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

摘要

The dependences of the EPR parameters on the local distortion parameters Delta theta and Delta R as well as the crystal-field parameters have been studied by diagonalizing the 364 x 364 complete energy matrices for a tetragonal Er3+ centre in the YVO4 and ScVO4 crystals. The results show that the local distortion angle Delta theta and the fourth-order crystal-field parameter (A) over bar (4) are most sensitive to the EPR g-factors g(parallel to) and g(perpendicular to), whereas the local distortion length Delta R and the second-order parameter (A) over bar (2) 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. (C) 2015 Elsevier B.V. All rights reserved.