Compensation temperature of the mixed-spin ising model on the hexagonal lattice

Abstract

We studied a layered mixed-spin Ising model, with spins σ = 1/2 and S=1, distributed on the sites of a hexagonal lattice. For this spin arrangement, any spin at one lattice site has two nearest-neigbor spins of the same type, and four of the other type. We assumed that the exchange interaction between spins σ and S is antiferromagnetic, with the value J1. J 2 is the exchange interaction between two nearest neighbor σ spins, and J3 is the coupling between two nearest neighbor S spins. We also considered a single-ion crystal-field contribution D to the S sites. We performed mean-field calculations and Monte Carlo simulations to determine the compensation point of the model. We have shown that a compensation point can be present for any positive value of D. We have also found a negative lower bound for D, below which a compensation point can not appear. For each value of D, we determined the range of values of the J2 and J3 couplings for which a compensation point is realizable.