JPS61242313A - Magnetoresistive thin film head - Google Patents

Abstract

PURPOSE:To obtain the title highly reliable magneto-resistance effect type thin film head with less thermal noises and sliding noises and having a long energizing life by providing a metallic thin film body which is a good thermal conductor on the side end part of a magneto-resistance effect element opposite to the surface opposed to a medium. CONSTITUTION:Conductor layers 2 are provided on both sides of a magnetic resistance element 1 and a metallic thin film body 4 consisting of a good conductor such as Al and Cu is furnished on the side end part opposite to the surface 3 opposed to a medium. The metallic thin film body 4 can be formed by sputtering and photolithography. A couple of magnetic shield layers 5 are provided through an insulating layer 6 on both sides of the metallic thin film body 4. Moreover, a biasing means for impressing a bias magnetic field on the magnetic resistance element 1 is needed in the actual magneto-resistance effect type thin film head. Since the heat generated in the magnetic resistance element can be rapidly removed by the metallic thin film body 4 provided on the side end part of the element, an increase in the temp. of the magnetic resistance element can be effectively controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetoresistive thin film head, and particularly to a magnetoresistive thin film head suitable for improving the reliability of the thin film head.

[Background of the invention]

2. Description of the Related Art Magnetoresistive thin film heads are being actively developed as read-only heads for high-density magnetic recording.

For magnetoresistive thin film heads, see IE Transactions on Magnetics, Mag 7.
, 150 (1971) (IEEE Trans.
.

Magnetics, MAG7, 150 (197
1) RoP in ), "Magnetoresistive readout transducer" by Hunt (
A MagnatoregistiveReadout
Transducer). In this magnetoresistive thin film head, the resistance of the magnetoresistive element used in the thin film head changes due to a signal magnetic field from a magnetic medium such as a magnetic disk or magnetic tape, and the resistance change is applied to both ends of the magnetoresistive element. The information recorded on the magnetic medium can be read by detecting the information from the pair of conductive layers. In general, the resistance change of the magnetoresistive element is detected by passing a detection current through the magnetoresistive element from the conductor layer and converting it into a voltage change proportional to the resistance change. Detected between layers. therefore,
Information recorded on the magnetic medium can be read with higher accuracy as the reproduction output voltage is higher, and since the reproduction output voltage increases in proportion to the increase in the detection current, it is possible to read the recorded information with higher accuracy. The detection current can be increased.

In high-density magnetic recording, the drop in reproduction output voltage is particularly large in high frequency bands, so it is necessary to increase the detection current. However, as the detection current increases, the heat generated by the Joule heat of the magnetoresistive element also increases, which causes the resistance of the magnetoresistive element to fluctuate, resulting in disadvantages such as increased thermal noise and shortened current-carrying life. . However, conventionally, no particular measures have been taken to improve such drawbacks.

Furthermore, since the magnetoresistive thin film head slides in almost intimate contact with the magnetic medium, the friction between the magnetoresistive element and the magnetic medium causes the resistance of the magnetoresistive element to fluctuate due to frictional heat. , there is also the disadvantage that sliding noise increases. However, no particular consideration was given to this point.

[Purpose of the invention]

An object of the present invention is to effectively remove the heat generated in the magnetoresistive element of a magnetoresistive thin-film head, and to provide a highly reliable magnetoresistive element that generates little thermal noise, sliding noise, etc., and has a long current life. An object of the present invention is to provide an effective thin film head.

[Summary of the invention]

As described above, in order to suppress the generation of thermal noise and the reduction in the energization life due to the heat generation of the magnetoresistive element, it is considered that the generated heat should be effectively and promptly removed from the magnetoresistive element. Therefore, first, the phenomenon of heat generation in the magnetoresistive element was investigated by passing an element current through the conductor layers provided at both ends of the magnetoresistive element without a protective film such as an insulating layer. As a result, as the element current increases, oxidation starts from the center of the magnetoresistive element, and oxidation gradually progresses toward the conductor layers at both ends, eventually breaking the center of the element. It was found that the device in the region close to was not oxidized at all. This phenomenon indicates that the heat generation of the magnetoresistive element is greatest at the center of the element, and also indicates that the heat dissipated from the conductor layers provided at both ends of the element is extremely large. Therefore, based on this result, in order to effectively remove the heat generated in the magnetoresistive element, a heat dissipation body such as the above-mentioned conductive layer is provided on the element, and in particular, the heat in the center of the element is preferentially removed. I thought that it would be good to have a structure that would remove it. Based on the above considerations, we devised a solution to the drawbacks of the magnetoresistive thin film head described above.

