JP2020158362A - SEED CRYSTAL FOR FeGa SINGLE CRYSTAL GROWTH, METHOD FOR MANUFACTURING THE SAME AND METHOD FOR MANUFACTURING FeGa SINGLE CRYSTAL - Google Patents

Abstract

To provide: a seed crystal for FeGa single crystal growth capable of easily matching the melting point of a raw material melt in the vicinity of the seed crystal with the melting point of a molten seed crystal when seeding in the raw material melt by a VB method or a VGF method and reducing polycrystal or anisotropic growth during growth; a method for manufacturing the same; and a method for manufacturing a FeGa single crystal.SOLUTION: The seed crystal for FeGa single crystal growth used for FeGa single crystal growth by a unidirectional solidification crystal growth method for solidifying a melt in a crucible has a concentration distribution that a Ga concentration is higher from one end toward the other end in the crystal growth direction.SELECTED DRAWING: Figure 3

Description

The present invention relates to a seed crystal for growing a FeGa single crystal, a method for producing the same, and a method for producing a FeGa single crystal.

The FeGa alloy is machinable and exhibits a large magnetostriction of about 100 to 350 ppm, and is therefore suitable as a material used for magnetostrictive vibration power generation and actuators, and has been attracting attention in recent years. Further, since the FeGa alloy causes a large magnetostriction to appear in a specific orientation of the crystal, the magnetostrictive type is used as a single crystal member in which the direction in which the magnetostrictive member requires magnetostriction and the orientation in which the magnetostrictive of the crystal is maximized are matched. It is considered to be most suitable for materials used for vibration power generation and actuators.

As for the method for producing a FeGa single crystal, for example, Patent Document 1 describes a method for growing a single crystal by the Czochralski method. In the Czochralski method, a crucible filled with a raw material that becomes a single crystal is heated to a high temperature to melt this raw material, and the seed crystal is brought into contact with the liquid surface of the raw material melt in the crucible from above and then raised. This is a method of growing a single crystal in the same orientation as the seed crystal.

However, in this method, the raw material is melted by the high frequency induction heating method, so that the power supply cost is high. Further, since the device configuration is complicated, the device cost is high, and as a result, the manufacturing cost is high.

On the other hand, the VB (Vertical Bridgeman) method and the VGF (Vertical Gradient Freeze) method, which are unidirectional solidification crystal growth methods, do not require pulling up the grown single crystal and are devices. Since there is no need for a space for pulling up a single crystal inside, the crystal growth device can be miniaturized and simplified, and the initial investment cost can be suppressed. When growing a single crystal by the VB method or the VGF method, a seed crystal is placed at the bottom of the crucible, and a required amount of a mixed raw material of Fe and Ga is put on the seed crystal, and this raw material is melted. Then, the crucible is lowered so as to be away from the heating means to grow a single crystal. Seeding is performed for the purpose of propagating the crystal orientation in the process. At the time of seeding, it is necessary that the mixed raw material is melted and a part of the seed crystal is melted, so that a single crystal in which the crystal orientation of the seed crystal is propagated can be grown.

Japanese Unexamined Patent Publication No. 2016-28831

However, at the time of seeding, a problem arises when the difference between the temperature of the mixed raw material melt and the melting point at which the seed crystal melts is significantly different. For example, when the temperature of the mixed raw material melt is lower than the melting point of the seed crystal, the seed crystal is grown in an unmelted state, so that crystal defects such as polycrystallization occur. If the temperature of the mixed raw material melt is too high above the melting point of the seed crystal, the seed crystal is completely melted and problems such as anisotropic growth occur. That is, in the one-way solidification crystal growth method, it is required that only the vicinity of the portion in contact with the mixed raw material of the seed crystal is melted and the lower part of the seed crystal is not melted. Therefore, the permissible control range of temperature control near the contact surface between the seed crystal and the mixed raw material is very small. Further, since the contact surface between the seed crystal and the mixed raw material is inside the crucible and the state cannot be observed from the outside, it is extremely difficult to perform delicate temperature control.

