JP3135988B2 - Acicular hexagonal ferrite magnetic powder having perpendicular magnetic anisotropy and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle-shaped hexagonal ferrite magnetic powder having perpendicular magnetic anisotropy and used as a coating medium of a perpendicular magnetic recording system for high-density magnetic recording and a method for producing the same. .

[0002]

2. Description of the Related Art Conventionally, plate-like particles and needle-like particles have been known as ferrite magnetic powders having perpendicular magnetic anisotropy. Various methods for producing plate-like ferrite particles are known, such as a coprecipitation method, a glass crystallization method, and a hydrothermal synthesis method. As a method for producing acicular particles, for example, a method in which acicular iron oxyhydroxide or the like is coated with barium carbonate and then fired (Japanese Patent Application Laid-Open No. 61-10460)
No. 2) is known. The metal added to control the coercive force (Hc) of the particles is 2
A combination of a valent metal Co and a tetravalent metal Ti is generally used.

[0003]

However, it is not easy for the above-mentioned plate-like particles to be coated flat with their easy axes of magnetization aligned in the same direction due to their shape. Further, regarding the acicular particles, in the above-described method, if the firing temperature is increased in order to obtain high saturation magnetization, the sintering between the particles proceeds, and the shape of the particles themselves tends to be broken, so that the acicularity tends to be unable to be maintained.

In a conventional needle-like ferrite magnetic powder represented by the following general formula (II), the coercive force (Hc)
Is controlled by replacing the substitution element M with Fe ³⁺ . That is, Hc7 suitable for magnetic recording tape
In order to obtain a needle-like ferrite magnetic powder of about 00 to 2000 Oe, the addition of the substitution element M is indispensable. At present, a common substitution element is a combination of Co ²⁺ and Ti ⁴⁺ or Sn ⁴⁺ , which is also effective in maintaining needle-like properties, but a Co compound is considerably expensive. In addition, Co-Ti based, Co-S
Raw materials to which an oxide such as an n-type is added require a higher firing temperature than those not added.

[0005]

Embedded image AFe _12-x M _x O ₁₉ (II) (where A is one or more elements selected from the group consisting of Ba, Sr and Pb, M is an element such as Co, and 0 ≦ X ≦ 1
2)

[0006] Therefore, the above-mentioned problems have been solved, and needle-shaped perpendicular magnetic anisotropy (the axis of easy magnetization is perpendicular to the long axis) having more excellent magnetic properties and lower cost is provided. Hexagonal ferrite magnetic powder has been desired. Therefore, an object of the present invention is to prevent intergranular sintering, maintain acicularity, and have a high saturation magnetization even at a relatively low firing temperature, and at a low cost acicular hexagonal ferrite magnetic powder and It is to provide a manufacturing method thereof.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the acicular ferrite magnetic powder represented by the above general formula (II) contains C
It has been found that the above object is achieved by including u or Mn.

The present invention has been made based on the above findings, and has the following general formula (I) of the following [Chemical Formula 3] (the same as [Chemical Formula 1]).
The present invention provides a needle-shaped hexagonal ferrite magnetic powder having a needle-like shape and perpendicular magnetic anisotropy represented by:

[0009]

Embedded _image AFe _12-2X B _Y M ¹ _(XY) M ² _X O ₁₉ (I) (where A is one or more elements selected from the group consisting of Ba, Sr and Pb, and B is Cu or Mn and M ¹ are Co,
One or more divalent metals selected from the group consisting of Ni and Zn, M ² is one or more tetravalent metals selected from Ti, Sn and Zr, and 0 <X <1.0, 0 <Y < 1.
0, Y ≦ X. )

The present invention also provides a preferred method for producing the acicular hexagonal ferrite magnetic powder according to the present invention, wherein the acicular iron oxyhydroxide or iron oxide is dispersed in an aqueous dispersion slurry as described in (a) or (b) below. , (C) and (d) at least four compounds selected from one or more of each compound group and alkali hydroxide in an appropriate order or simultaneously at pH 8 to 1
2 and, if necessary, one or more compounds selected from the following compound group (e) are also added under pH 8 to 12, and the surface of the iron oxyhydroxide or iron oxide is coated with the additional compound. , Filtration, washing and drying.
An object of the present invention is to provide a method for producing acicular hexagonal ferrite magnetic powder, which is fired at 0 to 1200 ° C. (A) water-soluble barium compound, water-soluble strontium compound and water-soluble lead compound (b) water-soluble copper compound and water-soluble manganese compound (c) water-soluble tetravalent metal (Ti, Sn and Zr) compound (d) carbonate And carbon dioxide (e) Water-soluble divalent metal (Co, Ni and Zn) compounds

