NMR Investigation of Energy Gap Formation in the Valence Fluctuating Compound CeNiSn

Abstract

119 Sn NMR study has been made in a gap-type valence fluctuating compound CeNiSn. From the measurements of Knight shift and the nuclear spin lattice relaxation time T 1 of 119 Sn, it is proved that no magnetic ordering occurs down to 0.38 K. The relaxation rate, 1/ T 1 markedly decreases below 30 K down to 0.40 K. This behavior can be well interpreted by a quasiparticle band model which possesses a band width of 140 K and a low energy excitation inside an energy gap of 14 K at the Fermi level. Then it is clarified from the microscopic point of view that the pseudo-gap formed at the Fermi level has a character that the quasiparticle density of state is linearly proportional to the energy near the Fermi level at low temperatures.