²⁷Al-NQR/NMR Study of Kondo Semiconductor CeFe₂Al₁₀

Abstract

27 Al-NQR/NMR measurements have been performed on CeFe 2 Al 10 in relevance to the novel phase below T 0 =27 K of isostructural CeRu 2 Al 10 . NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin–lattice relaxation rate 1/ T 1 above about 20 K, following the Korringa law ( T 1 T = const.) below 20 K, indicates a pseudogap opening near the Fermi level. The gap magnitude of 70 K with a mid-gap state of 42% is estimated based on a rectangular density of states. The gap magnitude is much larger than the gap of 15 K evaluated previously from the electrical resistivity, which suggests CeFe 2 Al 10 to be a Kondo semiconductor with a Kondo temperature much higher than 300 K.