We have observed non-linear behaviour of stationary spin waves localised on textural topological defects. We can explain our results in the framework of the Schrodinger equation with feedback. The new method gives us the ability to see many topological defects, which are undistinguished by traditional methods of NMR. We have Sound that some of the non-linear spin wave modes can be responsible for the extremely long lived induction decay signals called "Persistent signals".