  Measurements of electrodynamic response of of spin glass AuFe films in
comparison with pure gold films are performed at frequencies from 0.3 THz (10
cm-1) up to 1000 THz (33000 cm-1) using different spectroscopic methods. At
room temperatures the spectra of pure gold and of AuFe are typically metallic
with the scattering rate of carriers in AuFe being significantly enlarged due
to scattering on localized magnetic moments of Fe ions. In the spin-glass phase
of AuFe at T = 5 K a pseudogap in the conductivity spectrum is detected with
the magnitude close to the Ruderman-Kittel-Kasuya-Yosida (RKKY) energy for
AuFe: Delta(RKKY) = 2.2 meV. The origin of the pseudogap is associated with
partial localization of electrons which mediate the RKKY interaction between
localized magnetic Fe centers.
