Hexagonal ferrite magnetic powder for bonded magnets and its manufacturing method, and bonded magnets and their manufacturing method.

Abstract

To provide hexagonal crystal ferrite magnetic powder for bonded magnets which can achieve a high residual magnetic flux density Br when used for bonded magnetics and the method for manufacturing the same, as well as a bonded magnetic having a high residual magnetic flux density Br and the method for manufacturing the same.SOLUTION: Hexagonal crystal ferrite magnetic powder for bonded magnets has a composition represented by the composition formula (Sr1-xLax)*(Fe1-y-zCoyZnz)nO19-a (wherein 0<x≤0.500, 0.003≤y≤0.045, 0.001≤z≤0.020, 10.00≤n≤12.50, -1.000≤a≤3.500), and the coercive force iHc of the compact object of the hexagonal crystal ferrite magnetic powder for bonded magnets measured at a measured magnetic field of 10kOe is 2000 Oe or larger.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to hexagonal ferrite magnetic powder for bonded magnets, a method for producing the same, a bonded magnet, and a method for producing the bonded magnet. [Background Art]

[0002] Conventionally, ferrite-based sintered magnets have been used as high-coercivity magnets such as small motors used in audio-visual equipment, office automation equipment, automotive electrical components, and magnet rolls for copiers. However, in addition to the problems that ferrite-based sintered magnets are prone to chipping and cracking, have poor productivity due to the requirement for polishing, they also have the problem that processing into complex shapes is difficult. For this reason, in recent years, bonded magnets made of rare-earth magnets have been used as high-coercivity magnets for small motors used in audio-visual equipment, office automation equipment, automotive electrical components and the like. However, rare-earth magnets cost about 20 times as much as ferrite-based sintered magnets and are prone to rust. Therefore, it is desired to use ferrite-based bonded magnets instead of ferrite-based sintered magnets.

[0003] As such a ferrite magnetic powder for bonded magnets, Patent Document 1 discloses (Sr 1-x La x )·(Fe 1-y Co y ) n O 19-z discloses a ferrite magnetic powder for bonded magnets having a composition of (where 0 < x ≦ 0.5, 0 < y ≦ 0.04, 10.0 ≦ n ≦ 12.5, -1.0 ≦ z ≦ 3.5). [Prior Art Literature] [Patent Literature]

[0004] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2021-141151 [Brief Summary of the Invention] [Problem to be Solved by the Invention]

[0005] The hexagonal ferrite magnetic powder for bonded magnets described in Patent Document 1 was developed as a ferrite bonded magnet having excellent magnetic field orientation and high Br, but there is still a demand for a hexagonal ferrite magnetic powder for bonded magnets that can achieve a higher residual magnetic flux density Br as a bonded magnet.

[0006] An object of the present invention is to provide a hexagonal ferrite magnetic powder for bonded magnets that can obtain a high residual magnetic flux density Br when used in a bonded magnet, a method for producing the same, a bonded magnet having a high residual magnetic flux density Br, and a method for producing the same. [Means for Solving the Problem]

[0007] That is, the gist configuration of the present invention is as follows.

[0008] The present invention provides a composition formula (Sr 1-x La x )·(Fe 1-y-z Co y Zn z ) n O 19-a A hexagonal ferrite magnetic powder for bonded magnets having a composition represented by (wherein 0<x≤0.500, 0.003≤y≤0.045, 0.001≤z≤0.020, 10.00≤n≤12.50, -1.000≤a≤3.500), wherein 8 g of the hexagonal ferrite magnetic powder for bonded magnets and 0.4 cm of polyester resin 3 are kneaded, 7 g of the obtained kneaded product is filled into a mold with an inner diameter of 15 mmφ, compressed at a pressure of 196 MPa for 60 seconds, the obtained molded product is extracted from the mold, dried at 150° C. for 30 minutes, and the coercive force iHc of the obtained green compact measured at a measurement magnetic field of 10 kOe is 2000 Oe or more. Here, 0.4 cm of the polyester resin 3 is a measured value at 25° C. under atmospheric pressure.

[0009] 93.5 parts by mass of hexagonal ferrite magnetic powder for bonded magnets, 0.6 parts by mass of silane coupling agent, 0.8 parts by mass of lubricant, and 5.1 parts by mass of powdered polyamide resin were packed into a mixer and mixed. The resulting mixture was kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm. These kneaded pellets were then molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 N / mm². 2 A cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder) was fabricated by injection molding, and the residual magnetic flux density Br was measured when this bonded magnet A was measured in a measurement magnetic field of 10 kOe. A It is preferable that the value is 3200G or higher.

[0010] The maximum energy product BHmax of bonded magnet A, fabricated using the method described above, was measured at a magnetic field of 10 kOe. A It is preferable that the amount is 2.45 MGOe or greater.

[0011] The residual magnetic flux density Br of bonded magnet A, fabricated using the method described above, was measured at a measurement magnetic field of 10 kOe. A Then, 93.5 parts by mass of hexagonal ferrite magnetic powder for bonded magnets, 0.6 parts by mass of silane coupling agent, 0.8 parts by mass of lubricant, and 5.1 parts by mass of powdered polyamide resin were packed into a mixer and mixed. The resulting mixture was kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm. These kneaded pellets were then molded in a magnetic field of 9.7 kOe at a temperature of 300°C and a molding pressure of 8.5 N / mm². 2 A cylindrical bonded magnet B with a diameter of 15 mm and a height of 8 mm (the magnetic field orientation direction is along the central axis of the cylinder) was fabricated by injection molding, and the residual magnetic flux density Br was measured when this bonded magnet B was measured at a measurement magnetic field of 10 kOe. B Compared to Cr A / Br B However, it is preferable that it be 0.95 or higher.

[0012] In an image of a cross-section of bonded magnet A fabricated using the above method, observed at a magnification of 1000x using an electron microscope, more than 500 particles with an area of ​​0.5 μm were observed within a field of view of 85 μm × 120 μm. 2Preferably, the ratio a / b of the average major axis length a of the particles of the hexagonal ferrite magnetic powder for bonded magnets described above to the average particle diameter b of the hexagonal ferrite magnetic powder for bonded magnets measured by the air permeability method is 1.5 or more and less than 3.0.

[0013] Preferably, the average particle diameter b of the hexagonal ferrite magnetic powder for bonded magnets measured by the air permeability method is 1.00 µm or more and 1.50 µm or less.

[0014] Preferably, z is less than 0.010 in the compositional formula.

[0015] In an image obtained by observing a cross-section of the bonded magnet A produced by the above method with an electron microscope at a magnification of 1000×, among 500 or more particles of the hexagonal ferrite magnetic powder for bonded magnets having an area of 0.5 µm 2 or more observed within a visual field region of 85 µm × 120 µm, it is preferable that the proportion by number of particles having a ratio of major axis length to minor axis length (major axis length / minor axis length) of 1.5 or more is less than 60%.

[0016] Preferably, the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer is a bimodal or higher distribution having peaks in a particle diameter range of 0.5 µm or more and 2.0 µm or less and in a particle diameter range of 3.0 µm or more and 6.0 µm or less.

[0017] In another aspect, the present invention provides a method for producing hexagonal ferrite magnetic powder for bonded magnets, the method comprising: a raw material powder for hexagonal ferrite magnetic powder represented by the compositional formula (Sr 1-x1 La x1 )(Fe 1-y1 Co y1 ) n1 O 19-a1 (wherein 0<x1≦0.500, 0.005≦y1≦0.050, 10.00≦n1≦12.50, -1.000≦a1≦3.500), mixing the raw material powder and calcining the mixture at a first temperature to obtain a coarse powder of hexagonal ferrite; and a raw material powder for hexagonal ferrite magnetic powder represented by the compositional formula (Sr 1-x2 La x2 )(Fe 1-z2 Zn z2 ) n2 O19-a2 a step of mixing powder as a raw material for hexagonal ferrite magnetic powder represented by (where 0<x2≦0.500, 0.005≦z2≦0.050, 10.00≦n2≦12.50, -1.000≦a2≦3.500), then calcining the mixture at a second temperature to obtain fine hexagonal ferrite powder having a smaller particle diameter calculated from the BET specific surface area than that of the coarse powder; a step of mixing and pulverizing the coarse hexagonal ferrite powder and the fine hexagonal ferrite powder to obtain mixed powder that has been subjected to a mixing and pulverizing treatment; and a step of annealing the mixed powder that has been subjected to the mixing and pulverizing treatment.

[0018] In this method for producing hexagonal ferrite magnetic powder for bonded magnets, it is preferable that the particle diameter calculated from the BET specific surface area of the coarse hexagonal ferrite powder is 1.00 µm or more and 8.00 µm or less, and the particle diameter calculated from the BET specific surface area of the fine hexagonal ferrite powder is 0.05 µm or more and 0.50 µm or less.

[0019] In the step of obtaining mixed powder that has been subjected to the mixing and pulverizing treatment, it is preferable that the mass ratio of the coarse hexagonal ferrite powder to the total mass of the coarse hexagonal ferrite powder and the fine hexagonal ferrite powder is 60% by mass or more and 90% by mass or less.

