WO2024253437A1 - Permanent magnet - Google Patents

Abstract

The permanent magnet according to an embodiment of the present invention comprises: a Re =-Fe =-B-based base magnet; and a grain boundary diffusion metal disposed inside the base magnet, the base magnet including a plurality of grains and a grain boundary between the grains, wherein the grain boundary diffusion metal is disposed in the grain boundary, the grain boundary diffusion metal includes a praseodymium (Pr )-X-Y-based alloy, and X includes at least one metal among copper (Cu), aluminum (Al), and gallium (Ga), and Y includes at least one metal among titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), and molybdenum (Mo).

Description

permanent magnet

The invention relates to a permanent magnet and a method for manufacturing the same.

Re-Fe-B magnets are permanent magnets containing rare earth elements and compounds of iron and boron (B). The rare earth element (Re) may include neodymium (Nd), praseodymium (Pr), dysprosium (Dy), cerium (Ce), or terbium (Tb).

The above permanent magnets are used in fields such as electronic information, automobile industry, medical equipment, energy or transportation. Recently, the above permanent magnets are also used in electronic information devices, home electronic products, mobile phones, robot motors, wind power generators, small motors for automobiles or drive motors.

A post-processing method is proposed to improve the magnetic performance of the above permanent magnet. For example, a heavy rare earth element is coated on the surface of the above permanent magnet and then heat-treated. As a result, the heavy rare earth element can be concentrated and distributed around the grain boundary. As a result, the coercivity can be improved.

However, the heavy rare earth elements have the problem of difficulty in supply. In addition, the heavy rare earth elements have a high melting point. As a result, the diffusion speed of the heavy rare earth elements decreases, so the process efficiency may decrease.

In addition, there is a problem that the crystal grain size of the permanent magnet increases in the high-temperature process. As a result, the coercive force of the permanent magnet may decrease.

Therefore, a new structure of Re-Fe-B permanent magnets that can solve the above problems is required.

As a prior art document related to the above permanent magnet, Korean registered patent No. 10-1932551 is disclosed.

The invention provides a permanent magnet having improved coercivity.

A permanent magnet according to an embodiment includes a Re-Fe-B base magnet; and a grain boundary diffused metal disposed inside the base magnet, wherein the base magnet includes a plurality of crystal grains; and grain boundaries between the crystal grains, the grain boundary diffused metal is disposed at the grain boundaries, and the grain boundary diffused metal includes a praseodymium (Pr)-X-Y alloy, wherein X includes at least one metal among copper (Cu), aluminum (Al), and gallium (Ga), and Y includes at least one metal among titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), and molybdenum (Mo).

A permanent magnet according to an embodiment comprises a grain boundary diffused metal. The grain boundary diffused metal is arranged at a grain boundary of the permanent magnet.

The above grain boundary diffusion metal includes a grain boundary diffusion material having a set composition and composition ratio. In detail, the grain boundary diffusion material includes a PrXY alloy.

The above X includes copper (Cu), aluminum (Al), and gallium (Ga). The praseodymium (Pr) and the X metal form an alloy. Thereby, the melting point of the grain boundary diffusion material decreases. Accordingly, the grain boundary diffusion material can diffuse at a low temperature. Accordingly, the diffusion speed of the grain boundary diffusion material increases, thereby improving process efficiency.

In addition, the coarsening of the crystal grains of the permanent magnet can be prevented. Specifically, adjacent crystal grains can be prevented from reacting with each other due to high temperature. Accordingly, since the coarsening of the crystal grains is prevented, the coercive force of the permanent magnet is improved.

The above Y may include at least one metal among titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), and molybdenum (Mo). For example, the Y includes titanium (Ti).

The above titanium (Ti) can form a precipitate phase at the grain boundary. As a result, the reaction of adjacent grains is prevented by the precipitate phase. Therefore, the coarsening of the grains can be prevented. Therefore, the coercive force of the permanent magnet is improved.

Figure 1 is a perspective view of a permanent magnet according to an embodiment.

Figures 2 and 3 are cross-sectional views illustrating the interior of a permanent magnet according to an embodiment.

Figure 4 is an enlarged view of area A of Figure 3.

Figure 5 is a graph for explaining the relative ratio of element and compound contents in the B-B' region of Figure 4.

