Observation of D’yakonov-Perel’-type magnon spin relaxation in uniaxial antiferromagnetic insulators

Long-distance transport of magnon spin currents in antiferromagnetic (AFM) insulators is essential for the development of magnonics, however, their relaxation mechanisms remain elusive. Here, we report that the D’yakonov-Perel’-type magnon spin relaxation mechanism governs non-local spin current transport in two prototypical uniaxial AFM insulators, Cr₂O₃ and -Fe₂O₃. Three key pieces of evidence will be presented. (1) a significant enhancement of non-local spin currents is observed prior to the spin-flop transition, which cannot be fitted by a well-accepted magnon-gap-closure mode but is well-interpreted by our model incorporating D’yakonov-Perel’-type magnon spin relaxation. (2) We find that the magnon spin diffusion length in Cr₂O₃ increases by 35% at 35 K, from 0.63 m at zero magnetic field to 0.85 m above 1.00 Tesla, agreeing with the expectation of the D’yakonov-Perel’-type magnon spin relaxation model. (3) Temperature dependence of the zero-field magnon spin diffusion length and magnon momentum scattering time in both AFM insulators can be qualitatively explained very well through our model. This work opens a promising avenue to effectively manipulate the magnon spin relaxation that will benefit the applications using the long-distance spin currents transport in AFM insulators.