Role of Gallium in the charge transport mechanisms for La0.67Ca0.33Mn1-xGaxO3 manganites

In this communication, we report the results of the studies on structural, transport and magnetoresistance (MR) properties of nonmagnetic Ga - substituted La0.67Ca0.33Mn1-xGaxO3 (LCMGO) manganites synthesized using conventional ceramic route. Rietveld refined XRD patterns shows that all the samples possess single phasic nature without any detectable impurity. Resistivity behavior shows a systematic variation with Ga3+ - content (x) while metal to insulator transition temperature (TP) shifts towards lower temperature which has been discussed in the light of zener double exchange (ZDE) mechanism and magnetic lattice distortion due to nonmagnetic ion substitution. Observation of low temperature resistivity minima behavior has been explained in the context of electron - electron scattering mechanism. Various transport models and mechanisms have been employed to understand the charge transport in metallic and semiconducting regions of all LCMGO samples. Temperature and Field dependent MR studies reveal intrinsic and extrinsic MR contributions in presently studied LCMGO manganites.