Spectroscopy and imaging of edge modes in Permalloy nanodisks

This paper reports spectroscopy and imaging of spin wave modes using ferromagnetic resonance force microscopy (FMRFM) in Permalloy nano-disks with disk diameters that range from 100 nm to 750 nm. The ferromagnetic resonance spectra distinguish multiple edge modes, which are also resolved spatially within the disk. Imaging reveals signal maxima of distinct edge modes that separated by less than 100 nm. With rotation of the applied field, the fundamental edge mode resonance is used to probe the edge properties along the roughly circular edge of the disk, revealing a large asymmetry. Finally, we show the number of edge mode resonances depends upon the disk size, results that are confirmed by micromagnetic modeling.