Anomalous local magnetic field distribution and strong pinning in CaFe1.94Co0.06As2 single crystals

TL;DR

This study reveals anomalous magnetic field behavior and enhanced pinning in CaFe1.94Co0.06As2 single crystals, indicating a coexistence of superconductivity and magnetic correlations with unconventional local magnetization features.

Contribution

It provides new insights into the local magnetic field distribution and pinning phenomena in CaFe1.94Co0.06As2, highlighting the coexistence of superconductivity and magnetic correlations.

Findings

Anomalous remnant magnetization within Meissner-like regions.

Local magnetic field exceeds the applied field near transition temperature.

Enhanced bulk pinning observed in the crystals.

Abstract

Magneto-optical imaging of a single crystal of CaFe1.94Co0.06As2, shows anomalous remnant magnetization within Meissner like regions of the superconductor. The unconventional shape of the local magnetization hysteresis loop suggests admixture of superconducting and magnetic fractions governing the response. Near the superconducting transition temperature, local magnetic field exceeds the applied field resulting in a diamagnetic to positive magnetization transformation. The observed anomalies in the local magnetic field distribution are accompanied with enhanced bulk pinning in the CaFe1.94Co0.06As2 single crystals. We propose our results suggest a coexistence of superconductivity and magnetic correlations.