Base-line-subtracted calorimetric traces at a heating rate of for two FePt films showing the shift to lower temperature with increasing Fe content. The Curie temperature of the ordered phase is measured from the downward change in the slope of the base-line during a second heating run. The upward change observed here is a result of the base-line subtraction procedure. The change in the slope of the trace preceding the exothermic transformation peak likely represents the Curie transition of the phase.
X-ray diffraction scans for the alloy film (a) as-deposited and heated at to (b) 300 and (c) . The annealed sample shows the superlattice peaks (001), (110), and (201) for the phase, thereby confirming that the exothermic peak in Fig. 1 is the to transformation.
Bright-field transmission electron micrographs and selected area diffraction patterns (insets) for [(a), (c)] and [(b), (d)] films heated at [(a), (b)] and [(c),(d)]. For some annealed samples, the selected area diffraction patterns showed the presence of magnetite as a very fine-grained minor phase. This phase is believed to have formed on the sample surface during annealing.
Curie temperature as a function of Fe concentration for the alloy films studied here and for the bulk alloys reported previously (see Refs. 86–89).
(a) Transformation enthalpy, , (b) activation energy, , and (c) kinetic ordering temperature, , as a function of Fe content in the films.
Film compositions measured by energy dispersive x-ray fluorescence (EDXRF) and Rutherford backscattering spectrometry (RBS), the Curie temperature of the phase, , the kinetic ordering temperature, , the to transformation activation energy, , enthalpy, , and the Avrami exponent, , determined by two different methods. The number in parentheses represents the number of measurements for each parameter.
Lattice parameters for as-deposited and annealed films.
Article metrics loading...
Full text loading...