Microstructural, magnetic and transport properties of La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites

• We synthesized a series of pure La0.5Pr0.2Pb0.3−xSrxMnO3 manganites using ceramic technology.
• The crystalline structure depends on the Sr concentration.
• Small-angle neutron scattering reveals the presence of magnetic nanodomains at temperatures higher than Curie temperature.
• The crystalline structure, the shape and the concentration of magnetic nanodomains are correlated with transport phenomena.

The most interesting and studied materials for practical applications of colossal magnetorsistance effect are rare earth manganites with general formula RMnO3RMnO3 (where R is a rare/alkaline earth element). The coexisting of competing phases in manganites, such as metallic ferromagnetic, charge ordered, antiferromagnetic insulating and ferromagnetic insulating phases, determines an important change of magnetic and transport properties with the microstructure. In this paper, we report on the correlations between microstructural, magnetic and transport properties at temperatures ranging from 263 to 343 K of La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites synthesized by ceramic technology. The microstructure is studied using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) at Sr concentrations x=0.00,0.05,0.15x=0.00,0.05,0.15 and 0.20. SAXS and SANS data show the formation of magnetic nanodomains in the mosaic blocks, at temperatures higher than Curie temperature TCTC. SANS data reveal the shape and concentration of magnetic nanodomains, and their dependency on temperature. The La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites crystallize as cubic structure Pm3¯m (x=0.00x=0.00 and x=0.05x=0.05) or as rhombohedral structure R3¯c (x=0.15x=0.15 and x=0.20x=0.20). We found that transport phenomena at temperatures higher than TCTC are greatly influenced by nanodomains concentration and their shape. We show that about room temperature manganites with x=0.05x=0.05 and x=0.15x=0.15 have large intrinsic resistance maxima, generating an important magnetoresistance effect.