Small polaron transport and magnetoresistance in sol–gel prepared Nd0.7Sr0.3−xCaxMnO3 (0≤x≤0.3) nanomanganite system

Transport behavior and magnetoresistance in sol–gel prepared Nd0.7Sr0.3−xCaxMnO3 (0≤x≤0.3) nanomanganite system have been investigated in the temperature range 10–330 K. It is found that with increase in Ca2+ ion concentration metal–insulator transition temperature (TMI) decreases and on the application of magnetic field TMI shifts toward higher temperature with decrease in resistivity. It is shown that the correlated polaron model accounts for the temperature dependence of resistivity and magnetoresistance in the entire temperature range.