Antiferromagnetic Hysteresis Above the Spin Flop Field - source data for https://arxiv.org/abs/2109.00093

Magnetocrystalline anisotropy is essential in the physics of antiferromagnets and commonly treated as a constant, not depending on an external magnetic field. However, we demonstrate that in CoO the anisotropy should necessarily depend on the magnetic field, which is shown by the spin Hall magnetoresistance of the CoO | Pt device. Below the Néel temperature CoO reveals a spin-flop transition at 240 K at 7.0 T, above which a hysteresis in the angular dependence of magnetoresistance unexpectedly persists up to 30 T. This behavior is shown to agree with the presence of the unquenched orbital momentum, which can play an important role in antiferromagnetic spintronics.

磁晶各向异性（Magnetocrystalline anisotropy）在反铁磁体的物理机制中不可或缺，通常被视作与外磁场无关的恒定参数。然而，本研究证实，氧化钴（CoO）中的各向异性必然依赖于磁场，这一结论可通过CoO|铂（Pt）器件的自旋霍尔磁电阻（spin Hall magnetoresistance）得到验证。在奈耳温度（Néel temperature）以下，氧化钴在7.0特斯拉的磁场中于240开尔文处发生自旋翻转相变（spin-flop transition）；而在该相变临界磁场之上，磁阻角依赖性的磁滞现象出乎意料地延续至30特斯拉。研究表明，该行为与未淬灭轨道动量（unquenched orbital momentum）的存在相一致，而未淬灭轨道动量在反铁磁自旋电子学（antiferromagnetic spintronics）领域中可发挥关键作用。