A study of the dynamics of penetration and trapping of magnetic flux in polycrystalline YBa2Cu3O7−x samples

Abstract

In-phase and quadrature components of the first harmonic response of polycrystalline YBa2Cu3O7−x, were measured in a dc magnetic field. For small field modulation amplitude of 0.005 Oe, in-phase component of the first harmonic response of a sample was found to be proportional to the differential magnetic susceptibility. It was found that there is no pinning of Josephson vortices in a weakly coupled medium in magnetic fields below Hc2J, where Hc2J is the upper critical field of Josephson weak links. The obtained initial magnetization curve allowed us to describe the nonlinear part of the magnetization arising due to the weak bonds in ceramics. The size of a Josephson vortex and the critical parameters Hp, Hc2J and Hc1g were evaluated.