NMR study of the electronic state in the dense Kondo compoundCeNiAl4

Abstract

${}^{27}\mathrm{Al}$ NMR results are presented for a dense Kondo system ${\mathrm{CeNiAl}}_{4}$ in the temperature range 3--300 K. The Knight shift ${K}_{\mathrm{iso}}$ and the spin-lattice relaxation rate ${T}_{1}^{\ensuremath{-}1}$ exhibit a nonmagnetic behavior associated with a very low conduction electron density of states near the Fermi level. Both of them also reveal an insignificant role of $4f$ electrons in RKKY interactions in the range 50--300 K. However, below 50 K, $4f$ electrons participate in the excitation near the Fermi level and their extent of delocalization changes gradually down to 3 K. This is a consequence of a non-Fermi-liquid state below 50 K and contradicts the prediction of the existence of the heavy fermion state at low temperature from bulk measurements. Thus the present result gives a clear indication of the appearance of 4$f$ moment compensation due to the predominance of the Kondo effect over RKKY interaction.