Diluted magnetic interactions in an oxygen-deficient perovskite cobaltite:: magnetoresistance in the series SrCo1-xScxO3-δ (0<x≤0.5)

A series of the oxygen-deficient perovskite SrCo1-xScxO3-delta has been successfully prepared by using close ampoules for compositions in the range 0.05less than or equal toxless than or equal to0.5. The unit cell expansion with x is ascribed to the larger Sc3+ ionic radius than those of the Co3+/Co4+ cations. At 300 K, resistivity (rho) values of about similar to10(-2) Omega cm are measured for both x = 0.05 and 0.10, but for larger x values rho increases, reaching rho(300 K) = 10(2) Omega cm for x = 0.5. For the former, the lower resistivity values result from their weak ferromagnetic behavior characterized by a Curie temperature T-C of similar to60 K. Interestingly, these oxides exhibit similar negative magnetoresistance values, reaching 12% in 7 T at 5 K, to those reported for the SrFe1-xCoxO3-delta samples. It is concluded that the simultaneous presence of non-magnetic (3d(0)) Sc3+ species, substituted for cobalt, and of oxygen vacancies induce magnetic disordering, exemplified by the spin-glass like behavior of SrCo0.5Sc0.5O3-delta, which favors the existence of magnetoresistance. (C) 2004 Elsevier Inc. All rights reserved.