JP2005243884A - Rare earth permanent magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet exhibiting a pinning type initial magnetization curve in which microstructure is not observed but uniform structure is observed. <P>SOLUTION: The permanent magnet contains a magnetic intermetallic compound composed of R which is one kind or more of rare earth elements including Y, T which are two kinds or more of transition metal elements principally comprising Fe and Co, and inevitable impurities. In the magnetic intermetallic compound, T is 6-14 when R is set at 1, the crystalline anisotropy energy of the magnetic intermetallic compound is 1 MJ/m<SP>3</SP>or larger, and a Curie point is 100°C or higher. The magnetic intermetallic compound is composed of particles having a mean grain size of 3 μm or larger in which the structure is substantially uniform, and an initial magnetization curve imparts a pinning type. Furthermore, the magnetic intermetallic compound has TbCu<SB>7</SB>type structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rare earth permanent magnet, and more particularly to a rare earth permanent magnet having a homogeneous structure. The rare earth permanent magnet according to the present invention can be suitably used for electronic equipment, motors and actuators for electrical equipment, synchronous motors requiring heat resistance, position sensors for electrical equipment, rotation sensors, and the like.

2-17 type Sm-Co magnets (typical structure; Sm (CoFeCuT) _7.5 , T = Zr, Ti, etc.) exhibit high magnetic properties, good temperature properties, and corrosion resistance, and are widely used with NdFeB magnets. It is a rare earth magnet.

  The 2-17 type Sm-Co type magnet shows a domain wall pinning type coercive force mechanism (FIG. 1a), and a 1-5 type Sm-Co type magnet or NdFeB type magnet showing a nucleation growth type coercive force mechanism (FIG. 1b) Have different coercivity mechanisms. A domain wall pinning type magnet is one in which the magnetic moment of one phase separated into two phases is pinned everywhere in the domain wall with the finely precipitated phase, so the domain wall is moved unless a magnetic field of a certain level or more is applied. For this reason, it refers to a type of magnet that provides a large coercive force. The characteristic appears in the initial magnetization curve as shown in FIG. If an external magnetic field (H) above a certain level is not applied, the magnetization (M) does not increase, and an initial magnetization curve that suddenly approaches saturation when the magnetization begins to increase is shown.

As shown in the photograph of FIG. 2, the 2-17 type Sm—Co magnet is a two-phase separation in which the Cu-rich Sm (CoCuFe) ₅ grain boundary phase and the Fe-rich Sm ₂ (CoFeCu) ₁₇ phase have coherency. Has a fine structure. Although the size of the microstructure varies depending on the composition, the size of the 2-17 phase is approximately several tens of nm to 300 nm, and the size of the 1-5 boundary phase that divides it is approximately 10 nm or less. From the Lorentz electron microscope (Lorentz TEM) observation of the magnet, it is known that the domain wall exists in the 1-5 phase.

Since there is a difference in the domain wall energy between this observation result and the 1-5 phase / 2-17 phase, the domain wall is pinned to the 1-5 phase by the difference in the domain wall energy of the 1-5 phase / 2-17 phase. In general, the following equation is used to estimate the magnitude of the coercive force Hci.
Hci = (γ _2-17 −γ _1-5 ) / Msδ
(Γ: domain wall energy, Ms: saturation magnetization of domain wall, δ: domain wall width)

  The domain wall pinning cannot be eliminated unless a magnetic field is applied from the outside by a value corresponding to the difference in domain wall energy. This corresponds to the coercive force. Therefore, according to the conventional interpretation, in the domain wall pinning type coercive force mechanism, the separation of the structure, the heterogeneous structure, and the impurity precipitation that cause the difference in domain wall energy and the domain wall energy are indispensable. It has been thought that can not be obtained. In the above 2-17 type Sm-Co magnet, it is generally considered that it is realized by two-phase separation of 2-17 phase and 1-5 phase.

However, Sm (CoCu) ₅ , Ce (CoCo) _5, and Ce (CoFeCu) ₅ magnets are 2-17 type Sm—Co based magnets in contrast to the general recognition of the pinning type coercive force as described above. Similarly, although the initial magnetization curve shows a pinning type characteristic, a clear two-phase separated structure is not observed. Even in some observations using a transmission electron microscope (TEM), no two-phase separated structure has been found.

