Determination of superposition model parameters required for analysis of the zero-field splitting parameters for Ni 2+ ions in NiO 6 complexes

Abstract

Superposition model (SPM) analysis of the zero-field splitting parameters (ZFSPs), in short SPM/ZFSP, enables correlation of crystallographic, spectroscopic, and magnetic data for transition ions with an orbitally non-degenerate ground state in crystals. SPM analysis of ZFSPs requires knowledge of the model parameters, i.e. the intrinsic parameters - b¯ <inf>k</inf> (R <inf>0</inf> ), power law exponents - t <inf>k</inf> , and the reference distance - R <inf>0</inf> . An extensive survey of literature has revealed that the model parameters for Ni 2+ (S = 1) ions are not available as yet. Hence, in this study we set for determination of the model parameters sets applicable for SPM/ZFSP analysis of Ni 2+ ions in the six-fold coordinated NiO <inf>6</inf> with axial symmetry. Our method utilizes the relationships between the intrinsic parameters b¯ <inf>k</inf> (R <inf>0</inf> ) and the experimental data for the uniaxial-stress parameters obtained for Ni 2+ ions in several crystals. The present results enable modeling of the ZFSP b <inf>2</inf> 0 = D for Ni 2+ (S = 1) ions, which hitherto has been hindered by the lack of suitable model parameters sets. Applications of SPM/ZFSP analysis are carried out for Ni 2+ ions doped into α-Al <inf>2</inf> O <inf>3</inf> (corundum), α-LiIO <inf>3</inf> , and LiNbO <inf>3</inf> , as well as the series of fluosilicate crystals with general formula: ABF <inf>6</inf> ·6R <inf>2</inf> O (A = Zn, Mg, Co, Ni, Fe, B = Si, Ti, Sn, BF <inf>4</inf> , R = H, D). These results will be utilized in studies of Ni 2+ -based systems suitable for pressure sensors in high-pressure electron magnetic resonance (EMR) measurements and spectroscopic properties of Ni 2+ ions in Haldane gap systems. © 2019 Elsevier B.V., All rights reserved.