JPH0765327A - Method of applying magnetic field to magnetoresistive head - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to improve the yield of a magnetoresistive head based on the bias magnetic field strength. A strip-shaped magnetoresistive effect element is arranged such that a longitudinal side surface of the magnetoresistive effect element faces a magnetic recording medium so that a plane of the magnetoresistive effect element is perpendicular to the magnetic recording medium. By applying a longitudinal bias magnetic field in a direction parallel to the magnetic recording medium and a transverse bias magnetic field perpendicular to the magnetic recording medium with respect to the longitudinal direction of the magnetoresistive effect element, A magnetoresistive head 2 for reading information recorded on the magnetic recording medium based on the resistance value of the magnetoresistive element that changes in response to a given change in magnetic field strength. A magnetic field for increasing or weakening the strength of the longitudinal bias magnetic field and / or the strength of the lateral bias magnetic field is supplied from the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive head formed by a thin film process, and more particularly to a magnetoresistive effect capable of improving the yield of products based on the excess or deficiency of the bias magnetic field strength applied to the magnetoresistive element. The present invention relates to a method of applying a magnetic field to a mold head.

By applying an appropriate bias magnetic field strength, the magnetoresistive effect element improves the vertical asymmetry of the output reproduction waveform and suppresses the occurrence of discontinuous jumps in the output reproduction waveform called Barkhausen noise. You can

Therefore, when a magnetoresistive head is formed of a thin film on a substrate forming a slider by a thin film process, for example, in the SAL bias system, a soft adjustment layer (SA) using a magnetic material is used.
A non-magnetic spacer layer (tantalum, titanium, etc.) is formed on the L) layer, a magnetoresistive effect element is formed on this non-magnetic spacer layer, and BCS layers (iron manganese, etc.) are formed on both ends of this magnetoresistive effect element. By forming the, by the current flowing to detect the change in the resistance value of this magnetoresistive effect element,
The magnetic field induced by the SAL layer gives a bias magnetic field to the magnetoresistive effect element, and the BCS layer gives a magnetic field orthogonal to the magnetic field induced by the SAL layer to the magnetoresistive effect element.

However, due to variations in film thickness when forming a film in the thin film process and inadequate design target values,
If the bias magnetic field strength is inappropriate, the yield of products will deteriorate, but it is desired to improve this yield.

[0005]

2. Description of the Related Art FIG. 2 is a diagram for explaining an example of a magnetic head. FIG. 2A is a side view of the magnetic head, and FIG.
FIG. 2C is a rear view of the magnetic head, and FIG. 2C shows a configuration example of the magnetoresistive head. Reference numeral 1 is a slider, 2 is a magnetoresistive head formed by a thin film process on the rear surface of the slider, 3 is a lead wire, 4 is a magnetic recording medium, and 5 is a magnetoresistive element.

In the case of the SAL bias method, the magnetoresistive head 2 has a SAL layer 5a and a non-magnetic spacer layer 5 on the substrate constituting the slider 1, as shown in FIG. 2 (C).
b and the magnetoresistive effect element 5 are sequentially laminated, and the BCS layer 5c is provided on both ends of the magnetoresistive effect element 5 in the longitudinal direction.
Is formed on the rear surface of the slider 1 so that the longitudinal side surfaces of the strip-shaped magnetoresistive effect element 5 face the magnetic recording medium 4 and the strip plane is vertical. Has been formed.

The magnetoresistive effect element 5 of the magnetoresistive effect type head 2 changes its resistance value by the magnetic field applied from the magnetic recording medium 4, and therefore the magnetoresistive effect element 5 is used.
2B, a current is supplied through the lead wires 3 connected to both ends in the longitudinal direction, and the change in the resistance value is extracted as a signal waveform, so that the magnetic recording medium The information recorded in 4 has been read.

FIG. 3 is a diagram for explaining the bias magnetic field of the magnetoresistive effect element. 3A is a side view of the magnetoresistive effect element 5, and FIG. 3B is a sectional view of the magnetoresistive effect element 5.

As shown in the figure, the magnetoresistive effect element 5 has a longitudinal side surface facing the magnetic recording medium 4. As described above, the magnetoresistive effect element 5 has leads connected to both ends in the longitudinal direction. A current is supplied by the line to read the change in the resistance value. For example, a bias magnetic field in the direction indicated by an arrow A parallel to the magnetic recording medium 4 (hereinafter referred to as a longitudinal bias magnetic field) has an appropriate magnetic field strength. If not given, as shown by the arrow B, the uniaxial structure in which the magnetization directions are aligned is not formed, and if the strength of the longitudinal bias magnetic field is insufficient, the magnetization directions are disjointed, and Barkhausen noise is generated, causing the longitudinal bias magnetic field to change. If the strength is too high, the resistance value does not change and signal reproduction becomes impossible.

