Ferromagnetism Of Ca1-Ysryru1-Xmnxo3

Crystallographic, magnetic, and electrical properties of Ca1-ySryRu1-xMnxO3 were investigated. The lattice parameters decrease with increasing Mn content without following Vegard's law. Ferromagnetism with the Curie temperature T-C higher than 200 K occurs when the Ru site is replaced by Mn (x>0.3), and the T-C and the magnetization have a maximum at x=0.6-0.7. The occurrence of the ferromagnetism was explained assuming mixed valence states of Mn3+, Mn4+, Ru4+, and Ru5+ ions. Furthermore, T-C increased when the Ca site is replaced by Sr. The enhancement of T-C seems to be due to a change in the crystal symmetry caused by the Sr substitution. The maximum T-C=275 K was marked for specimen of Ca0.5Sr0.5Ru0.4Mn0.6O3. (C) 2008 American Institute of Physics.