Role of Co Clusters and Oxygen Vacancies in the Magnetic and Transport Properties of Co-Doped In2O3 Films

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• 作者：Yukai An ; Dongyan Yang ; Guanxiong Ma ; Yi Zhu ; Shiqi Wang ; Zhonghua Wu ; Jiwen Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：May 15, 2014
• 年：2014
• 卷：118
• 期：19
• 页码：10448-10454
• 全文大小：376K
• 年卷期：v.118,no.19(May 15, 2014)
• ISSN：1932-7455

文摘

The (In_1鈥?i>xCo_x)₂O₃ films with x = (0.055, 0.08, 0.10, 0.15) have been prepared by a radio frequency magnetron sputtering technique and investigated by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, Hall effect, and room-temperature magnetic measurements. The detailed structural analyses and full multiple-scattering ab initio calculations indicate that most Co²⁺ ions substitute for In³⁺ sites of In₂O₃ lattice and form Co_In²⁺ + V_O complexes with the O vacancy in the nearest coordination shell, whereas a portion of the Co atoms form the precipitate of Co metal clusters for all the (In_1鈥?i>xCo_x)₂O₃ films. Despite the formation of Co clusters, magnetic characterizations show that the saturated magnetization M_s of films first increases and then decreases with the increase of Co concentration, suggesting that the small Co clusters are superparamagnetic. The electronic conducting mechanism is dominated by Mott variable range hopping behavior for all the films. The strong localization of carriers suggests the bound magnetic polarons scenario. It can be concluded that the observed room-temperature ferromagnetism in the (In_1鈥?i>xCo_x)₂O₃ films is intrinsic and originates from electrons bound in defect states associated with oxygen vacancies. There exists an optimal localization radius 尉 of variable range hopping for achieving the largest M_s in the (In_1鈥?i>xCo_x)₂O₃ films.