Abstract The infrared (IR) reflectivity of the cubic metal oxides MgO, MnO, and NiO has been measured at room temperature using the technique of oblique incidence. The use of this technique at three angles of incidence provides multiple sets of spectra (including both s- and p-polarizations) to analyze when compared to the standard normal incidence case, which has been used extensively in the past for these compounds. It is shown that the transverse optic (TO) and longitudinal optic (LO) mode phonon parameters can be determined with greater accuracy by using the factorized model for the fits, as compared with the popular classical model used previously, and by fitting the derivative of the reflectivity. Our results for the phonon mode parameters are similar to those found earlier, as could be expected, but are generally more precise. An analysis of the difference in frequency of the TO mode in antiferromagnetic NiO at room temperature for the two polarizations of reflected light revealed a TO mode splitting of about 4 cm−1, with the p-polarized light TO mode having the higher frequency: This small splitting is in agreement with theoretical predictions. This more precise IR method for revealing the phonon mode behavior in such magnetically ordered cubic metal oxides, which are prototypes of strongly correlated electronic systems and have been found to be Mott-Hubbard insulators, may be readily applied to any similar antiferromagnetic system.

中文翻译：

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立方氧化镁、氧化锰和氧化镍中声子的斜入射红外反射光谱

摘要 使用斜入射技术在室温下测量了立方金属氧化物 MgO、MnO 和 NiO 的红外 (IR) 反射率。与标准法向入射情况相比，在三个入射角使用该技术可提供多组光谱（包括 s 和 p 偏振）进行分析，标准法向入射情况过去已广泛用于这些化合物。结果表明，与以前使用的流行经典模型相比，通过使用分解模型进行拟合，并通过拟合导数，可以更准确地确定横向光学 (TO) 和纵向光学 (LO) 模式声子参数反射率。正如预期的那样，我们对声子模式参数的结果与之前发现的结果相似，但通常更精确。对室温下反铁磁 NiO 中两种偏振反射光的 TO 模式频率差异的分析显示 TO 模式分裂约为 4 cm-1，p 偏振光 TO 模式具有更高的频率：小分裂与理论预测一致。这种用于揭示这种磁性有序立方金属氧化物中声子模式行为的更精确的 IR 方法可以很容易地应用于任何类似的反铁磁系统，这些氧化物是强相关电子系统的原型并且已被发现是莫特-哈伯德绝缘体。p 偏振光 TO 模式具有更高的频率：这种小的分裂与理论预测一致。这种用于揭示这种磁性有序立方金属氧化物中声子模式行为的更精确的 IR 方法可以很容易地应用于任何类似的反铁磁系统，这些氧化物是强相关电子系统的原型并且已被发现是莫特-哈伯德绝缘体。p 偏振光 TO 模式具有更高的频率：这种小的分裂与理论预测一致。这种用于揭示这种磁性有序立方金属氧化物中声子模式行为的更精确的 IR 方法可以很容易地应用于任何类似的反铁磁系统，这些氧化物是强相关电子系统的原型并且已被发现是莫特-哈伯德绝缘体。