[0020] In this method for producing hexagonal ferrite magnetic powder for bonded magnets, it is preferable that the saturation magnetization of the fine hexagonal ferrite powder is 57.0 emu / g or more.

[0021] In another aspect, the present invention provides a bonded magnet comprising the hexagonal ferrite magnetic powder for bonded magnets according to the present invention and a resin.

[0022] In still another aspect, the present invention provides a method for producing a bonded magnet, which uses the hexagonal ferrite magnetic powder for bonded magnets obtained by the method for producing hexagonal ferrite magnetic powder for bonded magnets according to the present invention.

Effects of the Invention

[0023] According to the present invention, there is provided a hexagonal ferrite magnetic powder for bonded magnets that can obtain a high residual magnetic flux density Br when used in a bonded magnet. Also provided are a method for producing a hexagonal ferrite magnetic powder for bonded magnets that can obtain a high residual magnetic flux density Br when used in a bonded magnet, and a bonded magnet having a high residual magnetic flux density Br, together with a method for producing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [Figure 1] It is a graph showing the particle size distribution of the hexagonal ferrite magnetic powder for bonded magnets of Example 1. [Figure 2] It is a 1000× SEM observation image of a cross section of bonded magnet A using the hexagonal ferrite magnetic powder for bonded magnets of Example 1. [Figure 3] It is a 1000× SEM observation image of a cross section of bonded magnet A using the hexagonal ferrite magnetic powder for bonded magnets of Example 2. [Figure 4] It is a 1000× SEM observation image of a cross section of bonded magnet A using the hexagonal ferrite magnetic powder for bonded magnets of Comparative Example 1. [Figure 5] It is a 1000× SEM observation image of a cross section of bonded magnet A using the hexagonal ferrite magnetic powder for bonded magnets of Comparative Example 2. DESCRIPTION OF EMBODIMENTS

[0025] (Hexagonal ferrite magnetic powder for bonded magnets) The hexagonal ferrite magnetic powder for bonded magnets of the present invention has a composition formula (Sr 1-x La x )·(Fe 1-y-z Co y Zn z ) n O 19-a It is a hexagonal ferrite magnetic powder for bonded magnets having a composition represented by (wherein 0<x≦0.500, 0.003≦y≦0.045, 0.001≦z≦0.020, 10.00≦n≦12.50, -1.000≦a≦3.500), wherein 8 g of the hexagonal ferrite magnetic powder for bonded magnets and 0.4 cm of polyester resin 3The mixture is kneaded, 7 g of the obtained kneaded product is filled into a mold with an inner diameter of 15 mmφ, compression-molded at a pressure of 196 MPa for 60 seconds, the obtained molded product is removed from the mold, dried at 150°C for 30 minutes, and the obtained green compact has a coercivity iHc of 2000 Oe or more when measured at a measurement magnetic field of 10 kOe. Hereinafter, aspects such as the composition, magnetic properties, and powder properties of the hexagonal ferrite magnetic powder for bonded magnets of the present invention will be described.

[0026] [Composition] The hexagonal ferrite magnetic powder for bonded magnets of the present invention has a composition formula (Sr 1-x La x )·(Fe 1-y-z Co y Zn z ) n O 19-a represented by the formula (wherein 0<x≦0.500, 0.003≦y≦0.045, 0.001≦z≦0.020, 10.00≦n≦12.50, -1.000≦a≦3.500), and is a hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure containing Sr, La, Co and Zn as essential elements. Here, by substituting La for Sr sites and Co or Zn for Fe sites in the crystal structure of Sr-based hexagonal ferrite magnetic powder, a hexagonal ferrite magnetic powder with higher magnetic force than Sr-based hexagonal ferrite magnetic powder can be obtained. To obtain the effect of improving magnetic force, the value of x in the above composition formula is set to a positive real number, the value of y is set to 0.003 or more, and the value of z is set to 0.001 or more. On the other hand, if the addition of La, Co, and Zn is excessive, it becomes difficult to maintain the crystal structure, so the value of x in the above composition formula is set to 0.500 or less, the value of y is set to 0.045 or less, and the value of z is set to 0.020 or less. The numerical range of x is preferably 0.100 or more and 0.400 or less, and more preferably 0.150 or more and 0.350 or less. The numerical range of y is preferably 0.005 or more and 0.040 or less, and more preferably 0.008 or more and 0.020 or less. The numerical range of z is preferably 0.001 or more and 0.015 or less, and more preferably 0.001 or more and less than 0.010. In order to obtain hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure, the value of n in the above composition formula is set to 10.00 or more and 12.50 or less. From the viewpoint of suppressing the amount of unreacted material remaining after firing, the value of n is preferably 10.50 or more and 12.00 or less. The hexagonal ferrite magnetic powder for bonded magnets of the present invention may contain unavoidable components such as impurities in the raw materials and impurities originating from the manufacturing equipment. Examples of such components include oxides of Mn and Ba. It is preferable to limit the total content of these components to 0.4% by mass or less. The above compositional formula is the compositional formula excluding unavoidable components.

[0027] [Particle size distribution] In order to obtain high packing performance, the hexagonal ferrite magnetic powder for bonded magnets of the present invention preferably has a bimodal distribution, with peaks (upward-convex mountain-shaped peaks) in the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer, specifically in the range of particle sizes from 0.5 μm to 2.0 μm and from 3.0 μm to 6.0 μm. High packing performance of the hexagonal ferrite magnetic powder for bonded magnets can only be obtained by using a mixed powder with such a particle size distribution, and together with the above composition, a higher residual magnetic flux density Br can be obtained when it is used as a bonded magnet. The inventors believe that a hexagonal mixed powder for bonded magnets is preferable in which, in the measured particle size distribution, the ferrite particles with a SrLaCo composition have larger particle sizes and mainly contribute to the larger particle size peak (in the range of 3.0 μm to 6.0 μm), and the ferrite particles with a SrLaZn composition have smaller particle sizes and mainly contribute to the smaller particle size peak (in the range of 0.5 μm to 2.0 μm). Although the mechanism is not entirely clear, we believe that using SrLaCo ferrite particles as coarse particles increases the coercivity Hc of the hexagonal ferrite magnetic powder for bonded magnets, and using SrLaZn ferrite particles, which have a high saturation magnetization σs and a low coercivity Hc, as fine particles increases the magnetic field orientation of the hexagonal ferrite magnetic powder for bonded magnets. The particle size distribution can be bimodal, with one peak in the range of 0.5 μm to 2.0 μm and one in the range of 3.0 μm to 6.0 μm.

[0028] [Magnetic properties of compacted powder] The hexagonal ferrite magnetic powder for bonded magnets of the present invention achieves high Br when used in bonded magnets. The magnetic properties when used in bonded magnets can be estimated from the magnetic properties of the compacted powder. The magnetic properties of the compacted powder are obtained by mixing 8g of the above-mentioned hexagonal ferrite magnetic powder for bonded magnets with 0.4cm of polyester resin. 3The powder can be evaluated by kneading the powder (measured at atmospheric pressure and 25°C), filling 7g of the resulting mixture into a mold with an inner diameter of 15mmφ, compressing it at a pressure of 196MPa for 60 seconds, removing the molded product from the mold, and drying it at 150°C for 30 minutes. The coercivity iHc of the powder compacted when measured under a magnetic field of 10kOe is preferably 2000Oe or more, more preferably 2100Oe or more, and more preferably 2300Oe or more. The higher the coercivity iHc of the powder compacted, the easier it is to obtain a high residual magnetic flux density Br when manufacturing bonded magnets using the hexagonal ferrite magnetic powder for bonded magnets.

[0029] [Magnetic properties of bonded magnets] Using the hexagonal ferrite magnetic powder for bonded magnets of the present invention, 93.5 parts by mass of the ferrite magnetic powder for bonded magnets, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 5.1 parts by mass of powdered polyamide resin were packed into a mixer and mixed to produce a kneaded mixture, which was then kneaded at 230°C to produce a kneaded material. From the resulting kneaded material, kneaded pellets with an average diameter of 2 mm were prepared, and these kneaded pellets were molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 N / mm². 2 By injection molding, a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (with the magnetic field orientation direction along the central axis of the cylinder) can be manufactured.

[0030] Residual magnetic flux density Br of bonded magnet A measured under a measurement magnetic field of 10 kOe A It is preferable that the maximum energy product BHmax be 3200G or higher, and more preferably 3250G or higher. A It is preferable that the amount is 2.45 MGOe or more, and more preferably 2.50 MGOe or more.

