A rare earth-iron-nitrogen-based magnetic powder according to this invention contains, as main constituent components, a rare-earth element (R), iron (Fe), and nitrogen (N). Moreover, this magnetic powder has an average particle size of 1.0-10.0 μm, and contains 22.0-30.0 mass % of a rare-earth element (R) and 2.5-4.0 mass % of nitrogen (N). Further, this magnetic powder includes: a core part having any one crystal structure among a Th.sub.2Zn.sub.17 type, a Th.sub.2Ni.sub.17 type, and a TbCu.sub.7 type; and a shell layer provided on the surface of the core part and having a thickness of 1-30 nm. The shell layer contains a rare-earth element (R) and iron (Fe) so that the R/Fe atomic ratio is 0.3-5.0, and further contains 0-10 at % (exclusive of 0) of nitrogen (N). Furthermore, this magnetic powder contains compound particles composed of a rare-earth element (R) and phosphorus (P).

Example nanoparticles may include an iron-based core, and a shell. The shell may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example alloy compositions may include an iron-based grain, and a grain boundary. The grain boundary may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example techniques for forming iron-based core-shell nanoparticles may include depositing a shell on an iron-based core. The depositing may include immersing the iron-based core in a salt composition for a predetermined period of time. The depositing may include milling the iron-based core with a salt composition for a predetermined period of time. Example techniques for treating a composition comprising core-shell nanoparticles may include nitriding the composition.

Techniques are disclosed for milling an iron-containing raw material in the presence of a nitrogen source to generate anisotropically shaped particles that include iron nitride and have an aspect ratio of at least 1.4. Techniques for nitridizing an anisotropic particle including iron, and annealing an anisotropic particle including iron nitride to form at least one α″-Fe.sub.16N.sub.2 phase domain within the anisotropic particle including iron nitride also are disclosed. In addition, techniques for aligning and joining anisotropic particles to form a bulk material including iron nitride, such as a bulk permanent magnet including at least one α″-Fe.sub.16N.sub.2 phase domain, are described. Milling apparatuses utilizing elongated bars, an electric field, and a magnetic field also are disclosed.

Disclosed herein is a permanent magnet comprising: a plurality of aligned iron nitride nanoparticles wherein the iron nitride nanoparticles include α″-Fe.sub.16N.sub.2 phase domains; wherein a ratio of integrated intensities of an α″-Fe.sub.16N.sub.2 (004) x-ray diffraction peak to an α″-α″-Fe.sub.16N.sub.2 (202) x-ray diffraction peak for the aligned iron nitride nanoparticles is greater than at least 7%, wherein the diffraction vector is parallel to alignment direction, and wherein the iron nitride nanoparticles exhibit a squareness measured parallel to the alignment direction that is greater than a squareness measured perpendicular to the alignment direction.

Disclosed herein is a permanent magnet comprising: a plurality of aligned iron nitride nanoparticles wherein the iron nitride nanoparticles include α″-Fe.sub.16N.sub.2 phase domains; wherein a ratio of integrated intensities of an α″-Fe.sub.16N.sub.2 (004) x-ray diffraction peak to an α″-α″-Fe.sub.16N.sub.2 (202) x-ray diffraction peak for the aligned iron nitride nanoparticles is greater than at least 7%, wherein the diffraction vector is parallel to alignment direction, and wherein the iron nitride nanoparticles exhibit a squareness measured parallel to the alignment direction that is greater than a squareness measured perpendicular to the alignment direction.

Example nanoparticles may include an iron-based core, and a shell. The shell may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example alloy compositions may include an iron-based grain, and a grain boundary. The grain boundary may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example techniques for forming iron-based core-shell nanoparticles may include depositing a shell on an iron-based core. The depositing may include immersing the iron-based core in a salt composition for a predetermined period of time. The depositing may include milling the iron-based core with a salt composition for a predetermined period of time. Example techniques for treating a composition comprising core-shell nanoparticles may include nitriding the composition.

An example composition may include a plurality of grains including an iron nitride phase. The plurality of grains may have an average grain size between about 10 nm and about 200 nm. An example technique may include treating a composition including a plurality of grains including an iron-based phase to adjust an average grain size of the plurality of grains to between about 20 nm and about 100 nm. The example technique may include nitriding the plurality of grains to form or grow an iron nitride phase.

Disclosed herein is a permanent magnet comprising: a plurality of aligned iron nitride nanoparticles wherein the iron nitride nanoparticles include α″-Fe.sub.16N.sub.2 phase domains; wherein a ratio of integrated intensities of an α″-Fe.sub.16N.sub.2 (004) x-ray diffraction peak to an α″-α″-Fe.sub.16N.sub.2 (202) x-ray diffraction peak for the aligned iron nitride nanoparticles is greater than at least 7%, wherein the diffraction vector is parallel to alignment direction, and wherein the iron nitride nanoparticles exhibit a squareness measured parallel to the alignment direction that is greater than a squareness measured perpendicular to the alignment direction.

Example nanoparticles may include an iron-based core, and a shell. The shell may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example alloy compositions may include an iron-based grain, and a grain boundary. The grain boundary may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example techniques for forming iron-based core-shell nanoparticles may include depositing a shell on an iron-based core. The depositing may include immersing the iron-based core in a salt composition for a predetermined period of time. The depositing may include milling the iron-based core with a salt composition for a predetermined period of time. Example techniques for treating a composition comprising core-shell nanoparticles may include nitriding the composition.

Provided is an ε-iron oxide type ferromagnetic powder with a ratio Hc.sub.173K/Hc.sub.296K between a coercive force Hc.sub.173K measured at a temperature of 173 K and a coercive force Hc.sub.296K measured at a temperature of 296 K is higher than 1.00 and less than 2.00, and a magnetic recording medium containing the ε-iron oxide type ferromagnetic powder in a magnetic layer.