JP2012204517A - Rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth magnet having excellent adhesive property between a magnet body and a protective layer, and excellent corrosion resistance to hydrogen.SOLUTION: A rare earth magnet 100 comprises a magnet body 10 including a rare earth element, and a protective layer 20 coating the magnet body 10. The protective layer 20 has a first layer 22 formed on a surface of the magnetic body 10, and a second layer 24 positioned on the opposite side of the magnet body 10 interposing the first layer 22. A surface region 2 of the magnet body 10 contains one kind or more of elements EA such as Si, and N, and the first layer 22 contains one kind or more of metals such as Ni or an alloy including the metals. The second layer 24 contains nitride, and the nitride contains one kind or more of elements E2 such as Si and Ti.

Description

  The present invention relates to a rare earth magnet having a protective layer.

  Rare earth magnets such as R-T-B magnets containing rare earth elements R, transition metals T, and boron B have high magnetic properties and are used in various fields as permanent magnets. Such rare earth magnets usually contain rare earth elements that are relatively easily corroded. For this reason, in order to suppress the deterioration of the magnetic characteristics as a permanent magnet, it has been proposed to provide protective layers of various materials on the magnet body.

  For example, in Patent Document 1 below, an attempt is made to improve the corrosion resistance of rare earth magnets against hydrogen or the like by providing a hydrogen-containing amorphous carbon film on a base film containing various metals.

Japanese Patent Laid-Open No. 2007-158030

  However, since the hydrogen-containing amorphous carbon film of the rare earth magnet as described in Patent Document 1 has bonds between elements having 4 valence electrons, a strong bond is formed between the elements. Since the degree of freedom of bonding is low, large internal stress (residual stress) is likely to occur, and structural defects tend to occur. For this reason, when used in a corrosive environment, a corrosive substance enters from a structural defect and the magnet body is corroded, making it difficult to maintain the original magnetic properties of the rare earth magnet. That is, it has been difficult to achieve sufficient corrosion resistance against hydrogen and the like in a rare earth magnet in which a corrosive substance such as hydrogen is physically blocked by a carbon coating.

  Another example of the protective layer provided on the surface of the magnet body is a silicon nitride film (nitride film). However, when the protective layer is a film containing a compound having a light element such as a nitride film, the adhesion between the magnet element body containing the rare earth element and the protective layer is not sufficient, and the protective layer is formed from the magnet element body. It was found that they could be peeled off and could cause corrosion of the magnet body and deterioration of magnetic properties.

  This invention is made | formed in view of the said situation, and it aims at providing the rare earth magnet which is excellent in the adhesiveness of a magnet element | base_body and a protective layer, and excellent in the corrosion resistance with respect to hydrogen.

  In order to achieve the above object, the present inventors have studied various materials and structures of the protective layer. Then, by forming a layer containing a specific compound as a protective layer on the surface of the magnet body and diffusing a specific element in the vicinity of the surface of the magnet body, the adhesion between the protective layer and the magnet body is increased. It was found that a rare earth magnet having excellent corrosion resistance against hydrogen can be obtained.

  That is, the rare earth magnet according to the present invention is a rare earth magnet including a magnet element body including a rare earth element and a protective layer covering the magnet element body, and the protective layer is formed on the surface of the magnet element body. A first layer and a second layer located on the opposite side of the magnet body across the first layer, and the surface area of the magnet body is Si, Al, Ta, Ti, Zr, Hf, Nb One or more elements EA selected from the group consisting of Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, Ca, Sr, Ce and Be And the first layer contains at least one metal selected from the group consisting of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, or the metal. The second layer contains nitride, which is composed of Si, Al, Ta, T , Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, Ca, Sr, Ce, and Be are selected. Contains one or more elements E2.

  The rare earth magnet according to the present invention has excellent adhesion between the magnet body and the protective layer, and also has excellent corrosion resistance against hydrogen.

  In the present invention, the N content in the surface region is XA atomic%, the total content of the elements EA in the surface region is YA atomic%, and the N content in the second layer is X2 atomic%. In addition, when the total content of the elements E2 in the second layer is Y2 atomic%, it is preferable that X2 / Y2 <XA / YA. Thereby, the corrosion resistance with respect to hydrogen of a rare earth magnet becomes easy to improve.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in the adhesiveness of a magnet body and a protective layer, the rare earth magnet excellent in the corrosion resistance with respect to hydrogen can be provided.

It is a perspective view which shows typically suitable embodiment of the rare earth magnet of this invention. It is a schematic cross section at the time of cut | disconnecting the rare earth magnet shown in FIG. 1 along the II-II line. It is sectional drawing which shows typically another Embodiment of the rare earth magnet of this invention.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings as the case may be. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

(Rare earth magnet)
As shown in FIG. 1, the rare earth magnet 100 includes a magnet body 10 and a protective layer 20 that covers the surface of the magnet body 10. The protective layer 20 has a stacked structure in which the first layer 22 and the second layer 24 are sequentially stacked from the magnet body 10 side.

  The surface region 2 of the magnet body 10 includes Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, and Ba. N is diffused with at least one element EA selected from the group consisting of La, Y, Ca, Sr, Ce and Be. The first layer 22 contains one or more metals selected from the group consisting of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, or an alloy containing the metal. The second layer 24 contains a nitride. The nitride includes Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, Ca And one or more elements E2 selected from the group consisting of Sr, Ce and Be.

  Hereinafter, the magnet body 10, the surface region 2, the first layer 22, and the second layer 24 will be described in detail.

  The magnet body 10 includes one or more elements selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanoids belonging to Group 3 of the long-period periodic table as rare earth elements. Here, the lanthanoid is lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy). , Holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

  The magnet body 10 is, as the rare earth element, at least one element selected from Nd, Pr, Ho and Tb, or La, Sm, Ce, Gd, Er, Eu, Tm, Yb and Y among the elements described above. It is preferable to contain at least one element selected from

The magnet body 10 may be a sintered magnet or a bonded magnet. Examples of the magnetic particles contained in the magnet body include Sm—Co based magnetic particles, Nd—Fe—B based magnetic particles, and Sm—Fe—N based magnetic particles. Among these, as the magnetic particles, Sm—Co based magnetic particles represented by SmCo ₅ and Sm ₂ Co ₁₇ or Nd—Fe—B based magnetic particles represented by Nd ₂ Fe ₁₄ B are used. preferable.

