JPS61258321A - Magneto-resistance effect type head - Google Patents

Abstract

PURPOSE:To obtain a magneto-resistance effect type head which has high mass productivity and high electromagnetic conversion characteristics, by increasing sufficiently the horizontal width compared with the vertical width of the 2nd magnetic thin film of high permeability against a rubbing surface and also compared with the horizontal width of a magneto-resistance effect element against the rubbing surface. CONSTITUTION:A magneto-resistacne effect element 2 is provided on a substrate 1 and a front gap 5 of 0.1mum is formed against the element 2. Then a front flux guide 3 is set at the gap 5. While a rear gap of 0.1mum is provided also to the element 2 for a rear flux guide 4. There the film thickness of both guides 3 and 4 are set at 0.3mum and 2mum respectively. Then the film thickness of an insulated layer 11 is set at 1mum. The layer 11 is formed between the element 2 and a bias coil 7 of Al having 2mum film thickness. Then these guides 3 and 4 and the layer 11 are covered entirely with a protecting layer 8 of Al2O3 having 30mum film thickness. The layer 8 and the substrate 1 form a rubbing surface 10 against a medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetoresistive head, and particularly to the structure of a so-called rear magnetoresistive head in which a magnetoresistive element is not exposed to a moving image of a medium.

[Background of the invention]

As an example of a conventional rear structure magnetoresistive head,
IEICE Technical Report Vol. 1.82. pp, 33-41 (198
2), the structure discussed in the document entitled "One reproduction method of perpendicular magnetic recording" by Takahashi et al. is known. As reported in detail in the above-mentioned literature, a head with the same structure has better stability and electromagnetic stability than a conventional magnetoresistive head with a so-called front-type structure in which the magnetoresistive element is exposed on the sliding surface of the medium. It is characterized by excellent conversion characteristics. However, when creating the above board, it is necessary to perform high-precision board processing.
This has been a problem in terms of improving mass productivity.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive head that eliminates the drawbacks of the prior art described above, is easily mass-producible, and has excellent electromagnetic conversion characteristics.

[Summary of the invention]

In order to achieve this object, the present invention has a magnetoresistive element sandwiched between first and second high permeability magnetic thin films, and the magnetoresistive element of the first high permeability magnetic thin film is In a magnetoresistive head in which the side surface opposite to the side surface facing the recording medium forms a sliding surface, the width of the second high permeability magnetic thin film in the direction parallel to the sliding surface is It is characterized by being sufficiently larger than the width in the vertical direction and sufficiently larger than the width in the direction parallel to the sliding surface of the magnetoresistive element.

Here, the present invention will be schematically explained with reference to FIGS. 4 to 9.

FIG. 4 is a side sectional view of a flux-guided magnetoresistive head according to the present invention, and FIG. 5 is a schematic front view of the flux-guided magnetoresistive head. In Figure 4, ■
2 is a non-magnetic substrate, 2 is a magnetoresistive effect element, 3 is a front flux guide made of a high permeability magnetic thin film, 4 is a rear flux guide made of a high permeability magnetic thin film, and 5 is a front flux guide 3 and a magnetoresistive effect element. 6 is a rear gap provided between the rear flux guide and the magnetoresistive element, and 7 generates a magnetic field necessary to bias the magnetoresistive element. 8 is a protective material, 9 is a lead wire, and 10 is a medium sliding surface. In addition, in FIG. 5, the protective material 8 and the one-turn coil 7
is not shown. The operating principle of the flux guided magnetoresistive head according to the present invention is as described below.

A signal magnetic flux from a recording medium (not shown) is guided to the magnetoresistive element by a front flux guide 3 and flows into the magnetoresistive element 2 via a front gap 5. The signal magnetic flux is converted into an electric signal by the magnetoresistive element 2. Thereafter, the signal magnetic flux passes through the rear gap 6, flows into the rear flux guide 4, and finally returns to the tape. In the magnetoresistive head having the same structure, the rear flux guide 4 has the effect of improving the magnetic flux utilization rate. Further, the reason why the film thickness of the rear flux guide 4 is larger than that of the front flux guide 3 is to suppress Barkhausen noise.

It can be seen that in the case of the flux guide type head shown in FIGS. 4 and 5, there is no need for high-precision substrate processing in the manufacturing process, and the head is suitable for mass production. However, as a result of a systematic study, the above-mentioned magnetoresistive head is more easily mass-produced than other conventional heads, but it is more likely to generate Barkhausen noise (and the frequency of occurrence is lower than that of flux). It was found that it greatly depends on the shape of the guide, especially the shape of the rear flux guide.

Below, we will discuss the frequency of Barkhausen noise and its relationship with the shape of the rear flux guide in Part 6.
This will be explained in more detail with reference to FIGS. 9 to 9.

6 and 7 both show the relative positional relationship between the rear flux guide 4 and the magnetoresistive element 2,
8 and 9 schematically show the magnetic domain structure of the rear flux guide having the shape shown in FIGS. 6 and 7, as observed by the Bitter method. In Figures 8 and 9,
12 is a 1800 domain wall, and 13 is a 90'' domain wall.

