JP4188907B2 - Rare earth magnets - Google Patents

Description

  The present invention relates to a rare earth magnet, and more particularly to a rare earth magnet having a protective layer provided on the surface.

  In recent years, so-called R—Fe—B magnets (R represents a rare earth element such as Nd) have been developed as permanent magnets having a high energy product of 25 MGOe or more. R-Fe-B magnets that are formed by high-speed rapid cooling are disclosed in Patent Document 2. However, since R-Fe-B magnets contain rare earth elements and iron that are relatively easily oxidized as main components, their corrosion resistance is relatively low, and as a result, magnets are manufactured and used. As a result, there are problems such as deterioration in performance and / or reliability of manufactured magnets being relatively low. For the purpose of improving the corrosion resistance of such R-Fe-B magnets, various protective films have been applied to the surface of the magnet body as described in, for example, Patent Documents 3 to 9 so far. Proposals to make are made.

More specifically, for example, in Patent Document 3, R (where R is at least one of rare earth elements including Y) is intended to improve the oxidation resistance of a permanent magnet mainly composed of rare earth, boron, and iron. Species) Oxidation-resistant plating layer is coated on the surface of permanent magnet body consisting mainly of tetragonal phase with 8 to 30 atom%, B2 to 28 atom%, and B42 to 90 atom% as the main component. Permanent magnets have been proposed. Patent Document 3 discloses plating of metals or alloys having oxidation resistance such as Ni, Cu, Zn, or composite plating thereof.
JP 59-46008 A JP-A-60-9852 JP-A-60-54406 JP-A-60-63901 JP 60-63902 A Japanese Patent Laid-Open No. 61-130453 JP-A-61-166115 JP 61-166116 A JP 61-270308 A

  However, the present inventors have made a detailed study of conventional rare earth magnets containing rare earth elements including those described in Patent Documents 1 to 9, and such conventional rare earth magnets are not sufficient. It was found that it does not have good corrosion resistance. That is, for example, when a salt spray test specified in JIS-C-0023 is performed on the rare earth magnet provided with the above-described oxidation-resistant plating layer described in Patent Document 3, a magnet body of the rare earth magnet The present inventors have found that corrosion is observed.

  Here, the “salt spray test” means, for example, a 5 ± 1 mass% NaCl aqueous solution (pH = 6.5 to 7.2) under a temperature condition of about 35 ° C. for 24 hours in a fine damp and dense fog state. This is done by contacting the sample and checking the corrosion state of the sample. As a factor in which corrosion is recognized in the magnet body by the salt spray test, it is considered that pinholes are generated in the protective layer (oxidation-resistant plating layer). When a pinhole is generated in the protective layer of the rare earth magnet, a corrosive substance in the atmosphere enters from the pinhole and becomes a factor that corrodes the magnet body. In particular, since rare earth magnets corrode very easily, conventional rare earth magnets in which corrosion of the magnet body is recognized by a salt spray test are not necessarily excellent in corrosion resistance even in actual usage environments. .

  Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a rare earth magnet having sufficiently excellent corrosion resistance.

A rare earth magnet of the present invention that solves the above problems comprises a magnet body containing a rare earth element and a protective layer containing oxynitride formed on the surface of the magnet body, the protective layer comprising an oxynitride. It has an oxynitride layer containing nitride, and the oxygen content in the oxynitride layer is an amount corresponding to 50 atomic% or less with respect to the total content of oxygen and nitrogen in the oxynitride layer. It is characterized by that.

  Even when the above-described salt spray test is performed on the rare earth magnet of the present invention, the corrosion of the magnet body as generated in the conventional rare earth magnet is not recognized. Although the factor is not clarified, the present inventors currently consider as follows. However, the factors are not limited to these.

A conventional rare earth magnet has a protective layer made of a metal, a resin, a metal oxide such as SiO ₂ (in this specification, silicon is also included in the metal) or a metal nitride. . Among these, rare earth magnets having a protective layer made of resin are used in the protective layer when the solution is dried or heated because a wet process such as a solution coating method is used as a method for forming the protective layer. Stress is generated, resulting in a gap such as a crack in the protective layer. As a result, when a salt spray test is performed on such a rare earth magnet, salt water intrudes from cracks and the like, and the magnet body is considered to corrode.

  Moreover, since the metal itself is easily corroded by salt water, the rare earth magnet provided with the protective layer made of metal constitutes a void penetrating through the corroded portion of the protective layer. As a result, when a salt spray test is performed on such a rare earth magnet, it is considered that salt water penetrates from the voids generated by the corrosion and the magnet body is corroded.

  Furthermore, the rare earth magnet provided with a protective layer made of a metal oxide or a metal nitride includes an atom (ion) based on a bond between a metal atom and an oxygen atom or between a metal atom and a nitrogen atom in the protective layer. ) Is considered to be fixed to some extent. It is estimated that due to this, there are vacant sites (sites) in which metal atoms and oxygen atoms or nitrogen atoms cannot exist in the protective layer, and fine pinholes or defects etc. are generated at the vacant sites. Is done. As a result, when a salt spray test is performed on such a rare earth magnet, salt water intrudes from the pinhole or the like, and the magnet body is considered to corrode.

  On the other hand, the rare earth magnet of the present invention contains any of metal atoms (metal ions), oxygen atoms (oxide ions) and nitrogen atoms (nitride ions) in the protective layer. Therefore, it is considered that a nitrogen atom exists at a site where an oxygen atom cannot exist, and an oxygen atom exists at a site where a nitrogen atom cannot exist. Furthermore, since the metal atom is in a state of being bonded to an oxygen atom and a nitrogen atom, it can be considered that the metal atom can also exist at a site different from the case of bonding to only one of the elements. As a result, the number of vacant sites is sufficiently reduced in the protective layer provided in the rare earth magnet of the present invention, the occurrence of pinholes or defects is sufficiently suppressed, and a sufficiently dense layer is formed. Presumed. As a result, even if the salt spray test is performed on the rare earth magnet of the present invention, the salt water is not in contact with the magnet body, so that the magnet body is not corroded.

  Moreover, since the protective layer which uses oxynitride as a constituent material can be formed by a vapor phase growth method (dry process), generation of cracks in the protective layer can be sufficiently suppressed. Furthermore, since oxynitride itself is a substance having high corrosion resistance, it can be sufficiently suppressed that the protective layer containing oxynitride as a constituent material is corroded by corrosive substances such as salt water.

  Furthermore, among rare earth magnet applications, rare earth magnets are exposed to relatively harsh atmospheres such as automobile motors, special motors, servo motors, linear actuators, voice coil motors, equipment motors, and industrial motors. In view of this, the rare earth magnet of the present invention in which corrosion is not recognized even in the various tests described above has sufficiently excellent corrosion resistance.