Therefore, in view of the above-mentioned problems, the present invention can easily match the temperature of the raw material melt in the vicinity of the seed crystal with the melting point of the seed crystal when seeding by the VB method or the VGF method. It is an object of the present invention to provide a seed crystal for growing a FeGa single crystal, a method for producing the same, and a method for producing a FeGa single crystal, which can reduce crystal defects such as polycrystallization due to ding and defects such as heterogeneous growth.

In order to achieve the above object, the seed crystal for growing a FeGa single crystal according to one aspect of the present invention is for growing a FeGa single crystal used for growing a FeGa single crystal by a unidirectional solidification crystal growth method in which a melt is solidified in a pit. Seed crystal
The Ga concentration increases from one end to the other in the crystal growth direction.

According to the present invention, even when there is a temperature difference between the melting point of the raw material and the melting point of the seed crystal, both can be appropriately melted to grow a single crystal.

It is a figure which showed an example of the crystal growth apparatus used for carrying out the manufacturing method of the FeGa single crystal which concerns on embodiment of this invention. It is a figure which showed an example which used the crucible which has the diameter-increasing part in the crystal growth apparatus used for carrying out the manufacturing method of the FeGa single crystal which concerns on embodiment of this invention. It is a figure which showed an example of the seed crystal which concerns on embodiment of this invention. It is a figure which showed an example of the Ga concentration distribution of the seed crystal which concerns on embodiment of this invention. It is a structural drawing which showed an example of the growth furnace for producing the seed crystal which concerns on embodiment of this invention. It is a structural drawing which showed an example which used the crucible which has the diameter-increasing part in the growth furnace for producing the seed crystal which concerns on embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

In the one-way solidification crystal growth method, if the difference between the melting point at which the seed crystal melts and the melting point near the seed crystal where the mixed raw material is melted is significantly different, the VB method adjusts by the position of the pit, and the VGF method adjusts the heater output. It becomes difficult to control the seed crystal, and proper seeding cannot be performed. Crystal defects such as polycrystal and heterogeneous growth may occur due to unmelting or complete melting of the seed crystal.

As a result of intensive research on a seed crystal for growing a single crystal, the present inventors should use a seed crystal having a high Ga concentration in the growth direction (upper side) of the crystal and a low Ga concentration on the opposite side (lower side). Therefore, it was found that the temperature of the raw material melt and the melting point of the seed crystal can be easily matched. That is, by using such a seed crystal, it is not necessary to finely adjust the crucible position and the heater output, and even if the adjustment fluctuates slightly back and forth, there is a difference in the melting point of the seed crystal, so that the seeding is surely performed. The present invention has been completed by obtaining the knowledge that it can be performed.

The seed crystal according to the embodiment of the present invention is a seed crystal used for growing a FeGa single crystal. Since FeGa crystals have a large magnetostrictive characteristic of about 100 to 350 ppm, they are used in magnetostrictive vibration power generation, actuators, and the like. In order to make this magnetostrictive characteristic appear in a specific orientation of the crystal, it is considered that a single crystal member in which the direction in which the magnetostrictive characteristic is required and the orientation in which the magnetic strain of the crystal is maximized match is optimal. There is.

The FeGa single crystal can be produced by using it in a pulling method (Czochralski method) or a unidirectional solidification crystal growth method. In the present invention, the seed crystal used in the unidirectional solidification crystal growth method will be described. Examples of the unidirectional solidification crystal growth method include a VB method and a VGF method.

FIG. 1 is a diagram showing an example of a crystal growing apparatus used for carrying out the method for producing a FeGa single crystal according to an embodiment of the present invention. FIG. 1 shows an example of the configuration of a crystal growth apparatus for growing a single crystal by the VB method among the unidirectional solidification crystal growth methods.

The crystal growing device shown in FIG. 1 includes a crucible 10, a crucible stand 20, a crucible shaft 30, and a heating element 40. Further, the seed crystal 50 and the raw material 60 according to the embodiment of the present invention are stored in the crucible 10.

The crucible 10 is a container for storing or holding the seed crystal 50 and the raw material 60. The crucible 10 is made of a material having high heat resistance, and may be made of, for example, alumina.

