Nonlinear amplification and mixing of spin waves in a microstrip geometry with metallic ferromagnets

We explore the nonlinear mixing and amplification of magnetic polariton modes in ultrasmall waveguides. Ultrasmall waveguide geometries can produce large oscillating microwave fields—up to about 500 Oe. Using these large fields, we examine nonlinear ferromagnetic dynamics in ribbons of Permalloy and Fe. In particular if two microwave signals at different frequencies are sent into the waveguide, we can increase the transmission of one wave by adding energy to the other wave. We also demonstrate the creation of new frequencies and the development of a comb of equally spaced frequencies. These experimental results are explained with perturbation theory and micromagnetics calculations.