Provided is a magnetic recording medium including: a recording layer containing a powder of particles containing ε iron oxide, in which a ratio ((Hc(50)/Hc(25))×100) of a coercive force Hc(50) measured in a thickness direction of the magnetic recording medium at 50° C. and a coercive force Hc(25) measured in the thickness direction of the magnetic recording medium at 25° C. is 95% or greater, the coercive force Hc(25) is 200 kA/m or greater, and a squareness ratio measured in a transport direction of the magnetic recording medium is 30% or less.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. A magnetic tape cartridge and a magnetic recording and reproducing device include the magnetic recording medium. The ferromagnetic powder is an ε-iron oxide powder, and a ferromagnetic powder filling rate of a magnetic layer cross section obtained by observing a cross section of the magnetic layer with a scanning electron microscope is 0.60 or more and 0.80 or less.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. A magnetic tape cartridge and a magnetic recording and reproducing device include the magnetic recording medium. The ferromagnetic powder is an ε-iron oxide powder, and a ferromagnetic powder filling rate of a magnetic layer surface obtained by observing a surface of the magnetic layer with a scanning electron microscope is 0.40 or more and 0.60 or less.

Provided is a magnetic recording medium having a recording track width of 2 μm or less, including: a recording layer containing a powder of particles containing ε iron oxide, in which a squareness ratio measured in a transport direction is 30% or less, a squareness ratio S1 measured in the transport direction and a squareness ratio S2 measured in a width direction satisfy a relationship S1≥S2, a coercive force is 220 kA/m or greater and 310 kA/m or less, an activation volume is 8000 nm.sup.3 or less, and in a switching field distribution (SFD) curve, a peak ratio X/Y of a main peak height X and a height Y of a sub-peak near zero magnetic field is 3.0 or greater.

[Solving Means] A method of producing a magnetic powder includes: coating a surface of each of silica-coated precursor particles with at least one type of coating agent of a metal chloride or a sulfate; and firing the precursor particles coated with the coating agent.

Disclosed are a particle of a 13-iron oxyhydroxide-based compound represented by Formula (1), in which an average equivalent circle diameter of primary particles is 5 nm to 30 nm, and a coefficient of variation of equivalent circle diameters of the primary particles is 10% to 30% [In Formula (1), A represents at least one kind of metal element other than Fe, and a represents a number that satisfies a relationship of 0≤a<1.], and applications thereof.
β-A.sub.aFe.sub.1-aOOH   (1)

The magnetic tape includes: a non-magnetic support; and a magnetic layer including ferromagnetic powder, in which the ferromagnetic powder is ferromagnetic powder selected from the group consisting of hexagonal strontium ferrite powder and ε-iron oxide powder, and an amount of an edge weave of a tape edge on at least one side of the magnetic tape is 1.5 μm or less.

[Problem] To provide a method for producing iron based oxide magnetic powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, and consequently has a narrow coercive force distribution and is suitable for the enhancement of the recording density of the magnetic recording medium. [Solution] ε-Type iron based oxide magnetic powder is obtained by a wet method, then a tetraalkylammonium salt as a surface modifier is added to a slurry containing the magnetic powder to make a concentration of 0.009 mol/kg or more and 1.0 mol/kg or less, and simultaneously to make pH of 11 or more and 14 or less, and the slurry is subjected to a dispersion treatment and then classified, so as to provide iron based oxide magnetic powder having a narrow particle size distribution and a narrow coercive force distribution.

The magnetic recording medium includes a non-magnetic support; and a magnetic layer including a ferromagnetic powder, in which the ferromagnetic powder is an ε-iron oxide powder having an average particle size of 9.0 nm to 20.0 nm, and in the ε-iron oxide powder, a content of particles having a particle size smaller than 8.0 nm is less than 20.0% by mass, a content of particles having a particle size smaller than 6.0 nm is less than 5.0% by mass, and a content of particles having a particle size greater than 25.0 nm is less than 20.0% by mass.

The average thickness t.sub.T of a magnetic recording medium meets the requirement that t.sub.T≤5.5 [μm], and the dimensional change amount Δw in the width direction of the magnetic recording medium with respect to the tension change in the longitudinal direction of the magnetic recording medium meets the requirement that 700 ppm/N≤Δw.