Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 18: Poster I : Bio Magn. (1-2); Mag.Imgaging (3-9); Magn. Semiconductors (10-16); Half Metals & Oxides (17-20); Coupl.Phenomena (21-27); Magn. Mat. (28-41); Micro & Nanostr. Magn. Materials (42-61); Micro Magn. (62-64); Surface Magnetism (65-70); Transport Phenomena (71-85)

MA 18.5: Poster

Dienstag, 26. Februar 2008, 15:15–18:30, Poster E

Imaging of electric transport mechanisms in a ferromagnetic Ga_0.96Mn_0.04As thin film by low-temperature scanning laser microscopy — •Jochen Tomaschko¹, Stefan Guenon¹, Sebastian T. B. Goennenwein², Andreas Brandlmaier², Matthias Althammer², Wladimir Schoch³, Wolfgang Limmer³, Reinhold Kleiner¹, and Dieter Koelle¹ — ¹Physikalisches Institut - Experimentalphysik II, Universität Tübingen, Germany — ²Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany — ³Institut für Halbleiterphysik, Universität Ulm, Germany

Due to its possible applications in spintronic devices the diluted magnetic semiconductor (DMS) Ga_1−xMn_xAs has been the subject of intense research. Integral measurements revealed an anisotropic magnetoresistance (AMR) and magnetothermopower (AMTP). Thus, both resistivity and thermopower depend on the orientation of magnetization. By examining a 250nm thick epitaxially grown Ga_0.96Mn_0.04As Hall-bar with scanning laser microscopy these two quantities (more precisely the bolometric signal dR/dT and the Seebeck-coefficient S_xx) could be imaged at temperatures down to 3K with a spatial resolution of ∼1µ m. We developed simple models to describe these signals and identified them as electric dipole and monopole plus quadrupole signals, respectively. Efforts to image ferromagnetic domains have been made. Furthermore, we discovered inhomogeneities, not visible with conventional optical microscopy and observed a signal possibly due to the diffusion of electron-hole-pairs created by the laser spot.

This work was supported by the DFG (KO 1303/8-1, GO 944/3-1).