Magnetic ordering and spin-state transition in R0.67Sr0.33CoO3 - art. no. 224416

A series of ceramic R0.67Sr0.33CoO3 samples with R = La, Pr, Pr0.5Nd0.5 Nd, Nd0.5Sm0.5 and Sm have been prepared. We report on detailed structural, el ectrical, magnetic, and thermodynamic studies. All samples reveal magnetic order, spanning the range from a ferromagnetic metal to a ferrimagnet close to a metal-to-insulator transition. We found a clear correlation between s tructural properties and resistivity as well as between structure and magne tic exchange interactions. In this context the importance of double exchang e is discussed. Heat-capacity experiments show a significant anomaly at the magnetic transition temperature of the La compound only. The samples with magnetic rare-earth ions reveal significant Schottky anomalies at low tempe ratures and allow for a rough estimate of the crystal-field splittings.