Fachgruppe Nanostrukturierte Materialien    

We use phase-resolved imaging to directly study the nonlinear modification of the wavelength of spin waves propagating in 100-nm-thick in-plane magnetized yttrium iron garnet waveguides. We show that, by using moderate microwave power, one can realize spin waves with large amplitudes corresponding to precession angles in excess of 10° and nonlinear wavelength variation of up to 18% in this system. We also find that, at large precession angles, the propagation of spin waves is strongly affected by the onset of nonlinear damping, which results in a strong spatial dependence of the wavelength. This effect leads to spatially dependent controllability of the wavelength by the microwave power. Furthermore, it leads to the saturation of nonlinear spectral shift effects several micrometers away from the excitation point. These findings are important for the development of nonlinear integrated spin-wave signal-processing devices and can be used to optimize their characteristics.