NiNbWTiO: Stabilization of the I-Type NiNbO Structure and First Magnetic Study of This Corundum-like Compound.

For the first time, we report on the structural and magnetic properties of a polycrystalline sample of NiNbO from I-type (2), obtained by the partial cosubstitution of Nb by Ti and W. The crystal structure is investigated by combining synchrotron X-ray, neutron, and electron diffraction at room temperature. This I-type structure is derived from the corundum-like NiNbO II-type () and is noncentrosymmetric and polar. The Ni-lattice is composed of the stacking of distorted honeycomb layers with double zigzag ribbons 60° disoriented from each other in two successive double layers. The connection between layers is ensured by the sharing of octahedra faces building (Nb,W,Ti)O, NiO, and NiO units. This study shows how the disruption of the NbO units by smaller d cations impacts the structure, significantly modifying the Ni network and, thus, the magnetic properties. The latter were studied by dc- and ac-magnetic susceptibility, and the magnetic structure was solved by neutron powder diffraction. A ferrimagnetic behavior occurs below 68 K, followed by a re-entrant spin-glass-like behavior below ≈50 K.