JP2023125603A - MANUFACTURING METHOD FOR FeCoV-BASED ALLOY-BASED HARD MAGNETIC MATERIAL - Google Patents

Abstract

To provide a manufacturing method for a FeCoV-based alloy-based hard magnetic material with which a FeCoV-based alloy-based hard magnetic material composed of a tetragonal FeCoV-based alloy capable of developing excellent uniaxial magnetic anisotropy with a desired thickness and size can be obtained.SOLUTION: A manufacturing method for a FeCoV-based alloy-based hard magnetic material composed of a tetragonal FeCoV-based alloy having a composition represented by the following general formula (1) has the following steps (I) and (II) in order. (Fe1-xCox)1-y-zVyNz ... (1) [In formula (1), x is a real number satisfying 0.40≤x≤0.70, y is a real number satisfying 0<y≤0.15, and z is a real number satisfying 0<z≤0.15.] Step (I): a step for rolling and processing a base metal including FeCoV alloy to obtain a rolled compact. Step (II): a step for gas nitriding the rolled compact.SELECTED DRAWING: None

Description

The present invention relates to a method for manufacturing a FeCoV-based alloy hard magnetic material.

Hard magnetic materials with high coercive force are used for permanent magnets, magnetic recording media, and the like. In order to improve the performance of hard magnetic materials, it is necessary to increase the uniaxial magnetic anisotropy (Ku) of the hard magnetic materials.

Conventionally, Fe(NdDy)B containing rare earth elements Nd and Dy has been mainly used as a hard magnetic material in high-performance permanent magnets. Further, in magnetic recording media, CoCrPt and FePt containing the noble metal Pt are mainly used as hard magnetic materials. From the viewpoint of stable supply of resources, it is desired to reduce the amount of these rare earth elements and precious metals used.

In response to such needs, for example, Patent Document 1 proposes a hard magnetic material that can exhibit good uniaxial magnetic anisotropy without using rare earth elements or noble metal elements, and a method for manufacturing the same. In particular, Patent Document 1 discloses a method for manufacturing a FeCoV-based alloy hard magnetic film using epitaxial growth.

Patent No. 6923185

Furthermore, when it is assumed that a magnetic material is generally used as a permanent magnet or the like, it is required that the magnetic material has a certain thickness and size from the viewpoint of ease of handling and practicality. However, when epitaxial growth is used, there is little freedom in designing the thickness and size of the FeCoV-based alloy hard magnetic film, and it has been particularly difficult to increase the thickness and size.

Therefore, the present invention aims to obtain a FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy that can exhibit good uniaxial magnetic anisotropy with a desired thickness and size. The purpose of the present invention is to provide a method for manufacturing a magnetic material.

The gist of the present invention is as follows.
[1] A method for producing a FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy having a composition represented by the following general formula (1),
The tetragonal FeCoV-based alloy has a tetragonal strain c/a of more than 1.02 and no more than 1.30,
A method for producing a FeCoV-based alloy hard magnetic material, comprising the following steps (I) and (II) in order.
(Fe _1-x Co _x ) _1-y-z V _y N _z ...(1)
[In formula (1), x is a real number that satisfies 0.40≦x≦0.70, y is a real number that satisfies 0<y≦0.15, and z satisfies 0<z≦0.15. Represents a real number. ]
Step (I): Step of rolling a base material made of FeCoV alloy to obtain a rolled body Step (II): Step of gas nitriding the rolled body [2] Composition represented by the following general formula (1) A FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy having
The tetragonal FeCoV-based alloy has a tetragonal strain c/a of more than 1.02 and no more than 1.30,
A FeCoV-based alloy hard magnetic material having a thickness of more than 0.1 μm and less than 200 μm.
(Fe _1-x Co _x ) _1-y-z V _y N _z ...(1)
[In formula (1), x is a real number that satisfies 0.40≦x≦0.70, y is a real number that satisfies 0<y≦0.15, and z satisfies 0<z≦0.15. Represents a real number. ]

According to the present invention, by combining rolling treatment (the above step (I)) and gas nitriding treatment (the above step (II)), it is possible to express good uniaxial magnetic anisotropy with a desired thickness and size. It is possible to provide a method for producing a FeCoV-based alloy hard magnetic material, which yields a FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy that is capable of .

