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

TL;DR

This study demonstrates strong vortex pinning in Co-doped BaFe2As2 thin films, with high critical current densities and effective pinning up to high magnetic fields, due to nanoscale columnar defects.

Contribution

It reveals that nanoscale columnar defects induce strong vortex pinning in epitaxial Co-doped BaFe2As2 films, enhancing their performance in high magnetic fields.

Findings

Jc comparable to single crystals

Fp(0.6Tc) > 5 GN/m3 at H/Hirr ~ 0.5

Jc along c-axis exceeds Jc in ab plane due to correlated pinning

Abstract

We report measurements of 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 Jc of single crystals and a maximum pinning force Fp(0.6Tc) > 5 GN/m3 at H/Hirr ~ 0.5 indicative of strong vortex pinning effective up to high fields. 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. HRTEM reveals that the strong vortex pinning is due to a high density of nanosize columnar defects.