Magnetoelastic coupling in single crystal MIT compound NiS

Nickel sulphide (NiS) is an important electronic material that has been used as interconnects and in nanoelectronics devices. In a recent work focusing on doped-NiS, it was found that structural changes play a critical role in driving the metal-insulator transition (MIT). This intriguing finding motivates for exploration of possible magnetoelastic coupling effect as a driving force for the MIT. The X-ray diffraction result on our synthesized NiS single crystal, reveals a hexagonal structure with lattice parameters of a=b=3.443(2) Å, c=5.350(3) Å at room temperature. Neutron scattering study of NiS reveals a magnetic peak at structural non-allowed position (001) was observed below ~ T = 250 K, indicating the onset of the AFM order. Further detailed peak scans at (100), (101), (002) reveal a change of the crystal structure right below the magnetic transition temperature at T ~ 220 - 240 K. The strong correlation between the magnetic and structural transition temperature implies the presence of possible magnetoelastic coupling effect, which could be closely related to the MIT. Given the technological importance of NiS, the study will shed light on the mechanism of MIT as well as establish a new paradigm for the exploration of AFM order in non-heavy electron metallic system.