[0031] Furthermore, as a bond magnet that differs from bond magnet A only in the magnitude of the magnetic field during injection molding, 93.5 parts by mass of hexagonal ferrite magnetic powder for bond magnets, 0.6 parts by mass of silane coupling agent, 0.8 parts by mass of lubricant, and 5.1 parts by mass of powdered polyamide resin were packed into a mixer and mixed, and the resulting mixture was kneaded at 230°C to produce a kneaded material. From the obtained kneaded material, kneaded pellets with an average diameter of 2 mm were produced, and these kneaded pellets were molded in a magnetic field of 9.7 kOe at a temperature of 300°C and a molding pressure of 8.5 N / mm 2 By injection molding, a cylindrical bond magnet B with a diameter of 15 mm and a height of 8 mm can be manufactured.

[0032] At this time, the residual magnetic flux density Br of bonded magnet A when bonded magnet A and bonded magnet B are measured in a measurement magnetic field of 10 kOe. A and the residual magnetic flux density Br of bonded magnet B B Compared to Cr A / Br B However, it is preferable that it be 0.950 or higher, and more preferably 0.955 or higher. The ferrite magnetic powder in the bonded magnet is sufficiently oriented in a magnetic field, thereby obtaining a large residual magnetic flux density Br as a bonded magnet. When manufacturing the bonded magnet, the ferrite magnetic powder in the bonded magnet with excellent orientation can be sufficiently oriented even at low magnetic fields. Therefore, Br A / Br B The closer the value of is to 1, the better the orientation of the hexagonal ferrite magnetic powder for bonded magnets, and the easier it is to obtain a high residual magnetic flux density Br when manufacturing bonded magnets using this hexagonal ferrite magnetic powder.

[0033] [Particle shape evaluation by cross-sectional observation of bonded magnet A] In measuring the shape of the hexagonal ferrite magnetic powder for bonded magnets according to the present invention, the cross-section of the bonded magnet A can be observed with an electron microscope. Specifically, in an image obtained by observing the cross-section of the bonded magnet A parallel to the magnetization direction with an electron microscope at a magnification of 1000x, the entire outer edge is observed within a field of view of 85 μm × 120 μm, with an area of ​​0.5 μm. 2The particles of the hexagonal ferrite magnetic powder for bonded magnets described above can be evaluated. In this method, the length of the line segment that maximizes the distance between two points on the contour of the target particle is defined as the major axis length, and the distance between two parallel lines that enclose the target particle is defined as the minor axis length. The number of particles used for measurement should be 500 or more. This evaluation method applies to the values ​​based on cross-sectional observation in the following indices. The above measurement can be performed by binarizing the cross-sectional image and performing image analysis; any image analysis software can be used.

[0034] <Ratio a / b of average particle length a to average particle size b> In the above evaluation method, the entire outer edge is observed within the field of view, with an area of ​​0.5 μm. 2 Since the above hexagonal ferrite magnetic powder particles for bonded magnets are the target, when calculating the average value a of the major axis length of the hexagonal ferrite magnetic powder particles for bonded magnets based on cross-sectional observation using the above evaluation method, the area of ​​the hexagonal ferrite magnetic powder for bonded magnets in the cross-sectional observation of bonded magnet A is 0.5 μm². 2 This does not include minute particles smaller than a certain size.

[0035] On the other hand, the average particle size b measured by the air permeation method is the average particle size obtained by passing air through the packed bed of hexagonal ferrite magnetic powder for bonded magnets and measuring the average particle size of the powder from the permeability, and this value includes the contribution of fine particles. Therefore, in the cross-sectional observation of bonded magnet A, the area of ​​the hexagonal ferrite magnetic powder for bonded magnets is 0.5 μm². 2 The larger the proportion of fine particles less than a certain size, the larger the value of a / b. In other words, the ratio a / b, which is the average value of the long axis length of the particles a to the average particle size b, is an indicator of the degree to which fine particles are contained in the hexagonal ferrite magnetic powder for bonded magnets, and it is preferable that a / b is 1.5 or greater and less than 3.0. Furthermore, it is even more preferable that the average particle size b measured by the air permeation method is 1.00 μm or greater and 1.50 μm or less.

[0036] <Ratio of the long axis length to the short axis length of a particle> According to the above evaluation method, it is preferable that the number ratio of particles having a ratio of major axis length to minor axis length (major axis length / minor axis length) of 1.5 or more based on cross-sectional observation is less than 60%. It is presumed that particles with a large value of this ratio (major axis length / minor axis length) are less likely to be oriented in response to an external magnetic field. Manufacturing a bonded magnet using the hexagonal ferrite magnetic powder for bonded magnets with a small proportion of such particles tends to facilitate obtaining a high residual magnetic flux density Br.

[0037] (Method for Producing Hexagonal Ferrite Magnetic Powder for Bonded Magnets) The method for producing hexagonal ferrite magnetic powder for bonded magnets according to the present invention comprises a composition formula (Sr 1-x1 La x1 )(Fe 1-y1 Co y1 ) n1 O 19-a1 (wherein 0<x1≦0.500, 0.005≦y1≦0.050, 10.00≦n1≦12.50, -1.000≦a1≦3.500), the method comprises: a step of mixing raw material powders for the hexagonal ferrite magnetic powder represented by the above formula, and then firing the mixture at a first temperature to obtain coarse hexagonal ferrite powder; a step of mixing raw material powders for hexagonal ferrite magnetic powder represented by the composition formula (Sr 1-x2 La x2 )(Fe 1-z2 Zn z2 ) n2 O 19-a2 (wherein 0<x2≦0.500, 0.005≦z2≦0.050, 10.00≦n2≦12.50, -1.000≦a2≦3.500), the method comprises: a step of mixing the raw material powders and then firing the mixture at a second temperature to obtain fine hexagonal ferrite powder; a step of mixing and pulverizing the coarse hexagonal ferrite powder and the fine hexagonal ferrite powder to obtain mixed powder subjected to mixed pulverization treatment; and a step of annealing the mixed powder subjected to mixed pulverization treatment. By using fine powder having a particle diameter calculated from the BET specific surface area smaller than that of the coarse powder, the fillability of the obtained hexagonal ferrite magnetic powder for bonded magnets can be improved. As a result, a bonded magnet having a high residual magnetic flux density Br can be obtained when the bonded magnet is manufactured using the magnetic powder. Here, the specific surface area of the coarse powder is generally smaller than that of the fine powder. Each step will be described in detail below.

[0038] [Coarse powder production process] Composition formula (Sr 1-x1 La x1 )(Fe 1-y1 Co y1 ) n1 O 19-a1 represented by the formula (where 0<x1≦0.500, 0.005≦y1≦0.050, 10.00≦n1≦12.50, -1.000≦a1≦3.500), this is a step of mixing powders that are raw materials for hexagonal ferrite magnetic powder, then calcining the mixture at a first temperature to obtain coarse powder of hexagonal ferrite. In the present specification, the ferrite substituted with La and Co may be referred to as "SrLaCo ferrite" or simply "SrLaCo".

[0039] As the powder serving as the raw material for the coarse powder of hexagonal ferrite, respective compounds of the constituent elements Sr, La, Fe and Co can be used. For example, examples of Sr compounds include strontium carbonate, strontium chloride and strontium sulfate; examples of La compounds include lanthanum oxide, lanthanum hydroxide and lanthanum sulfate; examples of Fe compounds include iron oxides (hematite, magnetite), iron chloride and iron sulfate, with hematite being preferred; and examples of Co compounds include cobalt oxide, cobalt chloride and cobalt sulfate.

[0040] As the powder serving as the raw material for the coarse powder of hexagonal ferrite, a composite oxide containing two or more of the constituent elements Sr, La, Fe and Co can also be used. Such a composite oxide (hereinafter also referred to as precursor powder), and compounds of the remaining portions of Sr, La, Fe and Co that are mixed with the precursor powder to achieve the composition of the coarse powder can be used as raw materials for the coarse powder.

[0041] In order to easily obtain a high compressive density as a hexagonal ferrite magnetic powder for bonded magnets, it is preferable to use a composite oxide containing Sr, La, and Co, which constitute the composition of the coarse powder, and Fe, which corresponds to a portion of the composition of the coarse powder, as the precursor powder. Such a precursor powder can be obtained by a manufacturing method in which powders of Sr compound, La compound, Fe compound, and Co compound are mixed, then calcined at 1000°C to 1250°C, and then pulverized. Such a precursor powder and hematite, which corresponds to the remainder of Fe that constitutes the composition of the coarse powder, can be used as raw materials for the coarse powder of hexagonal ferrite.

[0042] To obtain the effect of improving the magnetic force of the coarse powder, the value of x1 in the above composition formula is set to a positive real number, and the value of y1 is set to 0.005 or higher. Furthermore, since it becomes difficult to maintain the hexagonal ferrite crystal structure if the addition of La and Co is excessive, the value of x1 is set to 0.500 or lower, and the value of y1 is set to 0.050 or lower. The numerical range of x1 is preferably 0.100 to 0.400, and more preferably 0.150 to 0.350. The numerical range of y1 is preferably 0.005 to 0.040, and more preferably 0.008 to 0.020.

[0043] Furthermore, in order to obtain hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure, the value of n1 in the above compositional formula should be between 10.00 and 12.50. From the standpoint of suppressing the residue of unreacted material after calcination, it is preferable that the value of n1 be between 10.50 and 12.00.

