Production of Quasicrystalline Alloys, Their Structures and Physical Properties

本研究的目的是制备高质量的准晶合金，并研究准晶的物理性能特征。(1)高质量准晶的制备(A)Al-Mn基合金：我们首次确定了熔体淬火产生单一准晶相的Al-Mn双晶合金的成分范围。明确了Al-Mn-Si三元系准晶相的组成区域，并进一步尝试用14种过渡元素替代Mn来提高准晶相的质量。因此，对于Al-Ru-Mn-Si等四元系，我们成功地获得了高质量和非常稳定的准晶相。(B)简单金属系统：我们还测定了Mg-Al-Zn三元系的单准晶相的组成区域。我们还制备了Al-Li-Cu合金的大颗粒准晶。(2)准晶的电阻率我们测量了产生的单相准晶合金的电阻率和磁化率。Al-Mn系的电阻率高达1m cm量级，且具有负的温度系数。在50K以下，我们观察到了一个反常的电阻率增大，其大小与Mn的局域磁矩密切相关。在-logT相关区域，磁阻为负值，与近藤效应相反。用准晶态电子的临界态初步解释了这种电阻反常现象。对简单金属准晶，如镁铝锌和铝锂铜的系统测量正在进行中。

The purpose of the research in to produce high-quality quasicrystalline alloys and to investigate physical properties characteristic of quasicrystals.(1) Production of high-quality quasicrystals (a) Al-Mn based alloys: We have first determined the composition range of Al-Mn bianry alloys in which single-quasicrystalline phase is produced by melt-quenching. Then we have clarified the composition region of the quasicrystalline phase for ternary Al-Mn-Si system and further tried to improve the quality by subsitution of 14 transition elements for Mn. As a result, we have succeed in obtaining excellent-quality and very stable quasicrystalline phase for some quaternary systems such as Al-Ru-Mn-Si. (b) Simple Metal systems: We have also determined the composition region of single-quasicrystalline phase for the ternary Mg-Al-Zn systems. We have also produced large grain quasicrystals of Al-Li-Cu alloy.(2) Electrical resistivities of quasicrystals We have measured the electrical resistivity and the magnetic susceptivility for the produced single-phase quasicrystalline alloys. the resistivities of Al-Mn systems are as high as the order of 1 m cm and have a negative temperature coefficent. Below about 50K, we observed an anomalous resistivity increase, the amount of which has been found to be closely related to the localized magnetic moment of Mn. The magneto-resistance is negative in the -logT-dependent region, in contradictory with the Kondo effect. This resisitivity anomaly has been tentatively interpreted by the critical state of electrons in the quasicrystalline state. Systematic measurements for simple-metal quasicrystals such as Mg-Al-Zn and Al-Li-Cu are in progress.