# Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates

## TL;DR

This study investigates the crystal structures, electronic states, and magnetic properties of certain double perovskite iridates, revealing potential for Kitaev physics even with large Ir–Ir distances, broadening the search for quantum spin liquids.

## Contribution

It provides comprehensive structural and magnetic characterization of La2BIrO6 and A2CeIrO6 iridates, demonstrating that large Ir–Ir spacing does not preclude Kitaev interactions.

## Key findings

- All studied compounds host J_eff=1/2 moments.
- Ba2CeIrO6 has cubic Fm-3m structure; others show monoclinic distortions.
- Materials exhibit A-type antiferromagnetic order.

## 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$_2B$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 $J_{\rm eff}$ $=$ 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.