Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Postersession Superconductivity: Josephson Junctions, SQUIDs, Heterostructures, Andreev Scattering, Vortex Physics, Cryodetectors, Measuring Devices, Cryotechnique
TT 32.22: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Pinning investigation in NbN thin films — •Tetyana Shapoval, Silvia Haindl, Jan Engelmann, Volker Neu, Bernhard Holzapfel, and Ludwig Schultz — IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany
NbN thin films with Tc=16 K and a thickness of 100 nm were fabricated on MgO(100) substrates by UHV pulsed laser deposition by using a Nb (99.95%) target in nitrogen gas atmosphere. Low temperature magnetic force microscopic (LT-MFM) images were performed after field cooling in a magnetic field of -2 mT to study the temperature dependence of vortex distribution. At low temperatures vortices are organized in a slightly disordered Abrikosov lattice with an average inter-vortex distance of 930 nm. Increasing the temperature to above T = 75%Tc leads to a movement of vortices during the MFM scan, which is interpreted as a thermally activated depinning process initiated by the stray field of the tip. The local pinning force has been estimated from MFM-images and compared with global VSM magnetization measurements. In addition, the temperature dependence of the penetration depth, λ, was extracted from the magnetic field profiles of single vortices.
The work is partially funded from the European Community under the Sixth Framework Programme Contract Number 516858: HIPERCHEM, and SFB 463/A4.