Exchange Coupling Magnetostrictive Multilayers Micromagnetic Study

The exchange-coupling magnetostrictive multilayers (ECMM) have attracted much attention because of its high low-field magnetostrictive sensitivity. A theoretical model of the ECMM has been founded in this dissertation to study the magnetization and the magnetostrictive characteristics of the ECMM. The results are expected to provide a theoretical guidance for the designing and fabricating of the ECMM.Firstly, the exchange energy, magnetic anisotropic energy, Zeeman energy, magnetostrictive energy, pure elastic energy and stress energy have been introduced in the Landau free energy. Based on the law of minimum energy, a mathematical expression describing the magnetic characteristics of the ECMM under an external magnetic field has been deduced. And the mechanic balance conditions of the ECMM have been considered in this model. A new algorithm, which called"predictor-corrector", has been established based on the Stoner-Wohlfarth model and the Newton Down-hill numerical method. Numerical simulations have been performed based on the model and the results are listed below:The saturation field of the ECMM decreases reduced and the low-field magnetostrictive sensitivity of the ECMM is greatly improved compared with those of the monolayer magnetostrictive film. The simulation results are agreement well with the experimental results of the (TbFe2/α-Fe) n ECMM.If the magnetic anisotropy of the magnetostrictive layer is much larger than that of the soft layer, the magnetic hysteresis and magnetostriction of the ECMM magnetized along the easy axis of the magnetostrictive layer are different from those of hard axis of the magnetostrictive layer. A better low-field magnetostrictive sensitivity has been obtained when the ECMM is magnetized along the hard axis of the magnetostrictive layer. The simulation results are agreement with the experimental results qualitively.The direction of the easy axis of the soft layer has little influence on the magnetic hysteresis and magnetostriction of the ECMM when the magnetic anisotropy of the magnetostrictive layer is much larger than that of the soft layer. The ratio of the...