Pinning of a Magnetic Flux in Polycrystalline YBa2Cu3O6.92 HTSC during Cooling in a Weak Magnetic Field

Abstract

The behavior of fine-grained YBa₂Cu₃O_6.92 HTSCs during cooling in a weak magnetic field is investigated. The magnetization of samples, the crystallite sizes is which are comparable with the magnetic field penetration depth, is comprehensively analyzed in the range below the superconducting transition temperature. When the crystallite size is smaller than 0.5 μm, vortices are shown not to be fixed to pinning centers, and the temperature dependence of magnetization is completely determined by the screening of crystallites and the temperature of appearance of intercrystallite superconducting currents.