Berlin 2008 – scientific programme
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MA: Fachverband Magnetismus
MA 26: Spin Dynamics / Spin -Torque II
MA 26.1: Talk
Thursday, February 28, 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)