# Large and significantly anisotropic critical current density induced by planar defects in CaKFe4As4 single crystals

## TL;DR

This study investigates the anisotropic critical current densities in CaKFe4As4 single crystals, revealing the influence of unique planar defects on superconducting properties and critical current behavior.

## Contribution

It reports the discovery of planar defects in CaKFe4As4 and their correlation with highly anisotropic critical current densities, a novel finding in iron-based superconductors.

## Key findings

- Observation of fish-tail-like peaks in M-H loops for H//c
- Detection of a dip structure in M-H loops for H//ab
- Successful evaluation of anisotropic in-plane and out-of-plane Jc

## Abstract

Three independent components of critical current density, one for the H//c axis and the other two for the H//ab plane, have been studied in CaKFe4As4 single crystals. When the magnetic field is applied along the c axis, we observed fish-tail-like peaks in the M-H hysteresis loop, and the magnetization at higher temperatures exceeds that at lower temperatures at high fields. When the field is applied parallel to the ab plane, a dip structure is observed in the M-H hysteresis loop near the self-field. In addition, for the H//ab plane, we succeeded in separately evaluating the large and significantly anisotropic in-plane and out-of-plane Jc. Transmission electron microscopy revealed the presence of planar defects parallel to the ab plane in CaKFe4As4, which have not been observed in any other iron-based superconductors. We discuss the possible relationship between the anomalous Jc behavior and the planar defects.

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Source: https://tomesphere.com/paper/1903.00866