Charge carrier localization due to ferromagnetic clusters in concentrated AuFe alloys

The electrodynamic properties of Au1-xFex films are measured for various Fe contents x=0, 6, 17, and 22 at. %. From room-temperature optical measurements over a broad spectral range (10-3.3x10(4) cm(-1)), we obtain the frequency-dependent conductivity of the films. As the iron concentration increases, a stronger decrease in the magnetic contribution to the dc conductivity compared to ac conductivity (at frequency 10 cm(-1)) is detected. In addition, a broad absorption peak is discovered at frequency 1000-3000 cm(-1) for concentrations of 6-22 at. %. Both observations are associated with ferromagnetic clusters that cause partial localization of conduction electrons.