JPH06251320A - Magnetic head - Google Patents

Abstract

PURPOSE:To prevent crack of a gap film of a laminate of a nonmagnetic metal film and a nonmagnetic oxide film by specifying the thickness of the nonmagnetic metal film and forming the nonmagnetic oxide film out of TaOX. CONSTITUTION:A pair of magnetic core halves 1, 2 are butted, and an erasing magnetic gap (g) is formed on the butted surfaces. The one half 1 is formed, for example, of an auxiliary core part made of an oxide magnetic material such as Mn-Zn ferrite, etc., and a winding groove 4 for the coil is formed in the butted surfaces of the core 3. The groove 4 is provided substantially in a U-shape through a core in the thickness direction, and the depth of the gap (g) is specified by its oblique surface 4a. The length of the gap (g) is made 1mum or more, and the gap film has a laminated film structure of a nonmagnetic oxide film 14 and a nonmagnetic metal film 15. The thickness of the film 15 is set to 0.01mum to 0.3mum. The x of TaOx of the film 15 is 1.0<x<=2.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head useful as a flying erase head mounted on, for example, a commercial video tape recorder.

[0002]

2. Description of the Related Art Conventionally, in a magnetic head in which magnetic cores are joined together by glass fusion bonding, S is used as a gap film (gap spacer) for forming a magnetic gap.
An iO ₂ film is often used. Si as a gap film
When the O ₂ film is used, it reacts with the fused glass or bubbles are generated, so that a laminated gap film structure in which a non-magnetic metal film such as Cr is arranged on the SiO ₂ film is performed. ing.

Of these, the optimum thickness of Cr has not been clearly defined in the past, and has been empirically set to a fraction of the gap length. At gap lengths of a few μm, it often exceeds 1 μm. Generally, a metal film has a large stress in the film, although it depends on the sputtering conditions. Then, the in-film stress increases as the film thickness increases. Further, the columnar structure of the film develops as the film thickness increases. For this reason, Cr with a thickness of over 1 μm
In the case of having a film, the Cr film and Si are perpendicular to the film surface.
Cracks easily occur on the O ₂ film. Further, as the track width becomes wider, the stress in the film increases, so that cracks are likely to occur in the gap film.

Such cracks progress due to heat treatment during glass welding, which is a head manufacturing process, and glass penetrates into the cracks to cause a gap abnormality. In particular,
In a metal-in-gap type magnetic head in which a magnetic metal film such as sendust is arranged near the gap, the electromagnetic conversion characteristics deteriorate due to corrosion of the metallic magnetic film by the fused glass penetrating from the cracks. You Further, magnetic powder and the like generated by sliding contact with the magnetic recording medium enter the crack portion to generate noise and the like, and the Cr film is less likely to wear than Sendust, SiO ₂ , or ferrite, and depending on the film thickness, the tape may run. The Cr portion projects into the inside, and the contact characteristics with respect to the tape deteriorate, and the characteristics as a head deteriorate due to spacing loss.

[0005]

As described above, when cracks occur in the gap film, the yield in head manufacturing is reduced, and the reliability as a magnetic head is greatly reduced. Therefore, the present invention has been proposed in view of such conventional circumstances, and prevents the occurrence of cracks in the gap film and suppresses the occurrence of spacing loss due to the protrusion of the Cr film, thus providing a magnetic head with high reliability and yield. The purpose is to provide.

[0006]

In order to achieve the above-mentioned object, according to the present invention, a pair of magnetic core halves project via a gap film formed by laminating a nonmagnetic oxide film and a nonmagnetic metal film. In a magnetic head having a closed magnetic circuit, the nonmagnetic metal film has a thickness of 0.01 μm or more and 0.3 μm.
Below, the non-magnetic oxide film is TaO _x (1.0 <x ≦
2.5).

