JP2010258040A - High coercive force coating magnet powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet which has superior performance by applying a concept of improving coercive force by using crystallographic consistency to general magnets without limitation to sintered magnets. <P>SOLUTION: Coating magnet powder applied to a bond magnet includes magnet powder which has a R<SB>1</SB>-Fe-B-based composition, and also has an (a) axis, a (b) axis and a (c) axis having lattice constants (a), (b) and (c), R<SB>1</SB>being a rare earth element or Y; and a nonmagnetic coating which covers at least part of a periphery of the magnet powder and has an a' axis, a b' axis and a c' axis having lattice constants a', b' and c'. Here, a deviation between the (a) axis and a' axis, a deviation between the (b) axis and b' axis, and a deviation between (c) axis and c' axis are all ≤5°, and at least one of an expression (I) of ¾(a-la')¾/a<0.1, an expression (II) of ¾(b-mb')¾/b<0.1, and an expression (III) of ¾(c-nc')¾/c<0.1 (where (l), (m) and (n) are natural numbers) is satisfied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnet powder having a high coercive force and coated with a nonmagnetic coating (hereinafter referred to as a coated magnet powder). More particularly, the present invention relates to high coercivity coated magnet powders primarily for use in the manufacture of bonded magnets.

  Nd-Fe-B magnets have a high saturation magnetic flux density and a high coercive force, and are therefore used in various devices centering on motors. However, the required magnetic properties are increasing year by year, and improvements have always been required. In such a situation, the saturation magnetic flux density has been improved to the theoretical limit, but the coercive force still has room for improvement.

  Recently, as a mechanism for realizing a high coercive force, crystallographic consistency between the magnet powder and the Nd-rich phase at the grain boundary has attracted attention. In order to improve the coercive force, it is considered effective to suppress the occurrence of reverse magnetic domains. And it is thought that a reverse magnetic domain occurs at a grain boundary with many crystallographic defects when a magnetic field in the direction opposite to the magnetization of the magnet powder is applied. Therefore, if the defects are reduced by providing crystallographic consistency between the two phases at the interface between the magnet powder and the grain boundary phase, the reverse magnetic domains are less likely to occur, and as a result, the coercive force can be improved. . In fact, it has been proposed to realize crystallographic consistency between the magnet powder and the grain boundary phase by heat treatment, and to improve the holding power as compared with the case where the grain boundary phase is amorphous (Patent Document 1). reference).

However, Nd-Fe-B based Nd-O grain boundary phase of the magnet whereas a face-centered cubic (cubic fcc) structure of cubic, _Nd 2 _{Fe 14} B magnet powder is tetragonal a main phase The crystal structure of the system (tetragonal). Therefore, the lattice constants of the magnetic powder and the grain boundary phase are close to each other, and the lattice matching, which is effective for improving the coercive force, can be realized only in a specific direction. For example, a phenomenon has been reported that when a sintered magnet having anisotropy is cut out in a direction parallel to the c magnetic domain and Nd-O is aligned, the coercive force is restored (see Non-Patent Document 1). This is because the lattice constant a = 0.548 nm of Nd ₂ O _3-x constituting the Nd—O phase is the lattice constant (c / 2) in the c-axis direction of the main phase Nd ₂ Fe ₁₄ B magnet powder. It is presumed to be due to the approximation to 0.6 nm. However, if all the grain boundary phases are simply made into the Nd-O phase, the crystallographic consistency is obtained on the plane whose interface is parallel to the c-axis of the magnet powder (that is, the plane where the lattice including the lattice constant c exists). However, crystallographic consistency is not achieved in a plane whose interface is perpendicular to the c-axis of the magnet powder (that is, a plane in which no lattice including the lattice constant c exists). That is, crystallographic consistency cannot be achieved on all surfaces of the crystal grains. FIG. 1 shows a structure in which an Nd—O grain boundary phase 20 is formed around cubic Nd—Fe—B crystal grains 10 as a simple example. As shown in FIG. 1, crystallographic consistency can be achieved in the plane 30 parallel to the c-axis 50 of the Nd—Fe—B crystal, but in the plane 40 perpendicular to the c-axis 50, Consistency cannot be achieved. Since the surface where crystallographic matching is achieved is four of the six faces, the area of the surface where crystallographic matching is achieved is 2 of the total surface area of the Nd—Fe—B crystal grains 10. / 3 only.

  As described above, the concept of improving coercive force by utilizing crystallographic consistency is mainly applied to sintered magnets. However, in order to make the best use of the effect industrially, it is desirable to apply this concept not only to heat-treated sintered magnets but also to magnets in general.

JP 2000-49005 A

Journal of Applied Physics 104, 013911 (2008)

  The object of the present invention is not limited to sintered magnets, and provides a magnet having excellent performance by applying the concept of improving coercivity by utilizing crystallographic consistency to all magnets. There is.

The coated magnet powder of the first embodiment of the present invention is
A magnet powder having a composition of R ₁ -Fe-B system and having an a axis having a lattice constant a, a b axis having a lattice constant b, and a c axis having a lattice constant c, wherein R ₁ is a rare earth element Or magnet powder which is Y,
A nonmagnetic coating covering at least a part of the periphery of the magnet powder and having an a ′ axis having a lattice constant a ′, a b ′ axis having a lattice constant b ′, and a c ′ axis having a lattice constant c ′ The deviation between the a axis and the a ′ axis, the deviation between the b axis and the b ′ axis, and the deviation between the c axis and the c ′ axis are all within 5 °, and the following formulas (I) to (III) )
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
(Wherein l, m and n are natural numbers)
It is characterized in that at least one of the following holds. Here, when one or two of the formulas (I) to (III) are established, the dimension of the magnet powder in the direction parallel to the axis corresponding to the established formula is set to the corresponding axis that is not established. It is desirable that it is larger than the size of the magnet powder in the parallel direction. In addition, the nonmagnetic coating film may be an R ₂ —O oxide (wherein R ₂ is one or more elements selected from the group consisting of rare earth elements and Y), and preferably (Nd _1-y La _y ) ₂ —O _3-x oxide (0 <x <1, 0 <y <1) may be formed.

  The use of the coated magnet powder according to the second embodiment of the present invention is characterized in that the coated magnet powder described in the first embodiment is used in the production of a bonded magnet.

The method for producing a coated magnet powder according to the third embodiment of the present invention,
(1) A magnet powder having a composition of the R ₁ -Fe-B system and having an a-axis having a lattice constant a, a b-axis having a lattice constant b, and a c-axis having a lattice constant c, wherein R ₁ Preparing a magnet powder which is a rare earth element or Y;
(2) pressurizing the magnet powder in a uniaxial direction in a sealed container to form a flat magnet powder;
(3) forming a nonmagnetic film covering at least a part of the periphery of the flat magnet powder, wherein the nonmagnetic film has an a ′ axis having a lattice constant a ′ and b having a lattice constant b ′. The c 'axis with the' axis and lattice constant c ', and the deviation between the a axis and the a' axis, the deviation between the b axis and the b 'axis, and the deviation between the c axis and the c' axis are all Within 5 ° and the following formulas (I) to (III)
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
It is characterized in that at least one of the following holds. Here, the step (3) is a step of applying (i) an R ₂ complex to the surface of the flat magnet powder, wherein R ₂ is a rare earth element or Y, and (ii) an R ₂ complex. And a step of thermally oxidizing to form a nonmagnetic film made of an R ₂ —O oxide. Alternatively, step (3) is a step of (i ′) attaching R ₂ metal to the surface of the flat magnet powder, wherein R ₂ is a rare earth element or Y, and (ii ′) R ₂ And a step of thermally oxidizing a metal to form a nonmagnetic film made of an R ₂ —O oxide. Here, step (i ′) may be performed by a coating method, a vapor deposition method, a sputtering method, or a plating method. Alternatively, step (3) is a step of (i ″) depositing an R ₂ —O oxide on the surface of the flat magnet powder using a plating method, wherein R ₂ is a rare earth element or Y. And (ii ″) a step of heat-treating the R ₂ —O oxide to form a nonmagnetic film. Also, the non-magnetic _film, be formed of _{(Nd 1-y La y)} 2 -O 3-x oxide (0 <x <1,0 <y <1) desirable.

