JP6446817B2 - Manufacturing method of nanocomposite magnet - Google Patents

Description

The present invention relates to a method for producing a nanocomposite magnet and a hard magnetic phase and soft magnetic phases.

  Permanent magnets are widely used for electric motors, offshore wind power generators, industrial motors, and the like. In recent years, there has been an increasing demand for lightweight, long-time drive motors as drive sources for robots and remote control devices for business efficiency and disaster recovery. In response to such demand, permanent magnets are also required to be small and have excellent magnetic properties.

As a technique for improving the saturation magnetization and coercive force of a permanent magnet, a rare earth magnet containing iron or cobalt is proposed. Patent Document 1 describes a method for producing a rare earth magnet in which RTB rare earth magnet alloy fine powder and Fe _A Co _1-A alloy coarse powder or Fe _A Co _1-A -X alloy coarse powder are mixed and sintered. Disclosed.

  A nanocomposite magnet has a composite structure of a fine hard magnetic phase and a soft magnetic phase on the order of nanometers (nm), and is magnetic between a hard magnetic phase with a large coercive force and a soft magnetic phase with high saturation magnetization. A magnet having magnetic properties like a single-phase magnet by exchange interaction. A nanocomposite magnet is also referred to as an exchange spring magnet because it exhibits a magnetization behavior in which a hard magnetic phase and a soft magnetic phase are coupled by a magnetic spring.

In a nanocomposite magnet, the exchange interaction between the soft magnetic phase and the hard magnetic phase works by refining the hard magnetic phase and the soft magnetic phase to the order of nm. Therefore, in the nanocomposite magnet, the magnetization reversal of the soft magnetic phase is prevented by the magnetization of the hard magnetic phase even when a reversal magnetic field is applied. As a result, the nanocomposite magnet exhibits a magnetization curve that obtains a high saturation magnetization from the soft magnetic phase and a coercive force from the hard magnetic phase. That is, the nanocomposite magnet has a high energy product (BH) _max . From the viewpoint of improving exchange interaction, a nanocomposite magnet is proposed in which a core / shell structure is formed using a material having a small particle size.

Patent Document 2 discloses a nanocomposite magnet in which a core of NdFeB hard magnetic phase is coated with a shell of FeCo soft magnetic phase. The nanocomposite magnet contains 30 to 75 at% Fe in the NdFeB hard magnetic phase. Patent Document 3 discloses a nanocomposite magnet having a core-shell structure in which the core of an Nd ₂ Fe ₁₄ B compound has a Fe soft magnetic phase as a shell. According to Patent Document 3, it is confirmed that 10-20 nm spherical Fe nanoparticles are formed on Nd ₂ Fe ₁₄ B particles as the nanocomposite magnet.

  However, Fe takes various crystal structures in response to environmental changes. For this reason, the shell made of Fe may change its shape due to a temperature change or the like, and the core may not be coated with a homogeneous film. As a result, the magnetic properties of the magnet are adversely affected.

  Patent Document 4 discloses a nanocomposite magnet having a soft magnetic phase containing at least one soft magnetic material containing Fe, Co, or Ni, manufactured by a metallurgical method. Since the particles of the above soft magnetic material have a large average particle size, exchange interaction is unlikely to work between the hard magnetic phase and the soft magnetic phase. In that case, good magnetic properties cannot be obtained. Alternatively, only an aggregate of nanoparticles is formed on the core surface, and no core / shell structure is formed.

  Non-Patent Document 1 discloses a method for producing FeCo nanoparticles at a high temperature. However, in the nanocomposite magnet manufactured by the above method, the coercive force of the obtained NdFeB decreases at a high temperature.

Patent Document 5 discloses a rare earth quenching magnet manufactured by applying a predetermined quenching process. The metal structure of the above-mentioned rare earth quenched magnet is a mixture of a soft magnetic phase of iron or iron-based boride and a hard magnetic phase having an R ₂ Fe ₁₄ B type crystal structure, and the soft magnetic phase and the hard magnetic phase are exchanged. It is a nanocomposite structure that is magnetically coupled by interaction. The average crystal grain size of the soft magnetic phase and the hard magnetic phase are both 1 nm or more and 100 nm or less, and the average crystal grain size of the soft magnetic phase is preferably 30 nm or less. However, its magnetic properties are not specified.

