JPH06203322A - Magnetic head - Google Patents

Abstract

PURPOSE:To prevent cracking of gap films and to provide the magnetic head having excellent electromagnetic conversion characteristics and high reliability without being eroded by fusing glass by regulating the thicknesses of a nonmagnetic oxide film and nonmagnetic metallic film constituting the gap films. CONSTITUTION:Since the magnetic head is used as an erasing head, the gap length of the magnetic gap (g) is specified to >=1mum and the gap films 10, 11 are made of the laminated film structure composed of the nonmagnetic oxide film 10 and the nonmagnetic metallic film 11. The film 10 is formed in order to prevent the reaction with the glass 12, 13 and the film 10 and the film 11 are formed in this order on the magnetic metallic film 9 so as to avert contact with the film 10 and the fusing glass 12, 13 in order to prevent the generation of air bubbles. The film 10 and the film 11 are formed at such film thickness at which the ratio k=m/t attains k<=0.35 or k=0.8 in order to avert the generation of rupture and crack in the gap films to be generated at the time of fusing with the glass when the total thickness of the gap films is defined as (t) and the thickness of the film 11 is (m).

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.

[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 and bubbles are generated, so that a laminated gap film structure in which a metal non-magnetic film such as Cr is arranged on the SiO ₂ film is performed. ing.

By the way, in the case of a laminated type gap film structure in which a SiO ₂ film and a Cr film are laminated, two substances of a metal film and a SiO ₂ film are annealed at 500 ° C. to 800 ° C. which is required for glass fusion. Since the coefficient of thermal expansion of the is significantly different, strain due to this is generated in the gap film.

Particularly, in an erasing head for a video tape recorder in which the total thickness of the gap film is 1 μm or more,
The strain becomes larger, causing not only the inconvenience of cracking in the metal non-magnetic film but also cracking in the SiO ₂ film. Therefore, magnetic powder or the like generated by sliding contact with the magnetic tape may enter the cracks,
In the metal-in-gap type magnetic head, the electromagnetic conversion characteristics are deteriorated because the metal magnetic film is eroded by the fused glass penetrating from the crack portion.

Although it is possible to form the gap film only with a metal non-magnetic film, when the sliding surface of the magnetic recording medium is worn by sliding contact with the magnetic tape, a difference in hardness causes a step difference in the gap portion. , Causing spacing loss.

[0006]

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and it is excellent in electromagnetic conversion characteristics that prevent the occurrence of cracks in the gap film and prevent corrosion by the fused glass. It is an object of the present invention to provide a highly reliable magnetic head.

[0007]

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 an oxide nonmagnetic film and a metal nonmagnetic film. In a magnetic head having a closed magnetic path, the total thickness of the gap film is 1 μm or more, and the ratio of the thickness m of the metal non-magnetic film to the total thickness t of the gap film k = m /
It is characterized in that t is k ≦ 0.35 or k ≧ 0.8, and the oxide nonmagnetic film is SiO ₂ .

The present invention is also directed to a magnetic head in which a pair of magnetic core halves are butted against each other via a gap film formed by laminating an oxide nonmagnetic film and a metal nonmagnetic film to form a closed magnetic path. The total thickness of the gap film is 1 μm or more, and the linear expansion coefficient of the oxide nonmagnetic material forming the oxide nonmagnetic film is 6 × 10 ⁻⁷ or more. Is Ta ₂ O ₅ , Al ₂ O ₃ , Cr ₂ O
It is characterized by being one of the _three .

[0009]

In the present invention, since the thickness of the gap film formed by laminating the oxide nonmagnetic film and the metal nonmagnetic film is regulated, cracks do not occur in the gap film during the gap fusion. Therefore, the erosion of the metal magnetic film by the fused glass penetrating from the crack portion is prevented.

Further, in the present invention, since the linear expansion coefficient of the oxide non-magnetic material is specified, the metal non-magnetic material resulting from the difference in the linear expansion coefficient when gap fusion is performed using fused glass, etc. The thermal stress that occurs in the gap film is reduced, and the occurrence of cracks in the gap film is prevented.

