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

本项目以超导体与共振/非共振微波的相互作用为例，总结如下：(1)制作了简单的电阻率恒温器和Y、Bi基高T_c超导体，为YBCO情况下的电子束蒸发提供了一种比较满意的源材料。然而，在BSCCO的情况下，仍然存在一些问题，以改善样品中的氧浓度的均匀性。(2)通过X射线衍射和Rietveld分析，主要证实了YBCO的烧结条件、氧含量和超导性质之间的密切关系。这是研究磁通钉扎缺陷与氧缺乏之间关系的一个步骤。(3)为了通过对el…透射率的测量，清楚地观察到明显的邻近效应，需要相当剧烈的超导转变以及正常金属和超导体之间的适度耦合。更多的电子自旋共振。(4)对微波磁吸收的详细观察表明，Tl基铜酸盐的超导电性类似于铋基铜酸盐的准二维超导电性。H&lt；Fc&gt；场冷却后剩余吸收的对数弛豫和存在磁场H_a下的磁吸收的对数弛豫分别给出了磁通钉扎势U_O的估计值，其标度分别为U_OαH^&1/4和U_OαH^&2。这些观测结果与源于二维磁通晶格模型的U_OαB^&lt；-1/2&gt；依赖测量的微波不可逆性是一致的。场内微波吸收的衰减过程进一步表明，在较大外场中的吸收与磁化强度|M|密切相关，而不是与磁通密度B密切相关。进一步研究微波与超导体之间的相互作用将在未来的项目中继续进行，并伴随着相同样品的磁化测量。较少

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