Modulation corrections to the modulated microwave absorption of a pure mercury sample

Modulated-microwave-absorption spectra associated with the intermediate state have been observed at 15 GHz in a carefully prepared, pure mercury sample. Corrections to the measured critical fields were based on the assumption that the superconducting system follows the resultant of the sweep and modulation fields while the signal position is given by the sweep field only. The theory was tested on the behavior of a modulation-dependent transient signal amplitude observed below 2 K, which was associated with the onset of the truncated spectrum caused by ‘‘supercooling’’ of the normal state for downward sweeps. The values T_c=(4.159±0.002) K and H₀=(419±2) Oe were obtained by fitting the corrected data to the parabolic law.