On the other hand, Lectard et al. Show a concentration fluctuation of 10 nm or less, that is, a state in which Co-rich Sm (CoCu) ₅ and Cu-rich Sm (CoCu) ₅ are finely fluctuated, and the crystal structure is the same and a little. It is speculated that a domain wall pinning may be caused by a state in which a two-phase separation structure is not observed because only the lattice constant is different (see Non-Patent Document 1). This assumption for the pinning coercivity is based on the idea that the difference in domain wall energy due to concentration fluctuations is the origin of the pinning coercivity, although the two-phase separated structure is not the origin of the coercivity. This is the same as the conventional way of thinking.
E. Lectard, CH Allibert, J. Applied Physics, 75, (1994), 6277 XY Xiong, K. Hono, K. Ohashi and Y. Tawara, Proc. 17th Int. Workshop on RE Magnets and Their Applications, (2002), 893 GT Trammell Physical Review, 131, (1963), p932

  For the 1-5 type SmCo magnet added with Cu, the Takano group including the present inventor analyzed the fluctuation of the microstructure and the element concentration in the region of 10 nm or less by the three-dimensional atom probe method (Non-patent Document 2). reference). The analysis method is a powerful analysis capable of elemental analysis and distribution reconstruction including spatial distribution by applying high voltage to the tip of a magnet needle sample and stripping each element one by one. This method is superior in spatial resolution to TEM observation. Therefore, according to the analysis method, even if there is a concentration fluctuation of an element of 10 nm or less, it should be observable. However, although the concentration distribution of Co and Cu was examined in detail by the analysis means, no clear concentration fluctuation was found even at the atomic level. From this analysis result, the present inventor has reached the view that a pinning-type coercive force mechanism can occur even in an essentially homogeneous structure.

An intrinsic pinning mechanism is known as a mechanism capable of obtaining a coercive force regardless of two-phase separation or precipitates. In this mechanism, a thin magnetic wall is pinned everywhere due to the difference in the atom order spin arrangement, and a holding force is generated. For example, in Dy ₃ Al ₂ , Liq. A coercive force of 20 kOe has been reported at a He temperature (4.2 K) (see Non-Patent Document 3). In Sm (Co _0.5 Cu _0.5 ) ₅ and Sm (CoNi _0.4 ) ₅ , Liq. A high coercive force of 30 to 40 kOe is obtained at a He temperature (4.2 K). However, the coercive force due to intrinsic pinning varies greatly with temperature, and this coercive force rapidly decreases as the temperature rises.

  From these measurement results, it is thought that it is difficult to maintain a significant coercive force up to room temperature with conventional coercive force based on intrinsic pinning, and the coercive force mechanism is a phenomenon of only a low temperature that can realize a thin domain wall width. Therefore, it was thought that it could not be applied to practical magnets used at room temperature or higher. However, quantitatively, how much the domain wall width is judged to be thin, how much crystal magnetic anisotropy is judged to be sufficiently high, and the magnitude of the temperature change of the coercive force is a low Curie point. Whether or not it is a problem of intrinsic intrinsic pinning due to the above has not yet been clarified.

  An object of the present invention is to provide a permanent magnet that shows a pinning-type initial magnetization curve, which is a magnet that does not have a fine structure and looks like a uniform structure.

The present invention is based on the Sm (CoCu) analysis of the present inventors for _5, homogeneous microstructure and essentially no concentration fluctuations (in but nm or more) in the rare earth magnet, Sm (CoCu) ₅ magnets In addition, the inventors have found and invented a rare earth magnet having a pinning type coercive force mechanism.

Specifically, according to the present invention, a magnetic metal comprising R which is one or more of rare earth elements including Y, two or more transition metal elements T mainly composed of Fe and Co, and unavoidable impurities. A permanent magnet including an intermetallic compound, wherein the magnetic intermetallic compound has an atomic ratio of R of 1, T is 6 to 14, and the magnetic intermetallic compound has a magnetocrystalline anisotropy energy of 1 MJ / M ³ or more, the Curie point of the magnetic intermetallic compound is 100 ° C. or higher, the magnetic intermetallic compound is a particle having an average particle diameter of 3 μm or more, and the magnetic intermetallic compound is substantially uniform in structure. A rare earth permanent magnet is provided in which the initial magnetization curve has a pinning structure and the magnetic intermetallic compound has a TbCu ₇ structure.

