Abstract: An iron nitride magnetic powder consisting primarily of Fe16N2 phase whose average particle diameter determined by particle size measurement using a TEM micrograph is 20 nm or less and whose geometric standard deviation of the particle diameter is 1.4 or less. The iron nitride magnetic powder can be obtained by a method of producing an iron nitride magnetic powder consisting primarily of Fe16N2 phase includes a step of, at the time of producing an iron nitride magnetic powder consisting primarily of Fe16N2 phase by subjecting a reduced powder obtained by reduction of iron oxide to ammonia treatment, using goethite containing Al in solid solution as the iron oxide.

Abstract: An iron nitride system magnetic powder comprising of particles comprised primarily of Fe16N2 (having an average particle diameter of up to 25 nm, for example) is provided, to which one or more elements selected from Si, P and Ti is adhered. The powder has a C/Fe atomic ratio of 0.5 to 30%, preferably a (Si+P+Ti)/Fe atomic ratio of 0.1 to 10%. With ?Hc defined (Hc0·Hc1)/Hc0×100, the powder has a ?Hc of up to 5%, and with ??s defined as (?s0·?s1)/?s0×100, a ??s of up to 20%. The powder can provide an ignition temperature of 140° C. or above, and a tap density of 1.0 g/cm3 or above. Hc0 and ?s0 are the coercive force (kA/m) and saturation magnetization (Am2/kg), respectively, of the iron nitride system magnetic powder after adhesion, and Hc1 and ?s1 are the coercive force (kA/m) and saturation magnetization (Am2/kg), respectively, of the powder after it has been stored in a thermo-hygrostat for one week at a temperature of 60° C. and a relative humidity of 90%.

Abstract: An iron nitride magnetic powder comprised primarily of Fe16N2 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 Fe16N2 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.

Abstract: A magnetic powder is provided composed of particles that, even when the particle size is refined, exhibits excellent magnetic properties, in particular, a high coercive force, for use in a high-density recording medium. The invention also provides a magnetic recording medium using the powder. The powder is an iron system magnetic powder containing, as an atomic ratio of Fe, a total of 0.01 to 10 at. % of one or more selected from W and Mo, particularly a magnetic powder comprised mainly of Fe16N2. The magnetic powder is able to exhibit a high coercive force of 238 kA/m (3000 Oe) or more. In addition to the W and Mo, the magnetic powder may contain, as an atomic ratio of Fe, a total of up to 25 at. % of one or more selected from Al and a rare earth element (defined as including Y).

Abstract: A magnetic powder for magnetic recording medium comprises acicular particles constituted primarily of Fe, wherein the powder contains Co in an amount such that the Co/Fe ratio is 50 at. % or less and the Co is contained in a manner such that the surface portion has a higher concentration than the core portion of the particles, and upon subjecting the magnetic powder for magnetic recording medium to TG measurement, the powder exhibits at least two oxidation starting points: a low-temperature side oxidation starting point and a high-temperature side oxidation starting point. The magnetic powder achieves improved resistance to oxidation without sacrificing magnetic characteristics.

Abstract: An iron system magnetic powder, and particularly an iron system magnetic powder comprised chiefly of Fe16N2, is provided that has an atomic ratio of total noble metal content to Fe of 0.01-10%. The magnetic powder can be produced by subjecting iron oxy-hydroxide or iron oxide having an atomic ratio of total noble metal content to Fe of 0.01-10% to reduction treatment. The average particle volume of the magnetic powder is preferably 4,000 nm3 or less. The magnetic powder is suitable for fabricating high recording density media of low noise, high output and high C/N ratio that are suitable for use with a GMR head or the like.

Abstract: An iron nitride system magnetic powder comprising of particles comprised primarily of Fe16N2 (having an average particle diameter of up to 25 nm, for example) is provided, to which one or more elements selected from Si, P and Ti is adhered. The powder has a C/Fe atomic ratio of 0.5 to 30%, preferably a (Si+P+Ti)/Fe atomic ratio of 0.1 to 10%. With ?Hc defined (Hc0?Hc1)/Hc0×100, the powder has a ?Hc of up to 5%, and with ??s defined as (?s0??s1)/?s0×100, a ??s of up to 20%. The powder can provide an ignition temperature of 140° C. or above, and a tap density of 1.0 g/cm3 or above. Hc0 and ?s0 are the coercive force (kA/m) and saturation magnetization (Am2/kg), respectively, of the iron nitride system magnetic powder after adhesion, and Hc1 and ?s1 are the coercive force (kA/m) and saturation magnetization (Am2/kg), respectively, of the powder after it has been stored in a thermo-hygrostat for one week at a temperature of 60° C. and a relative humidity of 90%.

Abstract: A high-reliability iron nitride-based magnetic powder with markedly improved weatherability with respect to deterioration over time of the magnetic properties in fine particles smaller than 25 nm is formed by adhering one or more of the elements Si and P to the surface of an iron nitride-based magnetic powder constituted primarily of Fe16N2 with an average grain size of 25 nm or less, where the total content of Si and P in the magnetic powder may be 0.1% or greater as an atomic ratio with respect to Fe. In particular, the invention provides an iron nitride-based magnetic powder such that the value ?Hc as defined by Equation (1) below is 5% or less and the value ??s as defined by Equation (2) below is 20% or less. ?Hc=(Hc0?Hc1)/Hc0100??(1) ??s=(?s0??s1)/?s0100??(2) Here, Hc1 and ?s1 are the coercivity and saturation magnetization, respectively, of the magnetic powder after being kept for one week at a constant temperature and constant humidity of 60° C. and 90% RH.

Abstract: An iron nitride magnetic powder consisting primarily of Fe16N2 phase whose average particle diameter determined by particle size measurement using a TEM micrograph is 20 nm or less and whose geometric standard deviation of the particle diameter is 1.4 or less. The iron nitride magnetic powder can be obtained by a method of producing an iron nitride magnetic powder consisting primarily of Fe16N2 phase includes a step of, at the time of producing an iron nitride magnetic powder consisting primarily of Fe16N2 phase by subjecting a reduced powder obtained by reduction of iron oxide to ammonia treatment, using goethite containing Al in solid solution as the iron oxide.

Abstract: An iron nitride magnetic powder comprised primarily of Fe16N2 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 Fe16N2 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.