JPS61236177A - Magnetoresistance effect element - Google Patents

Abstract

PURPOSE:To decrease the variation in read-out output and to increase the read- out output value, by providing highly permeable magnetic films near a magnetoresistance effect film so as not to be contacted therewith and providing a single-domain magnetic pressure structure in the mangetoresistance effect film. CONSTITUTION:Thick and highly permeable films 6 are arranged adjacent to a magnetoresistance film 4 through insulation films so as to enable the focali zation of a magnetic field. According to this arrangement, a single magnetic domain can be provided in the magnetoresistance film with a good re producibility and the hysteresis can be eliminated. Accordingly, the variation in output voltage is not caused pratically and the output voltage can be almost its maximum value. Since the element can be used with a high output voltage, a maximum output value can be obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a ferromagnetic magnetoresistive element used in a magnetic sensor element, a magnetic head element, a magnetic pulp detection element, etc., and particularly relates to a highly sensitive ferromagnetic element in the element shape. This invention relates to a magnetoresistive element.

[Background of the invention]

In recent years, rapid progress has been made in the development of magnetic sensors that detect rotational angles and rotational speeds using ferromagnetic thin films having a magnetoresistive effect, magnetoresistive thin film magnetic heads, and magnetic pulp detection elements. A ferromagnetic magnetoresistive film having a thickness of 25 to 400 m is generally used in magnetic sensors, magnetoresistive thin film magnetic heads, magnetic pulp detection elements, and the like. Permalloy, which is an 82wt*Nt-xswt 1Fe alloy, is widely used for the ferromagnetic magnetoresistive effect of elements that utilize these ferromagnetic magnetoresistive effects.

A schematic diagram showing the relationship between the read magnetic sensor and the magnetic disk is shown in FIG. The magnetic sensor includes a magnetic disk 2 on which a magnetization pattern 6 is recorded and a magnetoresistive film 4.
and a conductive film 5 to which the magnetoresistive film 4 is connected. This magnetoresistive element 1 detects the magnetic field from the magnetic disk 2 as little as possible on the magnetization transition region at the boundary between each magnetization pattern 6 of the magnetic disk 2, and detects the magnetic field from the magnetic disk 2 at an intermediate position of the magnetization transition region, that is, at the center of the magnetization pattern 6. Above, magnetic disk 2
In order to sufficiently detect the magnetic field from the magnetoresistive element 1, the dimensions and shape of the spacing between the magnetoresistive films 40 constituting the magnetoresistive element 1 are determined, and the distance between the magnetoresistive element 1 and the surface of the magnetic disk 2 is set at a distance of 50 to 100 μm. It is well known that the magnetoresistive element 1 is made highly sensitive. In order to use a ferromagnetic film having a magnetoresistive effect as the magnetoresistive film 4, the axis of easy magnetization (spin direction) must be aligned in the stripe longitudinal direction (longitudinal direction of the magnetoresistive film 4) shown in FIG. It is a well-known fact that the -axis magnetically anisotropically oriented film is used.

However, even if the magnetoresistive film 4 is carefully formed, it is difficult to match the longitudinal direction of the stripe with the easy axis direction of magnetization. Cracks A often occur. Regarding this, Midde Iho
Report of ek (J, Appl.

Phys, 33s (1962) pptxix~111
Please refer to 2). Essentially, it must become 0 on the magnetization transition region, that is, it must always produce the same value in the state of magnetic field "0". However, when a film with such a three-domain structure is applied to a magnetoresistive element 1, there is hysteresis, and as is clear from FIG.
In this case, even in the magnetic field O, the resistance value differs, so the output voltage changes. That is, it is known that when a film with such a three-domain structure is applied to the magnetoresistive element 1, the output voltage fluctuates and zero drift occurs. Therefore, in order to prevent this, as a conventional method, a bias magnetic field is applied to the magnetoresistive film, and the operating point of the read magnetic sensor is brought to a region where the electrical resistivity changes greatly with respect to the signal magnetic field of the magnetic disk 2. (For example, Japanese Patent Laid-Open No. 57-21883).

