Frequency multiplication by collective nano-scale spin wave dynamics

Abstract

Frequency multiplication is a process where harmonic multiples of the input frequency are generated. It is usually achieved in non-linear electronic circuits or transmission lines. Such elements enable the up-conversion of electronic signals to GHz frequencies and are essential for frequency synthesizers and communication devices. Circuits based on the propagation and interaction of spin waves are a promising alternative to conventional electronics. Unfortunately, these systems usually require direct driving in the GHz range as magnonic frequency up-conversion is restricted to a few harmonics only. Here we show that the ferromagnetic material itself can act as a six octave spanning frequency multiplier. By studying low frequency magnetic excitations in a continuous ferromagnetic layer we show that the non-linearity of magnetization dynamics combined with disorder in the ferromagnet leads to the emergence of a dynamic phase generating high harmonics. The demonstrated broad band frequency multiplication opens exciting perspectives for magnonic and spintronic applications since the frequency is up-converted from MHz into GHz frequencies within the magnetic medium itself. Due to the ease at which magnetic media can be structured and modified spatially (and reversibly) we anticipate that a tailored non-linear dynamic phase can be engineered e.g. to stabilize magnetic solitons.