Spin modes of triangular magnetic nanodots in the vortex, Y, and buckle states

Abstract

We present a complete investigation on the spin normal modes of triangular nanoparticles in the vortex, Y, and buckle states. In order to get a micromagnetic representation of an equilateral triangle, we choose a base side of 360 nm and a height of 310 nm, while the thickness is 20 nm. This choice allows the vortex state as an equilibrium configuration at zero applied field. We calculate the principal modes of the three magnetic configuration through the dynamical matrix method and discuss in detail their frequencies and their profiles on the basis of the internal field behavior. We also explain the onset of the irregular nodal surfaces in the mode profiles beyond a critical node number, depending on the underlying magnetic configuration. The modes with nodal surfaces parallel to the direction of variation of the internal field are found to occur in a series with identical node number but different localization: this is related to the reduced coherent length of the modes because of the strongly varying internal field. We present also the calculated Brillouin light scattering (BLS) spectrum for each magnetic configuration, with discussion on the reasons that allow some modes to be BLS active.