JP2775740B2 - High frequency high permeability magnetic material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-frequency high-permeability magnetic material having excellent high-frequency characteristics used as a magnetic head material for a video tape recorder or a hard disk. It is about composition. (Summary of the Invention) The present invention is a high-frequency high-permeability magnetic material used as a magnetic head material, which has a basic composition of Fe ₂ O ₃ , ZnO, MnO, and a ferrite material mixed at a predetermined composition ratio, By adding a predetermined oxide material, it is intended to greatly improve various characteristics such as magnetic permeability in a high frequency band. [Prior art] Ferrite materials for magnetic heads used in video tape recorders, hard disk drives, and the like have good high-frequency characteristics, excellent workability, and good wear resistance in sliding with magnetic tape. Is required. Here, the present inventors have previously proposed that the workability can be improved favorably by adding a predetermined amount of ZrO ₂ to the basic ferrite composition. On the other hand, as a method for improving high-frequency characteristics, conventionally,
There is known a method of adding CaO or SiO ₂ (in general, both are often added simultaneously). However, the particular magnetic head used for recording and reproduction, such as a hard disk, more high frequency characteristics, that is, the high permeability of is required in the high frequency band, such as the CaO or SiO ₂ for improving the high frequency characteristics It is necessary to add a large amount of elements. However,
If the sintering temperature is increased for the purpose of increasing the density of the material when the high-frequency characteristic improving element is over-added, an abnormal sintering reaction occurs and the sintered structure has large and small crystals. , And these elements precipitate at the grain boundaries, causing deterioration of high-frequency characteristics and deterioration of material strength. That is,
There is a limit in improving the high frequency characteristics by adding the above-mentioned elements such as CaO or SiO ₂ , and there is naturally a limit in increasing the magnetic permeability in a high frequency band. [Problems to be Solved by the Invention] Even if a predetermined additive element is added to the basic composition of the ferrite material in order to achieve the high frequency characteristics and workability required for the ferrite material as described above, There is a limit to the effect of the improvement, and it is not sufficient to satisfy the desired high-frequency characteristics. Therefore, the present invention has been proposed in order to solve the above-mentioned problems, and the magnetic permeability in a high frequency band, including the magnetic permeability in a high frequency band, while maintaining good machining characteristics without deteriorating the coercive force. The purpose is to significantly improve various characteristics. The present invention [Means for Solving the Problems] In order to achieve the above object, Fe ₂ O _3: 50~
65 mol%, ZnO: 5 to 30 mol%, MnO: 10-40 mol% and a basic composition, ZrO _2: 0.01 to 0.2 wt%, CaO: with containing 0.01 to 0.5 wt%, further TiO ₂ 0.01 About 0.3% by weight. Here, the basic composition of the ferrite material used in the present invention, Fe ₂ O _3: 50~65 mol%, ZnO: 5 to 30 mol%, MnO: 10 to 40
It is generally called Mn-Zn ferrite consisting of mol%. The reason why the basic composition of the Mn-Zn ferrite is set within the range of the composition ratio described above is that the magnetic permeability becomes extremely small in other cases, and the saturation magnetic flux density decreases and the coercive force increases. This is because it lacks sex. Frequency high-permeability magnetic material of the present invention, in addition to the basic composition described above, first, the ZrO ₂ 0.01 to 0.2 wt%, the CaO .01-0.
The composition contains 5% by weight. By containing the above ZrO ₂ , a remarkable effect can be obtained in improving the magnetic loss characteristics of the ferrite material. The content of the ZrO ₂ is preferably 0.01 to 0.2 wt%. Z above
If the content of rO ₂ is less than 0.01% by weight, the workability cannot be sufficiently improved, and if the content of ZrO ₂ exceeds 0.2% by weight, the magnetic permeability decreases and the saturation magnetic flux density decreases. Also, magnetic loss such as increase in coercive force and the like is undesirably increased. On the other hand, a low magnetic loss can be obtained by adding CaO to the basic composition of the ferrite material. The CaO content is preferably 0.01 to 0.5% by weight. If the content of CaO is less than 0.01% by weight, the electric resistance becomes small, and the predetermined magnetic properties in a high frequency range cannot be obtained.
