High-energy-density permanent micromagnets formed from heterogeneous magnetic powder mixtures

In this paper, we report the microfabrication and magnetic characterization of parylene-bonded permanent micromagnets. Mixtures of two different sized and shaped isotropic Nd-Fe-B powders are used to form 255 μm × 255 μm × 315 μm thick micromagnets embedded in silicon substrates. The best properties are obtained for a 50:50 mixture of the powders, yielding remanence B_r = 0.69 T, intrinsic coercivity H_ci = 680 kA/m, and energy product BH_max = 45 kJ/m³. Enabled by newly released commercially available magnetic powders, the results show a doubling in the energy density and remanence values over previously reported parylene-bonded magnets. The rapid, simple, low-temperature fabrication of these magnets, as well as their thermal and chemical stability, makes them attractive for magnetic MEMS applications.