[0044] Crude powder may contain unavoidable components such as impurities from the raw materials and impurities originating from the manufacturing equipment. Examples of such components include oxides of Mn and Ba. It is preferable to keep the total content of these components below 0.4% by mass. The above compositional formula is the compositional formula excluding unavoidable components.

[0045] The first temperature, which is the calcination temperature in the manufacturing process of the coarse powder, is preferably 1220°C to 1400°C, and more preferably 1220°C to 1300°C.

[0046] In the coarse powder production process, a mixture of raw material powders may be granulated and then fired. The atmosphere during firing is preferably an oxidizing atmosphere, and more preferably an air atmosphere. Further, it is preferable to perform a pulverization treatment after firing. The method of the pulverization treatment is not particularly limited, and known methods using a roller mill or the like can be mentioned.

[0047] The coarse powder preferably has a particle diameter obtained from the specific surface area measured by the BET one-point method of 1.00 µm or more and 8.00 µm or less, and more preferably 2.00 µm or more and 5.00 µm or less.

[0048] [Fine Powder Production Step] Composition formula (Sr 1-x2 La x2 )(Fe 1-z2 Zn z2 ) n2 O 19-a2 (wherein 0 < x2 ≦ 0.500, 0.005 ≦ z2 ≦ 0.050, 10.00 ≦ n2 ≦ 12.50, -1.000 ≦ a2 ≦ 3.500) represented by the formula, this is a step of mixing powders that serve as raw materials for fine hexagonal ferrite powder, then firing the mixture at a second temperature to obtain fine hexagonal ferrite powder having a smaller particle diameter calculated from the BET specific surface area than the coarse powder. In the present specification, ferrite substituted with La and Zn may be referred to as "SrLaZn ferrite" or simply "SrLaZn".

[0049] As the powder serving as the raw material for the fine hexagonal ferrite powder, respective compounds of the constituent elements Sr, La, Fe and Zn can be used. For example, examples of Sr compounds include strontium carbonate, strontium chloride, and strontium sulfate; examples of La compounds include lanthanum oxide, lanthanum hydroxide, and lanthanum sulfate; examples of Fe compounds include iron oxides (hematite, magnetite), iron chloride, and iron sulfate, with hematite being preferred; and examples of Zn compounds include zinc oxide, zinc chloride, and zinc sulfate.

[0050] To obtain the effect of improving the magnetic force of the fine powder, the value of x² in the above composition formula is set to a positive real number, and the value of z² is set to 0.005 or higher. Furthermore, since it becomes difficult to maintain the hexagonal ferrite crystal structure if the addition of La and Zn is excessive, the value of x² is set to 0.500 or lower, and the value of z² is set to 0.050 or lower. The numerical range of x² is preferably 0.100 to 0.400, and more preferably 0.150 to 0.350. The numerical range of z² is preferably 0.005 to 0.040, and more preferably 0.008 to 0.020.

[0051] Furthermore, in order to obtain hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure, the value of n2 in the above compositional formula should be between 10.00 and 12.50. From the standpoint of suppressing the residue of unreacted material after calcination, it is preferable that the value of n2 be between 10.50 and 12.00.

[0052] Fine powders may contain impurities from the raw materials and unavoidable components derived from the manufacturing equipment. Examples of such components include oxides of Mn and Ba. It is preferable to keep the total content of these components below 0.4% by mass. The above compositional formula excludes these unavoidable components.

[0053] The second temperature, which is the calcination temperature in the manufacturing process of the fine powder, is preferably between 1000°C and 1350°C, and more preferably between 1100°C and 13000°C. Setting the second temperature to 1000°C or higher makes it easier to obtain fine powder with a hexagonal ferrite crystal structure.

[0054] In the manufacturing process of fine powder, the mixture of raw material powders may be granulated and calcined. An oxidizing atmosphere is preferred during calcination, and an air atmosphere is more preferred. Furthermore, it is preferable to perform a grinding treatment after calcination. The grinding treatment can be carried out by known methods using a roller mill or the like, but wet grinding treatment is preferred. Dry grinding treatment using a roller mill or the like and wet grinding treatment may be combined.

[0055] The fine powder preferably has a particle size of 0.05 μm or more and 0.50 μm or less, determined from the specific surface area measured by the BET single-point method, and more preferably 0.10 μm or more and 0.20 μm or less.

[0056] The saturation magnetization of the fine powder is preferably 57.0 emu / g or higher, and more preferably 58.0 emu / g or higher. By setting the saturation magnetization to 57.0 emu / g or higher, the saturation magnetization of the resulting hexagonal ferrite magnetic powder for bonded magnets becomes higher, making it easier to increase the residual magnetic flux density Br of the resulting bonded magnets.

[0057] [Mixing and grinding process] This process involves mixing and grinding separately obtained coarse powder and fine powder in a ratio such that the mass ratio of coarse powder to the total mass of coarse powder and fine powder is between 60% and 90% by mass, thereby obtaining a mixed powder. For the mixing and grinding process, a wet grinding apparatus is preferable, and an attritor is more preferable.

[0058] A vibrating ball mill can be used for the mixing and grinding process. From the viewpoint of promoting grinding with a vibrating ball mill, it is preferable to use balls with a media diameter of 5 mm to 20 mm, and it is preferable to perform the grinding process using balls with a media diameter of 10 mm to 20 mm as the first stage, and then perform the grinding process using balls with a media diameter of 5 mm to 10 mm as the second stage. For example, by using a vibrating ball mill after processing with an attritor, coarse particles that could not be ground by the attritor can be ground.

[0059] Thus, it was found that by using SrLaCo ferrite as the coarse powder and SrLaZn ferrite as the fine powder, the resulting bonded magnet exhibits extremely excellent magnetic properties. In coarse powder, high coarseness is difficult to obtain due to the large particle size, but by using SrLaCo ferrite, high magnetization and coercivity can be ensured. On the other hand, since fine powder has greater coercivity than coarse powder, it is presumed that by using SrLaZn ferrite, which has superior magnetization, as the fine powder, a hexagonal ferrite magnetic powder for bonded magnets with an excellent balance of magnetic properties was obtained through the combination of coarse and fine powders.

[0060] [Annealing process] This step involves annealing the mixed powder obtained in the mixing and grinding step to obtain hexagonal ferrite magnetic powder for bonded magnets. The annealing conditions are not particularly limited and can be carried out under conditions known for manufacturing hexagonal ferrite magnetic powder for bonded magnets. The annealing temperature is preferably 900°C to 1000°C, and more preferably 930°C to 980°C. Furthermore, an oxidizing atmosphere is preferred during annealing, and an air atmosphere is more preferred.

[0061] (Bonded magnets and their manufacturing method) A bonded magnet can be manufactured by molding a mixture containing hexagonal ferrite magnetic powder for bonded magnets and a resin, obtained by the method for manufacturing hexagonal ferrite magnetic powder for bonded magnets of the present invention, in a magnetic field. The method for manufacturing the bonded magnet is not particularly limited, and known methods can be used. For example, hexagonal ferrite magnetic powder for bonded magnets, a resin, and additives such as lubricants can be mixed and kneaded to produce a kneaded pellet, and then this kneaded pellet can be molded in a magnetic field to form a bonded magnet. [Examples]

[0062] The following describes in detail, with reference to examples, the hexagonal ferrite magnetic powder for bonded magnets according to the present invention, its manufacturing method, and the bonded magnet and its manufacturing method.

[0063] The evaluation in the examples was carried out as follows.

[0064] [Composition analysis] The compositional analysis of hexagonal ferrite magnetic powder for bonded magnets was performed using a fluorescent X-ray analyzer (ZSX100e, manufactured by Rigaku Corporation) by calculating the amount of each element using the fundamental parameter method (FP method). In this compositional analysis, the hexagonal ferrite magnetic powder for bonded magnets was packed into a measurement cell, molded under a pressure of 980 MPa for 20 seconds, and then qualitatively analyzed in a vacuum atmosphere using EZ scan mode, a measurement diameter of 30 mm, oxide sample form, and standard measurement time. After qualitative analysis, quantitative analysis was performed on the detected constituent elements.

[0065] [XRD measurement] For hexagonal ferrite magnetic powder used in bonded magnets, measurements were performed using powder X-ray diffraction (XRD) with a powder X-ray diffractometer (Miniflex600 manufactured by Rigaku Corporation) with a tube voltage of 40kV, tube current of 15mA, measurement range of 15° to 60°, scan speed of 1° / min, and scan width of 0.02°.

[0066] [BET specific surface area measurement] The BET specific surface area of ​​hexagonal ferrite magnetic powder for bonded magnets, coarse hexagonal ferrite powder, fine hexagonal ferrite powder, and composite oxides obtained during the manufacturing process of coarse hexagonal ferrite powder were measured using a specific surface area measuring device (Monosorb, manufactured by Cantachrome) with the BET single-point method.

