Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65

MA 20.52: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU C

Nano-structured exchange bias systems — •Björn Beckmann, Ulrich Nowak, and Klaus D. Usadel — Fachbereich Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany

Recently, attention has been drawn to exchange bias (EB) systems where the size of either the ferromagnetic (FM) or antiferromagnetic (AFM) layer or even both was modified on a nanoscale. Using Monte Carlo simulations of the domain state model [1,2] we study exchange bias of an array of squared ferromagnetic dots on a continuous antiferromagnetic substrate.

For sufficiently large dot sizes the results agree with those obtained earlier for continuous systems [2]. With decreasing FM dot size the average (over many dots) EB field decreases before it eventually vanishes when reaching a certain critical size. To explain this effect we note that during field cooling domains in the AFM layer are formed which then influence the FM. Thus, once the lateral size of the FM is below the average size of the AFM domains EB has to vanish. It is noteworthy, however, that for the single dots strong fluctuations of the bias field occur where both, negative or even positive bias may be observed.

Work supported by the Deutsche Forschungsgemeinschaft through SFB 491.

[1] P. Miltenyi, M. Gierlings, J. Keller, B. Beschoten, G. Güntherodt, U. Nowak, and K. D. Usadel, Phys. Rev. Lett. 84, 4224 (2000).

[2] U. Nowak, K. D. Usadel, P. Miltényi, J. Keller, B. Beschoten, and G. Güntherodt, Phys. Rev. B 66, 14430 (2002).