Dynamic magnetic susceptibilities of high-aspect-ratio permalloylike nanorings (outer
diameter 20 nm, inner diameter 12 nm, length (L) range 12–500 nm) are studied using three-
dimensional micromagnetic simulations. The investigated systems show two major
resonance modes associated with volume and shape resonance modes, corresponding to
low and high resonance frequencies, respectively. When L is below 40 nm, only the shape
resonance mode is seen with a frequency predicted using the Kittel's equation and …