[0067] [Compression density measurement] The compressed density of hexagonal ferrite magnetic powder for bonded magnets and hexagonal ferrite fine powder is determined by filling 10.0 g of magnetic powder into a cylindrical mold with an inner diameter of 2.54 cmφ and then compressing it at a pressure of 98 MPa using a cylindrical piston with a diameter of 2.44 cmφ. The compressed density of the hexagonal ferrite magnetic powder for bonded magnets is then expressed as the compressed density CD (g / cm³). 3 The measurement was performed as follows: Compression density CD (g / cm³). 3The formula (1) for calculating ) is as follows, where L (cm) is the height from the bottom surface inside the cylindrical mold to the tip of the piston after compression, and π is the value of pi. Compressed density CD (g / cm³) 3 ) = 10.00 / (2.54 2 (xπ / 4×L) ...Calculation formula (1)

[0068] [Average particle size measurement] The average particle size b (APD) of hexagonal ferrite magnetic powder for bonded magnets was measured using the air permeability method with a specific surface area measuring device (SS-100, manufactured by Shimadzu Corporation).

[0069] [Laser diffraction particle size distribution measurement] Laser diffraction particle size distribution measurement was performed using a dry laser diffraction particle size distribution analyzer (HELOS&RODOS, manufactured by Nippon Laser Co., Ltd.) with a focal length of 20 mm, dispersion pressure of 5.0 bar, and suction pressure of 130 mbar to measure the volume-based particle size distribution.

[0070] [Measurement of magnetic properties of compacted powder] 8g of hexagonal ferrite magnetic powder for bonded magnets and 0.4cm of polyester resin (P-Resin (main component) manufactured by Nichika Corporation). 3 (Measurements taken at atmospheric pressure and 25°C) The mixture was kneaded, and 7g of the resulting mixture was filled into a mold with an inner diameter of 15mmφ. The molded product was compressed at a pressure of 196MPa for 60 seconds, and the molded product was removed from the mold and dried at 150°C for 30 minutes to obtain a compacted powder. The magnetic properties of this compacted hexagonal ferrite magnetic powder for bonded magnets were measured using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.) at a measurement magnetic field of 10kOe to determine the coercivity p-iHc and residual magnetic flux density p-Br of the compacted powder.

[0071] <Measurement of major axis length, minor axis length, and area ratio> (1) Bonded magnet A was cut along a plane parallel to the magnetization direction, and the surface was polished by ion milling to obtain a sample for particle size evaluation. By performing electron microscope observation from a direction perpendicular to the polished surface, the major axis length and minor axis length of ferrite particle crystals when viewed from a direction horizontal to the ab plane can be measured. (2) A sample for particle size evaluation was observed for particle cross-sections in the sample using a scanning electron microscope (manufactured by JEOL Ltd., model: JSM-T220A), and a backscattered electron image at 1000× magnification was obtained. (3) The obtained backscattered electron image was binarized by automatic setting in the crystal grain size analysis mode using an image analysis program (manufactured by Asahi Kasei Engineering Corporation, A-zo-kun), after separating the bright regions as particles and dark regions as background, and the area was 0.5μm 2 The major axis lengths of all particles in the visual field (85μm×120μm) with the above condition were measured, the number average value thereof was calculated as the average value a of the major axis lengths of the particles, and 0.5μm relative to the total area of bright regions 2 The ratio of the total area of the above particles was calculated as the area ratio. Here, the length of the line segment that maximizes the distance between two points on the particle contour was defined as the major axis length, and the distance between two parallel lines that sandwich the particle, the two lines being parallel to the line segment for which the major axis length was measured, was defined as the minor axis length.

[0072] [Measurement of Fluidity (MFR)] 93.5 parts by mass of the obtained hexagonal ferrite magnetic powder for bonded magnets, 0.6 parts by mass of a silane coupling agent (Z-6094N manufactured by Dow Corning Toray Co., Ltd.), 0.8 parts by mass of a lubricant (VPN-212P manufactured by Henkel AG), and 5.1 parts by mass of powdered polyamide resin (P-1011F manufactured by Ube Industries, Ltd.) as a binder were weighed, filled into a mixer and mixed to obtain kneaded pellets. The kneaded pellets were placed in a melt indexer (Melt Indexer C-5059D2 manufactured by Toyo Seiki Seisaku-sho, Ltd.), and in accordance with JIS K7210-1:2014, the weight of the kneaded pellets extruded at 270°C under a load of 10 kg was measured, and this weight was converted into the amount extruded per 10 minutes, thereby obtaining the fluidity (MFR) of the kneaded pellets during injection molding.

[0073] [Measurement of Magnetic Properties of Bonded Magnets] Using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.), the coercivity iHc, residual magnetic flux density Br, and maximum energy product BHmax of bonded magnets A and B were measured at a measurement magnetic field of 10 kOe.

[0074] (Example 1) 1-1. Manufacturing of hexagonal ferrite magnetic powder for bonded magnets according to Example 1 (1) Manufacturing process for coarse hexagonal ferrite powder Strontium carbonate powder (SrCO3, specific surface area 5.8 m²) 2 ( / g), lanthanum hydroxide powder (La(OH)3, specific surface area: 5.0 m²) 2 / g), hematite powder (α-Fe2O3, specific surface area 5.3m 2 / g) and cobalt oxide powder (Co3O4, specific surface area: 3.3m²) 2 The granules ( / g) were weighed and mixed so that the molar ratio was Sr:La:Fe:Co = 0.70:0.30:0.85:0.15. This mixture was granulated in a pumpelette while water was added to obtain a first spherical granule with a diameter of 3 mm to 10 mm. The obtained first granule was calcined in an internal combustion rotary kiln under a flowing atmosphere at 1100°C for 20 minutes to obtain a first calcined product. This first calcined product was pulverized in a roller mill to obtain a SrLaFeCo composite oxide powder. The BET specific surface area of ​​the obtained SrLaFeCo composite oxide powder was measured and found to be 3.5 m². 2 It was / g.

[0075] This SrLaFeCo composite oxide powder and hematite (α-Fe2O3: specific surface area 5.3 m²) 2The powder ( / g) was weighed and mixed so that the mass ratio of SrLaFeCo composite oxide powder:hematite was 1.0:4.0 to obtain a mixture. To this mixture, 0.17 mass% boric acid and 2.3 mass% potassium chloride were added and mixed, and then granulated in a pumpelletizer while adding water to obtain a second spherical granule with a diameter of 3 mm to 10 mm. The obtained second granule was placed in an internal combustion rotary kiln and calcined in air at 1300°C (second calcination temperature) for 20 minutes, and the calcined product was crushed in a roller mill to obtain coarse hexagonal ferrite powder.

[0076] The BET specific surface area of ​​the obtained hexagonal ferrite coarse powder was measured to be 0.37 m². 2 The value is / g, and the true specific gravity of the coarse powder is 5.1 g / cm³. 3 The particle diameter (DBET) was calculated from the BET specific surface area and found to be 3.18 μm. Here, this particle diameter DBET (m 2 The particle size ( / g) can be calculated using the following formula (2), where SBET is the specific surface area of ​​the coarse powder. In this specification, the particle size calculated from the specific surface area of ​​the BET is calculated using this formula (2). DBET(μm)=6 / (true specific gravity(g / cm 3 )×SBET(m 2 / g)) ...Calculation formula (2)

[0077] Furthermore, the compositional analysis of the obtained hexagonal ferrite coarse powder was performed, and the compositional formula of the coarse powder was determined from the analytical values ​​of Sr, La, Fe, and Co (Sr 1-x1 La x1 )(Fe 1-y1 Co y1 ) n1 O 19-a1 When x1, y1, n1, and a1 were calculated using the notation, the results were x1=0.298, y1=0.014, n1=11.00, and a1=1.428. The evaluation results of the coarse powder are shown in Table 1 (the same applies to the following examples and comparative examples). In Table 1, the BET specific surface area of ​​the coarse powder is denoted as SBET1, and the particle size calculated from the BET specific surface area is denoted as DBET1.

[0078] (2) Firing process and grinding process (process for manufacturing fine hexagonal ferrite powder) As a powder used as a raw material for hexagonal ferrite fine powder, strontium carbonate powder (SrCO3, specific surface area 5.8 m²) is used. 2 ( / g), lanthanum hydroxide powder (La(OH)3, specific surface area: 5.0 m²) 2 / g), hematite powder (α-Fe2O3, specific surface area 5.3m 2 / g) and zinc oxide powder (ZnO, specific surface area: 4.5m²) 2 The powders were weighed out in a molar ratio of Sr:La:Fe:Zn = 0.70:0.30:11.50:0.30, and 2.45% by mass of potassium chloride powder was weighed out relative to the total mass of the weighed powders. After mixing these weighed powders, they were granulated in a pump pelletizer while adding water to obtain a third type of spherical granule with a diameter of 3 mm to 10 mm.

