JPS62257705A - Manufacture of rco5 rare-earth cobalt magnet - Google Patents
Manufacture of rco5 rare-earth cobalt magnetInfo
- Publication number
- JPS62257705A JPS62257705A JP61099351A JP9935186A JPS62257705A JP S62257705 A JPS62257705 A JP S62257705A JP 61099351 A JP61099351 A JP 61099351A JP 9935186 A JP9935186 A JP 9935186A JP S62257705 A JPS62257705 A JP S62257705A
- Authority
- JP
- Japan
- Prior art keywords
- pulverization
- water
- powder
- rco5
- permanent magnet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 12
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 12
- 229910017052 cobalt Inorganic materials 0.000 title claims abstract description 10
- 239000010941 cobalt Substances 0.000 title claims abstract description 10
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 title claims description 5
- 239000000843 powder Substances 0.000 claims abstract description 42
- 238000010298 pulverizing process Methods 0.000 claims abstract description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 23
- 239000000956 alloy Substances 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 17
- 238000001035 drying Methods 0.000 claims abstract description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 abstract description 30
- 239000002245 particle Substances 0.000 description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 238000000227 grinding Methods 0.000 description 9
- 239000012298 atmosphere Substances 0.000 description 8
- 239000003960 organic solvent Substances 0.000 description 8
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 230000001590 oxidative effect Effects 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000011282 treatment Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000008235 industrial water Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明はＲＣｏ５系希土類コバルト磁石の製造方法に関
する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an RCo5 rare earth cobalt magnet.
ＲＣｏ５系希土類コバルト磁石、（ＲはＹを含む希土類
金属を意味する）は、単磁区粒子による保磁力発生機構
を利用した磁石であるため、その製造のためには微粉末
を調製する工程が必要である。RCo5-based rare earth cobalt magnets (R means rare earth metal containing Y) are magnets that utilize a coercive force generation mechanism using single-domain particles, so a process of preparing fine powder is required to manufacture them. It is.
従来、微粉末調製は原料となるＲＣｏ、系合金を有機溶
剤中で数ミクロンまで粉砕することにより行なわれてい
る。Conventionally, fine powder preparation has been carried out by pulverizing raw materials such as RCo and alloys to several microns in an organic solvent.
特開昭４９−８６８９６号によると、ＳｍＣｏ５インゴ
ットをハンマークラッシャーで粗粉砕し、粗粉末をトル
エンを用いたアルミナセラミック質ポット中で微粉砕し
て粒度５〜８μの粉末が調製されている。According to JP-A No. 49-86896, a powder having a particle size of 5 to 8 microns is prepared by coarsely crushing an SmCo5 ingot with a hammer crusher, and finely crushing the coarse powder in an alumina ceramic pot using toluene.
特開昭４９−３１９６号によるとアセトンと自動うすを
用いてＲＣｏ、粉末が得られている。このＲＣｏ５粉末
には、０．ＩＮ塩酸浸せき、水洗、真空乾燥の処理が順
次節される。According to JP-A-49-3196, RCo powder is obtained using acetone and an automatic thinner. This RCo5 powder contains 0. The treatments of IN hydrochloric acid immersion, water washing, and vacuum drying are performed in sequence.
上述のように微粉砕工程において有機溶剤中で粉砕を行
なうのは希土類金属の酸化による磁気特性の劣化を避け
ることが必要であると従来解されていたためである。As mentioned above, the reason why pulverization is carried out in an organic solvent in the pulverization process is because it has been conventionally understood that it is necessary to avoid deterioration of magnetic properties due to oxidation of rare earth metals.
またＲＣｏｚ系合金粉表面を酸化させることにより保磁
力等の磁気特性が改善されることが知られている。ＲＣ
ｏ、系合金粉の表面を酸化させる方法として、例えば、
合金粉を空気中で加熱して合金粉表面を酸化させる方法
（特開昭５１−５５７２２号）や、合金粉を水を混入し
た有機溶剤中に浸？ｉＬ、その水分により合金粉表面を
酸化させる方法等が提案されている。It is also known that magnetic properties such as coercive force can be improved by oxidizing the surface of RCoz alloy powder. R.C.
o. As a method of oxidizing the surface of the alloy powder, for example,
There is a method of heating alloy powder in the air to oxidize the surface of the alloy powder (Japanese Patent Application Laid-Open No. 51-55722), and a method of soaking alloy powder in an organic solvent mixed with water. A method of oxidizing the surface of the alloy powder using iL and its moisture has been proposed.
