【作者】 杨晓东；

【导师】 严辉；

【作者基本信息】 北京工业大学 ， 材料物理与化学， 2004， 硕士

【摘要】 本论文针对既具有重要应用价值，又具基础理论研究意义的介观体系的电子输运行为，以及相应体系中的磁阻效应做了较为系统和深入的理论研究。其目的一方面在于揭示已知量子结构中的新效应，研究其磁输运现象的物理机制和规律，另一方面希望为基于这些量子结构的器件设计提供物理模型和理论依据。1. 对磁场调制下二维电子气系统的弹道输运作出了较系统的研究。研究结果表明周期对磁致输运中的透射系数有着很大的影响，随着周期的增加，共振峰呈现出更加丰富的震荡特性，同时原有的震荡峰也会相应的加强。在研究二维电子气的磁致输运中的透射系数基础上，分别研究了平行结构与反平行结构的弹道电导的共振分裂峰和周期对弹道电导的影响。计算中发现，电导共振出现了劈裂，在所考虑的费米能区，相同磁垒构成的每个共振区在周期增加的情况下分裂为多个亚共振区，振荡峰加强。2. 较为系统地研究了周期磁垒调制下的二维电子气的磁阻效应。结果表明铁磁条间距的变化对磁阻有很大的影响，同时磁垒结构的对称性越高磁阻越大。随着周期的增加，磁阻率峰值始终固定在特定的费米能保持不变。从应用的角度来讲，这种磁垒结构对于制造新型选择电子注入器件十分有利。更有趣的是，随着周期的增加，奇数周期（OP）的磁阻率总是大于偶数周期（EP）的磁阻率。所有这些特征都表明，优化磁垒结构有利于进一步的提高磁阻效应。3. 研究了加入背景磁场后的磁侧边超晶格的磁阻效应。结果表明，随着背景磁场的增加，对于特定的费米能，磁阻率线性减小，这一特征非常有希望用于低磁场传感器。这也是与以前研究结果完全不同的一种新的实现线性磁阻效应的有效途径。更多还原

【Abstract】 In this work, we have made a detailed investigation on single electron transportproperty in mesoscopic systems and the magnetoresistance effect in these structures，which owns great potential application in future devices. On the one hand，wediscover new effects in known mesoscopic structures; on the other hand，we expect tosupply physical model and make theoretical validity for device design based on thesestructures. 1. The ballistic transport of the two dimensional electron gas modulated by the magnetic field has been studied. The results show that the transmission coefficient influenced by the periods of the magnetic fields, and with the increase of the periods, resonant peaks show more complicated resonance, and also been enhanced. We also studied the conductance of the parallel and the antiparallel alignments, respectively. It is found that the conductance also appears the resonance and the features are same as that of the transmission coefficient. 2. We investigated a giant magnetoresistance effect of two-dimensional electron gas systems in a periodically modulated magnetic field. It is found that the magnetoresistance (MR) ratio of the present system shows strong dependence on the space of the potentials. The calculated results also show that the larger magnetoresistance effect can be obtained in the symmetric magnetic structures. Furthermore, with the number of periods increasing, the MR ratio shows oscillations and the system with odd periods is always larger than that with even ones in a given structure. Meanwhile, the peaks of the MR ratio locate at a specific Fermi energy for the given space of potentials. 3. Two dimensional electron gas systems modulated by lateral magnetic superlattieces are proposed and the magnetoresistance effect related is described here. It is found that the magnetoresistance ratio of the given structures depends - II -<WP=6>摘 要strongly on the uniform magnetic field, and the peaks of the MR ratio depressedlinearly with the increase in the magnetic field. This interesting feature may leadsto new practical linear magnetoresistance (LMR) devices.更多还原