銅奈米微粒隨氧化程度對自旋極化的影響

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题名:	銅奈米微粒隨氧化程度對自旋極化的影響
作者:	苟穎書;Kou,Ying-shu
贡献者:	物理學系
关键词:	銅;氧化亞銅;氧化銅;奈米微粒;自旋極化;磁性;Cu;Cu2O;CuO;nano particle;spin polarization;magnetic property
日期:	2013-06-27
上传时间:	2013-07-10 12:00:05 (UTC+8)
出版者:	國立中央大學
摘要:	我們使用熱蒸鍍法製備銅奈米微粒，並於空氣中加熱氧化，氧化過程為Cu氧化為Cu2O再氧化為CuO。樣品依不同氧化程度編上O0、 O1…至O6 的編號。我們以XRD 做樣品分析，以積分寬法和共同體積函數法對X 光繞射譜圖進行擬合得到粒徑及粒徑分佈，並以GSAS 結構晶算軟體計算其內容物的成份比例。銅和氧化亞銅奈米微粒均呈現不同於塊材時的反磁性而具有自旋極化現象。Langevin 順磁函數加上線性反磁項可以描述M(Ha)曲線，在低溫和高磁場需增加Brillouin 函數描述誘發Zeeman 磁化強度。而氧化亞銅與氧化銅的M(Ha)曲線需於Langevin 函數增加一個等效磁場因子α 來描述。我們對M(Ha)曲線進行擬合，以討論擬合參數於不同溫度及不同氧化程度間的關聯。 Cu nanoparticles were fabricated by employing the thermal evaporation method. The resultant Cu nanoparticles assembly can be progressively oxidized into Cu2O and CuO phases by using a heating plate in the air condition. The mean particle diameter of Cu (sample O0) obtained from the broadening X-ray diffraction (XRD) peak profiles of finite-sized particle is 6.1 nm. The composition of various degree of oxidization is determined by refining the XRD pattern using General Structural Analysis System (GSAS) program. Spin polarization is observed in series of Cu, Cu2O, and CuO nanoparticles. The M(Ha) curves of Cu nanoparticles may be described by a Langevin profile indicating randomly oriented magnetic moments are aligned upon application of magnetic field and a linear Lenz diamagnetic term. An additional Brillouin profile is needed to describe the Zeeman magnetization in the high-Ha regime. The effective magnetic field factor α is needed to incorporate in the Langevin profile to describe M(Ha) curves of Cu2O and CuO nanoparticles. Thermal profile of saturation magnetization MS(T) of Cu2O clearly departs from the Bloch's law for isotropic excitation, signaling the appearance of magnetic anisotropy. Ferromagnetic spin correlation is also observed in CuO nanoparicles, where the MS(T) curve shows Bloch's behavior for thermal magnons.
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