Sm-Fe-N-MAGNET

Abstract

An Sm-Fe-N magnet comprises first crystal grains containing samarium, iron, and nitrogen, with a samarium content of 9 atomic% or more and less than 13 atomic%, and second crystal grains with a samarium content of 13 atomic% or more, wherein in a distribution of mean distances between adjacent grains of the second crystal grains, a mean distance between adjacent grains at a cumulative frequency of 50% is 7 µm or less, and a mean distance between adjacent grains at a cumulative frequency of 90% is 12 µm or less.

Description

Technical field

[0001] The present invention relates to an Sm-Fe-N magnet. State of the art

[0002] Sm-Fe-N magnets are representative of rare-earth transition metal nitrogen magnets, and they exhibit a high anisotropic magnetic field and high remanence. Additionally, due to their relatively high Curie temperature compared to other rare-earth transition metal nitrogen magnets, they possess excellent heat resistance. Consequently, Sm-Fe-N crystal grains have been used as one of the excellent materials for magnetic powders. On the other hand, it is known that Sm-Fe-N magnets tend to experience a decrease in coercivity upon heat treatment.

[0003] Accordingly, patent document 1 discloses an Sm-Fe-N magnet, which is a magnetic powder in which the surface of the main phase containing samarium and iron is covered with a secondary phase having a higher content of rare earth elements. List of references Patent document

[0004] Patent document 1: International Publication No. 2019-189440 Brief description of the invention Technical task

[0005] According to patent document 1, the main phase is covered with the specific secondary phase to provide the magnet, which exhibits an increased coercive field strength after heat treatment. However, the magnet in patent document 1 includes the secondary phase, so the ratio of the main phase in the magnet is low, resulting in reduced remanence.

[0006] The present invention was made with regard to such a problem and one object of the present invention is to provide an Sm-Fe-N magnet which has a high coercive field strength and a high remanence. Solution to the problem

[0007] To solve the problem, an Sm-Fe-N magnet according to one aspect of the present invention comprises: first crystalline grains containing samarium, iron, and nitrogen, with a samarium content of 9 atomic percent or more and less than 13 atomic percent; and second crystal grains that have a samarium content of 13 atomic percent or more, wherein in a distribution of the mean distances between adjacent grains of the second crystal grains a mean distance between adjacent grains at a cumulative frequency of 50% is 7 µm or less, and a mean distance between adjacent grains is 12 µm or less at a cumulative frequency of 90%. Advantageous effects of the invention

[0008] The present invention provides an Sm-Fe-N magnet which has a high coercive field strength and a high remanence. Brief description of the drawings [ Fig. 1A] Fig. 1A is an example of a SEM image (magnification: 2000×) used for segmentation. [ Fig. 1B] Fig. 1B is an example of a SEM image created by binarizing Fig. 1A was obtained and represents the first crystal grains (main phase) in black. [ Fig. 1C] Fig. 1C is an example of a SEM image created by binarizing Fig. 1A was obtained and represents grain boundaries between the first crystal grains and the second crystal grains in black. [ Fig. 2] Fig. 2 represents a method for calculating distances between adjacent grains. [ Fig. 3] Fig. Figure 3 is a SEM image (magnification: 2000×) of a section of a sintered magnet obtained in Example 1. [ Fig. 4] Fig. Figure 4 is a SEM image (magnification: 2000×) of a section of a sintered magnet obtained in comparative example 1. [ Fig. 5] Fig. Figure 5 is a SEM image (magnification: 2000×) of a section of a sintered magnet obtained in comparison example 2. Description of embodiments Feature

[0009] A Sm-Fe-N magnet (samarium-iron-nitrogen magnet) according to the present disclosure comprises first crystalline grains containing samarium, iron, and nitrogen, having a samarium content of 9 atomic percent or more and less than 13 atomic percent. The Sm-Fe-N magnet according to the present disclosure further comprises second crystalline grains having a samarium content of 13 atomic percent or more (hereinafter also referred to as Sm-rich crystalline grains).

[0010] The first set of crystal grains contains samarium, iron, and nitrogen. These crystal grains (hereinafter also referred to as Sm-Fe-N crystal grains) exhibit an Sm-Fe-N crystal structure. The second set of crystal grains consists of crystal grains containing samarium oxide (without iron or nitrogen) or crystal grains containing samarium, iron, and nitrogen.

