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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.

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