JP2521922B2 - Magnetic head - Google Patents

Description

The present invention relates to a magnetic head suitable for recording / reproducing on / from a high coercive force magnetic / magnetic recording medium such as a so-called metal tape. The present invention relates to a magnetic head composed of a composite magnetic material of an oxide magnetic material and a magnetic alloy thin film.

[Outline of Invention]

The present invention provides a composite magnetic head comprising a magnetic core composed of an oxide magnetic material and a magnetic alloy thin film, wherein the oxide magnetic material has an absolute value (| λs |) of magnetostriction constant (λs) of 1 ×. By using a polycrystalline material of 10 ⁻⁶ or less, sliding noise during reproduction is significantly reduced, and an excellent reproduced image is obtained.

[Conventional technology]

In recent years, with the demand for miniaturization of devices such as video tape recorders, recording for a long time, and the advent of so-called digital video tape recorders, high-density recording and short-wavelength recording have been advanced, and in response to this, high resistance Magnetic force magnetic recording media have come into use.

Along with this, there is an increasing demand for improvement in performance of magnetic heads. Under such circumstances, a composite magnetic material composed of an oxide magnetic material (such as ferrite) and a magnetic alloy thin film (such as Fe-Al-Si alloy) is used as the magnetic core material, and the abutting portion between the magnetic alloy thin films is used as an operating gap. It is well known that a so-called composite type magnetic head has been proposed and put into practical use.

That is, in the composite magnetic head, the vicinity of the working gap is made of Fe--Al--Si alloy which is a high saturation magnetic flux density material, and most of the other is made of ferrite which is a high magnetic permeability material. . Therefore, at the time of recording, the entire magnetic head exhibits characteristics equivalent to those of a material having a high magnetic permeability, and sufficient recording can be performed even on a high coercive force magnetic recording medium. Since the average magnetic permeability is high, the structure has good electromagnetic conversion characteristics.

[Problems to be solved by the invention]

However, as described above, the magnetic head using ferrite for the magnetic core has a problem that so-called sliding noise occurs during reproduction and a good reproduced image cannot be obtained.

The sliding noise strongly depends on the magnetostriction of the magnetic core material,
Elastic vibrations are transmitted from the recording medium to the head, and due to the vibrations, an inverse magnetostriction effect is generated to cause a change in magnetic flux, which is detected as a coil or noise.

Since a single crystal ferrite that has been frequently used as a core material has a large absolute value of its magnetostriction constant, reduction of the above-mentioned sliding noise is a major problem in a magnetic head using the ferrite. In particular, in the above-mentioned composite type magnetic head, the influence of the sliding noise is more remarkable due to the influence of the magnetic alloy thin film material, the bonding material, etc., and there is an urgent need to improve this.

Therefore, the present invention has been proposed in view of such circumstances, and it is an object of the present invention to provide a magnetic head that exhibits extremely small sliding noise during reproduction and exhibits excellent recording / reproducing characteristics for a high coercive force magnetic recording medium. To aim.

[Means for solving problems]

The inventors of the present invention have conducted extensive research over a long period of time as a result of achieving the above object, and as a result, by using a polycrystalline material having a magnetostriction constant within a predetermined range as an oxide magnetic material, the sliding noise is effectively eliminated. I found that I could do it.

The present invention has been completed based on such findings, and in a composite magnetic head including a magnetic core half body composed of an oxide magnetic material and a magnetic alloy thin film, the oxide magnetic material is made of a polycrystalline material. And its composition (Fe ₂ O
₃ mol%, ZnO mol%, MnO mol%) range is (54,4,4
2), (54,24,22), (51,24,25), and the absolute value (| λs |) of magnetostriction constant (λs) is less than 1 × 10 ^-6. It is what

[Action]

In the above-mentioned polycrystalline oxide magnetic material, the magnetostriction that appears to the outside is averaged for all the small crystal grains, so that it is apparently isotropic. The magnetostriction constant λs at this time is the magnetostriction constant λ ₁₀₀ of the single crystal oxide magnetic material in the (100) direction,
It can be expressed as the following equation using the magnetostriction constant λ ₁₁₁ in the (111) direction.

Here, neither λ ₁₀₀ nor λ ₁₁₁ is 0, and λ ₁₀₀ <0 (shrinks in the magnetization direction) and λ ₁₁₁ > 0 (stretches in the magnetization direction).

