Hamburg 2001 – wissenschaftliches Programm
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AM: Magnetismus
AM 9: Poster: Magnetowid. (1-17), Dü. Schichten (18-34), Oberfl
ächenmag. (35,36), Mikr. Methoden (37-45), Mikromag. (46-58), Phasenüberg. (59-77), Spektroskop. (78-91), Nanokr.Mat.(92-96), Anisotrop. (97-101), Schmelzen(102-104),Sonst/postdeadl.(105-109)
AM 9.24: Poster
Dienstag, 27. März 2001, 14:45–19:00, Foyer S 3
Polarized Neutron Reflectivity of CoO/Co Exchange Biased Multilayers — •Florin Radu, Markus Etzkorn, Vincent Leiner, Andreas Schreyer, Kurt Westerholt, and Hartmut Zabel — Festörperphysik, Ruhr-Universität Bochum, 44780 Bochum
The exchange bias phenomenon is associated with an interfacial coupling between ferro- and antiferromagnetic layers, resulting in an unidirectional magnetic anisotropy. The macroscopic effects related to the exchange bias are the shift of the hysteresis loop (exchange field HE) and an increase of the coercitivity field (Hc) upon cooling the system in an applied magnetic field through the Neel temperature of the antiferromagnetic layer. Another macroscopic effect is the time relaxation of HE, which, however, has gained little attention so far. We have investigated via MOKE and PNR all three macroscopic effects and, especially the time relaxation of a CoO/Co sputtered multilayer. Neutron hysteresis loops taken at 240 K (50K below TN) reveal that the reversal of magnetisation in the sample occurs not by in-plane rotation but rather through domain nucleation and movement. HE in this multilayer relaxes with time from about 180 Oe towards 0 Oe with a half-life time of about 580 sec. Similar time dependencies are also present in Co/CoO bilayers, where the relaxation time depends on temperature and applied field. – Supported by the SFB 491: Magnetic Heterostructures