JP2021090263A - Magnetostrictor and manufacturing method of the same - Google Patents

Abstract

To provide an Fe-Ga system magnetostrictor having improved magnetic flux density change with magnetostriction even when a relatively low magnetic field is applied, and a manufacturing method of the same.SOLUTION: A magnetic element is made of Fe-Ga-based alloy in a rectangular parallelepiped shape with a thickness smaller than a width, where a magnetic domain on a main surface has a magnetic domain width of 10 μm to 200 μm, and an area of the magnetic domain of which an angular difference between a width direction of the main surface and a direction of a magnetic moment is 10° or less is 70 to 100% of an area of the main surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetostrictive element of a Fe—Ga based single crystal alloy and a method for producing the same.

In recent years, it is expected that the world of things that have the function of autonomous communication will exchange information and automatically control each other, that is, the world of the Internet of Things (IoT). ing.

When IoT permeates society, a large number of IoT devices with communication functions will be on the market. Such devices have various sensors and require a power source to operate IoT devices such as sensors. However, when the number of devices becomes enormous, it becomes difficult to secure a power source in terms of wiring and maintenance time and cost. Therefore, in order to realize IoT, a power supply technology suitable for IoT devices is required.

Based on this background, "energy harvesting," a technology that converts minute energy that is everywhere around us into electric power and utilizes it, is important. Vibration, which is one of the energy sources, is generated every time an automobile, a railroad, a machine, a person, or the like moves. Therefore, there are many places where vibration is generated, and it is an energy source that is not affected by weather or weather. Therefore, the construction of a system that supplies power to applications linked to the movement of these moving objects by vibration power generation can be a clue to the realization of IoT.

The power generation method of vibration power generation is classified into four types: magnetostrictive type, piezoelectric type, electrostatic induction type, and electromagnetic induction type. The magnetostrictive method is a method of converting the magnetic flux density inside the magnetostrictive material, which changes by applying stress, into electricity through a wound coil, and has a smaller internal resistance and a larger amount of power generation than other methods. Further, the magnetostrictive type has a feature of being excellent in durability because a metal alloy is used as the magnetostrictive material. Therefore, the magnetostrictive type is expected as a method capable of improving durability.

The magnetostrictive element is manufactured, for example, by obtaining a magnetostrictive material having a single crystal crystal orientation <100> from a FeGa single crystal alloy and cutting it out by electric discharge machining. In order to produce such a magnetic strain material, the melted FeGa alloy is pulled out from the inside of the tube furnace to the outside of the tube furnace by an elevating device at a constant speed, and the molten alloy is solidified in one direction from the lower part to the upper part. By solidifying in this way, the magnetostrictive material can be obtained by growing crystals in the direction of the crystal orientation <100>. Then, the solidified mass is cut out by electric discharge machining so as to align with the crystal orientation <100> of the single crystal to obtain individual magnetostrictive elements (see, for example, Patent Document 1 below).

When the magnetostrictive element manufactured as described above is used, the magnetic moments of the magnetostrictive element tend to be aligned in the longitudinal direction under the influence of the demagnetic field when the magnetostrictive element is cut into a rectangular parallelepiped used for the magnetostrictive vibration power generation device. Magnetostriction is caused by the rotation of the magnetic flux 90 ° with respect to the magnetic field application direction. Therefore, when the magnetostrictive element is cut out in the crystal orientation <100>, the magnetostrictive element in which the magnetic moments are already aligned in the longitudinal direction of the rectangular body is used. When a magnetic field is applied in the longitudinal direction, there is almost no change in magnetic flux density accompanied by magnetostriction, which contributes to power generation.

Further, in the case of a known magnetostrictive element, the magnetic field required for magnetic saturation is large, and it is not possible to sufficiently generate power with a generally required magnetic field (0.001T to 0.05T). Power generation characteristics deteriorate.

International Publication No. 2016/12132

In view of the known magnetostrictive elements as described above, the present invention provides an Fe-Ga-based magnetostrictive element in which the change in magnetic flux density accompanied by magnetostriction is improved even when a relatively low magnetic field is applied, and a method for manufacturing the same. To do.

As a result of diligent studies on the above problems, the present inventors have come up with a new magnetostrictive element and a method for manufacturing the same.

In the first gist, the present invention provides a rectangular parallelepiped shape Fe-Ga based magnetostrictive element (in terms of dimensions) whose thickness is smaller than its width.
The magnetic domain on the main surface has a magnetic domain width of 10 μm to 200 μm.
The area of the magnetic domain in which the angle difference between the width direction of the main surface and the direction of the magnetic moment is within 10 ° is 70% to 100%, preferably 75% to 95%, more preferably 80% to 90% of the area of the main surface. It is characterized by being.

In the present invention, the "main surface" means the surface having the largest area among the surfaces constituting the rectangular parallelepiped. From the viewpoint of putting the magnetostrictive element into practical use, the aspect ratio of the main surface of the magnetostrictive element (the ratio of the width to the length of the main surface, that is, the width of the main surface: the length of the main surface) is specifically 1: 1. It is preferably 1 to 1: 8, more preferably 1: 1.5 to 1: 6, and may be, for example, 1: 2 to 1: 4.

