JPH11120520A - Magnetoresistive effect head and magnetic memory system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower a reading error rate of a magnetic memory system occurring in the output fluctuation of a head and the asymmetricalness of waveforms by mounting a magnetic head which is small in the output fluctuation and the asymmetricalness of the waveforms. SOLUTION: A magnetic domain control layer 34 formed on an underlying metal layer 35 comes into contact with an MR layer 31 formed on a magnetosensitive part 38, a soft magnetic layer 32 and a nonmagnetic layer 33 in a joint part 37. The magnetic domain control layer 34 has a nearly perpendicular angle in the taper angle 40 of the three layer active regions and is, therefore, not formed on the MR layer 31 having soft magnetic characteristics and the soft magnetic layer 32. Since the film thickness of the underlying metal layer 35 is adequately thick, the magnetic domain control layer 34 and the MR layer 31 do not have exchange bond and the magnetic domain control layer 34 is laminated in the position where the MR layer 31 and the magnetostatic interaction are max. The magnetic domain control layer 34 having large coercive force is formed in the end region 39 and the longitudinal bias magnetic field, based on the magnetostatic interaction between the magnetic domain control layer 34 and the MR layer 31 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic storage system, and more particularly to an MR head used therein.

A magnetic head has a primary function of converting an electric signal into a magnetic signal in a magnetic storage system, and recording the magnetic signal on a magnetic storage medium as a magnetization pattern, or recording the magnetic signal on a magnetic storage medium. An object of the present invention is to read the magnetized pattern as a magnetic signal and convert it into an electric signal. Stably reproducing a magnetic signal read from a magnetization pattern on a magnetic storage medium by a magnetic head without distortion is equivalent to reducing output fluctuation of an electrical signal to be converted and asymmetry of a signal waveform. This means that the magnetic storage system is stable. Therefore, although the present invention is limited to a magnetic head, the present invention originally relates to a magnetic storage system using a magnetic head.

[0003] From the role of the magnetic head, the magnetic head converts an electric signal into a magnetic signal, and records the magnetic signal on a magnetic storage medium as a magnetization pattern, and a magnetic head that reads from the magnetization pattern on the magnetic storage medium. Read head for converting a target signal into an electrical signal. FIG. 1 shows an example of a recording / reproducing head, which is a composite type magnetic head including a reproducing MR head 11 utilizing a magnetoresistive effect and a recording inductive head 12 utilizing a magnetic induction effect formed directly thereon. Show the head. The present invention relates to the reproducing MR head 11 among them, and is therefore applicable not only to a composite magnetic head including a recording / reproducing head but also to a reproducing-only magnetic head using an MR head.

[0004]

2. Description of the Related Art At present, a magnetoresistive head (MR head: magnetoresistive head) utilizing anisotropic magnetoresistance effect of a ferromagnetic material is widely used as a magnetic head. In order to suppress Barkhausennoise, which is one of the main causes of the output fluctuation, a longitudinal bias magnetic field is applied to keep the MR layer in a single magnetic domain state and to reduce the asymmetry of the output waveform. It is well known to utilize a linear region of the magnetoresistive effect by applying a lateral bias magnetic field to maintain. Various methods have been described for applying these bias fields.

In Japanese Patent Application Laid-Open No. 3-125311, an MR layer is limited to a magnetically sensitive portion, and a soft magnetic layer to which a lateral bias magnetic field is applied is connected to a MR layer through a nonmagnetic layer that cuts off magnetic coupling between the soft magnetic layer and the MR layer. Layers, and these MR layers,
A magnetic head in which a magnetic domain control layer made of a hard magnetic material, which applies a longitudinal bias magnetic field to end regions of a nonmagnetic layer and a soft magnetic layer, is disclosed.

