JPH06333725A - High-density ferrite - Google Patents

Abstract

PURPOSE:To provide a high-density Mn-Zn ferrite suitable for magnetic heads containing lots of Fe2O3, which does not deteriorate in permeability and coercive force during machining, heat treatments or operation in the form of a magnetic head. CONSTITUTION:A high-density ferrite contains 62-68mol.% Fe2O3, 16-28mol.% MnO, 10-16mol.% Cod, and an additive including any of CaO, SiO2, ZrO2 and CoO. The ferrite has a temperature coefficient of permeability in which the second peak falls between 10 and 30 deg.C. As a result, it is possible to prevent the deterioration of initial permeability and coercive force at high frequency due to residual stresses and ambient temperature. This high-density ferrite has a high saturation flux density and a stable, high initial permeability in a high frequency region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density ferrite material used for a magnetic head, and more particularly to a magnetic head used for reading and writing information from a high recording density magnetic recording medium having a high coercive force such as a metal disk. And suitable Mn-Zn ferrite material with high magnetic flux density and high magnetic permeability.

[0002]

2. Description of the Related Art Ferrite materials have been widely used in electric equipment and electronic equipment parts, and are extremely popular electronic materials. Recently, FDD (floppy disk drive), RDD (fixed disk drive), VTR
It is widely used as a magnetic head material used in (video tape recorders), etc., and its mainstream material is high density Mn-Z.
It is an n-ferrite material.

Further, in recent years, in order to improve the recording density on a magnetic recording medium, as a material used for the recording medium, a metal-based material having a higher coercive force is often used instead of the iron oxide-based material. However, in a conventional magnetic head using a high-density Mn-Zn ferrite material containing 50 to 55 mol% of Fe2 O3, the saturation magnetic flux density is low, so that the material of the magnetic head used for reading and writing information from and to the metal-based magnetic medium. There was a difficulty that could not be used for. In order to improve the saturation magnetic flux density, it is possible to use a high-density Mn-Zn ferrite containing 60% or more of Fe2 O3 and having a high saturation magnetic flux density as a head material. But such F
Since the high density Mn-Zn ferrite containing a large amount of e2 O3 has a larger magnetostriction than the high density Mn-Zn ferrite of the conventional composition, the initial magnetic permeability and the initial permeability and There is a problem that coercive force and the like are greatly deteriorated. Also, when reading and writing to the medium as a magnetic head, the initial magnetic permeability of the ferrite changes due to the change in the operating temperature,
There is a problem that causes fluctuations in output.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and an object thereof is Fe2 O3.
In a high density Mn-Zn ferrite containing a large amount of, especially, deterioration of initial magnetic permeability and coercive force due to machining and heat treatment of the magnetic head is reduced, and initial magnetic permeability due to temperature change when operating as a magnetic head. It is to obtain a high-density ferrite which can suppress the change and can be favorably used as a magnetic head.

[0005]

In order to achieve the above-mentioned object of the present invention, the present invention has a molar ratio of 62 as a main component.
~ 68% Fe2 O3, 16-28% MnO and 10
-16% ZnO, with CaO and Si as secondary components
The present invention provides a high-density ferrite containing at least one of O2, ZrO2 and CoO, in which the second maximum value in the temperature characteristic of the initial permeability is 10 to 30 ° C.

In the present invention, the main component is 6 in molar ratio.
In a ferrite containing a large amount of Fe2 O3, which is composed of 2 to 68% Fe2 O3, 16 to 28% MnO, and 10 to 16% ZnO, the magnetic properties such as the initial magnetic permeability and the coercive force are different from those of the initial magnetic permeability. Before and after the temperature (hereinafter referred to as SMP) showing the second maximum value in the temperature characteristic, the S.P. M. P. It was found that the magnetic properties in the higher temperature range are better than those in the lower temperature range, and from this viewpoint, deterioration of initial permeability and coercive force due to residual stress and operating environment temperature is suppressed, and high saturation magnetic flux is achieved. A material having a high density and a high initial permeability at high frequencies can be provided.

