Magnetic order and electrical resistance in manganites

Abstract

The electrical resistance versus temperature behaviour of the manganites La₁_-xBa_xMnO₃ (x=0.3,0.4,0.5); La₁_-xPb_xMnO₃(<i style="">x</i> = 0.2,0.3,0.33) and La₁_-xSr_xMnO₃ (<i style="">x</i> = 0.1,0.2,0.4) has been investigated. The temperatures at which the substances have maximum resistance have been found to be much lower than their Curie temperatures. The variation of resistance with temperature is not smooth, but the graphs show different slopes. The electron paramagnetic resonance of these substances shows a new signal in the spectra on a little increase of microwave field from the usual values. It has been interpreted as phase separations in the materials with Mn³⁺ and Mn⁴⁺ spins aligned in opposite directions. Based on this idea, magnetic order and electrical resistance of the materials are shown to be directly correlated.