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Spin currents probed by magnetic circular dichroism in X-ray absorption spectroscopy (XMCD) - a theoretical study

X 射线吸收光谱 (XMCD) 中磁圆二色性探测自旋电流 - 理论研究

基本信息

批准号：
327501276
负责人：
Professor Dr. Hubert Ebert
金额：
--
依托单位：
Department Chemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/327501276?language=en
关键词：
Spin currents probed magnetic circular

项目摘要

The theory project aims to supply an ab-initio description of XMCD (X-ray magnetic circular dichroism in X-ray absorption) experiments used to monitor dynamical magnetic properties in the field of spintronics. The focus will be on experiments that monitor spin currents induced by an electric field (EFI-XMCD) or ferromagnetic resonance (FMR-XMCD) as well as the motivation of new experiments. All numerical work will be based on local spin density functional theory (LSDA) and its extensions with the electronic structure represented in terms of Green functions evaluated using the fully relativistic multiple scattering formalism.A first simplified description of the EFI-XMCD in FM/NM (FM and NM: ferromagnetic and normal metals, respectively) layered systems will be given by combining Kubo's linear response formalism with the theory on XMCD. Corresponding numerical work allow for a first comparison with experiments on systems in a steady state (SS). In the next step a more reliable description of the EFI-XMCD will be achieved by adopting the steady state non-equilibrium Green function (SS-NEGF) formalism. Corresponding calculations will clarify the applicability of linear-response theory and provide a detailed interpretation for on-going experiments meant to probe spin currents in the NM as well as FM part of FM/NM layered systems. This work will in particular reveal the mechanism giving rise to the observed XMCD together with its connection to the spin current. To describe recent FMR-XMCD experiments for which spin currents are stimulated by spin-pumping via FMR the adiabatic approximation will be used in a first step. This allows in particular to discuss the relation of the induced spin current and the XMCD spectra. Within further work the general Keldysh NEGF formalism will be used, making use of developments done by the applicant when dealing with pump-probe experiments in photo emission.Further work is meant to investigate the use of the EFI-XMCD to probe and verify new magneto-transport properties and to stimulate corresponding experiments. The Edelstein effect, i.e. the occurrence of a magnetization induced by an electric field in systems without inversion symmetry, will be investigated for NM bulk and NM/NM layered systems. The resulting spectra will be interpreted in terms of the magneto-electric susceptibility by adapting the XMCD sum rules. In addition calculations of EFI-XMCD spectra will be done to motivate experiments that verify the occurrence of induced longitudinal spin currents in low-dimensional solids predicted by the applicant. For this purpose NM/NM layered systems will be investigated that should show a pronounced effect that can be clearly distinguished from the Edelstein effect by symmetry considerations.

该理论项目的目的是提供一个从头计算描述的XMCD（X射线吸收中的X射线磁性圆二色性）实验，用于监测自旋电子学领域的动态磁性。重点将放在监测由电场（EFI-XMCD）或铁磁共振（FMR-XMCD）引起的自旋电流的实验以及新实验的动机。所有的数值计算工作将基于局域自旋密度泛函理论（LSDA）及其扩展，电子结构用绿色函数表示，使用完全相对论多重散射形式。（FM和NM：铁磁和正常金属，分别）分层系统将通过结合久保的线性响应形式主义与XMCD理论。相应的数值计算工作允许第一次比较系统的稳定状态（SS）的实验。在下一步中，将通过采用稳态非平衡绿色函数（SS-NEGF）形式主义来实现对EFI-XMCD的更可靠的描述。相应的计算将澄清线性响应理论的适用性，并提供一个详细的解释正在进行的实验意味着探测在NM以及FM/NM分层系统的FM部分的自旋电流。这项工作将特别揭示的机制，引起所观察到的XMCD连同其连接到自旋电流。为了描述最近的FMR-XMCD实验，其中自旋电流通过经由FMR的自旋泵浦来激发，绝热近似将在第一步中使用。这使得特别是讨论感生的自旋电流和XMCD光谱的关系。在进一步的工作中，一般Keldysh NEGF形式主义将被使用，利用申请人在处理光emission中的泵浦-探测实验时所做的开发，进一步的工作是为了研究使用EFI-XMCD来探测和验证新的磁输运性质，并刺激相应的实验。埃德尔斯坦效应，即在没有反转对称性的系统中由电场引起的磁化的发生，将针对NM体和NM/NM分层系统进行研究。由此产生的光谱将被解释的磁电磁化率方面，通过调整XMCD求和规则。此外，还将进行EFI-XMCD谱的计算，以激发实验，验证申请人预测的低维固体中诱导纵向自旋流的发生。为此目的，NM/NM分层系统将被调查，应该显示出明显的效果，可以清楚地区分从埃德尔斯坦效应的对称性考虑。