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，在频率范围从MHz到太赫兹的软金属铁磁微米和纳米线的基本属性。 由于高频电磁辐射的穿透取决于磁导率，因此被称为巨磁阻抗（GMI）的高频输运效应引起了相当大的兴趣。 真实的导线在这种状态下的行为与最佳电流模型所预测的行为非常不同，这表明这种影响应该比观察到的还要大。 我们正在进行实验，并在线性和非线性机制中对材料表面和体积的影响进行建模，因为在两者之间的极限处观察到最高的灵敏度。 铁磁纳米线阵列（FMNW）高频特性的研究发展迅速，部分原因是其应用于集成部分改进的微波器件的可能性。 我们最近已经证明，每根导线一旦开始反向，就会在一个小的场范围内完全开关。因此，在饱和以下，静态配置由两组线组成，具有向上或向下磁化。 这导致两个铁磁共振（FMR）峰，其位置和幅度可以通过适当的场历史来调整，并且可以保持零偏置。 这对于微波应用是非常重要的。 我们特别感兴趣的是这些阵列在50 GHz以上的FMR行为，并最终在100 GHz以上，进入太赫兹区域。 特别感兴趣的是FMR线宽和阻尼机制的起源，决定它。 目前，固有阻尼参数似乎相当小，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.