顆粒間交互作用對奈米金自發磁性之影響

The spontaneous magnetism of gold nanoparticles by interparticle interaction

郭彥廷(Yen-Ting Kuo)

指導教授 ： 李文献

國立中央大學/理學院/物理學系/碩士(2008年)

摘要

使用熱蒸鍍法製作金奈米微粒，以編號Au531601、Au070604表示，利用TEM與X光繞射譜圖，定出微粒粒徑；從X光繞射譜圖與X光螢光光譜分析儀分析，樣品成分為95%金與5%鎢，無其他可偵測成份。由TEM影像觀察到Au531601金奈米微粒形貌為二十面體(Icosahedron)。
3.5nm與6nm的金奈米微粒，皆觀察到自旋極化現象，且在不同溫度下變溫磁化強度出現一寬峰，推測與量子局域效應所造成的能隙差(Kubo gap)有關，而3.5nm金奈米微粒更觀察到激發磁矩現象。本論文更進一步壓合金奈米微粒，使得奈米微粒間交互作用影響增加，觀察自旋極化與激發磁矩現象的變化；我們亦發現隨著聚合密度變大，樣品的抗磁率也隨之增加。

關鍵字

交互作用 ； 奈米金 ； 自發磁性 ； 金

並列摘要

Two sets of gold nanoparticles were fabricated by the thermal evaporation method. X-ray diffraction patterns and TEM images showed the mean particle diameters for the two sets of samples to be 3.5 and 6 nm. TEM images reveal an icosahedral shape for the 3.5 nm Au nanoparticles, which corresponds to 923 atoms packed in six icosahedral shells.
Magnetic properties were studied by ac magnetic susceptibility and magnetization measurements. The M-H curves of 3.5 nm Au nanoparticles can be well described by a Langevin profile plus a Brilliun Zeeman one and a linear diamagnetic term. We found that the spin arrangements of 3.5 nm Au particles are ferrimagnetic in nature, which contained a net spontaneous magnetic moment of 26 μB per particle.
The effect of interparticle separation was also studied. The low temperature saturated magnetization MS and induced magnetization Mi of the fully packed power were 84% and 59% that of very loosely packed power.

並列關鍵字

interaction ； spontaneous ； nanoparticles ； gold

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