  As will be described in detail below, according to the present invention, there is provided a permanent magnet that shows a pinning-type initial magnetization curve, which is a magnet that does not have a fine structure and looks like a uniform structure. Since the two-phase separated structure as described in the background is formed by complicated heat treatment, it cannot be produced only by sintering. On the other hand, according to the present invention, since the permanent magnet can be configured with a homogeneous structure having no fine structure, the magnet can be manufactured by a relatively simple process without requiring a complicated heat treatment. In addition, when a permanent magnet can be configured with a homogeneous structure having no fine structure, a magnet having a small coercive force temperature change can be obtained because the holding force mechanism of the homogeneous magnet is a pinning mechanism.

  The present invention finds that a rare earth magnet having a homogeneous structure and no microstructure can be developed as a magnet having a pinning type coercive force mechanism, and invents a permanent magnet as a model thereof. Details are described below.

As described above, the Sm (Co _1-x Cu _x ) ₅ alloy (0 <x <0.5) does not show a two-phase separation structure even when TEM observation is performed (FIG. 3). Although fluctuations in the concentration of Co and Cu were not observed, it was thought that they could not be observed because the atomic numbers were close. Therefore, the inventor tried to observe Co / Cu concentration fluctuations by performing element mapping in the atom order using a three-dimensional atom probe apparatus. The basic structure of the 3D atom probe device is the same as that of Field Ion Microscopy (FIM). By applying a high electric field to the sample to be measured with a sharp tip, the atoms are peeled off from the tip, and then the mass spectrometer Or, it is an instrument that measures the element distribution in the three-dimensional real space in the atom order by applying to the two-dimensional PSD (Position Sensitive Detector) by the TOF method.

  In the 2-17 Sm-Co magnet, the domain wall is pinned to the 1-5 phase by the difference in domain wall energy between the two phases (1-5 phase / 2-17 phase in the 2-17 Sm-Co system) ( Conventionally, it was considered as shown in FIG. However, the conventional explanation is inconsistent. This is because the 1-5 boundary phase has much larger magnetocrystalline anisotropy than the 2-17 main phase, and even if the Cu site is replaced by Cu and its concentration is increased, the measured Cu The reversal of magnetocrystalline anisotropy cannot occur with the amount (about 20 atomic%). Nevertheless, from Lorentz TEM observation, it appears that the domain wall is pinned to the 1-5 phase. In the “domain wall energy difference model” regarding the coercive force, the domain wall should be pinned to a phase having a low domain wall energy, and therefore should be originally pinned to the 2-17 phase.

  The conventional model has the above-described contradiction. However, if the domain wall is considered to be intrinsic pinned in the 1-5 boundary phase, this contradiction is resolved. However, the 1-5 boundary phase in the 2-17Sm-Co magnet has only a very narrow width of 5 nm or less, and this hypothesis cannot be supported by actual measurement.

  Regarding the mechanism in which the domain wall is pinned despite the structure and fluctuation that impede the movement of the domain wall at first glance, the present inventor has shown that the coercive force mechanism called intrinsic pinning has the coercive force of the 1-5 Sm-Co based magnet. I think I can explain. When the domain wall is very thin, the spin rotation inside the domain wall can no longer be handled by the continuum model. According to the intrinsic pinning model, the domain wall width and domain wall energy are distributed by the fluctuation of the atom order of the spin rotation inside the domain wall, and this fluctuation of the atom order prevents the domain wall from moving and causes coercive force. .

The reason why intrinsic pinning has not been considered as a cause of causing a magnet coercive force is that the model is considered to be applicable only when a rare earth element has a large magnetocrystalline anisotropy at a low temperature. However, the SmCo ₅ compound has a very large magnetocrystalline anisotropy of 18 MJ / m ³ at room temperature, and the CeCo ₅ compound has a magnetocrystalline anisotropy of ³ MJ / m ³ although it is smaller. . Although the domain wall width of SmCo ₅ varies depending on the measurer, it falls within the range of 2 to ₅ nm. This domain wall width corresponds to 5 to 10 units in terms of the number of SmCo ₅ unit cells. The number of units is not sufficiently thick from the viewpoint of domain wall width, and discrete handling is required. Therefore, intrinsic pinning can be sufficiently realized as a coercive force mechanism of the present system.

