JP2022026698A - Ferrimagnetic material and its manufacturing method - Google Patents

Abstract

The present invention provides a compound that is said to have the potential for half-metallic antiferromagnetism and actually has ferrimagnetism, and an efficient method for producing the same. A ferrimagnetic material is composed of Fe, Cr, and S, and the atomic percentages of Fe, Cr, and S satisfy the following formulas (1) and (2). It is preferable that the ferrimagnetic material has a hexagonal crystal structure and consists only of a (FeCr)S compound in which the atomic arrangement in the crystal structure is P63mc in space group notation. 0.85<Fe/Cr<1.18(1), 50<S<55(2) [Selection diagram] None

Description

The present invention relates to a ferrimagnetic material that can be used in various magnetic devices and a method for producing the same.

Of the upward electron spin state and the downward electron spin state, one of the electron spin states exhibits properties as a metal, while the other electron spin state exhibits properties as an insulator or a semiconductor (half-metallic anti-strength). Magnetic material) has been proposed by van Leuken and de Glute (eg, Non-Patent Document 1).

Various substances have been proposed as such half-metallic antiferromagnets. For example, electronic states are calculated for Sr ₂ VCuO ₆ , La ₂ MnVO ₆ , and La ₂ MnCoO ₆ having a double perovskite structure. Among these intermetallic compounds, it is predicted that La ₂ MnVO ₆ may exhibit half-metallic antiferromagnetism (Non-Patent Document 2).

Further, in Patent Document 1 (Japanese Unexamined Patent Publication No. 2009-231471), with respect to various compounds, it is an object of the present invention to provide a half-metallic antiferromagnetic material which is chemically stable and has a stable magnetic structure. 1 Principle Electronic state calculation is performed and it is confirmed that a specific compound has half-metallic antiferromagnetism. As a result, it is a compound having a nickel arsenic type, a flash zinc ore type, a wurtz ore type, a chalcopyrite type or a rock salt type crystal structure, and is composed of two or more kinds of magnetic elements and chalcogen or punictogen. The types or more of magnetic elements include magnetic elements having less than 5 effective d-electrons and magnetic elements having more than 5 effective d-electrons, and the total number of effective d-electrons of two or more types of magnetic elements is 10 or more. A half-metallic anti-ferromagnetic material, which has a value close to 10, has been proposed.

van Leuken and de Groot, Phys. Rev. Let. 74,1171 (1995). W. E. Pickett, Phys. Rev. B57, 10613 (1998).

Japanese Unexamined Patent Publication No. 2009-231471

However, the half-metallic antiferromagnets described in Non-Patent Document 1, Non-Patent Document 2 and Patent Document 1 have only theoretically shown their possibility. That is, although many compounds have been proposed, a specific production method has not been shown, and magnetism as an actual substance has not been confirmed. In addition, the magnetism and the composition and crystal structure of the compound are The relationship etc. have not been clarified at all.

In view of the above-mentioned problems in the prior art, an object of the present invention is a compound which is considered to have a possibility of half-metallic antiferromagnetism, and which actually has ferrimagnetism and its efficient production. To provide a method.

As a result of intensive studies on the composition, crystal structure, magnetism, etc. of the compound composed of Fe, Cr, and S in order to achieve the above object, the present inventor has a specific composition range in the (FeCr) S compound. It has been found that it has ferrimagnetism clearly only in the case, and the present invention has been reached. In the claims and specification of the present application, "ferrimagnetism" is a concept including "antiferromagnetism", and "ferrimagnetic material" includes "antiferromagnetic material".

That is, the present invention
It is composed of Fe, Cr and S, and is composed of Fe, Cr and S.
The Fe, the Cr, and the atomic% of the S satisfy the following formulas (1) and (2).
Provided is a ferrimagnetic material, which is characterized by.
0.85 <Fe / Cr <1.18 (1)
50 <S <55 (2)
Fe / Cr is the ratio of Fe and Cr in atomic%.

