An X- and Q-Band Fe 3+ EPR Study of Nanoparticles of Magnetic Semiconductor Zn 1−x Fe x O
An X- and Q-Band Fe 3+ EPR Study of Nanoparticles of Magnetic Semiconductor Zn 1−x Fe x O
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DOI：
10.1016/j.jmmm.2014.03.031
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发表时间：
2014-08
影响因子：
2.7
通讯作者：
S. Misra;S. Andronenko;A. Thurber;A. Punnoose;A. Nalepa
中科院分区：
文献类型：
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作者：
S. Misra;S. Andronenko;A. Thurber;A. Punnoose;A. Nalepa
对两种类型的 Fe3+ 掺杂、0.1–10%、ZnO、NL 和 QJ 纳米粒子进行了 EPR 研究，分别使用类似的化学水解方法在二甘醇和工业乙醇溶液中制备，在 77 K 的 X 波段（~9.5 GHz）和 10、80 和 295 K 的 Q 波段（~34.0 GHz）进行。为了解释实验结果，EPR 光谱通过自旋哈密尔顿矩阵的精确对角化来模拟，以识别这些样品中不同磁活性位点的 Fe 离子。对NL样品的模拟表明，它们含有（i）Fe3+离子，它取代了Zn离子，由于第二配位层中的氧空位，零场分裂（ZFS）参数在样品上有很大的分布； (ii) 来自表面氧缺陷的 EPR 信号； (iii) 铁磁 (FM) 耦合 Fe 离子，其中 Fe 浓度超过 1%。 QJ 样品的 EPR 谱与 NL 样品的 EPR 谱有很大不同，仅表现出相当强烈的 FM EPR 谱线。发现 NL 和/或 QJ 样品中的 FM 和 EPR 光谱随着纳米颗粒表面形态的差异而发生很大变化。
EPR studies on two types of nanoparticles of Fe3+doped, 0.1–10%, ZnO, NL and QJ, prepared using similar chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions, respectively, were carried out at X-band (~9.5 GHz) at 77 K and at Q-band (~34.0 GHz) at 10, 80, and 295 K. To interpret the experimental results, EPR spectra were simulated by exact diagonalization of the spin-Hamiltonian matrix to identify the Fe ions at different magnetically active sites in these samples. The simulation for NL samples revealed that they contained (i) Fe3+ions, which substituted for Zn ions, the zero-field splitting (ZFS) parameter which has a large distribution over the sample due to oxygen vacancies in the second coordination sphere; (ii) EPR signal from surface oxygen defects; and (iii) ferromagnetically (FM) coupled Fe ions with concentration of Fe more than 1%. The EPR spectra for QJ samples are very different from those for NL samples, exhibiting only rather intense FM EPR lines. The FM and EPR spectra in NL and/or QJ samples are found to vary strongly with differences in the surface morphology of nanoparticles.