Patent Document 6 discloses a nanocomposite magnet containing a hard magnetic phase and a soft magnetic phase magnetically coupled by exchange interaction. In this nanocomposite magnet, each constituent phase is coarsened by adding a sufficient amount of Ti in an alloy structure in which the content of rare earth element R is less than 10 at% and the structure ratio of boron or the like exceeds 15 at%. To form a nanocomposite structure with suppressed The average crystal grain size G _hard of the hard magnetic phase of the nanocomposite magnet, the mean grain size G _soft soft magnetic _{phase, 1nm ≦ G hard ≦ 200nm,} 1nm ≦ G soft ≦ 200nm, and 0.5 ≦ G _hard / Satisfies the relationship of G _soft ≦ 10. Such a nanocomposite magnet has a coercive force of 600 kA / m or more.

  Patent Document 7 discloses that at%, Y, one or more of the lanthanide elements, or 2 to 7% rare earth metal (R) and the balance Co, at least a hard magnetic rare earth compound phase and a soft magnetic cobalt phase. And a rare earth magnet material in which each of the two phases has a crystal grain size of 500 nm or less. The rare earth magnet material can further increase the residual magnetic flux density and the Curie temperature by replacing a part of Co in the alloy with Fe at a substitution rate of 30 at% or less in the alloy composition. According to Patent Document 7, a part of the Co is Ni, Ti, V, Cr, Mn, Cu, Ga, Zr, Nb, Mo, Sn, Hf, Ta, W, B, Al, Si, P. Substitution with a transition metal or the like is also effective for improving the magnetic properties.

Further, it is known that the alloy fine particles of platinum and transition metal are formed with a small particle size. As an example of the above knowledge, Patent Document 8 discloses a nanocomposite magnet composed of a hard magnetic phase having an average particle diameter of 10 to 200 nm and a soft magnetic phase having an average particle diameter of 1 to 100 nm. The hard magnetic phase is R ₂ T ₁₄ M (R is at least one of rare earth elements (including Y), M is Ti, Al, Si, V, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag , Hf, Ta, W, Pt, Au, Pb), and the soft magnetic phase is a compound of α-Fe or Fe and B or C.

Patent Document 9 includes an α-Fe phase having an average crystal grain size of 1 to 50 nm as a soft magnetic phase, and an R ₂ T ₁₄ M phase having an average crystal grain size of 5 to 100 nm as a hard magnetic phase (R is one or more types) Rare earth element, M is at least one selected from the group consisting of Al, Si, V, Mn, Cu, Zn, Ga, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb An iron-based rare earth nanocomposite magnet having a metal structure containing a metal element is disclosed.

Patent Document 10 discloses an R ₂ T ₁₄ M compound phase (R is at least one rare earth element selected from the group consisting of Nd, Pr, Dy and Tb, and at least selected from the group consisting of Nd and Pr. Containing at least one rare earth element, and M is selected from the group consisting of Al, Si, V, Mn, Cu, Zn, Ga, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb 2 or more ferromagnetic crystal phases including at least one metal), the average crystal grain size of the hard magnetic phase is 5 nm to 200 nm and the average crystal grain size of the soft magnetic phase is 1 nm to 50 nm. Disclosed is a nanocomposite magnet having a tissue in range.

  Patent Document 11 includes a general formula PtM (wherein M is ruthenium (Ru), gold (Au), silver (Ag), palladium (Pd), rhodium (Rh), osmium (Os), iridium (Ir) or A platinum cluster for an electrode using platinum-based particles represented by (which is an element selected from transition metals) is disclosed. Patent Document 12 discloses fine particles in which a Fe—Pt alloy phase is contained in a cubic Fe or cubic Fe—Co alloy phase in a volume ratio of 30 to 70%. However, a nanocomposite magnet having a structure in which a shell of a soft magnetic phase is formed using alloy fine particles of platinum and a transition metal and a core of a hard magnetic phase is coated has not been found.

