JP4696191B2 - Permanent magnet with nanocomposite structure - Google Patents
Permanent magnet with nanocomposite structure Download PDFInfo
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- JP4696191B2 JP4696191B2 JP2000133201A JP2000133201A JP4696191B2 JP 4696191 B2 JP4696191 B2 JP 4696191B2 JP 2000133201 A JP2000133201 A JP 2000133201A JP 2000133201 A JP2000133201 A JP 2000133201A JP 4696191 B2 JP4696191 B2 JP 4696191B2
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0579—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B with exchange spin coupling between hard and soft nanophases, e.g. nanocomposite spring magnets
Description
【０００１】
【発明の属する技術分野】
本発明は、磁気特性に優れたナノコンポジット構造を有する永久磁石に関するものである。
【０００２】
【従来の技術】
従来永久磁石の磁気特性の改良は、強磁性体を構成する成分の選択、組合せ、その混合比率などを中心として行われてきたが、化学的組成のみならず、そのミクロ結晶構造も磁気特性に大きな影響を与えることが認識されつつある。
【０００３】
特公平7-78269号には、R（Yを含む希土類元素の一種以上）、Fe、Bを必須成分とし、格子定数のC0が約12Åの正方晶系の結晶構造を有する永久磁石用RFeB化合物であって、非磁性相により隔離されている永久磁石用RFeB正方晶化合物、或いはR、Fe、B及びA元素（Ti,Ni,Bi,V,Nb,Ta,Cr,Mo,W,Mn,Al,Sb,Ge,Sn,Zr,Hf,Cu,S,C,Ca,Mg,Si,O,及びP）を必須成分とし、格子定数のC0が約12Åの正方晶系の結晶構造を有する永久磁石用RFeBA化合物であって、非磁性相により隔離されている永久磁石用RFeBA正方晶化合物が開示され、上記正方晶化合物が適度な結晶粒径をもち、かつこの化合物を主相として、Rが多量に含まれた非磁性相が混在する微細組織が得られた場合に、永久磁石は特に良好な特性を示すと述べている。例えば、その実施例２によると、8at%B、15at%Nd、残部Fe合金を粉砕して平均粒度3μｍの粉末を作成し、この粉末を2t/cm2の圧力で10kOeの磁場中でプレスし2＊10-1TorrのAr中で1100℃で１時間焼結することにより、Br＝12.1kG、Hc＝9.3kOe、(BH)max＝34MGOeの永久磁石を得ている。この焼結体の主相は正方晶化合物であり、格子定数はA08.80Å、C012.23Åで、主相は体積比でFe、B及びNdを同時に含み90.5％を占め、主相の粒界相を成す、すなわち正方晶化合物を隔離する非磁性相の中、Ｒを80％以上含む非磁性化合物相は体積比4％で、残りはほとんど酸化物とポアであったと記載されている。
【０００４】
特開平11-307327号には、格子定数A0が約8.8Å、格子定数C0が約12Åの正方晶系の結晶構造を有するRFeB化合物又はRFeCoB化合物（但しＲは希土類元素の一種以上）の微結晶が、立方晶系の結晶構造を有するネオジム酸化物の微結晶とエピタキシャルに接合され、配向している複合体である永久磁石用組成物が開示されている。例えば、その実施例１によると、Feの一部がCoで置換され、またNdの一部がPrで置換された、基本的にNd2Fe14Bの組成に相当する原料の粗粉砕物100重量部とZn粗粉砕物1重量部とを、1容量％の酸素を含有するアルゴンガスを流通させながら水分100ppmを含むトルエン中で混合し粉砕して平均粒径2μの微粉砕物としたのちO2を含まないアルゴンガス気流中で乾燥し、この乾燥粉末を2t/cm２の圧力で30kOeの磁場中でプレスし、1.5Torrのアルゴンガス中、1080℃で１時間焼結することにより得られた永久磁石は、格子定数A0が約8.8Å、格子定数C0が約12Åの正方晶系の結晶構造を有するRFeCoB化合物の微結晶が、立方晶系の結晶構造を有するNd2O3の微結晶とエピタキシャルに接合され配向している複合体で、この磁石の磁気特性は、Br＝15.9kG、Hc＝6.99kOe、(BH)max＝55.9MGOeであったと記載されている。
