JPS62107436A - Magnetic powder for magnetic recording - Google Patents

Abstract

PURPOSE:To obtain magnetic powder which has excellent coercive force and saturation magnetization and is suitable for vertical magnetic recording by preparing the magnetic powder for magnetic recording having a specific average grain size and compsn. CONSTITUTION:The magnetic powder for magnetic recording which is expressed by the general compsn. formula FeaCObTicMIdMIIeOf and has 0.01-0.3mu average grain size is prepd. In the formula, MI is at least one kind of metallic element among Ba, Sr, Ca, and Pb, MII is at least one kind of metallic element among Mo, W, Ru, Rh, Pd, and Re, a-f are respectively numbers of atom of Fe, Co, Ti, MI, MII, O, a=8-11.8, b=0.05-2.0, c=0.05-2.0, d=0.5-3.0, e=0.01-2.0, and f is the number of atom of oxygen satisfying the valence of other elements. The magnetic powder having 300-2,000Oe coercive force and -40emu/g saturation magnetization is preferable. The magnetic powder is obtd. by co-depositing a metallic carbonate from an aq. soln. contg. prescribed amts. of the chlorides of the above-mentioned metallic elements and subjecting the same to rinsing, drying and calcining.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic powder for magnetic recording, and more specifically to macrogonal ferrite magnetic powder consisting of fine particles suitable for high-density magnetic recording media. be.

(Prior Art) In recent years, with the demand for higher density magnetic recording, perpendicular magnetic recording methods that record magnetic fields in the thickness direction of a magnetic recording medium have been attracting attention. The magnetic material used in such perpendicular magnetic recording systems needs to have an axis of easy magnetization in a direction perpendicular to the surface of the recording medium.

Ferrite with hexagonal crystal system and uniaxial magnetization anisotropy, such as Ba ferrite (B a Fe 12019), is a hexagonal plate-shaped crystal with an axis of easy magnetization perpendicular to the plate surface. This material satisfies the above requirements as a film-type magnetic material for perpendicular magnetic recording. The magnetic material has a moderate coercive force (Hc, usually 300 to 20,000 e
It is necessary that the average particle diameter of the magnetic powder be 0.3 μm or less in view of the relationship between the magnetic powder and the recording wavelength, and the saturation magnetization (σS) as large as possible.

By the way, Ba ferrite has a coercive force of 50,000e or more, which is too large to be used as a magnetic material for magnetic recording as it is, so a method has been proposed to reduce the coercive force by replacing part of Fe with Co and Ti. (For example, JP-A-55-86103, JP-A-59-175707, IEEET Trans, on Magn,
MAG 18. 16 (1982) P, 1122, etc.).

(Problems to be Solved by the Invention) By the way, in the known magnetic powder in which a part of Fe is replaced with Co and Ti, even if the composition ratio of the constituent elements is almost the same, the manufacturing method and manufacturing conditions of the magnetic powder are different. As shown in Table 1, the coercive force and saturation magnetization will vary if the values are different. This means that if only a part of Fe is replaced with Co and Ti,
This shows that the control of coercive force is still insufficient.

(Means for Solving the Problems) As a result of intensive study to develop a magnetic powder for perpendicular magnetic recording that does not have these conventional drawbacks, the inventors of the present invention discovered that in addition to the conventional Co and Ti, more specific They discovered that adding metal was effective and completed the present invention.

That is, according to the present invention, the general compositional formula % (where MI represents at least one metal element selected from Ba, Sr, Ca and Pb, and MI[ is Mo,
Represents at least one metal element selected from W, Ru, Rh, Pd and Re, a, b, c, d, e and f
are Fe and Co, respectively.

Ti, Ml, MI [and the number of atoms of O, a is 8 to 1
1.8. b is 0.05 to 2.0. c is 0.05-2
．． 0°d takes a value of 0.5 to 3.0, e takes a value of 0.01 to 2.0, and f represents the number of oxygen atoms satisfying the valences of other elements. ), and the average particle diameter o, oi ~
A magnetic recording magnetic powder characterized in that the particle size is 0.3 μm is provided.

