JPS60234213A - Magneto-resistance effect head - Google Patents

Abstract

PURPOSE:To secure an even output of reproduction by decreasing the space between both electrodes connected to a magneto-resistance effect MR element at the side close to a magnetic recording medium and therefore defining an area contributing to the smallest change of resistance as a reproduction output. CONSTITUTION:The space between electrodes 3 and 4 connected to an MR element 1 is decreased at an area close to a magnetic recording medium 2. Therefore a sense current flowing to the element 1 via electrodes 3 and 4 becomes uneven in the width direction of the element 1 and is concentrated at the area close to the medium 2. The change of resistance of said area contributes most to the reproduction output. Thus it is possible to secure easily an even reproduction output to a wide range of recording density without demagnetizing the medium 2. Furhtermore a bias current is obtained in proportion to the sense current in order to secure a bias state where the area close to the medium 2 has the maximum sensitivity. In this way, the reduction of the reproduction output is compensated in a high recording density mode and the satisfactory recording density characteristics are obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a ferromagnetic magnetoresistive element (hereinafter referred to as "ferromagnetic magnetoresistive element") that reads out magnetic information written in a magnetic storage medium by utilizing the so-called magnetoresistive effect. The present invention relates to a magnetoresistive head (hereinafter referred to as an MR head) equipped with a magnetoresistive head (hereinafter referred to as an 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 through which MR hydrogen atoms flow and the MR hydrogen element magnetization M is A biasing means is required to set it to a predetermined value. Furthermore, in response to the increase in recording density, there is a need for means for increasing the reproduction resolution, and numerous studies are being made.

In particular, the decrease in reproduction resolution at high recording densities is explained as follows. Now, the MR element 1 (length L
, width, thickness tM, and length L.
At low recording density, the signal magnetic field H8 from the magnetic storage medium 2 is , are sufficiently applied in the width direction of the MR element 1, and the entire MR element 1 contributes to the change in resistance, resulting in a large reproduction output. However, at high recording density,
It is said that a sufficient signal magnetic field H8 cannot reach the MR element 1, and only the region closest to the magnetic storage medium 2 contributes to the resistance change, resulting in a significant drop in reproduction output. Furthermore, the bias state of the magnetization M of the MR element 1 is generally set to be optimal at the center of the width (i.e., θb
However, in the region closest to the magnetic storage medium 2 VC, which contributes the most to the resistance change at high recording density, due to the demagnetizing field in the width direction of the MR element 10, the ideal bias The state is not realized (i.e. θb(
45 degrees), which lowered the playback sensitivity.

In order to solve the above-mentioned drawbacks of the MR head, Japanese Patent Laid-Open No. 57
-109121, the magnetization M is saturated at the center of the width of the MR element 1 (i.e., θb": set to 9 degrees), and the bias state of the region closest to the magnetic storage medium 2 is set to the maximum (i.e., θb"l). : '45 degrees) is disclosed. According to this method, only the region closest to the magnetic storage medium 2 contributes to resistance change over a range from low recording density to high recording density, so relatively good recording density characteristics can be obtained.

However, in order to realize such a bias state, M
The bias magnetic field applied to the R element 1 must be set at least higher than the demagnetizing field in the width direction of the MR element 1. For example, as MR$1, saturation magnetization M-800emu
/cc Permalloy is used, and its dimensions are tu-=0
．． If the setting is 0.05 pm and h=5 pm, Mr 2 will be demagnetized, resulting in a magnetic storage system that is not reliable.

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

(Structure of the Invention) According to the present invention, 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, A magnetoresistive head is obtained in which the distance 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-mentioned configuration. That is, in the present invention, since the interval between the two electrodes connected to the MR hydrogen element is set small in the region closest to the magnetic storage medium, the sense current flowing through the MR hydrogen element via the two electrodes is smaller than the MR hydrogen element. The hydrogen atoms flow non-uniformly in the width direction, and are 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 1viR element has a high recording density, it is possible to obtain a reproduction output that is almost uniform over a wide range of recording densities.

