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Evidence of tunable magnetic coupling in hydrogenated graphene
Physical Review B ( IF 3.7 ) Pub Date : 2020-07-01 , DOI: 10.1103/physrevb.102.045402
Shimin Cao , Chuanwu Cao , Shibing Tian , Jian-Hao Chen

Many efforts have been devoted to understanding the origin and effects of magnetic moments induced in graphene with carbon atom vacancy, and light adatoms like hydrogen or fluorine. In the meantime, the large negative magnetoresistance (MR) widely observed in these systems is not well understood, nor has it been associated with the presence of magnetic moments. In this paper, we study the systematic evolution of the large negative MR of in-situ hydrogenated graphene in ultrahigh-vacuum (UHV) environment. We find for most combinations of electron density (ne) and hydrogen density (nH), MR at different temperature can be scaled to α=μBB/kB(TT*), where T* is the Curie-Weiss temperature. The sign of T* indicates the existence of tunable ferromagneticlike (T*>0) and antiferromagneticlike (T*<0) coupling in hydrogenated graphene. However, the lack of hysteresis of MR or anomalous Hall effect below |T*| points to the fact that long-range magnetic order did not emerge, which we attribute to the competition of different magnetic orders and disordered arrangement of magnetic moments on graphene. We also find that localized impurity states introduced by H adatoms could modify the capacitance of hydrogenated graphene. This work provides a way to extract information from large negative MR behavior and can be a key to understanding interactions of magnetic moments in graphene.

中文翻译:

氢化石墨烯中可调磁耦合的证据

人们已经做出了许多努力来理解石墨烯中具有碳原子空位的感应磁矩的起源和影响,以及氢或氟等轻原子。同时,在这些系统中广泛观察到的大的负磁阻(MR)尚未得到很好的理解,也与磁矩的存在无关。在本文中,我们研究了很大的负面的系统进化MR原位氢化石墨烯在超高真空(UHV)环境。我们发现大多数电子密度组合(ñË)和氢密度(ñH),可以将不同温度下的MR缩放到α=μ/ķŤ-Ť*,在哪里 Ť*是居里-魏斯温度。的迹象Ť* 表示存在可调铁磁体(Ť*>0)和反铁磁类(Ť*<0)在氢化石墨烯中偶联。但是,下面没有MR的滞后现象或霍尔效应异常|Ť*|指出没有出现长程磁序这一事实,这归因于不同磁序的竞争以及石墨烯上磁矩的无序排列。我们还发现,由H原子引入的局部杂质态可以改变氢化石墨烯的电容。这项工作提供了一种从大的负MR行为中提取信息的方法,并且可能是理解石墨烯中磁矩相互作用的关键。
更新日期:2020-07-01
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