JP2979966B2 - Magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head and, more particularly, to a magnetic head capable of reproducing a high density perpendicular magnetic recording signal with high efficiency.

[0002]

2. Description of the Related Art In general, as a next-generation high-density recording method which replaces in-plane recording in which the magnetization direction is set in the in-plane horizontal direction,
Research and development on perpendicular magnetic recording in which the magnetization direction is set in the thickness direction of the medium has been actively conducted. On the other hand, as for a magnetic head, a high-density and high-output can be obtained, and therefore, a magneto-resistive element-type magnetic head utilizing a magneto-resistive effect has been attracting attention as a reproducing head, and some magnetic heads have already been put to practical use. I have.

As a magnetoresistive element type magnetic head for recording and reproducing signals from a perpendicular magnetic recording medium, for example, a plate-shaped magnetoresistive element is laminated in a two-layer structure, and a current flows in one direction in the entire element. , A bias magnetic field is applied in parallel to the other magnetoresistive element in the opposite direction,
There has been proposed a method of detecting, as a signal, a difference between changes in magnetization of two layers of magnetoresistive elements caused by a magnetic field generated from a magnetic recording medium (see Japanese Patent Publication No. Sho 63-29327).

In this case, when the magnetic head straddles the magnetization reversal portion of the magnetic recording medium, a change in magnetization occurs and an output is produced, and the isolated reproduction waveform becomes a single peak wave. Therefore, since the waveform of the in-plane recording medium in the magnetic recording / reproducing apparatus currently used is the same as the waveform when reproduced by the ring type magnetic head, the magnetic head of the magnetoresistive element type is used for the magnetic recording / reproducing apparatus. In this case, there is an advantage that a special waveform shaping operation becomes unnecessary.

[0005]

By the way, in the conventional magnetic head using the above-described magneto-resistance effect element, a pair of the magneto-resistance effect element and the magnetic recording medium laminated with an intermediate layer interposed therebetween. There is a problem that the leakage of magnetic flux in the magnetic circuit formed between them is relatively large and the reproduction output is relatively small.

Further, a large current is required to obtain a sufficiently large bias magnetic field. Increasing the current in such a manner increases power consumption, increases the size of a power supply device, increases noise due to heat generation, and the like. This causes a problem such as destruction of the element.

[0007] The present invention focuses on the above problems,
The present invention has been made to solve this problem effectively, and an object of the present invention is to provide a magnetic head capable of reducing the leakage magnetic flux and improving the reproduction efficiency.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a pair of magnetoresistive elements and a pair of magnetoresistive elements in a running direction of a magnetic recording medium.
An intermediate layer interposed therebetween, and a front side opposite to the magnetic recording medium.
A return connecting between the ends of the pair of magnetoresistive elements
In a magnetic head comprising a core , the intermediate layer is a conductive layer.
It is composed of a ferromagnetic or antiferromagnetic material having electrical conductivity .

[0009]

According to the present invention, the magnetic circuit is constituted by the recording medium, the magneto-resistive element of the magnetic head, and the return core when reproducing data from the magnetic recording medium. Therefore, since the end of the magnetoresistive element opposite to the recording medium is connected by the return core, the leakage magnetic flux is extremely reduced, and the reproduction efficiency can be greatly improved.

In particular, when a recording medium having a soft magnetic underlayer provided below the recording layer is used, this soft magnetic underlayer forms a part of a magnetic circuit, and furthermore, the leakage magnetic flux is increased. Can be reduced, so that the reproduction efficiency can be further improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic head according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing a magnetic head according to the present invention, and FIG. 2 is a II-II in FIG.
FIG. 3 is a diagram showing a relationship between a recording layer of a recording medium and a reproduced waveform.

As shown in the figure, the magnetic head 1 has a pair of plate-shaped magnetoresistive elements 2, 2, which are made of, for example, an insulating material or a magnetoresistive effect. The elements are sandwiched in the running direction of the magnetic recording medium 4, that is, in the X direction in the drawing, via an intermediate layer 3 made of a conductive material having a relatively large specific resistance to the elements.

The pair of magnetoresistive elements 2,
2 is connected between the opposite ends of the recording medium 4 to form, for example, Ni-Fe (Permalloy), Co-Zr-Nb, Co-
A return core 5 made of a soft magnetic material such as Zr-Ta is provided, thereby forming a closed loop that sequentially passes through one magnetoresistive element 2, the recording medium 4, the other magnetoresistive element 2, and the return core 5. A magnetic circuit is formed.

Electrodes 6 are provided on both ends of the magnetoresistive elements 2, 2 in a direction parallel to the plane of the recording medium 4.
6 are connected to these magnetoresistive elements 2, 2
And a bias / sense current I flowing in the same direction. Thus, the two magnetoresistance effect elements 2, 2
By flowing a bias and sense current in the same direction through the elements, magnetic fields generated by the action of the bias and sense current passing through the respective elements 2 and 2 are formed in the respective elements so as to be directed in mutually opposite directions. A bias magnetic field H is generated in the magnetic circuit in one direction. In FIG. 1, the bias / sense current flows upward in the vertical direction of the drawing.