  When the magnet body 10 is an Nd—Fe—B sintered magnet, the content ratio of the rare earth element in the magnet body 10 is preferably 8 to 40% by mass, more preferably 15 to 35% by mass. It is. If the content ratio of the rare earth element is less than 8% by mass, the rare earth magnet 100 having a high coercive force (iHc) tends to be hardly obtained. On the other hand, when the content of the rare earth element exceeds 40% by mass, the R-rich nonmagnetic phase increases, and the residual magnetic flux density (Br) of the rare earth magnet 100 tends to decrease.

  The content ratio of Fe in the magnet body 10 is preferably 42 to 90 mass%, more preferably 60 to 80 mass%. If the Fe content is less than 42% by mass, Br of the rare earth magnet 100 tends to decrease, and if it exceeds 90% by mass, the iHc of the rare earth magnet 100 tends to decrease.

  The content ratio of B in the magnet body 10 is preferably 0.5 to 5% by mass. If the B content is less than 0.5% by mass, the iHc of the rare earth magnet 100 tends to decrease, and if it exceeds 5% by mass, the B-rich nonmagnetic phase increases. It tends to decrease.

  A part of Fe may be substituted with cobalt (Co). As a result, the temperature characteristics can be improved without impairing the magnetic characteristics of the rare earth magnet 100. A part of B may be substituted with one or more elements selected from the group consisting of carbon (C), phosphorus (P), sulfur (S), and copper (Cu). As a result, the productivity of the rare earth magnet 100 can be improved and the production cost can be reduced.

  From the viewpoint of improving the coercive force of the rare earth magnet 100, improving productivity, and reducing the cost, the magnet body 10 is made of aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn ), Bismuth (Bi), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), antimony (Sb), germanium (Ge), tin (Sn), zirconium (Zr), nickel (Ni) ), Silicon (Si), gallium (Ga), copper (Cu), and / or hafnium (Hf), and the like.

  The magnet body 10 may contain oxygen (O), nitrogen (N), carbon (C), and / or calcium (Ca) as inevitable impurities.

  The surface region 2 of the magnet body includes Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La N, one or more elements EA selected from the group consisting of Y, Ca, Sr, Ce and Be. The element EA may be the same as or different from the element E2 included in the second layer 24. For example, EA may be Si and E2 may be Si and Ti. EA may be Si and Ti, and E2 may be Si. Further, the elements EA and N in the surface region 2 may or may not form a nitride.

  The protective layer 20 includes a first layer 22 and a second layer 24 in order from the magnet body 10 side.

  The first layer 22 contains as a main component at least one metal selected from the group consisting of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, or an alloy containing the metal. The total content of metals and alloys in the first layer 22 is preferably 90% by mass or more, more preferably 95% by mass or more. The metal elements other than Al described above are metal elements belonging to the D block of the fourth period of the long-period periodic table. Since such a metal element has an atomic radius smaller than that of the rare earth element contained in the magnet body 10, it is between the first layer 22 and the second layer 24 and between the magnet body 10 and the first layer 22. Both adhesiveness can be made high. The first layer 22 does not substantially contain nitrogen.

  More preferably, the first layer 22 includes at least one metal selected from the group consisting of Al, Ni, Cu, and Zn, or an alloy containing the metal, among the above metal elements. Since the metal element contained in such a metal or alloy has an atomic radius similar to that of the light element contained in the second layer 24, the adhesion between the first layer 22 and the second layer 24 is further improved. be able to.

  The second layer 24 contains a nitride. This nitride is composed of Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, Ca And one or more elements E2 selected from the group consisting of Sr, Ce and Be. Specific nitrides include silicon nitride, aluminum nitride, tantalum nitride, titanium nitride, zirconium nitride, hafnium nitride, niobium nitride, magnesium nitride, chromium nitride, nickel nitride, molybdenum nitride. Ride, Vanadium Nitride, Tungsten Nitride, Iron Nitride, Boron Nitride, Gallium Nitride, Germanium Nitride, Bismuth Nitride, Manganese Nitride, Barium Nitride, Lanthanum Nitride, Yttrium Nitride, Calcium Nitride, One or more nights selected from the group consisting of strontium nitride, cerium nitride and beryllium nitride Ido and the like.

  The nitrogen content X2 in the second layer 24 is preferably 10 to 70 atomic% based on the total number of atoms contained in the second layer 24 from the viewpoint of further improving the airtightness of the second layer 24. More preferably, it is 20-60 atomic%.

  The total value Y2 of the content ratio of the element E2 in the second layer 24 is preferably 10 to 80 atoms based on the total number of atoms contained in the second layer 24 from the viewpoint of further improving the airtightness of the second layer 24. %, And more preferably 20 to 70 atomic%.

  The second layer 24 preferably has a low carbon content. This is because if the graphite structure or the like is formed by containing carbon, cracks are likely to occur, and the sufficiently high density of the second layer 24 may be impaired. From such a viewpoint, the carbon content in the second layer 24 is preferably 5 atomic percent or less, more preferably 1 atomic percent or less.

  The second layer 24 may contain hydrogen and oxygen. By containing hydrogen having a valence number of 1 and oxygen having a valence number of 2, bonds between constituent elements are easily formed. In particular, by containing hydrogen, the bond ends can be made hydrogen, and therefore the number of lattices having unstable bond angles is reduced, so that the internal stress of the second layer 24 mainly composed of nitride is reduced. Can be reduced. From such a viewpoint, the total content of hydrogen and oxygen in the second layer 24 is 0.1 to 50 atomic%, more preferably 1 to 45 atomic%, and still more preferably 3 to 40 atomic%.

  The interface between the first layer 22 and the second layer 24 can be specified using a commercially available analyzer. For example, the content of the constituent element is measured by glow discharge emission spectroscopic analysis capable of analyzing the composition while cutting the protective layer 20 in the thickness direction (stacking direction), and the content of the constituent element is determined along the thickness direction. Locations that change discontinuously can be identified as layer interfaces.