FIG. 1 is an X-ray diffraction (XRD) spectrum of the FeCoV-based alloy produced in Example 1. FIG. 2 is an XRD spectrum of the FeCoV-based alloy produced in Comparative Example 1. FIG. 3 is an XRD spectrum of the FeCoV alloy body produced in Comparative Example 2. FIG. 4 shows the results of elemental analysis by energy dispersive X-ray spectroscopy (TEM-EDS) performed on the FeCoV-based alloy body produced in Example 1 through transmission electron microscopy. Fig. 4(a) is a photograph of elemental mapping, and Fig. 4(b) is the result of spectrum analysis of a region approximately 10 μm from the surface of the FeCoV-based alloy body (region surrounded by a square in Fig. 4(a)). FIG. 5 shows the results of scanning transmission electron microscopy (STEM) performed on the FeCoV-based alloy body produced in Example 1. In particular, FIG. Figure 5(b) is the electron diffraction pattern of the FeCo (100) plane, and Figure 5(c) is the image intensity profile of the a-axis and c-axis, and the interatomic distance and This is the result of calculating the tetragonal strain c/a. FIG. 6 is a graph showing the magnetization curve (magnetization M−magnetic field H) of the FeCoV-based alloy produced in Example 1. FIG. 7 is a graph showing the magnetization curve (magnetization M−magnetic field H) of the FeCoV-based alloy produced in Comparative Example 1. FIG. 8 is a graph showing the magnetization curve (magnetization M−magnetic field H) of the FeCoV alloy produced in Comparative Example 2.

Embodiments of the method for manufacturing a FeCoV-based alloy hard magnetic material according to the present invention will be described in detail below.
In addition, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

<Method for producing FeCoV-based alloy hard magnetic material>
The method for producing a FeCoV-based alloy hard magnetic material of the present invention is a method for producing a FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy having a composition represented by the following general formula (1), comprising: The tetragonal FeCoV-based alloy has a tetragonal strain c/a of more than 1.02 and 1.30 or less, and includes the following steps (I) and (II) in order.
(Fe _1-x Co _x ) _1-y-z V _y N _z ...(1)
[In formula (1), x is a real number that satisfies 0.40≦x≦0.70, y is a real number that satisfies 0<y≦0.15, and z satisfies 0<z≦0.15. Represents a real number. ]
Step (I): A step of rolling a base material made of an FeCoV alloy to obtain a rolled body. Step (II): A step of gas nitriding the rolled body.

According to the method for manufacturing a FeCoV-based alloy hard magnetic material of the present invention (hereinafter sometimes simply referred to as the "manufacturing method of the present invention"), good uniaxial magnetic anisotropy can be achieved with desired thickness and size. A FeCoV-based alloy-based hard magnetic material made of a tetragonal FeCoV-based alloy that is capable of developing is obtained.

The detailed reason why such an effect is obtained is not clear, but it is inferred that one of the reasons is the following mechanism.
First, by performing rolling treatment (step (I) above) on the base material FeCoV alloy, the external force caused by rolling causes (1) the crystal grains of the FeCoV alloy to become flattened, (2) the FeCoV alloy to (3) The crystal grains are oriented in a specific direction in the above (1) and (2) processes, and (4) FeCoV alloy. It is thought that physical strain is accumulated in the crystal lattice of the and V phases. That is, in the rolled body obtained by step (I), it is considered that the above (1) to (4) act in a complex manner.
As a result, in the next step, by further gas nitriding the rolled body (step (II) above), nitrogen (N) is effectively introduced into the crystal lattice of the FeCoV alloy and the V phase, resulting in a tetragonal crystal structure. It is believed that a FeCoV-based alloy hard magnetic material with a stabilized (bct) structure can be obtained.
Furthermore, in the manufacturing method of the present invention, by combining the rolling treatment and the gas nitriding treatment, it is considered that it becomes relatively easy to control the thickness, etc. of the FeCoV-based alloy hard magnetic material, which was difficult with epitaxial growth. That is, according to the manufacturing method of the present invention, by adjusting the thickness and size of the rolled body through the rolling treatment in step (I), the thickness and size of the FeCoV-based alloy hard magnetic material finally obtained can be adjusted. can be controlled in advance. According to the manufacturing method of the present invention, it is possible to obtain a relatively thick (for example, more than 0.1 μm, preferably 1 μm or more) FeCoV-based alloy-based hard magnetic material.

[FeCoV-based alloy hard magnetic material]
The FeCoV-based alloy hard magnetic material obtained by the production method of the present invention (hereinafter sometimes simply referred to as "FeCoV-based alloy hard magnetic material of the present invention") has a composition represented by the following general formula (1). The tetragonal FeCoV-based alloy has a tetragonal strain c/a of more than 1.02 and 1.30 or less.
(Fe _1-x Co _x ) _1-y-z V _y N _z ...(1)
[In formula (1), x is a real number that satisfies 0.40≦x≦0.70, y is a real number that satisfies 0<y≦0.15, and z satisfies 0<z≦0.15. Represents a real number. ]

The FeCoV-based alloy-based hard magnetic material of the present invention has tetragonal strain. Tetragonal strain is expressed as the ratio (c/a) of the length (c) in the c-axis direction of the tetragonal crystal lattice to the length (a) in the a-axis direction. The crystal structure of the FeCoV-based alloy is a body-centered cubic (bcc) structure in an equilibrium state, but when strain is introduced, the crystal structure changes to a body-centered tetragonal (bct) structure, thereby expressing uniaxial magnetic anisotropy. Note that tetragonal crystal in this specification refers to body-centered tetragonal crystal (BCT).

