MAGNETIC MATERIAL LOADED WITH MAGNETIC ALLOY PARTICLES AND METHOD FOR PRODUCING SAID MAGNETIC MATERIAL

Abstract

The present invention relates to a magnetic material containing a magnetic alloy particle having an ordered crystal structure. The magnetic material according to the present invention is the one composed of a magnetic alloy particle having crystal magnetic anisotropy and being composed of an FePt alloy, a CoPt alloy, an FePd alloy, a Co.sub.3Pt alloy, an Fe.sub.3Pt alloy, a CoPt.sub.3 alloy, an FePt.sub.3 alloy, or the like, and a silica carrier covering the magnetic alloy, in which the silica carrier contains an alkali-earth metal compound such as an oxide, hydroxide or silicate compound of Ba, Ca, or Sr. The magnetic material according to the present invention is excellent in magnetic properties such as coercive force.

Claims

1. A magnetic material comprising a magnetic alloy particle having crystal magnetic anisotropy and a silica carrier covering the magnetic alloy particle, wherein the silica carrier contains an alkali-earth metal compound.

2. The magnetic material according to claim 1, wherein the alkali-earth metal compound comprises at least any of oxide, hydroxide and silicic acid compounds of Ba, Ca, and Sr.

3. The magnetic material according to claim 1, wherein a ratio of a total molar number of alkali-earth metals and a total molar number of metals constituting the magnetic alloy particle (alkali-earth metal/magnetic alloy particle) is not less than 0.001 and not more than 0.8.

4. The magnetic material according to claim 1, wherein the magnetic alloy particle comprises any of an FePt alloy, a CoPt alloy, an FePd alloy, a Co.sub.3Pt alloy, an Fe.sub.3Pt alloy, a CoPt.sub.3 alloy, and an FePt.sub.3 alloy.

5. The magnetic material according to claim 1, wherein the magnetic alloy particle has a particle diameter of not less than 1 nm and not more than 100 nm.

6. A method for manufacturing a magnetic material, the magnetic material being defined in claim 1, comprising the steps of: generating a composite metal hydroxide particle in a water phase of a mixed liquid by mixing a raw material micellar solution in which a water phase that contains two or more kinds of metal compounds and is bonded with a surfactant is dispersed in an oil phase, and a neutralizing agent micellar solution in which a water phase that contains a neutralizing agent and is bonded with a surfactant is dispersed in an oil phase; forming a core/shell particle composed of the composite metal hydroxide particle/silica by covering the composite metal hydroxide particle with silica by adding a silicon compound to the mixed liquid; and generating directly a magnetic alloy particle by reducing the composite metal hydroxide particle and ordering a crystal structure by subjecting the core/shell particle composed of composite metal hydroxide particle/silica as a precursor to a calcination heat treatment, wherein the raw material micellar solution contains an alkali-earth metal salt in the water phase of the solution.

7. The method for manufacturing a magnetic material according to claim 6, wherein the metal compounds in the raw material micellar solution are two or more kinds of metal compounds for forming an FePt alloy, a CoPt alloy, an FePd alloy, a Co.sub.3Pt alloy, an Fe.sub.3Pt alloy, a CoPt.sub.3 alloy or an FePt.sub.3 alloy, and the metal compounds are two or more kinds of metal compounds selected from iron nitrate, iron sulfate, iron chloride, iron acetate, iron ammine complex, iron ethylenediamine complex, iron ethylenediamine tetraacetate, tris(acetylacetonato)iron, iron lactate, iron oxalate, iron citrate, ferrocene and ferrocene aldehyde, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt ammine complex, cobalt ethylenediamine complex, cobalt ethylenediamine tetraacetate, cobalt acetylacetonate complex, chloroplatinic acid, platinum acetate, platinum nitrate, platinum ethylenediamine complex, platinum triphenylphosphine complex, platinum ammine complex and platinum acetylacetonate complex, palladium acetate, palladium nitrate, palladium sulfate, palladium chloride, palladium triphenylphosphine complex, palladium ammine complex, palladium ethylenediamine complex and palladium acetylacetonate complex.

8. The method for manufacturing a magnetic material according to claim 6, wherein the neutralizing agent in the neutralizing agent micellar solution is at least any of ammonia, sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide.