  By adopting the configuration of the present invention, the concept of improving the coercive force of a magnet using crystallographic consistency, which has been conventionally known for sintered magnets, is applied to coated magnet powder for forming bonded magnets and the like. It becomes possible to apply to. Moreover, since the coated magnet powder obtained in this way has a high coercive force, if an anisotropic bonded magnet is produced using this, a bonded magnet having a higher coercive force than before can be obtained. The applicable range of magnets becomes wider.

It is sectional drawing which shows the cube-shaped coated magnet powder of a prior art. It is sectional drawing which shows the rectangular parallelepiped covered magnet powder of this invention.

  The coated magnet powder according to the first embodiment of the present invention includes an uncoated magnet powder that is a main phase and a nonmagnetic coating that covers at least a part of the periphery of the magnet powder, and the magnet powder and the nonmagnetic coating. The crystallographic consistency between is at least partially achieved.

The magnet powder as the main phase has an R ₁ —Fe—B composition, and has an a-axis having a lattice constant a, a b-axis having a lattice constant b, and a c-axis having a lattice constant c. Here, R ₁ is a rare earth element or yttrium (Y). In the present invention, “rare earth element” means an element from La having an atomic number of 57 to Lu having an atomic number of 71. The “R ₁ —Fe—B-based composition” in the present invention means a composition containing R ₁ , Fe and B as main components and optionally further containing an additive element. Additive elements that can be used include Cu, Ag, Al, Zr, and the like. Alternatively, in the “R ₁ —Fe—B composition” in the present invention, a part of Fe may be substituted with Co.

  The nonmagnetic coating covers at least a portion of the periphery of the magnet powder and has an a 'axis having a lattice constant a', a b 'axis having a lattice constant b', and a c 'axis having a lattice constant c'. Here, the “a′-axis”, “b′-axis”, and “c′-axis” of the nonmagnetic coating do not necessarily coincide with the crystallographic a-axis, b-axis, and c-axis. For example, the crystallographic c-axis may be treated as the “a′-axis”.

Materials that can be used to form the nonmagnetic coating include R ₂ —O-based oxides. Wherein, R ₂ may be a rare earth element or Y.

In the present invention, “the crystallographic consistency between the magnet powder and the nonmagnetic coating is at least partially achieved” means that the a-axis and the a′-axis shift, the b-axis and the b′-axis, And the deviation between the c-axis and the c′-axis are all within 5 °, and the following formulas (I) to (III)
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
(Wherein l, m and n are natural numbers)
It is characterized in that at least one of the following holds. In addition, regarding the formulas (I) to (III) of the present invention, when there is at least one natural number l, m, or n satisfying each relationship, the formula is regarded as “established”.

The above formulas (I) to (III) indicate that the value obtained by multiplying the lattice constant of any crystal axis of the material constituting the nonmagnetic coating by a natural number is the lattice of any crystal axis of the material constituting the magnet powder. It means that it is within the range of ± 10% of the constant. As described above, Nd ₂ O _3-x that is an Nd—O-based oxide has a lattice constant a of 0.548 nm, and the c-axis lattice of Nd ₂ Fe ₁₄ B that is an Nd—Fe—B-based material. Between constant c = about 1.2 nm, the formula (III) is satisfied (here, the lattice constant a of Nd ₂ O _3-x is treated as “c ′”, and the natural number n is 2). .

However, the integral multiple of the lattice constant of the rare earth oxide and yttrium oxide constituting the nonmagnetic coating is slightly smaller, and perfect crystallographic consistency is often not achieved. In order to achieve a more complete crystallographic consistency, a part of the rare earth element or yttrium can be replaced with La or the like having a larger ionic radius. Specifically, a part of Nd in Nd ₂ O _3-x was substituted with La (Nd _1-y La _y ) ₂ O _3-x (where 0 <x <1, 0 <y <1 ) Can be used to form a non-magnetic coating.

  The bonded magnet is obtained by solidifying coated magnet powder with a resin. Each of the coated magnet powders constituting the bonded magnet is composed of a magnet powder and a non-magnetic film that coats the magnet powder in a crystallographically aligned state using a material having the same crystal structure and lattice constant as the magnet powder. By constructing, in principle, defects appear only on the surface of the nonmagnetic coating, and defects at the interface between the magnet powder responsible for magnetism and the magnet powder and the nonmagnetic coating can be eliminated. At present, it is difficult to find such an ideal nonmagnetic coating material, but even when the lattice constants in a specific direction match and crystallographic consistency is achieved in that direction, It is considered that the coercive force can be increased.

