An e-type iron-based oxide magnetic particle powder has narrow particle size distribution and has a low content of fine particles which do not contribute to magnetic recording characteristics. As a result, a narrow coercive force distribution is achieved and the powder is suitable for increasing recording density of a magnetic recording medium. The powder containing substituting metal elements can be obtained by: adding an alkali to an aqueous solution containing trivalent iron ions and ions of the metals for partially substituting Fe sites to neutralize the aqueous solution to a pH of 1.5 to 2.5; then adding a hydroxycarboxylic acid; further adding the alkali to neutralize the aqueous solution to a pH of 8.0 to 9.0; washing with water a precipitation of an iron oxyhydroxide containing the substituting metal elements produced; and coating the iron oxyhydroxide containing the substituting metal elements with a silicon oxide and heating the resultant.

The hexagonal ferrite powder has an activation volume of greater than or equal to 800 nm.sup.3 but less than 1,200 nm.sup.3, a rare earth atom content falling within a range of 0.5 to 8.0 atom % per 100 atom % of iron atoms, and a localized presence of rare earth atoms in the surface layer portion, as well as is in the form of ellipsoidal powder.

Hexagonal ferrite powder has an average particle size falling within a range of 10 nm to 50 nm, a switching field distribution SFD.sub.23° C. measured at a temperature of 23° C. that is less than or equal to 0.80, and a ratio of a switching field distribution SFD.sub.−190° C. that is measured at a temperature of −190° C. to the SFD.sub.23° C. (SFD.sub.−190° C./SFD.sub.23° C.) that is greater than 0.80.

Provided are hexagonal ferrite magnetic powder for magnetic recording, being comprised of hexagonal ferrite magnetic particles having a crystalline metal oxide adhered to a surface thereof, a method for producing hexagonal ferrite magnetic particles having a crystalline metal oxide adhered to a surface thereof, and a magnetic recording medium.

Provided are hexagonal ferrite magnetic powder for magnetic recording, being comprised of hexagonal ferrite magnetic particles having a crystalline metal oxide adhered to a surface thereof, a method for producing hexagonal ferrite magnetic particles having a crystalline metal oxide adhered to a surface thereof, and a magnetic recording medium.

Provided is magnetic powder capable of enhancing simultaneously both magnetic characteristics including SNP and durability of a magnetic recording medium. The hexagonal ferrite magnetic powder for a magnetic recording medium has a Ba/Fe molar ratio of 8.0% or more, a Bi/Fe molar ratio of 2.5% or more and an Al/Fe molar ratio of from 3.0 to 6.0%. The magnetic powder preferably has an activation volume Vact of from 1,400 to 1,800 nm.sup.3. The magnetic powder particularly preferably has a coercive force Hc of from 159 to 279 kA/m (which is approximately from 2,000 to 3,500 Oe) and a coercivity distribution SFD of from 0.3 to 1.0. The magnetic powder may contain, as an element that substitutes an Fe site of the hexagonal ferrite, at least one kind selected from divalent transition metals M1 and tetravalent transition metals M2.

Provided is magnetic powder capable of enhancing simultaneously both magnetic characteristics including SNP and durability of a magnetic recording medium. The hexagonal ferrite magnetic powder for a magnetic recording medium has a Ba/Fe molar ratio of 8.0% or more, a Bi/Fe molar ratio of 2.5% or more and an Al/Fe molar ratio of from 3.0 to 6.0%. The magnetic powder preferably has an activation volume Vact of from 1,400 to 1,800 nm.sup.3. The magnetic powder particularly preferably has a coercive force Hc of from 159 to 279 kA/m (which is approximately from 2,000 to 3,500 Oe) and a coercivity distribution SFD of from 0.3 to 1.0. The magnetic powder may contain, as an element that substitutes an Fe site of the hexagonal ferrite, at least one kind selected from divalent transition metals M1 and tetravalent transition metals M2.

An aspect of the present invention relates to hexagonal ferrite powder, which comprises equal to or more than 70% on a particle number basis of isotropic hexagonal ferrite particles satisfying equation (1):
major axis length/minor axis length<2.0  (1),
having an average particle size of equal to or greater than 10.0 nm but equal to or less than 35.0 nm, and having a saturation magnetization of equal to or greater than 30 A.Math.m.sup.2/kg.

An aspect of the present invention relates to hexagonal ferrite powder, which comprises equal to or more than 70% on a particle number basis of isotropic hexagonal ferrite particles satisfying equation (1):
major axis length/minor axis length<2.0  (1),
having an average particle size of equal to or greater than 10.0 nm but equal to or less than 35.0 nm, and having a saturation magnetization of equal to or greater than 30 A.Math.m.sup.2/kg.

[Object] A cobalt ferrite magnetic powder includes magnetic particles that have a uniaxial crystal magnetic anisotropy and contain cobalt ferrite. A peak top 2θ of a (3, 1, 1) plane determined by powder X-ray diffractometry using a CoKα ray is 41.3° or more and 41.5° or less. Some Cos contained in the magnetic particles are substituted with at least one selected from the group consisting of Zn, Ge, and a transition metal element other than Fe.