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 4d/5d transition metal systems. A prime example is the [Formula: see text] state in iridate materials and α-RuCl(3) that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (λ(SOC)) and trigonal crystal field (Δ(T)), 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 Li(2)RhO(3) to Ag(3)LiRh(2)O(6). Using perturbation theory, we present an explicit expression for the [Formula: see text] state in the limit Δ(T) ≫ λ(SOC) realized in Ag(3)LiRh(2)O(6), different from the conventional [Formula: see text] state in the limit λ(SOC) ≫ Δ(T) realized in Li(2)RhO(3). The change of ground state is followed by a marked change of magnetism from a 6 K spin-glass in Li(2)RhO(3) to a 94 K antiferromagnet in Ag(3)LiRh(2)O(6).