Field Effect on the Cochran Modes in SrTiO 3 and KTaO 3
Field Effect on the Cochran Modes in SrTiO 3 and KTaO 3
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SrTiO 3 和 KTaO 3 中 Cochran 模的场效应
DOI：
10.1103/physrev.168.523
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发表时间：
1968
期刊：
影响因子：
--
通讯作者：
E. F. Steigmeier
中科院分区：
文献类型：
--
作者：
E. F. Steigmeier
结合Cochran铁电理论，研究了SrTiO 3在5 ~ 300 K和KTaO 3在2.5 ~ 300 K的热导率。对于温度高于其最大值，电导率显示在SrTi O 3中不存在KTa O 3的异常。这种行为解释的横向光学（Cochran模式）和纵向声学声子分支之间的简并。测量也采取了在电场高达55 kV/cm，施加垂直于温度梯度。在低于50 K的SrTi O 3中观察到热导率的显著增加，而在KTa O 3中的效果要小得多。这种效果的解释是通过假设在q= 0的横向光学模式，以转移在施加电场时的频率。一个简单的模型方面的实验数据的分析，从而导致定量值的SrTi O 3的频率偏移。KTa O 3得到的结果表明，在4.5 K的非铁电类型的相变的存在下，在类似的103 K转变已知的SrTi O 3。
In connection with the Cochran theory of ferroelectricity, the thermal conductivity has been investigated in SrTi O 3 between 5 and 300 K and in KTa O 3 between 2.5 and 300 K. For temperatures above its maximum value, the conductivity shows an anomaly in SrTi O 3 which is absent in KTa O 3. This behavior is explained in terms of the degeneracy between the transverse optic (Cochran modes) and the longitudinal acoustic phonon branches. Measurements were also taken in electric fields up to 55 kV/cm, applied perpendicular to the temperature gradient. A considerable increase in thermal conductivity is observed in SrTi O 3 below 50 K, while the effect is much smaller in KTa O 3. An interpretation of this effect is given by assuming the transverse optic mode at q= 0 to shift in frequency upon application of an electric field. An analysis of the experimental data in terms of a simple model is presented which leads to quantitative values for the frequency shifts in SrTi O 3. The results obtained for KTa O 3 indicate the presence of a phase transition of the nonferroelectric type at 4.5 K, in analogy to the 103 K transition known for SrTi O 3.