9. The method for manufacturing a magnetic material according to claim 6, wherein the surfactant in the raw material micellar solution and the neutralizing agent micellar solution is at least any of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, potassium oleate, sodium oleate, cetylpyridinum chloride, benzalkonium chloride, cetyldimethylethylammonium bromide, sodium di-2-ethylhexyl sulfosuccinate, sodium cholate, sodium caprylate, sodium stearate, sodium lauryl sulfate, polyoxyethylene ester, polyoxyethylene ether, polyoxyethylene sorbitan ester, sorbitan ester, polyoxyethylene nonylphenyl ether and N-alkyl-N,N-dimethylammonio-1-propanesulfonic acid.

10. The method for manufacturing a magnetic material according to claim 6, wherein the silicon compound is at least any of tetraalkoxysilane, mercaptoalkyltrialkoxysilane, aminoalkyltrialkoxysilane, 3-thiocyanatopropyltriethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]propyltriethoxysilane.

11. The method for manufacturing a magnetic material according to claim 6, wherein the calcination heat treatment of the core/shell particle composed of composite metal hydroxide particle/silica is a heat treatment performed at not less than 300 C. and not more than 1300 C. in a reducing atmosphere.

12. A method for manufacturing a magnetic alloy particle having crystal magnetic anisotropy, wherein the method removes a silica covering by etching, with an alkaline solution, a magnetic material manufactured by a method being defined in any of claims 6 to 11.

13. The method for manufacturing a magnetic alloy particle according to claim 12, wherein the alkaline solution is at least any of a sodium hydroxide aqueous solution, a tetramethylammonium hydroxide aqueous solution and a potassium hydroxide ethanol solution.

14. The magnetic material according to claim 2, wherein a ratio of a total molar number of alkali-earth metals and a total molar number of metals constituting the magnetic alloy particle (alkali-earth metal/magnetic alloy particle) is not less than 0.001 and not more than 0.8.

15. The magnetic material according to claim 2, wherein the magnetic alloy particle comprises any of an FePt alloy, a CoPt alloy, an FePd alloy, a Co.sub.3Pt alloy, an Fe.sub.3Pt alloy, a CoPt.sub.3 alloy, and an FePt.sub.3 alloy.

16. The magnetic material according to claim 2, wherein the magnetic alloy particle has a particle diameter of not less than 1 nm and not more than 100 nm.

17. A method for manufacturing a magnetic material, the magnetic material being defined in claim 2, comprising the steps of: generating a composite metal hydroxide particle in a water phase of a mixed liquid by mixing a raw material micellar solution in which a water phase that contains two or more kinds of metal compounds and is bonded with a surfactant is dispersed in an oil phase, and a neutralizing agent micellar solution in which a water phase that contains a neutralizing agent and is bonded with a surfactant is dispersed in an oil phase; forming a core/shell particle composed of the composite metal hydroxide particle/silica by covering the composite metal hydroxide particle with silica by adding a silicon compound to the mixed liquid; and generating directly a magnetic alloy particle by reducing the composite metal hydroxide particle and ordering a crystal structure by subjecting the core/shell particle composed of composite metal hydroxide particle/silica as a precursor to a calcination heat treatment, wherein the raw material micellar solution contains an alkali-earth metal salt in the water phase of the solution.

18. The method for manufacturing a magnetic material according to claim 17, wherein the metal compounds in the raw material micellar solution are two or more kinds of metal compounds for forming an FePt alloy, a CoPt alloy, an FePd alloy, a Co.sub.3Pt alloy, an Fe.sub.3Pt alloy, a CoPt.sub.3 alloy or an FePt.sub.3 alloy, and the metal compounds are two or more kinds of metal compounds selected from iron nitrate, iron sulfate, iron chloride, iron acetate, iron ammine complex, iron ethylenediamine complex, iron ethylenediamine tetraacetate, tris(acetylacetonato)iron, iron lactate, iron oxalate, iron citrate, ferrocene and ferrocene aldehyde, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt ammine complex, cobalt ethylenediamine complex, cobalt ethylenediamine tetraacetate, cobalt acetylacetonate complex, chloroplatinic acid, platinum acetate, platinum nitrate, platinum ethylenediamine complex, platinum triphenylphosphine complex, platinum ammine complex and platinum acetylacetonate complex, palladium acetate, palladium nitrate, palladium sulfate, palladium chloride, palladium triphenylphosphine complex, palladium ammine complex, palladium ethylenediamine complex and palladium acetylacetonate complex.

