Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 52: Magnetic Thin Films III

MA 52.2: Vortrag

Donnerstag, 17. März 2011, 11:15–11:30, HSZ 403

First principles investigation of the influence of excess Fe and Si(Al) on the magnetic properties of Co₂FeZ (Z = Si,Al)/MgO(001) — •Heike Herper and Peter Entel — Faculty of Physics, University of Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany

Ferromagnet/semiconductor spintronic devices make high demands on the magnetic material, i.e., high spin polarization and Curie temperature are prerequisites. Heusler alloys such as Co₂FeSi fulfill the requirements in their L2₁ bulk phase. However, in thin films the spin-polarization (P) is often smaller which seems to be related to structural disorder and formation of off-stoichiometric alloys. Furthermore, the Heusler alloys experience lattice strain if grown on MgO(001) which can also change the magnetic properties.

We investigate the influence of off-stoichiometry, disorder, and strain on the magnetic properties in bulk-like Fe-Co-Si(Al) systems and thin films on MgO(001) within density functional theory using VASP [1]. Exchange parameters and magnetic transition temperatures are obtained from KKR[2] calculations.

Our investigations show that the polarization depends on the interplay between composition, e.g., Fe excess can reduce P, and strain which increases P in case of excess Fe. Additional Co on the Fe sublattice improves the magnetic properties of the system.

[1] G. Kresse and J. Furthmueller, Comput. Mater. Sci. 6, 15 (1996). [2] The Munich SPR-KKR package, version 3.6, H. Ebert et al.