Electronic properties of icosahedral, approximant, and amorphous phases of an Al-Cu-Fe alloy

Electronic properties of icosahedral (i) and rhombohedral (r) phases of Al63.5{Cu}24.5Fe₁₂ and amorphous (a) Al₆₃{Cu}₂₅Fe₁₂ are studied. While the electron transport of the a phase resemble those commonly seen in metallic glasses, this first comparison of an ordered i phase and its higher-order (3/2) approximant r phase reveals that the properties of the i and r phases, while quite similar to each other, are strikingly different from the a phase. In the i and r phases, large resistivities and resistivity ratios {ρ}(4.2 K)/{ρ}(295 K) and strong temperature dependences of the thermopower and Hall coefficient are observed, as well as a low electronic density of states. A magnetic state is observed in the a phase. The results are discussed in terms of the electronic structure of icosahedral crystals.