Amorphous submicron particle chains with high permeability

Amorphous Fe-P-B particles with submicron sizes were synthesized by chemical precipitation in aqueous solutions. The particles having a spherical shape exhibit good magnetic softness and high saturation magnetization. When they are precipitated in a magnetic field, they are connected to each other to form a chain shape. The high aspect ratio of the chains reduces appreciably the demagnetization field associated with isolated particles, resulting in significant improvement of high permeability performance. In this paper, investigations on the external and internal structures of the chains, uniaxial anisotropy caused by aligning the chains in an external magnetic field, frequency dispersion of permeability, and thermal change of the high permeability feature are presented. Finally, comparison of permeability for particles with various sizes is made with the present chain samples. In addition to the superior high permeability feature compared to other magnetically soft particles, the chains exhibit low loss characteristics at high frequencies up to a few GHz. It is also demonstrated that permeability is improved by annealing at 150°C in vacuum. These results suggest that the particle chains have a high potential for high-frequency applications such as inductor cores and electromagnetic noise absorbers.