Domain wall dynamics in two-dimensional van der Waals ferromagnets
Domain wall dynamics in two-dimensional van der Waals ferromagnets
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DOI：
10.1063/5.0062541
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发表时间：
2021-12-01
影响因子：
15
通讯作者：
Santos, Elton J. G.
中科院分区：
文献类型：
--
作者：
Abdul-Wahab, Dina;Iacocca, Ezio;Santos, Elton J. G.
畴壁运动是许多信息技术的核心，这些信息技术的范围从存储[海滩等人，J·麦格·麦格·马特。320，1272-1281（2008）]、加工[Tatara等人，468，213-301（2008）]和感测[Ralph和Stiles，J.Magn.Magn.Mater. 320，1190-1216（2008）]直到新颖的跑道存储器架构[Parkin等人，Science 320，190-194（2008）]。在二维（2D）货车范德华（vdW）材料中发现磁性[Huang等人，Nature 546，270（2017）; Gong等人，Nature 546，265-269（2017）; Guguchia等人，Sci. Adv. 4，eaat 3672（2018）; Klein等人，Science 360，1218-1222（2018）]为探索和理解几个原子厚层极限下的畴壁提供了新的前沿。然而，为了使用2D vdW磁体来构建诸如基于畴壁的逻辑的自旋电子学纳米器件[Allwood等人，Science 309，1688-1692（2005）; Luo等人，Nature 579，214-218（2020）; Xu等人，天然纳米技术3，97-100（2008）]，需要通过诸如自旋极化电流或磁场的外部驱动力来获得对它们的畴壁动力学的控制，这迄今为止是难以捉摸的。在这里，我们表明，电流以及磁场可以有效地移动磁畴壁在最近发现的2D VDW磁铁CrI 3和CrBr 3在低温和强大的单层。我们实现了场和电流驱动的畴壁运动，速度高达1020 m s（-1），这与基于畴壁的应用的最新材料相当[Yang等人，天然纳米技术10，221-226（2015）; Woo等人，Nat.板牙. 15，501-506（2016）; Velez等人，国家通信10，4750（2019）; Siddiqui等人，物理修订信函121，057701（2018）; Ryu等人，天然纳米技术8，527-533（2013）]。畴壁保持它们的相干性，由电流和磁场诱导的自旋转移力矩驱动，分别高达约12 × 10 9 A cm（-2）和5 T的大值。对于更大幅度的电流或场，通过发射具有调制不稳定性的自旋波孤子的周期性序列观察到向流体动力学自旋液体状态的转变[Rabinovich和Trubetskov，振荡和波：线性和非线性系统，数学及其应用（Springer Netherlands，2011）]。发射的波形在宽的场和电流密度范围内实现太赫兹（THz）频率，这为可重构磁振子器件开辟了前景。此外，我们发现，这些自旋波可以传输自旋角动量通过层的距离长达10 μ m的自旋信息的运输没有损失。我们的研究结果推动了目前已知的二维vdW铁磁体中畴壁动态的边界，并揭示了设计高速，高速和高频自旋电子器件的策略。
Domain wall motion is in the core of many information technologies ranging from storage [Beach et al., J. Magn. Magn. Mater. 320, 1272-1281 (2008)], processing [Tatara et al., Phys. Rep. 468, 213-301 (2008)], and sensing [Ralph and Stiles, J. Magn. Magn. Mater. 320, 1190-1216 (2008)] up to novel racetrack memory architectures [Parkin et al., Science 320, 190-194 (2008)]. The finding of magnetism in two-dimensional (2D) van der Waals (vdW) materials [Huang et al., Nature 546, 270 (2017); Gong et al., Nature 546, 265-269 (2017); Guguchia et al., Sci. Adv. 4, eaat3672 (2018); Klein et al., Science 360, 1218-1222 (2018)] has offered a new frontier for the exploration and understanding of domain walls at the limit of few atom-thick layers. However, to use 2D vdW magnets for building spintronics nanodevices such as domain-wall based logic [Allwood et al., Science 309, 1688-1692 (2005); Luo et al., Nature 579, 214-218 (2020); Xu et al., Nat. Nanotechnol. 3, 97-100 (2008)], it is required to gain control of their domain wall dynamics by external driving forces such as spin-polarized currents or magnetic fields, which have so far been elusive. Here, we show that electric currents as well as magnetic fields can efficiently move domain walls in the recently discovered 2D vdW magnets CrI3 and CrBr3 at low temperatures and robust down to monolayer. We realize field- and current-driven domain wall motion with velocities up to 1020 m s(-1), which are comparable to the state-of-the-art materials for domain-wall based applications [Yang et al., Nat. Nanotechnol. 10, 221-226 (2015); Woo et al., Nat. Mater. 15, 501-506 (2016); Velez et al., Nat. Commun. 10, 4750 (2019); Siddiqui et al., Phys. Rev. Lett. 121, 057701 (2018); Ryu et al., Nat. Nanotechnol. 8, 527-533 (2013)]. Domain walls keep their coherence driven by the spin-transfer torque induced by the current and magnetic fields up to large values of about 12 x 10 9 A cm(-2) and 5 T, respectively. For larger magnitudes of current or field, a transition to a hydrodynamic spin-liquid regime is observed with the emission of a periodic train of spin-wave solitons with modulational instability [Rabinovich and Trubetskov, Oscillations and Waves: In Linear and Nonlinear Systems, Mathematics and its Applications (Springer Netherlands, 2011)]. The emitted waveform achieves terahertz (THz) frequency in a wide range of fields and current densities, which opens up perspectives for reconfigurable magnonic devices. Moreover, we found that these spin-waves can transport spin angular momentum through the layers over distances as long as 10 mu m without losses for the transport of spin information. Our results push the boundary of what is currently known about the dynamics of domain walls in 2D vdW ferromagnets and unveil strategies to design ultrathin, high-speed, and high-frequency spintronic devices.