The length is the longest dimension of the main surface of a rectangular parallelepiped. Therefore, with respect to the dimensions of the rectangular parallelepiped, thickness <width <length. As will be described later, in the magnetostrictive element of the present invention, a magnetostrictive material is cut out from an Fe—Ga-based single crystal alloy block so as to be parallel to the crystal orientation <100>, and the magnetostrictive material is processed into a predetermined form to be described later. It can be manufactured by heat treatment as in. Therefore, the length direction, the width direction, and the thickness direction of the rectangular body of the magnetostrictive element correspond to the crystal orientation <100> of the crystal plane of the single crystal.

In the magnetostrictive element of the present invention, the magnetic field at which the magnetic domain is saturated is 0.001T to 0.05T, preferably 0.005T or more, with respect to the application of a magnetic field in a direction in which the angle difference from the length direction of the main surface is within 10 °. It is 0.04T. That is, the magnetostrictive element of the present invention can exhibit a change in magnetic flux density accompanied by a sufficiently large magnetostriction in such a relatively low magnetic field.

The present invention provides, in the second gist, a method of manufacturing a magnetostrictive element, which method is:
(1) A step of obtaining a single crystal of an Fe-Ga alloy as a magnetostrictive material.
(2) From the obtained magnetic strain material, it has a rectangular parallelepiped shape whose thickness is smaller than the width of the main surface, preferably a plate-like rectangular parallelepiped shape, and the direction of the length of the main surface is the crystal orientation <100> of a single crystal. The process of cutting out parallel magnetic strain materials,
(3) The process of processing the cut out magnetostrictive material into a predetermined shape as a magnetostrictive element, and (4) the magnetostrictive material having a predetermined shape is heat-treated at a predetermined temperature in a state where a magnetic field is applied in the width direction. , A process of aligning the directions of magnetic moments of magnetic domains on the main surface in the width direction.

The magnetostrictive element obtained by the manufacturing method of the present invention has the characteristics of the magnetostrictive element of the first gist of the present invention. That is, in the obtained magnetostrictive element, the magnetic domain structure on the main surface has a magnetic domain width of 10 μm to 200 μm, and the area of the magnetic domain in which the angular difference between the width direction of the main surface and the direction of the magnetic moment is within 10 ° is the area of the main surface. The area is 70 to 100%.

The magnetostrictive element of the present invention can exhibit a change in magnetic flux density accompanied by a sufficiently large magnetostriction at a low magnetic field due to induced magnetic anisotropy when a magnetic field is applied in the length direction of the main surface. The induced magnetic anisotropy is anisotropy when, for example, heat treatment is performed in a magnetic field to forcibly induce the direction of the original magnetic moment in another direction so that the directions of the magnetic moments are uniformly aligned. Is. In particular, when the aspect ratio, which is the ratio of the width direction dimension to the length direction dimension of the main surface, is 1: 2 to 1: 4, the magnetic moments are originally aligned in the length direction due to the influence of the demagnetic field, but in the magnetic field. Even if the direction of the magnetic moment is rotated in the width direction by the heat treatment, the demagnetic field always affects the length direction, so that the magnetic moment in the width direction is usually more likely to be aligned in the length direction at a lower magnetic field.

Further, according to the method for manufacturing a magnetostrictive element of the present invention, it is possible to obtain a magnetostrictive element that exhibits a change in magnetic flux density accompanied by a sufficiently large magnetostriction in a low magnetic field and can improve the amount of power generated by the magnetostrictive vibration power generation device.

FIG. 1A schematically shows a plate-shaped rectangular parallelepiped magnetostrictive element according to one aspect of the present invention in a perspective view in an arrangement state in which the orientation corresponds to the crystal orientation <100>. (B) schematically shows the magnetic domain structure of the region P on the main surface. FIG. 2 schematically shows a plate-shaped non-rectangular magnetostrictive element according to one aspect of the present invention in a perspective view in an arrangement state in which the orientation corresponds to the crystal orientation <100>. FIG. 3 is a flowchart showing a process of the method for manufacturing a magnetostrictive element of the present invention. FIG. 4 schematically shows a state in which the angle θ between the length direction of the magnetostrictive element and the direction H of the magnetic field applied to the magnetostrictive element is 0 ° to 10 ° when evaluating the magnetostrictive element. FIG. 5 is Table 1 showing the conditions and results of Examples and Comparative Examples.

Next, an embodiment for carrying out the present invention will be described in detail with reference to the accompanying drawings and further explaining examples. The invention is not limited to such a form.

The magnetostrictive material constituting the magnetostrictive element of the present invention is a Fe-Ga based alloy, preferably a Fe-Ga based alloy represented by the following formula (1) or the following formula (2):
・ Fe _(100-α1) Ga _α・ ・ ・ (1)
(In the formula (1), α1 is the Ga content (at%) and satisfies 14 ≦ α1 ≦ 19.)
・ Fe _(100-α2-β) Ga _α2 X _β・ ・ ・ (2)
(In the formula (2), X is one or more elements selected from the group consisting of Sm, Eu, Tb, Dy, Cu, Ce, Gd and C, and α2 is the Ga content (at%). β is the X content (at%) and satisfies 5 ≦ α2 ≦ 19 and 0.05 ≦ β ≦ 4).

Regarding the magnetostrictive material (single crystal alloy) of the formula (1), the change in magnetic flux density accompanied by excellent magnetostriction is shown by dissolving Ga in Fe. Further, regarding the magnetostrictive material (single crystal alloy) of the formula (2), a part of Ga of the formula (1) is derived from another third element, that is, Sm, Eu, Tb, Dy, Cu, Ce, Gd and C. By substituting one or more elements selected from the group, particularly at least one element selected from the group, a change in magnetic flux density with better magnetostriction is exhibited.

