Fundamental Behaviors, and Contributions of Hopping and Tunneling Mechanisms to the Transport Characteristics of the La<sub>0.5</sub>Ca<sub>0.5</sub>MnO<sub>3</sub> Phase Separated Perovskite
Y. Moualhi, M. Smari, H. Rahmouni, K. Khirouni
Abstract
A ceramic method was employed to produce a polycrystalline manganite with the nominal composition La0.5Ca0.5MnO3. The single crystallographic phase of La0.5Ca0.5MnO3, with an orthorhombic structure, was confirmed using an X-ray diffraction study. As a phase separation concept, magnetic investigations demonstrate the presence of both charge order-antiferromagnetic (CO-AFM) and ferromagnetic (FM) domains. In the CO-AFM phase, substantial augmentations in magnetization were observed, which were explained by orderly delocalization. Impedance spectroscopy investigation reveals a variety of electrical transport mechanisms at the grains and the grain boundary regions. The direct current conductivity investigation validates the semiconductor behavior of La0.5Ca0.5MnO3. At low temperatures, the transport properties were explained using the Mott-VRH conduction process. For θD/4 ≤ T ≤ θD/2, the electrical conductivity was attributed to the contribution of the Shklovskii–Efros-VRH mechanism. The Shimakawa model was proposed to examine the presence of Coulomb interactions. For T > θD/2, the electrical conductivity was explained using the polaronic hopping process. The electrical conductivity spectra were analyzed using Bruce and Jonscher’s laws. At high frequencies, the electrical response of La0.5Ca0.5MnO3 was explained using the superlinear power law. The contributions of correlated barrier hopping, overlapping large polaron tunneling, and quantum mechanical tunneling conduction processes were predicted via the temperature-dependent frequency exponents. Furthermore, the contribution of polaronic and charge carriers governed the electrical transport phenomenon.