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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.48: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

Investigation of Spin Polarization by Point Contact Spectroscopy — •Christoph Jurecka, Martin Jourdan, and Hermann Adrian — Institut für Physik, Johannes Gutenberg Universität Mainz, 55099 Mainz

Materials with high spin polarization play a key role in modern magnetoelectronic devices. However, the experimental investigation of the spin polarization is in general a complex task. One possible method is Point Contact Spectroscopy (PCS) employing a superconducting tip [Sou98]. Intending to study the possibilities and limitations of PCS we realised a setup for PCS allowing variable tip pressure and tested our setup on conventional magnetic and non-magnetic materials. For non magnetic materials (e.g. Copper) we where able to identify Andreev Reflection by clear fits employing Mazin*s theory [Maz2001] and excluding any spin-polarization. Spectra of magnetic materials (Ni, Fe) showed a qualitatively different behaviour. However, only an upper limit for the spin polarization could be defined, which corresponds approximately to literature values measured by tunnel spectroscopy. Measurements on the Heusler compound Co2Cr0,6Fe0,4Al, for which a high spin polarization is predicted by band structure calculations, showed an upper limit for the spin polarisation of 40-50%. This is less than indicated by results of tunnel spectroscopy. The main reason for this apparently reduced spin polarization measured by ex-situ PCS could be surface oxidation effects. [Sou98] R. J. Soulen et al., Science 282, 85 (1998); [Maz2001] I. I. Mazin et al., Phys. Rev. B 68, 104430 (2003)