JPH09251910A - Magnetic powder for magnetic recording, magnetic recording medium using it, manufacturing method thereof and magnetic record reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic powder having high magnetization for magnetic recording and manufacturing method thereof by using a magnetic powder of alloy contg. Nd, Fe and B as main components. SOLUTION: A magnetic powder for magnetic recording used as a coated magnetic recording medium is of an alloy contg. Nd, Fe and B as main components. This alloy is mainly composed of α-Fe and Nd2 Fe14 B phases, α-Fe, Fe3 -B and Nd2 Fe14 B phases, or α-Fe, Fe3 B, amorphous and Nd2 Fe14 B phases. The mean grain size of the magnetic phase of the alloy is 0.1μm or less. The main component of the alloy is formulated by Ndx Fey Bz , x+y=z, x=2-12, y=83-94, z=2-6. Thus, it is possible to obtain a magnetic recording medium providing an improved security of magnetic recording information and manufacturing method thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic powder for magnetic recording used in a coating type magnetic recording medium, a magnetic recording medium using the same, a manufacturing method thereof and a magnetic recording reading method from the magnetic recording medium. .

[0002]

2. Description of the Related Art Conventionally, it has been considered that the magnetic powder for magnetic recording used in a magnetic card, for example, should have Br / 4πIs as close to 1 as possible, and that the squareness of the demagnetization curve should be as high as possible. In addition, since 4πIs and Br can have a high reproduction output, a value as high as possible has been desired. The magnetic powder for magnetic recording is inexpensive, has high stability, has a relatively high magnetization of 4πIs, and an appropriate coercive force iHc.
The Ba ferrite powder and the Sr ferrite powder having the above have been used. The 4πIs of these powders is about 4.3-4.
8 kG, remanent magnetization Br is about 4.0 to 4.5 kG, iHc
Is about 1.0 to 3.5 kOe.

However, Ba ferrite powder and Sr
Ferrite powder has the chemical formula BaO.6Fe ₂ O ₃ , Sr.
As can be seen from O · 6Fe ₂ O ₃ , a large amount of O, which is a non-magnetic ion, is included in the molecule, so the amount of magnetization cannot help becoming relatively low.

Therefore, it is necessary to increase the filling amount of the powder as much as possible, which may cause deterioration of the printing characteristics of the magnetic ink. On the other hand, the improvement of printing characteristics of magnetic ink is
This can be achieved by reducing the filling amount of the magnetic powder, but this tends to reduce the reproduction output and increase the error rate. As a countermeasure, there is a method of thickening the magnetic coating layer, but there has been a problem that a significant industrial disadvantage such as an increase in the drying time and the number of coatings occurs.

On the other hand, in a commonly used magnetic card (for example, a credit card, a prepaid card, etc.), information on the magnetic stripe can be read, and crimes such as forgery, alteration, and illegal use are remarkably increasing. . Therefore, it is very useful to improve the confidentiality of magnetically recorded information.

In order to improve the confidentiality of magnetic recording,
When using the conventional magnetic powder for magnetic recording, it makes it difficult for hardware to read the recorded information (eg magnetic concealment layer, multi-layer magnetic recording layer, etc.) and detects the authenticity of the card. How to add functions that can be added (eg,
There are magnetic bar codes, multi-track recording, etc.). or,
As a security measure by software, a combination of magnetic format and code conversion is implemented.

However, in these methods, forgery, alteration,
Improper use was not always satisfactory, and improvements were desired.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic powder for magnetic recording having a large amount of magnetization and a method for producing the same. Another object of the present invention is to provide a magnetic recording medium using the same and improving the confidentiality of magnetic recording information, and a method for manufacturing the same. Also, the present invention
An object of the present invention is to provide a method for reading magnetic recording on the medium.

