Theoretical studies of the dependence of EPR parameters on local structure for the tetragonal Er3+ centres in YVO4 and ScVO4

• The complete energy matrix is used in the studies of EPR spectra for the Er3+ ion.
• The abnormal EPR g-factors for the Er3+ ion in the ScVO4 are well explained.
• The dependence of g-factors on the local structural parameters is characterized.
• The dependence of EPR g-factors on the covalent bonding effect is studied.
• The contribution of J–J mixing effects to g-factors is quantitatively evaluated.

The dependences of the EPR parameters on the local distortion parameters Δθ and ΔR as well as the crystal-field parameters have been studied by diagonalizing the 364 × 364 complete energy matrices for a tetragonal Er3+ centre in the YVO4 and ScVO4 crystals. The results show that the local distortion angle Δθ and the fourth-order crystal-field parameter Ā4 are most sensitive to the EPR g-factors g// and g⊥, whereas the local distortion length ΔR and the second-order parameter Ā2 are less sensitive to the g-factors. Furthermore, we found that the abnormal EPR g-factors for the Er3+ ion in the ScVO4 may be ascribed to the stronger nephelauxetic effect and covalent bonding effect, as a result of an expanded local distortion for the Er3+ centre in the ScVO4 crystal. Simultaneously, the contributions of the J–J mixing effects from the terms of excited states to the EPR parameters have been evaluated quantitatively.

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