A quantitative estimation of the degree of localization of collective modes in binary magnonic crystals is given. This is accomplished by recalling the definition of the energy concentration factor in a photonic crystal written in terms of the spatially varying electric field and of the periodic non-uniform permittivity [1]. The binary magnonic crystals have periodicities in the nanometric range and are composed by a periodic arrangement of cylindrical cobalt (Co) nanodots completely embedded into a permalloy (Py, Ni80Fe20) continuous thin magnetic film. The lattice constant of the two-dimensional binary magnonic crystal is 600 nm and the external magnetic field is applied along the y direction in the plane of the system. The energy concentration factor for periodic binary magnonic crystals is defined as the ratio between the internal energy stored the collective mode in the region having the higher internal field and its total energy [2]. The collective mode in a two-dimensional periodic and binary magnonic crystal is characterized by an oscillating periodic dynamic magnetization depending on the Bloch wave vector. It can be shown that the magnitude of the energy concentration factor strictly depends on the contrast between the saturation magnetizations of Co and Py. As an example, a numerical estimation at the centre of the Brillouin zone at an external field of intensity H = 500 Oe gives a value of only 9% due to the weak variation of the internal field. The computation of the energy localization factor for different geometries and for different values of the Bloch wave vectors is also given. This work was partially supported by MIUR-PRIN 2010-11 Project2010ECA8P3 "DyNanoMag". [1] J.D. Joannopoulos, S.G. Johnson, J.N. Winn, R.D. Meade, Photonic Crystals: Molding the Flow of Light (Princeton University Press, Princeton, 2008). [2] R. Zivieri et al., Photon. Nanostruct: Fundam. Appl. 12, 387 (2014).
Energy concentration factor for collective modes in a binary magnonic crystal - Presentazione orale by R. Zivieri
ZIVIERI, Roberto
2015
Abstract
A quantitative estimation of the degree of localization of collective modes in binary magnonic crystals is given. This is accomplished by recalling the definition of the energy concentration factor in a photonic crystal written in terms of the spatially varying electric field and of the periodic non-uniform permittivity [1]. The binary magnonic crystals have periodicities in the nanometric range and are composed by a periodic arrangement of cylindrical cobalt (Co) nanodots completely embedded into a permalloy (Py, Ni80Fe20) continuous thin magnetic film. The lattice constant of the two-dimensional binary magnonic crystal is 600 nm and the external magnetic field is applied along the y direction in the plane of the system. The energy concentration factor for periodic binary magnonic crystals is defined as the ratio between the internal energy stored the collective mode in the region having the higher internal field and its total energy [2]. The collective mode in a two-dimensional periodic and binary magnonic crystal is characterized by an oscillating periodic dynamic magnetization depending on the Bloch wave vector. It can be shown that the magnitude of the energy concentration factor strictly depends on the contrast between the saturation magnetizations of Co and Py. As an example, a numerical estimation at the centre of the Brillouin zone at an external field of intensity H = 500 Oe gives a value of only 9% due to the weak variation of the internal field. The computation of the energy localization factor for different geometries and for different values of the Bloch wave vectors is also given. This work was partially supported by MIUR-PRIN 2010-11 Project2010ECA8P3 "DyNanoMag". [1] J.D. Joannopoulos, S.G. Johnson, J.N. Winn, R.D. Meade, Photonic Crystals: Molding the Flow of Light (Princeton University Press, Princeton, 2008). [2] R. Zivieri et al., Photon. Nanostruct: Fundam. Appl. 12, 387 (2014).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