In the FeCoV-based alloy hard magnetic material of the present invention, the tetragonal strain c/a is more than 1.02 and 1.30 or less, preferably 1.05 or more, and preferably 1.25 or less, More preferably it is 1.20 or less. When the tetragonal strain c/a is within the above range, it becomes possible to increase the uniaxial magnetic anisotropy of the FeCoV-based alloy hard magnetic material.
In particular, in the FeCoV-based alloy-based hard magnetic material of the present invention, it is believed that by containing a light element such as N (nitrogen) in the FeCoV alloy composition, the tetragonal structure is stabilized and the uniaxial magnetic anisotropy is improved. It will be done.
Note that the tetragonal strain c/a can be measured by the method described in Examples.

In the above general formula (1), x is 0.40 or more and 0.70 or less, preferably 0.45 or more, more preferably 0.50 or more, and preferably 0.65 or less, more preferably 0.60. It is as follows. When x is within the above range, it becomes possible to further enhance the uniaxial magnetic anisotropy of the FeCoV-based alloy hard magnetic material.

In the above general formula (1), y is greater than 0 and less than or equal to 0.15, preferably greater than or equal to 0.01, more preferably greater than or equal to 0.04, even more preferably greater than or equal to 0.08, and preferably greater than or equal to 0. .13 or less, more preferably 0.11 or less. When y is within the above range, it becomes possible to further enhance the uniaxial magnetic anisotropy of the FeCoV-based alloy hard magnetic material.

In the above general formula (1), z is greater than 0 and less than or equal to 0.15, preferably greater than or equal to 0.005, more preferably greater than or equal to 0.01, still more preferably greater than or equal to 0.02, and preferably greater than or equal to 0.005. It is 10 or less, more preferably 0.07 or less, even more preferably 0.05 or less. When z is within the above range, it becomes possible to further enhance the uniaxial magnetic anisotropy.

The shape of the FeCoV-based alloy hard magnetic material of the present invention is not particularly limited, and can have any desired shape. In particular, in step (I) described below, the shape of the FeCoV-based alloy hard magnetic material can be freely selected by rolling the rolled body into a desired shape.

In particular, the thickness (length perpendicular to the rolling direction) of the FeCoV-based alloy hard magnetic material of the present invention is, for example, more than 0.1 μm, and from the viewpoint of good handling, preferably 1 μm or more, more preferably is 10 μm or more. According to the manufacturing method of the present invention, a relatively thick FeCoV-based alloy-based hard magnetic material can be obtained. Note that the upper limit of the thickness of the FeCoV-based alloy hard magnetic material is not particularly limited, but from the viewpoint of ease of gas nitriding treatment, especially from the viewpoint of easy introduction of N into the crystal lattice of the FeCoV alloy and the V phase, Preferably it is 200 μm or less, more preferably 100 μm or less. Specifically, the thickness of the FeCoV-based alloy hard magnetic material is preferably more than 0.1 μm and less than 200 μm, more preferably 1 μm and more than 200 μm, even more preferably 10 μm and less than 200 μm, even more preferably 10 μm and less than 100 μm. It is.

In addition, for example, when the FeCoV-based alloy hard magnetic material is plate-shaped (including foil-shaped), its size can be adjusted as appropriate, taking into account the size of the manufacturing equipment, the ease of handling the rolled product, etc. Specifically, the length of the short side (the shorter of the two sides perpendicular to the thickness direction) of the FeCoV-based alloy hard magnetic material can be, for example, 1 mm or more and 5000 mm or less, preferably The length is 1 mm or more and 1000 mm or less, more preferably 10 mm or more and 100 mm or less. According to the manufacturing method of the present invention, it is believed that relatively large FeCoV-based alloy hard magnetic bodies can also be manufactured.

As described above, according to the present invention, the shape of the FeCoV-based alloy hard magnetic material can be designed relatively freely. It becomes possible to realize the body.
Specifically, according to the present invention, there is provided a FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy having a composition represented by the above general formula (1), A FeCoV-based alloy-based hard magnetic material having a strain c/a of more than 1.02 and less than 1.30 and a thickness of more than 0.1 μm and less than 200 μm can be obtained.
It has been difficult to manufacture such a FeCoV-based alloy hard magnetic material using the conventional manufacturing method of FeCoV-based alloy hard magnetic material using epitaxial growth. Furthermore, a FeCoV-based alloy-based hard magnetic material having the above-mentioned predetermined crystal structure and having the above-mentioned thickness is not yet known.

[Method for producing FeCoV-based alloy hard magnetic material]
The method for producing a FeCoV-based alloy hard magnetic material of the present invention includes the following steps (I) and (II) in this order.
Step (I): A step of rolling a base material made of an FeCoV alloy to obtain a rolled body. Step (II): A step of gas nitriding the rolled body.

(Step (I))
Step (I) is a step of rolling a base material made of an FeCoV alloy to obtain a rolled body.