[0079] The obtained third granule was calcined in a rotary kiln under an air-flowing atmosphere at 1250°C (third calcination temperature) for 20 minutes to obtain the third calcined product. The obtained third calcined product was processed in a roller mill to obtain crushed powder. The obtained crushed powder was subjected to dry grinding using a vibrating ball mill (Murakami Seiki Seisakusho: Uras Vibrator KEC-8-YH) to obtain finely ground powder. The grinding conditions were a steel ball with a diameter of 12 mm, a rotation speed of 1800 rpm, and an amplitude of 8 mm for 300 minutes. Water was added to the obtained finely ground powder to form a slurry with a crushed powder concentration of 20% by mass. This slurry was then put into an attritor, a grinding device with stirring blades, along with a steel ball with a diameter of 5.56 mm, and ground by stirring at a peripheral speed of 1.6 m / s for 10 minutes (grinding time) to obtain a slurry containing fine hexagonal ferrite powder. A sample was obtained from the slurry containing the obtained hexagonal ferrite fine powder, and then filtered and dried to obtain a fine powder sample for evaluation. The BET specific surface area of ​​the obtained fine powder sample was measured to be 8.09 m². 2 The value was / g, and the compressed density CD was measured to be 3.25 g / cm³. 3The particle size DBET2 was measured using formula (2) calculated from the BET specific surface area and found to be 0.15 μm. Furthermore, the saturation magnetization σs of the obtained fine powder sample was measured using a vibrating sample magnetometer (VSM-P7, manufactured by Toei Kogyo Co., Ltd.) with an applied magnetic field of 1 T and found to be 58.4 emu / g. Compositional analysis of the obtained fine powder sample was performed, and the compositional formula of the coarse powder was determined from the analytical values ​​of Sr, La, Fe, and Co (Sr 1-x2 La x2 )(Fe 1-z2 Zn z2 ) n2 O 19-a2 When x2, z2, n2, and a2 were calculated using the notation, the results were x2=0.301, z2=0.025, n2=11.82, and a2=0.267. The evaluation results of the above fine powder samples are shown in Table 2 (the same applies to the following examples and comparative examples).

[0080] (3) Mixing and grinding process In the grinding container of the attritor, the slurry containing the obtained hexagonal ferrite fine powder was mixed with the coarse powder obtained in (1) so that the mass ratio of coarse powder to fine powder (mass of coarse powder:mass of fine powder) was 70:30, and the mixture was further mixed and ground in the attritor for another 20 minutes. The slurry obtained by the mixing and grinding was then filtered and dried in air at 150°C for 10 hours to obtain a dried cake. The dried cake was crushed to obtain a mixed powder. The obtained mixed powder was ground using a vibrating ball mill (Murakami Seiki Seisakusho: Uras Vibrator KEC-8-YH). The grinding conditions were a steel ball with a diameter of 12 mm, a rotation speed of 1800 rpm, and an amplitude of 8 mm for 28 minutes, and the obtained ground powder was further ground using a steel ball with a diameter of 8 mm, at a rotation speed of 1800 rpm and an amplitude of 8 mm for another 28 minutes. This resulted in a mixed powder that had undergone the mixed grinding process.

[0081] (4) Annealing process The mixed powder, which had undergone a mixing and grinding process, was annealed in air at 965°C for 30 minutes to obtain the hexagonal ferrite magnetic powder for bonded magnets according to Example 1.

[0082] (5) Evaluation of hexagonal ferrite magnetic powder for bonded magnets When the hexagonal ferrite magnetic powder for bonded magnets according to Example 1 was measured by powder X-ray diffraction (XRD), all peaks were found to be SrFe. 12 O 19 Observed at the same location, it was confirmed that the hexagonal ferrite magnetic powder for bonded magnets in this embodiment has an M-type ferrite structure. The same result was obtained in the examples and comparative examples described below.

[0083] A compositional analysis was performed on the hexagonal ferrite magnetic powder for bonded magnets according to Example 1, and from the analytical values ​​of Sr, La, Fe, Co, and Zn, the compositional formula of the hexagonal ferrite magnetic powder for bonded magnets was determined to be (Sr 1-x La x )·(Fe 1-y-z Co y Zn z ) n O 19-a When x, y, z, n, and a are calculated using the notation, the results were x=0.316, y=0.009, z=0.006, n=10.89, and a=1.586. In addition to Sr, La, Fe, Co, and Zn, metal elements such as Mn and Ba, which are presumed to be derived from the raw materials, were also detected in the compositional analysis. However, since the total amount of each was less than 0.4% by mass in oxide terms, they were not included in the compositional formula.

[0084] The hexagonal ferrite magnetic powder for bonded magnets according to Example 1 was found to have a compressed density of 3.76 g / cm³. 3 The BET specific surface area was measured and found to be 1.90 m². 2 The particle size was measured at / g, and the average particle size b was found to be 1.48 μm when measured by air permeation. In addition, when the particle size distribution was measured by laser diffraction, one peak was observed in the range of 0.5 μm to 2.0 μm with a peak diameter of 1.3 μm, and one peak was observed in the range of 3.0 μm to 6.0 μm with a peak diameter of 5.5 μm. The graph of the particle size distribution for Example 1 is shown in Figure 1.

[0085] When the magnetic properties of the compacted hexagonal ferrite magnetic powder for bonded magnets according to Example 1 were measured, the coercivity p-iHc of the compacted powder was 2150 Oe, and the residual magnetic flux density p-Br of the compacted powder was 2010 G. The evaluation results are shown in Tables 3 and 4 (the same applies to the following examples and comparative examples).

[0086] 1-2. Manufacturing of Bond Magnet A according to Example 1 93.5 parts by mass of the hexagonal ferrite magnetic powder obtained for bonded magnets, 0.6 parts by mass of a silane coupling agent (Z-6094N manufactured by Toray Dow Corning Co., Ltd.), 0.8 parts by mass of a lubricant (VPN-212P manufactured by Henkel GmbH), and 5.1 parts by mass of powdered polyamide resin (P-1011F manufactured by Ube Industries, Ltd.) as a binder were weighed and filled into a mixer. The resulting mixture was kneaded at 230°C to obtain kneaded pellets with an average diameter of 2 mm. Using a melt indexer (melt indexer C-5059D2 manufactured by Toyo Seiki Seisakusho Co., Ltd.), the weight of the kneaded pellets extruded at 270°C under a load of 10 kg was measured. By converting this weight to the amount extruded per 10 minutes, the fluidity rate (MFR) when the kneaded pellets were injection molded was determined to be 69.2 g / 10 min. This kneaded pellet is loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.) and molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 N / mm². 2 By injection molding, a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the magnetic field orientation direction is along the central axis of the cylinder) was obtained (ferrite concentration 93.5 mass%, 4.3 kOe orientation).

[0087] Using a cross-sectional image of bonded magnet A obtained by SEM, the average length a and area ratio of the hexagonal ferrite magnetic powder for bonded magnets according to Example 1 were measured. The average length a was 2.4 μm, and the area ratio was 57.0%. The ratio a / b of the average length a to the average particle size b measured by the air permeation method was calculated to be 1.62. Here, in the cross-sectional image observed at a magnification of 1000x, the area observed within a field of view of 85 μm × 120 μm was 0.5 μm. 2The total number of particles whose major and minor axis lengths were measured was 1695. Of these particles, 36.58% had a major axis length to minor axis length ratio (major axis length / minor axis length) of 1.5 or greater. The evaluation results are shown in Table 4 (the same applies to the following examples and comparative examples).

[0088] When the magnetic properties of this bonded magnet A were measured, the coercivity iHc was found to be A It is 1748 Oe, and the residual magnetic flux density is Br A The value was 3304G. The above results, along with the fluidity (MFR), are shown in Table 5 (the same applies to the following examples and comparative examples). Figure 2 shows a cross-sectional image of bonded magnet A from Example 1 obtained by SEM.

[0089] 1-3. Manufacturing of Bonded Magnet B according to Example 1 The kneaded pellets obtained during the production of bond magnet A according to Example 1 were loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.) and molded in a magnetic field of 9.7 kOe at a temperature of 300°C and a molding pressure of 8.5 N / mm². 2 By injection molding, a cylindrical bonded magnet B (ferrite concentration 93.5 mass%, 9.7 kOe) with a diameter of 15 mm and a height of 8 mm (the direction of magnetic field orientation is along the central axis of the cylinder) was obtained.

[0090] When the magnetic properties of this bonded magnet B were measured, the coercivity iHc was found to be B The residual magnetic flux density is Br, which is 1691 Oe. B The residual magnetic flux density Br of bonded magnet A was 3450G. A and the residual magnetic flux density Br of bonded magnet B B Compared to Cr A / Br B The value was 0.958. The results are shown in Table 5 (the same applies to the following examples and comparative examples).

