Valence transition in ordered perovskites Ba2PrRu1−xIrxO6

The crystal structures and magnetic properties of ordered perovskites Ba2PrRu1−xIrxO6 are investigated. Powder X-ray diffraction measurements at room temperature show the Pr and (Ru,Ir) ions to be in the trivalent and the pentavalent states, respectively, for the Ru-rich compounds, while both of the Pr and (Ru,Ir) ions to be in the tetravalent state for the Ir-rich compounds. Two phases exist in the 0.1≤x≤0.5 region, which are composed of the two ordered perovskites, Ba2Pr3+(Ru,Ir)5+O6 and Ba2Pr4+(Ru,Ir)4+O6. The magnetic susceptibilities of Ba2PrRu0.90Ir0.10O6 show a magnetic anomaly in the temperature range 60≤T≤200 K, i.e. the hysteresis of the magnetic susceptibilities has been observed in this temperature range. Similar magnetic behavior has been observed for the susceptibility vs. temperature curves of the compounds with 0.15≤x≤0.40. The results of the X-ray diffraction and magnetic susceptibility measurements suggest the occurrence of valence transition.