Magnetic powder, a magnetic recording medium using the magnetic powder, and a method of surface treating a magnetic powder
AssigneeDowa Electronics Materials Co., Ltd.
InventorKimitaka Sato
Life of this patent
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Abstract
A magnetic powder composed primarily of Fe that has been surface-treated with a silane coupling agent, which magnetic powder 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/cm3 or greater, ignition point of 165° C. or higher, and oxygen content of 26 wt % or less.
Claims16
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/cm3 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 (nm3) calculated from a transmission electron micrograph.
A magnetic powder composed primarily of Fe, which is a magnetic powder that is made up of acicular particles and is for a coating-type magnetic recording medium that:
- has
- a particle volume (V) calculated from a transmission electron micrograph of not less than 1000 nm3 and not greater than 15000 nm3,
- contains
- Si such that Si/Fe expressed in atomic percent is 0.1-10 at. %, and
- C such that C/Fe expressed in atomic percent is 0.5-40 at. %,
- and has
- oxygen content of 26 wt % or less
- TAP density of 0.7 g/cm3 or greater,
- ignition point of 165° C. or higher,
- Δσs (amount of change (%) in saturation magnetization value as during storage for seven days under constant temperature and humidity at a temperature of 60° C. and relative humidity of 90%) of 20% or less, and
- saturation magnetization value as of less than 140 emu/g,
- 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 (nm3) calculated from a transmission electron micrograph.
Dependencies are inferred from the claim text.