Figures 6 and 7 are graphs for explaining the coercive force of a permanent magnet according to an embodiment.

Figure 8 is a drawing for explaining the difference in crystal grains according to the depth of the permanent magnet according to the examples and comparative examples.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical idea of the present invention is not limited to some of the embodiments described, but may be implemented in various different forms, and within the scope of the technical idea of the present invention, one or more of the components among the embodiments may be selectively combined or substituted for use.

In addition, terms (including technical and scientific terms) used in the embodiments of the present invention can be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, can be interpreted in consideration of the contextual meaning of the relevant technology.

Below, a permanent magnet according to an embodiment is described with reference to the drawings.

Referring to FIGS. 1 to 5, the permanent magnet (1000) includes a base magnet (300). The base magnet (300) may include a Re-Fe-B permanent magnet. The Re may include a rare earth element. For example, the Re may include neodymium (Nd), praseodymium (Pr), dysprosium (Dy), cerium (Ce), or terbium (Tb).

The above base magnet (300) is formed by sintering magnetic powder. For example, rare earth oxide, iron, boron, and a reducing agent are mixed and then heated. As a result, the rare earth oxide is reduced, and magnetic powder of the Re ₂ Fe ₁₄ B phase is formed. Then, the magnetic powder is heated to a set temperature range to form the base magnet (300).

Referring to FIG. 2, the base magnet (300) forms a plurality of crystal grains (100) by the sintering process. Accordingly, a boundary is formed between adjacent crystal grains. That is, a grain boundary (GB) is formed between adjacent crystal grains. Accordingly, the base magnet (300) includes a plurality of crystal grains (100) and grain boundaries between the crystal grains.

Referring to FIGS. 3 and 4, a grain boundary diffusion metal (200) is arranged at the grain boundary (GB). For example, a grain boundary diffusion material is coated on the surface of the permanent magnet. Then, a heat treatment is performed at a temperature in a temperature range. Accordingly, the grain boundary diffusion material is diffused into the interior of the permanent magnet. In detail, the grain boundary diffusion material is diffused into the grain boundary. Accordingly, the grain boundary diffusion metal (200) is arranged at the grain boundary (GB).

The above-mentioned grain boundary diffusion metal (200) includes a material having a set composition and composition ratio.

The above-mentioned grain boundary diffusion metal (200) includes a rare earth material. For example, the above-mentioned grain boundary diffusion metal (200) may include praseodymium (Pr). For example, the above-mentioned grain boundary diffusion metal (200) may include a metal compound including praseodymium (Pr). In detail, the above-mentioned grain boundary diffusion metal (200) may include a PrXY alloy. That is, the above-mentioned grain boundary diffusion metal (200) may include a metal alloy including Pr, X, and Y.

The above X includes at least one metal. For example, the X may include at least one metal among copper (Cu), aluminum (Al), and gallium (Ga). In one example, the X includes copper (Cu), aluminum (Al), and gallium (Ga).

The above Y includes at least one metal. For example, the Y may include a refractory metal. For example, the Y may include at least one metal among titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), and molybdenum (Mo). As an example, the Y includes titanium (Ti).

The above grain boundary diffusion metal (200) has a set composition ratio. The composition ratio of the grain boundary diffusion metal is expressed in atomic percent (atomoc percent). In detail, the atomic percent ratio of Pr and (X+Y) can be 6.5 (Pr):3.5 (X+Y) to 7.5 (Pr):2.5 (X+Y). In addition, the atomic percent ratio of Pr, X, and Y can be 6.5 (Pr):3.49 (X):0.01 (Y) to 7.5 (Pr):2.1 (X):0.4 (Y). The melting point of the grain boundary diffusion metal (200) decreases with the composition ratio. In addition, the coercive force of the permanent magnet increases with the composition ratio.

For example, the X may include copper (Cu), aluminum (Al), and gallium (Ga). Additionally, Y may include titanium (Ti). That is, the intergranular diffusion metal (200) may include a PrCuAlGaTi alloy.

When the atomic % of the above metal compound is 100 at%, the atomic % of the praseodymium (Pr) is greater than the atomic % of X and Y. In detail, the atomic % of the praseodymium (Pr) is greater than the sum of the atomic % of copper (Cu), aluminum (Al), gallium (Ga), and titanium (Ti).