However, in this conventional method, only a part of the magnetoresistive change rate of the entire magnetoresistive film can be used, so the amount of change in the output of the magnetoresistive element 1 becomes small, which becomes an obstacle to the magnetic encoder when achieving high resolution. It has become clear that when the magneto-resistance effect element is incorporated into a magnetic disk, the distance aa4m between the magnetoresistive element and the magnetic disk and the azimuth adjustment become difficult.

Another conventional method is to apply a bias magnetic field to prevent the constriction that occurs near the origin of the magnetization curve of a magnetoresistive film. Shown below. Figure 5 shows the longitudinal direction of the stripe (
This figure shows the change in magnetoresistance when a bias magnetic field is applied in the direction of the easy axis of the magnetic film. That is, it is shown that if a negative bias as shown in FIG. 5F or a positive bias as shown in FIG. 5A is applied, hysteresis disappears. By applying a bias magnetic field in the longitudinal direction of the stripe in this way, the hysteresis phenomenon of changes in magnetoresistance with respect to the magnetic field can be eliminated. The magnetic domain structure of the magnetoresistive film when this hysteresis phenomenon disappears is a square magnetic domain structure. However, when forming a single domain structure by applying a bias magnetic field in the longitudinal direction of the stripe, it depends on whether the magnetic field applied in the longitudinal direction of the stripe and the bias magnetic field are parallel or antiparallel due to the magnetic field recorded on the other magnetic disk. Figure 5: The optimum bias magnetic field size is different from that of the person or F. Therefore, when applied to a magnetic sensor in which the magnitude of this bias magnetic field cannot be determined, it is possible to have a single domain structure if the magnetic fields are applied in the same direction, but if the magnetic field is applied in the same direction, it can exist in a single magnetic domain structure, but if the magnetic field is applied in the same direction and the direction is opposite When there is a directional magnetic field, a single magnetic domain structure cannot exist, which makes it difficult to stabilize the output characteristics. For this reason, if such a magnetoresistive film is used in a magnetic sensor for reading, it has the drawback of erroneous detection.

[Purpose of the invention]

An object of the present invention is to provide a magnetoresistive element that can obtain a high output value without output fluctuation.

[Summary of the invention]

The magnetoresistive element of the present invention is characterized in that the ferromagnetic thin film having the magnetoresistive effect has a single magnetic domain structure.

By making the magnetic film have a single magnetic domain structure, the rate of change in successive output can be made extremely small, and the successive output value can be increased, as will be described later.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the present invention.

Incidentally, the magnetoresistive effect element assembly is formed together with the magnetoresistive effect film 4 on a non-magnetic substrate 3 with surface roughness suppressed as much as possible. The magnetoresistive film has a thickness of 20 to 501 m, a width of 5 to 4 Q nm, and a length of 100 to 3000 μm, so that the length is sufficiently larger than the width. The magnetoresistive film 4 is formed on the nonmagnetic substrate 3 by vapor deposition. This magnetoresistive film 4 has a characteristic of having a single magnetic domain structure.

A conductive film 5 connected to a lead wire is arranged so as to be electrically connected at both ends of the magnetoresistive film 4.

According to the magnetoresistive element having such a configuration, it is possible to stabilize the output characteristics and increase the continuous output.The reason will be explained below.

The instability of the output characteristics of a magnetoresistive element is caused by the hysteresis phenomenon of magnetoresistance changes in response to a magnetic field, and the systeresis phenomenon of magnetoresistive changes is based on the instability of the magnetic domain structure.

The sixth factor shows the results of examining the curve of magnetic field and magnetoresistance change and the magnetic domain structure under each magnetic field. Under a magnetic field that exhibits a hysteresis phenomenon, the magnetic domain structure has three magnetic domains with spins with three different characteristics. It has a structure. The arrow indicates the direction of spin. Due to this three-domain structure, the behavior of the magnetic moment within this structure changes, and this causes phenomena such as fin A.