【０００５】
【発明が解決しようとする課題】
本発明者らは、永久磁石について検討を重ねた結果、ナノメータースケールでの微細構造が磁気特性に大きな影響を与えることを見出し、本発明を完成するに至った。本発明は、強磁性体の潜在的特性を十分に発揮した優れた磁気特性を有する永久磁石を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明にかかわる永久磁石は、強磁性相の結晶粒の粒界に非磁性相が薄膜状又は粒子状で存在すると共に、強磁性相の結晶粒内に非磁性相がナノメータースケールの粒子状で存在するナノコンポジット構造を有することを特徴とする。
【０００７】
本発明は、正方晶構造を有するRFeB化合物又はRFeCoB化合物（但しRは希土類元素の一種以上）を主相とする永久磁石の微細構造についての研究過程で見出されたものである。しかし本発明の発明思想、即ちナノコンポジット構造とすることにより強磁性体の磁気特性を向上させるという発明思想は、他種の強磁性体についても適用されるものである。
【０００８】
【発明の実施の形態】
以下、強磁性相が正方晶構造を有するRFeB化合物又はRFeCoB化合物（但しRは希土類元素の一種以上）である場合を代表例として具体的に説明する。
【０００９】
【実施例１】
アルゴン雰囲気中で構成元素をストリップ鋳造することにより薄片状の強磁性物質Nd2.5Pr0.25Fe9Co2.5B4M0.13(M:微量金属元素)を調製した。ネオジム酸化物(NdOx, x=1.0-1.5)を局部的に析出させるため、平均粒径100nmの亜鉛微粉末O.1重量％を上記強磁性物質と混合し、直径5mmのZrO2ボールを用いてトルエン中でボールミル粉砕した。得られた平均粒径2.5μmの混合粉末を1.59MA/m (2T)の磁場中で整列させ、整列方向に直角に8MPaの圧力でプレスした。50＊40＊30mmブロックの素材は、最初真空中で3時間、次いでArガス中で5時間、900から1000℃で加熱焼成した。焼結サンプルは、300から1000℃で焼鈍し、それから急速に冷却した。
【００１０】
焼結サンプルのキュリー温度は振動サンプル磁力計(VSM)を用いて測定した。焼結サンプルの磁気配向方向に平行に1.59MA/m (2T)の磁界をかけた。焼結サンプルの磁気特性は、5.57MA/m(7T)のパルス磁場中で磁化した後、B-Hトレーサを用いて測定された減磁曲線から算出した。この測定のために10＊10＊10mmブロックのサンプルが用いられた。また、焼結した磁石の磁気特性は、フロリダ州大学のナショナル高磁場研究所で、最高15.9MA/m(20T)までの極めて高い磁場において、直径4mmの球形のサンプルを使ってVSM方法により評価された。上記磁気特性測定の補正のための標準サンプルとして、ニッケル金属(ASTM標準A 894089)を用いた。相識別はエックス線回折分析により行われた。マイクロ／ナノ構造は、主に、高解像度トランスミッション電子顕微鏡(TEM)及びナノ証明エネルギー分散エックス線分光計(EDX)によって調査された。ヴィッカース硬度及び３ポイント曲げ強度は、酸化抵抗と同様に、従来の方法により測定された。
【００１１】
焼結磁石の密度は、組成及び焼結条件に応じて7.56gから7.68g/cm3であった。強磁性相の平均粒径は、およそ10μmであった。エックス線回折分析により、焼結サンプルは主にNd2Fel4B正方晶及びNd203立方晶の相により構成されており、非磁性のNdFe4B4相の痕跡を示すことが明らかにされた。
【００１２】
EDXアナライザーによるTEMの観察結果は、微量のFe及びCoを含むNdOx(x=1.3-1.5)がマトリックス粒子の粒界及び／又は粒内に存在していることを示している。図１，２，３に見られるように、粒界はアモルファス及び／又はナノ結晶のNdOx相により構成されていた。これらの粒界NdOx物質は、高温で長時間の熱処理により亜鉛含有量が減少するにつれて、図４に示すように、部分的に結晶化した。直径約10nmから100nmの粒内結晶NdOxの分散物もまた、図４に示すように、マトリックス粒子内で識別された。