The present invention is further based on the following findings.

When considering a magnetoresistive element whose surface is coated with an insulating layer but does not have a magnetic shield layer, the Joule heat generated in the element is transferred to the conductive layer provided at both ends of the element and the substrate in contact with the element. It is transmitted through three paths: the surface and the insulating layer covering the surface of the element. therefore,
The amount of heat transferred from the element is expected to increase as the thermal conductivity of these three paths increases. Therefore, as a result of actually fabricating magnetoresistive elements on substrates with different thermal conductivities and investigating the current-carrying lifespan of these elements, we found that the current-carrying lifespan of magnetoresistive elements fabricated on substrates with high thermal conductivity was It was also found that when the element was coated with an insulating layer having high thermal conductivity, the energized life time of the element also became longer. Furthermore, it has been found that when a good thermal conductor such as a magnetic shield layer is provided to sandwich the magnetoresistive element, there is a phenomenon in which the energized life time of the element is further extended significantly. Taking these phenomena into consideration, we have devised a solution to the above-mentioned drawbacks of magnetoresistive thin film heads.

[Embodiments of the invention]

The present invention will be described in detail with reference to Examples below.

Embodiment 1 FIG. 1 is a plan view (FIG. 1(a)) of a magnetoresistive element portion of a magnetoresistive thin film head according to an embodiment of the present invention and its AA' cross-sectional view (FIG. 1(b)). ).The magnetoresistive element 1 according to the present invention is provided with a conductive layer 2 at both ends thereof, and is further provided with a conductive layer 2 such as AQ or Cu so as to be in contact with the side end opposite to the magnetic medium facing surface 3. A metal thin film body 4 made of a good thermal conductor is provided.This metal thin film body 4 can be produced by a method such as sputtering or vapor deposition, or a photolithography method.Furthermore, an insulating layer 6 is provided to sandwich the metal thin film body 4. A pair of magnetic shield layers 5 are provided through the magnetoresistive element 1.In addition, in an actual magnetoresistive thin film head, a bias application means is required to apply a bias magnetic field to the magnetoresistive element 1. However, it is omitted in this figure. Although there are various bias application means, the present invention is applicable to all bias application means. Incidentally, the magnetoresistive element 1 is provided with a signal magnetic field H from a magnetic medium.
In order to read the current, the element current is energized, but as described above, the magnetoresistive element generates heat due to the Joule heat of the element current, which causes an increase in thermal noise or a reduction in the energization life. However, according to the present invention, the heat generated in the magnetoresistive element can be quickly removed by the metal thin film body 4 provided on the side end of the element, as indicated by the arrow in FIG. , it is possible to effectively suppress the temperature rise of the magnetoresistive element. FIGS. 2 and 3 are diagrams showing the effects when the present invention is applied to a magnetoresistive thin film head. FIG. 2 shows the effect of the present invention on the relationship between the energization life time of the thin film head and the element current, and FIG. 3 shows the effect of the present invention on the relationship between the thermal noise of the thin film head and the element current. According to FIGS. 2 and 3, compared to the conventional magnetoresistive thin film head shown as curve 11, the current life time of the thin film head to which the present invention is applied (curve 12) is significantly longer at the same element current. It can be seen that the thermal noise increases and the thermal noise also decreases. As described above, the present invention has the effect of improving the reliability of the magnetoresistive thin film head.

Embodiment 2 FIG. 4 shows a plan view of a magnetoresistive element portion of a magnetoresistive thin film head according to a second embodiment of the present invention. In this example, the central part of the gold m thin film body 4 shown in Example 1 is made to protrude so as to cover at least the central part of the magnetoresistive element 1, and the heat generated in the element is removed. is more efficient than the case of Example 1 above. Therefore, the effect of this embodiment is larger than that of the above embodiment (curve m12) as shown by curve 13 shown in FIGS. It is possible to realize a thin film head.

