Berlin 2012 – wissenschaftliches Programm
MA 37.8: Vortrag
Donnerstag, 29. März 2012, 11:30–11:45, EB 301
Spatially modulated tunnel magnetoresistance on the nanoscale — •Hirofumi Oka, Kun Tao, Sebastian Wedekind, Guillemin Rodary, Valeri Stepanyuk, Dirk Sander, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
We investigate the tunnel magnetoresistance (TMR) effect within a single Co nano-island by low-temperature spin-polarized scanning tunneling microscopy in magnetic fields. We measure the tunnel current as a function of the bias voltage and extract the TMR. We find a TMR of 290 MΩ for the anti-parallel and 190 MΩ for the parallel state at −0.27 V at the center of a Co island. This gives a TMR ratio of ∼50%. The TMR ratio depends on energy and position within the nano-island. We observe a clear spatial modulation of the TMR ratio with an amplitude of ∼20% and a spacing of ∼1.3 nm between maxima and minima around the Fermi level. This result can be ascribed to a spatially modulated spin-polarization within the Co island due to spin-dependent quantum interference . Our combined experimental and theoretical study reveals that spin-dependent electron confinement affects all transport properties such as differential conductance, conductance and TMR. We demonstrate that the TMR within a nanostructured magnetic tunnel junction can be controlled on a length scale of 1 nm through spin-dependent quantum interference .
 H. Oka et al., Science 327, 843 (2010).
 H. Oka et al., PRL 107, 187201 (2011).