  In particular, the aspect ratio of the magnet powder is controlled, and the surface where crystallographic consistency is achieved, that is, the magnet powder extending in the direction of the crystal axis satisfying the formulas (I) to (III) is used as a raw material. It is effective for increasing the coercive force. In other words, when one or two of the formulas (I) to (III) are established, the dimension of the magnet powder in the direction parallel to the axis corresponding to the established formula is set to the corresponding axis that is not established. It is effective for increasing the coercive force to be larger than the size of the magnet powder in the direction parallel to the magnetic field. This is because the area of the surface where crystallographic consistency is achieved can be increased.

  As a simple example, as shown in FIG. 2, around the magnet powder 10 having a rectangular parallelepiped crystal structure having a dimensional ratio of a-axis direction: b-axis direction: c-axis direction = 1: 1: 2. Let us consider a case where the magnet powder is coated with a nonmagnetic coating 20 made of a cubic material having a lattice constant approximate to the c-axis lattice constant c. In this case, it is considered that the above formula (III) is established. Then, crystallographic consistency is achieved on the rectangular surface 30 parallel to the c-axis of the magnet powder, and crystallographic consistency is achieved on the square surface 40 perpendicular to the c-axis of the magnet powder. Not. However, the surface area of the surface where crystallographic consistency is achieved is 4/5 of the total surface area of the magnet powder, which is greater than that of the square magnet powder shown in FIG. In other words, when the formula (III) relating to the c-axis is satisfied, the size of the magnet powder in the direction parallel to the c-axis is larger than the size in the direction parallel to the a-axis and the size in the direction parallel to the b-axis. By doing so, the ratio of the surface area of the surface where crystallographic consistency is achieved can be increased and the coercivity can also be increased. Similarly, when the formula (I) concerning the a axis or the formula (II) concerning the b axis is established, the coercive force is increased by increasing the size of the magnet powder in the direction parallel to the a axis or the b axis. be able to.

  The second embodiment of the present invention is the use of the coated magnet powder of the first embodiment in the manufacture of bonded magnets. With respect to the coated magnet powder of the first embodiment, about 0.1 to 5% by mass of a curable binder resin is added and mixed based on the total mass of the coated magnet powder, and the mixture is applied while applying an external magnetic field. The bonded magnet can be formed by molding and finally performing a curing treatment of the curable binder resin. Curable binder resins that can be used include any thermosetting resin known in the art, such as an epoxy resin. For mixing the coated magnet powder and the curable binder resin, any kneading means known in the art such as a roll mill and a ball mill can be used. Furthermore, the molding of the mixture of the coated magnet powder and the curable binder resin can be performed using means such as compression (press) molding. The curing treatment of the curable binder resin depends on the curable binder resin used, but can be performed by heating to an appropriate temperature.

The third embodiment of the present invention is a method for producing a coated magnet powder according to the first embodiment. The method of the present invention comprises (1) a magnet powder having a composition of the R ₁ -Fe-B system and having an a axis having a lattice constant a, a b axis having a lattice constant b, and a c axis having a lattice constant c A step of preparing a magnet powder in which R ₁ is a rare earth element or Y, and (2) a step of pressing the magnet powder in a uniaxial direction in a sealed container to form a flat magnet powder, 3) forming a non-magnetic film covering at least a part of the periphery of the flat magnet powder, wherein the non-magnetic film has an a ′ axis having a lattice constant a ′ and b ′ having a lattice constant b ′. The axis and the c ′ axis having the lattice constant c ′, and the deviation between the a axis and the a ′ axis, the deviation between the b axis and the b ′ axis, and the deviation between the c axis and the c ′ axis are all 5 And within the following formulas (I) to (III)
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
It is characterized in that at least one of the following holds.

Step (1) can be performed using any means known in the art. For example, step (1) is performed by (a) forming a quenched ribbon of a magnet alloy having a composition of R ₁ —Fe—B system, and (b) forming a magnet powder made of the magnet alloy from the quenched ribbon. can do.

