FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] RARE EARTH SINTERED MAGNET, METHOD FOR PRODUCING RARE EARTH SINTERED MAGNET, ROTOR, AND ROTARY MACHINE MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7- 3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 2 DESCRIPTION TITLE OF THE INVENTION: RARE EARTH SINTERED MAGNET, METHOD FOR PRODUCING RARE EARTH SINTERED MAGNET, ROTOR, AND ROTARY MACHINE5 Field [0001] The present disclosure relates to a rare earth sintered magnet which is a permanent magnet obtained by sintering a material containing a rare earth element, a10 method for producing a rare earth sintered magnet, a rotor, and a rotary machine. Background [0002] R-T-B-based permanent magnets having a tetragonal15 R2T14B intermetallic compound as a main phase are known. Here, R is a rare earth element, T is a transition metal element such as Fe (iron) or Fe that is partially replaced by cobalt (Co), and B is boron. R-T-B-based permanent magnets are used for various components having a high added20 value, including for example industrial motors. In particular, Nd-Fe-B-based sintered magnets in which R is neodymium (Nd) are used for various components due to excellent magnetic properties. In addition, because industrial motors are often used in a high temperature25 environment exceeding 100°C, attempts have been made to improve coercive force by adding heavy rare earth elements such as dysprosium (Dy) to Nd-T-B-based sintered magnets. [0003] In recent years, the production of Nd-Fe-B-based sintered magnets has been expanded, and the consumption of30 Nd and heavy rare earth elements such as Dy and terbium (Tb) has been increased. However, Nd and heavy rare earth elements are expensive and also have a procurement risk due 3 to high distribution unevenness. In view of this, a possible measure for reducing the consumption of Nd and heavy rare earth elements is to use a magnet that forms a main phase including a low heavy rare earth phase, to use other rare earth elements as R, such as praseodymium (Pr),5 cerium (Ce), lanthanum (La), samarium (Sm), scandium (Sc), gadolinium (Gd), yttrium (Y), and lutetium (Lu), or to use a special production method such as subjecting a sintered body to hot plastic working. Hereinafter, hot plastic working applied to a sintered body is referred to as hot10 working. However, adding a heavy rare earth element to the main phase to no small extent contributes to improvement of the coercive force, but significantly degrades the residual magnetic flux density. In addition, replacing all or a part of Nd with elements such as Pr, Ce, La, Sm, Sc, Gd, Y,15 and Lu significantly degrades the magnetic properties of the residual magnetic flux density and the coercive force. Furthermore, subjecting the sintered body to hot working significantly degrades the magnetization of the magnet due to the refinement of the crystal grains. From the above,20 it has been difficult to achieve both saving of heavy rare earth elements and excellent magnetic properties and magnetization. Therefore, attempts have been conventionally made to develop technology that allows for improvement of magnetic properties at room temperature and25 prevention of degradation of magnetic properties associated with temperature rise in the case of using these elements for producing Nd-Fe-B-based sintered magnets. In particular, at present, a rare earth magnet that allows for both further reduction of heavy rare earth elements and30 excellent magnetic properties and magnetization is required. [0004] Patent Literature 1 discloses an R-T-B-based 4 sintered magnet containing main phase grains consisting of an R2T14B crystal, where R is one or more kinds of rare earth elements including a heavy rare earth element RH as an essential element, T is one or more kinds of transition metal elements including Fe or including Fe and Co as an5 essential element, B is boron. A part of the main phase grains of the R-T-B-based sintered magnet includes a plurality of low heavy rare earth element crystal phases therein, and the low heavy rare earth element crystal phase is a phase consisting of an R2T14B crystal and having a10 relatively low concentration of the heavy rare earth element with respect to the concentration of the heavy rare earth element in the entire main phase grains. According to the technique described in Patent Literature 1, it is possible to obtain an R-T-B-based sintered magnet having15 improved magnetic properties at low cost. [0005] Patent Literature 2 discloses a rare earth magnet including a main phase having an R2Fe14B crystal structure where R is a rare earth element, and a grain boundary phase present around the main phase. The main phase includes a20 core portion, a first shell portion present around the core portion, and a second shell portion present around the first shell portion. In the rare earth magnet described in Patent Literature 2, the abundance ratio of Nd and Pr in the first shell portion is higher than the abundance ratio25 of Nd and Pr in the core portion and the second shell portion. In the rare earth magnet described in Patent Literature 2, the abundance ratio of the heavy rare earth element in the second shell portion is higher than the abundance ratio of the heavy rare earth element in the30 first shell portion. As a result, a rare earth magnet having a further improved coercive force is obtained. 5 Citation List Patent Literature [0006] Patent Literature 1: Japanese Patent Application Laid-open No. 2018-174313 Patent Literature 2: Japanese Patent Application5 Laid-open No. 2021-174818 Summary of Invention Problem to be solved by the Invention [0007] However, in the R-T-B-based sintered magnet10 described in Patent Literature 1, a phase including a heavy rare earth element is present in the main phase, which improves coercive force but cannot yield the residual magnetic flux density required for industrial motors or the like, which may lead to degradation of magnetic properties.15 Furthermore, since heavy rare earth elements are diffused in the main phase particles, there is a problem that the amount of heavy rare earth elements used is large, and the procurement risk and cost cannot be reduced. In addition, since the rare earth magnet described in Patent Literature20 2 has one type of main phase, the rare earth magnet does not have a structure in which the anisotropic magnetic field is sufficiently enhanced, and there is a problem that it is difficult to obtain high magnetic properties. In addition, in the rare earth magnet described in Patent25 Literature 2, the shell portion of the main phase has a two-layer structure in which the abundance ratio of the heavy rare earth element is different, and the heavy rare earth element needs to be put in both shell portions, and thus there is also a problem that it is difficult to30 improve magnetic properties with less heavy rare earth element. [0008] The present disclosure has been made in view of 6 the above, and an object thereof is to obtain a rare earth sintered magnet capable of improving magnetic properties as compared with the related art, while reducing use of heavy rare earth elements as compared with the related art. 5 Means to Solve the Problem [0009] In order to solve the above-described problems and achieve the object, a rare earth sintered magnet according to the present disclosure includes: a main phase that satisfies a general formula (Nd, Pr, R)-Fe-B, where R10 is one or more rare earth elements selected excluding Nd and Pr, the main phase containing crystal grains based on an Nd2Fe14B crystal structure; and a subphase present between a plurality of the main phases. The main phase includes a core portion and a shell portion covering the15 core portion. The main phase includes a first main phase that satisfies CNd>CPr and a second main phase that satisfies CNdCPr and a second main15 phase 12 that satisfies CNdCPr is satisfied in the core portion 11c of the first main phase 11, and CNdCPr and the second main phase 12 that satisfies CNdC2Nd and C1PrCPr are present more than the second30 main phase 12 each of which satisfies CNdSNd and15 CPrSPr, where SNd is the concentration of Nd in the shell portions 11s and 12s and SPr is the concentration of Pr in the shell portions 11s and 12s. Specifically, the shell portion 11s of the20 first