Structural, magnetic and transport properties of the negative magnetoresistive Pr1−xPbxMnO3−y alloys

The nonstoichiometric perovskite Pr1−xPbxMnO3−y compounds have been synthesized by a standard combustion technique. The samples show uniphase solid solutions. The mixed valency of Mn ions was identified by X-ray absorption spectroscopy and the amount of Mn4+ ions was determined by the iodometric titration method. The nonstoichiometric chemical formulas of the Pr1−xPbxMn1−r3+Mnr4+O3−y compounds have been formulated. The Pr1−xPbxMnO3−y (x=0.1, 0.2, and 0.3) compounds show a transition from the ferromagnetic state to the paramagnetic state. The transport properties have been studied by electrical conductivity measurements under magnetic fields of 0 G and 3 kG. The magnetoresistant ratio increased with decreasing MnO distance. The magnetoresistant ratio is negative for all the samples.