Size controlled preparation of Fe–B–P submicrometre particles and magnetic performance

Fe–B–P submicrometre particles were synthesised by a novel chemical method. The size of the Fe–B–P particles (0·1–1 μm) is easily controlled by tuning the NaBH4 concentration and its dropping speed. The saturation magnetisation (Ms) of Fe–B–P submicrometre particles is >130 emu g−1, whereas the coercivity is <10 Oe. The permeability of the composites made of Fe–B–P particles (∼0·3 μm) and NiZn ferrite nanoparticles (10 nm) is ∼25 when the volume percentage of NiZn ferrite is 30–50%. The resonance frequencies are all ∼1 GHz for pure Fe–B–P particles and the composites.