Theoretical study on plea-rival and optical manipulation of magoetization

(1)推导并分析了电流作用下畴壁的运动方程。考虑两种驱动机制（自旋转移和动量转移）、内禀钉钉（磁各向异性）和外禀钉钉（样品不均匀性），对脱屑机制进行了分类。得到了每种情况下的阈值电流和畴壁速度，并对实验结果进行了讨论。(1)推导并分析了畴壁在电流作用下的运动方程。考虑两种驱动机制（自旋转移和动量转移）、内禀钉钉（磁各向异性）和外禀钉钉（样品不均匀性），对脱屑机制进行了分类，得到了每种情况下的阈值电流和畴壁速度，并对实验结果进行了讨论。(2)微观计算了一般磁化织构中电流对磁化产生的各种自旋力矩。两个理论框架已经发展得比较成熟，可以处理电子的自旋弛豫过程。它们是“小振幅法”和“规范场法”，前者可以可靠地处理非平衡状态，但仅限于小振幅动力学；后者可以处理有限振幅动力学。后一种方法的简单应用无法再现阻尼，但我们可以通过仔细处理自旋松弛过程来克服这一困难。作为副产物，获得了阻尼的新物理图像。(3)对磁涡流的电流驱动运动进行了理论研究。通过模拟（中谷教授，UEC）和实验（小野组，京都大学）研究/发现了磁芯的共振激发和磁芯磁化的反转。(4)自旋极化的。已知铁磁体中的电流会导致自旋波的软化，并最终导致均匀磁化状态的不稳定。我们发现，这种不稳定性之后会形成磁畴壁（在细导线中）或磁涡流（在薄膜或宽导线中）。根据涡度和极性对两个相互作用的涡旋在电流作用下的动力学进行了分类，很好地解释了模拟结果的基本特征。少

(1) The equation of motion of a domain wall under current was derived and analyzed. By taking account of two driving mechanisms (spin transfer and momenturn tinsfer), intrinsic pinning (magnetic anisotropy) and extrinsic pinning (sample inhomogeneity), the depinning mechanisms are classified. The threshold current and domain-wall velocity are obtained for each case, and experimental results are discussed therewith(1) The equation of motion of a domain wall under current was derived and analyzed. By taking account of two driving mechardems (spin transfer and momenturn tinsfer), intrinsic pinning (magnetic anisotropy) and extrinsic pinning (sample inhomogeneity), the depinning mechanisms are classified The threshold current and domain-wall velocity are obtained for each case, and experimental results am discussed therewith(2) Various spin torques that the currents exert on magnetization was microscopically calculated for general magnetization texture. Two theoretical frameworks have been … More developed that can treat electrons' spin-relaxation processes. They are "small-amplitude method", which offers a reliable treatment of non-equilibrium states but is restricted to small-amplitude dynamics, and "gauge-field method", which can treat finite-amplitude dynamics. Simple-minded application of the latter method failed to reproduce the damping but we could overcome this difficulty by a careful treatment of spin-relaxation proceeses. A new physical picture of the damping was obtained as a by-product.(3) Current-driven motion of a magnetic vortex, typically formed in a magnetic disk, was studied theoretically. Resonant excitation of the core, and the reversal of the core magnetization were studied/found by simulations (Prof. Nakatani, UEC) and confirmed experimentally (by Ono group, Kyoto University).(4) Spin-polarized. current in a ferromagnet was known to lead to the softening of spin waves, and eventually to the instability of the uniformly magnetized state. We have found that this instability is followed by the formation of magnetic domain walls (in thin wires) or magnetic vortices (in films or wide wires). The dynamics of two interacting vortices under current was classified according to their vorticity, and polarity which explains well the essential features of the simulation results. Less