Nanocrystalline soft magnetic alloy

Abstract

The present invention is an alloy which contains Fe, B, P and Cu and has an amorphous phase and multiple crystalline phases formed within the amorphous phase. The average Fe concentration in the entire alloy is 79 atm% or greater. The density of a Cu cluster is 0.20 × 1024 / m3 or greater, when the Cu cluster is defined as a region, from among a plurality of regions for which one side is 1.0nm, having a Cu concentration of 6.0 atm% or greater in atom probe tomography.　

Description

[Technical Field]

[0001] The present invention relates to nanocrystalline soft magnetic alloys, for example nanocrystalline soft magnetic alloys containing Fe, B, P and Cu. [Background technology]

[0002] A nanocrystalline alloy has multiple nano-sized crystalline phases formed within an amorphous phase, and an Fe-BP-Cu alloy with high saturation magnetic flux density and low coercive force is known as such a nanocrystalline alloy (e.g., Patent Documents 1 to 5). Such nanocrystalline alloys are used as soft magnetic materials with high saturation magnetic flux density and low coercive force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2010 / 021130 [Patent Document 2] International Publication No. 2017 / 006868 [Patent Document 3] International Publication No. 2011 / 122589 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-256453 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-185162 Summary of the Invention [Problem to be solved by the invention]

[0004] The crystalline phase is mainly an iron alloy with a body-centered cubic (BCC) structure, and a small crystalline phase improves soft magnetic properties such as coercivity. However, there is a demand for further improvement in the soft magnetic properties of nanocrystalline soft magnetic alloys.

[0005] The present invention has been made in view of the above problems, and has as its object to improve the soft magnetic properties of alloys. [Means for solving the problem]

[0006] The present invention relates to an alloy containing Fe, B, P, and Cu, and comprising an amorphous phase and a plurality of crystalline phases formed within the amorphous phase, wherein the average Fe concentration in the entire alloy is 79 atomic % or more, and when a region having a Cu concentration of 6.0 atomic % or more among a plurality of regions each having a side length of 1.0 nm in atom probe tomography is defined as a Cu cluster, the density of the Cu cluster is 0.20 × 10 24 / m 3 The alloy is as above.

[0007] The present invention relates to an alloy containing Fe, B, P, and Cu, and having an amorphous phase and multiple crystalline phases formed within the amorphous phase, wherein the average Fe concentration throughout the alloy is 79 atomic % or more, and the average Fe concentration in multiple regions with a side length of 1.0 nm as measured by atom probe tomography, where the Fe concentration is 80 atomic % or less, is 74.5 atomic % or less.

[0008] The present invention relates to an alloy containing Fe, B, P, and Cu, and comprising an amorphous phase and a plurality of crystalline phases formed within the amorphous phase, wherein the average Fe concentration in the entire alloy is 79 atomic % or more, and the average B atomic concentration in a region having an Fe concentration of 90 atomic % or more among a plurality of regions each having a side length of 1.0 nm in atom probe tomography is divided by the square root of the average B atomic concentration in the entire alloy, and is 0.56 atomic %. 0.5 The alloy is as above.

[0009] The present invention relates to an alloy containing Fe, B, P, and Cu, and having an amorphous phase and multiple crystalline phases formed within the amorphous phase, wherein the average Fe concentration throughout the alloy is 79 atomic % or more, and the value obtained by dividing the average Cu atomic concentration in multiple regions with a side length of 1.0 nm in atom probe tomography where the Fe concentration is 80 atomic % or less by the average Cu atomic concentration in multiple regions where the Fe concentration is 90 atomic % or more is 1.8 or more.

[0010] The present invention relates to an alloy that contains Fe, B, P, and Cu, and has an amorphous phase and multiple crystalline phases formed within the amorphous phase, wherein the average Fe concentration throughout the alloy is 79 atomic % or more, and in an atom probe tomography proxigram using multiple regions with a side length of 1.0 nm, where the Fe concentration has a boundary of 80 atomic %, the gradient of the Fe concentration at a position -2.0 nm from the boundary and a position -4.0 nm from the boundary is 0.03 atomic % / nm or more, when the direction approaching the crystalline phase is defined as positive.

[0011] The present invention relates to an alloy containing Fe, B, P, and Cu, and having an amorphous phase and a plurality of crystalline phases formed within the amorphous phase, wherein the average Fe concentration in the entire alloy is 79 atomic % or more, and the value obtained by dividing the density of Cu clusters in a plurality of regions with a side length of 1.0 nm in atom probe tomography where the Cu concentration is 1.5 atomic % or more by the density of Cu clusters in a plurality of regions where the Cu concentration is 6.0 atomic % or more is 15 or less.

[0012] The present invention provides an alloy containing Fe, B, P, and Cu, and comprising an amorphous phase and a plurality of crystalline phases formed within the amorphous phase, wherein the average Fe concentration throughout the alloy is 79 atomic % or more, and when atom probe tomography is performed on a plurality of regions each having a side length of 1.0 nm, in which the Fe concentration is 80 atomic % or less, and when the regions among the plurality of regions having a Cu concentration of 2.3 atomic % or more are considered to be Cu clusters, the average equivalent spherical diameter of the Cu clusters is 3.0 nm or more.

[0013] In the above configuration, the average Fe concentration in the entire alloy may be 83 atomic % or more and 88 atomic % or less, the average B concentration in the entire alloy may be 2.0 atomic % or more and 12 atomic % or less, the average P concentration in the entire alloy may be 2.0 atomic % or more and 12 atomic % or less, the average Cu concentration in the entire alloy may be 0.4 atomic % or more and 1.4 atomic % or less, the sum of the average Si concentration and the average C concentration in the entire alloy may be 0 atomic % or more and 3.0 atomic % or less, and the average atomic concentrations of elements other than Fe, B, P, Cu, Si, and C in the entire alloy may be 0 atomic % or more and 0.3 atomic % or less.

[0014] In the above-described configuration, the value obtained by dividing the average B atomic concentration by the average P atomic concentration in the entire alloy may be 1.5 or more and 3.5 or less.

[0015] In the above-described configuration, when the regions among the plurality of regions having a Cu concentration of 1.5 atomic % or more are regarded as Cu clusters, the value obtained by dividing the density of the Cu clusters by the average Cu atomic concentration in the entire alloy is 3.0 × 10 24 / m 3 % or less.

[0016] In the above-described configuration, the value obtained by dividing the average P atomic concentration in regions among the plurality of regions where the Fe concentration is 90 atomic % or more by the average P atomic concentration in the entire alloy may be 0.36 or less.

[0017] In the above-described configuration, the value obtained by dividing the average P atomic concentration in regions among the plurality of regions where the Fe concentration is 80 atomic % or less by the average P atomic concentration in the entire alloy may be 1.6 or more.

[0018] In the above configuration, in a proxygram using the plurality of regions with an Fe concentration of 80 atomic % as a boundary, the maximum value of the Cu concentration within a range of ±5.0 nm from the boundary can be 1.25 atomic % or more.

[0019] In the above configuration, in a proxygram using the plurality of regions with an Fe concentration of 80 atomic % as a boundary, the P atomic concentration / B atomic concentration can have a minimum value and a maximum value within a range of ±5.0 nm from the boundary.

[0020] In the above configuration, in a proxygram using the plurality of regions with an Fe concentration of 80 atomic % as a boundary, the maximum value of the P atomic concentration / B atomic concentration may be 1.0 or more within a range of ±3.0 nm from the boundary.

[0021] In the above configuration, in a proxygram using the plurality of regions with an Fe concentration of 80 atomic % as a boundary, the value obtained by dividing the maximum value of the P atomic concentration / B atomic concentration within a range of ±3.0 nm from the boundary by the average P atomic concentration / average B atomic concentration in the entire alloy may be 1.0 or more.

[0022] In the above configuration, when regions among the plurality of regions having an Fe concentration of 80 atomic % or more and regions among the plurality of regions having a Cu concentration of 2.3 atomic % or more are considered as Cu clusters, the average equivalent spherical diameter of the Cu clusters can be 3.0 nm or more. [Effects of the Invention]

[0023] According to the present invention, the soft magnetic properties of the alloy can be improved. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing the change in temperature over time, illustrating a model for the formation of nanocrystalline alloys. [Figure 2] Figures 2(a) to 2(c) are schematic diagrams illustrating the formation model of nanocrystalline alloys. [Figure 3] Figures 3(a) to 3(c) are schematic diagrams illustrating a model for the formation of nanocrystalline alloys. [Figure 4]Figures 4(a) to 4(c) are schematic diagrams of the vicinity of the boundary between the crystalline phase and the amorphous phase, explaining the formation model of nanocrystalline alloys. [Figure 5] FIG. 5(a) is a diagram for explaining a method for evaluating Cu clusters, and FIG. 5(b) is a diagram for explaining a method for setting the Fe concentration region. [Figure 6] 6(a) and 6(b) are proxygrams in Examples 1 and 2, respectively. [Figure 7] 7(a) and 7(b) are proxygrams in Comparative Example 1 and Example 3, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0025] [Hypothesized model for the formation of nanocrystalline alloys] The size (grain size) of the crystalline phase in a nanocrystalline alloy (nanocrystalline soft magnetic alloy) affects soft magnetic properties such as coercivity. When the size (grain size) of the crystalline phase is small, the coercivity decreases. This improves the soft magnetic properties. The inventors hypothesized a formation model for nanocrystalline alloys, taking into account the effects of factors other than the size of the crystalline phase on soft magnetic properties.