  The dimensions of the magnet body 10 are not particularly limited, but are about 4 to 50 mm in length, 5 to 100 mm in width, and about 0.5 to 10 mm in thickness. The thickness of the surface region 2 is about 0.5 to 20 μm.

  The thickness of the first layer 22 is preferably 0.1 μm or more, and more preferably 0.3 μm or more. Usually, since the arithmetic mean roughness Ra of the surface of the magnet body 10 is 0.7 to 3 [mu] m, when the thickness is less than 0.1 [mu] m, particularly in the convex portion of the magnet body 10, the adhesion is improved. Tends to be insufficient. When the thickness of the first layer 22 is 0.3 μm or more, the adhesion between the protective layer 20 and the magnet body 10 can be sufficiently increased.

  The thickness of the first layer 22 is preferably 50 μm or less, more preferably 30 μm or less. When the thickness exceeds 50 μm, the volume ratio of the magnet body in the rare earth magnet of a predetermined size is lowered, and it is difficult to obtain sufficiently excellent magnetic characteristics. When the thickness is 30 μm or less, the rare earth magnet 100 having sufficiently excellent adhesion can be produced at a low production cost.

  The thickness of the second layer 24 is preferably 0.1 μm or more, more preferably 1 μm or more. When the thickness is less than 0.1 μm, sufficiently excellent corrosion resistance and moisture resistance tend to be impaired. When the thickness is 1 μm or more, corrosion resistance and moisture resistance can be further improved.

  The thickness of the second layer 24 is preferably 10 μm or less, and more preferably 5 μm or less. If the thickness exceeds 10 μm, the manufacturing cost of the rare earth magnet 100 tends to increase. When the thickness of the second layer 24 is 5 μm or less, the rare earth magnet 100 having sufficiently excellent corrosion resistance and moisture resistance can be manufactured at a low manufacturing cost.

  The total thickness of the protective layer 20 is preferably 0.2 μm or more, more preferably 1.3 μm or more. When the thickness is less than 0.2 μm, sufficiently excellent corrosion resistance and moisture resistance tend to be impaired. When the thickness is 1.3 μm or more, corrosion resistance and moisture resistance can be further improved.

  The total thickness of the protective layer 20 is preferably 50 μm or less, and more preferably 30 μm or less. When the thickness exceeds 50 μm, the thickness of the protective layer 20 becomes too large, and the volume ratio of the magnet body in the rare-earth magnet of a predetermined size is lowered, and it is difficult to obtain sufficiently excellent magnetic characteristics. is there. When the thickness of the entire protective layer 20 is 30 μm or less, the rare earth magnet 100 having sufficiently excellent magnetic properties and excellent corrosion resistance and moisture resistance can be manufactured at a low manufacturing cost.

In the present embodiment, the present inventors consider that the second layer 24 containing nitride mainly contributes to the improvement of the corrosion resistance of the entire rare earth magnet for the following reason. That is, the second layer 24 contains N (nitrogen) constituting the nitride and the element E2. N atoms have 3 valence electrons and have lone pairs. Therefore, the degree of freedom of bonding between the N atom and the element E2 is high, and the bonding between the elements constituting the nitride becomes dense. That is, the second layer 24 becomes a dense nitride film. Therefore, even if H or H ₂ (hydrogen) or O or O ₂ (oxygen) that corrodes the rare earth magnet penetrates into the second layer 24, the nitride film is dense, so hydrogen or oxygen Is difficult to pass through the second layer 24. Moreover, hydrogen or oxygen is absorbed in the inside of a nitride by the high coupling | bonding freedom degree of a nitride. That is, the second layer 24 has room for absorbing hydrogen or oxygen. For these reasons, hydrogen or oxygen can be prevented from entering the magnet body 10. By such an action, the corrosion resistance of the rare earth magnet 100 is improved. However, the operational effects relating to the second layer 24 are not limited to those described above.

  In the present embodiment, for the following reason, the first layer 22 disposed closer to the magnet body 10 side than the second layer 24 mainly contributes to improving the adhesion between the magnet body and the protective layer 20. The inventors consider. That is, the magnet body 10 contains a rare earth element having a large atomic weight, whereas the second layer 24 contains an element having a small atomic weight such as the element E2 constituting nitrogen and nitrogen. For this reason, if the second layer 22 is laminated directly on the surface of the magnet body 10, there is a tendency that good adhesion between them is not obtained. However, in this embodiment, a predetermined metal or alloy excellent in compatibility with both the component contained in the magnet body 10 and the component contained in the second layer 24 between the magnet body 10 and the second layer 24. The 1st layer 22 containing is provided. That is, since the first layer 22 contains a metal element, the first layer 22 has good adhesion to the magnet body 10. And since the 1st layer 22 contains the metal element whose atomic radius is smaller than a rare earth element, the adhesiveness with the 2nd layer 24 is also favorable. By such an action, the adhesion between the magnet body 10 and the protective layer 10 is improved. However, the operational effects relating to the first layer 22 are not limited to those described above.

  In the present embodiment, not only the second layer 24 is disposed on the outermost surface of the magnet but also the surface region 2 is disposed at the boundary between the magnet body 10 and the first layer 22, so that hydrogen or Intrusion of oxygen into the magnet body 10 can be further suppressed. That is, by diffusing N and element EA that can form a nitride into the surface region 2, the surface region 2 has room for absorbing hydrogen or oxygen therein. Therefore, even if the intrusion of hydrogen or oxygen cannot be suppressed by the second layer 24 containing nitride, the surface region 2 complements the function of the second layer 24, so that hydrogen or oxygen is contained in the magnet body 10. Intrusion into the is suppressed. However, the operational effects relating to the surface region 2 are not limited to those described above. Further, N and element EA in the surface region 2 do not necessarily constitute a nitride.

