Effect of Fe doping on the magnetotransport properties in Nd0.67Sr0.33MnO3 manganese oxides

We have performed magnetic and transport measurements on a series of Nd0.67Sr0.33Mn1-xFexO3 polycrystalline compounds with x=0.0, 0.05, 0.10, and 0.15. For the Fe-undoped Nd0.67Sr0.33MnO3 (NSMO) materials, a magnetoresistance (MR) as high as similar to 33% was observed at the metal-insulator transition temperature, T-p=273 K, in a magnetic field of 10 kOe. Fe substitution in Mn sites leads to a reduction in T-p and an increase in the overall MR. A 10% Fe contribution increases the MR up to about 65% and lowers T-p to 88 K. The calculated magnetic moment at 5 K and an applied field at 9 T for the parent NSMO is 4.21 mu (B) and decreases continuously with an increasing amount of iron added. It was found that with the same amount of Fe doping, the Curie temperature, T-C, decreases much faster in the Nd-based system than in the corresponding La-based system. The enhanced colossal magnetoresistance and the suppression of ferromagnetism observed in this compound can be interpreted as due to the weakening of the double exchange mechanism by Fe3+ ions, which causes the localization of the hopping electrons. (C) 2002 American Institute of Physics.