JPH0232279A - Magneto-resistance effect element - Google Patents

Abstract

PURPOSE:To make the size relation between sensor parts of electrode parts clear and to produce an excellent bias magnetic field by setting the length of a part where a sensor part which senses an external magnetic field and a lead line contact each other equal to or longer than the width of the sensor part. CONSTITUTION:The sensor part 10 has an MR(magneto-resistance effect) film and a conductor film which is formed on its flank and comes into electric contact and senses the external magnetic field to provide MR. Then the MR element is formed of this sensor part and two lead wires 20 for leading variation in resistance out of both sides of the sensor part. In general, when a current flows through a conductor, its distribution depends upon the ratio of the conductor width and when the current flows from a narrow conductor to a wide conductor, the current is concentrated inside and comes not to flow uniformly in the wide conductor. For the purpose, the width W of the contacting between the sensor part 10 and lead wires 20 is set equal to or greater than the width L of the sensor part 10 to make the current nearly uniform.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of a magnetoresistive effect element (hereinafter abbreviated as MR element), and particularly relates to a magnetoresistive effect film (hereinafter abbreviated as MR film).
A shunt bias type M in which the conductor film is in electrical contact with the
This invention relates to an element structure for passing a -like current through an R element.

[Prior Art] Magnetic heads (hereinafter abbreviated as MR heads) using magnetoresistive films are being used. In the MR head, MR
In order to improve the sensitivity and linearity of the film, it is necessary to apply a constant magnetic field from the outside. This magnetic field is called a bias magnetic field, and its methods include (1) placing a permanent magnet near the MR film, (2) placing a conductive film in contact with the MR film, and (3) placing a conductive film near the MR film. Many methods have been proposed for placing soft magnetic films on the magnetic field. In particular, the method (2) is called the shunt bias method, and as shown in FIG. A structure has been proposed in which lead wires 20 and 25 are formed of both an MR film and a conductor film, which generate a bias magnetic field by passing a constant current and then extract the resistance change as a voltage change. However, in this structure, no consideration was given to @W and W' of the electrode portions provided on the surface opposite to the recording medium facing surface 15 of the MR element.

[Problems to be Solved by the Invention] In the above-mentioned prior art, no consideration is given to the relationship between the lead wire and the sensor section, and as a result, a current may not flow through the sensor section, and the MR film A suitable bias magnetic field could not be applied.

An object of the present invention is to provide an MR element structure in which the dimensional relationship between the electrode part and the sensor part can be clarified, and a -like current can be passed through the sensor part to generate a suitable bias magnetic field.

[Means for Solving the Problems] The above object is to adjust the length W of the part where the sensor section 10 sensitive to an external magnetic field and the lead 120 are in contact with each other with respect to the width of the sensor section, as shown in FIG. This is achieved by making it equal to or greater than. Since twice as much current flows through the intermediate terminal as in the terminals on both sides, the above object is achieved by making W' twice or more wide than @L of the sensor section.

[Operation] Generally, when current flows in a conductor bent at right angles, its distribution depends on the ratio of the conductor widths. FIG. 3(a) shows the current flow in such a case solved by computer simulation, and the density of the curve 30 in the figure represents the current density. As shown in the figure, one conductor 40 is narrow and the other conductor 5
When 0 is wide, the current is concentrated in the inner part 60 of the wide conductor 50 and does not flow uniformly through the wide conductor.

This is because the equipotential line 70 (current flows perpendicularly to this line) within the conductor is as shown in FIG. 3(b), and the conductive position changes more in the wider conductor portion.

FIG. 4 shows the inner portion (of the current passing through A-A' of the conductor 5o in FIG.
This is a calculation of how much of the total current flows through the width Lu), which means that exactly 50% of the current flows uniformly. From the figure, if W/L is 1 or more, it can be considered that the current is flowing almost uniformly. From this result, the first
As shown in the figure, a conductor 50 is a sensor section 10 of a shunt bias MR element. Considering that the conductor 4o is the same lead wire 20, W/L must be 1 or more in order to cause a uniform current to flow through the sensor section.

