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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 (T_m ≈ 130 K) and superconductivity (T_c ≈ 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 Bi₂Sr₂CaCu₂O_8+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-T_c 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.