The main component of the ferrite material used in the present invention is 62 to 68% of Fe 2 O 3 and MnO 16 to 2 in molar ratio.
8% and ZnO 10-16%, which gives 5
A fired body having a high saturation magnetic flux density of 800 G or more can be obtained. The reason why the main component of the ferrite material is set to the above range is that the saturation magnetic flux density is decreased and the coercive force is increased in a range other than this range, and it is not practical as a magnetic head material for a medium having a high coercive force. In addition to these main components, at least one of CaO, SiO2, ZrO2 and CoO is added as a subcomponent. Of these Ca
O, SiO2, and ZrO2 have the effect of increasing the resistivity of the fired body, and CoO has an anisotropic constant K depending on the amount of Fe2 O3.
It has the effect of adjusting 1, and both can improve the initial permeability at high frequencies.

Further, when a ferrite material containing a large amount of Fe2 O3 is fired, the reducing agent such as an organic binder can be added to the ferrite agent, if necessary, because the amount of oxygen released due to the spinelization reaction is large. .

The ferrite material thus obtained is
After molding, it is fired. The firing needs to be performed under the conditions such that hematite does not remain due to the release of oxygen, the number of pores is small, and a fired body with few crystal grain growth is obtained. For this reason, it is preferable to perform the firing at a temperature of 1150 to 1250 ° C. in an inert gas atmosphere with controlled oxygen concentration. After that, the fired body is subjected to hot isostatic pressing treatment (hereinafter referred to as HIP treatment). The conditions of HIP treatment are not particularly limited, but in order to increase the density while suppressing the growth of crystals, the HIP treatment is performed at a temperature lower than 30 to 100 ° C. and a pressure of 500 to 1500 kg / cm 2. Is preferred. HIP treated high density ferrite is HI
Annealing is performed to remove the residual stress due to P treatment. The condition of the annealing treatment is not particularly limited as long as the residual stress is removed, but in order to prevent the regeneration of pores inside the ferrite or the deterioration due to the oxidation of the surface portion,
700 to 10 in an inert gas atmosphere with controlled oxygen concentration
It is preferably carried out in the range of 00 ° C.

The S.D. of the initial permeability of the high density ferrite in the present invention is as follows. M. P. Is adjusted to be at 10-30 ° C. S. M. P. Is set in the above range depending on the temperature at which this high density ferrite is used. That is,
This high-density ferrite is used as a magnetic head core, and the temperature range for reading / writing from / to the medium usually changes within the range of 30 to 80 ° C. due to the heat generation of the core and the environmental temperature of the device. Therefore, in order to allow the initial permeability and the coercive force to be used without deterioration in such a temperature range, the S. M. P. Is set lower than this temperature range. Here, if S. M. P. If the setting is 30 ° C. or higher, the magnetic head read / write is S. M.
P. Since it is used in both temperature ranges of higher and lower temperatures, S. M. P. In the operating temperature range on the lower temperature side, deterioration such as initial permeability occurs and normal reading and writing cannot be performed. Also, S. M. P. If the setting is 10 ° C or less, the initial permeability and the like will not deteriorate in the operating temperature range, but the operating temperature will be S.I. M. P. Since it is too high, the magnetic anisotropy K1 becomes large, leading to a decrease in initial permeability and an increase in coercive force.

In the ferrite containing a large amount of Fe2 O3, the operating temperature is S. M. P. It is not clear why the higher one has a higher initial permeability and a smaller coercive force at high frequencies than the lower one. M. P. Starting from, the easy axis of magnetization is in the <111> direction on the low temperature side and <100> on the high temperature side.
Magnetostriction that acts on each direction when changing
111 | and | λ100 | are about 3 × 10 -5 and 5 × 10 -6 (at room temperature), respectively, and the latter is smaller,
When the <100> direction is the easy axis of magnetization, that is, the operating temperature is S.I. M. P. It seems that the higher the magnetic properties, the better. Further, when these ferrites are used in a magnetic head, the magnetic properties are deteriorated due to residual stress caused by machining and heat treatment. M. P. In the high-density ferrite set higher, the magnetostriction is small for the above reason, and it is considered to be small.

The high density ferrite S.
M. P. The adjusting method is not particularly limited, but depending on the composition of the ferrite material used, the firing temperature and firing atmosphere are controlled, the annealing temperature and annealing atmosphere are controlled, or the amount of CoO added is changed. For example, it can be arbitrarily selected within each allowable range.

[0013]

As described above, in the high-density ferrite Mn-Zn ferrite containing a large amount of Fe2 O3, the S. M.
P. By adjusting the temperature to 10 to 30 ° C., when used as a magnetic head core, deterioration of initial magnetic permeability, coercive force, etc. due to residual stress at the time of magnetic head processing or operating temperature can be suppressed, resulting in high saturation magnetic flux density. It is possible to provide a material having a high initial magnetic permeability at high frequencies.

