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Inducing and optimizing magnetism in graphene nanomeshes

机译：诱导和优化石墨烯纳米网中的磁性

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摘要

Using first-principles calculations, we explore the electronic and magnetic properties of graphene nanomesh (GNM), a regular network of large vacancies, produced either by lithography or nanoimprint. When removing an equal number of A and B sites of the graphene bipartite lattice, the nanomesh made mostly of zigzag (armchair) -type edges exhibit antiferromagnetic (spin unpolarized) states. In contrast, in situations of sublattice symmetry breaking, stable ferri(o)magnetic states are obtained. For hydrogen-passivated nanomesh, the formation energy is dramatically decreased, and ground state is found to strongly depend on the vacancies shape and size. For triangular-shaped holes, the obtained net magnetic moments increase with the number difference of removed A and B sites in agreement with Lieb's theorem for even A + B. For odd A + B triangular meshes and all cases of nontriangular nanomeshes, including the one with even A + B, Lieb's theorem does not hold anymore, which can be partially attributed to the introduction of armchair edges. In addition, large triangular-shaped GNMs could be as robust as nontriangular GNMs, providing a possible solution to overcome one of the crucial challenges for the sp magnetism. Finally, significant exchange-splitting values as large as ～0.5 eV can be obtained for highly asymmetric structures evidencing the potential of GNM for room-temperature carbon-based spintronics. These results demonstrate that a turn from zero-dimensional graphene nanoflakes throughout one-dimensional graphene nanoribbons with zigzag edges to GNM breaks localization of unpaired electrons and provides deviation from the rules based on Lieb's theorem. Such delocalization of the electrons leads the switch of the ground state of a system from an antiferromagnetic narrow gap insulator discussed for graphene nanoribons to a ferromagnetic or nonmagnetic metal.
机译：使用第一性原理计算，我们探索了石墨烯纳米网（GNM）的电子和磁性，石墨烯纳米网是通过光刻或纳米压印产生的大空位的规则网络。当去除相等数量的石墨烯二分晶格的A和B位点时，主要由之字形（扶手椅）型边缘制成的纳米网表现出反铁磁（自旋非极化）状态。相反，在亚晶格对称破坏的情况下，可获得稳定的亚铁（o）磁态。对于氢钝化的纳米网，其形成能大大降低，并且发现基态强烈依赖于空位的形状和大小。对于三角形孔，获得的净磁矩随被除去的A和B位点的数目差的增加而增加，这与偶数A + B的李布定理一致。对于奇数A + B三角形网格和所有非三角形纳米网格，包括一个即使是A + B，李布定理也不再成立，这可以部分归因于扶手椅边缘的引入。另外，大三角形的GNM可能与非三角形的GNM一样坚固，从而提供了一种可能的解决方案来克服sp磁性的关键挑战之一。最后，对于高度不对称的结构，可以得到高达〜0.5 eV的显着交换分裂值，证明了GNM对于室温碳基自旋电子学的潜力。这些结果表明，从零维石墨烯纳米薄片到带有锯齿形边缘的一维石墨烯纳米带到GNM的转变打破了未成对电子的局限性，并偏离了基于李布定理的规则。电子的这种离域化导致系统的基态从针对石墨烯纳米带讨论的反铁磁窄间隙绝缘体转换为铁磁或非磁性金属。

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  • 来源
    《Physical review》 |2011年第21期|p.214404.1-214404.7|共7页
  • 作者

    Hong-Xin Yang; Mairbek Chshiev; Danil W. Boukhvalov; Xavier Waintal; Stephan Roche;

  • 作者单位

    SPINTEC, CEA/CNRS/UJF-Grenoble 1/Grenoble-INP, INAC, FR-38054 Grenoble, France;

    SPINTEC, CEA/CNRS/UJF-Grenoble 1/Grenoble-INP, INAC, FR-38054 Grenoble, France;

    School of Computational Sciences, Korea Institute for Advanced Study (KIAS), Hoegiro 87, Dongdaemun-Gu, Seoul 130-722, Korean Republic;

    SPSMS-INAC-CEA, 17 rue des Martyrs, FR-38054 Grenoble, France;

    CIN2 (ICN-CSIC) and Universitat Autonoma de Barcelona, Catalan Institute of Nanotechnology, Campus de la UAB, ES-08193 Bellaterra (Barcelona), Spain and ICREA, Institucio Catalana de Recerca i Estudis Avancats, ES-08010 Barcelona, Spain;

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  • 正文语种 eng
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  • 关键词

    magnetic properties of thin films, surfaces, and interfaces;

    机译：薄膜;表面和界面的磁性;

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