The ferrimagnetic material of the present invention is composed of Fe, Cr and S, and in the above Patent Document 1, the compound may have half-metallic antiferromagnetism based on the result of the first-principles electronic state calculation. Sex is suggested.

Here, the greatest feature of ferrimagnetism of the present invention is the amount (atomic%) of each constituent element, which satisfies both "0.85 <Fe / Cr <1.18" and "50 <S <55". This makes it possible to impart ferrimagnetism to the compound. In addition, a very small amount of elements mixed as unavoidable impurities are allowed.

The ferrimagnetic material of the present invention preferably comprises only a (FeCr) S compound having a hexagonal crystal structure and having an atomic arrangement of P63 mc in the space group notation. Ferrimagnetism can be expressed more clearly by having only a (FeCr) S compound having a hexagonal crystal structure and having an atomic arrangement in the crystal structure of P63 mc in the notation of a space group.

Further, in the ferrimagnetic material of the present invention, it is preferable that the mass magnetization at 50 kOe and 5 K is 10 emu / g or less. The more preferable mass magnetization at 50 kOe and 5K is 5 emu / g or less, and the most preferable mass magnetization is 3 emu / g or less.

Further, the present invention
It is composed of Fe, Cr and S, and is composed of Fe, Cr and S.
Using a raw material in which the atomic% of Fe, Cr and S satisfy the following formulas (1) and (2).
Also provided is a method for producing a ferrimagnetic material, which is characterized by the above.
0.85 <Fe / Cr <1.18 (1)
50 <S <55 (2)

By using the method for producing a ferrimagnetic material of the present invention, the ferrimagnetic material of the present invention can be easily obtained. Here, as long as the composition of the raw material and the composition of the obtained ferrimagnetic material are substantially the same and the effect of the present invention is not impaired, the method of using the raw material as a bulk body or a film-forming body is not particularly limited, and various conventionally known methods are used. The sintering method, the physical vapor deposition method, or the like can be used.

In the method for producing a ferri magnetic material of the present invention, the first step of producing a green compact consisting of a mixed powder consisting of Fe powder, Cr powder and S powder, and the sintering of the green powder to obtain a sintered body. It is preferable to have a second step of obtaining. In addition to being able to strictly adjust the composition of the mixed powder by the amount of Fe powder, Cr powder and S powder added, ferrimagnetism of any size can be obtained by sintering. Further, the obtained sintered body (ferrimagnetic material) can also be used as a target material for a physical vapor deposition method.

Further, in the method for producing a ferrimagnetic material of the present invention, it is preferable to cool the sintered body immediately after sintering at a cooling rate of 100 to 10000 ° C./sec in the second step. A single-phase (FeCr) S compound can be obtained by cooling the sintered body immediately after sintering at a cooling rate of 100 to 10000 ° C./sec. Here, the cooling rate of 100 to 10000 ° C./sec can be realized, for example, by cooling the sintered body immediately after sintering with water.

Further, in the method for producing a ferrimagnetic material of the present invention, it is preferable that the sintering temperature is 700 to 1000 ° C. in the second step. By setting the sintering temperature to 700 to 1000 ° C., a (FeCr) S compound having a hexagonal crystal structure and having an atomic arrangement in the crystal structure of P63 mc in the space group notation can be reliably obtained.

Further, in the method for producing a ferrimagnetic material of the present invention, it is preferable to sinter the green compact in a state of being sealed in a quartz tube in the second step. By sintering the green compact in a state of being sealed in a quartz tube, oxidation of the green compact can be suppressed, and a ferrimagnetic material having a desired composition can be efficiently produced.

According to the ferrimagnetic substance of the present invention and a method for producing the same, a compound which is considered to have a possibility of half-metallic antiferromagnetism and which actually has ferrimagnetism and an efficient production method thereof are provided. be able to.