【００１３】
ZnOは、空気中でさえ、800から1200℃で、以下の平衡方程式に従って、Znと02に分解することが報告されている。
ZnO(s)←→Zn(g)+1/202 (1)
【００１４】
従って、焼結ナノコンポジット磁石中で識別されたNdOxの生成は、900℃から1100℃の温度範囲で焼成中にNd2Fel4B粉末とZnOからの酸素との選択的な表面化学反応に起因するものと考えられる。この反応により生じたZn金属は焼結の間に徐々に昇華する。
【００１５】
図５は、5.57MA/m(7T)でパルス磁化されたNd2.5Pr0.25Fe9Co2.5B4M0.13-NdOxナノコンポジット磁石(NSK 60)の第２象限の減磁曲線を示す。図６に示すように、この磁石の磁気ヒステリシス曲線も1.59MN/m(20T)までの高い磁場においてVSM方法で測定された。これらの測定結果の重要な違いは、ループのへこんだ肩である。このへこんだ肩は、磁気的ハード及びソフト相からなるナノコンポジット磁石に関して予測されることである。
【００１６】
図７に示されるように、この磁石の酸化抵抗は、市販のNd2Fel4B磁石より優れていることが確認された。Nd2Fel4Bの粒界にNdOx層を有するナノコンポジット構造から予期できるように、02雰囲気中500℃、７時間で形成されるFe203ベースの酸化物層の重量増加は市販のNd2Fel4B磁石の24分の1であった。Nd2.5Pr0.25Fe9Co2.5B4M0.13-NdOxナノコンポジット磁石(NSK 60)のヴィッカース硬度と破壊強度は、それぞれ7.1GPa及び330MPaであった。これらの値は、市販のNd2Fel4Bベースの磁石の6GPa及び245MPaよりずっと高い。
【００１７】
この磁石の重要な特性は、Nd2Fel4Bベースの磁石について世界記録として報告された新しいデータを含む表１に要約される。この表から、この磁石の特性は、これまで報告されたデータに比べて、特に(BH)max及びキュリー温度に関してずっと高いことが明らかである。この磁石の(BH)max値は、Nd2Fel4B単結晶に関する理論値(64 MGOe)とほとんど等しいか、又は少し高い。そして、キュリー温度はこれまで報告されたデータに比べて1.6倍高く、磁気特性の温度係数が優れていることを示す。Nd2Fel4Bベースの焼結磁石の高いエネルギー積(BH)max値を達成するために、以下の４つのファクターが非常に重要であることは広く認められている：1)組成の最適化、2)小さく、狭い粒径分布、3)より高度の結晶整列及び4)酸素含有量の減少。最後のファクターは最も重要であると信じられている。それにもかかわらず、この磁石の磁気特性は、報告されたデータより優れている。
【００１８】
【表１】
しかし、上記のように、この磁石では非磁性のNdOxが意図的に粒界及び粒内に組み込まれる。セラミック／セラミックナノコンポジット、特にAl203/SiC及びMgO/SiCコンポジットシステムに関する知見に基づくと、Nd2Fel4B粒子内及び／又は粒界に位置するNdOxのまわりで、２つの相の間に不均一な熱膨張に基づく極めて局地的な残留応力が生じる。この局地的な応力がこの磁石の磁気特性の改良に大きな役割を演じているのであろう。ZnOの添加もまた、この改良に重要である。なぜなら、焼結の間に方程式(1)に従ってZnOの分解によって形成されたZn金属の昇華は、Nd2Fel4B粒子をきれいにすることができるからである。
【００２０】
【発明の効果】
顕著に高められた磁気特性、酸化抵抗、及び機械的性質に基づき、新しく開発されたナノコンポジット磁石は強いインパクトを様々な技術分野に与える。
【図面の簡単な説明】
【図１】ナノコンポジット磁石のTEM観察結果を示す写真である。
【図２】ナノコンポジット磁石のTEM観察結果を示す写真である。
【図３】ナノコンポジット磁石のTEM観察結果を示す写真である。
【図４】ナノコンポジット磁石のTEM観察結果を示す写真である。
【図５】ナノコンポジット磁石の第２象限の減磁曲線である。
【図６】ナノコンポジット磁石の磁気ヒステリシス曲線である。
【図７】ナノコンポジット磁石と市販のNd2Fel4B磁石の酸化抵抗を比較した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet having a nanocomposite structure with excellent magnetic properties.
