Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity: Vortex Physics
TT 33.2: Vortrag
Dienstag, 1. April 2014, 10:00–10:15, HSZ 201
Neutron scattering studies of domain structures in type-II superconductor Niobium — •Tommy Reimann1,2, Michael Schulz1,2, Sebastian Mühlbauer1, Christian Grünzweig3, and Peter Böni2 — 1Heinz Maier-Leibnitz Zentrum (MLZ), TU München, Garching (D) — 2Physikdepartment E21, TU München, Garching (D) — 3Paul-Scherrer-Institut, Villigen (CH)
In the intermediate mixed state (IMS) of a type II superconductor (SC), the sample splits up into Meissner domains and Shubnikov domains which carry the vortex lattice (VL). A detailed investigation of these domain patterns offers the possibility to study general characteristics of domain nucleation and morphology as well as the physical properties of vortex-vortex and vortex-pinning interactions. In this talk we show that ultra small angle neutron scattering (USANS) can be used for the identification of VL properties. We have studied the VL domain morphology in a Nb single crystal disc that exhibit strong vortex pinning. USANS is sensitive to structures with sizes up to 20 microns and is therefore capable to probe IMS domains which is not possible with the commonly used small angle neutron scattering (SANS). Futhermore, USANS averages over the whole sample and hence probes the bulk of the material in contrast to magneto optical methods. Our investigation on the IMS of Nb reveals a preferred domain size with a strong dependence on magnetic field and sample thickness. Surprisingly , the average domain size is nearly independent of the temperature in a field cooled measurement giving some hint on the nature of field expulsion in the IMS of samples with significant pinning.