Strong vortex pinning in Co-doped BaFe2As2 single crystal thin films

We report the field and angular dependences of Jc of truly epitaxial Co-doped BaFe2As2 thin films grown on SrTiO3/(La,Sr)(Al,Ta)O3 with different SrTiO3 template thicknesses. The films show Jc comparable to single crystals and a maximum pinning force Fp(0.6Tc)>5 GN/m3 at H/Hirr∼0.5 indicative of strong high-field vortex pinning. Due to the strong correlated c-axis pinning, Jc for field along the c-axis exceeds Jc for H∥ab plane, inverting the expectation of the Hc2 anisotropy. High resolution transmission electron microscopy reveals that the strong vortex pinning is due to a high density of nanosize columnar defects.