JPS62139121A - Fine plate ba ferrite corpuscle powder for magnetic recording and its production - Google Patents

Abstract

PURPOSE:To obtain the titled plate Ba ferrite particles having an appropriate mean particle size by composing the particle surface of fine plate BaO.nFe2O3 corpuscle powder modified with spinel ferrite. CONSTITUTION:Fine plate Ba ferrite particulate powder for magnetic recording consisting of tine plate BaO.nFe2O3 (4<=n<=6) particles whose surfaces are modified by spinel ferrite (M<2+>xFe<2+>yO.Fe2O3, where 0<x<=1, 0<=y<1, and 0<x+y<=1, and M is one or >=2 kinds selected from Ni, Mn, Zn, Cu, and Mg) and fine plate BaO.nFe2O3 (4<=n<=6) corpuscle powder are mixed with an alkaline suspension at 8.0-14.0pH contg. 0.1-30.0atom%, based on the total Fe(III) in the fine plate BaO.nFe2O3 corpuscle powder, M<2+> (one or >=2 kinds selected from Ni, Mn, Zn, Cu, and Mg) or M<2+> and Fe<2+>. The liq. mixture is heated at 50-100 deg.C. Consequently, the surface of the particles is modified with the spinel ferrite, the mean particle diameter is controlled to 0.05-0.3mum, and the powder is appropriately used especially as the magnetic material for vertical magnetic recording medium.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing plate-shaped Ba ferrite fine particle powder, in which the particle surface is spinel-type ferrite (M
"x Fe"yO・Pe2's However, Q < x≦12
0≦y<L, O<x+y≦1, ladle is N1% Mns
Zn-.

The present invention provides a plate-shaped Ba ferrite fine particle powder for magnetic recording consisting of plate-shaped BaO.nFezos (4≦n≦6) fine particles modified with one or more selected from Cu and Mg, and a method for producing the same.

[Conventional technology]

In recent years, for example, as described in Japanese Patent Application Laid-Open No. 55-86103, it has a suitable coercive force and a large magnetization value,
In addition, ferromagnetic non-acicular particles having appropriate average grain size and size are increasingly desired as magnetic materials for recording, especially magnetic materials for perpendicular magnetic recording.

Generally, Ila ferrite particles are well known as ferromagnetic non-acicular particles.

Conventionally, one of the manufacturing methods of plate-shaped Ba ferrite is B
A method is known in which an alkaline suspension containing a ions and Fe1) is hydrothermally treated using an autoclave as a reaction device (hereinafter, this is simply referred to as a hydrothermal treatment method).

First, regarding magnetic properties, the coercive force of plate-shaped Ba ferrite particles for magnetic recording is generally 300 to 1000.
In order to reduce the coercive force of the ferrite fine particles produced in the above hydrothermal treatment method and to obtain an appropriate coercive force, some of the Fe(2) in the ferrite is replaced with Ti(5). and Co(I[l or Co0D and M
Substitution with divalent metal ion M(1) such as n, Zns, etc. has been proposed.

Also, the magnetization value needs to be as large as possible,
This fact is reflected in, for example, 1 of JP-A-56-149328: Magnetobrambite ferrite used as a magnetic recording medium material is required to have as large a saturation magnetization as possible. ” as stated.

Next, regarding the particle size of the plate-shaped Ba ferrite fine particle powder for magnetic recording, the particles should be as fine as possible, especially 0.3 μm.
m or less.

This fact can be seen, for example, in JP-A-56-125219, which states, However, in order to perform sufficient recording and reproduction in this wavelength range, the crystal grain size of the ferrite must be approximately 0.3μ.
m or less is desirable. However, if it is about 0.01 μm, it will not exhibit the desired ferromagnetism, so a suitable crystal grain size is required to be about 0.01 to 0.3 μm. ” is as stated.

[Problem that the invention seeks to solve]

Plate-shaped Ba ferrite particles having appropriate coercive force, large magnetization value, and appropriate average particle size are currently required in quantity, but in the hydrothermal treatment method described above, the reaction Various types of B can be created by selecting conditions.
a Ferrite particles are precipitated. These precipitated particles usually have a hexagonal plate shape, and their magnetic properties vary depending on the generation conditions as their particle size distribution and average diameter differ.

The present inventor has been involved in the research and development of plate-shaped Ba ferrite particles using a hydrothermal treatment method for many years.
It has been found that plate-like Ba ferrite particles having a diameter of ~0.3 μm can be obtained.

However, the plate-shaped Ba ferrite particles having the average diameter of 0.05 to 0.3 μm have a large magnetization value, especially 4
If you want to obtain more than 0 emug-', the coercive force is 100
Only those with a value of 008 or higher were obtained.

Therefore, it is strongly desired to establish a method for obtaining plate-shaped Ba ferrite particles having an appropriate coercive force, a large magnetization value, and an appropriate average particle size.

[Means for solving problems]

In view of the above, the present inventor set the coercive force of plate-shaped Ba ferrite particles having an average diameter of 0.05 to 0.3 μm to 300 to 10,000 e in a hydrothermal treatment method, and
The present invention was achieved as a result of various studies aimed at further increasing the magnetization value.

