Observation of coupled magnetic vortex structure dynamics by time-resolved magneto-optical Kerr effect microscopy

We report on the development of an analytical theory and a method of experimental observation of dynamic propertied of magnetic vortices excited in cylindrical ferromagnetic discs magnetostatically coupled into arrays. The theory, based on Thiele's equation of motion and the approximative rigid-vortex model, enables us to determine the eigenfrequencies of the vortices' harmonic oscillation within pairs [J. Shibata et al., Phys. Rev. B 67, 224404 (2003)] awl large arrays [J. Shibata and Y. Otani, Phys. Rev. B 70, 012404 (2004)] of the discs, the latter being a proposal to design a new type of artificial crystals with magnonic band structures. Then we briefly describe the basic principles of our time-resolved Kerr microscope and show the capabilities of our method to detect all the features studied theoretically. Finally we present an experimental example of observation of the dynamic evolution of short-pulse magnetic field excitation of a vortex weakly coupled within an array of cylindrical Permalloy discs.