Magnetic material and method for manufacturing sintered magnet

Abstract

This magnetic material is an Sm-Fe-N-based magnetic material having a main phase with a Th2Zn17-type or Th2Ni17-type crystal structure, wherein the main phase has a molar formula (Sm(1-a-b)αaβb)6Fe51N9, where a is 0.01-0.20, and b is 0.01-0.20.

Description

Magnetic material and method for manufacturing sintered magnet

[0001] The present disclosure relates to a Sm—Fe—N based magnetic material and a method for producing a sintered magnet. ２ Zn １７ Type or Th ２ Ni １７ The present invention relates to a Sm—Fe—N based magnetic material having a main phase with a crystalline structure of this type, and a method for producing a sintered magnet.

[0002] Although Sm-Co based magnetic materials and Nd-Fe-B based magnetic materials have been put to practical use as high performance magnetic materials, other magnetic materials have been investigated in recent years. ２ Zn １７ Type or Th ２ Ni １７ Sm--Fe--N based magnetic materials having a main phase with a crystal structure of this type have been investigated.

[0003] Sm-Fe-N magnetic materials are ２ Zn １７ Type or Th ２ Ni １７ The main phase has a crystal structure of the type described above. This main phase is believed to be formed by introducing nitrogen interstitially into a Sm--Fe crystal phase.

[0004] Patent Document 1 discloses a method for producing an Sm—Fe—N based magnetic material in which rare earth elements including La and Ce are substituted at the Sm site and one or more elements other than rare earth elements including Co and Ni are contained at the Fe site.

[0005] Japanese Patent Application Laid-Open No. 2022-53187

[0006] The magnetic properties of Sm—Fe—N magnetic materials, particularly saturation magnetization, are achieved by selecting Sm as a rare earth element. As Sm—Fe—N magnetic materials become more widespread, the price of Sm, a major element in Sm—Fe—N magnetic materials, is expected to rise. For this reason, there is a need for an Sm—Fe—N magnetic material and a method for producing the same that improves saturation magnetization even when the amount of Sm used is reduced, or that suppresses the decrease in saturation magnetization to a practically acceptable level.

[0007] The present disclosure has been made in view of the above, and aims to provide an Sm—Fe—N-based magnetic material that can improve saturation magnetization even when the amount of Sm used is reduced, or that can suppress the decrease in saturation magnetization to a practically negligible range.

[0008] In order to solve the above-mentioned problems and achieve the object, the magnetic material according to the present disclosure comprises: ２ Zn １７ Type or Th ２ Ni １７ The magnetic material of the Sm-Fe-N system has a main phase having a crystal structure of the type, and the main phase is represented by the molar ratio formula (Sm （１－ａ－ｂ） α ａ β ｂ ) ６ Fe ５１ N ９ where a is 0.01 or more and 0.20 or less, and b is 0.01 or more and 0.20 or less.

[0009] The magnetic material according to the present disclosure is a Sm—Fe—N-based magnetic material, and exhibits the effect of being able to improve saturation magnetization even when the amount of Sm used is reduced, or being able to suppress the decrease in saturation magnetization to a range that does not pose a practical problem.

[0010] Figure showing the calculation results of the binding energy and intrinsic coercivity at 300 K when the elements La, Eu, and Gd are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. Figure showing the calculation results of the binding energy and intrinsic coercivity at 800 K when the elements La, Eu, and Gd are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. Relationship α between intrinsic coercivity and remanence when two elements are substituted at the Sm substitution site in an Sm-Fe-N magnetic material ａ Figure 1 shows the relationship between the intrinsic coercivity and residual magnetic flux density when two elements are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. ａ Figure 2 shows the relationship between intrinsic coercivity and residual magnetic flux density when two elements are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. ｂ Figure 1 shows the relationship between intrinsic coercivity and residual magnetic flux density when two elements are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. ｂFigure 2 shows

[0011] Hereinafter, a magnetic material and a method for manufacturing a sintered magnet according to an embodiment will be described in detail with reference to the drawings.