The above praseodymium (Pr) has a set atomic %. In detail, the praseodymium (Pr) is included in an amount of 65 at % or more. More specifically, the praseodymium (Pr) is included in an amount of 65 at % to 75 at %.

The above praseodymium (Pr) diffuses into the interior of the permanent magnet. In detail, the praseodymium (Pr) diffuses into the interior of the permanent magnet through the grain boundary (GB). As a result, the coercivity of the permanent magnet is improved.

When the praseodymium (Pr) is less than 65 at%, the coercivity of the permanent magnet may decrease. In addition, when the praseodymium (Pr) exceeds 75 at%, the ratio of the X metal decreases. As a result, the melting point of the metal compound may increase. Accordingly, the diffusion speed of the grain boundary diffusion metal may decrease. As a result, the process efficiency of the permanent magnet may decrease. In addition, the heat treatment temperature of the grain boundary diffusion metal may increase. As a result, the crystal grains may also coarsen. Accordingly, the coercivity of the permanent magnet may decrease.

The above X has an atomic % in a set range. In detail, the above X is included in an amount of 20 at% or more. More specifically, the above X is included in an amount of 20 at% to less than 35 at%.

The above X includes at least one metal among copper (Cu), aluminum (Al), and gallium (Ga). The X is alloyed with the Pr. Thereby, the melting point of the metal compound decreases. That is, the melting point of the metal compound decreases due to the X metal. Accordingly, the diffusion speed of the metal compound increases, so that the process efficiency of the permanent magnet is improved. In addition, the grain boundary diffusion material is diffused at a low temperature. Therefore, the crystal grains can be prevented from coarsening due to a high temperature. Accordingly, the coercive force of the permanent magnet increases.

For example, the X includes copper (Cu), aluminum (Al), and gallium (Ga). The copper (Cu), the aluminum (Al), and the gallium (Ga) each have atomic % within a set range.

For example, the atomic % of the copper (Cu) is greater than the atomic % of the aluminum (Al) and the gallium (Ga). In detail, the copper (Cu) is included in an amount of 10 at% or more. More specifically, the copper (Cu) is included in an amount of 10 at% to 20 at%.

The atomic % of the aluminum (Al) may be greater than or less than the atomic % of the gallium (Ga). For example, the atomic % of the aluminum (Al) may be greater than the atomic % of the gallium (Ga). In detail, the aluminum (Al) is included in an amount of 5 at% or more. More specifically, the aluminum (Al) is included in an amount of 5 at% to 15 at%.

The atomic % of the gallium (Ga) may be greater than or less than the atomic % of the aluminum (Al). For example, the atomic % of the gallium (Ga) may be less than the atomic % of the aluminum (Al). In detail, the gallium (Ga) is included in an amount of 0.1 at% or more. More specifically, the gallium (Ga) is included in an amount of 0.7 at% to 7 at%.

The above gallium (Ga) forms a non-magnetic phase in the crystal grains around the crystal grain boundary. For example, the gallium (Ga) forms a Nd ₆ Fe ₁₃ Ga phase in the crystal grains around the crystal grain boundary. As a result, the non-magnetic property of the crystal grains of the permanent magnet is improved. Accordingly, the coercive force of the permanent magnet is increased, and thus the magnetic performance of the permanent magnet is improved.

The copper (Cu) and the aluminum (Al) promote the enhancement of the coercive force by the gallium (Ga). Specifically, the content of iron (Fe) in the permanent magnet decreases due to the gallium (Ga). Accordingly, the permanent magnet has an Nd ₆ Fe ₁₃ Ga phase of Nd-rich. The copper (Cu) and the aluminum (Al) further increase the non-magnetism of the crystal grains of the permanent magnet having the Nd ₆ Fe ₁₃ Ga phase of Nd-rich. As a result, the coercive force of the permanent magnet can be increased.

The above Y has an atomic % of a set range. In detail, the above Y is included in an amount of 0.1 at% or more. More specifically, the above Y is included in an amount of 0.1 at% to 4 at%.

The above Y may include at least one metal among titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), and molybdenum (Mo). For example, the Y includes titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), or molybdenum (Mo). In one example, the Y includes titanium (Ti).

