Abstract
We have studied the effect of Ar annealing on the electrical and magnetic transport properties of Pr 0.7Sr 0.3MnO 3 manganite. It is observed that, with increase in the annealing time there is a progressive decrease in T C and, resistivity, as functions of temperature become broader with the occurrence of two metal–insulator transitions. Electron-spin resonance analysis shows that for the Ar annealed sample, additional lines are present much above T C and the activated intensity behaviour and the paramagnetic linewidth behaviour points to the existence of spin clusters above T C. The metal–insulator transition was found to be percolative in nature with the high temperature transition having a temperature-dependent metallic volume fraction ( p) while the low-temperature broad hump could be described by a bond percolation model with temperature independent p.
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