  Considering what requirements are necessary to establish intrinsic pinning, 1) a thin domain wall width and 2) fluctuation of domain wall energy in the atom order are necessary.

1) To what extent the “thin domain wall width” can be said to be thin, it is not clear because the theory is not fixed, but the magnetocrystalline anisotropy constant is about 1 to 2 MJ / m ³ at about 10 nm or less. This is considered to be the above. Therefore, magnetic compounds that can satisfy such conditions are generally rare earth-transition metal intermetallic compounds.

  Further, in order to satisfy 2) “fluctuation of domain wall energy in the atom order”, it is necessary to increase the distribution of domain wall energy represented by the following formula (1).

｛ただし、Ａ（ｒ）；交換定数（場所ｒの関数）、Ｋ（ｒ）；結晶磁気異方性定数（場所ｒの関数）｝

{Where A (r); exchange constant (function of location r), K (r); magnetocrystalline anisotropy constant (function of location r)}

  Since A (r) is mainly determined by the transition metal and is determined by the interaction between the two bodies, the variation can be maximized when the transition metal site is mainly replaced by a nonmagnetic element.

From this point of view, the inventors searched for a magnetic compound system in which an intrinsic pinning model can be established, and found the following compound system.
That is, the present invention includes a magnetic intermetallic compound comprising R which is one or more of rare earth elements including Y, two or more transition metal elements T mainly composed of Fe and Co, and unavoidable impurities. A permanent magnet, wherein the magnetic intermetallic compound has an atomic ratio of R of 1, T is 6 to 14, and the magnetocrystalline anisotropy energy of the magnetic intermetallic compound is 1 MJ / m ³ or more. The Curie point of the magnetic intermetallic compound is 100 ° C. or higher, the magnetic intermetallic compound is a particle having an average particle size of 3 μm or more, and the magnetic intermetallic compound has a substantially uniform structure, There is provided a rare earth permanent magnet having a structure in which a magnetization curve gives a pinning type, and the magnetic intermetallic compound has a TbCu ₇ type structure.

The rare earth element R is a rare earth element containing Y. The transition metal element T includes Co, Fe, Cu, Zr, Ti, V, Mo, Nb, W, Hf, Mn, Cr, and the like. Here, “mainly Fe and Co” means that the total content of Fe and Co is 50 atomic% (atomic percentage) or more with respect to the total amount of the transition metal element T. Moreover, C, O, N, Si etc. are mentioned as an unavoidable impurity, When these are mixed as an impurity, the content is generally 1 weight% or less.
The “permanent magnet containing a magnetic intermetallic compound” is a permanent magnet in which the compound is preferably contained in an amount of 50% by volume or more in the permanent magnet, and may contain resin, rubber, etc. as other components.

The magnetic intermetallic compound has an atomic ratio of T of 6 to 14 when R is 1. When T is less than 6 or when T exceeds 14, the TbCu ₇ type structure may not be stable.

The magnetocrystalline anisotropy energy of the magnetic intermetallic compound is 1 MJ / m ³ or more. At this time, by the intrinsic pinning mechanism, a permanent magnet having a high holding force can be configured with a homogeneous structure having no fine structure. Further, it is preferable that the magnetocrystalline anisotropy energy is large because a high holding force is generally easily obtained by an intrinsic pinning mechanism.

  The Curie point of the magnetic intermetallic compound is 100 ° C. or higher. When the Curie point is less than 100 ° C., the temperature change of the magnetic characteristics is large, and the characteristic deterioration at high temperatures may be large. In addition, the higher the Curie point, the smaller the decrease in magnetic properties at high temperatures, and it is preferable that it can be used at high temperatures.

