Effect of strontium deficiency on the transport and magnetic properties of Pr0.7Sr0.3MnO3

Ceramic samples of Pr0.7Sr0.3−x□xMnO3 with x⩽0.2 have been investigated by various techniques including 55Mn nuclear magnetic resonance, SQUID magnetometry, resistivity and magnetoresistance measurements. On increasing x, the samples remain ferromagnetic at a low temperature with a decreasing Curie temperature, but a metal–insulator transition is observed. Besides, a positive magnetoresistance (MR) at very low temperatures with respect to a negative colossal MR at high temperatures is observed in the Pr0.7Sr0.2□0.1MnO3 sample.