Observation of Magnon Polarons in a Uniaxial Antiferromagnetic Insulator

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 Cr 2 O 3 . Despite the relatively higher energy of magnon than that of the acoustic phonons, near the spin-flop transition of ∼6 T, the lefthanded 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.

All‐Electrical Magnon Transport Experiments in Magnetically Ordered Insulators

“…External control parameters may be electric fields, modulating the local electron states, as well as strain, which couples via magnetoelastic effects to the magnonic system. In regard to strain effects, the first experimental observation of magnon-phonon coupling effects in AFIs [257] provides positive evidence for the feasibility of this approach. Advances in the field require a combined effort from the side of available materials and also from spectroscopy to investigate magnon transport in antiferromagnets.…”

Dynamic magnetoelastic boundary conditions and the pumping of phonons

“…We can adopt MEC generated, e.g., by exchange [19] or interfacial Dzyaloshinskii-Moriya interaction [34,58] to address phonon pumping by spin waves and magnetorotation coupling in basically any material combination with ferromagnets. In principle, the analysis can also be extended to antiferromagnets [59][60][61][62][63], but the MEC energy and its parameters are less established. The magnon frequencies in antiferromagnets are typically higher than that of ultrasound [19,62] and magnonphonon hybridization requires application of large magnetic fields [63].…”

“…In principle, the analysis can also be extended to antiferromagnets [59][60][61][62][63], but the MEC energy and its parameters are less established. The magnon frequencies in antiferromagnets are typically higher than that of ultrasound [19,62] and magnonphonon hybridization requires application of large magnetic fields [63]. Large MEC coefficients and large magnetization amplitudes are important for phonon pumping.…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…[467]), such that the phase space portion over which the lifetimes of magnonic spin current are enhanced is maximal, leading to the enhancement of SSE [467]. The magnon-phonon polaron induced anomalies in the SSE have been observed also for other magnetic insulators such as antiferromagnetic Cr2O3 [468] and (partially) compensated ferrimagnetic Lu2BiFe4GaO12 [60] and Gd3Ga5O12 [469]. In 2020, Yahiro et al reported that the anomalies show up also in the spin Peltier effect, the reciprocal of the SSE [470].…”