Abstract Ultrafast spin dynamics in ferromagnetic nanodot arrays with dot diameter 100 nm and thickness 20 nm arranged in honeycomb and octagonal lattice symmetries are studied to explore the tunability of the collective magnetization dynamics. By varying the inter-dot separation between 30 nm and 300 nm drastic variation in the precessional dynamics from strongly collective to completely isolated regime has been observed by using all-optical time-resolved magneto-optical Kerr microscope. Micromagnetic simulation is exploited to gain insights about the resonant mode profiles and magnetic coupling between the nanodots. A significant spectral and spatial variation in the resonant mode with increasing dipolar interaction is demonstrated with increasing inter-dot separation. The spins driven by effective field inside single nanodots are prone to precess independently, generating two self-standing centre and edge modes in the array that are influenced by the relative orientation between the inter-dot coupling direction and bias magnetic field. The anisotropic behavior of dipolar field is rigorously investigated here. Splitting of the centre mode in case of octagonal lattice is experimentally observed here as a consequence of the anisotropic dipolar field between the nanodot pairs coupled horizontally and vertically, which is not found in the honeycomb lattice. In addition, proper understanding of the modification of dynamic mode profile by neighboring dipolar interaction built up here, is imperative for further control of the dynamic dipolar interaction and the corresponding collective excitation in magnonic crystals. The usage of nanodot lattices with complex basis structures can be advantageous for the designing of high density magnetic recording media, spin-wave filter and logic devices.

中文翻译：

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各向异性偶极相互作用对排列在蜂窝和八边形晶格中的 Ni 80 Fe 20 纳米点阵列自旋动力学的影响

摘要 研究了以蜂窝和八边形晶格对称排列的点直径为 100 nm、厚度为 20 nm 的铁磁纳米点阵列中的超快自旋动力学，以探索集体磁化动力学的可调性。通过改变 30 nm 和 300 nm 之间的点间距，使用全光学时间分辨磁光克尔显微镜观察到进动动力学从强烈集体到完全孤立的剧烈变化。利用微磁模拟来深入了解纳米点之间的共振模式分布和磁耦合。随着点间间隔的增加，共振模式的显着光谱和空间变化随着偶极相互作用的增加而显着变化。由单个纳米点内的有效场驱动的自旋容易独立进动，在阵列中产生两种自立式中心和边缘模式，这些模式受点间耦合方向和偏置磁场之间的相对取向的影响。这里严格研究了偶极场的各向异性行为。由于水平和垂直耦合的纳米点对之间的各向异性偶极场，这里通过实验观察到在八边形晶格情况下中心模式的分裂，这在蜂窝晶格中没有发现。此外，正确理解此处建立的相邻偶极相互作用对动态模式轮廓的修改，对于进一步控制动态偶极相互作用和磁子晶体中相应的集体激发势在必行。