[0009]

Therefore, the above-mentioned problems have the same iHc as that of the above-mentioned ferrite powder,
By using the magnetic powder of an alloy containing Nd, Fe, and B as the main components, which has πIs and high Br, it is remarkably improved. Generally, 4πIs and Br are 20%
It is recognized that even a slight improvement in the field of magnetic recording is a significant improvement, but in the present invention, the raw material cost and the like are approximately doubled as compared with the ferrite powder, so that the values of 4πIs and Br are smaller than those of the ferrite powder. The range of about twice or more was set as the range of the present invention.

The improvement of the confidentiality of magnetic recording in the present invention is as follows.
This is achieved by using magnetic powder, which has a large variation in magnetization due to an applied magnetic field, as a medium, and by changing the direction of the applied magnetic field during reproduction, thereby reading the information with the reproduction output value changed. To achieve this, Br / 4π, which is the magnetic characteristic of the magnetic powder for magnetic recording, is used.
Is is preferably 0.85 or less.

That is, the present invention relates to (1) a magnetic powder for magnetic recording used in a coating type magnetic recording medium, which is characterized by comprising an alloy containing Nd, Fe and B as main components. It is a magnetic powder.

Further, the present invention is (2) the magnetic powder for magnetic recording according to the above (1), wherein the alloy is mainly composed of an α-Fe phase and an Nd ₂ Fe ₁₄ B phase.

The present invention also provides (3) the magnetic recording according to the above (1), wherein the alloy is mainly composed of α-Fe phase, Fe ₃ B phase and Nd ₂ Fe ₁₄ B phase. It is a magnetic powder.

Further, the present invention (4) is characterized in that the alloy is mainly composed of α-Fe phase, Fe ₃ B phase, amorphous phase and Nd ₂ Fe ₁₄ B phase. It is the magnetic powder for magnetic recording described.

Further, the present invention provides (5) the magnetic material according to any one of the above (1) to (4), wherein the average particle diameter of the magnetic phase constituting the alloy is 0.1 μm or less. It is a magnetic powder for recording.

In the present invention, (6) the composition of the main component of the alloy is represented by the formula Nd _x Fe _y B _z , and x + y + z = 1.
00, x = 2 to 12, y = 83 to 94, and z = 2 to 6, which is the magnetic powder for magnetic recording according to any one of the above (1) to (5).

Further, in the present invention, (7) the composition of the main component of the alloy is represented by the formula Nd _x Fe _y B _z , and x + y + z = 1.
00, x = 2 to 16, y = 72 to 80, and z = 6 to 20. The magnetic powder for magnetic recording according to any one of (1) to (5) above.

The present invention also provides (8) the magnetic recording according to any one of (1) to (7) above, wherein the alloy has a saturation magnetization of 14 kG or more and a residual magnetization of 9 kG or more. It is a magnetic powder.

The present invention also provides (9) the magnetic recording according to any one of the above (1) to (8), wherein the ratio of residual magnetization to saturation magnetization of the alloy is 0.85 or less. Magnetic powder for use.

Further, the present invention (10) is characterized in that an alloy containing Nd, Fe and B as main components is obtained by a liquid quenching method, and the alloy is heat-treated and pulverized.
The method for producing a magnetic powder for magnetic recording according to any one of (9).

The present invention also provides (11) the alloy of 60
The method for producing a magnetic powder for magnetic recording according to the above (10) is characterized in that the heat treatment is performed in the range of 0 ° C to 800 ° C.

The present invention also provides (12) above (1).
A magnetic recording medium comprising a magnetic layer containing the magnetic powder for magnetic recording according to any one of (9) on a substrate.

The present invention also provides (13) the magnetic recording medium as described in (12) above, wherein the magnetic layer is provided in a bar code shape.

Further, the present invention is (14) the magnetic recording medium according to the above (13), characterized in that a magnetic layer made of hard ferrite powder for magnetic recording is provided in a bar code shape.

The present invention also provides (15) above (1) to
(9) A method for producing a magnetic recording medium, which comprises mixing the magnetic powder for magnetic recording according to any one of (9) with a resin and then coating the mixture on a substrate.

Further, the present invention is (16) the method for producing a magnetic recording medium according to the above (15), characterized in that the substrate is printed and applied in the form of a bar code.

