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 TC higher than 200K occurs when the Ru site is replaced by Mn (x>0.3), and the TC 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, TC increased when the Ca site is replaced by Sr. The enhancement of TC seems to be due to a change in the crystal symmetry caused by the Sr substitution. The maximum TC=275K was marked for specimen of Ca0.5Sr0.5Ru0.4Mn0.6O3.