Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Spin Dynamics / Spin -Torque II

MA 26.1: Vortrag

Donnerstag, 28. Februar 2008, 14:30–14:45, EB 301

Relationship between the asymmetry of inelastic magnon excitation and the spin polarization — Nicolai Urban¹, Tobias Schuh¹, Albert F. Takacs¹, Timofey Balashov¹, Markus Däne², Arthur Ernst², Patrick Bruno², and •Wulf Wulfhekel¹ — ¹Physikalisches Instiut, Universität Karlsruhe (TH), Wolfgang - Gaede Str. 1, 76131 Karlsruhe — ²MPI für Mikrostukturphysik, Weinweg 2, 06108 Halle

Electrons tunneling between the non-magnetic tip of a scanning tunneling microscope and a ferromagnetic sample can scatter inelastically, creating spin waves in the ferromagnet [1]. These excitations can be created for both tunneling directions, i.e. by hot electrons or holes. We observe a strong asymmetry between these two processes. From the selection rules of the conservation of angular momentum follows that in the forward direction only tunneling minority electrons create spin waves, while in the backward direction only tunneling majority electrons create spin waves. Thus, the probability of spin wave creation for forward/backward tunneling is proportional to the local density of states (LDOS) of minority/majority electrons in the investigated magnetic material.

We examined the excitation asymmetry in bulk Fe(100), and thin Co films on Cu(111) and Cu(100). The experimental results of the asymmetry agree well with theoretical calculations of the spin polarization of the LDOS.

[1] T. Balashov, A. Takács, W. Wulfhekel, J. Kirschner, Phys. Rev. Lett. 97 187201 (2006)