2009 年 78 巻 12 号 p. 123713
The 27Al-NQR/NMR measurements of CeRu2Al10 were carried out to clarify the unusual phase transition at T0=27 K. Distinct NQR peaks associated with five nonequivalent Al sites have been observed at T>T0, and each peak is successfully assigned to their respective Al sites. Below the transition temperature T<T0, each peak simply splits into two peaks except for one site. This indicates that the phase transition is not accompanied by magnetic order, but is presumably associated with the onset of structural transition with lowering symmetry. The nuclear spin–lattice relaxation rate 1⁄T1 suggests a local moment picture above T*∼60 K, and the development of Kondo coherence toward T0. Below T0, 1⁄T1 shows a gaplike decrease with a gap magnitude of 106 K, being consistent with the macroscopic measurements. The Korringa term below 10 K after the gaplike decrease suggests a gap opening over a portion of the Fermi surface.