It is a schematic diagram which shows the temperature dependence of the magnetization of a compensating ferrimagnetic material. It is an XRD pattern of the sintered body obtained in Example 1. It is an XRD pattern of the sintered body obtained in Example 2. It is an XRD pattern of the sintered body obtained in Example 3. It is an XRD pattern of the sintered body obtained in Example 4. 5 is an XRD pattern of the sintered body obtained in Example 5. 6 is an XRD pattern of the sintered body obtained in Example 6. It is an XRD pattern of the sintered body obtained in Example 7. It is an XRD pattern of the sintered body obtained in Example 8. 6 is a magnetization curve of the sintered body obtained in Example 1. 6 is a magnetization curve of the sintered body obtained in Example 2. 6 is a magnetization curve of the sintered body obtained in Example 3. 6 is a magnetization curve of the sintered body obtained in Example 4. 6 is a magnetization curve of the sintered body obtained in Example 5. 6 is a magnetization curve of the sintered body obtained in Example 6. 6 is a magnetization curve of the sintered body obtained in Example 7. 6 is a magnetization curve of the sintered body obtained in Example 8. 6 is a thermomagnetic curve of the sintered body obtained in Example 2. 6 is a thermomagnetic curve of the sintered body obtained in Example 3. 6 is a thermomagnetic curve of the sintered body obtained in Example 5. 6 is a thermomagnetic curve of the sintered body obtained in Example 8. It is an XRD pattern of the sintered body obtained in Comparative Example 1. It is an XRD pattern of the sintered body obtained in Comparative Example 2. It is an XRD pattern of the sintered body obtained in Comparative Example 3. It is an XRD pattern of the sintered body obtained in Comparative Example 4. It is a magnetization curve of the sintered body obtained in Comparative Example 1. 6 is a magnetization curve of the sintered body obtained in Comparative Example 2. 6 is a magnetization curve of the sintered body obtained in Comparative Example 3. It is a magnetization curve of the sintered body obtained in Comparative Example 4. It is a thermomagnetic curve of the sintered body obtained in Comparative Example 1. It is a thermomagnetic curve of the sintered body obtained in Comparative Example 2. It is a thermomagnetic curve of the sintered body obtained in Comparative Example 3. It is a thermomagnetic curve of the sintered body obtained in Comparative Example 4. It is a figure which shows the relationship between the composition and the mass magnetization of the (FeCr) S compound obtained in an Example and a comparative example.

Hereinafter, typical embodiments of the ferrimagnetic material of the present invention and the method for producing the same will be described in detail with reference to the drawings, but the present invention is not limited to these.

(1) Ferrimagnetic material The ferrimagnetic material of the present invention is composed of Fe, Cr and S, and its composition range is strictly defined. Hereinafter, the ferrimagnetic material of the present invention will be described in detail.

The ferrimagnetic material of the present invention is composed of _two kinds of magnetic elements (Fe and Cr) and chalcogen (S). Regarding the composition formula (FeCr) S2, the first principle electronic state is described in Patent Document 1. Calculations suggest that it has half-metallic antiferromagnetism. Specifically, in the results showing the density of states curve in the antiferromagnetic state, it was confirmed that half-metallic was expressed from the density of states curve, and the upward spin total electron state density and the downward spin total electron state density were obtained. As a result of integrating up to Fermi energy, both integrated values are equal, and the magnetization is 0 as a whole, confirming that they are antiferromagnetic.

On the other hand, when the present inventor investigated in detail the relationship between the composition of Fe, Cr and S and the magnetism of the (FeCr) S compound, the atomic% was "0.85 <Fe / Cr <1.18". It was revealed that the (FeCr) S compound satisfying both "50 <S <55" exhibits ferrimagnetism, but the other (FeCr) S compounds do not exhibit clear ferrimagnetism. That is, it cannot be said that the compound whose expression of half-metallic antiferromagnetism is predicted by the first-principles electronic state calculation does not necessarily have the physical characteristics.

Here, the ratio of each constituent element is more preferably Fe amount: 23 to 25 atomic%, Cr amount: 23 to 25 atomic%, S amount: 50 to 55 atomic%. By setting each constituent element in these ranges, a (FeCr) S compound having ferrimagnetism can be obtained more reliably. The method for measuring the composition of the (FeCr) S compound is not particularly limited, but it is preferable to use ICP emission spectroscopic analysis.

