The electronic ground state and magnetism of Ir(5d) states in two series of iridium oxides, A2MIrO6 (A=Sr, La; M = Mg, Ca, Sc, Ti, Ni, Fe, Zn, In) and (Ba,Sr)IrO3, is probed by element and orbital-specific L2,3 edge x-ray absorption and magnetic circular dichroism measurements, mainly. All the studied compounds present a significant influence of spin-orbit (SO) interaction in the electronic ground state regardless of the electronic configuration (d3, d4 or d5). Besides, the SO ground state is found to be robust against lattice compression. On the other hand, the XMCD spectra of the different A2MIrO6 compounds show that the Ir 5d local magnetic moment has different character depending on the electronic state: Ir carries an orbital contribution comparable (or even bigger) to the spin contribution for Ir4+ (d5) and Ir5+ (d4) oxides, whereas the orbital contribution is quenched for Ir6+ (d3) samples. As for the total magnetic moment, our results in the A2MIrO6 compounds indicate that Ir may carry a significant, intrinsic local magnetic moment. For non-magnetic-M samples, the net magnetization is small due to the AFM 5d-5d coupling and strongly dependent upon the structural details in each double perovskite. When the double perovskite includes a magnetic M, we find that the net moment of Ir orders parallel to the net magnetic moment of Fe and Ni in Sr2FeIrO6 and Sr2NiIrO6, respectively, whereas it aligns antiparallel in La2NiIrO6. Finally, the disparate response of the magnetic properties of BaIrO3 to chemical (Sr-doping) and physical pressure illustrates the delicate interplay between lattice degrees of freedom, electronic bandwidth and exchange interactions in iridates.

Resumen del trabajo presentado a la 20th International Conference on Solid Compounds of Transition Elements, celebrada del 11 al 15 de abril de 2016 en Zaragoza (España).

Peer reviewed