The effect of the core formation on the vortex-state frequencies of spin modes in cylindrical magnetic disks at zero applied magnetic field is evaluated by means of an analytical approach [1]. In order to do this we force the static magnetization to lie on the disk surface also in the core region of finite size with the exclusion of an infinitesimal area in the disk centre where the magnetization is perpendicular to the disk plane. Then we calculate the frequencies of spin modes corresponding to this configuration. Due to dipolar effects the frequencies of the radial modes corresponding to this configuration are upshifted with respect to the ones determined in the ground state configuration for disks of nanometric and submicrometric size. Instead the core formation leads to an increase of the energy stored in one mode of the m = ± 1 doublet of azimuthal modes and a decrease of the energy stored in the other mode also for disks of micrometric size. The effect of core removal in the corresponding vortex-state magnetic rings with inner radius of finite size is also investigated and its influence on spin dynamics is compared with the previous effect. The frequency behavior of the most representative mode of the spectrum, the fundamental mode, is approximately described by means of static demagnetizing contributions. This description reminds qualitatively the one given for the F mode in a cylindrical dot in the saturated state with in-plane magnetization [2]. The frequencies of the most representative vortex modes at zero applied magnetic field calculated by means of the analytical model are compared with the ones of a recent micromagnetic model based on the dynamical matrix method for cylindrical nanodots [1]. The analytically calculated frequency splitting of the m = + 1 and m = -1 doublet compares well with available Time Resolved Kerr Microscopy and Brillouin Light Scattering data for different aspect ratios [3]. [1] R. Zivieri and F. Nizzoli, “Magnon modes in vortex-state ferromagnetic cylindrical dots: from standard disk to ring” in preparation [2] R. Zivieri and R.L. Stamps, Phys. Rev. B 73 (2006) 144422 [3] R. Zivieri and F. Nizzoli, Phys. Rev. B 78 (2008) 064418; R. Zivieri and F. Nizzoli in “Electromagnetic, Magnetostatic, and Exchange-Interaction Vortices in Confined Magnetic Structures” edited by E.O. Kamenetskii (Transworld Research Network, Kerala, India ) (2008) 1

Magnon modes in vortex-state ferromagnetic disks and rings -- Presentazione poster by R. Zivieri - Conferenza nazionale

ZIVIERI, Roberto
2009

Abstract

The effect of the core formation on the vortex-state frequencies of spin modes in cylindrical magnetic disks at zero applied magnetic field is evaluated by means of an analytical approach [1]. In order to do this we force the static magnetization to lie on the disk surface also in the core region of finite size with the exclusion of an infinitesimal area in the disk centre where the magnetization is perpendicular to the disk plane. Then we calculate the frequencies of spin modes corresponding to this configuration. Due to dipolar effects the frequencies of the radial modes corresponding to this configuration are upshifted with respect to the ones determined in the ground state configuration for disks of nanometric and submicrometric size. Instead the core formation leads to an increase of the energy stored in one mode of the m = ± 1 doublet of azimuthal modes and a decrease of the energy stored in the other mode also for disks of micrometric size. The effect of core removal in the corresponding vortex-state magnetic rings with inner radius of finite size is also investigated and its influence on spin dynamics is compared with the previous effect. The frequency behavior of the most representative mode of the spectrum, the fundamental mode, is approximately described by means of static demagnetizing contributions. This description reminds qualitatively the one given for the F mode in a cylindrical dot in the saturated state with in-plane magnetization [2]. The frequencies of the most representative vortex modes at zero applied magnetic field calculated by means of the analytical model are compared with the ones of a recent micromagnetic model based on the dynamical matrix method for cylindrical nanodots [1]. The analytically calculated frequency splitting of the m = + 1 and m = -1 doublet compares well with available Time Resolved Kerr Microscopy and Brillouin Light Scattering data for different aspect ratios [3]. [1] R. Zivieri and F. Nizzoli, “Magnon modes in vortex-state ferromagnetic cylindrical dots: from standard disk to ring” in preparation [2] R. Zivieri and R.L. Stamps, Phys. Rev. B 73 (2006) 144422 [3] R. Zivieri and F. Nizzoli, Phys. Rev. B 78 (2008) 064418; R. Zivieri and F. Nizzoli in “Electromagnetic, Magnetostatic, and Exchange-Interaction Vortices in Confined Magnetic Structures” edited by E.O. Kamenetskii (Transworld Research Network, Kerala, India ) (2008) 1
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1735174
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