Experimental study on the response of phason strains of the quasicrystals

研究了F型Al-Pd-Mn二十面体合金在温度变化后磁化率随时间的变化。磁化率随时间的平方根变化，这是准晶应变响应理论中相子弛豫的特征。这种磁化率的变化被认为是源于Al-Pd-Mn二十面体合金中局部磁矩形成的临界条件，这导致整个Mn原子中只有一小部分具有磁矩。这些事实导致了对Al-Pd-Mn二十面体相和相关晶体近似物中原子位置的研究。在研究中确定了Mn原子的原子团簇和位置，在F型Zn-Mg合金中，采用Ho原子位置模型，对磁结构进行了模拟计算，发现了一种与相子应变有关的新结构。Ho二十面体相在低温下的假设，Ho原子的相互作用通过RKKY类交替相互作用。在反铁磁相互作用的最短Ho-Ho距离和铁磁的第二短Ho-Ho距离的情况下，发现一个长程反铁磁秩序。在反号相互作用的情况下，只发现了短程反铁磁序。这些事实强烈地表明相子应变对二十面体相的磁性有显著的影响。

The dependence of the magnetic susceptibility on time was investigated in F-type Al-Pd-Mn icosahedral alloys after the change in the temperature. The susceptibility varied as a square root of time, which is characteristic of the relaxation of the phason in the theory of the strain response of the quasicrystal. Such a change in the susceptibility was considered to originate from the critical conditions for the formation of local magnetic moments in the Al-Pd-Mn icosahedral alloys, which resulted in the fact that only a small fraction of the whole Mn atoms had magnetic moment. These facts leaded to the investigations of the atomic positions in the Al-Pd-Mn icosahedral phases and related crystal approximants. Atomic clusters and the positions of Mn atoms were determined in the investigations, and a new structure related to the phason strains was found. The study of the time-dependence of the macroscopic strain is under way on applying stress.Simulation calculations were performed for the magnetic structures in a model of atomic positions of Ho in F-type Zn-Mg-Ho icosahedral phase at low temperatures on the assumption that the Ho atoms were interacting via RKKY-like alternating interactions. A long-range antiferromagnetic order was found in the case of the antiferromagnetic interaction for the shortest Ho-Ho distance and the ferromagnetic one for the second shortest Ho-Ho distance. Only a short-range antiferromagnetic order was found in the case of the reversed sign interactions. These facts strongly suggest that the phason strains affect the magnetism of the icosahedral phases drastically.