Synthesis, magnetic and electric transport properties of mixed-valence manganites La0.5+xSr1.5−xMn0.5Cr0.5O4 (x=0.1, 0.2 and 0.3)

Abstract

Abstract A series of mixed-valence manganites La0.5+xSr1.5−xMn0.5Cr0.5O4 were synthesized by sol–gel method. Rietveld profile analysis shows that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The lattice parameter c increases with increase in x while a parameter almost remains constant. The Weiss constant (θ) is positive for all the phases and found to increase with increase in x. The ferromagnetic interactions becomes more dominant with increase in x due to increase in Mn3+–O–Mn4+ and Mn3+–O–Cr3+ double exchange interactions. Resistivity can be described by the polaron hopping and the variable range hopping model. It was found that the transport mechanism is dominated by Mott's variable range hopping (VRH) model with a decrease of Mott localization energy with increase in x, which explains the decrease of resistivity.