JPS63107818A - Fine hexagonal ferrite particle and production thereof - Google Patents

Abstract

PURPOSE:To provide fine hexagonal ferrite particles having a specified compsn., a specified particle shape and superior magnetic characteristics, especially high saturation magnetization and suitable for high density magnetic recording. CONSTITUTION:The titled fine hexagonal ferrite particles have a compsn. represented by a general formula MO.(n/6)(Fe12-2xT2xO18) (where M is one or more kinds of metallic elements selected among Ba, Sr and Pb; T is Co-Ti, Co-Ge, Co-Sb, Co-Ta, Zn-Nb, Zn-V, Zn-Ge or In; x=0-1.1; and n=5.2-7.5). The particles have >=50emu/g saturation magnetization sigmas, 0.02-0.5mum average particle size and a flat shape. The flat shape of >=50% of all the particles are nongeometrically hexagonal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to hexagonal ferrite fine particles and a method for producing the same. More specifically, the present invention relates to hexagonal ferrite fine particles precipitated by heat treatment of a glassy substance obtained by rapidly cooling a melt, which has particularly high saturation magnetization and has a high density. The present invention relates to hexagonal ferrite fine particles suitable for magnetic recording and a method for producing the same.

[Prior Art] In recent years, coating-type media using hexagonal ferrite fine particles have attracted attention as high-density magnetic recording media.

As methods for producing the hexagonal ferrite fine particles for magnetic recording media, methods such as glass crystallization, hydrothermal synthesis, and coprecipitation are known. Among these, the present invention provides an improvement of hexagonal ferrite fine particles by a glass crystallization method and a method for manufacturing the same. In making a ferrite of one metal from the group consisting of barium, strontium and lead, a magnetic plumbite structure MO.6Fe203 (wherein M is selected from the group consisting of barium, strontium and lead) is prepared. Forming a homogeneous melt of oxides of said metals, boron oxide and ferric oxide having quantitative ratios within the AEFD zone of FIG. A process for producing ferrites of said metals comprising quenching the glass and heating the glass to effect nucleation and crystallization of the product in a borate-rich matrix is disclosed. In addition, special public service 1986-1557
Publication No. 7 includes rAo, B203. Fe 203 (
However, l''e20a includes a substituted component, and A is at least one of Ba, Sr, Ca, and Pb.
In the triangular component diagram shown in FIG. 13 whose apex is 1), the following four points (a) 820g = 44. AO=46. Fe
2O3 -10 mol%, (b) B203-40
．． AO-50, l”e 2Q, = 10 mol%, (
C) B203-10. AO-40゜1”e 20
a = 50 mol%, and (d) 820a -20°AO = 30. The mixture in the composition region surrounded by -50 mol% Fe2O3 (however, the composition on the line connecting points a and d and those two points is not included) is melted and rapidly cooled to become amorphous. process and this amorphous body from 650 to
A method for producing magnetic powder for magnetic recording comprising the steps of precipitating magnetoblanbite-type ferrite powder by heat treatment at 850° C. and then acid treatment.

[Problems to be Solved by the Invention] When hexagonal ferrite fine particles are used as a magnetic recording medium, the coercive force is so large that it is difficult to write with a magnetic head. Therefore, it is necessary to reduce the coercive force to a value suitable for magnetic recording by, for example, replacing some of the constituent atoms with other specific elements. Further, the average particle diameter of the hexagonal ferrite fine particles is 0.02 to 0.0.
It is desirable to select a volume in the range of 5 μl. The reason for this is
If the average particle size of the fine particles is less than 0.02 μm, the number of particles exhibiting superparamagnetic behavior will increase, resulting in a decrease in saturation magnetization as a whole.On the other hand, if the average particle size exceeds 0.5 μm, high-density recording will be difficult. This is because a problem arises in which the SN ratio decreases.