[0002]
[Prior art]
Conventionally, improvement of the magnetic properties of permanent magnets has been focused on the selection, combination, and mixing ratio of the components that make up a ferromagnetic material. However, not only the chemical composition but also the microcrystalline structure has become a magnetic property. It is being recognized that it will have a major impact.
[0003]
Japanese Patent Publication No. 7-78269 describes RFeB for permanent magnets having a tetragonal crystal structure having R (one or more rare earth elements including Y), Fe, and B as essential components and a lattice constant C 0 of about 12%. RFeB tetragonal compound for permanent magnets separated by non-magnetic phase, or R, Fe, B and A elements (Ti, Ni, Bi, V, Nb, Ta, Cr, Mo, W, Mn , Al, Sb, Ge, Sn , Zr, Hf, Cu, S, C, Ca, Mg, Si, O, and P) and the essential components, the crystal structure of the tetragonal C 0 of about 12Å lattice constant A permanent magnet RFeBA tetragonal compound isolated by a non-magnetic phase is disclosed, and the tetragonal compound has an appropriate crystal grain size, and this compound is used as a main phase. It is stated that permanent magnets exhibit particularly good characteristics when a microstructure in which a nonmagnetic phase containing a large amount of R is mixed is obtained. For example, according to Example 2, 8 at% B, 15 at% Nd, and the remaining Fe alloy were pulverized to produce a powder having an average particle size of 3 μm, and this powder was pressed in a magnetic field of 10 kOe at a pressure of 2 t / cm 2. By sintering at 1100 ° C. for 1 hour in Ar of 2 * 10 −1 Torr, a permanent magnet with Br = 12.1 kG, Hc = 9.3 kOe, (BH) max = 34 MGOe is obtained. The main phase of this sintered body is a tetragonal compound, the lattice constants are A 0 8.80%, C 0 12.23%, the main phase contains Fe, B and Nd at a volume ratio of 90.5%, It is described that among the nonmagnetic phases forming the grain boundary phase, that is, isolating the tetragonal compound, the nonmagnetic compound phase containing 80% or more of R has a volume ratio of 4%, and the rest are mostly oxides and pores. .
[0004]
JP-A-11-307327 discloses an RFeB compound or RFeCoB compound having a tetragonal crystal structure with a lattice constant A 0 of about 8.8% and a lattice constant C 0 of about 12% (where R is one or more of rare earth elements). A composition for a permanent magnet is disclosed which is a complex in which microcrystals are epitaxially bonded and oriented with microcrystals of neodymium oxide having a cubic crystal structure. For example, according to Example 1, a coarsely pulverized material 100 basically corresponding to the composition of Nd 2 Fe 14 B, in which part of Fe is substituted with Co and part of Nd is substituted with Pr. Part by weight and 1 part by weight of Zn coarsely pulverized product were mixed and pulverized in toluene containing 100 ppm of water while circulating argon gas containing 1% by volume of oxygen to obtain a finely pulverized product having an average particle size of 2μ. It was obtained by drying in an argon gas stream containing no O 2 , pressing this dry powder in a magnetic field of 30 kOe at a pressure of 2 t / cm 2 , and sintering at 1080 ° C. for 1 hour in an argon gas of 1.5 Torr. In the obtained permanent magnet, a microcrystal of RFeCoB compound having a tetragonal crystal structure having a lattice constant A 0 of about 8.8Å and a lattice constant C 0 of about 12Å is formed of Nd 2 O 3 having a cubic crystal structure. The magnetic properties of this magnet are Br = 15.9kG, Hc = 6.99kOe, (BH) max. It has been described as an which was 55.9MGOe.
