Study On The Stress And Magnetic Property Of Sm-Fe Giant Magnetostrictive Thin Films

Giant magnetostrictive thin films are very promising for microactuator elements like cantilevers or membranes as they combine high energy output, high frequency and remote control operation, simple actuator lay-out, and low process temperatures during fabrication. In this paper, Sm-Fe GMFs were fabricated by IBS on bronze, glass and si substrates. The surface profiles, composition, microstructure and magnetic property of Sm-Fe GMFs were determined and investigated by using SEM, XRD and VSM. By altering the substrate state, processing parameters and annealing treatment, the change of stress and structure in the thin film were obtained, which resulted in improving the magnetostriction of Sm-Fe GMFs. By using a self-constructed equipment, the DWS type Capacitance-displacement micrometer was calibrated accurately. The elastic modulus of substrate and films were determined by cantilever-load methods and nanoindentation methods. The results were shown as follows: 1. The thickness of thin films were measured by two methods. The results of two measuring methods are near. The deposited rate of Sm-Fe GMFs is the largest when deposited time is 4 hours . 2. The surfaces of Sm-Fe GMFs is obvious different on the different substrates. Sm-Fe GMFs of as-deposited and annealed at 200℃ and 300℃ exhibit amorphous structure. When it was annealed at 300℃ for 1 h, crystal structure appeared. 3. Compressive press is produced when Sm-Fe GMFs were fabricated by IBS on bronze and glass substrates. The stress of Sm-Fe thin films are near in different sputtering angles during 42.5o～57.5o. 4. The as-deposited film and the heat-treated film showed anisotropic magnetization with the easy axis parallel to the film surface. And the easy axis of the as-deposited film parallel to the orientation of the short side of the substrate. After heat treatment, the soft magnetic properties of Sm-Fe GMFs increased obviously. The thin film treated at 200℃ showed the largest saturation magnetization Ms. 5. The low-field magnetostriction coefficient of the as-deposited film is too small. Compressive press applied to the films makes its saturation magnetostriction coefficient increased slightly. After heat treatment, Sm-Fe GMFs shows an improved low-field magnetostriction properties as the magnetostrictive saturation field is reduced . The thin film treated at 200℃ has the largest saturation magnetostriction coefficientλs attained 398×10^-6. After treatment at 250℃ , the Sm-Fe films showed the best low-field magnetostriction attained 108.5×10^-6 at 0.02T.