JPH1011718A - Magneto-resistive head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magneto-resistive head for a high recording density which is stable in head performance, high in reliability and free from noise, by providing the underside of the hard magnetic film of a magnetic domain control layer with ruggedness by working flaws. SOLUTION: This magneto-resistive head 100 has an MR sensor part 52 and the magnetic domain control layer 60 imparted ruggedness by the working flaws on a lower gap film 20 which is a ground surface together with the hard magnetic films 64 parted on both sides of this MR sensor part 52. As a result, adequate longitudinal bias magnetic fields are stably impressed on the MR sensor part 52 and, therefore, the head characteristics free from Barkhausen noise is obtd. and the head characteristics excellent in stability with the lapse of time are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic transducer for reading an information signal from a magnetic recording medium, and more particularly to a magnetic recording device, and more particularly to a magnetoresistive head using a magnetoresistance effect used in a magnetic disk device. Things.

[0002]

2. Description of the Related Art The main problems of a magnetoresistive head are high output and Barkhausen noise control. Therefore, the prior art teaches that two bias magnetic fields must be applied to the magnetoresistive film so that the magnetoresistive element (MR sensor) operates optimally. One is a bias magnetic field applied to the magnetoresistive film so that the response to the magnetic field from the magnetic recording medium becomes linear for the purpose of increasing the output, and is called a lateral bias magnetic field. The other bias magnetic field is applied so as to form a single magnetic domain in the magnetoresistive film for the purpose of suppressing Barkhausen noise, and is called a longitudinal bias magnetic field.

It is well known that a lateral bias magnetic field is applied through a current to, for example, a three-layer structure in which a magnetoresistive layer, a metal layer, and a soft magnetic layer for applying a bias to the magnetoresistive layer are stacked. On the other hand, a method of applying a vertical bias magnetic field using the three-layer structure for applying the horizontal bias magnetic field is described in JP-A-3-125311. According to this specification, after patterning the three-layer structure into a predetermined shape, a hard magnetic film for applying a vertical magnetic field is disposed on both sides thereof. The hard magnetic layer is in contact with the MR sensor portion composed of the three-layer structure in a tip region coextensive with the electrode structure, and realizes a longitudinal bias by exchange coupling between the hard magnetic layer and the MR sensor. . Therefore, the MR sensor is magnetized in a specific direction along the longitudinal direction of the pattern. The problem with this method is that when the soft magnetic film and the hard magnetic film constituting the MR sensor are exchange-coupled, the squareness ratio and the coercive force of the hard magnetic film decrease.

One of the measures for improving the magnetic properties of the hard magnetic film for the magnetic domain control film is described in Japanese Patent Application No. 7-188812. This specification describes that a hard magnetic film is formed on a ferromagnetic base. By using a ferromagnetic underlayer, direct exchange coupling with the soft magnetic film constituting the MR sensor can be prevented, so that the magnetic properties of the hard magnetic film are not deteriorated. By applying the above invention, Barkhausen noise can be suppressed at a considerably high level, but it has not reached a perfect level.

[0005]

In the above-mentioned known example, it is possible to guide the pole generated from the hard magnetic film to the vicinity of the end of the MR sensor by improving the squareness ratio of the hard magnetic film. When the longitudinal bias magnetic field generated from the pole increases,
The effect of suppressing Barkhausen noise induced by the MR sensor is improved. The challenge is to maintain the poles with safety over time. This is because the magnetic field from the medium and the recording magnetic field naturally affect not only the MR sensor but also the hard magnetic films separated on both sides of the MR sensor. To minimize this effect, it is necessary to reduce the effect of the magnetic properties of the hard magnetic film on the external magnetic field, that is, to increase the coercive force of the hard magnetic film.

In the development of a conventional medium, a non-magnetic film such as Cr and CrTi is provided as a base film of a recording magnetic film,
Further, it is well known that by adding irregularities on the substrate on which the recording magnetic film and the underlying nonmagnetic film are formed, the squareness ratio and coercive force of the hard magnetic film can be improved.
However, the prior art in which the hard magnetic film at the end of the MR sensor is formed on the soft magnetic film and the magnetic characteristics of the hard magnetic film are affected by the irregularities on the substrate is not known.

An object of the present invention is to provide a magnetoresistive head having improved magnetic properties of a magnetic domain control film, that is, an increased coercive force without decreasing the squareness ratio of a hard magnetic film.

Another object of the present invention is to provide a magnetoresistive head whose magnetic domain is controlled so as to provide an optimum longitudinal bias in the active region of the MR sensor.

