Size dependence, nucleation, and phase transformation of FePt nanoparticles

Yi Ding; Majetich, Sara A.
July 2005
Applied Physics Letters;7/11/2005, Vol. 87 Issue 2, p022508
Academic Journal
Monolayers of chemically prepared FePt nanoparticles were deposited on silicon nitride membrane windows, and annealed under different conditions. Hysteresis loops showed a bimodal distribution of switching fields. The size dependence determined from transmission electron microscopy was correlated with the magnetic switching field distribution, assuming that all particles above a threshold size d* had high anisotropy. This simplified model yielded a common value of d*, independent of the annealing conditions. The dependence of d* on the initial particle size indicated the importance of grain boundaries as nucleation sites, and supports the hypothesis that the fcc-to-fct phase transformation is kinetically limited.


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