Effect of Ca and Ba Doping on the Magnetotransport Properties of NdMnO3

Mixed valence manganites of the type Nd0.7-xRxMnO3 where, R = divalent cation (Ca and Ba) have been synthesized using citrate pyrolysis process. It is interesting to see that the Ca and Ba doped NdMnO3 compounds have metal - insulating behavior but different TMI values at different magnetic field. Although the Ca and Ba ions have almost same ionic radii but different density. For Ca-doped NdMnO3 compound, a magnetoresistance as high as 79 % was observed at the insulator transition temperature Tp =102 K, while in Ba-doped NdMnO3 compound, lower magnetoresistance ~ 67% was observed at the metal insulator transition temperature Tp = 90 K. For both Ca & Ba doped NdMnO3 structural characterization shows same orthorhombic phase without impurities in the sample sintered at 900 °C, with the crystalline sizes in the nanometer scale. Grain size and morphology results show that the compounds have clear grain morphology and also nanoscale grain sizes.

Properties of the Colossal Magnetoresistivity and its Field Sensitivity of the Mixed-Valence Manganites Nd0.52Sr0.48MnO3

In this paper, according to the model proposed by Wagner et al., the properties of the magnetically aligned clusters in rare earth manganite Nd0.52Sr0.48MnO3 film are investigated. As we all have known, even at the same temperature and in the same external magnetic field the colossal magnetoresistivity (CMR) effects of different manganites are different. Through imitating the variation of the magnetoresistance (MR) with respect to some physics parameters, the built-in factors that can influence the value of MR and the field sensitivity are analyzed. The investigations show that the CMR effects, to some extent, can be governed by the size of the magnetically aligned clusters. In addition, through analyzing the different magnetoresistance scaling in different magnetic phases it is found that with the paramagnetic-ferromagnetic transition a sudden change in the size of the magnetically aligned clusters occurs, the physical origin of which are explored.