[0009]

The magnetic domain control film according to the present invention is spaced on both sides of an MR sensor section forming a central active region. The magnetic domain control film is for applying a longitudinal bias to the MR sensor unit. The magnetic domain control film according to the present invention does not impair the squareness ratio even on the soft magnetic film and aims to control the magnetic domain by exchange coupling with the MR sensor for the purpose of applying a required longitudinal bias magnetic field to the end of the MR sensor. is there. Further, in order to secure the stability of the magnetoresistive head against an external magnetic field, it is necessary to further improve the coercive force.

The magnetoresistive head according to the present invention is affected by an external magnetic field of both the medium magnetic field and the write magnetic field, and is required to always have stable head characteristics even under the influence of the external magnetic field. Therefore, the magnetic domain control film according to the present invention is also required to have a stable longitudinal bias magnetic field applied to the MR sensor. That is, in order to maintain the squareness ratio of the magnetic domain control film at a constant value with respect to the repetition of the direction and the number of times of the external magnetic field, the coercive force of the magnetic domain control film must be increased so as to be able to oppose the strength of the external magnetic field. Is essential.

In order to increase the coercive force of the magnetic domain control film, it is well known that the magnetic domain control film has been conventionally developed by the following three methods. (1) Optimizing the composition of the hard magnetic film constituting the magnetic domain control film, (2) Controlling the orientation of the hard magnetic film by selecting a base film such as Cr and CrTi, (3) Utilizing unevenness on the substrate There is control of the orientation of the hard magnetic film. However, the prior art in which the hard magnetic film at the end of the MR sensor is formed on the soft magnetic film and the magnetic characteristics of the hard magnetic film are affected by the unevenness on the substrate is not known. The coercive force of the hard magnetic film can be increased by controlling the unevenness on the lower gap film forming the hard magnetic film.

The magnetic domain control film according to the present invention is made of a hard magnetic film formed on the lower gap film by giving a scratch after forming the lower gap film. Here, the scratch is specified not in an in-plane unspecified direction but in the direction of the magnetic domain control film separated on both sides via the MR sensor unit or in the magnetization direction of the hard magnetic film constituting the magnetic domain control film. It is more desirable to apply scratches. This is because the coercive force of the hard magnetic film is further increased by imparting anisotropy induced by scratches in the magnetization direction of the magnetic domain control films spaced on both sides of the MR sensor unit. Take advantage of that. Also,
When the depth of the scratch to be applied becomes large, it also affects the inside of the MR sensor, and the depth of the scratch is 10 nm.
The extent is the limit. That is, if the scratch depth is 10 nm or more, orange peel coupling occurs between the magnetoresistive film and the soft bias ferromagnetic film in the MR sensor, which may cause Barkhausen noise.

The hard magnetic film constituting the magnetic domain control film is M
In order to apply a required longitudinal bias magnetic field to the R sensor portion, it is desirable to use a hard magnetic film on a ferromagnetic base. This is because the hard magnetic film on the ferromagnetic base not only exchange-couples with the MR sensor, but also does not impair the squareness ratio of the hard magnetic film on the soft magnetic film. Although the soft magnetic film has a footing structure at the end of the MR sensor, a necessary pole can be generated so that a longitudinal bias magnetic field can be applied to the end of the MR sensor. This is because a hard magnetic film having a high squareness ratio can be obtained. Of course, even if a hard magnetic film without a ferromagnetic underlayer is used, a good squareness ratio can be provided by selecting the forming conditions, and thus it is not necessary to use a ferromagnetic underlayer.

In the magnetoresistive head according to the present invention, since an appropriate longitudinal bias magnetic field is stably applied to the MR sensor, not only head characteristics free of Barkhausen noise can be obtained but also stability over time. It is possible to obtain head characteristics having excellent properties.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment, a magnetic disk drive to which a magnetoresistive head according to the present invention is applied will be described.
This will be described with reference to FIG.

FIG. 3 is a perspective view showing a schematic structure of the magnetic disk drive. The apparatus comprises a disk 203 (shown as one sheet in the figure) held on a spindle 202 and a spindle 2
02 and a movable carriage 205
The magnetic head 204 held by the
5 and a base 201 that supports these voice coil motors. Although not shown in the figure, a voice coil motor control circuit for controlling the voice control motor is provided according to a signal sent from a host device such as a magnetic disk control device.

