JPS59207675A - Magnetoresistance element - Google Patents

Abstract

PURPOSE:To make the intensity of a bias magnetic field sufficiently intense, by using a Permalloy film and a thin permanent magnet film as a multilayer shunt film in applying the bias magnetic field intensity. CONSTITUTION:On a substrate 1, a Permalloy film 2 comprising, e.g., Fe-82% Ni, is formed. Then, a Co-20%Pt alloy film 3, which is a permanent magnet film, is formed on the Permalloy film 2. Thereafter, an electrode 4 for conducting a current through said two-layer thin film is formed by Al, Au, or the like. The bias intensity is increased from a curve 6, which indicates the bias intensity caused by the magnetic field formed only by a current, by the amount of the permanent magnetic field, owing to the overlapped magnetic field of the magnetic field formed by the current and the magnetic field formed by the permanent magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetoresistive element to which a bias magnetic field is applied.

[Background of the invention]

In magnetoresistive heads used as reproduction magnetic heads for magnetic disks, magnetic tape devices, etc., an appropriate bias magnetic field is applied to the magnetoresistive film in order to increase the reproduction output. Various methods have been proposed for applying a bias magnetic field, but each has its own merits and demerits, and further improvements are needed to put them into practical use. - [Object of the Invention] The object of the present invention is to provide a magnetoresistive element to which a sufficient bias magnetic field can be applied and which has little noise.

[Summary of the invention]

The present invention relates to a shunt bias type magnetoresistive element characterized in that a current bias line is installed as a multilayer film so as to be in electrical contact with a magnetoresistive film (permalloy film), which is normally used as a shunt film. It is characterized by being made of a thin film that has permanent magnetic properties, rather than being made of non-magnetic metals such as Ti.

In this structure, a current is passed through the permanent magnet film, and the magnetic field generated by the current applies a bias magnetic field to the permalloy film, and at the same time, a bias magnetic field is also applied by the magnetic field generated by the permanent magnet film. With this method, a magnetic field strength that was insufficient in the conventional shunt bias applied magnetic field made of non-magnetic metal can now be obtained by using a permanent magnet film. Furthermore, by appropriately adjusting the direction of the magnetizing force of the permanent magnet film, the formation of a single magnetic domain in the permalloy film is promoted, which has a remarkable effect on reducing Barkhausen noise caused by domain wall movement.

The effects of the present invention will be explained in detail with reference to the following examples.

[Embodiments and effects of the invention]

Example 1 FIG. 1 shows the cross-sectional structure of a magnetoresistive element according to the present invention.
A permalloy film 2 made of Nj is formed, and then a C0-20% Pt3 film, which is a permanent magnet film, is formed on the permalloy.

Next, the electrode 4 for passing current through the two-layer thin film is kt
Alternatively, it is formed using AU or the like. As a result, a magnetoresistive element including a permalloy film exhibiting a magnetoresistive effect and a Co-20% Pt film serving as a shunt current permanent magnet film is manufactured. Figure 2 shows the output-voltage characteristics of the device, with curve 5
is the case when the permanent magnet thin film 3 is magnetized perpendicular to the current direction (the permalloy film's easy magnetization direction). Curve 6 showing bias strength
The bias strength increases by the amount of the permanent magnet film. Curve 6 is obtained by setting the direction of the magnetizing force of the permanent magnet film parallel to the direction of the current,
This effectively prevents the bias magnetic field from being applied from the permanent magnet film. The angle of magnetization of the permanent magnet (equal to the angle between the easy axis of magnetization of the permalloy film and the direction of magnetization) is set as the second
If this is done in the middle state of the curve shown in Figure 5.6, a curve 7 will be obtained. Furthermore, if the direction 10 in which the bias magnetic field is applied to the easy magnetization direction 9 of the permalloy film shown in FIG. The visible Barkhausen noise is significantly reduced. FIG. 4 shows a relationship curve between angles α of 9 and 10 shown in FIG. 3 and Barkhausen noise. This seems to be related to the formation of a single magnetic domain in the permalloy film. In order to exhibit the above-mentioned characteristics of this device, it is necessary to use c, which is a permanent magnet film and shunt current film.
It is necessary to prevent the deterioration of the characteristics of both due to the reaction with the o-pt. For this purpose, when forming a co-pt film on the permalloy film 2 shown in FIG. 1, the substrate must be sufficiently cooled so that the substrate temperature does not exceed 250C. If the temperature exceeds 250C, the characteristics shown in FIG. 2 cannot be obtained due to the reaction between the two.

As is clear from the above examples, the effects of the present invention are very large.

Next, a second invention related to the above invention will be explained. First, to describe an embodiment of the second invention, in a magnetoresistive magnetosensitive element using a desired magnetoresistive film such as permalloy, the element is made of metal so as to form a multilayer structure with the magnetoresistive film. This element structure forms a shunt thin film and applies a bias magnetic field to the magnetoresistive film.It uses a permanent magnet film as part of the shunt film, and prevents the diffusion reaction between the permanent magnet film and permalloy. This is a magnetoresistive element characterized by having a high melting point metal film as a part of the element.

In magnetoresistive heads used as reproduction magnetic heads for magnetic disks, magnetic tape devices, etc., an appropriate bias magnetic field is applied to the magnetoresistive thin film in order to increase the reproduction output. . Methods for applying a bias magnetic field include installing a permanent magnet film, barber pole electrode formation method, antiferromagnetic film method, current bias wire method, and magnetoresistive films are installed parallel to each other and bias is applied to each other. A method to do this has been developed. These methods have their advantages and disadvantages, and further improvements are required before they can be put into practical use.