JP 2003-217918 A JP 2010-74062 A JP 2008-117855 A Special Table 2008-505500 Japanese Unexamined Patent Publication No. 2005-64096 Japanese Patent Laid-Open No. 2003-158005 JP-A-6-333715 JP 2011-159733 A JP 2011-199230 JP 2003-221655 A JP 2010-129835 JP Japanese Patent No. 3360938

G. S. Chaubey, J. P. Liu et al., J. Am. Chem. Soc., 129, 7214 (2007)

  An object of the present invention is to improve the magnetic properties of a nanocomposite magnet. In particular, it is to provide a nanocomposite magnet having high saturation magnetization and high coercive force.

  The present invention is a method for producing a nanocomposite magnet, which is a soft magnetic phase containing alloy fine particles of platinum and a transition metal, and a shell made of a film covers all around the core of the hard magnetic phase, The hard magnetic magnet fine particles that form the core are dispersed in an organic solvent, and a platinum compound and a transition compound are added to the organic solvent together with a reducing agent to form the alloy fine particles on the surface of the hard magnetic magnet fine particles. The alloy fine particles are self-assembled to uniformly coat the entire fine particles of the hard magnetic magnet, thereby forming the shell to generate fine particles having a nanocomposite structure. The fine particles with the structure are sintered at a sintering temperature of 280 ° C. or higher and 800 ° C. or lower in a vacuum or an inert gas atmosphere. Lower, heat-treated at a heat treatment temperature 280 ° C. or higher 800 ° C. or less, the fine particles of the nanocomposite structure after the heat treatment by magnetizing treatment to obtain the nanocomposite magnet, a method for producing a nanocomposite magnet.

An exchange interaction between the soft magnetic phase and the hard magnetic phase can provide a nanocomposite magnet having high saturation magnetization and high coercivity .

It is the schematic which shows an example of the crystal structure of this invention.

[Nanocomposite magnet]
The present invention is a nanocomposite magnet in which a core of a hard magnetic phase is coated with a shell of a soft magnetic phase containing fine alloy particles of platinum and a transition metal. FIG. 1 is a schematic view showing an example of the crystal structure of the present invention. 1 is a core, 2 is a shell.

  In the soft magnetic phase shell constituting the present invention, 95 mass% or more of the total components are alloy fine particles of platinum and a transition metal. The alloy fine particles containing platinum are stable at a predetermined small particle size. Therefore, in the present invention, a good exchange interaction stably works between the soft magnetic phase shell using the alloy fine particles and the hard magnetic phase core. Thereby, saturation magnetization and coercive force can be improved. In addition, its magnetic characteristics are stable. The saturation magnetization of the present invention is at least greater than 40 emu / g. The coercive force is 8 kOe or more and 12 kOe or less.

  The transition metal contained in the alloy fine particles can be selected from those which are solid-solved with eutectic or are eutectic. Preferably, at least one selected from the group consisting of chromium, cobalt, manganese, iron, and nickel is used, and cobalt and iron are more preferable. One or more of the above transition metals can be contained. The shell may contain a small amount of impurities that do not impair the effects of the present invention.

  The platinum content contained in the alloy fine particles used in the present invention may be within the range of the platinum content contained in the conventionally known platinum alloy fine particles.

As a detailed example,
Fig.1 shows the Fe-Pt phase diagram. According to the Fe-Pt phase diagram above, Fe-Pt
The platinum content in the alloy fine particles is preferably 20 at% or more and 85 at% or less.

  An example is the Mn-Pt phase diagram disclosed in Fig. 1 of Journal of Phase Equilibria, December 2003, Volume 24, Issue 6, p 582 Mn-Pt (Manganese-Platinum), H. Okamoto, J. F. Smith. According to the above Mn—Pt phase diagram, the platinum content in the Mn—Pt alloy fine particles is preferably 20 at% or more and 80 at% or less.

As another example,
Fig.1 shows the Cr-Pt phase diagram. According to the above Cr—Pt phase diagram, the content of platinum in the Cr—Pt alloy fine particles is preferably 20 at% or more and 80 at% or less.

