Department of Optical Science and Engineering, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Fudan University , Shanghai 200433, China.
ACS Appl Mater Interfaces. 2018 Feb 7;10(5):5090-5098. doi: 10.1021/acsami.7b16978. Epub 2018 Jan 23.
Dynamic magnetic properties in perpendicularly exchange-coupled [Co/Ni]/Cu (t = 0-2 nm)/TbCo structures show strong dependences on the interfacial antiferromagnetic strength J, which is controlled by the Cu interlayer thickness. The precession frequency f and effective damping constant α of a [Co/Ni] multilayer differ distinctly for parallel (P) and antiparallel (AP) magnetization orientation states. For samples with a thin t, f of the AP state is apparently higher, whereas α is lower than that in the P state, owing to the unidirectional exchange bias effect (H) from the TbCo layer. The differences in f and α between the two states gradually decrease with increasing t. By using a uniform precession model including an additional H term, the field-dependent frequency curves can be well-fitted, and the fitted H value is in good agreement with the experimental data. Moreover, the saturation damping constant α displays a nearly linear correlation with J. It decreases significantly with J and eventually approaches a constant value of 0.027 at t = 2 nm where J vanishes. These results provide a better understanding and effective control of magnetization dynamics in exchange-coupled composite structures for spintronic applications.
垂直交换耦合 [Co/Ni]/Cu（t=0-2nm）/TbCo 结构的动态磁性能强烈依赖于界面反铁磁强度 J，J 由 Cu 中间层厚度控制。[Co/Ni] 多层的进动频率 f 和有效阻尼常数 α 对于平行（P）和反平行（AP）磁化取向状态有明显的区别。对于较薄 t 的样品，由于 TbCo 层的单向交换偏置效应（H），AP 状态的 f 明显更高，而 α 则低于 P 状态。随着 t 的增加，两种状态之间的 f 和 α 的差异逐渐减小。通过使用包括附加 H 项的均匀进动模型，可以很好地拟合场依赖的频率曲线，拟合的 H 值与实验数据非常吻合。此外，饱和阻尼常数 α 与 J 呈近似线性关系。它随 J 显著减小，最终在 t=2nm 处趋近于 0.027 的常数，此时 J 消失。这些结果为用于自旋电子学应用的交换耦合复合结构中的磁动力学提供了更好的理解和有效控制。