[0026] Figure 1 is a schematic diagram showing the change in temperature over time (a schematic diagram of the temperature history of heat treatment) that illustrates a model for the formation of nanocrystalline alloys. The precursor alloy (starting material) is an amorphous alloy. As shown in Figure 1, at time t1, the material is an amorphous alloy, and the temperature T1 is, for example, 200°C. During the heating period 40 from time t1 to t2, the temperature of the alloy increases from T1 to T2, for example, at an average heating rate 45. Temperature T2 is higher than the temperature at which a crystalline phase (metallic iron crystalline phase) of BCC iron begins to form (slightly lower than the first crystallization onset temperature Tx1) and lower than the temperature at which a crystalline phase (compound crystalline phase) begins to form (slightly lower than the second crystallization onset temperature Tx2). During the holding period 42 from time t2 to t3, the temperature of the alloy remains approximately constant at temperature T2. During the cooling period 44 from time t3 to t4, the temperature of the alloy decreases from T2 to T1, for example, at an average cooling rate 46. In FIG. 1, the heating rate 45 and the cooling rate 46 are constant, but the heating rate 45 and the cooling rate 46 may vary over time.

[0027] Figures 2(a) to 3(c) are schematic diagrams illustrating a nanocrystalline alloy formation model. Figures 4(a) to 4(c) are schematic diagrams illustrating the vicinity of the boundary between the crystalline phase and the amorphous phase, illustrating a nanocrystalline alloy formation model. Figures 4(a) to 4(c) schematically illustrate the average displacements of Fe, B, P, and Cu atoms, as well as the average displacement of the boundary 50 between the crystalline region 14 and the amorphous region 16. Figures 4(b) and 4(c) omit the depiction of atoms within the crystalline region 14.

[0028] As shown in Figure 2(a), before heating, alloy 10 is almost entirely amorphous region 16. As shown in Figure 2(b), when alloy 10 is heated, Cu clusters 12a and 12b with a higher Cu concentration than the Cu concentration of the precursor alloy are formed within amorphous region 16. The Cu clusters vary in size, but in Figure 2(b), the larger Cu clusters are designated 12a and the smaller Cu clusters are designated 12b.

[0029] As shown in FIG. 2(c), when the alloy 10 is further heated, a crystalline phase of iron with a BCC structure is generated from the surface of the larger Cu clusters 12a among the Cu clusters, and a crystalline region 14 made of this crystalline phase begins to grow.

[0030] FIG. 4(a) is an enlarged view of the vicinity of the boundary between the crystalline region 14 and the amorphous region 16 in FIG. 2(c). The crystalline region 14 is a region consisting of a crystalline phase (e.g., crystal grains), and the amorphous region 16 is a region consisting of an amorphous phase. Region 18 is a region of the amorphous region 16 near the crystalline region 14, where solutes such as P, B, and Cu are concentrated. The region of the amorphous region 16 far from the crystalline region 14 is referred to as region 17. Boundary 50 indicates the boundary between the crystalline region 14 and region 18. Boundary 52 indicates the boundary between regions 17 and 18, but is not a clear boundary.

[0031] First, the Fe concentration and solute concentration in the region 17 at the initial stage of the formation of the crystalline region 14 are approximately the same as the Fe concentration (for example, 79 atomic % or more) and solute concentration of the amorphous alloy (precursor alloy), respectively.

[0032] As indicated by arrow 30a, Fe atoms 20 in region 18 move near boundary 50, and near boundary 50, Fe atoms 20 bond with atoms near the surface of crystalline region 14. As a result, boundary 50 moves toward boundary 50a, as indicated by arrow 35, and the size of crystalline region 14 increases. Boundary 52 moves to boundary 52a. At this time, solute atoms (B atoms 22, P atoms 24, and Cu atoms 26) are not completely dissolved in the crystalline phase (in fact, they are difficult to dissolve), so some of the solute atoms are incorporated into crystalline region 14, but some (the remainder) of the solute atoms are expelled into amorphous region 16. In other words, the solute is distributed between crystalline region 14 and amorphous region 16 (between the regions on either side of boundary 50) so that the solute concentration in amorphous region 16 is higher. As a result, the solute concentration in amorphous region 16 increases more than the solute concentration in crystalline region 14, so the Fe concentration in amorphous region 16 becomes lower than the Fe concentration in crystalline region 14. Also, the solute concentration in region 18 increases more than the solute concentration in region 17, so the Fe concentration in region 18 becomes lower than the Fe concentration in region 17. In region 18, the concentration of each element changes, and the stability of amorphous region 16 decreases (free energy increases) in response to this change in concentration.

[0033] For example, in the amorphous region 16, P atoms 24 and Cu atoms 26 tend to approach each other, while P atoms 24 and B atoms 22 tend to move apart. Cu atoms 26 and B atoms 22 tend to move apart. As a result, the migration rate of B atoms 22 from region 18 to region 17, as indicated by arrow 32, is greater than the migration rates of P atoms 24 and Cu atoms 26 from region 18 to region 17, as indicated by arrows 34 and 36. As a result, concentration fluctuations occur for each element in the amorphous region 16 from region 18 to region 17. For example, the B concentration in region 17 tends to be higher than the B concentration in region 18. On the other hand, the P concentration and Cu concentration in region 17 tend to be lower than the P concentration and Cu concentration in region 18.

[0034] In addition, the Fe concentration in region 18 decreases over time, but the lower limit of the Fe concentration is determined by the most stable chemical composition in region 18. When alloy 10 contains Fe, B, P, and Cu, the P concentration tends to be high, so the chemical composition of region 18 is easily affected by P atoms 24. In this case, the amorphous phase in region 18 tends to be stable when there are three Fe atoms 20 for every P atom 24. (In other words, this composition ratio corresponds to the tendency for the compound Fe3P to form when the amorphous phase is crystallized.) Therefore, the Fe concentration in region 18 approaches 75 atomic % over time. As the crystalline region 14 increases, the Fe concentration in region 18 decreases and the solute concentration increases. Therefore, instability due to the concentration difference occurs at the boundary 52 between the amorphous phases in regions 17 and 18 (Fe concentration in region 18 becomes insufficient). This instability causes solute atoms in region 18 to migrate to region 17, while Fe atoms 20 in region 17 migrate to region 18. As a result, the solute concentration in region 17 begins to increase and the Fe concentration in region 17 begins to decrease.

[0035] In the above explanation, Alloy 10 contains only Fe, B, P, and Cu. However, if Alloy 10 contains Si and C in addition to these four elements, the explanation can be similarly applied as follows.

[0036] For example, the speed at which solutes move varies depending on the combination of solutes. First, the interaction between two solute atoms in the amorphous phase is important. For example, as mentioned above, in the amorphous phase, a strong attractive force acts between Cu atom 26 and P atom 24, but a strong repulsive force acts between Cu atom 26 and B atom 22. C and Si atoms also exert a repulsive force on Cu atom 26. The order of the repulsive force strength with respect to Cu atom 26 is, from strongest to weakest, B atom 22 (strong), C atom (medium), Si atom (medium), Cu atom 26 (attractive), and P atom 24 (attractive).

[0037] Next, interactions between solute atoms other than Cu atoms 26 in the amorphous phase are important. For example, the order of repulsive forces with B atoms 22 is, from strongest to weakest, C atoms (strong), Si atoms (strong), Cu atoms 26 (strong), B atoms 22 (weak), and P atoms 24 (weak). The order of repulsive forces with P atoms 24 is, from strongest to weakest, Si atoms (strong), P atoms 24 (medium), C atoms (medium), B atoms 22 (weak), and Cu atoms 26 (attractive). The order of repulsive forces with Si atoms is, from strongest to weakest, Si atoms (strong), P atoms 24 (strong), B atoms 22 (strong), C atoms (strong), and Cu atoms 26 (medium). The order of repulsive force against C atoms is, from strongest to weakest, C atoms (strong), B atoms 22 (strong), Si atoms (medium), P atoms 24 (medium), and Cu atoms 26 (medium). The order of ease of dissolution into the crystalline phase is, from weakest to strongest, Si atoms (strong), P atoms 24 (medium), B atoms 22 (weak), C atoms (weak), and Cu atoms (weak).

[0038] For these reasons, when alloy 10 further contains Si, Si avoids the regions containing B and P but readily dissolves in the crystalline phase, so it is likely to be distributed in the order of crystalline region 14, region 18, and region 17. When alloy 10 further contains C, C avoids the regions containing B and P but is also unlikely to dissolve in the crystalline phase, so it is likely to be distributed in the order of region 17, region 18, and crystalline region 14. When alloy 10 contains both Si and C, C is as described above, but Si also avoids the regions containing C, so it is more likely to be distributed preferentially in crystalline region 14.

