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Frequency dependence of the hopping and disorder energies and conduction mechanisms in Cr-(Pr/Ca) MnO3
Physica B: Condensed Matter ( IF 2.8 ) Pub Date : 2020-08-30 , DOI: 10.1016/j.physb.2020.412491
R. Jemaï , H. Rahmouni , K. Khirouni , S. Alaya , A. Cheikhrouhou

Transport properties of Pr0.7Ca0·3Mn0·85Cr0·15O3(Cr-PCMO) manganite have been studied in a large frequency and temperature ranges by mean of impedance spectroscopy. The conductance spectra are discussed in the outline of a double and single Jonscher laws for the temperature ranges [80 K–110 K] and [120–170 K] respectively. The correlated barrier hopping and the non small polaron tunneling (NSPT) conduction models are used to explain the dynamic of charge carriers in the ac regime. The lower temperature range is characterized by the coexistence of such two conduction processes. Below the frequency ν = 105 Hz, the compound exhibits a semiconductor behavior with no detectable electrical transition. A metal - semiconductor transition at around T = 190 K was observed at high frequency range (ν = 2.106 Hz). Beyond the Debye temperature, θD/2 = 130 K, the small polaron hopping (SPH) conduction process is thermally activated. Over the investigated frequency interval ν ≤ 105, the activation of the SPH conduction process needs the same activation energy Ea1 = 112 meV. At lower temperature range, the interaction between electron and acoustic phonon becomes important, the variable range hopping (VRH) mechanism was activated via a disorder energy WD. The temperature dependence of the local energy proves that type of the VRH process is sensitive to the frequency parameter and the investigated temperature range. The hopping and the disorder energies are strongly sensitive to frequency.



中文翻译:

Cr-(Pr / Ca)MnO 3中跃迁和无序能量的频率依赖性和传导机理

通过阻抗谱研究了Pr 0.7 Ca 0·3 Mn 0·85 Cr 0·15 O 3(Cr-PCMO)锰在大频率和大温度范围内的传输性能。在温度范围[80 K–110 K]和[120–170 K]的双重和单一Jonscher定律的概述中讨论了电导谱。相关的势垒跳跃和非小极化子隧穿(NSPT)传导模型用于解释交流电中电荷载流子的动态。较低的温度范围的特征在于这两个传导过程的共存。低于频率ν= 10 5 以Hz为单位,该化合物表现出没有可检测的电跃迁的半导体行为。在高频范围(ν= 2.10 6  Hz)下观察到在T = 190 K附近的金属-半导体跃迁。超过德拜温度,θ d / 2 = 130 K,小极化子跳跃(SPH)传导过程中被热激活。在研究的频率间隔ν≤10 5内,SPH传导过程的激活需要相同的激活能量E a1  = 112 meV。在较低的温度范围内,电子与声子之间的相互作用变得很重要,可变跳频(VRH)机制是通过无序能量W D激活的。局部能量的温度依赖性证明,VRH过程的类型对频率参数和所研究的温度范围敏感。跳跃能量和无序能量对频率非常敏感。

更新日期:2020-08-31
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