Evolução das propriedades estruturais e magnéticas induzidas pela substituição parcial de La por Ba na série de perovskitas duplas La2-xBaxCoIrO6

Abstract

Iridium-based oxides have recently attracted significant interest due to the unconventional physics that may arise from the strong spin-orbit coupling present in 5d ions. In this work, we explore the coupling between Ir and Co in the La₂₋ₓBaₓCoIrO₆ double-perovskites (x = 0, 0.5, and 1.0), where the structural, electronic, and magnetic properties of the series are investigated through powder X-ray diffraction (XRD) and magnetometry. The Rietveld refinement of the crystal structures, performed through the XRD patterns, have shown that the La2CoIrO6 (x = 0) and La1.5Ba0.5CoIrO6 (x = 0.5) compounds form in monoclinic structure, space group P2₁/n, while LaBaCoIrO6 (x = 1.0) belong to the triclinic I-1 space group. Such structural evolution is accompanied by a systematic increase of the unit cell volume and the Co—O—Ir bond length, as expected, since the Ba2+ ionic radius is significantly larger than that of La3+ . In addition to structural variations, chemical substitution plays a fundamental role in modulating the oxidation states of transition metal ions present in the system, directly influencing the magnetic exchange interactions established between them. Therefore, the evolution of magnetic properties along the series can be understood in light of the electronic changes induced by doping, which affect the coupling between Co and Ir ions and, consequently, the type of magnetic ordering stabilized in each composition.