As yet another example,
The Co-Pt phase diagram disclosed in Fig. 1 is given. According to the above Co-Pt phase diagram, the content of platinum in the Co-Pt alloy fine particles is preferably 20 at% or more and 75 at% or less.

  In addition, as another example, Bulletin of Alloy Phase Diagrams, June 1989, Volume 10, Issue 3, pp 258-262 The Ni-Pt (Nickel-Platinum) system, P. Nash, MF Singleton Fig. 1 Ni-Pt phase diagram. According to the above Ni-Pt phase diagram, the platinum content is preferably 40 at% or more and 70 at% or less.

  The platinum content in the alloy fine particles of the present invention derived from the above example is preferably 20 at% or more and 85 at% or less. Within the above preferable range, it is preferable to appropriately adjust the platinum content in accordance with the type of transition metal used. For example, when Fe is used as the transition metal, the platinum content is preferably 20 at% or more and 85 at% or less. When Mn is used, it is preferably 20 at% or more and 80 at% or less. When Cr is used, it is preferably 20 at% or more and 80 at% or less. When Co is used, it is preferably 20 at% or more and 75 at% or less. When Ni is used, it is preferably 40 at% or more and 70 at% or less. By containing platinum with the above content, stable alloy fine particles are obtained. By using such alloy fine particles, the present invention can suppress the occurrence of cracks in the shell of the soft magnetic phase. Moreover, the predetermined saturation magnetization and coercive force of the present invention can be obtained by a good mutual exchange action. When the platinum content is outside the above preferred range, the state of the alloy fine particles becomes unstable, and good magnetic properties cannot be obtained.

The alloy fine particles of platinum and transition metal are fine particles having a stable crystal structure, and the particle size in the crystal growth process is about 1 nm to 1000 nm as the median diameter D ₅₀ in the cumulative distribution of the alloy fine particles on a volume basis. Can be crystallized. D ₅₀ can be measured using a particle size distribution measuring apparatus by laser diffraction scattering method. Patent Document 9 discloses an α-Fe phase having an average crystal grain size of 1 nm to 50 nm as a general example of the particle diameter of fine particles of a soft magnetic phase.

D ₅₀ of the alloy fine particles of the present invention derived from the above findings is 1 nm or more and 1000 nm or less, preferably 1 nm or more and 100 nm or less, more preferably 1 nm or more and 50 nm or less. When the D ₅₀ of the alloy fine particles of platinum and transition metal is less than 1 nm, it is difficult to sufficiently improve the saturation magnetization. When it exceeds 1000 nm, it becomes difficult to coat the core of the hard magnetic phase with a shell having a uniform film thickness.

  By using alloy fine particles having the above preferable particle diameter, the present invention coats the surface of the core with a shell having an average film thickness of preferably 50 nm or more and 200 nm or less. In the present invention, since the core is coated with the above-described thin shell, the distance between the cores existing through the shell can be reduced, and an effective mutual coupling action can be exerted between the hard magnetic phases. Thereby, the saturation magnetization of the nanocomposite magnet can be improved.

  The alloy fine particles of platinum and transition metal have an extremely stable crystal structure and are not easily affected by changes in conditions such as temperature, acid, alkali and other pH resistance. Therefore, the present invention stably expresses high saturation magnetization.

  A known hard magnetic material can be used for the core of the present invention without limitation. Examples of known hard magnetic materials include AlNiCo magnets, ferrite magnets, samarium cobalt magnets, neodymium iron boron magnets, and samarium iron nitrogen magnets. Preferably, a samarium cobalt magnet or a neodymium iron boron magnet is used.

The particle diameter of the hard magnetic material of the core that is part 1 in FIG. 1 is 1 nm or more and 1000 nm or less, preferably 50 nm or more and 800 nm or less, as a median diameter D ₅₀ in the cumulative distribution of the hard magnetic material group on a volume basis. More preferably, it is 200 nm or more and 500 nm or less, and more preferably 5 nm or more and 100 nm or less.

