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TT: Fachverband Tiefe Temperaturen

TT 24: Magnetic Heuslers, Half-Metals and Oxides II (organized by MA)

TT 24.7: Vortrag

Montag, 31. März 2014, 17:15–17:30, BEY 118

Spin dependent lifetimes and non-degenerate spin hot spots in Heusler compounds — •Steffen Kaltenborn and Hans Christian Schneider — Physics Department and Research Center OPTIMAS, University of Kaiserslautern

We present results of an accurate ab-initio calculation of the dielectric function of the half-metallic Heusler compounds Co₂MnSi and Co₂FeSi. The numerical method is based on density functional theory [1,2] in combination with a wave-vector dependent linear tetrahedron method [3]. The dielectric function is used study optical, acoustic and intraband plasmon dispersions in these half metals. As in the case of simple metals, a negative intraband plasmon dispersion [3] is found. Furthermore, we use the dielectric function to analyze the k and spin-resolved electronic lifetimes in these materials. Qualitatively, the lifetimes reflect the lineup of electron and hole bands. We determine the spin-flip and spin-conserving contributions to the lifetimes and predict that different excitation conditions may lead to different spin-flip dynamics of excited electrons and may even give rise to an enhancement of the non-equilibrium spin polarization. Finally, we study in detail the behavior of the lifetimes around states that are strongly spin mixed by spin-orbit coupling. We find that, for non-degenerate bands, the spin mixing alone does not determine the energy dependence of the (spin-flip) lifetimes.
DFT-Program The Elk FP-LAPW Code, http://elk.sourceforge.net. [2] C. Ambrosch-Draxl et al., Comp. Phys. Commun. 175, 1-14, (2006). [3] S. Kaltenborn and H. C. Schneider, Phys. Rev. B 88, 045124 (2013).