However, the solid solution amount of the element other than Fe with respect to Fe may be contained in an amount that does not change the crystal structure. Specifically, it is preferably 20 at% or less, which is a sufficiently small amount with respect to 30 at% (the overall standard of the amount of elements after solid solution), which is considered to be the solid solution limit for Fe, and 15 at% or less. Is more preferable.

In a preferred embodiment, in the above formula (2), the other third element, X, may be one or more elements selected from the group consisting of Ce, Sm, Cu and C. Among them, Ce and Sm are particularly preferable because it is considered that the change in magnetic flux density accompanied by magnetostriction is improved by the quadrupole moment.

In the present disclosure, the content (also referred to as concentration) of each element in the magnetic strain material (single crystal alloy) of the formula (1) or the formula (2) is the content of each element with respect to the total number of atoms of the magnetic strain material (single crystal alloy). It is the ratio of the number of atoms, and is a value expressed using the unit of at% (atomic percentage).

Specifically, it refers to a value obtained by measuring the element content by analyzing a magnetic strain material (single crystal alloy) by fluorescent X-ray analysis (XRF). Specifically, it refers to a value measured by performing spot analysis by XRF on the main surface of the magnetostrictive element.

More specifically, it refers to the content rate (at%) obtained by analyzing an arbitrary point on the main surface of the magnetostrictive element by XRF. The magnetostrictive material (single crystal alloy) constituting the magnetostrictive element in the present embodiment is substantially composed of the listed elements, but is inevitably mixed with trace elements (for example, less than 0.005 at% oxygen). May include.

The magnetostrictive element according to one embodiment of the present invention is schematically shown in FIG. FIG. 1A is a schematic perspective view of the magnetostrictive element 10, and FIG. 1B is an enlarged schematic view of a region P on the main surface of the magnetostrictive element 10. FIG. 2 is a diagram in which the schematic inclination diagram and the coordinates of the magnetostrictive element 10 according to the embodiment of the present invention are combined.

The magnetostrictive element 10 according to the embodiment of the present invention is made of the above-mentioned single crystal alloy magnetostrictive material.
For example, as shown in FIG. 1A, it has a plate-like rectangular parallelepiped shape. As used herein, the term "plate-like rectangular parallelepiped" refers to three pairs of rectangular parallelepipeds having three dimensions: length, width and thickness, facing each other and having an equal area to each other. Of these, the surface that constitutes the pair that occupies the largest area and is defined by the length and width is called the "main surface". When the magnetostrictive element has a plate shape, the length and width dimensions are considerably larger than the thickness dimension, and the main surface corresponds to the so-called surface of the plate.

In the present specification, the direction along the length, which is the longest dimension of the main surface, is referred to as the "longitudinal direction" or the "longitudinal direction", and the width is shorter than the dimension orthogonal to the length direction. The direction along the width is called the "width direction" or the "short direction", and the direction along the thickness, which is the shortest dimension, is called the "thickness direction".

The term "plate-like" refers to a shape in which the distance between the main surfaces (corresponding to the thickness of the plate (t in FIG. 1)) is relatively small compared to the widthwise dimensions of the main surface, preferably considerably small. That is, it means a thin shape (specifically, the dimension in the thickness direction is 1/20 to 1/4 of the width direction dimension, for example, 1/15 to 1/5 dimension, particularly about 1/10). .. Therefore, in the magnetostrictive element of the present invention, the dimensional relationship is thickness <width <length.

In the magnetostrictive element of the present invention, the main surfaces 5 and 6 of the illustrated magnetostrictive element 10 (a pair of faces that form a rectangular parallelepiped and that face each other and have the same area as each other and occupy the widest area. Any parallel virtual surface located between the surfaces) may have the same characteristics as the main surface, and it is preferable to have such characteristics. Usually, a plate-shaped magnetostrictive element has such a feature.

The magnetostrictive element 10 shown in FIG. 1 is made of the above-mentioned single crystal alloy magnetostrictive material, and for convenience of explanation, the x-axis and length in the width direction are orthogonal to each other with the origin A of the main surface 5 of the magnetostrictive element 10 as the origin. It is a plate-shaped rectangular parallelepiped shape having vertices at predetermined positions on the y-axis in the orthogonal direction and the z-axis in the thickness direction.

In the magnetostrictive element of the present invention, the main surface thereof usually contains a plurality of magnetic domains, and the magnetic domains have a magnetic domain width of 10 μm to 200 μm. The "magnetic domain" means a region where the magnetic moments of atoms are arranged in the same direction. The "width" of a magnetic domain means the minimum distance between the opposing domain walls that partition the magnetic domain.

The width of the magnetic domain on the main surface and the direction in which the magnetic moment is oriented in each magnetic domain (hereinafter, also referred to as “magnetic domain structure” in the present specification) are determined by, for example, the Kerr effect. It is examined by observing the main surface by a method using a microscope. The Kerr effect microscope is a microscope that uses the Kerr effect, which becomes elliptically polarized light when linearly polarized light is applied to a specific material. The observation range is smaller than that of an optical microscope, and only the magnetic domain structure on the surface is extracted for observation. Can be done.

The magnetostrictive element of the present invention preferably has a plate shape as shown in the drawing, and since the thickness t is considerably smaller than other dimensions, the magnetostrictive structure is substantially formed on the main surfaces 5 and 6 and the parallel plane between them. Therefore, it is sufficient that at least one of the two opposing main surfaces 5 and 6 of the magnetostrictive element is satisfied in the above-mentioned magnetic domain structure. It is sufficient to observe the direction of the magnetic moment by observing one of the main surfaces.

