Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 18: Supraleitung: Tunneln, Josephson-Kontakte, SQUIDs
TT 18.7: Vortrag
Mittwoch, 10. März 2004, 16:00–16:15, H20
Intrinsic Josephson Effects in RuSr2GdCu2O8 — •Timo Nachtrab1, D. Koelle1, R. Kleiner1, C. T. Lin2, and C. Bernhard2 — 1Universität Tübingen, Physikalisches Institut -Experimentalphysik II, Auf der Morgenstelle 14, 72076 Tübingen, Germany — 2Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
We report on electrical transport measurements on single crystals of RuSr2GdCu2O8(Ru1212). The material shows coexistence of magnetic ordering (Tm ≈ 130 K) and superconductivity (Tc ≈ 55 K) at low temperatures. The crystal structure consists of alternating RuO2 layers (with a weak ferromagnetic (F) component in-plane) and superconducting (S) CuO2 layers, separated by insulating (I) layers of SrO. Ru1212 thus forms an intrinsic SIFIS multilayer structure. For transport perpendicular to the planes an intrinsic Josephson effect as, e.g., in Bi2Sr2CaCu2O8+δ (Bi2212) has been predicted. In addition, the magnetic component inside the barrier might provoke interesting phenomena like π-phases in the superconducting order parameter.
We measured the interlayer current transport in micron-sized Ru1212 single crystals in magnetic fields up to 7 T and temperatures between 4.2 K and 300 K. The system shows a clear intrinsic Josephson effect, e.g. the typical multi-branched current-voltage characteristics known from high-Tc cuprates. Our magnetic field measurements reveal that fluxon motion takes place in a very similar fashion as in Bi2212. So far, however, we did not observe any unconventional behavior due to the magnetism of the RuO2 layers.