EPR parameters and local geometry for Cr 3+ and V 2+ ions in HfS 2 crystals

Abstract

From the high-order perturbation formulas of EPR parameters (zero-field splitting D, g factors g ∥, g ⊥ and hyperfine structure constants A ∥, A ⊥) based on the two spin–orbit coupling parameter model for 3d 3 ions in trigonal symmetry, the EPR parameters of Cr 3+ and V 2+ ions in HfS 2 crystals are calculated. From the calculations, it is found that the local trigonal distortion angle θ of impurity center in HfS 2:Cr 3+ is smaller than that in HfS 2:V 2+. The dominant cause of the small zero-field splitting | D| and g-anisotropy |Δ g| = | g ∥ − g ⊥| in HfS 2:Cr 3+ (compound to HfS 2:V 2+) is due to the small local trigonal distortion angle θ rather than to the small impurity-ligand distance R in HfS 2:Cr 3+.