[0011]

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 for a 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. There is.

One magnetic core half 2 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. Track width regulating grooves 4 and 5 for regulating the track width Tw of the magnetic gap g are cut out on the abutting surface of the auxiliary core portion 3. The track width restricting grooves 4 and 5 are located on both sides of the magnetic gap g from both end edges thereof.
Is cut out as an inclined surface having a predetermined inclination angle. By forming the track width regulation grooves 4 and 5, the track width Tw of the magnetic gap g is determined, and the track width Tw becomes smaller than the head chip thickness Cw.

The other magnetic core half 1 is also Mn-Z.
It is composed of an auxiliary core portion 6 made of an oxide magnetic material such as n-type ferrite or Ni-Zn ferrite, and a metal magnetic thin film 9 serving as a main core portion adhered to the abutting surface of the auxiliary core portion 6. Has been done.

Like the auxiliary core portion 3 of the one magnetic core half body 2, the auxiliary core portion 6 has track width regulating grooves 7 and 8 for regulating the track width Tw of the magnetic gap g on the abutting surface.
have. The track width regulating grooves 7 and 8 are also cut out from both end edges of the magnetic gap g as inclined surfaces having a predetermined inclination angle with respect to the magnetic gap g. In particular, a winding groove 14 for winding a coil is formed on the abutting surface of the auxiliary core portion 6 as a through groove having a substantially U-shaped cross section.

The metal magnetic thin film 9 has the auxiliary core portion 6
Is formed from the sliding surface of the magnetic recording medium that comes into sliding contact with the magnetic recording medium along the abutting surface of the magnetic recording medium to the back surface. The metal magnetic thin film 9 is not formed in the winding groove 14 portion. The metal magnetic thin film 9 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.

The pair of magnetic core halves 1 and 2 configured as described above are butted against the gap films 10 and 11 formed on the metal magnetic thin film 9 of the other magnetic core half 1. A closed magnetic circuit is configured by joining and integrating the fused glasses 12 and 13. The fused glasses 12 and 13 are also filled in the track width regulating grooves 4, 5 and 7, 8 so as to secure the contact characteristics 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 10 and 11) is set to 1 μm or more, and the gap film 10 is used. , 11 are oxide non-magnetic films 1
0 and a metal non-magnetic film 11 are laminated. The oxide non-magnetic film 10 prevents contact between the oxide non-magnetic film 10 and the fusing glasses 12 and 13 in order to prevent reaction with the fusing glasses 12 and 13 and to prevent generation of bubbles. An oxide nonmagnetic film 10 and a metal nonmagnetic film 11 are sequentially formed on the metal magnetic thin film 9. In other words, the metal non-magnetic film 11 and the fused glasses 12, 13 are provided in contact with each other,
The metal nonmagnetic film 11 protects the oxide nonmagnetic film 10 from the fused glasses 12 and 13. The oxide nonmagnetic film 10 and the metal nonmagnetic film 11 are
Both are formed by a vacuum thin film forming technique such as sputtering.

When the total film thickness of the gap film is t and the thickness of the metal non-magnetic film 11 is m, the oxide non-magnetic film 10 and the metal non-magnetic film 11 are produced at the time of glass fusion or the like. In order to prevent the occurrence of fracture cracks in the gap film, these ratios k = m / t are set to k ≦ 0.35 or k ≧ 0.35.
It is designed to be 0.8. If the ratio k between the total thickness t of the gap film and the thickness m of the metal non-magnetic film 11 is in the above range, the metal non-magnetic film 11 or both the metal non-magnetic film 11 and the oxide non-magnetic film 10 are spread. The fact that fracture cracks do not occur is based on the experimental results shown in FIG.