In the present invention, the number of atoms of each component element of the magnetic powder a ”
It is necessary that -e falls within the above numerical range; outside this range, it is difficult to obtain magnetic powder with coercive force and saturation magnetization suitable for magnetic recording magnetic powder.

The preferable ratio of each component of the magnetic powder is a: 8 to 11.8°5
takes a value of 0.1 to 1.5, c takes a value of 0.1 to 1.5, d takes a value of 0.8 to 2.0, and e takes a value of 0.02 to 1.0,
f is the number of oxygen atoms satisfying the valences of other elements.

The magnetic powder of the present invention may contain particles whose crystals do not have a normal hexagonal plate shape depending on the manufacturing method or manufacturing conditions. Within this range, the object of the present invention can be fully achieved.

According to the magnetic powder of the present invention, even if the manufacturing method and manufacturing conditions are different, it has the coercive force and saturation magnetization required for magnetic recording magnetic powder. This means that the magnetic powder according to the present invention is different from conventional Co and T magnetic powders.
This is thought to be due to the fact that it has a completely different function from the magnetic powder containing i.

The magnetic powder according to the present invention can be prepared by various methods known in this field, such as glass crystallization method, coprecipitation method, flux method,
It can be produced by a hydrothermal synthesis method or the like. Raw materials for each element used include oxides, ammonium salts, nitrates, carbonates, organic acid salts, salts such as halides,
Examples include free acids, acid anhydrides, and condensed acids.

The magnetic powder according to the present invention is a plate-like particle having an axis of easy magnetization in the orthogonal C-plane, and is suitable as a magnetic material for perpendicular magnetic recording.

Among the magnetic powders according to the present invention, especially those with a coercive force of 300 to 200
00e and a saturation magnetization of 40 emu/g or more will be awarded.

The present invention will be explained in more detail with reference to Examples below. The coercive force and saturation magnetization in the examples were determined by filling a glass test tube with an inner diameter of 5 N and a length of 5 cm with the obtained magnetic powder, using a DC magnetization characteristic measuring machine, and measuring the maximum applied magnetic field of 3500.
I went with 0e. The average particle diameter was calculated by measuring the maximum diameter of 400 particles from a photograph taken with a transmission electron microscope and calculating the arithmetic average. X-ray diffraction was performed on the examples listed here, and in all cases the crystal phase of the magnetic powder was macrogonal ferrite having a magnetoblanbite structure.

Further, the experimental formula for magnetic powder shown in the examples uses the atomic ratio of each metal at the time of raw material preparation. The display of oxygen in the magnetic powder components has been omitted for the sake of brevity.

Example 1 Ba(l z '2H200, 55 mol, TiC1,
0,375 mol, CoCJ 2 ・6HzO0,375
mol, Rh(NO3)30,075 mol and I'eCi
5.25 moles of 2a' 6HzO were dissolved in 101 distilled water in this order, and this was used as liquid A. NaOH17,5
mol and 4.72 mol of NazCOz were dissolved in distilled water at room temperature of 151, and this was used as liquid B. After gradually adding Solution B to Solution A heated to 50°C, the mixture was stirred at 50°C for 16 hours.

The pi after stirring was 10.35. The coprecipitate thus obtained was separated, washed thoroughly with water, dried at 150°C, and dried at 90°C.
It was fired in an electric furnace at 0'C for 2 hours. The Ba-ferrite thus obtained contains Ba+, IFe+++, 5Co
o, , 5Tio, ysR) lo, +s.

This fine particle powder has a plate shape with an average particle size of 0.08 μm,
The coercive force was 7650e, and the saturation magnetization was 56 emu/g.

Comparative Example 1 Ba-ferrite was produced in exactly the same manner as in Example 1 except that rhodium nitrate was removed. The obtained Ba-ferrite is Ba, lFe10.5Coo, 7sTio, 7
5. This fine particle powder has an average particle size o of 25 μm.
It is plate-shaped, Hc is 4440e, a3 is 35emu/
It was g.

