Low-energy magnons in the altermagnet $\alpha$-MnTe

TL;DR

This study investigates the magnetic resonance properties of the altermagnetic material $ extalpha$-MnTe, revealing low-energy magnons with sharp resonance modes at low temperatures and insights into magnon interactions.

Contribution

First high-field ESR study of $ extalpha$-MnTe revealing isotropic AFMR mode and magnon interaction effects in an altermagnet.

Findings

Observed a single AFMR resonance line with $g_ ext{eff}=2.01$

Resonance mode is sharp at low temperatures (~50 mT width)

Mode broadens with increasing temperature, indicating magnon-magnon interactions

Abstract

We report high-field electron spin resonance studies of the altermagnetic material $\alpha$-MnTe. In magnetic fields applied parallel to the triangular Mn$^{2+}$ layers we observed a single resonance line, corresponding to an antiferromagnetic resonance (AFMR) mode. The resonance fields of this excitation exhibit an isotropic behavior with $g_\mathrm{eff}=2.01$, which is close to the free-electron $g$-factor value and agrees with the absence of orbital momenta for the Mn$^{2+}$ ions. At low temperatures, the AFMR mode is remarkably sharp ($\sim50$ mT for the full width at the half-maximum). This mode exhibits a noticeable broadening with increasing temperature, indicating the enhanced effect of magnon-magnon interactions. Based on this behavior, we estimate the strength of these interactions.