We establish the double perovskite Ba2CeIrO6 as a nearly ideal model system for j = 1/2 moments, with resonant inelastic x-ray scattering indicating that the ideal j = 1/2 state contributes by more than 99 % to the ground-state wavefunction. The local j = 1/2 moments form an fcc lattice and are found to order antiferromagnetically at TN = 14 K, more than an order of magnitude below the Curie-Weiss temperature. Model calculations show that the geometric frustration of the fcc Heisenberg antiferromagnet is further enhanced by a next-nearest neighbor exchange, and a significant size of the latter is indicated by ab initio theory. Our theoretical analysis shows that magnetic order is driven by a bond-directional Kitaev exchange and by local distortions via a strong magneto-elastic effect. Both, the suppression of frustration by Kitaev exchange and the strong magneto-elastic effect are typically not expected for j = 1/2 compounds making Ba2CeIrO6 a riveting example for the rich physics of spin-orbit entangled Mott insulators.
We report on a study of charge transport in EuTiO 3−δ single crystals with carrier density tuned across several orders of magnitude. Comparing this system with other quasi-cubic perovskites, in particular strontium titanate, we draw a comprehensive picture of metal-insulator transition and dilute metallicity in this ABO3 family. Because of a lower electric permittivity, the metal-insulator transition in EuTiO 3−δ occurs at higher carrier densities compared to SrTiO3. At low temperature, a distinct T 2 resistivity is visible. Its prefactor A smoothly decreases with increasing carrier concentration in a similar manner in three different perovskites. Our results draw a comprehensive picture of charge transport in doped quantum paraelectrics.
Cerinthe retorta Sibth. and Sm. has been detected in calcareous rocky slopes in Valle dell'Inferno on the Gargano promontory (Apulia, southeastern Italy). It is the first record of the species in Italy and the westernmost site of the distribution of this mostly Aegean species. This disjunction may provide evidence for past amphi-Adriatic/amphiIonic terrestrial connections. The IUCN assessment of the species in Italy and in Europe and the global assessment are briefly discussed.
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