Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon 34141, Korea.
School of Electrical Engineering, KAIST, Daejeon 34141, Korea.
Nat Nanotechnol. 2016 Oct;11(10):878-884. doi: 10.1038/nnano.2016.109. Epub 2016 Jul 11.
Spin-orbit torques arising from the spin-orbit coupling of non-magnetic heavy metals allow electrical switching of perpendicular magnetization. However, the switching is not purely electrical in laterally homogeneous structures. An extra in-plane magnetic field is indeed required to achieve deterministic switching, and this is detrimental for device applications. On the other hand, if antiferromagnets can generate spin-orbit torques, they may enable all-electrical deterministic switching because the desired magnetic field may be replaced by their exchange bias. Here we report sizeable spin-orbit torques in IrMn/CoFeB/MgO structures. The antiferromagnetic IrMn layer also supplies an in-plane exchange bias field, which enables all-electrical deterministic switching of perpendicular magnetization without any assistance from an external magnetic field. Together with sizeable spin-orbit torques, these features make antiferromagnets a promising candidate for future spintronic devices. We also show that the signs of the spin-orbit torques in various IrMn-based structures cannot be explained by existing theories and thus significant theoretical progress is required.
非磁性重金属的自旋轨道耦合会产生自旋轨道扭矩，从而实现垂直磁化的电切换。然而，在各向同性的横向结构中，这种切换并非完全是电驱动的。实际上，需要外加一个面内磁场才能实现确定性切换，这对于器件应用是不利的。另一方面，如果反铁磁体能够产生自旋轨道扭矩，它们可能实现全电确定性切换，因为所需的磁场可以被它们的交换偏置所取代。在这里，我们报告了 IrMn/CoFeB/MgO 结构中可观的自旋轨道扭矩。反铁磁 IrMn 层还提供了一个面内的交换偏置场，这使得无需外部磁场的辅助，就能实现垂直磁化的全电确定性切换。除了可观的自旋轨道扭矩外，这些特性使得反铁磁体成为未来自旋电子器件的一个很有前途的候选材料。我们还表明，现有理论无法解释各种基于 IrMn 的结构中的自旋轨道扭矩的符号，因此需要取得显著的理论进展。
