Fabrication of High Performance Thick Film Magnets by Aerosol Deposition Method

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1. PurposeRare earth magnets with small thickness are strongly demanded in the trend of downsizing motors and electromagnetic devices. The aerosol deposition (AD) method is one of the attractive methods for the fabrication of thick films with thickness of several μm to 500 μm. The deposition rate is around 5-50 μm/min, which 500-5000 times faster than conventional sputtering method. Therefore, in this investigation, we applied this method for the fabrication of high performance thick film magnets and investigated its possibility.2. Results(1) Fabrication of Sm-Fe-N AD Films and their Magnetic Properties : Since the thickness of Sm-Fe-N AD films fabricated on glass substrate was around 45 μm after deposition of 10 min, the thickness reached to 190 μm after the deposition using brass substrate. The deposition rate was estimated as 15-19 μm/min. The films showed the remanence (Br) of 0.4-0.6 T and the coercivities (μ_0H_<cJ>) increased from 1.6-1.8 T. These coercivities were higher than t … More hat of primary raw powders. The microvickers hardness of the AD films was around 500-700. The AD films consisted of α-Fe and Sm_2Fe_<17>N_x phases and the grain size was around 200-400 μm, which was one order smaller than that of primary powders.(2) Fabrication of anisotropic Sm-Fe-N AD Films : It is concluded that the c-axis of Sm-Fe-N has a tendency to align along the magnetic field by using magnets or solenoid coils. Especially, applying magnetic fields of 0.19 T in plane, the remanence measured along the applied field increased with increasing the magnetic field. The maximum value of remanence was 0.54 T, which was 29% higher than that without the applied field (0.42 T).(3) Possibility of Fe_3B/Nd_2Fe_<14>B Nanocomposite AD Films : Hysteresis loop and XRD analysis revealed that the raw powders was nanocomposite powders consisted of Fe_3B and Nd_2Fe_<14>B phase. The larger powder size of raw powders (12.45 μm) influenced the deposition rate and film thickness. The as-deposited AD film exhibited high remanence but low coercivity (H_<cJ>=0.84 kOe), though the film consisted of the Fe_3B and Nd_2Fe_<14>B phases. In addition, the coercivity further decreased by the annealing in Ar. These low coercivities were considered to be related to the relatively low anisotropy field of Nd_2Fe_<14>B phase, the defects induced during the AD method and the presence of α-Fe phase. Less