ELECTRON-TRANSPORT IN AL65CU20CO15-XFEX QUASI-CRYSTALS

We have studied the electrical resistivity and magnetoresistance for t he system Al65Cu20Co15-xFex (0 less than or equal to x less than or eq ual to 15). The sample with x=0 could be indexed as the decagonal (D) phase, whereas the sample with x=15 forms the icosahedral (I) phase. T he sample with intermediate x (2.5 less than or equal to x less than o r equal to 12.5), however, consists of both phases. The temperature co efficient of the resistivity (TCR) is positive when x less than or equ al to 17.5. The magnitude of the TCR for these samples is smaller than for icosahedral alloys. However, the other samples exhibit a negative TCR except below 30 K. The magnetoresistance of the samples with pure I or D phase, exhibits an increase of over 1% in a field of 45 kOe. T he samples with intermediate x on the other hand, show relatively smal ler increases. These results have been analyzed qualitatively in the f ramework of existing models. (C) 1997 Elsevier Science S.A.