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

为了实现利用电子量子性质的新型功能器件，为分析纳米磁性材料和器件的物理性质奠定了理论基础：1.阐明了外延隧道结和含有磁性杂质的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.改进了用于分析非共线自旋结构的第一性原理计算程序，以便在相干势近似下考虑原子和自旋组态的无序。用该程序研究了锰基无序合金的电子结构和磁性结构。(A.Sakuma)3.从全相对论Dirac方程出发，给出了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/反铁磁界面处的磁结构进行了理论分析。宽度约为0.8 nm的磁畴壁对Fe(110)单分子膜具有良好的能量效应。(K.Nakamura)5.开发了考虑非共线磁性的第一性原理分子动力学程序。通过对液氧的自旋动力学模拟，发现了反铁磁偶合氧分子二聚体(O_4单元)的形成。(T.Oda)6.用光电子发射显微镜观察了纳米磁体中的磁涡旋态。通过微磁模拟分析了磁体形状与涡流状态之间的关系。建立了用光电子发射显微镜观察磁涡动力学的实验方法。(K.Ono)

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)