JP2010212501A - Exchange spring magnetic powder - Google Patents
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Abstract
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本発明は、データテープ等の磁気記録媒体、あるいはボンド磁石やゴム磁石などに用いられる交換スプリング磁性粉末に関する。 The present invention relates to an exchange spring magnetic powder used for a magnetic recording medium such as a data tape, or a bond magnet or a rubber magnet.
例えば、磁石粉を磁気記録媒体、特に塗布型媒体に用いる場合、記録密度向上のために、粒子サイズを微細化する必要があるが、微細な粒子を使用するとテープに塗布した際の出力が低くなる。そのため、大きな飽和磁化を持った磁石粉が要求されるようになってきている。現在、金属磁石で主流のＮｄ−Ｆｅ−Ｂ系磁石は、大きな飽和磁化を持つものの、酸化されやすく耐食性が低いため、磁気記録媒体に使用した場合、信頼性に問題がある。一方、Ｓｍ−Ｃｏ系磁石の場合、Ｎｄ−Ｆｅ−Ｂ系磁石よりも耐候性に優れているものの、飽和磁化が低いという問題がある。 For example, when magnetic powder is used in magnetic recording media, particularly coating-type media, it is necessary to reduce the particle size in order to improve recording density, but if fine particles are used, the output when applied to tape is low. Become. Therefore, a magnet powder having a large saturation magnetization has been demanded. Currently, Nd—Fe—B magnets, which are the mainstream of metal magnets, have large saturation magnetization, but are easily oxidized and have low corrosion resistance. Therefore, when used for magnetic recording media, there is a problem in reliability. On the other hand, in the case of Sm—Co-based magnets, although it has better weather resistance than Nd—Fe—B-based magnets, there is a problem that saturation magnetization is low.
その対策のための研究あるいは新しい磁石材料の探索が進められている。その一例として、金属磁石材料の磁気特性、特に飽和磁化を改善する方法して、軟磁性材料と組み合せる交換スプリング方式の磁石材料の開発が、特許文献１を始めとして、以前から行われてきている。交換スプリング磁石とは、硬磁性相と軟磁性相の２相からなる超微細結晶組織で構成される永久磁石である。これは、一般に磁化の大きい軟磁性相と保磁力の大きい硬磁性相とを組み合せ、これらを交換相互作用により磁気的に結合させることで高いエネルギー積を得るという考え方に基づいている。 The research for the countermeasures or the search for new magnet materials is underway. As an example, development of an exchange spring type magnet material that can be combined with a soft magnetic material by improving the magnetic properties of the metal magnet material, particularly the saturation magnetization, has been carried out for a long time. Yes. The exchange spring magnet is a permanent magnet composed of an ultrafine crystal structure composed of two phases of a hard magnetic phase and a soft magnetic phase. This is based on the idea that a high energy product is generally obtained by combining a soft magnetic phase having a large magnetization and a hard magnetic phase having a large coercive force and magnetically coupling them by an exchange interaction.
しかしながら、特許文献１では、硬磁性相、軟磁性相ともに、急冷薄帯の粉砕等により作製されており、結晶サイズ自体は３０ｎｍ程度と小さいものの、粒子サイズ自体は４０μｍ程度と大きいものとなっている。このため、粒子自体が多結晶構造となっており、粒子内での結晶配向が乱れていたり、硬磁性相と隣接できない軟磁性相が発生したりして、保磁力の低下を招いている。また、硬磁性相と軟磁性相のサイズが近いために軟磁性相の比率を高くできなかったり、軟磁性相の比率を高めると保磁力が低下する、といった現象が見られる。さらに、急冷によるアモルファス相の発生による磁気特性の低下も見られたものである。 However, in Patent Document 1, both the hard magnetic phase and the soft magnetic phase are produced by pulverizing a quenched ribbon, and the crystal size itself is as small as about 30 nm, but the particle size itself is as large as about 40 μm. Yes. For this reason, the particles themselves have a polycrystalline structure, the crystal orientation in the particles is disturbed, or a soft magnetic phase that cannot be adjacent to the hard magnetic phase is generated, leading to a decrease in coercive force. Moreover, since the sizes of the hard magnetic phase and the soft magnetic phase are close, the ratio of the soft magnetic phase cannot be increased, and the coercive force decreases when the ratio of the soft magnetic phase is increased. In addition, the magnetic properties were also deteriorated due to the generation of an amorphous phase due to rapid cooling.
このため、後述するように、理論上は、軟磁性相の硬磁性相に対する体積比率を１０倍程度にできるにも拘らず、特許文献１中にも記載されているように、軟磁性相の硬磁性相に対する体積比率が４倍以上になると保磁力の低下が起こっている。よって、理論上予想されている飽和磁化の向上を始めとする大幅な磁気特性の改善は達成されていない現状にある。 For this reason, as will be described later, although the volume ratio of the soft magnetic phase to the hard magnetic phase can theoretically be about 10 times, as described in Patent Document 1, When the volume ratio to the hard magnetic phase is 4 times or more, the coercive force is lowered. Therefore, the present situation has not yet achieved a significant improvement in magnetic properties, such as the theoretically expected increase in saturation magnetization.
本発明は、上記に鑑みてなされたものであって、軟磁性相の硬磁性相に対する体積比率を上げても保磁力の低下を起こすことなく、飽和磁化を向上させることができる交換スプリング磁性粉末を提供することを目的とする。 The present invention has been made in view of the above, and an exchange spring magnetic powder capable of improving saturation magnetization without causing a decrease in coercive force even when the volume ratio of the soft magnetic phase to the hard magnetic phase is increased. The purpose is to provide.
上述した課題を解決し、目的を達成するために、本発明にかかる交換スプリング磁性粉末は、硬磁性相と軟磁性相との複合構造からなる交換スプリング磁性粉末において、前記硬磁性相と前記軟磁性相との各々の粒子サイズが、超常磁性臨界径より大きく単磁区臨界径以下であることを特徴とする。 In order to solve the above-described problems and achieve the object, an exchange spring magnetic powder according to the present invention is an exchange spring magnetic powder having a composite structure of a hard magnetic phase and a soft magnetic phase. Each particle size with the magnetic phase is larger than the superparamagnetic critical diameter and smaller than the single domain critical diameter.
