Structure and Magnetic Properties of Ni₄V₃O₁₀, an Antiferromagnet with Three Types of Vanadium−Oxygen Polyhedra

The compound Ni₄V₃O₁₀ forms a new structure type in the tetragonal space group P4/n. The material can be produced using solid-state synthesis in a narrow temperature range, and the structure was confirmed using X-ray and neutron powder diffraction data. The phase contains occupationally disordered Ni/V in regular-octahedral sites and V in tetrahedral and vanadyl-octahedral sites. Bond valence and neutron/X-ray co-refinement data are compatible with three vanadium oxidation states (V³⁺, V⁴⁺, V⁵⁺) existing in the material, which would make it distinct in the Ni−V−O system and would place it in a small class of oxides with transition metals exhibiting three oxidation states. With a Neél temperature of 38 K and a Curie−Weiss parameter θ = −234 K, it displays frustrated antiferromagnetism evidenced by a broad hump in the heat capacity below T_N. The structure has a percolating distorted rock-salt-like network, leading to strong superexchange, but vanadyl-octahedral linkages frustrate magnetic ordering. The magnetic structure is assumed to be incommensurate, as simple propagation vectors can be ruled out by powder neutron diffraction.