Hydrothermal synthesis and magnetic properties of RMn2O5 (R=La, Pr, Nd, Tb, Bi) and LaMn2O5+δ

RMn2O5 (R=La, Pr, Nd, Tb, Bi) crystallites were prepared by a mild hydrothermal method and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and magnetic measurement. The formation of manganates was sensitive to the alkalinities and Mn-containing precursors of the reaction mixtures. This family of manganates is isostructural and has a space group of Pbam. The magnetic measurements for RMn2O5 showed an antiferromagnetic transition. The strong irreversibility between the ZFC and FC curves indicated a helicoidally magnetic structure below 40 K. The max d.c. susceptibilities of LaMn2O5+δ (δ=0.01, 0.06, 0.08, 0.16, 0.17) were found to be variable and the excess oxygen (δ) in the compounds was influenced by the alkalinity used in the hydrothermal synthesis.

Several RMn2O5 (R=La, Pr, Nd, Tb, Bi) and LaMn2O5+δ crystallites were prepared by the mild hydrothermal treatment of mixtures of rare-earth oxides, K-birnessite gel and KOH. The magnetic susceptibility measurements show an antiferromagnetic transition in RMn2O5 (R=Pr, Nd, Bi). Magnetic susceptibility of the LaMn2O5+δ was variable at low temperature due to the different oxygen excess in the compound, which is dominated by the different KOH concentration used in the hydrothermal synthesis.Figure optionsDownload as PowerPoint slide