19. The method for manufacturing a magnetic material according to claim 18, wherein the neutralizing agent in the neutralizing agent micellar solution is at least any of ammonia, sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide.

20. The method for manufacturing a magnetic material according claim 19, wherein the surfactant in the raw material micellar solution and the neutralizing agent micellar solution is at least any of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, potassium oleate, sodium oleate, cetylpyridinum chloride, benzalkonium chloride, cetyldimethylethylammonium bromide, sodium di-2-ethylhexyl sulfosuccinate, sodium cholate, sodium caprylate, sodium stearate, sodium lauryl sulfate, polyoxyethylene ester, polyoxyethylene ether, polyoxyethylene sorbitan ester, sorbitan ester, polyoxyethylene nonylphenyl ether and N-alkyl-N,N-dimethylammonio-1-propanesulfonic acid.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1 illustrates structures that the magnetic alloy according to the present invention can form (L1.sub.0 structure, DO.sub.19 structure, Pmm2 structure, and L1.sub.2 structure).

[0043] FIG. 2 illustrates a method for manufacturing a magnetic material according to the present invention.

[0044] FIG. 3 illustrates an XRD pattern of a magnetic material in Example 1 of a first embodiment.

[0045] FIG. 4 shows a TEM image of the magnetic material in Example 1 of the first embodiment.

[0046] FIG. 5 illustrates an XRD pattern of a magnetic material in Example 2 of a second embodiment.

[0047] FIG. 6 shows a TEM image of the magnetic material in Example 2 of the second embodiment.

[0048] FIG. 7 illustrates an XRD pattern of a magnetic material in Example 3 of a third embodiment,

[0049] FIG. 8 shows a TEM image of the magnetic material in Example 3 of the third embodiment,

[0050] FIG. 9 illustrates a magnetic hysteresis curve of the magnetic material in Example 3 of the third embodiment.

[0051] FIG. 10 illustrates an XRD pattern of a magnetic material in Example 4 of a fourth embodiment.

[0052] FIG. 11 shows a TEM image of the magnetic material in Example 4 of the fourth embodiment.

DESCRIPTION OF EMBODIMENTS

[0053] Hereinafter, embodiments of the present invention will be described. In the present embodiments, there was manufactured a magnetic material containing an FePt alloy particle (first embodiment) and a CoPt alloy particle (second embodiment) as magnetic alloy particles, according to the above-described manufacturing process.

First Embodiment (Formation of FePt Alloy Particle)

[0054] (a) Production of Raw Material Micellar Solution

[0055] Iron nitrate (Fe(NO.sub.3).sub.3.9H.sub.2O) and chloroplatinic acid (H.sub.2[PtCl.sub.6].xH.sub.2O) were added to 6 mL of pure water, so as to be 0.12 M in the total of Fe and Pt. Further, 18.82 mg of barium nitrate (Ba(NO.sub.3).sub.2) (Ba: 0.012 M) was added. A charged amount of barium being an alkali-earth metal is 0.1 in molar ratio relative to the metals (Fe+Pt). 18.3 mL of octane and 3.6 mL of butanol were added to the aqueous solution as organic solvents to be an oil phase, and 3.52 g of CTAB was added as a surfactant. The solution was stirred for 30 minutes until it became uniform, and a raw material micellar solution was produced. Above operations are performed at room temperature. Meanwhile, plural raw material micellar solutions were produced so that the ratio of Fe and Pt (Fe:Pt) became 5:5 (Example 1), 10:0 (Reference Example 1), 9:1 (Reference Example 2), or 0:10 (Reference Example 3). Further, as Comparative Example 1, a raw material micellar solution with no addition of Ba was also produced (Fe:Pt is 5:5).

[0056] (b) Production of Neutralizing Agent Micellar Solution

[0057] 2.26 mL of ammonia (25%-NH.sub.3 aqueous solution) was added to 3.74 mL of pure water as a neutralizing agent. 18.3 mL of octane and 3.6 mL of butanol were added to the solution, and, further, 3.52 g of CTAB was added. The solution was stirred for 30 minutes until it became uniform, and a neutralizing agent micellar solution was produced.

[0058] (c) Generation of Composite Metal Hydroxide

[0059] The neutralizing agent micellar solution was dropped at 1 drop/sec into the produced raw material micellar solution. The neutralizing agent micellar solution was added with stirring of the mixed solution, and was stirred for additional 30 minutes after completion of the addition.