[0007]

In the present invention, of the gap films formed by laminating a non-magnetic oxide film and a non-magnetic metal film, the thickness of the non-magnetic metal film is 0.01 μm or more and 0.3 μm or less. Therefore, the film internal stress of the non-magnetic metal film is reduced,
Moreover, since the columnar structure of the film does not develop, cracks do not occur in the gap film. Therefore, the corrosion of the metal magnetic film by the fused glass entering from the crack portion, the invasion of dust due to the sliding contact with the magnetic recording medium, and the occurrence of spacing loss due to abrasion are suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. This embodiment is an example of a flying erase head mounted on a commercial video tape recorder. In the magnetic head of this embodiment, as shown in FIGS. 1 and 2, a pair of magnetic core halves 1 and 2 are butted against each other, and an erasing magnetic gap g is formed on the butted surface. .

One magnetic core half 1 is, for example, Mn-Z.
The auxiliary core portion 3 is made of an oxide magnetic material such as n-type ferrite or Ni-Zn-type ferrite. A winding groove 4 for winding a coil is formed on the abutting surface of the auxiliary core portion 3. The winding groove 4 is provided as a groove having a substantially U-shaped cross section so as to penetrate therethrough in the core thickness direction, and the inclined surface 4a regulates the depth of the magnetic gap g.

Further, a glass groove 5 for ensuring the bonding strength of the magnetic core halves 1 and 2 is formed on the abutting surface of the magnetic core halves 1. The glass groove 5 is provided below the winding groove 4 as a groove having a substantially U-shaped cross section, and penetrates in the core thickness direction similarly to the winding groove 4. A winding auxiliary groove 6 is formed on the side surface opposite to the winding groove 4 for improving the winding state of the coil.

On the other hand, the other magnetic core half 2 is also M
An auxiliary core portion 7 made of an oxide magnetic material such as n-Zn ferrite or Ni-Zn ferrite, and a metal magnetic thin film 8 serving as a main core portion adhered to the abutting surface of the auxiliary core portion 7. It consists of

The auxiliary core portion 7 has track width regulating grooves 9 and 10 for regulating the track width Tw of the magnetic gap g on the abutting surface. This track width regulation groove 9,1
0 is notched from both end edges of the magnetic gap g as inclined surfaces having a predetermined inclination angle with respect to the magnetic gap g. Since the head of this embodiment is an erasing head for business use, its track width Tw is 100.
It is said to be μm or more. In addition, in the auxiliary core portion 7,
A winding auxiliary groove 13 having a substantially U-shaped cross section is provided on a side surface opposite to the track width regulating grooves 9 and 10 at a position facing the winding groove 4.

The metal magnetic thin film 8 has the auxiliary core portion 7
Is formed as a continuous film from the magnetic recording medium sliding surface 11 that comes into sliding contact with the magnetic recording medium along the abutting surface to the back surface 12. The metal magnetic thin film 8 used here is a film made of a ferromagnetic material having a high saturation magnetic flux density and excellent soft magnetic characteristics. As the ferromagnetic material, any conventionally known material can be used, and it does not matter whether it is crystalline or amorphous.

In this embodiment, the metal magnetic thin film 8 is a film formed by sputtering sendust having a thickness of 5.0 μm.

The pair of magnetic core halves 1 and 2 constructed as described above are butted against the gap films 14 and 15 formed on the metal magnetic thin film 8 of the other magnetic core half 2. A closed magnetic circuit is configured by being integrally joined by the fused glass 16. Fused glass 1
6 is filled not only in the winding groove 4 and the glass groove 5 but also in the track width regulating grooves 9 and 10. The fused glass 16 filled in the track width regulating grooves 9 and 10 plays a role of ensuring the contact characteristic with respect to the magnetic recording medium.