また、本発明にかかる交換スプリング磁性粉末は、上記発明において、前記硬磁性相の粒子サイズが、２ｎｍより大きく５０ｎｍ以下であり、前記軟磁性相の粒子サイズが、８ｎｍより大きく５０ｎｍ以下であることを特徴とする。 In the exchange spring magnetic powder according to the present invention, in the above invention, the particle size of the hard magnetic phase is greater than 2 nm and 50 nm or less, and the particle size of the soft magnetic phase is greater than 8 nm and 50 nm or less. It is characterized by.
また、本発明にかかる交換スプリング磁性粉末は、上記発明において、前記硬磁性相は、一軸異方性を有し、室温における磁気異方性特性が５×１０７ｅｒｇ／ｃｍ３以上であることを特徴とする。 In the exchange spring magnetic powder according to the present invention, in the above invention, the hard magnetic phase has uniaxial anisotropy and a magnetic anisotropy characteristic at room temperature of 5 × 10 7 erg / cm 3 or more. It is characterized by.
また、本発明にかかる交換スプリング磁性粉末は、上記発明において、前記硬磁性相に対する前記軟磁性相の体積比率が４倍以上であることを特徴とする。 The exchange spring magnetic powder according to the present invention is characterized in that, in the above invention, the volume ratio of the soft magnetic phase to the hard magnetic phase is four times or more.
また、本発明にかかる交換スプリング磁性粉末は、上記発明において、前記軟磁性相は、Ｆｅ、ＣｏまたはＣｏ合金からなることを特徴とする。 The exchange spring magnetic powder according to the present invention is characterized in that, in the above invention, the soft magnetic phase is made of Fe, Co or a Co alloy.
また、本発明にかかる交換スプリング磁性粉末は、上記発明において、前記硬磁性相は、ＳｍおよびＣｏを含む合金からなることを特徴とする。 The exchange spring magnetic powder according to the present invention is characterized in that, in the above invention, the hard magnetic phase is made of an alloy containing Sm and Co.
本発明にかかる交換スプリング磁性粉末によれば、硬磁性相と軟磁性相との各々の粒子サイズが、超常磁性臨界径より大きく単磁区臨界径以下であり、粒子自体がナノサイズの単結晶粒子構造となっているため、軟磁性相の硬磁性相に対する体積比率を上げても保磁力の低下を起こすことなく、飽和磁化を向上させることができ、よって、大きな最大エネルギー積を有する交換スプリング磁性粉末を提供することができるという効果を奏する。 According to the exchange spring magnetic powder according to the present invention, the particle size of each of the hard magnetic phase and the soft magnetic phase is larger than the superparamagnetic critical diameter and smaller than or equal to the single domain critical diameter, and the particles themselves are nano-sized single crystal particles. Due to the structure, even if the volume ratio of the soft magnetic phase to the hard magnetic phase is increased, the saturation magnetization can be improved without causing a decrease in the coercive force, and thus the exchange spring magnet having a large maximum energy product. There exists an effect that powder can be provided.
以下、交換スプリング磁石の背景を踏まえつつ、本実施の形態の交換スプリング磁性粉末について説明する。 Hereinafter, the exchange spring magnetic powder according to the present embodiment will be described based on the background of the exchange spring magnet.
通常、永久磁石材において、硬磁性相と軟磁性相との混相状態では、逆磁界が印加されると、軟磁性相の一部で磁化反転が起きてしまい、保磁力が大きく低下してしまう。しかし、軟磁性相のサイズが磁壁幅よりも小さくなると、隣接する硬磁性相の影響で、逆磁界下における不均一磁化反転が抑制される。その結果、保磁力は主に硬磁性相の磁気異方性に支配され低下は抑えられる。 Usually, in a permanent magnet material, in a mixed phase state of a hard magnetic phase and a soft magnetic phase, when a reverse magnetic field is applied, magnetization reversal occurs in a part of the soft magnetic phase, and the coercive force is greatly reduced. . However, when the size of the soft magnetic phase is smaller than the domain wall width, non-uniform magnetization reversal under a reverse magnetic field is suppressed due to the influence of the adjacent hard magnetic phase. As a result, the coercive force is mainly controlled by the magnetic anisotropy of the hard magnetic phase, and the decrease is suppressed.
一方、軟磁性相によって一層高い磁束密度Ｂを得るためには、軟磁性相の体積比を上げる必要があるが、体積比を上げるだけでは保磁力が低下してしまう。併せて、高い保磁力を得るためには、軟磁性相のサイズを磁壁幅以下にまで小さくするとともに、軟磁性相に隣接して硬磁性相が存在する必要がある。このためには、一つの硬磁性相のサイズもできる限り小さくする必要がある。硬磁性相のサイズは、やはり磁壁幅以下であればよいが、あまり小さいと熱揺らぎによって保磁力を維持するのが困難となり磁性を発現しなくなるため、磁性を発現し得る臨界値である超常磁性臨界径よりは大きく保つ必要がある。磁壁幅は、π（Ａ／Ｋ）１／２（Ａ：交換スティッフネス定数、Ｋ：磁気異方性エネルギー）で見積もられるので、軟磁性相をＦｅ、硬磁性相をＳｍＣｏとすると、それぞれ６０ｎｍおよび数ｎｍ程度となる。 On the other hand, in order to obtain a higher magnetic flux density B by the soft magnetic phase, it is necessary to increase the volume ratio of the soft magnetic phase, but the coercive force decreases only by increasing the volume ratio. In addition, in order to obtain a high coercive force, it is necessary to reduce the size of the soft magnetic phase to be equal to or less than the domain wall width and to have a hard magnetic phase adjacent to the soft magnetic phase. For this purpose, it is necessary to make the size of one hard magnetic phase as small as possible. The size of the hard magnetic phase may be equal to or less than the domain wall width, but if it is too small, it will be difficult to maintain the coercive force due to thermal fluctuations and will not exhibit magnetism, so superparamagnetism is a critical value that can develop magnetism. It must be kept larger than the critical diameter. Since the domain wall width is estimated by π (A / K) 1/2 (A: exchange stiffness constant, K: magnetic anisotropy energy), assuming that the soft magnetic phase is Fe and the hard magnetic phase is SmCo, 60 nm respectively. And about several nm.
