JPH048848B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention detects a change in a signal magnetic field applied in the direction of the hard axis of magnetization of a metal ferromagnetic thin film having uniaxial magnetic anisotropy as a change in electrical resistance in the direction of the easy axis of magnetization. The present invention relates to an improvement in the structure of a thin film magnetic head (hereinafter referred to as a thin film MR head) which is equipped with a magnetoresistive element (hereinafter referred to as an MP element) to detect a signal magnetic field recorded on a magnetic recording medium.

<Prior Art> It has been known that thin-film MR heads have many advantages over wire-wound bulk magnetic heads. In other words, when a thin film MR head receives a signal magnetic field written on a magnetic recording medium such as a magnetic tape, the magnetization direction inside the magnetoresistive element changes, and the internal resistance changes accordingly. Since it is taken out as an external output, it is a magnetic flux response type head and can therefore reproduce the signal magnetic field without depending on the moving speed of the magnetic recording medium. This thin-film MR head is a fixed head type that can perform high-density recording because it is easy to achieve high integration and multi-element technology using semiconductor microfabrication technology.
It is seen as a promising magnetic head for playback of PCM recorders.

Now, since an MR element originally exhibits sensitivity characteristics with a square curve to an external magnetic field, when configuring an MR element as a reproduction head, the element shape is made into a stripe shape in order to stabilize the orientation of magnetization. At the same time, it is necessary to apply a predetermined bias magnetic field to the MR element in order to obtain linear response characteristics. Furthermore
In order to provide a high resolution function to the MR element, it is necessary to form a thin film made of a soft magnetic material (permalloy, sendust, etc.) as a magnetic shield layer on the upper and lower sides of the striped MR element with an insulating layer interposed therebetween. It is.

FIG. 1 is a perspective view of a conventional MR head. In the figure, 1 is a high permeability magnetic material for magnetic shielding, 2 is a permanent magnet for bias, 3 is an MR element, 4 is a conductor part that becomes the lead of MR element 3, and 5 is a high permeability magnetic material for magnetic shielding. be. In the head shown in the figure, a magnetic field (arrow A) entering from the tip of the gap is applied to the MR element 3, so that the MR element 3 is magnetized.

The angle between the direction of magnetization in this MR element 3 and the stripe longitudinal direction (X axis) of the MR element 3 is θ(y)
Then, the specific resistance ρ(y) of the MR element 3 is ρ(y) = ρ ₀ + Δρmax ^cos2 〓 (ρ ₀ : resistivity without magnetic field, Δρmax: maximum rate of change in magnetoresistance), and the resistance R of the MR element 3 is is track width l,
Letting the MR element film thickness be t, R=l/t [∫ ^w _p dy 1/ρ(y)] ^-1 . The magnetization on the MR element 3 interacts with the magnetization in the magnetic shields 1 and 5, but in any case, the behavior of the magnetization of the MR element 3 is reflected in the reproduction output of the MR head. It is something. By the way, since the MR element 3 is arranged so that the direction of the input magnetic field is in the direction of the hard magnetization axis, in an ideal case where the magnetization of the MR element 3 moves in rotation mode, My (magnetization in the y direction) is Hy. (magnetic field in the y direction), and the output of the MR element 3 changes quadratically with respect to the input magnetic field. This situation is shown in FIG. The output of the MR element 3 is saturated with the saturation of My in a high magnetic field.

The output of an ideal MR element is as described above, but in an actual element, changes in My do not occur only in the rotation mode, but rather cause domain splitting within the MR element, causing domain movement. often accompanied by In particular, as the track width of the MR element shown in FIG. 1 becomes smaller, changes in My due to movement of magnetic domains become more noticeable due to the relationship with magnetostatic energy. The movement of magnetic domains is called a Barkhausen jump (hereinafter abbreviated as B-jump). Accompanied by discontinuous changes in My.
When the above rotation mode and magnetic domain movement coexist,
Figure 3 shows the relationship between the output of the MR element and the input magnetic field. This Barkhausen jump becomes noise in the reproduced output and greatly deteriorates the S/N ratio of the MR head. Therefore, in order to obtain a good MR head, it is essential to suppress the B-jump of the element.

Conventionally, in order to suppress this B-jump,
By applying a weak magnetic field of several [Oe] in the easy axis direction (stripe longitudinal direction) of the MR element,
It is known that it is sufficient to make the MR element into a single magnetic domain state. The method of applying the magnetic field in the easy axis direction includes a method using a coil outside the head, a method using a permanent magnet outside the head,
Application methods using antiferromagnetic coupling between an MR element and an antiferromagnetic thin film have been proposed. FIG. 4 shows a head structure using the above method. In the figure, 6 is an MR element, 7 is an antiferromagnetic thin film,
8 is a conductor portion.

However, in the above method, since the magnetic field applying means is provided outside the head, there are restrictions on the casing of the head, and in the case of a multitrack head, the magnitude of the applied magnetic field depends on the position of the head inside the head case. In the case of the shield type MR head shown in FIG. 1, the applied magnetic field does not penetrate sufficiently into the shield, making it unusable. Although the method described above overcomes the disadvantages of , it still has the following disadvantages. That is, the antiferromagnetic film 7
By coupling with the MR element 6, a magnetic field is applied in the easy axis direction of the MR element, but on the other hand, this causes deterioration of the magnetic properties of the MR element. That is, the antiferromagnetic film 7 increases the coercive force H _C and the anisotropic magnetic field H _R of the MR element film. This has an undesirable effect on the properties of the head. Further, a FeMn thin film is used as the antiferromagnetic film 7, but this FeMn thin film is a conductor, so the current flowing from the lead 8 is distributed not only to the MR element 6 but also to the antiferromagnetic material 7. As a result, the sensitivity of the head decreases.

<Purpose> The present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional techniques. A ferromagnetic material with a large coercive force is formed under the leads of an MR element, and the ferromagnetic material and the MR element are combined. By ferromagnetic coupling, MR
The object of the present invention is to suppress the bulk house jump of an MR element by applying a weak magnetic field in the longitudinal direction of the stripe of the element, and to realize an MR head having a good S/N ratio.

<Example> Hereinafter, an example of the MR head according to the present invention will be described in detail.

FIG. 5 shows the structure of an embodiment of the thin film MR head according to the present invention, in which FIG.
Figure c is a side sectional view. In the figure, 9 and 17 are high permeability magnetic thin films (usually Ni-Zn ferrite, Mn-Zn ferrite,
Sendust and permalloy are used. ), 10,
12 and 16 are interlayer insulating materials (SiO ₂ , SiN, Al ₂ O ₃
), 11 is a bias thin film, 13 is an MR element (Ni-Fe, Ni-Co, etc.), 15 is a conductive thin film (Al, Cu, Au, etc.) that serves as a lead for the MR element 13,
14 is a ferromagnetic thin film with a large coercive force (Ni-Co, Ni
-Co-P, Co-P, Fe ₂ O ₅ , etc.), MR element 13
ferromagnetic exchange coupling. For example, when using a film with a small holding force (about 1 to 10 [Oe]) such as an MR element,
High holding power like Co-P (300~3K [Oe]
When films are stacked, the magnetic properties of the composite film are not simply the sum of the film properties of the two layers but are different due to the interaction of the two layers due to ferromagnetic exchange coupling at the boundary between the two layers. This situation is shown in FIG. Figure a is
This is the B-H characteristic in the direction of the easy axis of magnetization of a Ni-Fe single film (film thickness approximately 500 Å) for MR elements.
This is the B-H characteristic of a Co-P single film (film thickness approximately 800 Å). Figure c shows the characteristics of a composite film in which the single coated Co-P film shown in figure b is laminated on the Ni-Fe film shown in figure a. As can be seen from figure c, in a ferromagnetic exchange-coupled two-layer composite film of an appropriate thickness, the magnetization directions of the two films coincide due to the exchange interaction at the boundary between the two films, and the squareness ratio and The magnetic force takes an intermediate value between the two films. As an example, 500 [Å] Ni-Fe
The coercive force of the composite film when the Co-P plating film with different thickness is laminated on the vapor-deposited film of (80-20) is the seventh
As shown in the figure. It can be seen that the two-layer composite film of Co-P with a film thickness of 400 Å or more behaves like a composite film with a large coercive force. From a different perspective, it is also possible to consider that the magnetization direction of a magnetic film (Ni--Fe film) with a small coercive force is fixed to the magnetization direction of a magnetic film (Co--P film) with a large coercive force.

