JPS63164013A - Magneto-resistance type thin film magnetic head - Google Patents

Abstract

PURPOSE:To prevent the production of a magnetic wall in the operating region in an MRE by arranging the magneto-resistance element (MRE) having a minute gap very close to a closed magnetic path and a bias conductor to the lower face without being protruded from the MRE in the projection of the shape. CONSTITUTION:A sense current in the MRE 58 is fed from lead terminals 62, 63 and since a gap G is provided, the current flows only through a straight line part 59 of the MRE 58. A bias conductor 54 is arranged to the lower face of the MRE 58 while clipping an insulation film and the bias magnetic field to the MRE 58 is generated by giving a DC bias current from the lead terminals 52, 53. Thus, the sensitivity and linearity of the straight line part 59 of the MRE 58 are improved. The bias current flows through the straight line part 55 only by the presence of the gap (g) of the bias conductor 54 and does not flows through L-shaped parts 56, 57. The background part of the MRE 58 is smoothed by the shape of the bias conductor 54. Moreover, when the MRE 58 is not produced from the shape and size of the bias conductor 54, no step difference nor ruggedness is caused and stable magnetic wall structure is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetoresistive thin film magnetic head that can realize narrow tracks, narrow gaps, and even multi-tracks by making full use of thin film microfabrication technology.

BACKGROUND OF THE INVENTION Recently, magnetic recording devices have been using magnetoresistive elements (hereinafter referred to as MREs) as playback heads due to the shortening of track widths and slowing down of magnetic tape running speeds due to improved track density. type thin film heads (hereinafter referred to as MR heads) are widely used. The third representative structure
As shown in the figure. In Fig. 3, a magnetic substrate 1 such as ferrite
Ad on o.

A bias conductor 11 made of Au, Cu, etc. is arranged.

An MRE 12 made of permalloy (Ni-Fe alloy), N1-Go gold alloy, etc. is formed on the bias conductor 11 via an insulating film such as 5i02. The MRE 12 has a rectangular shape, and a magnetic field evaporation method is used to form the film, and uniaxial magnetic anisotropy is achieved so that the track width direction becomes the axis of easy magnetization. 13 is a front yoke, and 14 is a back yoke, which is made of a soft magnetic film having high magnetic permeability such as permalloy, sendust, or amorphous alloy film. Front yoke 13 and back yoke 14
A window 16 separated from each other is formed approximately at the upper center of the MRE 12. Both terminals of MRK12 have M
Lead terminal 16.17 that flows sense current to RIC:12
is provided. The above configuration is what is called a yoke type MR head, which is placed close to the magnetic tape 18 and reads information recorded on the magnetic tape 18.

The operation of the MRE 12 is as follows. That is, the signal magnetic flux from the magnetic tape 18 passes through the front yoke 13 to the MR
E12 rotates the magnetization of the MRE 12, and the resistance of the MRE 12 changes accordingly. At this time, MRE1
When a sense current Is is caused to flow through the lead terminals 16 and 17 of the MR1C12, the resistance change of the MR1C12 is converted into a voltage change and detected.

In general, the resistance change ΔR of the MRE 12 is ΔR − ΔRcosO, where the angle between the sense current direction and the magnetization direction of the MRE 12 is 0, and the maximum resistance change is ΔRmax.
...(1) It can be expressed as m&x. Also, the signal magnetic flux inside MRE12
g.

When the saturation magnetic flux density of MRE12 is Bs, approximately sin θ”Bs1g/Bs --(2
) is established, and from equations (1) and (2), ΔR=ΔRmax (' (Bs1g/Bs )
) is guided. That is, theoretically, the resistance change ΔR of the MRE 12 shows a resistance change as shown in FIG. In order to improve the output due to resistance change of MRE12 and make it linearly responsive,
It is necessary to set the magnetic equilibrium point at the position shown in FIG. 4B. For this reason, a DC bias current is passed through the bias conductor 11, and the magnetic field generated thereby is a bias magnetic field.

