Re-entrant structural phase transition and charge carrier conduction in La2−xSrxFeMnO6 solid solutions for electronic device applications

Abstract

This research explores the structural, dielectric, and electrical transport characteristics of polycrystalline La_2−xSr_xFeMnO₆ compounds with varying strontium concentrations (x = 0.0, 0.1, 0.2, 0.5, 1.0, 1.5, and 2.0). These compounds were prepared through the solid-state reaction technique at high temperatures. Rietveld refinement of their XRD data confirms a re-entrant structural phase transition (cubic–rhombohedral–cubic) induced by Sr doping. The vibrational study of (Fe/Mn)O₆ octahedra was carried out by Raman and FTIR spectroscopies. X-ray photoelectron spectroscopy (XPS) results demonstrated the presence of mixed valence oxidation states (+3 and +4) of Fe and Mn cations in the measured samples. The temperature-dependent resistivity data of these compounds have been explained by the long-range electron hopping and short-range polaron hopping conduction mechanisms at high- and low-temperature regions, respectively. Their dielectric constant (ε′) exhibits dispersion behavior, which is attributed to the Maxwell–Wagner interfacial polarization and hopping mechanism of charge carriers. The leakage current density has been explained on the basis of Ohmic conduction mechanism and space-charge-limited conduction (SCLC) mechanism. All these studied properties are strongly influenced by structural distortion-induced strain, oxygen vacancies, Schottky defects, and possible charge ordering. The low leakage current density of these materials with a high dielectric constant make them promising for application in electronic devices.