Spin-polarized scanning tunneling microscopy on ultrathin iron films on Be(0001)

在这个项目中，我们将使用自旋极化扫描隧道显微镜来研究在超高真空条件下在Be(0001)表面上制备的超薄铁膜。我们预计铁膜将延续铍衬底的六方密排原子晶格，导致铁结构的Epsilon相。Epsilon-Iron的磁性尚不明确，因此成为许多正在进行的科学辩论的主题。到目前为止，已经在极高压下的大块样品中实验实现了Epsilon-Fe。我们的方法首次允许以原子精度直接研究超薄和极其纯净的Epsilon-Iron薄膜中的磁性。衬底引起的晶格应力模拟了高达100 Gpa的外部压力，导致了Epsilon-Iron薄膜的相当大的压缩。随着薄膜厚度的增加，原子晶格有望弛豫为本征的Epsilon相，最终转变为常规的体心立方相。在Fe/Be(0001)界面，铍中的二维电子气与铁膜的局部磁矩之间存在有趣的相互作用，这将决定铁膜的磁性。自旋极化扫描隧道实验将允许获得作为薄膜厚度和温度的函数的磁态，因此将给Epsilon-Iron的磁性带来新的曙光。

Within this project ultrathin iron films prepared on a Be(0001) surface under ultrahigh vacuum conditions will be investigated using spin-polarized scanning tunneling microscopy. We expect the iron film to continue the hexagonal close packed atomic lattice of the beryllium substrate, resulting in the Epsilon-phase of the iron structure. The magnetism of Epsilon-iron is not yet unambiguously clear and consequently subject of many ongoing scientific debates. So far, Epsilon-iron has been realized experimentally in bulk samples under extreme high pressure. Our approach allows for the first time the direct investigation of magnetism in ultrathin and extremely pure Epsilon-iron films with atomic precision. The lattice stress induced by the substrate simulates external pressure of up to several 100 GPa, resulting in a considerable compression of the Epsilon-iron film. With increasing film thickness the atomic lattice is expected to relax into the intrinsic Epsilon phase and finally into the conventional body centered cubic phase. At the Fe/Be(0001) interface interesting interactions are expected between the two-dimensional electron gas in beryllium and the local magnetic moments of the iron film, which will be decisive for the magnetic properties of the iron film. Spin-polarized scanning tunneling experiments will allow to access the magnetic state as a function of film thickness and temperature and therefore will shed new light onto the magnetism of Epsilon-iron.