Observation of magnon-polarons in a uniaxial antiferromagnetic insulator

TL;DR

This paper reports the first observation of antiferromagnetic magnon-polarons in Cr2O3, showing hybridization of magnons and phonons near the spin-flop transition, with enhanced spin Seebeck signals at low temperatures.

Contribution

It demonstrates the existence of AFM magnon-polarons in Cr2O3 and their detection via spin Seebeck effect, revealing new hybrid excitations in uniaxial AFM insulators.

Findings

Magnon-polarons observed in Cr2O3 near spin-flop transition

Hybridization of magnons and phonons confirmed by spin Seebeck effect

Enhanced spin Seebeck signals at low temperatures due to magnon-polarons

Abstract

Magnon-polarons, a type of hybridized excitations between magnons and phonons, were first reported in yttrium iron garnet as anomalies in the spin Seebeck effect responses. Here we report an observation of antiferromagnetic (AFM) magnon-polarons in a uniaxial AFM insulator Cr2O3. Despite the relatively higher energy of magnon than that of the acoustic phonons, near the spin-flop transition of ~ 6 T, the left-handed magnon spectrum shifts downward to hybridize with the acoustic phonons to form AFM magnon-polarons, which can also be probed by the spin Seebeck effect. The spin Seebeck signal is founded to be enhanced due to the magnon-polarons at low temperatures.