[0012] The Sm—Fe—N magnetic material according to the embodiment is a material containing Th ２ Zn １７ Type or Th ２ Ni １７ The main phase has a crystal structure of the type Sm, Fe, iron, N, nitrogen, Th, thorium, Zn, and Ni. The main phase exhibits magnetism by being nitrided. When the main phase is composed of Sm, Fe, and N, the most typical composition of the main phase is Sm. ２ -Fe １７ -N ３ Sm ２ -Fe １７ -N ３ The phase is Sm ２ -Fe １７ It is obtained by nitriding the Sm phase. ２ -Fe １７ -N ３ The phase is Sm ２ -Fe １７ The phase has a crystal structure in which nitrogen is interstitially introduced.

[0013] The magnetic properties of a material are determined by the crystal structure and the atomic positions within the crystal. In this embodiment, the basic crystal structure is the Sm ２ -Fe １７ The basic crystal structure in this embodiment is determined by the Th described in "Masato Sagawa, Masaaki Hamano, Makoto Hirabayashi, "Permanent Magnets - Materials Science and Applications", Agne Technology Center, p. 223" ２ Zn １７ Type crystal structure, or Th ２ Ni １７It has a crystalline structure in which layers of Sm and Fe and layers of only Fe are stacked alternately. In this basic crystalline structure, one of La, Eu, and Gd is selectively placed as a substitution element at the position of Sm in the basic crystal lattice. La is lanthanum, Eu is eurobium, and Gd is gadolinium. The substitution site is determined by the energy value after the stabilization energy due to substitution is calculated by band calculation and Heisenberg molecular field approximation.

[0014] First, we will explain how to calculate the stabilization energy in La. The stabilization energy is calculated by ６ Fe ５１ N ９ Using a crystal cell, (Sm ６ La １ ) Fe ５１ N ９ +Sm and Sm ６ (Fe ５０ La １ ) N ９ +Fe. In other words, La is likely to be substituted at the atomic site with the smallest energy. In this calculation, when La is substituted for the original atom, Th ２ Zn １７ It is assumed that the lattice constants in the type crystal structure do not change with the atomic radii.

[0015] Fig. 1 is a diagram showing the calculation results of the binding energy and intrinsic coercivity at 300 K when the elements La, Eu, and Gd are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. Fig. 2 is a diagram showing the calculation results of the binding energy and intrinsic coercivity at 800 K when the elements La, Eu, and Gd are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. In Figs. 1 and 2, the binding energy is expressed as BE, and the intrinsic coercivity is expressed as iHc. Both Figs. 1 and 2 show the calculation results when one element of La, Eu, and Gd is substituted at the Sm substitution site.

[0016] The magnetic material used in this calculation is composed of a main phase, a subphase, and an interface between the main phase and the subphase. ２ T １７ Type Sm ２ Fe １７ N ３ The crystal is a rhombohedral crystal with 66 atoms in the unit cell. R is a rare earth element, and T is a transition metal. The subphase is R ２ T １７ Type (Sm １－ａ－ｂ R ａ R' ｂ ) ２ (Fe １－ｃ－ｄ T ｃ T' ｄ ) １７ N ｘ A supercell containing 4224 atoms was used. R' is a rare earth element, and T' is a transition metal. Each of R and R' is randomly arranged at the Sm atomic site corresponding to the set composition, and each of T and T' is randomly arranged at the Fe atomic site corresponding to the set composition.

[0017] The structure of the main phase was determined by the measured crystal structure, while the structure of the subphase was optimized using tight-binding band calculations. The structure of the interface between the main phase and the subphase was optimized by perturbation analysis based on tight-binding band calculations of the interfacial interactions. A random ensemble average was used for calculations involving the subphase. The tight-binding band calculations used calculation parameters that were fitted to reproduce the band structure obtained from first-principles calculations.