In the present invention, the rolling process applies external force due to rolling to the base material made of the FeCoV alloy, thereby making it easier to perform gas nitriding treatment in the subsequent process (making it easier for N to enter into the crystal lattice of the FeCoV alloy and the V phase). ), this is a treatment for improving the orientation of crystal grains. Specifically, we speculate as follows.

By performing rolling treatment on the base material FeCoV alloy, the external force caused by rolling (1) makes the crystal grains of the FeCoV alloy flat, and (2) contains a large amount of V in contact with the crystal grains of the FeCoV alloy. Flat crystal grains (V phase) are precipitated, (3) the crystal direction of each crystal grain is oriented in a specific direction in the above (1) and (2) processes, and (4) FeCoV alloy and V phase crystals are formed. It is thought that physical strain accumulates in the lattice.
In the present invention, due to the combined effects of (1) to (4) above, when the rolled body is subjected to gas nitriding treatment in step (II), which is a subsequent step, N is incorporated into the crystal lattice of the FeCoV alloy and the V phase. It is thought that it will be easier to enter. As a result, it is thought that in the resulting FeCoV-based alloy, the tetragonal structure is stabilized and the uniaxial magnetic anisotropy is improved.
Furthermore, the simply cast alloy body (base material) is a polycrystalline body, and the axial directions of the crystals are oriented in many directions. On the other hand, in a rolled body obtained by rolling a base material, such as the rolled body obtained in this step, the axial direction of the crystals is oriented in a specific direction. Therefore, when the rolled body is subjected to gas nitriding treatment in step (II), which is a subsequent step, it is considered that a FeCoV-based alloy-based hard magnetic material with excellent orientation can be obtained.

Further, in the present invention, the rolling treatment is also a treatment for adjusting the shape (particularly the thickness and size) of the rolled body, and by extension, the FeCoV-based alloy hard magnetic material, to a desired shape.
The FeCoV-based alloy hard magnetic material of the present invention is obtained by subjecting the rolled body obtained in this step to gas nitriding treatment in step (II). Therefore, the shape of the rolled body obtained in this step and the shape of the FeCoV-based alloy hard magnetic material obtained in step (II) are substantially the same. That is, in this step, by producing a rolled body having a desired shape, the shape of the FeCoV-based alloy hard magnetic material can be easily controlled.

The base material is made of a FeCoV alloy, specifically a FeCoV alloy having a composition represented by the following general formula (2).
(Fe _1-x Co _x ) _1-y V _y ...(2)
[In formula (2), x is a real number that satisfies 0.40≦x≦0.70, and y represents a real number that satisfies 0<y≦0.15. ]
Note that the preferred ranges of x and y in the above general formula (2) are the same as in the above general formula (1).

The method for obtaining the base material is not particularly limited, and it can be obtained by any known method, and specific examples include casting, arc melting, ball milling, powder sintering, and high-density molding. In particular, the base material used in this step is preferably manufactured by a casting method, which is a common method for manufacturing FeCoV alloys. Furthermore, if necessary, a homogenization treatment or the like may be performed by a known method as a pretreatment for the rolling treatment.

The shape of the base material is not particularly limited, but from the viewpoint of ease of handling and rolling processing, if it is plate-shaped, its thickness (length in the direction perpendicular to the plate surface, relative to the direction of rolling processing) The vertical length) is preferably 0.1 mm or more and 2.0 mm or less, more preferably 0.2 mm or more and 1.0 mm or less. In addition, when the base material is plate-shaped, its size is not particularly limited, but from the viewpoint of handling, the area of the plate surface is, for example, 10 mm ² or more and 1000 mm ² or less, preferably 20 mm ² or more and 500 mm ² or less, Preferably it is 50 mm ² or more and 200 mm ² or less.

The rolling treatment is not particularly limited and can be performed by a general method, preferably one or more rolling treatments selected from the group consisting of cold rolling and hot rolling, more preferably cold rolling. It is. Note that, if necessary, annealing treatment may be performed before the rolling treatment.

The shape of the rolled body is not particularly limited, and can be any desired shape depending on the use of the FeCoV-based alloy hard magnetic material.
As mentioned above, the FeCoV-based alloy-based hard magnetic material of the present invention is obtained by subjecting the rolled body obtained in this step to gas nitriding treatment in step (II). The shape of the rolled body and the shape of the FeCoV-based alloy hard magnetic material obtained in step (II) are substantially the same.
Therefore, the preferred range of the shape of the rolled body is the same as the preferred range of the FeCoV-based alloy hard magnetic material described above. For example, the thickness of the rolled body is preferably more than 0.1 μm and less than 200 μm.

The processing conditions for the rolling treatment are not particularly limited, and known conditions can be appropriately selected. Specifically, the following conditions may be mentioned.
The number of rolling treatments (number of passes) is not particularly limited, but from the viewpoint of increasing the effect of gas nitriding treatment in step (II), which is a subsequent step, due to the combined effects of (1) to (4) above, and orientation. From the viewpoint of obtaining a FeCoV-based alloy-based hard magnetic material with excellent properties, it is preferably repeated 2 times or more, more preferably 5 times or more, still more preferably 10 times or more, and even more preferably 15 times or more. It is thought that by repeating the rolling process, the effects of rolling (1) to (4) above can be further enhanced. The upper limit of the number of times of rolling treatment is not particularly limited, but is, for example, 50 times or less, preferably 40 times or less from the viewpoint of workability, and more preferably 30 times or less.