Problems to be Solved by the Invention However, in order to realize high-density recording, it is conceivable to increase the track density by reducing the track width. At this time, when the MRE is formed into a minute pattern, there is a problem in that noise is generated due to discontinuous domain wall movement, leading to deterioration in the quality of the reproduced output. That is, an MRIC in a demagnetized state has a large number of magnetic domains, and FIG. 6 shows an example of the magnetic domain structure of a strip-shaped MRIC having an axis of easy magnetization in the longitudinal direction. In this example, two main magnetic domains 20 have antiparallel magnetization to each other in the easy axis direction.
．． 21 and two magnetic domains 22 and 23i called reflux magnetic domains, and the MRK as a whole has no magnetization. As a result, the signal magnetic field from the magnetic tape is
When acting on C, the magnetic domain generates noise due to irregular movement. This situation is shown in FIG. In the figure, N to N4 are locations where the noise is generated. This Barkhausen noise has a noise distribution over a wide frequency range, and has been a major factor in deteriorating the S/Ni of the reproduced signal.

The present invention eliminates the occurrence of the Barkhausen noise,
The present invention provides an MR head with low noise.

Means for Solving the Problems In order to achieve this object, the MR head of the present invention forms an MRE having a gap G very close to a closed magnetic circuit structure, and further includes a bias conductor for applying a bias magnetic field to the MRIC. The shape is almost similar to the above MRE shape, and M
The structure is such that RK is completely placed on the bias conductor.

Effect: This configuration, in combination with the MRE and bias conductor of the present invention, can significantly reduce Barkhausen noise. That is, since the MRE has a structure that is very close to a closed magnetic circuit with a gap G between both ends in the longitudinal direction, when no external magnetic field acts, each of the four magnetic domains has magnetization in the demagnetized state, and the four locations of the MRE A 900 domain wall is generated only at the corner. This 90° domain wall is extremely stable and will not move even if an external magnetic field H6 is applied from a certain direction as long as H6X is about the same as the signal magnetic field on the magnetic tape. Therefore, it is possible to remove the noise caused by discontinuous domain wall movement.

Next, the effect of the shape of the bias conductor will be described.

The MRIC is formed of a thin film of Ni--Fe alloy, for example, with a thickness of 300 to 500 mm, and the generation of domain walls is extremely influenced by the smoothness of the underlying surface of the MRE.

In particular, if there is a fine step or unevenness on the base of the MRE, a complicated domain wall will be generated in the MRE located on the upper surface of the area. Generally, in an MR head, it is necessary to form a bias conductor for a bias magnetic field on the lower surface of the MRK with an insulating film interposed therebetween. At this time, when a part of the MRE is projected onto the lower surface and protrudes from the bias conductor, a step is generated in the protruding portion of the MRIC. The bias conductor of the present invention has a shape that completely envelops the MREI and has a similar shape to the MRE, thereby preventing the MRK from protruding.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a magnetoresistive thin film magnetic head according to an embodiment of the present invention. In FIG. 1, an insulating film 61 such as 5i02 is deposited on the entire surface of a ferromagnetic ferrite substrate 50. In FIG. Lead terminals 52 and s are provided on this insulating film 51.
3i bias conductor 64 is patterned. The main structure of the bias conductor 54, excluding the lead terminal portion, consists of a straight portion 55 and L-shaped portions 56 and 57, each having one end separated by a gap g. MR1! on the bias conductor 54 via an insulating film (not shown). :5B is the gap Gi
The structure is very similar to a closed magnetic circuit. The MRK 68 is patterned to form a straight portion 59 and a 5-shaped portion 60°61 without protruding onto the bias conductor 54.

62 and 63 are lead terminals through which a sense current flows to the MRE 58. The method of forming MRK5B is the same as the conventional strip-shaped one, using the magnetic field evaporation method, and the material is Ni-Fe alloy. The straight portion 59 of MR]1C58 is controlled by the above-mentioned deposition in the magnetic field so that the direction of the axis of easy magnetization 64 coincides with the track width direction. An insulating film (not shown) is sandwiched over the straight part 59 of the MREss, and one end of each of the front yoke 65 and the back yoke 66 is connected to the straight part 6 of the MRK 58.
It is formed so as to overlap with 9. For the above-mentioned yoke material, a soft magnetic film having high magnetic permeability such as Permalloy, Sendust, or an amorphous alloy film is used. The track width Tw is set at the time of patterning the front yoke 65. After this, 5102
A film 1203 film or a SiO film (not shown) is formed, and the sliding surface with the magnetic tape is processed and lapped into a predetermined shape, thereby completing a so-called yoke type MR head.

