| Giant Magnetostrictive thin Film (GMF) is expected to be used in microsystems such as microelectromechanical systems and micro sensors due to the advantages of the strong magnetostrictive effect, high response speed and electromechanical coupling coefficient, low hysteresis loss as well as non-contact drive. To fulfill the application of GMF component to the micro systems, film component should have excellent soft magnetic properties and high magnetostrictive sensitivity at low field.The magnetic structure and magnetic properties of amorphous GMF can be influenced by magnetic anisotropy induced by stress and induced-anisotropy caused by stress annealing due to magnetocrystalline anisotropy disappearance caused by the long range disorder. Soft magnetic properties and low field magnetic sensitivity can be improved by magnetic anisotropy and stress-annealing-induced-anisotropy.In this paper, Sm-Fe system negative magnetostrictive film (Sm-Fe-B GMF) are deposited on glass substrate at different prestrain by Ion Beam Sputtering Deposited (IBSD) method, and film samples in condition of no prestrain are stress annealed. The Sm-Fe-B GMF composition and microstructures before and after annealing are studied by spectrum analyzer and XRD diffraction, respectively. Magnetic domain structure, soft magnetic property, static magnetostrictive property and dynamic vibration characteristics (amplitude-frequency characteristic) of Sm-Fe-B GMF are investigated with magnetic force microscopy (MFM). alternating gradient magnetometer (AGM). static magnetostrictive characteristics testing system as well as the Helmholtz dynamic vibration testing system.The testing results of composition and structure for film samples show that the composition of film samples is Sn29Fe69B2, the samples have smooth surface and compact structure. The microstructure of samples changes slightly with the annealing temperature, but still keeps amorphous structure.The research results of samples prepared on different prestrain substrates show tension prestrain of substrate leads to increase of magnetic torque perpendicular to film plane, while compressive prestrain of substrate results in magnetic torque to film parallel to plane. Substrate prestrain leads to a change in easy magnetization direction, making the property of saturated magnetostriction slightly reduce, but the soft magnetic properties and the low field magnetostrictive sensitivity of the samples are significantly improved. Dynamic amplitude-frequency characteristic changes with thedifferent magnetized states of the samples under the influence of prestrain on the substrate.The research results of annealed samples show that magnetic anisotropy introduced by both free and stress annealing leads to magnetic domain structure changes. The saturated magnetostriction of samples reduces, while the soft magnetic properties and low field magnetostrictive sensitivity are improved whether in free or stress annealing, Low field magnetic sensitivity of samples is enhanced by tensile stress annealing at 350℃. Free annealing has little effects on resonance frequency of samples and causes great influence on amplitude of samples, However, stress annealing have a larger influence on both the resonance frequency and amplitude of samples. |
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