In this thesis, the results of time-resolved magneto-optical imaging experiments, micromagnetic simulations and analytical theory will be presented. These three approaches were used in order to understand how spin waves can be both excited and steered using magnetic non-uniformities (which gives rise to the graded magnonic index). The results presented in this thesis, as a whole, reveal that the graded magnonic index not only can be exploited either to excite or steer propagating spin waves in a deliberate manner, but is in fact a ubiquitous feature that needs to be taken into account when considering any dynamical phenomena in nano- and micro-magnetism.Engineering and Physical Sciences Research Council (EPSRC
