Periodic arrays of planar magnetic nanoparticles support collective spin excitations, whose properties depend on size and shape of the particles, on the interaction strength and the magnetic properties of the material. Depending on the interdot separation, the interaction ranges from loosely coupled particles, whose spin wave spectrum can be traced to the spin modes of a single particle and the interaction acts as a small perturbation, to strongly interacting particles where the spectrum of insulated particles is completely lost. We present a theoretical/numerical model for the calculation of the dispersion curves and spin mode profiles for a periodic array of planar magnetic particles of arbitrary shape and separation, mutually coupled through dipolar interaction, based on the dynamical matrix method. Results are shown for 1D and 2D arrays of weakly interacting circular dots; the modes of the insulated dot give rise to bands, where the frequency depends on the modulus and direction of the surface wavevector. The dependence of the dispersion on the applied field direction is also investigated. A preliminary comparison shows a good agreement with experimental results obtained by Brillouin light scattering.
Spin modes in 1D and 2D arrays of nanoparticles calculated with the dynamical matrix method
GIOVANNINI, Loris;MONTONCELLO, Federico;NIZZOLI, Fabrizio
2009
Abstract
Periodic arrays of planar magnetic nanoparticles support collective spin excitations, whose properties depend on size and shape of the particles, on the interaction strength and the magnetic properties of the material. Depending on the interdot separation, the interaction ranges from loosely coupled particles, whose spin wave spectrum can be traced to the spin modes of a single particle and the interaction acts as a small perturbation, to strongly interacting particles where the spectrum of insulated particles is completely lost. We present a theoretical/numerical model for the calculation of the dispersion curves and spin mode profiles for a periodic array of planar magnetic particles of arbitrary shape and separation, mutually coupled through dipolar interaction, based on the dynamical matrix method. Results are shown for 1D and 2D arrays of weakly interacting circular dots; the modes of the insulated dot give rise to bands, where the frequency depends on the modulus and direction of the surface wavevector. The dependence of the dispersion on the applied field direction is also investigated. A preliminary comparison shows a good agreement with experimental results obtained by Brillouin light scattering.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
