Origin and stability of highly spin polarized surface resonances

高自旋极化表面共振的起源和稳定性

• 批准号: 282078320
• 负责人: Professor Dr. Hubert Ebert
• 金额: --
• 依托单位: New Technologies - Research Centre
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/282078320?language=en
• 关键词: Origin; stability; highly; spin; polarized

The magnitude of the effective spin polarization of ferromagnetic materials at room temperature is a key property for their application in spintronics. However, for most applications it is not the electronic structure of the bulk, but of the surface or interface of the material, which is relevant. Investigating the Heusler compound Co2MnSi we recently observed in collaboration with our experimentally working partner (Dr. M. Jourdan, JGU Mainz) a high spin polarization (93%), which is related to a stable surface resonance in the majority spin band extending deep into the bulk. Here we want to investigate the physical origin of such highly spin polarized surface resonances. According to this central aim various Heusler and related compounds with different orientations of their surface and interface to suitable cover layers, respectively, will be investigated theoretically. In particular, the question whether a half metallic bulk band structure is a necessary precondition for the appearance of a 100% spin-polarized surface resonance will be answered. Considering potential applications it is of major importance whether the high spin polarization due to a surface resonance is conserved, if the free surface is replaced by an interface with an insulator or metal. The in-situ spin resolved photo electron spectroscopy (SR-UPS) applied by our experimental partner to Heusler compounds and related systems proved already extremely successful for the investigation of the surface and interface states. In particular the use of spin integrated high energy x-ray photo emission spectroscopy (HAXPES) allows to achieve a larger probing depth. Accordingly, the interpretation of the results of our experimental partner project running in parallel will be supported by direct comparison with first-principles band structure and photo emission calculations which consider all relativistic, surface and high energy effects. Special emphasize will be put on the influence of electronic correlations as well as various forms of disorder on the spin polarization. Apart from chemical disorder due to non-stoichiometry of the investigated alloy systems and inter-diffusion at an interface, respectively, thermally induced disorder will be considered in particular. This important aspect includes lattice vibrations as well as thermal spin fluctuations. To account for spin fluctuations within the photo emission calculations a method will be applied that was developed recently by the applicant and that is based on the CPA (Coherent Potential Approximation) alloy theory.

铁磁材料在室温下的有效自旋极化强度是其在自旋电子学中应用的一个关键性质。然而，对于大多数应用来说，相关的不是本体的电子结构，而是材料的表面或界面的电子结构。研究Heusler化合物Co2 MnSi，我们最近与我们的实验工作伙伴（M.高自旋极化（93%），这与深入延伸到体中的大多数自旋带中的稳定表面共振有关。在这里，我们要调查的物理起源，这种高度自旋极化的表面共振。根据这一中心目标的各种Heusler和相关化合物的不同取向的表面和界面，以适当的覆盖层，分别将进行理论研究。特别是，半金属体带结构是否是一个必要的先决条件出现的100%自旋极化表面共振的问题将得到回答。考虑到潜在的应用，如果自由表面被绝缘体或金属的界面所取代，则由于表面共振而引起的高自旋极化是否守恒是非常重要的。我们的实验合作伙伴应用于Heusler化合物和相关系统的原位自旋分辨光电子能谱（SR-UPS）证明已经非常成功地用于表面和界面态的研究。特别地，使用自旋积分高能X射线光发射光谱（HAXPES）允许实现更大的探测深度。因此，我们的实验合作伙伴项目并行运行的结果的解释将支持直接比较第一原理能带结构和光发射计算，考虑所有相对论，表面和高能量的影响。特别强调电子关联以及各种形式的无序对自旋极化的影响。除了由于所研究的合金系统的非化学计量和在界面处的相互扩散而引起的化学无序之外，将特别考虑热诱导的无序。这个重要的方面包括晶格振动以及热自旋涨落。为了说明光电发射计算中的自旋波动，将应用由申请人最近开发的基于CPA（相干势近似）合金理论的方法。

项目成果

Unraveling the spin structure of unoccupied states in Bi2Se3

揭示 Bi2Se3 中未占据态的自旋结构

• DOI: 10.1103/physrevb.95.115401
• 发表时间: 2017
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Ch. Datzer;A. Zumbülte;J. Braun;T. Förster;A. B. Schmidt;B. Iverson;P. Hofmann;J. Minár;H. Ebert;P. Krüger;M. Rohlfing;M. Donath
• 通讯作者: M. Donath

One-step model of photoemission at finite temperatures: Spin fluctuations of Fe(001)

有限温度下光电发射的一步模型：Fe(001) 的自旋涨落

• DOI: 10.1103/physrevb.102.035107
• 发表时间: 2020
• 期刊: arXiv: Materials Science
• 作者: J. Minár;S. Mankovsky;J. Braun;H. Ebert
• 通讯作者: H. Ebert