JPH0419809A - Magnetoresistive head - Google Patents

Abstract

PURPOSE:To suppress the generation of Barkhausen noises in reproduced waveforms and the fluctuation in the output level of a magneto-resistance effect type head (MR element) by forming the MR element to a circular annular shape which has no magnetic gap. CONSTITUTION:The MR element 11 consists of a ferromagnetic material, such as, for example, NiFe film. The MR element 11 is formed to the circular annular shape. The element is connected to a drawing out conductor layer 12 which is notched at a prescribed width and has a width t5 at both ends of a annular signal detecting region 16. The easy axis of the MR element coincides with the circumferential direction of the annular from the shape anisotropy of this MR element. Namely, the easy axis direction varies with the shape and coincides with the direction where the length is larger and in this case the circumferential direction of the infinite length. The MR element 11 is annular and the length thereof is not formed to the finite length with respect to the magnetization direction and, therefore, magnetic poles are not generated in the element and diamagnetic fields are not generated. Magnetostatic energy, therefore, decreases to zero and the element has the monodomain structure where magnetic walls are not generated. The fluctuation in the output level is prevented in this way.

Description

[Detailed Description of the Invention] [Summary] Regarding a magnetoresistive head, the purpose is to prevent Barkhausen noise occurring in the reproduced waveform of the magnetoresistive head and to avoid fluctuations in the output level of the magnetoresistive element. The magnetoresistive head is constituted by a magnetoresistive element formed in an annular shape without a magnetic gap.

[Industrial application field]

The present invention relates to a magnetoresistive head (hereinafter referred to as an MR head).

In recent years, with the increase in the capacity of magnetic disk drives, which are external storage devices for computers, there has been a demand for high-performance magnetic heads. An MR head that can obtain high output regardless of the speed of the recording medium is attracting attention as one that satisfies this requirement.

[Conventional technology]

The MR head is a read-only magnetic head made of a ferromagnetic thin film (MR film), and uses the magnetoresistance effect, which changes depending on the electrical resistance of the ferromagnetic thin film made of permalloy or the like or an external magnetic field, to generate a signal magnetic field. This method detects changes in electrical resistance as changes in electrical resistance. The element constituted by the ferromagnetic thin film is called a magnetoresistive element (hereinafter referred to as an MR element).

A conventional MR head has a structure as shown in FIGS. 6(a) and 6(b). 61 is a rectangular MR element, 62 is an extraction conductor layer, and 63a and 63b are magnetic shields.

The MR element 61 is patterned so that its longitudinal direction (y-axis direction) I: coincides with the easy axis direction of the MR film. Here, the easy axis is also called the easy axis of magnetization, and is the direction in which the MR film is easily magnetized. The lead-out conductor layer 62 is M
The R element 61 is cut with a predetermined width in the longitudinal direction and the MR
Both ends of the element 610 are connected to the element. The MR element 61 and the lead-out conductor layer 62 are composed of two magnetic nodes 3a,
63b (corresponding to the reproduction gap),
Magnetic shields 63a, 63b via nonmagnetic insulating layer 64
electrically insulated. A sense current 65 flows through the element through the extraction conductor layer 62 and into a rectangular signal detection area 66 defined by the MR element 61 and the extraction conductor layer 62. Then, the magnetic recording medium 67 moves under the head in the X-axis direction, and the MR head detects the signal magnetic field from the medium as a resistance change in the signal detection area 66.

Further, in this case, the sense current 65 is M
It was also used to linearize the reproduction of the R head.

That is, the MR element 61 is placed close to one magnetic shield 63a, and a bias magnetic field is applied in the element height direction by a leakage magnetic field from the surface of the magnetic shield 63a magnetized by the sense current 65 (this bias method (This is called the self-bias method.) [Problems to be solved by the invention] ■The shape of the conventional MR element 61 is easy axis (y-axis direction)
Since the MR element 61 has a finite length with respect to the magnetization direction, magnetic poles (N and S poles) are generated at the ends of the element, and a magnetic field (diamagnetic field) in the opposite direction to the magnetization direction is generated inside the element. Ta. For this reason, the MR element 61 has a magnetic domain structure divided into several magnetic domains as shown in FIG. was occurring.

On the other hand, in general, MR films have non-uniformities such as crystal grain boundaries, lattice defects, impurity inclusions, etc. due to incomplete film formation.

For this reason, in conventional MR heads, the domain wall moves from being caught in the signal magnetic field from the recording medium, causing magnetization rotation to become discontinuous, producing Barkhausen noise in the reproduced waveform, and causing the output level of the MR element to change. There was an issue with fluctuations.

(2) Furthermore, since the conventional MR element 61 is integrated with the signal detection area 66 or other parts, there is a problem that it is easily susceptible to site crosstalk from adjacent recording tracks. That is, the magnetic recording medium may be magnetized in the easy axis direction, or the magnetic field of a track adjacent to the track to be recorded and detected may affect the recording detection section, producing noise in the MR head and deteriorating the performance of reproduction processing. there were.

■Furthermore, if there are unevenly processed parts on the surface of the MR element,
The Barkhausen noise and 8.
There was also the issue of fluctuations in power level.

[Means to solve the problem]

In order to solve the problem (2) among the above problems, in the present invention, the MR element in the MR head is formed into an annular shape.

Furthermore, in order to solve the problem (2), in the present invention, an annular MR element is separated from the magnetic recording medium, and a part of the MR element that detects a signal from the recording medium (hereinafter referred to as a recording detection section) Only this was extended to recording media.

Furthermore, in order to solve the problem (2), in the present invention, a magnetic field such as an exchange coupling magnetic field or a current magnetic field is applied to the annular MR element in the direction of the easy magnetization axis, which is the circumferential direction.

[Effect]

Since the MR element is annular, no magnetic poles are generated and no demagnetizing field is generated. Therefore, the magnetostatic energy becomes zero, and the element has a single magnetic domain structure in which no domain walls are generated.

Furthermore, separating the MR element from the magnetic recording medium increases resistance to side crosstalk.

Furthermore, when the MR element is applied in the easy axis direction, the magnetic domains are stabilized.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining one embodiment of the present invention (a
) to (c) are shown.

FIG. 1(a) is a sectional view of a main part of the MR head of the present invention. As shown in the figure, the MR head has a structure in which an MR element 11 is placed inside an extraction conductor layer 12 with a nonmagnetic insulating layer 14 interposed between two magnetic shields 13a and 13b.

The MR element 11 is, for example, N or F. It is made of a ferromagnetic material such as a film, and has a thickness tl of 400 to 500 people, and a width t2.
is set to 3 μm, and the outer diameter t3 is set to about 50 to 100 μm. Here, the shape of the MR element 11 is annular as shown in FIG. 1(b). Then, the lead-out conductor layer 12 is cut out with a predetermined width and has a width t, and the lead-out conductor layer 12 shown in FIG.
), they are connected at both ends of the annular signal detection area 16.

Due to the shape anisotropy of the MR element, the easy axis of the MR element coincides with the circumferential direction of the ring. That is, the direction of the easy axis varies depending on the shape, and the easy axis direction coincides with the long direction, and in the second case, the direction of the circumference of infinite length. Here, since the MR element 11 has an annular shape and is not formed to have a finite length with respect to the magnetization direction, no magnetic pole is generated inside the element, and no demagnetizing field is generated. Therefore, the magnetostatic energy becomes zero, and the element has a single magnetic domain structure with no domain walls.

The lead conductor layer 12 is A. It consists of a membrane, etc. In this embodiment, as shown in FIG. 1(C), the MR element 11 has a width t that is almost the same as the radius t2, and is formed in a right-angled shape, but is not limited to such a shape. . This is because it is sufficient if only the sense current 15 flows through the signal detection region 16. The convergence t4 of the signal detection area is about 2 to 3 μm.

The magnetic shields 13a and 13b are made of N, F, ferrite, or the like. These serve to enhance the reproduction resolution of the MR element 11 with respect to the signal magnetic field from the recording medium 17.