The rare earth permanent magnet according to the present invention can be applied to both a bonded magnet and a sintered magnet. However, when the rare earth permanent magnet according to the present invention is applied to a bonded magnet, particles of the magnetic intermetallic compound (magnetic powder) are used. The average particle size is 3 μm or more, preferably 3 to 6 μm. Here, the magnetic powder means that in the process of manufacturing the magnet, R which is one or more of rare earth elements including Y, two or more transition metal elements T mainly composed of Fe and Co, and unavoidable. It is a powder obtained by pulverizing an alloy composed of impurities. When the average particle size of the magnetic powder is less than 3 μm, there may be a disadvantage that the characteristics are deteriorated due to oxidation of the fine powder.
When the rare earth permanent magnet according to the present invention is applied to a sintered magnet, the average particle diameter of the sintered body forming particles of the sintered body is 3 μm or more, preferably 3 to 6 μm. Here, the sintered body is obtained by sintering a molded body obtained by a molding process in which magnetic powder is pressure-molded in a magnetic field. It refers to particles that originate and form a sintered body. The average particle diameter of the sintered body forming particles can be measured by observing the sintered body using TEM.

The magnetic intermetallic compound has a substantially uniform structure. Preferably, a fine structure of 1 nm or more does not exist inside the magnetic intermetallic compound. This means that even a TEM or a three-dimensional atom probe method has a uniform structure to such an extent that a fine structure and concentration fluctuation cannot be found.
As described above, the three-dimensional atom probe method is a method in which a high electric field is applied to a sample to be measured with a sharp tip, thereby stripping off atoms from the tip and further removing it by a mass analyzer or TOF method. It is a method of measuring the element distribution in the three-dimensional real space by the atom order by applying it to the two-dimensional PSD (Position Sensitive Detector). According to this method, the accuracy is about 1 angstrom (0.1 nm). The distribution of elements can be measured.

  The initial magnetization curve is a pinning type. Unlike the nucleation and growth type, the initial magnetization curve is different from the nucleation growth type, as shown in FIG. 1A, the magnetization does not increase and the magnetization increases unless an external magnetic field of a certain level or more is applied. It means that it has a feature that it suddenly approaches saturation when it starts.

Preferably, the composition formula of the intermetallic compound is represented by the following formula (I).
_{R '(Co 1-xya Fe} x Cu y T' a) z ··· formula (I)
(In the formula, R ′ is one or more rare earth elements including Y mainly composed of Sm or Ce. T ′ is derived from Zr, Ti, V, Mo, Nb, W, Hf, Mn, and Cr. And at least one transition metal element selected from the group consisting of x, y, a and z, 0.05 ≦ x ≦ 0.30, 0.15 ≦ y ≦ 0.35, 0.001 ≦ a ≦ 0.05, 6.0 ≦ z ≦ 9.0.)

  Here, “R ′ mainly comprises Sm or Ce” means that the total content of Sm and Ce is 50% by weight or more with respect to the total amount of the rare earth element R ′.

R ′ (CoFeCuT ′) _z alloy (6.0 <z <9.0, T ′ = Zr, Ti, V, Mo, Nb, W, Hf, Mn, Cr, etc.) is used as a high-temperature stable phase. It is a phase having a TbCu ₇ structure. The TbCu ₇ structure is, for example, a rhombohedral Sm ₂ Co ₁₇ structure in which the Co dumbbell pair is not randomly replaced with A, B, C, A, B, C with respect to the R site, but randomly replaced. .

That is, intermetallic compounds having a composition ratio of rare earth elements R and Co of 1: 5 are widely present for R elements, and they have a hexagonal crystal structure called CaCu ₅ type shown in FIG. . This structure can be viewed as a structure in which a lattice plane in which R is arranged at the center of a Co kame noko lattice and a kagome-like lattice surface made of only Co are alternately stacked. As for the positional relationship of stacking, the R element is the center of the hexagon formed by the upper and lower kagome lattices, and the hexagon of the kameno lattice and the hexagon of the kagome lattice form an angle of 30 ° with each other.

The R ₂ Co ₁₇ compound has a crystal structure closely related to the RCo ₅ compound. That is, if one R is extracted from three RCo ₅ unit cells and two Cos are inserted at that position, R ₂ Co ₁₇ is obtained. Co pairs are arranged in a dumbbell shape along the c-axis, and the center of the line connecting Co is the position where R is replaced. There are multiple ways to substitute R atoms with Co pairs. If straight eyes only R in the basic grid of RCo _5, R sublattice is simple hexagonal piled a triangular lattice in layers. The triangular lattice formed by R is decomposed into three triangular sublattices as indicated by A, B, and C in FIG. One of the sublattices is replaced with a Co pair. When the substitution position in the Co pair is A, B, C, A, B, or C along the c-axis, a rhombohedral crystal called Th ₂ Zn ₁₇ type in FIG. Further, when R of the 1: 5 compound is randomly substituted with a pair of Co atoms instead of a specific position of R, a structure called TbCu ₇ type is obtained.

