Magnetotransport in Gd1-xSrxCoO3 (0 < x ≤ 0.30) perovskites

We introduce the magnetotransport properties of Gd1-xSrxCoO3 (0 < x less than or equal to 0.30) materials. These compounds are semiconducting and show a magnetic transition at T-c approximate to 160 K associated with the onset of magnetic order of cobalt ions within superparamagnetic clusters, which leave a freezing point T-B < T-c. Very remarkably, the more resistive samples showed rather large magnetoresistance at the lowest available temperature: MRmax(x = 0.10)approximate to -16% at T = 4.2 K under H-max = 40 kOe. We relate these results to the inhomogeneous electronic structure of these cobaltates and to the presence of the paramagnetic Gd3+ sublattice, which at low temperatures influences the cobalt ions of the superparamagnetic clusters, provoking an increase in the size of the hole-rich regions and in the hopping probability of the charge carriers, and gives rise to the negative magnetoresistance observed.