In FIG. 3, the total thickness t of the gap film is 1.5 μm.
A magnetic head in which the thickness m of the metal nonmagnetic film 11 is changed by using a film made of SiO ₂ as the oxide nonmagnetic film 10 and a film made of Cr as the metal nonmagnetic film 11 while being fixed to m. The following shows the rate of occurrence of fracture cracks in the gap film with respect to the ratio k = m / t of the total film thickness t of these gap films and the thickness m of the metal non-magnetic film 11. The rate of occurrence of fracture cracks is the ratio of the number n _X of heads having fracture cracks at one or more locations in the gap film to the ratio n _x / n of the number n ₀ of created heads, as determined by inspection with an optical microscope (× 1000). ₀ ) × 100%

As can be seen from these results, k ≦ 0.35
Alternatively, by setting k ≧ 0.8, due to the difference in thermal expansion between the oxide nonmagnetic film 10 and the metal nonmagnetic film 11 due to annealing at the time of glass fusion for joining and integrating the magnetic core halves 1 and 2 with each other. It is possible to prevent the occurrence of fracture cracks in the gap film due to the film thickness stress strain. This prevents the metal magnetic thin film 9 from being eroded by the fused glasses 12 and 13 flowing into the fracture cracks.
Therefore, the deterioration of the electromagnetic conversion characteristics can be avoided in advance. The upper limit of k is naturally determined within a range in which these gap films do not operate as a pseudo gap.

Further, in the present embodiment, since the occurrence of fracture cracks is caused by the film thickness stress strain due to the difference in thermal expansion between the oxide nonmagnetic film 10 and the metal nonmagnetic film 11, the oxide nonmagnetic film 10 is As the oxide nonmagnetic material forming the above, a material having a linear expansion coefficient close to that of the metal nonmagnetic material forming the metal nonmagnetic film 11 is selected and used. Specifically, a metal nonmagnetic material having a linear expansion coefficient of 6 × 10 ⁻⁷ (/ ° C.) or more is used. As a material corresponding to such a range, for example, TaOx
(1.0 <x ≦ 2.5) [Ta ₂ O ₅ ], Al ₂ O ₃ , C
r ₂ O _{3 and the} like can be mentioned. On the other hand, for the metal non-magnetic film 11, any metal non-magnetic material such as Cr, Ti, Zr, Nb, Ta, Au and Pt can be used. Table 1 exemplifies the linear expansion coefficient of typical metal non-magnetic materials.

[0022]

[Table 1]

By thus matching the linear expansion coefficient of the oxide nonmagnetic material forming the oxide nonmagnetic film 10 with the linear expansion coefficient of the metal nonmagnetic material forming the metal nonmagnetic film 11,
Thermal stress due to the difference in linear expansion coefficient between the two can be significantly reduced, and fracture cracks that occur in the metal non-magnetic film 11, cracks that occur in the fused glasses 12 and 13, cracks that occur in the ferrite core, etc. Both can be prevented. Further, since the stress applied to the magnetic core material forming the magnetic core halves 1 and 2 is reduced, deterioration of magnetic characteristics is reduced even with a magnetic material having large magnetostriction, and head efficiency can be expected to be improved. .

Here, actually, a magnetic head was prepared as follows, and the state of crack generation in the gap film of the magnetic head after glass fusion was observed. Mn-Zn
F on the abutting surface side of the auxiliary core portion 6 made of system ferrite
After e-Al-Si (sendust) is sputtered to form a metal magnetic thin film 9, Cr and Ta ₂ O ₅ are deposited on the metal magnetic thin film 9.
Were sequentially sputtered to form an oxide nonmagnetic film 10 and a metal nonmagnetic film 11. The one magnetic core half body 1 thus prepared and the other magnetic core half body 2 composed only of Mn—Zn-based ferrite were glass-fused with the fused glasses 12 and 13. The thickness of the metal magnetic thin film 9 is set to 2
μm, the thickness of the oxide nonmagnetic film 10 was 1.5 μm, and the thickness of the metal nonmagnetic film 11 was 1.5 μm. That is, k =
It is 0.5.