[0039] In this way, the difference in concentration of each element between regions 17 and 18 that occurs due to the formation of crystalline region 14 causes a difference in stability (free energy difference) in amorphous region 16 between regions 17 and 18. To eliminate this difference in stability, each atom distributes between regions 17, 18, and crystalline region 14 through each boundary 50, 52, so it is important to determine the chemical composition and heat treatment conditions according to the desired properties.

[0040] As shown in Figure 3(a), the crystalline region 14 continues to grow and become larger during the holding period 42. In Figure 4(b), as the Fe concentration in region 17 decreases and approaches 75 atomic %, the movement of Fe atoms 20 from region 17 to region 18, as indicated by arrow 30b, decreases, and the movement of Fe atoms 20 from region 18 to the vicinity of boundary 50, as indicated by arrow 30a, also decreases. As a result, the growth of crystalline region 14, as indicated by arrow 35, slows down (approaches saturation).

[0041] As shown in FIG. 3(b), the growth of crystalline region 14 saturates during hold period 42. In FIG. 4(c), the B concentration in region 17 becomes higher than that in region 18, and the P and Cu concentrations in region 17 become lower than those in region 18. Because the B concentration tends to be high in region 17, the chemical composition of region 17 is easily affected by B atoms 22. In this case, the amorphous phase in region 17 is likely to be stable when there are two Fe atoms 20 for every one B atom 22 (i.e., this composition ratio corresponds to the tendency for the compound to become FeB when the amorphous phase is crystallized). Therefore, the Fe concentration in region 18 is near 75 atomic %, while the Fe concentration in region 17 is less than 75 atomic %. For example, the Fe concentration in region 17 is between 66 atomic % and 75 atomic %. The migration of B atoms 22 from region 18 to region 17 is substantially eliminated, and the migration of Fe atoms 20 from region 17 to region 18 and from region 18 to the vicinity of boundary 50 is also substantially eliminated. This saturates the growth of crystalline region 14. The final concentration gradient of each element in crystalline region 14 and amorphous region 16 is determined by the chemical composition of alloy 10 and the heat treatment conditions.

[0042] 3(c), during the cooling period 44, as the temperature drops, Cu atoms become less likely to dissolve in the amorphous regions 16. As a result, Cu atoms generate Cu clusters 12c in the amorphous regions 16. Through the above heat treatment process, multiple crystalline regions 14 surrounded by the amorphous regions 16 are formed.

[0043] According to the above-described model for the formation of nanocrystalline alloys, in the early stages of the formation of nanocrystalline alloys (e.g., heating period 40), it is believed that the density of large Cu clusters 12a affects the size of crystalline regions 14. When the density of large Cu clusters 12a is high, the density of crystalline regions 14 is high, and therefore the size of crystalline regions 14 is thought to be small.

[0044] The Cu clusters 12a, 12b, and 12c can hinder the movement of domain walls and increase the coercive force. Therefore, it is preferable that the density of Cu clusters 12a, which serve as nuclei for the formation of crystalline regions 14, is high, but the total number of Cu clusters 12a, 12b, and 12c (i.e., the overall number density) is small. Furthermore, as the concentration of Cu dissolved in the crystalline regions 14 and amorphous regions 16 increases, the quantum mechanical interaction between Cu atoms and Fe atoms increases. This reduces the saturation magnetic flux density. Therefore, it is preferable that the concentration of dissolved Cu is low.

[0045] The formation of Cu clusters is thought to be related to the mechanism of spinodal decomposition. In the early stages of spinodal decomposition, Fe-rich and Cu-rich amorphous phases form a periodic structure with a wavelength λm. Subsequently, while maintaining this wavelength λm, the Cu concentration in the Cu-rich amorphous phase or the size of the amorphous phase increases, resulting in the formation of Cu clusters. When spinodal decomposition begins at low temperatures, the wavelength λm decreases; when spinodal decomposition begins at high temperatures, the wavelength λm increases. Therefore, when the heating rate 45 is high, the total number of Cu clusters at the time when crystalline domains 14 begin to form decreases, and the Cu clusters become larger. When the heating rate 45 is low, the total number of Cu clusters at the time when crystalline domains 14 begin to form increases, and the Cu clusters become smaller. Therefore, when the heating rate 45 is high, large Cu clusters can be used as nucleation sites, reducing the size of crystalline domains 14 and lowering the coercive force.

[0046] During the heat treatment, the Cu clusters contain crystals with body-centered cubic (BCC) and face-centered cubic (FCC) structures, as well as a Cu-rich amorphous phase. When the Cu-rich amorphous phase becomes a nucleation site for the crystalline regions 14, the Cu concentration in the Cu-rich amorphous phase increases, the B concentration in the Cu-rich amorphous phase decreases significantly, and the Fe concentration decreases. As a result, a region with a low B concentration and a relatively high Fe concentration is formed near the interface between the Cu-rich amorphous phase and the Fe-rich amorphous phase. Such a region is more likely to form as the size of the Cu-rich amorphous phase increases. Furthermore, in such a region, the stability of the amorphous phase decreases, causing the amorphous phase to transform into a crystalline phase. As a result, the crystalline regions 14 begin to form near the interface between the Cu-rich amorphous phase and the Fe-rich amorphous phase. The Cu-rich amorphous phase can also delay the growth of the crystalline regions 14.

[0047] Furthermore, when a face-centered cubic (FCC) crystalline phase (Cu) becomes a nucleation site for crystalline regions 14, the high coherence between the FCC crystalline phase (Cu) and the BCC crystalline phase (Fe) causes the BCC crystalline phase (Fe) to begin to form on the surface of the FCC crystalline phase (Cu). To promote crystallization through this high coherence, the FCC crystalline phase (Cu) must be large enough. This FCC crystalline phase (Cu) forms when a Cu-rich amorphous phase surrounded by an Fe-rich amorphous phase crystallizes, or when solute Cu in the Fe-rich amorphous phase crystallizes. On the other hand, a BCC crystalline phase (Cu) forms when a Cu-rich amorphous phase surrounded by a BCC crystalline phase (Fe) crystallizes, or when solute Cu in the BCC crystalline phase (Fe) crystallizes.

[0048] During the middle stage of nanocrystalline alloy formation (e.g., holding period 42), the P concentration and B concentration are thought to affect the size of the crystalline region 14. As shown in Figures 4(a) to 4(c), when the B concentration is high, many B atoms 22 move from region 18 to region 17, and many Fe atoms 20 move from region 17 to region 18. As a result, Fe atoms 20 are supplied to the boundary 50, and the crystalline region 14 becomes larger. On the other hand, when the P concentration is high, P atoms 24 are less likely to move from region 18 to region 17 than B atoms 22, and therefore fewer Fe atoms 20 move from region 17 to region 18. As a result, fewer Fe atoms 20 are supplied to the boundary 50, and the size of the crystalline region 14 does not easily become larger.

[0049] In addition, when the P concentration is high, an attractive force acts between the P atoms and the Cu atoms (the free energy decreases), so the region of the P atoms and the Cu atoms in the region 18 17 The rate at which the crystal regions 14 move to the nucleus decreases. As a result, the rate at which the size of the crystalline regions 14 increases decreases. This reduces the growth rate of the crystalline regions 14, lengthening the time for nucleation and increasing the number (number density) of the crystalline regions 14, and reducing the heat generation associated with crystallization per unit time, thereby preventing temperature increases and temperature variations in the alloy 10. As a result, the size of the crystalline regions 14 can be reduced.

[0050] Thus, it is believed that when the P concentration / B concentration is high, the size of the crystalline regions 14 becomes smaller. On the other hand, when the B concentration is high, a repulsive force acts between the B atoms and the Cu atoms (free energy increases), so the Cu clusters tend to become a crystalline phase (Cu) with an FCC structure. Compared to a Cu-rich amorphous phase, this crystalline phase (Cu) with an FCC structure hardly reduces the growth rate of the crystalline regions 14 (the crystalline regions 14 can grow while incorporating the crystalline phase (Cu) with an FCC structure), so the size of the crystalline regions 14 is less likely to become smaller.

[0051] Based on the above concept, an embodiment will be described.

[0052] [Chemical composition] The average atomic concentrations of Fe, P, B, and Cu in the entire alloy are defined as CFe, CP, CB, and CCu, respectively. CFe, CP, CB, and CCu correspond to the chemical compositions of Fe, P, B, and Cu in the entire alloy. These chemical compositions essentially match those of the precursor alloy.

[0053] In this embodiment, the alloy contains Fe, B, P, and Cu. The average Fe concentration CFe in the entire alloy is 79 atomic % or more. Increasing the Fe concentration in the alloy and decreasing the metalloid concentration can increase the saturation magnetic flux density. Therefore, CFe is preferably 80 atomic % or more, more preferably 82 atomic % or 83 atomic % or more, and even more preferably 84 atomic % or more. The average B concentration CB in the entire alloy is preferably 12 atomic % or less, more preferably 10 atomic % or less, and even more preferably 9.0 atomic % or less. The average P concentration CP is preferably 12 atomic % or less, more preferably 10 atomic % or less. The average concentration of metalloids (B, P, C, and Si) in the entire alloy is preferably 15 atomic % or less, and more preferably 13 atomic % or less.

[0054] By increasing the concentration of metalloids (B, P, C, and Si) such as P and B in the alloy, amorphous regions 16 can be formed between crystalline regions 14. This reduces the coercive force. Therefore, CFe is preferably 88 atomic % or less, more preferably 87 atomic % or less, and even more preferably 86 atomic % or less. C B and C P are each preferably 2.0 atomic % or more, more preferably 3.0 atomic % or more.

[0055] As shown in Figures 4(a) to 4(c), in order to reduce the size of the crystalline regions 14, it is preferable to reduce the B concentration / P concentration. From this perspective, the value C / C, which is the average B atomic concentration divided by the average P atomic concentration in the entire alloy, is preferably 3.5 or less, and more preferably 3.2 or less. Furthermore, if the B concentration is too low, the total amount of the crystalline regions 14 decreases, and the saturation magnetic flux density decreases. From this perspective, C / C is preferably 1.5 or more, and more preferably 2.0 or more.

[0056] To form the crystalline region 14, a high density of large Cu clusters 12a is preferred, as shown in FIG. 2(b). From this perspective, the average Cu concentration CCu in the entire alloy is preferably 0.4 atomic % or more, more preferably 0.5 atomic % or more, and even more preferably 0.6 atomic % or more. As the Cu concentration increases, many Cu clusters 12a, 12b, and 12c are formed in the crystalline region 14 and the amorphous region 16, as shown in FIG. 3(c). The Cu clusters 12a, 12b, and 12c hinder domain wall motion. Furthermore, even if the Cu concentration is too high, the wavelength λm becomes smaller, and the density of the Cu clusters 12a does not increase significantly. Furthermore, when Cu dissolves in the crystalline region 14 and the amorphous region 16, the quantum mechanical interaction between Fe atoms and Cu atoms increases. This reduces the saturation magnetic flux density. From this viewpoint, CCu is preferably 1.4 atomic % or less, more preferably 1.2 atomic % or less, and even more preferably 1.0 atomic % or less or 0.9 atomic % or less.

[0057] The alloy may contain Si. The inclusion of Si in the alloy improves the oxidation resistance of the alloy. Furthermore, the inclusion of Si in the alloy can increase the second crystallization onset temperature Tx2. The alloy may contain C. The inclusion of C, a small atom, in the alloy can improve the saturation magnetic flux density. To achieve these effects, the sum of the average Si concentration CSi and the average C concentration CC in the entire alloy may be 0 atomic % or more, preferably 0.5 atomic % or more. CSi may be 0 atomic % or more, preferably 0.2 atomic % or more, and more preferably 0.5 atomic % or more. CC may be 0 atomic % or more, preferably 0.2 atomic % or more, more preferably 0.5 atomic % or more, and even more preferably 1.0 atomic % or more. If the alloy contains a large amount of Si and C, it becomes difficult to control the formation of the crystalline region 14 by P and B as in the above model. Therefore, the sum of CSi and CC is preferably 3.0 atomic % or less, more preferably 2.0 atomic % or less, and more preferably 1.0 atomic % or less. CSi and C C are each preferably 3.0 atomic % or less, more preferably 2.0 atomic % or less, and even more preferably 1.0 atomic % or less. When Si and C are considered as impurities, the sum of CSi and C C is preferably 0.1 atomic % or less.

[0058] The alloy may contain impurities, such as at least one of Ti, Al, Zr, Hf, Nb, Ta, Mo, W, Cr, V, Co, Ni, Mn, Ag, Zn, Sn, Pb, As, Sb, Bi, S, N, O, and rare earth elements. High concentrations of these elements can make it difficult to control the formation of the crystalline regions 14 by P and B as described in the model above. For example, Ti and Al form precipitates such as oxides and nitrides, which act as heterogeneous nucleation sites, increasing the size of the crystalline regions 14. Furthermore, elements such as Cr, Mn, V, Mo, Nb, Ti, and W have an attractive force toward P in the amorphous regions 16, thereby eliminating the benefits of P to the nanocrystalline structure described above. Therefore, high concentrations of these elements can destabilize the formation of the crystalline regions 14 and amorphous regions 16. Therefore, the total average concentration of elements other than Fe, P, B, Cu, Si, and C in the entire alloy is preferably 0 atomic % or more and 0.3 atomic % or less, and more preferably 0 atomic % or more and 0.1 atomic % or less. The average concentration of each element other than Fe, P, B, Cu, Si, and C in the entire alloy is preferably 0 atomic % or more and 0.10 atomic % or less, and more preferably 0 atomic % or more and 0.02 atomic % or less.

[0059] [Evaluation method] A three-dimensional atom probe (3DAP) is used to evaluate alloys. Various software, such as IVAS (registered trademark), can be used for atom probe tomography analysis. In atom probe tomography analysis, the 3D map is divided into multiple regions (cubes: voxels) with a side length of 1.0 nm, and the concentration of each element in each region is calculated.

[0060] Figure 5(a) shows the Cu cluster evaluation method, and Figure 5(b) shows how to set the Fe concentration region and evaluate the proxygram. While atom probe tomography analyzes the position and concentration of each atom in three dimensions, Figures 5(a) and 5(b) explain the two-dimensional analysis.

[0061] For the analysis of Cu clusters, IVAS (registered trademark) cluster analysis (Cluster Analysis, Cluster Count Distribution Analysis, Cluster Size Distribution Analysis) or similar functions of equivalent software (methods that produce the same results as IVAS (registered trademark) cluster analysis) are used. This cluster analysis function can be roughly explained as follows.

[0062] As shown in FIG. 5(a), among multiple regions 60 (cubes) with a side length of 1.0 nm, regions with a Cu concentration equal to or greater than a threshold value (e.g., 6.0 atomic %) are extracted. The extracted regions with a Cu concentration equal to or greater than the threshold value are regions 60a (cross regions), and regions with a Cu concentration less than the threshold value are regions 60b (white regions). The boundary between regions 60a and 60b is a boundary 62 (thick line). Region 60a surrounded by boundary 62 is designated as Cu clusters 64a to 64d. The volumes of each of Cu clusters 64a, 64b, 64c, and 64d are calculated from the volume surrounded by boundary 62. The diameters (sphere-equivalent diameters) of Cu clusters 64a to 64d are calculated as the diameters of spheres with the same volume as Cu clusters 64a to 64d.

[0063] The concentration of each element in a region where the concentration of a specific element falls within a specific range is determined using IVAS® isoconcentration surface analysis or a similar function of equivalent software (a method that produces the same results as IVAS® isoconcentration surface analysis). The concentration determination function using this isoconcentration surface analysis is outlined as follows. As shown in FIG. 5(b), among multiple regions 60, the region 60 with an Fe concentration of 80 atomic % or less is designated as region 60c, the region 60 with an Fe concentration of 90 atomic % or more is designated as region 60e, and the region 60 with an Fe concentration greater than 80 atomic % but less than 90 atomic % is designated as region 60d. The boundary between region 60c and region 60d is boundary 66a. The boundary between region 60d and region 60e is boundary 66b. Boundaries 66a and 66b are isoconcentration surfaces of 80 atomic % and 90 atomic %, respectively. Region 68c, consisting of multiple regions 60c, is considered to be primarily amorphous region 16. Region 68d, which is made up of multiple regions 60d, can contain information from both amorphous regions 16 and crystalline regions 14. Region 68d is considered to include, for example, region 18. Region 68e, which is made up of multiple regions 60e, is considered to be mainly crystalline regions 14.

[0064] The relationship between the distance from a specific isoconcentration surface of a specific element and the concentration of each element is called a proxigram. This proxigram is created using the IVAS® proxigram creation function (Proxigrams) or a similar function of equivalent software (a method that produces the same results as the IVAS® isoconcentration surface analysis). The proxigram creation function using isoconcentration surface analysis can be roughly described as follows: To obtain a proxigram with the boundary where the Fe concentration is 80 atomic % as the specific isoconcentration surface, the distance between each region 60 and the specific isoconcentration surface (boundary 66a) is calculated for each region 60, and the concentration data for each element in each region for each distance division are compiled and averaged to determine the relationship between the distance and the concentration of each element. The direction from boundary 66a toward region 60e (the direction in which the Fe concentration increases) is the positive direction of the distance, and the direction from boundary 66a toward regions 60d and 60c (the direction in which the Fe concentration decreases) is the negative direction of the distance.

[0065] [Distribution of Cu clusters] In atom probe tomography, among multiple regions 60 each 1.0 nm long, a mass of region 60a having a Cu concentration of N atomic % or more is defined as Cu clusters 64a to 64d. The density of the Cu clusters is defined as CuN. In other words, the threshold Cu concentration for a Cu cluster is defined as N atomic %. For example, when the N atomic % is 6.0 atomic %, the density of the Cu cluster is expressed as Cu6.

