NOVELTY - Manufacture of iron silicon material and mu -90 iron magnetic powder core comprises introducing smelted alloy directly into nitrogen spraying mill; passing via 60-mesh sieve; performing hydrogen reduction; grading powder and proportioning into preheating oven at 100-200 degrees C; slowly adding pre-heating powder with 0.1-0.4% phosphoric acid; drying passivated powder in oven at 150-200 degrees C; sequentially adding dried powder with 0-0.4% talc or mica powder, 6% sodium silicate, and 0.5% zinc stearate; uniformly mixing; drying; molding; removing edge burr; and heat treating.    USE - Manufacture of iron silicon material and mu -90 iron magnetic powder core used for producing inductor for power supply, electric power active power factor compensation circuit, or solar photovoltaic system; or for producing high power density integrated inductor for point of load (POL) and voltage regulator module (VRM) power supply.    ADVANTAGE - The method provides iron silicon material with improved magnetic performance and smooth surface. It also provides magnetic powder core with high quality factor and excellent direct current superposition characteristic. It provides good passivation effect, has low cost, and is convenient to perform. The mu -90 powder core has permeability of 1000 e at 100 kHz, initial magnetic permeability coefficient of not less than 0.39, volume ratio of magnetic powder core loss (Pcv) at 25kHz and 100 mT of 310 mW/cm3, and temperature coefficient ( alpha L) of less than 520x 10-6/ degrees C at - 55 to 150 degrees C, thus meeting existing electronic industry low voltage, high current, high power density, and high frequency requirement.    DETAILED DESCRIPTION - Manufacture of iron silicon material and mu -90 iron magnetic powder core comprises smelting alloy in magnesia frequency induction furnace at greater than or equal to 1400 degrees C for more than 50 minutes; introducing smelted alloy directly into nitrogen spraying mill; passing spraying powder via 60-mesh sieve; performing hydrogen reduction by controlling hydrogen dew point at 60 degrees C; grading powder into -100 mesh and -60 mesh powder at particle size ratio of 3:7; proportioning powder into preheating oven at 100-200 degrees C; slowly adding pre-heating powder with 0.1-0.4% phosphoric acid to prepare phosphoric acid aqueous solution to carry out passivating treatment; drying passivated powder in oven at 150-200 degrees C; sequentially adding dried powder with 0-0.4% talc or mica powder, 6% sodium silicate, and 0.5% zinc stearate; uniformly mixing; drying; molding by pressing at 1900-2200 MPa; removing edge burr; heat treating magnetic powder core at 600-800 degrees C for 30-60 minutes under protection of inert gas including nitrogen or argon gas; and surface coating powder cores, in which mu -90 iron magnetic powder core comprises (wt.%) silicon (6.4-7) and iron (remainder).