Field-induced tricriticality in the zigzag antiferromagnet on the frustrated Ising honeycomb lattice

Recent experiments with the Ising van der Waals compound VBr 3 indicate the onset of tricriticality driven by an external magnetic field. In addition, recent neutron diffraction experiments suggest that the vanadium ions, forming a layered honeycomb lattice, order into a zigzag (ZZ) antiferromagnetic phase at low temperatures in this material. Motivated by the rich phase diagram reported for VBr 3 , we investigated the frustrated Ising model on a honeycomb lattice with exchange interactions between first ( J 1 ), second ( J 2 ), and third ( J 3 ) neighbors. By employing the cluster mean-field method and Monte Carlo simulations, we describe the field-induced phase transitions between ZZ and paramagnetic (PM) phases hosted by this model. Our cluster mean-field results for the free energy, entropy, magnetization, and ZZ order parameter indicate the onset of continuous phase transitions at weak magnetic fields and first-order phase transitions at stronger magnetic fields, with a tricritical point taking place at the ZZ-PM phase boundary for a certain range of exchange interactions. This method also indicates that the coordinates of the tricritical point depend on the exchange interactions, with continuous phase transitions favored by stronger antiferromagnetic interactions between second and third neighbors. Data for enthalpy, magnetization, and specific heat from Monte Carlo simulations indicate the onset of tricriticality, with hysteretic behavior at strong magnetic fields and low temperatures suggesting first-order phase transitions. Therefore, our findings support that the field-induced tricriticality observed in VBr 3 occurs in the J 1 - J 2 - J 3 Ising model on the honeycomb lattice, suggesting its relevance to investigate the phase transitions hosted by this compound. In addition, the present description of the field-induced phase transitions can help to identify exchange interactions in other Ising honeycomb lattice compounds that exhibit a ZZ phase.