Bonetti S, Kukreja R, Chen Z, Macià F, Hernàndez J M, Eklund A, Backes D, Frisch J, Katine J, Malm G, Urazhdin S, Kent A D, Stöhr J, Ohldag H, Dürr H A
Department of Physics, Stanford University, Stanford, California 94305, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
Nat Commun. 2015 Nov 16;6:8889. doi: 10.1038/ncomms9889.
Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.
自旋波作为自旋的集体激发，当由纳米接触中的电流激发时，可在纳米尺度上以非线性孤子的形式出现。这些孤子预计基本上具有圆柱对称性（即s形），但尚无直接的实验观测来证实这一图景。利用具有50皮秒时间分辨率和35纳米空间分辨率的高灵敏度时间分辨磁X射线显微镜，我们能够创建一个实空间自旋波电影，并观察到具有节点线的局域孤子的出现，即具有p形对称性。微磁模拟解释了这些测量结果，并揭示孤子的对称性可由磁场控制。我们的结果拓宽了对纳米尺度自旋波动力学的理解，对磁性纳米器件的设计具有重要意义。
