Iron nitride magnetic powder and method of producing the powder
View Patent ↗An iron nitride magnetic powder comprised primarily of Fe 16 N 2 phase is characterized in that its coercive force Hc is 200 KA/m or greater and bulk switching field distribution BSDF is 2 or less. The magnetic powder can be produced by allowing a nitriding reaction of Fe particles with a nitrogen-containing gas for producing nitrided particles of primarily Fe 16 N 2 phase to proceed under an increased pressure of 0.1 MPa or greater. The enhanced properties of the iron nitride magnetic powder make it suitable as a magnetic material for high-density magnetic recording media.
1. An iron nitride magnetic powder comprised primarily of Fe 16 N 2 phase, characterized in that its coercive force Hc is 200 KA/m or greater bulk switching field distribution BSFD is 2 or less.
2. An iron nitride magnetic powder according to claim 1 , wherein the ratio below Hc 120 KA/m in the bulk switching field distribution is 15% or less.
3. An iron nitride magnetic powder according to claim 1 , wherein the average particle diameter is 50 nm or less.
4. An iron nitride magnetic powder according to claim 1 , further comprising one or both of Co and Ni in a total amount expressed in atomic percent based on Fe of 0.1–30 at. %.
5. An iron nitride magnetic powder according to claim 4 whose oxidation resistance index Δσs is 15% or less, where Δσs is a percentage calculated from saturation magnetization values σs before and after storage of the iron nitride magnetic powder in a thermo-hygrostat for one week at 60° C., 90% RH, using the following equation:
100×{(saturation magnetization value before storage)−(saturation magnetization value after storage)}/(saturation magnetization value before storage).
6. An iron nitride magnetic powder according to claim 1 , the ratio of Fe 16 N 2 phase being 80% or more as determined by XRD peak integration.
7. An iron nitride magnetic powder according to claim 1 , further comprising sinter preventing agents comprising a combination of Al and a rare earth element defined as including Y, wherein Al content is in the range of 5–30 at. % based on Fe and the rare earth element content is in the range of 0.5–10 at. % based on Fe.
8. An iron nitride magnetic powder according to claim 1 , further comprising sinter preventing agents comprising a combination of Si and a rare earth element defined as including Y, wherein Si content is in the range of 1–10 at. % based on Fe and the rare earth element content is in the range of 0.5–10 at. % based on Fe.
9. A method of producing an iron nitride magnetic powder comprising:
allowing a nitriding reaction of Fe particles with a nitrogen-containing gas for producing nitrided particles of primarily Fe 16 N 2 phase to proceed under an increased pressure of 0.1 MPa or greater.
10. A method of producing an iron nitride magnetic powder comprising:
allowing a nitriding reaction of Fe particles with ammonia gas for producing nitrided particles of primarily Fe 16 N 2 phase to proceed under an ammonia gas increased pressure of 0.3 MPa or greater.