[0066] [Cu cluster distribution 1] Cu6 is 0.20 x 10 24 / m 3 (1m 3 It is preferable that the threshold Cu concentration is equal to or greater than the number of Cu clusters per unit area (number per unit area). It is believed that Cu clusters with a threshold Cu concentration of 6.0 atomic % are large clusters or clusters with a high number density of Cu atoms. In alloys with a high number density of Cu clusters, the density of large-sized Cu clusters 12a tends to be high in FIG. 3(b). Therefore, the size of the crystalline regions 14 is small and the coercivity is low. Furthermore, in alloys with many large Cu clusters 12a, the Cu concentration in the amorphous regions 16 is low. Therefore, in FIG. 4(c), the number of Cu clusters 12c that did not contribute to nucleation is small, and the coercivity is low. Furthermore, the saturation magnetic flux density is high because the concentration of dissolved Cu is low.

[0067] Cu6 is 0.25 x 10 24 / m 3 More than 0.28 × 10 is preferable. 24 / m 3 More preferably, in order to reduce the total number of Cu clusters, Cu6 is 5.0 × 10 24 / m 3 Less than 2.0 x 10 is preferable. 24 / m 3 The following is more preferable: The number density of Cu clusters can be controlled by the heating rate 45 in the heat treatment, the holding temperature T2 immediately after heating, and the cooling rate 46.

[0068] [Cu cluster distribution 2] The value obtained by dividing Cu1.5 by Cu6 is preferably 15 or less. It is believed that the Cu clusters at a threshold Cu concentration of 1.5 include both large and small Cu clusters. In other words, Cu1.5 is believed to correspond to the number density of large and small Cu clusters within the entire alloy. Therefore, alloys with a Cu1.5 / Cu6 ratio of 15 or less have a high Cu6 content, resulting in a high density of Cu clusters 12a in Figure 2(b) and small crystal regions 14. Furthermore, this alloy has a small total number of Cu clusters, which reduces the obstacles to domain wall movement. Therefore, this alloy has a low coercive force.

[0069] Cu1.5 / Cu6 is preferably 12 or less, and more preferably 10 or less. Cu1.5 / Cu6 is, for example, 1.0 or more. Cu1.5 / Cu6 can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, the length of the holding period 42, and the cooling rate 46 during the heat treatment.

[0070] [Cu cluster distribution 3] In the region where the Fe concentration is 80 atomic % or less, when the region where the Cu concentration is 2.3 atomic % or more is considered as a Cu cluster, the average spherical equivalent diameter Cuφ2 ​​of the Cu cluster is preferably 3.0 nm or more. In this alloy, the size of the Cu clusters 12c in the amorphous region 16 in FIG. 3(c) is large. Therefore, the total number of Cu clusters in the amorphous region 16 is small. Therefore, there is little obstruction to the movement of the domain wall, and the coercive force is likely to be low. In addition, there is little Cu dissolved in the amorphous region 16, and the saturation magnetic flux density is high.

[0071] Cuφ2 is preferably 3.1 nm or more, more preferably 3.2 nm or more. Cuφ2 ​​is preferably 10 nm or less, more preferably 5.0 nm or less. Cuφ2 ​​can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, the length of the holding period 42, and the cooling rate 46 during heat treatment.

[0072] [Cu cluster distribution 4] The value Cu1.5 / CCu obtained by dividing Cu1.5 by CCu is 3.0×10 24 / m 3An alloy with a small Cu1.5 / CCu ratio has a small total number of Cu clusters and many large Cu clusters, and therefore has a low coercive force.

[0073] Cu1.5 / CCu is 2.8×10 24 / m 3 / atom % or less is preferable, and 2.5 × 10 24 / m 3 If Cu1.5 / CCu is too small, large Cu clusters are not formed, the size of the crystalline regions 14 increases, and the coercive force increases. Therefore, Cu1.5 / CCu is preferably 1.0×10 24 / m 3 / atom% or more is preferable, and 1.5 × 10 24 / m 3 Cu1.5 / CCu can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the cooling rate 46 during the heat treatment.

[0074] [Cu cluster distribution 5] In the region where the Fe concentration is 80 atomic % or more, when the region where the Cu concentration is 2.3 atomic % or more is considered as a Cu cluster, the average spherical equivalent diameter Cuφ1 of the Cu cluster is preferably 3.0 nm or more. An alloy in which the Cu clusters 12a and 12c in the crystalline region 14 and the region 18 are large has a small total number of Cu clusters. Therefore, the coercive force is low. Furthermore, there is little Cu dissolved in the amorphous region 16. Therefore, the saturation magnetic flux density is high.

[0075] Cuφ1 is preferably 3.1 nm or more, more preferably 3.2 nm or more. Cuφ1 is preferably 10 nm or less, more preferably 5.0 nm or less. Cuφ1 can be controlled by the heating rate 45 and the holding temperature T2 immediately after heating during heat treatment.

[0076] [Cu concentration distribution] The average Cu concentration in the plurality of regions 60c where the Fe concentration is 80 atomic % or less is defined as C8Cu, and the average Cu concentration in the plurality of regions 60e where the Fe concentration is 90 atomic % or more is defined as C9Cu. The regions where the Fe concentration is 80 atomic % or less are mainly amorphous regions 16, and the regions where the Fe concentration is 90 atomic % or more are mainly crystalline regions 14.

[0077] [Cu concentration distribution 1] The value C8Cu / C9Cu obtained by dividing the average Cu atomic concentration C8Cu in the region 60c where the Fe concentration is 80 atomic % or less by the average Cu atomic concentration C9Cu in the region 60e where the Fe concentration is 90 atomic % or more is preferably 1.8 or more. After the nanocrystalline alloy is formed, the crystalline region 14 has a larger magnetic anisotropy than the amorphous region 16. In a crystalline phase with a large magnetic anisotropy, the width of the domain wall is smaller. Therefore, the effect of Cu clusters in preventing domain wall movement is greater in the crystalline region 14 than in the amorphous region 16. When C9Cu is low, there are fewer Cu clusters in the crystalline region 14. Therefore, an alloy with a large C8Cu / C9Cu ratio has a low coercive force because the increase in coercive force due to Cu clusters preventing domain wall movement is suppressed.

[0078] C8Cu / C9Cu is preferably 2.0 or higher, more preferably 2.1 or higher. If C9Cu is too low, the density of Cu clusters 12a decreases and the coercive force decreases in the early stage of nanocrystalline alloy formation in FIG. 3(b). Therefore, C8Cu / C9Cu is preferably 5.0 or lower, more preferably 3.0 or lower. C8Cu / C9Cu can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, the length of the holding period 42, and the cooling rate 46 during heat treatment.

[0079] [Cu concentration distribution 2] In a proxygram in which boundary 66a, where the Fe concentration is 80 atomic %, is the specific isoconcentration plane, the maximum Cu concentration, Cumax, within a range of ±5.0 nm from boundary 66a is preferably 1.25 atomic % or more. As shown in Figures 4(a) to 4(c), when the Cu concentration in region 18 is high, the P concentration in region 18 is also high, and the migration speed of Fe atoms 20 moving to boundary 50 decreases. This makes it difficult for the size of crystalline region 14 to increase. Therefore, alloys with a large Cumax have low coercivity.

[0080] Cumax is preferably 1.27 atomic percent or more, and more preferably 1.29 atomic percent or more. If Cumax is too high, the total number of Cu clusters increases, resulting in a high coercive force. Therefore, Cumax is preferably 2.0 atomic percent or less, and more preferably 1.5 atomic percent or less. Cumax can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, the length of the holding period 42, and the cooling rate 46 during heat treatment.

[0081] [Fe concentration distribution] The average Fe concentration in the plurality of regions 60c where the Fe concentration is 80 atomic % or less is defined as C8Fe, and the average Fe concentration in the plurality of regions 60e where the Fe concentration is 90 atomic % or more is defined as C9Fe.

[0082] [Fe concentration distribution 1] The average Fe concentration C8Fe in the region 60c where the Fe concentration is 80 atomic % or less is preferably 74.5 atomic % or less. An alloy with a low Fe concentration in the amorphous region 16 has a high proportion of crystalline regions 14 within the alloy. Therefore, the saturation magnetic flux density is high. As shown in FIG. 4(c), B atoms 22 move to region 17, and Fe atoms 20 travel through region 18 and bond with elements on the surface of the crystalline region 14 at boundary 50, increasing the crystalline region 14. At this time, the Fe concentration in region 17 becomes lower than 75 atomic %. Therefore, an alloy with a low C8Fe contains an appropriate amount of B to increase the total amount of crystalline regions 14.

[0083] C8Fe is preferably 74.0 atomic % or less, and more preferably 72.5 atomic % or less. On the other hand, if the Fe concentration in the amorphous region 16 becomes too low, the saturation magnetic flux density of the amorphous region 16 decreases or the region loses its magnetism. This reduces the saturation magnetic flux density of the alloy. Therefore, C8Fe is preferably 50 atomic % or more, more preferably 66 atomic % or more or 67 atomic % or more, and even more preferably 70 atomic % or more. C8Fe can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 during the heat treatment.

