SKM 2021 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 2: Focus Session: Magnon Polarons - Magnon-Phonon Coupling and Spin Transport (joint session MA/HL)

MA 2.7: Hauptvortrag

Montag, 27. September 2021, 16:15–16:45, H5

Magnon polarons in antiferromagnetic insulator Cr2O3 — •Jing Shi — Department of Physics & Astronomy, University of California, Riverside, USA

While magnon polarons in ferrimagnetic materials have been experimentally investigated by various meanings including the spin Seebeck effect, nonlocal transport, inelastic neutron scattering, spin pumping, etc., similar hybridized excitations in antiferromagnets have not been well explored. For typical antiferromagnets, the magnon dispersion lies well above the acoustic phonon dispersion, which prevents the formation of magnon polarons under accessible magnetic fields. In this talk, I will first review the main magnon polaron results in yttrium iron garnet [1], a ferrimagnetic insulator. My focus will be on a special antiferromagnetic insulator: Cr2O3. In this uniaxial antiferromagnet, the left-handed magnon branch can be effectively lowered to zero at ~6 T, the spin-flop transition, allowing for thermodynamic measurements. In our study of Cr2O3 spin Seebeck effect [2], We observe magnon polaron anomalies right below the spin flop transition. where the left-handed magnon dispersion intersect both longitudinal and transverse acoustic phonon dispersions. I will present our experimental data and analysis in my talk.

[1] H.R. Man et al., Direct observation of magnon-phonon coupling in yttrium iron garnet. Phys. Rev B 96, 100406(R) (2017). [2] J.X. Li et al., Observation of magnon-polarons in a uniaxial antiferromagnetic insulator Cr2O3. Phys. Rev. Lett. 125, 217201(2020).