上記した従来技術には次のような問題点がある。The above-mentioned conventional technology has the following problems.
（１）有機溶剤中で粉砕すると、粉末の残留カーボン量
が増加し、製品の磁気特性が劣化する。また、粉砕装置
を防Φ本構造にしなければならず、ハンドリングも複雑
になる。(1) When pulverized in an organic solvent, the amount of residual carbon in the powder increases and the magnetic properties of the product deteriorate. In addition, the crushing device must have a Φ-proof structure, and handling becomes complicated.
（２）不活性雰囲気中で粉砕すると、粉末が発火する危
険性が高い。(2) If crushed in an inert atmosphere, there is a high risk that the powder will catch fire.
（３）合金粉を空気中で加熱すると、均一に酸化させる
ことが困難であり、発火の危険性も高い。(3) When alloy powder is heated in air, it is difficult to oxidize it uniformly and there is a high risk of ignition.
（４）合金粉を水を混入した有機溶剤中に浸漬した場合
、有機溶剤中への水の分散が難しく、合金粉を均一に酸
化させることは困難である。また、ＲＣｏ５系合金は耐
酸化性が高いので酸化に時間がかかる。(4) When alloy powder is immersed in an organic solvent mixed with water, it is difficult to disperse the water into the organic solvent, and it is difficult to uniformly oxidize the alloy powder. Furthermore, since the RCo5 alloy has high oxidation resistance, it takes time to oxidize.
従来技術で採用されていた方法により、微粉末の残留炭
素量゛を少なくしようとすると、不活性ガス雰囲気中粉
砕法が採用されることになるが、発火の危険性があるこ
とのほかに、Ｎ２ガスやＡｒガスを、高圧でしかも多量
に必要とするため、粉砕コストが上界する。さらに、気
流粉砕機（ジェットミル）などの高価な設備を必要とす
る。In an attempt to reduce the amount of residual carbon in fine powder using the conventional method, pulverization in an inert gas atmosphere was adopted, but in addition to the risk of ignition, Since N2 gas and Ar gas are required at high pressure and in large quantities, the cost of pulverization increases. Furthermore, it requires expensive equipment such as a jet mill.
また従来技術によりＲＣｏ５系合金粉表面を酸化しよう
とすると均一酸化が難しいために、酸化による磁気特性
向上効果が十分ではない。Further, when attempting to oxidize the surface of RCo5 alloy powder using the conventional technology, it is difficult to oxidize uniformly, so that the effect of improving magnetic properties by oxidation is not sufficient.
本発明はＲＣｏ５系希土類コバルト磁石合金を水中で微
粉砕し、得られた粉末を乾燥し通常の方法で磁石とする
ことを特徴とする。The present invention is characterized in that an RCo5-based rare earth cobalt magnet alloy is pulverized in water, and the resulting powder is dried and made into a magnet using a conventional method.
以下、本発明の構成要件を説明する。Hereinafter, the constituent elements of the present invention will be explained.
ＲＣｏ５系希土類コバルト永久磁石合金は、ＲＣｏ５金
属間化合物を主成分とする永久磁石合金である。The RCo5-based rare earth cobalt permanent magnet alloy is a permanent magnet alloy whose main component is an RCo5 intermetallic compound.
この合金組成は何ら限定されず、Ｙ、Ｌａ、Ｃｅ。This alloy composition is not limited at all and may include Y, La, and Ce.
３ｍ、ｐｒ、ミツシュメタルのほぼ１モルに対してＣｏ
５モルより構成される組成などすべてのものを含む。3m, pr, Co for approximately 1 mole of Mitshu metal
This includes all compositions consisting of 5 moles.
