Abstract :
We have examined the effects of excess oxygen on the magnetization, electrical transport properties and crystal structure of La0.95Sr0.05MnOy. An antiferromagnetic insulator phase confirmed in the as-grown crystal at low temperatures changed to a ferromagnetic insulator phase after the introduction of excess oxygen. The ferromagnetic transition temperature, T C , systematically increased with increasing oxygen content, y , due to an increase in the mean valence of manganese. However, the T C of crystals with excess oxygen was lower than that of the La1−xSrxMnO3.00 having identical manganese valence. This is considered to be a result of the competition among the mean valence of manganese, the concentration of cation vacancies, and the mean ionic radius of cations at the A-site.
