Spin excitations of magnetoelectric LiNiPO${}_4$ in multiple magnetic phases

Abstract

Spin excitations of magnetoelectric LiNiPO${}_4$ are studied by infrared absorption spectroscopy in the THz spectral range as a function of magnetic field through various commensurate and incommensurate magnetically ordered phases up to 33\,T. Six spin resonances and a strong two-magnon continuum are observed in zero magnetic field. Our systematic polarization study reveals that some of the excitations are usual magnetic-dipole active magnon modes, while others are either electromagnons, electric-dipole active, or magnetoelectric, both electric- and magnetic-dipole active spin excitations. Field-induced shifts of the modes for all three orientations of the field along the orthorhombic axes allow us to refine the values of the relevant exchange couplings, single-ion anisotropies, and the Dzyaloshinskii-Moriya interaction on the level of a four-sublattice mean-field spin model. This model also reproduces the spectral shape of the two-magnon absorption continuum, found to be electric-dipole active in the experiment.

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Cited by in corpus (5)

• Time-Domain Terahertz Spectroscopy in High Magnetic Fields
• Magnetic structures and quadratic magnetoelectric effect in LiNiPO${}_4$ beyond 30T
• Magnetic anisotropy and exchange paths for octa- and tetrahedrally coordinated Mn${}^{2+}$ ions in the honeycomb multiferroic Mn${}_2$Mo${}_3$O${}_8$
• Selection rules and dynamic magnetoelectric effect of the spin waves in multiferroic BiFeO${}_3$
• Exceptional field dependence of antiferromagnetic magnons in LiFePO${}_4$