Secondary agglomerates of magnetic metal particles for magnetic recording and process for producing the same

Secondary agglomerates of magnetic metal particles for magnetic recording, said secondary agglomerates having an average particle diameter of 300 to 800 μm and an upper limit of particle diameters of 2,000 μm, wherein an amount of agglomerates having particle diameters of not more than 53 μm is not more than 30% by weight, a repose angle of repose of 38° to 45°, a water content of 0.5 to 1.5% by weight, a Co content of 0.5 to 45 atm %, an Al content of 5 to 20 atm %, and a rare earth element content of usually 1 to 15 atm %, a sodium content of not more than 20 ppm and a calcium content of not more than 40 ppm;

• comprising magnetic metal primary particles containing iron as a main component having an average major axis diameter of 0.05 to 0.25 μm.

Secondary agglomerates of magnetic metal particles for magnetic recording, having a coercive force of 111.4 to 143.2 kA/m (1,400 to 1,800 Oe), a Co content of from 0.5 to less than 5 atm % based on the total Fe content, a sodium content of not more than 20 ppm, a calcium content of not more than 40 ppm, a Δσs value of not more than 5.0%, and an ignition temperature of not less than 150° C., an average particle diameter of 300 to 800 μm and an upper limit of particle diameter of 2,000 μm;

• and
• comprising spindle-shaped magnetic metal particles containing iron as a main component having an average major axis diameter (L) of 0.05 to 0.15 μm, a crystallite size of from 150 to less than 170 Å and a specific surface area (S) represented by the following formula:
• S·−160×L+65.