Synthesis and structural and magnetic properties of the NaNiFe$_{2}$(VO$_{4}$)$_{3}$ compound

A new magnetic compound NaNiFe$_{2}$(VO$_{4}$)$_{3}$ has been obtained by the solid-phase synthesis and studied by X-ray diffractometry, nuclear gamma resonance, and magnetometry. The crystal structure of multicomponent vanadate is described by a triclinic symmetry space group $P1$. The unit cell contains six nonequivalent mixed cationic positions occupied by different-valence ions of transition metals, iron Fe$^{3+}$ and nickel Ni$^{2+}$, which facilitates the implementation of a state with the local charge neutrality violation. In addition, two types of iron atom sites have been found, which have an oxygen environment in the form of octahedra and square pyramids with their nonequiprobable population by iron and nickel. The temperature and field dependences of the magnetization have been found to be typical of a paramagnet containing ferromagnetic clusters in a wide temperature range.