[0014]

EXAMPLES Examples of the present invention will be described below. Fe2 O3, MnO and ZnO were selected as the main components in the composition range shown in the diagram of FIG. 1, which were mixed by a ball mill and calcined in a nitrogen atmosphere at 900 ° C. for 5 hours. CaO, SiO2, ZrO2 and CoO were added as auxiliary components in the ranges shown in the diagram of FIG. 1 and pulverized with a ball mill. Polyvinyl alcohol as a reducing agent was added to the ferrite raw material powder in an amount of 0.3 wt% to form a block of 50 × 10 × 8 mm. Then, the temperature of this molded body is raised in a nitrogen atmosphere, and the temperature is 1150 to 1250 ° C. in an atmosphere containing oxygen.
It baked in the range of 6 hours. This fired body was subjected to HIP treatment in an argon atmosphere at 1070 to 1170 ° C. and 1000 kg / cm 2 for 3 hours, and further oxygen was added to 5 to 10
6 in the range of 700 to 1000 ° C in an atmosphere containing 0 ppm
Annealing was performed for a time, and a ring of 5 mmφ in outer diameter, 3 mmφ in inner diameter, and 0.5 mmt in thickness was processed from each high-density ferrite block, and the saturation magnetic flux density Bs and coercive force Hc at 100e were processed.
, S. M. P. , 8 at 30 ° C and 50 ° C
The initial permeability μi was measured by MHZ. The results are shown in the diagram of FIG.

Further, Examples 1 to 4 shown in the diagram of FIG.
3 and 4 show the frequency characteristics of the initial magnetic permeability at 30 ° C. and 50 ° C. for the high-density ferrites of Example 1 and Comparative Example 1 of Comparative Examples 1 to 6, respectively.

As is clear from the above results, the high density ferrites of Examples 1 to 4 of the present invention show almost constant values without deterioration of initial permeability due to temperature change. In contrast, S. M. P. However, in the high-density ferrites of Comparative Examples 1 to 3 which are out of the range of the present invention, the initial magnetic permeability decreases and fluctuates significantly due to an increase in coercive force and a temperature change. Further, in the high-density ferrites of Comparative Examples 4 and 5 in which the composition of the main component is outside the range of the present invention and Comparative Example 6 containing no subcomponent of the present invention, S. M. P. Even if is in the range of 10 to 30 ° C., the initial magnetic permeability itself is low.

The ferrite material according to the present invention has a core in which the air gap at the tip faces the magnetic medium, and the effect is particularly remarkable when used in a magnetic head in which a coil is wound around the core. is there.

[0018]

As described in detail above, in the high density ferrite according to the present invention, the main components are 62 to 68% Fe2 O3, 16 to 28% MnO and 10 to 16% by molar ratio. Of ZnO and CaO as an accessory component,
It contains at least one of SiO2, ZrO2 and CoO, and has a second maximum value (S.
M. P. Is present at 10 to 30 ° C., deterioration of initial permeability and coercive force at high frequencies due to residual stress and operating environment temperature can be suppressed, and the saturation magnetic flux density is high and stable at high frequencies. A ferrite material having a high initial magnetic permeability can be obtained.

[Brief description of drawings]

FIG. 1 is a diagrammatic chart comparing the components contained in an example of the present invention and a comparative example.

FIG. 2 is a chart showing the types and addition amounts of reducing agents.

FIG. 3 is a characteristic diagram showing characteristics of an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing characteristics of a comparative example.

Claims (2)

[Claims] 1. A main component of which the molar ratio is 62 to 68% Fe.
2 O3, 16-28% MnO and 10-16% Zn
O, with CaO, SiO2, ZrO2 as subcomponents
A high-density ferrite containing at least one of CoO and CoO, wherein the second maximum value in the temperature characteristic of the initial magnetic permeability is 10 to 30 ° C. 2. A magnetic head having a core having a gap at the tip facing a magnetic medium, and a coil wound around the core, wherein the core has a molar ratio of 62 to 68% F.
e2 O3, 16-28% MnO and 10-16% Z
nO, with CaO, SiO2 and ZrO as subcomponents
2. A high-density ferrite magnetic head comprising a high-density ferrite containing at least one of 2 and CoO and having a second maximum value in the temperature characteristic of the initial magnetic permeability of 10 to 30 ° C.