Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)
MA 13.62: Poster
Dienstag, 9. März 2004, 15:00–19:00, Bereich A
Spin-Wave Modes in an Inhomogeneously Magnetized Stripe — •C. Bayer1,2, J.P. Park2, H. Wang2, M. Yang2, C.E. Campbell2, and P. Crowell2 — 1Fachbereich Physik und Forschungsschwerpunkt MINAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern — 2School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
Soft magnetic materials such as permalloy often have a very simple magnetic microstructure which is not single domain. It is physically interesting to ask whether such systems have collective excitations, i.e. spin-wave modes. We have studied the dynamic properties of an inhomogeneously magnetized 18 nm thick and 2.3 µm wide permalloy stripe using time-resolved Kerr microscopy. If the magnetic field, which is applied along the width of the stripe, is close to the shape anisotropy field, the equilibrium magnetization is strongly inhomogeneous: at the edges it is parallel to the stripe whereas it is aligned parallel to the applied field in the center. For this case we find a new class of modes at higher frequencies than that of the ordinary precessional mode at the center. These modes span the entire width of the stripe and are therefore collective excitations of the inhomogeneously magnetized region. Their effective wave vector increases over an order of magnitude from the edges to the center. Therefore this modes are totally dipolar dominated at the edges and have mainly exchange character in the center. We will present experimental data and semi-analytical calculations to confirm the proposed character of these modes.