Therefore, the absolute value (| λs |) of the magnetostriction constant λs of the polycrystalline oxide magnetic material is always smaller than the absolute values of the magnetostriction constants | λs ₁₀₀ | and | λs ₁₁₁ | of the single crystal oxide magnetic material.

That is, it is advantageous to use a polycrystalline material as the oxide magnetic material of the composite magnetic head in terms of the magnetostriction constant λs. In particular, the composition whose absolute value | λs | is 1 × 10 ⁻⁶ or less is selected. By doing so, sliding noise is significantly reduced.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an example of a magnetic head to which the present invention is applied, and FIG. 2 is an enlarged plan view of an essential part showing a sliding surface of the magnetic recording medium.

In this magnetic head, the magnetic core half body (I),
The magnetic core parts (11) and (12), which occupy most of (II), are composed of an oxide magnetic material having a polycrystalline structure, and the joint surfaces of these magnetic core parts (11) and (12) are cut out obliquely. Inclined surface (11
a) and (12a) show high saturation magnetic flux density alloys such as Fe-Al from the front gap surface to the back gap surface.
Magnetic alloy thin films (13A) and (13B) made of —Si alloy are deposited and formed as magnetic core halves (I) and (II), respectively. Then, the pair of magnetic core halves (I) and (II) are butted against each other through a gap spacer such as SiO _{2 so} that the contact surfaces of the magnetic alloy thin films (13A) and (13B) have the track width T _W. It is configured to have a gap g. On the magnetic alloy thin films (13A) and (13B) and in the track width regulating grooves (11b) and (12b), a non-magnetic material (16A) such as high melting point glass is provided to ensure contact with the magnetic recording medium. , (16B), (17A), and (17B) are melt-filled. A winding hole (18) for winding a coil is formed in one of the magnetic core halves (I).

Here, in the present invention, a polycrystalline oxide magnetic material is used as the magnetic core portions (11) and (12).

As the above-mentioned polycrystalline oxide magnetic material, those usually used in this type of magnetic head may be used, but among them, Mn-Zn ferrite, Ni-Zn ferrite and the like are preferable. Further, as the above-mentioned polycrystalline oxide magnetic material, a so-called high-density polycrystalline structure having a small pinhole size and an extremely small number of pinholes is more preferable. That is, the pinhole is large (5-
A polycrystalline oxide magnetic material that is not high density (10 μm or more) may cause pinholes to become clogged with debris from the medium during sliding contact with the recording medium, causing spacing loss and medium damage, and contributing to noise. In addition, the head wear increases, which is not preferable. On the other hand, in the case of a high-density polycrystalline structure, even if there are pinholes, it is about 0.5 μm, sagging occurs on the surface during sliding contact with the medium, and there are no pinholes in appearance, and a stable head is obtained. The characteristics are obtained.

In any case, in the present invention, the absolute value | λs | of the magnetostriction constant λs of the polycrystalline oxide magnetic material is 1 ×.
Less than 10 ^-6 is used.

That is, when the above | λs | exceeds 1 × 10 ⁻⁶ , the magnetic flux changes due to elastic vibration in the magnetic core parts (11) and (12),
As a result, the sliding noise level increases and the initial purpose cannot be achieved.

In this way, the magnetostriction constant λ is applied to the magnetic core parts (11) and (12).
By using a polycrystalline oxide magnetic material having an absolute value of s | λs | of 1 × 10 ⁻⁶ or less, sliding noise generated during reproduction can be significantly reduced. Therefore, a magnetic head having excellent reproduction characteristics can be provided.

The magnetostriction constant λs of the polycrystalline oxide magnetic material is greatly influenced by the composition of the oxide magnetic material. Therefore, the inventors of the present invention have variously changed the composition of each component (Fe ₂ O ₃ , ZnO, MnO) in the polycrystalline Mn-Zn ferrite to change the magnetostriction constant λs.
Was measured and the composition range in which the absolute value | λs | was 1 × 10 ⁻⁶ or less was determined. As a result, a region shown by an inclination in FIG.
That is, (Fe ₂ O ₃ mol%, ZnO mol%, MnO mol%) is the majority of the area surrounded by three points (54,4,42), (54,24,22), (51,24,24). It was found that the absolute value | λs | of the magnetostriction constant λs of crystalline ferrite was 1 × 10 ⁻⁶ or less.

