posted on 2021-08-10, 16:06authored byJiahao Han, Yabin Fan, Brooke C. McGoldrick, Joseph Finley, Justin T. Hou, Pengxiang Zhang, Luqiao Liu
Unequal
transmissions of spin waves along opposite directions provide
useful functions for signal processing. So far, the realization of
such nonreciprocal spin waves has been mostly limited at a gigahertz
frequency in the coherent regime via microwave excitation. Here we
show that, in a magnetic bilayer stack with chiral coupling, tunable
nonreciprocal propagation can be realized in spin Hall effect-excited
incoherent magnons, whose frequencies cover the spectrum from a few
gigahertz up to terahertz. The sign of nonreciprocity is controlled
by the magnetic orientations of the bilayer in a nonvolatile manner.
The nonreciprocity is further verified by measurements of the magnon
diffusion length, which is unequal along opposite transmission directions.
Our findings enrich the knowledge on magnetic relaxation and diffusive
transport and can lead to the design of a passive directional signal
isolation device in the diffusive regime.