A magnetic domain control layer 1 for applying a longitudinal bias magnetic field
One is a CoPt-based hard magnetic alloy (JP-A-3-12531).
1). Usually, this has magnetic anisotropy in the stacking direction (hexagonal c-axis), and in a simple stacking method, most of its magnetization component is oriented in the c-axis direction, and the plane in which a longitudinal bias magnetic field is formed is formed. The direction component is only caused by a slight inclination of the magnetization due to the demagnetizing field generated in the c-axis direction. There are several methods for directing the magnetization in the in-plane direction. One of the methods is to stack a CoPt-based hard magnetic alloy on a specific base metal layer (Japanese Patent Laid-Open No. -125311). This is obtained by laminating CoPt-based hard magnetic alloys such that the c-axis is oriented in the in-plane direction by utilizing the lattice constant of the crystal of the base metal layer. As a result, a magnetic domain control layer having a large in-plane coercive force and a residual magnetization proportional to the film thickness of the CoPt-based hard magnetic alloy can be obtained. It is also pointed out that in order for the MR layer to have a stable single magnetic domain structure, there must be magnetic exchange coupling between the MR layer and the magnetic domain control layer. Therefore, a magnetic metal alloy (Fe
In the case of using a non-magnetic metal (Cr, W, etc.), there is a case where the laminated film thickness is reduced.
However, the method of controlling the magnetic domain of the MR layer has the following disadvantages. That is, the magnetic domain control layer is structurally in contact with the MR layer and the end of the magnetically sensitive portion including the soft magnetic layer to which a transverse bias magnetic field is applied. At these junctions, the magnetic domain control layer is formed by the MR layer or the soft magnetic layer. It will be formed on top of the layer. For this reason, even when a magnetic metal alloy or a non-magnetic metal is used for the base metal layer, if the thickness of the laminated layer is small, the soft magnetic properties of the MR layer and the soft magnetic layer are affected. The coercive force in the in-plane direction is insufficient to control the MR layer into a single magnetic domain. When the coercive force is small as described above, the magnetic domain control layer becomes unstable with respect to an external magnetic field, and the unstable state is transmitted to the MR layer through exchange coupling at a junction with the magnetic layer. Will do. Furthermore, since the portion close to the junction is exchange-coupled with the magnetic domain control layer, the portion is substantially inactive, and the width of the inactive portion is in accordance with the state of the magnetic domain control layer. Greatly affected. This determines the effective read width of the data track of the MR sensor, and a large change in this directly affects the output fluctuation and the asymmetry of the output waveform.

FIG. 2 schematically shows a functional portion of an MR reproducing head used in a conventional magnetic head. In this example, the MR layer 21 is laminated on the soft magnetic layer 22 via the non-magnetic layer 23. Therefore, the soft magnetic layer 22
Has no ferromagnetic exchange coupling with the MR layer 21, and M
The magnetic field generated by the sense current flowing through the R layer 21 and the nonmagnetic layer 23 has a magnetization component in a direction perpendicular to the magnetization direction of the MR layer 21. Therefore, a lateral bias magnetic field is applied to the MR layer 21 by the magnetic field generated by the magnetization and the magnetic field generated by the current flowing through the soft magnetic layer 22. A magnetic domain control layer 24 for applying a longitudinal bias magnetic field to the MR layer 21 is formed on the end region 29 of the magneto-sensitive portion 28 using a non-magnetic or magnetic base metal layer 25, and is joined to the MR layer 21 and the soft magnetic layer 22 at the junction. 27. Since the base metal layer 25 is very thin, the magnetic domain control layer 24 has ferromagnetic exchange coupling with the MR layer 21 and the soft magnetic layer 22 through the junction 27. A longitudinal bias magnetic field is applied to the MR layer 21 and the soft magnetic layer 22 through this exchange coupling.

The magnetic sensing portion 28 is defined by the electrode layer 26 laminated on the magnetic domain control layer 24 in the end region 29. Also, in order to ensure electrical continuity between the electrode layer 26 and the MR layer 21 and the soft magnetic layer 22, the junction 27 has a length equal to or longer than that of the magneto-sensitive portion 28. It is formed. Therefore, the portion of the magnetic domain control layer 24 formed on the junction 27 is affected by the soft magnetic characteristics of the MR layer 21 and the soft magnetic layer 22 formed earlier through the thin underlying metal layer 25, Coercive force decreases, maximum externally applied magnetic field (eg, recording magnetic field)
Is magnetically unstable.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an
The magnetic layer and the soft magnetic layer are formed only in the magnetic sensing portion of the magnetic head, and the magnetic domain control layer is formed in each end region of the magnetic sensing portion without exchange coupling with the MR layer and the soft magnetic layer. It is an object of the present invention to provide an MR head that minimizes magnetic instability of a magnetic domain control layer in a portion and generates a sufficient longitudinal bias magnetic field for magnetic domain control of the MR layer.

[0010]

The read error rate of the magnetic storage system largely depends on the output fluctuation of the magnetic head as a magnetic sensor and the asymmetry of the output waveform. Therefore, in order to construct a magnetic storage system with a low read error rate, it is necessary to reduce the output fluctuation and the asymmetry of the output waveform of such a magnetic head.