As a comparative example, the coefficient of linear expansion is 4 × 10 ^-7.
A magnetic head using SiO ₂ (/ ° C.) as the oxide nonmagnetic film 10 was prepared. In this magnetic head, Si
The magnetic head was the same as the above magnetic head except that O ₂ was used.

As a result, Ta ₂ O ₅ was added to the oxide non-magnetic film 1
With the magnetic head used as 0, the magnetic head was produced without any inconvenience in producing the head, and no crack was observed in the gap film. On the other hand, in the magnetic head using SiO ₂ as the oxide nonmagnetic film 10, the ratio k between the total film thickness t of the gap film and the film thickness m of the metal nonmagnetic film 11 is 0.5, and Since the coefficient of linear expansion is 6 × 10 ⁻⁷ (/ ° C.) or less, as shown in FIG.
A crack 15 was generated on the surface.

As can be seen from the above experimental results, the magnetic gap g is formed by using an oxide nonmagnetic material having a linear expansion coefficient of 6 × 10 ⁻⁷ (/ ° C.) or more for the oxide nonmagnetic film 10. Generation of cracks in the gap film can be prevented, and deterioration of electromagnetic conversion characteristics can be avoided.

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, in the above-described embodiment, the present invention is applied to the metal-in-gap type magnetic head in which the magnetic metal thin film 9 is formed only on one of the magnetic core halves 1; The present invention can be applied to a magnetic head formed with the metal magnetic thin film 9 or a magnetic head not including the metal magnetic thin film 9 and made of only an oxide magnetic material, and the same operation and effect are obtained.

[0029]

As is apparent from the above description, in the magnetic head of the present invention, the thickness of the oxide nonmagnetic film and the metal nonmagnetic film forming the gap film is regulated, or the oxide nonmagnetic film is formed. By adjusting the linear expansion coefficient of the oxide non-magnetic material forming the film to the linear expansion coefficient of the metal non-magnetic material forming the metal non-magnetic film, a gap film and a fused glass produced by annealing during glass fusion, and Generation of cracks in the magnetic core can be prevented, and erosion of the metal magnetic thin film due to the fusion glass can be prevented.
Therefore, it is possible to provide a magnetic head having a high head output and high reliability without deterioration of electromagnetic conversion characteristics.

[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 metal non-magnetic film.
FIG. 7 is a characteristic diagram showing a fracture crack occurrence rate in a gap film with respect to a ratio k = m / t.

FIG. 4 is an enlarged plan view of an essential part showing an enlarged sliding surface portion of a magnetic recording medium of a magnetic head showing a state in which a crack has occurred in a metal non-magnetic film.

[Explanation of symbols]

 1, 2 ... Magnetic core half body 3, 6 ... Auxiliary core portion 4, 5, 7, 8 ... Track width regulating groove 9 ... Metal magnetic thin film 10 ... Oxide non-magnetic film 11 ... Metal non-magnetic film 12, 13 ... Fused glass 14 ... Winding groove

Claims (4)

[Claims] 1. A magnetic head in which a pair of magnetic core halves are butted against each other through a gap film formed by laminating an oxide non-magnetic film and a metal non-magnetic film to form a closed magnetic path, and the total of the gap films is The film thickness is 1 μm or more, and the ratio of the thickness m of the metal non-magnetic film to the total film thickness t of the gap film k = m
A magnetic head characterized in that / t is k ≦ 0.35 or k ≧ 0.8. 2. The magnetic head according to claim 1, wherein the oxide nonmagnetic film is SiO ₂ . 3. A magnetic head in which a pair of magnetic core halves are butted against each other via a gap film formed by laminating an oxide non-magnetic film and a metal non-magnetic film to form a closed magnetic path, wherein The film thickness is 1 μm or more and the linear expansion coefficient of the oxide nonmagnetic material forming the oxide nonmagnetic film is 6
A magnetic head having a size of × 10 ^-7 or more. 4. The oxide non-magnetic film is Ta ₂ O ₅ , Al ₂ O.
4. The magnetic head according to claim 3, wherein the magnetic head is one of Cr ₃ and Cr ₂ O ₃ .