JPH0572642B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a ferromagnetic magnetoresistive element (hereinafter referred to as "magnetoresistive element") that reads magnetic information written on a magnetic storage medium by using the so-called magnetoresistive effect. A magnetoresistive head (hereinafter referred to as MR element) equipped with
(referred to as MR head).

(Prior art and its problems) In recent years, MR heads have attracted attention as a device that greatly contributes to improving the recording density in magnetic recording.

As is well known, when an MR element is used as a highly efficient reproducing head that exhibits a linear response to a signal magnetic field from a magnetic storage medium, the angle formed by the sense current I flowing through the MR element and the magnetization M of the MR element is A biasing means is required to set it to a predetermined value. or,
In response to an increase in recording density, there is a need for means for increasing the maximum component resolution, and various studies are being conducted.
In particular, the decrease in reproduction resolution at high recording densities is explained as follows. Now, the MR element 1 shown in FIG. 1 (formed in a stripe shape with length L, width h, and thickness _tM ) is supplied with a sense current I in the direction of length L, and magnetized M and Θ by an appropriate bias magnetic field. _b ) and the magnetic storage medium 2, the signal magnetic field H _S from the magnetic storage medium 2 is sufficiently applied in the width h direction of the MR element 1 at low recording density, and the MR The entire element 1 contributes to the resistance change and a large reproduction output can be obtained. However, at high recording densities, a sufficient signal magnetic field H _S cannot reach the MR element 1, and only the region closest to the magnetic storage medium 2 contributes to resistance changes, resulting in a significant drop in reproduction output. . Furthermore, the magnetization M of the MR element 1
The bias condition of is generally set to be optimal at the center of the width h (that is, it is set so that Θ _b is 45 degrees), but the magnetic In the region closest to the storage medium 2, due to the demagnetizing field in the direction of the width h of the MR element 1, an ideal bias state was not realized (ie, Θ _b <<45 degrees), reducing the reproduction sensitivity.

In order to solve the above-mentioned drawbacks of the MR head, in Japanese Patent Application Laid-Open No. 57-109121, the magnetization M is saturated at the center of the width h of the MR element 1 (that is, Θ _b is set to 90 degrees), so that the head is closest to the magnetic storage medium 2. A method is disclosed to set the bias state of the region to the highest (ie, Θ _b 45 degrees). According to this method, only the region closest to the magnetic storage medium 2 contributes to resistance change from low to high recording densities.
Relatively good recording density characteristics can be obtained.

However, in order to realize such a bias state, the bias magnetic field applied to the MR element 1 must be set to be at least higher than the demagnetizing field in the width h direction of the MR element 1. For example, using permalloy with saturation magnetization M=800emu/cc as the MR element 1,
When the dimensions are set to t _M =0.05 μm and h = 5 μm, the demagnetizing field (4πMt _M /h) is about 100, and the bias magnetic field is required to be 100 to 200. As a result, such a large bias magnetic field demagnetizes the magnetization information Mr of the magnetic storage medium 2, resulting in a magnetic storage system with poor reliability.

(Object of the Invention) An object of the present invention is to provide a magnetoresistive head that can improve the characteristics at high recording density without causing such drawbacks.

(Structure of the Invention) According to the present invention, a magnetoresistive head having a structure in which a magnetoresistive element including a ferromagnetic thin film and two electrodes for supplying a sense current to the magnetoresistive element are connected. A magnetoresistive head is obtained in which the spacing between the two electrodes is smaller at the part closest to the magnetic storage medium than at the part furthest from the magnetic storage medium.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-described configuration. That is, in the present invention, MR
Because the distance between the two electrodes connected to the element is set small in the area closest to the magnetic storage medium,
The sense current that flows into the MR element via the two electrodes flows non-uniformly in the width direction of the MR element, and is particularly concentrated in the region closest to the magnetic storage medium. Therefore, the resistance change in the region closest to the magnetic storage medium contributes most to the reproduction output. That is, since the region that contributes most to the resistance change is always obtained as the reproduction output when the MR element has a high recording density, it is possible to obtain a substantially uniform reproduction output over a wide range of recording densities.

Furthermore, the magnetic field generated by the sense current can be used directly or indirectly through other magnetic materials.
In the MR head that realizes the bias state of the MR element, it is possible to obtain a bias magnetic field proportional to the sense current, thereby realizing a bias state in which the region of the MR element closest to the magnetic storage medium has maximum sensitivity. This corrects the decrease in reproduction output at high recording density, and provides good recording density characteristics.

Hereinafter, configuration examples of the present invention will be described in further detail with reference to the drawings.

FIG. 2 is a schematic perspective view showing the first example of the present invention, in which electrodes 3 and 4 for supplying the sense current I are provided on both sides of the short fence-like MR element 1 in the length direction. They are connected at an angle with respect to the width h direction. The spacing between the electrodes 3 and 4 is set to have a value of W ₂ in the region where the MR element 1 is close to the magnetic storage medium 2 and a value of W ₁ in the region farthest from the magnetic storage medium 2, and to satisfy the relationship W ₁ > W ₂ . has been done.