For example, in a 2-17 Sm-Co magnet that has been put into practical use, a stable TbCu ₇ structure is obtained in the solution temperature range just below the sintering temperature range, An alloy having a TbCu ₇ phase at room temperature can be produced by cooling the alloy heated to the solution temperature range more quickly than the solution temperature range.

Such a system 1-7 phase has a magnetocrystalline anisotropy of 1 MJ / m ³ or more when R = Sm, and can substitute an appropriate amount of Co site with nonmagnetic Cu. Of course, R may be two or more rare earths mainly containing Sm or Ce and containing Y.

  In a 2-17 type SmCo magnet that has been put into practical use, all 1-7 phases appear after sintering or solution forming. The question then arises as to why it has not been found so far that coercivity can be obtained in the 1-7 phase.

This is because in the development of practical magnets, in order to increase saturation magnetization and obtain a high (BH) _max , the composition has been studied only in the direction of decreasing Cu and increasing Fe. Since no region of a high Cu content that would reduce the saturation magnetization has been studied, no one has found that a pinning coercivity can be obtained with the 1-7 phase itself. A permanent magnet other than the 1-5 system based on an intrinsic pinning mechanism has been found in a temperature region above room temperature.

  By stabilizing the 1-7 phase in such an alloy system, a coercive force within 800 kA / m could be obtained without performing sintering and heat treatment. Of course, in order to improve the magnetic characteristics, it is preferable to perform orientation in a magnetic field to obtain an anisotropic sintered magnet.

The content of Cu is preferably 15 to 35 at% (at% is an abbreviation for atomic%), and particularly preferably 15 to 30 at%. The substitution of Co by Cu is represented by the formula R ′ (CoFeCuT ′) _z , and is preferably 10 at% or more, preferably 15 at% or more in the transition metal. If the substitution of Co with Cu is 10 at% or less, sufficient coercive force may not be obtained. In particular, in order to obtain a coercive force of 1.6 MA / m or more, Cu substitution of 25 at% or more is preferable. If Cu is substituted too much, the saturation magnetization may be lowered, so it is preferable to keep it by 35 at% substitution in the above formula.

  Further, the content of Fe is preferably 5 to 30 at%, particularly preferably 5 to 20 at%. The saturation magnetization increases as the amount of Fe increases. However, since the region where the 1-7 phase is stabilized becomes narrow at 20 at% or more, 20 at% or less is particularly preferable, and at 5 at% or less, the saturation magnetization decreases too much. Is preferred.

  Further, the content of T ′ is preferably from 0.1 to 5 at%, particularly preferably from 1 to 5 at%. T ′ is preferably 1 at% or more in order to stabilize the 1-7 phase in the composition formula, and 5 ′% or more is not preferable because saturation magnetization is excessively lowered. For T ′, in order to stabilize the 1-7 phase, a single transition metal element may be used, or two or more transition metal elements may be used.

  Moreover, the permanent magnet containing the magnetic intermetallic compound concerning this invention can be manufactured as follows, for example. That is, when manufacturing a sintered magnet, mainly from R which is one or more of rare earth elements including Y, two or more transition metal elements T mainly including Fe and Co, and inevitable impurities. A pulverizing step for obtaining magnetic powder by pulverizing the resulting alloy, a forming step for obtaining a compact by press-molding the magnetic powder in a magnetic field, and obtaining a sintered body by sintering the compact The permanent magnet according to the present invention can be manufactured by the sintering process. At this time, a high holding force can be obtained without performing an aging step of performing an aging treatment on the sintered body.

