Trapped flux in a small crystal of CaKFe$_4$As$_4$ at ambient pressure and in a diamond anvil pressure cell

TL;DR

This study demonstrates that measuring trapped magnetic flux in a small CaKFe$_4$As$_4$ crystal is feasible both at ambient pressure and under 2.2 GPa pressure inside a diamond anvil cell, extending previous work to high-pressure conditions.

Contribution

It shows that trapped flux measurements can be reliably performed on superconducting samples inside diamond anvil cells, enabling high-pressure superconductivity studies.

Findings

Comparable trapped flux results at ambient and high pressure

Validation of flux measurement techniques in DACs

Potential for high-pressure superconductor characterization

Abstract

In an extension of our previous work, [Sergey L Bud'ko et al 2023 Supercond. Sci. Technol. 36 115001] the measurements of temperature dependent magnetization associated with trapped magnetic flux in a small single crystal of CaKFe$_4$As$_4$, using zero-field-cooled and field-cooled protocols were performed, on the same crystal, at ambient pressure without a pressure cell and at 2.2 GPa in a commercial diamond anvil cell (DAC), showing comparable results. The data show that with a proper care and understanding, trapped flux measurements in superconductors indeed can be performed on samples in DACs under pressure, as was done on superhydrides [V S Minkov et al 2023 Nat. Phys. 19 1293].