That is, in the present invention, the particle surface is spinel type ferrite (M"
x Fe2′″yO・FeJ3 However, Q<x≦1.0≦
y<1, 0<x+y≦1, gate is N+1Mn5 Zn5
Magnetic recording plate-shaped Ba ferrite fine particle powder and plate-shaped BaO nFezos ( 4≦n≦6) Fine particles and total FeQID in the plate-shaped BaO nFezoz fine particles
On the other hand, M” (Ni.

one or more selected from Mn, Zn, Cu, Mg) or M! + and an alkaline suspension of 8.0 to 14.0 pt+ containing 0.1 to 30.0 atom % of pe2+, and the mixed solution is heat-treated in a temperature range of 50 to 100°C. By this, the above-mentioned plate-like BaO/nFe
The particle surface of the Gos fine particles is coated with spinel type ferrite (M”
X Fe”yO−PetOaHowever, 0<x≦1.0≦y
This is a method for producing a plate-shaped Ba ferrite fine particle powder for magnetic recording, which comprises performing metamorphosis such that <1, 0<x+y≦1).

1 Effect] First, the most important point in the present invention is that the plate-like BaO・n
M” (Nt , Mn, , Z
one or more selected from n, C11% Mg)
Or, mix with an alkaline suspension containing M2' and Fe' in a proportion of 0.1 to 30.0% or less and have a pH of 8.0 to 14.0, and heat the mixture in a temperature range of 50 to 100°C. In the case of treatment, the particle surface of the plate-shaped BaO-nFe20i fine particles is coated with spinel-type ferrite (M”x Fe”yO
・Fe20:I However, 0<x≦1.0≦y<l, Q<
x + y≦1), and as a result, the coercive force of the plate-like BaO nFeJs particles increases to 300
~10,000e, and the magnetization value can be increased.

In the present invention, the metamorphosis rate of spinel-type ferrite is mainly influenced by the excess Na011-1 degree and the heating temperature, and the metamorphosed BaO and
The magnetism and conductivity of nFezo:+ fine particles are influenced by the composition and the rate of metamorphosis by spinel ferrite.

Next, various conditions for implementing the present invention will be described.

The plate-shaped BaO-nFe2O3 fine particles in the present invention are plate-shaped Ba0-nFeJa fine particles produced from an aqueous solution and plate-shaped 11ao. nPe
20.1 fine particles may be used, and similar effects can be obtained in either case.

The amount of MZ "or MZ- and Fe" in the present invention is
It is 0.1 to 30.0% or less based on the total FeQID in the plate-shaped BaO-nFe2O3 fine particles.

If it is 0.1% or less, metamorphosis by spinel type ferrite is not sufficient.

If it is 30.0% or more, the coercive force will be extremely reduced, making it undesirable as a magnetic material for magnetic recording.

In the present invention, the plate-shaped BaFe+zO+q fine particles and the alkaline suspension containing M2'' or M2+ and Fe2'' may be mixed in either order or at the same time.

pll in the present invention is 8.0 to 14.0. pl
When l is 8.0 or less, it is difficult for the hydroxides of MZ- or H2" and Fe"+ to exist stably. In addition, if it is strongly alkaline, the hydroxides of M21 or H2" and Fe" will stably exist, and at the same time, the hydroxides of M21 or H2" and Fe" will exist stably.
Since a modification reaction of plate-shaped Ba ferrite particles by the hydroxide of e t + also occurs, considering the industrial effect, pl
The object of the present invention can be sufficiently achieved when l is 14.0 or less.

The heating temperature in the present invention is 50 to 100°C.

When the temperature is 50°C or lower, "1 or M" in the present invention
The modification reaction of the plate-shaped Ba ferrite particles by Z- and pez+ hydroxides becomes difficult to occur. Furthermore, although the modification reaction occurs even at temperatures above 100°C, considering that it is carried out in an aqueous solution, the object of the present invention can be sufficiently achieved at a temperature below 100°C.

〔Example〕

Next, the present invention will be explained with reference to Examples and Comparative Examples.

In addition, the average diameter of particles in the following Examples and Comparative Examples is a value measured by electron \a microphotography.

In addition, the magnetization value was measured in a powder state in a magnetic field of 10 KOe, and the coercive force was measured at a filling degree of 1.6 g/cff.
This is the value measured at 1.

Example 1 Platy BaFe I 201 q with an average diameter of 0.2 to 0.3 μm obtained by heat-treating plate-shaped Ha mitzerite powder produced by a hydrothermal treatment method at 700°C.
150 g of particles (specific surface area S value 23 n(/g, magnetic value 45 emug-', coercive force Hc 20000e), 0.10 mol Fe(Oll)z and 0.Olmo
1 of Mn (OH) 2 (Mn" and Pe2'" correspond to 6.8% or less with respect to PeOID), and then by adding water, the total volume was 1. ．． ! After setting the mixture to M (pl(12,3)), the temperature of the mixture was heated to 90°C, and the mixture was stirred at this temperature for 1 hour.