[0011] The first crystal grains form the main phase of the Sm-Fe-N magnet. These first crystal grains are a target material in the synthesis process of Sm-Fe-N crystal grains (an alloy containing samarium, iron, and nitrogen). In contrast, the Sm-rich crystal grains are byproducts inevitably generated during the synthesis of the alloy. It has been found that these inevitably generated Sm-rich crystal grains, which exist in a specific distribution state, provide improved coercivity.

[0012] In particular, in a distribution of mean distances between adjacent grains of the second type of crystal grains in the magnet of the present disclosure, a mean distance D50 between adjacent grains at a cumulative frequency of 50% is 7 µm or less, and a mean distance D90 between adjacent grains at a cumulative frequency of 90% is 12 µm or less. In other words, for 50% of the Sm-rich crystal grains on a numerical basis, other Sm-rich crystal grains exist within a mean distance of 7 µm, and for 90% of the Sm-rich crystal grains on a numerical basis, other Sm-rich crystal grains exist within a mean distance of 12 µm. This indicates that the Sm-rich crystal grains are not unevenly distributed, but are uniformly distributed in the magnet.

[0013] The reason why the magnet exhibits improved coercivity when the smoldering metal (Sm) crystal grains are uniformly distributed within the magnet is explained as described below. It should be noted that if the Sm-rich crystal grains are uniformly distributed within the magnet, then the Sm-rich crystal grains can also be considered uniformly distributed in precursor stages of the magnet (for example, magnets after forming and before sintering or curing).

[0014] When manufacturing a magnet from Sm-Fe-N crystal grains and the like (here: at least the first and second crystal grains), heat treatment can be performed. For example, heat treatment can be carried out during sintering or hardening. In this case, an oxidation-reduction reaction occurs, in which an oxide of Sm is formed, and α-type iron (α-Fe) can precipitate. α-Fe is a soft magnet, and a magnet containing α-Fe tends to experience a deterioration in coercivity. However, if the Sm-rich crystal grains are uniformly distributed in the magnet's precursor stage, Fe can readily react with the Sm, which is abundant in the Sm-rich crystal grains, before precipitation. As a result, the precipitation of α-Fe is suppressed. Therefore, a magnet manufactured in the presence of the Sm-rich crystal grains can exhibit a high coercivity.

[0015] In the present disclosure, as described above, the distribution state of the inevitably generated Sm-rich crystal grains is controlled in order to prevent a decrease in the ratio of the main phase in the magnet. Therefore, the inherently high remanence of the Sm-Fe-N magnet can be maintained, and the resulting magnet also exhibits high remanence.

[0016] The distribution state of the Sm-rich crystal grains can be controlled, for example, by pulverization conditions during the synthesis process of Sm-Fe-N crystal grains. These pulverization conditions will be described later.

[0017] The mean distance D50 between adjacent grains at a cumulative abundance of 50% (hereinafter also referred to simply as "adjacent grain distance D50") of the Sm-rich crystal grains can be 6.5 µm or less, 6.3 µm or less, or 5.4 µm or less. The adjacent grain distance D50 can be 3.0 µm or more, 3.5 µm or more, or 4.0 µm or more.

[0018] The mean distance D90 between adjacent grains at a cumulative abundance of 90% (hereinafter also referred to simply as "adjacent grain distance D90") of the Sm-rich crystal grains can be 11.5 µm or less, or 11.3 µm or less. The adjacent grain distance D90 can be 5.0 µm or more, or 8.0 µm or more.

[0019] The magnet according to the present disclosure comprises at least the first and second crystal grains described above. The Sm-Fe-N magnet may include other materials, for example α-Fe and trace elements, which are inevitably mixed in.

[0020] The magnet can be a bonded magnet or a sintered magnet. The sintered magnet is obtained by sintering Sm-Fe-N crystal grains and the like at high temperature. The Sm-Fe-N magnet, which is a sintered magnet according to the present disclosure, can essentially be composed of a sintered body of the first crystal grains and the second crystal grains. In the precursor stage of the magnet (the magnet after forming and before sintering), the Sm-rich crystal grains are also uniformly distributed, so that the precipitation of -Fe in the sintering step can be effectively suppressed. Methods for identifying crystal grains

[0021] The first and second crystal grains can be identified as follows.

[0022] First, the elemental distribution in a section of the magnet is obtained using an energy-dispersive X-ray (EDX) analysis method. The elemental distribution is typically measured using a SEM-EDX analyzer.

