JPS61134913A - Magnetoresistance type thin film head - Google Patents

Abstract

PURPOSE:To eliminate Barkhausen noises due to discontinuous magnetic wall movement by constituting a pat, which faces an MRE, of a conductor thin film for bias of a YMR head with soft magnetic materials at least. CONSTITUTION:Preliminarily, a bias current is flowed to the first conductor thin film 13 to generate a bias magnetic filed, and the magnetic balance point of an Ni-Fe film of an MRE17 is set to a point B in the figure. The reproducing sensitivity and the linear responsiveness are most excellent in this set bias position. an address magnetic field flowed from a magnetic recording medium passes a front yoke 20 and a rear yoke 21 and acts upon the MRE17, and the variance of the resistance of the MRE17 is detected as the variance of voltage if a sense current is flowed to the MRE17 at this time. Since the MRE17 is adjacent to a soft magnetic thin film 15 constituting the conductor thin film 13 for bias, magnetic wall do not exist, and thus, the Barkhausen noise is not generated at the reproducing time to obtain the reproduced output of high S/N.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is applicable to magnetic recording devices that use magnetic tapes and magnetic disks as magnetic recording media, as there is an increasing demand for higher recording density, higher reliability, lower cost, etc. In place of conventional magnetic heads fabricated from bulk materials, we have developed a magnetoresistive thin film that utilizes thin film fabrication technology and photolithography technology to realize narrow gaps and narrow tracks, and that also satisfies the above requirements. It is related to the head.

BACKGROUND OF THE INVENTION Recently, magnetoresistive elements (hereinafter referred to as MREs) have been used as playback heads in magnetic recording devices due to shorter track widths and slower magnetic tape running speeds due to improved track density.
Magnetoresistive thin film heads (hereinafter referred to as MR heads) using T-transducer, IEE
E, Trang Mag, page 7150) In FIG.
-Fe), ferromagnetic thin film such as Ni-Co alloy 5
A basic and conventionally used typical structure is one in which the magnetic recording medium 2 is formed into a rectangular shape and is placed close to the magnetic recording medium 53 to read information recorded on the magnetic recording medium 63.

The operation of the MRE will be described below. That is, the signal magnetic field from the magnetic recording medium 53 rotates the magnetization of the MRE 52, and the resistance of the MRE 62 changes accordingly. At this time M
The sense current I3 is passed through RE52 through all of the electric currents 54a and 64b.
When the voltage is allowed to flow, the change in resistance of the MRE 52 is converted into a change in voltage and detected as an output.

Generally, the resistance change ΔR of the MRE is determined by the direction of the sense current,
θ is the angle formed by the direction of magnetization of the MRE.

When the maximum resistance change is ΔRma, it can be expressed as the following equation (1).

ΔR=ΔRmaxcO32θ ・・・・・・−
...(1) Also, the signal magnetic flux density BIli in the MRE
9. When the saturation magnetic flux density of the MRE is f B3, equation (2) approximately holds true.

Equation (1), ? ), the following equation (3) can be derived.

That is, the MRE 62 exhibits resistance changes as shown in FIG. 6 in response to changes in the magnetic field. For the purpose of increasing the sensitivity and linear response of the output due to the resistance change of the MRE 52, a bias magnetic field is usually applied to bring the magnetic equilibrium point to the position of point B in FIG.

The conventional magnetoresistive thin film head shown in FIG. 5 has the following problems and is not used particularly in magnetic recording devices with high recording density.

(1) Affected by leakage magnetic fields from adjacent magnetizations on the magnetic recording medium 0C2) Reproduction sensitivity is low because it basically has an open magnetic circuit configuration.

(s) Since MRE is always in contact with a magnetic recording medium, there are problems with wear resistance and durability.

(4) In recent years, metal-deposited tape has been developed as a medium for high-density recording, and since the recording magnetic layer of this metal-deposited tape has conductivity, the sense current that should be sent to the MRE flows to the tape magnetic layer. become. As a result, not only a satisfactory reproduction output as an MR head cannot be obtained, but also a multi-track structure is impossible.

In addition, as a head that improves the problems shown above,
As shown in FIG. 7, Heads, I
EEE, Trans Mag 17, p. 2884))
In FIG. 7, a first insulating layer 102 of Sz02 or Al2O3 is formed on a ferromagnetic substrate 101 by sputtering or the like, and then a first conductive thin film for applying a bias magnetic field to the MRE is formed thereon. 103 is formed. Au or Al on CrF is used as the conductive material and patterned into a predetermined shape by photolithography. After that, a second layer such as SiO, 5L02, etc.
Insulating layer 10475; formed by vapor deposition, sputtering, etc.

On this second insulating layer 104, Ni-
After forming an Fe thin film by electron beam evaporation, sputtering, or the like, this Ni--Fe thin film is patterned by photolithography. At this time, the easy axis of magnetization of the Ni--Fe thin film is induced in the track width direction by deposition in a magnetic field or the like.

Next, a second conductive thin film (not shown) for passing a sense current through the MRE 106 is formed and patterned. After a third insulating layer 106 is formed on these, a ferromagnetic thin film, such as a Ni-Fe thin film or Fe-AI-
A Si thin film and an amorphous soft magnetic thin film are formed, and 7o)
The front yoke part 10 has been created using IJ printing technology.
A rear yoke portion 107b is configured. At this time, the front yoke part 107a and the rear yoke part 10ab are MRE10
5 and an insulating layer 106t, so that the signal magnetic field from the magnetic recording medium is easily guided to the MRII 105. Then Sio *Si
A Bassibasigon film 108 such as O2 is formed, and then a protective substrate 109 made of glass, ceramic, etc. is bonded with an adhesive or the like. After the above steps, the tape sliding surface is wrapped to complete the magnetic head. 1 in Figure 7
10 is a magnetic tape, and A is the tape running direction.

As described above, YMI't H has a closed magnetic circuit structure. That is, the signal magnetic flux from the magnetic recording medium flows from the front yoke part, and flows from the MRE 105 to the rear yoke part 1o7b,
It flows to the ferromagnetic substrate 101 and returns to the magnetic recording medium 110. Therefore, compared to the conventional example shown in FIG. 6, the reproduction sensitivity is higher, and since the gear part insulating layer can be formed thinner, shorter wave signals can be reproduced.

Furthermore, since the MRE 105 is located away from the magnetic recording medium 110, it not only solves the problems of wear resistance and durability, but also has advantages such as being able to use metal-deposited tape.

Problems to be Solved by the Invention However, in the above configuration, when the MRE is formed into a fine pattern as recording density increases, Barkhausen noise caused by discontinuous domain wall movement becomes noticeable. In an MRE having a relatively large shape, the locally occurring discontinuous domain wall movement is averaged over the entire sample, so the MRE exhibits a gentle resistance change in response to an external magnetic field as shown in FIG. 6. However, when MRK is micropatterned, the discontinuous domain wall movement is not averaged and is directly reflected in the MR characteristics, resulting in a bulk pattern as shown in Figure 8.
When E was made smaller, Barkhausen noise was generated, which caused the problem that good signal reproduction could not be achieved.

In view of the above points, the present invention has been developed to increase the track density by narrowing the tracks, and to increase the band of frequency characteristics by narrowing the gap. The present invention relates to a thin-film reproducing head to be realized, and is particularly aimed at reducing noise in an MR head having a yoke for guiding a signal magnetic field to an MRE.

Means for Solving the Problems To achieve this objective, the magnetoresistive thin film head of the present invention uses a ferromagnetic substrate as the lower magnetic layer, and divides the ferromagnetic thin film that acts as a yoke into a front yoke and a rear yoke. is,
MRK is formed between both magnetic layers. That is, the signal magnetic flux from the magnetic tape flows from the front yoke, and
The basic structure is a closed magnetic circuit structure in which RE = flows with the rear yoke, flows into the ferromagnetic substrate which is the lower magnetic layer at the back gap part, and finally returns to the magnetic tape, and in order to apply a bias magnetic field to the MRE, At least the portion of the bias conductor thin film facing MRK: is made of NL-Fe, F
e -AI -Si or Co -Z r -Nb
It is made of soft magnetic material such as an amorphous film.

That is, the MRE is magnetically coupled to the soft magnetic film that constitutes the bias conductor thin film.

In a magnetic thin film having a laminated structure in which the MRE and the soft magnetic thin film face each other, the intermediate layer has a conductivity of, for example, 20 to 1000 amps.
When the film thickness is 1, each magnetic film is magnetostatically coupled.
It has a magnetic domain structure different from that of a single layer film. That is, when an MRK having a two-layer structure is finely patterned, by selecting the manufacturing conditions such as energization, each layer can have a magnetic domain structure in which the layers are magnetized antiparallel to each other in the direction of the easy axis of magnetization. It is possible. Since domain wall motion essentially does not exist in such MRE, there is no Barkhausen noise caused by discontinuous domain wall motion.

Furthermore, even if a domain wall occurs, in the case of a multilayer structure, the K and magnetization, which are almost always accompanied by domain wall movement, tend to rotate all at once, so Barkhausen noise is less likely to occur compared to an MRE composed of a single layer. It is possible to suppress it.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged view of a main part of a bias conductor thin film of a magnetoresistive thin film magnetic head according to an embodiment of the present invention, FIG. 2 is a plan view of the magnetoresistive thin film magnetic head of the present invention, and FIG. It is the x-x' cross-sectional view.

In FIGS. 1 to 3, a ferromagnetic substrate 1o such as Mn to Zn single crystal ferrite is first used as a GC grindstone.

Alternatively, it is optically polished using diamond paste or the like.

Then, on this substrate, a first insulating layer 111, for example, A12O
3 film or S102 film is formed on the entire surface of the ferromagnetic substrate 1o by a method such as a sputter method. The gap length of the front gap portion 12 is controlled by this film thickness. A first conductive thin film 13 for applying a bias magnetic field to the MRE is formed on the first insulating layer 11. At this time, Au or Al as an Or base is first deposited and removed by partial tone etching facing the MRE formed in a later step, thereby dividing the layer into two nonmagnetic layers 14a and 14b. The length of the part to be etched at this time should be slightly shorter than the length of the opposing MRE.In the case of a multi-head, the bias conductor thin film is divided in all the parts facing the MRE provided in the same way. It turns out. Next, Ni-Fe, Fe-AI-St, Co
- Form a soft magnetic thin film 15 such as Zr-Nb, and divide each bias conductor thin film M by etching.
'e is patterned into a rectangular pattern of the same length as the opposing MRE to bridge and connect.

At this time, the axis of easy magnetization of the soft magnetic thin film is set in the length direction (track width direction) of arrow F, as shown in the conceptual diagram of Fig. 4, by an appropriate process such as deposition in a magnetic field or annealing in a magnetic field. Ru. Note that arrows M11M2 indicate the magnetization direction, and 14 is a nonmagnetic layer.

After that, the second insulating layer 1 such as S io , S io2
6 is formed with a film thickness of about 600 to 1000. Next, a Ni-F@ thin film that operates as the MRE 17 is formed on the second insulating layer 16 to a thickness of about 300 to 600 layers, and the width is 10 to 20 μm depending on the photolithography technology, and the length is approximately the same as the track width. It is finely patterned into the shape of . At this time as well, the axis of easy magnetization is set in the track width direction. The thickness of the second insulating layer 16 is the same as that of the bias conductor thin film 1.
3 and the insulating properties of MRE 17 and the opposing soft magnetic thin film 16
It is determined from the magnetostatic coupling with 500A to 1000A is appropriate.

Next, second conductive thin films 18a and 18b are formed to allow a sense current to flow through MREly. After a third insulating layer 19 is formed on these, a ferromagnetic thin film, for example Ni, is formed to guide the signal magnetic field fcMRE 17 from the magnetic recording medium.
-Fe, Fe-AI-3i film, C.

-Zr-Nb amorphous film is formed on the front yoke 20. by photolithography technique. A rear yoke 21 is configured.

Next, a banvation film 22 such as S io and S io2 is formed, and then the glass is bonded with an adhesive or the like.

A protective substrate 23 made of ceramic or the like is bonded. After the above steps, the tape sliding surface is wrapped to complete the head.

Next, the operation of the magnetoresistive thin film magnetic head shown in this embodiment will be explained.

In advance, a bias current is applied to the first conductive thin film 13 to generate a bias magnetic field, and the magnetic equilibrium point of the Ni--Fe film of the MRE 17 is set at the position of point B in FIG. This set bias position is where reproduction sensitivity and linear response are the best.

The signal magnetic field flowing in from the magnetic recording medium is applied to the front yoke 20.
It acts on the MRE 17 through the rear yoke 21. At this time, if a sense current is passed through the MRE 17, a change in resistance of the MRE 17 is detected as a change in voltage. Since the MRE 17 is adjacent to the soft magnetic thin film 15 constituting the bias conductor thin film 13, there is essentially no domain wall, and no Barkhausen noise is generated during reproduction, resulting in a high S/N.
This results in a playback output of .

In this embodiment, only the portion of the bias conductor thin film 13 that faces the MRE 17 is made of soft magnetic material.
A similar effect can be obtained even if the entire bias conductor thin film is made of a soft magnetic material. That is, at least only the portion facing the MRE may be made of a soft magnetic material.

Effects of the Invention As described above, according to the present invention, at least the portion of the bias conductor thin film of the YMR head that faces the MRE is made of a soft magnetic material. As a result, it has a magnetic domain structure that is magnetized antiparallel to the easy axis of magnetization. In such MRE, since there is no domain wall movement, Barkhausen noise due to discontinuous domain wall movement is not generated, and signal reproduction with high S/N is possible.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the main part of the bias conductor thin film portion of a magnetoresistive thin film head in an embodiment of the present invention, FIG. 2 is a plan view of the same magnetoresistive thin film head, and FIG. 3 is the same as that shown in FIG. x-x
Figure 4 is a conceptual diagram showing the magnetic domain structure of opposing soft magnetic thin films in a demagnetized state. Figure 6 is a schematic perspective view of a conventional MR head. Figure 6 shows magnetic field strength and resistance change of MRE. The characteristics diagram shown in Fig. 7 is a cross-sectional view of a conventional YMR head.
Figure 8 is a characteristic diagram showing the magnetic field strength and resistance change of a fine pattern MRE that generates Barkhausen noise.
...Nonmagnetic layer, 16...Soft magnetic thin film, 1
7... Magnetoresistive element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Figure 5 Figure 6 Figure 6/'l/2E 611 added to the three wisdoms of stone insult Figure 7 Figure 8.

Claims (1)

[Claims] A magnetoresistive element made of a ferromagnetic metal material, a pair of electrodes for passing a sense current through the magnetoresistive element, and a ferromagnetic metal material for guiding a signal magnetic flux from a magnetic recording medium to the magnetoresistive element on a ferromagnetic substrate. and a bias conductor thin film provided opposite to the magnetoresistive element in order to flow a bias current for applying a bias magnetic field to the magnetoresistive element, and at least one of the bias conductor thin films is provided. . A magnetoresistive thin film head, characterized in that a soft magnetic material is formed in a portion facing the magnetoresistive element.