Magnetic Properties and Specific Heat of Quasi-Two-Dimensional Triangular Lattice Antiferromagnet Ba3CoNb2O9 Single Crystals

Abstract

We successfully synthesized high-quality Ba₃CoNb₂O₉ single crystals on the millimeter scale using the flux method, which had not been reported in previous studies. As the temperature decreases, the system undergoes two corresponding antiferromagnetic phase transitions with different magnetic structures at T_N1 = 0.90 K and T_N2 = 0.55 K. At 0.4 K, as the magnetic field applied to the ab plane gradually increases, the magnetization value gradually increases without exhibiting a 1/3 magnetization plateau, indicating that the spin direction of Co²⁺ (S = 1/2) in the ground state tends to align along the c-axis rather than forming a 120° arrangement within the ab plane. In addition, the specific heat results of the Ba₃CoNb₂O₉ single crystal confirm that even below T_N2, the system still has strong frustration.