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TT: Fachverband Tiefe Temperaturen

TT 36: Focussed Session: Superconductivity and Magnetism in Ferropnictides and Related Materials

TT 36.7: Topical Talk

Donnerstag, 26. März 2009, 12:30–13:00, HSZ 03

C-axis transport of pnictide single crystals — •Paul Müller¹, Yuri Koval¹, Günter Behr², and Bernd Büchner² — ¹Department of Physics, Universität Erlangen-Nürnberg — ²IFW Dresden

Mesa structures were fabricated on the (ab) plane of small LaO_0.9F_0.1FeAs single crystals. Resistance vs. temperature measurements showed metallic behavior with a residual resistance ratio higher than 10. Both magnetic susceptibility and c-axis transport measurements showed the same value for the critical temperature, i.e. ∼20K. Current-voltage characteristics are typical for overdamped Josephson junctions with a critical current density of ∼10⁵ A/cm². Moreover, the critical current vs. temperature dependence follows the Ambegaokar-Baratoff relation for the maximum dc Josephson current. One possible explanation could be that we have observed an intrinsic Josephson effect in <c>-direction. This is supported by recent measurements of radiation emission between 11 and 12 GHz. Finally, we discuss current injection effects on Josephson critical current and T_c.