また、周知のように、交換スプリング磁石において、最大エネルギー積（ＢＨ）maxが最も大きくなるときの硬磁性相の体積比ｆｈは、近似的に、
ｆｈ＝μ０Ｍｓ２／４Ｋｈ
（ただし、Ｍｓ：軟磁性相の磁化、Ｋｈ：硬磁性相の磁気異方性エネルギー）
で与えられ、このときの最大エネルギー積（ＢＨ）maxは、
（ＢＨ）max＝(μ０Ｍｓ２／４)［１−｛μ０(Ｍｓ−Ｍｈ)Ｍｓ／２Ｋｈ｝］
（ただし、Ｍｈ：硬磁性相の磁化）
となる。
As is well known, in the exchange spring magnet, the volume ratio fh of the hard magnetic phase when the maximum energy product (BH) max is the largest is approximately:
fh = μ 0 Ms 2 / 4Kh
(Where Ms: magnetization of the soft magnetic phase, Kh: magnetic anisotropy energy of the hard magnetic phase)
The maximum energy product (BH) max at this time is
(BH) max = (μ 0 Ms 2/4) [1- {μ 0 (Ms-Mh) Ms / 2Kh}]
(However, Mh: magnetization of hard magnetic phase)
It becomes.
一般に、Ｓｍ−Ｃｏの磁気異方性エネルギーＫｈは、文献などによって異なるものの、概ね１１〜２０×１０７ｅｒｇ／ｃｍ３であって、Ｎｄ−Ｆｅ−Ｂ磁石の磁気異方性エネルギーＫｈの４．６×１０７ｅｒｇ／ｃｍ３の３〜４倍程度であるのに対し、軟磁性相を構成する、例えばＣｏ等の軟磁性体のμ０Ｍｓ２／４は、４．５×１０６ｅｒｇ／ｃｍ３程度であるので、硬磁性相の体積比ｆｈは、１０％程度あればよいことになる。従って、最大エネルギー積（ＢＨ）maxは、主に軟磁性相の特性に支配され、定量的にはμ０Ｍｓ２／４に僅かな補正が加わる形となる。 In general, although the magnetic anisotropy energy Kh of Sm—Co varies depending on literatures, it is approximately 11 to 20 × 10 7 erg / cm 3 , which is 4 of the magnetic anisotropy energy Kh of the Nd—Fe—B magnet. contrast in the range of about 3 to 4 times the .6 × 10 7 erg / cm 3 , constituting the soft magnetic phases, such as μ 0 Ms 2/4 of soft magnetic material such as Co is, 4.5 × 10 6 Since it is about erg / cm 3 , the volume ratio fh of the hard magnetic phase may be about 10%. Thus, maximum energy product (BH) max is mainly dominated by the characteristics of the soft magnetic phases, the quantitative the shape applied slight correction to μ 0 Ms 2/4.
以上より、最大エネルギー積（ＢＨ）maxの主要項は、μ０Ｍｓ２／４であるので、より大きなエネルギー積を得るためには、より大きなＭｓを持った軟磁性体を採用すればよいことが分かる。金属のＭｓは、Ｆｅ３０Ｃｏ７０を頂点とするスレーターポーリング曲線で知られており、大きなＭｓを得るためには、軟磁性相として、Ｆｅ、ＣｏまたはＣｏ合金を使用することが望ましい。 From the above, the main terms of maximum energy product (BH) max is because it is mu 0 Ms 2/4, in order to obtain a greater energy product may be be employed soft magnetic material having a larger Ms I understand. Metal Ms is known from a slater poling curve with Fe 30 Co 70 as the apex. In order to obtain a large Ms, it is desirable to use Fe, Co, or a Co alloy as the soft magnetic phase.
一方、硬磁性相に要求される性質は、一軸異方性を有し、かつ、室温における磁気異方性定数が大きいことである。磁気異方性定数が大きいほど、軟磁性相の体積比率を高めることができるため、１０７ｅｒｇ／ｃｍ３あることが好ましい。この値よりも小さい場合には、前述のｆｈ（最大エネルギー積が得られる軟磁性相の体積比率）が小さくなって、交換スプリング磁石の効果である、飽和磁化の向上効果が殆ど得られなくなってしまう。このような磁気異方性定数を満たす硬磁性材料としては、Ｎｄ２Ｆｅ１７Ｂ、ＣｏＰｔ、Ｃｏ３Ｐｔ、ＭｎＡｌ、ＦｅＰｔ等がある。 On the other hand, the properties required for the hard magnetic phase are uniaxial anisotropy and a large magnetic anisotropy constant at room temperature. Since the volume ratio of the soft magnetic phase can be increased as the magnetic anisotropy constant is increased, it is preferably 10 7 erg / cm 3 . When the value is smaller than this value, the above-described fh (the volume ratio of the soft magnetic phase at which the maximum energy product is obtained) becomes small, and the effect of improving the saturation magnetization, which is the effect of the exchange spring magnet, is hardly obtained. End up. Examples of hard magnetic materials satisfying such a magnetic anisotropy constant include Nd 2 Fe 17 B, CoPt, Co 3 Pt, MnAl, and FePt.
