The effect of magnetic field modulation on the microwave response in high-Tc superconductors

The origin of the strong enhancements of microwave response at the onset of the superconductivity has been investigated. Since the effect is only detectable when the measurements are made by making use of a ESR spectrometer, the effect of modulation is investigated. The origin of the enhancement is considered to be due to strong dependence of the microwave dissipation on the magnetic field.