main phase 11 has a higher concentration of Pr than the core portion 11c instead of having a lower concentration of Nd, and the shell portion 12s of the second main phase 12 has a higher concentration of Nd than the core portion 12c instead of having a lower25 concentration of Pr. By forming the first main phase 11 including the shell portion 11s having a high concentration of Pr in the main phase 10, the coercive force can be improved. Furthermore, by forming the second main phase 12 including the shell portion 12s having a high concentration30 of Nd in the main phase 10, it is possible to prevent degradation of the residual magnetic flux density while maintaining the coercive force. Through selective control 13 to achieve such a structure form, the rare earth sintered magnet 1 can exhibit excellent magnetic properties as compared with the related art. [0019] In addition, the main phase 10 includes a heavy rare earth element containing layer 31 containing a heavy5 rare earth element on at least a part of the surface. That is, a heavy rare earth element is present on at least a part of the surface of the main phase 10, that is, the first main phase 11 and the second main phase 12. More specifically, the heavy rare earth element exists on at10 least a part of the outer peripheral surfaces of the shell portions 11s and 12s, and the heavy rare earth element does not enter the core portions 11c and 12c. The heavy rare earth element is one or more elements selected from the group consisting of Dy, Tb, Gd, and Ho (holmium). As15 described above, the coercive force increases, since the heavy rare earth element enters the R sites of the first main phase 11 and the second main phase 12, but the heavy rare earth element does not enter the core portion 11c that is the inside of the first main phase 11 and the core20 portion 12c that is the inside of the second main phase 12, so that a significant decrease in residual magnetic flux density can be prevented. That is, it is possible to prevent a decrease in residual magnetic flux density while improving the coercive force. In order to obtain such an25 effect, the ratio of the heavy rare earth element in the main phase 10 is desirably more than 0 at.% but less than or equal to 10 at.%. [0020] When the magnetic properties are compared between the case where the heavy rare earth element is contained in30 the inside of the main phase 10 of the rare earth sintered magnet 1 and the case where the heavy rare earth element is contained in the surface layer of the main phase 10, it is 14 known that the same magnetic properties can be obtained by containing, in the surface of the main phase 10, the heavy rare earth element having a concentration lower than the concentration in the case where the heavy rare earth element is contained in the inside of the main phase 10.5 That is, in the rare earth sintered magnet 1 according to the first embodiment in which the heavy rare earth element is contained in the surface layer of the main phase 10, the amount of the heavy rare earth element used can be reduced as compared with the case where the heavy rare earth10 element is contained in the inside of the main phase 10. [0021] Further, the average grain size of the crystal grains of the main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm to 50 μm for improving magnetic properties. Furthermore, setting the average grain size to15 about 1 μm to 10 μm results in a grain size different from the microstructure produced by hot working, leading to the rare earth sintered magnet 1 that maintains good magnetizing ability and has excellent magnetic properties as compared with the related art.20 [0022] The rare earth sintered magnet 1 according to the first embodiment may contain an additive element M that further improves magnetic properties. The additive element M is one or more elements selected from the group consisting of Ga (gallium), Cu (copper), Al (aluminum), Co,25 Zr (zirconium), Ti (titanium), Nb (niobium), and Mn (manganese). Therefore, in the rare earth sintered magnet 1 according to the first embodiment, the general formula is expressed by (NdaPrbRcRHd)FeeBfMg, where RH is a heavy rare earth element which is one or more elements selected from30 the group consisting of Dy, Tb, Gd, and Ho, and R is a rare earth element other than Nd, Pr, and the heavy rare earth element RH. The additive element M is one or more elements 15 selected from the group consisting of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. It is desirable that a, b, c, d, e, f, and g satisfy the following relational expressions. [0023] 5≤a+b≤20 0CPr and the second main phase 12 that satisfies CNdC2Nd and C1PrSNd and CPrSPr. This also makes it possible to obtain the rare earth sintered magnet 1 in which magnetic properties and magnetization are improved, while reducing use of Nd and heavy rare earth elements. [0026] Furthermore, the heavy rare earth element is made5 to be present on at least a part of the surface of the first main phase 11 and the second main phase 12, and the heavy rare earth element is made not to be present inside the first main phase 11 and the second main phase 12. As a result, it is possible to obtain the rare earth sintered10 magnet 1 in which the coercive force is improved as compared with the related art while reducing the use of heavy rare earth elements, and a significant decrease in the residual magnetic flux density is prevented. That is, there is an effect that the magnetic properties of the rare15 earth sintered magnet 1 can be improved as compared with the conventional case. [0027] In the first embodiment, the first main phase 11 and the second main phase 12 have a core-shell structure having one layer of shell portions 11s and 12s, and the20 heavy rare earth element only needs to be present on at least a part of the surfaces of the shell portions 11s and 12s. On the other hand, in Patent Literature 2 having a two-layer core-shell structure, heavy rare earth elements need to be diffused into the two-layer core-shell portion.25 Thus, the rare earth sintered magnet 1 according to the first embodiment also has an effect of reducing the amount of heavy rare earth elements used as compared with Patent Literature 2. [0028] Second Embodiment.30 FIG. 2 is a diagram schematically illustrating an exemplary sintered structure of a rare earth sintered magnet according to the second embodiment. Note that 17 components identical to those in the first embodiment are denoted by the same reference signs, and the description thereof will be omitted. The rare earth sintered magnet 1 according to the second embodiment includes the main phase 10 and the subphase 20.5 [0029] The main phase 10 has the same structure as that of the first embodiment. That is, the main phase 10 has the first main phase 11 and the second main phase 12 having a core-shell structure, and the compositions of the core portions 11c and 12c and the compositions of the shell10 portions 11s and 12s are similar to those described in the first embodiment. However, in the second embodiment, the heavy rare earth element containing layer 31 is not present on the surface of the main phase 10. [0030] The subphase 20 is a phase based on an oxide15 phase represented by (Nd, Pr, R)-O as a main component. However, in the second embodiment, the subphase 20 contains a heavy rare earth element. The heavy rare earth element is distributed throughout the subphase 20. In one example, the heavy rare earth element is uniformly distributed20 inside the subphase 20. [0031] As described above, in the second embodiment, the subphase 20 having a heavy rare earth element is present between the main phase 10 and the main phase 10. It can also be considered that heavy rare earth element is25 uniformly distributed in the subphase 20, and the heavy rare earth element enters a part of the surface of the main phase 10 in contact with the subphase 20. That is, it is considered that the heavy rare earth element does not enter the core portions 11c and 12c of the main phase 10, but30 enters a part of the shell portions 11s and 12s. Therefore, similarly to the first embodiment, it is possible to prevent a decrease in residual magnetic flux 18 density while improving the coercive force of the rare earth sintered magnet 1. [0032] As illustrated in FIG. 2, in the rare