Solving the fundamental limitations for RT spintronics - the role of interfaces in electron spin detection and injection

在传统的半导体电子学中，电流是由施加在任何特定电子元件的各个部分上的电压控制的。然而，一种全新的控制电流的方法在大约二十年前被提出。这个新想法是基于观察到电子的内部角动量（自旋）及其相关的磁矩在纳米尺度距离上是守恒的。由此可见，当制备超薄层结构时，自旋“记住”其在整个结构厚度上的方向，这意味着具有不同自旋方向的电子不会像在两条平行连接的独立电线中一样混合和独立流动。如果层结构包含磁性层，则两个自旋通道变得不相等。此外，还发现具有给定自旋取向的电子的电阻取决于层结构中所有磁性组分的磁构型。由于磁场可以改变磁性结构，因此可以通过施加磁场来控制电子（电流）的流动。随着这一发现，一个全新的凝聚态物理领域——自旋电子学——的时代开始了。自旋电子学思想的成功应用取决于我们在原子尺度上生长近乎完美的超薄磁层结构的能力。在过去的12个月里，这已经实现了包含铁磁金属（FM）和氧化镁绝缘屏障的层结构。然而，对于含有调频层和半导体（SC）层的多层，这些理想条件尚未得到满足。然而，自旋电子学未来的成功取决于将自旋电子元件集成到传统的半导体结构中。本提案的主要目标是将经典自旋电子学领域的实验专业知识，特别是层结构外延生长的专业知识与从研究具有MgO势垒的接近完美磁结中获得的理论见解相结合。我们有信心，为具有MgO势垒的磁结开发的实验和理论方法都可以转移到FM/SC系统中，从而可以解决在FM/SC界面上实现近乎完美的自旋输运的突出问题。

Electric current in conventional semiconductor electronics is controlled by a voltage applied to various parts of any particular electronic component. However, a completely new way of controlling the flow of electric current was proposed some twenty years ago. This new idea is based on the observation that the internal angular momentum of electrons (spin) with its associated magnetic moment is conserved over nanoscale distances. It follows that, when an ultrathin layer structure is prepared, the spin 'remembers' its orientation across the whole thickness of the structure, which means that electrons with different spin orientations do not mix and flow independently as if in two separate wires connected in parallel. If the layer structures contains magnetic layers the two spin channels become inequivalent. Moreoever, it is found that the resistance of electrons with a given spin orientation depends on the magnetic configuration of all the magnetic components in the layer structure. Since the magnetic configuration can be altered by applying a magnetic field, one can control the flow of electrons (electrical current) by applying a magnetic field. With this discovery the era of an entirely new field of condensed matter physics called spintronics had began. Successful applications of the ideas of spintronics depends on our ability to grow ultrathin magnetic layer structures which are near perfect on an atomic scale. Within the last twelve months this has been achieved for layer structures containing ferromagnetic metals (FM) and MgO insulating barrier. However, for multilayers contaning FM layers and semidoncuctor (SC) layers these ideal conditions have yet to be reasloed. Yet the future success of spintronics depends on integration of spintronic components into conventional semiconductor structures. The main goal of this proposal is to combine experimental expertise in the area of classical spintronics and, in particular, expertise in epitaxial growth of layer structures with theoretical insights gained from studying near perfect magnetic junctions with an MgO barrier, We are confident that both experimental and theoretical methods developed for magnetic junctions with an MgO barrier can be transferred to FM/SC systems and thus the outstanding problem of achieving near perfect spin transport across FM/SC interfaces can be solved.