The produced dark brown particles were separated in a furnace, washed with water, treated with acetone, and then dried at room temperature.

As a result of electron microscopic observation, no significant difference in particle shape or size was found before and after the reaction.

The obtained dark brown particle powder has a specific surface area S value of 26 n(/
g, coercive force Hc 9000e, magnetization H value 50
It was emug-'.

As a result of the X-ray diffraction diagram and fluorescent X-ray analysis shown in Figure 1, the obtained dark brown particles show peaks of Ba ferrite and Fe-Mn ferrite, indicating that it has a two-phase structure. . In FIG. 1, peak A indicates the peak of Ba ferrite, and peak B indicates the peak of Fe-Mn ferrite.

Example 2 Platy BaFf3+□0++ with an average diameter of 0.15 to 0.25 #m obtained by heat-treating plate-shaped Ba ferrite particles produced by a hydrothermal treatment method at 800°C.
+ Particles 150 g (specific surface area S value 28 rd/g, magnetization H value 47 emug-', coercive force He 37000e)
and 0.21 mol of Fe (OR) 2 and 0.01
mol of Cu (OH) z (Mn"+ and Fe" for FeaID are 13.
This corresponds to 6 atom%. ) and then by adding water, the total volume is 1.57! (111112,4), the temperature of the mixture was brought to 90°C by heating, and the liquid was stirred at this temperature for 1 hour.

The produced dark brown particles were separated in a furnace, washed with water, treated with acetone, and then dried at room temperature.

As a result of electron microscopic observation, no significant difference in particle shape or size was found before and after the reaction.

The obtained dark brown particle powder has a specific surface area S (a2M/g, coercive force Hc 8000e, magnetization i value 55 em
It was ug-'.

In addition, the obtained black-brown particle powder was analyzed by X-ray diffraction and fluorescence
The line analysis results show peaks of Cu ferrite and Ba ferrite, indicating a two-phase structure.

Example 3 Plate-shaped BaFe+zO+ with an average diameter of 0.2 to 0.3 μm
++ Particles 150 g (specific surface area S value 32 rtr 7 g,
Magnetization M value 38emug-', coercive force Hc12000e)
and 0.31 mol of Fe(OH) and 0.04
mixed with an alkaline suspension containing mol of Ni (OH) z (Fe(2) vs. Fe(In and Ni0D = 21
．． This corresponds to 6 atom%. ) and then by adding water, the total volume is 1.5 j! After setting it to (pH 12.5),
The temperature of the mixed solution was brought to 70° C. by heating, and the solution was stirred at this temperature for 1 hour.

The produced dark brown particles were separated in a furnace, washed with water, treated with acetone, and then dried at room temperature.

As a result of electron microscopic observation, no significant difference in particle shape or size was found before and after the reaction.

The obtained dark brown particle powder has a specific surface area S value of 3 In? /g
, coercive force 11c 5500e, magnetization i value 52
It was emug-'.

In addition, the obtained black-brown particle powder was analyzed by X-ray diffraction and fluorescence
As a result of the line diffraction analysis, peaks of Fe-Ni ferrite and Ba ferrite are shown, indicating a two-phase structure.

〔effect〕

As shown in the above example, the plate-shaped Ba ferrite particles according to the present invention have a magnetization H value of 40 emu/g or more in a magnetic field of 10 KOe, and a coercive force 11c of 300 emu/g.
~10,000e, the particle surface is modified with spinel type ferrite, and the average diameter is 0.05 to 0.3 μm.Since it is possible to obtain BaO.nFezoa fine particles having an average diameter of 0.05 to 0.3 μm, it is suitable as a magnetic material for magnetic recording, especially for perpendicular magnetic recording. It is suitable as a magnetic material.

In addition, since the plate-shaped Ba ferrite fine particles obtained by the present invention have their surfaces modified with spinel-type ferrite, the entire particle surface is modified and the electrical resistance is lowered.

[Brief explanation of drawings]

FIG. 1 is an X-ray diffraction diagram of the dark brown particles obtained in Example 1. In FIG. 1, peak A indicates the peak of Ba ferrite, and peak B indicates the peak of Fe-Mn ferrite.

Claims (2)

[Claims] (1) The particle surface is spinel type ferrite (M^2^+_
xFe^2^+_yO・Fe_2O_3 However, 0<x≦
1, 0≦y<1, 0<x+y≦1, M is Ni, Mn,
Platy BaO・_nFe_2O_3 (4≦n
≦6) Plate-shaped Ba ferrite fine particle powder for magnetic recording consisting of fine particles. (2) Plate-shaped BaO・_nFe_2O_3 (4≦n≦6)
M^2^+(Ni, Mn, Z
one or more selected from n, Cu, Mg) or M
^2^+ and Fe^2^+ from 0.1 to 30.0 at%
The above-mentioned plate-shaped BaO・_nFe_2O
_3 The particle surface of the fine particles is coated with spinel type ferrite (M^2
^+_xFe^2^+_yO・Fe_2O_3However, 0
<x≦1, 0≦y<1, 0<x+y≦1) A method for producing a plate-shaped Ba ferrite fine particle powder for magnetic recording.