V. Kocsis, S. Bordács, Y. Tokunaga, J. Viirok, L. Peedu, T. Rõõm, U. Nagel, Y. Taguchi, Y. Tokura, and I. Kézsmárki
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.100.155124
We have studied spin excitations in a single-domain crystal of antiferromagnetic LiCoPO4 by terahertz 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 (ME) spin resonances in addition to conventional magnetic dipole active spin-wave excitations. Using the sum rule for the ME susceptibility, we determined the contribution of the spin excitations to all the different off-diagonal elements of the static ME susceptibility tensor in zero and finite magnetic fields. We conclude that the ME spin resonances are responsible for the static ME response of the bulk when the magnetic field is along the x axis, and the symmetric part of the ME tensor with zero diagonal elements dominates over the antisymmetric components.
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