Furthermore, in an MR head that achieves an MR hydrogen bias state by directly utilizing the magnetic field generated by the sense current or indirectly through another magnetic material, it is possible to obtain a bias magnetic field proportional to the sense current. As a result, a bias state is realized in which the region closest to the MR hydrogen magnetic storage medium has maximum sensitivity. This corrects the decrease in reproduction output at high recording density, and provides good recording density characteristics.

6- 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 a first example of the present invention, in which electrodes 3 and 4 for supplying a sense current (1) are installed at both ends of the short fence-like MR element (1) in the length direction of the MR element (1). They are connected at an angle in the width direction. The spacing between the electrodes 3 and 40 is W2 in the region where the MR element 1 is close to the magnetic storage medium 2;
The farthest region has a value of Wl, and is set so as to satisfy the relationship "+>W".

For the MR element 1, a NiCo alloy, a NiFe alloy (permalloy), or the like is selected, and its dimensions are selected such that the thickness ranges from several hundred Å to several thousand Å, and from several μm to several tens of pm. Further, the electrodes 3 and 4 are selected from materials having lower specific resistance than the MR element 1, such as An, AI, Cu, etc.

The magnetization M of the MR element l is set at a predetermined angle θb with respect to the sense current I by a suitable means (not shown) such as a permanent magnet.
is set to .

With this configuration, the sense current (2) supplied to the MR element 1 via the electrodes 3 and 4 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 resistor l. In FIG. 3, the zero scale on the horizontal axis indicates the side where the MR element l is closest to the magnetic storage medium 2, and h indicates the farthest side,
The current density on the vertical axis is normalized by the current density on the side closest to the magnetic storage medium 2.

From FIG. 3, when the width of the MR element 1 is constant, Wt
It is understood that the larger the value of -W, the more the sense current I concentrates 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. In other words, in the first embodiment, since the region with the largest resistance change is always obtained as the reproduction output when the MR probe 1 has a high recording density, good reproduction output can be obtained over a wide range of recording densities. , 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 most effectively determined for an MR head using a sense current. It is.

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, the first
For the MR element of the example, a nonmagnetic conductor thin film (for example, T
It has a structure in which bias conductors 5 made of (i, Mo, Ta, Cr, etc.) are laminated with a thickness of several hundred times to several thousand times.

In such a configuration, if the distance between the electrodes 3 and 40 is sufficiently larger than the film thickness of the MR element 1 and the bias conductor 5, the sense current I supplied from the electrodes 3 and 4 will be applied to the MR element 1 and the bias conductor 5. The flow is divided depending on the specific resistance and film thickness. The sense current shunted to the bias conductor 5 generates a bias magnetic field Hb in the direction of the 9-width width within the film plane of the MR element 1, and rotates the magnetization M of the MR element 1 by an angle θb with respect to the sense current. let Also, the sense current shunted to the bias conductor 5 is M
Like the R element 1, as shown in FIG. 3, since it is distributed in the width direction, a large bias magnetic field Hb is generated in the region closest to the magnetic storage medium 2, and θb increases accordingly.

FIG. 5 shows the distribution of θb in the width direction of the MR cord 1.

For diagnostic purposes, the distribution of θb in a conventional example in which the sense current is uniformly distributed in the width direction is shown by a broken line.

As is clear from FIG. 5, in the conventional example, the maximum value of θb is obtained at the center of the width, whereas in this embodiment, the maximum value of θb is shifted to the side closer to the magnetic storage medium 2. That is, in this example, the bias state of the region that contributes most to the reproduction output at high recording density is set optimally (preferably θ
b-450).

Therefore, in this configuration, at high recording density, the resistance change at 10- in the region closest to the magnetic storage medium 2 of the MR element 1 contributes the most to the reproduction output, and the resistance change has the maximum sensitivity to the signal magnetic field H8. This allows even better recording density characteristics to be obtained than in the first embodiment.