The above Y is arranged at the grain boundary. The above Y forms a precipitation phase (400) at the grain boundary. The precipitation phase (400) can prevent a reaction of adjacent grains. For example, the above Y may include titanium (Ti). The titanium (Ti) is precipitated at the grain boundary. Accordingly, a Ti precipitation phase is formed at the grain boundary. Accordingly, a reaction of adjacent grains is prevented by the titanium precipitation phase (400). Therefore, it is possible to prevent grains from coarsening due to a reaction of adjacent grains.

The above Y prevents the coarsening of the above crystal grains (200). Accordingly, the crystal grains of the above permanent magnet are prevented from growing larger. Accordingly, the coercive force of the above permanent magnet is improved.

Fig. 5 is a graph for explaining the ratio of the permanent magnet and the metal compound. Fig. 5 is a graph when the permanent magnet includes NdFeB, the X metal includes copper (Cu), the aluminum (Al), and the gallium (Ga), and the Y metal includes titanium (Ti).

The elements of the above metal compound are included in different ratios in the NdFeB crystal grains and grain boundaries (GB). In detail, the positional ratios of the Pr, Cu, Al, and Ga elements may be different from the positional ratios of the Ti element.

Referring to FIG. 5, the content of the ReFeB decreases in the direction of the grain boundary (GB). For example, the NdFeB decreases in the grain toward the grain boundary (GB). That is, the NdFeB is arranged only in the grain (100).

In addition, the content of the Pr, Cu, Al, and Ga elements includes a region where it increases from the crystal grain toward the grain boundary (GB). In addition, the content of the Pr, Cu, Al, and Ga elements includes a region where it decreases from the grain boundary (GB). That is, some of the Pr, Cu, Al, and Ga elements diffuse from the grain boundary (GB) to the grain (100).

In addition, the Ti element includes a region where it increases and decreases at the grain boundary (GB). That is, the Ti element is arranged at the grain boundary (GB).

In the region adjacent to the center of the crystal grain, the ReFeB ratio is greater than the ratios of the Pr, Cu, Al, and Ga elements. For example, the NdFeB ratio is greater than the ratios of the Pr, Cu, Al, and Ga elements. In addition, in the region distant from the center of the crystal grain, that is, in the region adjacent to the grain boundary (GB), the ratios of the Pr, Cu, Al, and Ga elements are greater than the ReFeB ratio.

The above Pr, Cu, Al and Ga elements diffuse from the grain boundaries (GB) and penetrate into the interior of the grains. Accordingly, the ratio of the Pr, Cu, Al and Ga elements in the grain region around the grain boundaries (GB) is greater than the ratio of NdFeB.

The ratio of the Ti element is the largest at the above grain boundary (GB). The Ti element hardly penetrates into the interior of the NdFeB grain. Accordingly, most of the Ti element is arranged at the grain boundary (GB). Accordingly, the Ti element can be precipitated at the grain boundary (GB). The reaction of adjacent grains (200) is reduced by the Ti precipitation phase precipitated at the grain boundary (GB). Therefore, the coarsening of the grain (200) is prevented.

Accordingly, the grain size deviation of the crystal grains of the permanent magnet can be reduced. In detail, the difference between the maximum grain size and the minimum grain size of the crystal grains (200) of the permanent magnet can be 30% or less. More specifically, the difference between the maximum grain size and the minimum grain size of the crystal grains (200) can be 5% to 30%, 10% to 25%, or 15% to 20%.

Accordingly, the grain size of the permanent magnet becomes uniform. Accordingly, the coercive force of the permanent magnet is improved.

Below, the magnetic properties of permanent magnets according to grain boundary diffusion materials are described through examples and comparative examples.

Example 1

Prepare a base magnet. The base magnet is formed by sintering magnetic powder. The base magnet is a Nd-Fe-B type magnet. The base magnet has a size of 15x15x4(t), (mm) and weighs 6.77g.

Next, an adhesive material mixed with polyvinyl alcohol (PVA), ethanol, and water is applied to the surface of the base magnet.

Next, a grain boundary diffusion material is applied to the surface of the base magnet. In detail, a grain boundary diffusion material having a composition and composition ratio of Pr ₇₀ Cu ₁₅ Al ₁₀ Ga ₄ Ti ₁ (at%) is applied to the surface of the base magnet.

When the sum of the weight % of the above-mentioned grain boundary diffusion material and the above-mentioned base magnet is 100 wt%, the above-mentioned grain boundary diffusion material is applied at 1 wt%.

