We report the experimental observation of net spin-orbit torques (SOT) in single conductive ferromagnets (FMs), e.g., ${\mathrm{Fe}}_{20}{\mathrm{Ni}}_{80}\left(\mathrm{Py}\right)$, Co, and Ni, despite the system symmetry constraint. Unlike the traditional FM/heavy metal (HM) bilayers, where only the in-plane (IP) damping-like SOT is presented, an unexpected out-of-plane (OOP) damping-like SOT is also unequivocally observed in the single FMs. Using the field angular-dependent, spin-torque ferromagnetic resonance technique, we quantify the IP and OOP SOT efficiencies of 0.018 ± 0.003 and 0.047 ± 0.002 in the pure Py, respectively. We argue that the IP SOT is primarily related to the Py bulk spin Hall effect, while the unconventional SOT is ascribed to the out-of-plane polarized spin current generated from the nonequilibrium spin swapping effect. Additionally, we confirm that such self-induced SOTs also generally exist in the most studied HM/FM multilayer systems, especially for the HMs with low conductivity. Hence, our findings provide a new perspective on understanding SOT control of magnetization reversal and dynamics by an in-plane current in thin, single FM and FM/HM bilayer systems.

中文翻译：

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单层铁磁金属中非平凡自旋轨道转矩的观察

我们报告了单导电铁磁体 (FM) 中净自旋轨道扭矩 (SOT) 的实验观察，例如，${铁}_{20}{你}_{80}\left(派\right)$、Co 和 Ni，尽管存在系统对称性约束。与传统的 FM/重金属 (HM) 双层仅呈现面内 (IP) 阻尼类 SOT 不同，在单个 FM 中也明确观察到意外的面外 (OOP) 阻尼类 SOT . 使用场角相关的自旋扭矩铁磁共振技术，我们量化了纯 Py 中 IP 和 OOP SOT 效率分别为 0.018 ± 0.003 和 0.047 ± 0.002。我们认为 IP SOT 主要与 Py 体自旋霍尔效应有关，而非常规 SOT 归因于非平衡自旋交换效应产生的面外极化自旋电流。此外，我们证实这种自诱导 SOT 通常也存在于研究最多的 HM/FM 多层系统中，特别是对于低电导率的 HM。因此，