Chiral magnetic order at surfaces driven by inversion asymmetry
Chiral magnetic order at surfaces driven by inversion asymmetry
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DOI：
10.1038/nature05802
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发表时间：
2007-05-10
期刊：
影响因子：
64.8
通讯作者：
Wiesendanger, R.
中科院分区：
文献类型：
--
作者：
Bode, M.;Heide, M.;Wiesendanger, R.
手性是一种迷人的现象，可以以微妙的方式表现出来，例如在生物化学（在观察到的生物分子的单手性（1））和粒子物理学（在电弱相互作用的电荷宇称破坏（2））中。在凝聚态物质中，磁性材料也可以显示单手或同手性的自旋结构。这可能是由Dzyaloshinskiii-Moriya相互作用引起的，该相互作用由电子在反转不对称晶体场中的自旋轨道散射引起（3，4）。这种效应在体金属中通常是不相关的，因为它们的晶体是反转对称的。然而，低维系统缺乏结构反转对称性，因此可能出现纯手性自旋结构（5）。本文报道了在钨（110）衬底上的锰单原子层中观察到的特定手性的磁序。自旋极化扫描隧道显微镜显示，相邻的自旋不是完美的反铁磁，但略有倾斜，导致在一个自旋螺旋结构的周期约为12 nm。我们通过定量理论表明，这种手性顺序是由Dzyaloshinskii - Moriya相互作用引起的，并导致左旋自旋摆线。我们的研究结果证实了这种相互作用的重要性，减少尺寸的磁铁。纳米级磁体中的手性可能在自旋电子器件中发挥关键作用，其中电子的自旋而不是电荷用于数据传输和操作。例如，流过手征磁性结构的自旋极化电流将在磁性结构（6，7）上施加自旋扭矩，引起磁化（8，9）的各种激励或操纵，并引起微波发射、磁化切换或磁性马达。
Chirality is a fascinating phenomenon that can manifest itself in subtle ways, for example in biochemistry ( in the observed single-handedness of biomolecules(1)) and in particle physics ( in the charge-parity violation of electroweak interactions(2)). In condensed matter, magnetic materials can also display single-handed, or homochiral, spin structures. This may be caused by the Dzyaloshinskii - Moriya interaction, which arises from spin - orbit scattering of electrons in an inversion-asymmetric crystal field(3,4). This effect is typically irrelevant in bulk metals as their crystals are inversion symmetric. However, low-dimensional systems lack structural inversion symmetry, so that homochiral spin structures may occur(5). Here we report the observation of magnetic order of a specific chirality in a single atomic layer of manganese on a tungsten ( 110) substrate. Spin-polarized scanning tunnelling microscopy reveals that adjacent spins are not perfectly antiferromagnetic but slightly canted, resulting in a spin spiral structure with a period of about 12 nm. We show by quantitative theory that this chiral order is caused by the Dzyaloshinskii - Moriya interaction and leads to a left-rotating spin cycloid. Our findings confirm the significance of this interaction for magnets in reduced dimensions. Chirality in nanoscale magnets may play a crucial role in spintronic devices, where the spin rather than the charge of an electron is used for data transmission and manipulation. For instance, a spin-polarized current flowing through chiral magnetic structures will exert a spin-torque on the magnetic structure(6,7), causing a variety of excitations or manipulations of the magnetization(8,9) and giving rise to microwave emission, magnetization switching, or magnetic motors.