Now, in FIG. 5, the NR element below the leads has the above-mentioned ferromagnetic exchange coupled composite film structure. Therefore, the magnetization direction of the MR element under the lead can be fixed to the magnetization direction of the ferromagnetic material 14 shown in FIG. The magnetization direction of the ferromagnetic material 14 shown in FIG. 5 can be controlled by applying an external magnetic field of about 10 KOe to magnetize it. Therefore, the fifth
In the figure, in the longitudinal direction of the stripe of the MR element,
By applying a magnetic field of about 10 KOe, the magnetization of the MR element under the leads and the magnetization of the ferromagnetic film 14 can be aligned in the longitudinal direction.
This situation is shown in FIG. However, the magnetic shield and bias thin film are omitted in this figure. In the figure, 18 is an MR element, 19 is a ferromagnetic film with a large coercive force, and 20 is a lead. Arrows M in the figure indicate the direction of magnetization of each part of the magnetic film. MR element 1 in the same figure
8, the part that actually feels the magnetic field, that is, lead 2
The portion between 0 and the lead 20 is directly coupled to both ends of the MR element 18 (that is, the MR element 18 and the ferromagnetic film 19 under the lead), and therefore a magnetic field _HX is applied in the longitudinal direction of the MR element 18. Ru. The magnetic field _HX in the longitudinal direction of the MR element 18 places the MR element in a single domain state, making it possible to suppress B-jump. Further, the value of this magnetic field _HX can be adjusted by controlling the thickness of the ferromagnetic film and by controlling the value of residual magnetization, as shown in FIG. or,
The part of the MR element 18 that senses the signal magnetic field is the normal one.
Since it is no different from an MR element, there is no risk of deterioration of MR characteristics or reduction of sensitivity as a head, and in this respect it is superior to conventional methods using antiferromagnetic coupling. Also, direct magnetic field
Since the ferromagnetic film that applies _H It's better than that.

Next, an example of a method for manufacturing the thin film MR head element described above will be described. In addition, the shield layer 9,
17. The method of manufacturing the bias thin film 11 and the like is the same as the conventional technique, so it will be omitted, and only the MR element portion will be described in detail. First, a Ni-Fe film (MR) is deposited on the base of the substrate by spuntering or vapor deposition in a uniform magnetic field.
After forming the film to a thickness of 1000 Å, photoresist is applied, masks are aligned, and exposure and development are performed to form stripes. Thereafter, using this resist layer as a mask, the exposed portion of the Ni--Fe film is removed by etching. Through this step, the MR element 13 is formed. Next, after removing the resist on the Ni-Fe film 13, a new resist is applied,
The resist in the portion overlapping the MR element 13 and the conductor portion 15 is removed to open a window. After that, the substrate is coated with Co-
Co-P or Ni-Co-P is immersed in an electroless plating solution for selective plating of Co-P (or Ni-Co-P).
A thin film 14 of Ni--Co--P is formed on the MR element 13. After this, the resist is removed. continue,
By depositing Al on the entire surface and photo-etching it using an etching means that is selective to Ni-Fe, Co-P, etc., the conductor part 15 is formed.
The element section is completed.

