Diluted magnetic interactions in an oxygen-deficient perovskite cobaltite: Magnetoresistance in the series SrCo 1-xSc xO 3-δ (0

International audienceA series of the oxygen-deficient perovskite SrCo 1- xSc xO 3-δ has been successfully prepared by using close ampoules for compositions in the range 0.05≤x≤0.5. The unit cell expansion with x is ascribed to the larger Sc 3+ ionic radius than those of the Co 3+/Co 4+ cations. At 300 K, resistivity (ρ) values of about ∼10 -2 Ω cm are measured for both x=0.05 and 0.10, but for larger x values ρ increases, reaching ρ 300 K=10 2 Ω 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 ∼60 K. Interestingly, these oxides exhibit similar negative magnetoresistance values, reaching 12% in 7 T at 5 K, to those reported for the SrFe 1-xCo xO 3-δ samples. It is concluded that the simultaneous presence of non-magnetic (3d0) Sc 3+ species, substituted for cobalt, and of oxygen vacancies induce magnetic disordering, exemplified by the spin-glass like behavior of SrCo 0.5Sc 0.5O 3-δ, which favors the existence of magnetoresistance. T dependence of the ac-magnetic susceptibility (χ′) for oxygen pressure annealed SrCo 1-xSc xO 3-δ samples showing the effect of magnetic dilution induced by Sc 3+. © 2004 Elsevier Inc. All rights reserved