Applying a gradually stronger magnetic field in the negative direction from 0 returns to 0 at a certain point (point 4 in Figure 4) and returns to point 5 in Figure 4.
), when applying a magnetic field in the positive direction, from point 6 to point 7 in Figure 4
Cracks A occur when moving to This is because a magnetic field is applied in the negative direction from point 1 in Figure 4 and brought back again.When it reaches the 0 point, it should have been demagnetized, but when it returns, it is completely magnetized. Therefore, the hysteresis phenomenon is thought to be caused by the magnetization process based on domain wall movement, which stabilizes the output characteristics of the magnetoresistive element. It can be seen that the magnetization process needs to have a single domain structure due to rotational magnetization. Therefore, a method for obtaining a magnetoresistive film having a single domain structure with good reproducibility will be explained by taking a Ni-:['e alloy film as an example of the magnetoresistive film.

Since the Ni-Fe alloy film used in the magnetoresistive element has uniaxial anisotropy, if the angle between the direction of anisotropy and the longitudinal direction of the stripe can be strictly controlled, the magnetic domain structure of the N1-Fe alloy film can be changed to a single magnetic domain. It is theoretically possible to do so. However, even if the Ni--Fe alloy film is carefully formed by evaporation in a magnetic field or the like, the easy axis of the N1--Fe alloy film is not in a constant direction but is usually shifted by several degrees with respect to the longitudinal direction of the stripe. For this reason, it is almost impossible to make a magnetoresistive film into a single magnetic domain by a film forming method.In the present invention, an attempt was made to make a magnetoresistive film into a single magnetic domain by using an element configuration as shown in FIG. That is, the configuration is such that a thick high magnetic permeability film 6 is placed adjacent to the magnetoresistive film 4 with an insulating film interposed therebetween so as to be able to focus the magnetic field.

FIG. 3 shows the magnetic domain structure of a magnetoresistive film having the element configuration shown in FIG. 2 and a curve of magnetoresistance change with respect to a magnetic field. By configuring the device as shown in FIG. 2, it becomes possible to monomagnetize the Ni--Fe alloy film easily and with good reproducibility.

That is, hysteresis can be eliminated. However, the output characteristics can be a single magnetic domain structure. That is, since hysteresis can be eliminated, there is almost no fluctuation rate in the output voltage, and the output voltage also exhibits a value close to the maximum value.

This is because the magnetic field O can be used because hysteresis is eliminated. If the fluctuation rate of the output voltage disappears,
Since it can be used in areas with high output voltage, the maximum output value can be obtained. The present invention can be modified in various ways without being restricted thereto.

For example, the magnetoresistive film may be formed of a magnetoresistive element using a Ni-Co alloy film.

〔Effect of the invention〕

As explained above, according to the present invention, stable output characteristics and a large output voltage can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of a magnetoresistive element showing an embodiment of the present invention, FIG. 2 is a schematic perspective view showing an embodiment of a magnetoresistive element of the invention, and FIG. 3 is a schematic perspective view of a magnetoresistive element of the invention. FIG. 4 is a schematic diagram showing the relationship between the magnetoresistive element and the magnetic disk. FIG. 5 is a diagram showing the change in magnetoresistive force when a bias magnetic field is applied in the longitudinal direction of the stripe. FIG. The figure shows a curve of magnetoresistance change with respect to a magnetic field and a magnetic domain structure under each magnetic field. 1... Magnetoresistive element, 2... Magnetic disk, 3
...Nonmagnetic substrate, 4...Magnetoresistive film, 5...
Conductor film, 6... High permeability magnetic film, 7... Insulating film.

Claims (1)

[Claims] 1. In a magnetoresistive element composed of a ferromagnetic film having a magnetoresistive effect and connected to a conductive film at both ends, a high permeability magnetic film is provided in the vicinity of the magnetoresistive film in a non-contact manner, and the magnetoresistive film is A magnetoresistive element characterized in that the magnetic pressure structure of the effect film is made into a single magnetic domain.