JPH0346885B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention detects signals recorded on a magnetic recording medium using a magnetoresistive element (hereinafter referred to as an MR element) that applies the magnetoresistive effect of a ferromagnetic thin film. Concerning thin film magnetic heads.

<Prior Art> Thin-film magnetic heads that utilize the magnetoresistive effect of ferromagnetic thin films are known to have many advantages over commonly used wire-wound magnetic heads. In other words, the thin film magnetic head receives a signal magnetic field generated from a magnetization pattern recorded on a magnetic recording medium and extracts this as a voltage change based on a resistance change of the MR element, so it does not depend on the transfer speed of the magnetic recording medium. It has the advantage of being able to reproduce a signal without any movement, particularly when the transport speed of the magnetic recording medium is low, and that a higher output reproduction signal can be obtained than with a wire-wound magnetic head. In actual use, rather than constructing a thin-film magnetic head with a single MR element, the MR element is separated from the tip of the head, and a magnetic flux introducing path (yoke) is arranged to guide the magnetic flux generated in the magnetic recording medium to the MR element. A thin film magnetic head, usually called a yoke type MR head (hereinafter referred to as MR head), with the structure shown in Figure 2, is more effective in improving signal resolution and durability of the MR element, and in recent years this type of magnetic head has become more effective. The head is a fixed head.
It is attracting attention as a playback head for digital audio (see ``Reproduction Characteristics of Yoke Type MR Head'', 8th Japanese Society of Applied Magnetics, Abstracts of Academic Lectures (1984), 14PB-11).

FIG. 2 is a cross-sectional view of a conventional YMR head in a direction perpendicular to the track width direction. Upper yoke 7, 8
is usually made of permalloy film with a film thickness of about 0.5 to 1.0 μm, and is used as a magnetic recording medium (magnetic tape) 10
This becomes a magnetic path for guiding the magnetic field generated in the MR element 5 to the MR element 5. The MR element 5 is made of a permalloy vapor-deposited film, and the film thickness is set to 300 to 500 μm, and the length is set to about 50 μm, which is the track width. In addition, a conductor 4 made of Al-Cu is used to apply a bias magnetic field to the MR element 5.
is arranged between the insulating films 2 and 3. Note that 3' is also an insulating film. The head gap 6 is set to about 0.2 to 0.3 μm since the minimum recording wavelength actually used is about 0.5 μm. The lower yoke 1 is made of a high permeability magnetic material, and generally a polycrystalline NiZn ferrite substrate or a single crystal (or polycrystalline) MnZn ferrite substrate is used. Track width is usually YMR
Since the head has a multi-track configuration, the thickness is set to about 50 μm.

In the thin film magnetic head configured as an MR element as described above, when the MR element 5 is manufactured, its axis of easy magnetization is selected to be in the track width direction. In addition, by passing a current I _B (hereinafter referred to as bias current I _B ) for generating a bias magnetic field through the conductor 4 (hereinafter referred to as bias conductor), a required bias magnetic field is applied to the MR element 5, and the MR element 5 is The operating point is moved to a point with good linearity. Furthermore, a sense current _IS is caused to flow in the track width direction of the MR element 5, and the signal magnetic field generated by the magnetic medium 10 is converted into a voltage change across the MR element 5. Note that the output signal obtained from the MR element 5 at this time includes Bulkhausen noise caused by the discontinuous movement of the magnetic domain inside the MR element 5, and this noise is generated by the YMR head described above. It is known that this has an extremely negative effect on the output signal processing of the yoke type MR head (see the above-mentioned 8th Japanese Society of Applied Magnetics, Abstracts of Academic Lectures (1984), 14PB-11, "Reproduction Characteristics of Yoke Type MR Head").

As mentioned above, Barkhausen noise is
This is caused by the movement of the magnetic domain inside the MR element 5, but the reason why the magnetic domain is generated inside the MR element 5 and moves discontinuously is due to disturbance of magnetic anisotropy (hereinafter referred to as anomaly) inside the MR element 5. (referred to as tropic dispersion). The MR element 5 is formed so as to have an axis of easy magnetization in the track width direction, as shown by K-K' in the plan view of FIG. When completed, this uniaxial anisotropy is disturbed. This external factor is
The film of the MR element 5 itself may deteriorate due to thermal history during the head manufacturing process, increasing anisotropic dispersion, or stress may be applied to the film of the MR element 5 from the outside.
For example, stress-induced magnetic anisotropy due to the inverse magnetostrictive effect of the film of the MR element 5 disturbs the uniaxial anisotropy generated in the MR element film during film formation.