In this case, when a conductive material is used for the intermediate layer 3, only one pair of electrodes 6 may be provided as shown in FIG. 2, but an insulating material is used for the intermediate layer 3. In this case, two pairs of electrodes 6, 6 are provided at both ends of each of the magnetoresistive elements 2, 2, respectively.
When a conductive material is used as the intermediate layer 3, it can function as a shunt film for generating a strong bias magnetic field. Further, as the intermediate layer 3, a ferromagnetic material or an antiferromagnetic material such as FeMn or CoMn, which magnetically interacts with the magnetoresistive elements 2 and 2 among conductive materials, can be used. Thus, the motion of the domain wall of the magnetoresistive element can be suppressed, and Barkhausen noise can be reduced.

[0016] On the other hand, recorded as the medium 4, for example, disc-shaped glass or disc-shaped recording medium of the perpendicular recording system having a recording layer 8 of the perpendicular magnetic recording on the non-magnetic group body 7 made of aluminum or the like 4, a soft magnetic underlayer 9 between the nonmagnetic substrate 7 and the recording layer 8 as shown in FIG.
In the case of using a recording medium in which a soft magnetic underlayer is interposed, the soft magnetic underlayer 9 acts so as to constitute a part of the magnetic circuit, so that it is possible to further suppress the leakage magnetic flux.

Next, the operation of the embodiment configured as described above will be described. First, during reproduction, the electrodes 6, 6
Through the pair of magnetoresistive elements 2 and 2 in the same direction (FIG. 1).
The bias and sense current I flowing in the direction perpendicular to the plane of the drawing (upward in the drawing) causes a bias magnetic field H that flows in the counterclockwise direction in FIG. In the closed-loop magnetic circuit formed by the resistance effect elements 2 and 2, the return core 5 and the recording medium 8, a bias magnetic field is generated in the counterclockwise direction in the drawing, and the elements 2 and 2 are directed in opposite directions. A magnetic field is generated.

[0018] By relatively moving the magnetic head 1 to the recording medium 4 in the horizontal direction in this state, the upper in accordance with the change direction of magnetization when the magnetic head 1 is straddling the magnetization reversal portion of the serial Rokuso 8 A downward or upward projection output is obtained (see FIG. 3). The arrow in the recording layer 8 indicates the direction of magnetization.

Here, a return core 5 made of a soft magnetic material is joined to the end (upper end in FIG. 1) of the magnetoresistive elements 2 and 2 on the side opposite to the recording medium 4 , so that the A strong closed loop with low resistance can be formed,
The magnetic flux generated from the recording layer 8 is less likely to leak on the way, and the magnetic flux density By in each of the magnetoresistive elements 2, 2 is increased, so that efficient reproduction can be performed.

Such a function of reducing the leakage magnetic flux can be exerted greatly only by providing the return core 5, and therefore, as the recording medium 4, the reproducing efficiency is improved for both the medium provided with the soft magnetic underlayer 9 and the medium not provided. be able to. However, when the soft magnetic underlayer 9 is provided in the recording medium 4 as shown in FIG. 1, this portion functions as a magnetic path of the magnetic circuit, so that a stronger closed loop can be formed, and thus the reproduction efficiency can be further improved. Can be improved.

Further, since the leakage magnetic flux can be greatly reduced as described above, a sufficiently large bias magnetic field can be generated even with a small bias and sense current I, and accordingly, power consumption is correspondingly reduced. It is possible to reduce it.

When a conductive material is used for the intermediate layer 3 instead of an insulating material, this layer also functions as a shunt film for generating a bias magnetic field, and can generate a stronger bias magnetic field H. In addition, only one pair of electrodes 6 for flowing the bias and sense current I to each of the elements 2 and 2 is required, and this structure can be simplified.

Further, each of the elements 2, 2
By using a ferromagnetic material or an antiferromagnetic material having a magnetic interaction with the magnetic field, the motion of the domain wall of the magnetoresistive element can be suppressed, and Barkhausen noise can also be suppressed.

Next, in order to confirm the operation and effect of the present invention, computer simulation was performed by magnetic field analysis using the finite element method, and the results are shown. The simulation conditions are as follows.

Recording layer 8: Hc = 1500 Oe, Bs
= 6500 G, thickness = 0.05 μm Soft magnetic underlayer 9: Bs = 12000 G, permeability μ =
2000, film thickness = 0.5 μm ・ Magnetoresistance effect element 2: Bs = 9000 G, permeability μ
= 1000, film thickness = 0.05 μm, height h = 3 μm, specific resistance = 1 ・ Intermediate layer 3: film thickness g = 0.2 μm, specific resistance = 5 ・ Return core 5: Bs = 12000 G, magnetic permeability μ =
1000 Spacing d: 0.05 μm Bias / sense current I: 40 mA (bias magnetic field H
(Only when calculating) ・ Number of element divisions: 1000 to 3000

First, the simulation results of the regeneration efficiency will be described. FIG. 4 is a graph showing the recording density characteristics of the reproduction efficiency with respect to the presence or absence of the return core and the soft magnetic underlayer. The reproduction characteristic is a value obtained by integrating in the height direction the magnetic flux density By in the y direction of the inside of the magnetoresistive elements 2 and 2 due to the magnetic flux from the recording medium 4: difference of ∫Bydy: Δ∫Bydy.
Defined. In the figure, curve A represents the case where neither the soft magnetic underlayer nor the return core is provided, curve B represents the case where the soft magnetic underlayer is provided and no return core is provided, and curve C represents the case where both the soft magnetic underlayer and the return core are provided. Shown respectively.

