Researchers from the Materials Growth and Measurement Laboratory (MGML) have recently published two papers in Communications Materials (Nature Portfolio) supported by the GAČR Q-MAG project 25-15448S. Published within a short period of each other and featured in the Nature Collection “Condensed Matter Physics at High Pressure”, these studies highlight the power of combining single-crystal growth, advanced characterization, high-pressure experiments, X-ray diffraction, spectroscopy, and theoretical modelling to uncover the mechanisms governing magnetic phases in van der Waals materials.
These publications demonstrate how the combination of complementary expertise and experimental techniques enables fundamental advances in the understanding of pressure-tunable magnetism and structure–property relationships in van der Waals materials. They also highlight the key role of the collaboration between Charles University and the Institute of Physics of the Czech Academy of Sciences (FZU) in developing novel materials with tailored magnetic functionalities.
The first publication, “Opposite pressure effects on magnetic phase transitions in NiBr₂” (DOI: 10.1038/s43246-026-01138-5), reports an unexpected pressure dependence of the magnetic phases in the van der Waals multiferroic material NiBr₂. High-quality single crystals were prepared in MGML, where they were also structurally and magnetically characterized. High-pressure magnetization measurements revealed that hydrostatic pressure stabilizes the collinear antiferromagnetic phase while rapidly suppressing the helimagnetic state. Theoretical analysis shows that this behaviour originates from a pressure-induced enhancement of the interlayer exchange interaction, particularly the second-nearest interlayer coupling J₂′, which shifts the balance between interlayer and intralayer exchange interactions towards collinear antiferromagnetic order. The results explain why the helimagnetic phase in NiBr₂ is much more fragile than previously expected and reconcile the predicted pressure evolution in earlier theoretical works. (Fig. 1)
The second publication, “Pressure-induced structure transformation and collapse of ferromagnetism in van der Waals insulator” (DOI: 10.1038/s43246-026-01278-8), investigates the response of the layered ferromagnetic insulator CrBr₃ to hydrostatic pressure. The study reveals a pressure-induced structural transformation in CrBr₃ accompanied by a collapse of ferromagnetic order. Single-crystal X-ray diffraction uncovered the coexistence of rhombohedral and trigonal structural phases, which is well described by a paracrystal model. Increasing pressure drives the growth of the AA-stacked trigonal phase at the expense of the rhombohedral phase, leading to a progressive modification of interlayer magnetic interactions. Theoretical calculations and atomistic simulations show that the increasing contribution of antiferromagnetically coupled Cr moments in the AA stacking destabilizes the ferromagnetic ground state and promotes competing antiferromagnetic correlations. These results establish the microscopic link between stacking, interlayer exchange coupling, and magnetic order in the prototypical vdW ferromagnet CrBr₃. (Figs. 2 and 3)