  In the rare earth magnet of the present invention, the oxynitride contained in the protective layer 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 preferably contain one or more elements selected from the group consisting of Be and Be. By providing a protective layer comprising oxynitride of these elements as a constituent material, the rare earth magnet of the present invention has further excellent corrosion resistance. Furthermore, from the viewpoint of film formation and ease of composition control, the oxynitride contained in the protective layer is silicon oxynitride, aluminum oxynitride, tantalum oxynitride, titanium oxynitride, zirconium oxynitride, Hafnium oxynitride, niobium oxynitride, magnesium oxynitride, chromium oxynitride, nickel oxynitride, molybdenum oxynitride, vanadium oxynitride, tungsten oxynitride, iron oxynitride, boronoxynitride, Gallium oxynitride, germanium oxynitride, bismuth oxynitride, manganese oxynitride, barium oxynitride, lanthanum Shi nitride, yttrium oxynitride, calcium oxynitride, strontium oxynitride, if it is one oxynitride selected from the group consisting of cerium oxynitride and beryllium oxynitride, and more preferred.

  In the rare earth magnet of the present invention, the protective layer may be a single-layered oxynitride layer containing oxynitride, and consists of a plurality of layers formed along the lamination direction of the magnet body and the protective layer. One or more of the protective layers may be an oxynitride layer containing oxynitride. Since the protective layer is composed of a plurality of layers, the adhesion between the magnet body and the protective layer can be improved, the reaction between the magnet body and the protective layer can be suppressed, and / or the surface roughness of the magnet body can be controlled. Therefore, the rare earth magnet of the present invention can be further imparted with effects such as improvement of magnetic properties and further suppression of deterioration.

  Moreover, when the rare earth magnet of the present invention includes a plurality of protective layers, it is preferable that at least a layer formed at a position farthest from the magnet body among the protective layers is the oxynitride layer described above. By adopting such a protective layer, the oxynitride layer can sufficiently prevent corrosion of other layers contained in the protective layer. As a result, the rare-earth magnet of the present invention is unlikely to impair the functions possessed by those layers, so that the lifetime tends to be further increased.

  Furthermore, it is preferable that at least a layer formed adjacent to the magnet element body is made of metal among these protective layers. By making the protective layer in this configuration, the adhesion between the magnet body and the protective layer is further increased, so that corrosion that may occur when the protective layer is peeled off from the magnet body, deterioration of magnetic properties due to it, etc. Can be further suppressed.

  In the rare earth magnet of the present invention, it is preferable that the protective layer covers the entire surface of the magnet body. By providing such a configuration, the rare earth magnet of the present invention can be used for a wider range of applications.

In the rare earth magnet of the present invention, the oxygen content in the oxynitride layer of the protective layer is an amount corresponding to 50 atomic% or less with respect to the total content of oxygen and nitrogen in the oxynitride layer. The By adjusting the oxygen content in the oxynitride layer as described above, the rare earth magnet of the present invention is more excellent in corrosion resistance. The reason for this is that if there are more oxygen atoms (oxide ions) than nitrogen atoms (nitride ions) in the oxynitride layer, the electrical neutral condition in the oxynitride layer is maintained. It is considered that a site where a metal atom (metal ion) should exist becomes a point defect (hole), and an empty site is generated there. As a result, pinholes or the like are generated in the vicinity of the generated empty site, and the denseness of the oxynitride layer is lowered, so that it is presumed that the corrosion resistance of the layer tends to be lowered. However, the factor is not limited to this.

  From the same viewpoint, the oxygen content in the oxynitride layer is preferably an amount corresponding to 0.1 to 30 atomic% with respect to the total content of oxygen and nitrogen in the oxynitride layer. When the oxygen content is less than 0.1 atomic%, the internal stress of the oxynitride layer increases, and the oxynitride layer tends to be peeled off from the magnet body.

  When the oxynitride layer of the protective layer is formed adjacent to the magnet body, the rare earth magnet of the present invention includes a first partial layer including a surface adjacent to the magnet body, the above surface, The second partial layer including the opposite surface is preferable, and the total content ratio of oxygen and nitrogen in the first partial layer is preferably smaller than the total content ratio of oxygen and nitrogen in the second partial layer.

  Since such an oxynitride layer tends to contain a large amount of metal components in the first partial layer adjacent to the magnet body, the adhesion between the magnet body and the protective layer tends to increase. Moreover, since the second partial layer has a composition (structure) as a metal oxynitride, it tends to have more excellent corrosion resistance.

  The oxynitride layer in the protective layer provided in the rare earth magnet of the present invention is preferably formed by a vapor deposition method (dry process). For example, the magnet body of the R-Fe-B rare earth magnet described above mainly includes a main phase 50, a rare earth rich phase 60 containing a relatively large amount of rare earth elements, and boron as schematically shown in FIG. And a boron-rich phase 70 containing a relatively large amount. Of these, most of the rare earth-rich phase 60 is considered to exist between the particles of the main phase 50. When the protective layer is formed on the surface of the magnet body having such a configuration using an acidic aqueous solution, the rare earth-rich phase 60 containing a relatively large amount of rare earth elements having a very low redox potential (standard electrode potential) It is considered that a local battery is formed with the main phase 50 or the boron rich phase 70 by contacting the acidic aqueous solution from the portion existing on the surface of the element body. As a result, the rare earth-rich phase 60 elutes in order from the surface existing on the surface of the magnet body, causing a phenomenon such as intergranular corrosion of the main phase 50, and the magnet body sufficiently functions as a magnet. It is estimated that it tends to disappear. Therefore, it is preferable to employ a vapor phase growth method that does not require the use of an aqueous solution when forming the protective layer.

  In the rare earth magnet of the present invention, the protective layer preferably has a thickness of 0.01 to 20 μm, and more preferably 0.1 to 20 μm, from the viewpoint of further improving the corrosion resistance and ensuring sufficient magnetic properties. More preferably, the oxynitride layer preferably has a thickness of 0.01 to 20 μm, and more preferably 0.1 to 20 μm.

  According to the present invention, it is possible to provide a rare earth magnet having sufficiently excellent corrosion resistance.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  FIG. 1 is a schematic perspective view showing a first embodiment of a rare earth magnet according to the present invention, and FIG. 2 is a diagram schematically showing a cross section that appears when the rare earth magnet of FIG. 1 is cut along line II. It is. As is apparent from FIGS. 1 and 2, the rare earth magnet 100 of the first embodiment is composed of a magnet element body 10 and a protective layer 20 formed so as to cover the entire surface of the magnet element body 10. It is.

(Magnet body)
The magnet body 10 contains R, iron (Fe), and boron (B). R represents one or more rare earth elements, specifically, one or more selected from the group consisting of scandium (Sc), yttrium (Y) and lanthanoids belonging to Group 3 of the long-period periodic table. Indicates an element. 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 composition of the above-described elements in the magnet body 10 is preferably as described below when the magnet body 10 is manufactured by a sintering method.

  R preferably includes one or more elements of Nd, Pr, Ho, and Tb among those described above, and further includes 1 of La, Sm, Ce, Gd, Er, Eu, Tm, Yb, and Y. It is also preferable to include more than one element.

  The content ratio of R in the magnet body 10 is preferably 8 to 40 atomic% with respect to the total amount of atoms constituting the magnet body 10. When the content ratio of R is less than 8 atomic%, the crystal structure has a cubic structure having the same structure as that of α-iron. Therefore, the rare earth magnet 100 having a high coercive force (iHc) tends not to be obtained. Further, when the content ratio of R exceeds 30 atomic%, 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 atomic% with respect to the total amount of atoms constituting the magnet body 10. If the Fe content is less than 42 atomic%, the Br of the rare earth magnet 100 tends to decrease, and if it exceeds 90 atomic%, the iHc of the rare earth magnet 100 tends to decrease.

