle coalescence. The obtained L₁₀-FePt nanoparticles exhibited ferromagnetic property with large coercivity at room temperature. The ordering degree of FePt nanoparticles was dependent on both the hydrogen pressure and treatment time.