Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 6: Magnetic Thin Films I (Heusler Alloys)
MA 6.6: Vortrag
Montag, 22. März 2010, 15:45–16:00, H10
Transport spin polarization of thin MBE-grown Co2FeSi-films — •Hauke Lehmann1, Jan M. Scholtyssek1,2, Jens Herfort3, Claudia Herrmann3, Guido Meier1, and Ulrich Merkt1 — 1Inst. f. Angew. Physik, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg — 2Inst. f. Elekt. Messtechnik und Grundlagen der Elektrotechnik, TU Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig — 3Paul-Drude-Institut f. Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin
The predicted half-metallicity of Co2FeSi in combination with its high Curie temperature of above 980 K [1] makes this Heusler alloy very interesting for spintronic applications. Thin Co2FeSi films grown by molecular-beam epitaxy are fabricated on GaAs substrates with a close lattice match. We determine the transport spin polarization at the Fermi energy by point-contact Andreev-reflection (PCAR) spectroscopy. A systematic study of PCAR measurements on different films, varying in thickness between 18 and 48 nm and in substrate temperature at the deposition process between 100 and 350oC is presented. The highest polarizations of about 60% can be observed for films grown at substrate temperatures of 200 to 300oC. At higher temperatures Cobalt might diffuse into the substrate [2], leading to a decrease of the polarization. A repetition of the measurements on samples stored in vacuum and in air after one year also shows a measurable decrease of the spinpolarization, presumably caused by oxidation.
[1] V. Niculescu et al., J. Magn. Magn. Mater. 5, 60 (1977)
[2] M. Hashimoto et al., J. Phys. D: Appl. Phys. 40, 1631 (2007)