Further, for example, if a bias magnetic field in the direction indicated by arrow C, that is, a direction perpendicular to the direction indicated by arrow A (hereinafter abbreviated as lateral bias magnetic field) is not applied with an appropriate magnetic field strength, the magnetic recording medium. The area in which the amount of change in the resistance value is proportional to the amount of change in the magnetic field strength is reduced, and the vertical symmetry of the output waveform deteriorates.

Incidentally, as the magnetoresistive head, there are a shunt type and a self type in addition to the SAL bias type head. However, the SAL bias type head is mainly used in view of good characteristics and process ease. System is being manufactured.

In the SAL bias system, as described above, the magnetic field induced by the SAL layer is applied to the magnetoresistive effect element 5 by the current flowing to detect the change in the resistance value of the magnetoresistive effect element 5, and the transverse bias magnetic field is applied to the magnetoresistive effect element 5. And BCS
A longitudinal bias field is provided by the layers.

Therefore, as described above, when the film is formed by the thin film process, the BCS layer for generating the longitudinal bias magnetic field and the SAL layer for generating the lateral bias magnetic field are formed, and the biases indicated by the arrows A and C are formed. Generates a magnetic field, but SA
Since the strength of the lateral bias magnetic field is determined by the thickness of the L layer,
Even if the value of the current flowing through the magnetoresistive effect element 5 is changed, this magnetic field strength is not affected.

Therefore, in order to give a proper lateral bias magnetic field strength to the magnetoresistive effect element 5, it depends on the film thickness when the SAL layer is formed in the thin film process.
The strength of the longitudinal bias magnetic field also depends on the variation in the process of the BCS layer.

[0015]

As described above, the SAL layer is conventionally formed by the thin film process. However, when the film is formed, the variation in the thin film process and the designed target value of the film formation are uncertain. Due to problems such as suitability, a SAL layer having a thickness out of the specified value may be formed.

Therefore, the strength of the lateral bias magnetic field induced by the SAL layer having a thickness deviating from the specified value due to the current flowing through the magnetoresistive element 5 becomes weaker or stronger than a predetermined strength. To do.

Further, the BCS layer also has a problem that the strength of the longitudinal bias magnetic field becomes weaker or stronger than a predetermined strength due to variations in the process.
When such a problem occurs, Barkhausen noise may be generated and a vertically asymmetric signal waveform may be reproduced. However, in the conventional magnetoresistive head 2,
Since there is no means for controlling the strength of the bias magnetic field, there is no method other than to make the head defective, which is a factor that deteriorates the product yield.

In view of the above problems, the present invention applies a magnetic field from the outside of the magnetoresistive head 2 to adjust the strengths of the longitudinal bias magnetic field and the lateral bias magnetic field to be appropriate, thereby improving the yield of products. Is intended to improve.

[0019]

[Means for Solving the Problems]
As shown in FIG. 2, by making the longitudinal side surfaces of the strip-shaped magnetoresistive effect element face the magnetic recording medium, the plane of the magnetoresistive effect element is perpendicular to the magnetic recording medium. And a longitudinal bias magnetic field is applied in a direction parallel to the magnetic recording medium with respect to the longitudinal direction of the magnetoresistive effect element and a transverse bias magnetic field is applied in a direction perpendicular to the magnetic recording medium. In the magnetoresistive head 2 for reading the information recorded on the magnetic recording medium based on the resistance value of the magnetoresistive element which changes corresponding to the change in the magnetic field strength applied from the recording medium, From the outside of the head 2, a magnetic field for strengthening or weakening the strength of the longitudinal bias magnetic field is supplied by the permanent magnets 6 and 7, and a transverse magnet is supplied by the permanent magnet 8. A magnetic field that either strengthens or weakens the magnetic field of As is supplied, or only the permanent magnets 6 and 7 are used to supply a magnetic field that strengthens or weakens the strength of the longitudinal bias field, or a permanent magnet 8 is used. Is used by providing a magnetic field that either strengthens or weakens the strength of the transverse bias field.

The strength of the magnetic field supplied from the outside is
It should be in the range of 5 to 30 oersteds.