Finally, the Co-P section 14 and the Ni under the Co-P
In order to fix the magnetization of the Fe film in the longitudinal direction of the Ni-Fe film 13, a magnetic field of about 10 KOe is applied in that direction to magnetize it.

FIG. 9 shows an example of the output characteristics of the MR head created through the above steps. Figure a shows the conventional structure.
This is an actual measured value of the output of the MR head, and the figure b shows the above structure according to the present invention. According to figure b, the B-jump is completely suppressed. The stripe width of the MR head with the characteristics shown in the same figure is 10
[μ], track width is 50 [μ], lead width is 20 [μ]
It is. In conventional MR heads, the narrower the track and the wider the stripe width, that is, the smaller the aspect ratio of the stripe, the more severe the magnetic domain splitting becomes and the more B-jumps occur, but in the case of the structure of the present invention, The smaller the aspect ratio, the B-
A strong magnetic field (H _x ) in the longitudinal direction of the stripe for suppressing the jump is applied, making it possible to strongly suppress the B-jump. Therefore, it was possible to confirm the effect of suppressing B-jump in a wide range of shapes other than the stripe size of the MR head described above.

In the above explanation, a case has been described in which a ferromagnetic material with a large coercive force is placed between the lead and the MR element, but as shown in FIG. It is possible to produce a similar effect with a structure that is reversed. Also, although we have explained the details of the shield type MR head, the barber pole type
The present invention is applicable to MR head yoke type MR heads, non-shielded MR heads, and even magnetic sensors that utilize the magnetoresistive effect of a simple ferromagnetic film.

<Effects> According to the head structure of the present invention, an MR head with a good S/N ratio that suppresses the Barkhausen jump can be realized.

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional thin film MR head, Figure 2 is a perspective view of a conventional thin film MR head.
The figure is a response characteristic graph of an ideal MR head, Figure 3 is a response characteristic graph of an MR head in which a B-jump occurs in an actual head, and Figure 4 is a 5 is a structural explanatory diagram of an embodiment of the head structure according to the present invention. FIG. 6 is a B-H characteristic diagram of a composite film with ferromagnetic exchange coupling. Figure 7 is a graph of the coercive force of a ferromagnetic exchange-coupled composite film.
FIG. 8 is a conceptual diagram for explaining the B-jump suppressing mechanism according to the present invention, FIG. 9 is a characteristic graph of the MR head, and FIG. 10 is a perspective view of another embodiment of the present invention. In the figure, 1: High permeability magnetic material for magnetic shielding,
2: thin film for bias, 3: MR element, 4: conductor part, 5: high magnetic permeability magnetic material for magnetic shielding, 6:
MR element, 7: antiferromagnetic thin film, 8: conductor part,
9: High permeability magnetic material for magnetic shielding, 10: Insulating film, 11: Thin film for bias, 12: Insulating film, 1
3: MR element, 14: ferromagnetic thin film with large coercive force, 15: conductor part, 16: insulating film, 17: high magnetic permeability magnetic material for magnetic shielding, 18: MR element, 1
9: ferromagnetic thin film with large coercive force, 20: conductor part,
21: MR element, 22: ferromagnetic thin film with large coercive force, 23: conductor part.

Claims (1)

[Scope of Claims] 1. A thin film magnetic head that detects a change in a signal magnetic field applied in the direction of the hard axis of magnetization of a metal ferromagnetic thin film having uniaxial anisotropy as a change in electrical resistance, comprising: a lead conductor portion and the metal ferromagnetic film; A ferromagnetic film having a sufficiently larger coercive force than the metal ferromagnetic thin film is provided in the overlapped portion with the thin film, and the metal ferromagnetic thin film and the ferromagnetic film having a larger coercive force are ferromagnetic exchange coupled. A thin film magnetic head characterized by: