Angular-dependent vortex pinning mechanism and magneto-optical characterizations of FeSe0.5Te0.5 thin films grown on CaF2 substrates

Magneto-optical (MO) characterizations and the angular-dependent critical current density (J(c)(Theta)) 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 J(c) over 2 x 10(6) A cm(-2) at 8 K was obtained. The vortex pinning mechanism is investigated measuring the magnetic field and angular-dependent critical current density J(c). The FST films exhibit small anisotropy of J(c) 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.