This apparatus also has a function of converting data sent from a higher-order apparatus into a current to be passed to a magnetic head and a function of converting data sent from the disk 203 into a digital signal. A write / read circuit having a function of converting into a signal and an interface are provided.

Next, the operation of the magnetic disk drive will be described by taking a read operation as an example. When an instruction of data to be read is given from the host device to the control circuit via the interface, the present device uses the control current from the voice coil motor control circuit to cause the voice coil motor to drive the carriage, and the designated data is transmitted. The magnetic head 204 is moved to the stored track position at a high speed and positioned accurately. For this positioning, a data surface servo method is used. That is, servo information is stored together with the data on the disk 203, and the positioning accuracy is improved by the servo information. The motor supported by the base 201 rotates a disk 203 having a diameter of 3.5 inches or less attached to the spindle 202. Next, in accordance with a signal from the write / read circuit, the designated predetermined magnetic head is selected, and after detecting the head position of the designated area, the data signal on the disk is read. This reading is performed by the data magnetic head 204 connected to the write / read circuit exchanging signals with the disk 203. The read data is converted into a predetermined signal.

Next, the magnetic disk drive uses
A magnetoresistive head 100 according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view showing a schematic structure of a dual head comprising a magnetoresistive head 100 according to the present invention. In FIG. 1, one side half of the write head above the upper shield film 90 is omitted. FIG. 2 is an enlarged perspective view of a magnetic sensing portion of the magnetoresistive head 100. In FIG. 2, the upper gap film and the upper shield film 90 are omitted.

As shown in FIGS. 1 and 2, the magnetoresistive head 100 has a lower magnetic shield layer 10, a lower gap film 20 formed on the lower magnetic shield layer 10, and a lower gap film 20. A soft bias film 30 formed on the film 20; a shunt metal film 40 formed on the soft bias film 30; a magnetoresistive film 50 formed on the shunt metal film 40; A magnetic domain control layer 60 composed of a pair of layers formed at predetermined locations on the resistive effect film 50 at predetermined intervals, a signal extraction electrode 70 formed by the same lift-off method as the magnetic domain control layer 60, An upper gap film 80 formed to cover each of the films, each layer, and the signal extraction electrode;
And an upper magnetic shield layer 90 formed on the upper gap film. FIG. 1 shows a structure in which the upper magnetic shield layer 90 also serves as the lower magnetic core of the write head. After forming an insulating film and a coil on the upper side of the magnetoresistive head 100, the upper magnetic core 110 is formed. 2 shows a dual head including a write head.

The function and material of each layer and cornea will be described below. The upper and lower magnetic sheet layers 90 and 10 prevent the magnetic field other than the signal detection electrodes from affecting the magnetoresistive film 50 and increase the signal resolution of the magnetoresistive magnetic head 100. The materials are NiFe alloy, Co
It is soft magnetic, such as system amorphous, Co system crystalline, and Fe system crystalline, and has a film thickness of about 2 to 4 μm.

Adjacent to the magnetic shield layers 90 and 10, the soft bias film 30, the shunt metal film 40, and
A magnetoresistive element (MR) comprising the magnetoresistive film 50
Sensor) and the upper and lower gap films 80 and 20 disposed so as to sandwich the magnetic domain control layer 60 and the signal extraction electrode conductor 70 electrically connect the MR sensor to the upper and lower magnetic shield layers 90 and 10. It acts magnetically and is made of a nonmagnetic or insulating material such as an alumina film. Top,
Since the thickness of the lower gap films 80 and 20 affects the reproduction resolution of the magnetoresistive head 100, it depends on the recording density desired for the magnetic head.
m is the shield interval. Here, in order to cope with the high recording density, it is necessary to reduce the output of the high frequency region by reducing the shield interval. However, when the thickness of the upper and lower gaps is on the order of 0.1 μm, there is a problem that the breakdown voltage is poor. As a countermeasure for this problem, a bias is applied during film formation, and A
By forming a film in a gas containing H ₂ or He mixed with r, or by adding SiO ₂ or Ta ₂ O ₅ to alumina, pinholes in the film are reduced, the film quality of alumina is improved, Have improved.

The magnetic domain control layer 60 is formed only at both ends of the MR sensor. The longitudinal magnetic field in the longitudinal direction is maintained so that the magnetoresistive film 50 is maintained in a single magnetic domain state using a hard magnetic film. Is applied to the magnetoresistive film. As a result, generation of domain walls in the magnetoresistive effect film 50 can be prevented, and Barkhausen noise caused by the generation of domain walls can be reduced. The reason why the magnetic domain control layer 60 is provided only at the end of the magnetoresistive film 50 is that if this end is maintained in a single magnetic domain state, the central region is forcibly changed to a single magnetic domain state. To do that. Further, in such a structure, since the magnetic moment in the central region can easily change its angle, it is possible to prevent a decrease in sensitivity caused when a magnetic domain control layer is formed on the entire magnetoresistive film 50.

