Insulator-like electrical transport in structurally ordered Al65Cu20+x Ru15−x (x =1.5, 1.0, 0.5, 0.0 and −0.5) icosahedral quasicrystals

Abstract: Low-temperature resistivities, in zero-field and 8T field, and magnetoresistance have been measured down to 1.4–300K for stable icosahedral quasicrystals Al65Cu20+x Ru15−x (x =1.5, 1.0, 0.5, 0.0 and −0.5). The analysis of the magnetoresistance data shows an overwhelming presence of anti weak-localization effect (τ so ∼10−12 s). But the sample with x =−0.5 shows anomalous magnetoresistance and the anti weak-localization effect breaks down (τ so to be 10−15 s). The in-field σ–T between 5K and 20K, for x =1.0, 0.5, 0.0 and −0.5 samples, and between 1.4K and 40K for x =1.5 sample, follow a power-law behavior with an exponent of 0.5 and above ∼30K the exponent ranges from 1.17 to 1.58. The observed power-laws basically characterize the presence of critical regime of the metal–insulator (MI) transition, dominated by electron–electron and electron–phonon inelastic scattering events respectively. In samples with x =1.0, 0.5, 0.0 and −0.5 the in field σ–T has been found to follow ln σ-vs-T 1/4 below 5K, which indicates the presence of variable range hopping. The observed transport features indicate the occurrence of proximity of metal–insulator transition in these Al–Cu–Ru quasicrystal samples. [Copyright &y& Elsevier]