  Step (2) is performed by pressurizing the crystal grains obtained in step (1) in a uniaxial direction in a sealed container. For example, (c) filling the uncoated magnet powder obtained in step (1) into a sealed container, and (d) compressing the inside of the sealed container in a uniaxial direction at a temperature of 650 to 900 ° C. The step (2) can be carried out by plastically deforming the magnet powder to form a flat magnet powder having a large aspect ratio in the c-axis direction. Here, the sealed container is preferably made of metal.

Step (3) can be performed by any of a method using an R ₂ complex as a raw material, a method using an R ₂ metal as a raw material, or a method using an R ₂ —O oxide as a raw material (here, R ₂ is a rare earth element or yttrium).

Step method of using the R ₂ complex is a first method (3) is, (i) a step of applying to the surface of the flat magnetic powder uncoated and R ₂ complex, thermal oxidation (ii) R ₂ complex And a step of forming a nonmagnetic film made of an R ₂ —O oxide. Step (i) can be performed using a solution of the R ₂ complex. R ₂ complexes that can be used include tris (acetylacetonato) complexes such as tris (acetylacetonato) neodymium. For example, tris (acetylacetonato) neodymium is dissolved in propanol to form a coating solution, and the flat magnet powder is coated with an R ₂ complex by immersing the flat magnet powder in the coating solution. Can be obtained.

Step (ii) can be performed by heating the flat magnet powder to which the coating film made of the R ₂ complex is attached in an oxygen-containing atmosphere. The oxygen-containing atmosphere that can be used preferably contains an inert gas such as Ar as a main component and contains a sufficient amount of oxygen to achieve the desired oxidation of the R ₂ complex. The R ₂ —O oxide produced by this heat treatment is automatically aligned in a direction that achieves crystallographic consistency with the flat crystal grains. Here, by appropriately setting the conditions of the heat treatment, a of R ₂ -O oxide forming the nonmagnetic film ', b' and c 'axis, of the corresponding flat magnet powder a, b and c It is desirable that the deviation from the shaft be within 5 °. For example, in the case of the above-mentioned flat crystal grains to which tris (acetylacetonato) neodymium is adhered, the flat shape is obtained by heating the propanol to a temperature of 350 ° C. for about 1 hour after evaporating propanol and drying the film. A nonmagnetic coating can be formed on the surface of the magnet powder.

By appropriately selecting the composition of the R ₁ , R ₂ , R ₁ —Fe—B magnet alloy and using the above method, the formulas (I) to (III)
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
It is possible to prepare a coated magnet powder composed of flat crystal grains and a non-magnetic film, in which at least one of the following is established.

Here, a mixture of two or more elements may be used as R ₂ in order to bring the left side of formulas (I) to (III) closer to 0, ie, to achieve more complete crystallographic consistency. . For example, lanthanum having a larger ionic radius can be added to rare earth elements such as neodymium. This can be achieved by using a mixture of a neodymium complex and a lanthanum complex having an appropriate mixing ratio in step (3) (i). By using the above-mentioned mixture, it is possible to obtain a coated magnetic powder having a non-magnetic film made of (Nd _1-y La _y ) ₂ O _3-x oxide (0 <x <1, 0 <y <1). it can.

As described above, it is a feature of the method of the present invention that is different from a sintered magnet that R ₂ having a composition different from R _{1 in} the crystal grains of the R ₁ —Fe—B magnet alloy can be used. In the preparation of a sintered magnet, even if a powder in which the periphery of the magnet alloy is coated with an oxide of a different rare earth element is used as the powder to be sintered, the rare earth element in the coating is diffused by the magnet alloy during sintering. It will be mixed with the rare earth elements that make up. Therefore, the sintering method gives a magnet powder having a uniform composition as a whole, and does not form a coated magnet powder having an oxide film of rare earth elements having different compositions on the surface.