[0023] EDX analysis is performed under the following conditions, for example. Table 1 EDX device HORIBA, Ltd., EMAX-Evolution Acceleration voltage 15 kV emission 10 µA WD (working distance) 15 mm signal SE (L) enlargement 5k Tilting no Pretreatment Milling and Pt coating Processing time 5 Frames 100 Length of stay 100 µs pixel count 256 dpi type TruMAP

[0024] An image obtained using a SEM (scanning electron microscope) that is used for EDX analysis can be obtained, for example, under the following conditions. Table 2 SEM device Hitachi, Ltd., SU8000 Acceleration voltage 5 kV (WD: 4100 PM) detector LA-BSE (for composition-sensitive backscattered electron imaging) pixel count 2560 × 1920 (Resolution: 0.0248 µm / pix) Number of fields 4 Image format BMP

[0025] Subsequently, based on the elemental distribution obtained by SEM-EDX analysis, an area with a samarium atomic content of 13 atomic percent or more (corresponding to the second crystal grains (Sm-rich crystal grains)) and an area with a samarium atomic content of 9 atomic percent or more and less than 13 atomic percent (corresponding to the first crystal grains) are segmented. As a result of the segmentation, grain boundaries between the first and second crystal grains are determined, and the first and second crystal grains are identified.

[0026] Segmentation can be performed by processing the above SEM image using deep learning image processing software (for example, "MIPAR 3.4", manufactured by Lightstone Corp.). Specific procedures for this process are as follows. Table 3 Segmentation methods Image preprocessing • MIPAR image processor tung • Noise removal (median filter → non-local mean) . • Normalizing image contrast (brightness / level / gamma correction / background flattening). Deep Learning • MIPAR Deep Learning Trainer • Conduct training using four-homogeneous SEM images as training data, in which main phase grains and secondary phase grains have been predefined. • Tiles: 5 × 5; Eras: 700 • Expand the training set by adding left-right flips / up-down flips / 180° rotation of the images. segmentation • MIPAR image processor • Applying the model obtained through deep learning to the SEM image to perform segmentation. • Perform segmentation as required using the Watershed method, the Segment Anything Model (SAM) method, or manual processing. • Removal of small noise particles (by setting thresholds with respect to area, equivalent circle diameter, aspect ratio and circumference). • Removal of particles at image edges. • Outputting shape / size information using the Measurement Features function.

[0027] Segmentation can also be performed by binarizing the SEM image above. Specific procedures for this method are as follows. Table 4 Segmentation methods Image preprocessing • MIPAR image processor tung • Noise removal (median filter → non-local mean) . • Normalizing image contrast (brightness / level / gamma correction / background flattening). Contrast-based • MIPAR image processor e Segmentation • Extract the bright-contrast phase as the Sm-rich phase (Basic Threshold) . • Removal of small noise particles (by setting thresholds with respect to area, equivalent circle diameter, aspect ratio and circumference). • Removal of particles at image edges. • Outputting shape / size information using the Measurement Features function.

[0028] Fig. 1A is an example of a SEM image (magnification: 2000). x ), which is used for segmentation. Fig. 1B is an example of a SEM image created by binarizing Fig. 1A was obtained and represents the first crystal grains (main phase) in black. Fig. 1C is an example of a SEM image created by binarizing Fig. 1A was obtained and represents grain boundaries between the first crystal grains and the second crystal grains in black. Distance between adjacent grains

[0029] The distance between adjacent grains can be obtained by performing a Delaunay triangulation on a section of a magnet. First, the centers of gravity of a plurality of Sm-rich crystal grains, identified by the segmentation described above, are considered as points, and these points are treated as a point set discretely distributed on a plane. This point set is then subjected to a Delaunay triangulation.

[0030] Then, as in Fig.Figure 2 shows an arbitrary vertex T0 selected from the plurality of Delaunay triangles. Vertex T0 is also the centroid of a sm-rich crystal grain (reference grain P1; reference symbol not shown in the figure). The two other vertices T1 and T2 of the Delaunay triangle encompassing vertex T0 are also the centroids of two other sm-rich crystal grains adjacent to (adjacent to) the reference grain P1. A distance D1 of a line segment connecting vertex T0 and vertex T1 represents the distance (inter-grain distance) between the reference grain P1 and another sm-rich crystal grain adjacent to (adjacent to) the reference grain P1.Similarly, a distance D2 of a line segment connecting vertex T0 and vertex T2 represents the distance (distance between adjacent grains) between the reference grain P1 and one other Sm-rich crystal grain adjacent to the reference grain P1. There are a plurality of Delaunay triangles encompassing vertex T0. For all Delaunay triangles encompassing vertex T0, distances D of line segments connecting vertex T0 and other vertices TX (reference symbols not shown in the figure; points surrounded by dashed lines) are determined, and the distances D are averaged. The distance D is determined as the mean distance Dave between adjacent grains, measured between the reference grain P1 and the plurality of Sm-rich crystal grains adjacent to the reference grain P1.

