Study of the Effects of a Domain Wall on an Electron Transfer in a Quantum Magnetic Wire

在纳米尺度金属中，畴壁形核及其动力学已成为当前研究的热点。特别是，由于DW在铁磁线的电阻率的负磁阻效应已被许多研究人员报道。此外，奇异的非线性输运在这些金属线含有铁磁畴壁报道。为了阐明的基本特征的铁磁线与DW，我们计算的自旋涨落的激发谱。在研究中，我们考虑了真实的样品结构，并对海森堡模型进行了处理。然后，在无规相位近似（RPA）的框架下，给出了获得该结构的绿色函数的方法。结果表明，低能量激发主要由DW引起，特征自旋波谱取决于DW的存在和结构引线的尺寸。结果表明，DW由于其周围的自旋涨落而使电阻增大，而钉扎中心对自旋涨落的抑制起着重要作用，当DW位于钉扎中心时，电阻减小.结果表明，所得结果与实验结果是一致的。

In the nanometer-scale metals, a domain wall(DW) nucleation and dynamics have become the subjects of current interest. Specifically, the negative magnetoresistance effect on the electrical resistivity due to the DW in ferromagnetic wires has been reported by many researchers. Also, exotic nonlinear transports were reported in these metallic wires containing ferromagnetic domain walls.To elucidate basic features of a ferromagnetic wire with a DW, we calculated the excitation spectrum for the spin fluctuation. In the study, we treated the Heisenberg model with taking the real sample structures into consideration. Then, we presented the method to obtain the Green function for the structure in a framework of the random phase approximation(RPA). It was shown that the low energy excitation is attributed to the DW and the characteristic spin-wave spectrum depends on the existence of the DW and the dimension of leads for the structure.Next, the effects of the DW and its pinning center on the electron conduction are studied in a framework of the RPA. We show that the DW enhances the resistance due to the spin fluctuation around it. Furthermore, the pinning center plays an important role of suppression of the spin fluctuation, which leads to the reduction of the resistance when the DW locates at the pinning center. It is shown that the results obtained are consistent with the experimental findings.