【作者】 蔺何；

【导师】 张军； 段海明；

【作者基本信息】 新疆大学 ， 理论物理， 2006， 硕士

【摘要】 目前使用的电子器件是利用电子的电荷特性来处理信息,然而对于信息的存储则使用的是电子的自旋特性。人们的想法是将这两种特性结合起来,以求提高和增加电子器件的功能,由此诞生了稀磁半导体材料。本文用密度泛函理论方法系统地研究了稀磁半导体材料。大部分计算采用局域密度近似下的离散变分原子团模型。文中描述了离散变分方法的理论基础?密度泛函理论。重点介绍离散变分方法(DVM),讨论基函数的构成、离散点的分布、势的构造。我们首先运用原子团模型研究了稀磁半导体GaN掺Cr((Ga,Cr)N)的局域电子结构和磁性。计算结果表明Cr原子的磁矩随掺杂浓度有明显的变化,变化趋势和实验吻合。在包含两个Cr原子的体系中Cr原子之间是铁磁性偶合,每个Cr原子的磁矩与相同浓度下掺杂一个Cr原子的磁矩相近。对于不同的掺杂浓度,Cr原子与最近邻N原子之间均为反铁磁偶合,Cr原子的3d电子与N原子的2p电子之间有很强的杂化,这和晶体的能带计算方法得到的结果一致。同时我们还运用原子团模型研究了(Ga,Mn)As,并将结果与(Ga,Cr)N进行对比。本文还对GaAs掺杂3d族过渡金属做了系统的研究,作为GaAs掺杂3d族过渡金属性质的总结。考虑到实验上制备DMS材料时,磁性元素的掺杂是非均匀的,所以我们计算得到的结果对于研究DMS的局域特性很有帮助,而且我们的原子团模拟方法还可以用来研究其他的掺杂体系。更多还原

【Abstract】 Modern electronic devices utilize the charge degree of freedom of electrons to process information and the spin degree of freedom to store information. If both the charge and spin of electrons can be combined, we many be able to accomplish mass storage and information processing at the same time. In this way the performance of electronic devices will be enhanced.First-principles methods based upon density functional theory are performed for diluted magnetic semiconductor. Most of the calculations are performed by using Discrete Variational cluster approach within local density approximation.Thus density functional theory (DFT) is introduced. The Discrete Variational Method (DVM) for clusters (DFT in real space) is described in detail. The basis functions, numerical grids utilized and potential are discussed.The local electronic structure and magnetic properties of diluted magnetic semiconductor (Ga,Cr)N have been studied by using DVM based on density functional theory. The magnetic moments per Cr atom vary significantly with Cr concentration, and the trend of variation is in agreement with that of the experiment. The coupling between Cr atoms in the system with two Cr atoms considered is found to be ferromagnetic, and the magnetic moment per Cr atom is similar to the case in which only one Cr atom is considered in the same doping concentration. For all doping concentrations, the coupling between Cr and the nearest neighbor N is found to be antiferromagnetic, and the Cr 3d states hybridize strongly with N 2p states, which are in agreement with the band calculations. The local electronic structure and magnetic properties of diluted magnetic semiconductor (Ga,Mn)As has also been studied by using Discrete Variational approach based.更多还原