[0060] (d) Silica Covering to Composite Metal Hydroxide

[0061] 1.5 mL of TEOS was added dropwise at 2 drops/sec into the mixed solution produced as described above. At this time, the addition amount of Si becomes 9.4 in mol ratio relative to the amount of metals (Fe+Pt) in the raw material micellar solution. After completion of the addition, the mixed solution was reacted over 20 hours with stirring. Hereby, silica was deposited onto the surface of a hydroxide particle to cover the particle, and precipitate was generated. Then, the solution was centrifuged (3500 rpm, for 5 minutes) and the solid content was collected, which was washed with mixed liquid of methanol and chloroform and centrifuged, and, further, was washed with methanol and centrifuged. The obtained solid content was dried (air dried and then vacuum dried), and there were obtained core/shell particles of composite hydroxide particle/silica to be a precursor of a magnetic material.

[0062] (e) Calcination Heat Treatment (Alloy Generation and Ordering)

[0063] The precursor was subjected to a calcination heat treatment in which heating was performed at 980 C. for 4 hours in a hydrogen atmosphere.

[0064] The magnetic material manufactured according to the above process was first subjected to X-ray diffraction (XRD), and a generated phase in the magnetic material was identified. Further, elemental analysis was performed using an inductively-coupled plasma mass spectrometer (ICP-MS) and X-ray fluorescence analysis (XRF). FIG. 3 shows the result of XRD of the magnetic material in Example 1, and FIG. 4 illustrates a TEM image of the magnetic material in Example 1. Further, magnetic properties were evaluated for respective magnetic materials. As to magnetic properties, a magnetic hysteresis curve was measured (temperature 300 K) with a superconducting quantum interference device (SQUID), and coercive force, residual magnetization and saturation magnetization of the magnetic material were measured. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Magnetic properties*.sup.2 Charged molar Coercive Residual Saturation ratio Generated force/ magnetization/ magnetization/ Fe Pt Ba Si phase*.sup.1 kOe emug.sup.1 emug.sup.1 Example 1 5 5 1 94 FePt(fct), 10 4 9 Pt.sub.2Si, -Fe, -Fe, BaO Comparative 5 5 0 94 FePt(fct), 0.2 0.9 8 example 1 -Fe Reference 10 0 1 94 Fe, BaO 0.2 0.7 19 example 1 Reference 9 1 1 94 -Fe, -Fe, 0.3 0.6 10 example 2 BaO Reference 0 10 1 94 Pt.sub.2Si, *.sup.3 *.sup.3 *.sup.3 example 3 Pt.sub.12Si.sub.5, Pt *.sup.1Silica phase (SiO.sub.2) is not described *.sup.2Measured value including silica (SiO.sub.2) being carrier *.sup.3Diamagnetic and unmeasurable

[0065] It is known from Table 1 that the magnetic material in Example 1, in which generation/ordering of an alloy was intended with the addition of an alkali-earth metal (Ba), has high coercive force and is favorable also in residual magnetization and saturation magnetization. In Comparative Example 1 with no addition of Ba, saturation magnetization is comparatively high, but coercive force is low. It is considered that, in the Comparative Example, generation of an FePt alloy of an fct structure was estimated in a part from the result of XRD, but that ordering was insufficient.

[0066] As the result of elemental analysis for Example 1 using ICP-MS and XRF, it was identified that the composition ratio of the whole including impurities was Fe:Pt=61:39. Further, when the composition ratio was corrected by refining of an XRD pattern in Rietveld refinement and addition of weight ratio of the FePt alloy particle and the impurity, it was calculated that the composition ratio of both metals in the FePt alloy particle was Fe:Pt=54:46. In contrast, the composition ratio of both metals in a sample in Comparative Example 1 was identified as Fe:Pt=75:25 from the result of elemental analysis, and, as the result of correcting this composition ratio by adding a weight ratio of impurities, it was calculated as Fe:Pt=69:31. From this result, consequently, it was confirmed that preferable FePt alloys had the composition ratio of Fe, Pt of nearly 50:50.

[0067] Further, in the magnetic material manufactured in Example 1, (Ba/(Fe+Pt)) was 0.10, which was the ratio of the molar number of the alkali-earth metal (Ba) and the total molar number of metals (Fe+Pt) constituting the magnetic alloy particle, obtained from the result of the elemental analysis. Further, (Si/(Fe+Pt)) was 6.1, which was the ratio of the molar number of Si contained in the silica carrier and the total molar number of metals (Fe+Pt) constituting the magnetic alloy particle, in Example 1.