[0084] [Fe concentration distribution 2] In a proxygram in which the boundary 66a, where the Fe concentration is 80 atomic %, is the specific isoconcentration plane, the gradient ΔFe of the Fe concentration at a position -2.0 nm from the boundary 66a and a position -4.0 nm from the boundary 66a, when the direction approaching the crystalline region 14 (the direction in which the Fe concentration increases) is taken as positive, is preferably 0.03 atomic % / nm or more. Alloys with a large ΔFe have a high proportion of the crystalline region 14 while exhibiting small fluctuations in the energy of the domain walls in the amorphous region 16 (particularly region 18). Therefore, the saturation magnetic flux density is high and the coercivity is low.

[0085] ΔFe is preferably 0.05 atomic % / nm or more, and even more preferably 0.10 atomic % / nm or more. If ΔFe is too large, atomic diffusion may occur over time, causing the element distribution in the amorphous region 16 to fluctuate, resulting in a deterioration in soft magnetic properties. Therefore, ΔFe is preferably 1.0 atomic % / nm or less, and more preferably 0.5 atomic % / nm or less. ΔFe can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, the length of the holding period 42, and the cooling rate 46 during heat treatment.

[0086] [B concentration distribution] The average B concentration in the plurality of regions 60c where the Fe concentration is 80 atomic % or less is defined as C8B, and the average B concentration in the plurality of regions 60e where the Fe concentration is 90 atomic % or more is defined as C9B.

[0087] [B concentration distribution 1] The average B atomic concentration C9B in the region 60e where the Fe concentration is 90 atomic % or more is divided by the square root of the average B atomic concentration CB in the entire alloy, C9B / √CB, which is 0.56 atomic %. 0.5 or more. As B atoms are incorporated into the crystalline regions 14, the total amount of B in the amorphous regions 16 decreases. This increases the proportion of the crystalline regions 14 in the alloy. Also, as explained in Figures 4(a) to 4(c), the number of B atoms 22 in the regions 18 decreases, resulting in a smaller crystalline region 14. Therefore, an alloy with a large C9B / √CB has a high saturation magnetic flux density and a low coercive force.

[0088] C9B / √CB is 0.58 atomic % 0.5 C9B / √CB is preferably 1.0 atomic % or more. 0.5 Preferably, 0.8 atomic % or less 0.5 The following is more preferable: C9B / √CB can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 in the heat treatment.

[0089] [Distribution of P concentration] The average P concentration in the plurality of regions 60c where the Fe concentration is 80 atomic % or less is defined as C8P, and the average P concentration in the plurality of regions 60e where the Fe concentration is 90 atomic % or more is defined as C9P.

[0090] [P concentration distribution 1] The value C9P / CP, obtained by dividing the average P atomic concentration C9P in the region 60e where the Fe concentration is 90 atomic % or more by the average P atomic concentration Cp in the entire alloy, is preferably 0.36 or less. If the P concentration in the crystalline region 14 is low, P atoms 24 are concentrated in the region 18. Therefore, as explained in Figures 4(a) to 4(c), the P concentration in the region 18 becomes high and the size of each crystalline region 14 becomes smaller. Therefore, an alloy with a small C9P / CP has a low coercive force.

[0091] C9P / CP is, for example, 0.5 or less. C9P / CP can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 in the heat treatment.

[0092] [P concentration distribution 2] The value C8P / CP, obtained by dividing the average P atomic concentration C8P in the region 60c where the Fe concentration is 80 atomic % or less by the average P atomic concentration Cp in the entire alloy, is preferably 1.6 or more. When the P concentration in the amorphous region 16 is high, P atoms 24 are concentrated in the region 18. Therefore, as explained in Figures 4(a) to 4(c), the P concentration in the region 18 becomes high and the size of each crystalline region 14 becomes smaller. Therefore, an alloy with a large C8P / CP has a low coercive force.

[0093] C8P / CP is preferably 1.7 or more. For example, C8P / CP is 2.0 or less. C8P / CP can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 during the heat treatment.

[0094] [P concentration / B concentration distribution 1] In a proxogram with boundary 66a, where the Fe concentration is 80 atomic %, as the specific isoconcentration plane, the P atomic concentration / B atomic concentration P / B preferably has minimum and maximum values ​​within a range of ±5.0 nm from boundary 66a. As illustrated in Figures 4(a) through 4(c), if B atoms 22 preferentially migrate to region 17 and P atoms 24 preferentially remain in region 18, P / B has a maximum within region 18 and a minimum near boundary 50. This reduces the size of each crystalline region 14 and decreases the coercivity. Therefore, alloys with maximum and minimum values ​​for P / B in the proxogram have low coercivity. The maximum and minimum values ​​of P / B within a range of ±5.0 nm from boundary 66a can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 during heat treatment.

[0095] [P concentration / B concentration distribution 2] In a proxygram in which the boundary 66a, where the Fe concentration is 80 atomic %, is the specific isoconcentration plane, the maximum value P / Bmax of the P atomic concentration / B atomic concentration P / B is 1.0 or more within a range of ±3.0 nm from the boundary 66a. In alloys with a large P / Bmax, P atoms are concentrated in the region 18. Therefore, as explained in Figures 4(a) to 4(c), the size of each crystalline region 14 is small and the coercivity is low.

[0096] P / Bmax is preferably 1.5 or more, more preferably 2.0 or more. If P / Bmax is too high, the magnetism in the vicinity of region 18 decreases, the saturation magnetic flux density of the alloy decreases, and the coercivity increases. Therefore, P / Bmax is preferably 10 or less, more preferably 5.0 or less. P / Bmax can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 during heat treatment.

[0097] [P concentration / B concentration distribution 3] In a proxygram in which boundary 66a, where the Fe concentration is 80 atomic %, is the specific isoconcentration plane, the maximum value P / Bmax of the P atomic concentration / B atomic concentration P / B in the range of ±3.0 nm from boundary 66a is divided by the average P atomic concentration / average B atomic concentration C / C in the entire alloy, and the value (P / Bmax) / (C / C) is preferably 1.0 or greater. In alloys with a large (P / Bmax) / (C / C) ratio, P atoms are concentrated in region 18, resulting in small sizes of each crystalline region 14 and low coercivity.

[0098] (P / Bmax) / (CP / CB) is preferably 1.1 or more, more preferably 1.2 or more. If P / Bmax is too high, the magnetism in the vicinity of region 18 decreases, the saturation magnetic flux density of the alloy decreases, and the coercivity increases. Therefore, (P / Bmax) / (CP / CB) is preferably 5.0 or less, more preferably 2.0 or less. (P / Bmax) / (CP / CB) can be controlled by the heating rate 45, the holding temperature T2 immediately after heating, and the length of the holding period 42 during heat treatment.

[0099] [Crystalline region size] To reduce the coercive force, the average equivalent spherical diameter of the crystalline regions 14 is preferably 50 nm or less, more preferably 30 nm or less, and may be 5.0 nm or more.

[0100] [Manufacturing method] A method for producing a nanocrystalline alloy will be described below, but the method for producing an alloy according to the embodiment is not limited to the method described below.

[0101] [Method for manufacturing amorphous alloys] The single roll method is used to produce amorphous alloys. The conditions of the roll diameter and rotation speed for the single roll method are arbitrary. The single roll method is suitable for producing amorphous alloys because it is easy to perform rapid cooling. The cooling rate of the molten alloy to produce amorphous alloys is, for example, 10 4 °C / sec or more is preferable, and 10 6 °C / sec or more is more preferable. 4 Methods other than the single roll method, including periods of °C / sec, may also be used. For example, the water atomization method or the atomization method described in Japanese Patent No. 6533352 may be used to produce amorphous alloys.

[0102] [Method of manufacturing nanocrystalline alloys] Nanocrystalline alloys are obtained by heat treatment of amorphous alloys. In the production of nanocrystalline alloys, the temperature history of the heat treatment affects the nanostructure of the nanocrystalline alloy. For example, in the heat treatment shown in Figure 1, the heating rate 45, holding temperature T2, length of holding period 42, and cooling rate 46 mainly affect the nanostructure of the nanocrystalline alloy.

[0103] [Heating rate] A fast heating rate 45 avoids the temperature range where small Cu clusters form, making it easier for many large Cu clusters to form in the early stages of crystallization. This reduces the size of each crystalline region 14. Furthermore, non-equilibrium reactions are more likely to occur, increasing the concentrations of P, B, Cu, and other elements within the crystalline regions 14. This increases the total volume of the crystalline regions 14 and the saturation magnetic flux density. Furthermore, as illustrated in Figures 4(a) to 4(c), P and Cu are concentrated in regions 18 near the crystalline regions 14, suppressing their growth and reducing their size. This reduces the coercive force. In the temperature range from 200°C to the holding temperature T2, the average heating rate ΔT is preferably 360°C / min or higher, more preferably 400°C / min or higher. It is also preferable that the average heating rate calculated in 10°C increments within this temperature range also meets the same conditions.

