Electrical Properties of Zn-Mg-RE (RE=Y, Gd) Icosahedral Quasicrystals

The electrical resistivity and the magnetoresistance have been measured for icosahedral phases of Zn-Mg-RE (RE=Y, Gd). Electrical resistivities of bulk samples of Zn₅₆Mg₃₆Y₈, annealed ribbon samples of Zn₆₂Mg₃₀Y₈ and annealed ribbon samples of Zn₅₅Mg_35.5Gd_9.5 are 1 mΩcm, 0.3mΩcm and 0.3 mΩcm, respectively. The resistivities of all the samples decrease by 5 - 7% from 4.2 K to 273 K. At low temperatures, the conductivity of Zn-Mg-Y obeys T^1/2 dependence, while the resistivity of Zn-Mg-Gd obeys In T dependence, where Gd atoms bear magnetic moments. In Zn-Mg-Y, the magnetoresistance is negative and insensitive to temperature, while in Zn-Mg-Gd it is positive in a low field range and becomes negative at high field with its magnitude larger at lower temperature. These results are interpreted by the theories of electron-electron interaction, weak localization and s-d exchange interaction.