顆粒間交互作用對奈米鎳粉末巨觀磁行為的影響

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题名:	顆粒間交互作用對奈米鎳粉末巨觀磁行為的影響
作者:	黃是衡;Shih-Heng Huang
贡献者:	物理研究所
关键词:	奈米;鎳;nickel;nanoparticle
日期:	2011-07-13
上传时间:	2012-01-05 14:41:45 (UTC+8)
摘要:	本實驗採用熱蒸鍍法製備鎳奈米微粒，藉由X光繞射實驗與結構精算軟體得知樣品分別含有氧缺陷的氧化鎳。而利用積分寬法擬合X光繞射譜圖，得到奈米微粒的粒徑為9 nm。為了觀察鎳奈米微粒間交互作用對其磁特性的影響，我們對樣品做壓合的動作，聚合密度（CD）的範圍大約從1 %到 70 %。由實驗所得的數據去探討奈米顆粒的磁行為，首先觀察到飽和磁化強度Ms對壓合密度有先上升後下降的趨勢，這是由於磁矩間的交互作用所致，而飽和磁化Ms在溫度的變化上觀察到隨著溫度的上升，Ms開始有下降的趨勢，在假設自旋間只有海森堡交互作用耦合能之下，以自旋波的模型去探討此現象。在頑磁力現象研究上，我們觀察到隨著壓合密度的增加，以及溫度的增加，皆會使得頑磁力有下降的趨勢。利用參考資料中所得到的模擬結果來做解釋，可發現隨壓合密度增加時，本樣品顆粒表面和顆粒內的磁矩將排列的越整齊一致。 The Ni nanoparticles were fabricated by the thermal evaporation method. The chemical composition of the samples are pure Ni and NiO by X-ray diffraction and General Structure Analysis System. The mean particle diameter of Ni nanoparticles are 9 nm determined using X-ray diffraction patterns. We controled the distance among particles by means of pressing the very loosely packed nanoparticle powder samples, characterized by the compacting density (CD) of the samples that ranging from 1 % to 70 % of the density of bulk Ni. By experimental data of nickel nanoparticles, we observed, first, the saturation magnetization Ms increase and then slightly decrease when the packing fraction increase, and this phenomenon is due to the interaction between magnetic moments. Second, the saturation magnetization Ms will decrease when temperature rise, we study this phenomenon by the spin-wave model under the assumption that only the Heisenberg interaction between the magnetic moment. In the study of coercivity magnetic phenomena, We observed that with the packing fraction and temperature increases, both will make a downward trend in magnetic coercivity. When use the simulation result of reference to explain the phenomenon, lead to that the surface and inside surface magnetic moment of nickel nanoparticle will arrange in the more consistent, when the packing fraction increase.
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