Influence of Ru doping on the structure, defect chemistry, magnetic interaction, and carrier motion of the La(1-x)Na(x)MnO(3+delta) manganite.

In this work, we report a structural, electrical, and magnetic characterization of the La(1-x)Na(x)Mn(1-y)Ru(y)O(3+delta) (LNMRO) system with x = 0.05 and 0.15 and y = 0, 0.05, and 0.15, also comprising an investigation of the role of the oxygen content on the related redox properties. The experimental investigation has been realized with the aid of X-ray powder diffraction, electron microprobe analysis, thermogravimetry, electrical resistivity and magnetization measurements, and electron paramagnetic resonance. We demonstrate that the effect of ruthenium doping on the studied LNMRO compounds is not only directly related to the Ru/Mn substitution and to the Ru oxidation state but also indirectly connected to the oxygen content in the sample. Our data show that ruthenium addition can "improve" electrical and magnetic properties of nonoptimally (low) cation-doped manganites, causing an increase of the T(C) value and the insurgence of magnetoresistance effect, as observed for the x = 0.05 and y = 0.05 sample (MR congruent with 60% at 7 T and at approximately 260 K).