JPH11273918A - Permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high magnetic performance, by having ferromagnetic phase and grain boundary phase, matching ferromagnetic phase with grain boundary phase, and regularizing atomic arrangement between which an interface between ferromagnetic phase and grain boundary phase is put. SOLUTION: In a permanent magnet, ferromagnetic phase is matched with grain boundary phase and atomic arrangement is regularized between which an interface between ferromagnetic phase and grain boundary phase is put. The grain boundary phase has crystal form, face index and orientation index (crystal orientation) which are matched with those of the ferromagnetic phase. Crystal magnetic anisotropy at a location adjacent to the interface of the ferromagnetic phase is half or more of crystal magnetic anisotropy inside ferromagnetic particles. Crystal magnetic anisotropy at the outermost shell in the ferromagnetic particles is half or more of crystal magnetic anisotropy inside ferromagnetic particles that is higher than crystal magnetic anisotropy inside ferromagnetic particles. Further, crystal magnetic anisotropy within five atom layers from the outermost shell of the ferromagnetic particles is higher than crystal magnetic anisotropy inside ferromagnetic particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet, and more particularly to a permanent magnet raw material, a permanent magnet intermediate and a permanent magnet as a final product.

[0002]

2. Description of the Related Art Coercive force generating mechanisms for permanent magnets in practical use include a single magnetic domain particle theory type, a nucleation type, and a pinning type. Among these, the nucleation type coercive force generation mechanism was introduced to explain the reason why a sintered magnet having a crystal grain size larger than a single magnetic domain particle size generates a large coercive force, The idea is that the easiness of nucleation of the reversed magnetic domain near the crystal grain boundary determines the coercive force of the crystal grain. This type of magnet is characterized by its magnetizing properties,
Saturation of the magnetization in the initial magnetization process occurs at a relatively low applied magnetic field, but a magnetic field higher than the saturation magnetization must be applied to obtain a sufficient coercive force. It is considered that this is because a high magnetic field completely drives out the reverse magnetic domains remaining in the grains, thereby generating a high coercive force. Magnets with a nucleation-type coercive force generation mechanism include SmCo ₅ sintered magnets, Nd-Fe
-B-based sintered magnets.

[0003]

SUMMARY OF THE INVENTION The present inventors have found that the prior art relating to the nucleation type magnet has the following problems. That is, in the prior art, it was predicted that the coercive force of the nucleation type magnet was dominated by the nucleation of the reverse magnetic domain. Sufficient knowledge has not been obtained on the means. For example, in an Nd-Fe-B based sintered magnet, it is known that the presence of an Nd-rich grain boundary phase acts to increase the coercive force, but details of the mechanism are unknown.

An object of the present invention is to provide a guide for designing a permanent magnet having high magnetic performance.

[0005]

Means for Solving the Problems Conventionally, the magnetic properties of a magnet,
Among them, the main phase that determines the coercive force (hereinafter, the “main phase” in this specification refers to “the phase exhibiting ferromagnetism”, and the main phase is preferably present in at least half or more). The structure of the interface between the boundary phases was unknown. For this reason, in the prior art, by optimizing various conditions in the magnet manufacturing process,
Experience has shown to improve the magnetic properties of magnets. Such an empirical approach is time-consuming and expensive for sample preparation and evaluation, and has limitations in further improving magnet properties.

The present inventors have investigated the fundamental problem of what the ideal interface structure should be, without relying on an empirical method. As a result, the present inventors have developed a nucleation-type coercive force generation mechanism. in various magnetic materials, ease of nucleation depends on the size of the crystal magnetic anisotropy in the outermost shell near the magnet phases, the value of the anisotropy constant K ₁ of the outermost shell near at least showing It has been found that nucleation can be suppressed and the coercive force of the magnet can be increased by controlling it to be equal to or more than the inside, and as a result of further intensive research, the present invention has been completed.

[0007] The first aspect has the following elements. The ferromagnetic phase and the grain boundary phase are matched. Second
From the point of view that the atomic arrangement sandwiching the interface between the ferromagnetic phase and the grain boundary phase is regular. In a third aspect, the grain boundary phase exists with a crystal type, a plane index, and an orientation index (crystal direction) that match the ferromagnetic phase. In a fourth aspect, the magnetocrystalline anisotropy at a position adjacent to the ferromagnetic phase interface is at least half the magnetocrystalline anisotropy inside the ferromagnetic particles.

In a fifth aspect, the crystal magnetic anisotropy in the outermost shell of the ferromagnetic particles is at least half of the internal crystal magnetic anisotropy. In a sixth aspect, the outermost shell of the ferromagnetic particles has a higher magnetocrystalline anisotropy than the inner magnetocrystalline anisotropy. In a seventh aspect, the crystal magnetic anisotropy of the outer shell within 5 atomic layers from the outermost shell of the ferromagnetic particles is higher than the inner crystal magnetic anisotropy. In an eighth aspect, the magnetocrystalline anisotropy of the ferromagnetic particles is expressed mainly by a crystal field of a rare earth element. In the grain boundary phase adjacent to the rare earth element ion located in the outer shell of the ferromagnetic particles, the cation is located in the direction in which the 4f electron cloud of the rare earth element ion extends. In the ninth aspect, the cation source is Be, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Zn, Ga, Sr, Zr, Nb, Mo, Cd, In, S
It must be at least one of n, Ba, Hf, Ta, Ir, and Pb.

