TbFe Magnetostrictive Thin Film Preparation And Performance

In this thesis, the relationship between the deflection of the magnetostrictive film-substrate cantilever and magnetostrictive coefficient of films is analyzed based on material mechanics principles. The derivation highly agrees with methods of the energy minimization and finite element modeling. The multi-layer structure is also extensively investigated and a precise expression is derived finally.The measurement of magnetostrictive coefficient of the films is transformed into the measurement of the displacement of reflected laser dot by the reflected laser beam method based on cantilever structure. The position of reflected laser dot can be adopted by the position sensitive detector (PSD) and signal processing circuit controlled by magnetostrictive coefficient test program developed on Testpoint platform. So, a computer aided test system of magnetostrictive coefficient of the films can be realized with resolution better than 1ppm. Magnetostrictive coefficient of film can be test accurately by this test system.The TbFe films are prapared by DC magnetron sputtering and the films are processed by a rapid circular annealing treatment successively. The technological parameters yielding to the best magnetostriction characters are obtained which are: 40W of sputtering power, 0.4Pa of work gas pressure (Ar), 7cm of distance between the target and the substrate, 550℃ of annealing temperature and four times of circular process. The results show that the easy direction of magnetization of the TbFe films is parallel to the surface of the substrate , that the TbFe films have soft magnetic properties, that there exists exchange-coupling effect between TbFe2 Laves nano-crystalline phase and α-Fe nano-crystalline phase ,and that the magnetostrictive coefficient of the TbFe films reaches 151ppm under the external magnetic field up to 1400Oe.The effect of the film thickness on magnetic domain structure of the as-deposited TbFe films is investigated by Magnetic Force Microscopy (MFM). The result indicates that the spontaneous magnetization is in-plane when the TbFe films are thin. And when the film thickness increasing, magnetization gradually turns to out-of-plane (the maze pattern) and with further increasing the thickness, the maze magnetic domains become wider.The effect of the angle between incidence direction of ion beam and the substrate normal on magnetostrictive properties of TbFe film is studied and the best angle derived is 60o. The effect of the increase of the angle on magnetostrictive properties of TbFe film is due to that the shape anisotropy of the columnar microstructure of TbFe film causes the easy direction of magnetization of TbFe film gradually turns to the direction parallel to the substrate.