Ab initio investigation of the role of the bridging atoms to the spin transferability between magnetic centrers

虽然磁盘正逐渐被存储信息的闪存装置（闪存、固态盘、SSD）所取代，但仍在努力用磁性对应物取代传统上为闪存的其他计算机部件。 与此同时，将（电子）电路小型化到原子水平已成为最理想的工业目标。这两个原因的结合导致了自旋电子器件的理论和实验研究以及纳米结构磁态的相干操纵的增加。本项目前两年的目标是研究相邻磁中心的电子桥接如何在纳米结构中产生。（这里是Fe、Co、Ni原子）影响自旋可转移性，从而影响多中心磁性分子的逻辑功能可操作性。这包括研究自旋转移作为化学性质（金属性）的函数，数量，和自旋和电荷极化的桥接atoms.When追求这些目标，我们得出了几种机制都自旋翻转和自旋转移，以及许多一般规则，支配他们。然而，这些一般规则似乎主要依赖于几何基础，而不是桥原子的化学性质。目前，我们知道一个团簇的对称性需要足够低，并且初/终态和中间态之间的能量差必须足够高，以确保成功的λ过程。在调查过程中，我们得到了一些额外的显著结果。详细地说，我们已经发现，一个重要的机制是声子自旋耦合作为我们的光驱动过程的调解人。这激发了对（i）桥连原子的金属性的作用、（ii）声子-自旋耦合的作用、（iii）电子态对间接声子-自旋耦合的作用以及（iv）包括声子在内的CO对自旋动力学过程的作用的更详细的研究。进一步阐明这些机制将有助于更成功的纳米结构的有针对性的设计。从而实质上有助于功能性纳米级磁性器件的开发。

While magnetic disks are gradually being replaced by nonmagnetic means of storing information (flash rams, solid state disks, SSD) there is an ongoing strive to replace other computer parts, traditionally nonmagnetic, by magnetic counterparts. At the same time the miniaturization of (electronic) circuits down to an atomic level has become a most desirable industrial goal. These two reasons combined have led to an increase of both the theoretical and experimental investigation of spintronic devices and coherent manipulation of the magnetic state of nanostructures.The goals of the first two-year period of the current project were to investigate how the electronic bridging of adjacent magnetic centers (here Fe, Co, Ni atoms) affects the spin transferability and thus the logic functional operability of multicenter magnetic molecules. This included the investigation of spin transfer as a function of the chemical nature (metallicity), the number, and the spin and charge polarization of the bridging atoms.When pursuing those goals we derived several mechanisms both for spin flip and for spin transfer, as well as many general rules which govern them. However, these general rules seem to rely mostly on geometrical grounds instead of the chemical nature of the bridge atoms. At present we understand that the symmetry of a cluster needs to be sufficiently low and the energetic difference between initial/final state and intermediate state(s) has to be sufficient high to ensure a successful Lambda-process. During the investigation we came to some additional remarkable results. In detail we have found that a substantial mechanism is the phonon-spin coupling which acts as a mediator for our optically driven processes. This motivates the more detailed study of (i) the role metallicity of the bridging atoms, (ii) the effect of phonon-spin coupling, (iii) the role of the electronic states on the indirect phonon-spin coupling, and (iv) the effect of CO including phonons on the spin dynamic processes.Elucidating further those mechanisms will ease the targeted designing of even more successful nanostructures, and thus substantially contribute to the development of functional, nanoscale magnetic devices.