A metamaterial description of two-dimensional (2D) magnonic crystals is presented according to micromagnetic and analytical calculations. Micromagnetic calculations were performed by using the Hamiltonian-based Dynamical Matrix Method extended to periodic systems. The one-component 2D systems are composed by periodic square arrays of circular nanoholes embedded into a permalloy ferromagnetic film. Magnonic modes dispersion is calculated and opening of band gaps at Brillouin zone boundaries is explained by accounting for the inhomogeneity of the internal field. The dynamics is described in terms of effective properties and an effective medium approximation is used to model the metamaterial wave in the propagative regime. The bi-component systems are composed by 2D periodic arrangements of circular nanodots of cobalts partially or totally embedded into a permalloy film. Band structure of the most representative collective modes is studied and the dependence of band gap amplitudes on cobalt volume and on cobalt position within the unit cell is also discussed. Effective surface magnetic charges are defined to explain the behaviour of demagnetizing fields and their influence on collective mode dispersion. Effective quantities are introduced to calculate the dispersion of the corresponding metamaterial wave in the propagative regime. The effect of the interchange between the two materials on mode dispersion is also investigated and an analytical expression of an energy concentration factor is also derived.

Metamaterial description of Magnonic Crystals - Invited talk by Roberto Zivieri - Conferenza internazionale

ZIVIERI, Roberto
2014

Abstract

A metamaterial description of two-dimensional (2D) magnonic crystals is presented according to micromagnetic and analytical calculations. Micromagnetic calculations were performed by using the Hamiltonian-based Dynamical Matrix Method extended to periodic systems. The one-component 2D systems are composed by periodic square arrays of circular nanoholes embedded into a permalloy ferromagnetic film. Magnonic modes dispersion is calculated and opening of band gaps at Brillouin zone boundaries is explained by accounting for the inhomogeneity of the internal field. The dynamics is described in terms of effective properties and an effective medium approximation is used to model the metamaterial wave in the propagative regime. The bi-component systems are composed by 2D periodic arrangements of circular nanodots of cobalts partially or totally embedded into a permalloy film. Band structure of the most representative collective modes is studied and the dependence of band gap amplitudes on cobalt volume and on cobalt position within the unit cell is also discussed. Effective surface magnetic charges are defined to explain the behaviour of demagnetizing fields and their influence on collective mode dispersion. Effective quantities are introduced to calculate the dispersion of the corresponding metamaterial wave in the propagative regime. The effect of the interchange between the two materials on mode dispersion is also investigated and an analytical expression of an energy concentration factor is also derived.
2014
magnonic crystals
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2042012
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