[0018] The atomic magnetic moment, exchange coupling constant, and magnetic anisotropy constant in the Heisenberg model were determined using the localized magnetic orbitals described in Japanese Patent No. 4357847. From these physical property values, a lattice spin model consisting of exchange interaction energy, magnetic anisotropy energy, and Zeeman energy was determined, and the remanence and intrinsic coercivity were calculated by simulating the magnetization reversal behavior using the Landau-Lifshitz-Gilbert equation.

[0019] Similarly, the calculation results when two elements are substituted at the Sm site are shown in Figures 3 to 6. Figure 3 shows the relationship α between the intrinsic coercivity and the residual magnetic flux density when two elements are substituted at the Sm substitution site in an Sm-Fe-N magnetic material. ａ 4 shows the relationship α between the intrinsic coercivity and the residual magnetic flux density when two elements are substituted at the Sm substitution site in a Sm—Fe—N based magnetic material. ａ 3 and 4, the intrinsic coercivity is expressed as iHc, and the remanence is expressed as Br. FIG. 3 shows the relationship between the intrinsic coercivity and the remanence when the elements are arranged by name, and FIG. 4 shows the molar concentration ratio of the elements arranged in FIG. 3. The temperature when sintering the magnetic powder is in the range of 300K to 800K.

[0020] FIG. 5 shows the relationship β between the intrinsic coercivity and the residual magnetic flux density when two elements are substituted at the Sm substitution site in a Sm—Fe—N based magnetic material. ｂ 6 shows the relationship β between the intrinsic coercivity and the residual magnetic flux density when two elements are substituted at the Sm substitution site in a Sm—Fe—N based magnetic material. ｂ 5 and 6, the intrinsic coercivity is expressed as iHc, and the remanence is expressed as Br. FIG. 5 shows the relationship between the intrinsic coercivity and the remanence when arranged by element name, and FIG. 6 shows the molar concentration ratio of the elements arranged in FIG. 5. The temperature when sintering the magnetic powder is in the range of 300K to 800K.

[0021] The magnetic properties of a magnet are primarily expressed by its intrinsic coercivity and remanent magnetic flux density, and while it is desirable for both to be high, the intrinsic coercivity and remanent magnetic flux density cancel each other out, making it difficult to increase both. From the results of calculations, it has been determined that the areas surrounded by ellipses in Figures 3 to 6 are areas where both the intrinsic coercivity and remanent magnetic flux density are relatively high, and are within a range that can be used in practical applications.

[0022] From the calculation results, (Sm （１－ａ－ｂ） α ａ β ｂ ) ６ Fe ５１ N９ In Sm-based magnetic materials, when a is 0.01 or more and 0.20 or less and b is 0.01 or more and 0.20 or less, both the intrinsic coercivity and the remanence are relatively high, and this is within a range that can be used in practice. Furthermore, it is preferable that α is La and β is Eu or Gd, or α is Eu and β is Gd. The Sm—Fe—N-based magnetic material according to the embodiment can improve saturation magnetization or suppress the decrease in saturation magnetization to a practically acceptable range, even if part of the Sm is substituted with La, Eu, or Gd to reduce the amount of Sm used. Furthermore, according to the embodiment, it is possible to provide an Sm—Fe—N-based magnetic material that can improve saturation magnetization or suppress the decrease in saturation magnetization to a practically acceptable range, even if the amount of Sm used is reduced by nitriding a precursor of the magnetic material in which part of the Sm is substituted with La, Eu, or Gd.

[0023] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

Claims

1. Th ２ Zn １７ Type or Th ２ Ni １７ A Sm—Fe—N based magnetic material having a main phase with a crystal structure of the type, wherein the main phase is represented by a molar ratio formula (Sm （１－ａ－ｂ） α ａ β ｂ ) ６ Fe ５１ N ９ a is 0.01 or more and 0.20 or less, and b is 0.01 or more and 0.20 or less.

2. The magnetic material according to claim 1, wherein α is La, and β is Eu or Gd.

3. The magnetic material according to claim 1, wherein α is Eu and β is Gd.

4. A method for producing a sintered magnet using the magnetic material according to any one of claims 1 to 3, characterized in that the temperature for producing the sintered magnet using the magnetic material is in the range of 300K to 800K.

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