A possible Hund's metal and unusual second-order metal insulator transition in perovskite La1-xPrxRuO3
Abstract
4d perovskite LaRuO3 is a paramagnetic metal whereas PrRuO3 is a paramagnetic insulator. Although Ru4+ ruthenates have shown very rich physics due to the subtle interplay of Coulomb repulsive potential U, Hund's rule coupling J, the crystal-field splitting Δ, and the spin-orbit coupling (SOC), limited information of Ru4+ perovskite RRuO3 (R=rare earth metals) family has been obtained since these perovskites have to be synthesized under high pressure. We report a successful synthesis of perovskite La1-xPrxRuO3 compounds by spark plasma sintering. A thorough characterization on La1-xPrxRuO3 system has been made by measurements of magnetic and transport properties and specific heat. The samples La1-xPrxRuO3 (0.2 < x < 0.8) exhibit a second-order metal-insulator transition as temperature decreases without any sign of magnetic order in the insulator phase. Due to the reduction of Ru-O-Ru bond angle, substituting La3+ ions with smaller Pr3+ ions reduces the bandwidth so as to lead to an insulator phase at low temperatures. The strong SOC and Hund's coupling on low spin 4d5 Ru3+ are responsible for the anomalous metallic phase found in LaRuO3 and the absence of magnetic ordering in the insulator phase in La1-xPrxRuO3.
This work was supported by a NSF Grant DMR-1729588.- Publication:
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APS March Meeting Abstracts
- Pub Date:
- 2019
- Bibcode:
- 2019APS..MARG70183L