Angular-dependent vortex pinning mechanism and magneto-optical characterizations of FeSe_0.5Te_0.5thin films grown on CaF₂substrates

Abstract

Magneto-optical (MO) characterizations and the angular-dependent critical current density (Jc(Θ)) of epitaxial FeSe0.5Te0.5 (FST) thin films grown on CaF2 single-crystalline substrates were performed. The MO images show typical rooftop patterns in the remanent state from which a large, homogeneous, and almost isotropic self-field Jc over 2 × 106 A cm−2 at 8 K was obtained. The vortex pinning mechanism is investigated measuring the magnetic field and angular-dependent critical current density Jc. The FST films exhibit small anisotropy of Jc in the whole applied magnetic field range below 15 K. The Dew-Hughes model and angular scaling analyses prove that pointlike normal cores, which are distributed randomly in the FST film, dominate the pinning in the FST films on CaF2 substrates.