Further, the rolling direction is not particularly limited, but from the viewpoint of improving the crystal orientation of the FeCoV alloy, it is preferable to roll in a certain direction.
Further, the rolled body may be cut into small pieces as necessary, and the small pieces may be stacked and rolled repeatedly. In this case, it is considered that the effects of rolling (1) to (4) above can be further enhanced.

(Step (II))
Step (II) is a step of gas nitriding the rolled body.

Gas nitriding is a heat treatment process in which nitrogen atoms (N) are permeated and diffused into the rolled body by heat treating the rolled body in a nitriding atmosphere.

As mentioned above, in the rolled product obtained by step (I), it is thought that the effects of the rolling described in (1) to (4) act in a complex manner. As a result, by gas nitriding the rolled body in step (II), N easily enters the crystal lattice of the FeCoV alloy and the V phase, and the resulting FeCoV-based alloy has a tetragonal structure. It is believed that this stabilizes the uniaxial magnetic anisotropy and improves the uniaxial magnetic anisotropy. In addition, in the present manufacturing method, in step (I), the rolled body that has been rolled into a desired shape in advance is subjected to gas nitriding treatment to form a FeCoV-based alloy made of a tetragonal FeCoV-based alloy using epitaxial growth. Compared to the case of producing a FeCoV-based hard magnetic material, the degree of freedom in designing the shape of the FeCoV-based alloy hard magnetic material is improved.

The conditions for the gas nitriding treatment are not particularly limited, and can be adjusted by appropriately combining conditions suitable for nitriding the FeCoV alloy within a normally selectable range. Specifically, the following conditions may be mentioned.

The nitriding atmosphere refers to the atmosphere in the furnace in which gas nitriding treatment is performed, and is preferably a nitriding gas atmosphere containing ammonia, specifically, ammonia (NH ₃ ), hydrogen (H ₂ ), nitrogen (N ₂ ), and other gases. , a gas atmosphere that inevitably contains impurities such as oxygen (O ₂ ) and carbon dioxide (CO ₂ ). A preferable nitriding atmosphere contains a total of 99.5% (vol%) or more of NH ₃ , H ₂ and N ₂ .

Further, the nitriding atmosphere is preferably controlled so that the nitriding potential (K _N ) is 0.05 or more and 2.0 or less.
Generally, the K _N value is used as an index representing the nitriding ability of the nitriding atmosphere, and is defined by the following equation (3) using the NH ₃ partial pressure and H ₂ partial pressure of the nitriding atmosphere.
K _N = (NH ₃ partial pressure)/[(H ₂ partial pressure) ^3/2 ] ... (3)
The K _N value can be controlled by the gas flow rate, but a certain amount of time is required after the flow rate is set for the K _N value of the nitriding atmosphere to reach an equilibrium state.

In this step, the nitriding potential (K _N ) of the nitriding atmosphere is preferably 0.05 or more and 2.0 or less, more preferably 0.05 or more and 1.0 or less, and even more preferably 0.07 or more and 0.0. 5 or less. It is considered that when the nitriding potential (K _N ) is within the above range, N becomes easy to enter into the crystal lattice of the FeCoV alloy.

The treatment temperature of the gas nitriding treatment is mainly correlated with the nitrogen diffusion rate, and affects the depth at which the FeCoV alloy (including V phase) is nitrided from the surface of the rolled body. If the processing temperature is too low, the nitrogen diffusion rate will be slow and the depth at which the FeCoV alloy will be nitrided will be shallow. Therefore, from the viewpoint of increasing the depth at which the FeCoV alloy is nitrided from the surface of the rolled body, the treatment temperature is preferably 300°C or higher, more preferably 500°C or higher, still more preferably 600°C or higher, and even more preferably is 620°C or higher. Further, from the viewpoint of productivity, the treatment temperature is preferably 800°C or lower, more preferably 700°C or lower. Specifically, the treatment temperature is preferably 300°C or more and 800°C or less, more preferably 500°C or more and 800°C or less, preferably 600°C or more and 700°C or less, and preferably 620°C or more and 700°C or less.

The processing time of the gas nitriding process is defined as the time of the entire nitriding process, that is, the time from the start to the end of the nitriding process. The treatment time is correlated with the penetration of nitrogen and influences the depth at which the FeCoV alloy is nitrided from the surface of the rolled body. If the treatment time is too short, the nitriding depth will be shallow. On the other hand, if the processing time is too long, the manufacturing cost will increase. Therefore, from the viewpoint of increasing the depth at which the FeCoV alloy is nitrided from the surface of the rolled body, the treatment time is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. From the viewpoint of cost, the time is preferably 10 hours or less, more preferably 8 hours or less. Specifically, the treatment time is preferably 1 hour or more and 10 hours or less, more preferably 2 hours or more and 8 hours or less, and still more preferably 3 hours or more and 8 hours or less.

