DIRECT OBSERVATION OF MAGNETIC-FLUX INHOMOGENEITY IN THE VICINITY OF HIGH-TEMPERATURE SUPERCONDUCTORS

A magneto-optical high resolution technique is described which uses Bi-containing ferrogarnet film as an indicator. The technique was used to visualize and make topograms of the magnetic flux distribution in the vicinity of high temperature superconductors over a wide range of temperatures (5 - 300 K) and magnetic fields (0 - 35 kOe). It is shown that analysis of the visual pattern may be helpful in studying the specific processes of interaction between the magnetic field and the high temperature superconducting samples. The distribution of magnetic flux density in the samples was found and structure defects revealed. In addition, the important macroscopic parameters, such as superconducting transition temperature, temperature dependence of the lower critical field, critical current density and volume pinning force, were estimated. Application of the technique for rapid analysis of high T(c) superconducting materials quality is substantiated.