If the content exceeds 0.5% by weight, an abnormal structure is liable to occur, and magnetic loss such as a decrease in magnetic permeability, a decrease in saturation magnetic flux density and an increase in coercive force increases. Here, the addition of ZrO ₂ and CaO alone improves the high-frequency characteristics of the magnetic permeability to some extent. However, in the high-frequency high-permeability magnetic material of the present invention, 0.01 to 0.3% by weight of TiO ₂ is further added. The reason why TiO ₂ is added to the above composition is that more excellent magnetic properties can be obtained by addition of CaO than in the case of adding CaO alone. The amount of TiO ₂ added is 0.01
Preferably, the content is less than 3.0% by weight, and if less than 0.01% by weight, the effect of improving the magnetic properties cannot be expected. If it exceeds 0.3% by weight, the magnetic permeability decreases, the saturation magnetic flux density decreases, and the coercive force increases. This leads to deterioration of the magnetic characteristics. In order to form the high-frequency high-permeability magnetic material according to the present invention, a normal dry method is employed, and it is preferable to further perform hot isostatic pressing (hereinafter, referred to as HIP). The above HIP treatment is a press treatment performed after the primary sintering, and the method by this HIP treatment is to apply a high pressure by a gas pressure in a high-pressure gas atmosphere to the press-fired material from the surroundings, and from the isotropic It was intended to be pressed, hundreds
Since it is possible to apply a high pressure of about kg / cm ² to 10,000 kg / cm ^2, it is possible to produce an extremely high-density ferrite. The above HIP processing conditions are not particularly limited as long as they are ordinary conditions, but processing is preferably performed under the following conditions. That is, first, the ferrite material is first sintered at a predetermined sintering temperature T ₃ (1050 ° C. ≦ T ₃ ), and a ferrite sintered body produced by causing crystal grain growth to a density of 90% or more is subjected to HIP processing. Prepare for. Here, the sintering temperature T ₃ is 1050
When the temperature is lower than ℃, the equilibrium oxygen pressure of the ferrite cannot be realistically set, so that the material tends to be oxidized and hematite may precipitate. Furthermore, since the temperature at which the ferrite reaction (spinelization) is completed is 1050 to 1100 ° C., even if a final product is formed, the spinelization is insufficient, and there is a possibility that predetermined magnetic properties cannot be obtained. In order to make the growth of grains (crystal particles) sufficient, it is preferable to set the sintering temperature T ₃ to 1250 ° C. or higher. However, when the grain growth is suppressed to 15 μm or less and the workability is to be improved, is the sintering temperature T ₃ is preferably suppressed to 1250 ° C. or less. In the primary sintering, it is necessary to appropriately select the oxygen partial pressure of the atmosphere at the time of sintering. If the oxygen partial pressure is too high, α-Fe ₂ O ₃ will precipitate during sintering, and if the oxygen partial pressure is too low and the amount of oxygen in the sintered ferrite body is small, In the HIP processing step, cracks easily occur in the ferrite. Therefore, the equilibrium oxygen pressure is usually set according to the ferrite composition and the sintering temperature. In particular, (may be a inert gas atmosphere is not limited to nitrogen.) Given nitrogen atmosphere while cooled during and after the sintering completion Atsushi Nobori to reach a sintering temperature T ₃ and then, at the sintering temperature T ₃ by setting the equilibrium oxygen pressure concentration degree corresponding to the temperature T ₃ only at the time of firing, little precipitation of wustite layer and hematite layer, a very good sintering state. Ferrite sintered body obtained by the primary sintering described above,
If necessary, after the surface is wrapped with ferrite powder (or embedded in ferrite powder), HIP processing is performed to increase the density. HIP treatment is one in which was to apply from the surrounding high pressure due to the gas pressure in a high-pressure gas atmosphere to the pressing pressure sintering was lower than the sintering temperature T ₁ of the said ferrite powder the HIP process, and the Performed at a temperature T ₂ lower than the primary sintering temperature T _{3 at} which grain growth does not substantially occur (however, 1000 ° C ≤ T ₂ ≤ 1250 ° C) to further increase the density of the ferrite sintered body while keeping the fine crystal grain size Preferably, the density is set to 99% or more. Temperature T ₂ during the HIP process is actually a _{1000 ℃ ≦ T 2 ≦ 1250 ℃} , the relationship between the sintering temperature T _3, it is preferable that T ₃ ≦ T ₃ -100 ℃. That is, by lowering the temperature T ₂ below 1250 ° C.