Next, the inventors of the present invention used Mn--Zn polycrystalline ferrite having the above composition range as the magnetic core portions (11) and (12) of the composite magnetic head shown in FIGS. A head was prepared and the sliding noise level was measured. For comparison, the sliding noise level was also measured for the magnetic heads prepared by using Mn-Zn single crystal ferrite in the magnetic head portions (11) and (12). The results are shown in FIG. 4 (this example) and FIG. 5 (comparative example), respectively.

The sliding noise level is, as a guideline, calculated from the noise level when the magnetic tape is slid (curve a in the figure).
The rest after subtracting the system noise level (curve b in the figure) was taken as the sliding noise level (curve c in the figure).

As is clear from FIGS. 4 and 5, it was found that by using a polycrystalline material as the oxide magnetic material forming the magnetic core, the sliding noise level during reproduction can be significantly reduced.

Furthermore, in a composite type magnetic head using Mn-Zn polycrystalline ferrite in the magnetic core portions (11) and (12), magnetic heads were prepared by varying the magnetostriction constant λs of the polycrystalline ferrite, and sliding The noise level was measured. Results are shown in FIG.

As shown in FIG. 6, the sliding noise has a correlation with the magnetostriction constant of the polycrystalline ferrite, and the magnetic noise using the polycrystalline ferrite with the magnetostriction constant λs of 1 × 10 ⁻⁶ or less has an extremely low sliding noise level. It was found that good reproduction characteristics were exhibited.

By the way, when a polycrystalline oxide magnetic material is used for the magnetic core, it is feared that a crystal grain agglomerate, that is, a so-called grain, may fall off during sliding contact with the medium. Since the oxide magnetic material of the structure does not exist and the magnetic alloy thin films (13A) and (13B) are arranged, there is no concern that the grains will fall off. Therefore,
The gap length of the operating gap g is stable for a long time, and a magnetic head having excellent reliability can be provided.

Furthermore, when a single crystal oxide magnetic material is used for the magnetic core portions (11) and (12), strain is accumulated due to the difference in thermal expansion coefficient between the magnetic alloy thin films (13A) and (13B), and Although it has been a serious problem in terms of the above or electromagnetic conversion characteristics, the use of an oxide magnetic material having a polycrystalline structure as described above has an advantage that the strain can be effectively dispersed. Therefore,
By using a polycrystalline oxide magnetic material for the magnetic core portions (11) and (12), electromagnetic conversion characteristics and yield are significantly improved.

Further, the oxide magnetic material having a polycrystalline structure can be manufactured at a cost of about 1/5 of that of a single crystal, and at the same time, the defect of platinum inclusion, which is a defect in the manufacturing method of a single crystal ferrite, is eliminated.
Therefore, the manufacturing cost can be significantly reduced, and at the same time, the substrate size can be increased, which is advantageous in terms of mass productivity.

Furthermore, since the present invention can be carried out without changing the conventional head structure or manufacturing process, it can be said that this practical value is extremely high.

In the above-mentioned embodiment, the magnetic alloy thin films (13A) and (13B) forming the working gap g are Fe-Al-Si based alloys. However, in addition to this, ferromagnetic amorphous alloys, A so-called ferromagnetic amorphous alloy (for example, an alloy composed of one or more elements of Fe, Ni, Co and one or more elements of P, C, B, Si, or Al, Ge, Be, Sn as the main component) , In, Mo, W, Ti, Mn, Cr, Zr, H
Metal-metalloid type amorphous alloys such as alloys containing f, Nb, etc., or metal-metal type alpha-moss alloys containing transition metals such as Co, Hf, Zr and rare earth elements as main components), Fe-Al alloys, Fe It may be a -Si alloy, Fe-Si-Co alloy, Ni-Fe alloy, Fe-Ga-Si alloy, or the like. Examples of the film forming method include vacuum thin film forming techniques such as a sputtering method, a vacuum evaporation method, a flash evaporation method, an ion plating method, and a cluster ion beam method. In addition, the magnetic alloy thin film (13A),
Although (13B) has a single layer structure in this example, for example, SiO ₂
A plurality of layers may be formed through a highly wear-resistant insulating film such as Ta ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ and Si ₃ N ₄ . In this case, the number of laminated magnetic alloy thin films can be set arbitrarily.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment and can be applied to a composite type magnetic head having various structures without departing from the spirit of the present invention.

