Microscopic mechanism to determine strain dependence of critical current for Yttrium-based high Tc superconducting film

点击翻译按钮获取中文摘要

Yttrium-based superconducting film exhibits reversible effect of strain on critical current. However, the origin of this phenomenon has not been clarified. In this study, we succeeded in evaluating strain dependence of critical current in magnetic field for YBCO film without grain boundaries grown on SrTiO_3 single crystal substrate by means of a 4-point bending method. As a result, the peak of the critical current at a certain applied strain was confirmed for a single-crystalline film similar with the practical biaxially-textured polycrystalline film. This suggests that lattice deformation within a grain contributes to the reversible effect of strain on critical current as well as strain at the grain boundaries. In addition, change in internal strain under tensile loading was directly evaluated along a-anb b-axes for Gd-based superconducting films with different strain sensitivity to critical current using synchrotron radiation based on X-ray diffraction technique. This experiment reveals that GdBCO film with small strain sensitivity orients its[110] direction parallel to the loading axis and induced strain along the a-and b-axes is smaller than the other film in which a-and b-axis orients to the conductor axis and width. As a result, it was clarified that difference in crystal orientation of superconducting film can be one of the microscopic origins to determine strain dependence of critical current.