Without causing grain growth substantially it can be of a predetermined density by the press while maintaining the grain size by sintering at a temperature T _3. Temperature T ₂ during HIP processing
If the temperature exceeds 1250 ° C., the ferrite sintered body and the ferrite powder cause a solid-phase reaction, and the two are sintered to be difficult to remove after the treatment. Further, by making the temperature T ₂ lower than the temperature T ₃ by 50 ° C. or more, it is possible to completely suppress the growth of crystal grains, and thus to completely prevent the accumulation of strain due to the crystal grain growth,
There is no need to perform annealing after processing. However, when the primary sintering temperature T ₃ is to be suppressed to 1250 ° C. or less and the grain growth is to be suppressed to 15 μm or less, the temperature T ₂ at the time of the HIP treatment is 1000 ° C. ≦ T ₂ ≦ 1200 ° C., T ₂ ≦ T ₃ −50 ° C. is preferred. Further, the pressure during the HIP processing is desirably 300 atm or more. When the pressure is 300 atm or more, the density can be increased until the density of the ferrite sintered body becomes 99% or more. In this case, there is a certain relationship between the pressure and the time at the time of pressing.
Atmospheric pressure may be 4 hours, and 2,000 atm may be 30 minutes. In performing the above HIP treatment, since the density of the ferrite sintered body is set to 90% or more (the ratio of the measured density corresponding to the X-ray density or the theoretical density) by the primary sintering, pores are present. The ferrite sintered body is almost closed, so that even if it is directly put into a high-pressure gas, the atmospheric gas does not penetrate from the surface, and it is vacuum sealed in a platinum, nickel or glass container as before. It can be placed directly in a high-pressure vessel for HIP processing without performing. [Function] By adding ZrO ₂ to a ferrite material for a magnetic head, workability is improved and grain boundary strength is improved. In addition, CaO was added to this ferrite material, and TiO ₂
By adding, magnetic properties, particularly high frequency properties, are improved while maintaining workability, material strength, and low coercive force. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. ZrO ₂ and CaO were added to a ferrite raw material powder composed of 53 mol% of Fe ₂ O ₃ , 16 mol% of ZnO, and 31 mol% of MnO in the range shown in Table 1, and TiO ₂ was added as a third additive element. Was added in the range shown in Table 1 and ordinary wet mixing was performed, followed by molding. Then, in consideration of the equilibrium oxygen pressure, the molded body was subjected to primary sintering for ferrite formation in a nitrogen gas atmosphere containing oxygen at 1250 ° C. for 4 hours. Then, 1200 ℃, 1000kg / cm ²
HIP treatment was performed at a pressure of 3 hours in an argon gas atmosphere to produce a desired ferrite material. 10φ for the ferrite material formed as described above
After processing into a toroidal shape of × 6φ × 1 mm, the effective magnetic permeability μ ′, saturation magnetic flux density Bs, coercive force Hc, and workability were measured. Table 2 shows the results. As is apparent from Table 2 above, even when ZrO ₂ and CaO were only added to the ferrite material composed of the basic composition, 5 MHz
Although the effective magnetic permeability at z exceeds 700, the coercive force shows a high value exceeding 900 by adding a little TiO ₂ . Here, it shows the relationship of the addition amount of TiO ₂ and the effective magnetic permeability mu 'in the case of adding TiO ₂ in Figure 1. In FIG. 1, the black circles indicate the relationship between the amount of TiO ₂ added and the effective magnetic permeability μ ′ at a frequency of 1 kHz. In FIG. 1, the symbol ▲ indicates the relationship between the amount of TiO ₂ added and the effective magnetic permeability μ ′ at a frequency of 1 MHz. In FIG. 1, the symbol ■ indicates the relationship between the amount of TiO ₂ added and the effective magnetic permeability μ ′ at a frequency of 5 MHz. As is clear from FIG. 1, the addition of a tetravalent element such as TiO ₂ in addition to ZrO ₂ and CaO achieves high permeability in a high frequency band. [Effects of the Invention] As is clear from the above description, in the high-frequency high-permeability magnetic material according to the present invention, ZrO ₂ which improves the processing characteristics to a basic composition comprising Fe ₂ O ₃ , ZnO, and MnO is used. And low loss material
Since it contains CaO and TiO ₂ which improves magnetic properties such as magnetic permeability in the high frequency band, it is possible to maintain the workability, material strength, etc. while maintaining the magnetic permeability in the high frequency band. Various magnetic properties can be greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a characteristic diagram showing the relationship between the amount of TiO ₂ added and the effective magnetic permeability μ ′.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01F 1/34

Claims (1)

(57) [Claims] Fe ₂ O _3: 50~65 mol%, ZnO: 5 to 30 mol%, MnO: 10 to 40
Mol% as a basic composition, ZrO ₂ : 0.01 to 0.2% by weight, CaO: 0.0
1 to 0.5% by weight, and TiO _{2 in an amount} of 0.01 to
A high-frequency high-permeability magnetic material characterized by containing 0.3% by weight.