Magnetic Flux Trapping in Granular HTSC near Superconducting Transition

TL;DR

This study investigates how magnetic flux is trapped in granular high-temperature superconductors near their transition temperature, revealing inhomogeneous trapping and differences between ceramic and film forms.

Contribution

It introduces a model explaining flux trapping via superconducting loops in Josephson weak links, highlighting differences between ceramic and film superconductors.

Findings

Inhomogeneous magnetic trapping in the resistive transition region.

Films trap lower critical temperatures than ceramics.

Good agreement between observed and calculated flux trapping behavior.

Abstract

The temperature and field dependences of the trapped magnetic fields and of the frozen magnetoresistance of (Pb)Bi-Sr-Ca-Cu-O ceramics and Bi-based magnetron films are investigated. It is found that in the resistive transition region of granular Bi-HTSC the trapped magnetic fields become highly inhomogeneous and alternating in sign at scale of less than 50 microns. Unlike ceramic the films have critical temperature of trapping lower than the upper temperature of magnetoresistance disappearance. The experimental results are explained by a model in which the magnetic fields are trapped in superconducting loops embedded in Josephson weak links medium. The loops nature which is essentially different for films and ceramics is discussed. Observed temperature and field dependences of trapped field are in good agreement with those calculated for normal law of the loops distribution on critical fields.