Systematic Studies of Electron Transport in Amorphous Alloys

为了便于讨论无序体系中的电子输运机制，我们建议将非晶态合金按磁态分为五类。其中，根据费米能级在sp带和d带中的位置，非磁性合金分为(5)和(4)两组。主要结论如下：(1)电子输运主要由费米能级的sp电子主导，而族(4)的电子输运主要由d电子主导。我们发现，费米能级载流子性质的不同导致了不同族合金中独特的电子输运特征。(2)族(5)中的散射机制随着电阻率的增加而变化，其中只有sp电子负责输运。在电子平均自由程大于平均原子距离的200&lt；Mu&gt；&lt；omega&gt；-cm的低电阻区，用Boltzmann方程描述的正常散射机制是有效的。当电阻率超过约500&lt；Mu；&lt；-cm时，导电电子的迁移率大大降低。在这样的高电阻区，电子-电子关联和量子干涉效应变得重要，并在300K以下的宽温度范围内产生独特的电阻率与温度的关系。(3)我们证明了在d-电子传导显著的组(4)中的电子输运机制与在高阻组(5)中的电子传输机制本质上是相同的，高阻组(5)的电阻率约在500&lt；u&g；-cm以上。由此我们得出结论，无论费米能级电子结构的差异如何，都可以在相同的基础上理解(4)和(5)两种非磁性非晶合金中的电子输运。

We have proposed to classify amorphous alloys in five groups in terms of magnetic states, to facilitate the discussion of the electron transport mechanism in a disordered system. Among them, non-magnetic alloys are grouped into groups (5) and (4), depending on the location of the Fermi level in the sp-band and d-band, respectively. They are considered to be of fundamental importance in understanding the scattering mechanism.Major conclusions are summarized here.(1) The electron transport in group (5) is found to be dominated by sp-electrons at the Fermi level, whereas that in group (4) by d-electrons. We found that the difference in the character of the carriers at the Fermi level yields unique electron transport features in the respective group alloys.(2) The scattering mechanism in group (5),where only sp-electrons are reaponsible for the transport, changes with increasing resistivity. In the low-resistivity regime of less than 200 <mu><omega> -cm, where the electron mean free path is longer than the average atomic distance, the normal scattering mechanism described by the Boltzmann equation, is found to be valid. The mobility of conduction electrons is greatly lowered as the resistivity exceeds about 500 <mu><omega>-cm. In such high- resistivity regime, the electron-electron correlation and quantum interference effect becomes substantial and yield unique temperature dependence of resistivity over a wide temperature range below 300 K. (3) We demonstrated that the electron transport mechanism in group (4),where d-electronconduction is significant, is essintially the same as that in high-resistivity group (5) having resistivities above about 500 <mu><omega>-cm. From this we concluded that the electron transport in non-magnetic amorphous alloys including both group (4) and (5) can be understood on the same footing, regardless of the difference in the electronic structure at the Fermi level.