Spindle ferromagnetic alloy particles

Claim 2

Spindle ferromagnetic iron base alloy particles substantially dendrite free and having an aspect ratio (major:minor) of not more than 3:1, a coercive force of about 500 to 1000 Oe, and containing about 0.1 to 13 atomic % of Si to Fe.

Claim 3

Spindle ferromagnetic iron base alloy particles according to claim 1, which particles have the aspect ratio (major:minor) orf less than 2:1, and the coercive force of about 500 to 850 Oe, and contain about 0.3 to 8 atomic % of Si to Fe.

Claim 4

Spindle ferromagnetic iron base alloy particles according to claim 1, which particles contain about 0.3 to 13 atomic % of Si to Fe and further contain about 0.1 to 2.5 atomic % of P to Fe.

Claim 5

Spindle ferromagnetic iron base alloy particles according to claim 3, which particles have the aspect ratio of less than 2:1 and the coercive force of about 500 to 850 Oe, and contain about 0.5 to 11 atomic % of silicon to iron and about 0.1 to 2.5 atomic % of P to Fe

Claim 6

The particles of any one of claims 1-4 for use in preparing magnetic recording media.

Claim 7

The particles of any one of claim 1-4 for use in preparing magnetic recording media for use in recording short wave signals.

Claim 8

Metal powder for use in magnetic recording media comprising: substantially dendrite free particles of substantially uniform shape wherein the particles contain about 0.1 to 13% Si to Fe and the major length of the particles does not exceed three times the minor length of the particles.

Claim 9

Metal powder for use in magnetic recording media comprising: substantially dendrite free particles of substantially uniform shape wherein the particles contain about 0.1 to 13% Si to Fe and the major length of the particles does not exceed three times the minor length of the particles.

Claim 10

The powder of claim 7 having a coercive force of about 500 to 1000 Oe.

Claim 11

Spindle ferromagnetic iron base alloy particles according to claim 1, which particles are produced by oxidizing FeCO 3 , in an aqueous suspension by blowing an oxygen-containing gas into the aqueous suspension containing FeCO 3 , obtained by reacting an aqueous solution of a ferrous salt with an alkali carbonate, wherein a water-soluble silicate is added into said alkali carbonate, into said aqueous solution of a ferrous salt or into said aqueous suspension containing FeCO 3 , before blowing said oxygen-containing gas thereinto in an amount of 0.1 to 13 atomic % (calculated as Si) to Fe (of said ferrous salt), thereby obtaining spindle goethite particles containing Si, and subjecting the thus obtained spindle goethite particles containing Si or the spindle hematite particles containing Si obtained by thermally dehydrating said spindle goethite particles containing Si to thermal reduction in a reducing gas.

Claim 12

Spindle ferromagnetic iron base alloy particles according to claim 9, wherein said water-soluble silicate is added in amount of 0.3 to 8 atomic % (calculated as Si) to Fe of said ferrous salt.

Claim 13

Spindle ferromagnetic iron base alloy particles according to claim 9, wherein the thus obtained spindle goethite particles containing Si or the spindle hematite particles containing Si obtained by thermally dehydrating said spindle goethite particles containing Si is brought into suspension in water, a phosphate is added into said suspension in an amount of 0.1 to 2.5 atomic % (calcualted as P) to Fe of said ferric iron oxide hydroxide at a pH of higher than 8, a water-soluble silicate is further added into the resultant aqueous suspension in an amount of 0.2 to 8.0 atomic % (calculated as Si) to Fe of said ferric iron oxide hydroxide so that the total amount of said added silicate is less than 13 atomic % (calculated as Si) to Fe of said ferric iron oxide hydroxide, the pH of the thus obtained aqueous suspension is adjusted to from 3 to 7, thereby obtaining spindle goethite particles containing Si or spindle hematite particles containing Si coated with a phosphorus compound and a silicon compound, and the thus obtained spindle goethite particles containing Si coated with phosphorus compound and silicon compound or the thus obtained spindle hematite particles containing Si coated with phosphorus compound and silicon compound is subjected to thermal reduction in a reducing gas.

Claim 14

Spindle ferromagnetic iron base alloy particles according to claim 9, which particles are produced by oxidizing FeCO 3 , in an aqueous suspension by blowing an oxygen-containing gas into the aqueous suspension containing FeCO 3 , obtained by reacting an aqueous solution of a ferrous salt with an alkali carbonate, wherein a water-soluble silicate is added into said alkali carbonate, into said aqueous solution of a ferrous salt or into said aqueous suspension contaning FeCO 3 , before blowing said oxygen-containing gas thereinto in an amount of 0.1 to 13 atomic % of Si to Fe of said ferrous salt, thereby obtaining spindle goethite particles containing Si, subjecting the thus obtained spindle geothite particles containing Si to thermal treatment in a non-reducing atmosphere at a temperature of from 400 to 600 degrees Celsius, thereby obtaining spindle hematite particles containing Si which are substantially high in density, and subjecting the thus obtained spindle hematite particles containing Si to thermal reduction in a reducing gas.

Claim 15

Spindle ferromagnetic iron base alloy particles according to claim 12, wherein said water-soluble silicate is added in amount of 0.3 to 8 atomic % of Si to Fe of said ferrous salt.

Claim 16

Spindle ferromagnetic iron base alloy particles according to claim 12, wherein the thus obtained spindle goethite particles containing Si is brought into suspension in water, a phosphate is added into said suspension in amount of 0.1 to 2.5 atomic % (calculated as P) to Fe of said ferric iron oxide hydroxide at a pH of higher than 8, a water-soluble silicate is further added into the resultant aqueous suspension in an amount of 0.2 to 8.0 atomic % (calculated as Si) to Fe of said ferric iron oxide hydroxide so that the total amount of said added silicate is less than 13 atomic % (calculated as Si) to Fe of said ferric iron oxide hydroxide, the pH of the thus obtained aqueous aqueous suspension is adjusted to from 3 to 7, thereby obtaining said spindle goethite particles containing Si coated with a phosphorus compound and a silicon compound, the spindle goethite particles containing Si covered with phosphorus compound and silicon compound are subjected to thermal treatment in a nonreducing atmosphere at 500 to 900 degrees Celsius, thereby obtaining the spindle hematite particles containing Si which are substantially high in density and are coated with phosphorus compound and silicon compound, and thus obtained spindle hematite particles containing Si coated with phosphorus compound and silicon compound are subjected to thermal reduction in a reducing gas.

Claim 17

Spindle ferromagnetic iron base alloy particles according to claim 1, which particles have an average length of the major axis of 0.15 to 0.38 μm.