  The content ratio of B in the magnet body 10 is preferably 2 to 28 atomic% with respect to the total amount of atoms constituting the magnet body 10. If the B content is less than 2 atomic%, the crystal structure has a rhombohedral structure, so the iHc of the rare earth magnet 100 tends to be insufficient. If it exceeds 28 atomic%, there are many B-rich nonmagnetic phases. Therefore, the Br of the rare earth magnet 100 tends to decrease.

  Further, the magnet body 10 may be configured by replacing part of Fe with cobalt (Co). By adopting such a configuration, the temperature characteristics tend to be improved without impairing the magnetic characteristics of the rare earth magnet 100. In this case, the content ratio of Fe and Co after substitution is preferably such that Co / (Fe + Co) is 0.5 or less on an atomic basis. If the amount of substitution of Co is larger than this, the magnetic properties of the rare earth magnet 100 tend to deteriorate.

  Furthermore, even if a part of B is replaced with one or more elements selected from the group consisting of carbon (C), phosphorus (P), sulfur (S), and copper (Cu), the magnet body 10 is configured. Good. By adopting such a configuration, the productivity of the rare earth magnet 100 is improved and the production cost tends to be reduced. In this case, the content of C, P, S and / or Cu is preferably 4 atom% or less with respect to the amount of all atoms constituting the magnet body 10. When the content of C, P, S and / or Cu is more than 4 atomic%, the magnetic properties of the rare earth magnet 100 tend to deteriorate.

  Further, from the viewpoint of improving the coercive force of the rare earth magnet 100, improving productivity, and reducing the cost, 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 ( The magnet body 10 may be configured by adding one or more elements of Si), gallium (Ga), copper (Cu), and / or hafnium (Hf). In this case, it is preferable that the addition amount of the element is 10 atomic% or less with respect to the total amount of atoms constituting the magnet body 10. When the addition amount of these elements exceeds 10 atomic%, the magnetic properties of the rare earth magnet 100 tend to deteriorate.

  In the magnet body 10, oxygen (O), nitrogen (N), carbon (C), and / or calcium (Ca), etc. as unavoidable impurities are included in the amount of all atoms constituting the magnet body 10. And may be contained within a range of 3 atomic% or less.

  As shown in FIG. 5, the magnet body 10 includes a main phase 50 having a substantially tetragonal crystal structure, a rare earth-rich phase 60 containing a relatively large amount of rare earth elements, and a boron rich material containing a relatively large amount of boron. And the phase 70 is formed. The particle size of the main phase 50 which is a magnetic phase is preferably about 1 to 100 μm. The rare earth-rich phase 60 and the boron-rich phase 70 are nonmagnetic phases and exist mainly at the grain boundaries of the main phase 50. These nonmagnetic phases 60 and 70 are usually contained in the magnet body 10 by about 0.5 volume% to 50 volume%.

  The magnet body 10 is manufactured, for example, by a sintering method as described below. First, a desired composition containing the elements described above is cast to obtain an ingot. Subsequently, 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 powder. .

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

  Subsequently, the obtained 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 as described above is obtained by performing heat treatment (aging treatment) at 500 to 900 ° C. for 1 to 5 hours in an inert gas atmosphere.

(Protective layer)
The protective layer 20 is formed on the surface of the magnet body 10 and contains oxynitride.

  In the present embodiment, the protective layer 20 is a single oxynitride layer. Accordingly, the oxynitride layer 20 in the present embodiment is in an exposed state, exposed to the atmosphere around the rare earth magnet 100, and adjacent to the magnet body 10.

  In the rare earth magnet 100 of the present embodiment, the protective layer 20 contains any of metal atoms (metal ions), oxygen atoms (oxide ions), and nitrogen atoms (nitride ions). Accordingly, it is considered that nitrogen atoms can exist stably even in sites where oxygen atoms cannot exist stably in the protective layer 20. Further, it is considered that oxygen atoms can exist stably even at sites where nitrogen atoms cannot exist stably. Furthermore, since the metal atom is in a state of being bonded to an oxygen atom and a nitrogen atom, it is presumed that the metal atom can exist at a site different from the case of bonding to only one of the atoms. From the above, in the protective layer 20 provided in the rare earth magnet 100 of the present embodiment, each atom (ion) exists sufficiently densely, and as a result, the occurrence of pinholes, defects, or the like occurs. It is presumed that a sufficiently dense layer is formed that is sufficiently suppressed. As a result, even if a salt spray test is performed on the rare earth magnet 100 of the present embodiment, the salt water does not come into contact with the magnet body 10, and thus the magnet body 10 is considered not to corrode.

  Moreover, since the protective layer 20 containing oxynitride as a constituent material can be formed by a vapor phase growth method (dry process), generation of cracks in the protective layer 20 is sufficiently suppressed. Furthermore, since oxynitride itself is a substance having high corrosion resistance, it can be sufficiently suppressed that the protective layer 20 containing the oxynitride as a constituent material is corroded by a corrosive factor substance such as salt water.

  Rare earth magnets are used for line printers, starters and motors for automobiles, special motors, servo motors, disk drives for magnetic recording devices, linear actuators, voice coil motors, motors for devices, industrial motors, speakers, and nuclear magnetic resonance. Such as a diagnostic magnet. In particular, when used in an environment where oil such as an automobile motor is splashed, it is difficult to obtain a rare earth magnet having sufficiently excellent corrosion resistance if the protective layer has only oxidation resistance. Also from this point of view, the rare earth magnet 100 of the present embodiment has a sufficiently excellent corrosion resistance because it has resistance to various corrosion factor substances such as sulfide and salt water.

  The constituent material of the protective layer 20 is not particularly limited as long as it forms a stable bond with oxygen atoms (oxide ions) and nitrogen atoms (nitride ions). Specific examples include Si, Al, Ga, Ge, and transition metals. Among these, the oxynitride preferably contains one or more elements (atoms) selected from the group consisting of Si, Al, Ta, Ti, Zr, Hf and Nb, and Mg, Cr, Ni, Mo, V , W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, Ca, Sr, Ce, and Be, it is preferable to contain one or more elements (atoms) selected from the group consisting of Be and Be. That is, oxynitride is Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, It is preferable to contain one or more elements (atoms) selected from the group consisting of Ca, Sr, Ce and Be. By providing the protective layer 20 made of oxynitride of these atoms as a constituent material, the rare earth magnet 100 of the present embodiment has further excellent corrosion resistance.

