Magnetic microscopy and topological stability of homochiral Néel domain walls in a Pt/Co/AlOx trilayer.
Magnetic microscopy and topological stability of homochiral Néel domain walls in a Pt/Co/AlOx trilayer.
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DOI：
10.1038/ncomms9957
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发表时间：
2015-12-08
影响因子：
16.6
通讯作者：
McVitie S
中科院分区：
文献类型：
--
作者：
Benitez MJ;Hrabec A;Mihai AP;Moore TA;Burnell G;McGrouther D;Marrows CH;McVitie S
在考虑驱动薄膜动态行为的转矩时，薄膜磁畴壁的微观磁化变化是一个至关重要的特性。对于具有面外各向异性的薄膜，由于静磁的考虑，通常不赞成存在nsamel壁。然而，它们有正确的结构来响应自旋霍尔效应施加的扭矩。它们的存在是界面Dzyaloshinskii-Moriya相互作用（DMI）的一个指标。在这里，我们使用洛伦兹透射电子和克尔显微镜在器件制备的Pt/Co/AlOx薄膜中直接成像具有固定手性的n<s:1>畴壁。结果表明，薄膜中任何独立成核的壁对在相遇时会形成难以被场湮灭的绕组对，证实了它们都具有相同的拓扑圈数。后者由DMI强制执行。湮灭这些缠绕壁对所需的场用于测量DMI强度。这样的域墙具有很强的抗碰撞能力，是密集数据存储的理想选择。在铁磁薄膜中，与重金属界面处对称性的破坏引起了手性交换相互作用，可用于控制磁畴壁。在这里，作者展示了这种效应如何在Pt/Co/AlOx三层中加强拓扑稳定的同手性畴壁。
The microscopic magnetization variation in magnetic domain walls in thin films is a crucial property when considering the torques driving their dynamic behaviour. For films possessing out-of-plane anisotropy normally the presence of Néel walls is not favoured due to magnetostatic considerations. However, they have the right structure to respond to the torques exerted by the spin Hall effect. Their existence is an indicator of the interfacial Dzyaloshinskii–Moriya interaction (DMI). Here we present direct imaging of Néel domain walls with a fixed chirality in device-ready Pt/Co/AlOx films using Lorentz transmission electron and Kerr microscopies. It is shown that any independently nucleated pair of walls in our films form winding pairs when they meet that are difficult to annihilate with field, confirming that they all possess the same topological winding number. The latter is enforced by the DMI. The field required to annihilate these winding wall pairs is used to give a measure of the DMI strength. Such domain walls, which are robust against collisions with each other, are good candidates for dense data storage. Broken symmetry at the interface with a heavy metal gives rise to a chiral exchange interaction in ferromagnetic thin films, which may be used to control magnetic domain walls. Here, the authors demonstrate how this effect enforces topologically stable homochiral domain walls in a Pt/Co/AlOx trilayer.