The second invention relates to the improvement of a shunt bias type magnetoresistive element characterized in that a current bias line is provided as a multilayer film so as to be in electrical contact with a magnetoresistive film. In this case, by using a thin metal film with permanent magnetic properties as part of the shunt bias film,
A magnetoresistive thin film element characterized in that a bias magnetic field is effectively applied to a magnetoresistive thin film by superimposing the magnetic field from a permanent magnet thin film on the magnetic field created by a current.

This reduces the current density required to be applied to the shunt thin film, including the permanent magnet thin film, extends the current rupture life of the shunt thin film, improves the reliability of the device, and adjusts the magnetization direction of the permanent magnet thin film. By doing so,
It also has the effect of reducing Barkhausen noise generated in the magnetoresistive film. However, when a permanent magnetic film made of a metal such as Co-pt or co-Be and a permalloy film are directly formed into two layers, a reaction occurs between the two at the contact interface when the device process temperature exceeds 200 to 300C. The properties of the permalloy film, which is the raw material, deteriorate. Therefore, by forming a barrier layer between the permalloy film and the permanent magnet film that does not react with both, it becomes possible to manufacture a magnetoresistive element with less deterioration of characteristics. As described above, the second invention is a magnetoresistive element characterized in that when a permanent magnet thin film is used as a shunt bias film, a barrier layer is formed between the permanent magnet thin film and the permalloy film, and is composed of the above three layers. . The invention of this document 2 will be described in detail below using examples.

Example 2 FIG. 5 is a cross-sectional view of an element showing an example of the magnetoresistive element according to the second invention, in which a permalloy film 12 having a Fe-82% Ni composition is formed on a desired substrate 11 such as glass. Next, a permanent magnetic film of Co-20 is placed on the permalloy.
An MO thin film 13 is formed to prevent mutual diffusion between the %pt film 14 and the permalloy film, and this film itself generates a current bias magnetic field, and an electrode 15 necessary for current conduction is formed thereon. FIG. 6 shows the output voltage-magnetic field characteristics of the device. Curve 16 shows the case where the permanent magnet thin film 14 is magnetized perpendicular to the direction of current flow. According to curve 17 showing the bias strength due to the magnetic field, the bias strength increases by the amount of the permanent magnet film.

Curve 17 indicates that the permanent magnet film is magnetized parallel to the direction of the current so that no bias magnetic field is effectively applied from the permanent magnet film. When the permanent magnet is magnetized with the angle of magnetization (equal to the angle between the axis of easy magnetization and the magnetization direction of the permalloy film) in the middle of the curve shown in Figure 6, 16.17, it will be as shown in curve 18. An element exhibiting a bias magnetic field strength between the curves 1116 and 17 is obtained. therefore,
Due to the role of the permanent magnet film, a larger bias magnetic field strength can be obtained than when bias strength is applied solely by current bias. Further, the direction 21 in which a bias magnetic field is applied to the easy magnetization direction 20 of the permalloy film shown in FIG.
When the angle with respect to the direction of 20 is set to 60 degrees or less, Barkhausen noise observed in the output power-magnetic field characteristics of the magnetoresistive element is significantly reduced. Fig. 8 shows a relationship curve 22 between the angle α (magnetization angle) of 20 and 21 shown in Fig. 7 and Barkhausen noise, where the magnetization angle α is 60°.
Below, the noise shows a significant reduction.

This seems to be related to the single magnetic domain of the permalloy film.

Therefore, by the method of the second invention, it was possible to increase the bias magnetic field strength and reduce device noise.

Even when this element was heat-treated at 400C for 3 to 5 hours, the characteristics did not change from those before heat treatment (9) due to the reaction inhibiting effect of the MO barrier layer.

Example 3 A co-pt permanent magnet film 14 is formed on the same substrate 11 as in Example 2, and then Mo2B, a high melting point metal, is deposited to prevent the reaction of the permanent magnet film of the co-pt film. Next, when characteristics similar to those shown in FIG. 6 were measured for an element in which a permalloy film 12 and an electrode 15 for conducting current were formed thereon, an element exhibiting exactly the same effect was obtained.

Example 4 In an element having the same structure as Examples 2 and 3, the same effect was obtained when Ta was used as the reaction inhibiting metal shown in 13.

Example 5 In an element having the same structure as in Example 2.3, the same effect was obtained when the permanent magnet film shown in 14 was made of Co-10%Re.

The effects of the second invention are clear from the above examples.

[Brief explanation of drawings]

(10) Fig. 1 is a cross-sectional view showing the structure of the element of the present invention, Fig. 2 is a graph showing the output voltage-magnetic field characteristics of the element, and Fig. 3 is a perspective view showing the direction of magnetization of the permanent magnet film. 4 is a graph showing the Barkhausen noise of the device, FIG. 5 is a diagram showing the cross-sectional structure of the magnetoresistive element of the second invention, and FIG. 6 is a voltage-magnetic field diagram of the device of the second invention. A graph showing the characteristics, FIG. 7 is a graph showing the angle between the current direction of the second invention element and the direction of magnetization of the permanent magnet, and FIG. 8 is a graph showing the magnetization angle and noise generation rate. , FIG. 9 is a sectional view showing an element in which the order of the laminated films of the element structure shown in FIG. 5 is changed. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Permalloy film, 3...co-
pt combination (11) 1st figure 9 dumb 2 figure χ 3 figure n ¥:14 figure θ 3I! 760 2j

Claims (1)

[Claims] In a magnetoresistive element using a desired magnetoresistive film such as permalloy, an element having a structure in which a shunt current film is formed by forming a multilayer with a permalloy film in order to apply a bias magnetic field intensity to the magnetoresistive element. A magnetoresistive element characterized by using a permanent magnet thin film as a shunt film.