Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 85: Spincaloric Transport II (organized by MA)

TT 85.9: Talk

Thursday, April 3, 2014, 11:45–12:00, HSZ 04

Thermally induced spin accumulation at Al/Co₂TiSi and Al/Co₂TiGe contacts — •Voicu Popescu, Benjamin Geisler, and Peter Kratzer — Faculty of Physics, University Duisburg-Essen, Duisburg, Germany

Spin injection from a ferromagnet in a semiconductor subtrate can be accomplished either by applying an external voltage or a temperature gradient. In the latter case, one exploits the Seebeck effect, with the temperature gradient across the contact directly resulting in a difference in chemical potentials in the two spin channels due to the spin-dependence of the Seebeck coefficient.

The magnetic Heusler alloys Co₂TiSi or Co₂TiGe exhibit half-metallic ferromagnetism in their ideal L2₁ crystal structure, with a potentially high degree of spin polarization of the injected current. As such, they recommend themselves for integrated spin injectors in combination with the closely lattice-matched Al contact layer.

We investigate the possibility of employing Al/Co₂TiX/Al (X=Si,Ge) trilayers as thermally driven spin injectors by means of first-principles calculations of the electronic structure and of the thermoelectric transport properties. Our results show that the spin-dependent Seebeck effect is sensitive to the atomic structure of the Heusler/Al interface. In particular, for a thin Co₂TiSi or Co₂TiGe layer terminated by a TiSi or TiGe atomic plane, the thermal spin accumulation is found to be of the same order of magnitude as the conventional, effective Seebeck coefficent.