LOCALIZED MAGNETIC-MOMENTS AND SPIN FREEZING IN AL-BASED AMORPHOUS, QUASI-CRYSTALLINE AND CRYSTALLINE APPROXIMANT PHASES

Al-based amorphous and quasicrystalline alloys have been prepared by high-rate sputtering and melt-quenching, respectively. The Al67Cu20Mn13 crystalline approximant phase also has been made by annealing the quasicrystalline counterpart. The formation of the localized magnetic moments of 3d metals in the Al matrix is difficult except for Mn. The ratio of the magnetic Mn atoms estimated from the saturation magnetization and the Curie constant in the quasicrystalline phase is smaller than that in the amorphous phase. In the crystalline approximant phase, the ratio is comparable to that in the amorphous phase, but the average magnetic moment of magnetic Mn atoms is much smaller than that in the amorphous and quasicrystalline phases. The ratio of magnetic Mn atoms and their average magnetic moments are significantly affected by other solute atoms. The spin glass behavior has been confirmed in the three alloy systems; Al100-xMnx, Al80-xCu20Mnx and Al85-xPd15Mnx, in both amorphous and quasicrystalline phases. The spin freezing in the latter two alloy systems occurs in a more dilute concentration range than that in the Al100-xMnx alloy system. The magnetization of the Al80-xCu20Mn. and Al85-xPd15Mnx alloy systems in the amorphous state is larger than in the quasicrystalline state and the spin freezing temperature in the former state is higher than that in the latter one. From these results, it is concluded that the magnetic properties of Al-base alloys are quite sensitive to the kind of solute atoms and the phase structure.