Magnetic properties of ultrafine Fe-Ni-B particles

Ultrafine Fe-Ni-B particles were synthesized by reducing iron and nickel salts with NaBH4 in aqueous solutions. The particles had diameters in the range of 100–300 Å. X-ray diffraction patterns showed that particles with boron concentration 18 at. % or more were amorphous; otherwise they were crystalline. It was also found that the amorphous particles contain less than 50 at. % of Fe. The coercivity of Fe-B particles was increased by an addition of a small amount of Ni to the system. The room-temperature coercivity and saturation magnetization for particles of composition Fe63Ni24B13 and of diameter 100 Å were 1275 Oe and 70 emu/g, respectively.