The method using R ₂ metal, which is the second method of step (3), is a step of (i ′) attaching R ₂ metal to the surface of the uncoated flat magnet powder, wherein R ₂ is a rare earth And (ii ′) a step of thermally oxidizing the R ₂ metal to form a nonmagnetic film made of an R ₂ —O oxide. Here, the step (i ′) can be performed using a vapor deposition method, a sputtering method, or a plating method. For example, a metal film of rare earth elements such as neodymium or yttrium can be formed by performing vapor deposition or sputtering while applying vibration to the flat crystal grains as the main phase. Here, the adhesion amount of the R ₂ metal is desirably about 1% based on the volume of the flat magnet powder. This is because the metal coating is converted into a nonmagnetic coating in step (ii ′).

  Step (ii ') can be performed by heating the flat magnet powder having a metal coating to an appropriate temperature in an oxygen-containing atmosphere. The oxygen-containing atmosphere that can be used preferably contains an inert gas such as Ar as a main component and contains a sufficient amount of oxygen to achieve the desired oxidation of the metal film. By this step, the crystal axes in the nonmagnetic coating and the crystal axes of the flat crystal grains as the main phase are aligned. Further, by appropriate selection of the material, any one of the formulas (I) to (III) is established, and crystallographic consistency between the flat crystal grains and the nonmagnetic film is achieved.

Here, also in the step (i ′), as in the first method of the step (3), more complete crystallographic consistency can be realized by using two or more metals as R _2. . When the vapor deposition method is used, a vapor deposition source in which two or more metals are mixed can be used, or a co-vapor deposition method in which two or more metals are vapor-deposited from separate vapor deposition sources can be used. When the sputtering method is used, a metal mixture film can be formed using a target in which two or more metals are mixed. In the plating method, a plating solution containing two or more metal precursors can be used.

The method using the R ₂ oxide which is the third method in the step (3) includes (i ″) a step of attaching the R ₂ —O oxide to the surface of the uncoated flat magnet powder using a plating method; (Ii ″) heat-treating the R ₂ —O oxide to form a nonmagnetic film. Step (i ″) can be performed by plating the R ₂ metal precursor or R ₂ —O oxide precursor in the presence of an oxidant. Also, step (ii ″) can be performed using oxygen. It can be carried out by heating the flat crystal grains having the R ₂ —O oxide film to an appropriate temperature in a non-containing atmosphere or an oxygen-containing atmosphere. By this step, the crystal axes in the nonmagnetic coating and the crystal axes of the flat crystal grains as the main phase are aligned. Further, by appropriate selection of the material, any one of the formulas (I) to (III) is established, and crystallographic consistency between the flat crystal grains and the nonmagnetic film is achieved.

Example 1
As a flat magnet powder that can be actually realized by the above method, for example, it is conceivable to use a plate-like powder having a length ratio in three directions of 5: 5: 1. At this time, the ratio of the alignment surface is about 86% ([(5 × 5) × 2 + (5 × 1) × 2] / [(5 × 5) × 2 + (5 × 1) × 4]) Compared to 67% in the case of magnet powder, it can be increased by about 20%.

(Example 2)
The lattice constant of the rare earth oxide R ₂ O ₃ having a cubic structure is 0.568 nm when R = La and 0.554 nm when R = Nd. On the other hand, the length of the c-axis length of Nd ₂ Fe ₁₄ B having a tetragonal structure is 1.22 nm. The value of 1/2 of the length of the c-axis length of Nd ₂ Fe ₁₄ B is 0.61 nm, which is further larger than the value of R ₂ O ₃ where R = La is 0.568 nm. That is, even if y = 1 is not yet sufficient to completely establish crystallographic consistency in (Nd _1-y La _y ) ₂ O _3-x . In addition, when x is 0 or more, the lattice constant of (Nd _1-y La _y ) ₂ O _3-x is expected to further decrease. Therefore, y = 1 is best from the viewpoint of crystallographic consistency. However, if a large amount of La is contained around the magnet powder as the main phase, La diffuses into the magnet powder during the heat treatment and replaces a part of Nd in Nd ₂ Fe ₁₄ B. Since the coercivity of La ₂ Fe ₁₄ B produced by such substitution is not so high, as a result, the coercivity of the coated magnet powder after coating with an oxide does not increase as expected. In view of the above, the optimum value of y may be adopted in consideration of crystallographic consistency and a decrease in retention due to La nucleic acid.

