30 research outputs found
Experimental study of intrinsic multiple Andreev reflections effect in GdO(F)FeAs superconductor array junctions
We report the first observation of the intrinsic multiple Andreev reflections
effect (IMARE) in S-n-S-...-S-arrays (S = superconductor, n = normal metal)
formed by "break-junction" technique in GdO(F)FeAs superconductor (Tc = 48 - 53
K). We show that superconducting gap peculiarities at dI/dV-spectra sharpen
dramatically in the arrays as compared with that in the single-contact spectra;
this enables to improve significantly accuracy of the bulk superconducting
parameters determination. Using IMARE, we determined the large and the small
gap values \Delta_L = 11 +- 1.1 meV and \Delta_S = 2.6 +- 0.4 meV. The
BCS-ratio 2\Delta_L/kTc^{local} = 5.0 - 5.9 > 3.52 (Tc^{local} is the contact
area critical temperature) evidences for a strong electron-boson coupling. The
results obtained agree well with our previous data by Andreev spectroscopy for
single SnS-contacts.Comment: 6 pages, 6 figure
Superconducting and magnetic properties of a new EuAsFeO0.85F0.15 superconductor
Polycrystalline samples of a new superconducting EuAsFeO0.85F0.15 compound
with critical temperature Tc=11K were prepared by solid state synthesis. Its
electric and magnetic properties have been investigated in magnetic fields from
0.1 to 140000 Oe. Critical magnetic fields Hc1, and Hc2 were measured and hence
the magnetic penetration depths and the coherence length have been estimated.
The temperature dependence Hc2 (T) exhibits clear hyperbolic - type behavior
starting with the lowest fields. The data derived were used to estimate
probable high Tc and Hc2 in compounds doped with rare-earths having small
atomic radii.Comment: 12 pages, 10 figures, 13 reference