Regarding the magnetostrictive element manufactured by the method for manufacturing the magnetostrictive element of the present invention, the direction of the magnetic moment is the width direction by observing only a part of the main surface (for example, the region P in FIG. 1A). It is known that the ratio of the area of a certain region (that is, the region aligned in the width direction) may be obtained. Regarding the selection of such a region P, any size of any region may be used as long as the main surface edge portion of the magnetostrictive element is not included. This is because the magnetic domain may be missing at the edge in some cases. Therefore, it is preferably a region near the center of the main surface. The size of the region P may be any size as long as it is not defective, and may be, for example, 500 μm × 500 μm, 400 μm × 300 μm, 300 μm × 300 μm, or the like.

For example, a certain region of the main surface is the observation target, and for each magnetic domain in the observation target region, an angle (that is, the direction of the width direction of the main surface (x-axis direction in this embodiment) and the direction of the magnetic moment of the magnetic domain) is formed. , Angle difference), the total area of the magnetic domains with the angle difference of 10 ° or less can be obtained, and the ratio of the total area of the magnetic domains with the angle difference of 10 ° or less to the area of the observation target area can be calculated. ..

In the present invention, the "angle difference between the width direction of the main surface and the direction of the magnetic moment of the magnetic domain" (also simply referred to as "angle difference") means the absolute value of the difference between the angles formed by the two directions (hence,). , The minimum value of the angle difference is 0 °).

"The angle difference is 10 ° or less" is based on one direction (for example, the width direction of the main surface) as a reference (0 °), counterclockwise from this reference, and the other direction (for example, the magnetic moment of the magnetic domain). When the angle formed by (direction) is measured, it means that the measurement angle is within ± 10 °.

FIG. 1B is typically an enlarged schematic view of the region P on the main surface 5, where the direction of the magnetic moment in the magnetic domain is indicated by an arrow, and the domain wall, which is the boundary of the magnetic domain, is shown by a solid line. Shown. In the schematic example of FIG. 1 (b), the region P of the main surface 5 is occupied by a plurality of (specifically, 6) magnetic domains.

Judgment is made by examining the angle in the direction of the magnetic moment of each magnetic domain, considering the counterclockwise direction from the x-axis direction shown as the width direction of the main surface as a reference. In the magnetic domain 2, the direction of the magnetic moment is 180 ° and the angle in the width direction is 0 °, so that the angle difference as the angle formed by these directions is 0 °. In the magnetic domain 3, the direction of the magnetic moment is 0 ° and the angle in the width direction is 0 °, so that the angle difference is 0 °. Further, in the magnetic domain 4, the direction of the magnetic moment is −90 ° and the angle in the width direction is 0 °, so that the angle difference as the angle formed by these directions is 90 °. Therefore, in the example shown in FIG. 1B, the ratio of the areas of the magnetic domains 2 and 3 corresponding to the angle difference of 10 ° or less to the area of the observation region P on the main surface is, for example, about 90%.

Based on the observation with the Kerr effect microscope as described above, in the magnetostrictive element 10 of the present invention, the magnetic domain has an area 70 of the main surface in which the angular difference between the width direction of the main surface and the direction of the magnetic moment of the magnetic domain is ± 10 ° or less. It occupies ~ 100%, preferably 80-98%, especially 85% -95% or more. The magnetic domain constituting the main surface of the magnetostrictive element has a magnetic domain width of 10 μm to 200 μm.

The shape of the magnetostrictive element of the present invention is particularly preferably a rectangular parallelepiped shape as described above, but it does not necessarily have to be a plate-shaped rectangular parallelepiped shape as shown in the figure. Instead of the rectangular parallelepiped shape, the magnetostrictive element may have any other suitable plate-like shape (ie, non-cuboidal shape). For example, as schematically shown in FIG. 2, the magnetostrictive element of the present invention may have a plate-like shape in which the shape of the main surface is oval. Even in such a non-rectangular shape magnetostrictive element 10', the characteristics of the aspect ratio range described above apply. However, the aspect ratio in the case of such a rectangular parallelepiped magnetostrictive element is calculated by associating the crystal orientation of the single crystal alloy constituting the non-cuboidal magnetostrictive element with the x-axis, y-axis, and z-axis.

Specifically, the magnetic strain element is positioned so that the crystal orientation <100> of the single crystal constituting the magnetic strain element 10'corresponds to the x-axis, y-axis, and z-axis shown by the broken lines in FIG. The longest dimension of the main surface of the magnetic strain element 10'in the x-axis direction (for example, the length a as shown) corresponds to the dimension in the width direction of the rectangular magnetic strain element 10 and is the main of the non-rectangular magnetic strain element 10'. The aspect ratio is defined by making the longest dimension of the surface in the y-axis direction (for example, the length b as shown) correspond to the dimension m in the length direction of the rectangular magnetic strain element 10. Therefore, in the case of a magnetostrictive element having a non-rectangular shape, the longest dimension a in the x-axis direction of such a main surface is regarded as a width, and the longest dimension b in the y-axis direction is regarded as a length. The description of the magnetostrictive element can be applied.