(17) The magnetic powder for magnetic recording and the hard ferrite powder for magnetic recording are each formed into a magnetic ink and then applied by printing. A method of manufacturing a recording medium.

The present invention also provides (18) above (12).
After the magnetic recording medium according to any one of (14) is magnetized, a magnetic reading is performed while applying a magnetic field in the same direction and in a direction opposite to the magnetization direction of the medium.

As the magnetic powder, an alloy containing Nd, Fe, and B as the main components is used. The α-Fe phase, Fe ₃ B phase, Nd ₂ Fe ₁₄ B phase, and amorphous phase produced by these components are used. Each phase has a high saturation magnetization, about 15 kG or more. Among them, the Nd ₂ Fe ₁₄ B phase shows hard magnetism and contributes to the improvement of iHc and Br. On the other hand, α-Fe phase, Fe ₃
The B phase and the amorphous phase exhibit soft magnetism, and contribute to the improvement of 4πIs and Br and the magnitude of the fluctuation of the magnetization due to the applied magnetic field. Among these, particularly the α-Fe phase exhibits a high 4πIs.

The magnetic phase constituting the magnetic recording alloy is 0.1
The reason why the thickness is less than or equal to μm is as follows. It is effective that the coating type magnetic recording powder has a thickness of about 3 μm or less, preferably 1 μm or less, in order to prevent deterioration of the coating and printing characteristics of the magnetic coating material. On the other hand, among the magnetic particles precipitated in the alloy powder of the present invention, Nd ₂ Fe ₁₄ B contributes to iHc.
Phase. This compound has a property that iHc remarkably decreases with respect to mechanical stress applied by pulverization and the like. Therefore, in order to stably obtain a magnetic powder having an appropriate iHc by pulverization, N which is not damaged by the pulverization is used.
It is necessary to contain an appropriate amount of d ₂ Fe ₁₄ B particles. To this end, the size of the precipitated particles in this alloy should be 0.1 μm.
It must be:

The composition of the alloy in the present invention is calculated by the formula Nd _x F
In e _y B _z (where x + y + z = 100), x =
2 to 12,, y = eighty-three to ninety-four, was in the range of z = 2 to 6, in this composition range, primary precipitates constituting the magnetic powder is alpha-Fe phase, Nd ₂ Fe _{1 4} B phase And again,
In the region of x ≧ 4 and z ≧ 3, in addition to the above two phases, formation of Fe ₃ B phase and amorphous phase is also recognized, 4πIs is about 15 kG or more, Br is about 9 kG or more, and iHc is about 1.5 kOe or more. This is because, as compared with the Ba ferrite powder, 4πIs is 3 times or more, Br is 2 times or more higher, Br / 4πIs is 0.85 or less, and the pulverizability of the powder is also good.

Further, the composition of the alloy is represented by the formula Nd _x Fe _y B _z (where x + y + z = 100), where x = 2 to 16,
The range of y = 72 to 80 and z = 6 to 20 is that the main precipitates constituting the magnetic powder are α in this composition range.
-Fe phase, Fe ₃ B phase and Nd ₂ Fe ₁₄ B phase, and 4π
Is is about 14 kG or more, Br is about 9 kG or more, iHc is about 2.5 kOe or more, and 4πIs is about 3 times or more and Br is 2 times or more higher than that of Ba ferrite powder, and Br / 4πIs is 0 or more. This is because it is 0.85 or less, and the pulverizability of the powder is also good.

4πIs of the magnetic powder is 14 kG or more, Br
The value of 9 kG or more means that the magnetic characteristics of the powder and the cost performance of the price are equal to or more than those of the conventionally used Ba ferrite powder and Sr ferrite powder, and the coating characteristics are high output characteristics. This is because the contribution to magnetic reproduction and the like becomes extremely large.

The Br / 4πIs of the magnetic powder for magnetic recording is set to 0.85 or less when the confidentiality of magnetic recording is to be imparted by a bias magnetic field during reproduction.
This is because it can be easily carried out by setting it to 85 or less. By the way, the value of Ba ferrite and the like is around 0.95, and it is impossible to impart the confidentiality by a similar method.