In this step, by subjecting the rolled body to gas nitriding treatment, nitrogen atoms (N) can be permeated and diffused into the FeCoV alloy from the surface of the rolled body. The N diffusion region is not particularly limited, but from the viewpoint of improving magnetic properties, the depth from the surface to the center of the FeCoV-based alloy hard magnetic material is preferably 0.5 μm or more, more preferably 1 μm or more, More preferably, it is 5 μm or more. Note that the upper limit of the N diffusion region is not particularly limited, and it is preferable that the FeCoV-based alloy hard magnetic material is nitrided deeper from the surface toward the center, but from the viewpoint of ease of nitriding treatment, , for example, 200 μm or less, preferably 100 μm or less, more preferably 50 μm or less.
Note that the N diffusion region can be measured by the method described in Examples.

[Applications of FeCoV-based alloy hard magnetic material]
The FeCoV-based alloy-based hard magnetic material obtained by the production method of the present invention has tetragonal strain, and thereby exhibits uniaxial magnetic anisotropy. Such a FeCoV-based alloy hard magnetic material can be used for a permanent magnet.

In particular, the FeCoV-based alloy-based hard magnetic material obtained by the production method of the present invention has tetragonal crystal strain and thus has magnetocrystalline anisotropy, and is thought to exhibit good uniaxial magnetic anisotropy due to this. It will be done. Note that the FeCoV-based alloy hard magnetic material may further have shape magnetic anisotropy or other magnetic anisotropy.

The method for producing a permanent magnet is not particularly limited, and any known method can be used, including the following methods.
First, there is a method in which a FeCoV-based alloy hard magnetic material is directly used as a permanent magnet. The FeCoV-based alloy hard magnetic material obtained by the production method of the present invention has characteristics as a permanent magnet. Further, according to the manufacturing method of the present invention, there is a high degree of freedom in designing the shape of the obtained FeCoV-based alloy hard magnetic material, so a permanent magnet with a desired shape can be obtained.
Note that even if the FeCoV-based alloy hard magnetic material is used as a permanent magnet as it is, the FeCoV-based alloy hard magnetic material may be cut into a desired shape as necessary, and multiple FeCoV-based alloy hard magnetic materials may be cut into a desired shape. A laminate may be formed by laminating hard magnetic materials.

Another method is to make particles of FeCoV-based alloy hard magnetic material, mold the particles under pressure (sintered magnet), or mix them with resin etc. and form them into a desired shape (bond magnet), and then create a permanent magnet. There are several ways to obtain this.
The method of particleizing the FeCoV-based alloy hard magnetic material is not particularly limited, and includes, for example, mortar mill grinding, ball milling, shock wave grinding, mechanical polishing, Ar etching, ion etching, focused ion beam (FIB) processing, electron beam lithography, etc. These known microfabrication methods can be used alone or in combination.

In any of the above methods, if necessary, a process of magnetizing at least one of the FeCoV-based alloy hard magnetic material and the permanent magnet may be further performed. For example, a method for magnetizing the FeCoV-based alloy hard magnetic material includes a method of press-molding powder of the FeCoV-based alloy hard magnetic material while applying a magnetic field.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and includes all aspects included in the concept of the present invention and the scope of the claims. It can be modified to .

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to the following examples. In addition, various measurements and evaluations in Examples and Comparative Examples were performed as follows.

<Crystal structure>
The crystal structure was evaluated by X-ray diffraction measurement (XRD). In addition, regarding Example 1, scanning transmission electron microscopy (STEM) was also performed. Each measurement was performed using the following method.

1. X-ray diffraction measurement (XRD)
The XRD measurement was performed under the following conditions using an X-ray diffraction device ("RINT2000", manufactured by Rigaku Co., Ltd.).
(Measurement condition)
Radiation source: CuKα
Voltage: 40kV
Current: 40mA
Measurement range: 10°~150°
Scan step: 0.04°
Counting time: 1.0 seconds/step The XRD spectra of Example 1 and Comparative Examples 1 and 2 are shown in FIGS. 1, 2, and 3, respectively.

