JPS62146420A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To simplify a head by dividing a yoke part to the plural 1st yoke parts positioned on the medium side and the common 2nd yoke part positioned behind said parts and supplying electric current to an MR element from the 2nd yoke part in the stage of providing a magnetic substrate and yoke part sandwiching the thin film of the MR element along the sliding contact surface of a magnetic recording medium. CONSTITUTION:A high magnetic permeability substrate 1 consisting of MnZn, NiZn, etc. is disposed along the magnetic recording medium 9 apart at a gap therefrom and the thin film 4 of the MR element is attached via an insulating film 2 onto said substrate. The substrate is then enclosed with an insulating film to embed the thin film 4 into the insulating film. The yoke consisting of an NiFe alloy or the like is then provided on the insulating film and in this stage, the yoke is divided to the discrete 1st yokes 7 facing the medium 9 and the 2nd yoke 8 common to each track positioned behind said yokes apart at a spacing therefrom. The 2nd yoke 8 is made to commonly serve as a current supplying path and the current IB for biasing is supplied from said part to the thin film 4. The control of characteristics is thus made easy while the structure is made simple.

Description

[Detailed Description of the Invention] Technical Field> The present invention detects signals recorded on a magnetic recording medium using a magnetoresistive element (hereinafter referred to as an MR element) that applies the magnetoresistive effect of a ferromagnetic thin film. It relates to a thin film magnetic head.

<Prior Art> Thin-film magnetic heads that utilize the magnetoresistive effect of ferromagnetic thin films are known to have many advantages over commonly used wire-wound magnetic heads. In other words, a thin film magnetic head receives a signal magnetic field generated from a magnetization pattern recorded on a magnetic recording medium and extracts this as a voltage change based on a change in resistance of an MR element, so it does not depend on the transfer speed of the magnetic recording medium. can play the signal,
It has the advantage that a higher output reproduction signal can be obtained than a wire-wound magnetic head when the transport speed is low. In actual use, rather than constructing a thin-film magnetic head with a single Mrt element, the MR element part is separated from the head tip, and a magnetic flux introducing path (yoke) is arranged to guide the magnetic flux generated in the magnetic recording medium to the MR element part. A thin film magnetic head, commonly called a yoke type MR head (hereinafter referred to as YMR head), with the structure shown in Figure 2 is more effective in improving signal resolution and magnetic resistance of the MR element, and in recent years this type of head has become popular. It is attracting attention as a playback head for fixed head digital audio (see ``Reproduction characteristics of 14PB-11r yoke type MR head'' in the 8th Japan Society of Applied Magnetics Academic Conference Abstracts (1984)).

FIG. 3 is a diagram of a conventional YMR head viewed from above the substrate, and FIG. 4 is a sectional view of the main part taken along a plane perpendicular to the substrate in the direction BB' in FIG. In Figures 3 and 4, the upper yoke +8°19 is usually 0.5 to 1.0
It is made of a permalloy film with a thickness of approximately μm, and serves as a magnetic path for guiding the magnetic field generated in the magnetic recording medium 20 to the MR element 15. Mr (element 15 is made of a permalloy vapor-deposited film, the film thickness is set to 300 to 500, the length is set to approximately 50 μm of the track width, and it is provided with a lead portion 16 for supplying a sense current Is'. A conductor 13 made of A, 9-Cu is provided to apply a bias magnetic field to the MR element 15.The head gap 14 is set to 0.5 μm since the minimum recording wavelength actually used is about 0.5 μm.
The thickness is set to about 2 to 0.3 μm. The bridge plate (lower yoke) 10 is made of a high permeability magnetic material, and is generally made of polycrystalline Ni.
A -Zn ferrite substrate or a crystalline or polycrystalline Mn--Zn ferrite substrate is used. l・Rack width is usually YMR
Since the head has a multi-track configuration, the thickness is set to about 50 μm.

Here, the axis of easy magnetization of the MR element 15 is often selected in the longitudinal direction of the stripe of the MR element 15 from the viewpoint of sensitivity and noise. In other words, the output) is proportional to the square of the applied magnetic field.Therefore, it is necessary to apply an external bias magnetic field to shift the operating point to the linear region.
In the YMR head shown in FIG. 3, a bias current Is' is externally supplied to the conductor I3 made of AJij-Cu,
The magnetic field generated by the current IB' is defined as a bias magnetic field.

However, the conventional YMR head shown in FIG. 3 requires a bias current conductor 13 in addition to the magnetic circuit, and has the disadvantage that the manufacturing process is complicated. Furthermore, since the MR element section 15 is formed on the bias conductor layer 13 with the insulating layer 12 in between, the bias conductor layer 13
Characteristics such as surface roughness adversely affect the magnetic properties of the MR element 15, resulting in lower sensitivity and increased noise of the YMR head.

<Objective of the Invention> Therefore, the object of the present invention is to eliminate the need for a bias current conductor, thereby simplifying the manufacturing process, and
It is an object of the present invention to provide a thin film magnetic head that can eliminate the negative influence of a bias conductor on the magnetic properties of an MR element.

<Structure of the Invention> In order to achieve the above object, the present invention provides a first yoke, an MR element, and a magnetic recording medium on a substrate having high magnetic permeability, one end of which is exposed to the sliding surface of the magnetic recording medium. A second yoke that is not exposed on the sliding surface is sequentially magnetically coupled and arranged to form a closed magnetic path, and a head gap is formed between the high magnetic permeability magnetic substrate and the first yoke. In the YMR type thin film magnetic head, the second yoke is insulated from the MR element;
The present invention is characterized in that it includes a supply means for supplying a current from the outside so that it flows in parallel with the R element.