11 hexagonal ferrite fine particles that meet the above conditions! One way to avoid this is to mix the basic component of the macrogonal ferrite, a substitute component for reducing the coercive force, and a glass-forming substance, melt it, and then rapidly cool it with a roll to form a flaky glassy substance. By heat-treating the flakes, hexagonal ferrite fine particles are precipitated therein, and then treated with a weak acid such as acetic acid.
There is a so-called glass crystallization method that removes components other than hexagonal ferrite.

However, this method involves handling a complex system of components, including the basic components of hexagonal ferrite, substitution components for reducing coercive force, and components for glass formation. , finding the optimal composition for this has been a very big problem. In other words, the conventional method was to investigate the characteristics of various component compositions for each target coercive force He, and then asymptotically find the optimal composition based on this. , this required a huge amount of experimentation. Moreover, even then, the optimum composition cannot be determined, and there are many cases where the composition deviates from the composition that provides the maximum value of the magnetic properties, especially the saturation magnetization σs.

The present invention has been made in view of the above circumstances, and its object is to provide hexagonal ferrite fine particles having excellent magnetic properties, particularly high saturation magnetization, and a method for producing the same.

[Means for solving the problems] The hexagonal ferrite fine particles of the present invention have the general formula MO・(
n/6) (f”Jz-2zT2z Olg
) (ill, M is one or more metal elements selected from the group of 3a, 3r and pb, and T is Co-
Ti, C.

-Ge, Co-8b, Co-Ta, 7
．． n-Nb.

One or more of Zn-V, Zn-Ge, in, and ×
is a value of 0 to 1.1, and n is a value of 5.2 to 7.5), and the value of saturation magnetization σ is 50e.
rgu /Q or more, and each particle has a flat plate shape with an average particle size of 0.02 to 0.5 μl, and 50% or more of the total number of particles has a non-geometric hexagonal plate shape. (This refers to polygons other than hexagons and irregular shapes that are composed of three sets of parallel opposite sides).

As king, co-Ti.

Co-Ge, Co-8b, Co-Ta
, Zn-Nb, Zn-V, Zn-Ge, In
By selecting one or more substituting elements or a combination of elements, the coercive force can be reduced to a value suitable for magnetic recording.

By adjusting the value of X between 0 and 1.1, the
A desired value of Ha can be obtained in the range of ~40,000e. In particular, when the combination of Co--Ti is selected as (2), the purpose of reducing 1-1c can be effectively achieved. For high-density magnetic recording, usually 400
Since it is sufficient to consider the range from 15,000e to 15000e, the value of however,
When x reaches 1.1, Hc becomes sufficiently small, and even if x is increased further, the effect of reducing Hc will be lost, so the upper limit was set at 1.1.

n from 5.2 to 7.5. Preferably 5.5 to 1.2. More preferably 5.8 to 7. Hexagonal ferrite fine particles having high saturation magnetization can be obtained by selecting O2 most preferably above 6.0 and below 6.8, particularly above 6.1 and below 6.6.

The reason why it is preferable to select the average particle size of the particles from 0.02 to 0.5 μm is as described above.

In addition, 50% or more of the total number of particles may have a non-geometric hexagonal plate shape (referring to polygons other than hexagons and irregular shapes consisting of three pairs of parallel opposite sides). The formation of particles can be achieved by selecting the value of β in the range of 5.2 to 12, which will be described later, and thereby the saturation magnetization σs can be increased.

The number of particles exhibiting a non-geometric hexagonal shape varies depending on the heat treatment conditions in addition to the composition, but the ratio to the total number of particles is 50% or more, preferably 70% or more.

A high σs can be obtained when it is more preferably 75% or more, most preferably 80% or more.

The present invention also provides a method for producing hexagonal ferrite fine particles that satisfies the conditions described above, as follows.

