JPS6323217A - Magneto-resistance effect type magnetic head - Google Patents

Abstract

PURPOSE:To surely improve the Barkhausen noise by providing a magneto- resistance (MR) magnetic sensing part where a pair of soft magnetic thin films having the MR effect are laminated with a nonmagnetic thin film between them. CONSTITUTION:An MR magnetic sensing part 2 having the MR effect is provided on a substrate 1 to constitute an MR type magnetic head. In the magnetic sensing part 2, the first and second soft magnetic thin films 4 and 5 are laminated with a nonmagnetic thin film 6 between them. At least one of the first and second soft magnetic thin films 4 and 5 consists of a metal like Fe, Co, or Ni having the MR effect or an alloy consisting of two out of these metals. The nonmagnetic thin film 6 interposed between soft magnetic thin films 4 and 5 is formed with an inorganic thin film, nonmagnetic metallic thin film, or the like consisting of SiO2, Al2O3, Ti, Mo, Ag, etc. Front electrodes 7 and rear electrodes 8 for supply of a sense current is are formed in end parts of the side of a face 3 and the opposite side and front and rear end parts of the magnetic sensing part 2 by sticking. In this case, the power supply direction of an arrow (a) to the magnetic sensing part 2 of front electrodes 7 and the power supply direction of an arrow (b) of a bias conductor 10 are equalized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetoresistive (hereinafter referred to as MR) effect type magnetic head.

[Requirement of the invention]

The present invention has an MR magnetically sensitive part having an MR effect, which is formed by laminating a pair of soft magnetic thin films, at least one of which has an MR effect, with a nonmagnetic thin film interposed therebetween, and a sense current is applied to the MR magnetically sensitive part. The direction of the current flowing through the electrodes, especially the electrodes on the front end side of the MR magnetically sensitive section, and the bias conductor that generates the bias magnetic field to be applied to the MR magnetically sensitive section are made to match. To more reliably avoid noise generation.

[Conventional technology]

Conventionally, a general MR type magnetic head has a magnetic sensing part made of a single layer M.
It is composed of a soft magnetic film having an R effect, and a sense current is passed through this MR magnetic film to detect a change in resistance based on a signal magnetic field applied thereto as a change in voltage, for example. However, M due to such a single layer structure
R-type magnetic heads have a problem with Barkhausen noise.

[Problem that the invention seeks to solve]

The present invention attempts to reliably solve the problem of Barkhausen noise in an MR type magnetic head.

The present applicant has proposed a structure of a magnetoresistive magnetic head or a soft magnetic thin film which aims to improve the problem of Barkhausen noise as described in Japanese Patent Application No. 179135/1982.
Patent application No. 1988-234971, patent application No. 1987-247
This invention was proposed in the No. 752 application, etc., and in the magnetic head or magnetic thin film proposed in these,
Furthermore, we will definitely improve Barkhausen noise.

[Means for solving problems]

As shown in FIG. 1 as a plan view and as shown in FIG. 2 as a cross-sectional view, the present invention provides an M
An MR type magnetic head is constructed by providing an R magnetic sensing part (2).

(3) indicates a surface that faces or faces the magnetic medium, and although the magnetic medium is not shown, it moves relative to or in opposition to this surface (3) in a direction perpendicular to the plane of the paper in FIG. It is done like this.

As shown in FIG. 3, the magnetically sensitive part (2) is formed by laminating a pair of first and second soft magnetic thin films (4) and (5) with a nonmagnetic thin film (6) in between. First and second soft magnetic thin films (4
) and (5) are made of a soft magnetic thin film having an MR effect, for example, Fe, Co, Ni, or an alloy of two or more of these. Also, these soft magnetic thin!
One of jl (41 and (5)) is Sendust, Co-based amorphous alloy, which has no or almost no MR effect.
It can be constructed from a high magnetic permeability soft magnetic thin film such as Mo permalloy. The non-magnetic thin film (6) interposed between the soft magnetic thin films (4) and (5) has a thickness of 5t(h + A12(
h + Ti.

It is composed of an inorganic thin film such as Mo or Ag, a nonmagnetic metal thin film, etc. The non-magnetic thin film (6) is formed between the soft magnetic thin films (4) and (5) such that magnetostatic interaction is more dominant than exchange interaction.
The thickness is selected to be between 5 and 500 people, for example.