First, the acicular hexagonal ferrite magnetic powder of the present invention will be described in detail. In the acicular hexagonal ferrite magnetic powder of the present invention, Cu ²⁺ or Mn ²⁺ is conventionally used as a divalent metal in the substitution element M in the general formula (II) of [Chemical Formula 2]. It is added to the raw material instead of Co ²⁺ or the like. In addition, as the divalent metal in the substitution element, the above Cu ^{2+
Alternatively} , divalent metals such as Mn ²⁺ and Co ²⁺ (Co, Ni, Zn
Or more selected ones) may be used in combination as needed. The Cu ²⁺ or Mn ²⁺ enters the ferrite crystal structure and controls the coercive force.

In the acicular hexagonal ferrite magnetic powder of the present invention, the Cu ²⁺ or Mn ²⁺ is used together with a tetravalent metal such as Ti, Sn, or Zr as the substitution element,
In particular, in combination with Ti (Cu ²⁺ -Ti ⁴⁺ or M
n2 ⁺ -Ti4 ⁺ ) is preferable. When the Cu ²⁺ -Ti ⁴⁺ system or the Mn ²⁺ -Ti ⁴⁺ system is used as the substitution element, the sintering temperature of the ferrite magnetic powder is the same as when ordinary Co ²⁺ is used (Co ²⁺ -Ti 4 ⁴⁺ system), and can be baked at the same temperature as in the case where no substitution element is added to form ferrite. This also helps to keep the ferrite particles acicular. Further, the above Cu ²⁺ and Mn ²⁺
The water-soluble compound is considerably less expensive than the water-soluble compound such as Co ²⁺ , which is also a great advantage.

Next, a preferred embodiment of the method for producing acicular hexagonal ferrite magnetic powder of the present invention will be described in detail.

First, at least two kinds of compounds selected from each of the above-mentioned compound groups (a) and (d) are added to a needle-shaped aqueous dispersion of iron oxyhydroxide or iron oxide at a pH of 8 to 12 at least. To be added.

The amount of dispersion of the needle-like iron oxyhydroxide or iron oxide in the aqueous dispersion slurry is usually preferably 0.02 to 0.2 mol / l with respect to water.

The compound (a) is usually added to the above slurry as an aqueous solution, and the concentration thereof is usually 0.0
About 18 to 0.22 mol / l is preferable. The aqueous solution is adjusted so that the amount of barium, strontium, or lead in the aqueous solution is an amount necessary for obtaining the target acicular hexagonal ferrite magnetic powder calculated from the general formula (I). What is necessary is just to add to the said slurry.

The compound of the above (d) is BaCO ₃
Etc. to form a carbonate.

Next, at least two compounds selected from the above-mentioned compound groups (b) and (c) are added to the slurry to which the compounds (a) and (d) are added at a pH of 8 to 8. Add under 12 with alkali hydroxide.

The compound (b) is usually added to the above slurry as an aqueous solution, and its concentration is usually 0.03.
It is preferably about 01 to 0.2 mol / l. The slurry is prepared such that the amount of copper or manganese in the aqueous solution is an amount necessary for obtaining the target acicular hexagonal ferrite magnetic powder calculated from the general formula (I). May be added.

The compound (c) is usually added to the above slurry as an aqueous solution, and the concentration thereof is usually
It is preferably about 0.001 to 0.2 mol / l. The aqueous solution such that the amount of titanium, tin and zirconium in the aqueous solution is an amount necessary to obtain the target acicular hexagonal ferrite magnetic powder calculated from the general formula (I), What is necessary is just to add to the said slurry.

The alkali hydroxide is mainly composed of Co (OH)
₂ to form a hydroxide such as ₂
It also has the function of adjusting H.

Further, together with the compounds (b) and (c), the compound (e) can be added to the slurry, if necessary. The compound (e) is usually added as an aqueous solution to the slurry, and the concentration is usually preferably about 0.001 to 0.2 mol / l. The aqueous solution is adjusted so that the amount of cobalt, nickel and zinc in the aqueous solution is an amount necessary to obtain the target acicular hexagonal ferrite magnetic powder calculated from the general formula (I). What is necessary is just to add to the said slurry.

