Trapped flux in pure and Mn-substituted CaKFe4As4 and MgB2 superconducting single crystals

Measurements of temperature dependent magnetization associated with trapped magnetic flux in single crystals of CaKFe4As4, CaK(Fe0.983Mn0.017)(4)As-4 and MgB2 using zero-field-cooled and field-cooled protocols are presented. The results allow for the determination of the values of superconducting transition temperature, lower critical field and self-field critical current density. These are compared with the literature data. Possible experimental concerns are briefly outlined. Our results, on these known superconductors at ambient pressure, are qualitatively similar to those recently measured on superhydrides at megabar pressures (Minkov et al 2023 Nat. Phys.https://doi.org/10.1038/s41567-023-02089-1) and, as such, hopefully serve as a baseline for the interpretation of high pressure, trapped flux measurements.

Automated summary

This study presents measurements of temperature dependent magnetization associated with trapped magnetic flux in single crystals of CaKFe4As4, CaK(Fe0.983Mn0.017)(4)As-4, and MgB2 using zero-field-cooled and field-cooled protocols. The results provide values for the superconducting transition temperature, lower critical field, and self-field critical current density and are compared with literature data. Potential experimental concerns are briefly discussed. The results of this study, on known superconductors at ambient pressure, exhibit qualitative similarities to recent measurements on superhydrides at megabar pressures, and can serve as a baseline for interpreting high-pressure trapped flux measurements.