The magnetoresistive film 50 is made of a Ni—Fe alloy,
It is formed of a ferromagnetic thin film whose electric resistance changes depending on the direction of magnetization using a Ni-Co alloy, a Ni-Fe-Co alloy, or the like. Its thickness is 0.01 to 0.04 μm.

The electrode conductor 70 for extracting a signal is provided with a sufficient current (for example, 1 × 10 ⁶ to 1 × 1) for the magnetoresistive film 50.
0 ⁸ A / cm ² ), it is desirable to use a Ta thin film having high withstand current.

The shunt bias metal film 40 and the soft bias ferromagnetic film 30 act to apply a lateral bias magnetic field to a level sufficient to make the magnetoresistive film 50 highly sensitive. The direction of application of the lateral bias magnetic field is perpendicular to the direction given by the magnetic domain control film 60 according to the present invention. Ti, Ta, N
Materials such as b and Mo are used. Usually, the film thickness is 1
0 to 40 nm. NiFeRh, NiFeRu, NiFeCr,
A material having a relatively high saturation magnetic flux density and specific resistance, such as CoZrMo, is used. This is because the higher the saturation magnetic flux density, the thinner the film thickness, and the higher the specific resistance, the greater the shunt ratio to the magnetoresistive film,
This is to improve the output. For that, NiF
It is also possible to use a composite material in which a ceramic material such as ZrO ₂ or Al ₂ O ₃ is added to e-metal.

Next, a method of manufacturing the magnetoresistive head shown in FIG. 1 will be described. The following thin film forming method and patterning method are performed by using sputtering, photolithography, ion milling, dry etching, and the like.

First, an amorphous CoNbZr film as the lower shield film 10 is formed to a thickness of 2 μm, and an alumina film as the lower gap film 20 is formed on the CoNbZr film in a thickness of 0.05-0.
It is formed to a thickness of 20 μm. Then, a scratch is formed on the lower gap film. The direction in which the flaw is applied is not particularly limited, but it is desirable to limit the direction to the magnetic domain control films separated on both sides via the MR sensor unit. As a result, the hard magnetic film formed on the lower gap film has induced anisotropy due to scratches, which leads to an improvement in the magnetic properties of the hard magnetic film. Next, the lower shield film 10 and the lower gap film 20 are patterned into a predetermined shape. Here, the end of the lower shield film 10 is patterned so as to be inclined with respect to the substrate surface as shown in FIG. this is,
This is to prevent the signal detection electrode 70 formed so as to cover the lower shield film 10 from breaking at the end of the lower shield film 10. Next, a NiFeCr film is formed on the lower gap film 20 as a soft bias ferromagnetic film 30.
After a 5 nm thick film is formed, a Ta film of the shunt bias metal film 40 is formed to a thickness of 8 nm, and a NiFe alloy film of the magnetoresistive film 50 is formed to a thickness of 20 nm. Thereafter, ion milling is performed at a time to form the shape shown in FIG. Subsequently, before the magnetic domain control film and the electrodes are formed in a predetermined shape by the lift-off method, M is formed to prevent an increase in contact resistance.
A process of removing the surface oxide film of the MR sensor by lightly dry etching the R sensor is included. Magnetic domain control film 6
Numeral 0 is a ferromagnetic underlayer 62 formed of an FeCr film having a thickness of 5 nm and a hard magnetic film 64 formed of CoCrPt having a thickness of 48 nm. Thereafter, T is deposited on the TaW film serving as the signal detection electrode 70.
A two-layer film a is formed to a thickness of 0.15 μm by a lift-off method. After that, a NiFe alloy film as the upper gap film 80 and further as the upper shield film 90 is formed with a thickness of 3 to 4 μm, and an alumina film as the protective film is formed with a thickness of 10 μm.

Here, the magnetoresistive head according to the present invention is the dual head shown in FIG. 1 (a recording head is disposed above the magnetoresistive head). The recording head has the same basic structure as a conventional self-recording / reproducing thin film magnetic head.

