Quantitative Kinetic Models of the A1 to ${\rm L}1_{0}$ Transformation in FePt and Related Ternary Alloy Films

Quantitative kinetic models for the A1 to L1
₀
transformation in FePt and related ternary alloy films are derived for three nucleation conditions for both isothermal and constant heating rate annealing. The nucleation conditions are: 1) continuous nucleation, 2) burst nucleation, and 3) pre-existing nuclei. For the first nucleation condition, new nuclei are formed continuously throughout the transformation. For the second nucleation condition under isothermal annealing, nucleation is constrained to occur at a constant rate over only a short period of time. In the limit of this time period going to zero, the nucleation sites are saturated very rapidly and nucleation can be considered to have occurred as a burst. For the third nucleation condition, the nuclei are pre-existing, having formed prior to the start of the transformation. No new nuclei form during the transformation. To identify the nucleation condition that best describes the transformation in FePt and related ternary alloy films, model predictions must be compared with experimental kinetic results.