Calorimetric studies of the A1 to L10 transformation in binary FePt thin films with compositions in the range of 47.5-54.4 at.% Fe -: art. no. 024902

Differential scanning calorimetry, in conjunction with x-ray and electron diffraction, is used to investigate the A1 to L1(0) 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 degreesC/min, decreases from 447 to 357 degreesC in this composition range. In contrast with the kinetic ordering temperature, the Curie temperature of the L1(0) ordered phase increases from 384 to 455 degreesC 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 kJ/g-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 c/a ratio of the L1(0) phase decrease with increasing Fe content. (C) 2005 American Institute of Physics.