The magnetic powder containing Nd, Fe, and B as the main components is prepared by rapidly cooling the liquid, then heat-treating and pulverizing the magnetic powder for the following reason. First, the raw material is liquid-quenched to obtain a flaky alloy containing amorphous or extremely fine precipitation particles (several tens of nm or less). Next, heat treatment is performed to control the precipitation of the compound, the particle size, etc. to obtain a magnetic powder with stable magnetic properties. The heat treatment may be after liquid quenching or crushing. In general, the heat treatment improves the pulverizability of the liquid quenched alloy, and therefore, the powdering is industrially advantageous after the heat treatment. On the other hand, the method of crushing the liquid quenched alloy into powder and then heat-treating it can significantly reduce the effect of lowering iHc due to crushing, and is therefore useful when the precipitation particle size is relatively large or when the composition has a low iHc. Is.

The heat treatment of the liquid-quenched alloy in the range of 600 ° C. to 800 ° C. is such that at 600 ° C. or less, a precipitate phase is produced from the quenched alloy within an industrially useful time (in the present invention, within 30 hours). It is difficult to do so, and at 800 ° C., the grain size of the precipitation phase may exceed 0.1 μm.

Further, the magnetic powder of the present invention is mixed with a resin and then coated to form a magnetic recording medium, or after printing in a bar code, magnetic recording is performed, and the magnetic field is applied in the same direction or in the opposite direction. The reason why the reproduction output is controlled by applying the bias magnetic field in the direction is that the confidentiality of the magnetic recording can be remarkably improved by the processing of the read condition and the output value which can be easily executed.

As the alloy composition in this embodiment, Nd,
Although only Fe and B are mentioned, for example, a small amount of C
o, Ni, Cu, Cr, Al, Si, Ti, C, P,
V, Zr, Hf, Nb, Mo, Ti, W, Ga etc. and P
Even if a rare earth element such as r, Ce, or La or an unavoidable impurity is contained, the mechanism of manifestation of magnetic properties is α-Fe phase, Fe
₃ B Eich due to amorphous phase and R ₂ Fe ₁₄ B phase, high iHc
Is within the scope of the invention if it is retained in the R ₂ Fe ₁₄ B phase.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(Example 1) Commercially available neodymium (N
d), pure iron (Fe) and boron (B) are used, melted by high frequency heating in Ar, and then sprayed on a Cu roll,
The composition of the alloy of the main component is Nd _x Fe _(95-x) B ₅ (where x
= 2,4,6,8,10,12,14) and the width is about 10
A ribbon-like quenched alloy having a thickness of not more than mm and a thickness of not more than about 30 μm was obtained. Next, this alloy is subjected to 1 in Ar at 600 to 800 ° C.
After heat treatment for a long time, coarse pulverization was performed, and pulverization was performed using a ball mill so that the average particle diameter was about 0.8 μm. When the alloy was examined by an electron microscope, a large amount of α-Fe phase and Nd ₂ Fe _{1 4} B phase of 0.1 μm or less were formed. When x is 4 or more, in addition to the above two phases, an amorphous phase and F
Precipitation of the e ₃ B phase was also observed.

When the magnetic characteristics of this powder were measured by VSM, the saturation magnetization 4πIs was about 15 kG or more, the residual magnetization Br was about 10 kG or more, and the coercive force iHc was about 2 kOe or more between x = 2 to 12. . Since the Br / 4πIs value is obviously smaller than 1, it can be seen that the squareness of the magnetization curve is lowered and the magnetization value is remarkably lowered by the bias magnetic field. In addition, the magnetic characteristics of the powder are approximately twice as high as that of the conventionally used Ba ferrite powder for magnetic recording, and the coercive force thereof is about the same, and the magnetic recording powder has high output.

Next, 20 wt% of these alloy powders were mixed and dispersed in polyurethane resin to prepare a magnetic ink, which was then coated on a PET film to a thickness of about 3 μm to obtain a magnetic recording medium.

