Ferromagnetic dislocations in antiferromagnetic NiO
Ferromagnetic dislocations in antiferromagnetic NiO
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DOI：
10.1038/nnano.2013.45
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发表时间：
2013-04-01
影响因子：
38.3
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
--
作者：
Sugiyama, Issei;Shibata, Naoya;Ikuhara, Yuichi
晶格缺陷通常会降低器件的功能性（1，2），但工程这些缺陷可能在未来的电子和磁性器件应用中具有价值。例如，位错-具有局部不同原子尺度结构的一维晶格缺陷（3，4）-表现出独特的局部电学性质（5，6），并且可以用作在绝缘晶体中生产导电纳米线的模板（7-11）。还预测自旋极化电流可以沿着拓扑绝缘体中的位错流动（12）。尽管位错的磁性与晶格的磁性不同（5，13，14），但它们在个体水平上的基本特征却很少受到关注。在这里，我们证明了NiO晶体中的位错具有独特的磁性。磁力显微镜成像清楚地揭示了反铁磁NiO中单个位错的铁磁有序性，源于位错核心的局部非化学计量比。铁磁位错由于与周围反铁磁体相的强相互作用而具有高的矫顽力。虽然已经报道了岩盐NiO的纳米晶体显示出铁磁行为（15），但我们的研究表征了单个晶格缺陷的铁磁特性。我们讨论了出乎意料的铁磁性的起源在单位错的原子尺度的核心结构的物理性质，并证明了它是可能的，制造稳定的纳米磁性元件内的晶体环境组成的这些微结构。
Crystal lattice defects often degrade device functionality(1,2), but engineering these defects may have value in future electronic and magnetic device applications. For example, dislocations-one- dimensional lattice defects with locally distinct atomic-scale structures(3,4)-exhibit unique and localized electrical properties(5,6) and can be used as a template for producing conducting nanowires in insulating crystals(7-11). It has also been predicted that spin-polarized current may flow along dislocations in topological insulators(12). Although it is expected that the magnetic properties of dislocations will differ from those of the lattice(5,13,14), their fundamental characterization at the individual level has received little attention. Here, we demonstrate that dislocations in NiO crystals show unique magnetic properties. Magnetic force microscopy imaging clearly reveals ferromagnetic ordering of individual dislocations in antiferromagnetic NiO, originating from the local non-stoichiometry of the dislocation cores. The ferromagnetic dislocations have high coercivity due to their strong interaction with the surrounding antiferromagnetic bulk phase. Although it has already been reported that nanocrystals of rock-salt NiO show ferromagnetic behaviour(15), our study characterizes the ferromagnetic properties of individual lattice defects. We discuss the origin of the unexpected ferromagnetism in terms of the physical properties of the atomic-scale core structures of single dislocations, and demonstrate that it is possible to fabricate stable nanoscale magnetic elements inside crystalline environments composed of these microstructures.