Therefore, the aspect ratio (a: b in FIG. 2) of the non-rectangular magnetostrictive element is preferably 1: 1.1 to 1: 8, similarly to the rectangular parallelepiped magnetostrictive element 10. It is more preferably 5 to 1: 6, and may be, for example, 1: 2 to 1: 4. The other shape of the main surface of the non-rectangular magnetostrictive element may be any suitable shape as long as it has the characteristics of the aspect ratio, for example, polygonal shape, semicircular shape, semi-elliptical shape, and these. It may have various combinations of shapes.

The magnetostrictive element of the present invention described above can be manufactured by the method for manufacturing a magnetostrictive element of the present invention. FIG. 3 shows an example of the method for manufacturing the magnetostrictive element of the present invention in a flowchart. The method for manufacturing a magnetostrictive element of the present invention comprises the following steps:
(1) A step of obtaining a single crystal of an Fe-Ga alloy as a magnetostrictive material.
(2) From the obtained magnetic strain material, a rectangular parallelepiped shape whose thickness is smaller than the width of the main surface, preferably a plate-like rectangular parallelepiped shape, and the direction of the length of the main surface is the crystal orientation <100> of a single crystal. The process of cutting out parallel magnetic strain materials,
(3) A step of processing the cut out magnetostrictive material into a predetermined shape as a magnetostrictive element, and (4) a magnetostrictive material having a predetermined shape at a predetermined temperature (preferably 400 ° C. or higher) in a state where a magnetic field is applied in the width direction. A step of heat treatment at 700 ° C.).

The magnetic domain on the main surface of the magnetostrictive element manufactured by the manufacturing method of the present invention has, for example, a magnetic domain width of 10 μm to 200 μm. By the heat treatment in the step (4), the directions of the magnetic moments on the main surface can be aligned in the width direction. In the present specification, "aligning in the width direction" means that the feature of the magnetic element of the present invention, that is, the angle difference between the width direction of the main surface of the magnetostrictive element and the direction of the magnetic moment in the magnetic domain of the main surface is within 10 °. It means that the area of the magnetic domain is, for example, 70 to 100% of the area of the main surface.

In step (1), for example, a columnar magnetic strain material is formed by mixing, heating, melting, and then cooling a predetermined amount of elements constituting the single crystal alloy represented by the above formula (1) or formula (2). To get. Any known method may be used for producing such a magnetostrictive material, and examples thereof include a Czochralski method (CZ method), a Bridgman method, and a quick-cooling solidification method. When manufactured by the CZ method, the chemical composition and crystal orientation can be accurately manufactured in a large crystal.

In the step (2), a rectangular parallelepiped shape, preferably the above-mentioned plate-shaped rectangular parallelepiped magnetostrictive material is cut out from the obtained columnar single crystal alloy block so as to be parallel to the crystal orientation <100>. In a cylindrical single crystal alloy, the length in the radial direction of the cylinder becomes shorter as it is closer to the end of the cylinder, but the length of the main surface of the rectangular parallelepiped is substantially the length of the straight body of the cylindrical single crystal alloy. It is preferable to cut out so as to be equal to each other, and it is more preferable to cut out in a plate shape. The crystal orientation <100> of the single crystal alloy can be determined by a known method, but in particular, it can be determined by an electron backscatter diffraction method (EBSD).

In the step (3), the magnetostrictive material cut out in the step (2) is processed into a predetermined shape. For example, it is processed into a rectangular parallelepiped shape having a predetermined length and width, preferably a plate-shaped rectangular parallelepiped shape. The shape and dimensions of the magnetostrictive material obtained by processing are substantially unchanged by the heat treatment in the step (4). Therefore, the matters described above regarding the magnetostrictive element apply to the step (3). Therefore, the predetermined shape of the magnetostrictive material is preferably a rectangular parallelepiped shape, particularly a plate-like rectangular parallelepiped shape, but in another embodiment, a non-rectangular parallelepiped shape, for example, one having a suitable shape whose main surface is not rectangular. It may be, and particularly preferably has such a plate-like shape.

In the above-mentioned manufacturing method, the step (2) and the step (3) are independent steps, but in another embodiment, a magnetostrictive material having a predetermined shape is obtained from the single crystal alloy ingot obtained in the step (1). It may be cut out directly. Therefore, step (2) and step (3) may be carried out together. The cutting in the step (3) step (2) and the processing in the step (3) may be carried out by any suitable known method. For example, laser machining, wire electric discharge machining and the like can be used.

In step (4), by performing a heat treatment (also called "heat treatment in a magnetic field") in a state where a magnetic field is applied, the direction of the magnetic moment on the main surface of the magnetic material having a predetermined shape is set in the width direction as described above. Can be aligned. This heat treatment is carried out by placing the magnetostrictive element in an environment of a predetermined temperature in a state where a magnetic field is applied in the width direction of the magnetostrictive element. It is preferable that such application in a magnetic field is performed so that the angle formed by the width direction of the manufactured magnetostrictive element and the application direction of the magnetic field is 10 ° or less.

Whether or not the magnetic moments are aligned in the width direction can be determined by a known method. For example, it can be determined particularly by a Kerr effect microscope, and it is possible to confirm how a plurality of magnetic domains exist on the main surface and in which direction the magnetic moment is oriented in each magnetic domain.

The conditions for heat treatment in a magnetic field (for example, the strength of the applied magnetic field, the heating temperature, the temperature profile from the start of heating to the end of heating to cooling, etc.) are particularly limited as long as the direction of the magnetic moment on the main surface can be aligned in the width direction. It is not limited. For example, the magnetostrictive material is heated in an inert atmosphere (eg, nitrogen or argon atmosphere) or a vacuum atmosphere. When aligning the application direction of the magnetic field with the width direction of the magnetostrictive element to be manufactured, a magnetic field of preferably 0.2T to 1T, more preferably a magnetic field of 0.3T to 1T, and particularly preferably a magnetic field of 0.5T to 1T is applied. Apply.