  By covering the core of the hard magnetic phase formed of the hard magnetic material having such a particle size with the predetermined shell, the present invention has a saturation magnetization as compared with a permanent magnet including a shell made of iron. Can be improved by about 10 to 20%.

The particle diameter of the nanocomposite magnet of the present invention in which the core of the hard magnetic phase using the hard magnetic material is coated with the shell of the soft magnetic phase containing the soft magnetic alloy fine particles having the above preferable particle diameter, that is, the core The particle size of both the hard magnetic material and the soft magnetic alloy fine particles as the shell is preferably a median diameter D ₅₀ in the cumulative distribution of the particle group on a volume basis, preferably 2 nm or more and 2000 nm or less, more preferably 5 nm or more. 1500 nm or less, more preferably 10 nm or more and 1000 nm or less. The D ₅₀ of the particles obtained by coating the core of the hard magnetic phase with the shell of the predetermined soft magnetic phase of the present invention can be measured using a particle size distribution measuring apparatus by a laser diffraction scattering method.

[Manufacturing method of nanocomposite magnet]
Although the manufacturing method of the nanocomposite magnet of this invention is not specifically limited, Usually, a micronization process, a formation process, a sintering process, and a heat treatment process are included. In the heat treatment step, the nanocomposite structure fine particles obtained in the fine particle formation step are sintered at a predetermined sintering temperature in a vacuum or an inert gas atmosphere, and the sintered body of the nanocomposite structure fine particles is vacuum or Heat treatment is preferably performed at a predetermined heat treatment temperature in an inert gas atmosphere. The heat treatment step described above can prevent the nanocomposite structured fine particles from being oxidized, and contributes to the improvement of the saturation magnetization of the resulting nanocomposite magnet.

[Micronization process]
In the fine particle forming step, nanocomposite structured fine particles are produced in which the core of the hard magnetic phase is coated with the shell of the soft magnetic phase containing the predetermined platinum alloy fine particles of the present invention. The core can be manufactured by the following method. A predetermined raw material component is arc-melted to obtain a hard magnetic material. The hard magnetic material is pulverized into fine particles.

  As the pulverizing means, a ball mill, a bead mill or the like can be used, and it is preferable to select a means capable of forming particles having a smooth fine particle surface and a nearly spherical shape. Hard magnetic fine particles having a shape close to a spherical shape can increase the sintering density of particles in a sintering process performed by filling particles into cavities. Moreover, it becomes easy to make the film thickness of the soft magnetic phase uniform. As a result, the present invention provides a nanocomposite magnet with less anisotropy and equivalent exchange interaction in any region of the nanocomposite structured fine particles.

  The hard magnetic fine particles are pulverized until the particle diameter is 1 nm to 1000 nm, preferably 50 nm to 800 nm, more preferably 200 nm to 500 nm, and further preferably 5 nm to 100 nm. The obtained hard magnetic fine particles become the core of the hard magnetic phase of the present invention.

  In order to coat the platinum alloy fine particles on the hard magnetic fine particles, first, the hard magnetic fine particles are added to an organic solvent and stirred until homogeneously dispersed. As the organic solvent, ethanol, hexane, tetrahydrofuran, N-methylpyrrolidone, diphenyl ether, ethylbenzene and the like can be used. Anhydrous ethanol, anhydrous hexane, anhydrous tetrahydrofuran and the like are more preferable because they are highly volatile and have a low water concentration and dissolved oxygen concentration.

After adding the reducing agent to the hard magnetic fine particle dispersion, the raw material component of the platinum-containing alloy that becomes the soft magnetic phase is added. Examples of the platinum source include PtCl ₂ , Pt (OH) ₂ , PtSO ₄ , Pt (acac) _{3 and the} like. Transition metal sources include iron acetylacetonate, iron compounds such as Fe (Co) ₅ , FeCl ₃ , FeSO ₄ , CoCl ₂ , Co (OH) ₃ , CoSO ₄ , Co (NO ₃ ) ₂ , Co (acac) Cobalt compounds such as ₃ are preferred.