In the MR head configured as described above, the signal magnetic flux from the magnetic tape flows through the path of the front yoke 66 -> the straight part 59 of the MRE 58 -> the back yoke 66 -> the substrate 50. In this path, the signal magnetic flux flows through the MRF, 58 Straight line part 5
9'jli: Crossing causes a change in resistance of MREss, and information written on the magnetic tape is detected.
At this time, the bias conductor has a bias current, MRIC: 5
It goes without saying that a sense current is applied to 0MRK58, but the sense current in MRK58 is applied by the lead terminals 62 and 63, but since there is a gap (i7), it flows only to the straight part 59 of MRIC: 5B. In other words, the operating region of the MRIC 68 is only the straight portion 69.

A bias conductor 54 is installed on the lower surface of the MRK5B with an insulating film interposed therebetween. By passing a DC bias current through the lead terminals 52 and 63, a bias magnetic field is generated to the MRE 6B, thereby improving the sensitivity and linearity of the straight portion 69 of the MREss. At this time, the bias current flows only to the straight portion 55 due to the presence of the gap g in the bias conductor 54, and does not flow to the 5-shaped portions 66 and 57. The shape of the bias conductor 54 flattens the base of the MRK5B.

Furthermore, if the MRK5B does not protrude from the shape and dimensions of the bias conductor 64, no steps or irregularities will occur in the MREss, resulting in a stable domain wall structure as shown in FIG.

With the above structure, since the straight portion 69 of the MRK 58 does not have a magnetic domain wall, the park noise is removed and a good reproduced signal can be obtained. Further, although the bias conductor 54 and the MRE 58 each have a shape close to a closed circuit, there is a gap grczk in a part of the circuit. This results in a bias current.

The sense current does not flow through the figure 5 portion 60, 61, but through the straight portion 5.
9, the resistance change efficiency and bias efficiency in the effective operating region in the straight portion 59 of the MRE 5B can be increased.

Although this embodiment has been explained using a one-track configuration, the same effect can be obtained even in a multiple-truss structure.Advantageous Effects of the Invention The present invention provides an MRE having a micro gap extremely close to a closed magnetic path.
By arranging the bias conductor on the lower surface of the MRE without protruding from the MRE when this shape is projected, it is possible to prevent the generation of domain walls in the operating region within the MRE. Therefore, even when a signal magnetic field is applied from the magnetic tape, Barkhausen noise caused by discontinuous domain wall movement within the MRE does not occur, and a reproduced signal with a high S/H can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a magnetoresistive thin film magnetic head according to an embodiment of the present invention, and FIG. 2 is an MRT! 3 is a perspective view of a conventional magnetoresistive thin film magnetic head, and 4 is a plan view showing the shape of the bias conductor and the domain wall and magnetization state during demagnetization in the MRE. Theoretical characteristic diagram showing resistance changes. Figure 6 is a plan view showing an example of the magnetization state of a conventional strip-shaped MRK during demagnetization. Figure 6 shows the magnetic field strength and resistance change of a micropattern MRE that generates Parkz-Usen noise. FIG. 60... Substrate, 54... Bias conductor, 58... Magnetoresistive element, 55.69...
...Straight line part, 66°57.80.61...L-shaped part, 62.63...Lead 744, 65-front yoke, 66...back yoke. Name of agent: Patent attorney Toshio Nakao and one other person 5θ
- Substrate requirement - Bias angle 65° - Front yoke Figure 4 Figure 5 2: / 2θ

Claims (2)

[Claims] (1) A magnetoresistive element made of a ferromagnetic metal material, a pair of lead terminals for passing a sense current through the magnetoresistive element, and a bias conductor for applying a bias magnetic field to the magnetoresistive element are provided on a substrate, and magnetic recording is possible. A magnetic head for detecting signal magnetic flux from a medium as a change in resistance of the magnetoresistive element, wherein the magnetoresistive element has a shape extremely close to a closed magnetic path with a minute gap G at both longitudinal ends thereof, and A magnetoresistive thin film magnetic head, characterized in that it is placed on the bias conductor with an insulating film sandwiched therebetween. (2) A magnetoresistive thin film magnetic head according to claim 1, characterized in that the bias conductor path located on the lower surface of the microgap portion of the magnetoresistive element has a microgap g (≦G).