Next, when a magnetic recording head magnetically recorded in stripes on this magnetic recording medium at 210 bpi and reproducing it in the absence of an applied magnetic field using a reproducing magnetic head, a pulsed output according to the recorded contents was obtained. was gotten.

Next, when a DC magnetic field of about 300 Oe was applied in the same direction as the direction of the magnetically recorded magnetic field and reproduction was performed using a reproducing magnetic head, the output was about 1.8 times that of the non-applied magnetic field reproduction. became. On the other hand, when a DC magnetic field of about 300 Oe was applied in the direction opposite to the direction of the magnetically recorded magnetic field for reproduction, the output was about 20% as compared with the non-applied magnetic field reproduction.

Therefore, by using the present alloy powder,
Compared with the conventional ferrite powder, not only a magnetic recording medium with remarkably high output can be obtained, but by applying a magnetic field in the forward and reverse directions of the magnetic field applied during recording during reproduction, it is possible to achieve significantly different reproduction output. The confidentiality can be improved.

[0046] In the same manner as Example 2 Example 1, the composition of the main component of the alloy _{Nd (22-z) Fe 78} B z ( where, z =
6, 8, 10, 12, 14, 16, 18, 20, 22)
Then, liquid quenching, heat treatment, pulverization, microscopic analysis, magnetic property measurement, and magnetic recording property measurement were performed.

As a result, in the range of z = 6 to 20, 4πIs of the powder is about 14 kG or more, Br is about 9 kG or more, and iH.
c was about 2.5 kOe or more.

In the present alloy, α having a grain size of about 0.1 μm or less is used.
A large amount of —Fe phase, Fe ₃ B phase, and Nd ₂ Fe ₁₄ B phase were formed.

When a magnetic recording medium coated with this powder was magnetically recorded and reproduced, a pulsed output corresponding to the recorded content was obtained, and a DC magnetic field was applied in the same direction as the magnetic field applied during recording for reproduction. In this case, the output was about 1.7 times that of the non-magnetic field bias reading, and when reproducing by applying a magnetic field in the opposite direction, the output dropped to about 25%.

Therefore, since the present alloy powder has a high 4πIs, it can be used not only as a magnetic recording medium having a high output as compared with the ferrite powder, but also when the direction of the bias magnetic field is changed at the time of reproduction, the reproduction output is remarkably different. As a result, the confidentiality of the card can be improved.

(Embodiment 3) In the same manner as in Embodiment 1, the composition of the alloy of the main component is Nd ₄ Fe _(96-z) B _z (where z =
1, 2, 3, 4, 5, 6, 6), and liquid quenching,
Heat treatment, crushing, microscopic analysis, magnetic property measurement, and magnetic recording property measurement were performed.

As a result, in the range of z = 2 to 6, 4 of the powder
πIs is about 16 kG or more, Br is about 9 kG or more, iHc
Was about 1.5 kOe or more.

In the present alloy, α having a grain size of about 0.1 μm or less is used.
A large amount of —Fe phase and Nd ₂ Fe ₁₄ B phase were formed. When z is 3 or more, in addition to the above two phases, an amorphous phase and Fe ₃ B
Precipitation of phases was also observed.

When a magnetic recording medium coated with this powder was magnetically recorded and reproduced, a pulsed output corresponding to the recorded content was obtained, and a DC magnetic field was applied in the same direction as the magnetic field applied during recording for reproduction. In this case, the output was about 1.9 times that of the non-magnetic field bias reading, and when reproducing by applying a magnetic field in the opposite direction, the output dropped to about 15%.

Therefore, since the present alloy powder has a high 4πIs, it can be used as a magnetic recording medium having a higher output than ferrite powder, and the reproduction output can be remarkably different by changing the direction of the bias magnetic field during reproduction. As a result, the confidentiality of the card can be improved.

