Polarization-Dependent THz Photon Absorption by Magnons in α-Hematite Fe₂O₃

α-Hematite is an antiferromagnet which transitions from a low-temperature easy axis to a high-temperature canted phase which has been well studied using linear spin wave theory [1]. In its canted phase in the presence of an external lab magnetic field hematite demonstrates a highly polarization- and frequency-dependent photon absorption due to magnon-photon interaction in the approximate 150 GHz frequency range [2,3]. In collaboration with experiment we construct a microscopic model of this interaction capable of accurately predicting both the polarizaton dependent relative magnitude and absolute magnitude of the absorption due to the magnon-polariton hybridization process. By careful system-specific analysis of photon decay and scattering channels we fully predict the photon absorption by each magnon mode as a function of the photon frequency and relative polarization. The average fractional error of our predictions is below 10% indicating high agreement with experiment.

[1]: Dannegger, Tobias, et al. “Magnetic properties of hematite revealed by an ab initio parameterized spin model.” Physical Review B, vol. 107, no. 18, 12 May 2023

[2]: Boventer, I., et al. “Antiferromagnetic cavity magnon polaritons in collinear and canted phases of hematite.” Physical Review Applied, vol. 19, no. 1, 30 Jan. 2023

[3]: Netto, Giovanni Budroni, et al. “Birefringence in an α-hematite single-crystal in terahertz range.” CLEO 2024, May 2024