MODERN PHYSICS LETTERS B, cilt.20, ss.971-979, 2006 (SCI İndekslerine Giren Dergi)
The Next Nearest Neighbor (NNN) effect in Ni2+-[2 x 2] using the isotropic Heisenberg model has been investigated in this article. Although the NNN effect is commonly very weak in this kind of grid, it was calculated that its response is quite big to the outsider perturbations in certain regions. Two different antiferromagnetic arrangements of spins interacting via the Heisenberg exchange type in a square were discussed in terms of their stability regions. Using the isotropic Heisenberg exchange Hamiltonian, the zero field energy spectrum has been calculated for this particular Ni2+-[2 x 2] grid geometry. The average magnetic moments with and without the next nearest neighbors interactions were also calculated. In order to verify the calculations, the results were compared with experimental data which had been published in literature.