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 J(eff) = 1/2 state in iridate materials and alpha-RuCl3 that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (lambda SOC)( )and trigonal crystal field (Delta(T)), we restructure the spin-orbital wave functions into a previously unobserved mu = 1/2 state that drives Ising interactions. This is done via a to-pochemical reaction that converts Li2RhO3 to Ag3LiRh2O6. Using perturbation theory, we present an explicit expression for the mu =1/2 state in the limit Delta(T )>> lambda(SOC) realized in Ag3LiRh2O6, different from the conventional J(eff) =1/2 state in the limit lambda(SOC) << Delta(T) realized in Li2RhO3. The change of ground state is followed by a marked change of magnetism from a 6 K spin-glass in Li2RhO3 to a 94 K antiferromagnet in Ag3LiRh2O6.