Magnetic and dielectric properties of Ba-lacunar La_(0.5)Eu_(0.2)Ba_(0.3)MnO_3 manganites synthesized using sol-gel method under different sintering temperatures

摘要

Structural, magnetic and dielectric properties of La_(0.5)Eu_(0.2)Ba_(0.3-x)□_xHMnO_3 (x = 0.00, 0.05 and 0.15) per-ovskites are investigated. Nano-polycrystalline samples prepared using sol-gel wet chemical method were subjected to annealing in two different temperatures and investigated by powder X-ray diffraction (XRD), magne-tometry, and ac impedance spectroscopy. XRD characterizations indicated that all samples exhibited a single rhombohedral phase. The temperature-dependent magnetizations indicate the ferromagnetic transition. The resistivity decreased and the magnetic ordering temperature increased as Ba-deficiency increased. The dielectric constant dependent on frequency shows normal behavior. The samples with a lower sintering temperature show the highest resistivity and dielectric constant. Dielectric anomaly dependent on temperature was observed close to the magnetic ordering temperature, indicating the possibility of ferroelectricity and further magnetoelectric coupling. The dielectric behaviors have been interpreted based on space charge polarization according to Maxwell-Wagner's two-layer model and hopping of charge between Mn~(3+) and Mn~(4+) ions.