In experiments and their interpretation usually the spin magnetic moment of magnons is considered. In this Letter, we identify a complementing orbital magnetic moment of magnons brought about by spin-orbit coupling. Our microscopic theory uncovers that spin magnetization ${\mathit{M}}^S$ and orbital magnetization ${\mathit{M}}^O$ are independent quantities; they are not necessarily collinear. Even when the total spin moment is compensated due to antiferromagnetism, ${\mathit{M}}^O$ may be nonzero. This scenario of orbital weak ferromagnetism is realized in paradigmatic kagome antiferromagnets with Dzyaloshinskii-Moriya interaction. We demonstrate that magnets exhibiting a magnonic orbital moment are omnipresent and propose transport experiments for probing it.

• Received 19 June 2020
• Accepted 23 July 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.117209