Large magnon dichroism and other optical properties of hexagonal ferrite h-Lu0.6Sc0.4FeO3 with altermagnetic A2 spin ordering

TL;DR

This study reveals large magnon dichroism and unique optical properties in hexagonal ferrite h-Lu0.6Sc0.4FeO3, highlighting its altermagnetic behavior and phase transition characteristics through advanced spectroscopic techniques.

Contribution

It demonstrates the strong altermagnetic properties and optical dichroism of h-Lu0.6Sc0.4FeO3, providing new insights into its magnetic and optical behavior with potential applications.

Findings

Magnons observed at 0.85 THz and 1.2 THz that harden with temperature.

Strong magnon dichroism observed at zero magnetic field.

Magnon doublet splitting yields a g-factor of 3.0 for Fe3+ ions.

Abstract

Multiferroic hexagonal h-Lu0.6Sc0.4FeO3 single crystals with non-collinear spins were studied using the THz and Raman scattering spectroscopies and ellipsometry. Antiferromagnetic resonances, or magnons, were found at about 0.85 THz and 1.2 THz. These magnons harden as temperature increases and disappear above 130 K. This behavior is consistent with the magnetic susceptibility and a phase transition to a previously reported weak ferromagnetic state. A strong dichroism at the resonance with the AFM doublet has been observed at zero external magnetic field using both conventional circular polarization and THz vector vortex beams. This observation is attributed to the strong altermagnetic properties of h-Lu0.6Sc0.4FeO3 with a broken PT symmetry. The splitting of the magnon doublet in an external magnetic field applied long the c axis yields a g-factor of 3.0 for the Fe3+ ions. Raman spectra of the optical phonons revealed a Fano-type asymmetry due to their interaction with a continuum of polar excitations. Electronic transitions were studied with ellipsometry and the results were compared with the modelled using DFT+eDMFT.