Temperature-dependent NMR features of the ${\mathrm{Al}}_{65}$${\mathrm{Cu}}_{20}$${\mathrm{Ru}}_{15}$ icosahedral alloy

The ${\mathrm{Al}}_{65}$ ${\mathrm{Cu}}_{20}$ ${\mathrm{Ru}}_{15}$ icosahedral alloy was studied by ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ nuclear magnetic resonance from 150 to 1110 K. The Knight shift of the unresolved resonance line was observed to significantly increase above 500 K. This uncommon temperature dependence of the Knight shift is interpreted in terms of the presence of a pseudogap at the Fermi level. The spin-lattice relaxation rate deviates from the linear temperature dependence of Korringa relaxation below 500 K, and above 500 K it is dominated by a thermally activated process with a small activation energy of 0.48 eV. This energy is distinctly different from the activation energy observed in simple metallic alloys.