In the pulverization step, an alloy made of each metal as a raw material is pulverized to obtain a magnetic powder. Grinding can be performed by changing the tool step by step. The first stage is “smashing”, which can be performed by a stamp mill or a jaw crusher. The second stage can be “ground” by a brown mill or the like based on the principle of a mill. Thus far, coarse powder of about several hundred μm is obtained. This coarse powder is further finely pulverized into a single crystal fine powder having an average particle size of preferably 2 to 10 μm, more preferably 3 to 5 μm. For pulverization, a ball mill or a jet mill can be used. The jet mill applies high pressure to an inert gas such as N ₂ gas and opens it from a narrow nozzle to generate a high-speed gas flow, and accelerates powder particles by this high-speed gas flow. This is a method of generating a collision between powder particles and a collision with a target or a container wall, and crushing.

In the molding step, the magnetic powder obtained in the pulverization step is filled in a mold held by an electromagnet, and is pressure-molded with its crystal axis oriented by applying a magnetic field. Preferably, the packing density of the fine powder is about 10 to 30% of the true density, and the green body density is set to the true density by molding at a pressure of about 0.5 to ² ton / cm ² in a magnetic field of 8 to 20 kOe. A molded body of about 30 to 50% can be obtained. Naturally, the magnetic field should be high, but there are restrictions on the production of electromagnets. When the packing density of the fine powder is increased, the above-described orientation may be hindered due to friction between the powders, and the degree of orientation may be lowered. An organic lubricant can be used to improve the degree of powder orientation and the density of the compact. An organic binder can also be used to increase the strength of the molded body. Such organic substances cause oxidation and carbonization and may adversely affect the characteristics of the magnet. Therefore, it can be removed by decomposition and volatilization, preferably at around 100 to 300 ° C., before entering the sintering. This is called dewaxing. The direction in which the magnetic field is applied is naturally the direction in which the product should finally be magnetized.

  In the sintering process, a sintered body is obtained by sintering the molded body obtained in the molding process. Sintering is preferably performed in vacuum or argon gas. Sintering is preferably performed at 1100 to 1250 ° C. for 0.5 to 3 hours. This sintering temperature is a standard, and should be adjusted under various conditions such as composition, pulverization method, difference in particle size and particle size distribution, and amount of co-firing.

  The aging step is a step for controlling the coercive force. For example, the aging step is 800 after a multi-step aging in which heat treatment is sequentially performed at a low temperature or preliminary aging performed at a relatively high cooling rate from a relatively low temperature. It refers to double aging, etc., in which the main aging is performed in which continuous cooling is performed slowly after holding at a temperature of ˜900 ° C. According to the present invention, since a permanent magnet having a high holding force can be configured without performing an aging treatment, it is not necessary to perform this step, and the magnet can be manufactured in a simpler step.

  Further, for example, when manufacturing a bonded magnet, mainly R, which is one or more of rare earth elements including Y, two or more transition metal elements T, mainly Fe and Co, and inevitable impurities The permanent magnet according to the present invention can be manufactured by a pulverization step of pulverizing an alloy made of the above-described material to obtain a magnetic powder, and a resin molding step of mixing the magnetic powder with a resin or the like and curing it.

The pulverization step can be performed in the same manner as in the case of the sintered magnet. In the resin molding step, a raw material obtained by mixing or kneading magnetic powder and resin or the like can be used. This is molded by means such as compression, injection, extrusion, and then cured. In injection molding or extrusion molding, it is preferable to mold a material that has been heated and softened to a fluidized state, and then cooled and cured. As the resin, it is preferable to use a thermosetting resin for compression molding and a thermoplastic resin for injection molding. In the former, epoxy type is mainly used, and in the latter, nylon type is mainly used.
As the resin or the like, an epoxy resin or the like is preferable. The amount of the resin is preferably 50% by volume or less with respect to the total amount of the bonded magnet.

Sm, Co, Fe, Cu, and Zr having a purity of 99.9% are weighed so as to be Sm ( _Cores Fe _0.20 Cu _0.15 Zr _0.025 ) _7.5 , dissolved in an Ar reduced pressure atmosphere in a high frequency furnace, and cast into a water-cooled mold. To produce an alloy. The alloy was finely pulverized by a jet mill using N ₂ gas to obtain a fine powder having an average particle diameter of 4 μm. The fine powder was compacted at a pressure of 1 ton / cm ² while being magnetically oriented in a magnetic field of 15 kOe to obtain a compact. The molded body was sintered in an Ar gas atmosphere at 1210 ° C. for 1 hour, and subsequently subjected to a solution treatment at 1195 ° C. for 2 hours to produce a sintered body. No aging heat treatment was performed as in a general 2-17 SmCo magnet.

