Münster 1999 – wissenschaftliches Programm

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AM: Magnetismus

AM 9: Spektroskopie II

AM 9.3: Vortrag

Dienstag, 23. März 1999, 15:00–15:15, F4

Spin motion of electrons across ferromagnets — •Wolfgang Weber, Daniel Oberli, Stefan Riesen, and Hans-Christoph Siegmann — Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Schweiz

In order to fully describe the transmission of spin-polarized electrons through ferromagnets, it turns out that it is important to consider the motion of the spin polarization vector P₀^→. For this purpose electrons with P₀^→ perpendicular to the sample magnetization M^→ were spin-analyzed after transmission through free standing Au/Co/Au layers.

If P₀^→ is chosen perpendicular to M^→, the incident spin wavefunction can be described by a coherent superposition of a spin wavefunction parallel to M^→ and one antiparallel to it. Due to spin-dependent absorption, the amplitude of the two wave functions becomes different on passing the ferromagnet. A phase difference develops as well. This results in a rotation of the spin polarization vector into the direction of M^→ and a precession around it.

We find that the precession angle is about 16 degrees per 1 nm of Co film thickness, measured for an electron energy of 8 eV. This phase difference is a consequence of the different velocities for the majority-spin and the minority-spin wavefunction caused by the spin dependence of the inner potential. This motion of the spin polarization vector is in analogy to the Faraday effect observed when a light beam passes through a ferromagnetic material.