Beyond Bean's critical state model: On the origin of paramagnetic Meissner effect

TL;DR

This paper introduces a new macroscopic model combining London theory and Bean's model to explain both reversible and irreversible magnetic properties in superconductors, including the paramagnetic Meissner effect.

Contribution

It proposes a unified macroscopic framework that extends Bean's model by incorporating flux shares and explains the paramagnetic Meissner effect.

Findings

Introduction of 'flux share' concept for magnetic flux penetration

Explanation of paramagnetic Meissner effect using the model

Analysis of reversible and irreversible magnetization behaviors

Abstract

Solving phenomenological macroscopic equations instead of microscopic Ginzburg-Landau equations for superconductors is much easier and can be advantageous in a variety of applications. However, till now, only Bean's critical state model is available for the description of irreversible properties. Here we propose a plausible overall macroscopic model for both reversible and irreversible properties, combining London theory and Bean's model together based on superposition principle. First, a simple case where there is no pinning is discussed, from which a microscopic basis for Bean's model is explored. It is shown that a new concept of 'flux share' is needed when the field is increased above the lower critical field. A portion of magnetic flux is completely shielded, named as 'Meissner share' and the rest penetrates through vortices, named as 'vortices share'. We argue that the flux shares are irreversible if there is pinning. It is shown that the irreversible flux shares can be the reason for observed peculiar reversible magnetization behavior near zero field. The overall macroscopic model seems to be valuable for the analysis of fundamental physical properties as well. As an example, it is shown the origin of paramagnetic Meissner effect can be explained by the phenomenological macroscopic model.