[论文解读] Electrically controlled long-distance spin transport through an antiferromagnetic insulator

Romain Lebrun, Andrew Ross+7 more|arXiv (Cornell University)|May 7, 2018

Magnetic properties of thin films参考文献 25被引用 167

一句话总结

展示通过血赤石血红铁（α-Fe2O3）实现的远距离自旋电流输运，利用自旋霍尔注入，显示自旋流通过界面自旋偏置和磁场调谐反铁磁共振来控制。

ABSTRACT

Spintronics uses spins, the intrinsic angular momentum of electrons, as an alternative for the electron charge. Its long-term goal is in the development of beyond-Moore low dissipation technology devices. Recent progress demonstrated the long-distance transport of spin signals across ferromagnetic insulators. Antiferromagnetically ordered materials are however the most common class of magnetic materials with several crucial advantages over ferromagnetic systems. In contrast to the latter, antiferromagnets exhibit no net magnetic moment, which renders them stable and impervious to external fields. In addition, they can be operated at THz frequencies. While fundamentally their properties bode well for spin transport, previous indirect observations indicate that spin transmission through antiferromagnets is limited to short distances of a few nanometers. Here we demonstrate the long-distance, over tens of micrometers, propagation of spin currents through hematite (α-Fe2O3), the most common antiferromagnetic iron oxide, exploiting the spin Hall effect for spin injection. We control the spin current flow by the interfacial spin-bias and by tuning the antiferromagnetic resonance frequency with an external magnetic field. This simple antiferromagnetic insulator is shown to convey spin information parallel to the compensated moment (Néel order) over distances exceeding tens of micrometers. This newly-discovered mechanism transports spin as efficiently as the net magnetic moments in the best-suited complex ferromagnets. Our results pave the way to ultra-fast, low-power antiferromagnet-insulator-based spin-logic devices that operate at room temperature and in the absence of magnetic fields.

研究动机与目标

• 用反铁磁绝缘体（AFIs）实现低耗散的自旋电子设备的动机。
• 展示通过 AFI 在数十微米尺度内的远距离自旋电流传输。
• 展示通过自旋霍尔效应的电注入，并通过界面自旋偏置和磁场调谐实现控制。
• 强调 AFIs 相对于铁磁材料在稳定性和 THz 工作方面的优势。

提出的方法

• 使用自旋霍尔效应向血赤石（α-Fe2O3）注入自旋作为反铁磁绝缘体。
• 在远端界面检测传输的自旋信息以量化输运长度尺度。
• 用外部磁场调谐反铁磁共振频率以调制自旋输运。
• 通过 AFI 边界的界面自旋偏置控制自旋流动。
• 将输运效率与铁磁材料进行对比以评估用于低功耗自旋逻辑的潜力。

实验结果

研究问题

• RQ1 自旋电流是否能在血赤石反铁磁绝缘体中通过数十微米进行传输？
• RQ2 界面自旋偏置如何影响通过 AFI 的自旋传输？
• RQ3 通过外部场调谐 AF 共振在多大程度上改变自旋传输？
• RQ4 在室温下，AFI 是否能够提供与铁磁材料相当的自旋信息传输效率？
• RQ5 对于基于反铁磁绝缘体的自旋逻辑装置，有何影响？

主要发现

• 自旋电流可在血赤石中传播数十微米，证明了在 AFI 中的远距离传输。
• 通过自旋霍尔效应实现的自旋注入使自旋能够穿过 AFI。
• 界面自旋偏置控制跨越 AFI 界面的自旋电流输送量。
• 外部磁场对反铁磁共振频率的调谐可调制自旋传输。
• 这种机制在室温下无需净磁化也能高效传递自旋信息。
• 结果表明对基于 AFI 的自旋逻辑装置具有潜在的超高速、低功耗前景。