[0031] Subsequently, all other sm-rich crystal grains are used as reference grains and subjected to operations similar to those for reference grain P1 to determine a mean distance Dave between adjacent grains, measured between each sm-rich crystal grain and other sm-rich crystal grains that are adjacent to it. The majority of the determined mean distances Dave between adjacent grains are converted into a histogram to obtain a frequency distribution of the mean distances Dave. In the frequency distribution of the mean distances Dave, a mean distance D50 between adjacent grains is determined at a cumulative frequency of 50% and a mean distance D90 between adjacent grains at a cumulative frequency of 90%. First crystal grains

[0032] The first crystal grains form the main phase of the magnet. These first crystal grains are Sm-Fe-N crystal grains and have a samarium content of 9 atomic percent or more and less than 13 atomic percent. Examples of the crystal structure of the first crystal grains include an SmFe9N1.5 structure and an Sm2Fe structure. 17 N3 structure; however, the crystal structure is not limited to this and can be any crystal structure composed of Sm, Fe, and N. A typical crystal structure of the first crystal grains is Sm₂Fe₂. 17 N3 structure.

[0033] The mean grain size of the first crystal grains is not particularly restricted. For example, the mean grain size of the first crystal grains can be 0.04 µm or more and 5 µm or less. If the mean grain size of the first crystal grains is 0.04 µm or more, a transition of the Sm-Fe-N crystal grains to a superparamagnetic state can be effectively suppressed. If the mean grain size of the first crystal grains is 5 µm or less, the coercive field strength can be effectively improved.

[0034] The procedure for calculating the mean grain size of the first crystal grains is as follows. First, a section of the magnet is photographed using a field emission scanning electron microscope (FE-SEM) such that it contains at least 50 crystal grains. The first and second crystal grains in the photographed image are identified in the same manner as described above. Then, a total area A1 of sections containing the first crystal grains and a number N1 of crystal grains in the photographed image are determined. A1 / N1 is used as the mean cross-sectional area per first crystal grain, and the square root of the mean cross-sectional area a1 is calculated to determine the mean grain size of the first crystal grains. Second crystal grains

[0035] The second crystal grains have a samarium content of 13 atomic percent or more. These second crystal grains are samarium oxide (Sm₂O₃) or Sm-Fe-N crystal grains. The samarium content of the second crystal grains can be 14 atomic percent or less. Examples of the crystal structure of the second crystal grains, which are Sm-Fe-N crystal grains, include Sm₅Fe₁₇N and SmFe₃N; however, the crystal structure is not limited to these and can be any crystal structure composed of Sm, Fe, and N. The second crystal grains are uniformly distributed within the magnet.

[0036] The mean grain size of the second crystal grains can be 0.2 µm or more and 1 µm or less. If small second crystal grains with a mean grain size of 0.2 µm or more and 1 µm or less are uniformly distributed within the magnet, the coercive field strength can be further improved. The mean grain size of the second crystal grains can be 0.95 µm or less, 0.90 µm or less, or 0.86 µm or less. The mean grain size of the second crystal grains can be 0.70 µm or more, 0.75 µm or more, or 0.76 µm or more.

[0037] The mean grain size of the second crystal grains can also be calculated, as with the mean grain size of the first crystal grains, from a total area A2 of sections of the second crystal grains and a number N2 of crystal grains in the photographed image.

[0038] In a section of the magnet, the ratio of the total area of ​​the second crystal grains to the total area of ​​the first crystal grains can be, for example, 2% or more and 10% or less. If the area ratio of the second crystal grains is 2% or more, the effect of improving the coercive field strength is easily maintained. If the area ratio of the second crystal grains is 10% or less, the decrease in remanence is suppressed.

[0039] The area ratio of the second crystal grains is obtained from the total area A2 of the sections of the second crystal grains and the total area A1 of the sections of the first crystal grains, which are obtained in the same way as in the case of determining the mean grain sizes of the first and second crystal grains, by the formula 100 × A2 / A1 (%).

[0040] 100 × A2 / A1 (%) can be 3% or more, 3.5% or more, 4.0% or more, or 5.0% or more. 100 × A2 / A1 (%) can be 9.0% or less, or 8.0% or less. Manufacturing process

[0041] The following describes an example of a process for manufacturing a sintered magnet. First, a coarse Sm-Fe-N magnet powder, serving as raw material, is pulverized. The pulverization is carried out under suitable conditions so that the adjacent grain spacing D50 can be reduced to 7 µm or less and the adjacent grain spacing D90 can be reduced to 12 µm or less.

[0042] The Sm-Fe-N magnet coarse powder is pulverized, for example, by repeatedly performing a cycle of pulverization treatment and classification. As a result, Sm-rich crystal grains contained in the Sm-Fe-N magnet coarse powder are pulverized more finely and distributed more evenly, and the adjacent grain distances D50 and D90 are more likely to fall within the ranges mentioned above.

[0043] The pulverization treatment can be performed, for example, at a pulverization pressure of 0.3 MPa or more and 1.2 MPa or less. The pulverization pressure can be 0.5 MPa or more, 0.6 MPa or more, or 0.7 MPa or more. The pulverization pressure can be 1.0 MPa or less, or 0.9 MPa or less. The number of cycles can be, for example, 2 or more, 3 or more, or 4 or more.

[0044] Pulverization can be carried out using, for example, a jet mill (airflow pulverization type or similar) or a ball mill. The airflow pulverization type jet mill could, for example, be an MC44 manufactured by Micromacinazione.

[0045] Pulverization is preferably carried out in a glovebox that has been replaced with an inert gas (one type or a mixture of two or more types of nitrogen, argon, helium, and the like). Pulverization can also be carried out in a glovebox connected to a gas recirculation oxygen and moisture purifier.

[0046] In powder after pulverization, fine powder (corresponding to extremely small grains in the powder's particle size distribution) exhibits a higher proportion of grains damaged by pulverization and lower crystallinity than larger grains. To obtain pulverized powder with good crystallinity, such fine powder with low crystallinity can be removed by classification. The removal of the fine material can be carried out using an airflow classifier or similar device, but is not limited to this method. The removed fine powder can, for example, consist of grains with a particle size of less than 0.04 µm.

[0047] The mixture, comprising the first and second crystal grains, is then pressure-sintered. This produces a sintered magnet.

[0048] Prior to pressure sintering, the mixture can undergo an alignment step and a magnetization step. This aligns the directions of the minor magnetization axes of the crystal grains, resulting in improved magnetic properties. The applied magnetic field can be, for example, a static magnetic field of 2 T or more.

[0049] Pressure sintering is performed, for example, under a low-oxygen atmosphere. It can be carried out using any pressure sintering method, including spark plasma sintering. For instance, pressure sintering can be performed by filling a mold with magnetic powder, installing the mold (without exposing it to the atmosphere) in a pulsed electric current sintering machine equipped with a pressure mechanism using a servo-controlled press, applying constant pressure to the mold while maintaining a vacuum in the machine, and then performing electric current sintering while maintaining the pressure. The mold used can be of any shape, including cylindrical, but is not limited to this.The interior of the pulsed electric current sintering machine is maintained at a vacuum of 5 Pa or less. The applied pressure can be any pressure higher than atmospheric pressure that allows for the formation of a sintered magnet, and can range, for example, from 100 MPa or more to 2000 MPa or less. The electric current sintering is performed, for example, at a temperature of 400 °C or more to 600 °C or less, and for a time of 30 seconds or more to 10 minutes or less.

[0050] The method for producing the mixture comprising the first and second crystal grains is not limited to the method described above, and any suitable method may be used. The method for producing the magnet is not limited to the method described above, and any suitable method may be used. EXAMPLES Examples 1 to 4 and comparison examples 1 and 2

[0051] The following procedures were carried out to produce Sm-Fe-N sintered magnets. A coarse powder with a composition of Sm₂Fe₁₇N₃ and a mean particle size of approximately 25 µm was prepared as the raw material for the magnetic powder. Using an air-flow pulverizing mill, the prepared coarse powder was pulverized under various conditions. The pulverization conditions are described in the following table. Table 5 Pulverizing pressure (MPa) Number of cycles Example 1 0,7 2 Example 2 0,9 2 Example 3 0,5 4 Example 4 0,7 2 Comparative example 1 0,7 2 Comparative example 2 0,7 2

[0052] Pulverization was carried out in a glovebox under a low-oxygen atmosphere. After pulverization, an airflow classifier was used to remove fine powder (grains with a particle size of less than 0.04 µm). This yielded Sm-Fe-N crystal grains.

