Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)
MA 13.51: Poster
Dienstag, 9. März 2004, 15:00–19:00, Bereich A
Thermally induced changes of magnetic coupling in a pinned artifical antiferromagnet used in magnetic tunnel junctions — •Jan Schmalhorst1, Hubert Brueckl1, Guenter Reiss1, Guenter Gieres2, and Joachim Wecker2 — 1University of Bielefeld, Department of Physics, Nano Device Group, P.O. Box 100131, 33501 Bielefeld, Germany — 2Siemens AG, Corporate Technology CT MM 1, P.O. Box 3220, 91050 Erlangen, Germany
The thermally induced changes of the magnetic coupling in an artifical antiferromagnet exchange biased by an antiferromagnetic layer in a magnetic tunnel junction (Mn-Ir / Co-Fe / Ru / Co-Fe / AlOx / Ni-Fe) is investigated for annealing temperatures up to 450oC. Beside the usual increase of the tunneling magnetoresistance by annealing (maximum TMR 43.9%@325oC) the degradation of the artificial antiferromagnet causes a well defined 90o-coupling of the Co-Fe layers in a narrow temperature window around 325oC. At higher temperature, both Co-Fe layers are coupled ferromagnetically but the exchange biasing by the Mn-Ir is still present. This behaviour results from an interplay of different coupling mechanisms of the two Co-Fe layers: (1) indirect antiferromagnetic interlayer exchange coupling across the Ru spacer, (2) ferromagnetic coupling by pinholes in the Ru spacer and (3) exchange coupling between the lower Co-Fe layer and the antiferromagnet Mn-Ir. The importance of each contribution is discussed with respect to thermally activated diffusion processes.