The heating temperature at this time is preferably 400 ° C. to 700 ° C., more preferably 450 ° C. to 650 ° C., and particularly preferably 450 ° C. to 600 ° C. Within such a temperature range, the state of the Fe-Ga based alloy does not change substantially on the phase diagram, and the magnetism changes when the heating temperature is less than 400 ° C or exceeds 700 ° C. It may not be possible to align the directions of the magnetic moments sufficiently.

The characteristics of the magnetostrictive element 10 manufactured by the method for manufacturing a magnetostrictive element of the present invention will be further described based on the results of Examples described later.

In the case where the theoretical limit value of the saturation magnetic flux density of Fe is 2.2T and the magnetostrictive element of the present invention manufactured in the examples described later (iron atomic% is 80 to 83 atomic%), the magnetostriction is sufficiently large. It shows a quantity L (for example, about 285 ppm on average), and at this time, it is manufactured from a Fe-Ga-based single crystal alloy based on the fact that the magnetostrictive density change ΔB is about 1.32 T on average and the result of a separately conducted experiment. It is estimated that the maximum value of the change in saturation magnetic flux density of the magnetostrictive element of the present invention is about 2.0 T. Therefore, the change in saturation magnetic flux density of the magnetostrictive element of the present invention is 1.1 to 2 (T). The magnetic flux density change ΔB is the maximum value of the difference between the magnetic flux density B when a tensile stress is applied to the magnetostrictive element and the magnetic flux density B when a compressive stress is applied to the magnetostrictive element.

Considering that the change in the magnetostrictive magnetic flux density of the magnetostrictive element of the present invention is 1.32T and the amount of magnetostriction is 285ppm, and that the maximum value of the change in the saturation magnetic flux density is estimated to be about 2T as described above. The maximum value of the magnetostrictive amount of the magnetostrictive element of the present invention is estimated to be about 450 to 600 ppm based on the results of various experiments so far. Further, the minimum value of the magnetostrictive amount of the magnetostrictive element of the present invention is about 150 ppm based on the result of another experiment. Therefore, the amount of magnetostriction of the magnetostrictive element of the present invention is 150 ppm to 600 ppm.

Power can be generated by vibrating the magnetostrictive element of the present invention. For example, a magnetostrictive element can be placed on a U-shaped magnetostrictive vibration power generation device to vibrate the exciter to generate electricity. For example, when the amount of power generation is measured using the magnetostrictive element of the present invention manufactured in the examples described later with an acceleration of 0.3 G and a frequency of 13 Hz, the magnetic flux density change ΔB is 1.32 T and the power generation amount is 530 μW on average. It became. Considering this result and the above-mentioned maximum value of ΔB being 2.0T, the amount of power generation is improved in proportion to the square of ΔB from the calculation method, so that the maximum value of the amount of power generation is about 2. It can be estimated to be about 1200 μW, which is four times as large. Therefore, when the magnetostrictive element of the present invention is used in an oscillating power generation device, an improvement in the amount of power generation can be expected. For example, considering the results of Examples and Comparative Examples described later, the amount of power generation increases by at least 30% or more.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the method for manufacturing the magnetostrictive element and the magnetostrictive element of the present invention is not limited to these Examples and Comparative Examples. ..

In Examples and Comparative Examples, a plate-shaped square-shaped magnetostrictive element shown in FIG. 1 was obtained from a magnetostrictive material of a single crystal alloy (Fe ₈₃ Ga ₁₇ single crystal alloy and Fe _80.9 Ga ₁₉ Sm _{0.1 single crystal alloy).} It was manufactured and evaluated as follows.

The magnetic domain structure of the main surface of the magnetostrictive element was investigated by observing the main surface using a Kerr effect microscope. A region (central region of the main surface; size: about 400 μm × about 300 μm) at substantially the same position on the main surface of the magnetostrictive element was selected and evaluated.

A magnetic field was applied in the length direction of the magnetostrictive element, and the amount of magnetostriction when saturated and magnetized, the magnetic field where the magnetic flux density was saturated, and the change in magnetic flux density when compressive / tensile stress was applied to the magnetostrictive element were measured. Specifically, the measurement of the saturation magnetic flux density is performed by installing the magnetostrictive element on a jig capable of applying compressive / tensile stress in the longitudinal direction (y-axis direction, see FIG. 4), and winding a coil around the magnetostrictive element to apply a current. Shed. In FIG. 4, the magnetic field is applied in the magnetic field application direction (angle θ, where 0 ° ≤ θ ≤ 10 °) shown by the solid line H, and the magnetic field is applied with a compressive / tensile stress of 30 MPa using electromagnetic induction. Hysteresis, which is the change in magnetic flux density with respect to, was measured.

As shown in FIG. 4, the magnetostrictive amount is the rate of dimensional change due to the magnetostrictive effect measured in the magnetic field application direction H (angle θ, where 0 ° ≤ θ ≤ 10 °) as the magnetostrictive amount L (ppm). Measure. This measurement was carried out in a room temperature environment (25 ° C.) by the commonly used strain gauge method. More specifically, the strain gauge is attached to the magnetostrictive element so that the gauge axis of the strain gauge is parallel to the length direction of the xy plane of the magnetostrictive element, and a magnetic field is applied parallel to the xy plane of the magnetostrictive element. The value when the magnetostriction was saturated was taken as the amount of magnetostriction of the magnetostrictive element. A vibrating sample magnetometer (VSM) was used as the magnetic field generator, and the strength of the magnetic field was changed from 0T to 1T for measurement.