When the hysteresis curve of the sintered body was measured with a BH tracer, it showed a pinning-type initial magnetization curve as shown in FIG. 6 and had a coercive force of H _ci = 7.5 kOe (in FIG. Is the strength of the external magnetic field, 4πIm is the magnetic flux density). Moreover, powder X-ray diffraction, EPMA observation, and TEM observation were performed using a part of the sintered body.

The peaks of the diffraction pattern by X-ray diffraction can all be indexed with the TbCu ₇ structure, and the peaks are also thin and sharp, indicating that the 1-7 phase is stable. Further, the components constituting the magnetic main phase showed almost uniform element distribution by EPMA observation, and no particular element bias was observed. A secondary electron image (composition image) is shown in FIG. 7, but no light and shade showing compositional deviation was observed except for the oxide phase of Sm ₂ O _{3 and} the ZrCo phase that is somewhat observed. FIG. 8 shows a photograph magnified 1 million times by TEM observation, but no specific microstructure was found. Although there are twin boundaries, the structure is homogeneous because it only extends in the C-plane direction and does not relate to the coercive force.

  From these observation results, it was found that the magnet sintered body was a magnet having a pinning-type coercive force mechanism although it did not have a fine structure. Of course, the composition of the present invention is not limited to this example.

It is a graph which shows two coercive force mechanisms of a rare earth permanent magnet. (A) Pinning type initial magnetization curve (b) Nucleation growth type initial magnetization curve It is the fine structure photograph (about 70,000 times) by the TEM of the conventional 2-17 type | mold Sm-Co magnet. It is the fine structure photograph (about 110,000 times) by TEM of Sm (CoCu) 5 magnet. It is a schematic diagram of the conventional domain wall pinning model in a 2-17Sm-Co type | system | group magnet. (A) RCo ₅ crystalline structure is a schematic diagram showing a (hexagonal). (B) the crystal structure of the R ₂ Co ₁₇ is a schematic diagram showing a (rhombohedral). It is a graph which shows the hysteresis curve of the alloy concerning an example of this invention. It is a secondary electron image (about 300 times) by EPMA of the alloy concerning an example of this invention. It is the structure | tissue enlarged photograph (about 150,000 times) by the TEM of the alloy concerning an example of this invention.

Claims (4)

A permanent magnet comprising a magnetic intermetallic compound comprising R, which is one or more of rare earth elements including Y, two or more transition metal elements T mainly composed of Fe and Co, and unavoidable impurities,
The magnetic intermetallic compound has an atomic ratio where T is 6 to 14 when R is 1.
The magnetocrystalline anisotropy energy of the magnetic intermetallic compound is 1 MJ / m ³ or more,
The Curie point of the magnetic intermetallic compound is 100 ° C. or higher,
The magnetic intermetallic compound is a particle having an average particle size of 3 μm or more;
The magnetic intermetallic compound has a substantially uniform structure;
A rare earth permanent magnet having a structure in which an initial magnetization curve gives a pinning type, and wherein the magnetic intermetallic compound has a TbCu ₇ type structure.   The rare earth magnet according to claim 1, wherein the magnetic intermetallic compound particles are sintered body-forming particles.   3. The rare earth magnet according to claim 1, wherein a microstructure of 1 nm or more does not exist inside the magnetic intermetallic compound. The rare earth permanent magnet according to any one of claims 1 to 3, wherein a composition formula of the intermetallic compound is represented by the following formula (I).
_{R '(Co 1-xya Fe} x Cu y T' a) z ··· formula (I)
(In the formula, R ′ is one or more rare earth elements including Y mainly composed of Sm or Ce. T ′ is derived from Zr, Ti, V, Mo, Nb, W, Hf, Mn, and Cr. And at least one transition metal element selected from the group consisting of x, y, a and z, 0.05 ≦ x ≦ 0.30, 0.15 ≦ y ≦ 0.35, 0.001 ≦ a ≦ 0.05, 6.0 ≦ z ≦ 9.0.)

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