NMR evidence for the partially gapped state in CeOs(2)Al(10)

Abstract

We report the results of a (27)Al nuclear magnetic resonance (NMR) study of CeOs(2)Al(10) at temperatures between 4 and 300 K. This material has been of current interest due to indications of hybridization gap behavior below the transition temperature T(o)similar or equal to 29 K. Five (27)Al NMR resonance lines that are associated with five nonequivalent crystallographic aluminum sites have been resolved. For each individual aluminum site, the low-temperature NMR Knight shift goes over a thermally activated response. The temperature-dependent spin-lattice-relaxation rate exhibits a rapid drop below T(o), indicative of the formation of an energy gap in this material. We interpret the Knight shift and the relaxation-rate data in light of the presence of a pseudogap with residual electronic density of states at the Fermi level. Moreover, the magnitude of the pseudogap of 120 K is extracted from NMR results, in agreement with the value obtained from the inelastic neutron-scattering experiment.