Fishtail effect and vortex dynamics in LiFeAs single crystals

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. Moreover, we find that the calculated magnetic relaxation rate is very low in LiFeAs. 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.