Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 63: [MA] Surface magnetism III

O 63.8: Vortrag

Donnerstag, 17. März 2011, 12:45–13:00, HSZ 103

Qualitative extraction of spin polarization on a single magnetic nanostructure — •Hirofumi Oka, Pavel Ignatiev, Sebastian Wedekind, Guillemin Rodary, Larissa Niebergall, Valeri Stepanyuk, Dirk Sander, and Jürgen Kirschner — Max-Planck-Institute of Microstructure Physics, Weinberg 2, D-06120, Halle, Germany

We present a qualitative extraction of spin polarization on single Co nanoislands using SP-STM. We use low-temperature STM in magnetic fields to manipulate parallel (P) and anti-parallel (AP) states of the magnetization orientation between a Co island on Cu(111) and a magnetic tip [1]. We measure the differential conductance (dI/dV) on the same island in both states as a function of energy, and obtain the asymmetry of the dI/dV, (dI/dV_AP−dI/dV_P)/(dI/dV_AP+dI/dV_P), which is related to the spin polarization of a sample [2]. We find that the sign and magnitude of the dI/dV asymmetry strongly depend on energy. In conjunction with ab initio calculations, we demonstrate that the dI/dV asymmetry obtained by our method is proportional to the spin-polarization of the sample [3]. We find in the theoretical results a minimum and a maximum spin-polarizations on a Co film at energies of −0.25 and +0.15 eV, respectively, which agrees with the energy dependence of the dI/dV asymmetry.

[1] G. Rodary et al., JJAP 47, 9013 (2008). [2] D. Wortmann et al., PRL 86, 4132 (2001). [3] H. Oka et al., Science 327, 843 (2010).

*Present address (G.R.): Laboratoire de Photonique et Nanostructures, CNRS UPR20, 91460 Marcoussis, France.