That is, the method for producing hexagonal ferrite fine powder of the present invention comprises a method for producing hexagonal ferrite fine powder in which MO
O3 is b mol%, King's oxide is 0 mol%, B2O3 is e
After melting a mixture containing mol%, it is rapidly cooled, then this rapidly cooled rJ1 body is heat-treated to produce ferrite crystals, and then phases other than ferrite are dissolved and removed from this heat-treated product. In the method for producing ferrite fine particles, each blending amount is selected so that (I) the value of e is 20 or more and 40 or less (II) the value of effective molar ratio β is 5.2 to 12. It is characterized by

Here, the effective molar ratio β is a value calculated by the following formula using the effective Fe2.03 mol% EFe2O3]. That is, lump・β=[Fe20a] (a/e) However, the effective Fe2O3 mol% [Fe2　・03] is calculated by adding the mol% value obtained by converting King's oxide to l"e 203 to b. [F e 203 ]' -b +b X (total 1i
It is calculated as: i element T + 7) total atomic %)/(atomic % of Fe).

The purpose of the present invention can be achieved more effectively if a combination of co-Ti is selected as the main ingredient, but in this case, COo is 0.1 mol %.

If T + 02 contains C2T nil%, the value of β is β
= (b 10.5 (cl+c2) ) / (a
-e).

In addition, although the raw material compounds have been described as MO, Fe 2 O 3 , T oxide, and B 2 O 3 , the oxides used in the present invention are those that have been commonly used in the past, and therefore can be used based on the conventional technology. . That is, for example, the MO is BaO.

It may be an oxide itself such as Sr 2 O or Pb 2 O, or it may be an oxide that can be converted into the above-mentioned oxide under the heating conditions of the melting process of the raw material mixture, such as a carbonate or nitrate of Ba 2 , Sr 2 or Pb. The same applies to other oxides.

By selecting the value of e to be 20 or more and 40 or less, particularly more than 30 and 40 or less, fine hexagonal ferrite particles in which individual particles are individually separated and have good dispersibility can be obtained with high efficiency.

If the value of e is less than 20, particles tend to aggregate, while if the value of e exceeds 40, a large amount of components other than hexagonal ferrite will be eluted, resulting in a significant decrease in efficiency in industrial production. The value of e is more than 30 and less than 40, especially 32 to 3
By selecting No. 5, hexagonal ferrite fine particles can be obtained particularly stably and efficiently.

The usefulness of the present invention is best exhibited when the relational expression β=[F8203'/(a-8) provided by the present invention is utilized.

As a result, the raw material mixture of hexagonal ferrite fine particles manufactured by glass crystallization, which is a complex system containing many components as described above, can be optimized according to the desired Hc value by simply specifying the value of e. The blend value can be uniquely determined.

The value of β is 5.2 to 12. Preferably 5.8 to 12. More preferably 6.0 to 10. Most preferably 6.0-8.
By selecting 0°, particularly 6.0 to 7.0, hexagonal ferrite having a high σs can be obtained. Furthermore, by selecting the value of β as described above, it is also possible to obtain the desired Hc more stably. That is, in the process of studying the present invention, it was found that Hc has a strong dependence on the value of β, but since no such sorting method has been found so far, it is difficult to accurately determine the compositional dependence of %HC. It can be said that this was not fully captured.

When the value of β is less than 5.2, fine hexagonal ferrite particles exhibiting a geometrical hexagonal shape are obtained, and the value of Hc is also quite good, but the value of σs is low. On the other hand, if β exceeds 8, σ8 will drop significantly, which is not preferable.

The value of Hc can be adjusted by adjusting the mixture m of the Co-Ti oxide. For example, as ■, Co-Ti
If you select the combination of , set the value of c1/b to 0 to 0,
225. By selecting the value of c2/b between 0 and 0.225, the value of X described above can be adjusted between 0 and 1.1, that is, the value of Hc can be adjusted to a desired value. cl/
Normally, b and c2/b should be selected to be the same value, but Co
Depending on the yield of O and -r+02, these may be chosen to different values if adjustments are necessary. Yield 100%
If it is assumed that c1/b, c2/b and X have the following relationship.

c1/b = c2/b = x / (6-x)
As mentioned above, Japanese Patent Publication No. 48-22265 and Japanese Patent Publication No. 60-60 are similar in composition to the present invention.
Publication No. 15577 can be mentioned, but here,
These and the present invention will be explained in detail.