Furthermore, the amount of power generation was simply measured using a magnetostrictive vibration power generation device. Power was generated by vibrating the obtained magnetostrictive element. Specifically, the magnetostrictive element was placed on a U-shaped magnetostrictive vibration power generation device to generate electricity by vibrating the exciter, and the amount of power generated at this time was simply measured. The acceleration G at the time of measuring the amount of power generation was 0.3 G, and the frequency was 13 Hz.

<Examples 1-1 to 1-3>
The single crystal alloy sample was grown using a high frequency induction heating type CZ furnace.
A plate-shaped magnetostrictive element was produced from a magnetostrictive material from a _{Fe 83} Ga _{17 single crystal alloy.} First, the raw materials of the alloys were weighed and placed in a crucible, and argon gas was introduced into a vacuumed high-frequency induction heating type CZ furnace. Then, when the pressure inside the furnace reached atmospheric pressure, heating of the furnace was started and heated until it became a melt.

A FeGa single crystal cut out in the crystal orientation <100> was used as a seed crystal, and the seed crystal was lowered close to the melt to bring the tip of the seed crystal into contact with the melt. Crystal growth was carried out by gradually lowering the temperature of the furnace and then raising the seed crystal while rotating it. As a result, a columnar single crystal alloy mass having a diameter of 10 mm and a straight body portion length of 80 mm was obtained. This single crystal alloy had a <100> crystal orientation in the height direction of the cylinder.

Next, a plate having a length of 80 mm, a width of 10 mm, and a thickness of 1 mm in the height direction (<100> crystal orientation) of the cylinder from the rectangular parallelepiped portion of the single crystal alloy obtained by wire discharge processing. Three pieces of magnetic strain materials (plate A, plate B, and plate C) having a rectangular parallelepiped shape were cut out.

A plate-shaped rectangular parallelepiped having a main surface of 32 mm in length, 8 mm in width and 1 mm in thickness so that the height direction of the cylinder coincides with the length direction of the magnetostrictive element to be manufactured by processing the cut out plates A to C. A magnetostrictive material of shape was obtained.

Next, using a heat treatment device in a magnetic field, a magnetic field H (0.3T) is applied at a temperature of 500 ° C. so that the angle difference between the application direction of the magnetic field H and the width direction of the magnetostrictive element is 10 ° or less. The magnetostrictive materials A to C were heat-treated in a magnetic field to obtain magnetostrictive elements a to c. The angle difference between the application direction of the magnetic field H and the width direction of the magnetostrictive element was 10 ° or less.

<Examples 2-1 and 2-2>
Example 2 was carried out by repeating Example 1 except that Fe _80.9 Ga ₁₉ Sm _{0.1 single crystal alloy was produced as the single crystal alloy.} However, Example 2 is carried out twice in the same procedure, and each is referred to as Example 2-1 and Example 2-2, and the obtained elements are referred to as a magnetostrictive element d and a magnetostrictive element e.

<Comparative Examples 1-1 to 1-3>
Examples 1-1 to 1-3 were repeated, but differed in the following points: In Comparative Example 1-1, the heat treatment in a magnetic field was not performed. In Comparative Example 1-2, the magnetic field applied in the heat treatment in the magnetic field was 0.1 T. In Comparative Example 1-3, the temperature of the heat treatment in the magnetic field was 200 ° C. Magnetostrictive elements f to h were obtained in each of these comparative examples.

<Comparative Examples 2-1 to 2-3>
Comparative Example 2 was carried out by repeating Example 2 except that the heat treatment in the magnetic field was not carried out to obtain magnetostrictive elements i and j.

The conditions of Examples and Comparative Examples and the evaluation results of the obtained devices are shown in Table 1 as FIG.

As is clear from Table 1, with respect to the magnetic domain structure of the main surface, in the elements of the embodiment, the directions of the magnetic moments are aligned with the width direction of the magnetostrictive element in a region of 70% or more of the main surface, whereas comparison is made. In the example magnetostrictive element, the directions of the magnetic moments are only aligned with the width direction of the magnetostrictive element in a region of 20% or less of the main surface.

The magnetostrictive element of the example saturates the magnetization at a low magnetic field of 0.04 T or less, whereas the magnetostrictive element of the comparative example requires a magnetic field of 0.06 T or more. In the magnetostrictive element of the example, the magnetic flux density change ΔB was as large as 1.2 T or more, whereas in the magnetostrictive element of the comparative example, it was as small as 0.5 T or less. In a separate experiment, the magnetization was saturated even in a lower magnetic field, for example, 0.005T and 0.001T. Therefore, in the magnetostrictive element of the present invention, the magnetic field at which the magnetic domain is saturated is 0.001T to 0.05T, preferably 0. It is 005T to 0.04T. That is, the magnetostrictive element of the present invention can exhibit a change in magnetic flux density accompanied by a sufficiently large magnetostriction in such a relatively low magnetic field.

The magnetostrictive amount L was 270 ppm or more in the magnetostrictive element of the example, whereas it was 20 ppm or less in the magnetostrictive element of the comparative example, which was a very small value. Further, the amount of power generated by using the magnetostrictive element is increased by at least 50% or more when the magnetostrictive element of the present invention is used as compared with the case of the comparative example.