  The constituent material of the protective layer 20 in this embodiment (hereinafter also referred to as “oxynitride layer” in some cases in this embodiment) 20 may contain a plurality of metal atoms, but silicon oxynitride, aluminum Oxynitride, tantalum oxynitride, titanium oxynitride, zirconium oxynitride, hafnium oxynitride, and preferably one oxynitride selected from the group consisting of niobium oxynitride, magnesium oxynitride, Chromium oxynitride, nickel oxynitride, molybdenum oxynitride, vanadium oxynitride, tungsten oxynitride, iron oxynitride, boronoxynitride, galliumoxynitride From germanium oxynitride, bismuth oxynitride, manganese oxynitride, barium oxynitride, lanthanum oxynitride, yttrium oxynitride, calcium oxynitride, strontium oxynitride, cerium oxynitride and beryllium oxynitride One kind of oxynitride selected from the group consisting of That is, the constituent material of the protective layer 20 is silicon oxynitride, aluminum oxynitride, tantalum oxynitride, titanium oxynitride, zirconium oxynitride, hafnium oxynitride, niobium oxynitride, magnesium oxynitride, Chromium oxynitride, nickel oxynitride, molybdenum oxynitride, vanadium oxynitride, tungsten oxynitride, iron oxynitride, boronoxynitride, galliumoxynitride, germaniumoxynitride, bismuthoxynitride, Manganese oxynitride, barium oxynitride, lanthanum oxynitride, yttrium oxynitride, Cie um oxynitride, strontium oxynitride, even one oxynitride selected from the group consisting of cerium oxynitride and beryllium oxynitride preferred. When the protective layer 20 is composed of such an oxynitride containing a single metal atom, the protective layer tends to be easily formed and the composition can be controlled, and the chemical stability becomes higher. There is a tendency.

  The protective layer 20 may be crystalline, amorphous, or a mixture of these states.

  The structure of the oxynitride layer 20 is not clarified because it is a very thin film. However, the present inventors currently consider the structure as follows. That is, for example, it is considered that the structure has a structure in which a part of the oxygen atom is replaced with a nitrogen atom based on the above-described metal oxide. Alternatively, it is considered that the structure has a structure in which a part of the nitrogen atom is substituted with an oxygen atom based on the above-described metal nitride. Further, based on the above-described metal carbides, borides or silicides, it is also considered that the structure has a structure in which most of carbon atoms, boron atoms or silicon atoms are substituted with oxygen atoms and nitrogen atoms, respectively. It is done. In any case, since at least both oxygen and nitrogen atoms (both ions) are contained as anion components, it is estimated that the formation of vacant sites is sufficiently suppressed and the oxynitride layer 20 is rich in density. Is done.

  Examples of the oxide that is the source of the oxynitride layer include silicon oxide (silica), aluminum oxide (alumina), tantalum oxide, titanium oxide (titania), zirconium oxide (zirconia), hafnium oxide, niobium oxide, and bismuth oxide. Iron oxide, manganese oxide, nickel oxide, barium oxide, lanthanum oxide, chromium oxide, yttrium oxide, beryllium oxide, calcium oxide, strontium oxide, cerium oxide and magnesium oxide, and complex oxides thereof.

  Examples of the nitride that is the source of the oxynitride layer include silicon nitride, aluminum nitride, beryllium nitride, niobium nitride, vanadium nitride, titanium nitride, zirconium nitride, boron nitride, tantalum nitride, and hafnium nitride, and composite nitridation thereof. Such as things. In the case of silicon nitride and boron nitride, it is presumed that oxygen atoms are preferentially replaced with nitrogen atoms.

  Examples of the carbide that is the source of the oxynitride layer include silicon carbide, boron carbide, molybdenum carbide, vanadium carbide, tungsten carbide, titanium carbide, zirconium carbide, niobium carbide, hafnium carbide and tantalum carbide, and composite carbides thereof. Is mentioned. In the case of silicon carbide and boron carbide, it is considered that oxygen atoms and nitrogen atoms are preferentially substituted with carbon.

  Examples of the boride that is the basis of the oxynitride layer include molybdenum boride, vanadium boride, niobium boride, tantalum boride, tungsten boride, hafnium boride, titanium boride and zirconium boride, and their A compound boride etc. are mentioned.

  Examples of the silicide that is the source of the oxynitride layer include nickel silicide, molybdenum silicide, titanium silicide, tungsten silicide, tantalum silicide, zirconium silicide, and hafnium silicide, and composite silicides thereof. Is mentioned.

  Moreover, you may form the structure of an oxynitride layer based on what combined 2 or more types among the oxide, nitride, carbide, boride, and silicide which were mentioned above. Moreover, the valence of the metal element of the oxide, nitride, carbide, boride, and silicide described above may be any valence as long as it can be taken.

In the present embodiment, the oxygen content in the oxynitride layer 20, Ru amount der corresponding to 50 atomic% or less of the total content of oxygen and nitrogen in the oxynitride layer 20. By adjusting the oxygen content in the oxynitride layer 20 to be within this range, the rare earth magnet 100 of the present embodiment has further excellent corrosion resistance.

  If there are more oxygen atoms (oxide ions) than nitrogen atoms (nitride ions) in the oxynitride layer 20, the corrosion resistance effect of the oxynitride layer 20 tends to decrease. The cause of this is not clear, but in order to maintain the electrical neutral condition in the oxynitride layer 20, the site where the metal atom (metal ion) should exist becomes a point defect (hole). An empty site can be generated. This is presumably because pinholes or the like are generated in the vicinity of the generated empty site and the denseness of the oxynitride layer 20 is lowered.

  In addition, when the number of oxygen atoms is significantly larger than that of nitrogen atoms, the oxynitride layer 20 is considered to be stabilized as an oxide structure rather than an oxynitride structure. Thus, when the oxynitride layer 20 has an oxide structure, as described above, the denseness of the layer 20 is lowered, so that the corrosion resistance effect of the layer 20 tends to be lowered. .

  From the viewpoint of maintaining the denseness of the oxynitride layer, the oxygen content in the oxynitride layer 20 is 0.1 to 30 atomic% with respect to the total content of oxygen and nitrogen in the oxynitride layer 20. A corresponding amount is more preferred. When the oxygen content is less than 0.1 atomic%, the oxynitride layer 20 is considered to be stabilized as a nitride structure rather than as an oxynitride structure. Thus, when the oxynitride layer 20 has a nitride structure, as described above, the internal stress of the layer 20 increases, and as a result, the oxynitride layer 20 peels from the magnet body 10. It is estimated that it tends to be easy to do.

  In addition, the following factors can be considered as preferable factors when the number of oxygen atoms in the oxynitride layer 20 is slightly less than the number of nitrogen atoms. That is, when the number of oxygen atoms (oxide ions) in the oxynitride layer 20 is somewhat smaller than the number of nitrogen atoms (nitride ions), the metal atoms try to maintain the electrical neutral condition of the layer 20. It is considered that (metal ions) are present between atoms (between ions) like so-called interstitial defects in the crystal structure. As a result, since the denseness of the oxynitride layer 20 is improved, it is considered that the corrosion resistance of the rare earth magnet 100 is improved.

  The oxynitride layer 20 has a first partial layer including a surface 32 adjacent to the magnet body 10 and a second partial layer including a surface 34 opposite to the surface 32, and the first portion. The total content of oxygen and nitrogen in the layer is preferably less than the total content of oxygen and nitrogen in the second partial layer. Here, the “first partial layer” and the “second partial layer” may be layers in which the total content ratio of oxygen and nitrogen in each partial layer is substantially constant in the thickness direction.

