Abstract
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.
Published Version
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