Low-temperature order in the heavy-fermion compoundCeCu6

Abstract

We have used nuclear-quadrupole-resonance (NQR) techniques to study Cu nuclei in two single-crystal samples of ${\mathrm{CeCu}}_6$ between 200 μK and 20 mK. We present measurements of the NQR intensities and spin-lattice relaxation times, ${\mathit{T}}_1$, at frequencies corresponding to three different sites in the crystal. Below 5 mK we observe deviations from standard metallic behavior in both signal intensity and spin-lattice relaxation times. These deviations are unusual in that they are site dependent; they reveal the presence of one or more types of order in this system.