Structural, transport and magnetic properties of monovalent doped La1−xNaxMnO3 manganites

In this communication, we report the results of the structural, magnetic and transport studies on monovalent doped La1−xNaxMnO3 mixed valent manganites synthesized by conventional ceramic route. Structural study using XRD and Rietveld refinements of raw data shows that all the samples are single phasic in nature without any detectable impurities within the measurement range. Magnetic study and Arrott plots confirm the second order ferromagnetic (FM)–paramagnetic (PM) phase transition observed for all the samples. Effect of monovalent substitution and ration of Mn3+ to Mn4+ ions on resistivity and metal to insulator transition temperature (TP) has been discussed in the context of tolerance factor, size variance, zener double exchange (ZDE) mechanism and Jahn–Teller (JT) disorder. Metallic nature of the samples has been discussed using ZDE polynomial fittings while low temperature transport has been explained by resistivity minima. Temperature and field dependent magnetoresistance (MR) studies reveal the spin polarization effect and intrinsic and extrinsic MR contributions observed in presently studied samples.