The crucible stand 20 is a support stand for supporting the crucible 10. The crucible stand 20 is also made of a material having high heat resistance.

The crucible shaft 30 is a shaft for moving the crucible base 20 up and down, and supports the crucible base 20 at the upper end.

The heating element 40 is a heating means for heating the crucible 10 and melting the seed crystal 50 and the raw material 60 stored and held inside the crucible 10. The heating element 40 may be composed of, for example, a heater using a resistor. As the heating element 40, for example, a carbon heating element may be used.

As shown in FIG. 1, in the VB method, a seed crystal 50 is placed on the bottom of the crucible 10, a required amount of a mixed raw material 60 of Fe and Ga is put therein, the raw material 60 is melted, and then the crucible 10 is added. This is a method of growing a single crystal by lowering it away from the heating element 40, which is a heating means.

The VGF method is a method of growing crystals by melting the raw material 60 and then lowering the output of the heating element 40, which is a heating means, while maintaining a high temperature gradient above the crucible 10 and a low temperature gradient below. .. In these methods, the seed crystal 50 is placed at the bottom of the crucible 10 in order to align the orientation of the grown crystals. Therefore, the diameter of the seed crystal is the same as the inner diameter of the crucible 10, and is, for example, about 100 to 150 mm.

The present invention is an invention relating to this kind crystal.

The FeGa single crystal is a crystal having a mismatched composition, and the Ga concentration between the liquid phase and the solid phase is different. The FeGa single crystal, which is said to have good magnetostrictive characteristics, has a Ga concentration of around 18.5 at%. Therefore, the raw materials for growing a single crystal are mixed so that the Ga concentration is around 18.5 at%. As the seed crystal, a seed crystal that matches the Ga concentration of the growing raw material is used. The concentration variation of the seed crystal at this time is generally within 1%.

The seed crystal according to the embodiment of the present invention has a Ga concentration difference in the direction from the surface side (crystal growth direction / upper surface side) in contact with the raw material melt to the opposite surface, the crucible bottom surface side (lower surface side). ing. This Ga concentration difference is set so that the Ga concentration on the surface side in contact with the raw material melt is high and the Ga concentration on the bottom surface side of the crucible is low. The Ga concentration difference at this time is 2 at% or more, preferably 3 at% or more, and more preferably 6 at% or more. As described above, the melting point of the FeGa crystal decreases as the Ga concentration increases.

The crystal growth apparatus used for carrying out the method for producing a FeGa single crystal according to the embodiment of the present invention may be a crystal growth apparatus using a crucible 110 having a diameter-increasing portion 112 as shown in FIG. Good. FIG. 2 is a diagram showing an example in which a crucible 110 having a diameter-increasing portion 112 is used in a crystal growing device used for carrying out the method for producing a FeGa single crystal according to an embodiment of the present invention. The crucible 10 in FIG. 1 has a columnar shape, and the seed crystal 50 used for the crucible 10 has the same diameter as the single crystal to be grown. On the other hand, the pit 110 of the crystal growth apparatus shown in FIG. 2 has a well-shaped small diameter portion 113 in which the seed crystal 150 is installed, and an inverted conical tubular shape whose diameter increases upward from the small diameter portion 113. It is composed of a diameter-increasing portion 112 and a cylindrical fixed-diameter portion 111 that continues upward from the diameter-increasing portion 112 as a crystal growth portion. The seed crystal 150 has a diameter of about φ10 mm and is installed in the small diameter portion 113. In the aspect of FIG. 1, the seed crystal 50 often has a diameter of about 100 mm. Therefore, in the aspect of FIG. 2, the diameter of the seed crystal 150 can be significantly reduced. The inner wall of the diameter-increasing portion 112 has an angle of 30 to 60 degrees with respect to the horizontal direction. After seeding, the crystal is grown in the diameter-increasing portion 112 while increasing the diameter, and then is grown in the constant-diameter portion 111 to have a constant diameter. By using such a crucible 110, the shape of the seed crystal 150 can be reduced, and the production cost of the seed crystal 150 can be reduced.

