We report the direct observation of strong coupling between magnons and phonons in a two-dimensional antiferromagnetic semiconductor ${\mathrm{FePS}}_3$, via magneto-Raman spectroscopy at magnetic fields up to 30 Tesla. A Raman-active magnon at $121{\mathrm{cm}}^{-1}$ is identified through Zeeman splitting in an applied magnetic field. At a field-driven resonance with a nearby phonon mode, a hybridized magnon-phonon quasiparticle is formed due to strong coupling between the two modes. We develop a microscopic model of the strong coupling in the two-dimensional magnetic lattice, which enables us to elucidate the nature of the emergent quasiparticle. Our polarized Raman results directly show that the magnons transfer their spin angular momentum to the phonons and generate phonon spin through the strong coupling.

Mechanical deformations and ensuing strain are routinely exploited to tune the band gap energy and to enhance the functionalities of two-dimensional crystals. In this Letter, we show that strain leads also to a strong modification of the exciton magnetic moment in ${\mathrm{WS}}_2$ monolayers. Zeeman-splitting measurements under magnetic fields up to 28.5 T were performed on single, one-layer-thick ${\mathrm{WS}}_2$ microbubbles. The strain of the bubbles causes a hybridization of $k$-space direct and indirect excitons resulting in a sizable decrease in the modulus of the $g$ factor of the ground-state exciton. These findings indicate that strain may have major effects on the way the valley number of excitons can be used to process binary information in two-dimensional crystals.

Antiferromagnetic systems with rich spin dynamics and pronounced interplay between magnetic and lattice degrees of freedom are of great interest in the emerging field of terahertz and subterahertz magnonics and spintronics. Here we report on spin and lattice dynamics of single crystals of ${\mathrm{Ni}}_2{\mathrm{NbBO}}_6$ studied with the use of polarized Raman spectroscopy in the temperature range of 10–300 K which includes the antiferromagnetic transition at $T_N=23.5$ K. Well-defined and highly polarized magnetic excitations were observed below and partly above $T_N$. Three magnetic modes at 30, 84, and 113 ${\mathrm{cm}}^{-1}$ (at $T=10$ K) were detected. The two high-energy magnetic excitations were identified as two-magnon modes. In total, 57 out of the expected 60 Raman-active phonons were registered and identified. Several modes revealed a nontrivial spin-phonon coupling manifesting either hardening or softening mostly below $T_N$. The possible magnetic space groups were determined through symmetry analysis. Spin-wave spectra and density of states were calculated within the linear spin-wave theory for supporting the experimental findings.

Lattice and magnetic dynamics of ${\mathrm{NiWO}}_4$ single crystals were studied with the use of polarized Raman spectroscopy in a wide temperature range of 10–300 K including the antiferromagnetic ordering temperature $T_N=62$ K. Static magnetic measurements were used for characterizing the single crystals. All Raman-active phonons predicted by the group theory were observed and characterized. Magnetic symmetry analysis was used to determine possible magnetic space groups for ${\mathrm{NiWO}}_4$ which can be also applied to any other isostructural crystal with the same magnetic propagation vector $\mathbf{k}=(1/2,0,0)$. Although the magnetic structure of ${\mathrm{NiWO}}_4$ is relatively simple, a rich set of narrow and broad magnetic excitations with different polarization properties and temperature behavior in the very broad frequency range of 10–200 ${\mathrm{cm}}^{-1}$ was observed, with some modes surviving at temperatures much higher than $T_N$ up to 220 K. Part of the magnetic excitations were identified as acoustic and optical spin-wave branches which allowed us to construct exchange structure and estimate exchange and anisotropy constants with the use of linear spin-wave theory.

Nickel orthoborate $\mathrm{N}{\mathrm{i}}_3{\left(\mathrm{B}{\mathrm{O}}_3\right)}_2$ having a complex orthorhombic structure Pnnm (No. 58, $Z=2$) of the kotoite type is known for quite a long time as an antiferromagnetic material below $T_{\mathrm{N}}=46\mathrm{K}$, but up to now its physical properties including the lattice dynamics have not been explored. Six $\left[\mathrm{Ni}{\mathrm{O}}_6\right]$ units of $2a$ and $4f$ types are linked via rigid $\left[\mathrm{B}{\mathrm{O}}_3\right]$ groups and these structural particularities impose restrictions on the lattice dynamics and spin-phonon interactions. We performed the symmetry analysis of the phonon modes at the center of the Brillouin zone. The structural parameters and phonon modes were calculated using the dmol3 program. We report and analyze results of infrared and Raman studies of phonon spectra measured in all required polarizations. Most of the even and odd phonons predicted on the basis of the symmetry analysis and theoretical calculations were reliably identified in the measured spectra. Clear evidence of the spin-phonon interaction was found for some particular phonons below $T_{\mathrm{N}}$. An unexpected emergence of several very narrow and weak phonon lines was observed in the infrared absorption spectra exactly at the magnetic ordering temperature $T_{\mathrm{N}}$. Moreover, anomalous behavior was found for some Raman phonons. The emergence of new phonon modes in the infrared and Raman spectra exactly at $T_{\mathrm{N}}$ proves the existence of a magnetostructural phase transition of a new type in $\mathrm{N}{\mathrm{i}}_3{\left(\mathrm{B}{\mathrm{O}}_3\right)}_2$. A possible nature of this transition is discussed.