Focusing of spin waves in YIG thin films

Previous investigations using YIG found that spin waves showed distinct focusing in two different directions as they hit some impurity in the material.An important property for a material to exhibit focusing is anisotropy, so that the group and phase velocities point in different directions. Since magnetic materials have an inherent anisotropy, we study the focusing behavior of magneto-static waves in ferromagnetic thin films.We also found the focusing effects by varying the applied magnetic field at a constant frequency.We have also studied the focusing of the surface waves. The slowness surface for surface wave shows no points of zero curvature, but the curvature is not same at all points and hence we have weak focusing. The surface wave focusing is also tunable with the external field. One also finds focusing effects of the higher order bulk modes. Finally, we note that it should be experimentally possible to observe the focusing effects using Brillouin light scattering.