Further, the ferrimagnetic material of the present invention preferably comprises only a (FeCr) S compound having a hexagonal crystal structure and having an atomic arrangement of P63 mc in the space group notation. Ferrimagnetism can be expressed more clearly by having only a (FeCr) S compound having a hexagonal crystal structure and having an atomic arrangement in the crystal structure of P63 mc in the notation of a space group.

Further, it is preferable that the a-axis lattice spacing of the crystal structure is 0.343 to 0.345 nm and the c-axis lattice spacing is 0.573 to 0.575 nm. The method for evaluating the crystal structure and lattice spacing of the (FeCr) S compound is not particularly limited, and for example, a general X-ray diffraction method can be used.

In the ferrimagnetic material of the present invention, the mass magnetization at 50 kOe and 5 K is preferably 10 emu / g or less. The more preferable mass magnetization at 50 kOe and 5K is 5 emu / g or less, and the most preferable mass magnetization is 3 emu / g or less. The smaller the value of the mass magnetization, the more remarkable the characteristics of ferrimagnetism (compensated ferrimagnetism).

Further, the ferrimagnetic material of the present invention preferably has the characteristics of a compensatory ferrimagnetic material. By evaluating the temperature dependence of magnetization in a strong magnetic field and confirming the temperature change of spontaneous magnetism as shown in FIG. 1, it can be confirmed that the (FeCr) S compound is a compensatory ferrimagnetic material.

The shape and size of the ferrimagnetic material of the present invention are not particularly limited as long as the effects of the present invention are not impaired, and various shapes and sizes conventionally known as ferrimagnetic materials can be used.

(2) Method for producing ferrimagnetic material The most characteristic feature of the method for producing a ferrimagnetic material of the present invention is that the composition of the raw material is strictly defined. Hereinafter, one aspect of the method for producing a ferrimagnetic material of the present invention will be described in detail.

1. 1. Raw Material The raw material used in the method for producing a ferrimagnetic material of the present invention is composed of Fe, Cr and S, and each element is "0.85 <Fe / Cr <1.18" and "50 <S <" in atomic%. It is necessary to satisfy both "55".

The shape and size of the raw material are not particularly limited, but for example, the ratio of each element can be easily adjusted by mixing Fe powder, Cr powder and S powder. Here, in order to suppress the mixing of impurities, it is preferable to use each powder having the highest possible purity, and for example, it is preferable to use a powder having a purity of 99.9% by mass or more.

The size of the raw material powder is preferably 10 to 300 μm. By setting the size of the raw material powder to 10 μm or more, it is possible to suppress the mixing of impurities into the (FeCr) S compound. On the other hand, by setting the size of the raw material powder to 300 μm or less, the distribution of each element in the green compact can be made uniform, and the reaction and densification by sintering can be facilitated.

2. 2. Manufacturing process The method for producing a ferri magnetic material of the present invention is a first step of producing a green compact consisting of a mixed powder consisting of Fe powder, Cr powder and S powder, and a sintered body by sintering the green powder. It is preferable to have a second step of obtaining.

(1) First step (manufacturing of green compact)
The first step is a step for obtaining a green compact for sintering in the second step. After accurately weighing the Fe powder, Cr powder and S powder so that the composition satisfies both "0.85 <Fe / Cr <1.18" and "50 <S <55" in atomic%, each powder becomes Mix until evenly dispersed. The mixing method is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known mixing methods can be used.

Next, by pressurizing the obtained mixed powder at room temperature to obtain a dense green compact, a dense (FeCr) S compound can be obtained by sintering in the second step. The pressurizing method is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known pressurizing methods can be used, for example, a uniaxial press can be used.

(2) Second step (sintering of green compact)
The second step is a step for sintering the green compact obtained in the first step and obtaining a (FeCr) S compound by the reaction and densification of the raw material powder.