In a tenth aspect, a cation source is added to ferromagnetic particles whose crystal magnetic anisotropy mainly develops due to the crystal field of a rare earth element. Precipitating a crystal containing a cation source at least in a grain boundary phase portion adjacent to the ferromagnetic particles. In the crystal structure of the grain boundary phase adjacent to the ferromagnetic phase, the cations are positioned in a direction orthogonal to the direction in which the 4f electron cloud of the rare earth element ion located at the outermost shell of the ferromagnetic particles extends. In the eleventh viewpoint, the composition of the grain boundary phase, the crystal type, the plane index, and the orientation in a state where both phases coexist according to the crystal structure of the ferromagnetic phase so that the ferromagnetic phase and the grain boundary phase match. Determining the index (crystal direction).

Referring to FIGS. 1, 2A and 2B,
The difference in the distribution of magnetocrystalline anisotropy near the interface between the case where the main phase (ferromagnetic phase) and the grain boundary phase match at the interface and the case where they do not match will be described. FIG. 1 or FIG.
In (A) and (B), the “outermost shell” on the horizontal axis indicates the position of the outermost atomic layer of the main phase, and the “second layer” and “third layer” indicate the outermost shell positions, respectively. The positions of the second and third atomic layers counted from the inside toward the inside are shown. The n-th layer indicates a position where the distance from the outermost shell is long and the influence from the interface can be ignored. In the graph of FIG. 1, the vertical axis represents the uniaxial anisotropy constant K of the main phase.
₁ (indicating the strength of crystal magnetic anisotropy), and K ₁
Is larger, the direction of the spontaneous magnetization of the main phase is stabilized in the direction of the axis of easy magnetization (c-axis). In FIG. 1, the example (the present invention) shows the calculated value of K _{1 under} the condition that the main phase and the grain boundary phase are matched at the interface as shown in FIG. 2 (A). As shown in FIG. 2B, the calculated value of K1 in the case where there is an interface mismatch due to a lack of a grain boundary phase or the like is shown.

[0011] Referring to FIG. 1, in the comparative example, the size is largely changed in the anisotropy constant K1 according to the distance from the interface, the value of K ₁ is significantly reduced compared to the inside of the outermost shell I have. On the other hand, in the embodiment, without much change in the magnitude of the anisotropy constant K ₁ by the distance from the interface, the anisotropy constant K ₁ is increased in the outermost shell phase rather. Therefore,
According to the comparative example, the energy required for nucleation of the reverse magnetic domain in the outermost shell is locally reduced, and nucleation and magnetization reversal are facilitated, so that the coercive force of the magnet is reduced. On the other hand, according to the embodiment, since K ₁ in the outermost shell is rather higher than that in the inner part, nucleation of reverse magnetic domains at the interface is suppressed, and as a result, the coercive force of the magnet increases.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to the specific composition described below. Is provided. The present invention is particularly applied to a nucleation type permanent magnet, but can also be applied to a single domain particle theory type, a pinning type, and the like. Examples of nucleation type permanent magnets include Nd-Fe-B (Nd ₂ Fe ₁₄ B, etc.), Sm ₂ Fe
₁₇ N _x , SmCo ₅ . Here, as an example, in the case of the Nd ₂ Fe ₁₄ B phase, the reason why the presence of the grain boundary phase increases the crystal magnetic anisotropy of the main phase near the interface will be described.

[Function of Grain Boundary Phase] The magnetocrystalline anisotropy of the Nd ₂ Fe ₁₄ B phase, which is the main phase of the Nd—Fe—B magnet, is determined by the position of Nd atoms in the crystal. Nd atoms and B atoms exist only on the bottom surface of the Nd ₂ Fe ₁₄ B tetragonal crystal and on the plane at z = 1 / 2c ₀ . Nd atoms emit electrons in the crystal and exist in the form of Nd ³⁺ ions.

The 4f electrons of the Nd ³⁺ ion have a spatial distribution spread in a donut shape, and the direction of the magnetic moment J is perpendicular to the plane in which the 4f electron cloud is spread. A donut-like electron cloud of 4f electrons of the Nd3 ⁺ ion is close in the base
The magnetic moment J is oriented in the direction perpendicular to the bottom surface, ie, c, because it is pulled by the + charges of Nd ³⁺ ions and B ³⁺ ions.
Fixed in the axial direction. This is the cause of the strong uniaxial magnetic anisotropy of the Nd ² Fe ¹⁴ B phase. In a compound of a light rare earth such as Nd and a transition metal such as Fe, the magnetic moments of both tend to be parallel due to exchange interaction, and as a result, the magnetic moment of the entire Nd ₂ Fe ₁₄ B phase is in the c-axis direction. Turn to.

