Micromagnetic simulations studies on Permalloy (Ni80Fe20) nanodot with different shape and edge-to-edge separation (s) down to 25nm arranged in square lattice are reported. We observe the significant variation of spin-wave (SW) dynamics of nanodots of different shapes (triangular, diamond and hexagon) and of fixed dot diameter 100nm with varying s. Modes for single dot are transformed in an array into multiple quantized, edge and centre modes for different shapes and edge-to-edge separations, with different spin wave frequencies and peak intensities. Specifically, in the triangular dot sample, a broad range of mode frequencies is observed with highest SW frequency 14.7 GHz. For separation less than 100nm, the SW frequencies undergoes significant modification due to the varying nature of the magnetostatic and dipolar interaction in the array while for separation above 100nm, the SW frequency mostly remain constant. The power profiles confirm the nature of the observed modes. The spatial profiles of magnetostatic field are determined by a combination of internal magnetic-field profiles within the nanodots and the magnetostatic fields within the lattice. The inter-dots interaction of magnetostatic field shows dipolar and quadrupole contributions for all the shapes. Interestingly, vortex states with shifted core and polarity are observed in the array for all the shapes at Hbias = 0. Our results provide important understanding about the tunability of SW spectra in the array of triangular, diamond and hexagon shaped nanoelements.
Emergence of the stripe-domain phase in patterned Permalloy films
在铁磁坡莫合金（Py=Fe $_{20}$ Ni $_{80}$）中出现条纹畴是一种众所周知的现象，已被广泛观察和表征。这种特殊的磁结构只出现在厚度超过临界值（$d_{cr}$）的薄膜中，临界值强烈地取决于溅射条件（即沉积速率、温度、磁场）。到目前为止，$d_{cr}$通常被认为是均匀畴（H）和条纹畴（SD）之间的边界，分别位于$d_{cr}$之上和之下。在这项工作中，我们研究了从H到SD制度的过渡，在薄膜和微结构桥的Py具有不同的厚度。我们发现有一个中间制度，在一个相当显着的厚度范围低于d $_{cr}$，这是在受限的结构由一个快速变化的畴壁配置和由一个扩大的磁阻下降在矫顽场的信号。我们称之为新兴条带域（ESD）制度。从ESD到SD制度的过渡是伴随着在MFM中出现条纹的厚度处的磁阻比的急剧增加。
The Deformed Image Vortex Ansatz: A Perturbation-Aware Description of Magnetic Vortices in In-Plane Fields
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain（凝聚态物质与纳米科学研究所，天主教鲁汶大学）；Univ. Grenoble Alpes, CEA, CNRS, Grenoble INP, SPINTEC（格勒诺布尔阿尔卑斯大学，法国原子能和替代能源委员会，法国国家科学研究中心，格勒诺布尔国立理工学院，SPINTEC）
Vortex Dynamics-Mediated Low-Field Magnetization Switching in an Exchange-Coupled System
磁涡旋是软磁纳米盘中拓扑稳定的磁性结构，因此引起了人们的广泛关注。人们对孤立系中磁涡旋的性质进行了大量的研究。在这里，我们展示了一个新的方面的磁涡旋的动力学强烈影响的磁结构的环境。我们利用一个纳米点的交换耦合双层与软磁Ni 81 Fe 19（坡莫合金; Py）具有磁涡旋和垂直磁化的L10-FePt表现出大的开关场（HSW）。在低磁场条件下，自旋波的涡旋动力学使得Py中的过剩能量积累，从而触发L10-FePt的反畴形核。我们的研究结果揭示了反畴成核的非局域机制，并提供了一个有效的HSW减少，是超低功率自旋电子器件所需的路线。