earth sintered magnet 1, the main phase 10 is in contact with another main phase 10 without the subphase 20 interposed5 therebetween, or is in contact with another main phase 10 via the subphase 20. That is, at least a part of the surface of the main phase 10 is in contact with the subphase 20. The subphase 20 contains a heavy rare earth element. Therefore, at least a part of the surface of the10 main phase 10 is covered with the subphase 20 containing the heavy rare earth element. Viewing the form of the distribution of the heavy rare earth element with respect to the main phase 10, the heavy rare earth element is present on at least a part of the surface of the main phase15 10. That is, for the same rare earth sintered magnet 1, the first embodiment shows the distribution of the heavy rare earth element by focusing on the interface between the main phase 10 and the subphase 20, and the second embodiment shows the distribution of the heavy rare earth20 element by focusing on the subphase 20. Thus, the first embodiment and the second embodiment can be said to be the same rare earth sintered magnet 1 viewed from different angles. [0033] Also in the second embodiment, similarly to the25 first embodiment, it is possible to obtain the rare earth sintered magnet 1 in which the coercive force is improved as compared with the related art while reducing the use of heavy rare earth elements, and a significant decrease in the residual magnetic flux density is prevented. That is,30 there is an effect that the magnetic properties of the rare earth sintered magnet 1 can be improved as compared with the conventional case. 19 [0034] Third Embodiment. FIG. 3 is a diagram schematically illustrating an exemplary sintered structure of a rare earth sintered magnet according to the third embodiment. The rare earth sintered magnet 1 according to the third embodiment5 includes the main phase 10 and the subphase 20. The main phase 10 includes the first main phase 11 and the second main phase 12 as described in the first embodiment, but in FIG. 2, the first main phase 11 and the second main phase 12 are collectively denoted by the main phase 10. The10 subphase 20 is present between the main phases 10. [0035] In the rare earth sintered magnet 1 according to the third embodiment, a case where La and Sm are selected as the rare earth element R will be described. In a case where La and Sm are selected as the rare earth element R,15 the effect of improving the magnetic properties and having excellent magnetization as compared with the related art, while reducing use of Nd and heavy rare earth elements, is further enhanced. In this example, the main phase 10 has the composition formula (Nd,Pr,La,Sm)2Fe14B. The reason why20 the rare earth element R of the rare earth sintered magnet 1 having a tetragonal R2Fe14B crystal structure is rare earth elements including La and Sm is that the calculation of magnetic interaction energy with the use of a molecular orbital method shows that a composition in which La and Sm25 are added can produce the rare earth sintered magnet 1 which is suitable for practical use in that degradation of magnetic properties associated with temperature rise can be significantly prevented. In addition, by intentionally segregating La and Sm also in the grain boundary, which is30 an example of the subphase 20, it is possible to cause Nd and Pr to be relatively diffused throughout the main phase 10, resulting in enhanced magnetocrystalline anisotropy of 20 the main phase 10. As a result, a core-shell structure in which a portion having high magnetic anisotropy and a portion having low magnetic anisotropy exist in the main phase 10 is formed, and a state in which the rare earth sintered magnet 1 in which the first main phase 11 that5 satisfies CNd>CPr and the second main phase 12 that satisfies CNd(C+D) is preferably satisfied, where A, B, C, and D are the composition ratios of Nd, Pr, La, and Sm, respectively. [0037] In the rare earth sintered magnet 1 according to15 the third embodiment, given R=La and/or Sm, the rare earth sintered magnet 1 includes the subphase 20 in addition to the first main phase 11 and the second main phase 12 in the first embodiment. The subphase 20 includes a crystalline first subphase 21 based on an oxide phase having a main20 component represented by (Nd, Pr, La, Sm)-O, and a crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O. The concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. That is, the first subphase 2125 forms an Sm enrichment portion 41 having a higher Sm concentration than the second subphase 22. This achieves the effect of preventing not only degradation of the magnetic properties at room temperature but also degradation of the magnetic properties associated with30 temperature rise. [0038] Here, “the concentration of Sm is higher in the first subphase 21 than in the second subphase 22” means 21 that the detection intensity of Sm is higher on average in the first subphase 21 than in the second subphase 22 by mapping analysis using EPMA. [0039] The crystalline subphase 20 is a generic name for the crystalline first subphase 21 and the crystalline5 second subphase 22, and is present between the main phases 10. The crystalline first subphase 21 is represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22 is represented by (Nd, Pr, La)-O. Here, (Nd, Pr, La, Sm) means that a part of Nd and Pr is replaced by La and Sm.10 Note that the elements of the main components are described in parentheses; therefore, the first subphase 21 and the second subphase 22 may contain a small amount of another component, in addition to the elements indicated in parentheses. In one example, the second subphase 2215 represented by (Nd,Pr,La)-O contains an extremely small amount of Sm. [0040] In the rare earth sintered magnet 1 according to the third embodiment, there is a concentration difference of La and Sm between the main phase 10 and the subphase 20,20 and La and Sm are segregated in the subphase 20 more than in the main phase 10. That is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of La in the main phase 10, and the sum of25 the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of Sm in the main phase 10. Specifically, the concentrations of La and Sm in the subphase 20 are equal to or higher than the concentrations of La and Sm in30 the main phase 10. Here, the concentration of La of the main phase 10 is the sum of the concentration of La of the first main phase 11 and the concentration of La of the 22 second main phase 12. That is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is higher than the sum of the concentrations of La in the first main phase 11 and the second main phase 12. Here, the concentration of Sm of the5 main phase 10 is the sum of the concentration of Sm of the first main phase 11 and the concentration of Sm of the second main phase 12. That is, the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is higher than the sum of the10 concentrations of Sm in the first main phase 11 and the second main phase 12. [0041] Here, given that X represents the concentration of La contained in the main phase 10, X1 represents the concentration of La contained in the first subphase 21, X215 represents the concentration of La contained in the second subphase 22, Y represents the concentration of Sm contained in the main phase 10, Y1 represents the concentration of Sm contained in the first subphase 21, and Y2 represents the concentration of Sm contained in the second subphase 22,20 the relationship of Formula (1) below is satisfied. [0042] 1<(Y1+Y2)/Y<(X1+X2)/X •••• (1) [0043] Furthermore, from the viewpoint of improving the magnetic properties, the relationships of Formulas (2) and (3) below are satisfied with respect to the concentrations25 of Nd and Pr contained in the main phase 10. [0044] (CNd+SNd)>(X+Y) •••• (2) (CPr+SPr)>(X+Y) •••• (3) [0045] In the above description, the concentration of La in the main phase 10 is the sum of the concentrations of La30 in the first main phase 11 and the second main phase 12, and the concentration of Sm in the main phase 10 is the sum of the concentrations of Sm in the first main phase 11 and 23 the second main phase 12. This indicates that both La and Sm are segregated in the subphase 20 more than in the main phase 10. However, when