In particular, in this embodiment, since it is used as a magnetic head for erasing, the gap length of the magnetic gap g (total film thickness t of the gap films 14 and 15) is set to 1 μm or more, and the gap film 14 is used. , 15 are non-magnetic oxide films 1
4 and the non-magnetic metal film 15 are laminated. The non-magnetic metal film 15 includes the non-magnetic oxide film 14 and the fused glass 16
The non-magnetic oxide film 14 and the fused glass 16 are arranged so as not to come into contact with each other in order to prevent the reaction with the above or the generation of bubbles. That is, the nonmagnetic oxide film 14 and the nonmagnetic metal film 15 are formed in this order on the metal magnetic thin film 8.
The nonmagnetic oxide film 14 is protected from the fused glass 16 by the nonmagnetic metal film 15. The nonmagnetic oxide film 14 and the nonmagnetic metal film 15 are both formed by a vacuum thin film forming technique such as sputtering.

The nonmagnetic oxide film 14 and the nonmagnetic metal film 1
As the film 5, there is used a film which not only functions as a gap film but does not cause cracks in the gap film even if the track width is large. For example, a film made of TaO _x (1.0 <x ≦ 2.5) is used for the non-magnetic oxide film 14, and Cr, Ti, Zr, and
A film made of Nb or the like is used. If the thickness of the non-magnetic metal film 15 is too thick, a crack is generated from the non-magnetic metal film 15 to the non-magnetic oxide film 14 perpendicularly to the film surface due to the influence of internal stress of the film. Therefore, use a thin film as much as possible. For example, the film thickness is
Those having a thickness of 0.01 μm or more and 0.3 μm or less are preferable. More preferably, the film thickness is 0.03 μm or more,
It is 0.15 μm or less.

In this embodiment, the nonmagnetic oxide film 14 is used.
A film made of Ta ₂ O ₅ having a film thickness of 4.0 μm was used as the film, and a film made of Cr having a film thickness of 0.1 μm was used as the nonmagnetic metal film 15.

As described above, the thin nonmagnetic metal film 15 is used as the gap film, and the nonmagnetic oxide film 14 made of TaO _x is used as the underlayer, so that the inside of the nonmagnetic metal film 15 is formed. The stress is reduced, and the columnar structure of the film is suppressed from developing, so that the occurrence of cracks in the gap film is suppressed. Therefore, it is possible to prevent the gap abnormality from being caused by the fusion glass 16 entering the cracks, and there is no possibility that the metal magnetic thin film 8 is eroded by the fusion glass 16 entering from the cracks. Further, since the non-magnetic metal film 15 is thin, the non-magnetic metal film 15 does not jump out and project due to wear of the sliding surface 11 of the magnetic recording medium, and spacing loss can be suppressed.

As described above, TaO is added to the nonmagnetic oxide film 14.
It is based on the following experimental results that the occurrence of cracks in the gap films 14 and 15 can be suppressed by using a film made of _x and regulating the film thickness of the nonmagnetic metal film 15. Experiment 1 SiO ₂ and TaO _x (1.0 <
x ≦ 2.5) and a non-magnetic metal film 15 made of Cr were used to manufacture the magnetic heads shown in FIGS. 1 and 2 as described above. Then, the state of crack generation in the gap films 14 and 15 when the thickness of the Cr film was changed was examined. The results are shown in Table 1.

In the evaluation, the thickness of the SiO ₂ film and the TaO _x film was fixed to 4.0 μm, and the metal magnetic thin film 8 was a film of sendust having a thickness of 5.0 μm. The number of samples was set to 20, and the ratio of the head chips having even one crack in the gap films 14 and 15 and the degree of the crack were evaluated. Cracks enter from the Cr film S
The case of reaching the iO ₂ film was evaluated as x, the case of only the Cr film was evaluated as Δ, and the very few cases were evaluated as o. Further, in the evaluation, observation was performed with a microscope with an objective lens of 100 and an eye lens of 10. The crack is always C
It was confirmed that the film entered from the r film, and when no crack was generated, the evaluation of ◯ Δx was omitted.

