Mean field and Monte Carlo simulations techniques are applied to study the behavior of a mixed Ising spin model in a square lattice where spins 7/2 are located in alternating sites with spins 3/2. There is an antiferromagnetic interaction between nearest neighbors, ferromagnetic interactions between next-nearest neighbors, crystal fields, and a magnetic external field. The role of the different interactions in the magnetic behavior of the system is explored. It is found that depending on the combination of parameters in the Hamiltonian this system presents multiple hysteresis loops, exchange bias, compensation temperatures, and discontinuous magnetizations. The results are compared with previous studies that do not include the ferromagnetic next-nearest neighbor interactions and found that they can have a strong effect in the magnetic behavior of the system.

We perform Monte Carlo simulations in order to study the magnetic properties of the mixed spin-S = ± 3/2, ± 1/2 and spin-σ = ± 5/2, ± 3/2, ± 1/2 Ising model. The spins are alternated on a square lattice such that S and σ are nearest neighbors. We found that when the Hamiltonian includes antiferromagnetic interactions between the S and σ spins, ferromagnetic interactions between the spins S, and a crystal field, the system presents compensation temperatures in a certain range of the parameters. The compensation temperatures are temperatures below the critical point where the total magnetization is zero, and they have important technological applications. We calculate the finite-temperature phase diagrams of the system. We found that the existence of compensation temperatures depends on the strength of the ferromagnetic interaction between the S spins.

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