External stresses applied to the film of the MR element 5 include the gap insulating film 3' shown in FIG. 3, which is a thin film laminated on the MR element 5, the first yoke film 7,
A force applied to the MR element 5 can be considered as a reaction to the internal stress generated in the second yoke film 8.
Here, since the internal stress of any of the above-mentioned films is considered to be isotropic, a film uniformly deposited on the MR element 5 like the gap insulating film 3'
The stress applied to the MR element 5 is considered to be isotropic, and based on this, it is considered that stress-induced magnetic anisotropy does not occur in the MR element 5. but,
MR is removed from films that are patterned and deposited near the MR element 5, such as the yoke films 7 and 8.
Since anisotropic stress is applied to the element 5, stress-induced magnetic anisotropy occurs in the MR element 5 due to this stress. This phenomenon is shown in FIG. In FIG. 4, the MR element 5 in which the internal stress of the first and second yoke films 7 and 8 is a compressive stress δ _Y generates stresses shown as δ _MR and δ' _MR in the figure, and here the MR element When the magnetostriction constant λ _S of the film is negative, stress-induced magnetic anisotropy occurs in a direction perpendicular to the track (direction of anisotropy of the MR element during film formation). Therefore, the direction of the anisotropy becomes biaxial, which disturbs the magnetic anisotropy during film formation, increases anisotropic dispersion, and causes Bulkhausen noise. In this way, the internal stress of the yoke film causes stress-induced anisotropy in the MR element, which has a detrimental effect on the head characteristics, but it is impossible to form the yoke film with zero internal stress. , which is difficult in reality. In other words, Fe-Al-Si is used as the yoke material.
-Alloys, Ni-Fe alloys, etc. are used, but they have inherent internal stress no matter which film formation method is used, such as sputtering, vapor deposition, plating, etc., and they maintain sufficient magnetic properties required as a yoke material. However, it was impossible to reduce the internal stress.

<Object of the Invention> The object of the present invention is to provide a YMR head with less Bulkhausen noise by canceling out or reducing the internal stress of the yoke film that has a detrimental effect on the above-mentioned MR element characteristics. .

<Embodiment> FIG. 1 shows an embodiment of a thin film magnetic head according to the present invention, and shows a sectional view taken in a plane perpendicular to the track width direction. In this figure, the same parts as in FIG. 2 are designated by the same reference numerals.

In FIG. 1, reference numeral 1 indicates a high magnetic permeability substrate, for example, a Ni--Zn ferrite substrate is used. 5 is
This is the MR element part and is made of a ferromagnetic thin film such as Ni-Fe or Ni-Co. Note that these films have a magnetostriction constant of a finite value. After applying the gap part insulating film 6, yoke films 7 and 8 (for example, Ni-Fe film) are applied.
When the yoke films 7 and 8 are formed by sputtering, the internal stress of the yoke films 7 and 8 generally becomes strong compressive stress.
Therefore, in order to cancel the stress applied to the MR element section 5, the yoke films 7 and 8 having tensile stress are used.
After stacking the stress cancel film 9 on the yoke films 7 and 8, the yoke films 7 and 8 and the stress cancel film 9 are simultaneously processed into a predetermined yoke shape by etching such as ion milling. As the stress cancel film 9, a deposited Ni-Fe film was used.

FIG. 5 shows the state of stress acting on the thin film magnetic head of FIG. 1. In the figure, δ _Y is the yoke membranes 7 and 8.
δ C is the compressive stress of the Ni-Fe sputtered film, and δ _C is the tensile stress of the Ni-Fe vapor deposited film, which is the stress cancel film 9. Here, the stress applied to the MR element portion 5 is proportional to (δ _Y −δ _C ), so if δ _Y δ _C is selected, the stress applied to the MR element portion 5 can be significantly reduced.

