Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 3: Magnetic Semiconductors

MA 3.8: Vortrag

Montag, 25. Februar 2008, 12:00–12:15, H 1012

Control of Magnetic Anisotropy by Strain Engineering in (Ga,Mn)As Nanostructures — •Jan Wenisch, Charles Gould, Lars Ebel, Jan Storz, Katrin Pappert, Manuel J. Schmidt, Christian Kumpf, Georg Schmidt, Karl Brunner, and Laurens W. Molenkamp — Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

Understanding and utilizing the magnetic properties of semiconducting materials is one of the key issues in the field of modern electronic device technology. In this presentation, we report control of magnetic anisotropy in ferromagnetic epitaxial (Ga,Mn)As by anisotropic strain relaxation. A thin MBE-grown, pseudomorphic (Ga,Mn)As layer is patterned lithographically into an array of 200nm x 100μm stripes, which induces a large degree of elastic strain relaxation perpendicular to the stripe axis, while retaining pseudomorphic conditions along this axis. We find that the magnetic anisotropy, which shows biaxial easy axes along [100] and [010] before patterning, is replaced by a hard axis in the direction of large elastic strain relaxation and a uniaxial easy axis along the stripes. We model the strain distribution in such nanostructures by finite element simulations and find the results to be in good agreement with real structures characterized by x-ray techniques. We anticipate that this technique of local, lithographic engineering of magnetism in (Ga,Mn)As nanostructures, especially when used in conjunction with simulations to optimize sample parameters, proves very useful for realizing novel spintronic memory and logic devices.