  In the present embodiment, in order to improve the corrosion resistance against hydrogen or oxygen, it is not necessary to form a coating layer made of N and element E2 between the magnet body 10 and the first layer 22 as in the second layer 24. . Instead, in the present embodiment, the first layer is formed without damaging the corrosion resistance by forming the surface region 2 in which N and the element EA similar to the elements constituting the nitride are diffused in the second layer 24. By arranging 22 directly on the surface of the magnet body 10, it becomes possible to maintain the adhesion between the protective layer 20 and the magnet body 10. By such an action, the surface region 2 contributes to improvement in the adhesion between the magnet body 10 and the protective layer 20 and the corrosion resistance of the rare earth magnet 100. However, the operational effects relating to the surface region 2 are not limited to those described above.

  In the present embodiment, the N content in the surface region 2 is XA atomic%, the total value of the element EA content in the surface region 2 is YA atomic%, and the N content in the second layer 24 is X2. When it is atomic% and the total content of the elements E2 in the second layer 24 is Y2 atomic%, it is preferable that X2 / Y2 <XA / YA.

When all of N and the element E2 included in the second layer 24 constitute a nitride, X2 is the content of N constituting the nitride in the second layer 24, and Y2 is in the second layer 24. Is the content of the element E2 constituting the nitride. Therefore, the nitride in the second layer 24 can be expressed as E2 _Y2 N _X2 . The stoichiometric ratio Y2: X2 of the elements E2 and N is uniquely specified by the type of the element E2. On the other hand, in the surface region 2, N and the element EA do not necessarily constitute a nitride. Therefore, in the surface region 2, the ratio of N to the element EA can be set to a value larger than the stoichiometric ratio of the nitride composed of EA and N. That is, the inequality X2 / Y2 <XA / YA is in contrast to the second layer 24 in which the number of elements E2 and N satisfies the stoichiometric ratio, and the surface region 2 has 3 valence electrons and is isolated. It means that the ratio of N atoms having electron pairs to the element EA is higher than the stoichiometric ratio. This increases the room for absorbing hydrogen or oxygen inside the surface region 2. As a result, the surface region 2 can effectively supplement the function of the second layer 24 that suppresses the entry of hydrogen or oxygen. For the above reason, when X2 / Y2 <XA / YA, the penetration of hydrogen or oxygen into the magnet body 10 can be further suppressed. However, the operational effects relating to the ratio of X2, Y2, XA and YA are not limited to those described above.

  The rare earth magnet according to the present embodiment is used, for example, as a magnet for an electromagnetic relay (electromagnetic relay device) mounted on a hybrid vehicle or an electric vehicle. In the electromagnetic relay device, the contact point of the relay is arranged in a sealed structure in which hydrogen gas is sealed for the purpose of improving the thermal conductivity of the atmosphere near the contact point of the relay. In the sealed structure, the magnetic field of the permanent magnet is applied to the arc. Thereby, the arc voltage generated between the contact points of the relay is controlled to be higher than the battery voltage, and the DC high voltage is cut off. In such an electromagnetic relay device, corrosion resistance of a permanent magnet in hydrogen gas is required. Therefore, the rare earth magnet of this embodiment which is excellent in corrosion resistance against hydrogen is suitable for an electromagnetic relay device. Moreover, the rare earth magnet of this embodiment is suitable as a magnet for a rotating machine or a reciprocating motor. A rotating machine or a reciprocating motor provided with a rare earth magnet having excellent corrosion resistance can maintain excellent performance over a long period of time even when used in a harsh environment.

[Method of manufacturing rare earth magnet 100]
Next, an example of a method for manufacturing the rare earth magnet 100 of the present embodiment will be described. The manufacturing method of the rare earth magnet 100 includes a first step of manufacturing the magnet body 10 and the surface region 2 thereof, a second step of forming the first layer 22 on the surface of the magnet body 10, And a third step of forming the second layer 24 on the surface. Details of each step will be described below.

  In the first step, when the magnet body 10 is a sintered magnet mainly composed of R-Fe-B based magnetic particles, the magnet body 10 is manufactured by a sintering method described below. First, a composition containing rare earth elements (R), iron (Fe), boron (B), and other elements described above in a predetermined ratio is cast to obtain an ingot. The obtained ingot is roughly pulverized to a particle size of about 10 to 100 μm using a stamp mill or the like, and then finely pulverized to a particle size of about 0.5 to 5 μm using a ball mill or the like to obtain a magnetic powder.

  Next, the obtained magnetic powder is preferably molded in a magnetic field to prepare a molded body. In this case, the applied magnetic field strength is preferably 10 kOe or more, and the molding pressure is preferably about 1 to 5 ton / cm 2.

  The prepared molded body is sintered at 1000 to 1200 ° C. for about 0.5 to 5 hours and rapidly cooled. The sintering atmosphere is preferably an inert gas atmosphere such as Ar gas. And preferably, the magnet body 10 is obtained by performing heat treatment (aging treatment) at 500 to 900 ° C. for 1 to 5 hours in an inert gas atmosphere.

  When the magnet body 10 is a bonded magnet, the magnet body 10 can be manufactured by the method described below. First, a magnetic powder is obtained in the same manner as in the production of a sintered magnet. After mixing the obtained magnetic powder, a binder resin, a curing agent, and the like, the mixture is put into a kneader such as a pressure kneader and kneaded to obtain a kneaded product. The mixing ratio of the magnetic powder and the binder resin is preferably 95 to 98 parts by mass of the magnetic powder with respect to 100 parts by mass of the total of the magnetic powder and the binder resin.

  Next, the kneaded product is compression-molded by a compression molding machine or the like. At this time, magnetization may be performed simultaneously by performing compression molding in a magnetic field. Magnetization may be performed separately after compression molding. From the viewpoint of obtaining the magnet body 10 having excellent magnetic properties, it is preferable to perform compression molding at a high pressure of about 784 to 980 MPa.

  As the binder resin, a thermosetting resin or a thermoplastic resin capable of binding magnetic powders can be used. Examples of such binder resins include thermosetting resins such as epoxy resins and phenol resins, styrene-based, olefin-based, urethane-based, polyester-based, polyamide-based elastomers, ionomers, ethylene-propylene copolymers (EPM), and ethylene. -Thermoplastic resins such as ethyl acrylate copolymer. Especially, a thermosetting resin is preferable and an epoxy resin or a phenol resin is more preferable.