[0068] In each of Example 1 and Comparative Example 1, the ratio of Fe, Pt in manufacturing was set to 1:1 (50:50), but the composition ratios of Fe, Pt of formed alloy particles were different. It is considered that the difference is caused by the presence/absence of the addition of the alkali-earth metal in the manufacturing process. However, in Reference Examples 1 to 3, alloy manufacturing is performed at a charge ratio that is predicted to deviate clearly from a suitable composition ratio, and, therefore, sufficient magnetic properties cannot be exerted even if an alkali-earth metal is added.

[0069] Next, for the magnetic material in Example 1, the silica carrier was removed and the magnetic alloy particles were collected, and magnetic properties were evaluated. The removal of the silica carrier was performed by an immersion treatment in a sodium hydroxide aqueous solution of 5 M in concentration at 75 C. in temperature for 24 hours. For obtained FePt alloy particles, XRD measurement was performed, purity was analyzed and coercive force was measured with a SQUID magnetometer.

[0070] FePt alloy particles having high purity of 98.0% by mass was collected by the silica removal by etching. Magnetic properties of the FePt alloy particle were approximately the same as those before the etching (coercive force: 10 kOe). Accordingly, it was confirmed that useful FePt alloy particles was obtained by the etching treatment.

Second Embodiment (Formation of CoPt Alloy Particle)

[0071] A magnetic material of a CoPt alloy particle with a silica covering was manufactured in the same process as the manufacturing process of the magnetic material of the first embodiment (FePt alloy particle). In the production process of a raw material micellar solution, cobalt nitrate (Co(NO.sub.3).sub.2.6H.sub.2O) and chloroplatinic acid were added to 6 mL of pure water so as to become 0.12 M in the total of Co and Pt. Barium nitrate was added to the liquid in the same way as in the first embodiment, and, after that, an oil phase (octane+butanol) and a surfactant (CTAB) were added. The addition amount of barium and respective additives are set to the same amount as in the first embodiment. Further, the solution was stirred to produce a raw material micellar solution. Plural solutions were produced so that the ratio of Co and Pt (Co:Pt) in the raw material micellar solution became 5:5 (Example 2), 10:0 (Reference Example 4), 9:1 (Reference Example 5), and 0:10 (Reference Example 6). A raw material micellar solution with no addition of Ba was also produced as Comparative Example 2 (Co:Pt was 5:5).

[0072] As a neutralizing agent micellar solution, the same one as in the first embodiment was produced. Then, the neutralizing agent micellar solution was dropped into the raw material micellar solution produced as described above in the same way as in the first embodiment. Further, TEOS was added dropwise into the mixed solution in the same way as in the first embodiment, and was reacted over 20 hours with stirring of the mixed solution. When precipitate was generated in the solution, centrifugation was performed and the solid content was collected, the solid content obtained by repeating washing/centrifugation was dried, and a precursor of the magnetic material was obtained. Finally, the precursor was subjected to a calcination heat treatment, in which heating was performed at 980 C. for 4 hours in a hydrogen atmosphere.

[0073] For the magnetic material (CoPt alloy particle covered with silica) manufactured in the present embodiment, too, X-ray diffraction analysis (XRD), elemental analysis (ICP-MS and XRF) and evaluations of magnetic properties were performed. FIGS. 5 and 6 illustrate an XRD result and a TEM image of the magnetic material in Example 2. Further, evaluation results of magnetic properties are shown in Table 2.

TABLE-US-00002 TABLE 2 Magnetic properties*.sup.2 Charged molar Coercive Residual Saturation ratio Generated force/ magnetization/ magnetization/ Co Pt Ba Si phase*.sup.1 kOe emug.sup.1 emug.sup.1 Example 2 5 5 1 94 CoPt(fct), 1.1 3 7 -Co Comparative 5 5 0 94 CoPt(fct), 0.4 1 7 example 2 -Co Reference 10 0 1 94 -Co 0.2 2 11 example 4 Reference 9 1 1 94 Co.sub.3Pt(fct), 0.2 2 11 example 5 -Co Reference 0 10 1 94 PtSi, Pt.sub.2Si, *.sup.3 *.sup.3 *.sup.3 example 6 Pt.sub.3Si, Pt *.sup.1Silica phase (SiO.sub.2) is not described *.sup.2Measured value including silica (SiO.sub.2) being carrier *.sup.3Diamagnetic and unmeasurable

[0074] It is known from Table 2, also for the embodiment (CoPt alloy particle), that the magnetic material (Example 2), for which it was intended to perform generation/ordering of the alloy with addition of the alkali-earth metal, has excellent coercive force and good residual magnetization and saturation magnetization as compared with Comparative Example 2 with no addition of Ba.

