Comparative study of thermal conductivity and surface impedance of Bi2Sr2CaCu2Oy in the mixed state

We measured the magnetic-field (H) dependence of thermal conductivity kappa (H) and microwave impedance Z(s)(H) in exactly the same peaces of crystal. In a sample where the plateau was observed in kappa (H), we could not find any anomaly at the onset of the plateau. This result suggests that the ori gin of the plateau in kappa (H) is not a drastic phase transition but is ra ther somewhat gradual crossover. We also found that there were no qualitati ve difference between Z(s)(H) of this sample and that of another sample whi ch did not show the plateau kappa (H).