Study On Film-forming Techniques And Properties Of Sm-Fe-B GMF Prepared In The External Magnetic Field Environment

Rare-earth Giant Magnetostrictive thin Film (RGMF) has been widely used in microsystems such as microelectromechanical systems and micro-sensors due to the merits of the strong magnetostrictive effect, high response speed and electromechanical coupling coefficient, low hysteresis loss as well as non-contact drive. Hence, it’s well important to develop the film-forming techniques of GMF to obtain the film of excellent soft magnetostrictive properties.In this paper, Sm-Fe system negative magnetostrictive film (Sm-Fe-B GMF) were deposited on glass substrate in a steady or pulse magnetic environment by Ion Beam Sputtering Deposited (IBSD) method, and then under the 300℃ vacuum annealing treatment. The Sm-Fe-B GMF composition and microstructures before and after vacuum annealing were 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 under different magnetic environment or 300℃ vacuum annealing treatment were 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 showed that the compositions of film samples prepared in external magnetic field environment or non-magnetic field environment were Sm34Fe62B4 and Sm29Fe69B2 respectively, the samples have smooth surface and compact structure. Sm-Fe-B GMF prepared by different magnetic environment still keeps amorphous structure and the microstructure of samples changes slightly with the 300℃ vacuum annealing treatment.The research results showed that samples prepared at different magnetic field parallel the film plane leads to decrease of magnetic moment perpendicular to film plane, and magnetic domain or magnetic moment mainly exist in film plane. On the other hand, sample prepared without magnetic field shows increase of magnetic domain or magnetic moment perpendicular to film plane. Anisotropy could be induced by magnetic field, which results in easy axis parallel to the direction of applied magnetic field. So, the distribution of magnetic domain or magnetic moment could be adjusted by magnetic field during deposition process. When the direction of testing or applied magnetic field perpendicular to the easy axis of Sm-Fe-B GMF always show very well magnetostrictive properties than that parallel to easy axis. The larger intensity of steady magnetic field, the better magnetostrictive performance showed. The stress states and magnetic states changed by pulse magnetic field (the frequency、strength and applied time of pulse magnetic field were important parameters) during deposition process, leading to the change of static and dynamic magnetostrictive properties.The research results of vacuum annealed samples showed that low field magnetostrictive sensitivity of Sm-Fe-B GMF prepared by non-magnetic field or steady magnetic field were improved under the 300℃ vacuum annealing treatment, while the saturated magnetostriction of samples reduced. At the same time, magnetic properties, low field magnetostrictive sensitivity and even the saturated magnetostriction of Sm-Fe-B GMF prepared by pulse magnetic field were improved under the 300℃ vacuum annealing treatment. The results also showed that a vacuum annealing treatment has little effects on resonance frequency, and greatly improve dynamic amplitude of samples prepared in pulse magnetic field environment.