  When a thermosetting resin is used as the binder resin, the magnet body 10 can be obtained by curing the binder resin by heating the obtained molded body at about 100 to 250 ° C. after compression molding. . When a thermoplastic resin is used as the binder resin, such thermosetting may not be performed.

Next, the surface region 2 is formed on the obtained magnet body 10. The method for forming the surface region 2 is not particularly limited. For example, in a state where the surface of the magnet body 10 held in a vacuum atmosphere is heated to about 50 to 500 ° C., the above-described element EA compound (for example, hydride) gas and N ₂ gas are supplied to the magnet body 10. By supplying, EA and N are diffused into the magnet body 10, and the surface region 2 is formed. The composition and thickness of the surface region 2 can be controlled by adjusting the temperature of the magnet body 10, the supply amounts of each of the element EA compound and N ₂ (gas flow rate), the atmospheric pressure, and the like. The surface region may be formed by exposing the magnet body to the plasma of the elements EA and N.

  In the second step, at least selected from the group consisting of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn on the surface of the magnet body 10 obtained as described above. The first layer 22 containing a kind of metal or an alloy containing the metal is formed. When the first layer 22 is a metal plating layer, the first layer 22 can be formed by normal electrolytic plating or electroless plating. Specifically, each plating layer can be formed by electrolytic Ni plating, electroless Ni plating, or electrolytic Cu plating. Moreover, the formation method of the 1st layer 22 is not limited to the above-mentioned manufacturing method, For example, sputtering and vapor deposition may be sufficient.

For example, the electrolytic Ni plating layer can be formed using a plating bath such as a watt bath or a sulfamic acid bath. A preferred plating bath composition is as follows.
NiSO ₄ .6H ₂ O: 200 to 500 g / l.
NiCl _2: 10~100g / l.
_{H 3 BO 4: 10~100g / l} .

The electrolytic copper plating layer can be formed by preparing an electrolytic copper plating solution and immersing the magnet body in the electrolytic copper plating solution using a barrel tank or a hooking jig. As the electrolytic copper plating solution, one having a copper sulfate concentration of 20 to 150 g / L and a chelating agent concentration of 30 to 250 g / L such as ethylenediaminetetraacetic acid (EDTA) can be used. The current density in electrolytic copper plating can be 0.1-1.5 A / dm < ² >, and the temperature of an electrolytic copper plating bath can be 10-70 degreeC.

  The electroless Ni plating layer contains a predetermined amount of nickel ions and, for example, a nickel chemical plating solution containing a reducing agent such as sodium hypophosphite, a complexing agent such as sodium citrate, and ammonium sulfate (temperature: It can be formed by immersing the magnet body 10 in about 80 ° C.).

  The first layer 22 may be composed of one type of plating layer, or may be a combination of two or more types of plating layers. In addition, a layer other than the plating layer described above may be formed by a known method to form the first layer 22.

In the third step, the second layer 24 containing a nitride composed of the elements E2 and N is formed. As a raw material for the second layer 24, a compound of element E2, N ₂ gas, or the like may be used. As a method for forming the second layer 24, a vacuum deposition method, a sputtering method, an ion plating method, a vapor phase growth method such as a CVD method or a thermal spraying method, a liquid phase growth method such as a coating method or a solution deposition method, or a sol-gel method. A known film forming technique such as, for example, can be used. Among these, the CVD method is advantageous in that layers having different compositions can be continuously formed and the protective layer 20 can be reliably formed on the surface even if the surface of the magnet body 10 has some unevenness. preferable. Examples of the CVD method include a plasma CVD method, a thermal CVD method, and a Cat-CVD method.

For example, when the second layer 24 made of silicon nitride is formed by the CVD method, for example, SiH ₄ gas, N ₂ gas, NH ₃ gas, H ₂ gas or the like is used as a source gas, and these are reacted under predetermined conditions. Thus, the second layer 24 made of an amorphous material containing silicon, nitrogen, and hydrogen as constituent elements is formed on the surface of the magnet body 10. At this time, the supply ratio of SiH ₄ gas, N ₂ gas, NH ₃ gas, and H ₂ gas is adjusted, and the hydrogen content in the second layer 24 is preferably 0.1 to 50 atomic%, more preferably 1 ˜45 atomic%, more preferably 3 to 40 atomic%. In order to easily form the second layer having such a composition, a mixed gas of SiH ₄ gas, H ₂ gas, and NH ₃ gas is preferably used as the source gas. When such a mixed gas is used, the volume ratio of the NH ₃ gas to the entire raw material gas is preferably 0 to 90% by volume, more preferably from the viewpoint of efficiently forming the second layer 24 having a predetermined hydrogen content. Is 5 to 85% by volume, more preferably 10 to 80% by volume. On the other hand, the volume ratio of H ₂ gas to the entire source gas is preferably 0 to 30 volume, more preferably 0 to 20 volume%, and the volume ratio of SiH ₄ gas to the entire source gas is preferably 1 to 30 volume. %, More preferably 2 to 12% by volume. By using such a source gas, the first layer 22 having a desired hydrogen content can be easily formed. The CVD method may be performed in the same manner as described above using a gas of a compound of another element E2.

  In the CVD method, Ar gas or He gas may be used as the carrier gas in addition to the above-described source gas. Note that the flow rate of the carrier gas is not used for calculating the volume ratio of each raw material gas in the mixed gas. That is, regardless of whether or not the carrier gas is used, the preferable range of the volume ratio of each source gas is the above-described range.

  Through the above steps, the rare earth magnet 100 having the protective layer 20 composed of the first layer 22 and the second layer 24 on the surface region 2 of the magnet body 10 can be manufactured. Such a rare earth magnet 100 includes a protective layer 20 having a dense second layer 24 containing a nitride and a first layer 22 that is firmly adhered to the second layer 24. The protective layer 20 is excellent in adhesion with the magnet body 10, and the second layer 24 and the surface region 2 have a corrosion resistance function. Therefore, even if the rare earth magnet 100 according to the present embodiment is used in a corrosive environment, the corrosion of the magnet body 10 due to the corrosive substance can be sufficiently suppressed. That is, the rare earth magnet 100 can maintain sufficiently excellent corrosion resistance over a long period of time.