Example 4 As in Example 1, the composition of the alloy of the main component was Nd _x Fe _(82-x) B ₁₈ (where x =
2, 4, 6, 8, 10, 12), and liquid quenching, heat treatment, pulverization, microscopic analysis, magnetic property measurement, and magnetic recording property measurement were performed.

As a result, in the range of x = 2 to 10, 4πIs of powder is about 14 kG or more, Br is about 9 kG or more, iH
c was about 2.5 kOe or more.

In the present alloy, α having a grain size of about 0.1 μm or less is used.
A large amount of —Fe phase, Fe ₃ B phase, and Nd ₂ Fe ₁₄ B phase were formed.

When the magnetic recording medium coated with this powder was magnetically recorded and reproduced, a pulsed output corresponding to the recorded content was obtained, and a DC magnetic field was applied in the same direction as the magnetic field applying direction during recording for reproduction. In this case, the output was about 1.7 times that of the non-magnetic field bias reading, and when reproducing by applying a magnetic field in the opposite direction, the output dropped to about 25%.

Therefore, since the present alloy powder has a high 4πIs, it can be used as a magnetic recording medium having a higher output than ferrite powder, and the reproduction output can be remarkably different by changing the direction of the bias magnetic field during reproduction. As a result, the confidentiality of the magnetic card can be improved.

(Embodiment 5) Among the magnetic powders produced in Embodiments 1 to 4, 4πIs is about 14 kG or more and Br is about 9 k.
As in the case of Example 1, the magnetic field applied direction during magnetic recording and the direction of the direct current applied magnetic field during reproduction were reversed, and the ratio of the reproduction output value was obtained by using a magnetic recording medium of G or more.

Here, the magnetic characteristic Br / 4πIs of the powder was 0.64 to 0.90, and the reproduction output V positive / V reverse due to the forward / reverse applied magnetic field during reproduction was about 1.5 to 10. Here, if the V forward / V reverse is about 3 or more, it can be easily used as a method for improving the confidentiality of a magnetic card or the like. The Br / 4πIs
Was less than about 0.85.

Therefore, in order to improve the airtightness of magnetic recording, it is useful for the magnetic powder for magnetic recording of the present invention to have Br / 4πIs of 0.85 or less.

As can be seen from the above examples, when the present magnetic powder is used as a magnetic recording medium, the main generation phase is α
-Fe phase and Nd ₂ Fe ₁₄ B phase, the main generation phase is α-Fe phase, Fe ₃ B phase and Nd ₂ Fe ₁₄ B phase, or the main generation phase is α-Fe phase, Fe ₃ B phase, Nd ₂
The Fe ₁₄ B phase and the amorphous phase are indispensable.

In the magnetic powder of the present invention, when the composition of the main component is Nd _x Fe _y B _z , x + y + z =
It can be said that the range of 100, x = 2 to 12, y = 83 to 94, z = 2 to 6 and the range of x = 2 to 16, y = 72 to 80, z = 6 to 20 are particularly useful.

Example 6 4πIs prepared in Example 3
Is about 17 kG, Br is about 12 kG, and iHc is about 1.5 kG.
Using Oe powder, a magnetic ink made of 30 wt% urethane resin was prepared. Further, a commercially available Ba ferrite powder for magnetic recording (4πIs: about 4.5 kG, Br: about 4.3 kG, iHc: about 1.8 kOe) was used to prepare a magnetic ink in the same manner.

Next, using these magnetic inks, silk-screen printing was performed on a substrate in a bar code shape having a length of 4 mm, a width of 0.2 mm and a thickness of about 10 μm.

Then, after magnetizing this magnetic bar code in a magnetic field of about 5 kOe, a magnetic ink character reader (MICR) designed to generate a magnetic field of about 500 Oe in the magnetic head section is used. The read critical output of the magnetic signal was set to 200 mV and 500 mV, and the presence or absence of bar code signal recording was detected.

Read magnetic field 500O in the same direction as the applied magnetic field
When e was applied, the output was detected with all the bar codes at the critical output of 200 mV, but when the critical output was 500 mV, only the bar code using the alloy powder of the present invention was detected.