The green compact is preferably sintered in a state of being sealed in a quartz tube. By sintering the green compact in a state of being sealed in a quartz tube, oxidation of the green compact can be suppressed, and an antiferromagnetic material having a desired composition can be efficiently produced. Encapsulation in a quartz tube is preferably performed, for example, in a depressurized argon atmosphere.

The sintering temperature in the second step is preferably 700 to 1000 ° C. By setting the sintering temperature to 700 to 1000 ° C., a (FeCr) S compound having a hexagonal crystal structure and having an atomic arrangement in the crystal structure of P63 mc in the space group notation can be reliably obtained. Here, in order to obtain a sufficiently compositionally homogeneous compound (because diffusion sufficiently occurs within 24 hours), the temperature is more preferably 950 to 1000 ° C., and in order to obtain a homogeneous body in a shorter time. Most preferably, it is 1000 ° C.

Further, it is preferable to cool the sintered body immediately after sintering at a cooling rate of 100 to 10000 ° C./sec. A single-phase (FeCr) S compound can be obtained by cooling the sintered body immediately after sintering at a cooling rate of 100 to 10000 ° C./sec. Further, in order to maintain the regularity of the compound phase, the cooling rate is more preferably 100 to 1000 ° C./sec.

Although the typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all of these design changes are included in the technical scope of the present invention. Will be.

<< Example >>
Fe powder (purity: 99.9% by mass or more, particle size: less than 53 μm), Cr powder (purity: 99.9% by mass or more, particle size: 180 to 300 μm) and S powder (purity: 99.99% by mass or more) , Particle size: less than 75 μm) was used as a raw material powder, and these were weighed and mixed so as to be the respective ratios of Examples 1 to 8 in Table 1.

Each of the obtained mixed powders was uniaxially pressed at about 300 MPa to prepare a green compact. Next, the green compact was sealed in a quartz tube under a reduced pressure of 0.1 MPa in an argon atmosphere, and then sintered under the conditions shown in Table 2 to obtain a sintered body.

As a typical example, the composition of the sintered body obtained in Example 2 was measured by ICP emission spectroscopic analysis using IRIS Advantage DUO instrument manufactured by Thermo Fisher Scientific Co., Ltd., and found that Fe: 24.3 atomic%, Cr. : 23.1 atomic%, S: 52.5 atomic%. Since the element ratio of the raw material powder is Fe: 24.1 atom%, Cr: 23.3 atomic%, S: 52.6 atomic%, the composition of the raw material powder and the sintered body can be regarded as the same. can.

In order to identify the constituent phase of the sintered body, XRD measurement was performed using Rint-Ultima III manufactured by Rigaku (using Cu-Kα ray). The XRD patterns of the sintered bodies obtained in Examples 1 to 8 are shown in FIGS. 2 to 9, respectively.

The XRD patterns of FIGS. 2 to 9 are all caused by the (FeCr) S compound whose atomic arrangement is P63 mc in the notation of the space group. From the results, all the sintered bodies obtained in the examples have a hexagonal crystal structure, and the atomic arrangement in the crystal structure is P63 mc in the notation of the space group (FeCr) S compound only. Can be confirmed.

Next, the magnetic properties of the obtained sintered body were investigated. Specifically, the magnetization curve at 5K was measured using MPMS manufactured by Quantum Design Japan. The magnetization curves of the sintered bodies obtained in Examples 1 to 8 are shown in FIGS. 10 to 17, respectively. Table 3 shows the mass magnetization at 50 kOe. It can be seen that the mass magnetizations of the sintered bodies obtained in the examples are all 10 emu / g or less.

Moreover, the thermomagnetic curve of the sintered body obtained in the Example was measured using PPMS (VSM-OVEN option) manufactured by Nippon Quantum Design Co., Ltd. The magnetic field was 5 kOe or 500 Oe, and the temperature range was 300 to 600 K. The thermomagnetic curves of the sintered bodies obtained in Example 2, Example 3, Example 5, and Example 8 are shown in FIGS. 18, 19, 20, and 21, respectively. The thermomagnetic curves of FIGS. 18 to 21 show the temperature dependence of the magnetization of the compensatory ferrimagnetic material shown in FIG. 1.

