Pseudo-Goldstone mode in altermagnetic $\alpha$-MnTe: high-field electron spin resonance studies

Abstract

We report multi-frequency electron spin resonance spectroscopy studies of $\alpha$-MnTe in magnetic fields up to $16$ T, applied along the easy anisotropy axis. At temperatures below $T_{\mathrm{N}}=310$ K, we observe a single resonance line corresponding to the pseudo-Goldstone mode of the antiferromagnetic resonance (AFMR). This mode exhibits the isotropic behavior with $g_{\mathrm{eff}}=2.01$, consistent with a complete quench of the orbital angular momenta for Mn${}^{2+}$ ions. At low temperatures, the resonance mode is remarkably narrow ($\sim 50$ mT for the full width at the half-maximum at $5$ K). The AFMR mode exhibits substantial broadening with increasing temperature, which can be understood in terms of the magnon-magnon scattering

Main - 6 pages, 5 figures; Supplement - 3 pages

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