As described above, the slurry (a)
By adding and mixing each of the compounds (e) to (e) and the alkali hydroxide, the surface of the iron oxyhydroxide or iron oxide in the slurry is coated with the additive compound. The obtained iron oxyhydroxide or iron oxide coated on the surface is filtered, washed with water, and dried, and then calcined at 700 to 1200 ° C., preferably 800 to 1000 ° C., thereby obtaining the acicular hexagonal crystal of the present invention. Ferrite magnetic powder can be manufactured. The above-described firing method can be performed in the same manner as the usual method for firing magnetic powder.

The preferred embodiment of the method for producing acicular hexagonal ferrite magnetic powder of the present invention has been described above.
The order of addition of the above compounds may be appropriately changed,
All of them may be mixed at the same time, and in such a case, the conditions such as the addition amount may be set in the same manner as in the above-described preferred embodiment.

[0025]

Examples Examples and comparative examples are given below to further specifically explain the acicular hexagonal ferrite magnetic powder of the present invention.

Example 1 Barium chloride (BaCl ₂ .2H ₂ O) 1 was added to an aqueous dispersion slurry of 66.6 g of acicular goethite (α-FeOOH).
8.3 g dissolved in deionized water are added with sodium carbonate at pH 10 and then copper chloride (CuCl
₂ · 2H ₂ O) 5.8g, titanium chloride (TiCl ₄₎
A solution prepared by dissolving 6.5 g in deionized water and sodium hydroxide were added at pH 10 and stirred well. The obtained slurry was filtered, washed with water, and dried to obtain a solid. This solid is fired in an air atmosphere at 900 ° C. for 1 hour,
Acicular barium ferrite magnetic powder was obtained.

The obtained barium ferrite magnetic powder was confirmed to be of a magnetoplumbite type by X-ray diffraction spectrum. The magnetic properties of each of these barium ferrite magnetic powders were measured with a vibrating sample magnetometer, and the state of the needle-like holding was determined with a transmission electron microscope (good in the order of ◎, ○, △). Is shown). The results are shown in Table 1 below.

Example 2 20.1 g of barium chloride (BaCl ₂ , 2H ₂ O)
Example 1 except that 6.4 g of copper chloride (CuCl ₂ .2H ₂ O), 14.2 g of titanium chloride (TiCl ₄ ), and 8.9 g of cobalt chloride (CoCl ₂ .2H ₂ O) were added. In the same manner as in the above, acicular barium ferrite magnetic powder was obtained. For each of the obtained acicular barium ferrite magnetic powders, measurement of magnetic properties and judgment of acicular holding state were performed in the same manner as in Example 1. The results are shown in Table 1 below.

Example 3 Copper chloride (CuCl_Two・ 2H_TwoO) instead of manganese chloride
(MnCl_Two・ 4H _TwoO) Except that 6.7 g was used,
Acicular barium ferrite magnetic powder was obtained in the same manner as in Example 1.
Was. Each of the obtained needle barium ferrite magnetic powder
Then, measurement of magnetic properties and needle
The state of state retention was determined. The results are shown in Table 1 below.
Shown in

Example 4 Tin chloride (SnC) was used instead of titanium chloride (TiCl ₄ ).
l ₄ ) except that 8.9 g was used and the firing time was 5 hours.
A needle barium ferrite magnetic powder was obtained in the same manner as in Example 3. For each of the obtained acicular barium ferrite magnetic powders, measurement of magnetic properties and judgment of acicular holding state were performed in the same manner as in Example 1. The results are shown in Table 1 below.

Example 5 Copper chloride (CuCl_Two・ 2H_TwoO) instead of manganese chloride
(MnCl_Two・ 4H _TwoO) Using 5.7 g, burr chloride
Um (BaCl_Two, 2H_TwoO), 19.4 g, titanium chloride
(TiCl_Four) To 10.9 g, and
(CoCl_Two・ 6H_TwoO) Add 6.9 g and bake
Except that the time was set to 5 hours, the needle-shaped
A lithium ferrite magnetic powder was obtained. Needle barium obtained
For each of the ferrite magnetic powders, as in Example 1.
To measure the magnetic properties and determine the state of the needle-like holding
Was. The results are shown in Table 1 below.