  By adjusting the composition distribution of oxygen and nitrogen in the oxynitride layer 20 in this way, sufficient adhesion between the magnet body 10 and the protective layer 20 is ensured even if the protective layer 20 is a single layer. be able to. In addition, it is possible to ensure sufficiently excellent corrosion resistance of the rare earth magnet 100. That is, in the first partial layer including the surface 32 adjacent to the magnet body 10 in the oxynitride layer 20, the content ratio of the metal atoms constituting the oxynitride is relatively high. It tends to be able to sufficiently increase the adhesion with the magnet body 10 as a component. On the other hand, in the second partial layer including the surface 34 of the oxynitride layer 20 that is in contact with the atmosphere in which a corrosion-causing substance such as sulfide exists, a relatively large amount of oxygen and nitrogen serves as a metal oxynitride. Since it has a composition (structure), it tends to have sufficiently excellent corrosion resistance.

  In this case, another partial layer may be provided between the first partial layer and the second partial layer, and the total content ratio of oxygen and nitrogen in the other partial layer is not particularly limited. Therefore, the total content ratio of oxygen and nitrogen in the other partial layer may be larger than that of the second partial layer, or smaller than that of the first partial layer, and oxygen and nitrogen in the first and second partial layers. It may be a numerical value such that it is between the total content ratios. Moreover, since the suitable thickness of a 1st partial layer and a 2nd partial layer changes with the constituent materials of the magnet element | base_body 10, the oxynitride layer 20, etc., it is not uniquely determined.

  Further, the total content ratio of oxygen and nitrogen in the oxynitride layer 20 is from the side closer to the magnet body 10 (the surface 32 side adjacent to the magnet body 10), the side away from the magnet body 10 (exposed). It may change continuously toward the surface 34 side), that is, toward the outer side in the thickness direction of the oxynitride layer 20. For example, the total content ratio of oxygen and nitrogen may continuously decrease toward the outer side in the thickness direction of the oxynitride layer 20.

  In this case, from the viewpoint of further improving the corrosion resistance of the rare earth magnet 100, the oxygen content at the surface 34 in the oxynitride layer 20 and the vicinity thereof is relative to the total content of oxygen and nitrogen constituting the oxynitride layer 20. The amount corresponding to 50 atomic percent or less is more preferable, and the amount is more preferably 0.1 to 30 atomic percent. Further, at the surface of the oxynitride layer 20 on the side of the interface 32 with the magnet body 10 and in the vicinity thereof, the lower the oxygen content, the higher the adhesion with the magnet body 10, which is more preferable. .

  The content of each constituent material such as oxygen and nitrogen in the oxynitride layer 20 is EPMA (X-ray microanalyzer method), XPS (X-ray photoelectron spectroscopy), AES (Auger electron spectroscopy) or EDS (energy dispersive type). It can be confirmed using a known composition analysis method such as X-ray fluorescence spectroscopy. Furthermore, each layer in the rare earth magnet 100 exposed by using a known method such as etching or a cross section that appears by cutting the rare earth magnet 100 is analyzed by using the above-described composition analysis method. The composition distribution of the constituent material of each layer can be grasped.

  In the rare earth magnet 100 of the present embodiment, the thickness of the protective layer 20 is preferably 0.01 to 20 μm, and preferably 0.1 to 20 μm from the viewpoint of improving corrosion resistance and securing sufficient magnetic properties. More preferably, it is more preferably 0.3 to 10 μm from the viewpoint of production cost and the like.

  The protective layer (oxynitride layer) 20 can be formed by vapor deposition such as vacuum deposition, sputtering, ion plating, CVD or spraying, liquid phase growth such as coating or solution deposition. Or a known film forming technique such as a sol-gel method can be used. Among these, from the viewpoint of preventing functional degradation of the rare earth magnet 100 due to elution of the constituent material of the magnet body 10 and from the viewpoint of more easily controlling the oxygen and nitrogen contents in the oxynitride layer 20, A phase growth method (dry process) is preferably used, and a reactive vacuum deposition method, a reactive sputtering method, a reactive ion plating method, a plasma CVD method, a thermal CVD method, or a Cat-CVD method is more preferable.

  Further, from the viewpoint of forming the protective layer 20 at a lower cost, it is preferable to use a method capable of uniformly forming a large area at a time. Examples of a method for forming such a protective layer 20 include a sputtering method and a CVD method. These methods can be applied by applying film forming techniques for uniformly forming a large area layer in the field of flat panel displays.

  On the other hand, in the vacuum deposition method, since the deposition source is generally a point source, there is a disadvantage in using it for forming a display that needs to form a large-area layer uniformly at a time. Since the rare earth magnet 100 is relatively small, the protective layer 20 can be easily formed as compared with the formation of a display. However, the vacuum deposition method tends to increase the cost of forming the protective layer 20 because the area that can be formed at one time is small in the first place. In the case of using the vacuum deposition method, it is necessary to increase the deposition rate in order to reduce the formation cost of the protective layer 20. However, when the film formation rate increases, coarse particles such as splash are generated, and as a result, there is a tendency that the protective layer 20 having a uniform surface cannot be obtained.

  In addition, the ion plating method uses a coating material (a constituent material of the protective film 20 in the present embodiment) as an anode and a substrate to be coated (a magnet body 10 in the present embodiment) as a cathode in a vacuum container. Place the coating material into atomic, molecular or particulate form by heating the anode in the presence or absence of reactive gas, and ionize it with thermionics etc. on the coated substrate of the cathode It is a technique to make it adhere. In this ion plating method, anions may be formed by the above ionization depending on the type of material. In this case, the film can be formed with the polarity of the coating material and the material to be coated reversed.

  In the ion plating method, as a method for heating the substance to be ionized, a crucible or direct resistance heating resistance heating method, a high frequency induction heating method, an electron beam heating method, or the like can be used. Of these, the resistance heating method tends to be unsuitable for forming an inorganic compound having a low vapor pressure. In addition, although the electron beam heating method can evaporate various materials, when the film formation rate increases, coarse particles such as splash are generated, and as a result, the protective layer 20 having a uniform surface is obtained. There is no tendency.

  Furthermore, in the ion plating method, since the vapor deposition source is a point source, it is difficult to form the protective layer 20 at a relatively low cost as in the case of the vacuum vapor deposition method. Therefore, in order to form the protective layer 20 at a relatively low cost by using the ion plating method, the pressure gradient type hollow cathode plasma proposed in the September issue of 1999, page 28 of “Monthly Display”. A film forming apparatus using high-density plasma by a gun may be used. This method is a kind of ion plating method and uses a sheet-like plasma as described in JP-A-2-209475, so that a large-area layer can be uniformly formed at a relatively low cost. it can. In addition, this method has an extremely high ionization rate of the plasma gun as compared with the conventional one, so the ionization rate of the evaporated particles is high, and the film density can be kept high even when the substrate temperature is relatively low. There is a tendency that effects of improving film quality such as crystallinity and reactivity including the surface shape can be obtained.

  The film formation temperature when forming the protective layer 20 is not particularly limited, but it is preferable that the thermal history during film formation is such that the magnetic properties of the magnet body 10 are not deteriorated. From such a viewpoint, the film forming temperature is preferably 500 ° C. or lower, and more preferably 300 ° C. or lower.

