Spin wave theory for low-dimensional magnetic systems and excitations in non-magnetic systems

低维磁系统的自旋波理论和非磁系统的激励

• 批准号: 355399-2009
• 负责人: CostaFilho, Raimundo
• 金额: $ 1.38万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=431551
• 关键词: Spin; wave; theory; low; dimensional

In magnetic systems when the temperature is lowered below the critical one there is a breaking of rotational symmetry leading to a magnetic stiffness of the magnetic moments. Because the systems resist twisting the magnetization locally, but don't resist a uniform twist, they have low energy spin wave excitations. Therefore, spin waves are propagating disturbances in the ordering of magnetic materials. They are observed through experimental methods like: inelastic neutron scattering, inelastic light scattering (Brillouin scattering, Raman scattering and inelastic X-ray scattering), and others. From the practical point of view, the reciprocal of the lowest frequency of the characteristic spin waves of a magnetic material gives a time scale for the switching of a device based on that material and other constraints like geometry and presence of impurities. A fundamental understanding of the effect of geometry and impurities on low-dimensional magnetic structures is important for identifying their potential for e.g. high-frequency nanostructure devices and switches, as well as for an understanding of the basic science and the intrinsic materials properties. For example, thin magnetic films have impurities that affect their electronic properties. Therefore manipulating these impurities can bring the possibility of new physical properties in these materials. Another experimentally feasible manipulation is the geometry of the magnetic structures. Several important phenomena have been detected and studied in planar trilayer magnetic structures. However, there are not many studies of trilayers in a cylindrical geometry. These two aspects of the low-dimensional magnetic system (impurities and geometry) will be investigated in this research project. The theoretical methods for this study include many body theory, classical electromagnetism, and Monte Carlo simulations. Non-magnetic systems, like for example carbon based materials, are also affected by impurities and geometry constraints. Therefore, to adapt the theoretical models developed for the magnetic systems is of great interest to better understand these systems. This is another aspect that will be covered by this proposal.

在磁系统中，当温度降低到临界温度以下时，旋转对称性就会被破坏，从而导致磁矩的磁刚度。由于系统抵抗局部磁化扭曲，但不抵抗均匀扭曲，因此它们具有低能量自旋波激励。因此，自旋波正在传播磁性材料有序性的干扰。 它们可以通过非弹性中子散射、非弹性光散射（布里渊散射、拉曼散射和非弹性 X 射线散射）等实验方法进行观察。从实用的角度来看，磁性材料的特征自旋波的最低频率的倒数给出了基于该材料和其他约束（例如几何形状和杂质的存在）的器件切换的时间尺度。对几何形状和杂质对低维磁性结构的影响的基本了解对于识别它们的潜力非常重要。高频纳米结构器件和开关，以及了解基础科学和固有材料特性。例如，磁性薄膜含有影响其电子特性的杂质。 因此，操纵这些杂质可以为这些材料带来新的物理性质的可能性。另一种实验上可行的操作是磁结构的几何形状。在平面三层磁结构中已经检测和研究了几个重要的现象。然而，对于圆柱形几何结构中的三层结构的研究并不多。本研究项目将研究低维磁系统的这两个方面（杂质和几何形状）。本研究的理论方法包括多体理论、经典电磁学和蒙特卡罗模拟。非磁性系统，例如碳基材料，也会受到杂质和几何限制的影响。因此，适应为磁系统开发的理论模型对于更好地理解这些系统非常有意义。这是该提案将涵盖的另一个方面。