DESCRIPTION OF SYMBOLS 10 Magnet powder 20 Nonmagnetic coating 30 Plane parallel to c-axis of crystal grain 40 Plane perpendicular to c-axis of crystal grain 50 C-axis of crystal grain

Claims (13)

A magnet powder having a composition of R ₁ -Fe-B system and having an a axis having a lattice constant a, a b axis having a lattice constant b, and a c axis having a lattice constant c, wherein R ₁ is a rare earth element Or magnet powder which is Y,
A nonmagnetic coating covering at least a part of the periphery of the magnet powder and having an a ′ axis having a lattice constant a ′, a b ′ axis having a lattice constant b ′, and a c ′ axis having a lattice constant c ′ A coated magnet powder comprising:
The deviation between the a axis and the a ′ axis, the deviation between the b axis and the b ′ axis, and the deviation between the c axis and the c ′ axis are all within 5 °, and the following formulas (I) to (III)
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
(Wherein l, m and n are natural numbers)
A coated magnet powder characterized in that at least one of the following holds:   The dimension of the magnet powder in the direction parallel to the axis corresponding to the established formula is one or two of the formulas (I) to (III) and the direction parallel to the corresponding axis not established The coated magnet powder according to claim 1, wherein the coated magnet powder is larger than the size of the magnet powder. The nonmagnetic film is formed of an R ₂ —O oxide (wherein R ₂ is one or more elements selected from the group consisting of rare earth elements and Y). 3. The coated magnet powder according to 1 or 2. The coated magnet powder according to claim 3, wherein R ₂ has a composition different from that of R ₁ . The non-magnetic film is formed of (Nd _1-y La _y ) ₂ -O _3-x oxide (0 <x <1, 0 <y <1). Coated magnet powder.   Use of the coated magnet powder according to any one of claims 1 to 5 in the production of a bonded magnet. (1) A magnet powder having a composition of the R ₁ -Fe-B system and having an a-axis having a lattice constant a, a b-axis having a lattice constant b, and a c-axis having a lattice constant c, wherein R ₁ Preparing a magnet powder which is a rare earth element or Y;
(2) pressurizing the magnet powder in a uniaxial direction in a sealed container to form a flat magnet powder;
(3) forming a nonmagnetic film covering at least a part of the periphery of the flat magnet powder, wherein the nonmagnetic film has an a ′ axis having a lattice constant a ′ and b having a lattice constant b ′. The c 'axis with the' axis and lattice constant c ', and the deviation between the a axis and the a' axis, the deviation between the b axis and the b 'axis, and the deviation between the c axis and the c' axis are all Within 5 ° and the following formulas (I) to (III)
| (A−la ′) | / a <0.1 (I)
| (B−mb ′) | / b <0.1 (II)
| (C−nc ′) | / c <0.1 (III)
A method for producing a coated magnet powder, wherein at least one of the following holds: Step (3) is
(I) a step of applying an R ₂ complex to the surface of the flat magnet powder, wherein R ₂ is a rare earth element or Y;
And (ii) thermally oxidizing the R ₂ complex to form a non-magnetic film made of an R ₂ —O oxide. Step (3) is
(I ′) attaching R ₂ metal to the surface of the flat magnet powder, wherein R ₂ is a rare earth element or Y;
The method of manufacturing a coated magnet powder according to claim 7, further comprising: (ii ′) thermally oxidizing the R ₂ metal to form a nonmagnetic film made of an R ₂ —O oxide.   The method for producing a coated magnet powder according to claim 9, wherein step (i) is performed by a coating method, a vapor deposition method, a sputtering method, or a plating method. Step (3) is
(I ″) a step of attaching an R ₂ —O oxide to the surface of the flat magnet powder using a plating method, wherein R ₂ is a rare earth element or Y;
The method for producing a coated magnet powder according to claim 7, further comprising: (ii ″) a step of heat-treating the R ₂ —O oxide to form a nonmagnetic film. The method for producing a coated magnet powder according to claim 8, wherein R ₂ has a composition different from that of R ₁ . The nonmagnetic film is formed of (Nd _1-y La _y ) ₂ O _3-x oxide (0 <x <1, 0 <y <1). The manufacturing method of the coated magnet powder as described in 1 ..

Images