Giant microwave losses in a YBaCuO bicrystal

Abstract

We have observed a large peak in microwave losses, as a function of temperature, in a superconducting Y1Ba2Cu 3O7 bicrystal containing a large-area, low-angle grain boundary. The maximum observed loss was approximately twice the normal state loss. We attribute the peak to enhanced losses occurring within the grain boundary due to the concentration of microwave field lines in the boundary as they are expelled from the superconducting regions. At high microwave powers, bistability in the absorption was observed, resulting in hysteretic absorption curves as a function of both T and magnetic field H.