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Zusammenfassung:
The electronic and magnetic properties of distorted monoclinic double
perovskite Sr2CeIrO6 were examined based on both experiments and
first-principles density functional theory calculations. From the
calculations we conclude that low-spin-state Ir4+ (5d(5)) forms a rare
weakly antiferromagnetic (AFM) orbital ordered state derived from
alternating occupation of slightly mixed c(g)(pi) symmetry states in the
presence of spin-orbit coupling (SOC). This orbital ordering is caused
due to the competition between the comparable strength of Jahn-Teller
structural distortion and SOC. We found both electron-electron
correlation and SOC are required to drive the experimentally observed
AFM-insulating ground state. Electronic structure investigation suggests
that this material belongs to the intermediate-SOC regime, by comparing
our results with the other existing iridates. This single active site
double perovskite provides a rare platform with a prototype
geometrically frustrated fcc lattice where among the different degrees
of freedom (i.e., spin, orbital, and lattice) SOC, structural
distortion, and Coulomb correlation energy scales compete and interact
with each other.
