Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 63: Poster II (Surface Magnetism/ Magnetic Imaging/ Topological Insulators/ Spin Structures and Magnetic Phase Transitions/ Graphene/ Magnetic Thin Films/ Magnetic Semiconductors/ Magnetic Half-metals and Oxides/ Spin-dependent Transport/ Spin Excitations and Spin Torque/ Spin Injection and Spin Currents in Heterostructures/ Spintronics/ Magnetic Storage and Applications)

MA 63.37: Poster

Freitag, 18. März 2011, 11:00–14:00, P2

Ab initio study of MnSi thin films on the Si(111) surface — •Benjamin Geisler and Peter Kratzer — Fakultät für Physik, Universität Duisburg-Essen

One of the challenges in the field of spintronics is the injection of a spin-polarized electric current into a semiconductor. This can be achieved by combining the semiconducting material with a ferromagnetic one, e. g., by growing thin films of a transition metal like Mn on top of a Si(111) surface. Due to the high reactivity of Mn and Si, thin films of MnSi will form instead of pure Mn films.

We perform density functional theory calculations for thin films of MnSi on Si(111) in their ground state crystal structure, the B20 structure. This structure lacks inversion symmetry, and the (111) films show a periodicity of 12 layers, which can be decomposed into three groups, each consisting of four different layers: a dense Si, a sparse Mn, a sparse Si and a dense Mn layer. Changing the number of layers, the orientation and termination of the layer stack alters the thin film properties, resulting in different magnetic ordering, STM pattern or STM contrast. The calculated formation energies or surface energies can be used to compare the thermodynamic stability and / or probability of different film terminations. STM images are calculated in order to improve the understanding of recently observed experimental STM images. Furthermore, the question of ferro- vs. antiferromagnetism is addressed.