また、軟磁性相の体積比率を高めつつ、軟磁性相と硬磁性相とが隣接する状況を得るには、硬磁性相の大きさを、可能な限り小さくする必要がある。このためには、硬磁性相の磁気異方性定数が、５×１０７ｅｒｇ／ｃｍ３以上となることが、より好ましい。この値を下回ると、超常磁性限界径が大きくなって、硬磁性相の粒子サイズを５ｎｍより大きくする必要がある。このため、同じ体積当りの硬磁性相の数が減少してしまい、軟磁性相と硬磁性相とが隣接する状況にできる軟磁性相の数が制限される。これにより、ｆｈの値自体が大きくても軟磁性相の体積比率が制限される。逆に、磁気異方性定数が５×１０７ｅｒｇ／ｃｍ３以上になれば、硬磁性相の粒子サイズを２ｎｍ程度まで小さくできるため、軟磁性相と硬磁性相とが隣接する状況にできる軟磁性相の数が多くなり、軟磁性相の体積比率をｆｈに近づけることができる。この条件を満たす硬磁性材料としては、ＳｍＣｏ５やＦｅＰｔが挙げられる。 Further, in order to obtain a situation where the soft magnetic phase and the hard magnetic phase are adjacent to each other while increasing the volume ratio of the soft magnetic phase, it is necessary to reduce the size of the hard magnetic phase as much as possible. For this purpose, it is more preferable that the magnetic anisotropy constant of the hard magnetic phase is 5 × 10 7 erg / cm 3 or more. Below this value, the superparamagnetic limit diameter becomes large, and the particle size of the hard magnetic phase needs to be larger than 5 nm. For this reason, the number of hard magnetic phases per the same volume decreases, and the number of soft magnetic phases that can be in a state where the soft magnetic phase and the hard magnetic phase are adjacent to each other is limited. Thereby, even if the value of fh itself is large, the volume ratio of the soft magnetic phase is limited. Conversely, if the magnetic anisotropy constant is 5 × 10 7 erg / cm 3 or more, the particle size of the hard magnetic phase can be reduced to about 2 nm, so that the soft magnetic phase and the hard magnetic phase can be adjacent to each other. The number of soft magnetic phases increases, and the volume ratio of the soft magnetic phases can be made closer to fh. Examples of the hard magnetic material satisfying this condition include SmCo 5 and FePt.
また、軟磁性相の体積比率を高めつつ、軟磁性相と硬磁性相とが隣接する状況を得るには、硬磁性相の粒子サイズを小さくすることに加えて、硬磁性相の粒子サイズに比して軟磁性相の粒子サイズの方が大きいことが好ましい。軟磁性相の粒子サイズに関しても超常磁性臨界径よりは大きく保つことが必要であることを考慮すると、８ｎｍより大きいことが好ましい。また、軟磁性相および硬磁性相の粒子サイズの上限値としては、いずれも多磁区構造にならない範囲、すなわち単磁区臨界径以下でなくてはならない。これにより、結晶径が粒子径とほぼ同一となり、粒子自体が、一つの粒子に一つの相しか存在しない単結晶構造が確保される。このような単磁区臨界径は、例えば５０ｎｍである。ここで、軟磁性相および硬磁性相の粒子サイズの上限値を５０ｎｍ以下とすることにより、塗布型磁気記録媒体として要求される上限値にも合致し、本実施の形態の交換スプリング磁石を塗布型磁気記録媒体に好適に適用可能となる。 In addition to increasing the volume ratio of the soft magnetic phase and obtaining a situation where the soft magnetic phase and the hard magnetic phase are adjacent to each other, in addition to reducing the particle size of the hard magnetic phase, the particle size of the hard magnetic phase can be reduced. In comparison, the particle size of the soft magnetic phase is preferably larger. Considering that the particle size of the soft magnetic phase needs to be kept larger than the superparamagnetic critical diameter, it is preferably larger than 8 nm. Further, the upper limit value of the particle size of the soft magnetic phase and the hard magnetic phase must be within a range where no multi-domain structure is formed, that is, a single domain critical diameter or less. This ensures a single crystal structure in which the crystal diameter is substantially the same as the particle diameter, and the particles themselves have only one phase in one particle. Such a single domain critical diameter is, for example, 50 nm. Here, by setting the upper limit value of the particle size of the soft magnetic phase and the hard magnetic phase to 50 nm or less, the upper limit value required as a coating type magnetic recording medium is also met, and the replacement spring magnet of this embodiment is applied. The present invention can be suitably applied to a type magnetic recording medium.
ところで、粒子サイズが５０ｎｍ以下といったナノサイズの微細な硬磁性相および軟磁性相を、急冷薄帯等の粉砕で作製するのは非常に困難である。そのため、本実施の形態では、液相合成方式によって各磁性相を作製している。後述の実施例では、各金属元素のアセチルアセトナートのポリオール還元法を用いているが、逆ミセル法、マイクロ波合成法等も用いることが可能である。これ以外にも、金属カルボニルの熱分解等、ナノサイズの微細な粒子作製方法であれば応用可能である。 By the way, it is very difficult to produce a nano-sized fine hard magnetic phase and soft magnetic phase having a particle size of 50 nm or less by pulverization of a quenched ribbon or the like. Therefore, in this embodiment, each magnetic phase is produced by a liquid phase synthesis method. In the examples described later, a polyol reduction method of acetylacetonate of each metal element is used, but a reverse micelle method, a microwave synthesis method, or the like can also be used. Other than this, any nano-sized fine particle production method such as thermal decomposition of metal carbonyl can be applied.
このように、粒子サイズがナノサイズからなる硬磁性相と軟磁性相との複合構造からなる交換スプリング磁性粉末によれば、粒子自体がナノサイズの単結晶構造となっているため、後述の実施例の結果に示すように、飽和磁化向上のための軟磁性層の硬磁性相に対する体積比率を、保磁力の低下を起こすことなく、従来の２倍を超える１０倍まで増加させることが可能となったものである。 Thus, according to the exchange spring magnetic powder having a composite structure of a hard magnetic phase and a soft magnetic phase having a particle size of nano-size, the particle itself has a nano-size single crystal structure. As shown in the result of the example, the volume ratio of the soft magnetic layer for improving the saturation magnetization to the hard magnetic phase can be increased to 10 times, which is more than twice the conventional value, without causing a decrease in coercive force. It has become.
