Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 71: Surface Magnetism (jointly with MA)
O 71.8: Vortrag
Donnerstag, 14. März 2013, 17:15–17:30, H3
Spin-dependent Smoluchowski effect — •Marco Corbetta1, Oleg Polyakov1,2, Oleg Stepanyuk1,2, Hirofumi Oka1, Aleksander Saletsky2, Dirk Sander1, Valeriy Stepanyuk1, and Jürgen Kirschner1 — 1Max-Planck-Institut für Mikrostrukturphysik, Halle (Saale), Germany — 2Faculty of Physics, Moscow State University, Moscow, Russia
The Smoluchowski effect [1] focuses on the total electron charge density and it neglects that electrons carry a spin. In spin-polarized materials, it is not clear how majority and minority states contribute to the spin-dependence of this effect. To elucidate this point we perform spin-polarized scanning tunneling microscopy at the step edge of a bilayer high Co island on Cu(111) at 8 K. We measure maps of the differential conductance (dI/dV) for states of parallel (P) and anti-parallel (AP) orientation between tip and sample magnetization. From these maps we extract the asymmetry A of the differential conductance A=(dI/dVAP-dI/dVP)/(dI/dVAP+dI/dVP). This quantity is proportional to the spin polarization of the sample. We reveal striking spatial variations of the spin-polarization at the transition between the Co step and the Cu substrate with sub-nm spatial resolution and investigate its energy dependence. We find a variation of the tunnel magneto resistance ratio of more than 20% on a length scale of few Angstroms. We discuss our results on the basis of ab-initio calculations, spin-dependent electron charge flow supports our findings [2]. [1] R. Smoluchowski, Phys. Rev. 60, 661 (1941). [2] O. P. Polyakov et al., Phys. Rev. B, accepted (2012).