微粉砕はＲＣｏ、金属間化合物を単磁区粒子にするため
の粉砕を指す。微粉砕はボールミル、振動ミル、アトラ
イター等の液体中の粉砕に適したあらゆる粉砕機で実施
される。ジェットミル等の気体により粉砕を行なう粉砕
機では本発明は実施されない。通常微粉砕の前に粗粉砕
が実施されるが、粗粉砕で本発明を実施しても所期の効
果は達成されない。微粉砕により得る粒度は公知の値で
あってよいが、その中でも特に平均粒度３〜５μｍにお
いてすぐれた保磁力が得られる。Fine pulverization refers to pulverization of RCo, an intermetallic compound, into single-domain particles. Fine grinding is carried out in any grinder suitable for grinding in liquids, such as ball mills, vibratory mills, attritors, etc. The present invention cannot be practiced with a pulverizer such as a jet mill that performs pulverization using gas. Coarse pulverization is usually carried out before fine pulverization, but even if the present invention is carried out with coarse pulverization, the desired effect will not be achieved. The particle size obtained by fine pulverization may be any known value, but particularly excellent coercive force can be obtained with an average particle size of 3 to 5 μm.
微粉砕の媒体となる水は水道水、工業用水などが本発明
において使用される。有機物質は本発明による効果を妨
げるために、有機物質が水に含有することが避けられな
い場合は有機物質混入量が極力低い水を使用しなければ
ならない。無機物質である酸、塩類は振動ミル等を腐食
させることがあるから、酸、塩類を水中に混合させるこ
とは好ましくない。さらに、酸、塩類は、希土類金属お
よび／またはコバルトと反応してＲＣｏ５の組成を変え
るために、好ましくはない。唯、少量の酸、塩類が水中
に含有されても本発明の効果は得られる。水の温度は０
℃以上であればよい。特に水を加温もしくは冷却する必
要はなく室温で十分なる効果が得られる。In the present invention, tap water, industrial water, and the like are used as water as a medium for pulverization. Since organic substances interfere with the effects of the present invention, if the presence of organic substances in water is unavoidable, water with as low an amount of organic substances as possible must be used. Since acids and salts, which are inorganic substances, may corrode vibrating mills, etc., it is not preferable to mix acids and salts with water. Furthermore, acids and salts are not preferred because they react with rare earth metals and/or cobalt and change the composition of RCo5. However, even if a small amount of acid or salt is contained in water, the effects of the present invention can be obtained. water temperature is 0
It is sufficient if the temperature is above ℃. There is no need to particularly heat or cool the water, and sufficient effects can be obtained at room temperature.
微粉砕の方法は、トルエン等を使用しないとの粉砕媒体
条件が異なることを除くと通常の方法である。The method of fine pulverization is a normal method except that the conditions of the pulverizing medium are different in that toluene and the like are not used.
上述の微粉砕により、微粉末は所定の粒度を付与されか
つ均一に酸化される。以降、水分の乾燥による除去を行
なった後焼結磁石あるいはボンド磁石を得る通常の工程
を行なう。乾燥を行なわないで、湿った微粉末を圧粉す
ると所望の圧粉密度が得られないために、乾燥工程を経
た後通常の工程で粉末を処理することが必要である。微
粉末の真空乾燥、凍結乾燥などで行なう。微粉末を永久
磁石にする工程は通常の条件で行なえばよいが、酸化が
さらに進行することは避けることが望ましい。微粉末か
ら永久磁石までの工程で起こる酸化はガス酸化であるか
ら、水中酸化に比較して不均一に進行し、せっかく得ら
れた均一酸化が失われる。By the above-mentioned pulverization, the fine powder is given a predetermined particle size and uniformly oxidized. Thereafter, after removing moisture by drying, the usual process for obtaining a sintered magnet or a bonded magnet is performed. If wet fine powder is compacted without drying, the desired compacted powder density cannot be obtained, so it is necessary to process the powder in a normal process after passing through the drying process. This is done by vacuum drying, freeze drying, etc. of fine powder. The process of turning fine powder into a permanent magnet may be carried out under normal conditions, but it is desirable to avoid further progress of oxidation. Since the oxidation that occurs during the process from fine powder to permanent magnet is gas oxidation, it progresses unevenly compared to underwater oxidation, and the uniform oxidation that has been achieved is lost.
