Rodriguez Raul D, Sheremet Evgeniya, Deckert-Gaudig Tanja, Chaneac Corinne, Hietschold Michael, Deckert Volker, Zahn Dietrich R T
Institute of Physics, Technische Universität Chemnitz, D-09107 Chemnitz, Germany.
Nanoscale. 2015 Jun 7;7(21):9545-51. doi: 10.1039/c5nr01277e.
Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm(-1) attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced.
纳米材料具有展现出与其块状材料不同的物理性质这一显著特性。当氧化物纳米颗粒与金属纳米结构相互作用时,会产生额外的复杂性和功能性。在此背景下,本文报道了由于氧化铁纳米晶体的等离子体增强而产生的拉曼光谱,显示出自旋波的激活。发现在金和银尖端上的氧化铁纳米颗粒在1584 cm(-1) 附近显示出一个波段,归因于自旋波磁振子模式。对于沉积在硅 (111) 或玻璃基板上的纳米颗粒,未观察到这种磁振子模式。金属 - 纳米颗粒相互作用和强局部电磁场促成了这种模式的出现。通过尖端增强拉曼光谱 (TERS) 证实了产生这种模式的局部激发。仅当TERS尖端靠近纳米晶体边缘时自旋波才出现,这表明局部等离子体与自旋波的耦合是由于纳米颗粒边界处的对称性破缺和额外的电场限制而产生的。除了先前在类似系统中报道的声子限制效应外,这项工作为等离子体辅助产生和检测光诱导自旋波提供了重要见解。
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