JP2000182222A - Magnetoresistive magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the thermal stability and ESD durability of an MR head. SOLUTION: In this magnetoresistive magnetic head provided with a thin-film magneto-resistance element 9, a couple of electrode layers which are electrically connected to the right and left ends of the element 9, and shield layers 7 and 12 which are stacked on the top and reverse sides of the thin-film magneto- resistance element 9 and electrode layer 10 across gap layers 9 and 11, a thermal buffer film 20 consisting of a material having larger heat conductivity than the constituent materials of the gap layers 8 and 11 is formed adjacently inside the thin-film magneto-resistance element 9 in the direction of stripe height SH.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-resistance effect type magnetic head incorporated in a magnetic recording device such as a hard disk device for reading information recorded on a magnetic recording medium.

[0002]

2. Description of the Related Art As a reproducing magnetic head built in a current hard disk drive, a magnetoresistive magnetic head having a thin film magnetoresistive element as a magnetic sensing portion is mainly used. The magnetoresistive effect is an effect in which when a magnetic field is applied to a conductive magnetic material, the electric resistance changes. Using a device having this effect, a change in the magnetic field is detected, and information recorded on a magnetic medium is read. This magnetoresistive effect element (MR
The device has a ferromagnetic thin film having uniaxial anisotropy in the sense current direction, and when an external magnetic field is applied from the magnetic recording medium in the direction of hard magnetization, the electric resistance of the ferromagnetic thin film changes due to magnetization rotation. There are an anisotropic magnetoresistance effect element (AMR element) and a spin valve element exhibiting a large magnetoresistance effect. These magnetoresistive elements detect a resistance change by applying a sense current, that is, detect a magnetic field instead of a time derivative of a magnetic flux, so that the output is not affected by the moving speed of the magnetic recording medium and is 100 MHz. The following practical bandwidths have essentially no frequency limit, no inherent noise mechanism that degrades the signal-to-noise ratio, are easy to miniaturize, and are recorded at extremely high areal recording densities on magnetic recording media. There is an advantage that the information can be easily identified and taken out.

The principle of such an MR head has been clarified by Robert Hunt's paper published in 1970. Hunt's first MR head was an exposed MR head with the MR element exposed. However, exposed MR
The head has a problem that the output pulse is spread and the short wavelength spectrum is rapidly rolled off.

In order to avoid such a problem and accurately read information recorded on a recording medium at a high density, a shield type MR head in which an MR element is sandwiched between upper and lower shield layers having high magnetic permeability has been developed. According to such a shield type MR head, the sensing of the magnetic pole can be delayed until the MR element passes just above the magnetic pole of the medium.
With the advent of such a shield type MR head, practical characteristics have been obtained, and it has become the mainstream of the reproducing head in the present small and large-capacity hard disk.

In the shield type MR head, a gap layer made of a non-magnetic insulator is provided between the shield layer and the MR element. That is, the MR element is buried in the gap layer. As a constituent material of the gap layer, alumina is generally used in consideration of various factors such as film forming workability, cost, and electric and magnetic properties.

[0006]

In a hard disk drive incorporating the above MR head, the temperature of the MR element is raised by the operating environment such as the heat generated by the disk drive motor, and the sense current applied to the MR element causes the MR element to increase in temperature.
The R element itself generates heat. According to the experiments of the present inventors,
It has been found that the lower the device temperature, the better the thermal stability and the more stable the output of the MR device. Improving the thermal stability of the MR element is an indispensable solution for further improving the recording density.

Another important problem of the MR head is ESD durability. Since the MR element has a very thin film thickness on the order of nanometers in order to improve the sensitivity to an external magnetic field, the charge charged on the disk surface jumps into the MR element at the time of contact start / stop. A pulse current is generated in the MR element. Further, at the time of manufacture and inspection of the device, charge may jump from the terminal side, and a pulse current may be applied to the MR element through the electrode. There is a concern that the yield may be reduced due to device destruction due to the pulse current, and improvement in durability is required.

Accordingly, an object of the present invention is to provide a magnetoresistive magnetic head capable of preventing an excessive rise in temperature of an MR element, improving output stability, and improving ESD durability. And

[0009]

Means for Solving the Problems The present inventors have developed an MR element (thin film magnetoresistive element), a pair of electrode layers electrically connected to the left and right ends of the element, and an MR element and an electrode layer. First, various considerations were made to improve the thermal stability of a magnetoresistive head having a shield layer stacked above and below a gap layer via a gap layer. The improvement of thermal stability can improve the heat radiation from the MR element by securing the heat radiation area by increasing the surface area, and shield the heat generated by self-heating by the sense current from the upper and lower layers through the gap layer. It is believed that this is achieved by efficient transmission to the layers.