[0005]
[Problems to be solved by the invention]
As a result of repeated investigations on permanent magnets, the present inventors have found that a fine structure on the nanometer scale has a great influence on magnetic properties, and have completed the present invention. An object of this invention is to provide the permanent magnet which has the outstanding magnetic characteristic which fully exhibited the latent characteristic of the ferromagnetic material.
[0006]
[Means for Solving the Problems]
In the permanent magnet according to the present invention, the nonmagnetic phase is present in the form of a thin film or particles at the grain boundaries of the ferromagnetic phase grains, and the nonmagnetic phase is in the form of nanometer scale grains within the ferromagnetic phase grains. It has the nanocomposite structure which exists in.
[0007]
The present invention has been found in the course of research on the microstructure of permanent magnets whose main phase is an RFeB compound or RFeCoB compound having a tetragonal structure (where R is one or more of rare earth elements). However, the inventive idea of the present invention, that is, the inventive idea of improving the magnetic properties of a ferromagnetic material by adopting a nanocomposite structure is also applicable to other types of ferromagnetic materials.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the case where the ferromagnetic phase is an RFeB compound or an RFeCoB compound having a tetragonal crystal structure (where R is one or more of rare earth elements) will be specifically described as a representative example.
[0009]
[Example 1]
A flaky ferromagnetic material Nd 2.5 Pr 0.25 Fe 9 Co 2.5 B 4 M 0.13 (M: trace metal element) was prepared by strip casting the constituent elements in an argon atmosphere. In order to precipitate neodymium oxide (NdOx, x = 1.0-1.5) locally, 0.1% by weight of zinc fine powder with an average particle size of 100 nm is mixed with the above ferromagnetic material, and ZrO 2 balls with a diameter of 5 mm are used. And ball milled in toluene. The obtained mixed powder having an average particle diameter of 2.5 μm was aligned in a magnetic field of 1.59 MA / m (2T) and pressed at a pressure of 8 MPa perpendicular to the alignment direction. The material of the 50 * 40 * 30 mm block was first heated and fired at 900 to 1000 ° C. in vacuum for 3 hours and then in Ar gas for 5 hours. The sintered sample was annealed at 300 to 1000 ° C. and then cooled rapidly.
[0010]
The Curie temperature of the sintered sample was measured using a vibrating sample magnetometer (VSM). A magnetic field of 1.59 MA / m (2T) was applied parallel to the magnetic orientation direction of the sintered sample. The magnetic properties of the sintered samples were calculated from demagnetization curves measured using a BH tracer after being magnetized in a 5.57 MA / m (7T) pulsed magnetic field. A 10 * 10 * 10 mm block sample was used for this measurement. In addition, the magnetic properties of sintered magnets were evaluated by the VSM method using a 4 mm diameter spherical sample at the National High Magnetic Field Laboratory at the University of Florida at extremely high magnetic fields up to 15.9 MA / m (20T). It was done. Nickel metal (ASTM standard A 894089) was used as a standard sample for correction of the magnetic property measurement. Phase discrimination was performed by X-ray diffraction analysis. Micro / nanostructures were mainly investigated by high resolution transmission electron microscope (TEM) and nano-proof energy dispersive x-ray spectrometer (EDX). Vickers hardness and 3-point bending strength were measured by conventional methods, as was oxidation resistance.
[0011]
The density of the sintered magnet was 7.56 g to 7.68 g / cm 3 depending on the composition and sintering conditions. The average particle size of the ferromagnetic phase was approximately 10 μm. The X-ray diffraction analysis, the sintered samples are mainly Nd 2 Fe l4 B tetragonal Akiraoyobi
[0012]
The observation result of TEM by the EDX analyzer indicates that NdO x (x = 1.3-1.5) containing a trace amount of Fe and Co is present in the grain boundaries and / or grains of the matrix particles. As can be seen in FIGS. 1, 2 and 3, the grain boundaries were composed of amorphous and / or nanocrystalline NdOx phases. These grain boundary NdOx substances were partially crystallized as shown in FIG. 4 as the zinc content decreased by heat treatment at high temperature for a long time. A dispersion of intragranular crystalline NdOx having a diameter of about 10 nm to 100 nm was also identified within the matrix particles, as shown in FIG.
