Intercalation Induced Structural Transition and Magnetic Properties in NixNbS₂

We report the effect of Ni intercalation on the structure and magnetic properties of Ni x NbS 2 . Pristine NbS 2 crystallizes in the rhombohedral 3R phase, which undergoes a structural transition to a mixture of hexagonal (2H) and rhombohedral (3R) phases with Ni intercalation in the range of 0 < x < 0.15 and finally to pure 2H phase in the range of 0.15 ≤ x ≤ 0.25. Further Ni intercalation in NbS 2 , in the range of 0.33 ≤ x ≤ 0.4, the 2H phase transforms to an ordered superstructure (Space Group: P 6 3 22) with lattice parameters of √3 a o × √3 a o × 1 c o . Raman studies shows Ni–S stretching vibration peak at 492.3 cm −1 suggesting strong bonding of Ni with the host NbS 2 lattice. XPS studies further confirm the charge transfer from Nb to Ni in the Ni intercalated compounds. Theoretical studies show that the 3R phase has lower total energy for pristine NbS 2 while for the intercalated compound, Ni 0.25 NbS 2 , the 2H phase has lower total energy. Magnetic properties study shows a distinct antiferromagnetic transition at 78 K for Ni 0.33 NbS 2 , and a kink at 30 K for Ni 0.25 NbS 2 suggesting a weak ordering, while no magnetic ordering is observed for Ni 0.15 NbS 2 .