Fishtail effect and vortex dynamics in LiFeAs single crystals

TL;DR

This study explores the fishtail effect, vortex dynamics, and critical current in LiFeAs single crystals, revealing a vortex lattice phase transition and strong pinning mechanisms distinct from conventional defects.

Contribution

It provides new insights into vortex behavior and phase transitions in LiFeAs, a less-studied iron-based superconductor, with detailed phase diagram construction.

Findings

Fishtail effect observed only with field || c-axis

High critical current density, lower than other FeAs compounds

Strong pinning behavior similar to Sr2RuO4

Abstract

We investigate the fishtail effect, critical current density ($J_c$) and vortex dynamics in LiFeAs single crystals. The sample exhibits a second peak (SP) in the magnetization loop only with the field $||$ c-axis. We calculate a reasonably high $J_c$, however, values are lower than in 'Ba-122' and '1111'-type FeAs-compounds. Magnetic relaxation data imply a strong pinning which appears not to be due to conventional defects. Instead, its behavior is similar to that of the triplet superconductor Sr$_2$RuO$_4$. Our data suggest that the origin of the SP may be related to a vortex lattice phase transition. We have constructed the vortex phase diagram for LiFeAs on the field-temperature plane.