Microstructure, interparticle interactions and magnetotransport of manganite-polyaniline nanocomposites

• A SAXS study on the microstructure of manganite-polyaniline nanocomposites is reported.
• We report the presence of attractive interactions for the composites with higher concentration in manganite.
• Interparticle dipole–dipole interactions were estimated by means of the SAXS interference function.
• Coercive field and remanent magnetization studies showed agreement with SAXS analysis.
• Magnetotransport showed an enhancement in relation to the decrease of these interactions.

In this report, we present the study on the microstructure and interparticle interactions of manganite-polyaniline nanocomposites using grazing incidence small angle X-ray scattering (SAXS). In order to determine the nanoparticles mean diameter and correlation distances, data analysis was performed using the Guinier and Beaucage fits, in good agreement with transmission electron microscopy and X-ray diffraction analysis. The analysis of the interference functions revealed the existence of attractive interactions between nanoparticles. The nanocomposites with higher manganite concentration showed best fitting using the sticky hard sphere approximation. A weakening in the attractive interaction with increasing the dilution of nanoparticles in the polymer matrix was observed until a critical volume fraction (ϕc ∼ 0.4) is reached, upon which the hard sphere approximation showed best fitting. The interaction potentials were estimated at room temperature revealing a decrease in the depth and width of the square well with increasing nanoparticle dilution. Coercive field and remanent magnetization showed a decrease with increasing polymer addition suggesting the declining of dipole–dipole interactions, in agreement with SAXS analysis. Magnetoresistance also showed an enhancement that could be probably associated to the decrease in the dipole–dipole interactions between ferromagnetic La2/3Sr1/3MnO3 (LSMO) nanoparticles at a critical separation distance in these nanocomposites.

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