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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 20.70: Poster

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

Localized spin waves in nanostructured permalloy rings — •Jan Podbielski, Fabian Giesen, and Dirk Grundler — Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstraße 11, 20355 Hamburg.

Due to the increased data transfer rates in magnetoelectronic devices the dynamic properties of ferromagnetic nanostructures have become increasingly important. Using a broadband microwave spectrometer (45 MHz - 20 GHz) we have studied the ferromagnetic resonance (FMR) in periodic arrays of Ni₈₀Fe₂₀ rings. The outer diameter of the rings was 2 µm and the ringwidth w was varied in the different arrays down to 300 nm. The devices were deposited on broadband coplanar wave guides. For all rings we observe a series of FMR modes which shift characteristically as a function of w and external magnetic field. These modes are attributed to localized spin waves.[1] We developed an extended macrospin model subdividing the ring into characteristic segments which explains the observed features. Further intriguing observations are made on rings with a small width: hysteretic behavior and irreversible jumps of FMR modes as well as microwave assisted switching. We explain these features by the magnetic-field dependent spin configurations, namely the onion and vortex states in the rings. We thank D. Heitmann, T. Korn and M. Steiner. Financial support by the BMBF via 13N8283 and by the DFG is gratefully acknowledged.

[1] F. Giesen, J. Podbielski, T. Korn, and D. Grundler, J. Appl. Phys. (in press).