[0013]
ZnO has been reported to decompose into Zn and 0 2 at 800 to 1200 ° C, even in air, according to the following equilibrium equation.
ZnO (s) ← → Zn (g) +1/20 2 (1)
[0014]
Thus, the formation of NdOx identified in sintered nanocomposite magnets is due to the selective surface chemical reaction of Nd 2 Fe l4 B powder with oxygen from ZnO during firing in the temperature range of 900 ° C to 1100 ° C. It is thought to do. Zn metal produced by this reaction gradually sublimates during sintering.
[0015]
FIG. 5 shows the demagnetization curve in the second quadrant of a Nd 2.5 Pr 0.25 Fe 9 Co 2.5 B 4 M 0.13 —NdO x nanocomposite magnet (NSK 60) pulsed at 5.57 MA / m (7T). As shown in FIG. 6, the magnetic hysteresis curve of this magnet was also measured by the VSM method in a high magnetic field up to 1.59 MN / m (20 T). An important difference between these measurements is the looped shoulder. This concave shoulder is what is expected for a nanocomposite magnet consisting of a magnetic hard and soft phase.
[0016]
As shown in FIG. 7, it was confirmed that the oxidation resistance of this magnet was superior to that of a commercially available Nd 2 Fe l4 B magnet. As can be expected from a nanocomposite structure having NdOx layer at the grain boundaries of the Nd 2 Fe l4 B, 0 2
[0017]
The important properties of this magnet are summarized in Table 1, which contains new data reported as a world record for Nd 2 Fe l4 B based magnets. From this table it is clear that the properties of this magnet are much higher, especially with respect to (BH) max and Curie temperature, compared to the data reported so far. (BH) max value of this magnet, Nd 2 Fe l4 theory regarding B single crystal (64 MGOe) and little or equal, or slightly higher. The Curie temperature is 1.6 times higher than the data reported so far, indicating that the temperature coefficient of magnetic properties is excellent. In order to achieve high energy product (BH) max values for Nd 2 Fe l4 B-based sintered magnets, it is widely recognized that the following four factors are very important: 1) Composition optimization 2) small and narrow particle size distribution, 3) higher crystal alignment and 4) reduced oxygen content. The last factor is believed to be the most important. Nevertheless, the magnetic properties of this magnet are superior to the reported data.
[0018]
[Table 1]
However, as described above, in this magnet, nonmagnetic NdOx is intentionally incorporated in the grain boundaries and grains. Ceramic / ceramic nanocomposites, especially based on the knowledge of
[0020]
【The invention's effect】
Based on significantly enhanced magnetic properties, oxidation resistance, and mechanical properties, newly developed nanocomposite magnets have a strong impact on various technical fields.
[Brief description of the drawings]
FIG. 1 is a photograph showing a TEM observation result of a nanocomposite magnet.
FIG. 2 is a photograph showing a TEM observation result of a nanocomposite magnet.
FIG. 3 is a photograph showing a TEM observation result of a nanocomposite magnet.
FIG. 4 is a photograph showing a TEM observation result of a nanocomposite magnet.
FIG. 5 is a demagnetization curve in the second quadrant of the nanocomposite magnet.
FIG. 6 is a magnetic hysteresis curve of a nanocomposite magnet.
FIG. 7 is a diagram comparing the oxidation resistance of a nanocomposite magnet and a commercially available Nd 2 Fe l4 B magnet.
Claims (2)
前記強磁性相が正方晶構造を有するRFeB化合物又はRFeCoB化合物（但しRは希土類元素の一種以上）よりなる、
永久磁石。It has a nanocomposite structure in which the nonmagnetic phase exists in the form of thin films or particles at the grain boundaries of the ferromagnetic phase grains, and the nonmagnetic phase exists in the nanometer scale grains within the ferromagnetic phase grains. A permanent magnet,
The ferromagnetic phase is composed of an RFeB compound or an RFeCoB compound having a tetragonal crystal structure (where R is one or more of rare earth elements),
permanent magnet.
The permanent magnet according to claim 1, wherein R is Nd.
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