Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 7: SC: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 7.6: Talk

Monday, March 22, 2010, 15:15–15:30, H20

Re-analysis of experimental point contact Andreev spectra: the case of half-metallic CrO₂ — •Matthias Eschrig¹, Roland Grein², and Tomas Löfwander³ — ¹Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany — ²Institut für Theoretische Festkörperphysik und DFG-Zentrum für funktionelle Nanostrukturen, KIT, D-76128 Karlsruhe, Germany — ³Department of Microtechnology and Nanoscience MC2, Chalmers University of Technology, S-41296 Göteborg, Sweden

Point-contact Andreev spectroscopy has been extensively used to probe the spin-polarization of strong ferromagnets. In this method a nano-sized point contact is formed between a superconducting tip and the ferromagnetic material under investigation (or vice versa). The conductance-versus-voltage is recorded at a low temperature. Subsequently, a fitting procedure is undertaken to extract the polarization of the ferromagnet. We re-analyze existing data using a new theoretical treatment that accounts for spin-mixing effects and magnetic inhomogeneities, and that is based on a new formulation of boundary conditions taking into account these effects. We find that for the prominent case of CrO₂ the data are consistent with a spin polarization close to 100%, in agreement with the notion of half-metallic behavior for this material.