Influence of oxygen non-stoichiometry on physical properties of NdSr2Mn2O7±δ

NdSr2Mn2O7+δ compounds were synthesized by ceramic method under three different cooling conditions. The NdSr2Mn2O7+δ samples were characterized by powder X-ray diffraction (XRD). Oxygen non-stoichiometry data for the studied powders were determined by using gravimetric and X-ray photoelectron spectroscopy (XPS) methods. The correlation of cooling method and oxygen as non-stoichiometry was established. The electroconductivity in samples was studied by using four-point probe method, and the strong correlation with non-stoichiometry was found out. Magnetization measurements were carried out. It was found that the magnetic and transport properties of the samples were also influenced by oxygen non-stoichiometry. The evolution of the magnetic properties could be explained by the formation of magnetic clusters in the vicinity of oxygen vacancies (OV) and strong competition between the superexchange and double exchange interactions.

Graphical AbstractZFC and FC magnetizations of NdSr2Mn2O7+δ compounds quenched in liquid nitrogen (a) and cooled down with furnace (b) in a field of 0.01 TFigure optionsDownload as PowerPoint slide