Therefore, in order to increase the heat dissipation area, the inventors of the present invention firstly use a heat source made of a material having a higher thermal conductivity than the material of the gap layer adjacent to the inside of the MR element in the stripe height direction. A buffer film was formed. Due to the presence of the thermal buffer film, the heat of the MR element is smoothly dispersed in the thermal buffer film, and thereby a large heat radiation surface area can be secured, so that the thermal stability is improved and, consequently, the output of the MR element is stabilized. Is achieved.

It is preferable to use a material having a large specific heat capacity as a material constituting the thermal buffer film. further,
By increasing the volume (dimensions) of the thermal buffer film, a large heat capacity of the thermal buffer film is ensured, so that the amount of heat stored in the thermal buffer film has a margin and the heat of the MR element can be sufficiently received. Is preferable. Furthermore, MR
In order to improve the flow of heat from the element, it is desirable that the thermal conductivity of the thermal buffer film be higher than the thermal conductivity of the MR element.

The constituent material of the thermal buffer film has a heat transfer coefficient:
Those ^{5W / m 2 · K~500W / m} 2 · K are preferred.

The specific heat capacity is from 0.1 J / kg · K to
Those having 1.0 J / g · K are preferred.

Further, in order to suppress a decrease in the reproduction sensitivity of the MR element, the larger the electrical resistivity of the constituent material of the thermal buffer film, the better. Preferably, the electrical resistivity of the thermal buffer film is higher than that of the MR element. Because the output of the MR element is
(Resistance change due to MR effect × current density). Therefore, if most of the sense current flows through the thermal buffer film, M
This is because the current density in the R element is greatly reduced, and the sensitivity is deteriorated. The most preferable property of the thermal buffer film in this case is an electrical insulator, and
It has excellent thermal conductivity. However, in general, these properties tend to conflict. Therefore, the material is appropriately selected according to the required performance. However, in order to form a thermal buffer film with a material having a relatively small electric resistivity and to suppress a significant decrease in the read sensitivity, it is necessary to use a thermal element with the MR element. At the boundary with the buffer film, the thermal coupling can be good and the electrical coupling can be bad.
Such a boundary portion may be formed, for example, by sandwiching a very thin insulating layer between the MR buffer and the thermal buffer film, by sandwiching a high-resistance body, or by forming a stripe of the MR element after the MR element is formed. This can be obtained by forming an insulating boundary layer having a higher electrical resistivity than the thermal buffer film at the boundary between the MR element and the thermal buffer film, for example, by oxidizing the inner end in the height direction by an oxidation process to make it insulating.

As described above, in order to improve the thermal stability of the MR head, the constituent material of the thermal buffer film is not limited, and the thermal conductivity is higher than that of the gap layer represented by alumina. May be selected from known metals, alloys, and other materials as appropriate according to the required performance, reproduction characteristics, and the like. For example, the thermal buffer film may be composed of a thermistor whose electric resistance decreases as the temperature rises. With the thermistor as described above, when the temperature of the element is relatively low, the sense current is selectively passed through the MR element to ensure reproduction sensitivity, while when the element is relatively high temperature, By diverting a part of the sense current to the thermal buffer film composed of the thermistor, the amount of heat generated by the MR element can be suppressed.
Further, the thermal buffer film can be formed of a negative resistor having a property that the voltage applied to both ends thereof decreases as the current flowing inside increases.

Further, the existence of the above-mentioned thermal buffer film makes it possible to improve the ESD durability of the MR element by diverting a high-frequency pulse current generated by electrostatic discharge to the thermal buffer film. Thus, according to the present invention,
It is also possible to achieve at once the heat radiation of self-heating by the sense current and the durability against pulse-like electric stress due to electrostatic discharge.

When importance is attached to the improvement of the ESD durability,
It is advantageous that the thermal buffer film is made of a conductor film.
That is, in a magnetoresistive magnetic head including an MR element and a pair of electrode layers electrically connected to the left and right ends of the element, the left and right widths of the element are adjacent to the inside of the MR element in the stripe height direction. By forming a conductor film over almost the entire length in the direction, the pulse current generated due to the electrostatic discharge is shunted to the conductor film, preventing application of a large pulse current to the MR head, and improving the ESD durability. It is planned.

