High frequency properties of soft metallic ferromagnetic micro- and nano-wires

我们的研究主要包括两个密切相关的活动，涉及从MHz到THz频率范围内的软金属铁磁性微米和纳米线的基本性质。微丝具有一种称为巨磁阻抗(GMI)的高频输运效应，这种效应的产生是因为高频电磁辐射的穿透依赖于磁导率。在这种情况下，实际导线的行为与目前最好的模型预测的行为有很大的不同，这表明这种影响应该比观察到的更大。我们正在进行实验，并模拟材料表面和整体在线性和非线性区域的影响，因为在两者之间的极限观察到最高的灵敏度。铁磁纳米线阵列(FMNW)的高频特性研究正在迅速发展，部分原因是它们有可能应用于集成部分改进的微波器件。我们最近已经证明，一旦开始反转，每根导线完全在一个很小的磁场范围内开关。因此，在饱和以下，静态构型由两组具有向上或向下磁化的导线组成。这导致了两个铁磁共振(FMR)峰，其位置和幅度可以通过适当的场历史来调整，并且可以在零偏压下保持不变。这对微波应用有很大的意义。我们特别感兴趣的是这些阵列在50 GHz以上的铁磁共振行为，并最终在100 GHz以上进入太赫兹区域。特别令人感兴趣的是FMR的线宽和决定它的减振机制的起源。目前，本征阻尼参数似乎很小，这表明高频线宽可能不会太大。

Our research consists principally of two closely related activities concerning fundamental properties of soft metallic ferromagnetic micro- and nano-wires at frequencies ranging from MHz to THz. Microwires are of considerable interest for a high frequency transport effect, called giant magnetoimpedance (GMI), which arises because the penetration of high frequency electromagnetic radiation depends upon the magnetic permeability. The behavior of real wires in this regime is very different from that predicted by the best curent models, which indicate that the effect should be even larger than what is observed. We are performing experiments and modeling the effect of material surface and bulk in both the linear and non-linear regimes, since the highest sensitivity is observed at the limit between the two. The study of high frequency properties of ferromagnetic nanowire arrays (FMNW) is developing rapidly, in part due to the possibility of their application to integrated part improved microwave devices. We have recently shown that each wire switches completely in a small field range, once it begins to reverse. Thus, below saturation the static configuration consists of two populations of wires, with up or down magnetizations. This leads to two ferromagnetic resonance (FMR) peaks, whose positions and amplitudes can be adjusted by the proper field history, and which can be maintained with zero bias. This is of great interest for microwave applications. We are particularly interested in the FMR behavior of these arrays above 50 GHz, and eventually, above 100 GHz, entering into the THz region. Of particular interest is the FMR linewidth and the origin of the damping mechanisms which determine it. At present, the intrinsic damping parameter appears to be quite small, suggesting that high frequency linewidths may not be too large.