Phase transformations in Pt/Fe bilayers during post annealing probed by resistometry

Abstract

X-ray diffraction (XRD), secondary neutral mass spectrometry (SNMS) depth profiling, and electrical resistivity measurements were used to follow the phase transformations in Pt/Fe bi-layered thin films during annealing. Initially, the electrical resistivity increases linearly with temperature up to 150 °C due to the contribution of phonon scattering of the metallic Pt and Fe bilayer. Further increase of the annealing temperature leads to a steeper linear increase, which is associated with the initial formation of the chemically disordered A1-phase followed by the formation of the chemically ordered L10-FePt phase, as confirmed by XRD and SNMS studies. Finally, at about 620 °C the single L10-FePt phase has formed throughout the film. Moreover, the electrical resistivity contains also the magnetic contribution to the total resistivity. In this case, the loss in magnetic order is indicated by a change in temperature dependence of the resistivity at about 310 °C, representing the Curie temperature of the initially formed A1-FePt alloy, while the finally formed L10-FePt alloy reveals a higher magnetic transition temperature of about 410 °C. In this study, it has been demonstrated that resistometry in combination with structural and chemical analysis provides valuable information on diffusion processes, structural phase formations and its stability range, as well as on the magnetic transition temperature.

Atomic level mechanism of disorder-order transformation kinetics at nanoscale in FePt based systems

“…Post deposition treatments of the FCC phase are required to obtain the L1 0 ordered FCT phase. Moreover, structural and magnetic properties of L1 0 ordered FePt sensitively depend on the relative concentration of Fe and Pt, approaches of synthesis, post-deposition treatments, film structure in an as-deposited state, etc [6][7][8][9][10][11]. Therefore, wide research interest is directed at the optimization of structural and magnetic properties of FePt by synthesizing FePt films in diverse structures via various synthesis routes [12][13][14].…”