Since the other components are the same as those in FIG. 1, the components corresponding to FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 3 is a diagram showing an example of a seed crystal according to an embodiment of the present invention. As shown in FIG. 3, the Ga concentration of the upper surface 51 in contact with the raw material is set high, and the Ga concentration of the lower surface 52 in contact with the bottom surface of the crucible 10 is set low.

As described with reference to FIG. 1, in the crystal growth method by the VB method or the VGF method, the seed crystal 50 is arranged at the bottom of the crucible 10, and the required amount of the mixed raw material 60 of Fe and Ga is put on the seed crystal 50. The raw material 60 is melted and then seeded. Seeding is a state in which the mixed raw material 60 is melted and a part of the seed crystal 50 is melted. The Ga concentration of the raw material 60 is often set to around 18.5 at%, which is considered to have good magnetostrictive characteristics, and in general, the seed crystal 50 uses a seed crystal 50 of 18 to 19 at% according to the Ga concentration. I often do it.

The seed crystal 50 according to the embodiment of the present invention can have, for example, a Ga concentration difference of 3 at% and 16.5 to 19.5 at%. Since the seed crystal 50 has a Ga concentration difference, a part of the seed crystal 50 can be melted and seeded in response to a wide range of temperatures as compared with the case where a conventional seed crystal is used. That is, even if the seed crystal 50 is heated according to the temperature at which the raw material 60 melts, the lower part of the seed crystal 50 does not melt because of the difference in melting point. Therefore, it is possible to prevent a situation in which the heating temperature is too high and the seed crystal 50 is melted too much, or a situation in which the raw material 60 is not heated to a temperature at which the raw material 60 is melted due to such a situation. Therefore, it is not necessary to finely adjust the position of the crucible 10 in the VB method and the heater output in the VGF method at the time of seeding, and even if the adjustment is slightly deviated, the adjustment error can be tolerated by providing the concentration difference. As a result, unmelting or complete melting of the seed crystal 50 can be prevented, and polycrystallization and anisotropic growth can be suppressed.

The Ga concentration range of the seed crystal 50 may be set evenly above and below with the Ga concentration of the mixed raw material of Fe and Ga as the median value, but the upper limit of the Ga concentration of the seed crystal 50 is set to the Ga concentration of the mixed raw material of Fe and Ga + 1at. %, And the lower limit side of the Ga concentration of the seed crystal 50 may be set wide. At the time of seeding, it is necessary to melt at least a mixed raw material of Fe and Ga, which is limited. Therefore, unmelting of the seed crystal 50 can be prevented by setting the upper limit of the Ga concentration of the seed crystal 50 to be + 1 at% of the Ga concentration of the mixed raw material, including variations such as segregation of the mixed raw material. By setting the lower limit of the Ga concentration of the seed crystal 50 widely, it is possible to further prevent the seed crystal 50 from completely melting even at a temperature higher than the melting point of the mixed raw material 60. Preferably, the Ga concentration difference of the seed crystal 50 is set to 6 at% or more, the upper limit of the Ga concentration range is set to the Ga concentration of the mixed raw material 60 + 1 at%, and the lower limit is set to the Ga concentration of the mixed raw material 60 to -5 at% or less.

The thickness of the seed crystal 50 is about 10 mm to 50 mm. It is preferable that the concentration gradient is evenly distributed within this thickness range, but the concentration gradient does not have to be uniform.

FIG. 4 is a diagram showing an example of the Ga concentration distribution of the seed crystal according to the present embodiment.

In FIG. 4, an example of the Ga concentration distribution of the seed crystal 50 according to the present embodiment is shown, and the Ga concentration distribution can be seen from 13.0 at% to around 19.5 at%, which is less than 20.0.

