Static and dynamic magnetic properties of densely packed magnetic nanowire arrays
Static and dynamic magnetic properties of densely packed magnetic nanowire arrays
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DOI：
10.1103/physrevb.87.174429
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发表时间：
2013-05-28
影响因子：
3.7
通讯作者：
Matefi-Tempfli, S.
中科院分区：
文献类型：
--
作者：
Dmytriiev, O.;Al-Jarah, U. A. S.;Matefi-Tempfli, S.
通过静态、时间分辨磁光克尔效应测量和微磁模拟，研究了高堆积密度（> .4）、线径远大于交换长度的磁性纳米线阵列的静态和动态磁性能。纳米线通过电沉积在纳米孔模板内形成，使得它们的对称轴垂直于衬底平面。在单线和连续铁磁薄膜的极限情况下，对该阵列的静态和动态特性进行了定量和系统的研究。特别是，与单个纳米线的形状相关的各向异性和阵列作为一个整体的各向异性之间的竞争已经被研究。测量和模拟的磁滞回线在很大程度上是非滞回的，剩磁为零，微磁结构使得净磁化在与外加磁场正交的方向上消失。剩余物态的模拟揭示了相邻纳米线的反铁磁定向以及在每条纳米线的末端形成涡流通量闭合结构。在平行和垂直于纳米线轴线的磁场下，实验和微磁模拟得到的激发谱在定性上是一致的。对于平行于纳米线轴线的场，实验结果与仿真结果也有很好的一致性。最初发现谐振频率随着外加磁场的增大而减小。这是由于基态随着外加电场的增大而变化，阵列平面内的模态分布从非均匀到均匀。当电场垂直于纳米线轴方向时，可以观察到实验光谱与模拟光谱之间的定量差异。研究了磁激发谱与阵列填充密度的关系，给出了平行于纳米线轴线的自旋波在阵列内传播的色散曲线。最后，在纳米线的中间区域观察到端模隧穿现象。由于动态退磁场在导线中间的穿透范围扩大，以及阵列的静态退磁场降低了隧穿势垒，因此对于形成密集排列的导线来说，隧穿效率更高。
The static and dynamic magnetic properties of magnetic nanowire arrays with high packing density (>0.4) and wire diameter much greater than the exchange length have been studied by static and time-resolved magneto-optical Kerr effect measurements and micromagnetic simulations. The nanowires were formed by electrodeposition within a nanoporous template such that their symmetry axes lay normal to the plane of the substrate. A quantitative and systematic investigation has been made of the static and dynamic properties of the array, which lie between the limiting cases of a single wire and a continuous ferromagnetic thin film. In particular, the competition between anisotropies associated with the shape of the individual nanowires and that of the array as a whole has been studied. Measured and simulated hysteresis loops are largely anhysteretic with zero remanence, and the micromagnetic configuration is such that the net magnetization vanishes in directions orthogonal to the applied field. Simulations of the remanent state reveal antiferromagnetic alignment of the magnetization in adjacent nanowires and the formation of vortex flux closure structures at the ends of each nanowire. The excitation spectra obtained from experiment and micromagnetic simulations are in qualitative agreement for magnetic fields applied both parallel and perpendicular to the axes of the nanowires. For the field parallel to the nanowire axes, there is also good quantitative agreement between experiment and simulation. The resonant frequencies are initially found to decrease as the applied field is increased from remanence. This is the result of a change of mode profile within the plane of the array from nonuniform to uniform as the ground state evolves with increasing applied field. Quantitative differences between experimental and simulated spectra are observed when the field is applied perpendicular to the nanowire axes. The dependence of the magnetic excitation spectra upon the array packing density is explored, and dispersion curves for spin waves propagating within the array parallel to the nanowire axis are presented. Finally, a tunneling of end modes through the middle region of the nanowires was observed. The tunneling is more efficient for wires forming densely packed arrays, as a result of the extended penetration of the dynamic demagnetizing fields into the middle of the wires and due to the lowering of the tunneling barrier by the static demagnetizing field of the array.