Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.38: Poster

Montag, 27. März 2006, 14:00–17:45, P1

Proximity effect in superconducting MgB₂/Fe/MgB₂ trilayer — •B. Sahoo¹, W. Keune¹, V. Kuncser², A. I. Chumakov³, and R. Rueffer³ — ¹Fachbereich Physik, Universität Duisburg-Essen, Duisburg, Germany — ²National Institute for Physics of Materials, Bucharest-Magurele, Romania — ³European Synchrotron Radiation Facility, Grenoble, France

By Mössbauer spectroscopy (CEMS) we have observed, at about Tc, an anomaly in a annealed superconducting MgB₂(500 Å)/ ⁵⁷Fe(40 Å)/MgB₂(500 Å) trilayer (Tc = 25 K) in the T-dependence of the spectral center-line shift, which does not follow the usual Debye behavior. This anomaly is absent in a nonsuperconducting multilayer. We have not observed anomalies in the T-dependence of the magnetic hyperfine field, and also not in the ⁵⁷Fe phonon density of states (PDOS) measured by nuclear resonant inelastic X-ray scattering with 3 meV resolution. Hence the observed anomaly at Tc may be either due to the modification of the low-energy part (< 3 meV) of the PDOS (at present not accessible experimentally), or due to the change of the s-electron density at the ⁵⁷Fe nucleus, because of Cooper pair formation in the superconducting state. Sponsored by DFG (GRK277)