[0022]

[Table 1]

As can be seen from the results of Table 1, the crack occurrence rate in the gap films 14 and 15 decreases when the thickness of the Cr film is reduced regardless of the SiO ₂ film and the TaO _x film. In the SiO ₂ film, the generation of cracks cannot be prevented unless the thickness of the Cr film is 0.01 μm or less. In practice, it is practically difficult to reduce the film thickness to this extent when forming a film. On the other hand, in the TaO _x film, Si
Compared to the O ₂ film, the degree of cracking is reduced and C
It can be seen that the allowable range of the r film thickness is widened. That is, in the case of the combination of the Cr film and the TaO _x film, the generation of cracks can be prevented in a wider range as compared with the combination of the Cr film and the SiO ₂ film. From this result, in order to prevent the occurrence of cracks in the gap films 14 and 15,
It is necessary to set the thickness of the Cr film to 0.01 μm or more and 0.3 μm or less, and to use a film made of TaO _{x for the} nonmagnetic oxide film 14.

Experiment 2 In Experiment 2, the thickness of the Cr film was fixed at 0.2 μm and Si was used.
The dependence of the Cr film on the occurrence of cracks was investigated when the thickness of the O ₂ film was changed. The results are shown in Table 2.

[0025]

[Table 2]

From the results shown in Table 2, even if the film thickness of the SiO ₂ film is changed, the crack generation state in the gap films 14 and 15 does not change, and effective measures against cracks are to control the film thickness of the Cr film and use the TaO _x film. It can be confirmed that

Experiment 3 In Experiment 3, the value of x of TaO _x was changed and the crack generation state in the gap films 14 and 15 at that time was examined.
The results are shown in Table 3. In the evaluation, sputtering was performed in an atmosphere of Ar 100% and Ar + O ₂ so that the TaO _x film had a thickness of 4.0 μm and the Cr film had a thickness of 0.1 μm to fabricate a magnetic head. The value of x was estimated by the state analysis by the ESCA method which is one of the surface analysis methods.

[0028]

[Table 3]

As can be seen from Table 3, x does not depend on the occurrence of cracks. That is, T
In the case of aO _x , there is no need to perform severe sputtering condition control, which is practically advantageous.

Experiment 4 In Experiment 4, the combination of the SiO ₂ film and the Cr film and TaO _{x were used.}
A magnetic head was manufactured by a combination of a (1.0 <x ≦ 2.5) film and a Cr film, and the crack width in the gap films 14 and 15 was examined by changing the track width Tw at that time. The result is shown in FIG. The vertical axis of FIG. 3 is the ratio k = m / t where t is the total thickness of the gap film and m is the thickness of the Cr film, and the horizontal axis is the track width Tw.

As can be seen from FIG. 3, the nonmagnetic oxide film 1
When using the TaO _x film compared to those using the SiO ₂ film as 4, it is possible to move the boundary line without cracking region / generating region more in the upper right (direction of the arrow in the drawing). That is, the use of the TaO _x film has an effect of expanding the crack-free region to a range where the track width Tw is larger. In particular, the erase head of the present embodiment, which has a large track width Tw of 100 μm or more, is very advantageous from the viewpoint of preventing cracks.

As the track width Tw becomes larger in this way, the value of k = m / t at which no crack is generated becomes very small. For example, when the track width Tw = 165 μm, it is appropriate to represent k. Not. Therefore, it is appropriate to express the absolute value of the thickness of the Cr film, and in this embodiment, C
The film thickness of the r film was set to 0.01 μm or more and 0.3 μm or less.

Further, in this embodiment, the upper limit of the film thickness of the nonmagnetic metal film 15 is fixed at 0.3 μm. This is because the influence of the track width Tw is much more dominant than the film thickness on the stress generated by the non-magnetic metal film 15, which is a major factor in the generation of cracks. This can be explained as follows.

In general, the stress caused by attaching the film is as shown in FIG. 4, when the substrate 18 formed by depositing the film 17 on one side surface is supported by the supporting portion 19 in a cantilevered state. Is proportional to the magnitude of the warpage δ of the substrate 18. This can be expressed by equation (1). In the equation (1), σ is strain of the film, Es is Young's modulus of the substrate, ν is Poisson's ratio of the substrate, t _f is the thickness of the Cr film, t _s is the thickness of the substrate, and 1 is the length of the substrate. (Corresponding to the track width Tw).