水中で微粉砕することにより合金粉の表面を酸化させ、
磁石化後の磁気特性を改善できる。By pulverizing the alloy powder in water, the surface of the alloy powder is oxidized,
The magnetic properties after magnetization can be improved.
以下、実施例によりさらに詳しく本発明を説明する。 Hereinafter, the present invention will be explained in more detail with reference to Examples.
Ｓｍ ３６．２ ｗ ｔ％、 Ｃｏ ６３．７ｗ ｔ
％のインゴットが得られるように原料を配合した後アル
ゴンガス中の高周波溶解炉で溶解してインゴットを得た
。Sm 36.2 wt%, Co 63.7wt
% ingot was obtained, and then melted in a high frequency melting furnace in argon gas to obtain an ingot.
得られたインゴットをスタンプミルで粗粉砕して粒径０
．５〜１．２ｍの粉末を得、これを室温の水中で振動ミ
ルで微粉砕した。この際得られる粉末の平均粒径が２〜
７μｍの範囲で変化するように粉砕時間を変えて微粉砕
を行なった。得られた粉末を、次に磁場１５ｋｏｅ、圧
力１．５ ｔｏｎ ７ｃｍ”の条件で磁場中成形し、続
いてアルゴン雰囲気中１０８０℃の条件で焼結を行なっ
た。The obtained ingot was coarsely pulverized with a stamp mill to a particle size of 0.
．． A powder of 5-1.2 m was obtained, which was milled in a vibratory mill in water at room temperature. The average particle size of the powder obtained at this time is 2~
Fine pulverization was carried out by changing the pulverization time so that the particle size varied within a range of 7 μm. The obtained powder was then compacted in a magnetic field under the conditions of a magnetic field of 15 koe and a pressure of 1.5 ton 7 cm'', followed by sintering at 1080° C. in an argon atmosphere.
比較のために、水中微粉砕をトルエン中微粉砕に変えた
ほかは上記方法と同一方法で焼結磁石を得た。For comparison, a sintered magnet was obtained in the same manner as above except that fine pulverization in water was changed to pulverization in toluene.
焼結磁石の保磁力（ｉＨｃ）、炭素量（％）および酸素
量（％）を測定した結果を第１図に示す。FIG. 1 shows the results of measuring the coercive force (iHc), carbon content (%), and oxygen content (%) of the sintered magnet.
第１図より、トルエン中粉砕の場合は平均粒径が小さく
なるほど、炭素量は増大しているのに対し、水中粉砕の
場合は炭素量は一定であり、しかも平均粒径に関係なく
炭素含有量がトルエン中粉砕の場合より極めて低いとい
う、粉砕雰囲気による顕著な差異が認められる。水中微
粉砕の際には粉砕雰囲気から粉末に炭素は侵入しない。From Figure 1, in the case of pulverization in toluene, the amount of carbon increases as the average particle size decreases, whereas in the case of pulverization in water, the amount of carbon remains constant, and carbon content is independent of the average particle size. A significant difference is observed due to the grinding atmosphere, with the amount being much lower than in the case of grinding in toluene. During underwater pulverization, carbon does not enter the powder from the pulverization atmosphere.
したがって炭素は主としてＣｏ金属中の不純物であると
考えられる。Therefore, carbon is considered to be mainly an impurity in Co metal.
また、トルエン中粉砕、水中粉砕何れの場合も酸素量は
平均粒径が小さくなるほど増大しておりまた酸素量は水
中微粉砕の場合がトルエン中粉砕よりも約２倍多い。し
たがって、酸素は粉砕雰囲気より粉末中に侵入するが、
水の方がトルエンよりも酸化性が強いことが分かる。Further, in both cases of pulverization in toluene and pulverization in water, the amount of oxygen increases as the average particle size becomes smaller, and the amount of oxygen in pulverization in water is about twice as large as that in pulverization in toluene. Therefore, oxygen enters the powder from the grinding atmosphere, but
It can be seen that water has stronger oxidizing properties than toluene.
さらに、保磁力（ｉＨｃ）は平均粒径に関係なく水中微
粉砕の方がトルエン中微粉砕よりすぐれている。Furthermore, in terms of coercive force (iHc), pulverization in water is superior to pulverization in toluene, regardless of the average particle size.