viewed locally, each of the sum of the concentrations of La and Sm in the first main phase 11 and the second main phase 12 and each of the sum of the5 concentrations of La and Sm in the first subphase 21 and the second subphase 22 may not satisfy the above relationship. Therefore, more specifically, the concentration of La in the main phase 10 indicates the average of the concentrations of La in the first main phase10 11 and the second main phase 12, and the concentration of Sm in the main phase 10 indicates the average of the concentrations of Sm in the first main phase 11 and the second main phase 12. In this case, the concentration of La of the subphase 20, that is, the sum of the15 concentrations of La in the first subphase 21 and the second subphase 22 means the average of the concentrations of La in the first subphase 21 and the second subphase 22, and the concentration of Sm of the subphase 20, that is, the sum of the concentrations of Sm in the first subphase20 21 and the second subphase 22 means the average of the concentrations of Sm in the first subphase 21 and the second subphase 22. [0046] La is present at a high concentration in the grain boundary in the process of production, particularly25 in the heat treatment, whereby Nd and Pr are relatively diffused throughout the main phase 10. As a result, in the rare earth sintered magnet 1 according to the third embodiment, Nd and Pr in the main phase 10 are not consumed at the grain boundary, leading to improved30 magnetocrystalline anisotropy. Sm is also present at a higher concentration in the subphase 20, particularly in the first subphase 21, than in the main phase 10, whereby 24 Nd is relatively diffused throughout the main phase 10 as in the case of La, resulting in improved magnetocrystalline anisotropy. [0047] As described in the second embodiment, since the subphase 20 contains the heavy rare earth element, the5 first subphase 21 and the second subphase 22 contain the heavy rare earth element, but in the third embodiment, the distribution of the heavy rare earth element is different between the first subphase 21 and the second subphase 22. In the second subphase 22 having a lower Sm concentration10 than the first subphase 21, the heavy rare earth element is uniformly distributed in the second subphase 22. On the other hand, in the first subphase 21 forming the Sm enrichment portion 41, the heavy rare earth element is not uniformly distributed in the first subphase 21, but is15 selectively distributed between the outer contour of the first subphase 21 and the Sm enrichment portion 41, that is, in the inner peripheral portion of the outer contour of the first subphase 21. Specifically, the heavy rare earth element exists so as to selectively surround the outer20 contour of the Sm enrichment portion 41, which has a high Sm concentration in the first subphase 21. From this, it can be said that the first subphase 21 has the Sm enrichment portion 41 and a heavy rare earth element containing portion 32 in which the heavy rare earth element25 selectively surrounding the outer contour of the Sm enrichment portion 41 exists. The outer contour of the first subphase 21 is a boundary portion between the first subphase 21 and the main phase 10. [0048] Similarly to the second embodiment, the first30 subphase 21 and the second subphase 22 having a heavy rare earth element is present between the main phase 10 and the main phase 10. It can be considered that the heavy rare 25 earth element enters a part of the surface of the main phase 10 in contact with the first subphase 21 and the second subphase 22 having the heavy rare earth element. That is, it is considered that the heavy rare earth element does not enter the core portions 11c and 12c of the main5 phase 10, but enters a part of the shell portions 11s and 12s. Therefore, similarly to the first embodiment, it is possible to prevent a decrease in residual magnetic flux density while improving the coercive force of the rare earth sintered magnet 1.10 [0049] FIGS. 4 and 5 are element maps obtained by analyzing a cross section of a rare earth sintered magnet according to the third embodiment with a field emission electron probe microanalyzer (FE-EPMA). FIG. 4 is an element map of Sm, and FIG. 5 is an element map of Tb. In15 these drawings, a state in which the subphase 20 exists between the main phase 10 and the main phase 10 is illustrated. The subphase 20 includes the first subphase 21 having the Sm enrichment portion 41 and the second subphase 22 having a lower Sm concentration than the first20 subphase 21. In the second subphase 22, Tb which is a heavy rare earth element is uniformly distributed as described above. On the other hand, in the first subphase 21, the distribution of Tb is uneven. Referring to FIGS. 4 and 5, the heavy rare earth element containing portion 3225 is present so as to selectively surround the Sm enrichment portion 41 having a high Sm concentration in the first subphase 21. In addition, almost no heavy rare earth element is present in the Sm enrichment portion 41. Furthermore, the concentration of the heavy rare earth30 element selectively distributed around the Sm enrichment portion 41 is higher than the concentration of the heavy rare earth element entirely distributed inside the second 26 subphase 22. [0050] Next, at which atomic sites of the tetragonal R2Fe14B crystal structure La and Sm are substituted will be described. FIG. 6 is a diagram illustrating atomic sites in a tetragonal Nd2Fe14B crystal structure. Note that the5 crystal structure illustrated in FIG. 6 is described, in one example, in FIG. 1 of Reference Literature 1 shown below. The sites of substitution are determined from the numerical value of the stabilization energy associated with substitution computed using band calculation and molecular10 field approximation based on the Heisenberg model. (Reference Literature 1): J. F. Herbst et al., “Relationships between crystal structure and magnetic properties in Nd2Fe14B”, PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, p. 4176–4178.15 [0051] First, a method for calculating stabilization energy in La will be described. The stabilization energy in La can be computed as the energy difference between (Nd7La1)Fe56B4+Nd and Nd8(Fe55La1)B4+Fe using Nd8Fe56B4 crystal cells. The smaller the energy value, the more stable it is20 when the atom is substituted at that site. That is, La is likely to be substituted at an atomic site having the smallest energy among the atomic sites. This calculation assumes that substituting La for the original atom does not change the lattice constant in the tetragonal R2Fe14B25 crystal structure due to the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site at various environmental temperatures. [0052] [Table 1] 27 [0053] Table 1 indicates that stable substitution sites for La are Nd (f) sites at temperatures of 1000K and higher, and Fe (c) sites at temperatures of 293K and 500K. As will be described later, the raw material of the rare5 earth sintered magnet 1 according to the third embodiment is heated and melted at a temperature of 1000K or higher and then rapidly cooled. Therefore, it is considered that the raw material of the rare earth sintered magnet 1 is maintained in a state of 1000K or higher, that is, 727°C or10 higher, and more preferably about 1300K, that is, 1027°C. In this case, La is considered to be substituted at Nd (f) sites or Nd (g) sites. Here, La is considered to be preferentially substituted at energetically stable Nd (f) sites, but may be substituted at Nd (g) sites having a15 small energy difference among the substitution sites for La. This is why Nd (g) sites are also mentioned as a candidate for the substitution sites for La. 28 [0054] Furthermore, when the rare earth sintered magnet 1 is produced with the production method described later, the temperature is 1000K or higher at the time of sintering, but the Fe (c) sites described in Table 1 are held in an energetically stable temperature zone repeatedly5 through the primary aging step, the secondary aging step, the tertiary aging step, the quaternary aging step, and the cooling step. In other words, the substitution of La at Nd sites of the main phase 10 is maintained in an unstable energy state. That is, La is mainly substituted at Nd10 sites of the main