[0021]

With the above-mentioned structure, even if the thickness of the SAL layer deviates from the specified value, the strength of the bias magnetic field applied to the magnetoresistive effect element can be optimized from the outside of the magnetoresistive head 2. Therefore, the yield of products can be improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining an embodiment of the present invention. When adjusting the longitudinal bias magnetic field with respect to the magnetoresistive head 2 formed on the slider 1 by a thin film process, the data actually recorded on the magnetic recording medium is read and its output is large. When the output is too small, the longitudinal bias magnetic field is weak. When the output is too small, the longitudinal bias magnetic field is strong. This direction can be detected by performing a ρH test), and when the strength of the longitudinal bias magnetic field is weak, the magnetic field is applied in the direction indicated by the arrow A.

By doing so, when the strength of the longitudinal bias magnetic field of the magnetoresistive effect element 5 shown in FIG. 3 is insufficient, the insufficient magnetic field strength can be compensated. At this time, the magnetic field strength generated by the permanent magnets 6 and 7 needs to be at least 5 Oersted, and in order to prevent the magnetoresistive effect element 5 from being magnetically destroyed, it is preferable to set it to 30 Oersted or less.

If the strength of the longitudinal bias magnetic field shown by the arrow A in FIG. 3 is too strong, the direction of the magnetic field provided by the permanent magnets 6 and 7 is, of course, opposite to that of the arrow A. In addition, when the lateral bias magnetic field is adjusted for the magnetoresistive head 2 formed on the slider 1 by a thin film process, the read waveform of the magnetoresistive head 2 varies depending on the strength of the lateral bias magnetic field. Because of asymmetry, the permanent magnet 8 is attached at the position shown in the figure, and when the strength of the lateral bias magnetic field shown by the arrow C in FIG. 3 is weak, a magnetic field is applied in the direction shown by the arrow C.

By doing so, when the strength of the lateral bias magnetic field of the magnetoresistive effect element 5 shown in FIG. 3 is insufficient, the insufficient magnetic field strength can be supplemented. At this time, the magnetic field strength generated by the permanent magnet 8 needs to be at least 5 Oersted, and in order to prevent the magnetoresistive effect element 5 from being magnetically destroyed, it is better to set it to 30 Oersted or less.

If the strength of the lateral bias magnetic field shown by the arrow C in FIG. 3 is too strong, the direction of the magnetic field provided by the permanent magnet 8 is, of course, opposite to that of the arrow C. The direction of the magnetic field of the permanent magnet 8 can be determined by the symmetry of the read waveform.

When adjusting the lateral bias magnetic field, a permanent magnet 9 may be attached at the position shown in the figure instead of the permanent magnet 8 and a magnetic field may be applied in the direction of arrow C or in the opposite direction.

[0028]

As described above, according to the present invention, a longitudinal bias magnetic field and a lateral bias magnetic field are applied to the magnetoresistive effect element so that the change in the resistance value of the magnetoresistive effect element is caused by the change in the magnetic field strength generated by the recording medium. Since the longitudinal bias magnetic field and the lateral bias magnetic field can be adjusted to the optimum strength from the outside of the corresponding magnetoresistive head, the product yield can be improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a magnetic head.

FIG. 3 is a diagram illustrating a bias magnetic field of a magnetoresistive effect element.

[Explanation of symbols]

 1 slider 2 magnetoresistive head 3 lead wire 4 magnetic recording medium 5 magnetoresistive element 5a SAL layer 5b non-magnetic spacer layer 5c BCS layer 6-9 permanent magnet

Claims (2)

[Claims] 1. A strip-shaped magnetoresistive effect element is arranged such that a longitudinal side surface thereof faces a magnetic recording medium so that a plane of the magnetoresistive effect element is perpendicular to the magnetic recording medium. Then, with respect to the longitudinal direction of the magnetoresistive effect element, a longitudinal bias magnetic field is applied in a direction parallel to the magnetic recording medium, and a lateral bias magnetic field is applied in a direction perpendicular to the magnetic recording medium, whereby the magnetic recording is performed. In the magnetoresistive head (2) for reading information recorded on the magnetic recording medium based on the resistance value of the magnetoresistive element that changes in response to the change in magnetic field strength given from the medium, A magnetic field for increasing or weakening the strength of the longitudinal bias magnetic field and / or the strength of the lateral bias magnetic field is supplied from the outside of the mold head (2) to the magnetoresistive head. Field application method. 2. The strength of the magnetic field supplied from the outside is 5
2. The method for applying a magnetic field to a magnetoresistive head according to claim 1, wherein the magnetic field is in the range of 30 to 30 oersteds.