Of course, even if the conductor film is arranged adjacent to the MR element and the sense current is diverted to the conductor film,
It is not necessary to provide an insulating layer between the conductor film and the MR element, provided that sufficient reproduction sensitivity can be obtained by the film configuration or other structure of the MR element. When the MR element and the conductor film are coupled so that the electrical coupling between the MR element and the conductor film is good, the conductor film is joined to the thin film magnetoresistive element over substantially the entire length in the left-right direction. At the same time, by forming the stripe height in the direction of the stripe height to be high at the center in the left-right direction and to be low at the end in the left-right direction, the flow rate of the sense current to the conductor film at the center in the left and right directions is increased, and The current density flowing through the film can be increased at the left and right end portions and reduced at the center portion. In the conventional MR head, since the current density of the MR element is constant over the entire length in the left-right direction,
Although the temperature at the central portion of the element, which is difficult for heat to escape, is likely to rise and the element is likely to be destroyed, according to the above configuration, the current density at the central portion can be reduced, and the calorific value at the central portion can be suppressed. Occurrence is reduced.

In the case where a conductor film is arranged adjacent to the MR element, if the reproduction sensitivity is degraded due to the distribution of the sense current, which is a direct current, to the conductor film, the sense current is not applied to the MR film. In order to prevent a high-frequency pulse current from flowing through the conductor film while preventing the shunt from flowing into the body film, it is useful to form a slit extending in the stripe height direction at an intermediate portion in the left-right direction of the conductor film. . If such a slit is formed, a sense current cannot flow through the slit portion, but a high-frequency pulse current can flow through the slit portion by the principle of electrostatic discharge. Therefore, while preventing a significant decrease in the reproduction sensitivity, E
SD durability can be ensured. The slit is
Left and right pairs can be provided. Alternatively, considering the current density in the element width (track width) direction, a plurality of, preferably bilaterally symmetrical ones may be inserted. Further, it is preferable to provide slits on the left and right end sides, respectively. Note that the insulating material forming the gap layer enters the slit portion of the conductor film by forming the gap layer, and as a result, an insulating layer extending in the stripe height direction is formed in the middle of the conductor film in the left-right direction. Will be formed.

When the conductor layers are arranged adjacent to each other, the respective electrode layers are connected to the left and right ends of the thin-film magnetoresistive element and the left and right ends of the conductor film, respectively. Can be applied directly to the conductor layer.

When a spin valve film composed of an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductor layer and a free magnetic layer is employed as the MR element, the stripe height of the antiferromagnetic layer is By forming the free side magnetic layer larger than the stripe height, the spin valve element itself can have properties of ESD durability, thermal stability, and prevention of reduction in reproduction sensitivity. Preferably, a spin-valve magnetic head including a bottom-type spin-valve element in which an antiferromagnetic layer, a fixed-side magnetic layer, a non-magnetic conductive layer, and a free-side magnetic layer are stacked one above the other in this order In the above, the inner end face in the stripe height direction of the spin valve element is formed in a tapered shape so that the stripe height of the spin valve element gradually increases from the upper end side to the lower end side. . In addition, even if it is not tapered,
Each constituent layer of the element may be formed in a step shape.

According to the spin valve element having such a configuration,
The sense current selectively flows through the non-magnetic conductive layer having a relatively small electric resistance, and the stripe height of the free magnetic layer can be reduced to secure a large aspect ratio. Since the magnetization direction is stabilized, the antiferromagnetic layer can function as a heat buffer to reduce the element temperature while preventing the deterioration of the read sensitivity, and the high frequency pulse current due to the electrostatic discharge is also reduced. The current is shunted to the ferromagnetic layer to improve the ESD withstand voltage.

By applying each of the above-described means to the MR head independently or in combination, an action corresponding to the means can be obtained. The embodiment can be variously changed according to required performance.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a central longitudinal sectional view of a main portion of a magnetic head device 1, that is, a recording / reproducing element portion. The device 1 has an MR-inductive composite thin film magnetic head as a recording / reproducing element portion. 2 is provided. The composite head 2
Is formed by vertically integrating a magneto-resistance effect type magnetic head 3 and an inductive head 4 so that the inductive head 4 performs recording on a magnetic recording medium, and the magneto-resistance effect head 3 Reproduce information.

The magnetoresistive head 3 comprises a lower magnetic shield layer 7 made of a soft magnetic material having a high magnetic permeability and a nonmagnetic material formed on a substrate (slider) 6 whose surface is covered with a nonmagnetic undercoat 5. A lower half-gap layer 8, a thin-film magnetoresistive element 9 (MR element) whose electric resistance changes according to an external magnetic field strength, a conductive electrode layer 10 connected to both ends of the film 9, and a nonmagnetic material. Upper half gap layer 1
1. Upper magnetic shield layer 1 made of a soft magnetic material having a high magnetic permeability
2 are sequentially laminated.