In Fig. 4, the sense current shunted to the bias conductor 5
Although the bias magnetic field HB was applied to the element 1, a conductive ferromagnetic thin film 6 may be further laminated on the bias conductor 5, as shown in the cross-sectional view of FIG.

In this configuration, the sense current is shunted to the MR element 11, bias conductor 5, and 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. Sense current (■) shunted to the bias conductor 5 and the conductive ferromagnetic thin film 6.

and 1. provides a bias magnetic field similar to that shown in FIG. 4, and the conductive ferromagnetic thin film has the effect of greatly reducing the demagnetizing field in the width direction of the MR element 10.

Therefore, the MR head having the configuration shown in FIG. 4 can also realize the bias state shown in FIG. 5 with a small sense current.

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, Japanese Patent Application Laid-Open No. 51-26510
A permalloy film or the like having exactly the same characteristics as the MR element 1 may be used, as disclosed in the above publication. In this case, the conductive ferromagnetic thin film 6 also causes a resistance change with respect to the signal magnetic field H8 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, an MR having the configuration shown in FIG. It may be the head.

FIG. 7 shows an M with a magnetic shield, which is equipped with a magnetic shield made of a high magnetic permeability magnetic material disclosed in JP-A No. 50-59023, and in which the present invention shown in FIG. 2 is applied to the MR element part.
FIG. 3 is a cross-sectional view of the R head.

In the figure, SiO,, Ai,
The magnetic shields 7 and 8 are connected to the MR via an insulating layer such as 0°.
Element 1, G1 and G are arranged side by side with an interval between them.

With this configuration, the sense current (2) flowing in the width direction of the MR element 1 with a distribution as shown in FIG.
magnetize. Among the magnetized magnetic shields 7 and 8, the magnetic shield closest to the MR element 1 (for example, in FIG. 7, since G*>G+, the magnetic shield 7)
However, the strongest bias magnetic field is applied to the MR element 1 to bias the magnetization Mff of the MR element 1. M of the bias magnetic field
Since the distribution within the R element I 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-mentioned effect more pronounced, it is desirable that the difference between G and G be larger. In an extreme case, either G or G1 may have an infinite size, that is, a magnetic shield may be provided only on one side of the MR element 1.

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 curved configuration, and various modifications may be made without departing from the gist of the present invention.

In the present invention, the track width on the magnetic storage medium - 13 = (width of the area where magnetic information is written with respect to the length direction of the MR element) is defined as the track width on the magnetic storage medium on the side closest to the magnetic storage medium of the MR element. It is desirable that the distance be smaller than the electrode spacing. 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 to be smaller on the side closer to the magnetic storage medium, the resistance change is the largest when the MR element is at 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, and it is extremely easy to use for a wide range of recording densities without demagnetizing the magnetic storage medium. Almost uniform playback output can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic perspective view of a conventional magnetoresistive head; Figure 2 is a schematic perspective view of a conventional magnetoresistive head;
3 is a graph showing the distribution of the sense current flowing through the magnetoresistive head, and FIG. 4 is a diagram showing the second configuration example of the present invention. 5 is a graph showing the bias state of the magnetoresistive head, FIG. 6 is a sectional view showing a third configuration example of the present invention, and FIG. 7 is a graph showing a fourth configuration example of the present invention. FIG. 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... magnetic shield, respectively. Figure 4 Circle r Figure 5 OL h ? Figure 6 Figure 7

Claims (6)

[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, the spacing between the two electrodes on the mounting plate is equal to that of the magnetic storage medium. A magnetoresistive head characterized in that a portion closest to the magnetic storage medium is smaller than a 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 conductive 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 element according to claim 1, 2, or 3, wherein a magnetic shield made of a high permeability magnetic material is formed through an insulating layer. effect head.