Where is the Ag in FePt-Ag composite films?

The miscibility of Ag with FePt composited films was investigated with anomalous x-ray scattering (AXS) and extended x-ray absorption fine structure (EXAFS) at Ag K edge. In the AXS spectra for FePt Bragg peaks, the cusp near Ag K edge was observed, indicating alloying between Ag and FePt in the FePt-Ag thin films. Semiquantitative analysis showed 4.2 at. % and 5.9 at. % Ag were in FePt lattice for the samples with 20 vol % and 30 vol % Ag, respectively. EXAFS studies indicated in the alloyed FePt-Ag phase, Ag replaced the Fe sites in FePt lattice. Most of Ag segregated from FePt and formed fcc phase. This segregated Ag phase only had short range order, which may be due to that segregated Ag had small grain size and/or some disordered Ag phase existed in FePt grain boundaries. (C) 2011 American Institute of Physics. [doi:10.1063/1.3574538]