≪Comparison example≫
The element ratio of the raw material powder was set to Comparative Examples 1 to 4 in Table 1, and the sintered body was obtained in the same manner as in Examples except that the sintering conditions of Comparative Examples 1 to 4 in Table 2 were used. rice field.

The XRD patterns of the sintered bodies obtained in Comparative Examples 1 to 4 measured in the same manner as in Examples are shown in FIGS. 22 to 25, respectively. In the XRD pattern of the sintered body obtained in Comparative Example 1, in addition to the XRD pattern of the sintered body obtained in the example, there is a diffraction pattern caused by FeCr ₂ S ₄ . Further, in the XRD pattern of the sintered body obtained in Comparative Example 4, although it is difficult to identify, there is a diffraction pattern other than the XRD pattern of the sintered body obtained in the example. These results mean that the sintered bodies obtained in Comparative Example 1 and Comparative Example 2 are not single-phase.

The magnetization curves of the sintered bodies obtained in Comparative Examples 1 to 4 measured in the same manner as in Examples are shown in FIGS. 26 to 29, respectively. Table 3 shows the mass magnetization at 50 kOe. It can be seen that the mass magnetizations of the sintered bodies obtained in the comparative examples are all larger than 10 emu / g.

The thermomagnetic curves of the sintered bodies obtained in Comparative Examples 1 to 4 measured in the same manner as in Examples are shown in FIGS. 30 to 33, respectively. The thermomagnetic curve of the sintered body obtained in the comparative example is completely different from the thermomagnetic curve of the sintered body obtained in the example, and does not have the characteristics of ferrimagnetism.

The relationship between the composition of the (FeCr) S compound obtained in Examples and Comparative Examples and the mass magnetization is shown in FIG. 34. The numerical values shown in the circles in the figure are the values of mass magnetization shown in Table 3. In the (FeCr) S compound, the value of mass magnetization is extremely sensitive to the composition, and in order to make the value 10 emu / g or less, "0.85 <Fe / Cr <1.18" and "1.85 <Fe / Cr <1.18" in atomic%. It is necessary to satisfy both 50 <S <55 ".

Claims (8)

It is composed of Fe, Cr and S, and is composed of Fe, Cr and S.
The Fe, the Cr, and the atomic% of the S satisfy the following formulas (1) and (2).
Ferrimagnetic material characterized by.
0.85 <Fe / Cr <1.18 (1)
50 <S <55 (2) It has a hexagonal crystal structure and consists only of (FeCr) S compounds whose atomic arrangement in the crystal structure is P63 mc in the space group notation.
The ferrimagnetic material according to claim 1. The mass magnetization at 50 kOe and 5 K is 10 emu / g or less.
The ferrimagnetic material according to claim 1 or 2. It is composed of Fe, Cr and S, and is composed of Fe, Cr and S.
Using a raw material in which the atomic% of Fe, Cr and S satisfy the following formulas (1) and (2).
A method for producing a ferrimagnetic material.
0.85 <Fe / Cr <1.18 (1)
50 <S <55 (2) The first step of producing a green compact consisting of a mixed powder consisting of Fe powder, Cr powder and S powder, and
Having a second step of sintering the green compact to obtain a sintered body,
The method for producing a ferrimagnetic material according to claim 4. In the second step, cooling the sintered body immediately after sintering at a cooling rate of 100 to 10000 ° C./sec.
The method for producing a ferrimagnetic material according to claim 5. In the second step, the sintering temperature should be 700 to 1000 ° C.
The method for producing a ferrimagnetic material according to claim 5 or 6. In the second step, sintering the green compact in a state of being sealed in a quartz tube,
The method for producing a ferrimagnetic material according to any one of claims 5 to 7.

Images