Research papers
Written by Paltsun

Saturday, 10 May 2014 12:53 
Theoretical study of spin excitations in a spherical nanoshell comprised of an ‘easy axis’ ferromagnet is carried out. For such system, a linearized LandauLifshitz equation with the relaxation term in the Hilbert form is written with regard for the dissipation effects, the magnetic dipoledipole interaction, the exchange interaction, and anisotropy effects. From Landau—Lifshitz equation, an equation for the magnetic potential for such excitations (in the magnetostatic approximation) is derived using one of the Maxwell equations. It is shown that in general case of standing spin waves in the nanoshell this equation does not admit a solution in the form of spherical functions by the radial coordinate, however, it admits an approximate solution in such form in the case of a shell that is thin compared to its size. Using this solution, a dispersion equation and characteristic damping time for nonzero (by the radial wavenumber) spin excitation modes, the only possible frequency and a characteristic damping time of the spin excitations for a zero mode and a radial wavenumber spectrum (in the implicit form) are obtained for the abovedescribed case of the thin shell. From the exchange restriction and the nanoshell size restriction on the spin excitation wavenumber, limitations on the number of possible radial and azimuthal modes of spin excitations are obtained. Appropriate numerical evaluations are performed, and the abovementioned limitations are obtained for typical nanoshells.

Last Updated on Saturday, 10 May 2014 14:12 

Written by Paltsun

Saturday, 10 May 2014 12:50 
Spin waves in a periodically layered ferromagnetic nanotube (a nanotube magnetophotonic crystal) are investigated. External magnetic field is considered to be applied parallel to the nanotube symmetry axis. The linearized LandauLifshitz equation in magnetostatic approximation is used, taken into account the magnetic dipoledipole interaction, the exchange interaction and the anisotropy effects. As a result, the the local dispersion relation (for uniform nanotube sections), the radial wave number spectrum and the longitudinal quasiwave number spectrum (for the entire nanotube) for spin waves in the abovedescribed nanotube are found. From the radial wave number spectrum, limitations on the transverseangular modes are defined. The longitudinal quasiwavenumber spectrum in the “effective medium” limit is shown to have the same form as for a uniform nanotube (with averaged parameters). 
Last Updated on Saturday, 10 May 2014 14:13 
Written by Paltsun

Saturday, 10 May 2014 12:44 
In this paper spin excitations in spherical ferromagnetic nanoshells are investigated. The magnetic dipoledipole interaction, the exchange interaction and the anisotropy eﬀects are taken into consideration. For such spin excitations, an equation for the magnetic potential perturbation is obtained. For a nanoshell that is thin compared to its size, the dispersion relation for nonzero spin excitation modes and the only possible frequency for zeromode spin excitations are found. Limitations on the mode numbers are derived. 
Last Updated on Saturday, 10 May 2014 14:13 



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