The role of temperature in the magnetic irreversibility of type-I Pb superconductors

TL;DR

This study investigates how temperature influences magnetic irreversibility in type-I superconducting lead samples, revealing that flux behavior and pinning effects vary with temperature and sample geometry.

Contribution

It provides new insights into the temperature dependence of magnetic irreversibility and pinning mechanisms in type-I superconductors, highlighting differences between cylindrical and disk geometries.

Findings

Flux expulsion depends on temperature in disks but not in cylinders.

Irreversibility onset and remnant magnetization decrease with temperature in disks.

Pinning barriers decrease with magnetic field, affecting irreversibility.

Abstract

Evidence of how temperature takes part in the magnetic irreversibility in the intermediate state of a cylinder and various disks of pure type-I superconducting lead is presented. Isothermal measurements of first magnetization curves and magnetic hysteresis cycles are analyzed in a reduced representation that defines an equilibrium state for flux penetration in all the samples and reveals that flux expulsion depends on temperature in the disks but not in the cylinder. The magnetic field at which irreversibility sets in along the descending branch of the hysteresis cycle and the remnant magnetization at zero field are found to decrease with temperature in the disks. The contributions to irreversibility of the geometrical barrier and the energy minima associated to stress defects that act as pinning centers on normal-superconductor interfaces are discussed. The differences observed among the disks are ascribed to the diverse nature of the stress defects in each sample. The pinning barriers are suggested to decrease with the magnetic field to account for these results.