A nonlinear magnetomechanical coupling model of giant magnetostrictive thin films at low magnetic fields

As magnetomechanical coupling model plays an important role in the application of giant magnetostrictive thin films (GMFs) to the microactuators and the microsensors, in this paper, the properties of GMFs at low magnetic fields, including the large magnetostriction, the soft magnetization and the hysteresis under internal stress (prestress), are analyzed firstly. Thereafter, with neglecting the change of internal stress during magnetic polarization and magnetostriction, a nonlinear magnetomechanical coupling model of GMFs at low magnetic fields is established, which is composed of the modified Rayleigh model for the magnetic polarization and the “butterfly curve” model for the strain. Experiments on TbDyFe-polyimide (PI)-SmFe and TbDyFe-Cu-SmFe are conducted, respectively, to verify the proposed model. Results indicate that the model curve coincides well with the experimental results of the magnetic polarization and the magnetostriction for TbDyFe-PI-SmFe and TbDyFe-Cu-SmFe under a given prestress at a low magnetic field. Besides, the proposed model is also in good conformity with the published experimental data of TbFe, SmFe and TbDyFe thin films.