JPH03108303A - Magnetic powder for high-density magnetic recording - Google Patents

Abstract

PURPOSE:To improve the temperature dependency of the saturation magnetization characteristic and coercive force of the title magnetic powder by adding specific quantities of ZnO and NiO to the powder of a magnetic ferrite of the hexagonal system. CONSTITUTION:The powder of a magnetic ferrite of the hexagonal system used for this magnetic powder contains ZnO and NiO by 1-7mol% and 5-25mol%, respectively. The average particle diameter and coercive force of this magnetic powder are selected within prescribed ranges and, at the same time, ZnO and NiO are added to the magnetic powder in addition to prescribed quantities of CoO and TiO2 added for substituting for the Fe2O3 component. When the magnetic powder is manufactured in such way, the powder can have and exert excellent diffusivity, coercive force, and saturation magnetization and the temperature characteristic is sharply improved for the coercive force.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to magnetic powder used in the production of high-density magnetic recording media, and in particular to hexagonal powder with improved temperature characteristics of coercive force. Regarding ferrite magnetic powder.

(Prior Art) Conventionally, as a method for manufacturing high-density magnetic recording media or perpendicular magnetic recording media, a magnetic paint is prepared by mixing fine powder of hexagonal ferrite with a binder, a solvent, and various additives. A method of applying this magnetic paint onto a support such as a film is known. By the way, in the above-mentioned single hexagonal ferrite, the coercive force He is large (this makes the magnetic head saturated during recording, making magnetic recording difficult, so some of the Pe atoms constituting the hexagonal ferrite are It is also known that by substituting atoms and TI atoms, the coercive force Ha can be reduced to a value suitable for magnetic recording.-
It is also known to add a small amount of tin oxide Sn02 to improve the increase in coercive force lie of hexagonal ferrite magnetic powder with temperature.

The above-mentioned hexagonal ferrite magnetic powder is generally manufactured in the following manner. In other words, the basic components of hexagonal ferrite, substitution components for reducing coercive force, additive components for improving ferrite characteristics, and gala-forming components are mixed (raw material mixture), heated and melted, and this melt is rapidly cooled. This is made into an amorphous body, which is heat-treated to precipitate hexagonal ferrite fine particles, which are then crushed and the resulting fine powder is treated with dilute acid such as phosphoric acid or acetic acid to form glass. A so-called glass crystallization method is often employed in which hexagonal ferrite is separated and extracted by dissolving and removing its components.

(Problem to be Solved by the Invention) By the way, from the viewpoint of magnetic recording properties, the average particle size of hexagonal ferrite magnetic powder such as Ba ferrite used in such high-density magnetic recording media is 0.0.
The thickness is about 2 to 0.2 μm, and the plate ratio is preferably about 5 to 1 O to obtain high orientation and saturation magnetization. However, some of the Fe atoms constituting the hexagonal ferrite are replaced with Co atoms and T1 atoms to reduce the coercive force He to a value suitable for magnetic recording, while adding a small amount of SnO2 Even if the characteristics are improved, at most 1.5 to 2.0
It has not yet been achieved that the level of construction is sufficiently satisfactory. Moreover, the addition of Sn02 causes a problem in that the particle size of the hexagonal ferrite magnetic powder becomes smaller, and as the particle size becomes smaller, the saturation magnetization decreases.

The present invention was made in response to these circumstances, and an object of the present invention is to provide a magnetic powder having a required average particle size and effectively improving the temperature dependence of coercive force lie.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides that a part of the Fez 03 component is Coo and TI.
o 2 and whose coercive force is adjusted to 200 to 2000 Oe and has an average particle size of 0.02 to 0.2 μm, the hexagonal ferrite magnetic powder contains 1 to 7101% of Z.
It is characterized by containing nO and 5 to 25 mo1% of NIO.

In the present invention, the base hexagonal ferrite magnetic powder has the general formula: AFeMO 12-x x 19 (wherein A is one or more elements selected from Ba%Sr and Pb, and M is In, Zn-Ge, Zn-Nb5 Zn-
VSCo-Ti, Co-Ge, 18 or more substitutional elements or a combination of elements, and X represents a positive number from 0 to 2.5, respectively. ), but is not limited thereto.

