A novel two-dimensional NiCl₂O₈ lattice with negative Poisson's ratio and magnetic modulation

Two-dimensional (2D) materials with simultaneous magnetic semiconducting properties and a negative Poisson's ratio are crucial for fabricating multifunctional electronic devices. However, progress in this area has been generally constrained. Based on first-principles calculations, we engineered a 2D Ni-based oxyhalide with a honeycomb lattice structure. It was observed that the NiCl₂O₈ monolayer exhibits both high- and low-buckling states in its geometry, along with intrinsic magnetic semiconductor properties in its electronic structure. Importantly, we demonstrated that the magnetic ordering of the NiCl₂O₈ lattice is susceptible to applied strain, which resulted in a phase transition from paramagnetic to ferromagnetic under biaxial strain. The Curie temperature was also evaluated using Monte Carlo simulations within the Ising model. Additionally, our research uncovered that the 2D NiC_l2O₈ lattice chain displays a negative Poisson's ratio (NPR) along the z-direction. The triangular hinge structure in its centrosymmetric configuration was identified as the origin of this unique phenomenon. The coexistence of NPR and magnetic phase transition properties in the NiCl₂O₈ lattice makes it quite promising for applications in nanoelectronic and spintronic devices.