As a constituent material of each layer, for example, permalloy (NiFe alloy), F
eAl alloy or Co-based amorphous alloy, and silicon oxide (SiO ₂ ), alumina (Al
₂ O ₃ ), aluminum nitride (AlN), or aluminum nitrate oxide (AlNO) can be used, and these layers can be formed by using an appropriate vacuum thin film forming technique such as a sputtering method. Further, as the MR element 9, a conventionally known AMR element or a GMR element such as a spin valve element or a granular element can be used.

The inductive head 4 includes a lower magnetic pole layer 12 made of a soft magnetic material, a magnetic gap layer 13 made of a nonmagnetic material, an insulating layer 14 serving as a coil base, an induction coil layer 15 made of a conductive material, and a coil layer 15. An insulating layer 16 made of a non-magnetic material and an upper magnetic pole layer 17 made of a soft magnetic material are sequentially laminated. The lower magnetic pole layer 12 of the head 4 is formed of a soft magnetic layer common to the upper magnetic shield layer of the magnetoresistive head 3. Note that the composite head 2 is covered with a protective layer 18 made of a nonmagnetic material, and terminals (not shown) electrically connected to both ends of the MR element 9 and both ends of the coil 15 are provided on the protective layer 18. 18 is exposed on the surface.

In FIG. 1, the lower surface is the surface facing the magnetic recording medium (ABS surface), and the slider 6 is mounted on the suspension so that magnetic information can be written to and reproduced from the hard disk by contact start / stop. Is mounted on the hard disk device.

In the magnetoresistive head 3 for reproduction according to the embodiment of the present invention, as shown in FIGS. 1 and 2, a thermal buffer film 20 is provided on the inside of the MR element 9 in the stripe height (SH) direction. Are formed adjacent to each other. This thermal buffer film 20 has substantially the same thickness as that of the MR element 9 and is formed so as to be embedded in the upper and lower half gap layers 8 and 11. Further, the planar shape may be, for example, a rectangular shape as shown in FIG.

The thermal buffer film 20 is made of a material having a higher thermal conductivity than the material of the gap layers 8 and 11. For example, when alumina is used as a constituent material of the gap layer, the thermal buffer film 20 can be made of bismuth or nichrome. With these materials, it is possible to form a film by a sputtering process.

Items to be considered when selecting materials include:
In order to increase the cooling efficiency of the MR element, it is preferable that the specific heat capacity is large. Specifically, carbon (DLC), tungsten, iron, gold, Pt, or the like can be used. In addition, by increasing the volume (dimension) of the thermal buffer film 20, a large heat capacity of the thermal buffer film 20 can be secured.

The thermal buffer film 20 may be made of a conductive material. However, when the sense current applied to the MR element 9 is diverted to the thermal buffer film 20, the current density in the MR element 9 is reduced and the reproduction is performed. In order to prevent the sensitivity from being significantly reduced, a material is selected such that the electrical resistivity of the thermal buffer film 20 is higher than the electrical resistivity of the MR element 9. Bismuth and nichrome are promising as such materials. Further, carbon (eg, graphite or DLC) can be used.

Further, the thermal buffer film 20 can be constituted by a thermistor or a negative resistor.

At the boundary between the thermal buffer film 20 and the MR element 9, a thin insulating boundary layer 21 is formed, and the heat transfer from the MR element 9 to the thermal buffer film 20 is good.
The sense current flowing through the element 9 is configured to hardly flow to the thermal buffer film 20. Such an insulating boundary layer 21
For example, it can be formed by laminating a high-resistance body on the inner end face of the MR element 9 or by insulating the surface layer portion by an oxidation process.

FIG. 3 shows a second embodiment of the present invention. In this embodiment, the thermal buffer film 20 is made of a conductor, has no insulating boundary layer, and is joined to the MR element 9 over substantially the entire length of the MR element 9 in the left-right direction. Further, the thermal buffer film 20 is formed such that the height in the stripe height direction is high at the center in the left-right direction and low at the ends in the left-right direction. Therefore, the current density due to the sense current of the MR element 9 is large at the left and right ends and small at the left and right center. As a result, the amount of heat generated in the central portion of the element where heat is difficult to escape is reduced, and the central portion of the element is prevented from being destroyed due to excessive temperature rise.