Also, both soft magnetic thin films (4) and (5) of this magnetically sensitive part (2)
), the magnetic flux is completely closed for both films (4) and (5) by selecting the saturation magnetic flux density, thickness, etc. so that the magnetic flux amounts of both films (4) and (5) match. are selected as follows. When both soft magnetic thin films (4) and (5) are magnetic thin films having an MR effect, it is desirable that both soft magnetic thin films (4) and (5) be made of the same material and have the same dimensions and shape. When one is made of a material that has no or almost no MR effect, the soft magnetic thin film is made of a material that has a sufficiently large electrical resistance compared to the other soft magnetic thin film that has an MR effect. resistivity of.

Select thickness, etc.

A sense current is is passed through the magnetic sensing part (2) to detect a change in resistance. The direction of conduction of the sense current js in the magnetically sensitive portion (2) is selected to be along the signal magnetic field Hs applied from the magnetic medium, that is, in the direction perpendicular to the facing surface (3) or facing the magnetic medium. Therefore, the magnetic sensing part (2) has a front electrode (7) and a rear electrode for supplying the sense current is at each end on the surface (3) side and the opposite side, that is, at each front and rear end. (8) and are deposited and formed. Specifically, both the front and rear electrodes (7) and (8) are attached so as to overlap both the front and rear ends of the magnetic sensing part (2). Here, in particular, the front electrode (7) is directed from above the terminal lead-out, at least from the part attached to the magnetically sensitive part (2), in the direction along the surface (3), that is, approximately the direction in which the IS lightning current is originally energized. They are forced to extend in orthogonal directions.

Therefore, the current direction in the vicinity of the connection part of the front electrode (7) with the magnetically sensitive part (2) is different from the original sense current is in the magnetically sensitive part (2), as shown by arrow a in FIG. The directions are almost perpendicular. In addition, the magnetic sensing part (2) is provided with a required bias from the outside so that the magnetization is oriented at a required angle, for example approximately 45 degrees, with respect to the direction of the sense current is when no signal magnetic field is applied, as usual. For this reason, a bias conductor (10) that generates a required bias magnetic field by energization is placed across the top or bottom of the magnetically sensitive part (2), and the direction of the current is set to the magnetically sensitive part (2). 2
), the direction is selected to be substantially perpendicular to the direction of the signal magnetic field. and,
In particular, the present invention provides the above-mentioned front electrode (
7), the current direction a to the magnetic sensing part (2) and the bias conductor (
Select the same direction of current flow for 1O).

[Effect]

According to the configuration of the present invention described above, Barkhausen noise is effectively removed. This will be explained.

First, to explain the cause of Barkhausen noise, when the magnetically sensitive part is composed of a single-layer MR magnetic thin film, as in the conventional general MR type magnetic throat, this MR magnetic thin film is magnetically In order to maintain a state in which the sum of magnetostatic energy caused by anisotropy energy, shape anisotropy, etc. is minimized for the entire layer, a magnetic domain structure as shown in FIG. 8 is adopted. That is, when this single-layer magnetic thin film is a rectangular magnetic thin film (51) and has magnetic anisotropy in the short side direction, magnetic domains with opposite magnetization directions alternate along the short side direction within the plane. (52) is generated, and magnetic domains (53) in opposite directions are generated sequentially along the long side direction of the magnetic layer between both ends of the adjacent magnetic domains (52) so as to form a closed loop. Therefore, when an external magnetic field is applied to such a magnetic layer, the domain wall (54),
(55) moves, which causes Barkhausen noise.

In contrast, in the configuration of the present invention, the magnetically sensitive portion (2)
However, the soft magnetic thin film (4) and (
5) has a stacked structure, so that when no external magnetic field is applied, the magnetic layer III! 1(4) and (5) are in a magnetized state antiparallel to each other in the direction of the easy axis of magnetization, as shown by arrows M1 and M2, respectively, and no domain wall is generated. The absence of domain walls was confirmed by magnetic domain observation using the Bitter method using magnetic fluid. Then, when the external magnetic field H is strengthened in the direction of the difficult magnetization axis to such a magnetically sensitive part (2),
The magnetization state is schematically shown in FIGS. 9A to 3 with solid line arrows for the magnetic thin film (5) and broken line arrows for the magnetic thin film (4) in FIGS. 9A to 9C. From the antiparallel magnetization state shown, the external magnetic field H causes the magnetization to rotate through the rotational magnetization process as shown in Figure 9B, and an even stronger external magnetic field causes the bimagnetic thin H odor ( 4)
and (5) are magnetized in the same direction. In this case, since the magnetization of both magnetic thin films (4) and (5) rotates within their planes, no domain wall is generated, and the generation of noise is avoided. In other words, both magnetic thin films (4) and (
Barkhausen noise caused by domain wall movement is avoided by setting the direction of the axis of difficult magnetization in 5) as the propagation direction of the magnetic flux.

Furthermore, the operation of the magnetic head having such a magnetic sensing portion (2) will be explained with reference to FIGS. 10 to 12. Figure 10~
Figure 12 shows the bimagnetic thin films (4) and (5) of the magnetically sensitive part (2).
) are shown schematically, and these magnetic thin films (4)
and (5) have easy magnetization axes in the directions shown by e and a in FIG. 10 in the initial state. A sense current is is then passed through these magnetic thin films (4) and (5). This energization causes bimagnetic thin films (
4) and (5), mutually opposite magnetic fields perpendicular to the current is are generated, which causes the magnetic layers FA (4) and (5) to
) are magnetized as shown by solid line and broken line arrows M1 and M2 in the figure. On the other hand, when a bias magnetic field H8 is externally applied to the magnetically sensitive part (2) in the direction along the current is, the bias magnetic field H causes the magnetic thin films (4) and (5
) is rotated by a required angle as shown by arrows Me and MB2 in FIG. The magnitude of the bias magnetic field Ha is selected so that the direction of magnetization given by the bias magnetic field Ha is approximately 45 degrees with respect to the direction of the current is. Incidentally, as described above, the bias magnetic field HB causes approximately 4% of the sense current i5.
The fact that high sensitivity and linearity can be obtained by providing magnetization of 5° is the same as in ordinary MR type magnetic heads.

In this state, as shown in FIG. 12, the signal magnetic field H
s rotates by angles θ1 and −θ1 in the direction along the sense current is, that is, in the clockwise direction of the magnetic needle.

As a result, if the magnetic ys films (4) and (5) are both MR magnetic thin films, a change in resistance will occur, but the change in resistance of this MR magnetic thin film is caused by a change in angle of θ. Since it is proportional to cos2 θ,
Now, assuming that the magnetizations M81 and MB2 of both magnetic thin films (4) and (5) in FIG.
), the increase or decrease in resistance matches. That is, if the resistance of one magnetic N film (4) increases, the resistance of the other magnetic thin film (5) also changes in the direction of increasing.

And the resistance change of these magnetic thin films (4) and (5),
That is, a resistance change occurs between the terminals t1 and t2 at both ends of the magnetic sensing part (2), and this resistance change can be detected as a voltage change between the terminals t1 and t2.

As described above, the MR magnetic sensing part (2) has a structure in which the first and second soft magnetic thin films (4) and (5) are stacked with the nonmagnetic thin film (6) interposed therebetween, so that bulk Although the Hausen noise is improved, in the present invention, the magnetic sensing part (2) is arranged in a direction perpendicular to the original direction of conduction of the sense current is in the front electrode (7), especially in the magnetic sensing part (2).
) is connected to the bias conductor (10
), the Barkhausen noise can be improved more reliably by selecting the same direction as the current direction.

To explain this, if the front electrode (7) and bias conductor (10) are arranged in the arrangement pattern shown in FIG. ) is set to 20 mA, and the distribution of magnetization M in each part of the magnetically sensitive part (2) is calculated as shown in FIG. 13. In this figure, the horizontal axis indicates the distance from the origin to the front end of the MR magnetic sensing part (2), and the vertical axis indicates the magnetization at each position, and each curve ( 131) to (135) are
The DC bias current 1b to the bias conductor (10) is set to 50 mA and 40 mA in the same direction as the current direction of the electrode (7), respectively.
, 30mA, 20mA, and 10mA, the curve (136) is the curve (137) when Ib = OmA.
(141') means that the current 1b is 10 mA in the opposite direction to the current direction of the electrode (7), -2On+A, -30 mA,
This is the case where the current was changed to -40mA and -50mA. As is clear from this, in addition to the original bias magnetic field from the bias conductor (10), the MR magnetic sensing part (2) has an electrode (
7) Magnetization (Ib=O
There is a curve (1'16)) when the magnetic field sensing part (2) is not in a --like bias magnetization state. For this reason, especially when Ib<0, that is, when arrows a and b in Fig. 1 are reversed, not only the magnetization state changes greatly in the north of the magnetically sensitive part (2), but also the direction of magnetization changes. An inverted portion occurs, resulting in the generation of domain walls and, therefore, Barkhausen noise. Furthermore, in the case of Ib<O, the overall output from the magnetic sensing part (2) has the disadvantage that the output depending on each part of the positive bias magnetization part and the negative bias magnetization part cancels out, resulting in a decrease in the output level. Furthermore, in the magnetically sensitive portion (2), a portion deviates from the optimum bias magnetization state occurs, causing asymmetry in the output waveform.