[0015] Now, considering the outermost shell of the Nd ₂ Fe ₁₄ B crystal that is not co-exist with the grain boundary phase, the outermost Nd ³⁺ ions, Nd ³⁺ close than in the interior of Nd ³⁺ ions ^Small number of ions and ^{B3 +} ions. Therefore, the force for fixing the spread of the 4f electron cloud in the inward direction of the bottom surface is weak, and as a result, the magnetic moment is insufficiently fixed in the c-axis direction. In such an outermost shell portion, the crystal magnetic anisotropy is locally greatly reduced, the energy required for nucleation of the reverse magnetic domain is reduced, and nucleation easily occurs, and the coercive force of the magnet is reduced.

Here, when a grain boundary phase such as Ca metal exists adjacent to the outermost shell of the main phase, a cation serving as a substitute for the missing Nd ³⁺ ion or B ³⁺ ion is adjacent. Therefore, the magnetocrystalline anisotropy increases as compared with the case where there is no grain boundary phase. In particular, when the two phases have a positional relationship such that the strong cation of the grain boundary phase is located near the a-axis direction of the outermost shell Nd ³⁺ ion of the main phase, the value of K ₁ is smaller than that inside the main phase. Conversely, the magnet becomes higher and a magnet with a high coercive force is obtained. In the above preferred positional relationship, the main phase and the grain boundary phase are in contact at a compatible interface,
In addition, when both phases have a specific crystal orientation relationship, the rate of formation increases.

If the cations of the grain boundary phase are arranged near the c-axis direction of the main phase Nd ³⁺ ions, the crystal magnetic anisotropy will be low. However, the actual stacking order in the c-axis direction at the interface is such that the grain boundary phase is not stacked adjacent to the main phase Nd atomic layer, but the grain boundary phase is stacked on the main phase Fe atomic layer. Because
The charge of the cation in the grain boundary phase is shielded by the Fe atomic layer,
The magnetocrystalline anisotropy does not decrease so much.

[Crystallographic Orientation Relationship at Interface] FIG.
Is a micrograph of the R ₂ TM ₁₄ B main phase (R: Y-containing rare earth element, TM: Fe or Co) and the R-TM grain boundary phase, which are mutually matched, and FIG. 4 is shown in FIG. FIG. 5 is a selected area electron diffraction image of the main phase, and FIG. 5 is a selected area electron diffraction image of the grain boundary phase shown in FIG. 3. As a result of the analysis, the crystallographic orientation relationship between the two phases at the interface is expressed as follows, and the deviation of the orientation relationship is within 5 ° from parallel.

[0019]

Embedded image

The coercive force of a sintered magnet having such a matched interface is significantly higher than the coercive force of a sintered magnet having a similar composition but having an unmatched interface (in the case of matching, iHc = 15.3kOe, 7.2kOe in case of inconsistency). Note that it is preferable that the main phase and the grain boundary phase match at least 50% at the interface.

[Anisotropy Constant] In the permanent magnet according to the present invention, the value of the anisotropy constant K1 near the outermost shell of the ferromagnetic phase is preferably equal to or greater than that of the inside. Equivalence in this case is at least 50% or more of the internal value. It is preferable that the magnetocrystalline anisotropy in the outermost shell of the ferromagnetic particles be enhanced as compared with the magnetocrystalline anisotropy of the outermost shell of the ferromagnetic particles in the absence of the grain boundary phase.

[Distribution of Crystalline Magnetic Anisotropy] In addition, at least one of a metal, alloy, or intermetallic compound which has a specific crystal structure which is not amorphous and which is ferromagnetic at room temperature.
In a permanent magnet composed of seed crystal grains, the crystal magnetic anisotropy at the outermost shell position of the crystal grains is equal to or improved within the crystal grains (center portion) where the influence of the crystal grains outside can be ignored. However, it is preferable that it does not greatly decrease compared to the inside. In order to obtain a practical coercive force, the crystal magnetic anisotropy at the outermost shell position of the crystal grain is preferably at least half of the internal crystal magnetic anisotropy where the influence of the crystal grain outside can be ignored.

[Enclosed Main Phase, Separated Structure] A main phase comprising a metal, alloy, or intermetallic compound having a specific non-amorphous crystal structure and being ferromagnetic at room temperature, and a metal, alloy, Alternatively, it is preferable to be composed of at least two phases of a grain boundary phase which are made of an intermetallic compound and exist around the main phase. The grain boundary phase can improve the coercive force by surrounding a part or all of the ferromagnetic phase (ferromagnetic particles) constituting the main phase. It is preferable that the ferromagnetic phase (ferromagnetic particles) is surrounded by a grain boundary phase by half or more. It is preferable that one ferromagnetic particle constituting the main phase and another ferromagnetic particle are separated from each other. Preferably, one ferromagnetic particle and another ferromagnetic particle are partially or wholly separated from each other by a substantially nonmagnetic grain boundary phase.