The Ga concentration distribution can be variously set according to the application. For example, as shown in FIG. 4, the concentration gradient on the side where the concentration of Ga is low may be gentle, and the concentration gradient on the side where the concentration of Ga is high may be steep. At this time, the difference between the seed crystal length and the Ga concentration is taken into consideration. In FIG. 4, by collecting seed crystals with a crystal length of 17 mm to 42 mm, a seed crystal having a seed crystal length of 25 mm and a Ga concentration of 13.5 at% to 19.5 at% and a Ga concentration difference of 6% can be obtained. In this way, the required concentration gradient and seed crystal length can be appropriately set, and the seed crystal can be collected from the required location. Then, the end face having a high Ga concentration distribution is arranged at a position in contact with the raw material 60, and the end face having a low Ga concentration distribution is arranged in the crucible 10 so as to come into contact with the bottom surface of the crucible 10. As described above, when the height difference of Ga concentration is as much as 6.0 at%, the melting point difference can be set large, and seeding can be performed very easily.

Next, a method for producing the seed crystal 50 according to the embodiment of the present invention will be described. In the method for producing a seed crystal 50 according to the embodiment of the present invention, a crystal is grown by using a unidirectional solidification crystal growth method. The unidirectional solidification crystal growth method includes a VB method and a VGF method. As described above, in the VB method, a seed crystal 50 is placed on the bottom of the crucible 10, a required amount of a mixed raw material 60 of Fe and Ga is put therein, the raw material 60 is melted, and then the crucible 10 is heated by a heating means. This is a method of growing a single crystal by lowering it away from a certain heating element 40. The VGF method is a method of growing crystals by melting the raw material 60 and then lowering the output of the heating element 40, which is a heating means, while maintaining a high temperature gradient above the crucible 10 and a low temperature gradient below.

Hereinafter, with reference to FIG. 5, the details of the method for producing FeGa seed crystals will be described by taking the VB method as an example. FIG. 5 is a structural diagram of a growing furnace for producing a seed crystal according to an embodiment of the present invention using the VB method. The structure of the crystal growing apparatus is the same as that of FIG. 1, and only the seed crystal 55 is different from that of FIG.

The crucible 10 is placed on the crucible stand 20, and the seed crystal 55 is stored in the crucible 10. As the seed crystal 55 at this time, one having a constant Ga concentration is used. A desired amount of Fe powder is added to the melted Ga, and a required amount of the mixed raw material 60 is added thereto. There is a carbon heating element 40 around the crucible 10, and the heating element 40 is arranged so that the upper part is high and the lower part is low. The inside of the furnace may have an inert gas atmosphere (Ar gas or the like). In this state, the crucible shaft 30 is gradually raised so that the height of the seed crystal 55 is melted by about half, and seeding is performed. After seeding, the melted solid-liquid interface shape of the seed crystal 55 is stabilized and held for about 1 hour for the purpose, and then the crucible shaft 30 is lowered at a constant speed. After solidifying all the melt in the crucible 10, the furnace is cooled at a rate of about 300 ° C./h, and after confirming that the temperature has reached about room temperature, the crystals are taken out to obtain crystals having a Ga concentration gradient. be able to.

The seed crystal 55 used at this time shall have a Ga concentration of the mixed raw material within ± 1 at%. The concentration of the mixed raw material and the seed crystal 55 at this time is set to 17.5 at%. The target value of the FeGa single crystal is 18.5 at%, which is generally considered to have good magnetostrictive characteristics, but in the method for producing this kind of crystal, the target value is 1.0 at% lower than 18.5 at%. The FeGa single crystal is a crystal having a mismatched composition, the Ga concentration between the liquid phase and the solid phase is different, and the grown single crystal can grow a single crystal having a Ga concentration gradient.

Further, the concentration difference of the Ga concentration gradient and the length of growth can be appropriately adjusted by adjusting the descending speed of the crucible in the VB method and the output in the VGF method. If the descent speed is high, the difference in Ga concentration of the crystals tends to be small by reducing the output quickly.

For example, when producing a seed crystal having a Ga concentration of 13.5 to 19.5 at%, the Ga concentration of the initial seed crystal is set to 13.5 at%, and the descending speed of the crucible is 2.0 mm / hour. You just have to descend. When producing a seed crystal with a Ga concentration of 16.5 to 19.5 at%, the Ga concentration of the initial seed crystal is set to 16.0 at%, and the crucible descends at a rate of 5.0 mm / hour. Just do it.

