Magnetic Hardening in Isolated FePt Nanoparticles

The effect of isolation on the phase transition temperature of FePt nanoparticles has been studied systematically by thermal, magnetic and structural characterizations and analyses. Isolated monodisperse L1₀ FePt nanoparticles embedded in carbon matrix were obtained by adding enough surfactants after chemical synthesis and by post-annealing during which the surfactant decomposed into carbon. It was found that the Al to L1₀ phase transition temperature is dependent sensitively on the amount of isolation medium. The transition temperature shift reaches 150-200 square from non-isolated particle assemblies to completely isolated particles.