If the value of W/L is too large, when a plurality of MR elements are used to form a multi-track, the lower limit of the track pitch is determined, making it difficult to increase the track density. Furthermore, since current does not flow in the direction of the track width T in a region 35 (indicated by diagonal lines) surrounded by the lead wire 20 and the sensor section 10, the bias is not suitable, and the sensitivity as an MR element is low. However, an MR film, which is a magnetic thin film, is present in this part (area 35), and in a magnetic storage device that overwrites information on this MR element, if the head deviates from the recorded track, The magnetization recorded in the sensor becomes noise and magnetizes the MR film portion in the shaded area 35, and the magnetization due to the noise is transmitted to the sensor section and reproduced as noise. As a result, the S/N of the signal from the head is reduced. Therefore, it is not desirable to make W/L larger than necessary, and it is usually best to keep it within a range of about 2 to 2.5.

The above has described the electrodes 20 at both ends of the sensor section, but as shown in FIG. Since twice the current flows through each of the electrodes 20, in order to flow the current uniformly, it is necessary to
The relationship between 1W' and L needs to be twice the relationship between W and L. That is, it is clear that a homogeneous current distribution can be obtained by setting W'/L to 2 or more.

Also, if the width W' of the intermediate terminal electrode 25 is made larger than necessary, there will be a problem. That is, in the part of the sensor having a width of W' in FIG. 1 (the shaded area 36 in FIG. 1), current does not flow in the direction of the track cap. becomes a dead zone, does not contribute to signal reproduction, and causes low output.

The case where the electrode part is rectangular has been explained above from Fig. 1 to Fig. 4, but for example, as shown in Fig. 5, the part where the electrode part is in contact with the sensor part is narrow and widens as it moves away from the sensor part. If we consider the contact widths to be w and w', it is clear that the above relationship is a condition for uniform current to flow through the sensor section.

[Examples] Examples of the present invention will be described below. A schematic diagram of a shunt bias MR head embodying the present invention is shown in FIG. The manufacturing method of this MR head is basically
This method is the same as that shown in No. 74522. That is, an insulating film 1 made of alumina or the like is placed on a ferrite base 100.
Sputter 10. Titanium is vacuum-deposited thereon as a conductor film 120, and an MR film 130 is further attached so that an axis of easy magnetization is formed in the direction of the arrow in the figure. On top of this, an insulating film such as alumina is formed as a protective film (not shown).
A lead conductor (not shown) is attached to form an MR element.

In order to form an MR head, a block 140 made of the same material as the basic 100 or a thin film such as permalloy is attached on the above element. This block forms a magnetic circuit with the base 100, acts as a shield, and increases the resolution of the MR head.

The shape of the MR element, as shown in FIG. 7, is the same as the shape shown in FIG. 1 with the intermediate terminal. In the example, Tw
= 20 μm, L = 10 μm, and the electrode width W is:
20ILm as the value to which the present invention is applied, 5ILm for comparison
There were two types: μm. The electrode width W' of the intermediate terminal is W'=2W
And so. Other values such as MR film thickness of 600 and conductor film thickness of 1800 were made to be the same between the two types of heads as much as possible.

A commercially available one-inch magnetic tape recorded with the shunt bias MR head thus prepared was reproduced using the same device. At this time, the current to the MR element was configured to flow from the terminals on both sides to the intermediate terminal.

The magnetic tape 150 is arranged at a smaller interval (usually 1 μm or less) than the MR head and is moved in the direction of the white arrow in the figure.

The MR hesode with W=20μm by applying the present invention has W=
Compared to a head with a diameter of 5 μm, the output was improved by 4 dB when the same current was passed through the element. This is because the current flowing through the MR element, particularly the current flowing through the conductor film 120, becomes uniform by applying the present invention. This will be explained with reference to FIG. The horizontal axis shows the position in the height direction of the MR film, and the vertical axis shows the bias and signal magnetic field. ■ is the signal magnetic field distribution, ■ is the bias magnetic field distribution when a uniform current flows, and ■ is when the current is biased toward the rear end. This is the bias magnetic field distribution at the time.