  The composition of the atmospheric gas when forming the protective layer 20 is not particularly limited, and may be adjusted as necessary.

  Further, when forming the protective layer 20, first, after forming the metal element constituting the metal oxynitride, the amount of oxygen or nitrogen is controlled by post-treatment such as high temperature oxidation method, plasma oxidation method, anodic oxidation method and the like. May be.

  Next, a second embodiment of the rare earth magnet of the present invention will be described with reference to FIG. 3 which is a schematic sectional view of the rare earth magnet.

  The rare earth magnet 200 according to the second embodiment of the present invention is composed of a magnet body 10 and a protective layer 20 formed by covering the entire surface of the magnet body 10. Further, the protective layer 20 is formed by laminating a functional layer 22 and an oxynitride layer 24 in this order from the interface side with the magnet body 10.

  Here, the oxynitride layer 24 contains the same constituent material as the oxynitride layer 20 in the first embodiment described above. In addition, the functional layer 24 has functions for improving the adhesion between the magnet body 10 and the protective layer 20, preventing reactivity between the layers, and controlling the surface roughness of the magnet body 10. It is provided to grant.

  In the rare earth magnet 200 of the present embodiment, the oxynitride layer 24 is provided so as to be exposed to the atmosphere, and further, the functional layer 22 and the magnet body 10 are covered with the oxynitride layer 24 so that the atmosphere is out of the atmosphere. Since it is completely cut off, the rare earth magnet 200 tends to have better corrosion resistance. In particular, in the case where the functional layer 22 is made of a material that corrodes relatively easily, if the functional layer 22 is not formed by covering the functional layer 22 with the oxynitride layer 24, the functional layer 22 is corroded, and the rare earth Since the magnetic characteristics and the like of the magnet 200 tend to be lowered, it is more preferable to provide the oxynitride layer 24.

  In addition, it is preferable that the functional layer 22 is a layer made of a metal because the adhesiveness with the magnet body 10 can be further improved, and as a result, the magnetic characteristics and corrosion resistance are further improved. Examples of such metals include Al, Cr, Si, Ti, and Ni. These can be used singly or in combination of two or more.

  Alternatively, it is preferable to select a material having a thermal expansion coefficient that is relatively close to the thermal expansion coefficient of the constituent material of the magnet body 10 as the constituent material of the functional layer 22 that improves the adhesion between the magnet body 10 and the protective layer 20. . Such a material can maintain better adhesion even when the rare earth magnet 200 is exposed to a high temperature or is subjected to a thermal shock that is repeatedly exposed to high and low temperature atmospheres. Examples of such a material include an epoxy resin and a polyimide resin in addition to the above metal, and any material having the above-described thermal expansion coefficient may be used.

Examples of the constituent material of the functional layer 22 that prevents the reaction between the magnet body 10 and the protective layer 20 include metals such as Al, Ni, Cr, Si, and Ti, resins such as epoxy resins and polyimide resins, and metal oxides Inorganic compounds such as metal nitrides and metal carbides may be used. Among these, when a metal is used as a constituent material of the functional layer 22, it is preferable to form an alloy with the constituent material of the magnet body 10 so as not to deteriorate the magnetic characteristics. In the case of using the resin, at the time of deposition of the functional layer 22, H 2 _O, preferably with those which do not contain residual impurities such as O _2, also thermosetting resin shape it is stable in a high temperature atmosphere Etc. are preferable.

  Further, the inorganic compound may contain a constituent material (element) of the oxynitride layer 24, or may be a constituent material different from the oxynitride layer 24. In particular, when the inorganic compound includes the constituent material of the oxynitride layer 24, the composition range of oxygen, carbon, and / or nitrogen, etc., is included so that the reaction with the constituent material of the magnet body 10 does not occur. It may be adjusted.

  The constituent material of the functional layer 22 that controls the surface roughness of the magnet body 10 may be the same as the constituent material of the functional layer that improves the adhesion described above. When the surface of the magnet body 10 is rough, the coverage with the protective layer 20 is lowered, and for example, pinholes tend to be generated. Therefore, by applying the above-described material on the surface of the magnet body 10 and making the surface flat to some extent, the function of the protective layer 20 tends to be more effectively and reliably extracted.

In order to make the surface of the magnet body 10 flat to some extent using the above-described material, the functional layer 22 may be formed using the material prepared in an amorphous state or a state close thereto. As such a material, for example, SiO ₂ is preferable because it has good fluidity on the substrate surface during film formation and is difficult to crystallize.

  In the rare earth magnet 200 of the present embodiment, the thickness of the protective layer 20 is preferably 0.01 to 20 μm, more preferably 0.1 to 20 μm, from the viewpoint of ensuring sufficient magnetic properties and the like. Furthermore, it is more preferable that it is 0.3-10 micrometers from viewpoints, such as production cost. The film thickness of the oxynitride layer 24 is preferably 0.01 to 20 μm, more preferably 0.1 to 20 μm from the viewpoint of improving corrosion resistance, and further 0.3 from the viewpoint of production cost and the like. More preferably, it is 10 micrometers.

  Next, a third embodiment of the rare earth magnet of the present invention will be described with reference to FIG. 4 which is a schematic sectional view of the rare earth magnet.

  The rare earth magnet 300 according to the third embodiment of the present invention includes a magnet body 10 and a protective layer 20 formed so as to cover the entire surface of the magnet body 10. Further, the protective layer 20 is formed by laminating the first functional layer 22, the second functional layer 26, and the oxynitride layer 24 in this order from the interface side with the magnet body 10.

  Among these, the constituent material of the oxynitride layer 24 can be the same as that in the second embodiment, and the constituent material of the first functional layer 22 is the functional layer in the second embodiment. The same as 22 can be used.

  In order to further improve the corrosion resistance effect of the protective layer 20, the second functional layer 26 may be the same material as the constituent material of the oxynitride layer 24 and may have a different composition ratio. However, a metal element different from the metal element used for the oxynitride layer 24 may be used. The second functional layer 26 may be made of the same material as the constituent material of the first functional layer 22 and having a different composition ratio in order to further improve the function of the first functional layer 22. Further, the second functional layer 26 may have a function different from that of the oxynitride layer 24 and the first functional layer 22. More specifically, when a metal such as Al, Ni, or Cr is used as the constituent material of the first functional layer, it is preferable to use oxynitride containing the metal element as the constituent material of the second functional layer 26. By doing so, the second functional layer 26 has a function of improving the adhesion (bonding) between the first functional layer 22 and the oxynitride layer 24.

  As mentioned above, although preferred embodiment of the rare earth magnet of this invention was described, this invention is not limited to the said embodiment. For example, the shape of the rare earth magnet according to another embodiment of the present invention is not limited to the rectangular parallelepiped as illustrated, and may have a shape corresponding to the application. Specifically, when used in a drive portion of a hard disk device or a motor for an automobile, a column shape having an arc-shaped section may be used. Moreover, when used for an industrial processing machine, a ring shape or a disk shape may be sufficient.

