Proenca Mariana P, Rial Javier, Araujo Joao P, Sousa Celia T
IFIMUP - Institute of Physics for Advanced Materials, Nanotechnology and Photonics, Physics and Astronomy Department, Faculty of Sciences, University of Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal.
Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040, Madrid, Spain.
Sci Rep. 2021 May 12;11(1):10100. doi: 10.1038/s41598-021-89474-z.
Cylindrical magnetic nanowires are key elements of fast-recording and high-density 3D-storage devices. The accurate tuning of the magnetization processes at the nanoscale is crucial for the development of future nano-devices. Here, we analyzed the magnetization of Ni nanostructures with 15-100 nm in diameter and 12-230 nm in length and compared our results with experimental data for periodic arrays. Our modelling led to a phase diagram of the reversal modes where the presence of a critical diameter (d ≈ 30 nm) triggered the type of domain wall (DW) formed (transverse or vortex); while a critical length (L ≈ 100 nm) determined the number of DWs nucleated. Moreover, vortex-DWs originated from 3D skyrmion tubes, reported as one of the best configurations for storage devices. By increasing the diameter and aspect-ratio of nanowires with L > 100 nm, three reversal modes were observed: simultaneous propagation of two vortex-DWs; propagation of one vortex-DW; or spiral rotation of both DWs through "corkscrew" mechanism. Only for very low aspect-ratios (nanodisks), no skyrmion tubes were observed and reversal occurred by spiral rotation of one vortex-DW. The broad range of nanostructures studied allowed the creation of a complete phase diagram, highly important for future choice of nanoscaled dimensions in the development of novel nano-devices.
圆柱形磁性纳米线是快速记录和高密度三维存储设备的关键元件。在纳米尺度上精确调节磁化过程对于未来纳米器件的发展至关重要。在此，我们分析了直径为15 - 100纳米、长度为12 - 230纳米的镍纳米结构的磁化情况，并将我们的结果与周期性阵列的实验数据进行了比较。我们的建模得出了反转模式的相图，其中临界直径（d≈30纳米）的存在触发了形成的畴壁（DW）类型（横向或涡旋）；而临界长度（L≈100纳米）决定了成核的DW数量。此外，涡旋DW起源于三维斯格明子管，这被报道为存储设备的最佳配置之一。通过增加长度大于100纳米的纳米线的直径和纵横比，观察到三种反转模式：两个涡旋DW同时传播；一个涡旋DW传播；或两个DW通过“螺旋”机制进行螺旋旋转。仅对于非常低的纵横比（纳米盘），未观察到斯格明子管，并且反转通过一个涡旋DW的螺旋旋转发生。所研究的广泛纳米结构范围使得能够创建一个完整的相图，这对于新型纳米器件开发中未来纳米尺度尺寸的选择非常重要。
