Magnetoresistance of highly resistive AlPdRe quasicrystals

The temperature dependence of the conductivity, σ(T), and the magnetoresistance (MR), Δρ(B)/ρ, have been studied from below 0.05–300 K for two i-AlPdRe samples on the insulating side of the metal insulator transition. The temperature dependence of resistivity and MR show that there is a definite change in transport mechanism below 20 K. The MR is positive below 1 K. At intermediate temperatures a negative component develops and at temperatures above ∼40 K the MR is small. The magnetoresistance results are discussed in the framework of Efros–Shklovsksii (ES) variable range hopping. With decreasing temperature the characteristic field regions that describe ES hopping are successively depressed towards smaller magnetic fields and vanish. These results support an insulating ground state in samples with large resistance ratios.