NUCLEAR MOMENTS AND HYPERFINE STRUCTURE ANOMALY FOR GADOLINIUM

The technique of ENDOR has been used on the isotopes 155Gd and 157Gd in Gd3+ in CeO2 single crystals in order to obtain accurate values of the nuclear magnetic moments and the hyperfine structure parameters. The values obtained are given below. 155Gd 157Gd 155Gd/157Gd A(kHz) +12048(3) +15809(5) 0·7621(5) μn(nm) -0·2567(6) -0·3363(12) 0·7633(45) From the numbers in the last column, which we call R(A) and R(g) respectively, one can calculate a hyperfine structure anomaly Δ whose accuracy is limited primarily by that of R(g). It is shown that a more accurate value of R(g) = 0·76252(17) may be derived from the atomic beam work of Unsworth. This accurate value leads to a hyperfine structure anomaly of Δ = (+0·05±0·09)%. From a knowledge of the fraction of the hyperfine interaction which is contributed by s electrons one can derive that the hyperfine structure anomaly which would be exhibited by a single unpaired s electron is Δs = (+0·07±0·12)%. Discrepancies between these values and those indicated by other data are discussed. Discrepancies with optical determinations are shown to be probably not significant; those with determinations using nuclear magnetic resonance in magnetically ordered material are significant, but are not understood.