Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle (Saale), Germany.
Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
Adv Mater. 2023 Jun;35(23):e2209616. doi: 10.1002/adma.202209616. Epub 2023 Apr 27.
Antiferromagnets with non-collinear spin structures display various properties that make them attractive for spintronic devices. Some of the most interesting examples are an anomalous Hall effect despite negligible magnetization and a spin Hall effect with unusual spin polarization directions. However, these effects can only be observed when the sample is set predominantly into a single antiferromagnetic domain state. This can only be achieved when the compensated spin structure is perturbed and displays weak moments due to spin canting that allows for external domain control. In thin films of cubic non-collinear antiferromagnets, this imbalance is previously assumed to require tetragonal distortions induced by substrate strain. Here, it is shown that in Mn SnN and Mn GaN, spin canting is due to structural symmetry lowering induced by large displacements of the magnetic manganese atoms away from high-symmetry positions. These displacements remain hidden in X-ray diffraction when only probing the lattice metric and require measurement of a large set of scattering vectors to resolve the local atomic positions. In Mn SnN, the induced net moments enable the observation of the anomalous Hall effect with an unusual temperature dependence, which is conjectured to result from a bulk-like temperature-dependent coherent spin rotation within the kagome plane.
具有非共线自旋结构的反铁磁体表现出各种性质，使它们成为自旋电子器件的理想选择。其中一些最有趣的例子是反常霍尔效应，尽管磁化强度可以忽略不计，以及自旋霍尔效应中不寻常的自旋极化方向。然而，只有当样品主要处于单个反铁磁畴状态时，才能观察到这些效应。只有在补偿自旋结构受到干扰并由于自旋倾斜而显示出微弱的磁矩时，才能实现这一点，自旋倾斜允许外部畴控制。在立方非共线反铁磁体的薄膜中，这种不平衡以前被认为需要由衬底应变引起的四方畸变。在这里，我们表明，在 MnSnN 和 MnGaN 中，自旋倾斜是由于磁性锰原子从高对称位置的大位移引起的结构对称性降低所致。这些位移在仅探测晶格度量时隐藏在 X 射线衍射中，并且需要测量大量散射矢量来解析局部原子位置。在 MnSnN 中，诱导的净磁矩使反常霍尔效应能够以不寻常的温度依赖性进行观察，这被推测是由于在 kagome 平面内的体相温度相关的相干自旋旋转。
