Short Wavelength Magnons in Magnetic Vortex Structures

In recent years magnonics has become one of the prime topics in magnetics research. The prospect of possible technological applications has played a major part in this development. The reliable generation of spin waves with short wavelengths is an ongoing challenge in this eld, as it is di cult by means of a patterned stripline antenna. Here we report on the imaging of spiral shaped short wavelength spin waves emitted by a magnetic vortex core in a permalloy disc. We take advantage of the magnetic perturbation generated by the small moving core, 10-20nm in diameter, to generate spin waves of sub-100nm wavelength. Imaging of these waves has been done using Time-Resolved Scanning Transmission X-Ray Microscopy at the MAXYMUS endstation of the BESSY II synchrotron facility. The experimentally derived dispersion relations match with analytical expressions for hybridized modes between Damon-Eshbach and exchange dominated magnons in in nite ferromagnetic lms. This holds as well for our micromagnetic simulations in these vortex structures.