Evaluation of flux-trapping and magneto-resistibility of superconductors by ESR spectroscopy

The abnormal signal, which was observed in the ESR measurement of superconductors, was confirmed to be a non-ESR (non resonant) signal, from an ESR experiment applying parallel and vertically polarized microwave fields and from the calculation of the ESR transition probabilities. The field modulation dependence of the spectra revealed that the signal was composed of two components. From the modulation-scheme analysis and a study of type I and II superconductors, two components were assigned to the microwave responses to magnetizations trapped in the crystalline portion and at intergranular Josephson junctions. The former B and the latter J components are observed in the first derivative and absorption form, respectively, and their polarities differently behave for the field sweep reversal. Based on these results, we have improved an ESR spectrometer, which makes it possible to measure separately two kinds of magnetization and to study the trapping ability and quantum flux. (author)