According to the present invention, the magnetic head has the MR layer and the soft magnetic layer which form a magnetically sensitive portion and whose ends are formed at an angle close to vertical. However, the MR layer and the soft magnetic layer are stacked via the non-magnetic layer, and are in a state without ferromagnetic exchange coupling. A magnetic domain control layer having a non-magnetic base metal layer is formed at each end region of the magnetic sensing portion. The magnetic domain control layer has no appropriate ferromagnetic exchange coupling with the MR layer because the underlying metal layer has an appropriate thickness. The magnetic flux generated by the magnetic poles appearing in the portion adjacent to the MR layer is used for the MR.
It couples magnetostatically with the layer and provides a longitudinal bias magnetic field within the MR layer. In the magnetic domain control layer, since the ends of the MR layer and the soft magnetic layer are formed at an angle close to vertical, the junction thereof also has an angle close to vertical. Therefore, the magnetic domain control layer is not laminated on the MR layer having the soft magnetic property and the soft magnetic layer, and maintains a large coercive force even at the end of the magneto-sensitive portion, and is always stable against an external magnetic field. Can be kept. Further, in order to ensure the magnetostatic coupling between the MR layer and the magnetic domain control layer, the thickness of the underlying metal layer is set to be at least half of the thickness of the soft magnetic layer and the thickness of the soft magnetic layer and the non-magnetic layer. It has a thickness equivalent to the total thickness of the layers.

As described above, the present invention is to eliminate the instability factor which increases the output fluctuation and the asymmetry of the output waveform of the MR head, and uses a completely different principle from the conventional magnetic head. I have. This will be described with reference to the schematic diagram shown in FIG. The MR layer 31 and the soft magnetic layer 32 are laminated via the non-magnetic layer 33 in the magnetic sensing section 38, as in the conventional magnetic head. Similarly, the magnetic domain control layer 34 is also stacked in the end region 39 with the base metal layer 35 as a base, and further over the electrode layer 36.
Are laminated. The method of applying the lateral bias magnetic field to the MR layer 31 is essentially the same as that of the conventional magnetic head.
The method of applying the longitudinal bias magnetic field is essentially different from the conventional magnetic head. That is, while the conventional magnetic head uses a bias magnetic field based on ferromagnetic exchange coupling between the magnetic domain control layer 24 and the MR layer 21 at the junction 27, the magnetic head according to the present invention uses Then, the film thickness 41 at the junction 37 of the base metal layer 35 is appropriately increased, the ferromagnetic exchange coupling between the magnetic domain control layer 34 and the MR layer 31 is cut off, and the magnetostatic between the magnetic domain control layer 34 and the MR layer 31 is stopped. A bias magnetic field based on a typical interaction is used.

In order to realize this, it is necessary to maintain the coercive force of the magnetic domain control layer 34 at the junction 37 at a level that is not affected by the maximum external magnetic field. Further, it is necessary to arrange the magnetic domain control layer 34 and the MR layer 31 so as to be magnetostatically continuous, that is, to maximize the magnetostatic interaction of the magnetization of the MR layer 31 and the magnetic domain control layer 34. In order to keep the coercive force of the magnetic domain control layer 34 sufficiently large, the MR layer 31 and the soft magnetic layer 32 are formed such that the taper angle 40 is ideally perpendicular.
For the magnetic domain control layer 34, the MR layer 31 and the soft magnetic layer 3
2 are formed so as to reduce the influence of the soft magnetic characteristics.

In order to realize magnetostatic continuity between the MR layer 31 and the magnetic domain control layer 34, the magnetic domain control layer 34 and the underlying metal layer 3
5 is formed so that the film thickness is appropriately increased, and the magnetic flux generated by the magnetic pole appearing on the joint portion 37 side of the magnetic domain control layer 34 enters the MR layer 31 almost linearly. That is,
MR layer 31 and magnetic domain control layer 34 appearing at junction 37
Are formed so that the distance between the magnetic poles of the two is shortest. Practically, the thickness of the underlying metal layer 35 is made as thick as the thickness of the soft magnetic layer 32, and the magnetic domain control layer 34 having a residual magnetization equal to or higher than the saturation magnetization of the MR layer 31 is formed thereon. .

