Prof.dr. B. Hillebrands, Technical University Kaiserlautern, Germany
The fundamental eigen excitations of a magnetic system are spin waves. It is of fundamental importance to understand their properties, in particular in view of applications in fast data storage. In my lecture I will discuss two essential aspects: 1) in small magnetic objects the knowledge of the eigen-excitation spectrum is of central importance. Since objects are commonly inhomogeneously magnetized the spectrum is complex, and new phenomena, like localization and tunnelling of modes appear. 2) At larger excitation amplitudes interactions between quanta of the spin waves, the magnons, must be taken into account. A new measurement technique, the space- and time-resolved Brillouin light scattering spectroscopy, allows to study distinct nonlinear phenomena like propagation of nonlinear wave packets (solitons, bullets) in a magnetic film and to present the results in a movie like format. I will present recent experiments which demonstrate, that such nonlinear spin-wave packets can be amplified coherently, and the magnetic analogue of a laser can be realized. In magnetic rings new nonlinear eigen-excitations appear like “Möbius solitons”, which have symmetry breaking properties in comparison to their linear counterparts.