标题： 垂直磁化的W/CoFeB/MgO结构中自旋轨道转矩驱动的准Bloch磁畴壁运动 显示英文标题

标题： Spin orbit torque-driven motion of quasi-Bloch domain wall in perpendicularly magnetized W/CoFeB/MgO structure

摘要： 自旋轨道转矩（SOT）驱动的手性磁畴壁（DWs）在具有垂直磁各向异性的重金属/铁磁材料异质结构中的运动已经被广泛研究。本研究特别关注近布洛赫态下的SOT驱动的畴壁，我们将其称为“准布洛赫畴壁”。这些准布洛赫畴壁相较于奈尔型畴壁表现出更慢的运动速度，这为实现高度可控的畴壁位置提供了可能性。在这里，我们研究了由W/CoFeB/MgO组成的垂直磁化超薄膜中SOT驱动的准布洛赫畴壁运动特性。为了分析畴壁的运动，我们采用了一维模型，并结合从样品实验数据中获得的参数。我们的模型成功地再现了实验结果，揭示了不同样品中畴壁运动方向和阈值电流密度的变化。通过理论分析，我们发现畴壁在运动过程中保持准布洛赫态，其中SOT为主要驱动力而非自旋传递转矩（STT）。运动方向不仅取决于Dzyaloshinskii-Moriya相互作用（DMI）和自旋霍尔角的符号组合，还取决于DMI、STT以及外加畴壁钉扎力的强度。此外，我们给出了SOT驱动的准布洛赫畴壁运动所需的阈值电流密度的解析表达式。这些发现为设计具有特定薄膜结构的未来畴壁器件提供了宝贵的见解。 显示英文摘要

摘要： The motion of chiral magnetic domain walls (DWs) driven by spin-orbit torque (SOT) has been extensively studied in heavy metal/ferromagnet heterostructures with perpendicular magnetic anisotropy. This study specifically focuses on SOT-driven DWs in near Bloch-states, which we refer to as ``quasi-Bloch DWs". These quasi-Bloch DWs exhibit slower motion compared to Neel-type DWs, offering potential for achieving highly controllable DW positions. Here, we investigate the characteristics of SOT-driven motion of quasi-Bloch DWs in perpendicularly magnetized ultra-thin films consisting of W/CoFeB/MgO. For analyzing the DW motion, we employ a one-dimensional model incorporating parameters derived from experimental data obtained from our samples. Our model successfully reproduces the experimental results, which reveal variations in the direction and threshold current density of DW motion among different samples. Through theoretical analysis, we unveil that the DW remains in quasi-Bloch states during motion, with SOT serving as the primary driving force rather than spin transfer torque (STT). The direction of motion is determined not only by the sign combination of Dzyaloshinskii-Moriya interaction (DMI) and spin Hall angle but also by the strength of DMI, STT, and extrinsic DW pinning. Furthermore, we provide analytical expressions for the threshold current density required for SOT-driven quasi-Bloch DW motion. These findings provide valuable insights for the design of future DW devices with specific film structures.