Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 24: Magnetic Semiconductors
MA 24.4: Vortrag
Mittwoch, 25. März 2009, 15:30–15:45, HSZ 401
Room temperature ferromagnetism without element specific ferromagnetism? A detailed XMCD study on doped ZnO — T. Tietze1, M. Gacic2, G. Schuetz1, G. Jakob2, S. Brück1, A. Myatiev3, B. Straumal1,3, P. Straumal3, and •E. Goering1 — 1MPI-MF, Stuttgart, Germany — 2Institute of Physics, Johannes Gutenberg-University, Mainz, Germany — 3Moscow Institute of Steel and Alloys, Moscow, Russia
On the quest for the intrinsic origin of ferromagnetism (FM) in ZnO doped with a few percent of nonmagnetic (d0) and magnetic transition metals, we present detailed XMCD measurements, performed in various detection modes to be sensitive to the surface, bulk, and interface related magnetism. The PLD prepared samples show strong FM at room temperature (RT) (SQUID: about 2muB/Co). On the other hand, XMCD at the Co L2,3 edges revealed only very small paramagnetic moments, while the Zn L2,3 and the O K edge measurements do not show any sign for magnetism at all. The Co L2,3 edge spectra reveal a multiplet like shape, which is clear evidence for Co located at the Zn site in a 3d7 configuration, also excluding metallic precipitates [1,2]. Therefore, we can exclude without doubt Co as a possible origin for FM in this system [2]. In addition, we have performed systematic investigations on the role of grain boundaries. These results strongly suggest grain boundary based vacancies, most likely at the oxygen site, as the source for the intrinsic RT-FM in doped ZnO. [1] M. Gacic et al., Phys. Rev. B 75 (2007) 205206 and APL 93 (2008) 152509 [2] T. Tietze et al., New Journal of Physics 10 (2008) 055009.