Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 7: Superconductivity & Solids At Low Temperature - Poster Session
TT 7.15: Poster
Montag, 27. März 2006, 14:00–17:45, P1
dc and rf transport in normal and superconducting HTS, MgB2, and Nb networks — •Jürgen Halbritter — Forschungszentrum Karlsruhe, Postfach 36 40
Island/grain boundaries occur naturally in film growth or sintering. The hindrance of electric transport by boundary resistances Rbn (Wcm2) in distances aJ (≤ 10 mm) is easy to measure in normal conducting transport in such granular networks. The resistivity r(T) = Rbn/aJ + p (ρi (T) + ρi (0)) is fitted to observations with percolation factors p > 1 by current diverting aJ ρi (300K) boundaries with Rbn ≥ aJ ρi(300 K) where ρi (T) + ρi (0) is due to the grain interior (IG) and Rbn/aJ and p describes the effects of boundaries (GB) and the network. In the superconducting transport GB may act as Josephson junctions (JJ) with jcJ (A/cm2) as current density. For superconducting networks is a simple separation in IG and GB not possible. But low Ic values, p > 1 and large Rbn values are clear indications for growth boundary limitations. Analysis of Ic(T,B,q,ω) as junction of temperature, field B, angle q and frequency ω give crucial information about GB and flux low or pinning of Josephson (JF) or Abrikosov fluxons (AF) in the network. The combination of normal and superconducting analysis is of crucial importance for dc, ac and rf engineering applications and for the understanding of the related material science.