Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates

Abstract

Quantum magnets with significant bond-directional Ising interactions, so-called Kitaev materials, have attracted tremendous attention recently in the search for exotic spin liquid states. Here we present a comprehensive set of measurements that enables us to investigate the crystal structures, Ir${}^{4+}$ single ion properties, and magnetic ground states of the double perovskite iridates La${}_{2}B$IrO${}_6$ ($B$ $=$ Mg, Zn) and $A_2$CeIrO${}_6$ ($A$ $=$ Ba, Sr) with a large nearest neighbor distance $>$ 5 Angstroms between Ir${}^{4+}$ ions. Our neutron powder diffraction data on Ba${}_2$CeIrO${}_6$ can be refined in the cubic space group Fm$\bar{3}$m, while the other three systems are characterized by weak monoclinic structural distortions. Despite the variance in the non-cubic crystal field experienced by the Ir${}^{4+}$ ions in these materials, X-ray absorption spectroscopy and resonant inelastic x-ray scattering are consistent with $J_{\mathrm{eff}}$ $=$ 1/2 moments in all cases. Furthermore, neutron scattering and resonant magnetic x-ray scattering show that these systems host A-type antiferromagnetic order. These electronic and magnetic ground states are consistent with expectations for face-centered-cubic magnets with significant antiferromagnetic Kitaev exchange, which indicates that spacing magnetic ions far apart may be a promising design principle for uncovering additional Kitaev materials.

12 pages, 7 figures

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• Nearly itinerant electronic groundstate in the intercalated honeycomb iridate Ag${}_3$LiIr${}_2$O${}_6$
• Spin-orbit effects in pentavalent Iridates: Models and materials
• The interplay between structural, magnetic and electronic states in the pyrochlore iridate Eu2Ir2O7
• Charge transfer energy in iridates: a hard x-ray photoelectron spectroscopy study
• Magnetic excitations in double perovskite iridates La${}_2$$M$IrO${}_6$ ($M$ = Co, Ni, and Zn) mediated by 3$d$-5$d$ hybridization
• Study of Nontrivial Magnetism in 3$d$-5$d$ Transition Metal based Double Perovskites
• Rotational phase transitions in antifluorite-type osmate and iridate compounds
• Disordered magnetism in the double perovskite LaCaScIrO6 with a distorted fcc lattice of Ir4+