The magnetic state of exchanged biased $\mathrm{CoO}\left(20\mathrm{nm}\right)/\mathrm{Co}\left(d_F\right)$ bilayers ($d_F=5-20\mathrm{nm}$) was studied by means of polarized neutron reflectometry. By introducing a Nb(20 nm) spacer layer between the CoO/Co bilayer and the ${\mathrm{Al}}_2{\mathrm{O}}_3$ substrate, we designed a resonator structure with significantly enhanced intensity of the spin-flip (SF) scattering at the position of the optical resonances. For the trained sample with thinnest Co layer ($d_F=5\mathrm{nm}$), we detected strong SF scattering at the resonance position to the amount of 30% of the incoming intensity, pointing to a high degree of non-collinearity of the magnetization. With increasing $d_F$, the intensity of the SF scattering decreases linearly. Furthermore, an unconventional asymmetry of up-down and down-up scattering channels at the resonance positions was observed, which we ascribe to the out-of-plane magnetic stray field generated by chiral Bloch domain walls. This field leads to Zeeman splitting of the neutron energies depending on the initial neutron spin polarization. The chirality of the domain walls is assigned to the Dzyaloshinskii-Moriya interaction emerging at the CoO/Co interface. Our observations might prove useful for the design of spintronic devices based on the exchange bias effect.

中文翻译：

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通过波导增强中子自旋翻转散射研究交换偏置 CoO/Co 双层中布洛赫畴壁的手性

交换偏磁状态 $\mathrm{首席运营官}\left(20\mathrm{纳米}\right)/\mathrm{公司}\left(d_F\right)$ 双层（$d_F=5-20\mathrm{纳米}$) 是通过偏振中子反射计研究的。通过在 CoO/Co 双层和${铝}_2{\mathrm{哦}}_3$在基板上，我们设计了一种谐振器结构，在光学谐振位置具有显着增强的自旋翻转 (SF) 散射强度。对于具有最薄 Co 层的训练样本 ($d_F=5\mathrm{纳米}$)，我们在共振位置检测到强 SF 散射，达到入射强度的 30%，这表明磁化具有高度的非共线性。随着增加$d_F$，SF 散射的强度线性下降。此外，观察到共振位置上上下散射通道的非常规不对称性，我们将其归因于手性布洛赫畴壁产生的面外杂散磁场。根据初始中子自旋极化，该场导致中子能量的塞曼分裂。畴壁的手性归因于 CoO/Co 界面上出现的 Dzyaloshinskii-Moriya 相互作用。我们的观察可能证明对基于交换偏置效应的自旋电子器件的设计很有用。