Example 2 Ba(J z ・2HzO0.55 mol, TiCff1
n 0.375 mol, CoCjl! 2' 6Hz0
0.375 Mo) Ii, Rh (NO3) yo, 0
75 mol and FeCl! 25 moles of z.68zO5,' were dissolved in 10f of distilled water in this order, and this was used as liquid A. NaOHI 7.5 mol and NazCO34,7
2 mol was dissolved in 15A distilled water, and this was used as liquid B.

Add liquid A and liquid B heated to 50℃ to the autoclave 3.
After stirring at 00° C. for 4 hours, it was cooled to room temperature.

The pH at this time was 10.44. The thus obtained precipitate was thoroughly washed with water, dried at 150°C, and heat-treated in an electric furnace at 750°C for 8 hours.

The Ba-ferrite thus obtained has Ba 1. +F e +o, sCOo, 75T
It is indicated by lo, tsRho, +s.

This fine particle powder has an average particle size of 0.10. It was plate-like with czm, Hc was 7800e, and σS was 54 emu/g. From this result, it can be seen that magnetic powder having almost the same magnetic properties can be obtained whether the hydrothermal synthesis method of this example is used or the coprecipitation method of Example 1 is used.

Comparative Example 2 Ba-ferrite was produced in exactly the same manner as in Example 2, except that rhodium nitrate was removed. The obtained Ba-ferrite has the following properties: Bad, +Fe+ o, 5Coo, ? 5r
It is denoted by iO,ff5. The average particle size of this fine particle powder is plate-like with 0.33 μm, Hc is 2250e,
σS was 21 emu/g.

Example 3 Same as Example 1 except that NaOH in liquid B was 25.0 mol.
Ba-ferrite was produced in exactly the same manner.

This fine particle powder was plate-shaped with an average particle size of 0.10 μm, Hc was 7540e, and σS was 55 emu/g.

Comparative Example 3 Comparative Example 1 except that NaOH in liquid B was 25.0 mol.
Ba-ferrite was produced in exactly the same manner.

This fine particle powder had a plate shape with an average particle size of 0.13 μm, Hc of 9200e, and σS of 23 emu/g.

From the results of Examples 1 to 3, it can be seen that the magnetic powder according to the present invention has almost the same performance even if the manufacturing conditions are different.

Examples 4-18 M1 component M! [Example 1 except that the components and composition ratio were changed
Magnetic powders shown in Table 2 were prepared in the same manner as above. Note that chloride was used as the raw material for the Ml component, oxides were used for MO and W, and chlorides were used for the others. However, MoO and WO were dissolved in the B solution.

Claims (1)

[Claims] 1. Represented by the following general compositional formula, and having an average particle size of 0.0
Magnetic powder for magnetic recording Fe_aCo_bTi_cM^I_dM^II_eO_, characterized by having a particle size of 1 to 0.3 μm
f (here, M^I represents at least one metal element selected from Ba, Sr, Ca, and Pb, and M^II represents at least one metal element selected from Mo, W, Ru, Rh, Pd, and Re) Represents an element, a, b, c, d, e
and f are Fe, Co, Ti, M^I, M^II respectively
and the number of atoms of O, a is 8 to 11.8, b is 0.0
5-2.0, c is 0.05-2.0, d is 0.5-3.
0 and e take values of 0.01 to 2.0, and f is the number of oxygen atoms that satisfies the valences of other elements. ). 2, a is 8-11.8, b is 0.1-1.5, c is 0.
1-1.5, d is 0.8-2.0 and e is 0.02-1
．． The magnetic powder for magnetic recording according to claim 1, wherein the value is 0, and f is the number of oxygen atoms satisfying the valences of other elements. 3. Coercive force is 300-2000 Oe and saturation magnetization is 4.
The magnetic powder for magnetic recording according to claim 1, wherein the magnetic powder has a particle diameter of 0 emu/g or more.