The two-dimensional van der Waals (vdW) magnets retaining magnetic order in atomically thin limit demonstrate challenging physical phenomena and they are considered as prospective building blocks for construction of advanced spintronics and nanoelectronics devices. Here, we present experimental evidence for negative thermal expansion of lattice volume and vdW layers and strong spin–phonon coupling effects, caused by formation of the long-range ferromagnetic order in the vdW material CrBr₃. The neutron and X-ray diffraction measurements revealed anomalous temperature variation of lattice parameters and interatomic distances and angles in the vicinity of Curie temperature (T_C). A pronounced rise of the frequencies of the most of the observed vibrational modes and unusual reversal broadening of their full widths at half maximum below T_C was found from Raman spectroscopy measurements.

The crystal and magnetic structures of van der Waals layered ferromagnet Cr${\mathrm{Br}}_3$ were studied using X-ray powder diffraction and neutron powder diffraction at pressures up to 23 GPa at ambient temperature and up to 2.8 GPa in the temperature range 6–300 K, respectively. The vibration spectra of Cr${\mathrm{Br}}_3$ were studied using Raman spectroscopy at pressures up to 23 GPa at ambient temperature. The anomalous pressure behavior of structural parameters and vibrational modes was observed, associated with a gradual isostructural phase transition in the pressure range 2.5–7 GPa. The Curie temperature T_C reduced rapidly with a pressure coefficient $d{T}_C/dP=-4.1\left(4\right)$ K/GPa. A full suppression of the ferromagnetic state was expected at P_C~8.4 GPa, where onset of the antiferromagnetic spin arrangement or magnetically disordered state may take place. Anomalies in Raman spectra at P~15 GPa point to another possible phase transformation in Cr${\mathrm{Br}}_3$, which may be related to the proximity of metallization of this van der Waals ferromagnet.

The crystal structure, vibrational spectra, and magnetic structure of quasi-two-dimensional layered van der Waals material ${\mathrm{MnPS}}_3$ were studied using x-ray diffraction and Raman spectroscopy at high pressures up to 28 GPa, and neutron diffraction up to 3.6 GPa, respectively. A structural phase transition between two monoclinic modifications of the same $C2/m$ symmetry was observed, evolving gradually in the pressure range of about 1–6 GPa. The transition is accompanied by abrupt shortening of lattice parameters, significant reduction of the monoclinic distortion, and anomalies in the pressure behavior of several Raman-mode frequencies. No more structural phase transitions were revealed in the studied pressure range. The antiferromagnetic (AFM) state with a propagation vector $k$ = (0, 0, 0) remains stable in ambient pressure and high-pressure structural phases of ${\mathrm{MnPS}}_3$ at least up to 3.6 GPa. The Néel temperature increases noticeably with a pressure coefficient of $d{T}_{\mathrm{N}}/dP=6.7$ K/GPa, leading to modification of the dominant first-neighbor magnetic interaction exchange parameter with a relevant coefficient ${dJ}_1/dP\approx -0.6$ meV/GPa. This observation is in contrast to the pressure behavior of ${\mathrm{FePS}}_3$, demonstrating modification of the AFM state from 2D-like to 3D-like at the similar pressure-induced structural phase transition. The different pressure response of the magnetic states of ${\mathrm{MnPS}}_3$ and ${\mathrm{FePS}}_3$ is analyzed in terms of competing in-plane and interplane magnetic interactions.

The rock fabric of two lamprophyre dike samples from the Koy-Tash granitoid intrusion (Koy-Tash, Jizzakh region, Uzbekistan) has been studied, using the neutron tomography method. We have performed virtual segmentation of the reconstructed 3D model of the tabular igneous intrusion and the corresponding determination of dike margins orientation. Spatial distributions of inclusions in the dike volume, as well as further analysis of size distributions and shape orientations of inclusions, have been obtained. The observed shape preferred orientations of inclusions as evidence of the magma flow-related fabric. The obtained structural data have been discussed in the frame of the models of rigid particle motion and the straining of vesicles in a moving viscous fluid.