[Preferred Combination of Main Phase and Grain Boundary Phase] In the present invention, the metal, alloy or intermetallic compound preferable as the main phase preferably has excellent properties as the main phase of the permanent magnet. , A material having a high saturation magnetization and a sufficiently high Curie temperature at room temperature or higher. Examples of ferromagnetic materials satisfying the above conditions include Fe, Co, Ni, and Fe-Co.
Alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Pt-Co alloys, Mn-Bi _{alloy, SmCo 5, Sm 2 Co 17} , Ne 2 Fe 14 B, there are such Sm ₂ Fe ₁₇ N _3, or Are not intended to limit the scope of the invention.

In the present invention, the metal, alloy or intermetallic compound preferable as the grain boundary phase has a melting point or decomposition temperature higher than room temperature and lower than the melting point or decomposition rate of the main phase. What is easy to diffuse around the main phase by using is preferred. Further, it is preferable that the atoms constituting the grain boundary phase behave as cations with respect to the outermost shell atoms of the main phase to enhance the crystal magnetic anisotropy of the main phase. As an example of a metal satisfying the above conditions, Be, Mg, Ca, Sr,
Ba, all transition metal elements (including Zn and Cd), Al, Ga,
In, Tl, Sn, Pb and the like. In addition, alloys of these metals or intermetallic compounds can also be the grain boundary phase, but the examples given above do not limit the scope of the present invention.

The combination of the main phase and the grain boundary phase is preferably such that both phases coexist in equilibrium in a certain temperature range, for example, a SmCo5 main phase and a Y grain boundary phase. Also, for example, Sm ₂ Fe ₁₇ N ₃
The main phase and the second phase may react with each other to form a preferred third phase at the grain boundary, such that an intermetallic compound phase (Γ-FeZn) is formed by the reaction between the main phase and the Zn phase. In the latter case, the third phase is the grain boundary phase in the present invention.

[Range of Trace Additive Element] In the present invention,
It is a preferred embodiment to mainly add a trace amount of a metal element in order to enhance the consistency between the main phase and the grain boundary phase. The above-mentioned trace added elements are concentrated and unevenly distributed in the grain boundary phase to enhance the wettability of the interface, or diffuse to an inconsistent position of the interface to adjust the lattice constant of the grain boundary phase to lower the interface energy, Has the effect of improving the coherence of the magnet, and as a result, the coercive force of the magnet improves.

[0028] As the trace addition element having the above function,
Elements that can form a solid solution in the grain boundary phase are preferable, for example, Al, S
i, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, N
There are b, Mo, the above-mentioned metal elements other than these, and the like, but the examples given above do not limit the applicable scope of the present invention. The addition amount of the element to be added for the above purpose is 1.0% by weight or less with respect to the whole magnet to obtain a good residual magnetic flux density of the magnet, and the predetermined effect is obtained at 0.05% by weight or more. Is preferably 0.05 to 1.0 wt%. A more preferred range is from 0.1 to 0.5 wt%. The addition method of the trace addition element is
It can be selected as appropriate according to the method of manufacturing the magnet, such as adding it to the mother alloy from the beginning or adding it later by powder metallurgy. Further, the above-mentioned trace elements may invade the main phase (ferromagnetic phase) or replace the elements constituting the main phase.

[Crystal Structure of Magnetic Phase and Grain Boundary Phase] The crystal structure of the grain boundary phase is preferably similar to the crystal structure of the magnetic phase. Further, it is preferable that the crystal structure of the grain boundary phase and the crystal structure of the magnetic phase have a specific orientation relationship. by this,
The consistency between the specific atom on the grain boundary phase side and the specific atom on the main phase side is enhanced. For example, in a permanent magnet composed of a main phase composed of a tetragonal R2TM14B intermetallic compound (a rare earth element containing R: Y, TM: Fe or Co) and a grain boundary phase composed of an R-TM alloy, the main phase The crystal structure of the grain boundary phase in the vicinity of the interface between the grain boundary phase and the grain boundary phase is preferably a face-centered cubic structure. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.

[0030]

Embedded image

In a permanent magnet composed of a tetragonal R2TM14B intermetallic compound (a rare earth element containing R: Y, TM: Fe or Co) and a grain boundary phase composed of an R3TM alloy, the main phase is The crystal structure of the grain boundary phase in the vicinity of the interface of the grain boundary phase is preferably an orthorhombic structure. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.

[0032]

Embedded image

The grain boundary phase may be any one as long as atoms near the interface with the main phase (at most several atomic layers) match the main phase.
It may be partially amorphous and mostly amorphous. Although the effect can be obtained when a part of the interface is matched, it is preferable that half or more of the interface is matched. The main phase and the grain boundary phase preferably have regularity without lattice defects near the interface and maintain continuity, but may have some lattice defects.

