The influence of the pinning centres dimensions on the critical current in high-Tc superconductors

An analysis of the influence of the pinning centres dimensions on the critical current and pinning forces of the high temperature oxide superconductors is presented. Individual interaction of the pinning centres with pancake type vortices is considered for the layered structure of the copper-oxide superconductors. The phenomenological model was elaborated in which the change of the system energy has been constructed taking into account the pinning interaction, Lorentz forces, and elastic energy of the vortex lattice. The resistivity criterion has been used for detection of the critical current. Especially important results have been obtained for the range of the pinning centres dimensions smaller than twice the value of the coherence length.