Patent ID: 6872326

Claim:
A magnetic powder which is manufactured by milling a ribbon-shaped magnetic material which has been obtained by colliding a molten alloy of a magnetic material to a circumferential surface of a rotating cooling roll so as to cool and then solidify it, comprising: a plurality of particles, each particle including: an average particle size Dμm in the range of 10-20 μm; a plurality of ridges and recesses, each ridge and recess having an average pitch in the range of 3-50 μm, a length of D/30 μm and an average depth or height in the range of 0.3-μm; and a composite structure composed of a hard magnetic phase and a soft magnetic phase, each of the hard and soft magnetic phases having an average crystal grain size in the range of 1-100 mn; wherein the cooling roll is formed with gas flow passages as gas expelling means defined by a plurality of grooves for expelling gas entered between the circumferential surface and a puddle of the molten alloy in the circumferential surface thereof, a width of the grooves preventing the molten alloy from fully entering the grooves; and when an average pitch of these gas flow passages is defined as Pμm and the average particle size of the magnetic powder is defined as Dμm, a relationship represented by a formula P<D is satisfied.