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A novel amorphous soft magnetic composites (ASMCs) for hundreds MHz frequency applications have been prepared under the hot-pressing molding by ultrafine submicron FeBP amorphous powders. These ultrafine submicron FeBP amorphous particles were synthesized with the NaBH 4 chemical reduction method and the particles size was regulated by the drop rate of the reducing agent. The morphology, microstructure, elemental composition and high-frequency magnetic properties of the amorphous soft magnetic composites was systematically investigated. The particle sizes of FeBP amorphous powders are distributed in 600–900 nm which gradually increase with the decrease of the drop rate of the NaBH 4 aqueous solution. Meanwhile, the Fe element content and saturation magnetization strength of the amorphous powder increase and the coercivity gradually decreases. The corresponded ASMCs also appear a commensurate permeability in the range of 6–9 responding to the GHz high frequency range with the lowest loss tangent only 0.20 and 0.44 at 500 MHZ and 1 GHz, respectively. Such ultrafine amorphous soft magnetic composites have enormous potential for high frequency applications in wide band gap semiconductor switching power supplies, RF inductors and chips. • The spherical amorphous powder was prepared by chemical reduction method with outstanding magnetic properties. • The particle size of the amorphous powder was regulated by adjusting the drop rate of the reducing agent solution. • The relationship between the powder particle size and the magnetic and electrical properties of ASMCs was elucidated. [ABSTRACT FROM AUTHOR]

• A novel hybrid amorphous soft magnetic composite (SMC) for MHz power applications is fabricated using amorphous powders of ultrafine spherical FeSiBCr and submicron FeBP powders. • The regularly spherical particles of submicron amorphous FeBP powders are found to occupy the gaps between the micron-sized FeSiBCr amorphous powders. • The magnetic loss of the soft magnetic composite mixed with only 1 wt% submicron amorphous FeBP particles is just 511 kW/m3 at 30 mT/1 MHz, and the permeability of DC bias superposition under 100 Oe reaches 90%. • The soft magnetic composite constructed by the pure submicron amorphous FeBP particles also shows excellent magnetic properties within a few hundred MHz region, with the permeability of 4–6 and the low loss tangent of only 0.019 at 200 MHz and 0.05 at 500 MHz. • This amorphous soft magnetic composite exhibits a great potential for the applications in wide band gap semiconductor switching power supplies, RF inductors and chips. A novel hybrid amorphous soft magnetic composite (SMC) for MHz power applications is fabricated using amorphous powders of ultrafine(<10 μm) spherical FeSiBCr and submicron(100 nm∼1 μm) FeBP powders. The submicron amorphous FeBP powders are found to occupy the gaps between the micron-sized FeSiBCr amorphous powders, enabling one to enhance the density and magnetic properties (permeability and loss) of the composite in a MHz frequency range. The magnetic loss of the soft magnetic composite mixed with only 1 wt% submicron amorphous particles is just 511 kW/m3 at 30 mT/1 MHz, and the permeability of DC bias superposition under 100 Oe reaches 90%. In addition, the permeability of the hybrid soft magnetic composite and the submicron amorphous composite reach 20 and 5, and the loss tangent is only 0.03–0.08 and 0.02 in 100 MHz region, respectively. This amorphous soft magnetic composite exhibits a great potential for the applications in wide band gap semiconductor switching power supplies. [ABSTRACT FROM AUTHOR]