（１）合金粉の表面を酸化させることにより、保磁力等
の磁気特性が向上する。(1) Magnetic properties such as coercive force are improved by oxidizing the surface of alloy powder.
（２）粉砕雰囲気を水としたのでハンドリングが容易で
あり、有機溶剤を使用する場合の危険性がなく、残留カ
ーボン量も低く抑えられる。(2) Since water is used as the grinding atmosphere, handling is easy, there is no danger when using organic solvents, and the amount of residual carbon can be kept low.
（３）粉砕雰囲気を有機溶剤とした場合、粉砕・乾燥装
置が複雑になり廃液処理等の問題があるが、粉砕雰囲気
を水とした場合、装置類は複雑にならず廃液処理も容易
である。(3) When the grinding atmosphere is an organic solvent, the grinding/drying equipment is complicated and there are problems with waste liquid treatment, but when the grinding atmosphere is water, the equipment is not complicated and waste liquid treatment is easy. .
【図面の簡単な説明】
第１図は微粉末の平均粒径と磁石の特性の関係を示すグ
ラフである。
微粉末の平均粒径 （ｕｍ）
第１図BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between the average particle size of fine powder and the characteristics of a magnet. Average particle size of fine powder (um) Figure 1
Claims (1)
微粉砕し、得られた微粉末を乾燥し、通常の方法で磁石
とするＲＣｏ＿５系希土類コバルト磁石の製造方法。1. A method for manufacturing an RCo_5 rare earth cobalt magnet, which involves pulverizing an RCo_5 rare earth cobalt permanent magnet alloy in water, drying the resulting fine powder, and making a magnet using a normal method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61099351A JPS62257705A (en) | 1986-05-01 | 1986-05-01 | Manufacture of rco5 rare-earth cobalt magnet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61099351A JPS62257705A (en) | 1986-05-01 | 1986-05-01 | Manufacture of rco5 rare-earth cobalt magnet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS62257705A true JPS62257705A (en) | 1987-11-10 |
Family
ID=14245189
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61099351A Pending JPS62257705A (en) | 1986-05-01 | 1986-05-01 | Manufacture of rco5 rare-earth cobalt magnet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62257705A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5129964A (en) * | 1989-09-06 | 1992-07-14 | Sps Technologies, Inc. | Process for making nd-b-fe type magnets utilizing a hydrogen and oxygen treatment |
| US5244510A (en) * | 1989-06-13 | 1993-09-14 | Yakov Bogatin | Magnetic materials and process for producing the same |
| EP1850355A1 (en) * | 2002-05-31 | 2007-10-31 | FUJIFILM Corporation | Magnetic particle and its production method |
| US7384449B2 (en) | 2001-09-05 | 2008-06-10 | Fujifilm Corporation | Ferromagnetic nanoparticles, material coated with dispersion of ferromagnetic nanoparticles, and magnetic recording medium using the material |
-
1986
- 1986-05-01 JP JP61099351A patent/JPS62257705A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5244510A (en) * | 1989-06-13 | 1993-09-14 | Yakov Bogatin | Magnetic materials and process for producing the same |
| US5129964A (en) * | 1989-09-06 | 1992-07-14 | Sps Technologies, Inc. | Process for making nd-b-fe type magnets utilizing a hydrogen and oxygen treatment |
| US5286307A (en) * | 1989-09-06 | 1994-02-15 | Sps Technologies, Inc. | Process for making Nd-B-Fe type magnets utilizing a hydrogen and oxygen treatment |
| US7384449B2 (en) | 2001-09-05 | 2008-06-10 | Fujifilm Corporation | Ferromagnetic nanoparticles, material coated with dispersion of ferromagnetic nanoparticles, and magnetic recording medium using the material |
| EP1850355A1 (en) * | 2002-05-31 | 2007-10-31 | FUJIFILM Corporation | Magnetic particle and its production method |
| US7335393B2 (en) | 2002-05-31 | 2008-02-26 | Fujifilm Corporation | Magnetic particle, its production method, magnetic recording medium and its production method |
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