In the permanent magnet according to the present invention, the ferromagnetic phase only needs to exhibit a practical coercive force under certain conditions, and may be formed of one or more of metals, alloys, intermetallic compounds, semimetals, and other compounds. It is possible to configure. In addition, the principle of the present invention is applied to permanent magnet raw materials, intermediates, permanent magnets as final products, and methods for producing them. For example, as raw materials for permanent magnets, casting and pulverization methods, quenched thin plate pulverization methods, ultra-quench methods, direct reduction methods, hydrogen-containing collapse methods,
There is a powder obtained by an atomizing method. Examples of the intermediate include a quenched thin plate that is pulverized and used as a raw material for the powder metallurgy method, and an amorphous body (part or all) that is partially or wholly crystallized by heat treatment. As permanent magnets as final products, magnets made by bulking these powders by sintering or bonding, cast magnets, rolled magnets, further sputtering method,
There is a thin film magnet by an ion plating method, a PVD method, a CVD method, or the like. Furthermore, as a method of manufacturing a permanent magnet as a permanent magnet raw material or a final product, a mechanical alloying method, a hot pressing method, a hot forming method,
There are a hot / cold rolling method, an HDR method, an extrusion method, a die upset method, and the like, and there is no particular limitation.

[0035]

[Example 1] Nd ₂ Fe ₁₄ B crystal grains having a particle size of 10 μm were press-formed while oriented in a magnetic field, and then pressed on the surface of the formed body.
5 wt% of Ca metal crushed to 200 μm or less was coated, heated at 800 ° C. for 1 hour in a vacuum, and then cooled. The obtained sample had a structure in which the grain boundary phase of Ca metal surrounded the Nd ₂ Fe ₁₄ B crystal grains as the main phase, and both phases were in direct contact with each other via a matching interface. The coercive force of this sample was 1.3 MA / m.

[Comparative Example 1] The molded product obtained in Example 1 was
After heating at 1060 ° C. for 1 hour in vacuum as it was, it was cooled. The Nd ₂ Fe ₁₄ B crystal grains of the obtained sample contain many voids except that a sintering neck is formed at the point of mutual contact, and an oxide phase is formed on the surface of the crystal grains in the voids. Was. The coercive force of this sample was 0.1 MA / m.

Example 2 Sm ₂ Fe ₁₇ N _x (x is about 10 μm in particle diameter)
3) Zn was coated on the surface of the crystal grains by 2 wt% by an electroless plating method, then heated at 450 ° C. for 1 hour in a vacuum, and then cooled. The obtained sample was composed of Sm ₂ Fe ₁₇ N _x
It has a structure in which Zn metal phase surrounds the crystal grains,
Both phases were in direct contact via a consistent interface. The coercive force of this sample was 1.9 MA / m.

[Comparative Example 2] In the sample after Zn plating obtained in Example 2, the crystallinity of the interface between the main phase and the Zn metal phase was disordered, and the interface was not consistent. The coercivity of this sample is 0.3M
A / m.

Example 3 On a surface of an 80 μm thick SmCo ₅ thin film produced by sputtering while heating the substrate to 700 ° C., Y was sputtered to 5 μm while heating the substrate to 400 ° C. Coated as follows. By X-ray diffraction, the crystal structure of SmCo _{5 in} the obtained sample film was hexagonal CaC
u ₅ type structure, Y is taken La type structure which is hexagonal close-packed structure, any crystal orientation of both c-axis was perpendicular to the film plane. Further, as a result of observing the cross-sectional structure of the sample with a transmission electron microscope, it was found that the SmCo ₅ phase was a columnar crystal having a diameter of several μm, and the interface between the SmCo ₅ phase and the Y phase was consistent. The coercive force of this thin film was 1.5 MA / m.

Comparative Example 3 The thickness of 80 μm obtained in Example 3
The surface of the SmCo ₅ thin film was coated with Y to a thickness of 5 μm by a sputtering method without heating the substrate. The crystal structure of SmCo _{5 in} the obtained sample film has a hexagonal CaCu ₅ type structure, and Y has a La type structure which is a hexagonal close-packed structure.
o The crystal orientation of the _five phases was such that the c-axis was perpendicular to the film surface, while the c-axis of the Y phase was oriented in a random direction with respect to the film surface. The interface between the SmCo ₅ phase and the Y phase was inconsistent. The coercive force of this thin film was 0.2 MA / m.

[Example 4: Example of trace addition element] Particle size 1
90 g of Sm ₂ Co ₁₇ powder of 0 μm, and 10 g of Nd alloy powder containing 0.2 wt% of Zr were mixed and molded in a magnetic field.
Sintered at ℃ for 2 h and cooled to room temperature. The obtained sintered body is Sm
_It consisted of a main phase of ₂ Co ₁₇ and a grain boundary phase of Nd-Zr alloy, and the interface of both phases was consistent. The coercive force of this sintered body was 1.1 MA / m.