[0035]

[Equation 1]

From the equation (1), the generated stress ∝δ∝l ² · t
_It can be seen that _f , where l (Tw) is squared, and its effect is more dominant than t _f .

Experiment 5 In Experiment 5, the amount of protrusion of the Cr film when the sliding surface of the magnetic recording medium was abraded by sliding contact with the magnetic recording medium was examined. The results are shown in Table 4. Figure 5
As shown in FIG. 5, the ferrite cores 22 and 23 on which the sendust films 20 and 21 are formed are respectively provided with the Cr films 24 and 25.
A magnetic head was manufactured by joining and integrating a pair of magnetic core halves formed by forming the SiO ₂ films 26 and 27 as a gap film, and the thickness of the Cr film at that time was changed. The thickness of the sendust films 20 and 21 is 4.0 μm, and Si
The thickness of the O ₂ films 26 and 27 was fixed to 4.0 μm. Then, the magnetic tape 28 was brought into sliding contact with the sliding surface of the magnetic recording medium of this magnetic head, and the protrusion amount d of the Cr films 24 and 25 was measured. Note that the protrusion amount d of the Cr films 24 and 25 is, as shown in FIG. 6, the tip of the Cr films 24 and 25 and the sendust film 2.
The height difference is 0,21.

[0038]

[Table 4]

As can be seen from Table 4, the Cr films 24 and 25
As the thickness of the Cr film is reduced, the protrusion amount d of the Cr films 24 and 25 is reduced, thereby eliminating the characteristic failure (output down). Therefore, based on these results, it is desirable that the film thickness of the Cr films 24 and 25 be 0.3 μm or less.

By the way, the magnetic head shown in FIGS. 1 and 2 is manufactured by the following procedure.
First, as shown in FIG. 7, a flat rectangular shape having a thickness of 1 mm
A plurality of track width regulating grooves 30 for regulating the track width of the magnetic gap are formed on the ferrite substrate 29 according to the number of magnetic heads to be manufactured.

As shown in FIG. 8, the track width regulating groove 30 is a groove having a substantially U-shaped cross section and is continuously cut at a predetermined pitch from one side surface of the ferrite substrate 29 to the other side surface opposite thereto. The grooves are formed in parallel.

Next, as shown in FIG. 9, sendust is sputtered to form a metal magnetic thin film 31 on the main surface where the track width regulating groove 30 is formed. Then, Ta ₂ O is also deposited on the metal magnetic thin film 31 by sputtering.
₅ films and Cr film are sequentially formed to form a gap film 3 having a laminated film structure.
Form 2. Then, as shown in FIG. 10, the ferrite substrate 29 is cut into a predetermined size to form one magnetic core half block 33.

Next, as shown in FIG. 11, a magnetic core half block 34 made of a simple ferrite is formed so as to be joined and integrated with the magnetic core half block 33. In this magnetic core half block 34, a winding groove 35 and a glass groove 36 for winding a coil are formed. Next, these magnetic core half blocks 33 and 34 are butted to each other as shown in FIG. 12, low melting point lead glass 37 is placed in the winding groove 35 and the glass groove 36, and the glass is melted at ˜600 ° C. To join.

Next, with respect to the magnetic head integrated and joined, the portion which becomes the sliding surface of the magnetic recording medium is cylindrically polished into an arc shape, and then a winding assist is formed to a predetermined size. By cutting the chip in this manner, the magnetic head shown in FIGS. 1 and 2 described above is manufactured.

The specific embodiments to which the present invention is applied have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, although the present invention is applied to the metal-in-gap type magnetic head in which the metal magnetic thin film 8 is formed only on one of the magnetic core halves 2 in the above-described embodiment, The present invention can be applied to a magnetic head formed with the metal magnetic thin film 8 or a magnetic head not including the metal magnetic thin film 8 and made of only an oxide magnetic material, and the same operation and effect are obtained.

