Electric and magnetic properties of Al65Cu20(Fe1-xMnx)15 quasi-crystals with x=0.0, 0.2, 0.4 and 0.6

Abstract

The authors have prepared the alloys Al65Cu20(Fe1-xMnx)15 with x=0.0, 0.2, 0.4 and 0.6 by the liquid-quenching method. The alloys with x=0.0 and 0.6 are examined by the transmission electron microscopy. Their electron diffraction patterns demonstrate fivefold, threefold and twofold symmetries of the typical icosahedral symmetries of quasi-crystals. The X-ray diffraction patterns of the samples with x=0.0, 0.2, 0.4 and 0.6 can be indexed with six independent Miller indices of the icosahedral structure of quasi-crystals. Thus they can determine the quasi-lattice constant, which was found to increase with increase in the manganese concentration. The differential thermal analysis measurements show that the icosahedral quasi-crystals Al65Cu20(Fe1-xMnx)15 with x=0.0, 0.2, 0.4 and 0.6 are in thermodynamically good stable phases. The room-temperature resistivity of the samples are in the range 15.47-30.93 mu Omega m, which increases with increase in the manganese concentration. The very high resistivities may be caused by the high density of distorted icosahedral structure defects and the possible s-d resonant scattering. The inversed susceptibility versus temperature for x=0.4 and 0.6 can fit the Curie-Weiss formula. The local magnetic moments are 1.64 mu B and 1.27 mu B per Mn atom for samples with x=0.4 and 0.6, respectively. In contrast the samples with x=0.0 and 0.2 do not display a Curie-Weiss-like behaviour.