Chiral spin textures are fundamentally interesting, with promise for device applications. Stabilizing chirality is conventionally achieved by introducing Dzyaloshinskii–Moriya interaction (DMI) in asymmetric multilayers, where the thickness of each layer is at least a few monolayers. Here we report an ultrasensitive chirality switching in (Ni/Co)_n multilayer induced by capping with only 0.22 monolayer of Pd. Using spin-polarized low-energy electron microscopy, we monitor the gradual evolution of domain walls from left-handed to right-handed Néel walls and quantify the DMI induced by the Pd capping layer. We also observe the chiral evolution of a skyrmion during the DMI switching, where no significant topological protection is found as the skyrmion winding number varies. This corresponds to a minimum energy cost of <1 attojoule during the skyrmion chirality switching. Our results demonstrate the detailed chirality evolution within skyrmions during the DMI sign switching, which is relevant to practical applications of skyrmionic devices.

中文翻译：

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超灵敏亚单层钯诱导的手性转换和 Skyrmions 的拓扑演化

手性自旋纹理从根本上说是有趣的，有望用于设备应用。稳定手性通常是通过在不对称多层中引入 Dzyaloshinskii-Moriya 相互作用 (DMI) 来实现的，其中每层的厚度至少为几个单层。在这里，我们报告了 (Ni/Co) _{n中的超灵敏手性转换}多层由仅用 0.22 单层 Pd 封盖引起。使用自旋极化低能电子显微镜，我们监测畴壁从左旋到右旋 Néel 壁的逐渐演变，并量化 Pd 覆盖层引起的 DMI。我们还观察到在 DMI 切换过程中斯格明子的手性演化，随着斯格明子绕组数的变化，没有发现明显的拓扑保护。这对应于斯格明子手性切换期间<1 attojoule 的最小能量成本。我们的结果证明了在 DMI 符号切换期间 skyrmions 内的详细手性演变，这与 skyrmionic 器件的实际应用有关。