2. Scanning transmission electron microscopy (STEM)
Elemental analysis by energy dispersive X-ray spectroscopy (TEM-EDS) and aberration-corrected STEM observation were performed using an atomic resolution analytical electron microscope (manufactured by JEOL Ltd., "JEM-ARM200F").
The observation surface is a cut surface obtained by cutting out the FeCoV-based alloy body of Example 1 in a plane perpendicular to the rolling direction.
In the EDS analysis, component analysis was performed on the FeCoV-based alloy body of Example 1. The results are shown in Figure 4. FIG. 4(a) is a photograph showing the results of TEM-EDS analysis, and FIG. 4(b) is the result of spectrum analysis of a region approximately 10 μm from the surface (the region surrounded by a square in FIG. 4(a)).
Furthermore, in the aberration-corrected STEM observation, the crystal lattice of the FeCoV-based alloy of Example 1 was confirmed, and the tetragonal strain c/a was calculated. The results are shown in FIG. Figure 5(a) is a HAADF-STEM image in a region approximately 10 μm from the surface of the FeCoV-based alloy body, and Figure 5(b) is an enlarged image of the area surrounded by a square in Figure 5(a). A lattice image of the 100) plane can be confirmed, and FIG. 5(c) shows the results of calculating the image intensity profiles of the a-axis and c-axis, the interatomic distance, and the tetragonal strain c/a.

<Magnetic properties>
The magnetic properties were evaluated using a magnetization curve (magnetization M−magnetic field H).
The magnetization curve was measured using a vibrating sample magnetometer (VSM) (manufactured by Toei Kogyo Co., Ltd., "VSM5S type-15") with a maximum magnetic field setting of 20 kOe (input value). Further, the magnetic field was applied in both the horizontal and vertical directions to the surface of the measurement sample.
Graphs of magnetization curves of Example 1 and Comparative Examples 1 and 2 are shown in FIGS. 6, 7, and 8, respectively. In Figures 6 to 8, "in-plane" means that the magnetic field is applied in-plane (horizontal to the surface of the measurement sample), and "vertical" means that the magnetic field is applied perpendicularly (horizontal to the surface of the measurement sample). The case where the voltage is applied perpendicularly to the surface is shown.
In this example, when the magnetic field is applied in-plane and when it is applied perpendicularly, a good result is obtained when both ends of each magnetization curve are far apart (do not match) in the region where the magnetic field value is 18 kOe or less. It was determined that uniaxial magnetic anisotropy was expressed, and the magnetic properties were evaluated as "good." In addition, if both ends of each magnetization curve match in the magnetic field value of 18 kOe or less when the magnetic field is applied in-plane and when it is applied perpendicularly, sufficient uniaxial magnetic anisotropy is expressed. It was determined that the magnetic properties were "poor".

(Manufacturing example 1)
The raw materials were melted in a furnace so as to have a predetermined composition, and an ingot (5 mm x 20 mm, thickness 0.5 mm) having an alloy composition of Fe _0.375 Co _0.500 V _0.125 was obtained.

(Example 1)
[Step (I)]
The ingot obtained in Production Example 1 was used as a base material, and the base material was rolled in the atmosphere at room temperature (25°C ± 3°C) to form a foil-shaped rolled body (size 25 mm x 35 mm, thickness 55 μm) was obtained.
In addition, the said rolling process was performed 20 times (pass) from one direction by cold rolling.

[Step (II)]
The rolled body obtained in step (I) was subjected to gas nitriding treatment under the following conditions to obtain a FeCoV-based alloy body.
A rolled body is charged into a nitriding furnace, and ammonia (NH ₃ ) and hydrogen (H ₂ ) are supplied into the furnace to detect the presence of atomic nitrogen (N), hydrogen (H ₂ ), and undecomposed ammonia (NH ₃ ). The rolled body was subjected to gas nitriding treatment at 650° C. for 5 hours under the conditions of nitriding potential K _N =0.10.

The crystal structure and magnetic properties of the obtained FeCoV-based alloy body were evaluated.
The results are shown in Table 1. In Table 1, the presence or absence of tetragonal crystallization was determined by the presence or absence of twin peaks near 2θ = 65° from the XRD spectrum, and the tetragonal distortion c/a was measured by the XRD spectrum and aberration-corrected STEM observation. The magnetic properties were determined from the magnetization curve.

(Comparative example 1)
In Comparative Example 1, the FeCoV alloy body (5 mm x 20 mm, thickness 0.5 mm) obtained in Production Example 1 was processed under the same conditions as in Step (II) of Example 1 without performing Step (I). Gas nitriding treatment was performed. Table 1 shows the evaluation results of crystal structure and magnetic properties.

(Comparative example 2)
In Comparative Example 2, a rolled body was obtained under the same conditions as in Step (I) of Example 1. Note that gas nitriding treatment (step (II)) was not performed. Table 1 shows the evaluation results of crystal structure and magnetic properties.

As a result of X-ray diffraction measurement (XRD), twin peaks were observed near 2θ = 65° in the FeCoV-based alloy body obtained in Example 1, suggesting that it was tetragonal (BCT). (Figure 1). Furthermore, as a result of SEM-EDS elemental analysis, the FeCoV-based alloy body was clearly nitrided in a region approximately 10 μm from its surface, and furthermore, (Fe _0.43 Co _0.57 ) _0.87 V _0.10 It was confirmed that the alloy had an alloy composition of N _0.03 . Furthermore, as a result of aberration-corrected STEM observation, it was confirmed that the tetragonal distortion c/a was 1.07.