In this way, in case (1), the bias magnetic field is larger on the side facing the magnetic tape where the signal magnetic field is larger than in case (2).

Therefore, as shown in the resistance change characteristics of the MR film in Figure 8,
A larger signal field results in a larger resistance change under a suitable bias field, resulting in increased output.

[Effects of the Invention] According to the present invention, since a homogeneous current can flow through the sensor section of the shunt bias MR element, a suitable bias magnetic field can be applied to the MR film, increasing the reproduction output and providing an output with good linearity. It will be done. Furthermore, since there is no concentration of current in either the sensor section or the electrode section, the life of the MR element is extended.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an MR element pattern to which the present invention is applied;
Fig. 2 is a diagram showing the MR element pattern for explaining the conventional technology, Fig. 3 is an enlarged view of part B in Fig. 2, and also a diagram showing the flow of current, and Fig. 4 is a diagram showing the conductor width and current. FIG. 5 is a diagram showing a modification of the electrode shape. FIG. 6 is a diagram for explaining the MR head of the example. FIG. 7 is a diagram showing the bias magnetic field in the MR film due to the bias current distribution. FIG. 8 is a diagram for explaining the distribution of the signal magnetic field, and FIG. 8 is a diagram showing the relationship between the resistance change of the MR film and the external magnetic field. 10...Sensor section showing the magnetoresistive effect of the MR element, 2
0.25... Electrode part, 30... Current flow, 35° 36... Electrode lower region, 40.50... Conductor, 60
...The area inside the conductor. 7th eye 2 @ 9th eye 3rd figure Δ eye '1.21. r horn 1t/!

Claims (1)

[Claims] 1. A sensor section that exhibits a magnetoresistive effect in response to an external magnetic field, which has a magnetoresistive film and a conductor film that is formed on the side surface of the film and is in electrical contact with the sensor; A magnetoresistive element comprising first and second lead wires that are drawn out from both sides of the sensor section and for extracting a resistance change of the sensor section, the width of which the sensor section and the lead wires are in contact with each other ( A magnetoresistive element characterized in that W) satisfies L≦W with respect to the width (L) of the sensor section. 2. In the magnetoresistive element according to claim 1, the width (W) of the contact between the sensor section and the lead wire satisfies W≦2.5L with respect to the width (L) of the sensor section. Characteristic magnetoresistive element. 3. The magnetoresistive element according to claim 1, which includes a third lead wire drawn out from an intermediate position of the sensor portion and for extracting a resistance change of the sensor, and the lead wire and the sensor The width (W') where the parts come into contact with each other is
A magnetoresistive element characterized in that 2L≦W'. 4. Width (W') of contact between the third lead wire and the sensor section in the magnetoresistive element according to claim 3
A magnetoresistive element characterized in that W'≦5L. 5. A sensor section disposed on a magnetic recording medium and having a magnetoresistive film for detecting changes in the magnetic field of the medium; and a sensor section extending from both sides of the sensor section in a direction opposite to the medium; A width (L) of the sensor from the medium surface side of the sensor section;
Width of the above lead wire when cut by a plane at a distance of (
W) is a magnetoresistive element characterized in that L≦W. 6. In the magnetoresistive element according to claim 5, the width (L) of the sensor and the width (W) of the lead wire
is a magnetoresistive element characterized by satisfying W≦2L. 7. In the magnetoresistive element according to claim 5, a third lead is pulled out from an intermediate position of the sensor section in a direction opposite to the medium, and is for extracting a change in magnetoresistance of the sensor section. The lead wire has a width (W') of 2L≦W' when cut by a plane at a distance of the sensor width (L) from the medium surface side of the sensor section. 8. A magnetoresistive element according to claim 7, wherein the sensor width (L) and the lead wire width (W') satisfy W'≦5L.