  Next, another embodiment of the rare earth magnet of the present invention will be described.

  FIG. 3 is a cross-sectional view schematically showing still another embodiment of the rare earth magnet of the present invention. The rare earth magnet 300 includes a magnet body 10 and a protective layer 30 on the magnet body 10. The protective layer 30 has a stacked structure in which a first layer 32, an intermediate layer 34, and a second layer 36 are sequentially stacked from the magnet body 10 side. The first layer 32 and the second layer 36 are the same layers as the first layer 22 and the second layer 24 of the above embodiment. That is, the rare earth magnet 300 is different from the rare earth magnet 100 of the above embodiment in that the intermediate layer 34 is provided between the first layer 32 and the second layer 36.

  The intermediate layer 34 includes at least one metal hydride selected from the group consisting of metals Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn contained in the first layer 32 or the metal. As a main component, a hydride of an alloy containing is contained. Since the intermediate layer 34 contains the hydride of the metal or alloy contained in the first layer 32, the strain generated in the compound contained in the second layer 36 is sufficiently reduced when the second layer 36 is formed. can do.

  Further, since the intermediate layer 34 contains the same metal component as that of the first layer 32, the intermediate layer 34 can be firmly adhered to the first layer 32. Furthermore, since the intermediate layer 34 contains hydrogen, it can be firmly adhered to the second layer 36. Thus, since the protective layer 30 has sufficiently good adhesion between layers, the rare earth magnet 300 has sufficiently excellent corrosion resistance and maintains excellent magnetic properties for a long period of time. be able to.

  The intermediate layer 34 can be formed by performing a hydrogenation treatment in which the first layer 32 is formed and then heated in a hydrogen atmosphere at a temperature of 50 to 300 ° C. for 0.1 to 1 hour.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments. The hydride may be included in the vicinity of the contact surface between the first layer 22 and the second layer 24 of the rare earth magnet 100 without forming a layer like the intermediate layer 34 of the rare earth magnet 300. Moreover, the rare earth magnets 100 and 300 have a layer (for example, a layer made of a compound not containing hydrogen as a constituent element) having a composition different from that of the layer constituting the protective layer on the protective layers 20 and 30. May be.

  The contents of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Preparation of rare earth magnets]
Example 1
<Formation of magnet body>
An ingot made of an Nd—Dy—B—Fe alloy was obtained by powder metallurgy. The composition of this ingot was Nd content: 27.4% by mass, Dy content: 3% by mass, B content: 1% by mass, and Fe content: 68.6% by mass. The ingot was pulverized by a stamp mill and a ball mill to obtain fine alloy powder having the above composition.

  The obtained alloy fine powder was press-molded in a magnetic field to prepare a compact. The molded body was sintered under the conditions of a holding temperature of 1100 ° C. and a holding time of 1 hour to obtain a sintered body. Thereafter, the sintered body was subjected to an aging treatment under the conditions of a holding temperature of 600 ° C. and a holding time of 2 hours in an argon gas atmosphere. The sintered body subjected to the aging treatment was processed into a rectangular parallelepiped shape having a size of 20 × 10 × 1 (mm), and chamfered by barrel polishing treatment to obtain a magnet body.

<Pretreatment>
The magnet body was subjected to a pretreatment in which an alkaline degreasing treatment, water washing, acid washing treatment with a nitric acid solution, water washing, smut removal treatment by ultrasonic washing, and water washing were sequentially performed. After the pre-processed magnet body is placed inside the vacuum film formation chamber, the vacuum film formation is performed until the pressure inside the vacuum film formation chamber becomes a predetermined value (1 × 10 ⁻³ Pa) or less. The chamber was evacuated.

<Formation of surface region>
In the vacuum film formation chamber after evacuation, the following gas was introduced for 5 minutes under the following conditions to form a surface region in which Si and N were diffused.
Introduced gas: SiH ₄ (silane), N ₂ (nitrogen).
Flow rate of introduced gas: SiH ₄ = 40 ml / min, N ₂ = 600 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Pressure in the chamber: 30 Pa.
Surface temperature of magnet body: 100 ° C.

<Formation of the first layer>
After forming the surface region, the vacuum film formation chamber was evacuated until the pressure inside the vacuum film formation chamber became a predetermined value (1 × 10 ⁻³ Pa) or less. Next, a metal nickel layer (first layer) was formed on the surface of the magnet body so as to have a thickness of 5 μm by using a vacuum vapor deposition method which is a vapor phase growth method. The metal nickel layer was formed by irradiating a metal nickel vapor deposition source with an electron beam.

<Formation of second layer>
After forming the first layer, the vacuum film formation chamber was evacuated until the pressure inside the vacuum film formation chamber became a predetermined value (1 × 10 ⁻³ Pa) or less. Next, a second layer (thickness: 2 μm) made of nitride containing Si and N as constituent elements was formed on the surface of the first layer by a plasma CVD vapor deposition method. The conditions of the plasma CVD vapor deposition method were as follows.
Introduced gas: SiH ₄ (silane), N ₂ (nitrogen).
Flow rate of introduced gas: SiH ₄ = 40 ml / min, N ₂ = 600 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Pressure in the chamber: 30 Pa.
Surface temperature of magnet body: 170 ° C.
High frequency power: 300W.

  Thus, the magnet body having a surface region containing Si and N, the first layer made of Ni covering the entire surface of the magnet body, and the nitride containing Si and N covering the entire first layer. A rare earth magnet of Example 1 including the second layer was obtained.

(Example 2)
A rare earth magnet of Example 2 was obtained in the same manner as in Example 1 except that the surface temperature of the magnet body when forming the surface region was 200 ° C.

(Example 3)
Similar to Example 1, a pre-treated magnet body was obtained. After the magnet body is placed inside the vacuum film formation chamber, the vacuum film formation chamber is evacuated until the pressure inside the vacuum film formation chamber becomes a predetermined value (1 × 10 ⁻³ Pa) or less. went.

