Size-Dependent Chemical and Magnetic Ordering in L10-FePt nanoprticles
Abstract
Direct evidences for the size-dependent chemical ordering and magnetic ordering in L10 FePt nanoparticles have been obtained by measuring the monodisperse nanoparticles prepared by the "salt-matrix annealing" technique. Quantitative correlations between particle size and the structural and magnetic properties show that the long-range chemical ordering parameter S drops significantly with decreasing particle size d especially when d 6 nm. When d 2 nm, the phase transition from disordered face-centered cubic structure to the ordered L10 structure does not occur even at elevated temperature for extended time. The magnetic properties, including the Curie temperature, magnetization and coercivity of the L10 nanoparticles, are co-defined by the size effect and the chemical ordering effect. It has been revealed that the Curie temperature of the ferromagnetic nanoparticles can be described by the finite-size-scaling theory after considering the influence of particle size on the chemical ordering.
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