Low-temperature thermal properties of icosahedral Al-Re-Pd

Abstract

We report measurements of the thermal conductivity λ(T) and the specific heat Cp(T) of icosahedral Al70Re8.6Pd21.4 at low temperatures. Below 1 K, the behaviour of the quasilattice thermal conductivity λph(T) is compatible with the scattering of vibrational excitations involving tunnelling states and grain boundaries. The specific heat Cp(T) contains a small linear contribution γT. Our λph(T) results indicate that a substantial part of γT may be attributed to the excitations of tunnelling states. Below 0.4 K Cp(T) increases with decreasing T and at the lowest temperatures it varies as T−2, suggestive of an interaction of the quadrupolar moments of 185Re and 187Re nuclei with the gradient of electric fields induced by their neighbours.