In contrast, as described above, in the present invention, the electrode (7) and the bias conductor (10) are energized in the same direction, a and b, so that reversal of magnetization is avoided, and the magnetically sensitive part In conjunction with the overlapping structure of the magnetic thin films (4) and (5), Barkhausen noise is reliably avoided, and especially, for example, near Ib = 30 m-A, the magnetically sensitive part (2)
Since a uniform magnetization state can be obtained over a wide range, it is possible not only to lower the output level but also to improve the asymmetry of the output waveform.

That is, looking at the output waveform, the heights of both the positive and negative output levels of the output waveform are h'', h'', as shown in Figure 4.
``'', a highly symmetrical waveform is obtained when h=h-, but if we simulate the case when a signal magnetic field is applied based on the results shown in Fig. 13, the curve in Fig. 5 (
51) and (52), and the directions a and b in FIG. 1 are the same.

There is an optimal Ib value where both h'' and h- agree well.Furthermore, Fig. 6 shows the actual measured values, and the curve (6
As shown in 1) and (62), the presence of a region where both positive and negative output levels are good (corresponding) at heights h" and h- of the signal waveform is seen when rb>o.

〔Example〕

An example of the present invention will be further described in detail with reference to FIGS. 1 and 2.

In this case, the MR sensing section (2) is provided on the base 1 (11).

The substrate +11 is made of, for example, Ni-Zn ferrite, An-
It is made of a magnetic substrate such as Zn-based ferrite. On the substrate (1), if this substrate (1) has conductivity, 5t0
A second insulating layer (11) is formed, a bias conductor (10) for generating a bias magnetic field Ha by energization is formed on this, and an insulating layer (11) is further formed on this. An MR magnetic sensing part (2) is formed thereon. This M
The R magnetic sensing part (2) has a surface that faces or faces the magnetic medium (
The bias conductor (10) is formed so as to extend in a direction perpendicular to this surface (3) with its front end facing the MR magnetic sensing part (2).
) or across the bias conductor (10) (not shown).

The magnetically sensitive part (2) is made by successively forming a first soft magnetic thin film (4), a non-magnetic thin film (6), and a second soft magnetic thin film (5) in one work step by sputtering or vapor deposition. That is, it can be formed using a sputtering device or a vapor deposition device having a sputtering source or a vapor deposition source for each material.

The non-magnetic thin film (6) is made of an insulating or conductive non-magnetic material such as 5i02+'', and its thickness is substantially equal to that between the two magnetic thin films (4) and (5) as described above. For example, a thickness of 20 is selected so that exchange interaction is hardly excited and coupling by interaction according to Coulomb's law, that is, magnetostatic coupling occurs.

At least one of the magnetic thin films (4) and (5) may be made of Fe, Ni+Co, or an alloy of two or more of these, as described above.

And electrodes (7) and (8) for passing the sense current is along the signal magnetic field given to the MR magnetic sensing part (2).
are electrically adhered to both ends of the magnetically sensitive part (2) so that a portion thereof is overlapped with each other. The part of the front electrode (7) (or the part attached to the magnetically sensitive part (2)) is arranged so that it is almost orthogonal to the original direction of the sense current is along the facing surface (3) or facing the magnetic medium. In other words, the terminals t1 and t2 are extended in the same direction as the current direction of the bias conductor (10), and are led out from the electrodes (7) and (8).

In addition, the bias conductor (10) is energized in the same direction as the current flow in the vicinity of the connecting portion of the electrode (7) with the magnetically sensitive portion (2), orthogonal to the sense current is to the magnetically sensitive portion (2). , the bias in the direction along the sense current is applies the field Hs to the magnetically sensitive part (2). tBl and tB2 indicate current-carrying terminals of this bias conductor (10).

