  BaCo2(AsO4)2 (BCAO) has seen extensive study since its initial identification
as a proximate Kitaev quantum spin liquid candidate. Thought to be described by
the highly anisotropic XXZ-J_1-J_3 model, the ease with which magnetic order is
suppressed in the system indicates proximity to a spin liquid phase. Upon
chemical tuning via partial arsenic substitution with vanadium, we show an
initial suppression of long-range incommensurate order in the BCAO system to T
= 3.0 K, followed by increased spin freezing at higher substitution levels.
Between these two regions, at around 10% substitution, the system is shown to
pass through a critical point where the competing J_1/J_3 exchange interactions
become more balanced, producing a more complex magnetic ground state, likely
stabilized by quantum fluctuations. This state shows how slight compositional
change in magnetically-frustrated systems may be leveraged to tune ground state
degeneracies and potentially realize a quantum spin liquid state.