The component ranges of these two publications and the present invention are shown superimposed on FIG. In addition, here, as a representative example of a king, co-
The case where a combination of Ti is selected will be shown.

In addition, the component composition range of the present invention is too narrow, and the first
Since it is difficult to see it accurately in the figure, an enlarged view is shown in Fig. 2.

8203, MO, Fe 20a (+Co o+”r
When expressed on a triangular component diagram with i 02 ) as the vertex, the component range of the present invention differs depending on the value of X, so the minimum value of X (x −0 ) is shown by the solid line PQR8, and the case where the maximum value of X (x = 1.1) is shown by the broken line P-Q-R-8-. X between these
In the case of , it is located between these two shapes.

From these figures, the component region considered important by the present invention (center: B203 = 30 mol%, MO = 35 mol%) is the component IA considered important by Japanese Patent Publication No. 48-22265.
Area (center: B 20 s ”: 22.5 mol%, MO
-43.3 mol%) and the component region considered important in Japanese Patent Publication No. 60-15577 (center 2B2O3', 2
8.5 mol%.

It can be seen that it is clearly different from MO-41.5 mol %). This is based on the fact that the idea behind the invention is different.

More importantly, the component range disclosed by the present invention is significantly narrower than that of the above two publications, and therefore the composition has to be very specifically determined in order to obtain hexagonal ferrite fine particles with good properties.
It is clearly identified and selected. As a result, the present invention is much easier to put into practical use than the techniques disclosed in the above two publications.

[Example 1] A composition that satisfies all the above-mentioned conditions in the manufacturing method of the present invention can be easily determined as follows.

(1) Select the type of metal element T.

(2) Select the value of e.

(3) Select X according to the desired Hc value. (See, for example, Figure 9 for this) Based on this, c1/b,
Determine c2/b, etc. In the normal case, cl/b - c2/b = x / (6-x).

(4) Select the value of β. In normal cases, it is β-6 to 7.

(5) Solve simultaneous equations using the conditional expression that the total composition of the raw material compounds is 100% and each of the above conditional expressions.

These can be calculated very easily using, for example, a personal computer.

Example 1 B 203-32mo) Li%, CoO=3.25
M) Lt%.

Ti O2-3, 25 mol% constant L Te, 3a C
o3 (used as a raw material compound for BaO).

In order to investigate the characteristics when the amount of 1"e20a was varied, raw materials were mixed at the blending values shown in Table 1.

Incidentally, in order to help the effects of the present invention be more clearly understood, compositions outside the scope of the present invention are also shown here.

After melting these in a platinum crucible by a conventional method, they were rapidly cooled using twin rolls to obtain 1 q of flaky material. next,
After heat-treating this flaky substance at 800°C for 5 hours,
Phases other than ferrite were dissolved and removed by treatment with acetic acid. Then, it was washed with water and dried to obtain ferrite powder.

When examined by X-ray diffraction, no peaks other than the diffraction lines representing hexagonal ferrite were observed in aha 1 to 5, but diffraction lines representing α-Fe203 in addition to hexagonal ferrite were observed in aha e and 7. was also recognized.

The results of measuring the magnetic properties of these powders using VSM are shown in the third section.
As shown in the figure.

aha according to the present invention 3. 4. 55emu in 5
/(It can be seen that a high σs of 7 or more is obtained. σ9
shows a peak in the sample of β-6, ie, aha 4, and it is clearly seen that as β deviates from this peak, σ tends to decrease.

More interestingly, not only σ, but also the value of Hc
=6 is the peak, and it shows a tendency to decrease whether β becomes smaller or larger than this. Among these, the fact that Hc increases in the left half, that is, going from aha 1 to 4, means that the value of x decreases in this order, that is, the addition of Co and Ti for the purpose of reducing Hc. This is explained by the fact that m becomes smaller.