FIG. 4 shows a third embodiment of the present invention. In the present embodiment, the thermal buffer film 20 is made of a conductor, and the electrode layers 10 are also connected to left and right ends of the thermal buffer film 20. However, since the slits 22 extending in the stripe height direction are formed at two places in the middle part in the left-right direction, the sense current applied via the electrode layer 10 cannot pass through the thermal buffer film 20. Therefore, MR
The current density of the element 9 can be kept high, and the reproduction sensitivity can be made good. Further, when a high-frequency pulse current due to electrostatic discharge is applied, the high-frequency current can pass through the slit 22, so that the heat buffer film 2
The pulse current can flow to 0, and the pulse current flowing through the MR element 9 can be reduced accordingly. Thereby, the ESD durability of the MR element 9 can be improved. In the present embodiment, an electrical insulating layer may be provided at the boundary between the MR element 9 and the thermal buffer film 20.

[0038]

According to the present invention, it is possible to prevent the MR element from being excessively heated by inducing the heat of the MR element to the thermal buffer, thereby improving the thermal stability. In addition, a structure effective for improving the ESD durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional view of a magnetic head device including a magnetoresistive head according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a thermal buffer film of the magnetoresistive head according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a thermal buffer film of a magneto-resistance effect type magnetic head according to a second embodiment of the present invention.

FIG. 4 is a plan view showing a configuration of a thermal buffer film of a magnetoresistive head according to a third embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 magnetoresistive head 7 lower shield layer 8 lower half gap layer 9 thin film magnetoresistive element 10 electrode layer 11 upper half gap layer 12 upper shield layer 20 thermal buffer film (conductor film) 21 insulating boundary layer 22 slit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Higuchi 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture Inside ReadWrite SMI Corporation (72) Inventor Hideyasu Nagai 2 Egawa, Shimamoto-cho, Mishima-gun, Osaka No. 15-17, Readlight SMI Co., Ltd. (72) Inventor Masaya Hashimoto 4-53, Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. System Engineering Division (72) Inventor Masayuki Takagishi 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka F-term in ReadWrite SMI Co., Ltd. 5D034 BA03 BA09 BA17 BA19 BA21 BB01 CA02 DA07

Claims (11)

[Claims] 1. A thin film magnetoresistive element, a pair of electrode layers electrically connected to left and right ends of the element, and lamination layers above and below the thin film magnetoresistive element and the electrode layer via a gap layer. In a magnetoresistive head having a shield layer, a thermal buffer film made of a material having a higher thermal conductivity than the material of the gap layer is formed adjacent to the inside of the thin film magnetoresistive element in the stripe height direction. A magnetoresistance effect type magnetic head characterized by the following. 2. The magnetoresistive head according to claim 1, wherein the electrical resistivity of the thermal buffer film is higher than the electrical resistivity of the thin-film magnetoresistive element. 3. The magnetoresistive head according to claim 1, wherein the thermal conductivity of the thermal buffer film is higher than the thermal conductivity of the thin film magnetoresistive element. 4. The magnetoresistive head according to claim 1, wherein the thermal buffer film is made of a thermistor. 5. An insulating boundary layer having a higher electrical resistivity than the thermal buffer film is formed at a boundary between the thin film magnetoresistive element and the thermal buffer film. 2. A magnetoresistive head according to claim 1. 6. The magnetoresistive head according to claim 1, wherein the thermal buffer film is made of a conductor film. 7. A magnetoresistive head including a thin film magnetoresistive element and a pair of electrode layers electrically connected to left and right ends of the element, wherein the thin film magnetoresistive element is disposed inside a stripe height direction of the thin film magnetoresistive element. A magnetoresistive magnetic head, wherein a conductive film is formed adjacently over substantially the entire length of the element in the left-right width direction. 8. The conductive film is joined to the thin-film magnetoresistive element over substantially the entire length in the left-right direction of the element, and the height in the stripe height direction is high at the center in the left-right direction, and at the end in the left-right direction. 8. The magnetoresistive head according to claim 6, wherein the magnetoresistive head is formed low. 9. The magnetoresistive effect type magnetic head according to claim 6, wherein a slit extending in the stripe height direction is formed in a middle portion of the conductor film in the left-right direction. 10. The magnetoresistive head according to claim 9, wherein a pair of slits are provided on the left and right. 11. The method according to claim 6, wherein each electrode layer is connected to the left and right ends of the thin-film magnetoresistive element and the left and right ends of the conductor film. Magnetoresistive magnetic head.