Some Features of Critical Parameters Calculations of Nonhomogeneous Superconducting Films Using the Ginzburg–Landau Theory

Abstract

A method for calculating the critical state of inhomogeneous superconducting films using the Ginzburg–Landau (GL) theory is proposed. From the condition of minimizing the functional of the GL free energy, a system of equations describing the superconducting state of an inhomogeneous plate is derived. The dependences of the critical current of the plate on the external magnetic field are numerically calculated. It is shown that the critical current in a zero external magnetic field decreases with increasing degree of film inhomogeneity, while the critical magnetic field (at a zero transport current) increases. An analysis of the calculated dependences of the product of the critical current and the external magnetic field (an analogue of the volume pinning force) of superconducting films on the external magnetic field shows that the maximum of this value shifts to stronger fields with increasing degree of inhomogeneity, i.e., an increase in inhomogeneity leads to an increase in the pinning force.