[0091] (Example 2) Hexagonal ferrite magnetic powder for bonded magnets was obtained using the same procedure as in Example 1, except that the second firing temperature in the manufacturing process of the coarse hexagonal ferrite powder was set to 1230°C, and the third firing temperature in the manufacturing process of the fine hexagonal ferrite powder was set to 1150°C. The obtained coarse powder, the fine powder sample for evaluation, and the hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured using the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. Figure 3 shows a cross-sectional image of bonded magnet A from Example 2 obtained by SEM. The number of particles for which the long axis length and short axis length were measured was 1493.

[0092] (Example 3) In the manufacturing process of hexagonal ferrite fine powder, hexagonal ferrite magnetic powder for bonded magnets was obtained by the same procedure as in Example 1, except that the powder to be used as the raw material for hexagonal ferrite fine powder was weighed so that the molar ratio was Sr:La:Fe:Zn = 0.85:0.15:11.65:0.15, and the third firing temperature was set to 1150°C. The obtained coarse powder, evaluation fine powder sample, and hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured using the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. The number of particles for which the long axis length and short axis length were measured was 842.

[0093] (Example 4) Hexagonal ferrite magnetic powder for bonded magnets was obtained using the same procedure as in Example 1, except that the second firing temperature was set to 1230°C in the manufacturing process of the coarse hexagonal ferrite powder, the third firing temperature was set to 1150°C in the manufacturing process of the fine hexagonal ferrite powder, and the coarse powder obtained in (1) was added in the mixing process so that the mass ratio of coarse powder to fine powder was 60:40. The obtained coarse powder, the fine powder sample for evaluation, and the hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured using the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. The number of particles whose long axis length and short axis length were measured was 622.

[0094] (Comparative Example 1) (2) In the calcination and grinding processes, strontium carbonate powder (SrCO3, specific surface area 5.8 m²) is used as the raw material for the fine powder of hexagonal ferrite. 2 ( / g) and hematite powder (α-Fe2O3, specific surface area 5.3m²) 2 Hexagonal ferrite magnetic powder for bonded magnets was obtained using the same procedure as in Example 1, except that the weight was measured using ( / g) so that the molar ratio of Sr:Fe = 1.00:11.00, the third firing temperature was set to 970°C, and the grinding time in the vibrating ball mill was set to 56 minutes. The obtained coarse powder, the fine powder sample for evaluation, and the hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured using the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. Figure 4 shows a cross-sectional image of bonded magnet A of Comparative Example 1 obtained by SEM. The number of particles for which the long axis length and short axis length were measured was 1272.

[0095] (Comparative Example 2) (2) In the calcination and grinding processes, instead of zinc oxide powder, cobalt oxide powder (Co3O4, specific surface area: 3.3m²) is used as the raw material for the hexagonal ferrite fine powder. 2Hexagonal ferrite magnetic powder for bonded magnets was obtained using the same procedure as in Example 1, except that a ( / g) was used, the weight was measured so that the molar ratio was Sr:La:Fe:Co = 0.70:0.30:11.20:0.30, and the third firing temperature was set to 1150°C. The obtained coarse powder, the fine powder sample for evaluation, and the hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured using the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. Figure 5 shows a cross-sectional image of bonded magnet A of Comparative Example 2 obtained by SEM. The number of particles for which the long axis length and short axis length were measured was 1734.

[0096] (Comparative Example 3) As a raw material for coarse hexagonal ferrite powder, strontium carbonate powder (SrCO3, specific surface area 5.8 m²) is used. 2 / g), hematite powder (α-Fe2O3, specific surface area 5.3m 2 The ferrite (Sr:Fe) was weighed and mixed so that the molar ratio was Sr:Fe = 1.00:11.80. 0.17% by mass of boric acid and 2.3% by mass of potassium chloride were added to the mixture and mixed. The mixture was then granulated in a pumpelette while adding water to obtain spherical granules with a diameter of 3 mm to 10 mm. The obtained granules were placed in an internal combustion rotary kiln and calcined in air at 1250°C for 20 minutes. The calcined product was then crushed in a roller mill to obtain coarse hexagonal ferrite powder.

[0097] Hexagonal ferrite magnetic powder for bonded magnets was obtained by the same procedure as in Example 1, except that in the mixing step (3) of Example 1, the coarse powder of hexagonal ferrite obtained above was used instead of the coarse powder obtained in (1). The obtained coarse powder, the fine powder sample for evaluation, and the hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured by the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. The number of particles whose long axis length and short axis length were measured was 605.

[0098] (Comparative Example 4) As a raw material for coarse hexagonal ferrite powder, strontium carbonate powder (SrCO3, specific surface area 5.8 m²) is used. 2 ( / g), lanthanum hydroxide powder (La(OH)3, specific surface area: 5.0 m²) 2 / g), hematite powder (α-Fe2O3, specific surface area 5.3m 2 / g) and zinc oxide powder (ZnO, specific surface area: 4.5m²) 2 The granules ( / g) were weighed and mixed so that the molar ratio was Sr:La:Fe:Zn = 0.70:0.30:11.60:0.30. To this mixture, 0.17 mass% boric acid and 2.3 mass% potassium chloride were added and mixed. Then, the mixture was granulated in a pumpelette while adding water to obtain spherical granules with a diameter of 3 mm to 10 mm. The obtained granules were placed in an internal combustion rotary kiln and calcined in air at 1300°C for 20 minutes. The calcined product was then crushed in a roller mill to obtain coarse hexagonal ferrite powder.

[0099] Furthermore, as a powder used as a raw material for hexagonal ferrite fine powder, strontium carbonate powder (SrCO3, specific surface area 5.8 m²) is used. 2 ( / g), lanthanum hydroxide powder (La(OH)3, specific surface area: 5.0 m²) 2 / g), hematite powder (α-Fe2O3, specific surface area 5.3m 2 / g) and cobalt oxide powder (Co3O4, specific surface area: 3.3m²) 2 The granules ( / g) were weighed and mixed so that the molar ratio was Sr:La:Fe:Co = 0.70:0.30:11.20:0.30. Then, granulation was carried out in a pan pelletizer while adding water to obtain spherical granules with a diameter of 3 mm to 10 mm. The obtained granules were placed in an internal combustion rotary kiln and calcined in air at 1150°C for 20 minutes to obtain calcined material. The obtained calcined material was subjected to the calcination process and the operations from the roller milling process onward in the grinding process of Example 1 (2) to obtain a slurry containing fine hexagonal ferrite powder.

[0100] Hexagonal ferrite magnetic powder for bonded magnets was obtained by the same procedure as in Example 1, except that in the mixing step (3) of Example 1, a slurry containing the fine hexagonal ferrite powder obtained above and the coarse hexagonal ferrite powder obtained above were used. The obtained coarse powder, the fine powder sample for evaluation, and the hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured in the same procedure as in Example 1. Bonded magnets A and B were manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets, and their magnetic properties and fluidity (MFR) were measured. The number of particles whose long axis length and short axis length were measured was 599.

[0101] (Comparative Example 5) Strontium carbonate powder (SrCO3, specific surface area 5.8 m²) 2 ( / g), lanthanum hydroxide powder (La(OH)3, specific surface area: 5.0 m²) 2 / g), hematite powder (α-Fe2O3, specific surface area 5.3m 2 / g), cobalt oxide powder (Co3O4, specific surface area: 3.3m²) 2 / g) and zinc oxide powder (ZnO, specific surface area: 4.5m²) 2The ions ( / g) were weighed and mixed so that the molar ratio was Sr:La:Fe:Co:Zn = 0.70:0.30:11.50:0.20:0.10. To this mixture, 0.17 mass% boric acid and 2.3 mass% potassium chloride were added and mixed. Then, the mixture was granulated in a pumpelette while adding water to obtain spherical granules with a diameter of 3 mm to 10 mm. The obtained granules were placed in an internal combustion rotary kiln and calcined in air at 1300°C for 20 minutes. The calcined product was then pulverized in a roller mill to obtain coarse hexagonal ferrite powder. This coarse powder was then pulverized in a vibrating ball mill (Murakami Seiki Seisakusho: Uras Vibrator KEC-8-YH) to obtain pulverized powder. The grinding treatment was carried out for 28 minutes using a steel ball with a diameter of 12 mm at a rotation speed of 1800 rpm and an amplitude of 8 mm. The resulting pulverized powder was then subjected to further grinding treatment for 28 minutes using a steel ball with a diameter of 8 mm at a rotation speed of 1800 rpm and an amplitude of 8 mm. The resulting pulverized powder was annealed in air at 965°C for 30 minutes to obtain the hexagonal ferrite magnetic powder for bonded magnets according to Comparative Example 5.

[0102] The obtained coarse powder and hexagonal ferrite magnetic powder for bonded magnets were analyzed and measured using the same procedure as in Example 1. Furthermore, attempts were made to manufacture bonded magnets A and B and measure their fluidity (MFR) using the obtained hexagonal ferrite magnetic powder. However, the resulting mixture did not flow, making it impossible to measure the fluidity (MFR) or perform molding. Therefore, electron microscopy observation of ferrite particles was performed using a bonded magnet obtained using the same procedure as for manufacturing bonded magnet A, except that the magnetic powder was 90 parts by mass and the polyamide resin was 8.6 parts by mass. The number of particles whose long axis length and short axis length were measured was 1109.

