Evidence of nickel ions dimerization in NiWO${}_4$ and NiWO${}_4$-ZnWO${}_4$ solid solutions probed by EXAFS spectroscopy and reverse Monte Carlo simulations

Abstract

The existence of exchange-coupled Ni${}^{2+}$ ions -- the so-called magnetic dimers -- in wolframite-type NiWO${}_4$ and Zn${}_c$Ni${}_{1-c}$WO${}_4$ solid solutions with high nickel content was discovered by X-ray absorption spectroscopy combined with reverse Monte Carlo (RMC) simulations. Temperature- (10--300 K) and composition-dependent x-ray absorption spectra were measured at the Ni K-edge, Zn K-edge, and W L${}_3$-edge of microcrystalline NiWO${}_4$, Zn${}_c$Ni${}_{1-c}$WO${}_4$ and ZnWO${}_4$. Structural models were obtained from simultaneous analysis of the extended x-ray absorption fine structure (EXAFS) spectra at three metal absorption edges using RMC simulations. The obtained radial distribution functions for different atomic pairs made it possible to trace in detail the changes in the local environment of metal ions and the effect of thermal disorder. Dimerization of Ni${}^{2+}$ ions within quasi-one-dimensional zigzag chains of [NiO${}_6$] octahedra was evidenced in NiWO${}_4$ in the whole studied temperature range. It manifests itself as the splitting of the Ni-Ni radial distribution function into two separate peaks. The effect is further preserved in solid solutions Zn${}_c$Ni${}_{1-c}$WO${}_4$ for $c\le 0.6$, which is related to the probability to find two Ni${}^{2+}$ ions in neighboring positions.

References in corpus (2)

• Combined Raman scattering and ab initio investigation of pressure-induced structural phase transitions in the scintillator ZnWO4
• Lattice and spin dynamics in a low-symmetry antiferromagnet NiWO${}_4$

Cited by in corpus (3)

• Peculiarities of the local structure in new medium- and high-entropy, low-symmetry tungstates
• Chemical-state analyses of Ni, Zn, and W ions in NiWO${}_4$-ZnWO${}_4$ solid solutions by X-ray photoelectron spectroscopy
• Unraveling the interlayer and intralayer coupling in two-dimensional layered MoS${}_2$ by X-ray absorption spectroscopy and ab initio molecular dynamics simulations