Dresden 2006 – scientific programme

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MA: Magnetismus

MA 21: Invited Talks Hickey / Temst

MA 21.2: Invited Talk

Wednesday, March 29, 2006, 14:30–15:00, HSZ 03

Exchange bias in patterned magnetic structures — •Kristiaan Temst¹, Elena Popova¹, Steven Brems¹, Chris Van Haesendonck¹, Helmut Fritzsche², Marita Gierlings², Florin Radu³, Hartmut Zabel³, Peter Leunissen⁴, and Rik Jonckheere⁴ — ¹Laboratorium voor Vaste-Stoffysica en Magnetisme, K.U.Leuven, Belgium — ²BENSC, Hahn-Meitner-Institut, Berlin, Germany — ³Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, Germany — ⁴IMEC vzw, Leuven, Belgium

We have studied the influence of finite dimensions and shape anisotropy on the exchange bias effect in patterned polycrystalline Co/CoO ferromagnet/antiferromagnet exchange bias systems prepared by combining electron beam lithography and thin-film deposition methods. A particular feature of Co/CoO exchange bias systems is that they exhibit a strong asymmetry in the magnetization reversal mechanism: the magnetization reversal mechanism is different in the two branches of the hysteresis loop. We have investigated by polarized neutron reflectivity experiments if and how this asymmetry is affected by the finite size and shape anisotropy of the Co/CoO structures. We will demonstrate that the asymmetry remains present even down to very small structure size, but that the shape anisotropy does have a strong influence on the presence of the asymmetry. This effect may be explained by the presence of interfacial domains at the Co/CoO interface. Anisotropic magnetoresistance measurements and magnetization experiments show that it is possible to re-induce the untrained state by applying a field in the direction perpendicular to that of the initial cooling field.