Spin-phase assignment of the c-axis–polarized electromagnon at 0.68 THz

Ascertain whether the c-axis–polarized electromagnon at 0.68 THz (22.5 cm−1) observed in hexagonal h-Lu0.6Sc0.4FeO3 corresponds to excitations of the A1 spin configuration or the A2 spin configuration, by resolving its selection rules and associated nonreciprocal effects.

Background

In addition to magnons M1 and M2, the authors observed an electromagnon (EM) at 0.68 THz that is excited by the electric field component along the c-axis and exhibits strong temperature dependence. While dichroism and selection rules for the M1 magnon supported the presence of the A2 spin structure, the EM could not be conclusively linked to either A1 or A2.

The authors suggest that further experiments involving THz light propagation in the ab plane with external magnetic field (configurations with k parallel to B and k parallel to P) will be necessary to observe symmetry-allowed nonreciprocal effects that could distinguish between A1 and A2 ab-plane spin orders and thus resolve the EM’s spin-phase assignment.