  One or more of each of the platinum source and the transition metal source can be added. In the production method, the additive amount ratio and the composition ratio of the soft magnetic alloy fine particles are almost the same. Therefore, the alloy fine particles according to the present invention can be formed by adjusting the addition amount of each raw material component within the range of the addition ratio.

It is preferable to add a reducing agent before the addition of the platinum compound or the transition metal compound. This improves the reactivity of the system and makes it possible to produce alloy fine particles of platinum and a transition metal at room temperature. Therefore, it is possible to avoid a reduction in saturation magnetization of the hard magnetic fine particles due to a high temperature condition. Examples of reducing agents include sodium borohydride (NaBH ₄ ), lithium borohydride, sodium cyanotrihydroborate, lithium aluminum hydride, tetrabutylammonium boron hydrate, diborane, diisobutylaluminum hydride, tributyltin hydride, etc. Can be mentioned. The addition amount of the reducing agent is preferably at least 1.5 times in molar ratio with respect to the addition amount of the transition metal compound.

  By sufficiently stirring the hard magnetic fine particle dispersion solution to which the above platinum compound, transition metal compound, and reducing agent are added, platinum and transition metal are precipitated on the surface of the hard magnetic fine particles. The precipitated platinum and transition metal form alloy fine particles on the surface of the magnetic fine particles. The alloy fine particles uniformly coat the entire hard magnetic fine particles by self-organization. Thereby, nanocomposite structured fine particles in which hard magnetic fine particles are coated with alloy fine particles of platinum and a transition metal can be produced.

[Molding process]
The obtained nanocomposite structured fine particles are filled into a cavity of a rectangular shape, a cylindrical shape or the like and molded in a magnetic field according to a conventional method. The molding magnetic field is preferably 15 kOe, and the molding pressure is preferably 10 MPa or more and 30 MPa or less.

[Sintering process and heat treatment process]
After the molding step is completed, the obtained molded body is sintered, and after rapid cooling, further heat-treated. The sintering process and the heat treatment process are performed in a vacuum or an inert gas atmosphere. For example, it is preferable that the oxygen concentration is 1 ppm or less and the water concentration is 1 ppm or less in the glove box. Thereby, the oxidation of the nanocomposite fine particles can be prevented, and the magnetic properties of the resulting nanocomposite magnet can be improved. Examples of the inert gas include helium, nitrogen, and argon.

  As specific sintering conditions for the sintering step, the sintering temperature is preferably 280 ° C. or higher and 800 ° C. or lower, and more preferably 300 ° C. or higher and 550 ° C. or lower. The pressure condition during sintering is preferably 10 MPa or more and 30 MPa or less. The sintering time is preferably 1 hour or more and 10 hours or less. The obtained sintered body is rapidly cooled to room temperature and then heat-treated in a vacuum or an inert gas atmosphere. The heat treatment temperature in the heat treatment step is preferably from 280 ° C. to 800 ° C., more preferably from 300 ° C. to 550 ° C. The heat treatment time is preferably 60 minutes or more and 120 minutes or less. Then cool to room temperature. By adjusting the sintering temperature and the heat treatment temperature within the above-mentioned preferable ranges, both the soft magnetic phase shell and the hard magnetic phase core of the nanocomposite structured fine particles can be uniformly crystallized.

  After the sintering step and the heat treatment step, the nanocomposite magnet of the present invention can be obtained by performing a magnetizing treatment according to a conventional method. In the nanocomposite magnet of the present invention, the soft magnetic phase and the hard magnetic phase containing fine alloy fine particles using platinum are both uniformly crystallized, and the surface of the hard magnetic fine particles is formed by a shell of alloy fine particles that is self-organized. Exposure is suppressed and equivalent exchange interaction works on the whole nanocomposite magnet. As a result, uniform magnetic properties are expressed in the entire magnet.

  The present invention is homogeneous and highly saturated. Therefore, it contributes to miniaturization of the nanocomposite magnet. As a result, it is possible to reduce the size and weight of a motor using a nanocomposite magnet as a drive source. The present invention is suitable as a drive source for robots and remote control devices whose demand is increasing in disaster areas.

