2 research outputs found
DC superconducting quantum interference devices fabricated using bicrystal grain boundary junctions in Co-doped BaFe2As2 epitaxial films
DC superconducting quantum interference devices (dc-SQUIDs) were fabricated
in Co-doped BaFe2As2 epitaxial films on (La, Sr)(Al, Ta)O3 bicrystal substrates
with 30deg misorientation angles. The 18 x 8 micro-meter^2 SQUID loop with an
estimated inductance of 13 pH contained two 3 micro-meter wide grain boundary
junctions. The voltage-flux characteristics clearly exhibited periodic
modulations with deltaV = 1.4 micro-volt at 14 K, while the intrinsic flux
noise of dc-SQUIDs was 7.8 x 10^-5 fai0/Hz^1/2 above 20 Hz. The rather high
flux noise is mainly attributed to the small voltage modulation depth which
results from the superconductor-normal metal-superconductor junction nature of
the bicrystal grain boundary
Point-contact study of ReFeAs(1-x)Fx (Re=La, Sm) superconducting films
Point-contact (PC) Andreev-reflection (AR) measurements of the
superconducting gap in iron-oxipnictide ReFeAsO_{1-x}F_x (Re=La, Sm) films have
been carried out. The value of the gap is distributed in the range 2\Delta
\simeq 5-10 meV (for Re=Sm) with a maximum in the distribution around 6 meV.
Temperature dependence of the gap \Delta(T) can be fitted well by BCS curve
giving reduced gap ratio 2\Delta /kT_c^*\simeq 3.5 (here T_c^* is the critical
temperature from the BCS fit). At the same time, an expected second larger gap
feature was difficult to resolve distinctly on the AR spectra making
determination reliability of the second gap detection questionable. Possible
reasons for this and the origin of other features like clear-cut asymmetry in
the AR spectra and current regime in PCs are discussed.Comment: 6 two-column pages, 6 figs., 26 Refs., to be published in
Superconductor Science and Technolog