Magnetic field dependence of quantized and localized spin wave modes in thin rectangularmagnetic dots

Abstract

The magnetic field dependences of the frequencies of standing spin-wavemodes in a tangentially magnetized array of thin rectangular permalloy dots(800 × 550 nm) were measured experimentally by a Brillouin light scattering technique and calculatedtheoretically using an approximate size-dependent quantization of the spin-wavevectorcomponents in the dipole-exchange dispersion equation for spin waves propagating in acontinuous magnetic film. It was found that the inhomogeneous internal bias magnetic fieldof the dot has a strong influence on the profiles of the lowest spin-wave standing modes. Inaddition, the dynamic magnetization distributions found for both longitudinally andtransversely magnetized long magnetic stripes gives a good approximation for modedistributions in a rectangular dot magnetized along one of its in-plane sides. Anapproximate analytic theory of exchange-dominated spin-wave modes, strongly localizedalong the dot edge that is perpendicular to the bias magnetic field, is developed. Agood quantitative agreement with the results of the BLS experiment is found.