Chung Sunjae, Eklund Anders, Iacocca Ezio, Mohseni Seyed Majid, Sani Sohrab R, Bookman Lake, Hoefer Mark A, Dumas Randy K, Åkerman Johan
Department of Physics, University of Gothenburg, 412 96 Gothenburg, Sweden.
Materials and Nano Physics, School of ICT, KTH-Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden.
Nat Commun. 2016 Apr 18;7:11209. doi: 10.1038/ncomms11209.
Static and dynamic magnetic solitons play a critical role in applied nanomagnetism. Magnetic droplets, a type of non-topological dissipative soliton, can be nucleated and sustained in nanocontact spin-torque oscillators with perpendicular magnetic anisotropy free layers. Here, we perform a detailed experimental determination of the full droplet nucleation boundary in the current-field plane for a wide range of nanocontact sizes and demonstrate its excellent agreement with an analytical expression originating from a stability analysis. Our results reconcile recent contradicting reports of the field dependence of the droplet nucleation. Furthermore, our analytical model both highlights the relation between the fixed layer material and the droplet nucleation current magnitude, and provides an accurate method to experimentally determine the spin transfer torque asymmetry of each device.
静态和动态磁孤子在应用纳米磁学中起着关键作用。磁滴作为一种非拓扑耗散孤子，可以在具有垂直磁各向异性自由层的纳米接触自旋扭矩振荡器中形核并维持。在此，我们针对广泛的纳米接触尺寸，在电流-磁场平面上对完整的磁滴形核边界进行了详细的实验测定，并证明其与源自稳定性分析的解析表达式高度吻合。我们的结果调和了近期关于磁滴形核对磁场依赖性的相互矛盾的报道。此外，我们的解析模型既突出了固定层材料与磁滴形核电流大小之间的关系，又提供了一种准确的方法来通过实验确定每个器件的自旋转移扭矩不对称性。
