TRANSFERRED HYPERFINE INTERACTION AND ZERO-FIELD SPLITTING OF THE GD3+ ION IN KY3F10

We have investigated the E.P.R. spectra of Gd3+ in KY3F10 single cryst al. Gd3+ substitutes for Y3+ in an eight-fold fluorine coordinated sit e forming an antiprism (GdF8)(5-). We have determined the fine structu re and transferred hyperfine structure spin hamiltonian parameters. Th e former are discussed by using the superposition model of Newman and we compare our values with previous ones obtained for Gd3+ center in o ther host crystals as in LiYF4 and ReF3 (Re=La, Ce, Pr, Nd) which allo ws us to propose intrinsic parameters for eightfold fluorine coordinat ed Gd3+. The latter indicate some spin polarisation effect of the Gd3 5s and 5p shells due to inner unpaired 4f(7) electrons.