The MR element 1 is made of, for example, a NiCo-based alloy, a NiFe-based alloy (permalloy), etc., and its dimensions are selected to have a thickness of several hundred angstroms to several thousand angstroms, and a width h of several μm to several tens of μm. Further, for the electrodes 3 and 4, a material having a lower specific resistance than that of the MR element 1, such as An, Al, or Cu, is selected.

The magnetization M of the MR element 1 is set relative to the sense current I by a suitable means (not shown) such as a permanent magnet.
It is set at a predetermined angle Θ _b .

With this configuration, via the electrodes 3 and 4,
The sense current I supplied to the MR element 1 is concentrated in the region where the electrode spacing is the smallest, that is, in the region closest to the magnetic storage medium 2.

FIG. 3 shows the current distribution in the width direction of this MR element 1. In Figure 3, the zero scale on the horizontal axis is
The side where the MR element 1 is closest to the magnetic storage medium 2, h
indicates the farthest side, and the current density on the vertical axis is a value normalized by the current density on the side closest to the magnetic storage medium 2. Also, as a parameter
2h/W ₁ −W ₂ is taken.

From FIG. 3, it is understood that when the width h of the MR element 1 is constant, the larger the value of W ₁ - W ₂ is, the more the sense current I is concentrated on the side closest to the magnetic storage medium 2. .

As a result, the resistance change in the region of the MR element 1 closest to the magnetic storage medium 2 contributes most to the reproduction output. That is, since the region with the largest resistance change is always obtained as the reproduction output when the MR element 1 has a high recording density, it is possible to obtain a good reproduction output over a wide range of recording densities.

In the first embodiment, the bias state of the MR element was uniquely determined by an external magnetic field, but in the present invention, the bias state of the MR element is determined using a sense current. Most effective against MR heads.

An example of an MR head having such a configuration will be described below.

FIG. 4 is a schematic perspective view showing a second example of the present invention.

In the figure, a bias conductor 5 made of a non-magnetic conductive film (for example, Ti, Mo, Ta, Cr, etc.) is used for the MR element of the first example explained using FIGS. 2 and 3. It has a laminated structure with a thickness of several hundred Å to several thousand Å.

In such a configuration, the distance between the electrodes 3 and 4 is
If the film thickness is sufficiently larger than that of the MR element 1 and the bias conductor 5, the sense current I supplied from the electrodes 3 and 4 is divided into the MR element 1 and the bias conductor 5 according to their specific resistances and film thicknesses. The sense current shunted to the bias conductor 5 passes through the film surface of the MR element 1 and generates a bias magnetic field H _b in the direction of the width h.
The magnetization M of the MR element 1 is rotated by an angle Θ _b with respect to the sense current. Furthermore, since the sense current shunted into the bias conductor 5 is distributed in the width h direction as shown in FIG.
H _b is generated, and Θ _b also increases accordingly.
FIG. 5 shows the distribution of Θ _b in the width h direction of the MR element 1. For reference, the distribution of Θ _b in a conventional example in which the sense current is uniformly distributed in the width h direction is also shown by a broken line.

As is clear from FIG. 5, in the conventional example, the maximum value of Θ _b is obtained at the center of the width h, whereas in this example, the maximum value of Θ _b is shifted to the side closer to the magnetic storage medium 2. There is. That is, in this example, it is possible to optimally set the bias state (preferably Θ _b =45°) in the region that contributes the most to reproduction output at high recording density.

Therefore, with this configuration, at high recording density
Compared to the first embodiment, the resistance change in the region of the MR element 1 closest to the magnetic storage medium 2 contributes the most to the reproduction output, and the resistance change has the maximum sensitivity to the signal magnetic field H _S. Furthermore, good recording density characteristics can be obtained.

In FIG. 4, a bias magnetic field H _B is applied to the MR element 1 by a sense current that is shunted to the bias conductor 5, but as shown in the cross-sectional view of FIG. It may be laminated.
In this configuration, the sense current I is divided into the MR element 1, the bias conductor 5, and the conductive ferromagnetic thin film 6 with a distribution such that the maximum current density is on the side closer to the magnetic storage medium 2. The sense currents I ₂ and I ₃ shunted into the bias conductor 5 and the conductive ferromagnetic thin film 6 provide a bias magnetic field similar to that shown in FIG.
This has the effect of greatly reducing the demagnetizing field in the direction. Therefore, the bias state shown in FIG. 5 can be achieved with a smaller sense current than the MR head having the configuration shown in FIG.

