轻金属/亚铁磁异质结构中轨道电流驱动的畴壁运动面临的挑战
Challenges in orbital current-driven domain wall motion in light metal/ferrimagnet heterostructures
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中文总结 AI 辅助
本研究探究轻金属/亚铁磁异质结构中轨道电流驱动畴壁运动的可行性，发现轻金属/GFC异质结构阻尼类力矩弱、无法驱动畴壁，插入Pt转换层可改善，明确了关键挑战。
中文摘要 AI 辅助
自旋电子学的最新进展表明，轻金属中电荷注入产生的轨道霍尔电流可提供非平衡角动量，且无需依赖强自旋轨道耦合（SOC）。本研究探究此类轨道电流是否能驱动非晶亚铁磁合金Gd$_{25}$(Fe$_{9}$Co$_{1}$)$_{75}$（简称GFC）中的畴壁（DW）运动，其中稀土亚晶格可提供强SOC以实现轨道-自旋转换。研究对比三类代表性异质结构：作为自旋霍尔参考的Pt/GFC、用于直接轨道电流注入的轻金属（Mn或Ti）/GFC、包含超薄Pt层以实现轨道-自旋转换的轻金属/Pt/GFC。Pt/GFC表现出稳定且可重复的自旋轨道力矩驱动畴壁运动，而Mn/GFC或Ti/GFC中未检测到电流驱动的畴壁运动。不过，二次谐波霍尔测量显示Mn/GFC和Ti/GFC中均存在有限的阻尼类力矩，表明角动量确实已传递至GFC，但强度远弱于Pt/GFC。插入1纳米厚的Pt转换层可显著增强阻尼类力矩并恢复畴壁运动。厚度依赖性分析进一步表明，畴壁迁移率与脱钉阈值和界面Dzyaloshinskii-Moriya相互作用及畴壁宽度相关，凸显弱力矩转换与手性畴壁的界面稳定不足是轻金属/亚铁磁异质结构中轨道驱动畴壁运动的关键挑战。
英文摘要
Recent advances in spintronics suggest that orbital Hall currents generated by charge injection in light metals can provide nonequilibrium angular momentum without relying on strong spin-orbit coupling (SOC). Here, we examine whether such orbital currents can drive domain wall (DW) motion in an amorphous ferrimagnetic alloy, Gd$_{25}$(Fe$_{9}$Co$_{1}$)$_{75}$ (GFC), where the rare-earth sublattice offers strong SOC for orbital-to-spin conversion. We compare three representative heterostructures: Pt/GFC as a spin Hall reference, light-metal (Mn or Ti)/GFC for direct orbital-current injection, and light-metal/Pt/GFC incorporating an ultrathin Pt layer for orbital-to-spin conversion. Whereas Pt/GFC exhibits robust and reproducible spin-orbit-torque-driven DW motion, no current-driven DW motion is detected in Mn/GFC or Ti/GFC. Second-harmonic Hall measurements nevertheless reveal finite damping-like torques in both Mn/GFC and Ti/GFC, demonstrating that angular-momentum transfer into GFC does occur but is far weaker than in Pt/GFC. Inserting a 1-nm-thick Pt conversion layer strongly enhances the damping-like torque and restores DW motion. Thickness-dependent analysis further shows that DW mobility and depinning thresholds correlate with the interfacial Dzyaloshinskii-Moriya interaction and domain-wall width, highlighting weak torque conversion and insufficient interfacial stabilization of chiral DWs as key challenges for orbital-driven DW motion in light-metal/ferrimagnet heterostructures.
发表机构
- ETH Zurich（苏黎世联邦理工学院）
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