Patent ID: 7854807

Claim:
A metal magnetic powder for a magnetic recording medium, wherein particles of the powder have a metal magnetic phase, composed mainly of Fe or Fe plus Co, and an oxide layer on a surface of the particle, wherein the average major axis length of the powder particles is 10-50 nm, the average particle volume including the oxide layer is 5,000 nm 3 or less, and the atomic ratio (R+Al+Si)/(Fe+Co) calculated using the content values (at. %) of the elements contained in the powder particles is 20% or less, where R is rare earth element (Y being treated as a rare earth element), and the metal magnetic powder satisfies the relationship of Formula (1) between saturation magnetization σs (Am 2 /kg) and average particle volume including the oxide layer V (nm 3 ): σ s ≧0.0185 V + 58 (1).