The influence of local structure and intrinsic crystal-field on the EPR parameters for Nd3+ ions in Bi4Ge3O12 crystal

Abstract The dependencies of EPR g-factors on the local structural parameter and intrinsic crystal-field parameters for a 4f3 configuration ion Nd3+ in Bi4Ge3O12 crystal have been studied by diagonalising 364×364 complete energy matrices. The results indicate that the local structure of (NdO6)9- cluster exhibits an oblate distortion in Bi4Ge3O12 crystal, where the ligand ions O2- undergo an outward departure (Δθ1≈0.92°, Δθ2≈1.27°) away from the C3 axis. An inflexion with six-order intrinsic parameter Ā6≈10 cm-1 was found that may well account for previous abnormal g-factors evaluation. Furthermore, our studies show that a stronger covalence between the ligand ions O2- and the central Nd3+ ions may exist in the (NdO6)9- cluster. Also, the high-order mixing effects on EPR parameters have been evaluated. It is shown that the dominant high-order contribution to EPR g-factors is from the J-J mixture between the terms 4I9/2 and 2H9/2, which accounts for about 3.3%.