arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1610.01577cond-mat.str-el
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温度相关散射时间在理解强关联体系La $_{0.75}$ Ba $_{0.25}$ CoO $_{3}$高温热电行为中的重要作用

An important role of temperature dependent scattering time in understanding the high temperature thermoelectric behavior of strongly correlated system: La$_{0.75}$Ba$_{0.25}$CoO$_{3}$

Saurabh Singh, Devendra Kumar, Sudhir K. Pandey

摘要:

本文报道了La $_{0.75}$ Ba $_{0.25}$ CoO $_{3}$化合物在300-600 K温度范围内的变温热电势($α$)行为。利用Heikes公式,计算了Co-$^{3+}$和Co-$^{4+}$离子高自旋组态的$α$值为$\sim$ $16$ $μ$ V/K,与实验值$\sim$ 13 $μ$ V/K接近。结合WIEN 2K和BoltzTrap程序研究了该化合物的TE行为随温度的变化。自洽场计算表明该化合物具有铁磁基态结构。电子结构的计算给出了半金属特性与$\sim$ 50 meV的下自旋通道的小间隙。由于下自旋通道具有独特的能带结构,因此下自旋通道具有较大的正值。考虑了自旋通道电荷载流子的弛豫时间随温度的变化,研究了300-600 K温度范围内的热电势数据。考虑了$τ_{up}$的几乎线性值和$τ_{dn}$的非线性值用于评价$α$。在300-600 K温度范围内,采用双电流模型计算的$α$的弛豫时间与实验值符合得很好。在300 K下,发现通过使用相同的弛豫时间值(即,对于自旋向上为0.1 $\times $ × 10 $^{-14}$秒,对于自旋dn通道为0.66 $\times $ × 10 $^{-14}$秒)计算的电导率值等于实验报道的值。

英文摘要:

In the present work, we have reported the temperature dependent thermopower ($α$) behavior of La$_{0.75}$Ba$_{0.25}$CoO$_{3}$ compound in the temperature range 300-600 K. Using the Heikes formula, the estimated value of $α$ corresponding to high-spin configuration of Co$^{3+}$ and Co$^{4+}$ ions is found to be $\sim$$16$ $μ$V/K, which is close to the experimental value, $\sim$13 $μ$V/K, observed at $\sim$600 K. The temperature dependent TE behavior of the compound is studied by combining the WIEN2K and BoltzTrap code. The self consistency field calculations show that the compound have ferromagnetic ground state structure. The electronic structure calculations give half metallic characteristic with a small gap of $\sim$50 meV for down spin channel. The large and positive value for down spin channel is obtained due to the unique band structure shown by this spin channel. The temperature dependent relaxation time for both the spin-channel charge carriers is considered to study the thermopower data in temperature range 300-600 K. An almost linear values of $τ_{up}$ and a non-linear values of $τ_{dn}$ are taken into account for evaluation of $α$. By taking the temperature dependent values of relaxation time for both the spin channels, the calculated values of $α$ using two current model are found to be in good agreement with experimental values in the temperature range 300-600 K. At 300 K, the calculated value of electrical conductivity by using the same value of relaxation time, i.e. 0.1 $\times $10$^{-14}$ seconds for spin-up and 0.66 $\times $10$^{-14}$ seconds for spin-dn channel, is found to be equal to the experimentally reported value.

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