ELECTRONIC-PROPERTIES OF ICOSAHEDRAL, APPROXIMANT, AND AMORPHOUS PHASES OF AN AL-CU-FE ALLOY

Electronic properties of icosahedral (i) and rhombohedral (r) phases of Al63.5Cu24.5Fe12 and amorphous (a) Al63 Cu25Fe12 are studied. While the electron transport properties 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 p(4.2 K)/p(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 electornic structure of icosahedral crystals.