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    Title: Effect of magnetic element doping on the electronic and magnetic properties of CeO2 nano-particles
    Other Titles: 磁性元素摻雜對CeO2奈米粒子電子結構與磁性之影響
    Authors: 王偉丞;Wang, Wei-Cheng
    Contributors: 淡江大學物理學系博士班
    張經霖;Chan, Ching-Lin
    Keywords: X 光吸收光譜;X 光放射光譜;二氧化鈰;奈米粒子;稀磁性半導體;XAS;XES;DMS;CeO2 nanoparticles
    Date: 2014
    Issue Date: 2015-05-04 09:47:45 (UTC+8)
    Abstract: 本論文利用同步輻射X光吸收光譜(XAS)與X光放射光譜(XES)的量測來研究磁性元素摻雜對二氧化鈰(CeO2)納米粒子的電子結構,並針對其變化加以討論,藉此了解電子結構與磁性之間的關連性。利用Ce L3-edge和M4,5-edge的量測可以觀察出的Ce的價電子數的改變情況。觀察摻雜物(Fe與Cr)的價數變化,則可利用其K-edge和L2,3-edge的量測,也可以說明在摻雜時的其價電子數的改變情況。利用O K-edge吸收光譜,可以發現在其吸收前景所形成的特徵峰,是因為Ce 4f的電子與O 2p的電子混成所形成的,此混成軌域的吸收強度隨著磁性元素摻雜濃度的增加有很明顯的改變。
      實驗結果說明,利用不同磁性元素的摻雜,在CeO2 NP的系統中所引起的磁性機制是不同的。在Fe摻雜系列的樣品,在Fe摻雜濃度較低時(低於5%),會形成具有鐵磁性的Fe3+-Vo-Ce3 +的電子組態(Vo表示為氧空缺),因此在Fe低濃度摻雜時,其磁性會隨著摻雜量增加而提高。然而,隨著Fe摻雜濃度持續增加,除了原來具有磁性的Fe3+-Vo-Ce3 +的電子組態外,因為Fe摻雜濃度增加,也產生了反鐵磁的電子組態Fe3+-Vo-Fe3+,反而造成磁性的降低。而在Cr摻雜系列的樣品,隨著Cr3+摻雜濃度的增加,對系統形成了具有鐵磁性的Cr3+-Vo-Ce3+電子組態也隨之增加,因此造成了磁性的提升。
    This study reports the electronic structure of magnetic element doped CeO2 nanoparticles (NPs). Systematic synchrotron radiation based X-ray spectroscopy analysis was utilized to investigate the electronic structures in CeO2 NPs, which is determined by coupled X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES). The result revealed that the magnetic properties are correlated to the electronic structures. Ce L3-edge and M4,5-edge spectra reveal the variations of the charge states of Ce. Transition metal (TM) K-edge and L2,3-edge spectra indicate the variations of their valence states upon TM doping. The pre-edge features of oxygen K-edge spectra due to the hybridization between cerium 4f and oxygen 2p states depend strongly on the concentration of magnetic element doping. Our results indicate that, for Fe-doped samples, ferromagnetic Fe3+-Vo-Ce3+ configuration is formed at low Fe concentrations (below 5%). While, at higher Fe concentrations, anti-ferromagnetic Fe3+-Vo-Fe3+ configuration is formed. For Cr-doped samples, the major effect of magnetic properties in Cr3+ doping system is formed the ferromagnetic Cr3+-Vo-Ce3+ configuration.
    Appears in Collections:[物理學系暨研究所] 學位論文

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