<Formation of surface region>
In the vacuum film formation chamber after evacuation, the following gas was introduced for 5 minutes under the following conditions to form a surface region in which Si and N were diffused.
Introduced gas: SiH ₄ (silane), N ₂ (nitrogen), NH ₃ (ammonia).
Flow rate of introduced gas: SiH ₄ = 40 ml / min, N ₂ = 600 ml / min, NH ₃ = 20 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Pressure in the chamber: 30 Pa.
Surface temperature of magnet body: 100 ° C.

<Formation of the first layer>
After forming the surface region, the first layer was formed in the same manner as in Example 1.

<Formation of second layer>
After forming the first layer, the vacuum film formation chamber was evacuated until the pressure inside the vacuum film formation chamber became a predetermined value (1 × 10 ⁻³ Pa) or less. Next, a second layer (thickness: 2 μm) made of nitride containing Si and N as constituent elements was formed on the surface of the first layer by a plasma CVD vapor deposition method. The conditions of the plasma CVD vapor deposition method were as follows.
Introduced gas: SiH ₄ (silane), N ₂ (nitrogen), NH ₃ (ammonia).
Flow rate of introduced gas: SiH ₄ = 40 ml / min, N ₂ = 600 ml / min, NH ₃ = 20 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Pressure in the chamber: 30 Pa.
Surface temperature of magnet body: 250 ° C.
High frequency power: 300W.

  Thus, the magnet body having a surface region containing Si and N, the first layer made of Ni covering the entire surface of the magnet body, and the nitride containing Si and N covering the entire first layer. A rare earth magnet of Example 3 including the second layer was obtained.

Example 4
Similar to Example 1, a pre-treated magnet body was obtained. After the magnet body is placed inside the vacuum film formation chamber, the vacuum film formation chamber is evacuated until the pressure inside the vacuum film formation chamber becomes a predetermined value (1 × 10 ⁻³ Pa) or less. went.

<Formation of surface region>
The following gas was introduced into the vacuum film forming chamber after evacuation under the following conditions.
Introduced gas: Ar (argon), N ₂ (nitrogen).
Flow rate of introduced gas: Ar = 10 ml / min, N2 = 10 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Pressure in chamber: 1 × 10 ⁻³ Pa
Surface temperature of magnet body: 100 ° C

By irradiating a metal titanium vapor deposition source with an electron beam for 5 minutes, the metal titanium is evaporated, and at the same time, the above introduced gas and metal titanium are ionized by an ionization power source, thereby generating a plasma atmosphere containing Ti ⁺ ions and N ⁺ ions It formed in the vacuum film-forming chamber. By exposing the magnet body to this plasma atmosphere, a surface region in which Ti and N were diffused was formed. In addition, the formation method of the surface area | region of Example 4 is the same method as the arc ion plating method except the point which does not apply an ion plating voltage to a to-be-plated board | substrate (magnet body of Example 4).

<Formation of the first layer>
After forming the surface region, the first layer was formed in the same manner as in Example 1.

<Formation of second layer>
After forming the first layer, the vacuum film formation chamber was evacuated until the pressure inside the vacuum film formation chamber became a predetermined value (1 × 10 ⁻³ Pa) or less. Next, a second layer (thickness: 2 μm) made of nitride containing Ti and N as constituent elements was formed on the surface of the first layer by an arc ion plating method. The conditions of the arc ion plating method were as follows.
Introduced gas: Ar (argon), N ₂ (nitrogen).
Flow rate of introduced gas: Ar = 10 ml / min, N ₂ = 10 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Vapor deposition material: Titanium metal.
Pressure in chamber: 1 × 10 ⁻³ Pa.
Surface temperature of magnet body: 300 ° C.

  Thus, the magnet body having a surface region containing Ti and N, the first layer made of Ni covering the entire surface of the magnet body, and the nitride containing Ti and N covering the entire first layer. A rare earth magnet of Example 4 having the second layer was obtained.

(Comparative Example 1)
Similar to Example 1, a pre-treated magnet body was obtained. Only the first layer was formed on the magnet body in the same manner as in Example 1 without forming the surface region. Through the above steps, a rare earth magnet of Comparative Example 1 including a magnet body and a first layer made of Ni covering the entire surface of the magnet body was obtained.

(Comparative Example 2)
In the same manner as in Example 1 except that the surface area was not formed on the magnet body, a magnet body having no surface area, a first layer made of Ni covering the entire surface of the magnet body, A rare earth magnet of Comparative Example 2 having a second layer made of a nitride containing Si and N covering the entire first layer was obtained.

(Comparative Example 3)
Similar to Example 1, a pre-treated magnet body was obtained. Only the first layer was formed on the magnet body in the same manner as in Example 1 without forming the surface region.

After forming the first layer, the vacuum film formation chamber was evacuated until the pressure inside the vacuum film formation chamber became a predetermined value (1 × 10 ⁻³ Pa) or less. Next, a second layer (thickness: 2 μm) containing C and H as constituent elements was formed on the surface of the first layer by plasma CVD vapor deposition. The conditions of the plasma CVD vapor deposition method were as follows.
Introduced gas: CH ₄ (methane).
Introduction gas flow rate: CH ₄ = 100 ml / min.
(The flow rate of the introduced gas is a value obtained by converting the temperature and pressure into 25 ° C. and 1 atm.)
Pressure in the chamber: 10 Pa.
Surface temperature of magnet body: 100 ° C.

  In this way, the magnet body having no surface region, the first layer made of Ni covering the entire surface of the magnet body, and the second layer (DLC layer: CLC) covering C and H covering the entire first layer. And a rare earth magnet of Comparative Example 3 having a Diamond Like Carbon layer.

(Comparative Example 4)
Similar to Example 1, a pre-treated magnet body was obtained. A base layer made of nitride containing Si and N was formed on the magnet body by the same method as the second layer forming method of Example 3 without forming a surface region.

  After forming the underlayer, a first layer and a second layer were sequentially formed on the underlayer in the same manner as in Example 3. From the above steps, a magnet body having no surface region, a base layer made of nitride containing Si and N covering the entire surface of the magnet base body, a first layer made of Ni covering the whole base layer, A rare earth magnet of Comparative Example 4 having a second layer made of a nitride containing Si and N covering the entire first layer was obtained.

