The effects of the thickness of MgO and Fe on the electronic structure and magnetic properties of Fe/MgO/Fe magnetic tunnel junction was studied using the first principle method. Two series of models with MgO of different thicknesses: Fe(3)MgO(t)Fe(3) (t=1,3,5,7) and with Fe of varied thicknesses: Fe(t)MgO(3)Fe(t) (t=3,4,5,6,7) were established. Calculated results show that in all the models the magnetic moment of Fe increases at the Fe/MgO interface and surface as compared with that of the inner layers. The mag-netic moment of each Fe layer was found to be independent of MgO thicknesses, while the spin-polarization of Fe layer at the interface shows a slight change in function of the MgO thicknesses. The tunneling magnetoresistance (TMR) ratio estimated by the Julliere model has the same change tendency as the spin-polarization has, and the largest value is obtained at the MgO thickness of 5 atomic layers. When the Fe thickness increases, the spin-polarization of interface Fe layer follows up an increase with a decrease. The highest TMR value is achieved when the Fe thickness is of 4 atomic layers.
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