(Function) The magnetic powder according to the present invention has an average particle size and a coercive force within a predetermined range, and a predetermined amount of C.

While the O component and the TiO2 component are added to replace a part of the Fe201 component, ZnO and N10 are also added. Therefore, the magnetic powder according to the present invention maintains and exhibits good dispersibility, coercive force, and saturation magnetization suitable for high-density magnetic recording, and does not cause a decrease in saturation magnetization due to the addition of ZnO and N10. , the temperature characteristics of coercive force are significantly improved.

(Example) Next, an example in which the present invention is applied to a magnetoblanbite type Ba ferrite will be described.

First, the ferrite component Fθ203 of Ba ferrite,
The replacement component 102°CoO for reducing the coercive force, the glass forming components BaO and B203, and the ferrite property improving components ZnO, NIO, and SnO are contained in the composition ratio (m
o1%) BaO, Pe2031 TiO2
, CoO, B 203 , ZnO, NIO.

Each Sn02 was weighed.

Table 1 After thoroughly mixing these, the mixture is placed in a platinum crucible, heated and melted at a temperature of 1300°C or higher using a high-frequency induction heater, and then this melt is rapidly cooled by rolling on water-cooled high-speed twin rolls. An amorphous body was created.

Next, this amorphous body was heated to 800°C, and then heat-treated at that temperature, that is, 800°C, for 8 hours to precipitate Ba ferrite crystals in the glass matrix (BaO-820x).

Thereafter, this heat-treated product was pulverized using a dry pulverizer, and the resulting fine powder was treated with a 10% acetic acid solution to dissolve and remove the BaO.B2O3 phase of the glass-forming substance.

After this acid treatment, it was repeatedly washed with water, dehydrated, and dried in a hot air circulation dryer to obtain Ba ferrite magnetic powder. In addition, in the Ba ferrite magnetic powders (samples 1 to 3) according to the present invention obtained above, the contents of ZnO and NIO are as follows for sample 1 (Zn04゜77mol%, NIO
7,35 mol%), for sample 2 (Zn04゜61m
o1%, NIO13,2 mol%), in the case of sample 3 (Z
nO4°40mol%, N1020.3mol%).

Each Ba ferrite magnetic powder thus obtained was fine with an average particle size of 50 tv.

Table 2 also shows the results of measuring the coercive force 11c and saturation magnetization σg (esu/g) (at 1 OKOe) for these Ba ferrite magnetic powders.
Temperature dependence ΔIlc of coercive force lie at 5-40°C
...Temperature change... (Oe/"C) was measured using a VSM equipped with a precision temperature supply device. Table 3 shows the results.
Shown below.

Table 2 Table 3 In the present invention, in order to improve the temperature dependence of Ba ferrite magnetic powder, the amounts of added ZnO and prior O were selected and set within the numerical ranges mentioned above. This is because it is difficult to obtain the desired effect in any case outside the above numerical range.

[Effects of the Invention] As is clear from the above description, the magnetic powder according to the present invention has excellent saturation magnetization characteristics and temperature dependence of coercive force, and is suitable for manufacturing magnetic recording media. In other words, it has an appropriate particle size and good dispersibility, and not only can the packing density of the magnetic powder be increased in the recording medium, but also the saturation magnetization, which is related to the output among electromagnetic conversion characteristics, is Go (emu/g).
It is large as above, and the coercive force is 0 (Oc/”C)
Exhibits good temperature characteristics as below. Thus, the magnetic powder according to the present invention can be said to be suitable for producing magnetic powder for high-density magnetic recording media or perpendicular magnetization recording media.

Claims (1)

[Scope of Claims] A hexagonal ferrite magnetic powder in which a part of the Fe_2O_3 component is replaced with CoO and TiO_2, the coercive force is adjusted to 200 to 2000 Oe, and the average particle size is 0.02 to 0.2 μm, comprising: Crystalline ferrite magnetic powder contains 1 to 7 mol% Z
A magnetic powder for high-density magnetic recording, characterized in that it contains nO and 5 to 25 mol% of NiO.