Observation of the Nonreciprocal Magnon Hanle Effect

The precession of magnon pseudospin about the equilibrium pseudofield, the latter capturing the nature of magnonic eigenexcitations in an antiferromagnet, gives rise to the magnon Hanle effect. Its realization via electrically injected and detected spin transport in an antiferromagnetic insulator demonstrates its high potential for devices and as a convenient probe for magnon eigenmodes and the underlying spin interactions in the antiferromagnet. Here, we observe a nonreciprocity in the Hanle signal measured in hematite using two spatially separated platinum electrodes as spin injector or detector. Interchanging their roles was found to alter the detected magnon spin signal. The recorded difference depends on the applied magnetic field and reverses sign when the signal passes its nominal maximum at the so-called compensation field. We explain these observations in terms of a spin transport direction-dependent pseudofield. The latter leads to a nonreciprocity, which is found to be controllable via the applied magnetic field. The observed nonreciprocal response in the readily available hematite films opens interesting opportunities for realizing exotic physics predicted so far only for antiferromagnets with special crystal structures.

Automated summary

The magnon Hanle effect, caused by the precession of magnon pseudospin about the equilibrium pseudofield, has been realized in an antiferromagnetic insulator through electrically injected and detected spin transport. The nonreciprocity in the measured Hanle signal in hematite using spatially separated platinum electrodes as spin injector or detector has been observed, and it can be controlled by the applied magnetic field. This nonreciprocal response opens up opportunities for realizing exotic physics in readily available hematite films.