We investigate the low-frequency spin wave dynamics involved in the magnetization reversal of a ‎Penrose P2 tiling using the dynamical matrix method. This system consists of a two-dimensional, ‎connected wire network of elongated thin-film segments, whose complete reversal occurs as a cascade ‎of successive local segment reversals. Using soft mode theory, we interpret the reversal of an individual ‎segment as a first order magnetic transition, in which magnetization curve of the system suffers a small ‎discontinuity. In proximity of this discontinuity a specific mode of the spin wave spectrum goes soft (i.e., ‎its frequency goes to zero), triggering a local instability. We show that this mode is localized, and is at the ‎origin of the local reversal. We discuss the correlation of the mode spatial profile with the “reversal ‎mechanism”, which is the passage of a domain wall through the segment. This process differs from ‎reversal in periodic square or honeycomb artificial spin ices, where a cascade of reversing segments (e.g., ‎‎“Dirac string”) follows an extended (though irregular) path across the sample; here the spatial distribution ‎of successive segment reversals is discontinuous, but strictly associated with the area where a soft mode ‎is localized. The migration of the localization area across the P2 tiling (during reversal in decreasing applied ‎fields) depends on changes in the internal effective field map. We discuss these results in the context of ‎spin wave localization due to the unique, low translational symmetry of the P2 tiling.‎

Dynamic Origin of Segment Magnetization Reversal in Penrose Quasicrystals‎

MONTONCELLO, Federico;GIOVANNINI, Loris;
2016

Abstract

We investigate the low-frequency spin wave dynamics involved in the magnetization reversal of a ‎Penrose P2 tiling using the dynamical matrix method. This system consists of a two-dimensional, ‎connected wire network of elongated thin-film segments, whose complete reversal occurs as a cascade ‎of successive local segment reversals. Using soft mode theory, we interpret the reversal of an individual ‎segment as a first order magnetic transition, in which magnetization curve of the system suffers a small ‎discontinuity. In proximity of this discontinuity a specific mode of the spin wave spectrum goes soft (i.e., ‎its frequency goes to zero), triggering a local instability. We show that this mode is localized, and is at the ‎origin of the local reversal. We discuss the correlation of the mode spatial profile with the “reversal ‎mechanism”, which is the passage of a domain wall through the segment. This process differs from ‎reversal in periodic square or honeycomb artificial spin ices, where a cascade of reversing segments (e.g., ‎‎“Dirac string”) follows an extended (though irregular) path across the sample; here the spatial distribution ‎of successive segment reversals is discontinuous, but strictly associated with the area where a soft mode ‎is localized. The migration of the localization area across the P2 tiling (during reversal in decreasing applied ‎fields) depends on changes in the internal effective field map. We discuss these results in the context of ‎spin wave localization due to the unique, low translational symmetry of the P2 tiling.‎
spin waves, artificial quasi-crystals, soft modes, macrospin, magnetization reversal
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2359787
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