We provide direct experimental evidence which demonstrates that, in the presence of a large spin-orbit coupling, the lifetime, amplitude, group, and phase velocity of the magnons propagating along two opposite (but crystallographically equivalent) directions perpendicular to the magnetization are different. A real time and space representation reveals that magnons with the same energy (eigenfrequency) propagate differently along two opposite directions. Our findings can inspire ideas for designing new spintronic devices.

• Received 16 January 2012

DOI:https://doi.org/10.1103/PhysRevLett.108.197205