For example, as shown in FIG. 7, a track width restricting groove for restricting the track width (around the contact surface of the magnetic core portions (21) and (22) made of a polycrystalline oxide magnetic material ( 21a) and (22a) are cut out, and the magnetic alloy thin film (2) is formed on the contact surface including the inside of the track width regulating grooves (21a) and (22a).
3), (24) are formed, and these magnetic alloy thin films (23),
The magnetic head may be a magnetic head in which the parallel portions (21a) and (22a) of (24) are butted to each other to form an operating gap g. This magnetic head has a track width T _W of a magnetic metal thin film (23),
Since it can be increased regardless of the film thickness of (24), it is suitable for a wide track magnetic head.

〔The invention's effect〕

As is clear from the above description, in the present invention, in order to reduce sliding noise generated during reproduction, a polycrystalline oxide magnetic material having a magnetostriction constant in a predetermined range and a magnetic alloy thin film are used as the magnetic core material. Since the composite magnetic material is used, it is possible to provide a magnetic head exhibiting excellent recording and reproducing characteristics. Therefore, according to the magnetic head to which the present invention is applied, it is of course possible to obtain sufficient recording characteristics for a high coercive force magnetic recording medium compatible with high-density recording, and sliding noise is extremely low and excellent. A reproduced image is obtained.

Further, since the oxide magnetic material having the polycrystalline structure can effectively disperse the strain caused by the thermal strain or the thermal expansion coefficient, there is no fear that the magnetic core is cracked or the like in the process of manufacturing the head. Therefore, the magnetic characteristics of the oxide magnetic material and the magnetic alloy thin film are sufficiently exhibited, the head exhibits good electromagnetic conversion characteristics, and the yield is significantly improved.

Furthermore, the above-mentioned polycrystalline ferrite can be produced at a lower cost than the conventional single-crystal ferrite, so that the material cost can be reduced.

Further, according to the present invention, there is also an advantage that the sliding noise level can be reduced without changing the manufacturing process or the head structure.

These advantages greatly contribute to the demand for improving the performance of the magnetic head accompanying the recent remarkable progress of video tape recorders and the like, and it becomes possible to provide a magnetic head of high practical value.

[Brief description of drawings]

FIG. 1 is an external perspective view showing an example of a magnetic head to which the present invention is applied, and FIG. 2 is an enlarged plan view of an essential part showing a magnetic recording medium sliding contact surface of the magnetic head shown in FIG. FIG. 3 is a ternary composition diagram of Mn-Zn polycrystalline ferrite and shows the composition range in which the magnetostriction constant is 1 × 10 ⁻⁶ or less. FIG. 4 is a characteristic diagram showing a frequency characteristic of a sliding noise level of an embodiment (using polycrystalline ferrite) to which the present invention is applied,
Fig. 5 shows a conventional magnetic head (using single crystal ferrite)
The characteristic diagram which shows the frequency characteristic of the sliding noise level of is shown. FIG. 6 is a characteristic diagram showing the relationship between the magnetostriction constant of polycrystalline ferrite and sliding noise. FIG. 7 is an enlarged plan view of an essential part showing a magnetic recording medium sliding contact surface of another example of the structure of the magnetic head to which the present invention is applied. 11,12 …… Magnetic core (oxide magnetic material) 13A, 13B …… Magnetic alloy thin film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiyuki Kunigami 6-5-6 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Magne Products Co., Ltd. (72) Kiyoki Imano 6 Kita-Shinagawa, Shinagawa-ku, Tokyo 5-6, Sony Magne Products Co., Ltd. (56) References Japanese Patent Laid-Open No. 61-73210 (JP, A) Actual No. 61-118105 (JP, U)

Claims (1)

(57) [Claims] 1. A composite magnetic head comprising a magnetic core half body composed of an oxide magnetic material and a magnetic alloy thin film, wherein the oxide magnetic material is a polycrystalline material and has a composition (Fe ₂ O ₃ The range of (mol%, ZnO mol%, MnO mol%) is defined as the region surrounded by (54,4,42), (54,24,22), (51,24,25), and the magnetostriction constant (λs) Absolute value (| λs |) is 1
A magnetic head characterized by having a size of × 10 ^-6 or less.