The MR element 11 and the extraction conductor layer 12 are arranged between two magnetic shields 13a and +3b, and both are electrically insulated from the magnetic shield via a nonmagnetic insulating layer 14 of S, O2 film or Δ1203 film. It becomes. M.R.
Element 11 is arranged inside nonmagnetic insulating layer 14 .

This is to avoid being influenced by external magnetic fields or external currents.

The sense current 15 flows into the signal detection region 16 of the MR element 11 through the extraction conductor layer 12. Then, the MR head detects a signal magnetic field from the magnetic recording medium 17 moving directly below by linearly operating the MR using the above-described self-bias method. In the second case, the MR element 11 has a single magnetic domain structure according to the above-described inventive principle, and no Barkhausen noise is generated. Furthermore, fluctuations in the output level of the MR element can be avoided.

FIG. 3 shows a second embodiment of the present invention, and is a plan view of an MR herad. In the figure, an MR element 31, an extraction conductor layer 3
2 has the same configuration as in FIG. 1, and a magnetic shield (not shown) also has the same configuration as in FIG.

In the embodiment shown in FIG. 3, the MR element 31 is separated from the magnetic recording medium 33, and the signal detecting section 34a is arranged to extend from the magnetic recording medium 33. In this example, M
Since the R element 31 is located further away from the magnetic recording medium 33, compared to the embodiment shown in FIG.
It has the characteristic of being resistant to crosstalk. Specifically, if the dimensions are the same as those shown in Figure 1, it is about 1 μm. That is, it must be within a range where the circular ring shape can be maintained.

This is to prevent the generation of domain walls. Regardless of the shape of the MR element, the method of separating the MR element from the magnetic recording medium and extending only the recording detection section to the magnetic recording medium is the side
It has the characteristic of being resistant to strokes.

In a third embodiment of the present invention shown in FIG. 4(a), a film 42 for generating an exchange coupling magnetic field is laminated in the circumferential direction of an MR element 41. The exchange coupling magnetic field is a magnetic field that attempts to direct a locally generated magnetic field in the easy axis direction. Films that generate exchange coupling magnetic fields include antiferromagnetic films (F, M, ) or ferrimagnetic films (T, C,),
High antimagnetic films (N, F, C0') are suitable, and these films are formed by vapor deposition or sputtering. Among these, the one with the strongest exchange coupling magnetic field is the textured magnetic film, followed by the antiferromagnetic film and the high antimagnetic film.
The purpose of the present invention can be achieved no matter which one is used.

FIG. 4(b) is a right sectional view of the laminated portion in FIG. 4(a). The lamination is as shown in the same figure (b): f: MR element 4
] It is sufficient if it is laminated only on one side of the MR element 4.
This is more suitable for generating an exchange coupling magnetic field than covering the entire surface of the magnetic field. In the laminated portion, the vertical width t6 of the laminated portion in FIG. 4A is only required to be larger than the radius t2 of the MR element 41, and the horizontal width t7 is not particularly limited as long as it does not extend to the signal detection area 36. This is because if it reaches the signal detection area 36, it will affect signal detection.

Further, the film 42 that generates the exchange coupling magnetic field is the MR element 41.
It is not necessary to stack the layers according to the curvature of.

This is because an exchange coupling magnetic field is generated as long as it is connected to the MR element.

FIG. 5 shows a fourth embodiment of the present invention in which a thin film coil 53 formed by vapor deposition or sputtering is wound around the MR element to apply a current magnetic field to the MR element 51i. Here, it is sufficient that the thin film coil 53 is wound around the MR element 51 several turns. Further, the thin film coil 53 has a sense current 5
4 (for example, about 10 mA) is applied. In the embodiment shown in FIGS. 4 and 5, the magnetic field is MR
The voltage is applied to the easy axis (circumferential direction) of the element, and
The magnetic domain can be further stabilized compared to the embodiment shown in the figure. These may be due to the uneven surface processing of the MR element, resulting in domain walls.
It has the effect of suppressing Barkhausen noise. Note that in these examples, the self-bias method is used as the linearization method for MR head reproduction, and the present invention does not particularly limit the bias means for linearization. The bias method may be any other shunt bias method, permanent magnet bias method, current bias method, barber pole bias method, etc. Further, in this embodiment, the magnetic fields applied in the easy axis direction in FIGS. 4 and 5 are an exchange coupling magnetic field and a current magnetic field, but the applied magnetic fields are not limited to these.

