Theory of magnetic coupling and magnetization reversal in non-equilibrium state

本课题旨在研究磁性纳米结构中的自旋积累、电流感应磁化开关以及自旋极化电流驱动下的磁畴壁运动，从而实现新型磁性纳米器件。得到了以下结果：1)利用微观模型阐明了二维电子、气体与Rashba自旋轨道相互作用的非平衡态存在自旋积累。2)研究了自旋积累在双隧道势垒磁点中的作用，阐明了通过调节磁点的尺寸和各向异性能量，电流驱动的磁化开关是可能的。3)利用包含电荷和自旋自由度的电流广义表达式，研究了非共线磁化的铁磁体/非磁体/铁磁体结中极化自旋的分布。4)对自旋极化电流驱动的畴壁运动进行了理论研究。结果表明，自旋电流和电荷电流分别对厚畴壁和薄畴壁有重要影响。

The purpose of this project is to study the spin accumulation in magnetic nano-structure, current induced magnetization switching, and magnetic domain wall motion driven by spin polarized current in order to realize novel magnetic nano-devices. Following results have been obtained.1)It has been clarified that the spin accumulation exists in the non-equilibrium state of two-dimensional electron, gas with Rashba spin-orbit interaction by using a microscopic model.2)Role of spin accumulation in magnetic dots with double tunnel barrier has been studied and clarified that the current driven magnetization switching is possible by adjusting the size of the dots and anisotropy energy.3)Distribution of polarized spins in ferromagnet/nonmagnet/ferromagnet junctions with non-collinear magnetizations has been studied by using a generalized expression for current which includes both charge and spin degrees of freedom.4)Theoretical study on the domain wall motion driven by spin polarized current has been done. It has been shown that the spin and charge currents are important for thick and thin domain walls, respectively.