Time-temperature-transformation diagrams for the A1 to L10 phase transformation in FePt and FeCuPt thin films

The kinetics of the A1 to L1(0) transformation are given in the form of time-temperature-transformation diagrams. These diagrams are calculated using experimentally measured data for 1 mu m thick FePt and FeCuPt thin films and three variations of the Johnson-Mehl-Avrami-Kolmogorov kinetic theory. For the FePt alloys, an increase in Pt content from 45.6 to 52.5 at.% results in a >300 times increase in the annealing time needed to reach a fraction transformed of 0.95 at 300 degrees C. Extension of the calculations for 1 mu m thick films to 10 nm thick films using geometric corrections shows not only that thinner films result in slower kinetics for all temperatures, but also that film composition has a significant impact on the transformation behavior. Transformation in nanoparticles is highly dependent on the nucleation of the L1(0) phase. (c) 2007 American Institute of Physics.