Spin order and dynamics in the topological rare-earth germanide semimetals

IF 6.4 1区 物理与天体物理 Q1 PHYSICS, MULTIDISCIPLINARY
Yuhao Wang, Zhixuan Zhen, Jing Meng, Igor Plokhikh, Delong Wu, Dariusz J. Gawryluk, Yang Xu, Qingfeng Zhan, Ming Shi, Ekaterina Pomjakushina, Toni Shiroka, Tian Shang
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Abstract

The REAl(Si,Ge) (RE = rare earth) family, known to break both the inversion- and time-reversal symmetries, represents one of the most suitable platforms for investigating the interplay between correlated-electron phenomena and topologically nontrivial bands. Here, we report on systematic magnetic, transport, and muon-spin rotation and relaxation (uSR) measurements on (Nd,Sm)AlGe single crystals, which exhibit antiferromagnetic (AFM) transitions at TN = 6.1 and 5.9 K, respectively. In addition, NdAlGe undergoes also an incommensurate-to-commensurate ferrimagnetic transition at 4.5 K. Weak transverse-field µSR measurements confirm the AFM transitions, featuring a ∼90% magnetic volume fraction. Zero-field (ZF) µSR measurements reveal a more disordered internal field distribution in NdAlGe than in SmAlGe, reflected in a larger transverse muon-spin relaxation rate λT at TTN. This may be due to the complex magnetic structure of NdAlGe, which undergoes a series of metamagnetic transitions in an external magnetic field, while SmAlGe shows only a robust AFM order. In NdAlGe, the topological Hall effect (THE) appears between the first and the second metamagnetic transitions for Hc, while it is absent in SmAlGe. Such THE in NdAlGe is most likely attributed to the field-induced topological spin textures. The longitudinal muon-spin relaxation rate λL, diverges near the AFM order, followed by a clear drop at T < TN. In the magnetically ordered state, spin fluctuations are significantly stronger in NdAlGe than in SmAlGe. In general, our longitudinal-field μSR data indicate vigorous spin fluctuations in NdAlGe, thus providing valuable insights into the origin of THE and of the possible topological spin textures in REAl(Si,Ge) Weyl semimetals.

拓扑稀土锗半金属中的自旋秩序和动力学
众所周知,REAl(Si,Ge)(RE = 稀土)家族可以打破反转对称和时间反转对称,是研究相关电子现象和拓扑非三维带之间相互作用的最合适平台之一。在这里,我们报告了对(Nd,Sm)AlGe 单晶进行的系统磁性、输运和μ介子自旋与弛豫(uSR)测量,这些单晶在 TN = 6.1 和 5.9 K 时分别表现出反铁磁性(AFM)转变。此外,NdAlGe 还在 4.5 K 时发生了不相称到相称的铁磁转变。弱横向场 µSR 测量证实了 AFM 转变,其特点是磁性体积分数达到了 90%。零场 (ZF) µSR 测量显示 NdAlGe 的内部磁场分布比 SmAlGe 更无序,这反映在 T≪ TN 时更大的横向μ介子-自旋弛豫率 λT。这可能是由于 NdAlGe 的磁性结构复杂,在外加磁场中会发生一系列的元磁转变,而 SmAlGe 只显示出稳健的 AFM 有序。在 NdAlGe 中,当 H ∥ c 时,拓扑霍尔效应(THE)出现在第一次和第二次元磁转变之间,而在 SmAlGe 中则不存在。钕铝锗中的这种拓扑霍尔效应很可能是由场诱导的拓扑自旋纹理引起的。纵向μ介子自旋弛豫速率λL在AFM有序附近发散,随后在T <TN时明显下降。在磁有序状态下,NdAlGe 的自旋波动明显强于 SmAlGe。总的来说,我们的纵向场 μSR 数据表明 NdAlGe 中存在强烈的自旋波动,从而为了解 THE 的起源以及 REAl(Si,Ge)Weyl 半金属中可能存在的拓扑自旋纹理提供了宝贵的见解。
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来源期刊
Science China Physics, Mechanics & Astronomy
Science China Physics, Mechanics & Astronomy PHYSICS, MULTIDISCIPLINARY-
CiteScore
10.30
自引率
6.20%
发文量
4047
审稿时长
3 months
期刊介绍: Science China Physics, Mechanics & Astronomy, an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China, and published by Science China Press, is committed to publishing high-quality, original results in both basic and applied research. Science China Physics, Mechanics & Astronomy, is published in both print and electronic forms. It is indexed by Science Citation Index. Categories of articles: Reviews summarize representative results and achievements in a particular topic or an area, comment on the current state of research, and advise on the research directions. The author’s own opinion and related discussion is requested. Research papers report on important original results in all areas of physics, mechanics and astronomy. Brief reports present short reports in a timely manner of the latest important results.
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