Investigation of structural changes in chiral magnet Cr_1/3NbS₂ under application of pressure

We perform structural analysis experiments on the chiral magnet Cr_1/3NbS₂, in which Cr³⁺ ions are inserted between hexagonal NbS₂ layers. The noncentrosymmetrical nature of the inserted Cr³⁺ appears as a distorted CrS₆ octahedron. Under the application of hydrostatic pressure, the lattice shrinks significantly along the c-axis rather than the a-axis. However, at a pressure P of approximately 3-4 GPa, a kink in the rate of decrease in the lattice parameters is observed, and the slight movement of a Nb atom along the c-axis brings about a decrease in the distortion of the CrS₆ octahedron. This structural change qualitatively suggests a decrease in the strength of the Dzyaloshinskii-Moriya (D-M) interaction. Under hydrostatic pressure, the magnetic ordering temperature T_C decreases, and dT_C/dP exhibits a slight change at around 3 GPa. A series of experiments indicates that the change in the structural symmetry of the CrS₆ octahedron influences the exchange network between Cr³⁺ ions as well as the D-M interaction.