Effects of Fe doping on the magnetic and transport properties of La0.5Sr0.5(Co1-xFex)O3 (0≤x≤0.6)

Magnetic and transport properties of the series La0.5Sr0.5Co1-xFexO3 (0less than or equal toxless than or equal to0.6) have been investigated. With increasing Fe content in the region up to x=0.2, T-C slightly decreases, implying a development of a rather weak antiferromagnetic (AF) Co-O-Fe superexchange compared to the pre-existing ferromagnetic Co-O-Co double-exchange (DE). An upturn of the resistivity emerges at low temperatures. In the context of the DE model, this upturn could be linked to the weakening of ferromagnetic correlations and the development of frustration and disorder. Further substitution (xgreater than or equal to0.3) leads to strong suppression of the ferromagnetism and the conductivity, probably due to the appearance of Fe-O-Fe AF superexchange interactions. Insulator-like behavior is observed for all of the xgreater than or equal to0.3 samples and spin-glass-like behavior for xgreater than or equal to0.5. (C) 2002 Elsevier Science B.V. All rights reserved.