A STUDY OF SOME PHYSICAL PROPERTIES OF HIGH TEMPERATURE SUPERCONDUCTORS

Abstract

In the field of high temperature superconductors (HTSc) the transition temperature Tc, the current density Jc and the pinning energy UP are very important in characterizing such materials. It is well established now that such quantities are affected by the method of preparation, magnetic field and the temperature.

In this thesis, we have prepared two of the most common ceramic HTSc systems; YBa2Cu30, (YBCO) with nominal critical temperature Tc=91 K and Bi2Sr2Ca1Cu30, (BSCO) with Tc= 108 K. Dynamics of vortices in the different pinning regimes were extensively studied through electrical measurements under zero field cooled (ZFC) and field cooled (FC) conditions, i.e. cooling the sample from about 300 K down to 12 K in zero magnetic field and cooling the sample in a constant magnetic field, respectively. The field cooled mechanism is known to prevent vortices from reaching an equilibrium configuration. So, the dimensionality of the movement of vortices, the activation energy as well as the critical current density were examined according to different models, such as,