However, the fact that the value of Hc decreases as one moves toward the right half, ie, from aha 4 to 1, cannot be explained from the value of X. Therefore, in this case, as the value of β deviates from 6, the hexagonal ferrite departs from its ideal state.
That is, conversely, this can be interpreted as indicating that the state of β=6 is the most ideal state of hexagonal ferrite.

As a result of electron microscopy (TEM) observation, aha according to the present invention
3. 4. In Sample No. 5, it was confirmed that 50% or more of the total number of particles were non-geometric hexagonal shapes (meaning those that were not hexagonal shapes consisting of three sets of parallel opposite sides).

A TEM photograph of aha 4 is shown in FIG. It can be seen that the average particle size is approximately 0.09 μm1, and that more than 80% of the total particles have a non-geometric hexagonal shape.

Ch#3. For No. 5, the average particle size was approximately 0.09 μm and approximately 0.08 μm, respectively.

Example 2 Ferrite powder was obtained in the same manner as in Example 1, except that the heat treatment temperature of the rapidly cooled flaky material was 750°C. The magnetic properties in this case are shown in FIG.

Ch#3 according to the present invention. 4. 5, 50emu
A high σB of 7g or more was obtained. However, in this case, the peak position is at aha3 (β-5, 3), and the value of β that gives the peak is shifted to a slightly lower side than 6, which is different from Example 1.

For Ha, the peak position is still at β=6 (Q
This suggests that this is the ideal state for hexagonal ferrite.

A TEM photograph of the sample of Ch#4 is shown in FIG. The average particle size is approximately 0.06 μm, and 80% of the total number of particles
It can be seen that the above particles have a non-geometric hexagonal shape.

Example 3 Ferrite powder was obtained in the same manner as in Example 1 except that the heat treatment temperature of the rapidly cooled flaky material was 850°C. The magnetic properties in this case are shown in FIG.

In this case, a high σ5 is obtained overall, but Ch#3. 4. This is especially high for 5, and 60e
Some samples exceeding mu/g have been obtained.

In this case, just opposite to Example 2, the peak position is ah
a5, and the value of β that gives the peak has shifted to a slightly higher side than 6.

However, in this case as well, the peak position for Hc is still at the β-6 position, suggesting that this is the ideal state of hexagonal ferrite.

A TEM photograph of the aha4 sample is shown in FIG. It can be seen that the average particle size is approximately 0.13 μm, and more than 70% of the total particles have a non-geometric hexagonal shape.

Example 4 B203-32 mol% (constant), β = 6 (constant),
In order to investigate the characteristics when the value of x was changed, samples with the blending values shown in Table 2 were prepared. The sample preparation method was the same as in Example 1, except that the blending values were as shown in Table 2.

As a result of X-ray analysis, it was confirmed that all of these samples were hexagonal ferrite.

The magnetic properties of these samples are shown in FIG.

It can be seen that all the samples have a high σs of ssemu/g or more.

It can also be seen that Hc monotonically decreases as the value of X increases, which is significantly different from the results of Examples 1 to 3. this is,
This seems to be because β=6 is satisfied in all samples.

A T and M photograph of Ch #15 is shown in FIG. It can be seen that the average particle size is approximately 0.08 μm, and more than 80% of the total particles have a non-geometric hexagonal shape.

Example 5 B203 = 30 mol% (constant), x = 0.90
In order to examine the characteristics when β was set to 0 (constant) and the value of β was changed, samples were prepared with the blending values shown in Table 3. The sample preparation method was the same as in Example 1, except that the blending values were as shown in Table 3.

The magnetic properties of these samples are shown in FIG.

It can be seen that the samples with β=5.2 to 12 have a high value of 558 mU/Q or more.

