NMR-STUDIES IN ICF-SYSTEMS OF RECU2SI2 COMPOUNDS

The rare-earth compounds exhibiting the mixed valence or the interconfiguration fluctuation (ICF) behaviour have been investigated by a number of techniques. However, no NMR work has yet been reported in the literature which is aimed at studying the effects associated with the fluctuating electric fields which themselves arise from the fluctuating charges on the rare-earth atoms in these systems. The authors report the first magnetic resonance studies of these effects. The systems chosen for these investigations are the members of the series RECu2Si2 and RECu 2Ge2 (RE=rare earths) which belong to the ThCr 2Si2 structure in which copper atoms occupy sites with non-cubic symmetry. These studies show that in favourable circumstances the quadrupole interaction measurements provide an attractive and sensitive alternative to the Mossbauer measurements in those cases where the latter cannot be performed. In conclusion, it has been pointed out that through the spin-lattice relaxation measurements of copper isotopes (which are quadrupolar nuclei) and silicon nuclei (I=1/2), it may be possible to investigate the charge and the spin fluctuation times.