<Function> When a current is supplied to the supply means from the outside, the current flows through the second yoke in parallel to the MR element, and a bias magnetic field is applied to the MR element. In this way, the second yoke can also serve as a conductor for bias current, simplifying the process.
Moreover, the adverse effects caused by the bias conductor can be eliminated.

<Embodiment> FIG. 1 shows a two-track Y'M according to an embodiment of the present invention.
FIG. 2 is a plan view of the R head, and FIG. 2 is a sectional view taken along a plane perpendicular to the track width direction (A-A° in FIG. 1). In FIG. 1.2, [ is a substrate having high permeability magnetism, 2 is an insulating film, 3 is a magnetic gap layer, 4 is an MR element, 5 is a lead portion for flowing a sense current Is to the MR element 4, 7 8 is a first yoke, 8 is a second yoke, and 9 is a magnetic recording medium. As the substrate 1, a high permeability magnetic substrate (for example, !vln-4n ferrite, Ni-Zn ferrite, etc.) or a high permeability magnetic film coated on the substrate is used. The magnetic flux incident from the magnetic recording medium 9 is introduced by the second yoke 7, passes through the 1vHN element 4, passes through the second yoke 8, and exits to the ferromagnetic substrate l. In this way, the first and second yokes 7.8, the MR element 4, and the high permeability magnetic substrate l constitute a closed magnetic path. A magnetic gap filled with the magnetic gap layer 3 is formed between the ferromagnetic substrate l and the first yoke 7.

The first yoke 7 and the second yoke 8 are made of a metal ferromagnetic material such as a Ni-Fe alloy or a Fe-A/-Si alloy. An insulating layer 22 between the second yoke 8 and the MR element 4
is provided. The second yoke 8 is formed commonly for each track as shown in FIG.
A current inflow terminal portion 21.2, which is a supply means, allows the current to flow.
1 at the same time. The 1u flow IB flowing through the portion 8a of the second yoke 8 is parallel to the MIN element 4. Therefore, it is possible to apply an effective bias magnetic field to the MR element 4 by flowing the current IB through the second yoke 8 instead of flowing the current IB through the bias conductor I3 shown in FIGS. 3 and 4. Here, the second yoke 8 is M
It is formed in a closed magnetic path including the R element 4, and as shown in Figure 1, the bias current [B flows within the closed magnetic path and parallel to the MR element 4 (perpendicular to the closed magnetic path), so the bias efficiency is very high. (bias current - bias magnetic field ratio) is excellent.

In this case, it is conceivable to flow the bias N current through the first yoke 7, but this is not preferable due to the following two points.

That is, one end of the first yoke 7 is exposed to the sliding surface of the magnetic recording medium, and when a bias current is passed there, it combines with moisture in the atmosphere, causing electrolytic corrosion, which is disadvantageous in terms of reliability. . Furthermore, in a multi-track head as shown in FIG. 1, by forming the first yoke 7 in common, crosstalk between tracks increases, making it unusable. According to the configuration of the present invention, the above two problems are solved, and it becomes possible to apply a bias magnetic field to the MR element 4 with a low bias current 1B. In addition, 17 is a pack gap part.

In the above embodiment, a two-track head has been described, but it is obvious that the present invention is also effective in a multi-track head or a single-track head.

<Effects of the Invention> As explained above, according to the present invention, in the YMR head, MR is supplied from the outside to the second yoke through the supply means.
A current can be supplied so as to flow parallel to the element, and a bias magnetic field can be applied to the MR element.

Therefore, as you can see by comparing Figures 2 and 4,
The conventional bias conductor layer 13 and insulating layer I2 can be omitted, and the process can be simplified. Additionally, as an additional advantage, since there is no conductor layer for bias current under the MR element, the magnetic properties of the MR element part are the same as those of the conductor part.
thermal expansion coefficient, surface roughness, etc.), and MR
It becomes easier to control the characteristics of the element.

[Brief explanation of drawings]

FIG. 1 is a view of a thin-film magnetic head according to an embodiment of the present invention viewed from the top surface of the substrate, and FIG. 2 is a cross-sectional view of the main parts of the head in a plane perpendicular to the substrate in the direction of AA' in FIG. , Figure 3 is
FIG. 4 is a cross-sectional view of the main parts of the head taken along line BB' in FIG. 3 and perpendicular to the substrate. 1.10...Substrate, 2.11.12...Insulating film,
13... Conductor layer, 3, 14... Magnetic gap layer, 4, I5... MR element, 5, 16... Lead part, 6... Back gap part, 7. [Death...1st
yoke, 8, 19... second yoke, 9.
20... Magnetic recording medium, 21... Supply means.

Claims (1)

[Claims] (1) On a substrate having high magnetic permeability, a first yoke, one end of which is exposed to the sliding surface of the magnetic recording medium, a magnetoresistive element, and a second yoke that is not exposed to the sliding surface of the magnetic recording medium.
In a magnetoresistive thin film magnetic head, the thin film magnetic head is of the magnetoresistive effect type, in which the first yoke is magnetically coupled to the second yoke in order, the first yoke is arranged to form a closed magnetic path, and a head gap is formed between the substrate and the first yoke. A thin film magnetic head characterized in that the yoke is insulated from the magnetoresistive element, and further includes supply means for supplying a current from outside so as to flow parallel to the magnetoresistive element.