以下、上記の実施の形態に即した、本発明のナノサイズのＳｍＣｏ系交換スプリング磁性粉末の製造方法の実施例について比較例とともに説明する。 Hereinafter, examples of the method for producing nano-sized SmCo-based exchange spring magnetic powder of the present invention according to the above embodiment will be described together with comparative examples.
（実施例１〜４）
まず、サマリウムアセチルアセトナート水和物（［ＣＨ３ＣＯＣＨ＝Ｃ（Ｏ−）ＣＨ３］３Ｓｍ・ｘＨ２Ｏ）２２３．８ｍｇ（２．５ｍｍｏｌ）を、テトラエチレングリコール（ＨＯＣＨ２ＣＨ２ＯＣＨ２ＣＨ２ＯＨ）１００ｍｌに溶解させ、第１の溶液を作る。なお、以降この明細書では、サマリウムアセチルアセトナート水和物をＳｍ（ａｃａｃ）３・ｘＨ２Ｏ、テトラエチレングリコールをＴＥＧと表記する。
(Examples 1-4)
First, samarium acetylacetonate hydrate ([CH 3 COCH = C ( O-) CH 3] 3 Sm · xH 2 O) 223.8mg of (2.5 mmol), tetraethylene glycol (HOCH 2 CH 2 OCH 2 (CH 2 OH) is dissolved in 100 ml to make a first solution. Hereinafter, in this specification, samarium acetylacetonate hydrate will be referred to as Sm (acac) 3 .xH 2 O, and tetraethylene glycol as TEG.
次に、コバルトアセチルアセトナート（［ＣＨ３ＣＯＣＨ＝Ｃ（Ｏ−）ＣＨ３］３Ｃｏ）５３４．４ｍｇ（５．０ｍｍｏｌ）を、ＴＥＧ１００ｍｌに溶解させ、第２の溶液を作る。なお、以降この明細書では、コバルトアセチルアセトナートを、Ｃｏ（ａｃａｃ）３と表記する。 Next, 534.4 mg (5.0 mmol) of cobalt acetylacetonate ([CH 3 COCH═C (O—) CH 3 ] 3 Co) is dissolved in 100 ml of TEG to make a second solution. Hereinafter, in this specification, cobalt acetylacetonate is referred to as Co (acac) 3 .
また、ＴＥＧ１００ｍｌに、ポリ（Ｎ−ビニル−２−ピロリドン）、すなわち、（Ｃ６Ｈ９ＯＮ）ｎを２２２０．０ｍｇ（２０．０ｍｍｏｌ）溶解させ、第３の溶液を作る。なお、以降この明細書では、ポリ（Ｎ−ビニル−２−ピロリドン）をＰＶＰと表記する。 Further, 2220.0 mg (20.0 mmol) of poly (N-vinyl-2-pyrrolidone), that is, (C 6 H 9 ON) n, is dissolved in 100 ml of TEG to form a third solution. Hereinafter, in this specification, poly (N-vinyl-2-pyrrolidone) is referred to as PVP.
なお、ＰＶＰに代えて、他の親水性高分子（例えば、ポリアクリル酸、ポリマレイン酸、ポリグルタミン酸、およびそれらの塩、ビニルアルコール、ポリエチレングリコール、ポリプロピレングリコール、ポリアクリルアミド、ポリビニルアミン、ポリエチレンイミン、あるいはこれらの誘導体および共重合体）を使うことも可能である。 In place of PVP, other hydrophilic polymers (for example, polyacrylic acid, polymaleic acid, polyglutamic acid and salts thereof, vinyl alcohol, polyethylene glycol, polypropylene glycol, polyacrylamide, polyvinylamine, polyethyleneimine, or These derivatives and copolymers) can also be used.
つづいて、上記第１、第２の溶液および第３の溶液を所定量混合して反応溶液を作る。この際、好ましくは、上記第１の溶液と第２の溶液を、ＴＥＧ（例えば１００ｍｌのうちの２０ｍｌ）で洗い流しながら、反応容器に流し込んで第３の溶液に添加する。 Subsequently, a predetermined amount of the first, second and third solutions are mixed to form a reaction solution. At this time, preferably, the first solution and the second solution are poured into the reaction vessel while being washed away with TEG (for example, 20 ml of 100 ml) and added to the third solution.
ここで重要な点は、Ｓｍ（ａｃａｃ）３・ｘＨ２ＯとＣｏ（ａｃａｃ）３とＴＥＧを混合し、反応溶液を作ることである。そのため、上記第１の溶液と第２の溶液におけるＴＥＧの量はこの例における量である必要はない。ＰＶＰの量も同様に、本実施例に開示された量でなくてもよい。場合によっては、ＰＶＰの量をゼロにすることも可能である。すなわち、Ｓｍ（ａｃａｃ）３・ｘＨ２ＯとＣｏ（ａｃａｃ）３とＴＥＧとを直接的に混合して反応溶液を作ることも可能である。しかし、本実施例のように、第１と第２と第３の溶液をまず作って、これらを混合すると、反応溶液を早く確実に作ることができるという利点がある。 The important point here is that Sm (acac) 3 .xH 2 O, Co (acac) 3 and TEG are mixed to form a reaction solution. Therefore, the amount of TEG in the first solution and the second solution need not be the amount in this example. Similarly, the amount of PVP may not be the amount disclosed in this example. In some cases, the amount of PVP can be zero. That is, it is possible to directly mix Sm (acac) 3 .xH 2 O, Co (acac) 3 and TEG to make a reaction solution. However, as in this embodiment, the first, second and third solutions are first prepared and then mixed, so that there is an advantage that the reaction solution can be prepared quickly and reliably.
ここで、第１の溶液と第２の溶液を混合する際に、第１の溶液の比率が高いと、反応後にＳｍＣｏ５以外にＳｍＣｏ２等を生成し磁気特性が低下する。逆に、第２の溶液の比率が高いと、反応後にＳｍＣｏ５およびＣｏ以外にＳｍ２Ｃｏ１７を生成するため、飽和磁化は向上するものの、保磁力が大幅に低下してしまう。そこで、本発明の交換スプリング磁性粉末を実現するためには、硬磁性相は磁気異方性定数の大きなＳｍＣｏ５である必要があるため、第１の溶液と第２の溶液の混合比率は、Ｓｍ：Ｃｏ＝１：４〜８となるようにすることが好ましい。 Here, when the first solution and the second solution are mixed, if the ratio of the first solution is high, SmCo 2 or the like is generated in addition to SmCo 5 after the reaction, and the magnetic characteristics are deteriorated. On the other hand, if the ratio of the second solution is high, Sm 2 Co 17 is generated in addition to SmCo 5 and Co after the reaction, so that the saturation magnetization is improved, but the coercive force is greatly reduced. Therefore, in order to realize the exchange spring magnetic powder of the present invention, since the hard magnetic phase needs to be SmCo 5 having a large magnetic anisotropy constant, the mixing ratio of the first solution and the second solution is It is preferable that Sm: Co = 1: 4 to 8.
得られた反応溶液を約１２時間、攪拌・混合する。この際、マグネチックスターラ等の磁気で攪拌を行うものを用いると、生成した磁石粉が磁化されて、磁気凝集が発生し、攪拌や洗浄の際の再分散が困難になる場合があるため、メカニカルスターラの使用が好ましい。 The obtained reaction solution is stirred and mixed for about 12 hours. At this time, if a magnetic stirrer or the like that stirs magnetically is used, the generated magnet powder is magnetized, magnetic aggregation occurs, and redispersion during stirring and washing may be difficult. The use of a mechanical stirrer is preferred.
反応溶液には、Ｓｍ（ａｃａｃ）３・ｘＨ２Ｏの水和水を始めとした水分が含まれている。この水分を除去するため、不活性気体（例えば、窒素、アルゴン）気流下で、油浴を１１０℃に保ち約４０分間維持した後、真空ポンプにて１０Ｐａ以下まで減圧し、さらに３時間程度１１０℃維持して脱水処理することが好ましい。 The reaction solution contains water such as hydrated water of Sm (acac) 3 .xH 2 O. In order to remove this moisture, the oil bath is maintained at 110 ° C. for about 40 minutes under a stream of inert gas (for example, nitrogen or argon), and then the pressure is reduced to 10 Pa or less by a vacuum pump, and further about 110 hours. It is preferable to perform dehydration while maintaining the temperature.
つづいて、不活性気体（例えば、窒素、アルゴン）気流下で、油浴またはマントルヒータを用いて反応溶液を１５０〜３２０℃、好ましくは２５０〜２８０℃に保ち、１〜３時間加熱還流し、化学反応を起させる。これにより、ＳｍＣｏ系磁性微粒子が生成される。 Subsequently, the reaction solution is kept at 150 to 320 ° C., preferably 250 to 280 ° C. using an oil bath or a mantle heater under an inert gas (for example, nitrogen, argon) stream, and heated to reflux for 1 to 3 hours. Cause a chemical reaction. As a result, SmCo magnetic fine particles are generated.
この反応溶液を冷却した後、所定量の第２の溶液と必要に応じて第３の溶液を添加し、再度、（例えば、窒素、アルゴン）気流下で、油浴またはマントルヒータを用いて反応溶液を１５０〜３２０℃、好ましくは２５０〜２８０℃に保ち、１〜３時間加熱還流し、化学反応を起させる。これにより、ＳｍＣｏ系磁性微粒子とＣｏ微粒子の複合微粒子が生成される。反応が終わった後、溶液から溶媒を除き、固体粉末として生成物を得ることもできる。 After cooling this reaction solution, add a predetermined amount of the second solution and, if necessary, the third solution, and react again using an oil bath or mantle heater under a stream of air (for example, nitrogen, argon). The solution is kept at 150 to 320 ° C, preferably 250 to 280 ° C, and heated to reflux for 1 to 3 hours to cause a chemical reaction. Thereby, composite fine particles of SmCo magnetic fine particles and Co fine particles are generated. After the reaction is complete, the solvent can be removed from the solution to give the product as a solid powder.
固体粉末として生成物を得ることは、例えば、化学反応が終わった後、室温になるまで放置し、その後、ウルトラフィルタを用いて脱水エタノール等で溶液変換と粒子の洗浄を行い、さらに、エバポレータを用いて溶媒を留去し、最後に、４０℃温度で１２時間以上かけて真空乾燥させることにより、実現できる。 To obtain the product as a solid powder, for example, after the chemical reaction is completed, the product is allowed to stand until it reaches room temperature, and then the solution is converted with dehydrated ethanol or the like using an ultrafilter, and the particles are washed. It can be realized by distilling off the solvent and finally vacuum drying at 40 ° C. over 12 hours.
ここで、実施例１〜４では、それぞれ硬磁性相に対する軟磁性相の体積比率を異ならせ、実施例１では４倍、実施例２では６倍、実施例３では８倍、実施例４では１０倍としたものである。 Here, in Examples 1 to 4, the volume ratio of the soft magnetic phase to the hard magnetic phase is made different, 4 times in Example 1, 6 times in Example 2, 8 times in Example 3, and in Example 4. 10 times.
（比較例１〜２）
ＳｍおよびＣｏ原料をアーク溶解し、各種混合比のＳｍ−Ｃｏインゴットを作製した。得られたインゴットを再度加熱溶解し、周速３０ｍ／ｓｅｃで高速回転する水冷されたロール上に溶湯を噴出させ、急冷薄帯を作製した。得られた薄帯をスタンプミルで粉砕し、フレーク状にした後、結晶を析出させるために５００〜８００℃で１時間真空中熱処理した。熱処理したフレークをさらにアルゴン気流中のジェットミルで粉砕し、１０μｍ以下に粒度調整した。粉砕により得られた粒子に、必要に応じて、同様の急冷法によって作製したＣｏ微粒子を混合した。
(Comparative Examples 1-2)
Sm and Co raw materials were arc-melted to produce Sm-Co ingots with various mixing ratios. The obtained ingot was heated and melted again, and the molten metal was ejected onto a water-cooled roll that rotated at a high speed at a peripheral speed of 30 m / sec to produce a quenched ribbon. The obtained ribbon was pulverized with a stamp mill to form flakes, and then heat-treated in a vacuum at 500 to 800 ° C. for 1 hour in order to precipitate crystals. The heat-treated flakes were further pulverized by a jet mill in an argon stream to adjust the particle size to 10 μm or less. Co fine particles prepared by the same rapid cooling method were mixed with the particles obtained by pulverization, if necessary.
すなわち、比較例１〜２は、特許文献１に示される急冷薄帯の粉砕法により作製したものであり、硬磁性相に対する軟磁性相の体積比率を、比較例１では４倍、比較例２では６倍としたものである。 That is, Comparative Examples 1 and 2 were prepared by the quenching ribbon pulverization method shown in Patent Document 1, and the volume ratio of the soft magnetic phase to the hard magnetic phase was 4 times in Comparative Example 1, Comparative Example 2 Then, it is 6 times.
（比較例３〜４）
比較例３は、実施例方式において、硬磁性相のみ（硬磁性相に対する軟磁性相の体積比率が０）で作成したものである。比較例４は、実施例方式において、硬磁性相に対する軟磁性相の体積比率を２倍としたものである。
(Comparative Examples 3-4)
Comparative Example 3 was prepared using only the hard magnetic phase (the volume ratio of the soft magnetic phase to the hard magnetic phase is 0) in the example system. In Comparative Example 4, in the example system, the volume ratio of the soft magnetic phase to the hard magnetic phase is doubled.
（比較例５〜８）
比較例５〜８は、実施例方式において、硬磁性相を磁気異方性定数Ｋｕが２×１０６ｅｒｇ／ｃｍ３のＣｏＰｔＣｒとしたものである。
(Comparative Examples 5 to 8)
In Comparative Examples 5 to 8, the hard magnetic phase is CoPtCr having a magnetic anisotropy constant Ku of 2 × 10 6 erg / cm 3 in the embodiment method.
これらの実施例および比較例により得られた固体粉末の磁気特性（飽和磁化Ｍｓ、保磁力Ｈｃ）はＶＳＭで確認し、粉末の粒子サイズは、透過電子顕微鏡写真を計測することで求めた。結果を表１に示す。 The magnetic properties (saturation magnetization Ms, coercive force Hc) of the solid powders obtained in these examples and comparative examples were confirmed by VSM, and the particle size of the powder was determined by measuring a transmission electron micrograph. The results are shown in Table 1.
まず、表１に示す結果によれば、比較例１、２の場合、硬磁性相、軟磁性相それぞれの結晶径が小さくても粒子径が大きいと、飽和磁化Ｍｓは向上するが、保磁力Ｈｃが低下していることが分かる。また、比較例５〜８の場合によれば、硬磁性相の磁気異方性定数Ｋｕが小さいと、硬磁性相の粒子径が大きくならないと磁気特性が得られず、かつ、軟磁性相の体積比率を高くできないことが分かる。 First, according to the results shown in Table 1, in the case of Comparative Examples 1 and 2, the saturation magnetization Ms is improved when the particle diameter is large even if the crystal diameters of the hard magnetic phase and the soft magnetic phase are small, but the coercive force is increased. It turns out that Hc is falling. Further, according to the cases of Comparative Examples 5 to 8, if the magnetic anisotropy constant Ku of the hard magnetic phase is small, the magnetic properties cannot be obtained unless the particle diameter of the hard magnetic phase is increased, and the soft magnetic phase It can be seen that the volume ratio cannot be increased.
一方、硬磁性相の粒子径が結晶径とほぼ同じ２ｎｍ程度、軟磁性相の粒子径が結晶径とほぼ同じ８ｎｍ程度に作製された実施例１〜４および比較例３〜４の場合、室温での飽和磁化Ｍｓは、比較例３に示すＳｍＣｏ５合金のみの場合は８９ｅｍｕ／ｇであるのに対して、実施例１〜４に示すＳｍＣｏ５合金とＣｏとの複合微粒子の場合には１２５〜１３５ｅｍｕ／ｇと、５０％近く向上したものである。一方、保磁力Ｈｃは、比較例３に示すＳｍＣｏ５合金のみの場合は１０２０Ｏｅであるのに対して、実施例１〜４に示すＳｍＣｏ５合金とＣｏとの複合微粒子の場合には１０２２〜１０５２Ｏｅ程度であり、殆ど変化がみられなかったものである。つまり、硬磁性相に対する軟磁性相の体積比率を実施例１〜４のように４倍以上にしたときの保磁力Ｈｃが、硬磁性相自体の保磁力の９０％以上は確保されていることが分かる。なお、軟磁性相の体積比率が低い比較例４の場合も、比較例３の場合と同様に、飽和磁化Ｍｓが低いものとなっている。すなわち、実施例１〜４の場合、保磁力Ｈｃの低下なしに飽和磁化Ｍｓが向上していることから、本発明の磁石粉が交換スプリング磁石として作用してｓいることが確認できる。 On the other hand, in the case of Examples 1 to 4 and Comparative Examples 3 to 4 in which the particle diameter of the hard magnetic phase was approximately 2 nm, which is approximately the same as the crystal diameter, and the particle diameter of the soft magnetic phase was approximately 8 nm, which is approximately the same as the crystal diameter, The saturation magnetization Ms is 89 emu / g in the case of only the SmCo 5 alloy shown in Comparative Example 3, whereas it is 125 in the case of the composite fine particles of SmCo 5 alloy and Co shown in Examples 1 to 4. It is improved by nearly 50%, to ~ 135 emu / g. On the other hand, the coercive force Hc is 1020 Oe in the case of only the SmCo 5 alloy shown in Comparative Example 3, whereas it is 1022 to 1052 Oe in the case of the composite fine particles of SmCo 5 alloy and Co shown in Examples 1 to 4. The degree of change was almost unchanged. That is, 90% or more of the coercive force of the hard magnetic phase itself is secured when the volume ratio of the soft magnetic phase to the hard magnetic phase is four times or more as in Examples 1 to 4. I understand. In the case of Comparative Example 4 in which the volume ratio of the soft magnetic phase is low, the saturation magnetization Ms is low as in the case of Comparative Example 3. That is, in Examples 1 to 4, since the saturation magnetization Ms is improved without a decrease in the coercive force Hc, it can be confirmed that the magnet powder of the present invention is acting as an exchange spring magnet.
以上、本発明にかかるＳｍＣｏ系磁性微粒子とＣｏ微粒子との複合微粒子からなるＳｍＣｏ系交換スプリング磁性粉末の製造方法の好適な実施例を説明したが、本発明は、何ら上述の実施の形態や実施例に限定されず、特許請求の範囲に記載した本発明の技術的思想の範囲内において、種々の変形及び変更が可能であることは当然である。 The preferred embodiment of the method for producing the SmCo-based exchange spring magnetic powder composed of the composite fine particles of the SmCo-based magnetic fine particles and the Co fine particles according to the present invention has been described above. The present invention is not limited to the examples, and various modifications and changes are naturally possible within the scope of the technical idea of the present invention described in the claims.
例えば、上記反応で親水性高分子ＰＶＰに代えて、あるいは上記親水性高分子と共に、アルキル基やアリル基の付いたアミン類、カルボン酸類、フォスフィン類、フォスフィンオキシド類、アミド類、チオール類などの、低分子量配位子を用いることも可能である。なお、これらの高分子や低分子量配位子は、反応前に添加しても、あるいは、反応後に添加しても構わない。 For example, amines, carboxylic acids, phosphine, phosphine oxides, amides, thiols, etc. having an alkyl group or an allyl group instead of the hydrophilic polymer PVP in the above reaction or together with the hydrophilic polymer It is also possible to use a low molecular weight ligand. These polymers and low molecular weight ligands may be added before the reaction or after the reaction.
低分子量の配位子、例えば、オレイン酸１ｍｍｏｌとオレイルアミン１ｍｍｏｌを用いて、同様に反応処理し、ウルトラフィルタの代わりに、メタノールやエタノールで再沈処理により分離すると、固体粉末としてＳｍＣｏ合金ナノ粒子を得ることができる。このときの粒子径は３０ｎｍであり、保磁力は１５００Ｏｅであった。 When a low molecular weight ligand, for example, 1 mmol of oleic acid and 1 mmol of oleylamine, is similarly reacted and separated by reprecipitation treatment with methanol or ethanol instead of an ultrafilter, SmCo alloy nanoparticles are obtained as a solid powder. Obtainable. The particle size at this time was 30 nm, and the coercive force was 1500 Oe.
また、上記反応で、オレイン酸１ｍｍｏｌとオレイルアミン１ｍｍｏｌの代わりに、トリブチルフォスフィン１ｍｍｏｌとドデシルアミン１ｍｍｏｌを用いて処理すると、粒子径１２ｎｍのＳｍＣｏ合金ナノ粒子を得ることができた。このときの保磁力は１１５０Ｏｅであった。 Further, in the above reaction, when treated with 1 mmol of tributylphosphine and 1 mmol of dodecylamine instead of 1 mmol of oleic acid and 1 mmol of oleylamine, SmCo alloy nanoparticles having a particle diameter of 12 nm could be obtained. The coercive force at this time was 1150 Oe.
Claims (6)
前記硬磁性相と前記軟磁性相との各々の粒子サイズが、超常磁性臨界径より大きく単磁区臨界径以下であることを特徴とする交換スプリング磁性粉末。 In exchange spring magnetic powder consisting of a composite structure of hard magnetic phase and soft magnetic phase,
The exchange spring magnetic powder characterized in that the particle size of each of the hard magnetic phase and the soft magnetic phase is larger than the superparamagnetic critical diameter and smaller than the single domain critical diameter.
前記軟磁性相の粒子サイズが、８ｎｍより大きく５０ｎｍ以下であることを特徴とする請求項１に記載の交換スプリング磁性粉末。 The particle size of the hard magnetic phase is greater than 2 nm and less than or equal to 50 nm,
The exchange spring magnetic powder according to claim 1, wherein a particle size of the soft magnetic phase is greater than 8 nm and 50 nm or less.
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| JPH07263210A (en) * | 1994-03-18 | 1995-10-13 | Sumitomo Special Metals Co Ltd | Permanent magnet, alloy powder for permanent magnet and their production |
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| JP2006245313A (en) * | 2005-03-03 | 2006-09-14 | Tokyo Univ Of Science | METHOD OF MANUFACTURING SmCo-BASED MAGNETIC PARTICULATE |
| JP2006278470A (en) * | 2005-03-28 | 2006-10-12 | Toyota Motor Corp | Nano composite magnet |
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| JPS6163530A (en) * | 1984-09-03 | 1986-04-01 | Toyo Kohan Co Ltd | Production of hard magnetic material |
| JPH0356630A (en) * | 1989-07-26 | 1991-03-12 | Taiyo Yuden Co Ltd | Rare earth cobalt magnet and its manufacture |
| JPH07263210A (en) * | 1994-03-18 | 1995-10-13 | Sumitomo Special Metals Co Ltd | Permanent magnet, alloy powder for permanent magnet and their production |
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