phase 10 in the raw material stage of the rare earth sintered magnet 1; however, in the rare earth sintered magnet 1 produced with the production method described later, by intentionally holding the Nd sites of the main phase 10 repeatedly in a temperature range in an15 unstable energy state, a certain amount of La is selectively released from the Nd sites of the main phase 10, and as a result, La is segregated in the subphase 20. As a result, the main phase 10 promotes the formation of the characteristic structure, namely the core-shell20 structure. [0055] Next, a method for calculating stabilization energy in Sm will be described. The stabilization energy of Sm can be computed as the energy difference between (Nd7Sm1)Fe56B4+Nd and Nd8(Fe55Sm1)B4+Fe. Similarly to the25 case of La, atomic substitution does not change the lattice constant in the tetragonal R2Fe14B crystal structure. Table 2 shows the stabilization energy of Sm at each substitution site at various environmental temperatures. [0056] [Table 2]30 29 [0057] Table 2 indicates that stable substitution sites for Sm are Nd (g) sites at any temperature, unlike in the case of La. Sm is also considered to be preferentially substituted at energetically stable Nd (g) sites, but may5 be substituted at Nd (f) sites having a small energy difference among the substitution sites for Sm. [0058] When the rare earth sintered magnet 1 is produced with the production method described later, substitution at Nd (g) sites of the main phase 10 is most stable in terms10 of energy. However, as described above, holding in a temperature range where the substitution of La at Nd sites of the main phase 10 is unstable causes a part of Sm to be released from the Nd sites of the main phase 10 together with La and segregated in the subphase 20. As a result,15 the concentrations of La and Sm differ between the main phase 10 and the subphase 20: the sum of the concentrations 30 of La in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of Sm in the main5 phase 10. More specifically, the average of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the average of the concentrations of La in the first main phase 11 and the second main phase 12, and the average of the10 concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the average of the concentrations of Sm in the first main phase 11 and the second main phase 12. That is, La and Sm can be said to be segregated in the subphase 20.15 [0059] Comparing La and Sm, La held in a temperature range in an unstable energy state is overwhelmingly more likely to be segregated in the subphase 20 from the viewpoint of energy. As a result, in the case of the rare earth sintered magnet 1 prepared with almost the same20 concentrations of La and Sm, comparing La and Sm present in the rare earth sintered magnet 1, La has a larger segregation ratio to the subphase 20. By being held repeatedly in this temperature region, the subphase 20 produces a concentration difference in Sm that has a small25 segregation ratio, and the first subphase 21 and the second subphase 22 are formed. This promotes the formation of the core-shell structure in the main phase 10. [0060] Here, Nd is representatively described as illustrated in FIG. 6, but Nd and Pr are produced as a30 mixture as represented by didymium (Di), and thus it is considered that the energy levels of Nd and Pr are close to each other. Therefore, the same applies to a case where Nd 31 is replaced with Pr. As the two types of Nd and Pr are present, the main phase 10 having two types of core-shell structures can be formed. [0061] As described above, the rare earth sintered magnet 1 according to the third embodiment includes the5 main phase 10 that satisfies a general formula (Nd, Pr, R)- Fe-B, where R is one or more rare earth elements selected excluding Nd and Pr, the main phase 10 containing crystal grains based on an Nd2Fe14B crystal structure, wherein the main phase 10 includes core portions 11c and 12c and shell10 portions 11s and 12s covering the core portions 11c and 12c, and given R=La and/or Sm, the rare earth sintered magnet 1 includes the subphase 20 in addition to the first main phase 11 and the second main phase 12 described in the first embodiment. The subphase 20 includes the crystalline15 first subphase 21 having a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O and the crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O, and the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. That20 is, the two types of main phases 10 and the two types of subphases 20 exist. As a result, it is possible to provide the rare earth sintered magnet 1 having excellent magnetic properties, such as temperature properties of magnetic properties, as compared with the related art. In addition,25 by setting R to La and Sm, the main phase 10 is in a state in which the first main phase 11 that satisfies CNd>CPr and the second main phase 12 that satisfies CNd In the coating diffusion method, the grain boundary diffusion step includes a diffusion element adhesion step 40 of adhering a heavy rare earth element supply portion which is a material containing a heavy rare earth element and serves as a supply source of the heavy rare earth element to the diffusion precursor, and a diffusion heat treatment step of performing heat treatment for diffusing the heavy5 rare earth element from the heavy rare earth element supply portion to the diffusion precursor. In the diffusion element adhesion step, a slurry obtained by mixing a powdery heavy rare earth element mixture with water, an organic solvent, or the like is adhered to the surface of10 the diffusion precursor. The slurry adhered to the surface of the diffusion precursor becomes a heavy rare earth element supply portion. The adhesion of the slurry can be performed by spray spraying, dip coating, spin coating, screen printing, electrodeposition, or the like. In the15 diffusion heat treatment step, the diffusion precursor to which the heavy rare earth element supply portion is adhered is subjected to heat treatment at a diffusion temperature lower than the sintering temperature in the sintering step S23 to diffuse the heavy rare earth element20 into the diffusion precursor. Conditions for the heat treatment are a diffusion temperature lower than the sintering temperature and a time within the range of 0.1 hours to 100 hours. The diffusion temperature is, for example, a temperature in the range of 300°C to 1000°C,25 which is lower than the sintering temperature. The heat treatment is preferably performed in an atmosphere containing an inert gas or in a vacuum in order to prevent oxidation. [0082] 30 Also in the sputtering diffusion method, similarly to the coating diffusion method, the grain boundary diffusion step includes a diffusion element adhesion step and a 41 diffusion heat treatment step. In the diffusion element adhesion step, a thin film having a simple metal or alloy composition of a heavy rare earth element is formed on the surface of the diffusion precursor under a dry environment. The thin film formed on the surface of the diffusion5 precursor becomes a heavy rare earth element supply portion. The thin film is formed by, for example, a sputtering method. In the diffusion heat treatment step, the diffusion precursor in which the heavy rare earth element supply portion is formed is subjected to heat10 treatment at a diffusion temperature lower than the sintering temperature in the sintering step S23 to diffuse the heavy rare earth element into the diffusion precursor. Conditions for the heat treatment are a diffusion temperature lower than the sintering temperature and a time15 within the range of 0.1 hours to 100 hours. The diffusion temperature is, for example, a temperature in the range of 300°C to 1000°C, which is lower than the sintering temperature. The heat treatment is preferably performed in an atmosphere containing an inert gas or in a vacuum in20 order to prevent oxidation. [0083] In the vapor diffusion method, a diffusion precursor and a heavy rare earth element supply source are placed in a vacuum furnace, and then the diffusion precursor is25 subjected to a heat treatment at a temperature lower than the sintering temperature in the sintering step S23 in the vacuum furnace to diffuse the heavy rare earth element into the diffusion