For example, it is also possible to apply using a permanent magnet.

〔Effect of the invention〕

As explained above, the present invention produces the following effects. That is, (1) By forming the MR element into a circular tube shape that does not create a magnetic gap, the occurrence of Barkhausen noise in the reproduced waveform is suppressed, and fluctuations in the output level of the MR element are prevented.

■ By separating the MR element from the magnetic recording medium and extending the signal detection section to the magnetic recording medium, side tarostalk from tracks adjacent to the detected track is prevented.
Reduce noise.

(2) By applying a magnetic field in the circumferential direction, which is the easy axis direction of the MR element, Barkhausen noise due to locally generated domain walls can be suppressed even if the surface treatment is uneven.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of essential parts of an MR head according to a first embodiment of the present invention, FIG. 1(b) is a plan view of an MR element according to a first embodiment of the present invention, FIG. 1(C) 1 is a perspective view of essential parts of an MR head according to the first embodiment of the present invention, FIG. 2 is a diagram illustrating the current flowing in the signal detection region when the MR element has a closed loop structure, and FIG. 3 is a diagram illustrating a second embodiment of the present invention. A diagram explaining an example, Figure 4 (a
) is a diagram illustrating the third embodiment of the present invention, FIG. 4(b) is a right sectional view of the laminated portion in FIG. 4(a), and FIG. 5 is a diagram illustrating the fourth embodiment of the present invention. , Figure 6 (a
) is a sectional view of a main part of a conventional MR head, FIG. 6(b) is a diagram of a conventional MR head, and FIG. 6(c) is a diagram of a conventional MR head element magnetic domain structure. In the MR diagram in the oblique view of the main parts showing the code, 1 is the MR element, 2 is the extraction conductor layer, 3a is the magnetic shield, 3b is the magnetic shield, 4 is the nonmagnetic insulating layer, 5 is the sense current, 6 is the signal detection area , 6a is a signal detection unit, 7 is a magnetic recording medium, 7a is a bonding surface 1 of the magnetic recording medium is an MR element, 2 is an extraction conductor layer, 3 is a magnetic recording medium, 33a is a bonding surface of the magnetic recording medium, 34 is a signal Detection region, 34a is a signal detection section, 41 is an MR element, 42 is a film that generates an exchange coupling magnetic field, 43 is an extraction conductor layer, 51 is an MR element, 52 is an extraction conductor layer, 53 is a thin film coil, 54 is a sense current shows.

Claims (5)

[Claims] (1) In a magnetoresistive head that detects changes in the magnetic field as changes in the resistance value of a magnetoresistive element (11), the magnetoresistive element (11) is formed in an annular shape with no magnetic gap. A magnetoresistive head characterized by: (2) In the magnetoresistive head according to claim 1,
The magnetoresistive element (31) is separated from the magnetic recording medium (33), and the magnetic recording medium (33) of the magnetoresistive element is separated from the magnetic recording medium (33).
) A magnetoresistive head characterized in that only a signal detecting portion (34a) extends to a magnetic recording medium (33). (3) The magnetoresistive head according to claim 1 or 2, further comprising a member (42) for applying an exchange coupling magnetic field in the circumferential direction of the magnetoresistive element (41). Magnetoresistive head. (4) The magnetoresistive head according to claim 1 or 2, further comprising a member (53) for applying a current magnetic field in the circumferential direction of the magnetoresistive element (51). Magnetoresistive head. (5) The magnetoresistive head according to claim 1 or 2, wherein a magnetic field is applied in the circumferential direction of the magnetoresistive element.