Magnetoelectric spectroscopy of spin excitations in LiCoPO4

TL;DR

This study investigates spin excitations in LiCoPO4 using THz spectroscopy, revealing electromagnons and magnetoelectric resonances that contribute to the material's static magnetoelectric response.

Contribution

It identifies and characterizes magnetoelectric spin resonances and electromagnons in LiCoPO4, linking them to the static magnetoelectric susceptibility tensor.

Findings

Detection of electromagnons and magnetoelectric spin resonances.

Magnetoelectric spin resonances dominate the static response.

Symmetric magnetoelectric tensor components are significant.

Abstract

We have studied spin excitations in a single-domain crystal of antiferromagnetic LiCoPO4 by THz absorption spectroscopy. By analyzing the selection rules and comparing the strengths of the absorption peaks in the different antiferromagnetic domains, we found electromagnons and magnetoelectric spin resonances besides conventional magnetic-dipole active spin-wave excitations. Using the sum rule for the magnetoelectric susceptibility we determined the contribution of the spin excitations to all the different off-diagonal elements of the static magnetoelectric susceptibility tensor in zero as well as in finite magnetic fields. We conclude that the magnetoelectric spin resonances are responsible for the static magnetoelectric response of the bulk when the magnetic field is along the x-axis, and the symmetric part of the magnetoelectric tensor with zero diagonal elements dominates over the antisymmetric components.