Comparative Example 4 90 g of Sm ₂ Co ₁₇ powder having a particle size of 10 μm
And 10 g of Nd powder were mixed, molded in a magnetic field, sintered in vacuum at 1150 ° C. for 2 hours, and cooled to room temperature. The obtained sintered body was composed of a main phase of Sm ₂ Co ₁₇ and a grain boundary phase of Nd. Many stacking faults and dislocations were found near the interface between the two phases, and the interface was inconsistent. The coercive force of this sintered body was 0.4 MA / m.

[0043]

According to the present invention, a guide for designing a permanent magnet having high magnetic performance (particularly, coercive force) is provided. Conventionally, the structure of the interface between the main phase and the grain boundary phase that determines the coercive force was unknown, but the present invention has revealed a new ideal interface structure for improving the coercive force. In addition to providing guidance for the development of a permanent magnet, the coercive force of the existing permanent magnet can be further improved. As a result, a new magnet material can be easily discovered, a permanent magnet that has not been used because of its low coercive force can be put to practical use, and the optimum composition can be easily determined.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a relationship between a distance from an interface and crystal magnetic anisotropy, in which a white circle indicates a uniaxial anisotropy constant of an example.
K1 and black circles indicate the uniaxial anisotropy constant K1 of the comparative example.

FIG. 2A is a model diagram showing a state where a main phase and a grain boundary phase match, and FIG. 2B is a model diagram showing a state where a main phase and a grain boundary phase do not match.

FIG. 3 is an electron micrograph of a permanent magnet in which a main phase and a grain boundary phase are matched.

FIG. 4 is a photograph of a crystal structure showing a selected area electron beam diffraction image of the main phase shown in FIG. 3;

5 is a photograph of a crystal structure showing a selected area electron beam diffraction image on the grain boundary phase side shown in FIG. 3;

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[Procedure amendment]

[Submission date] April 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

Referring to FIGS. 1, 2A and 2B,
The difference in the distribution of magnetocrystalline anisotropy near the interface between the case where the main phase (ferromagnetic phase) and the grain boundary phase match at the interface and the case where they do not match will be described. FIG. 1 or FIG.
In (A) and (B), the “outermost shell” on the horizontal axis indicates the position of the outermost atomic layer of the main phase, and “the second layer”, “the third layer”.
The "layer" indicates the position of the second and third atomic layers counted from the outermost shell position toward the inside. The distance from the outermost shell is far from the nth layer, and the influence from the interface is negligible. In the graph of Fig. 1, the vertical axis represents the uniaxial anisotropy constant of the main phase.
Indicates the magnitude of K ₁ (indicating the strength of magnetocrystalline anisotropy), and K ₁
Is larger, the direction of the spontaneous magnetization of the main phase is stabilized in the direction of the axis of easy magnetization (c-axis). In FIG. 1, the example (the present invention) shows the calculated value of K _{1 under} the condition that the main phase and the grain boundary phase are matched at the interface as shown in FIG. 2 (A). such as by 2 (B) lack of grain boundary phase, as shown in shows the calculated values of K ₁ in the case where there is such an interface mismatch.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Referring to FIG. 1, in the comparative example, the magnitude of the anisotropy constant K ₁ changes greatly depending on the distance from the interface, and the value of K ₁ in the outermost shell is significantly lower than that in the interior. ing. On the other hand, in the embodiment, without much change in the magnitude of the anisotropy constant K ₁ by the distance from the interface, the anisotropy constant K ₁ is increased in the outermost shell phase rather. Therefore,
According to the comparative example, the energy required for nucleation of the reverse magnetic domain in the outermost shell is locally reduced, and nucleation and magnetization reversal are facilitated, so that the coercive force of the magnet is reduced. On the other hand, according to the embodiment, since K ₁ in the outermost shell is rather higher than that in the inner part, nucleation of reverse magnetic domains at the interface is suppressed, and as a result, the coercive force of the magnet increases.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

The 4f electrons of the Nd ³⁺ ion have a spatial distribution spread in a donut shape, and the direction of the magnetic moment J is perpendicular to the plane in which the 4f electron cloud is spread. A donut-like electron cloud of 4f electrons of the Nd3 ⁺ ion is close in the base
The magnetic moment J is oriented in the direction perpendicular to the bottom surface, ie, c, because it is pulled by the + charges of Nd ³⁺ ions and B ³⁺ ions.
Fixed in the axial direction. This is the cause of the strong uniaxial magnetic anisotropy of the Nd ₂ Fe ₁₄ B phase. In a compound of a light rare earth such as Nd and a transition metal such as Fe, the magnetic moments of both tend to be parallel due to exchange interaction, and as a result, the magnetic moment of the entire Nd ₂ Fe ₁₄ B phase is in the c-axis direction. Turn to.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

[Anisotropy Constant] In the permanent magnet according to the present invention, the value of the anisotropy constant K ₁ near the outermost shell of the ferromagnetic phase is preferably equal to or greater than that of the inside. Equivalence in this case is at least 50% or more of the internal value. It is preferable that the magnetocrystalline anisotropy in the outermost shell of the ferromagnetic particles be enhanced as compared with the magnetocrystalline anisotropy of the outermost shell of the ferromagnetic particles in the absence of the grain boundary phase.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

