Low temperature EPR investigation of Co2+ ion doped into rutile TiO2 single crystal: Experiments and simulations
Low temperature EPR investigation of Co2+ ion doped into rutile TiO2 single crystal: Experiments and simulations
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DOI：
10.1016/j.jmmm.2016.09.081
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发表时间：
2017-02
影响因子：
2.7
通讯作者：
A. Zerentürk;M. Açıkgöz;S. Kazan;F. Yildiz;B. Aktaş
中科院分区：
文献类型：
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作者：
A. Zerentürk;M. Açıkgöz;S. Kazan;F. Yildiz;B. Aktaş
本文报道了最有前途的忆阻材料之一的Co ~（2+）掺杂金红石（TiO_2）的X波段EPR谱。在液氦（7-13 K）温度下，我们得到了三个相互垂直平面上的光谱角变化。由于杂质离子具有1/2的有效自旋和7/2的核自旋，因此使用了仅包含电子塞曼和超精细项的相对简单的自旋哈密顿量。理论分析中采用了两种不同的方法。首先研究了基于微扰理论的光谱线性回归分析方法。然而，这种方法是不足以分析Co+2光谱，并导致复杂的本征向量的G和A张量由于大的各向异性的本征值。因此，对所有光谱进行了自旋哈密顿量精确对角化的重新分析，并考虑了由于实验条件导致的小样品偏离精确晶面的影响，得到了GandAtensors的高精度本征值和本征向量.结果表明，g张量和A张量的本征轴平行于晶体学方向。因此，我们的EPR实验证明，Co ~（2+）离子取代了晶格中的Ti ~（4+）离子。g张量的主值为gx=2.110（6），戈伊=5.890（2），gz=3.725（7），超精细张量的主值为Ax=42.4，Ay=152.7，Az=26（单位10−4/cm）。
In this paper, we present the results of X-band EPR spectra of Co2+ion doped rutile (TiO2) which is one of the most promising memristor material. We obtained the angular variation of spectra in three mutually perpendicular planes at liquid helium (7–13 K) temperatures. Since the impurity ions have ½ effective spin and 7/2 nuclear spin, a relatively simple spin Hamiltonian containing only electronic Zeeman and hyperfine terms was utilized. Two different methods were used in theoretical analysis. Firstly, a linear regression analysis of spectra based on perturbation theory was studied. However, this approach is not sufficient for analyzing Co+2spectra and leads to complex eigenvectors for G and A tensors due to large anisotropy of eigenvalues. Therefore, all spectra were analyzed again with exact diagonalization of spin Hamiltonian and the high accuracy eigenvalues and eigenvectors ofGandAtensors were obtained by taking into account the effect of small sample misalignment from the exact crystallographic planes due to experimental conditions. Our results show that eigen-axes of g and A tensors are parallel to crystallographic directions. Hence, our EPR experiments proves that Co2+ions substitute for Ti4+ions in lattice. The obtained principal values of g tensor are gx=2.110(6), gy=5.890(2), gz=3.725(7) and principal values of hyperfine tensor are Ax=42.4, Ay=152.7, Az=26 (in 10−4/cm).