Investigation of Proximity Effects between Normal Metal and Superconductor through Transmission Electron Spin Resonance and Microwave Magnetoabsorption

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The results of this project, regarding the interaction between superconductors and resonant / non-resonant microwaves as an woof, is summarized below.(1) Fabrication of a simple resistivity cryostat and Y- and Bi- based high-T_c superconductors resulted in a fairly satisfying source material for electron-beam evaporation in YBCO case. In BSCCO case, however, there remained some problems for improving homogeneity of oxygen concentration within the sample.(2) Close correlations among sintering conditions, oxygen contents and superconducting qualities have been confirmed mainly in YBCO through X-ray diffraction and Rietveld analyses. This has been one step towards studies of correlation between flux-pinning defects and oxygen deficiency.(3) The necessity of rather sharp transition of superconductivity as well as moderate coupling between normal metal and superconductor has been pointed out for the distinct proximity effect to be clearly observed through measurements of the transmission el … More ectron spin resonance.(4) The detailed observations of the microwave magnetoabsorption have shown that superconductivity in the Tl-based cuprate is quasi-two dimensional similar to the Bi-based cuprate. The observed logarithmic relaxations in the remanent absorption after H_<FC> field cooling and in the magnetoabsorption under existing field H_a provided estimations of the flux pinning potential U_O which scaled as U_O alpha H^<-1/4>_ and as U_O alpha H^<-1/2>_, respectively. These observations are consistent with the microwave irreversibility measurements with U_O alpha B^<-1/2> dependence which originates in the two-dimensional flux lattice model. Decaying process of the in-field microwave absorption further suggested that the absorption in larger applied field is closely correlated with magnetization |M| rather than flux density B. Further investigations on the interactions between microwaves and superconductors will be continued in the future project accompanied by magnetization measurements in the same samples. Less