[0075] Further, a composition ratio of both metals in the CoPt alloy particle in Example 2 was calculated similar to the first embodiment, and Co:Pt=58:42 was identified from elemental analysis by ICP-MS and XRF. Further, when the composition ratio was corrected by refining of an XRD pattern in Rietveld refinement and addition of weight ratio of the CoPt alloy particle and the impurity, it was calculated that the composition ratio of both metals in the CoPt alloy particle was Co:Pt=50:50. In the same way, the composition ratio of the CoPt alloy particle in Comparative Example 2 was identified as Co:Pt=60:40 from elemental analysis, and, as the result of correction with addition of a weight ratio of impurities, it was calculated as Co:Pt=30:70.

[0076] Further, (Ba/(Co+Pt)) was 0.021, which was the ratio of the molar number of the alkali-earth metal (Ba) and the total molar number of metals (Co+Pt) constituting the magnetic alloy particle in the magnetic material manufactured in Example 2. Furthermore, (Si/(Co+Pt)) was 5.9, which was the ratio of the molar number of Si contained in the silica carrier and the total molar number of metals (Co+Pt) constituting the magnetic alloy particle in Example 2.

Third Embodiment (Formation of FePt Alloy Particle)

[0077] In the embodiment, an FePt alloy particle (Example 3) was manufactured based on the FePt alloy particle in the first embodiment, while increasing the used amount of raw materials etc. 4 times.

[0078] (a) Production of Raw Material Micellar Solution

[0079] Iron nitrate (Fe(NO.sub.3).sub.3.9H.sub.2O) and chloroplatinic acid (H.sub.2[PtCl.sub.6].xH.sub.2O) were added to 24 mL of pure water so that the total of Fe and Pt became 0.12 M. Further, 75.32 mg of barium nitrate (Ba(NO.sub.3).sub.2) (Ba: 0.012 M) was added. The charged amount of barium being an alkali-earth metal becomes 0.1 relative to metals (Fe, Pt) in terms of a molar ratio ([A]/[M+PM]). 73.2 mL of octane and 14.4 mL of butanol were added to the aqueous solution as organic solvents to be an oil phase, and 14.08 g of CTAB was added as a surfactant. The solution was stirred for 90 minutes until it became uniform, and a raw material micellar solution was produced. Above operations are performed at room temperature. In the raw material micellar solution, the ratio of Fe and Pt (Fe:Pt) is 5:5, similar to Example 1.

[0080] (b) Production of Neutralizing Agent Micellar Solution

[0081] 9.04 mL of ammonia (25%-NH.sub.3 aqueous solution) was added to 14.96 mL of pure water as a neutralizing agent. 73.2 mL of octane and 14.4 mL of butanol were added to the solution, and, further, 14.08 g of CTAB was added. The solution was stirred for 90 minutes until it became uniform, to produce a neutralizing agent micellar solution.

[0082] (c) Generation of Composite Metal Hydroxide

[0083] The neutralizing agent micellar solution was dropped into the produced raw material micellar solution at 1 drop/sec. The mixed solution was stirred when the neutralizing agent micellar solution was added, and was stirred for additional 30 minutes after completion of the addition.

[0084] (d) Silica Covering to Composite Metal Hydroxide

[0085] 6.0 mL of TEOS was added dropwise at 2 drops/sec to the mixed solution produced as described above. At this time, the addition amount of Si ([Si]) becomes 9.4 in molar ratio relative to molar numbers of metals (Fe, Pt) ([M+PM]) in the raw material micellar solution. After completion of the addition, a reaction was performed over 20 hours with stirring of the mixed solution. Hereby, silica was deposited onto the surface of a hydroxide particle to cover the particle, and precipitate was generated. Then, the solution was centrifuged (3500 rpm, for 5 minutes) and the solid content was collected, which was washed with mixed liquid of methanol and chloroform and centrifuged, and, further, was washed with methanol and centrifuged. The obtained solid content was dried (air dried and then vacuum dried), and there were obtained core/shell particles of composite hydroxide particle/silica to be a precursor of a magnetic material.

