Theoretical studies on spin-structure and dynamics in nano-scale magnetic materials

为了有助于利用电子的量子特性实现新的功能器件，本文构建了分析纳米磁性材料和器件物理性质的理论基础：1.阐明了外延隧穿结和含磁性杂质金属纳米线的原子结构与自旋相关输运现象之间的关系。（M.Shirai，Y.Miura，K.Nagao）2.改进了分析非共线自旋结构的第一性原理计算程序，使之在相干势近似下能考虑原子和自旋组态的无序。利用计算程序研究了Mn基无序合金的电子结构和磁结构。（A.Sakuma）3.在全相对论Dirac方程的基础上，建立了能正确计算螺旋磁结构的计算方法。（H.Yamagami）4.为了理解交换偏置现象，对铁磁/反铁磁界面的磁结构进行了理论分析。磁畴壁的宽度约为0.8nm，这对Fe（110）单分子层的形成是有利的。（中村）5.发展了能计算非共线磁性的第一性原理分子动力学程序。通过对液态氧的自旋动力学模拟，发现了反铁磁耦合氧分子二聚体（O_4单元）的形成。（T.Oda）6.利用光电子发射显微镜观察了纳米尺度磁体中的磁涡旋态。利用微磁模拟方法分析了磁体形状与涡旋状态的关系。本文介绍了用光电子发射显微镜观察磁涡旋动力学的实验方法。（小野康树）

In order to contribute to the realization of new functional devices exploiting quantum nature of electrons, the theoretical basis for analyzing physical properties of nanometer-scale magnetic materials and devices has been constructed as follows :1.The relation between atomic structures and spin-dependent transport phenomena has been clarified for epitaxial tunneling junctions and for metallic nanowires containing magnetic impurities. (M.Shirai, Y.Miura, K.Nagao)2.The first-principles computational code for analyzing non-collinear spin structure has been improved so as to account the disorder in atomic and spin configurations within the coherent potential approximation. The electronic and magnetic structures in Mn-based disordered alloys have been investigated by using the computational code. (A.Sakuma)3.The computational procedure which can account spiral magnetic structures correctly has been formulated on the basis of full-relativistic Dirac equations. (H.Yamagami)4.The magnetic structure at ferromagnet/antiferromagnet interfaces has been analyzed theoretically in order to understand exchange-bias phenomena. The magnetic domain wall with a width of about 0.8 nm is found to be favorable energetically for Fe (110) monolayer. (K.Nakamura)5.The first-principles molecular dynamics code which can account non-collinear magnetism has been developed. The formation of antiferromagnetically coupled oxygen molecule dimer (O_4 unit) has been found by the spin-dynamics simulation for liquid oxygen. (T.Oda)6.The magnetic vortex states in nanometer-scale magnets have been observed by using the photoelectron emission microscopy. The relation between the shape of the magnet and the vortex states has been analyzed by using micro-magnetic simulation. The experimental procedure has been developed for observing the dynamics of magnetic vortex by means of photoelectron emission microscopy. (K.Ono)