Regensburg 2013 – scientific programme
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MA: Fachverband Magnetismus
MA 48: Spin-dependent Transport Phenomena
MA 48.6: Talk
Friday, March 15, 2013, 10:45–11:00, H23
Anisotropy of Spin Relaxation in Metals — •Bernd Zimmermann, Phivos Maropoulos, Swantje Heers, Nguyen H. Long, Stefan Blügel, and Yuriy Mokrousov — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
We predict a giant anisotropy of the spin relaxation time T1, i.e. the dependence of T1 on the orientation of the electron-spin polarization relative to the crystal lattice [1], that has not been considered so far. Our theory is based on the spin-orbit caused Elliott-Yafet (EY) mechanism, which yields the relation T1−1 ∼ b2, where we determine the EY spin-mixing parameter b2 and its anisotropy by ab initio calculations employing the Korringa-Kohn-Rostoker Green function method.
We investigate various 5d and 6sp metals and find gigantic anisotropy values for hcp-metals (up to 830% for Hf), which means that T1 can be adjusted within one order of magnitude by changing the spin-polarization direction. We identify the formation of extended spin-flip hot areas (i.e. parts of the Fermi surface where the states are almost fully spin mixed) at nested Fermi-surface sheets or hot loops at the hexagonal face of the Brillouin zone boundary as source of the extremely high anisotropy. Our explanation is based on the spin-flip part of spin-orbit coupling in combination with the reduced symmetry of the hcp-lattice. Our findings should also be important for other effects in spintronics, e.g. the spin Hall effect. Funding by HGF (VH-NG-513) and DFG (MO 1731/3-1) is acknowledged.
[1] B. Zimmermann et. al , PRL in press, preprint: arXiv:1210.1801