precursor. In the heat treatment, the heavy rare earth element supply source is turned into a gas phase30 by vacuum heating, and the heavy rare earth element is supplied to the diffusion precursor via the gas phase. Conditions for the heat treatment are a diffusion 42 temperature lower than the sintering temperature and a time within the range of 0.1 hours to 100 hours. The diffusion temperature is, for example, a temperature in the range of 600°C to 900°C, which is lower than the sintering temperature. Further, in the vapor diffusion method,5 unlike the coating diffusion method and the sputtering diffusion method, it is not necessary to adhere the heavy rare earth element supply portion to the diffusion precursor, and the diffusion element adhesion step can be omitted, so that the time of the grain boundary diffusion10 step can be shortened. [0084] Returning to FIG. 7, in the final cooling step S40, the diffusion precursor into which the heavy rare earth element has been diffused in the grain boundary diffusion step is held at a temperature lower than 200°C15 for 0.1 to 5 hours. Thereafter, the diffusion precursor is cooled to room temperature, whereby the rare earth sintered magnet 1 described in the first to third embodiments is formed. In the case of the first embodiment, the rare earth sintered magnet 1 in which the heavy rare earth20 element is present on at least a part of the surface of the main phase 10 is formed, in the case of the second embodiment, the rare earth sintered magnet 1 in which the heavy rare earth element is diffused into the subphase 20 is formed, and in the case of the third embodiment, the25 rare earth sintered magnet 1 is formed in which the heavy rare earth element is diffused so as to selectively surround the outer contour of the Sm enrichment portion 41 of the first subphase 21, and is uniformly diffused into the second subphase 22. The cooling is preferably30 performed in an atmosphere containing an inert gas or in a vacuum in order to prevent oxidation. [0085] As described above, the rare earth sintered 43 magnet 1 having a desired shape is obtained by grain boundary diffusion of the heavy rare earth element into the diffusion precursor having the final shape of the rare earth sintered magnet 1. [0086] As described above, by controlling the5 temperature and time in the sintering step, the aging step, and the sintered body cooling step, the sintered body is repeatedly held in a temperature range in an unstable energy state. As a result, the first main phase 11 consisting of CNd>CPr and the second main phase 1210 consisting of CNdCPr and the second main30 phase 12 consisting of CNdCPr and the second main phase 12 that satisfies CNdCPr and the second main phase 12 that satisfies CNdCPr and the second main phase 12 that satisfies CNdCPr is larger than the number of second main phases 12 that are CNdSNd and CPrSPr. [0118] Next, the results of measurement of the magnetic properties in each sample according to Examples 1 to 8 and10 Comparative Examples 1 to 12 will be described. The shape of each sample that is the subject of magnetic measurement is a block shape having a length, a width, and a height of 7 mm. The first measurement temperature T1 is 23°C, and the second measurement temperature T2 is 200°C. 23°C is15 room temperature. 200°C of the second measurement temperature T2 is a temperature that can occur as an environment in which automobile motors and industrial motors operate. [0119] First, the residual magnetic flux density and the20 coercive force in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 are determined in comparison with Comparative Example 1. When the values of the residual magnetic flux density and the coercive force of each sample at 23°C are within an allowable measurement25 error of 1% compared with the values of Comparative Example 1, the values are rated as “equivalent”. Values of 1% or more higher are rated as “good”, and values of 1% or more lower are rated as “poor”. [0120] Next, the temperature coefficient α of residual30 magnetic flux density is calculated using the residual magnetic flux density at the first measurement temperature T1 of 23°C and the residual magnetic flux density at the 59 second measurement temperature T2 of 200°C. The temperature coefficient β of coercive force is calculated using the coercive force at the first measurement temperature T1 of 23°C and the coercive force at the second measurement temperature T2 of 200°C. The temperature5 coefficient of residual magnetic flux density and the temperature coefficient of coercive force in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 are determined in comparison with Comparative Example 1. When the values of each sample are within an allowable10 measurement error of ±1% compared with the absolute value |α| of the temperature coefficient of residual magnetic flux density and the absolute value |β| of the temperature coefficient of coercive force in the sample of Comparative Example 1, the values are rated as “equivalent”. Values of15 −1% or more lower are rated as “good”, and values of +1% or more higher are rated as “poor”. Because the samples determined to be “good” have a smaller temperature coefficient, it is possible to provide the rare earth sintered magnet 1 having stable magnetic properties even in20 a high temperature environment while preventing degradation of magnetic properties associated with temperature rise. [0121] The results of determination of the residual magnetic flux density, the coercive force, the temperature coefficient of residual magnetic flux density and the25 temperature coefficient of coercive force are shown in Table 3. [0122] Comparative Example 1 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of Nd-Fe-B with the30 production method described in Patent Literature 1 using Nd, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the method described 60 above, due to the absence of Pr, La, and Sm, no core-shell structure is confirmed in the main phase 10, and it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of5 this sample with the method described above shows that the residual magnetic flux density is 1.3 T and the coercive force is 1250 kA/m. The temperature coefficients of residual magnetic flux density and coercive force are |α|=0.191 %/°C and |β|=0.460 %/°C, respectively. These10 values of Comparative Example 1 are used as a reference. [0123] Comparative Example 2 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd,Dy)-Fe-B with the production method described in Patent Literature 1 using15 Nd, Dy, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the method described above, due to the absence of Pr, La, and Sm, no core-shell structure is confirmed in the main phase 10, and it is not confirmed that the concentration of Sm in the20 subphase 20 is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient25 of residual magnetic flux density is “equivalent”, and the temperature coefficient of coercive force is “equivalent”. This result reflects the fact that the coercive force is improved by substituting Dy having high magnetocrystalline anisotropy for a part of Nd. In addition, since the30 magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor 61 does not improve the magnetic properties. [0124] Comparative Example 3 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd,Pr)-Fe-B with the production method described in Patent Literature 1 using5 Nd, Pr, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the method described above, the main phase 10 in which Nd and Pr are provided mixedly is confirmed due to the addition of Pr, but a core-shell structure is not formed. In addition, due10 to the absence of La and Sm, it is also not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic15 flux density is “equivalent”, the coercive force is “good”, the temperature coefficient of residual magnetic flux density is “equivalent”, and the temperature coefficient of coercive force is “poor”. This result reflects the fact that the magnetic anisotropy of the main phase 10 is20 increased and the coercive force is improved by the addition of Pr, but the structure form is not optimal in the main phase 10 and the subphase 20. In addition, since the magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a25 heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0125] Comparative Example 4 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, La, Sm)-Fe-B with the30 production method described in Patent Literature 1 using Nd, La, Sm, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the 62 method described above, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in one subphase 20 along with the segregation of La, but the second subphase 22 does5 not exist. Furthermore, it is also not confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic flux density is10 “equivalent”, the coercive force is “equivalent”, the temperature coefficient of residual magnetic flux density is “good”, and the temperature coefficient of coercive force is “good”. This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase15 20 gives a good result in the temperature coefficient of the magnetic properties, but the magnetic properties at room temperature are not improved, and the structure form is not optimal in the main phase 10 and the subphase 20. In addition, since the magnetic properties depend on the20 structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0126] Comparative Example 5 is a sample of the rare25 earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, La, Sm)-Fe-B with the production method described in Patent Literature 1 using Nd, La, Sm, Fe, and FeB as raw materials. The composition ratio of Nd, La, and Sm is different from that of30 Comparative Example 4. From the observation of the structure form of this sample with the method described above, no core-shell structure is confirmed in the main 63 phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in one subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is also not confirmed that the5 concentration of Sm is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic flux density is “equivalent”, the coercive force is “equivalent”, the10 temperature coefficient of residual magnetic flux density is “good”, and the temperature coefficient of coercive force is “good”. This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 gives a good result in the temperature coefficient of15 the magnetic properties, but the magnetic properties at room temperature are not improved, and the structure form is not optimal in the main phase 10 and the subphase 20: the change in the composition ratio of Nd, La, Sm results in almost the same result as in Comparative Example 4. In20 addition, since the magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties.25 [0127] Comparative Example 6 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, Pr, La, Sm)-Fe-B with the production method described in Patent Literature 1 using Nd, Pr, La, Sm, Fe, and FeB as raw materials. From30 the observation of the structure form of this sample with the method described above, the main phase 10 in which Nd and Pr are provided mixedly is confirmed due to the 64 addition of Pr, but a core-shell structure is not formed. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in one subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is also not confirmed that the5 concentration of Sm is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic flux density is “equivalent”, the coercive force is “good”, the temperature10 coefficient of residual magnetic flux density is “good”, and the temperature coefficient of coercive force is “equivalent”. This result reflects the fact that the addition of Pr increases the magnetic anisotropy of the main phase 10 to improve the coercive force, and the15 presence of La and Sm in the main phase 10 or the subphase 20 improves the temperature coefficient of the magnetic properties, particularly the temperature coefficient of the coercive force, but the structure form is not optimal in the main phase 10 and the subphase 20. In addition, since20 the magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0128] Comparative Example 7 is a sample of the rare25 earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of Nd-Fe-B with the production method including the hot working method described in Patent Literature 2 using Nd, Fe, and FeB as raw materials. From the observation of the structure form30 of this sample with the method described above, due to the absence of Pr, La, and Sm, no core-shell structure is confirmed in the main phase 10, and it is not confirmed 65 that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. However, the refinement of the structure, which is a characteristic of a magnet produced with the hot working method, is confirmed. The evaluation of the magnetic5 properties of this sample with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient of residual magnetic flux density is “equivalent”, and the temperature coefficient of coercive force is “equivalent”.10 This result reflects the decrease in residual magnetic flux density despite the improvement of the coercive force associated with the refinement of the structure through the hot working method. In addition, since the magnetic properties depend on the structure of the diffusion15 precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0129] Comparative Example 8 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused,20 which is prepared in the form of (Nd, Dy)-Fe-B with the production method including the hot working method described in Patent Literature 2 using Nd, Dy, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the method described above, due to25 the absence of Pr, La, and Sm, no core-shell structure is confirmed in the main phase 10, and it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample30 with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient of residual magnetic 66 flux density is “equivalent”, and the temperature coefficient of coercive force is “equivalent”. This indicates that the coercive force is significantly improved by the substitution of Dy having high magnetocrystalline anisotropy for a part of Nd in addition to the manufacture5 with hot working, but the other properties reflect the structure refinement. In addition, since the magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not10 improve the magnetic properties. [0130] Comparative Example 9 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, Pr)-Fe-B with the production method including the hot working method15 described in Patent Literature 2 using Nd, Pr, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the method described above, the core-shell structure is confirmed through hot working in addition to the addition of Pr, but there is only one type20 of main phase 10 having a high Pr concentration in the core portion. In addition, due to the absence of La and Sm, it is also not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic25 properties of this sample with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient of residual magnetic flux density is “equivalent”, and the temperature coefficient of coercive force is “equivalent”.30 This indicates that the coercive force is significantly improved to the level of the rare earth sintered magnet 1 containing Dy due to the formation of the core-shell 67 structure having a high Pr concentration in the core portion, but the other properties reflect the structure refinement. In addition, since the magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element5 into such a diffusion precursor does not improve the magnetic properties. [0131] Comparative Example 10 is a sample of the rare earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, La, Sm)-Fe-B with the10 production method including the hot working method described in Patent Literature 2 using Nd, La, Sm, Fe, and FeB as raw materials. From the observation of the structure form of this sample with the method described above, no core-shell structure is confirmed in the main15 phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in one subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is also not confirmed that the20 concentration of Sm is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient25 of residual magnetic flux density is “good”, and the temperature coefficient of coercive force is “good”. This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 gives a good result in the temperature coefficient of the magnetic properties, but30 the residual magnetic flux density at room