Moreover, it was confirmed from the results of magnetic property evaluation that the FeCoV-based alloy body obtained in Example 1 exhibited good uniaxial magnetic anisotropy (FIG. 6).
In particular, when the in-plane and perpendicular magnetization curves in FIG. 6 are extrapolated to estimate the magnetic field value at which both ends coincide, the value is at least 20 kOe or more. This value greatly exceeds the demagnetizing field value (about 12 kOe) of the plate-shaped sample calculated from the saturation magnetization value (about 1000 emu/cm ³ ) shown in FIG. From this, the FeCoV-based alloy body of Example 1 has magnetic anisotropy other than shape magnetic anisotropy, especially magnetocrystalline anisotropy associated with tetragonal crystallization, which results in good uniaxial magnetic anisotropy. It is presumed that the directionality is expressed.

From these results, the manufacturing method of Example 1 can exhibit good uniaxial magnetic anisotropy at a desired thickness (for example, 55 μm) by having Step (I) and Step (II) in this order. It was confirmed that a FeCoV-based alloy hard magnetic material made of a possible tetragonal FeCoV-based alloy could be obtained.

On the other hand, when only gas nitriding is performed on the FeCoV alloy body without rolling (Comparative Example 1), and when only rolling is performed on the FeCoV alloy body without gas nitriding (Comparative Example 2), In both cases, no twin peaks were observed near 2θ = 65° in XRD (Figures 2 and 3), which indicates that the tetragonal strain c/a is 1.000 and that the FeCoV-based alloy is made of a tetragonal FeCoV-based alloy. It was confirmed that a hard magnetic material based on this method could not be obtained.

Furthermore, in any of the above cases (Comparative Examples 1 and 2), sufficient uniaxial magnetic anisotropy was not confirmed as a result of magnetic property evaluation (FIGS. 7 and 8).
In particular, in FIGS. 7 and 8, both ends of the magnetization curves coincide in the region where the magnetic field value is 18 kOe or less (approximately 15 kOe) when the magnetic field is applied in-plane and when it is applied perpendicularly. ing. These values are not much different from the demagnetizing field values of the plate-shaped sample calculated from the saturation magnetization values in FIGS. 7 and 8. From this, it is presumed that in the FeCoV-based alloy bodies of Comparative Examples 1 and 2, no magnetic anisotropy other than shape magnetic anisotropy existed, and sufficient uniaxial magnetic anisotropy was not expressed.

According to the manufacturing method of the present invention, a FeCoV-based alloy-based hard magnetic material made of a tetragonal FeCoV-based alloy that can exhibit good uniaxial magnetic anisotropy with a desired thickness and size can be obtained. Such FeCoV-based alloy hard magnetic materials are expected to be used as high-performance permanent magnets.

Claims (7)

A method for producing a FeCoV-based alloy hard magnetic material made of a tetragonal FeCoV-based alloy having a composition represented by the following general formula (1),
The tetragonal FeCoV-based alloy has a tetragonal strain c/a of more than 1.02 and no more than 1.30,
A method for producing a FeCoV-based alloy hard magnetic material, comprising the following steps (I) and (II) in order.
(Fe _1-x Co _x ) _1-y-z V _y N _z ...(1)
[In formula (1), x is a real number that satisfies 0.40≦x≦0.70, y is a real number that satisfies 0<y≦0.15, and z satisfies 0<z≦0.15. Represents a real number. ]
Step (I): A step of rolling a base material made of an FeCoV alloy to obtain a rolled body. Step (II): A step of gas nitriding the rolled body. The method for producing a FeCoV-based alloy hard magnetic material according to claim 1, wherein the thickness of the rolled body is more than 0.1 μm and not more than 200 μm. The method for producing a FeCoV-based alloy hard magnetic material according to claim 1 or 2, wherein the nitriding atmosphere in the gas nitriding treatment is a nitriding gas atmosphere containing ammonia. The method for producing a FeCoV-based alloy hard magnetic material according to claim 3, wherein the nitriding potential (K _N ) of the nitriding atmosphere is 0.05 or more and 2.0 or less. The method for producing a FeCoV-based alloy hard magnetic material according to any one of claims 1 to 4, wherein the gas nitriding treatment temperature is 300° C. or higher and 800° C. or lower. The method for producing a FeCoV-based alloy hard magnetic material according to any one of claims 1 to 5, wherein the gas nitriding treatment time is 1 hour or more and 10 hours or less. A FeCoV-based alloy-based hard magnetic material made of a tetragonal FeCoV-based alloy having a composition represented by the following general formula (1),
The tetragonal FeCoV-based alloy has a tetragonal strain c/a of more than 1.02 and no more than 1.30,
A FeCoV-based alloy hard magnetic material having a thickness of more than 0.1 μm and less than 200 μm.
(Fe _1-x Co _x ) _1-y-z V _y N _z ...(1)
[In formula (1), x is a real number that satisfies 0.40≦x≦0.70, y is a real number that satisfies 0<y≦0.15, and z satisfies 0<z≦0.15. Represents a real number. ]