銅與氧化銅奈米微粒之自旋極化效應; The spin polarization effect of Cu and CuO nanoparticles

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题名:	銅與氧化銅奈米微粒之自旋極化效應;The spin polarization effect of Cu and CuO nanoparticles
作者:	沈奕廷;Yiting Shen
贡献者:	物理研究所
关键词:	奈米微粒;氧化銅;自旋極化;spontaneous;nanoparticles;CuO
日期:	2011-01-28
上传时间:	2011-06-04 15:56:36 (UTC+8)
出版者:	國立中央大學
摘要:	本實驗採用熱蒸鍍法製備銅奈米微粒，並利用熱板對其加熱得到氧化銅奈米微粒。藉由X光繞射實驗與結構精算軟體得知樣品分別為純銅及含有氧缺陷的氧化銅，其化學式為CuO0.94。利用積分寬法和共同體積函數擬合X光繞射譜圖，得到銅和氧化銅奈米微粒的粒徑分別為29 nm與4.2 nm。　　使用物理特性量測系統測量銅與氧化銅奈米微粒在不同實驗溫度下的磁化曲線，並利用朗之萬函數、布里淵函數和反磁線性項對其M-H圖作擬合。在低場時可由自旋極化現象描述，高場部分則隨溫度上升，黎曼效應逐漸減小而反磁行為逐漸增加，最後由冷次反磁項所主導。銅與氧化銅奈米微粒之磁矩在低溫(T<100K)時皆可以由熱磁激發效應來解釋。銅奈米微粒之飽和磁化強度隨溫度關係可由自旋波之熱激發解釋，氧化銅奈米微粒則無法利用此模型描述。兩樣品之磁化強度隨溫度關係圖於低溫時皆由朗之萬項所主導，但銅在55K附近有一小峰值發生，且高溫時的自旋波貢獻並不明顯；而氧化銅則是於135K附近磁化強度隨溫度有緩慢遞增的現象。 The copper nanoparticles were fabricated by the thermal evaporation method, heated to form cupric oxide nanoparticles. The chemical composition of the samples are pure Cu and CuO0.94 by X-ray diffraction and General Structure Analysis System. The mean particle diameter of Cu and CuO nanoparticles are 28.69 nm and 4.2 nm respectively determined using X-ray diffraction patterns. Magnetic properties were measured by Physical Property Measurement System. The M-H curve of Cu and CuO0.94 nanoparticles can be characterized by a Langevin function, a Brillouin function plus a diamagnetic term. The M-H curves of two samples can be elucidated by the spin polarization in the low applied magnetic field, but the magnetization in the high field is predominated by diamagnetic term with temperature increment. The magnetic moment of Cu and CuO0.94 nanoparticles can be explained by thermal-induced effect at low temperature. The saturated magnetization of the copper nanoparticles can be described by the spin-wave excitation model, but the Cupric oxide can’t. The M-T curves of two samples are dominated by Langevin function at low temperature. The magnetization of Cu nanoparticles has a small peak value occurrence nearby 55K, and spin-wave contribution is not obvious at high temperature. The magnetization of CuO0.94 nanoparticles increases gradually with temperature nearby 135K.
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