The above-mentioned intergranular diffusion material can be formed by melt spinning or jet milling by melting the Pr ₇₀ Cu ₁₅ Al ₁₀ Ga ₄ Ti ₁ alloy, pouring it onto a high-speed rotating wheel, and rapidly cooling it.

Next, the adhesive material is dried using a heat gun or an oven so that the Pr ₇₀ Cu ₁₅ Al ₁₀ Ga ₄ Ti ₁ alloy is well attached to the surface of the base magnet.

Next, heat treatment is performed. The base magnet is subjected to a first heat treatment at a temperature of 970°C for 15 hours in a vacuum. Next, the base magnet is subjected to a second heat treatment (annealing) at a temperature of 550°C for 2 hours.

In this way, Nd-Fe-B permanent magnets are manufactured.

Next, the coercive force of the permanent magnet is measured.

Example 2

An Nd-Fe-B permanent magnet was manufactured in the same manner as in Example 1, except that the above-mentioned grain boundary diffusion material was applied at 2 wt%.

Next, the coercive force of the permanent magnet is measured.

Example 3

An Nd-Fe-B permanent magnet was manufactured in the same manner as in Example 1, except that the above-mentioned grain boundary diffusion material was applied at 3 wt%.

Next, the coercive force of the permanent magnet is measured.

Example 4

An Nd-Fe-B permanent magnet was manufactured in the same manner as in Example 1, except that the above-mentioned grain boundary diffusion material was applied at 4 wt%.

Next, the coercive force of the permanent magnet is measured.

Example 5

An Nd-Fe-B permanent magnet was manufactured in the same manner as in Example 1, except that the above-mentioned grain boundary diffusion material was applied at 8 wt%.

Next, the coercive force of the permanent magnet is measured.

Example 6

An Nd-Fe-B permanent magnet was manufactured in the same manner as in Example 1, except that the above-mentioned grain boundary diffusion material was applied at 12 wt%.

Next, the coercive force of the permanent magnet is measured.

Comparative example 1

A Nd-Fe-B permanent magnet without coating the above-mentioned grain boundary diffusion material is manufactured.

Next, the coercive force of the permanent magnet is measured.

Comparative example 2

The above grain boundary diffusion material includes Pr ₇₀ Cu ₁₅ Al ₁₀ Ga ₅ , and an Nd-Fe-B permanent magnet is manufactured in the same manner as in Example 1, except that the above grain boundary diffusion material is applied at 8 wt%.

Next, the coercive force of the permanent magnet is measured.

Referring to FIG. 6, the permanent magnets according to Examples 1 to 4 have improved coercivity compared to the permanent magnet according to Comparative Example 1.

The permanent magnet according to Comparative Example 1 does not include a grain boundary diffusion material. Accordingly, the permanent magnet according to Comparative Example 1 has a small coercive force of about 8 kOe.

On the other hand, the permanent magnets according to examples 1 to 4 contain Pr, Cu _, Al, It includes a grain boundary diffusion material including Ga and Ti. Accordingly, the permanent magnet according to the embodiments has a coercivity exceeding 8 kOe. That is, the coercivity of the permanent magnet according to the embodiments is increased by the grain boundary diffusion material. In detail, the permanent magnet according to the embodiments has a coercivity that is greatly increased without a significant decrease in magnetization.

Referring to FIG. 7, the permanent magnets according to Examples 5 and 6 have improved coercivity compared to the permanent magnets according to Comparative Examples 1 and 2.

The permanent magnet according to Comparative Example 1 does not include a grain boundary diffusion material. Accordingly, the permanent magnet according to Comparative Example 1 has a small coercive force of about 8 kOe.

The permanent magnet according to Comparative Example 2 is composed of Pr, Cu _, Al, and It includes a grain boundary diffusion material including Ga. That is, the grain boundary diffusion material of the above Comparative Example 2 does not include Ti. The permanent magnet of the above Comparative Example 2 has a coercivity of about 26 kOe.

