Systematic Studies of Electron Transport in Amorphous Alloys

我们提出将非晶合金按磁态分为五类，以便于讨论无序系统中的电子传递机制。其中，根据费米能级在sp波段和d波段的位置，将非磁性合金分为(5)和(4)组。它们被认为对理解散射机制具有根本的重要性。主要结论总结如下。(1)在费米能级上，组(5)中的电子输运主要由sp电子控制，而组(4)中的电子输运主要由d电子控制。我们发现载流子在费米能级上的不同性质在各自的族合金中产生了独特的电子输运特征。(2)族(5)中只有sp电子负责输运的散射机制随着电阻率的增加而变化。在小于200 <mu><omega> -cm的低电阻率区，当电子平均自由程大于平均原子距离时，用玻尔兹曼方程描述的正态散射机制是有效的。当电阻率超过500 <mu><omega>-cm时，导电电子的迁移率大大降低。在这种高电阻率状态下，电子-电子相关和量子干涉效应变得实质性，并在低于300 K的宽温度范围内产生独特的电阻率温度依赖性。(3)我们证明了在d-电子传导显著的组(4)中，电子传递机制与电阻率高于约500 <mu><omega>-cm的高电阻率组(5)基本相同。由此我们得出结论，无论在费米能级上电子结构的差异如何，非磁性非晶合金(4)和(5)中的电子输运都可以在相同的基础上理解。

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.