Synthesis, structural, magnetic and electrical properties of nominal La_0.67Ba_0.33-xNa_xMnO₃(0 ≤ x ≤ 0.33) manganites

Abstract

Abstract.Complete nominal solid solutions La 0.67 Ba 0.33-x Na x MnO 3 (0 ≤ x ≤ 0.33) have been elaborated by ceramic route at 1200°C. ICPAES chemical analysis and XRD Rietveld structure refinement revealed that the nominal Na content is not achieved by our ceramic method. The chemical formula should be rather written as La α Ba β Na λ MnO 3-δ with a significantly lower Na content (λ), than the nominal one (x), and with a slight deficit (δ) in oxygen content, leading to the appearance of two minor secondary phases identified as Mn 3 O 4 and Na 0.55 Mn 2 O 4 . 1.5H 2 O. Magnetization and electrical resistance vs. temperature show paramagnetic/semiconductor -ferromagnetic/metallic transitions with only a slight decrease in magnetic and electrical transition temperatures when Na content increases. Such amount of this decrease is not expected according to the nominal Na content giving a significant difference between nominal and experimental Mn 4+ /Mn 3+ ratios.

Structural and Morphological La_0.85-xBa_xNa_0.15MnO₃ (x = 0, 0.05, 0.10 and 0.15) Perovskite Manganite

“…The existence of both Mn 3+ and Mn 4+ cation will induce an electronic transport from Mn 3+ cation to the nearest Mn 4+ cation, mediated by O 2anion. This mechanism is known as double exchange (DE) mechanism, which serves as the foundation of the ferromagnetism in the substituted lanthanum manganite compounds [2,3].…”