Ultrafast current and field driven domain-wall dynamics in van der Waals antiferromagnet MnPS3
Ultrafast current and field driven domain-wall dynamics in van der Waals antiferromagnet MnPS3
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DOI：
10.21203/rs.3.rs-90731/v1
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发表时间：
2020-10
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通讯作者：
Ignacio M. Alliati;R. Evans;K. Novoselov;E. Santos
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作者：
Ignacio M. Alliati;R. Evans;K. Novoselov;E. Santos
二维（2D）范德华（vdW）材料磁性的发现[1 - 4]为解决磁学基本问题以及在计算、传感和存储技术方面的潜在应用作出了新的努力[5 - 10]。特别令人感兴趣的是反铁磁体11,12，由于其固有的反铁磁交换耦合，与铁磁体相比，它们表现出一些优势，例如对外部磁扰动的鲁棒性。这一性质是反铁磁畴的基础之一，并意味着存储在反铁磁畴中的信息对外加磁场是不可见的，从而防止其被擦除或操纵。在这里，我们表明，尽管有这种基本的理解，最近发现的2D vdW MnPS3反铁磁体14,15的磁畴可以通过外部磁场和电流来控制。我们实现了超快的畴壁动力学，速度分别高达~ 1500 m s - 1和~ 3000 m s - 1，场强范围（0.0001 - 22 T）和电流密度（108 - 1010 a cm - 2）。这两种畴壁动力学都是由边缘终止决定的，边缘终止产生的无补偿自旋遵循蜂窝结构的潜在对称性。我们发现，属于不同磁亚晶格的边缘原子起着防止壁位移的几何收缩作用，而在材料的两个边缘具有相同亚晶格的原子允许场驱动的畴壁运动，这只受反铁磁体超过25 t的自旋翻转跃迁的限制。电流可以在大多数边缘诱导畴壁的运动，除了那些在边界上存在两个子晶格的地方（例如扶手椅边缘）。此外，层相对于电流的方向为MnPS3中控制和操纵磁畴提供了额外的自由度。我们的研究结果表明，在实际应用中实现二维vdW反铁磁体需要对层边缘进行工程设计，从而在超薄器件平台中实现前所未有的功能特征。
The discovery of magnetism in two-dimensional (2D) van der Waals (vdW) materials1–4 has flourished a new endeavour of fundamental problems in magnetism as well as potential applications in computing, sensing and storage technologies5–10. Of particular interest are antiferromagnets 11, 12, which due to their intrinsic antiferromagnetic exchange coupling show several advantages in relation to ferromagnets such as robustness against external magnetic perturbations. This property is one of the cornerstones of antiferromagnets13 and implies that in formation stored in antiferromagnetic domains is invisible to applied magnetic fields preventing it from being erased or manipulated. Here we show that, despite this fundamental understanding, the magnetic domains of recently discovered 2D vdW MnPS3 antiferromagnet14, 15 can be controlled via external magnetic fields and electric currents. We realize ultrafast domain-wall dynamics with velocities up to ∼1500 m s−1 and ∼3000 m s−1 respectively to a broad range of field magnitudes (0.0001−22 T) and current densities (108 − 1010 A cm−2). Both domain wall dynamics are determined by the edge terminations which generated uncompensated spins following the underlying symmetry of the honeycomb structure. We find that edge atoms belonging to different magnetic sublattices function as geometrical constrictions preventing the displacement of the wall, whereas having atoms of the same sublattice at both edges of the material allows for the field-driven domain wall motion which is only limited by the spin-flop transition of the antiferromagnet beyond 25 T. Conversely, electric currents can induce motion of domain walls in most of the edges except those where the two sublattices are present at the borders (e.g. armchair edges). Furthermore, the orientation of the layer relative to the current flow provides an additional degree of freedom for controlling and manipulating magnetic domains in MnPS3. Our results indicate that the implementation of 2D vdW antiferromagnets in real applications requires the engineering of the layer edges which enables an unprecedented functional feature in ultrathin device platforms.