Studies on controle method of structural and physical properties of quasicrystals

为了阐明准晶的物理性质，我们对准晶的结构以及准晶的结构完备性与磁化率、电阻率、磁阻等物理性质之间的关系进行了细致的研究。为此选择了Al-Pd-Mn和Zn-Mg-Ho准晶，这两种准晶都属于所谓的“理想准晶”群。对于Al-Pd-Mn，发现在高温下稳定的F型二十面体准晶在约750℃以下变得不稳定，并在合金成分Al71Pd21Mn8处转变为复杂的调制准晶。在锌-镁-Ho二十面体准晶上，发现F型化学有序度取决于合金成分，只有在合金成分附近才能实现高有序状态。此外，随着退火温度的升高，X射线衍射谱中的超晶格反射强度降低。实验表明，强度的减小与电阻率和磁阻行为的变化有关。这一结果开辟了通过改变化学有序性和准周期性的完善程度来控制准晶物理性质的新方法。

In order to clarify physical properties of a quasicrystal, we have carried out careful investigation of quasicrystal structure and the relation between the structural perfection of quasicrystals and the physical properties such as magnetic susceptibility, electrical resistivity and magneto resistance. The Al-Pd-Mn and Zn-Mg-Ho quasicrystals were selected for this purpose, both of which belong to so-called "ideal quasicrystal" group. With respect to the Al-Pd-Mn, it was found that the F-type icosahedral quasicrystal, which is stable at high temperature, becomes unstable below approximately 750 C, and transforms to a complicated modulated quasicrystal at the alloy composition of Al71Pd21 Mn8.On the Zn-Mg-Ho icosahedral quasicrystals, it was discovered that the degree of F-type chemical ordering depends on the alloy composition ; highly ordered state realized only near the composition of Zn60Mg30Ho10. Further, increase of annealing temperature causes decrease in the intensity of superlattice reflections in the X-ray diffraction pattern. It was experimentally shown that the decreuse of the intensity is related to change of behavior of electrical resistivity and magneto resistance. This result opened the new controlling method of physical properties of quasicrystals by changing chemical ordering and thus degree of perfection of quasiperiodicity.