Considering these results, after obtaining a magnetostrictive element having a predetermined shape from a single crystal alloy ingot, the region where the angular difference between the direction of the magnetic moment and the width direction of the main surface is within 10 ° is at least the area of the main surface. By performing heat treatment in a magnetic field so as to be 70%, the strain characteristics and magnetic characteristics of the obtained magnetostrictive element are improved, and as a result, the use of such a magnetostrictive element for power generation can lead to an improvement in the amount of power generation. it can.

If the heating temperature at that time is too low or the applied magnetic field is too weak even if the conventional method without performing the heat treatment in the magnetic field or the heat treatment in the magnetic field is performed, the obtained magnetostrictive element has a magnetostriction in the length direction in the low magnetic field. The change in magnetic flux density is small, and the amount of power generated is small. In other words, it is suggested that the amount of power generation can be improved by cutting out the magnetostrictive element in the crystal orientation <100> and then performing heat treatment in the magnetic field in the width direction as in the method for manufacturing the magnetostrictive element of the present invention. There is.

The magnetostrictive element of the present invention and a method for manufacturing the same provide a FeGa-based magnetostrictive element and a method for manufacturing the same, which exhibit a change in magnetic flux density accompanied by a sufficiently large magnetostriction at a low magnetic field in the length direction. Therefore, according to the manufacturing method, it is possible to improve the magnetic characteristics of the magnetostrictive element cut out from the FeGa-based single crystal alloy, thereby improving the power generation characteristics of the device. As a result, the manufactured magnetostrictive element can be positively applied to a magnetostrictive vibration power generation device or the like for a self-sustaining power source for monitoring social infrastructure or factory equipment.

2 ... Magnetic domain in which the angular difference between the width direction of the main surface of the magnetostrictive element and the direction of the magnetic moment in the magnetic domain is 0 ° 3 ... The angular difference between the width direction of the main surface of the magnetostrictive element and the direction of the magnetic moment in the magnetic domain is 0 ° Magnetic domain 4 ... Magnetic domain in which the angular difference between the width direction of the main surface surface of the magnetostrictive element and the direction of the magnetic moment of the magnetostrictive element is 90 ° 5, 6 ... Main surface of the magnetostrictive element 10 ... Magnetostrictive element P ... Main surface of the magnetostrictive element Area (observation area)
x-axis: width or width direction of the main surface of the magnetostrictive element y-axis: length or length direction of the main surface of the magnetostrictive element z-axis: thickness direction of the magnetostrictive element

Claims (9)

A rectangular parallelepiped Fe-Ga alloy magnetostrictive element whose thickness is smaller than its width.
The magnetic domain on the main surface has a magnetic domain width of 10 μm to 200 μm.
The area of the magnetic domain in which the angle difference between the width direction of the main surface and the direction of the magnetic moment is within 10 ° is 70 to 100% of the area of the main surface.
A magnetostrictive element characterized by. The magnetostrictive element according to claim 1, wherein the aspect ratio of the main surface is 1: 2 to 1: 4. A claim characterized in that the magnetic field at which the magnetic domain of the main surface is saturated is 0.001T to 0.05T with respect to the application of a magnetic field in a direction in which the angular difference from the length direction of the main surface of the magnetostrictive element is within 10 °. Item 2. The magnetostrictive element according to Item 1 or 2. The Fe-Ga alloy has the following formula (1) or the following formula (2).
・ Fe _(100-α1) Ga _α1・ ・ ・ (1)
(In the formula (1), α is the Ga content (at%) and satisfies 10 ≦ α1 ≦ 19)
・ Fe _(100-α2-β) Ga _α2 X _β・ ・ ・ (2)
(In the formula (2), the Ga content (at%) is α and the X content (at%) is β.
X is one or more elements selected from the group consisting of Sm, Eu, Tb, Dy, Cu, Ce, Gd and C, satisfying 5 ≦ α2 ≦ 19 and 0.05 ≦ β ≦ 4).
The magnetostrictive element according to any one of claims 1 to 3. The magnetostrictive element according to any one of claims 1 to 4, which has a plate-shaped rectangular parallelepiped shape. It is a manufacturing method of a magnetostrictive element manufacturing method.
(1) A step of obtaining a single crystal of an Fe-Ga alloy as a magnetostrictive material.
(2) From the obtained magnetic strain material, a rectangular parallelepiped shape whose thickness is smaller than the width of the main surface, preferably a plate-like rectangular parallelepiped shape, and the direction of the length of the main surface is the crystal orientation <100> of a single crystal. The process of cutting out parallel magnetic strain materials,
(3) A step of processing the cut out magnetostrictive material into a predetermined shape, and (4) a magnetostrictive material having a predetermined shape is heat-treated at a predetermined temperature with a magnetic field applied in the width direction on the main surface. A step of aligning the directions of magnetic moments in the width direction A manufacturing method comprising a step of obtaining a magnetostrictive element. The manufacturing method according to claim 6, wherein the predetermined temperature in the step (4) is 400 ° C. to 700 ° C. The manufacturing method according to claim 6 or 7, wherein a magnetic field of 0.2T to 1T is applied in the step (4). The manufacturing method according to any one of claims 6 to 8, wherein in the step (4), the angle difference between the direction of the applied magnetic field and the width direction of the magnetostrictive material is 10 °.

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