[0086] (e) Calcination Heat Treatment (Generation and Ordering of Alloy)

[0087] The precursor was subjected to a calcination heat treatment in which heating was performed at 980 C. for 4 hours in a hydrogen atmosphere.

[0088] The magnetic material in Example 3 manufactured in the above-described processes was subjected to X-ray diffraction analysis (XRD), and a generated phase in the magnetic material was identified. Further, elemental analysis using X-ray fluorescence analysis (XRF) was performed. FIG. 7 shows the result of XRD of the magnetic material in Example 3. FIG. 8 shows a TEM image of the magnetic material. Further, magnetic properties were evaluated for the magnetic material. As to magnetic properties, a magnetic hysteresis curve was measured (temperature 300 K) with a superconducting quantum interference device (SQUID), and coercive force, residual magnetization and saturation magnetization of the magnetic material were measured. The results are shown in Table 3. In Table 3, both results of Example 1 and Comparative Example 1 in the first embodiment are shown together. Moreover, FIG. 9 illustrates a magnetic hysteresis curve measured for the magnetic material in Example 3.

TABLE-US-00003 TABLE 3 Magnetic properties*.sup.2 Charged molar Coercive Residual Saturation ratio Generated force/ magnetization/ magnetization/ Fe Pt Ba Si phase*.sup.1 kOe emug.sup.1 emug.sup.1 Example 3 5 5 1 94 FePt(fct), 21 5 9 -Fe, -Fe Example 1 5 5 1 94 FePt(fct), 10 4 9 Pt.sub.2Si, -Fe, -Fe, BaO Comparative 5 5 0 94 FePt(fct), 0.2 0.9 8 example 1 -Fe *.sup.1Silica phase (SiO.sub.2) is not described *.sup.2Measured value including silica (SiO.sub.2) being carrier

[0089] From Table 3, the magnetic material in Example 3 had very good coercive force, residual magnetization and saturation magnetization. It has good magnetic properties when compared with the magnetic material in Example 1. Meanwhile, it was identified as Fe:Pt=60:40 in the magnetic material in Example 3 from the result of elemental analysis. Then, when the composition ratio was corrected by refining of an XRD pattern in Rietveld refinement and addition of weight ratio of the FePt alloy particle and the impurity, it was calculated that the composition ratio of both metals in the FePt alloy particle was Fe:Pt=53:47. Further, a molar ratio ([Ba]/[Fe+Pt]) of the content of the alkali-earth metal ([Ba]) and the content of metals [Fe+Pt] constituting the magnetic alloy particle was 0.02.

Fourth Embodiment (Formation of FePt Alloy Particle)

[0090] In the embodiment, an FePt alloy particle (Example 4) was manufactured based on the FePt alloy particle in the first embodiment, while applying calcium as an alkali-earth metal to be added in a process of producing a raw material micellar solution.

[0091] (a) Production of Raw Material Micellar Solution

[0092] Iron nitrate (Fe(NO.sub.3).sub.3.9H.sub.2O) and chloroplatinic acid (H.sub.2[PtCl.sub.6].xH.sub.2O) were added to 24 mL of pure water so that the total of Fe and Pt became 0.12 M. Further, 68.01 mg of calcium nitrate (Ca(NO.sub.3).sub.2.4H.sub.2O) (Ca:0.012 M) was added. The charged amount of calcium being an alkali-earth metal becomes 0.1 relative to metals (Fe, Pt) in terms of a molar ratio ([A]/[M+PM]). 73.2 mL of octane and 14.4 mL of butanol were added to the aqueous solution as organic solvents to be an oil phase, and 14.08 g of CTAB was added as a surfactant. The solution was stirred for 90 minutes until it became uniform, and a raw material micellar solution was produced. Above operations are performed at room temperature. In the raw material micellar solution, the ratio of Fe and Pt (Fe:Pt) is 5:5, similar to Example 1.

