The magnetic properties of Fe3O4 thick films as described by third order perturbed Heisenberg Hamiltonian

Thick films of Fe₃O₄ up to 10000 spin layers have been explained using third order perturbed modified Heisenberg Hamiltonian with seven magnetic parameters. Total magnetic energy and orientation of magnetic easy directions were determined for spinel structure of Fe₃O₄ with octahedral and tetrahedral sites. The effect of number of spin layers and stress induced anisotropy on magnetic properties was investigated. 3-D plot of energy versus angle and number of spin layers was plotted to determine the number of spin layers corresponding to minimum magnetic energy. Magnetic easy axis was found by plotting a graph of energy versus angle for one particular value of the previously-mentioned number of spin layers. Similarly, 3-D and 2-D graphs were plotted for stress induced anisotropy. For film with 4 spin layers, magnetic easy directions were found to be θ = 2.3, 2.5, 5.6 radians, …. When the ratio of stress induced anisotropy to strength of long-range dipole interaction is 2, magnetic easy direction was found to be θ = 2.6 radians. Here the angles were measured with respect to a line drawn normal to the film plane. Because Fe₃O₄ is a soft magnetic material, Fe₃O₄ finds potential applications in magnetic memory devices.