The magneto-resistance effect type head according to the present invention is an MR head.
There is a feature in that irregularities are provided on the base of the sensor portion and the hard magnetic film separated on both sides thereof. FIG. 4 shows a frequency distribution of the output fluctuation rate of the magnetoresistive head having the magnetic domain control film. The figure also shows, for comparison, the results of a magnetic head using a magnetic domain control film before the present invention (no irregularities due to scratches on the lower gap film). Here, in each case, the longitudinal bias magnetization ratio (Br of the hard magnetic film)
(The ratio between t and Bs · t of the magnetoresistive film) is the same as 1.7. Output fluctuation rate is 10 for read / write evaluation.
Repeated 00 times and displayed as the maximum / minimum output ratio between 1000 measurements. The average value of the fluctuation occurrence level is 6% in the magnetoresistive head having the magnetic domain control film of the present invention.
It can be seen that the degree is low and good. The characteristic difference is considered to be a difference in coercive force of the hard magnetic film.

FIG. 5 shows the relationship between the coercive force of the hard magnetic film and the depth of the scratch before forming the hard magnetic film. By providing scratches, the coercive force increases, but the coercive force cannot be further increased if the scratch depth is too deep. In contrast,
It has been separately confirmed that if the scratch depth is too deep to be 10 nm or more, orange peel coupling occurs between the magnetoresistive film and the soft bias ferromagnetic film in the MR sensor, which may cause Barkhausen noise. is there.

The present invention is not limited to FIG. Another embodiment is shown in FIG.

The present invention is an example in which the underlying layer of the hard magnetic film 64 is the lower gap film and the ferromagnetic underlying film 62 is not provided. According to the present invention, the squareness ratio and the coercive force of the hard magnetic film can be improved without the ferromagnetic underlayer. The effect of another embodiment is at the same level as the result shown in FIG.

Further, the magnetoresistive head of the present invention is not limited to a magnetic disk drive, but is also applicable to a magnetic tape and further to a magnetic sensor for detecting various magnetic fields.

[0036]

According to the present invention, a magneto-resistive head for high recording density with high reliability and no noise can be realized.

Further, according to the present invention, it is possible to realize a magnetoresistive head having high process stability and suppressing the above-mentioned variation in head performance.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a dual head having a magnetic domain control film according to the present invention.

FIG. 2 is a perspective view showing a magnetoresistive head according to one embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a magnetic disk drive of the present invention.

FIG. 4 is a frequency distribution of the output fluctuation rate of the magnetic domain resistance effect type head having the magnetic domain control film of the present invention.

FIG. 5 is a diagram showing the relationship between the coercive force of a hard magnetic film and the depth of a scratch before forming a hard magnetic film.

FIG. 6 is a perspective view showing a magnetoresistive head according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Lower magnetic shield layer, 20 ... Lower gap film, 30 ... Soft bias ferromagnetic film, 40 ... Shunt metal film, 50 ... Magnetoresistance effect film, 52 ... MR
Sensor, 60: magnetic domain control layer, 62: magnetic film, 64: hard magnetic film, 70: signal detection electrode, 80: upper gap film, 90: upper magnetic shield film, 100: magnetoresistive head, 11
0: upper magnetic core for write head, 201: base,
202: spindle, 203: disk,
204: magnetic head; 205: carriage.

Claims (1)

[Claims] (1) A structure in which a thin magnetoresistive layer of a ferromagnetic material, a thin metal layer in contact with the magnetoresistive layer, and a thin soft magnetic layer for applying a bias to the magnetoresistive layer is laminated. A magnetoresistive effect in which a hard magnetic film that becomes an active area against an external magnetic field and controls the magnetic domain so that the magnetic film of the structure constituting the active area is maintained in a single magnetic domain state is disposed on both sides of the active area. A magnetoresistive head, wherein the head has a processing flaw below a hard magnetic film that controls the magnetic domain of the structure. (2) In the magnetoresistive head according to claim 1, wherein the hard magnetic film for controlling the magnetic domain has a processing flaw in the same direction as the magnetization direction of the magnetic domain control film. Resistance effect type head. (3) In the magnetoresistive head according to claim 1, a processing scratch on a base of the hard magnetic film for controlling the magnetic domain has a thin magnetoresistive layer of the ferromagnetic material, and a thin metal in contact with the magnetoresistive layer. Before forming a structure in which a layer and a thin soft magnetic layer for applying a bias to the magnetoresistive layer are laminated, the process is formed on a lower gap insulating film which is a base of the structure. Magnetoresistive head. (4) A magnetic disk drive equipped with the magnetoresistive head according to any one of claims 1, 2 and 3.