We report far-infrared transmittance measurements on granular free-standing thin films of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{x}}$ in the frequency range 10–650 ${\mathrm{cm}}^{\mathrm{-}1}$. The transmittance was measured both on metallic films, in the normal (110-K) and superconducting (10-K) states, and on insulating films. The metallic samples behave as a mixture of conducting and insulating small grains in the vicinity of the percolation threshold. We obtained a fit to the measured transmittance with the two-dimensional effective-medium approximation. The frequency-depenent effective conductivity was calculated and the absorption coefficient was observed to change as ${\mathrm{\omega }}^{0.67}$.

Close

PrevNext

View figure in article