First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice.

Recent observations of novel spin-orbit coupled states have generated interest in 4/5 transition metal systems. A prime example is the [Formula: see text] state in iridate materials and α-RuCl that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (λ) and trigonal crystal field (Δ), we restructure the spin-orbital wave functions into a previously unobserved [Formula: see text] state that drives Ising interactions. This is done via a topochemical reaction that converts LiRhO to AgLiRhO. Using perturbation theory, we present an explicit expression for the [Formula: see text] state in the limit Δ ≫ λ realized in AgLiRhO, different from the conventional [Formula: see text] state in the limit λ ≫ Δ realized in LiRhO. The change of ground state is followed by a marked change of magnetism from a 6 K spin-glass in LiRhO to a 94 K antiferromagnet in AgLiRhO.