JPS61104413A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To omit a conductor film for generation of a bias magnetic field by forming two MREs at both upper and lower sides of a yoke via an insulated layer and then connecting those MREs in terms of DC. CONSTITUTION:The 1st and 2nd MREs 13 and 19 are connected in series to each other and the sense currents flowing both MREs are parallel to each other and flow in opposite directions to each other. Therefore the induction field produced by the sense current flowing through the MRE13 functions as a bias magnetic field to the MRE19. While the induction field due to the sense current flowing through the MRE19 function as a bias magnetic field in the same direction as that of the MRE13. In other words, the sense current of each MRE has a function to apply a bias magnetic field of the other side with each other. Furthermore the bias magnetic fields of both MREs function in the same direction. As a result, the reproduction sensitivity is improved by 6dB by connecting those MRE13 and 19 in series to each other.

Description

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

2. Description of the Related Art Recently, magnetoresistive heads that use magnetoresistive elements (hereinafter referred to as MRK) as playback heads have been introduced in magnetic recording devices due to the shortening of track widths and slowing down of magnetic tape running speeds due to improved track densities. (hereinafter referred to as MB heads) are becoming widely used. A typical structure thereof is shown in FIG. (For example, [Magnetresist Tip Heads J
(mgnetoreSiiti Ma0heads I
ICIEICT Trans Vog 17.2884 pages)
) In Fig. 3, a ferromagnetic substrate, for example Mn-Zn,
A first insulating layer 2 such as 5102 is laminated on a ferrite substrate 1 such as Ni-Zn using the vine method, and MR is applied on top of it.
A Ni--Fe film 3 as E is formed and patterned by photolithography so as to be in contact with the magnetic tape 9.

Then 8i0. A second insulating layer 4, such as SiO□, is deposited.

It is formed by sputtering or the like. After forming a ferromagnetic thin film such as a Ni-Fe film 6 on the second insulating layer 4 by electron beam evaporation or sputtering, a film of SiO, SiO2, etc.
A protective layer 6 is laminated by vapor deposition, sputtering, or the like.

Thereafter, a protective substrate 8 made of glass or ceramic is bonded with an adhesive 7 or the like. Head after the above process.

The tape sliding surface is wrapped and completed. However, the conventional structure shown in FIG. 3 had the following problems.

(1) It is necessary to apply a sense current to the MRE in order to extract the playback output. However, in recent years, a metal-deposited magnetic tape for high-density recording has been developed, and since the recording magnetic layer of this metal-deposited tape has conductivity, the sense current that should be passed through the MRH flows into the tape magnetic layer. This result is HR
Not only is it impossible to obtain a satisfactory reproduction output as a head, but a multi-track structure is essentially impossible.

(2) The first insulating layer 2 and the second insulating layer 4 must be formed on both sides of the MRE 3 in FIG. 3.

For the magnetic gap length in this MR head, if the film thicknesses of the first insulating layer 2 and the second insulating layer 4 are made equal, this film thickness becomes the equivalent gap length. However, if the thicknesses of the insulating layers 2 and 4 are different, a double-gap behavior is exhibited.

(3) If the current method is applied as a means of applying a magnetic bias to the MREs shown in Figure 3, it is necessary to form a bias line with the same width as the MRE in a layer below or above the MRE, and the gap length is equal to the thickness of the bias line. This is extremely inconvenient when reproducing short wavelength signals.

(4) Since the tip of the MRE is exposed at the tip of the head and is constantly in contact with the tape surface during playback, there are problems with the wear resistance of the MRE3 and its durability depending on ambient environmental conditions.

(5) As a solution to the problem in (1), there is a configuration in which the MRE 3 is placed deep from the tip of the head, but in this system, the MR head is spaced apart from the magnetic tape 9 by the recess amount of the MRE 3. This is equivalent to causing a large amount of attenuation in the short wavelength reproduction output. Furthermore, as a head to improve the above-mentioned drawbacks, a conventional magnetic head (hereinafter referred to as YMRH) having a yoke for guiding the signal magnetic field from the magnetic recording medium to the MRE, as shown in FIG. Are known. (For example, "Magnetoresist Tip Heads J (MaEnetoresig
tiveHeads IE [Trans Ma(17,
(page 2884)) In FIG.
in2 or mu120. A first insulating layer 42f, such as
Formed with snow ivy etc., then MRK on top of it.
A first conductive thin film 43 for applying a bias magnetic field is formed. As a material, Or base material or Al
It is patterned into a predetermined shape using photolithography technology. Thereafter, a second insulating layer 44 of SiO, SiO□, etc. is formed by vapor deposition, vine vine, or the like. On this second insulating layer 44, Ni-
After forming the Fe thin film by electron beam evaporation, sputtering, etc., this Ni--Fe thin film is turned into patterns by photolithography. Next, a second conductive thin film (not shown) is formed for flowing a sense current to the MRE 46,
patterned. After a third insulating layer 46 is formed on these, a ferromagnetic thin film, such as a Ni-Fe film or F
e-A11. A -8i film and an amorphous soft magnetic film are formed, and a front yoke portion 48a and a rear yoke portion 48b are constructed by photolithography technology. At this time, the front yoke part 48a and the rear yoke part 48b are M RE
45 and a part of it are arranged so that the signal magnetic field from the magnetic recording medium is easily guided to the MRE. Next, a passivation film 49 such as Sin or 5in2 is formed, and then an adhesive film is formed. A protective substrate 6o made of glass, ceramic, or the like is bonded with an adhesive or the like.

After the above steps, the head tape sliding surface is wrapped and completed. In FIG. 4, numeral 51 is a magnetic tape and fiB is the tape running direction.

The operation of this YMRH will be described below.

The resistance change ΔR in MRE 4 ts is the angle between the direction of current and the direction of magnetization of MRE 45.

When the maximum resistance change is ΔRmaz, ΔR=ΔRmaICO32θ ・・・・・・・・・
・・・・・・・・・(1)′ Also, the signal magnetic flux density in MRE45 is Bs4cr9, and the saturation magnetic flux density of MRE45 is B8
Then, approximately 51g 5irl＞□ ・・・・・・・・・ −・・・・・・・
・・・・・・・・・(2) holds and (1)
, (2) is derived from equation (2). That is, the MRE exhibits resistance changes as shown in FIG. 5 in response to magnetic field changes.

Therefore, a bias magnetic field is applied to the MRE, and the fifth
In the YMRH shown in the figure, a current is passed through a conductive thin film, and the induced magnetic field thereby is used as a bias magnetic field. By setting the magnetic equilibrium point at point E in FIG. 6, it is used to achieve high sensitivity change and linear response. The YMRH has a closed magnetic path structure, and the signal magnetic flux from the magnetic recording medium of the magnetic tape 61 is transmitted to the front yoke portion 48.
a flows into the MRE 45, flows from the MRE 45 to the rear yoke portion 48b, the ferromagnetic substrate 41, and returns to the magnetic recording medium.

Problems to be Solved by the Invention However, in the conventional thin film magnetic head configured as described above, the signal magnetic flux from the magnetic recording medium first flows into the MRE 45 from the front yoke portion 48a. After leaking to the ferromagnetic substrate 41 at the part 48a and attenuating, M
Reach RE45.

For these reasons, the reproduction sensitivity of YMRH is low, and the S/N ratio deteriorates particularly in the short wavelength region.

Means for solving the problems In order to solve the above problems, the technical means of the present invention are as follows:
Two MREs are formed on both sides of the upper and lower parts of the yoke via an insulating layer and are connected to the two MREs in a DC manner.

Effect of the Invention The present invention improves the reproduced output voltage with the above configuration, and in particular, by making the directions of the sense currents leading to the two MREs parallel and opposite to each other, the induced magnetic field generated by the sense current is suppressed from the other side. By using this as a bias magnetic field for MRE, a conductor thin film for generating a bias magnetic field becomes unnecessary.

EMBODIMENT A thin film magnetic head according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a plan view of a thin film magnetic head according to an embodiment of the present invention, and FIG. 1 is a sectional view taken along the line xx', in which the same parts are given the same numbers.

In FIGS. 1 and 2, a ferromagnetic substrate 10 such as Mn--Zn single crystal ferrite is first optically polished using a GC grindstone or diamond paste. Then, as the first insulating layer 11, for example, a SiO2 film is formed on the entire surface of the ferromagnetic substrate 1o):lc by sputtering or the like. The gap length of the front gap portion 12 is controlled by this film thickness. A first MREla having a magnetoresistive effect is formed on the first insulating layer 11 by vapor deposition and photolithography techniques. At this time, Ni as MRE
The axis of easy magnetization of the -Fe film is set in the track width direction by evaporation in a magnetic field or the like. Next, one lead wire 14 for passing a sense current through the MRE is formed. As the lead wire material, Au with a Cx base or the like is used. Then Sin or 8102 to insulate the MRE.
A second insulating ferromagnetic thin film such as
and the front yoke 1 so as to partially overlap the second insulating layer 15.
It is formed as a 6° rear yoke 17.

Next, a third insulating layer 18 is formed over these.

At this time, the insulating layer of the portion 18a/fi on the opposite side of the lead wire connection portion of the first MREla is removed by etching. Thereafter, the second MREle is formed into a predetermined pattern by photolithography technology, but at this time, the second MRE19 connects to the first MREla and the connecting portion 18a.
electrically connected. Next, after the second lead wire 20 is formed, a passivation film 21 of Sin, 5i02, etc. is formed. Then, a protective substrate 22, such as glass or ceramic, is bonded, and the tape sliding surface is lapped to complete the magnetic head.

In FIG. 1, arrow C indicates the direction in which the magnetic tape 23 runs. Further, arrow i indicates the flow of sense current.

As mentioned above, the first. The second MREs are connected in series, and the sense currents flowing through the MREs are parallel to each other and flow in opposite directions. For this reason,
The induced magnetic field generated by the current flowing through one MRE1a acts as a bias magnetic field for the MREls. Conversely, the magnetic field induced by the sense current flowing through MRE19 is M
The bias magnetic field of HI, 13 acts in the same direction as the bias magnetic field. That is, the sense current of each MRE has the effect of applying the bias magnetic field of the other.

Moreover, since the bias magnetic fields acting on the two MRHs are in the same direction, the first. By connecting the second MREs 13 and 19 in series, it is possible to improve the reproduction sensitivity by 6 dB.

That is, the reproduction output Δvd sense current is set to 1. The resistance change is ΔR
Then ΔV=JR@i ・・・・・・・・・・・・・・・
・・・・・・・・・・・・It can be expressed as (4).

Also, as is well known, when the specific resistance change at this time is Δρ, the length of the MRE, and the cross-sectional area are 8, ΔR=Δρヱ ・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・Atonement is achieved.

In other words, from formula (→, (5)), the longer the length of the MRH, the greater the resistance change (the reproduction output of the MRE increases. In the embodiment, two Two MRs
By connecting E in series, the length of MRH can be reduced by approximately 2
Since it is doubled, the resistance change is about twice as much.When the sense current is constant, the reproduction output is about edB according to equation (4).
It will improve.

In addition, the film thickness of the MRE used is very thin, ranging from 300A to 500A, and the magnetic resistance of the MRE portion is generally large.
This greatly affects the reproduction efficiency of the magnetic head.

In this embodiment, since the signal magnetic flux flowing in from the front yoke 16 passes through the upper and lower MREs, the magnetic resistance in these parts is reduced, which also has the effect of increasing the reproduction efficiency.

Effects of the Invention As described above, according to the present invention, not only does a conductor thin film for generating a bias magnetic field become unnecessary, but also the reproduction sensitivity is improved, and the S/N ratio is improved particularly in the short wavelength region. It is extremely useful in practical terms.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a thin film magnetic head according to an embodiment of the present invention, FIG. 2 is a plan view thereof, FIGS. 3 and 4 are sectional views of a conventional thin film magnetic head, and FIG. 5 is a cross sectional view of a conventional thin film magnetic head. FIG. 3 is a characteristic diagram showing resistance changes due to magnetic field changes. 10...Ferromagnetic substrate, 13...Lower M
RE, 16... Front yoke, 17... Rear yoke, 18... MRE connection part, 19...
... Name of the upper MRE agent Patent attorney Toshi Nakao and one other person Figure 1 W... Shige Kensei Grade/6... Ii? Part 1 Yoke Figure 2 Figure 3 Figure 4 Figure 5 IfEE is aghast, 6 Shameful S imitation procedure correction form (method) % formula % 2 Name of invention Thin film magnetic head 3 Person who corrects Relationship to the incident Patent application Address 1006 Kadoma, Kadoma City, Osaka Name Name
(582) Matsushita Electric Industrial Co., Ltd. Representative Yama
Toshihiko Shimo 4 Agent 571 Address 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] (1) A magnetoresistive element made of a ferromagnetic metal material provided on a ferromagnetic substrate via a first insulating layer, a pair of electrodes for passing a sense current through the magnetoresistive element, and a signal magnetic flux from a magnetic recording medium. A thin film magnetic head comprising a yoke made of a ferromagnetic metal material for guiding the magnetic field to the magnetoresistive element, and the magnetoresistive element is formed on both upper and lower sides of the yoke with an insulating layer interposed therebetween. . (2) The thin film magnetic head according to claim 1, wherein the sense currents flowing through the magnetoresistive elements are caused to flow in parallel and opposite directions.