  The following examples further illustrate the present invention. However, the present invention is not limited to the following examples.

[Example 1]
Nd ₂ Fe ₁₄ B particles produced in a single roll furnace are pulverized in a glove box maintained at an oxygen concentration of 1 ppm and a moisture concentration of 1 ppm using a mortar, ball mill, or bead mill to form fine particles.

Add Nd ₂ Fe ₁₄ B fine particles to absolute ethanol and stir until homogeneously dispersed. After NaBH ₄ is added, CoCl ₂ and PtCl ₂ are further added so that the Pt content in the total mass of the nanocomposite magnet of the present invention is 35% by mass, and stirring is continued. When the CoPt alloy is deposited on the entire surface of the Nd ₂ Fe ₁₄ B fine particles, stirring is terminated and the Nd ₂ Fe ₁₄ B fine particles coated with the CoPt alloy are recovered.

  The collected fine particles are filled into a rectangular cavity and molded with a molding magnetic field of 15 kOe and a molding pressure of 20 MPa. The obtained molded body is sintered at a sintering temperature of 300 ° C. under vacuum. The obtained sintered body is heat-treated in an argon atmosphere at a heat treatment temperature of 300 ° C. and a heat treatment time of 90 minutes, and then rapidly cooled to room temperature. Thereafter, a magnetizing process is performed, and the nanocomposite magnet of Example 1 can be manufactured.

[Example 2]
The nanocomposite magnet of Example 2 can be obtained in the same manner as in Example 1 except that FeCl ₃ is added instead of CoCl ₂ .

[Comparative example]
In place of CoCl ₂ and PtCl ₂ , FeCl ₃ is added as an Fe source, and the other magnets are obtained in the same manner as in Example 1 to obtain a comparative magnet.

  “Helmut Kronmueller and Stuart Parkin, Handbook of Magnetism and Advanced Magnetic Materials, John Wiley and Sons, 2013” describes saturation magnetization of a comparative example. Based on the value of this saturation magnetization (as “1” in Table 1), the saturation magnetization of Examples 1 and 2 was determined according to “Markus E. Gruner, George Rollmann, Peter Enetel, and Michael Farle,“ Multiply Twinned Morphologies of FePt. and CoPt Nanoparticles ”, Physical Review Letters, 100 (2008) 087203”. Table 1 shows the magnetic characteristics of Examples 1 and 2 and the comparative example. Compared to the comparative example, the saturation magnetization of Example 1 and Example 2 is improved by about 10 to 16%.

1 core
2 shell

Claims (4)

A soft magnetic phase containing alloy fine particles of platinum and a transition metal, shell of film, a method for producing a nanocomposite magnet coated around all of the core of the hard magnetic phase,
Disperse the fine particles of the hard magnetic magnet that becomes the core in an organic solvent,
A platinum compound and a transition compound are added to the organic solvent together with a reducing agent to form the alloy fine particles on the surface of the fine particles of the hard magnetic magnet, and the alloy fine particles are self-organized to form the hard magnetic material. The shell is formed by uniformly covering the entire magnet fine particles to produce nanocomposite fine particles,
The produced nanocomposite structure fine particles are sintered at a sintering temperature of 280 ° C. or higher and 800 ° C. or lower in a vacuum or an inert gas atmosphere.
The sintered nanocomposite structure fine particles are heat-treated at a heat treatment temperature of 280 ° C. or higher and 800 ° C. or lower in a vacuum or an inert gas atmosphere,
The nanocomposite fine particles after the heat treatment are magnetized to obtain the nanocomposite magnet.
A method for producing a nanocomposite magnet.   The method for producing a nanocomposite magnet according to claim 1, wherein the content of platinum in the alloy fine particles is 20 at% or more and 85 at% or less. The method for producing a nanocomposite magnet according to claim 1 or 2, wherein the transition metal is selected from the group consisting of chromium, cobalt, manganese, iron and nickel. The method for producing a nanocomposite magnet according to any one of claims 1 to 3, wherein the particle diameter of the alloy fine particles is 1 nm or more and 1000 nm or less as D50.