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Magnetization dynamics in lanthanide metals probed by photoelectron spectroscopy with higher-order harmonic radiation

用高次谐波辐射光电子能谱探测稀土金属的磁化动力学

基本信息

批准号：
169010978
负责人：
Professor Dr. Martin Weinelt
金额：
--
依托单位：
Institut für Experimentalphysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/169010978?language=en
关键词：
Magnetization dynamics lanthanide metals probed

项目摘要

In the proposed project we intend to study the ultrafast magnetization dynamics in magnetically ordered films of lanthanide metals. To this end we use femtosecond pulses of extreme-ultraviolet radiation from a tunable higher-order harmonics beamline to map transients of the exchange-split (5d6s)^3 valence band structure and follow the magnetic linear dichroism (MLD) of the 4f core-levels in angle-resolved photoemission. Femtosecond IR pulses will be used as pump pulses to initiate the ultrafast magnetization dynamics.Our previous photoemission work shows a significant difference in the response of the 4f spin system of pure Gadolinium and Terbium metal, which we attribute to their different orbital momentum (L=0 vs. L=3). For Gd, the dynamics of 5d and 4f spin systems occurs on largely disparate timescales (~0.8 vs. ~14ps), while for Tb both spin systems react synchronously and faster (~0.4ps). These results are not only in contrast to X-ray magnetic circular dichroism (XMCD) measurements but generally challenge the microscopic description of ultrafast magnetic switching in 3d4f alloys.We now plan for three types of specifically designed experiments which allow us to further develop the microscopic understanding of the 4f coupling and magnetization dynamics in the rare-earths. (i) The influence of the orbital momentum on the magnetization dynamics will be studied for GdTb compounds. Varying the GdTb composition we will map transient exchange splitting and Gd and Tb 4f MLD and address whether they respond differently in the alloy. (ii) We want to answer whether there is a different magnetization dynamics at the Gd surface as compared to its bulk. To separate surface from bulk contributions we will study a Gd film covered with one monolayer of europium (4f^7 (5d6s)^2). (iii) As a third approach, we will investigate the intermetallic compound TbFe, where the magnetization is determined by the interplay between the exchange couplings of the different sublattices. Depending on the concentration, TbFe films can show very low coercivity and we expect a significant weaker 4f spin - lattice coupling as in pure Tb films. This should result in slower 4f spin dynamics.

在这个项目中，我们打算研究镧系金属磁有序薄膜的超快磁化动力学。为此，我们使用来自可调谐高次谐波光束线的极紫外辐射的飞秒脉冲来映射交换分裂（5d 6s）^3价带结构的瞬态，并在角分辨光电发射中跟踪4f芯能级的磁性线性二色性（MLD）。飞秒红外脉冲将被用作泵浦脉冲来启动超快磁化动力学。我们以前的光电子能谱工作表明，纯金属钆和铽的4f自旋系统的响应存在显着差异，我们将其归因于它们不同的轨道动量（L=0 vs. L=3）。对于Gd，5d和4f自旋系统的动力学发生在很大程度上不同的时间尺度上（~0.8 vs.~ 14 ps），而对于Tb，两个自旋系统的反应同步且更快（~0.4ps）。这些结果不仅是在对比X射线磁性圆二色性（XMCD）测量，但一般挑战的微观描述超快磁开关在3d 4f alloys.We现在计划为三种类型的专门设计的实验，使我们能够进一步发展的微观理解的4f耦合和磁化动力学的稀土。(i)将研究GdTb化合物的轨道动量对磁化动力学的影响。不同的GdTb组合物，我们将映射瞬态交换分裂和Gd和Tb 4f MLD，并解决它们是否在合金中有不同的反应。(ii)我们想回答是否有一个不同的磁化动力学在Gd表面相比，其体积。为了将表面贡献与体贡献区分开来，我们将研究一个单层铕（4f^7（5d 6s）^2）覆盖的Gd膜。(iii)作为第三种方法，我们将研究金属间化合物TbFe，其中磁化强度由不同子晶格的交换耦合之间的相互作用决定。取决于浓度，TbFe膜可以显示非常低的介电常数，并且我们预期如在纯Tb膜中一样显著较弱的4f自旋-晶格耦合。这将导致较慢的4f自旋动力学。