The conductive ferromagnetic thin film 6 is preferably an amorphous soft magnetic material that has a small magnetoresistive effect and a high specific resistance. Also, as a conductive ferromagnetic thin film 6
As disclosed in No. 26510, a permalloy film or the like having exactly the same characteristics as the MR element 1 may be used. In this case, the conductive ferromagnetic thin film 6 also causes a resistance change in response to the signal magnetic field H _S and contributes to signal reproduction.

Furthermore, similar to the example explained using FIGS. 4 and 6, in order to realize a bias state in which the region of the MR element closest to the magnetic storage medium has maximum sensitivity, the configuration shown in FIG. 7 is used. It may be an MR head.

FIG. 7 shows a device equipped with a magnetic shield made of a high magnetic permeability magnetic material disclosed in Japanese Patent Application Laid-Open No. 50-59023,
FIG. 2 is a sectional view of a magnetically shielded MR head to which the present invention shown in FIG. 2 is applied to the MR element portion.

In the figure, SiO ₂ and Al ₂ O ₃ are placed on both sides of MR element 1.
The magnetic shields 7 and 8 are connected via insulating layers such as
It is arranged in parallel with the MR element 1 with an interval of G ₁ and G ₂ . With this configuration, the sense current I flowing in the width h direction of the MR element 1 with a distribution as shown in FIG. Magnetize. Among the magnetized magnetic shields 7 and 8, the most MR element 1
magnetic shield in close proximity to (for example, in Figure 7
Since G ₂ > G ₁ , the magnetic shield 7) applies the strongest bias magnetic field to the MR element 1.
bias the magnetization M of . of the bias magnetic field
Since the distribution within the MR element 1 corresponds to the distribution of the sense current I, a bias state similar to that shown in FIG. 5 is realized. In order to make the above-described effects more pronounced, it is desirable that the difference between G ₂ and G ₁ be larger. In an extreme case, either G ₂ or G ₁ may have an infinite size, that is, the MR element 1 may have a magnetic shield on only one side.

Although the configuration examples of the present invention have been described above, the electrodes shown in the present invention are not limited to the structure that extends linearly in the width direction of the MR element, as shown in FIGS. 2 and 4. , it may have a configuration that spreads out in a curved shape, and various modifications and changes can be made without departing from the gist of the present invention.

In the present invention, the track width on the magnetic storage medium (width of the area where magnetic information is written in the longitudinal direction of the MR element) is smaller than the electrode spacing on the side of the MR element closest to the magnetic storage medium. Preferably small. This is effective in minimizing the resistance change in the region on the MR element farthest from the magnetic storage medium at low recording densities.

(Effects of the Invention) As explained above, in the present invention, since the spacing between the electrodes connected to the MR element is set smaller on the side closer to the magnetic storage medium, the resistance change is the largest when the MR element has a high recording density. It is possible to obtain the contributing region as the reproduction output, and also to realize a bias state in which this region has the maximum sensitivity.It is extremely easy to achieve this, without demagnetizing the magnetic storage medium, and for a wide range of recording densities. Uniform playback output can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a conventional magnetoresistive head, FIG. 2 is a schematic perspective view showing a first configuration example of the present invention, and FIG. 3 is a graph showing the distribution of sense current flowing through the magnetoresistive head. , FIG. 4 is a schematic perspective view showing a second configuration example of the present invention, FIG. 5 is a graph showing the bias state of the magnetoresistive head, and FIG. 6 is a sectional view showing a third configuration example of the present invention. , FIG. 7 is a sectional view showing a fourth configuration example of the present invention. In the figure, 1... Magnetoresistive element (MR element), 2... Magnetic storage medium, 3, 4... Electrode, 5
...bias conductor, 6...conductive ferromagnetic thin film,
7, 8...indicate magnetic shields, respectively.

Claims (1)

[Scope of Claims] 1. In a magnetoresistive head having a structure in which a magnetoresistive element including a ferromagnetic thin film and two electrodes for supplying a sense current to the magnetoresistive element are connected, an interval between the two electrodes is provided. A magnetoresistive head characterized in that the portion closest to the magnetic storage medium is smaller than the portion furthest from the magnetic storage medium. 2. The magnetoresistive head according to claim 1, wherein the magnetoresistive element has a structure in which a nonmagnetic conductive thin film and a ferromagnetic thin film are laminated. 3. The magnetoresistive head according to claim 1, wherein the magnetoresistive element has a structure in which a ferromagnetic thin film, a nonmagnetic conductor thin film, and a conductive ferromagnetic thin film are laminated in this order. 4. The magnetoresistive head according to claim 3, wherein the ferromagnetic thin films sandwiching the nonmagnetic conductive thin films are made of the same material. 5. The magnetoresistive head according to claim 3, wherein the conductive ferromagnetic thin film is an amorphous soft magnetic material. 6. The magnetoresistive head according to claim 1, wherein the magnetoresistive element is provided with a magnetic shield made of a high permeability magnetic material via an insulating layer.