On the other hand, the permanent magnets according to examples 5 and 6 contain Pr, Cu _, Al, A grain boundary diffusion material including Ga and Ti is included. That is, the grain boundary diffusion material of the embodiments includes Ti. Accordingly, the coercivity of the permanent magnet is improved. In detail, the permanent magnet according to the embodiments has a coercivity exceeding 26 kOe. In detail, the permanent magnet according to the embodiments has a coercivity exceeding 26 kOe to 28 kOe. In detail, the permanent magnet according to the embodiments has a coercivity greatly increased without a significant decrease in magnetization.

Fig. 8 is a drawing for explaining the difference in grain size of crystal grains of Example 5 and Comparative Example 2. Fig. 8 (a) is a grain size photograph of Example 5, and Fig. 8 (b) is a grain size photograph of Comparative Example 2.

Referring to Fig. 8, it can be seen that the permanent magnet according to the embodiment has a smaller difference in grain size as the depth increases from the surface. In detail, it can be seen that the grain sizes are similar at a depth of 100 μm, a depth of 200 μm, and a depth of 300 μm from the surface.

On the other hand, it can be seen that the permanent magnet according to the comparative example has a large difference in grain size as the depth increases from the surface. In detail, it can be seen that the grain size differences are large at a depth of 100 μm, a depth of 200 μm, and a depth of 300 μm from the surface. In detail, the grain size at a depth of 100 μm from the surface is larger than the grain size at a depth of 300 μm. That is, the permanent magnet according to the comparative example does not contain titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), or molybdenum (Mo), which prevent coarsening of grains. Accordingly, the nodular grains react at high temperature and coarsen while the grain boundary diffusion material is diffused. Accordingly, the coercive force of the permanent magnet decreases, as shown in Fig. 6.

The features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified and implemented in other embodiments by a person having ordinary knowledge in the field to which the embodiments belong. Therefore, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the above has been described with reference to embodiments, these are merely examples and do not limit the present invention, and those with ordinary skill in the art to which the present invention pertains will recognize that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiments. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, the differences related to such modifications and applications should be interpreted as being included in the scope of the present invention defined in the appended claims.

Claims (10)

Re-Fe-B base magnet; and Including a grain boundary diffusion metal arranged inside the above base magnet, The above base magnet comprises a plurality of crystal grains; and grain boundaries between the plurality of crystal grains, The above grain boundary diffusion metal includes a praseodymium (Pr)-X-Y alloy arranged at the grain boundary, The above X contains at least one metal among copper (Cu), aluminum (Al) and gallium (Ga), The above Y is a permanent magnet including at least one metal among titanium (Ti), tungsten (W), niobium (Nb), rhenium (Re), and molybdenum (Mo). In paragraph 1, The above X contains copper (Cu), aluminum (Al) and gallium (Ga), The above Y is a permanent magnet containing titanium (Ti). In the second paragraph, A permanent magnet wherein the atomic % ratio of Pr and (X+Y) is 6.5(Pr):3.5(X+Y) to 7.5(Pr):2.5(X+Y). In the second paragraph, A permanent magnet wherein the atomic % ratio of Pr, X, and Y is 6.5(Pr):3.49(X):0.01(Y) to 7.5(Pr):2.1(X):0.4(Y). In the second paragraph, The above Pr is contained in an amount of 65 at% to 75 at%, The above Cu is contained in an amount of 10 at% to 20 at%, The above Al is contained in an amount of 5 at% to 15 at%, The above Ga is contained in an amount of 0.7 at% to 7 at%, A permanent magnet containing the above Ti in an amount of 0.1 at% to 4 at%. In the second paragraph, The above Ti is a permanent magnet precipitated at the crystal grain boundary. In the second paragraph, The content of the above Pr, Cu, Al and Ga elements includes a region in which the content increases from the crystal grain to the crystal grain boundary, A permanent magnet including a region in which the contents of the above Pr, Cu, Al and Ga elements decrease at the grain boundaries. In the second paragraph, The ratio of the Re-Fe-B in the center and adjacent regions of the above crystal grains is greater than the ratio of the Pr, Cu, Al and Ga elements, A permanent magnet wherein the ratios of the Pr, Cu, Al and Ga elements in the region adjacent to the grain boundaries are greater than the ratio of the Re-Fe-B. In paragraph 1, A permanent magnet in which the proportion of the Ti element is the largest at the above grain boundaries. In paragraph 1, A permanent magnet wherein the difference between the maximum and minimum grain sizes of the above-mentioned crystal grains is 5% to 30%.

Images