Microwave absorption from superconducting crystals of the Tl-Ca-Ba-Cu-O system

The authors present the results of non-resonant, magnetic field-dependent microwave absorption experiments carried out on five superconducting crystals from the Tl-Ca-Ba-Cu-O system. The absorption was found to be anisotropic with respect to the applied DC magnetic field. On cooling the sample, the onset of the absorption with the field parallel to the crystal c axis was detected at a higher temperature than with the field perpendicular to the c axis for all the crystals studied.