The combination of the main phase and the grain boundary phase is preferably such that both phases coexist in equilibrium in a certain temperature range, for example, a SmCo ₅ main phase and a Y grain boundary phase. Also, for example, Sm ₂ Fe ₁₇ N ₃
The main phase and the second phase may react with each other to form a preferred third phase at the grain boundary, such that an intermetallic compound phase (Γ-FeZn) is formed by the reaction between the main phase and the Zn phase. In the latter case, the third phase is the grain boundary phase in the present invention.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

[Crystal Structure of Magnetic Phase and Grain Boundary Phase] The crystal structure of the grain boundary phase is preferably similar to the crystal structure of the magnetic phase. Further, it is preferable that the crystal structure of the grain boundary phase and the crystal structure of the magnetic phase have a specific orientation relationship. by this,
The consistency between the specific atom on the grain boundary phase side and the specific atom on the main phase side is enhanced. For example, in a permanent magnet composed of a main phase composed of a tetragonal R ₂ TM ₁₄ B intermetallic compound (a rare earth element containing R: Y, TM: Fe or Co) and a grain boundary phase composed of an R-TM alloy, Preferably, the crystal structure of the grain boundary phase near the interface between the main phase and the grain boundary phase is a face-centered cubic structure. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

In a permanent magnet composed of a main phase composed of a tetragonal R ₂ TM ₁₄ B intermetallic compound (a rare earth element containing R: Y, TM: Fe or Co) and a grain boundary phase composed of an R ₃ TM alloy Preferably, the crystal structure of the grain boundary phase near the interface between the main phase and the grain boundary phase is an orthorhombic structure. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG. 1 is a diagram for explaining a relationship between a distance from an interface and crystal magnetic anisotropy, in which a white circle indicates a uniaxial anisotropy constant of an example.
K ₁ and black circles indicate the uniaxial anisotropy constant K ₁ of the comparative example. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 13, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

Referring to FIGS. 1, 2A and 2B,
The difference in the distribution of magnetocrystalline anisotropy near the interface between the case where the main phase (ferromagnetic phase) and the grain boundary phase match at the interface and the case where they do not match will be described. FIG. 1 or FIG.
In (A) and (B), the “outermost shell” on the horizontal axis indicates the position of the outermost atomic layer of the main phase, and “second layer”, “third layer”.
The “layer” indicates the position of the second and third atomic layers counted from the outermost shell position toward the inside. The nth layer is far from the outermost shell, and the influence from the interface is negligible. 1, the vertical axis indicates the magnitude of the uniaxial anisotropy constant K ₁ (indicating the strength of the crystalline magnetic anisotropy) of the main phase,
Spontaneous magnetization direction of higher values of K ₁ is large main phase is stabilized in the direction of easy magnetization (c axis). Further, in FIG. 1, Example (the invention) shows the calculated values of K ₁ in the condition where the main phase and a grain boundary phase as shown in FIG. 2 (A) is aligned at the interface, the comparative example FIG. such as by 2 (B) lack of grain boundary phase, as shown in shows the calculated values of K ₁ in the case where there is such an interface mismatch.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Referring to FIG. 1, in the comparative example, the magnitude of the anisotropy constant K ₁ changes greatly depending on the distance from the interface, and the value of K ₁ in the outermost shell is significantly lower than that in the interior. ing. On the other hand, in the embodiment, without much change in the magnitude of the anisotropy constant K ₁ by the distance from the interface, the anisotropy constant K ₁ is increased in the outermost shell phase rather.
Therefore, according to the comparative example, the energy required for nucleation of the reverse magnetic domain in the outermost shell is locally reduced to facilitate nucleation and magnetization reversal, so that the coercive force of the magnet is reduced. On the other hand, according to the embodiment, since higher internal rather is K ₁ in the outermost shell, the nucleation of reverse magnetic domains at the interface is suppressed, so that the coercive force of the magnet is increased.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

The 4f electron of the Nd ³⁺ ion has a spatial distribution spread like a donut, and its magnetic moment J
Stands perpendicular to the plane where the 4f electron cloud spreads.
For donut-shaped electron cloud of 4f electrons of Nd ³⁺ ions is pulled to + charge of Nd ³⁺ ions and B ³⁺ ions adjacent in the bottom, the orientation of the magnetic moment J is a direction perpendicular to the bottom surface, namely the c-axis direction Fixed. This is,
This is the cause of the strong uniaxial magnetic anisotropy of the Nd ₂ Fe ₁₄ B phase. In a compound of a light rare earth such as Nd and a transition metal such as Fe, the magnetic moments of the two tend to be aligned in parallel by exchange interaction. As a result, Nd ₂ Fe
The magnetic moment of the entire ₁₄ B phase is oriented in the c-axis direction.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