On the other hand, the reading magnetic field 5 is applied in the direction opposite to the applied magnetic field.
When 00Oe was applied, at the critical output of 200 mV, the bar code output using the present alloy powder was not detected, but only the bar code output using the ferrite powder was detected.

When the read applied magnetic field was set to 0, the output was detected with all bar codes. Therefore, it can be seen that the confidentiality can be improved by printing the barcode.

[0072]

As described above, according to the present invention, a magnetic powder for magnetic recording having a large amount of magnetization and a method for producing the same can be provided. Further, according to the present invention, it is possible to provide a magnetic recording medium in which the confidentiality of magnetic recording information is improved by using the same, and a manufacturing method thereof. Further, according to the present invention, it is possible to provide a method for reading magnetic recording on the medium.

Claims (18)

[Claims] 1. A magnetic powder for magnetic recording used in a coating type magnetic recording medium, which is made of an alloy containing Nd, Fe and B as main components. 2. The alloy is mainly composed of α-Fe phase and Nd ₂
The magnetic powder for magnetic recording according to claim 1, wherein the magnetic powder comprises an Fe ₁₄ B phase. 3. The alloy is mainly composed of α-Fe phase, Fe ₃ B
The magnetic powder for magnetic recording according to claim 1, wherein the magnetic powder comprises a phase and an Nd ₂ Fe ₁₄ B phase. 4. The alloy is mainly composed of α-Fe phase and Fe ₃ B.
The magnetic powder for magnetic recording according to claim 1, comprising a phase, an amorphous phase, and an Nd ₂ Fe ₁₄ B phase. 5. The magnetic powder for magnetic recording according to claim 1, wherein the average particle size of the magnetic phase constituting the alloy is 0.1 μm or less. 6. The composition of the main component of the alloy has the formula Nd _x F
When represented by e _y B _z , x + y + z = 100, x = 2-1
2. The magnetic powder for magnetic recording according to claim 1, wherein y = 83 to 94 and z = 2 to 6. 7. The composition of the main component of the alloy has the formula Nd _x F
When represented by e _y B _z , x + y + z = 100, x = 2-1
6, y = 72-80, z = 6-20, The magnetic powder for magnetic recording in any one of Claims 1-5 characterized by the above-mentioned. 8. The saturation magnetization of the alloy is 14 kG or more, and the residual magnetization is 9 kG or more.
7. The magnetic powder for magnetic recording according to any one of 7. 9. The magnetic powder for magnetic recording according to claim 1, wherein a ratio of residual magnetization to saturation magnetization of the alloy is 0.85 or less. 10. The magnetic recording according to claim 1, wherein an alloy containing Nd, Fe and B as main components is obtained by a liquid quenching method, and the alloy is heat-treated and pulverized. Method for producing magnetic powder for use. 11. The method for producing magnetic powder for magnetic recording according to claim 10, wherein the alloy is heat-treated in the range of 600 ° C. to 800 ° C. 12. A magnetic recording medium comprising a magnetic layer containing the magnetic powder for magnetic recording according to claim 1 provided on a substrate. 13. The magnetic recording medium according to claim 12, wherein the magnetic layer is provided in a bar code shape. 14. A magnetic recording medium according to claim 13, wherein a magnetic layer made of hard ferrite powder for magnetic recording is provided in a bar code shape. 15. A method for manufacturing a magnetic recording medium, comprising mixing the magnetic powder for magnetic recording according to claim 1 with a resin and then coating the mixture on a substrate. 16. The method for producing a magnetic recording medium according to claim 15, wherein the substrate is printed and applied in the form of a bar code. 17. The method for producing a magnetic recording medium according to claim 16, wherein the magnetic powder for magnetic recording and the hard ferrite powder for magnetic recording are each made into a magnetic ink and then applied by printing. 18. A magnetic recording method according to claim 12, wherein the magnetic recording medium is magnetized, and then magnetic reading is performed while applying a magnetic field in the same direction and in a direction opposite to the magnetization direction of the medium. How to read records.