[Composition analysis of rare earth magnets]
Using a glow discharge optical emission spectrometer (manufactured by JOBIN YVON, device name: GD-PROFILER 2), it is included in each part of the surface region, the first layer and the second layer of the rare earth magnet of each example and each comparative example. The element and the content of each element in each part were analyzed. The results are shown in Table 1. The analysis conditions were as follows.
Glow discharge power: 20W.
Discharge range: 2 mm in diameter.

  In Table 1, XA (unit: atomic%) means the N content in the surface region. YA (unit: atomic%) means the total content of element EA in the surface region. The element EA in Examples 1 to 3 and Comparative Example 4 is only Si. The element EA of Example 4 is only Ti. In addition, although the base layer of the comparative example 4 does not correspond to the surface region in this invention, the composition of the base layer of the comparative example 4 was described in the column of the surface region of Table 1 for convenience. The underlayer of Comparative Example 4 contained Si, N, and H. The Si content in the underlayer was 30 atomic%, the N content was 40 atomic%, and the hydrogen content was 30 atomic%. .

  In Table 1, X2 (unit: atomic%) means the N content in the second layer. Y2 (unit: atom) means the total content of the element E2 in the second layer. The element E2 of Examples 1 to 3 and Comparative Examples 2 and 4 is only Si. The element E2 of Example 4 is only Ti. Note that C constituting the second layer of Comparative Example 3 does not correspond to the element E2 in the present invention, but for convenience, the C content in the second layer of Comparative Example 3 (unit: E2 in Table 1) : Atomic%).

[Characteristic evaluation of rare earth magnets]
The corrosion resistance of the rare earth magnets of each Example and each Comparative Example and the adhesion between the magnet body and its coating layer were evaluated by the following procedure.

<Evaluation of adhesion>
The adhesion between the magnet body of each rare earth magnet and the coating layer was evaluated by a cross-cut tape method in accordance with JIS K5400. Specifically, a grid pattern (100 spots) was cut at 1 mm intervals in a 10 mm square area on the surface of the rare earth magnet. On top of that, one tape was applied, and when the tape was peeled off, the number of locations where the coating layer did not peel from the magnet body was determined. Of the 100 eyes, a magnet having 95 or more places where the coating layer was not peeled was determined as “A”. A magnet having 94 or less locations where the coating layer was not peeled was determined as “B”. The determination results are shown in Table 1.

<Evaluation of corrosion resistance>
In accordance with the standard of JIS C0023, a salt spray test (SST) was performed on each rare earth magnet. After each rare earth magnet was held in an atmosphere sprayed with salt water for 24 hours, the surface state of each rare earth magnet was visually observed to evaluate the presence or absence of rust, peeling of the coating layer, and swelling. The concentration of NaCl in the salt water used for the test was adjusted to 5% by mass. The test temperature (atmosphere temperature) was set to 35 ° C. A magnet in which rust, peeling of the coating layer and swelling were not observed was determined as “A”. A magnet in which at least one of rust, peeling of the coating layer and swelling was observed was determined as “B”. The determination results are shown in Table 1.

<Hydrogen exposure test>
Each rare earth magnet was held in a hydrogen atmosphere at 100 ° C. and 1 atm for 1 hour, and then the surface state of each rare earth magnet was visually observed to evaluate the presence or absence of rust, coating layer peeling, or magnet collapse. A sample in which rust, peeling of the coating layer and magnet collapse were not observed was determined as “A”, a sample in which peeling of the coating layer was observed was determined as “B”, and a sample in which magnet collapse was observed was determined as “C”. The determination results are shown in Table 1.

<Evaluation of magnetic properties>
Twenty rare earth magnets before the hydrogen exposure test were prepared. Each magnet is magnetized at 2T (Tesla), and the magnetic flux [mWb · turn] at a position 0.5 mm away from the magnet is measured using a 7-turn search coil and a flux meter. The average value was calculated from By the same method, the average value of the magnetic flux of 20 rare earth magnets after the hydrogen exposure test was calculated. And from the average value (A) of the magnetic flux of the magnet before the hydrogen exposure test and the average value (B) of the magnetic flux of the sample after the hydrogen exposure test, the rate of decrease of the magnetic flux was calculated by the following formula (1). The magnet whose magnetic flux reduction rate was less than 1% was determined as “A”. The magnet whose magnetic flux reduction rate was greater than 1% was determined as “B”. A magnet whose magnetic flux could not be measured due to peeling of the coating layer or magnet collapse during the hydrogen exposure test was determined as “C”. The results are shown in Table 1.
Reduction rate of magnetic flux (%) = [(A−B) / A] × 100 (1)

  Since the rare earth magnet according to the present invention has excellent adhesion between the magnet body and the protective layer and excellent corrosion resistance against hydrogen, the electromagnetic relay (electromagnetic relay device), rotating machine or Suitable for motors and the like.

  2 ... surface area of magnet body, 10 ... magnet body, 20, 30 ... protective layer, 22, 32 ... first layer, 24, 36 ... second layer, 34 · ..Intermediate layer, 100, 300 ... rare earth magnet.

Claims (2)

A rare earth magnet comprising a magnet body containing a rare earth element and a protective layer covering the magnet body,
The protective layer includes a first layer formed on a surface of the magnet body, and a second layer located on the opposite side of the magnet body with the first layer interposed therebetween,
The surface area of the magnet body is Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La. , Y, Ca, Sr, Ce and Be, containing one or more elements EA selected from the group consisting of Be and N,
The first layer contains at least one metal selected from the group consisting of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, or an alloy containing the metal,
The second layer contains a nitride,
The nitride includes Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, Ca Containing one or more elements E2 selected from the group consisting of Sr, Ce and Be,
Rare earth magnet. The N content in the surface region is XA atomic%;
The total content of the element EA in the surface region is YA atomic%,
The N content in the second layer is X2 atomic%;
When the total content of the element E2 in the second layer is Y2 atomic%,
X2 / Y2 <XA / YA.
The rare earth magnet according to claim 1.

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