Discrete model analysis of the critical current density measurements in superconducting thin films by a single coil inductive method

TL;DR

This paper presents a discrete model for analyzing the critical current density in superconducting thin films using a contactless inductive method, validated through experiments on YBa2Cu3O7-d films.

Contribution

It introduces a realistic discrete model for magnetic coupling in inductive measurements of superconducting films, improving accuracy over previous methods.

Findings

The model accurately predicts the magnetic field profile on the film surface.

Experimental validation confirms the model's effectiveness in determining J_C.

The method is contactless and non-destructive, suitable for thin film analysis.

Abstract

The critical current density of a superconducting film can be easily determined by an inductive and contactless method. Driving a sinusoidal current in a single coil placed in front of a superconducting sample, a non zero third harmonic voltage V_3 is induced in it when the sample goes beyond the Bean critical state. The onset of V_3 marks the value of current beyond which the sample response to the magnetic induction is no more linear. To take into account, in a realistic way, the magnetic coupling between the film and the coil we have developed a discrete model of the inducing and induced currents distribution. In the framework of this model the magnetic field profile on the sample surface and the coefficient linking the current flowing in the coil and the critical current density J_C of superconducting thin films is evaluated. The numerical results are checked measuring J_C of several thin films of YBa_2Cu_3O_(7-d) of known superconducting properties, used as a control material.