The yoke films 7 and 8 used in this example
The internal stress of the Ni-Fe sputtered film is approximately -7×
10 ⁹ dyne/cm ² , and the Ni-
The internal stress of the Fe deposited film was approximately +15×10 ⁹ dyne/cm ² . Therefore, the film thickness is 1/2 that of NiFe sputtered film.
By laminating Ni-Fe vapor deposited films, the yoke film 7,
The stress applied to the MR element portion 5 from the two-layer film of the MR element 8 and the stress cancel film 9 could be significantly reduced. This situation is shown in FIG. This figure is a cross-sectional view taken in a plane perpendicular to the track width direction, and shows a state in which stress is canceled as a whole by laminating a stress canceling film 9 with a thickness of 1/2 on the yoke films 7 and 8. show.

FIG. 7 shows an example in which both a thin film magnetic head according to the present invention and a conventional thin film magnetic head are arranged side by side on one substrate. In the figure, each chip consists of 20 track heads. Of these, 8 chips marked with diagonal lines have a thin film magnetic head structure according to the present invention, and the remaining 8 chips have a conventional thin film magnetic head structure, which were prototyped using the same substrate. In this case, among the tracks (20 x 8 = 160 tracks) of the head (8 chips) according to the present invention, the number of tracks where Bulkhausen noise appeared is 87/
160 tracks, while for tracks with conventional head structure (8 chips), 140 tracks/
It was 160 trucks. As described above, the thin film magnetic head according to the present invention has a remarkable effect of reducing Bulkhausen noise.

Here, in the above embodiment, the yoke film 7,
An example was shown in which a Ni-Fe film formed by a sputtering method was used as the film 8, and a Ni-Fe film formed by a vapor deposition method was used as the stress cancel film 9, but the reverse combination may also be used. In addition, various combinations of the yoke films 7, 8 and the stress cancel films 9, 9 can be used.

That is, as the yoke films 7 and 8, Ni-Fe film (compressive stress), Fe-Al-Si vapor deposited film (tensile stress), Fe
-Al-Si sputtered film (compressive or tensile stress), anti-metal such as Si, B, P or Zr on Co,
Amorphous amorphous vapor deposited film (tensile stress) containing about 10 to 20% of metals such as Ti, Nb, Ta, Hf, W, etc., Si in Co, antimetal or Zr in B, P, etc.
10-20% transition metals such as Ti, Nb, Ta, Hf, W, etc.
An amorphous sputtered film (compressive stress) containing a certain amount of stress can be applied.On the other hand, in addition to the films to which the yoke films 7 and 8 can be applied as the stress cancel films 9 and 9, W, Ti, Ta, Zr, and Nb can be used. , metal vapor deposition film (tensile stress) such as Hf, W, Ti, Ta, Zr, Nb,
Metal spatter film (compressive stress) such as Hf, SiO ₂ ,
Insulator sputtered film such as Al ₂ O ₃ , Si ₃ N ₄ (compressive stress)
is applicable. However, it goes without saying that it is necessary to select materials whose stress directions are opposite to each other.

<Effects of the Invention> As explained above, according to the present invention, it is possible to reduce the occurrence of stress-induced magnetic anisotropy in the MR element section, and as a result, it is possible to reduce the occurrence of stress-induced magnetic anisotropy in the MR element section, and as a result, it is possible to reduce the occurrence of stress-induced magnetic anisotropy in the MR element section. Since it is possible to implement a YMR head, it has the advantage of faithfully reproducing signals from magnetic media.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the thin film magnetic head according to the present invention, Fig. 2 is a cross-sectional view of a conventional YMR head, Fig. 3 is a plan view thereof, and Fig. 4 is an explanation showing the effect of stress. 5 and 6 are explanatory diagrams showing the effect of stress on the thin film magnetic head according to the present invention, and FIG.
The figure shows a top view of the substrate. In the figure, 1: high magnetic permeability substrate, 5: MR element part,
6: Gap part insulating film, 7, 8: Yoke film, 9:
Stress canceling membrane.

Claims (1)

[Claims] 1. A magnetoresistive element is coated with a yoke film pattern for guiding magnetic flux, and the yoke film pattern is covered with a stress cancel film that cancels out or reduces stress generated inside the yoke film. thin film magnetic head.