The microwave absorption R in the Y-Ba-Cu-O single crystals was investigated near { T_c \approx 92 K} and in the external magnetic field { 0<H \leq 9 kOe}. A modified ESR spectrometer was used in the experiment. The method of temperature modulation, along with the usual method of magnetic-field modulation, was first applied in studying of the microwave response of these crystals. Peaks in the temp erature dependencies of the signals { \partial R}/ { \partial H} and { \partial R} /{ \partial T} observed in the vicinity of { T_c} were differently shaped and slightly shifted one with respect to another. The evolution of the peaks with variation of the magnetic field and angle { \theta} between { \bf H} and the { \bf c}-axis was traced. It has been shown that the observed difference of the temperature dependencies of the derivatives { \partial R}/{ \partial H} and { \partial R}/{ \partial T} occures due to the field-induced broadening of the superconducting transition, which is inherent in the high-{ T_c} superconductors.
Categories: cond-mat