Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany.
Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany.
Phys Rev Lett. 2023 May 26;130(21):216703. doi: 10.1103/PhysRevLett.130.216703.
The precession of magnon pseudospin about the equilibrium pseudofield, the latter capturing the nature of magnonic eigenexcitations in an antiferromagnet, gives rise to the magnon Hanle effect. Its realization via electrically injected and detected spin transport in an antiferromagnetic insulator demonstrates its high potential for devices and as a convenient probe for magnon eigenmodes and the underlying spin interactions in the antiferromagnet. Here, we observe a nonreciprocity in the Hanle signal measured in hematite using two spatially separated platinum electrodes as spin injector or detector. Interchanging their roles was found to alter the detected magnon spin signal. The recorded difference depends on the applied magnetic field and reverses sign when the signal passes its nominal maximum at the so-called compensation field. We explain these observations in terms of a spin transport direction-dependent pseudofield. The latter leads to a nonreciprocity, which is found to be controllable via the applied magnetic field. The observed nonreciprocal response in the readily available hematite films opens interesting opportunities for realizing exotic physics predicted so far only for antiferromagnets with special crystal structures.
磁子赝自旋围绕平衡赝磁场的进动，后者捕捉反铁磁体中磁振子本征激发的性质，导致了磁子 Hanle 效应。通过在反铁磁绝缘体中电注入和检测自旋输运来实现这一效应，展示了其在器件中的巨大潜力，并作为探测反铁磁体中磁振子本征模式和潜在自旋相互作用的便捷探针。在这里，我们使用两个空间上分离的铂电极作为自旋注入器或探测器，在赤铁矿中观察到 Hanle 信号的非互易性。发现它们的角色互换会改变检测到的磁子自旋信号。记录到的差异取决于所施加的磁场，并且在所谓的补偿场处信号通过其标称最大值时反转符号。我们根据依赖于自旋输运方向的赝磁场来解释这些观察结果。后者导致了非互易性，并且可以通过施加的磁场来控制。在易于获得的赤铁矿薄膜中观察到的非互易响应，为实现迄今为止仅在具有特殊晶体结构的反铁磁体中预测的奇异物理现象提供了有趣的机会。