[0021] The permanent magnet that is based on the anisotropy constant present invention, it is preferred values of the anisotropy constant K ₁ of outermost vicinity of the ferromagnetic phase is inside the same, or more.
Equivalent in this case is at least 50% or more of the internal value. It is preferable that the magnetocrystalline anisotropy in the outermost shell of the ferromagnetic particles be enhanced as compared with the magnetocrystalline anisotropy of the outermost shell of the ferromagnetic particles in the absence of the grain boundary phase.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

As the combination of the main phase and the grain boundary phase, it is preferable that both phases coexist in equilibrium in a certain temperature range, such as the SmCo ₅ main phase and the Y grain boundary phase. Also, for example, Sm
_The main phase and the second phase react with each other to form a preferred third phase at the grain boundary, such that an intermetallic compound phase (Γ-FeZn) is formed by the reaction between the ₂ Fe ₁₇ N ₃ main phase and the Zn phase. May be. In the latter case, the third phase is the grain boundary phase in the present invention.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

[Crystal Structure of Magnetic Phase and Grain Boundary Phase] The crystal structure of the grain boundary phase is preferably similar to the crystal structure of the magnetic phase. Further, it is preferable that the crystal structure of the grain boundary phase and the crystal structure of the magnetic phase have a specific orientation relationship. by this,
The consistency between the specific atom on the grain boundary phase side and the specific atom on the main phase side is enhanced. For example, a tetragonal R ₂ TM ₁₄ B intermetallic compound (R:
In a permanent magnet composed of a main phase made of a rare earth element containing Y, TM: Fe or Co) and a grain boundary phase made of an R-TM alloy, the particles near the interface between the main phase and the grain boundary phase The crystal structure of the boundary phase is preferably a face-centered cubic structure. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

The tetragonal R ₂ TM ₁₄ B intermetallic compound (R:
In a permanent magnet composed of a main phase composed of a rare earth element containing Y, TM: Fe or Co) and a grain boundary phase composed of an R ₃ TM alloy, the grain size near an interface between the main phase and the grain boundary phase is reduced. The crystal structure of the interphase is preferably an orthorhombic structure. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG. 1 is a diagram for explaining a relationship between a distance from an interface and crystal magnetic anisotropy, wherein a white circle indicates a uniaxial anisotropy constant K _{1 of} an example, and a black circle indicates a uniaxial anisotropy constant K of a comparative example. ₁ is shown.

Claims (11)

[Claims] 1. A permanent magnet having a ferromagnetic phase and a grain boundary phase, wherein the ferromagnetic phase and the grain boundary phase are matched. 2. The permanent magnet according to claim 1, wherein the atomic arrangement sandwiching the interface between the ferromagnetic phase and the grain boundary phase is regular. 3. The permanent magnet according to claim 1, wherein the grain boundary phase exists with a crystal type, a plane index, and an orientation index matching the ferromagnetic phase. 4. The ferromagnetic phase according to claim 1, wherein the magnetocrystalline anisotropy at a position adjacent to the interface of the ferromagnetic phase is at least half the magnetocrystalline anisotropy inside the ferromagnetic phase. The permanent magnet according to any one of the above. 5. The permanent magnet according to claim 1, wherein the crystal magnetic anisotropy in the outermost shell of the ferromagnetic particles is at least half the crystal magnetic anisotropy inside the ferromagnetic particles. 6. The permanent magnet according to claim 5, wherein the crystal magnetic anisotropy in the outermost shell of the ferromagnetic particles is higher than the crystal magnetic anisotropy inside the ferromagnetic particles. 7. The ferromagnetic particle, wherein the crystal magnetic anisotropy of the outer shell within 5 atomic layers from the outermost shell is higher than the crystal magnetic anisotropy inside the ferromagnetic particle. The permanent magnet as described. 8. A ferromagnetic particle mainly exhibiting magnetocrystalline anisotropy due to a crystal field of a rare earth element, and a grain boundary phase, adjacent to a rare earth element ion located at the outermost shell of the ferromagnetic particle. In the grain boundary phase, the rare earth element ion
A permanent magnet characterized in that cations are located in the direction in which the 4f electron cloud extends. 9. The cation source is Be, Mg, Al, Si, P, C
a, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sr,
9. The permanent magnet according to claim 8, wherein the permanent magnet is at least one of Zr, Nb, Mo, Cd, In, Sn, Ba, Hf, Ta, Ir, and Pb. 10. A cation source is added to ferromagnetic particles in which crystal magnetic anisotropy mainly develops due to a crystal field of a rare earth element, and the cation source is included in at least a grain boundary phase portion adjacent to the ferromagnetic particles. Depositing crystals, and positioning cations in the crystal structure of the grain boundary phase adjacent to the ferromagnetic particles in the direction in which the 4f electron cloud of the rare earth element ion located at the outermost shell of the ferromagnetic particles extends. A method for producing a permanent magnet, comprising: 11. The composition of the grain boundary phase, the crystal type in a state where both phases coexist, and the plane index and orientation according to the crystal structure of the ferromagnetic phase so that the ferromagnetic phase and the grain boundary phase match. A method for designing a permanent magnet, comprising setting an index.