Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 23: Posters Superconductivity, Solids at Low Temperature
TT 23.28: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU D
Magnetic quantum oscillations in the normal and superconducting state of YNi2B2C — •O. Ignatchik1, J. Wosnitza1, M. Jäckel1, D. Souptel2, G. Behr2, and P. Canfield3 — 1Institut für Festkörperphysik, TU Dresden, D-01062 Dresden, Germany — 2Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW), D-01069 Dresden, Germany — 3Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
The de Haas–van Alphen (dHvA) effect, or quantum oscillations of the magnetization, is the most direct method to study Fermi-surface properties in metals. It is remarkable, that these magnetic quantum oscillations persist deep into the vortex state of many type-II superconductors. The damping of the oscillation amplitude below the upper critical field can be related to the magnitude of the superconducting gap. For YNi2B2C, however, quite controversial results for the dHvA signal in the superconducting state have been reported. We will present dHvA measurements of YNi2B2C single crystals prepared by different methods. The flux-grown crystals exhibit dHvA oscillation in the superconducting state down to 3 T as reported in literature. However, we observed an unexpectedly sudden vanishing of the dHvA signal in the mixed state for crystals grown by a zone-melting method. The very quick disappearance of the oscillating signal below Bc2 suggests an unexpected fast opening of a large superconducting gap. At high magnetic fields six different dHvA frequencies could be detected.