[0103] The results are shown in Tables 1-5.

[0104] [Table 1]

[0105] Table 2

[0106] Table 3

[0107] Table 4

[0108] Table 5

Claims

1. Composition formula (Sr １－ｘ La ｘ )・(Fe １－ｙ－ｚ Co ｙ Zn ｚ ) ｎ O １９－ａ A hexagonal ferrite magnetic powder for bonded magnets having a composition represented by the formula (wherein 0 < x ≤ 0.500, 0.003 ≤ y ≤ 0.045, 0.001 ≤ z ≤ 0.020, 10.00 ≤ n ≤ 12.50, -1.000 ≤ a ≤ 3.500), 8 g of hexagonal ferrite magnetic powder for bonded magnets and 0.4 cm of polyester resin ３ The following steps were performed: kneading the mixture, filling 7 g of the resulting mixture into a mold with an inner diameter of 15 mm, compressing it at a pressure of 196 MPa for 60 seconds, removing the molded product from the mold, and drying the compacted powder at 150°C for 30 minutes. The coercivity iHc of the compacted powder was measured at a magnetic field of 10 kOe and was 2000 Oe or more. 93.5 parts by mass of hexagonal ferrite magnetic powder for bonded magnets, 0.6 parts by mass of silane coupling agent, 0.8 parts by mass of lubricant, and 5.1 parts by mass of powdered polyamide resin were packed into a mixer and mixed to obtain a mixture which was kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm. These kneaded pellets were injection molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 MPa to produce a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder). In an image obtained by observing the cross section of this bonded magnet A with an electron microscope at a magnification of 1000 times, the area of 0.5 μm observed in a visual field of 85 μm × 120 μm among 500 or more particles ２ The ratio a / b between the average value a of the major axis length of the particles of the hexagonal ferrite magnetic powder for bonded magnet and the average particle diameter b measured by the air permeation method for the hexagonal ferrite magnetic powder for bonded magnet is 1.5 or more and less than 3.0, Hexagonal ferrite magnetic powder for bonded magnets, wherein the average particle size b measured by the air permeation method of the hexagonal ferrite magnetic powder for bonded magnets is 1.00 μm or more and 1.50 μm or less.

2. The hexagonal ferrite magnetic powder for bonded magnets according to claim 1, 0.6 parts by mass of the silane coupling agent, 0.8 parts by mass of the lubricant, and 5.1 parts by mass of the powdered polyamide resin are packed into the mixer and mixed, and the mixture obtained is kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm, and these kneaded pellets are injection molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 MPa to produce a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder), The residual magnetic flux density Br when the bonded magnet A is measured in a measuring magnetic field of 10 kOe Ａ The hexagonal ferrite magnetic powder for bonded magnets according to claim 1, wherein the hardness is 3200G or more.

3. The hexagonal ferrite magnetic powder for bonded magnets according to claim 1, 0.6 parts by mass of the silane coupling agent, 0.8 parts by mass of the lubricant, and 5.1 parts by mass of the powdered polyamide resin are packed into the mixer and mixed, and the mixture obtained is kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm, and these kneaded pellets are injection molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 MPa to produce a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder), The maximum energy product BHmax when the bonded magnet A is measured at a magnetic field of 10 kOe Ａ The hexagonal ferrite magnetic powder for bonded magnets according to claim 1 or 2, wherein the amount is 2.45 MGOe or more.

4. The hexagonal ferrite magnetic powder for bonded magnets according to claim 1, 0.6 parts by mass of the silane coupling agent, 0.8 parts by mass of the lubricant, and 5.1 parts by mass of the powdered polyamide resin are packed into the mixer and mixed, and the mixture obtained is kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm, and these kneaded pellets are injection molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 MPa to produce a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder), The residual magnetic flux density Br when the bonded magnet A is measured in a measuring magnetic field of 10 kOe Ａ and, A mixture obtained by filling a mixer with 93.5 parts by mass of hexagonal ferrite magnetic powder for bonded magnets, 0.6 parts by mass of silane coupling agent, 0.8 parts by mass of lubricant, and 5.1 parts by mass of powdered polyamide resin, and mixing the resulting mixture was kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm. These kneaded pellets were injection molded in a magnetic field of 9.7 kOe at a temperature of 300°C and a molding pressure of 8.5 MPa to produce a cylindrical bonded magnet B with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder). The residual magnetic flux density Br of this bonded magnet B was measured at a measurement magnetic field of 10 kOe. Ｂ The ratio of Br Ａ / Br Ｂ However, the hexagonal ferrite magnetic powder for bonded magnets according to any one of claims 1 to 3, wherein the coefficient is 0.950 or higher.

5. The hexagonal ferrite magnetic powder for bonded magnets according to any one of claims 1 to 4, wherein z in the composition formula is less than 0.

010.

6. The hexagonal ferrite magnetic powder for bonded magnets according to claim 1, 0.6 parts by mass of the silane coupling agent, 0.8 parts by mass of the lubricant, and 5.1 parts by mass of the powdered polyamide resin are packed into the mixer and mixed, and the mixture obtained is kneaded at 230°C to produce kneaded pellets with an average diameter of 2 mm, and these kneaded pellets are injection molded in a magnetic field of 4.3 kOe at a temperature of 300°C and a molding pressure of 8.5 MPa to produce a cylindrical bonded magnet A with a diameter of 15 mm and a height of 8 mm (the direction of the magnetic field orientation is along the central axis of the cylinder), In an image of the cross-section of the bonded magnet A observed with an electron microscope at a magnification of 1000x, more than 500 areas of 0.5 μm are observed within a field of view of 85 μm × 120 μm. ２ The hexagonal ferrite magnetic powder for bonded magnets according to any one of claims 1 to 5, wherein, when the particles of the hexagonal ferrite magnetic powder for bonded magnets are observed, the number proportion of particles with a ratio of major axis length to minor axis length (major axis length / minor axis length) of 1.5 or more is less than 60%.

7. The hexagonal ferrite magnetic powder for bonded magnets according to any one of claims 1 to 6, wherein the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer has two or more peaks, with peaks in the range of particle size 0.5 μm to 2.0 μm and the range of particle size 3.0 μm to 6.0 μm.

8. Composition formula (Sr １－ｘ１ La ｘ１ ) (Fe １－ｙ１ Co ｙ１ ) ｎ１ O １９－ａ１ The process involves mixing powders that will be used as raw materials for hexagonal ferrite magnetic powder (wherein the formula 0 < x1 ≤ 0.500, 0.005 ≤ y1 ≤ 0.050, 10.00 ≤ n1 ≤ 12.50, -1.000 ≤ a1 ≤ 3.500), and then firing them at a first temperature to obtain coarse hexagonal ferrite powder, Composition formula (Sr １－ｘ２ La ｘ２ ) (Fe １－ｚ２ Zn ｚ２ ) ｎ２ O １９－ａ２ A step of mixing powders that will be used as raw materials for hexagonal ferrite magnetic powder represented by the formula (wherein 0 < x² ≤ 0.500, 0.005 ≤ z² ≤ 0.050, 10.00 ≤ n² ≤ 12.50, -1.000 ≤ a² ≤ 3.500), and then firing them at a second temperature to obtain fine hexagonal ferrite powder with a particle size smaller than the coarse powder, calculated from the BET specific surface area, and A step of mixing and grinding the coarse powder of the hexagonal ferrite and the fine powder of the hexagonal ferrite to obtain a mixed powder obtained by mixed grinding treatment, The process of annealing the mixed powder that has undergone the aforementioned mixing and grinding treatment, A method for producing hexagonal ferrite magnetic powder for bonded magnets, including the above.

9. The particle size calculated from the BET specific surface area of ​​the coarse hexagonal ferrite powder is 1.00 μm or more and 8.00 μm or less. A method for producing hexagonal ferrite magnetic powder for bonded magnets according to claim 8, wherein the particle size calculated from the BET specific surface area of ​​the hexagonal ferrite fine powder is 0.05 μm or more and 0.50 μm or less.

10. In the process of obtaining the mixed powder that has undergone the aforementioned mixing and grinding treatment, The mass ratio of the coarse hexagonal ferrite powder to the total mass of the coarse hexagonal ferrite powder and the fine hexagonal ferrite powder is 60% by mass or more and 90% by mass or less. A method for producing hexagonal ferrite magnetic powder for bonded magnets according to claim 8 or 9.

11. A method for producing hexagonal ferrite magnetic powder for bonded magnets according to any one of claims 8 to 10, wherein the saturation magnetization of the hexagonal ferrite fine powder is 57.0 emu / g or more.

12. A bonded magnet comprising a hexagonal ferrite magnetic powder and resin for bonded magnets according to any one of claims 1 to 7.

13. A method for manufacturing a bonded magnet, using hexagonal ferrite magnetic powder for bonded magnets obtained by the manufacturing method described in any one of claims 8 to 11.

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