Magnetic and magnetotransport behavior of overdoped nanocrystalline Nd1-xSrxMnO3 (0.50≤x≤0.63)

The nanocrystalline samples of Nd1-xSrxMnO3 (NSMO) (x=0.5, 0.55, 0.60, 0.63) were synthesized by sol-gel based polymeric precursor route. Structural, magnetic and magnetotransport properties were studied systematically. It was found that in the composition range (x=0.50-0.63), Nd1-xSrxMnO3 showed paramagnetic to ferromagnetic (PM-FM) transition in the vicinity of T-C similar to 270 K but the FM phase was weakened as the Sr concentration increased. The appearance of weak ferromagnetism was explained in terms of the core-shell model. Moreover, for x=0.63 sample, a second transition is observed below T-C at T=185 K, which is possibly due to the appearance of A-AFM/C-AFM or a mixture of both the phases. Resistivity vs temperature (rho-T) curve showed that the resistivity of all the samples was much larger than the single crystals of corresponding compositions due to large contribution of the grain boundaries in the present nanocrystalline samples. In all samples, extrinsic kind of MR behavior dominated because of nanocrystalline nature of the samples, which was nearly of the same order (similar to 10%) in all samples. However, the intrinsic kind of MR behavior was also significant in x=0.50 sample, because of the strongest FM feature in this sample.