Frist-principle Studies Of The Ferromagnetism In Sr_xPb_1-xRuO₃ (0≤X≤1)

Transition-metal oxides with perovskite and perovskite-related structures have been extensively studied in recent years. Density functional theory with local spin density approximation is appplid to study the evolution of ferromagnetism in Sr_xPb_1-xRuO₃ (0≤x≤1). Besides the enhanced Pb-O covalence and Pb-Ru hybridization, the Jahn-Teller effect, which favors the low-spin state (S = 0) of Ru⁴⁺ in a stretched oxygen octahedra, is found to be the origin of the observed paramagnetism in PbRuO₃. With the introduction of Sr, the Pb-Ru hybridization is weakened and an intermediate-spin state (S = 1) is preferred via the opposite Jahn-Teller effect in a compressed oxygen octahedra, leading to the appearance of ferromagnetism for x > 0.5. Our calculations provide a comprehensive understanding of itinerant ferromagnetism in 4d oxides.