Dynamical processes in nanostructured and low-dimensional magnetic materials

在纳米或亚微米范围内具有一个或多个维度的磁性材料的基本过程的当前研究是由它们在诸如新型磁存储器，超快开关和高频器件等领域的巨大技术应用潜力驱动的。这与生长和制造技术的最新进展相结合，这些技术允许可靠地生产各种由磁性元素及其阵列组成的纳米结构。因此，在理论方面，迫切需要在基本层面上理解这些材料在这些小长度尺度上发生的动态过程，以便设计和增强设备和应用的特性，以及预测新的效应。这为这个拟议的理论研究项目提供了主要目标和重点。计算将通过使用不同的量子力学技术进行，通常与数值模拟方法相结合，并应用于材料中的集体激发或波，例如，自旋波（或磁振子），有时与振动波（或声子）和电子激发一起。由于这些波在有限材料中的空间量子化以及多个表面和界面的存在，预计会产生新的效应。众所周知，纳米结构材料有时可能表现出其本体材料所不具备的新特性，例如巨磁电阻现象，并可作为新技术的基础。这为这一领域的研究提供了另一种动力。

The current research into fundamental processes in magnetic materials that have one or more dimensions in the nanometer or submicron ranges is being driven by their immense potential for technological applications in the areas (for example) of new types of magnetic memory, ultrafast switching, and high-frequency devices. This is coupled with recent advances in growth and fabrication techniques that allow a wide variety of nanostructures composed of magnetic elements and their arrays to be reliably produced. Consequently, on the theoretical side there is a pressing need to understand at a fundamental level the dynamical processes taking place within such materials on these small length scales in order to engineer and enhance the properties of the devices and applications, as well as to predict new effects. This provides the primary objective and focus for this proposed program of theoretical research. The calculations will be carried out by using different quantum-mechanical techniques, often in conjunction with numerical simulation methods, and applied to the collective excitations or waves in the materials, e.g., the spin waves (or magnons), sometimes together with the vibrational waves (or phonons) and electronic excitations. Novel effects are expected to arise due to the spatial quantization of these waves confined in the finite materials and due to the presence of multiple surfaces and interfaces. It is known that nanostructured materials may sometimes display novel characteristics that are absent in their bulk constituent materials, as in the phenomenon of giant magnetoresistance for example, and can be utilized as the basis for new technologies. This provides another motivation for this field of research. Some areas of focus concern (i) magnonic crystals, which are artificial materials consisting of periodic arrays of nanoelements or periodic patterning of films used to control the spin-wave properties, and (ii) phenomena associated with the nonlinear spin dynamics in nanostructures. For example, in the latter case, the interactions of the spin waves amongst themselves or with other (nonmagnetic) waves are of interest. Both of the above are areas of intense study for their fundamental scientific challenges and for potential device applications.