Hamburg 2001 – scientific programme

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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

Tuesday, March 27, 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 H_E) and an increase of the coercitivity field (H_c) 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 H_E, 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 T_N) reveal that the reversal of magnetisation in the sample occurs not by in-plane rotation but rather through domain nucleation and movement. H_E 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