Enhanced flux pinning properties in superconducting FeSe0.5Te0.5 thin films with secondary phases

In this paper we report epitaxial superconducting FeSe0.5Te0.5 thin films grown on single crystal SrTiO3 (STO) (100) substrates by a pulse laser deposition (PLD) technique. The films include a single layer grown under vacuum, a single layer grown in controlled oxygen atmosphere and a tri-layer film with a 7 nm thick CeO2 interlayer. All the films show a similar transition temperature Tc ranging from ∼12 K () to ∼10 K (), while the CeO2 nanolayer sample shows a significantly enhanced critical current density under magnetic field. The calculated critical current density of the film with the CeO2 interlayer is ∼105A cm−2 at 2 K in self-field and 2.8 × 104 A cm−2 at 7 T at 2 K. The power-law exponent α value of the sample is determined to be as low as 0.21 at 2 K. Microstructural analysis shows that both the oxygen grown sample and the sample with the CeO2 nanolayer have uniform nanoclusters in the film matrix. These secondary phases as well as the defects around the interlayer interfaces might be responsible for the enhanced pinning properties.