Embodiment 3 FIGS. 5 and 6 are plan views of a magnetoresistive element portion of a magnetoresistive thin film head according to a third embodiment of the present invention. This embodiment has a structure in which a vertical groove 8 is provided from one side of the metal thin film body 4 made of a good thermal conductor shown in Examples 1 and 2 above on the side opposite to the magnetoresistive element until it approaches the element. . In this embodiment, it is possible to suppress a decrease in the output voltage caused by bringing the thin metal film 4 into contact with the element without significantly reducing the efficiency of dissipating heat generated in the element.

Embodiment 4 FIG. 7 shows a plan view of a magnetoresistive element portion of a magnetoresistive thin film head according to a fourth embodiment of the present invention. In this embodiment, only the central portion of the metal thin film body 4, which is a good thermal conductor, is made to protrude so as to cover at least the central portion of the magnetoresistive element. Therefore, in this example, Example 3
Similarly, it is possible to suppress a decrease in the output voltage caused by bringing the metal thin film body 4 into contact with the element without significantly reducing the efficiency of dissipating heat generated in the element.

Embodiment 5 FIG. 8 shows a sectional view of a magnetoresistive thin film head according to a fifth embodiment of the present invention. In the magnetoresistive thin film head according to the present invention, a lower shield layer 12 is laminated on a substrate 11, and a metal thin film body 14 made of a non-magnetic material such as An or Cu, which is a good thermal conductor, is placed on top of the lower shield layer 12 via an insulating layer 13. are alternately laminated with insulating layers 13, further a magnetoresistive element 15 is provided on the metal thin film body 14 with an insulating layer 13 interposed therebetween, and an upper shield layer 16 is further laminated thereon with an insulating layer 13 interposed therebetween. ing. Although not shown in this figure, in an actual magnetoresistive thin film head, a conductive layer is provided at both ends of the magnetoresistive element 15 to allow a detection current to flow, and a bias magnetic field is applied to the magnetoresistive element 15. A bias applying means is provided for applying the bias.

Although there are various bias application means, the present invention is applicable to all of them. Further, in this embodiment, the metal thin film body 14 is made of two layers, but the metal thin film body 14 may be made of a single layer or may have any number of layers as long as it is within the distance between the lower shield layer 12 and the magnetoresistive element 15. In this case, the thinner the insulating layer 13 between the magnetoresistive element 15 and the metal thin film body 14, the greater the effect. In addition, the substrate substrate 1
A lower shield layer 12 and an upper shield layer 1 laminated on 1
6 is made of a soft magnetic film such as a permalloy film or an amorphous magnetic film, but it is also possible to have a structure in which both the substrate 11 and the lower shield layer 12 are made of a soft magnetic material such as ferrite. The magnetoresistive thin film head having such a configuration passes a detection current through the conductive layer to the magnetoresistive element 15 and detects an output voltage corresponding to a change in resistance of the magnetoresistive element due to a signal magnetic field H from the magnetic medium 17. By doing so, the information recorded in the magnetic medium 17 can be read. However, as mentioned above, in the magnetoresistive element 15,
There is a problem in that the element temperature rises due to heat generated by Joule heat of the detection current and frictional heat during sliding with the magnetic medium, which in turn increases thermal noise or shortens the energization life. However, according to the present invention, since the multilayer film of the metal thin film body 14 provided between the magnetoresistive element 15 and the lower shield layer 12 has extremely good thermal conductivity, the heat generated in the magnetoresistive element 15 is transferred to the metal thin film body 14. Since it can be quickly removed from the multilayer film of the thin film body 14, it is possible to effectively suppress the temperature rise of the magnetoresistive element 15. Figure 9 and 1
FIG. 0 is a diagram showing the effect of the magnetoresistive thin film head according to the embodiment shown in FIG. Figure 9 shows the effect on the relationship between the energization life time of the thin film head and the detected current, and Figure 10 shows the effect on the relationship between the thermal noise of the thin film head and the element current. For example, compared to the conventional magnetoresistive thin film head shown as curve 18, the current life time of the thin film head to which this embodiment is applied (curve 19) is significantly increased at the same detection current, and thermal noise is also reduced. It can be seen that this decreases significantly. As described above, this embodiment has the effect of improving the reliability of the magnetoresistive thin film head.

Note that the insulating layer 13 is made of Sin, etc.
If an insulating layer with good thermal conductivity such as Afi, O, etc. is used, the effects of the present invention will be even greater.