[0027] This graph as is clear from, it is possible to improve the regeneration efficiency I by the the use of the recording medium 4 having a soft magnetic underlayer 9 to some extent (curve A, B
It is found that the provision of the return core can form a strong closed loop of the magnetic circuit, thereby greatly improving the reproduction efficiency (see curve C).

FIG. 5 is a graph showing the relationship between the magnetic permeability μ of the soft magnetic underlayer and the reproduction efficiency when no return core is provided. As is apparent from this graph, if the permeability μ is about 10 or more of the soft magnetic underlayer 9 can exhibit a sufficient effect on the regeneration efficiency, therefore, lower when using the magnetic head 1 of this embodiment By combining a recording medium having a magnetic permeability μ of the underlayer of about 10 or more, the reproduction efficiency can be remarkably improved. Also, since the return core 5 provided on the magnetoresistive elements 2 and 2 has the same effect as the underlayer, its magnetic permeability μ is preferably set to about 10 or more. The return core 5 and the soft magnetic underlayer 9
The film thickness may be made sufficiently large by judging from the dimensions of the entire magnetic head, spacing d, film thickness of the perpendicular recording layer, and the like.

Next, the optimum bias and sense current value I _opt
The simulation results of the bias electric field will be described in order to study. Table 1 shows the optimum bias and sense current value I _opt flowing through the entire device when the presence or absence of the soft magnetic underlayer and the return core are appropriately combined. I
_opt is defined as a current at which the vertical bias magnetic field Hy at the center of the magnetoresistive element becomes 800 A / m, which is の of the anisotropic magnetic field Hk of the magnetoresistive element. Further, R in Table 1 is the specific resistance of the intermediate layer with respect to the magnetoresistive element, and ∞ means that the intermediate layer is an insulator.

[0030]

[Table 1]

It is apparent from Table 1 that the provision of the return core 5 makes it possible to make the current value I _opt extremely small irrespective of the presence or absence of the soft magnetic underlayer 9. It was found that a magnetic field could be obtained. In particular, it has been found that the current value can be significantly reduced by combining the recording medium 4 having the soft magnetic underlayer 9 .

When a conductive material having a specific resistance of about five times that of the magnetoresistive element is used as a material of the intermediate layer interposed between the pair of magnetoresistive elements, a shunt film for generating a bias electric field is used. Therefore, the current value I _opt can be further reduced, and the efficiency can be improved. In order to sufficiently exhibit the function as the shunt film, the value of the specific resistance is appropriately determined depending on the MR characteristics, the film thickness, and the like.

[0033]

As described above, according to the magnetic head of the present invention, the following excellent functions and effects can be exhibited. Since one end of the pair of magnetoresistive elements is connected by a return core, a strong closed-loop magnetic circuit can be formed. Therefore, the leakage magnetic flux can be greatly reduced, thereby greatly improving the reproduction efficiency. it can. Further, since the leakage magnetic flux can be reduced as described above, the current for generating the necessary bias magnetic field can be reduced, and the power consumption can be reduced accordingly. Change
The use of a ferromagnetic or antiferromagnetic material for the intermediate layer
The movement of the domain wall of the magnetoresistive effect element can be suppressed.
The magnetic head, since Barkhausen noise can be suppressed.
The S / N ratio of the gate can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a magnetic head according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a diagram showing a relationship between a recording layer of a recording medium and a reproduced waveform.

FIG. 4 is a graph showing a recording density characteristic of a reproduction efficiency with respect to a recording density of a reproduction efficiency with or without a return core and a soft magnetic underlayer.

FIG. 5 is a graph showing the relationship between the magnetic permeability of the soft magnetic underlayer and the reproduction efficiency when no return core is provided.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic head, 2 ... Magnetoresistance effect element, 3 ... Intermediate layer,
4 ... magnetic recording medium, 5 ... return core, 6 ... electrode, 7 ...
Nonmagnetic substrate, 8: recording layer, 9: soft magnetic underlayer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-129007 (JP, A) JP-B-63-29327 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/39

Claims (1)

(57) [Claims] 1. A pair of magnetoresistive elements, between a pair of magnetoresistive elements in a running direction of a magnetic recording medium.
And an intermediate layer interposed in the magnetic recording medium.
A return cable that connects between the ends of a pair of magnetoresistive elements
In the magnetic head comprising:
A magnetic head comprising a ferromagnetic or antiferromagnetic material having properties .