From order to disorder: magnetic phase evolution of diluted triangular lattice Ba₃CoNb₂O₉

Magnetic lattice dilution in geometrically frustrated systems provides a platform to investigate the presence of unconventional magnetic phases as the dilution is expected to destabilize the conventional magnetic order and creates randomness in exchange interactions. In this context, we have investigated the impact of non-magnetic Zn²⁺doping on an effective spin (J_eff)-½ geometrically frustrated triangular lattice Ba₃CoNb₂O₉. The successful formation of pure single phase and preservation of crystal symmetry is confirmed via x-ray diffraction studies. Magnetic susceptibility measurements confirm the persistence ofJ_eff= ½ state, along with the suppression of antiferromagnetic (AFM) ordering with the critical concentration (x_c= 0.4) corresponding to disordered state. This transition from AFM to disordered state abovex= 0.4 is further confirmed from isothermal magnetization (M(H)). Along with this, a field-induced transition identical to a spin-flop transition is observed in the saturation region ofM(H) curves which become more dominant for higher concentration. The dilution of magnetic lattice results in randomness in exchange interactions with reduced AFM coupling between the spins which lowers the energy barrier for spin reorientation and gives rise to these unique spin-flop transitions. Our results highlight the role of magnetic dilution in tuning the balance between frustration and exchange interactions, offering insight into such field-driven behavior of quantum magnets.