[0104] To reduce the coercive force, it is preferable that the P concentration (CP) / B concentration (CB) is large. This is thought to be because as the B concentration increases, small Cu clusters are more likely to form. Therefore, to offset the reduction in size of Cu clusters that accompanies the increase in B concentration, the temperature (CP / CB × (ΔT + 20)) calculated using CP / CB and ΔT is preferably 40°C / min or more, more preferably 50°C / min or more, and even more preferably 100°C / min or more. It is even more preferable that (CP / CB × (ΔT + 20)) calculated in 10°C increments within this temperature range also satisfies the same condition.

[0105] [Retention period length] The length of the holding period 42 is preferably a time that allows for determination that crystallization has progressed sufficiently. To determine that crystallization has progressed sufficiently, it is necessary to confirm that a first peak corresponding to the first crystallization onset temperature Tx1 is not observable or has become very small (for example, the heat generation amount is 1 / 100 or less of the total heat generation amount of the first peak) in a curve (DSC curve) obtained by heating the nanocrystalline alloy to about 650°C at a constant heating rate of 40°C / min using differential scanning calorimetry (DSC).

[0106] When crystallization (crystallization at the first peak) approaches 100%, the crystallization rate becomes so slow that it may be impossible to determine whether crystallization has progressed sufficiently using DSC. For this reason, it is preferable to hold the sample for a longer period than expected from the DSC results. For example, the holding period is preferably 0.5 minutes or longer, and more preferably 5.0 minutes or longer. By achieving sufficient crystallization, the saturation magnetic flux density can be increased. If the holding period is too long, the gradient of the concentration distribution of solute elements in the amorphous phase may become gentle due to atomic diffusion. For this reason, the holding period is preferably 60 minutes or shorter, and more preferably 30 minutes or shorter.

[0107] [Holding temperature] The maximum temperature Tmax of the holding temperature T2 is preferably equal to or greater than the first crystallization onset temperature Tx1-20°C and equal to or less than the second crystallization onset temperature Tx2-20°C. If Tmax is less than Tx1-20°C, crystallization does not proceed sufficiently. If Tmax exceeds Tx2-20°C, a compound crystalline phase is formed, resulting in a significant increase in coercivity. The recommended temperature for Tmax is equal to or greater than Tx1+(CB / CP)×5°C and equal to or less than Tx2-20°C to offset the reduction in Cu cluster size associated with an increase in B concentration. Tmax is more preferably equal to or greater than Tx1+(CB / CP)×5+20°C. Furthermore, Tmax is preferably equal to or greater than the Curie temperature of the amorphous phase. Increasing Tmax increases the temperature at which spinodal decomposition begins and increases λm. This reduces the total number of Cu clusters at the initial stage of crystallization while increasing the number of large Cu clusters.

[0108] [Cooling rate] As shown in Figure 3(c), when cooling begins, Cu dissolved in the Fe-rich phase forms new Cu-rich phases, such as Cu cluster 12c, or grows Cu-rich phases, such as Cu clusters 12a and 12b. The Fe-rich phase has magnetization, but the Cu atoms dissolved in this phase and the Fe atoms act together to reduce the Fe magnetization more than expected due to quantum mechanical interactions. This results in a decrease in the saturation magnetic flux density. Therefore, a slow cooling rate 46 is preferable. On the other hand, if the cooling rate 46 is too slow, it takes a long time to produce a nanocrystalline alloy. Therefore, the average cooling rate from the time the alloy temperature reaches Tmax or Tx1 + (CB / CP) × 5 to 200°C is preferably 0.2°C / s or more and 0.5°C / s or less. [Example]

[0109] The samples were prepared as follows.

[0110] [Manufacturing amorphous alloys] The starting materials for the alloy were iron (impurities of 0.01 wt% or less), boron (impurities of less than 0.5 wt%), triiron phosphide (impurities of less than 1 wt%), and copper (impurities of less than 0.01 wt%). It was confirmed in advance that no loss of elements occurs during the process of producing nanocrystalline alloys from the mixture of these reagents.

[0111] Table 1 shows the chemical composition, CB / CP ratio, Tc (Curie temperature), Tx1 (first crystallization onset temperature), and Tx2 (second crystallization onset temperature) of each mixture. The concentration of each element in the nanocrystalline alloy corresponds to the concentration of each element in the mixture, assuming no element loss during the manufacturing process of the ingot, amorphous alloy, or nanocrystalline alloy. In other words, the chemical composition of B, P, Cu, and Fe in Table 1 corresponds to CB, CP, CCu, and CFe, respectively. The sum of the chemical compositions of B, P, Cu, and Fe is 100.0 atomic %. Furthermore, Tx1 and Tx2 are the two temperatures obtained by heating the amorphous alloy to approximately 650°C at a constant heating rate of 40°C / min using a differential scanning calorimeter, and are defined in Figure 2 of Patent Document 4. [Table 1]

[0112] As shown in Table 1, Steel No. 1 and Steel No. 2 have the same Fe and Cu compositions, and Steel No. 1 has a CB / CP ratio of 0.52, while Steel No. 2 has a CB / CP ratio of 3.11.

[0113] A 200 gram mixture was prepared to have the chemical composition shown in Table 1. The mixture was heated in a crucible in an argon atmosphere to form a homogeneous molten metal, which was then solidified in a copper mold to produce an ingot.

[0114] An amorphous alloy was produced from the ingot using the single-roll process. A 30-gram ingot was melted in a quartz crucible and ejected onto a pure copper rotating roll through a nozzle with a 10 mm x 0.3 mm opening. An amorphous ribbon 10 mm wide and 20 μm thick was formed on the rotating roll. The amorphous ribbon was then peeled off from the rotating roll using an argon gas jet.

[0115] Using an infrared gold image furnace, heat treatment was carried out in an argon atmosphere as shown in Figure 1, and ribbons of nanocrystalline alloys were produced from the amorphous alloys of Steels No. 1 and No. 2.

[0116] Table 2 shows the heat treatment conditions for producing nanocrystalline alloys from amorphous alloys. [Table 2]

[0117] The heating rate is the heating rate from room temperature to the maximum temperature Tmax and is approximately constant. The maximum temperature Tmax is the maximum temperature of the holding temperature T2. The holding temperature T2 during the holding period 42 is the maximum temperature Tmax and is approximately constant. The first average cooling rate is the average cooling rate from Tmax to 300°C, and the second average cooling rate is the average cooling rate from Tmax to 200°C. As shown in Table 2, the heating rate was 40°C / min for Productions No. 1 to No. 5, and 400°C / min for Productions No. 6 to No. 10. The maximum holding temperature Tmax, the first average cooling rate, and the second average cooling rate were varied within Productions No. 1 to No. 5. Tmax, the first average cooling rate, and the second average cooling rate were varied within Productions No. 6 to No. 10. The length of the holding period 42 was constant at 10 minutes.

[0118] Table 3 shows the steel number, production number and coercive force Hc of each sample. [Table 3]

[0119] Samples No. 1 to No. 10 are samples of Steel No. 1 that were heat-treated under the conditions of Production Nos. 1 to 10, respectively. Samples No. 12 to No. 21 are samples of Steel No. 2 that were heat-treated under the conditions of Production Nos. 1 to 10, respectively. Samples No. 11 and 22 are samples of Steels No. 1 and No. 2, respectively, that were not heat-treated to form crystalline regions 14.

[0120] [Coercive force measurement] The coercive force of the prepared samples was measured using a DC magnetization characteristic measuring device model BHS-40. As shown in Table 3, the coercive force depends on the heating rate 45, the maximum temperature Tmax, and the average cooling rate 46. Of samples No. 1 to No. 5, sample No. 2 had the lowest Hc and was designated Example 1. Of samples No. 6 to No. 10, sample No. 8 had the lowest Hc and was designated Example 2. Of samples No. 12 to No. 16, sample No. 14 had the lowest Hc and was designated Comparative Example 1. Of samples No. 17 to No. 21, sample No. 20 had the lowest Hc and was designated Example 3.

[0121] The coercive force Hc of the samples of Examples 1, 2, and 3 is lower than that of the corresponding samples No. 11 and No. 22 before heat treatment. Comparative Example 1 (sample No. 14) has a very high coercive force Hc of over 30 A / m. Examples 1, 2, and 3 (samples No. 2, No. 8, and No. 20) have a low coercive force Hc of 10 A / m or less.

[0122] Table 4 shows the saturation magnetic flux density, coercive force Hc, CP / CB×(ΔT+20), and Tx1+5×(CB / CP) in the examples and comparative examples. [Table 4]

[0123] As shown in Table 4, the saturation magnetic flux densities of the samples of Examples 1 to 3 and Comparative Example 1 are comparable. The samples of Examples 1 to 3 have a lower coercivity Hc than the sample of Comparative Example 1. CP / CB × (ΔT + 20) is large in Examples 1 to 3 and small in Comparative Example 1. Thus, the coercivity Hc is low in Examples 2 and 3, where the heating rate ΔT is large. The coercivity Hc is low in Example 1, where CP / CB is large, even though the heating rate ΔT is small. This is because the size of each crystalline region 14 becomes smaller when the heating rate ΔT and CP / CB are large. Tx1 + 5 × (CB / CP) is 387°C in Examples 1 and 2, and 423°C in Comparative Example 1 and Example 3.

