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Spin Wave Modes in Ferromagnetic Stripes and
Unconventional Magnetic Vortex Structures Observed
in Micromagnetc Simulations
Ming Yan
University of Minnesota
Hosted by Gary Leaf
10:30 AM, May 17, 2004
Building 223, Conference Room S105
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| Abstract |
Spin wave modes in Permalloy stripes were studied both by micromagnetic
simulations and by solving the linearized Landau Lifshitz- Gilbert equation. With an external field applied in the plane of the stripe in
the direction perpendicular to the long axis of the stripe, different spin wave modes are observed in different field regimes. In high external
fields, the lowest frequency modes are localized near the edges of the stripe due to the demagnetizing field. At low fields, crossover spin wave
modes of mixed Damon-Eshbach and backward volume character are observed; these modes are due to the inhomogeneous magnetization near the edges of
the stripe. The characteristic wave vector for these modes is a strong function of the position but is real everywhere, unlike the localized
modes at higher fields. At extremely high fields, the lowest frequency localized mode completely softens
when the magnetization is saturated in the direction of the external fields.
By choosing a special shape and different sizes of ferromagnetic samples, unconventional 2-D magnetic vortex structures are observed in the
micromagnetic simulations. These structures have the same exchange energy and surface magnetic charges as conventional vortices but different
volume charges.
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