[0053] 0.5 g of the obtained Sm-Fe-N crystal grains were weighed and placed into a cylindrical hard metal mold with an inner diameter of 6 mm. The mold was installed, without exposure to the atmosphere, in a pulsed electric current sintering machine equipped with a pressure mechanism using a servo-controlled press. Subsequently, while maintaining a vacuum of 2 Pa or less and an oxygen concentration of 0.4 ppm or less inside the pulsed electric current sintering machine, a pressure of 1200 MPa was applied, and electric current sintering was carried out for 2 minutes at a sintering temperature of 500 °C while maintaining the pressure; sintered magnets were thus obtained. SEM images of sections of the sintered magnets are shown in the Fig. 3, Fig. 4 to Fig.Figure 5 is shown. In the SEM images, areas shown in light gray are the second crystal grains, and areas shown in black or dark gray are the first crystal grains. Evaluation

[0054] The sintered magnets obtained were evaluated as follows. The evaluation results are described in the following table. (1) Mean grain sizes of the crystal grains, A2 / A1

[0055] A SEM image of a section of such a sintered magnet was photographed, and the first and second crystal grains in the photographed image were identified using the deep learning image processing software described above (“MIPAR 3.4”, manufactured by Lightstone Corp.). The total area A1 and the number N1 of the sections of the first crystal grains, as well as the total area A2 and the number N2 of the sections of the second crystal grains in the photographed image, were determined, and the mean grain sizes of the crystal grains and A2 / A1 were calculated in the same manner as described above. (2) Mean distances D50 and D90 between adjacent grains

[0056] A SEM image of a section of such a sintered magnet was subjected to Delaunay triangulation, the mean distances between adjacent grains were calculated in the same way as described above, and the values ​​were converted into a histogram. (3) Remanence and coercivity

[0057] Remanence and coercive field strength were measured using a vibrating sample magnetometer (VSM). Table 6 Example 1 Example 2 Example 3 Example 4 Comparison example 1 Comparative example 2 Average grain size of the first crystal grains (µm) 0,74 0,52 0,65 0,56 0,44 0,59 Average grain size of the second crystal grains (µm) 0,84 0,76 0,86 0,81 0,99 1,49 Adjacent grain distance D50 (µm) 6,3 5,4 4,5 5,0 8,6 8,1 Adjacent grain distance D90 (µm) 10,6 11,3 8,7 8,3 1,8 13,9 A2 / A1 (%) 3,5 5,6 8,0 6,4 3,2 4,5 Remanence (T) 0,99 0,98 0,99 0,97 1,00 0,99 Coercive field strength (kA / m) 951 1027 956 1053 887 826 Industrial applicability

[0058] The sintered magnet and magnetic powder of the present invention can be used in a wide range of applications in various motor fields. For example, the sintered magnet and magnetic powder can be used in auxiliary on-board motors, main motors for EV / HEVs, and the like, and can be used in particular in oil pump motors, electric power steering motors, EV / HEV drive motors, and the like.

[0059] This application claims priority over Japanese patent application No. 2023-170759, filed in Japan on September 29, 2023, the entire contents of which are hereby incorporated by reference. List of reference symbols T0 is one of the vertices of a Delaunay triangle and the center of gravity of the reference grain P1 T1 is another vertex of the Delaunay triangle and the center of gravity of another Sm-rich crystal grain that borders (is adjacent to) the reference grain P1. T2 is another corner point of the Delaunay triangle and the center of gravity of yet another Sm-rich crystal grain that borders (is adjacent to) the reference grain P1. D1 Distance of a line segment connecting vertex T0 and vertex T1 D2 Distance of a line segment connecting vertex T0 and vertex T2 QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2019-189440

[0004] JP 2023-170759

[0059]

Claims

[1] Sm-Fe-N magnet, comprising: first crystalline grains containing samarium, iron, and nitrogen, with a samarium content of 9 atomic percent or more and less than 13 atomic percent; and second crystal grains that have a samarium content of 13 atomic percent or more, wherein in a distribution of the mean distances between adjacent grains of the second crystal grains a mean distance between adjacent grains at a cumulative frequency of 50% is 7 µm or less, and a mean distance between adjacent grains is 12 µm or less at a cumulative frequency of 90%. [2] Sm-Fe-N magnet according to claim 1, wherein the second crystal grains have a mean grain size of 0.2 µm or more and 1 µm or less. [3] Sm-Fe-N magnet according to claim 1 or 2, which is a sintered body comprising the first crystal grains and the second crystal grains.

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