[0124] [Atom probe tomography analysis] Atom probe tomography analysis was performed using a three-dimensional atom probe (3DAP) CAMECA LEAP5000XS for Examples 1 to 3 and Comparative Example 1. For this analysis, the analysis program IVAS (registered trademark) attached to the 3DAP device was used.

[0125] Table 5 shows the Cu cluster densities Cu1.5, Cu3, Cu4.5 and Cu6, as well as Cu1.5 / CCu and Cu1.5 / Cu6 in the examples and comparative examples. [Table 5]

[0126] As shown in Table 5, in Examples 2 and 3 where the heating rate ΔT is large, even though Cu1.5, which is thought to correlate with the total number of Cu clusters, is similar to or small in Example 1 and Comparative Example 1, respectively, Cu6, which is thought to correlate with the density of large Cu clusters, is larger than in Example 1 and Comparative Example 1, respectively. Also, in alloys with a small C B / C P as in Examples 1 and 2, Cu6 is large even in Example 1 where the heating rate ΔT is small. Thus, when the heating rate ΔT is large and C B / C P is small, it is thought that the number of large Cu clusters increases and the coercive force decreases.

[0127] Table 6 shows the average atomic concentrations of each element, C9Fe, C9P, C9B, and C9Cu, in region 68e where the Fe concentration is 90 atomic % or more, and the average atomic concentrations of each element, C8Fe, C8P, C8B, and C8Cu, in region 68c where the Fe concentration is 80 atomic % or less, in the examples and comparative examples. [Table 6]

[0128] Table 7 shows C9P / CP, C8P / CP, C9B / √CB, and C8Cu / C9Cu in the examples and comparative examples. [Table 7]

[0129] As shown in Table 7, alloys with large C8P / CP, C9B / √CB, and C8Cu / C9Cu have low coercivity, which can be explained by the model described in Figures 4(a) to 4(c).

[0130] 6(a) to 7(b) are proxygrams for Examples 1 and 2, Comparative Example 1, and Example 3, respectively. The equiconcentration surface where the Fe concentration is 80 atomic % is set as a distance of 0 (boundary 66a), and the side with higher Fe concentration (the direction toward the crystalline region 14) is set as positive. In these figures, the Fe concentration, P concentration, B concentration, Cu concentration, P+B concentration, P concentration / B concentration, and count number are shown on the vertical axis.

[0131] As shown in Figures 6(a) to 7(b), the Fe concentration is high when the distance is positive and low when the distance is negative. When the Fe concentration is 90 atomic % or higher, it is considered to be mostly crystalline region 14. When the distance is near 0, it is considered to be region 18. The P concentration and Cu concentration are low when the distance is positive, have a maximum value when the distance is near 0 or slightly on the negative side, and decrease as the distance becomes more negative from the maximum. The B concentration is low when the distance is positive and increases as the distance becomes more negative. These can be explained by a model in which B preferentially moves from region 18 to region 17 in Figures 4(a) to 4(c).

[0132] Table 8 shows P / Bmax, P / Bmax / (CP / CB), ΔFe, Cumax, Cuφ1, and Cuφ2 ​​in the examples and comparative examples. [Table 8]

[0133] As shown in Table 8, a large ΔFe results in a low coercivity. A large Cumax results in a low coercivity. This is thought to be because, as explained in Figures 4(a) to 4(c), P and Cu are concentrated in region 18, which reduces the size of crystalline regions 14. When Cuφ1 and Cuφ2 ​​are large, the coercivity Hc decreases. This is thought to be because, when Cuφ1 and Cuφ2 ​​are large, not only are crystalline regions 14 smaller, but the total number of Cu clusters also decreases, which reduces the obstacles to domain wall movement and results in a low coercivity.

[0134] Although the preferred embodiment of the invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0135] 10 alloy 12a-12c Cu cluster 14 Crystal region 16 Amorphous region 17, 18 areas 20 Fe atoms 22 B atoms 24 P atoms 26 Cu atoms 60, 60a-60e, 68c-68e area

Claims

1. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; When a region having a Cu concentration of 6.0 atomic % or more among multiple regions each having a side length of 1.0 nm in atom probe tomography is defined as a Cu cluster, the density of the Cu cluster is 0.20 × 10 ２４ / m ３ (1m ３ An alloy with a minimum number of pieces per square meter.

2. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; An alloy in which the average Fe concentration in regions having a side length of 1.0 nm and having an Fe concentration of 80 atomic % or less is 74.5 atomic % or less in atom probe tomography.

3. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; The average B atomic concentration in the regions with an Fe concentration of 90 atomic % or more among the regions with a side length of 1.0 nm in atom probe tomography divided by the square root of the average B atomic concentration in the entire alloy was 0.56 atomic %. ０．５ Alloy that is more than.

4. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; An alloy in which the average Cu atomic concentration in regions of a plurality of regions with a side length of 1.0 nm in atom probe tomography where the Fe concentration is 80 atomic % or less divided by the average Cu atomic concentration in regions of the plurality of regions where the Fe concentration is 90 atomic % or more is 1.8 or more.

5. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; In an atom probe tomography proxygram using multiple regions with sides of 1.0 nm in length, with the Fe concentration at a boundary of 80 atomic %, when the direction approaching the crystalline phase is defined as positive, the gradient of the Fe concentration at a position -2.0 nm from the boundary and at a position -4.0 nm from the boundary is 0.03 atomic % / nm or more.

6. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; The density of Cu clusters (1 m ３ The density of Cu clusters (number of clusters per m) is calculated by dividing the regions among the plurality of regions where the Cu concentration is 6.0 atomic % or more into Cu clusters. ３ An alloy in which the value divided by the number of pieces per square meter is 15 or less.

7. Fe, B, P and Cu, The method comprises the steps of: forming an amorphous phase; and forming a plurality of crystalline phases within the amorphous phase; the average Fe concentration in the entire alloy is 83 atomic % or more and 88 atomic % or less; the average B concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average P concentration in the entire alloy is 2.0 atomic % or more and 12 atomic % or less; the average Cu concentration in the entire alloy is 0.4 atomic % or more and 1.4 atomic % or less; the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 3.0 atomic % or less; the average atomic concentration of elements other than Fe, B, P, Cu, Si, and C in the alloy as a whole is 0 atomic % or more and 0.3 atomic % or less; An alloy in which, in atom probe tomography, in a region where the Fe concentration is 80 atomic % or less among multiple regions with a side length of 1.0 nm, when the region where the Cu concentration is 2.3 atomic % or more among the multiple regions is considered to be a Cu cluster, the average spherical equivalent diameter of the Cu cluster is 3.0 nm or more.

8. The alloy according to any one of claims 1 to 7, wherein the sum of the average Si concentration and the average C concentration in the entire alloy is 0 atomic % or more and 0.1 atomic % or less.

9. The alloy according to claim 1 , wherein a value obtained by dividing the average B atomic concentration by the average P atomic concentration in the entire alloy is 1.5 or more and 3.5 or less.

10. The density of Cu clusters (1 m ３ The value obtained by dividing the number of Cu atoms per 1000 particles by the average Cu atomic concentration in the entire alloy is 3.0 × 10 ２４ / m ３ 10. The alloy of claim 1, wherein the atomic percent of Si is 0.1 to 0.5 atomic percent.

11. 11. An alloy according to claim 1, wherein the average P atomic concentration in the regions among the plurality of regions where the Fe concentration is 90 atomic % or more is divided by the average P atomic concentration in the entire alloy, and the value is 0.36 or less.

12. 12. An alloy according to claim 1, wherein the average P atomic concentration in the regions among the plurality of regions where the Fe concentration is 80 atomic % or less is divided by the average P atomic concentration in the entire alloy, and the value is 1.6 or more.

13. An alloy according to any one of claims 1 to 12, wherein in a proxigram using the multiple regions in which the Fe concentration is bounded at 80 atomic %, the maximum Cu concentration is 1.25 atomic % or more within a range of ±5.0 nm from the boundary.

14. 14. The alloy according to claim 1, wherein in a proxigram using the plurality of regions in which the Fe concentration is 80 atomic % as a boundary, the P atomic concentration / B atomic concentration has a minimum value and a maximum value within a range of ±5.0 nm from the boundary.

15. 15. The alloy according to claim 1, wherein in a proxigram using the plurality of regions with an Fe concentration of 80 atomic % as a boundary, the maximum value of the P atomic concentration / B atomic concentration is 1.0 or more within a range of ±3.0 nm from the boundary.

16. 16. The alloy according to claim 1, wherein in a proxogram using the plurality of regions with an Fe concentration of 80 atomic % as a boundary, a value obtained by dividing the maximum value of the P atomic concentration / B atomic concentration within a range of ±3.0 nm from the boundary by the average P atomic concentration / average B atomic concentration in the entire alloy is 1.0 or more.

17. 17. An alloy according to any one of claims 1 to 16, wherein in a region among the plurality of regions having an Fe concentration of 80 atomic % or more, when a region among the plurality of regions having a Cu concentration of 2.3 atomic % or more is considered to be a Cu cluster, the average equivalent spherical diameter of the Cu cluster is 3.0 nm or more.

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