Regensburg 2002 – scientific programme
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MA: Magnetismus
MA 10: Poster : Dünne Schichten(1-21),Spinabh.Transp.(22-39),Exch.Bias(40-51),Spindyn.(52-55),Mikromag.(56-66),Partikel(67-74),Abb.Verf.(75-77),Oberfl.+Spinelektr.+Elektr.Theo+Mikromag(75-87),PÜ+Aniso+Werkst/Leg.(88-103),Mol.Mag.+N-dim+Messm.+Postdead(104-111
MA 10.44: Poster
Tuesday, March 12, 2002, 15:00–19:00, Bereich A
Positive Exchange Bias in CoO/Co Bilayers — •Florin Radu, Markus Etzkorn, Till Schmitte, Kurt Westerholt, and Hartmut Zabel — Institut für Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
We have studied the temperature dependence of exchange bias and coercive fields in CoO/Co very thin films by SQUID magnetometry. Several Co (FM, Tc=1403 K) layers were grown by rf-sputtering on a sapphire substrate. The CoO (AFM, TN=291 K) layer is formed on top of the Co layer by oxidation in air. The system is cooled in an applied magnetic field of Ha= − 2000 Oe through the Neel temperature of the antiferromagnet to different temperatures where the magnetic hysteresis loop is measured. The temperature dependence of the exchange bias shows a striking behavior. It starts with positive values at below the blocking temperature (TB=187 K), reaches a maximum of HEB=+30 Oe and, after changing the sign, it decreases steadly as the temperature is decreased. The dependence on the thickness of the ferromagnet is shown as well. The positive exchange bias increases as the thickness of the Co layer decreases.
This work is supported by SFB 491.