As shown in FIG. 3, FeGa has a disagreeable composition as a method for producing a seed crystal having a Ga concentration difference by using a seed crystal having a Ga concentration difference at a crystal length of 25 mm with respect to the crystal aiming there. Ga concentration fluctuates during growing. Taking advantage of these advantages, the crucible 10 was grown at a descent speed of 2 mm / hr by the VB method. This time, the concentration difference was set to 6 at%, but it is possible to reduce or increase the concentration difference by changing the descent speed of the crucible 10. In addition, it is possible to deal with the target concentration by changing the concentration of the raw material. The growing method may be the VGF method.

FIG. 6 is a structural diagram showing an example in which a crucible having a diameter-increasing portion is used in a growing furnace for producing a seed crystal according to an embodiment of the present invention. As shown in FIG. 6, a crucible 110 having a diameter-increasing portion 112 can also be used.

The seed crystal 155 used for producing the seed crystal 150 has a uniformly distributed Ga concentration. The difference from FIG. 5 is that a seed crystal 155 is placed in the small diameter portion 113, and a seed crystal having a large diameter and a Ga concentration gradient is obtained through the diameter increasing portion 112 and the constant diameter portion 113 while growing a single crystal. It is a point. Since the production procedure itself is the same as that described in FIG. 5 and the configuration of the apparatus itself is the same as that in FIG. 2, a detailed description of the method for producing a seed crystal having a Ga concentration gradient will be omitted.

Hereinafter, examples of the method for producing a FeGa single crystal according to the present embodiment using the VB method will be described. For the sake of easy understanding, the components corresponding to the components described in the embodiments will be described with the same reference numerals as those in the embodiments.

First, as shown in FIG. 3, a seed crystal 50 for a FeGa single crystal having a length of 25 mm and a diameter of 50 mmφ having a difference in Ga concentration in the crystal growth direction was prepared.

As shown in FIG. 1, a growth test was carried out using the seed crystal 50 according to this example. The crucible 10 was made of alumina and had an inner diameter of 51 mmφ, a height of 150 mm, and a thickness of 3 mm. The crucible 10 was placed on the crucible stand 20, and the seed crystal 50 according to the present embodiment was stored in the crucible 10.

At that time, the one having a low melting point and a high Ga concentration was designated as the upper side facing the raw material 60, and the one having a high melting point and a low Ga concentration was designated as the lower side facing the bottom surface of the crucible 10. A desired amount of Fe powder was added to the melted Ga, and a required amount of the mixed raw material 60 was added thereto. A carbon heating element 40 was arranged around the crucible 10, and the heating element 40 was set to have a high temperature distribution in the upper part and a low temperature distribution in the lower part. The inside of the furnace was carried out in an inert gas atmosphere (Ar gas). In this state, the crucible shaft 30 was adjusted while gradually increasing so that the height of the seed crystal 50 was melted by about half, and seeding was performed.

After seeding, the crucible shaft 30 was lowered for about 1 hour to start crystal growth. After solidifying all the melt in the crucible 10, the furnace was cooled at a rate of about 300 ° C./h, and after confirming that the temperature had reached about room temperature, crystals were taken out. In this cycle, the seed crystal concentration difference and the condition that the crucible position at the time of seeding was moved up and down were shaken, and the seeding possibility test was carried out. The results are shown in Table 1.

(Evaluation)
With respect to the seed crystal length of 25 mm, the temperature of the raw material melt becomes low and the seeds are moved away from the heating element 40 when the crucible position, which is seeded around 4.5 mm from the upper surface, is set as appropriate and lowered from the appropriate position (-direction). The crystal 50 is difficult to melt, and conversely, when it is raised from an appropriate position (+ direction), it becomes closer to the heating element 40, so that the temperature of the raw material melt rises and the seed crystal 50 is easily melted.

In the test, as a result of changing the crucible position from the proper position in 4 mm increments by -8 mm to +16 mm, the seed crystal 50 having a Ga concentration difference of 6.0 at% according to Example 1 was seeded from -4 mm to +12 mm without any problem. Was done. On the other hand, for the seed crystal having a concentration difference of 3.0 at% according to Example 2, the good range was narrowed to -4 mm to +4 mm.