[0093] (b) Production of Neutralizing Agent Micellar Solution

[0094] 9.04 mL of ammonia (25%-NH.sub.3 aqueous solution) was added to 14.96 mL of pure water as a neutralizing agent. 73.2 mL of octane and 14.4 mL of butanol were added to the solution, and, further, 14.08 g of CTAB was added. The solution was stirred for 90 minutes until it became uniform, and a neutralizing agent micellar solution was produced,

[0095] (c) Generation of Composite Metal Hydroxide

[0096] The neutralizing agent micellar solution was dropped into the produced raw material micellar solution at 1 drop/sec. The mixed solution was stirred when the neutralizing agent micellar solution was added, and was stirred for additional 30 minutes after completion of the addition.

[0097] (d) Silica Covering to Composite Metal Hydroxide

[0098] 6.0 mL of TEOS was added dropwise at 2 drops/sec to the mixed solution produced as described above. At this time, the addition amount of Si ([Si]) becomes 9.4 in molar ratio relative to molar numbers of metals (Fe, Pt) ([M+PM]) in the raw material micellar solution. After completion of the addition, a reaction was performed over 20 hours with stirring of the mixed solution. Hereby, silica was deposited onto the surface of a hydroxide particle to cover the particle, and precipitate was generated. Then, the solution was centrifuged (3500 rpm, for 5 minutes) and the solid content was collected, which was washed with mixed liquid of methanol and chloroform and centrifuged, and, further, was washed with methanol and centrifuged. The obtained solid content was dried (air dried and then vacuum dried), and there were obtained core/shell particles of composite hydroxide particle/silica to be a precursor of a magnetic material.

[0099] (e) Calcination heat treatment (generation and ordering of alloy)

[0100] The precursor was subjected to a calcination heat treatment in which heating was performed at 980 C. for 4 hours in a hydrogen atmosphere.

[0101] The magnetic material in Example 4 manufactured in the above-described processes was subjected to X-ray diffraction analysis (XRD), and a generated phase in the magnetic material was identified. Further, elemental analysis using X-ray fluorescence analysis (XRF) was performed. FIG. 10 shows the result of XRD of the magnetic material in Example 4. FIG. 11 shows a TEM image of the magnetic material. Further, magnetic properties were evaluated for the magnetic material. As to magnetic properties, a magnetic hysteresis curve was measured (temperature 300 K) with a superconducting quantum interference device (SQUID), and coercive force, residual magnetization and saturation magnetization of the magnetic material were measured. The results are shown in Table 4. In Table 4, both results of Example 1 and Comparative Example 1 in the first embodiment are described together.

TABLE-US-00004 TABLE 4 Charged molar ratio Magnetic properties*.sup.2 Alkali- Coercive Residual Saturation earth Generated force/ magnetization/ magnetization/ Fe Pt metal Si phase*.sup.1 kOe emug.sup.1 emug.sup.1 Example 4 5 5 1 94 FePt(fct), 11 5 8 (Ca) -Fe Example 1 5 5 1 94 FePt(fct), 10 4 9 (Ba) Pt.sub.2Si, -Fe, -Fe, BaO Comparative 5 5 0 94 FePt(fct), 0.2 0.9 8 example 1 -Fe *.sup.1Silica phase (SiO.sub.2) is not described *.sup.2Measured value including silica (SiO.sub.2) being carrier

[0102] From Table 4, the magnetic material in Example 4 had very good coercive force, residual magnetization and saturation magnetization. It has good magnetic properties when compared with the magnetic material in Example 1. From the result of the present embodiment, it was confirmed that calcium was also effective as an alkali-earth metal to be applied in a production process of the raw material micellar solution. Meanwhile, it was identified as Fe:Pt=60:40 in the magnetic material in Example 4 from the result of elemental analysis. Then, when the composition ratio was corrected by refining of an XRD pattern in Rietveld refinement and addition of weight ratio of the FePt alloy particle and the impurity, it was calculated that the composition ratio of both metals in the FePt alloy particle was Fe:Pt=59:41. Further, a molar ratio ([Ca]/[Fe+Pt]) of the content of the alkali-earth metal ([Ca]) and the content of metals [Fe+Pt] constituting the magnetic alloy particle was 0.11.

INDUSTRIAL APPLICABILITY

[0103] The magnetic material according to the present invention holds a magnetic alloy particle having crystal magnetic anisotropy, has an effectively ordered crystal structure regarding the magnetic alloy particle, and has suitable magnetic properties. Developments of magnetic recording media with more enhanced recording density as compared with conventional one can be expected by suitable picking out and utilization of the magnetic alloy particle.