Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)
MA 40.98: Poster
Friday, March 27, 2009, 11:00–14:00, P1A
Measurement of the spin polarisation of the current through nanostructured Al/Fe and Nb/Fe point contacts — •Konstantin Mirlin1, Samuel Bouvron1, Michael Marz1,2, Gernot Goll1, Christoph Sürgers1,2, and Hilbert v. Löhneysen1,2,3 — 1Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — 2DFG-Zentrum für funktionelle Nanostrukturen der Universität Karlsruhe, 76128 Karlsruhe — 3Institut für Festkörperphysik, Forschungszentrum Karlsruhe, 76021 Karlsruhe
Point-contact spectroscopy can be used to determine the spin polarisation P of the current through a S/F point contact. We used this method to study nanostructured Al/Fe and Nb/Fe contacts produced by electron-beam lithography. We measured the differential conductance spectra G(V) = dI/dV(V) of the Nb/Fe contacts in a 4He cryostat down to 1.5 K and described the spectra within two different theoretical models, the Mazin model [1] and the Cuevas model [2]. The first one considers the current through the F/S contact as composed of a fully polarised and an unpolarised part. The second one is based on the Landauer-Büttiker formalism with spin dependent transmission coefficients τ↑(↓) with a single P = (τ↑−τ↓)/(τ↑+τ↓). P depends on the contact size and is reduced with increasing contact size, possibly due to spin-orbit scattering in the contact region [3]. This scenario is supported by a larger decrease of P for Nb/Fe contacts compared to Al/Fe contacts, as expected for spin-orbit scattering.
[1] I.I. Mazin, PRL 83(7), 1427 (1999); [2] J.C. Cuevas et al., PRB 69, 140502 (2004); [3] M. Stokmaier et al., PRL 101(14), 147005 (2008)