Comparative Example 1 Barium chloride (BaCl ₂ , 2H ₂ O) 1 was added to an aqueous dispersion slurry of 66.6 g of acicular goethite (α-FeOOH).
Acicular barium ferrite magnetic powder was obtained in the same manner as in Example 1 except that 6.8 g was dissolved in deionized water and only sodium carbonate was added. For each of the obtained acicular barium ferrite magnetic powders, measurement of magnetic properties and judgment of acicular holding state were performed in the same manner as in Example 1. The results are shown in Table 1 below.

Comparative Example 2 Copper chloride (CuCl_Two・ 2H_TwoOval chloride instead of O)
(CoCl_Two・ 6H _TwoO) Firing time using 8.1 g
Was changed to 5 hours in the same manner as in Example 1 except that
Um ferrite magnetic powder was obtained. The obtained needle barium f
For each of the ferrite magnetic powders,
To measure the magnetic properties and judge the needle-hold state.
Was. The results are shown in Table 1 below.

Comparative Example 3 Cobalt chloride (CoCl_Two・ 6H_TwoO) 17.8 g,
Titanium chloride (TiCl _Four) Is set to 14.2 g and firing conditions
Was carried out in the same manner as in Comparative Example 2 except that
Thus, acicular barium ferrite magnetic powder was obtained. Needle obtained
Examples for each barium ferrite magnetic powder
In the same manner as in 1, the measurement of the magnetic properties and the
The judgment was made. The results are shown in Table 1 below.

[0035]

[Table 1]

[0036]

The acicular hexagonal ferrite magnetic powder of the present invention can control the coercive force in various ways, prevent interparticle sintering, maintain the acicular shape, and have a relatively low firing temperature. However, it has high saturation magnetization and is inexpensive.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Suzuki 425 Kanai, Shibukawa-shi, Gunma Kanto Denka Kogyo Co., Ltd. R & D Center (72) Inventor Mitsuo Sugimoto 4-56-5 Hikawadai, Nerima-ku, Tokyo (56 References JP-A-62-123024 (JP, A) JP-A-4-1499031 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 1/11 C01G 49/00 G11B 5/706

Claims (3)

(57) [Claims] A needle-shaped hexagonal ferrite magnetic powder having a needle-like shape having perpendicular magnetic anisotropy and represented by the following general formula (I): Embedded _image AFe _12-2X B _Y M ¹ _(XY) M ² _X O ₁₉ (I) (where A is one or more elements selected from the group consisting of Ba, Sr and Pb, B is Cu or Mn and M ¹ are Co,
One or more divalent metals selected from the group consisting of Ni and Zn, M ² is one or more tetravalent metals selected from Ti, Sn and Zr, and 0 <X <1.0, 0 <Y < 1.
0, Y ≦ X. ) 2. A needle-like aqueous dispersion of iron oxyhydroxide or iron oxide is added to at least four compounds selected from the following compounds (a), (b), (c) and (d). The species compound and the alkali hydroxide are added in an appropriate order or simultaneously under pH 8 to 12 and, if necessary, one or more compounds selected from the following compound group (e) are also added under pH 8 to 12, Production of needle-shaped hexagonal ferrite magnetic powder, characterized in that the surface of the iron oxyhydroxide or iron oxide is coated with the additive compound, filtered, washed with water and dried, and then calcined at 700 to 1200 ° C. Law. (A) water-soluble barium compound, water-soluble strontium compound and water-soluble lead compound (b) water-soluble copper compound and water-soluble manganese compound (c) water-soluble tetravalent metal (Ti, Sn and Zr) compound (d) carbonate And carbon dioxide (e) Water-soluble divalent metal (Co, Ni and Zn) compounds 3. A needle-like aqueous dispersion of iron oxyhydroxide or iron oxide is mixed with at least two compounds selected from one or more of the above compounds (a) and (d) at a pH of 8 to 12. And then at least two compounds selected from one or more of each of the above compound groups (b) and (c) are selected from the group consisting of alkali hydroxide and the following compound (e) to be added as required. 3. The needle-shaped hexagonal ferrite magnetic powder according to claim 2, wherein the iron oxide oxyhydroxide or the iron oxide is coated with the additional compound at a pH of 8 to 12 together with the at least one compound thus obtained. Manufacturing method.