Anomalous magnetic hysteresis in the microwave surface resistance of MgB2 superconductor

TL;DR

This paper investigates the unusual magnetic hysteresis in the microwave surface resistance of MgB2 superconductors, revealing behaviors that challenge existing critical-state models through experimental field-sweep measurements.

Contribution

It presents experimental evidence of anomalous hysteresis in MgB2's microwave surface resistance, highlighting phenomena not explained by current critical-state theories.

Findings

Detected magnetic hysteresis in MgB2 samples

Hysteresis shape is unusual and inconsistent with standard models

Results suggest new physics in fluxon lattice behavior

Abstract

We report experimental results of the field-induced variations of the microwave surface resistance in samples of MgB2, produced by different methods. By sweeping the DC magnetic field at increasing and decreasing values, we have detected a magnetic hysteresis that can be ascribed to the different magnetic induction, due to the critical state of the fluxon lattice. The hysteresis observed in the bulk samples has an unusual shape, which cannot be justified in the framework of the critical-state models.