In other words, as a result of a systematic study on the relationship between the frequency of occurrence of Barkhausen noise and the shape of the rear flux guide, the frequency of occurrence of Barkhausen noise in the head with the structure shown in Fig. 6 is the same as that in the head shown in Fig. 7. It became clear that it was very large. The aforementioned results are supported experimentally and theoretically as explained below.

As is well known, Barkhausen noise is caused by irreversible movement of domain walls. As schematically shown in FIGS. 8 and 9, the magnetic domain structure of the rear flux guide differs greatly depending on its shape.

In other words, when the short and long sides of a quadrilateral are approximately equal, the frequency of domain walls per unit length is greater than when the short and long sides are significantly different, and the ratio of 90° domain walls 13 to 1806 domain walls 12 is also becomes larger. Compared to the 180′ domain wall 12, the 90″ domain wall 13 has the eighth and ninth domains.
It is easy to move with respect to the magnetic field H in the direction of the arrow shown in the figure, and the movement is irreversible. In other words, in the head having the structure shown in FIG. 6, irreversible movement of the domain wall is likely to occur due to the signal magnetic field from the medium, and in addition, the width of the magnetoresistive element 2 and the width of the rear flux guide are approximately equal to each other. Since they are equal, the magnetoresistive element is directly affected by the above-mentioned irreversible movement of the domain wall. On the other hand, in the case of FIG. 7, as mentioned above, the ratio of the 90" domain wall 13 is small and its position is far from the magnetoresistive element 2.
Compared to the case shown in FIG. 7, the influence of irreversible movement of the 90° domain wall is smaller.

As described above, the frequency of occurrence of Barkhausen noise in the flux-guided magnetoresistive head according to the present invention is closely related to the magnetic domain structure of the rear flux guide, that is, the same shape, and It has become clear that Barkhausen noise can be suppressed by making the width of the rear flux guide 4 sufficiently larger than the width of No. 2, and by making the ratio of the long side to the short side large.

Note that theoretical considerations regarding the magnetic domain structure and pattern shape have already been made by our predecessors, and are described in detail in, for example, "Magnetic Thin Film Engineering" published by Maruzen Publishing.

The above-mentioned results are consistent with the theoretical considerations.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view showing an embodiment of the magnetoresistive head according to the present invention, and FIG. 2 is a front view showing the relationship between the magnetoresistive element and the flux guide in FIG. 1 is a substrate, 2 is a magnetoresistive element, 3 is a front flux guide, 4 is a rear flux guide, 5.6 is a gap, 7 is a bias coil, 8 is a protective layer, 9 is an extraction electrode, 10 is a medium sliding surface , 11 are insulating layers. Note that the bias coil 7 and the protective layer 8 are not shown in FIG.

In FIGS. 1 and 2, a magnetoresistive element 2 made of 131wt% Ni permalloy with a film thickness of 0.04 μm is provided on a substrate 1 of a Zn ferrite sintered body, and a A front gap 5 with a length of 0.1 μm is provided, and a front guide 3 made of 81 wt% Ni permalloy is arranged, and an insulating layer 11 made of 5iCh is provided between the magnetoresistive elements 2 with a length of 0.1 μm.
A rear gap 6 of 100 mm is provided, and a rear flux guide made of 81 wt% Ni permalloy is arranged.

Here, the film thickness of the front flux guide 3 is set to 0°3μ.
The film thickness of the m1 rear flux guide 4 is 2 μm. Furthermore, a bias coil 7 made of AI with a film thickness of 2 μm
The film thickness of the insulating layer 11 between and the magnetoresistive element 2 is set to 1 μm.
The entire structure is covered with a protection layer 8 made of AJ2Ch having a thickness of 30 μm, and the protection layer 8 and the substrate 1 form a medium sliding surface 10.

Next, a method of manufacturing the magnetoresistive head of this embodiment will be explained with reference to FIG. In addition, FIG. 5A is a process diagram of the manufacturing method, and FIG. 2B is a schematic side sectional view of the magnetoresistive head at each step.

81wt%Ni was deposited on the mirror-wrapped Zn-coated ferrite sintered body using a magnetic field deposition method (magnetic field strength: approx. 500e).
permalloy at a substrate temperature of 300"C.
Form 4 μm. Thereafter, the magnetoresistive element 2 is patterned using an ion etching method. At this time, the magnetoresistive element is formed so that the longitudinal direction of the magnetoresistive element 2 and the above-described magnetic field direction are aligned.

After forming the magnetoresistive element 2, a Stow film with a thickness of 0.1 μm is formed by RF battering to form front and rear gaps 5.6.

After forming the front and rear gaps, the film thickness is 0.3μ
A $1 wt % N+ permalloy of m is formed by DC facing sputtering method, and the front flux guide 3 shown in FIGS. 2 and 3(b) is formed by patterning.

