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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.58: Poster

Montag, 27. März 2006, 14:00–17:45, P1

Polarised neutron scattering on the flux line lattice (FLL) in Niobium — •Sebastian Mühlbauer¹, Robert Georgii², and Peter Böni¹ — ¹Physikdepartment E21, TU-München, 85747 Garching — ²ZWE FRM-II, 85747 Garching

Recent polarised small angle neutron scattering (SANS) measurements of the flux line lattice (FLL) of superconducting niobium, performed on the SANS-2 at GKSS and on MIRA at the FRM-II showed clear polarisation dependent scattering, similarly measured by [1,2], that cannot be explained by means of the ideal model of the FLL. In ideal isotropic superconductors no spin dependent scattering occurs, because the flux lines are orientated parallel to the applied magnetic field B as well as the polarization of the neutrons is parallel to B [3]. Spin dependent scattering only occurs either i) assuming a non zero nuclear scattering length distribution with the same periodicity as the FLL (interference term) corresponding to the pinning centres or ii) assuming an individual bending of the flux lines, ruling out the geometrical constraint B ∥ FLL. We present new results, obtained by means of polarised neutron scattering on several niobium samples of a different residual resistivity ratio (RRR) and hence different pinning properties. These measurements were conducted on the cold spectrometer MIRA at the FRM-II in Garching.

[1] K. Neumann, et al, Eur. Phys. J. B 1, 5-9, (1998)

[2] Experimental Report 5-51-229

[3] E. M. Forgan, et al., Physica B 267-268, 115 (1999)