On the other hand, for the seed crystal having a Ga concentration difference of 0 at% according to the comparative example, anisotropic growth was already observed at ± 4 mm. From the above results, it was confirmed that the good range of seeding was widened by using seed crystals with different Ga concentration differences.

As described above, according to the seed crystal for growing FeGa single crystal and the method for producing the same according to the present embodiment, and the method for producing the FeGa single crystal, the difference between the seed crystal and the melting point of the raw material at the time of seeding is suppressed. Fine adjustment of the position of the pot and the heater output is not required, and polycrystallization and anisotropic growth can be reduced.

Further, according to the seed crystal for growing FeGa single crystal and the method for producing the same according to the present embodiment, and the method for producing the FeGa single crystal, when seeding is performed by the VB method or the VGF method, the growth direction side of the Ga concentration is high. By using a seed crystal with a low lower side, the seed crystal melts in a self-adjusting manner to the point where it matches the temperature of the raw material melt, so fine adjustment of the pot position and heater output is not necessary, and the adjustment fluctuates slightly back and forth. Since there is a difference in concentration between seed crystals, that is, a difference in melting point, it is possible to easily match the melting points of both. In addition, this can reduce polycrystals and anisotropic growth during growth.

Although the preferred embodiments and examples of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and examples, and does not deviate from the scope of the present invention. Various modifications and substitutions can be added to the examples.

10 Crucible 20 Crucible stand 30 Crucible shaft 40 Heating element 50 Seed crystal 60 Raw material

Claims (7)

A seed crystal for growing a FeGa single crystal used for growing a FeGa single crystal by a unidirectional solidification crystal growth method in which the melt is solidified in a crucible.
A seed crystal for growing a FeGa single crystal having a Ga concentration distribution in which the Ga concentration increases from one end to the other in the crystal growth direction. The seed crystal for growing a FeGa single crystal according to claim 1, wherein the concentration difference of the Ga concentration is 2.0 to 6.0 at%. The seed crystal for growing a FeGa single crystal according to claim 1 or 2, wherein the concentration gradient of the Ga concentration becomes steeper as the Ga concentration increases. The process of arranging FeGa seed crystals with a uniform Ga concentration distribution on the bottom of the crucible, and
A step of charging the raw material for growing a FeGa single crystal onto the FeGa seed crystal in the crucible, and
A seeding step of melting a part of the FeGa seed crystal including a part in contact with the raw material for growing the FeGa single crystal, and
It has a step of lowering the crucible and growing a FeGa single crystal.
The Ga concentration of the FeGa seed crystal is within ± 1 at% of the Ga concentration of the raw material for growing the FeGa single crystal.
A method for producing a FeGa seed crystal having a Ga concentration gradient, which lowers the crucible at a speed faster than when the FeGa single crystal produces a FeGa single crystal having a Ga concentration of 18.5 at%. The method for producing a FeGa seed crystal according to claim 4, wherein the Ga concentration of the raw material for growing a FeGa single crystal is set to 17.5 at%. The Ga concentration is on the bottom of the pit of the crystal growth device that grows the FeGa single crystal growth seed crystal in which the Ga concentration increases from one end to the other end in the crystal growth direction by the unidirectional solidification crystal growth method. The process of arranging so that the higher end face is the upper surface,
A step of putting the raw material for growing a FeGa single crystal onto the seed crystal for growing a FeGa single crystal in the crucible, and
A seeding step of dissolving a part of the seed crystal for growing a FeGa single crystal, including a part in contact with the raw material for growing a FeGa single crystal,
A method for producing a FeGa single crystal, which comprises a step of lowering the crucible to grow a FeGa single crystal. The Ga concentration of the end face of the seed crystal for growing a FeGa single crystal in contact with the raw material for growing a FeGa single crystal is set higher than the Ga concentration of the raw material for growing a FeGa single crystal according to claim 6. A method for producing a FeGa single crystal.