Thereafter, 81 wt% Ni permalloy having a thickness of 2.0 μm is further formed in the same manner, and the rear flux guide 4 is patterned and formed. Also at this time, the magnetoresistive element 2
Buttering is performed using the ion etching method as in the case of buttering.

After forming the flux guide 3.4, a 5fO2 film 11 having a thickness of 1 μm is formed by RF sputtering, and an A/film having a thickness of 2 μm is formed by using a vacuum evaporation method. A
The bias coil 7 is formed by patterning the 1 film using a conventional wet etching method.

Thereafter, a 30 μm thick Auto thin film as a protective layer is formed and processed into a predetermined head structure, completing the head according to the present invention.

In the case described above, the width of the rear flux guide 4 in the direction parallel to the medium brushing surface is about 10 times that of the magnetoresistive element 2.

The magnetoresistive head formed by the method described above was attached to a metal powder tape (Hj 15000e).

Br; 2500G), it was found that Barkhausen noise could be suppressed to such an extent that it would not be a problem in practice.

Furthermore, the frequency of Barkhausen noise depends on the magnetic domain structure of the flux guide, and is higher in the case of a magnetic domain structure with uniaxial anisotropy parallel to the media brushing surface 10 than in the case of magnetic isotropy. However, the occurrence of Barkhausen noise is less. This is because in the case of an isotropic magnetic domain structure, as shown in FIG. 10, the magnetic domain of the flux guide easily moves with respect to the signal magnetic field H, and the movement is irreversible. This may cause noise.

On the other hand, in the case of a uniaxially anisotropic boundary structure parallel to the media brushing surface 10, as shown in FIG. There is a 906 domain wall 13 that is the boundary between these magnetic domains and the domain whose magnetization direction is 90° with the magnetization direction of these domains, and when the signal magnetic field H is applied, the 90° domain wall 13 moves irreversibly, causing Barkhausen noise. However, the ratio occupied by the 90° domain wall 13 in the flux guide is 180" domain wall 1
2, and the 90° domain wall 1
The position No. 3 is optically separated from the center of the magnetoresistive element, and therefore Barkhausen noise is extremely small. The above was also confirmed experimentally.

Therefore, in the present invention, Barkhausen noise can be further suppressed by making the magnetic domains of the front flux guide 3 and the rear flux guide 4 uniaxially anisotropic.

〔Effect of the invention〕

As explained above, according to the present invention, the width of the second high permeability magnetic thin film in the direction parallel to the brushing surface is sufficiently larger than the width in the perpendicular direction, and By being sufficiently large compared to the width parallel to the brushing surface, it is easy to mass produce and has good electromagnetic conversion characteristics, and can suppress Barkhausen noise to a practically negligible level.
It is possible to provide a magnetoresistive head with excellent functionality by eliminating the drawbacks of the prior art described above.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the magnetoresistive head according to the present invention, FIG. 2 is a front view showing the relationship between the magnetoresistive element and the flux guide in FIG. 1, and FIG. FIG. 1 is an explanatory diagram showing a method of manufacturing the magnetoresistive head shown in FIG. 1, FIG. 4 is a side sectional view of the flux-guided magnetoresistive head for explaining the outline of the present invention, and FIG. 5 is a front view of the same. , FIGS. 6 and 7 are schematic diagrams showing the relative relationship between the magnetoresistive element and the flux guide, and FIG.
9 and 9 are schematic diagrams showing the magnetic domain structure of the flux guide, and FIGS. 10 and 11 are schematic diagrams for explaining the cause of Barkhausen noise caused by the domain walls of the flux guide. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Magnetoresistive element, 3... Front blacks guide, 4... Rear flux guide, 7... Bias coil, 8... Protective layer, 9...
- Extracting electrode, 10... Medium brushing surface, 11... Insulating layer. Agent Patent Attorney Kenji Take (1 idiot) Figure 1 Figure 3 Figure 4 Figure 6 Figure 7 Figure 8 Figure 9

Claims (3)

[Claims] (1) having a magnetoresistive element sandwiched between first and second high permeability magnetic thin films, a side surface opposite to the side surface of the first high permeability magnetic thin film that faces the magnetoresistive element; In the magnetoresistive head in which the second high permeability magnetic thin film forms a sliding surface with the recording medium, the width of the second high permeability magnetic thin film in the direction parallel to the sliding surface is compared to the width in the perpendicular direction. 1. A magnetoresistive head, characterized in that the width of the magnetoresistive element is sufficiently large, and the width of the magnetoresistive element is sufficiently larger than the width of the magnetoresistive element in a direction parallel to the sliding surface. (2) Claim (1) is characterized in that the thickness of the second high permeability magnetic thin film is set to be larger than the thickness of the first high permeability magnetic thin film. Magnetoresistive head. (3) In claim (1) or (2), the magnetic domain structure of the first and second high permeability magnetic thin films is uniaxially anisotropic parallel to the sliding surface. A magnetoresistive head featuring: