Mössbauer spectra and electronic structure of nonequilibrium Fe-Cu alloys produced by vapor quenching

Abstract

Mössbauer spectra have been observed for nonequilibrium bcc and fcc Fe−Cu alloys sputter-deposited at several Ar gas pressures,P _Ar. These alloys are ferromagnetic at low temperatures and show sextet spectra. The fcc alloys which are paramagnetic at 290 K show asymmetric doublet spectra, indicating no serious segregation. In the alloys deposited at highP _Ar, the weak intensity ratios of the second and fifth lines of the sextet indicate a tendency of perpendicular magnetic anisotropy, while a large magnetic hyperfine field component of about 40 MA/m (500 kOe) at 4.2 K and a large quadrupole splitting component of about 0.7 mm/s at 290 K imply CuFeO₂ formation. The nonequilibrium, bcc and fcc Fe−Cu, alloys are maintained below 500 K and the phase separation is detected above 550 K. X-ray photoemission spectroscopy studies of these alloys reveals individual Fe- and Cu-d bands. The concentration dependence of peak intensities and peak positions indicate that Fe and Cu electronically intermix.