Determination of transition curves of high-Tc superconductors by phase contrast microscopy

A new method which allows the detection of the superconducting phase transition of high-Tc superconductors (HTSC) on a microscopic scale is reported. Micro-size holes in thin foils of superconducting material are examined in a transmission electron microscope at varying temperatures. The superconducting transition induces small changes in the image intensity within the holes, which can be detected by using electronic image analysis. Superconducting transition curves are then obtained for various types of high-Tc superconductors and for given values of the applied magnetic field.