Martin Bauer, Christoph Mathieu, Serguei Demokritov, Burkhard Hillebrands, P.A. Kolodin, S. Sure, H. Dötsch, A. N. Slavin

• The first observation of self-focusing of dipolar spin waves in garnet film media is reported. In particular, we show that the quasi-stationary diffraction of a finite-aperture spin wave beam in a focusing medium leads to the concentration of the wave power in one focal point rather than along a certain line (channel). The obtained results demonstrate the wide applicability of non-linear spin wave media to study non-linear wave phenomena using an advanced combined microwave-Brillouin light scattering technique for a two-dimensional mapping of the spin wave amplitudes.