Moreover, as a constituent material of the magnet body 10 of another embodiment, a material containing one or more rare earth elements and Co, or a material containing one or more rare earth elements, Fe, and nitrogen (N) Etc. Specifically, for example, a material containing Sm and Co such as Sm—Co ₅ system or Sm ₂ —Co ₁₇ system (the number represents an atomic ratio), or Nd such as Nd—Fe—B system. And those containing Fe and B.

  Furthermore, the rare earth magnet of the present invention may be provided with a plurality of oxynitride layers, and these oxynitride layers may be laminated continuously, or may be laminated with another layer provided therebetween. Good. For example, the protective layer 20 described in the first embodiment described above, in which the total content of oxygen and nitrogen decreases toward the outside in the thickness direction of the oxynitride layer 20, is a metal element in the oxynitride. A plurality of continuously laminated oxynitride layers having different content ratios of oxygen and nitrogen, and the total content of oxygen and nitrogen in one of the plurality of layers is outside the layer It may be considered that the layer consists of a plurality of layers that are less than the total content of oxygen and nitrogen in the layer.

  In addition, after forming the magnet body 10 included in the rare earth magnet 200 according to the second embodiment of the present invention, a chemical conversion treatment using nitric acid or the like is performed before the functional layer 22 that reduces the surface roughness of the magnet body 10 is provided. The protrusions on the surface of the magnet body 10 may be chemically etched. Furthermore, atoms or ions accelerated using reverse sputtering or the like may collide with the surface of the magnet body 10, and the protrusions on the surface may be physically etched. In that case, the functional layer 22 may be formed by introducing a reactive gas that causes a surface reaction in plasma. Furthermore, these methods may be combined. By using these methods, it becomes possible to further reduce the surface roughness of the magnet body 10, and in combination with the formation of the functional layer 22 described above, the function of the protective layer 20 tends to be exhibited synergistically. .

  Furthermore, in the method for forming the protective layer 20, it is preferable to form the protective layer 20 using so-called barrel deposition in order to provide the protective layer 20 so as to cover the entire surface of the magnet body 10.

  In addition to the salt spray test described above, the rare earth magnet of the present invention is not corroded by a constant temperature and humidity test and a pressure cooker test which are evaluation methods for corrosion resistance. Here, the “constant temperature and humidity test” refers to a corrosion resistance evaluation test specified in JIS-C-0097. After the sample is exposed to an atmosphere of 85 ° C. and 85% relative humidity for 504 hours, the corrosion state is confirmed. It is a test to be performed. The “pressure cooker test” is a test in which a sample is exposed to an atmosphere of 120 ° C. and saturated water vapor for 24 hours, and then a corrosion state is confirmed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Example 1)
First, a sintered body having a composition of 14Nd-1Dy-7B-78Fe (the number represents an atomic ratio) manufactured by powder metallurgy was subjected to heat treatment at 600 ° C. for 2 hours in an Ar gas atmosphere. Next, the sintered body after the heat treatment was cut into a size of 56 × 40 × 8 (mm), and further chamfered by barrel polishing to obtain a magnet body.

Next, the obtained magnet body was washed with an alkaline degreasing solution, and then the surface of the magnet body was activated with a 3% nitric acid aqueous solution and further thoroughly washed with water. Subsequently, the magnet body after washing with water was fixed in a vacuum film forming chamber and evacuated until a vacuum degree of 1 × 10 ⁻³ Pa or less was obtained.

Next, a reactive layer made of silicon oxynitride (SiO _x N _y ) is formed on the surface of the magnet body so as to have a film thickness of 5 μm by using a reactive sputtering method that is a vapor phase growth method. Formed. The protective layer is formed using a Si sputtering target, and Ar, O ₂ and N ₂ gases are circulated in the film forming chamber at flow rates of 10 sccm, 1.0 sccm and 10 sccm, respectively, and the pressure in the chamber is maintained at 0.7 Pa. , By generating a 300 W high frequency discharge. The surface temperature of the magnet body at this time was adjusted to 200 ° C. Thus, the rare earth magnet of Example 1 provided with a silicon oxynitride protective layer having a thickness of 5 μm was obtained.

  As a result of fluorescent X-ray analysis of the protective layer provided in the obtained rare earth magnet, the oxygen content in the protective layer was an amount corresponding to 10 atomic% in O / (O + N).

(Example 2)
The rare earth magnet of Example 2 having a 5 μm thick silicon oxynitride protective layer in the same manner as in Example 1 except that Ar was 10 sccm, O ₂ was ₂ sccm, and N ₂ was 10 sccm. Got. When a fluorescent X-ray analysis of the protective layer provided in the obtained rare earth magnet was performed, the oxygen content in the protective layer was an amount corresponding to 30 atomic% in O / (O + N).

(Example 3)
A titanium oxynitride protective layer with a film thickness of 0.1 μm was used in the same manner as in Example 1 except that a Ti sputter target was used instead of the Si sputter target and the flow rate of O ₂ gas was changed from 1.0 sccm to 0.1 sccm. A rare earth magnet of Example 3 comprising: When the X-ray fluorescence analysis of the protective layer with which the obtained rare earth magnet was provided, the oxygen content in the protective layer was an amount corresponding to 1 atomic% in O / (O + N).

Example 4
Instead of the Si sputter target, an Al sputter target and a Mo sputter target are used together so that the area ratio of the sputtered surface is 100: 85 in Al: Mo, and the flow rate of O ₂ gas is 1.0 sccm to 0.5 sccm. A rare earth magnet of Example 4 provided with an aluminum molybdenum oxynitride protective layer having a thickness of 0.1 μm was obtained in the same manner as Example 1 except that was replaced with. As a result of fluorescent X-ray analysis of the protective layer provided in the obtained rare earth magnet, the metal atom composition in the protective layer was 0.9% for Mo and 99.1% for Al. Further, the oxygen content in the protective layer was an amount corresponding to 1 atomic% in O / (O + N).

(Example 5)
First, the magnet body after washing with water was fixed in a vacuum film formation chamber in the same manner as in Example 1, and evacuated until a vacuum degree of 1 × 10 ⁻³ Pa or less was obtained. Subsequently, a reactive sputtering method similar to that in Example 1 was used to form a protective layer having a thickness of 0.1 μm on the surface of the magnet body using zirconium oxynitride as a constituent material. The conditions for forming this protective layer were that the silicon oxynitride of Example 1 was used except that a Zr sputter target was used instead of the Si sputter target and the flow rate of O ₂ gas was changed from 1.0 sccm to 0.1 sccm. The conditions were the same as when the ride protective layer was formed.

  Next, similarly, a reactive sputtering method was used to form a 0.05 μm-thick protective layer containing tungsten oxynitride on the surface of the zirconium oxynitride protective layer. The conditions for forming this protective layer were the same as the conditions for forming the silicon oxynitride protective layer in Example 1 except that a W sputter target was used instead of the Si sputter target. In this way, the rare earth magnet of Example 5 provided with the zirconium oxynitride protective layer and the tungsten oxynitride protective layer laminated from the magnet body side was obtained.