Embodiment 6 FIG. 11 shows a sectional view of a magnetoresistive thin film head according to a sixth embodiment of the present invention. In this embodiment, the insulating layer 13 between the magnetoresistive element 15 and the upper shield layer in the magnetoresistive thin film head of the fifth embodiment shown in FIG. It has a multilayer structure including a body 21 and an insulating layer 13. The operation of the magnetoresistive thin film head according to this embodiment is exactly the same as that of embodiment 5, but the effect is that the multilayer film of the metal thin film body 14 and 21 is provided on both sides of the magnetoresistive element 15. Therefore, it becomes even larger as shown by curve 20 in FIGS. 9 and 10. Therefore, according to this embodiment,
Furthermore, it is possible to realize a highly reliable magnetoresistive thin film head.

〔Effect of the invention〕

According to the present invention, Joule heat generated in a magnetoresistive element used in a magnetoresistive thin-film head and frictional heat generated when sliding with a magnetic medium can be absorbed by providing the magnetoresistive element at the side ends or in the center. Since it can be removed more quickly than a metal thin film, which is a good thermal conductor, it is possible to suppress fluctuations in the resistance of the magnetoresistive element due to an increase in temperature of the element. This has the effect of reducing thermal noise and sliding noise caused by resistance fluctuations of the magnetoresistive element. Additionally, as the temperature of the magnetoresistive element increases, the current life of the element also decreases.
As described above, according to the present invention, it is possible to suppress the temperature rise of the element, and therefore, there is also the effect of increasing the energized life of the element. That is, according to the present invention, it is possible to realize a highly reliable magnetoresistive thin film head.

[Brief explanation of drawings]

FIG. 1 is a plan view of a first embodiment according to the present invention and A-
A' sectional view, FIGS. 2 and 3 are views showing the effects of the present invention, and FIGS. 4, 5, 6, 7, 8 and 11 are views showing other effects of the present invention. The plan view of the embodiment, FIGS. 9 and 10, are diagrams for explaining the effects of the embodiment shown in FIG. 8. DESCRIPTION OF SYMBOLS 1... Magnetoresistive element, 2... Conductor layer, 3... Magnetic medium opposing surface, 4... Metal thin film body, 5... Magnetic shield layer, 6... Insulating layer, 7... ... Substrate, 8... Vertical groove, 11... Characteristic curve of conventional thin film head, 12...
Characteristic curve of the thin film head according to Example 1, 13 Characteristic curve of the thin film head according to Example 2. Venerable 2nd Companion 1f-3rd V4th

Claims (1)

[Claims] 1. In a magnetoresistive thin film head having a magnetoresistive element and a pair of shield films provided on both sides of the magnetoresistive element with an insulating layer interposed therebetween, a medium of the magnetoresistive element is provided. A magnetoresistive thin film head, characterized in that a metal thin film body, which is a good thermal conductor, is provided in contact with the opposite side end of the opposing surface. 2. A central portion of a metal thin film body which is a good thermal conductor and is provided in contact with the end portion of the side opposite to the medium facing surface of the magnetoresistive element is made to protrude so as to cover at least the central portion of the element. A magnetoresistive thin film head according to claim 1, characterized in that: 3. From one side of the metal thin film body, which is a good thermal conductor, provided so as to be in contact with the end of the side opposite to the medium facing surface of the magnetoresistive element, on the side opposite to the element, to the extent that it is close to the element. A magnetoresistive thin film head according to claim 1 or 2, characterized in that a vertical groove is provided. 4. A metal thin film body that is a good thermal conductor is provided on the side opposite to the medium facing surface of the magnetoresistive element so as to be close to the sides of the element, and only the center portion of the metal thin film body is connected to at least one of the elements. A magnetoresistive thin film head characterized by a protruding part that covers the central part. 5. A magnetoresistive thin film consisting of a magnetoresistive element, a pair of magnetic shield layers provided on both sides of the magnetoresistive element via an insulating layer, and a pair of conductor layers for flowing current through the magnetoresistive element. In the magnetic head, at least one of the insulating layers between the magnetoresistive element and the magnetic shield layer is made of a multilayer consisting of a thin non-magnetic metal film that is a good thermal conductor and an insulating layer. Resistance effect thin film head.