Example 6 3a Co, = 30.9 mol%, Fex O, = 32.
6 mol%, CoO=5.75 mol%, TiO,=
5.75 mol%, B20. A sample was prepared in the same manner as in Example 1 except that the raw materials were blended at a ratio of 25 mol%. The value of β for this sample is 6.5, and cl/b
= The value of c2/b is 0.176, that is, the value of X is 0.
It corresponds to 900.

When we measured the magnetic properties of this sample, we found that the saturation magnetization as
= 57,5 cmu / O-coercive force) 1c = 63
It was good with 0Qe.

Further, the average particle size of this fine powder was approximately 0.08 μm, and more than 80% of the total number of particles had a non-geometric hexagonal shape.

Example 7 3a co, = 35.3 mol%, Fe, 0S-26,8
Mol%, ZnO=fy, 32mol%, Nb2O,=
A sample was prepared in the same manner as in Example 1 except that the raw materials were blended at a ratio of 1.58 mol% and BLO3-30 mol%. The value of β for this sample is 6.0, and the value of X is 0
．． It corresponds to 900.

When we measured the magnetic properties of this sample, we found that the saturation magnetization a5
=52. Oemu 7g, coercive force Hc = 14500
It was 8.

Further, the average particle size of this fine powder was approximately 0.09 μm, and more than 70% of the total number of particles had a non-geometric hexagonal shape.

[Advantageous Effects of the Invention 1] According to the present invention, hexagonal ferrite fine particles having excellent magnetic properties, particularly high saturation magnetization, can be obtained.

These fine particles are tabular, and more than 50% of the total particles have a non-geometric hexagonal shape, so when used as a magnetic recording medium, the coating properties and backing Good sex.

Furthermore, since the average particle size is as small as 0.02 to 0.5 μm, a good SN ratio can be obtained even when performing high-density recording.

[Brief explanation of the drawing]

Figures 1 and 2 are triangular component diagrams comparing conventionally known formulations and the formulation of the present invention, Figures 3 and 11 are diagrams showing examples of the present invention, and Figures 12 and 13. is a triangular component diagram showing a conventionally known compounding composition. 4th.
Figure 6.8.10 is a photograph of the particle structure. 1st wind ~ tr't o-4th song 16 Shouto 8 eup de) Oh 0.4 (LS 6 匡7
Q, 8 (L9 1.0 +, IX
of Fa(12-2x)Co(x)Tiω(FQ
2+, 5co+, 5Ti)/(Bo-82)-6B20
3=32molχ, pr9cipitatio
n: 800°Cf 10 Figure II Ek 5 7 9 11
13 l5bt+ta-CF
Q203h, 5TIO2 mulberry, 5can)/C day, +B2
Kutaku8203=30molZ, X=0.9
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Claims (13)

