Patent ID: 7407705

Claim:
A magnetic powder composed primarily of Fe that has been surface-treated with a silane coupling agent, which magnetic powder is made up of acicular particles and is characterized in that: it contains Co such that Co/Fe expressed in atomic percent is 20-50 at. %, Al such that Al/Fe expressed in atomic percent is 5-30 at. %, and one or more rare earth elements R (including Y) such that R/Fe expressed in atomic percent is 4-20 at. %, and has average particle diameter of smaller than 80 nm, TAP density of 0.7 g/cm 3 or greater, ignition point of 165° C. or higher, oxygen content of 26 wt % or less, and satisfies the relation of Formula 1 below between its coercive force and particle volume: Hc ≧325 ×In ( V )−900, Formula 1 where, in Formula 1, Hc represents coercive force (Oe) and V represents particle volume (nm 3 ) calculated from a transmission electron micrograph.