[0046]

As is apparent from the above description, in the magnetic head of the present invention, the film thickness of the nonmagnetic metal film in the gap film formed by laminating the nonmagnetic oxide film and the nonmagnetic metal film. And TaO _x is used for the non-magnetic oxide film, it is possible to reliably prevent the occurrence of cracks in the gap film. Therefore, it is possible to prevent erosion of the metal magnetic film by the fused glass entering from the crack portion and dust entering the crack portion due to sliding contact with the magnetic recording medium. In addition, since the thickness of the non-magnetic metal film is specified to be small, the amount of protrusion of the non-magnetic metal film caused by uneven wear of the sliding surface can be suppressed, which can reduce the spacing loss and the head. The life can be greatly extended.

Further, according to the magnetic head of the present invention, since the TaO _x film is used as the underlayer film of the non-magnetic metal film, even if the track width is increased, the gap film is significantly cracked. Suppressed. Therefore,
The effect is great for a magnetic head having a large track width such as an erase head. As described above, according to the present invention, it is possible to provide a magnetic head which is not only improved in the manufacturing yield of the head but also has no crack and which is excellent in reliability.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a magnetic head to which the present invention is applied.

FIG. 2 is an enlarged plan view of an essential part showing an enlarged sliding surface portion of a magnetic recording medium of the magnetic head of FIG.

FIG. 3 is a total thickness t of the gap film and a thickness m of the nonmagnetic metal film.
FIG. 6 is a characteristic diagram showing the track width dependence of the crack occurrence rate in the gap film with respect to the ratio k = m / t.

FIG. 4 is a diagram for explaining that the cause of cracks is dominated by the influence of the track width rather than the thickness of the nonmagnetic metal film.

FIG. 5 is an enlarged sectional view of an essential part showing a state in which a magnetic recording medium slides on a sliding surface of the magnetic recording medium.

FIG. 6 is an enlarged cross-sectional view of a main part of a sliding surface portion of a magnetic recording medium showing a state in which a nonmagnetic metal film is projected due to abrasion.

FIG. 7 is a perspective view sequentially showing a process of manufacturing the magnetic head of the present invention, showing a track width regulating groove forming process.

FIG. 8 is an enlarged front view of essential parts showing a step of forming a track width regulating groove, which sequentially shows steps of manufacturing the magnetic head of the present invention.

FIG. 9 is an enlarged front view of essential parts showing the steps of forming a magnetic metal thin film and a gap film, which sequentially show steps of manufacturing the magnetic head of the present invention.

FIG. 10 is a perspective view showing the steps of manufacturing the magnetic head of the present invention sequentially, showing the steps of manufacturing the magnetic core half block.

FIG. 11 is a perspective view sequentially showing a process of manufacturing the magnetic head of the present invention, showing a magnetic core half block manufacturing process in which a winding groove and a glass groove are formed.

FIG. 12 is a perspective view showing the steps of manufacturing the magnetic head of the present invention in sequence and showing the step of joining the magnetic core half blocks.

FIG. 13 is a perspective view sequentially showing the steps of manufacturing the magnetic head of the present invention, showing the step of cylindrically polishing the magnetic core half block.

[Explanation of symbols]

 1, 2 ... Magnetic core half body 3, 7 ... Auxiliary core portion 4 ... Winding groove 5 ... Glass groove 8 ... Metal magnetic thin film 9, 10 ... Track width regulating groove 11 ... Sliding surface of magnetic recording medium 14 ... Non-magnetic oxide film 15 ... Non-magnetic metal film 16 ... Fused glass

Claims (2)

[Claims] 1. A magnetic head in which a pair of magnetic core halves are butted against each other via a gap film formed by laminating a non-magnetic oxide film and a non-magnetic metal film to form a closed magnetic circuit, wherein the non-magnetic metal film is formed. Thickness of 0.01μm or more, 0.3μ
A magnetic head characterized by being m or less. 2. The non-magnetic oxide film is TaO _x (1.0 <x
2. The magnetic head according to claim 1, wherein ≦ 2.5).