  In order to investigate the composition of the protective layer provided in the obtained rare earth magnet, a rare earth magnet obtained by laminating only a zirconium oxynitride protective layer on the same magnet magnet as obtained in Example 1 under the same conditions as described above, And the rare earth obtained by directly laminating only the tungsten oxynitride protective layer under the same conditions as described above without laminating the zirconium oxynitride protective layer on the magnet body obtained in the same manner as in Example 1. Each magnet was prepared. As a result of fluorescent X-ray analysis of these rare earth magnets, the oxygen content in the zirconium oxynitride protective layer was O / (O + N) equivalent to 0.2 atomic%, and the tungsten oxynitride protection The oxygen content in the layer was O / (O + N) corresponding to 8 atomic%.

(Example 6)
First, a magnet body was obtained in the same manner as in Example 1. The obtained magnet body was washed with an alkaline degreasing solution, and then the surface of the magnet body was activated with a 3% nitric acid aqueous solution and further thoroughly washed with water. Subsequently, the magnet body after washing with water was fixed in a vacuum film forming chamber and evacuated until a vacuum degree of 1 × 10 ⁻³ Pa or less was obtained. Next, a metal aluminum layer was formed on the surface of the magnet body using a vacuum vapor deposition method, which is a vapor phase growth method, so as to have a film thickness of 5 μm. The metal aluminum layer was formed by irradiating a metal aluminum vapor deposition source with an electron beam.

Subsequently, on the surface of the metal aluminum layer, a Ta sputter target was used instead of the Si sputter target, and the flow rate of O ₂ gas was changed from 1.0 sccm to 5.0 sccm. A reactive sputtering method was used to form a tantalum oxynitride layer having a thickness of 3 μm. In this way, a rare earth magnet of Example 6 having a metal aluminum layer and a tantalum oxynitride protective layer laminated from the magnet body side was obtained.

  When the X-ray fluorescence analysis of the protective layer with which the obtained rare earth magnet was provided, the oxygen content in the protective layer was an amount corresponding to 3 atomic% in O / (O + N).

(Comparative Example 1)
Instead of flowing Ar, O ₂ and N ₂ gases at a flow rate of 10 sccm, 1.0 sccm, and 10 sccm, respectively, in the deposition chamber, 10 ppm each of Ar and O ₂ gas is supplied into the deposition chamber. A rare earth magnet of Comparative Example 1 was obtained in the same manner as in Example 1 except that each was distributed. When a fluorescent X-ray analysis of the protective layer provided in the obtained rare earth magnet was performed, nitrogen atoms were not confirmed in the protective layer.

(Comparative Example 2)
During the protective layer formation, Ar into the deposition chamber, _{O 2} and _{N 2} gas each 10 sccm, instead of being distributed in 1.0sccm and 10 sccm flow rate, each 10 sccm Ar and _{N 2} gas into the deposition chamber A rare earth magnet of Comparative Example 2 was obtained in the same manner as in Example 1 except that each was distributed. The obtained rare earth magnet had cracks on the entire surface that were visible to the surface protective film.

[Evaluation of corrosion resistance]
The rare earth magnets obtained in Examples 1 to 6 and Comparative Example 1 were subjected to a constant temperature and humidity test and a salt spray test under the conditions described above. And the external appearance of each rare earth magnet after each test was confirmed visually. As a result, no corrosion (generation of rust) was confirmed in the rare earth magnets of Examples 1 to 6 and Comparative Example 1 after the constant temperature and humidity test. On the other hand, after the salt spray test, corrosion of the rare earth magnets of Examples 1 to 6 was confirmed, whereas corrosion of the rare earth magnet of Comparative Example 1 was confirmed. Further, in Comparative Example 2, the magnet was corroded from the crack portion.

It is a schematic perspective view which shows the rare earth magnet of the 1st Embodiment of this invention. It is a schematic sectional drawing which shows the rare earth magnet of the 1st Embodiment of this invention. It is a schematic sectional drawing which shows the rare earth magnet of the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the rare earth magnet of the 3rd Embodiment of this invention. It is a model enlarged view which shows the phase structure of a R-Fe-B type magnet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Magnet body, 20 ... Protective layer, 100 ... Rare earth magnet.

Claims (13)

Comprising a magnet body containing a rare earth element, and the coercive Mamoruso formed on the surface of the magnet body, and
The protective layer has an oxynitride layer containing oxynitride, and the oxygen content in the oxynitride layer is 50 atoms with respect to the total content of oxygen and nitrogen in the oxynitride layer. % Rare earth magnet, characterized in that the amount corresponds to less than 1%.       The oxynitride is Si, Al, Ta, Ti, Zr, Hf, Nb, Mg, Cr, Ni, Mo, V, W, Fe, B, Ga, Ge, Bi, Mn, Ba, La, Y, 2. The rare earth magnet according to claim 1, comprising at least one element selected from the group consisting of Ca, Sr, Ce, and Be.       The oxynitride is silicon oxynitride, aluminum oxynitride, tantalum oxynitride, titanium oxynitride, zirconium oxynitride, hafnium oxynitride, niobium oxynitride, magnesium oxynitride, chromium oxynitride , Nickel oxynitride, molybdenum oxynitride, vanadium oxynitride, tungsten oxynitride, iron oxynitride, boronoxynitride, galliumoxynitride, germaniumoxynitride, bismuthoxynitride, manganeseoxynitride , Barium oxynitride, lanthanum oxynitride, yttrium oxynitride, calcium Oxynitride, strontium oxynitride, cerium oxynitride, and a rare earth magnet according to claim 1, characterized in that a kind of oxynitride selected from the group consisting of beryllium oxynitride. Rare earth magnet according to claim 1, wherein the protective layer is in the oxynitride layer of the single layer containing the oxynitride. The protective layer is, the oxynitride said a plurality of layers formed along the stacking direction between the magnet body and the protective layer, one or more layers of the protective layer containing the oxynitride The rare earth magnet according to claim 1, wherein the rare earth magnet is a layer.       The rare earth magnet according to claim 5, wherein at least a layer of the protective layer formed at a position farthest from the magnet body is the oxynitride layer.       The rare earth magnet according to claim 5 or 6, wherein at least a layer formed adjacent to the magnet body of the protective layer is made of metal.       The rare earth magnet according to claim 1, wherein the protective layer covers the entire surface of the magnet body. Claim 1, wherein the oxygen content of the oxynitride layer, characterized in that oxygen and an amount corresponding to 0.1 to 30 atomic% based on the total content of nitrogen of said oxynitride layer The rare earth magnet as described in any one of -8. The rare earth magnet according to claim 1 , wherein the oxynitride layer is formed by a vapor deposition method. The rare earth magnet according to claim 1 , wherein the protective layer has a thickness of 0.01 to 20 μm. The rare earth magnet according to claim 1 , wherein the oxynitride layer has a thickness of 0.01 to 20 μm. The protective layer is formed by laminating the functional layer and the oxynitride layer in this order from the interface side with the magnet body.
The functional layer contains a metal selected from Al, Ni, Cr, Si and Ti, a resin selected from epoxy resins and polyimide resins, or an inorganic compound selected from metal oxides, metal nitrides and metal carbides. The rare earth magnet according to any one of claims 1 to 12, characterized in that

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