Possible ferromagnetic interactions between ISCo3+ ions in Nb doped cobaltites

Magnetic and electrotransport properties studies have been performed for La1-xSrxCo1-x/2Nbx/2O3 solid solutions containing cobalt ions in three valence electronic state. It was shown that these solid solutions are spin glasses with temperature of magnetic moment freezing (T-f) of about 25 K. The ferromagnetic component is the most pronounced in the sample with x = 0.15. This result can be explained by a model according to which Co ions near to Sr ones are in intermediate spin state and the Co3+-O-Co3+ superexchange interactions are ferromagnetic due to local dynamic orbital correlations. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.