temperature is not improved, and the structure form is not optimal in the main phase 10 and the subphase 20. In addition, since the 68 magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0132] Comparative Example 11 is a sample of the rare5 earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, La, Sm)-Fe-B with the production method including the hot working method described in Patent Literature 2 using Nd, La, Sm, Fe, and FeB as raw materials. The composition ratio of Nd, La, and10 Sm is different from that of Comparative Example 10. From the observation of the structure form of this sample with the method described above, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the15 concentration of Sm is segregated in one subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is also not confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic20 properties of this sample with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient of residual magnetic flux density is “good”, and the temperature coefficient of coercive force is “good”. This25 result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 gives a good result in the temperature coefficient of the magnetic properties, but the residual magnetic flux density at room temperature is not improved, and the structure form is not optimal in the30 main phase 10 and the subphase 20. The change in the composition ratio of Nd, La, Sm results in almost the same result as in Comparative Example 10. In addition, since 69 the magnetic properties depend on the structure of the diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0133] Comparative Example 12 is a sample of the rare5 earth sintered magnet 1 in which 0.15at.% Dy is diffused, which is prepared in the form of (Nd, Pr, La, Sm)-Fe-B with the production method including the hot working method described in Patent Literature 2 using Nd, Pr, La, Sm, Fe, and FeB as raw materials. From the observation of the10 structure form of this sample with the method described above, the core-shell structure is confirmed through hot working in addition to the addition of Pr, but there is only one type of main phase 10 having a high Pr concentration in the core portion. In addition, due to the15 addition of La and Sm, the concentration of Sm is segregated in one subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is also not confirmed that the concentration of Sm is higher in the first subphase 21 than20 in the second subphase 22. The evaluation of the magnetic properties of this sample with the method described above shows that the residual magnetic flux density is “poor”, the coercive force is “good”, the temperature coefficient of residual magnetic flux density is “good”, and the25 temperature coefficient of coercive force is “good”. This indicates that the coercive force is significantly improved to the level of the rare earth sintered magnet 1 containing Dy due to the formation of the core-shell structure having a high Pr concentration in the core portion, and the30 presence of La and Sm in the main phase 10 or the subphase 20 improves the temperature coefficient of the magnetic properties, particularly the temperature coefficient of the 70 coercive force. However, the result also reflects the fact that the residual magnetic flux density at room temperature is not improved, and the structure form is not optimal in the main phase 10 and the subphase 20. In addition, since the magnetic properties depend on the structure of the5 diffusion precursor as a base material, diffusing Dy as a heavy rare earth element into such a diffusion precursor does not improve the magnetic properties. [0134] The samples of Examples 1 to 8 are the rare earth sintered magnet 1 including the main phase 10 that10 satisfies a general formula (Nd, Pr, R)-Fe-B, where R is one or more rare earth elements selected excluding Nd and Pr, the main phase 10 containing crystal grains based on an Nd2Fe14B crystal structure, wherein the main phase 10 includes the core portions 11c and 12c and the shell15 portions 11s and 12s covering the core portions 11c and 12c, the main phase 10 includes the first main phase 11 that satisfies CNd>CPr and the second main phase 12 that satisfies CNdCPr and a second main phase that satisfies CNdCPr and a second main phase that satisfies CNdSNd and CPrSPr, where SNd is concentration of Nd in the shell portion and SPr is concentration of Pr in the shell portion.15 [Claim 5] The rare earth sintered magnet according to claim 1, wherein given that R is La and/or Sm, the subphase includes a first subphase that is crystalline and has a main component20 based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and a second subphase that is crystalline and has a main component represented by (Nd, Pr, La)-O, and concentration of Sm is higher in the first subphase than in the second subphase.25 [Claim 6] The rare earth sintered magnet according to claim 2, wherein given that R is La and/or Sm, the subphase includes a first subphase that is crystalline and has a main component30 based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and a second subphase that is crystalline and has a main component represented by (Nd, Pr, La)-O, and 75 the first subphase forms an Sm enrichment portion having a higher concentration of Sm than the second subphase. [Claim 7] The rare earth sintered magnet according to claim5 6, wherein the heavy rare earth element is present so as to surround an outer contour of the Sm enrichment portion in the first subphase. [Claim 8] A method for producing the rare earth sintered10 magnet according to any one of claims 1 to 7, the method comprising: a rare earth sintered magnet alloy production step of producing a rare earth sintered magnet alloy to be a raw material of a diffusion precursor before the heavy rare15 earth element is diffused into the rare earth sintered magnet; a diffusion precursor production step of producing the diffusion precursor; a diffusion step of diffusing the heavy rare earth20 element into the diffusion precursor; and a cooling step of cooling the diffusion precursor in which the heavy rare earth element is diffused, wherein the rare earth sintered magnet alloy production step includes:25 a melting step of melting a raw material of a rare earth sintered magnet alloy containing an element constituting the diffusion precursor; a primary alloy cooling step of cooling the raw material molten in the melting step to obtain a solidified30 alloy; and a secondary alloy cooling step of further cooling the solidified alloy to obtain a rare earth sintered magnet 76 alloy, the diffusion precursor production step includes: a pulverizing step of pulverizing the rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B; a molding step of preparing a molded body by molding5 powder of the rare earth sintered magnet alloy pulverized in the pulverizing step; a sintering step of obtaining a sintered body by sintering the molded body at a sintering temperature that is a predetermined temperature;10 a primary aging step of holding the sintered body at a primary aging temperature that is a temperature lower than the sintering temperature; a secondary aging step of holding the sintered body held in the primary aging step at a secondary aging15 temperature that is a temperature lower than the primary aging temperature; a tertiary aging step of holding the sintered body held in the secondary aging step again at the primary aging temperature;20 a quaternary aging step of holding the sintered body held in the tertiary aging step again at the secondary aging temperature; and a sintered body cooling step of cooling the sintered body held in the quaternary aging step to obtain the25 diffusion precursor, and in the diffusion step, the diffusion precursor is subjected to heat treatment at a temperature lower than the sintering temperature under a condition that the diffusion precursor and the heavy rare earth element are present.30 [Claim 9] A rotor comprising: a rotor core; and 77 the rare earth sintered magnet according to any one of claims 1 to 7 provided in the rotor core. [Claim 10] A rotary machine comprising: the rotor according to claim 9; and5 an annular stator facing the rotor and including, on an inner surface on a side where the rotor is placed, windings provided on teeth protruding toward the rotor.