Calorimetric studies of the A1 to L 10 transformation in binary FePt thin films with compositions in the range of 47.5-54.4 at.% Fe

Abstract

Differential scanning calorimetry, in conjunction with x-ray and electron diffraction, is used to investigate the A1 to L 10 ordering transformation in binary FePt films with compositions in the range of 47.5-54.4 at. % Fe. The kinetic ordering temperature, taken as the calorimetric peak temperature at a heating rate of 40°Cmin, decreases from 447 to 357 °C in this composition range. In contrast with the kinetic ordering temperature, the Curie temperature of the L 10 ordered phase increases from 384 to 455°C as the Fe content is increased. The activation energies of ordering lie between 1.4 and 2.0 eV, and the transformation enthalpies are in the range of -8.2 to -13.6 kJg-at. The Avrami exponent for the transformation is lower than expected and lies in the range of 1.1-1.8. The lattice parameter of the A1 phase and the ca ratio of the L 10 phase decrease with increasing Fe content. © 2005 American Institute of Physics.