Effects of Splayed Columnar Defects on Critical Current Density in CaKFe4As4

Abstract

Introduction of columnar defects to superconductors through particle irradiation enhances their critical current density (J c) . Further enhancement of J c by dispersing the direction of columnar defects has been confirmed. Moreover, in such systems with splayed columnar defects, an anomalous peak effect in J c at a certain magnetic field determined by the irradiation dose accompanied by the in-plane anisotropy of J c between those parallel and perpendicular to the splay direction were observed. We introduce splayed columnar defects to CaKFe4As4 single crystals, which was recently found as a new type of iron-based superconductors (1144-type IBS), by irradiating 2.6 GeV U and 320 MeV Au ions and measure their J c properties.