[Claims] (1) General formula MO・(n/6)(Fe_1_2_-_2
_xT_2_xO_1_8) (However, M is one or more metal elements selected from the group of Ba, Sr, and Pb, and T is Co-Ti, Co-Ge, Co-Sb, Co-Ta.
, Zn-Nb, Zn-V, Zn-Ge, and In, one or more substituting elements or a combination of elements, and x is 0 to 1
．． 1, n represents a value of 5.2 to 7, and 5, respectively), and the value of saturation magnetization σ_s is 50 emu/
g or more, and each particle has an average particle size of 0.02 to
1. Hexagonal ferrite fine particles having a flat plate shape of 0.5 μm, and in which 50% or more of the total number of particles have a non-geometric hexagonal plate shape. (2) In the hexagonal ferrite fine particles according to claim 1, the general formula MO・(n/6)(Fe_1
_2_-_2_xCo_xTi_xO_1_8) (However, M is one or more metal elements selected from the group of Ba, Sr, and Pb, x is a value of 0 to 1.1, and n is 5.2
~7.5, respectively), and the value of saturation magnetization σ_s is 50 emu/g or more, and each particle has a flat plate shape with an average particle size of 0.02 to 0.5 μm. , and hexagonal ferrite fine particles characterized in that 50% or more of the total particles have a non-geometric hexagonal plate shape. (3) In the hexagonal ferrite fine particles according to claims 1 to 2, the value of n is 5.5 to 7.
2, the value of σ_s is 52 emu/g or more, and 60% or more of the total number of particles have a non-geometric hexagonal plate shape. (4) In the hexagonal ferrite fine particles according to claim 3, the value of n is 5.8 to 7.0, the value of σ_s is 53 emu/g or more, and the total number of particles is Hexagonal ferrite fine particles characterized in that 70% or more of the particles have a non-geometric hexagonal plate shape. (5) In the hexagonal ferrite fine particles according to claim 4, the value of n exceeds 6.0 and is 6.8 or less, the value of σ_s is 54 emu/g or more, and all particles Hexagonal ferrite fine particles characterized in that 75% or more of the particles have a non-geometric hexagonal plate shape. (6) In the hexagonal ferrite fine particles according to claim 5, the value of n exceeds 6.1 and is 6.6 or less, the value of σ_s is 55 emu/g or more, and all particles Hexagonal ferrite fine particles characterized in that 80% or more of the particles have a non-geometric hexagonal plate shape. (7) MO (where M represents one or more metal elements selected from the group of Ba, Sr and Pb) in a mol%, F
e_2O_3 is b mol%, T (however, T is Co-Ti,
Co-Ge, Co-Sb, Co-Ta, Zn-Nb, Z
n-V, Zn-Ge, In, one or more substituting elements or combinations of elements) in total c mol %, B_2
It consists of melting a mixture containing e mol % of O_3, then rapidly cooling it, then heat-treating this rapidly cooled body to produce ferrite crystals, and then dissolving and removing phases other than ferrite from this heat-treated product. In the method for producing hexagonal ferrite fine particles, the mixture (I) has an e value of 20 or more and 40 or less (II) has an effective molar ratio β of 5.2 to 12. Here, what is the effective molar ratio β? , effective Fe_2O_3
This is a value calculated using the following formula using mol% [Fe_2O_3]^*. That is, β=[Fe_2O_3]^*(a/e) However, the effective Fe_2O_3 mol% [Fe_2O_
3] ^* is the value obtained by adding the mol% value of T oxide converted to Fe_2O_3 to b, [Fe_2O_3]^* = b + b × (total atomic % of metal element T) / (fe atoms A method for producing hexagonal ferrite fine particles, characterized in that each compounding amount is selected so as to obtain a desired value (%). (8) In the method for producing hexagonal ferrite fine particles according to claim 7, the mixture contains c1 mol% of CoO and c2 mol% of TiO_2 as T oxides, and (I) β={ b+0.5(c1+c2)}/(a-e
) is 5.2 to 12 (II) c1/b is 0 to 0.225 (III) c2/b is 0 to 0.225. A method for producing hexagonal ferrite fine particles. (9) In the method for producing hexagonal ferrite fine particles according to claims 7 to 8, the value of e is set to 3.
A method for producing hexagonal ferrite fine particles, characterized in that the particle size is greater than 0 and less than or equal to 40. (10) The method for manufacturing hexagonal ferrite fine particles according to claims 7 to 9, characterized in that the value of β is 5.8 to 12. Method. (11) In the method for producing hexagonal ferrite fine particles according to claim 10, the value of β is 6.0 to 1.
A method for producing hexagonal ferrite fine particles, characterized in that the hexagonal ferrite fine particles are set to 0. (12) In the method for producing hexagonal ferrite fine particles according to claim 11, the value of β is 6.0 to 8.
．． A method for producing hexagonal ferrite fine particles, characterized in that the hexagonal ferrite fine particles are set to 0. (13) In the method for producing hexagonal ferrite fine particles according to claim 12, the value of β is 6.0 to 7.
．． A method for producing hexagonal ferrite fine particles, characterized in that the hexagonal ferrite fine particles are set to 0.