Then, on the substrate (1), a non-magnetic or A magnetic upper substrate (14) is bonded.

In the above configuration, each layer, such as the insulating layer (11), the bias conductor (10), the electrodes (7) and (8), etc., is connected to each of the magnetic thin films (4) and (5) of the magnetically sensitive part (2). Similarly to the nonmagnetic thin film (6), each layer is formed by sputtering or vapor deposition, and can be formed into a desired pattern by photolithography.

In the above configuration, by moving the magnetic recording medium in a direction perpendicular to the paper plane in FIG. 1 while facing or facing the surface (3) facing the magnetic recording medium, Signal magnetic field H3 according to recording magnetization
is applied in the same direction as the sense current is of the MR magnetic sensing part (2), and a resistance change occurs in the magnetic sensing part (2) according to the change in this signal magnetic field H5, and this resistance change is caused by the sense current rs. By detecting the information, the recording on the magnetic recording medium can only be read.

In addition, the magnetic layer 11ii (4) or (5) of either one of the bimagnetic thin films (4) and (5) of the MR magnetic sensing part (2) is M
It can be composed of a magnetic thin film with almost no R effect, and in this case, as described above, the thickness etc. are selected so that the magnetic flux amounts of the ambiguous layers (4) and (5) match. Regarding the magnetic thin film that has almost no MR effect, the resistance between the electrodes (7) and (8) at both ends of this non-MR magnetic film is set so that the main part of the sense current flows through the magnetic thin film that has the MR effect. , FeCo51B has a large specific resistance so that it is sufficiently larger than that of the MR magnetic thin film.
CoZrNb series, CoZrNb series amorphous alloys or Fe
- It can be constituted by a high specific resistance and high permeability magnetic layer such as an Al-5i based so-called Sendust alloy. Mo permalloy or the like may be considered as a material that can be used for this high permeability magnetic layer with a small MR effect.

Of course, these materials can also be considered as materials for electrodes (7) and (8).

In the above example, the bias conductor (
10) is provided to apply an external magnetic field H to the magnetically sensitive part (2), but the arrangement position and pattern of the bias conductor (10) can take various configurations, for example, a multilayer conductor (10). It can also be a structure.

Regarding the magnetic sensing part (2), for example, as shown in FIG. connected by a common electrode (7), with a respective electrode (8) at each rear end.
It can also be applied when adopting a configuration in which A) and (8B) are arranged.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to configure an MR type magnetic head that can reliably avoid Barkhausen noise, has a high output level, and has excellent characteristics of obtaining output with excellent symmetry. .

[Brief explanation of the drawing]

FIG. 1 is an enlarged plan view of an example of the magnetoresistive magnetic head according to the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is an explanatory diagram of the magnetic sensing part, and FIG. 4 is an explanation of the output waveform. Figures 5 and 6 are diagrams showing the calculation results and actual measurement results of the symmetry of the output waveform, respectively, and Figure 7 is a plan view showing another example of the magnetically sensitive part.
Figure 8 is a diagram showing the magnetic domain structure of a single-layer magnetic thin film, Figure 9A-
C is an explanatory diagram of the magnetization state of the magnetic sensing part due to the external magnetic field, No. 10
12 to 12 are explanatory diagrams of the operation of the magnetic head, and FIG. 13 is a magnetization distribution curve diagram of the magnetically sensitive portion. (1) is the substrate, (2) is the magnetically sensitive part, (4) and (5) are the first and second soft magnetic thin films, (6) is the nonmagnetic thin film, (
7) and (8) are electrodes, and (10) is a bias conductor.

Claims (1)

[Claims] A magnetoresistive magnetic sensing part in which a pair of soft magnetic thin films, at least one of which has a magnetoresistive effect, are laminated with a nonmagnetic thin film interposed therebetween, and a sense current is supplied to the magnetoresistive magnetic sensing part. The electrode has a bias conductor for applying a bias magnetic field to the magnetoresistive sensing section, and the electrode attached to the front end of the magnetoresistive sensing section has a bias conductor for applying a bias magnetic field to the magnetoresistive sensing section. A magnetoresistive magnetic head characterized in that a direction of current conduction is selected to be substantially orthogonal to a sense current direction, and a direction of current conduction of the front electrode and a direction of current conduction of the bias conductor are selected to be the same direction.