Structure Of NiS Research Articles

Fourth Order Interaction Effects on the Antiferromagnetic Structures. II. A Phenomenological Model for NiS2

Possible fourth order interactions among localized spins in an orbital-degenerate case ( S >1/2) are discussed as an expansion from the Mott insulator limit, with reference to a model for the electronic structure of NiS 2 . Then a phenomenological model to study the antiferromagnetic structure of NiS 2 is presented.

Fourth Order Spin Interactions and the Antiferromagnetic Structure of NiS2

Fourth Order Spin Interactions and the Antiferromagnetic Structure of NiS<SUB>2</SUB>

Band Structure of NiS as Calculated Using a Simplified Linear-Combination-of-Muffin-Tin-Orbitals Method

Hexagonal NiS undergoes a first-order metal-to-nonmetal transition as the temperature is lowered below 264 K. NiS appears to be a normal Pauli-paramagnetic $d$-band metal above the transition temperature ${T}_{t}$, while below ${T}_{t}$ it is antiferromagnetic (moment $\ensuremath{\sim}1.7{\ensuremath{\mu}}_{B}$) and either metallic or semimetallic. By use of a simplified (linear-combination-of-muffin-tin-orbitals) method that no longer requires a secular equation to be calculated as a function of energy, the band structure for NiS is calculated. These results indicate that the S $p$ bands overlap the bottom of the $d$ bands as hypothesized by White and Mott. It appears that this overlap increases with temperature, as a result of lattice vibrations which are included in the calculation through a Debye-Waller factor. We suggest a Mott-Hubbard transition occurs for a critical electron-phonon coupling which may be associated with a critical temperature.

On the density of states of NiS

The valence band structure of NiS, obtained by X-ray photoelectron spectroscopy, exhibits a relatively narrow nickel 3d band overlapping the sulphur 3p band. This result supports the conjecture that metallic NiS is a d-electron conductor because the Coulomb correlation energy is reduced by p-electron screening.