Electronic structure of the quasi two-dimensional Mott system BaCo(1-x)Ni(x)Sa

By means of neutron powder diffraction on antiferromagnetic samples of BaCo1-xNixS2, the spin structure has been determined. The magnitudes of the ordered moments are similar to 2.9 mu(B) at 10 K for x = 0.0 and similar to 1.7 mu(B) at 100 K for x = 0.175. The results are not compatible with the electronic configuration (3d(3z)2(-r)2)(1+x), which was previously assumed to explain the physical behavior of the system. Instead, the configuration seems to be (3d(yz) or 3d(zx))(1)(3d(3z)2(-r)2)(1)(3d(x)2(-y)2)(1) in BaCoS2. Each Ni atom substituted for Co adds one electron to this system. Based on this basic picture of the electronic structure, various physical properties of BaCo1-xNixS2 ever published are discussed.