Title: BaFe2(As1-xPx)2 (x = 0.22-0.42) thin films grown on practical metal-tape substrates and their critical current densities,
Abstract: We optimized the substrate temperature (Ts) and phosphorus concentration (x)
of BaFe2(As1-xPx)2 films on practical metal-tape substrates for pulsed laser
deposition from the viewpoints of crystallinity, superconductor critical
temperature (Tc), and critical current density (Jc). It was found that the
optimum Ts and x values are 1050 degree C and x = 0.28, respectively. The
optimized film exhibits Tc_onset = 26.6 and Tc_zero = 22.4 K along with a high
self-field Jc at 4 K (~1 MA/cm2) and relatively isotropic Jc under magnetic
fields up to 9 T. Unexpectedly, we found that lower crystallinity samples,
which were grown at a higher Ts of 1250 degree C than the optimized Ts = 1050
degree C, exhibit higher Jc along the ab plane under high magnetic fields than
the optimized samples. The presence of horizontal defects that act as strong
vortex pinning centers, such as stacking faults, are a possible origin of the
high Jc values in the poor crystallinity samples.