At this time, the magnetic domain control layer 34 necessary to minimize the output fluctuation of the MR head and the asymmetry of the waveform.
Is different depending on the thickness of the film thickness 41 at the bonding portion 37 of the base metal layer 35, but is at least larger than the saturation magnetization of the MR layer 31. In a specific embodiment, the thickness of the underlying metal layer 35 is substantially equal to the thickness of the soft magnetic layer 32, and the thickness of the magnetic domain control layer 34 is the same as that of the MR layer 31 and the nonmagnetic layer 33.
Is formed so as to be substantially equal to the combined film thickness. Br of the magnetic domain control layer 34 (CoPtCr) used at this time is
0.86T, MR layer (permalloy) Bs is almost 1T
Therefore, these ratios are approximately 1.2. At this time, the film thickness 41 of the bonding portion 37 of the base metal layer 35 is substantially equal to the film thickness of the MR layer 31.

According to the principle of the present invention, it is possible to manufacture a magnetic head having a small output fluctuation and waveform asymmetry. However, another advantage is obtained by using this principle. That is, when a conventional ferromagnetic exchange coupling is used as a principle of applying a longitudinal bias magnetic field, the MR layer 21 is exchange-coupled with the magnetic domain control layer 24, so that the MR layer 21 Although an inactive region appears widely, when the magnetostatic coupling is used, the MR layer 31 is used.
The inactive region at the end of is small, and a larger output signal can be obtained. In one embodiment, an output 1.5 times as high as that in the case of using the conventional ferromagnetic exchange coupling is obtained. Also, the small inactive area means that
This means that the difference between the geometric size of the magneto-sensitive portion 38 and the size of the magnetically active region defined by the distance between the electrode layers 36 is small. Therefore, the use of the principle of the present invention means that, when defining the magnetically sensitive portion 38 at the interval between the electrode layers 36, the narrower the magnetically sensitive portion 38 is, the more effective it becomes.

[0017]

According to the most preferred embodiment (Embodiment 1), first, an MR layer 31 having a thickness of 20 nm, a nonmagnetic layer 33 having a thickness of 8 nm, and a soft magnetic layer 32 having a thickness of 19 nm are arranged in this order. It is formed on the magnetic sensing portion 38 and the end region 39 by a sputtering method. Thereafter, the MR layer 31, the nonmagnetic layer 33, and the soft magnetic layer 32 are limited to the magnetically sensitive portion 38 by Ar ion milling,
The taper angle 40 is formed in the range of 60 to 90 degrees. Next, 2
The magnetic sensing portion 38 is masked using a layer resist, and a base metal layer 35 having a thickness of 25 nm, a magnetic domain control layer 34 and an electrode layer 36 having a thickness of 28 nm are formed by a lift-off method. At this time, the thickness 41 of the bonding portion 37 of the base metal layer 35 is 20 nm.
The MR layer 31 is made of permalloy (Bs = 1T), the soft magnetic layer 32 is made of permalloy added with zirconia (Bs = 0.67T), the base metal layer 35 is made of Cr, and the magnetic domain control layer 34 is made of Uses CoPtCr (Br = 0.86T). From this, the magnetic domain control layer 34 for the saturation magnetization of the MR layer 31 will be described.
Is about 1.2. In this embodiment, the output fluctuation of the MR head is within 1% as a ratio of the standard deviation to the average value, and the output fluctuation of the conventional MR head is 3%.
In contrast to the above, there is a remarkable suppression effect. However, when the taper angle 40 is 60 degrees or less, the output fluctuation suddenly increases. It is considered that in such an MR head, the magnetostatic coupling between the MR layer 31 and the magnetic domain control layer 34 is insufficient.

In the next embodiment (Embodiment 2), the thickness of the underlying metal layer 35 is 10 nm, the thickness of the magnetic domain control layer 34 is 28, 38,
48, 58 nm, and the other geometrical conditions are the same as in Example 1. In this case, since the thickness of the underlying metal layer 35 is small, the magnetic domain control layer 34 is partly and magnetostatically coupled to the soft magnetic layer 32. Among the four film thicknesses of the magnetic domain control layer 34, the smallest output variation is 38 nm, and the output variation tends to increase in the order of 48, 58, and 28 nm.

This is interpreted as follows. When the thickness of the magnetic domain control layer 34 is 28 nm, the thickness of the underlying metal layer 35 is 10 nm.
Since the magnetic domain control layer 34 is as thin as nm, the magnetic domain control layer 34 is disposed at an intermediate height between the MR layer 31 and the soft magnetic layer 32 (FIG. 4). Therefore,
The amount of magnetic flux of the magnetic domain control layer 34 that enters the soft magnetic layer 32 increases, and the amount of magnetic flux that enters the MR layer 31 becomes insufficient for controlling the magnetic domain of the MR layer.

When the thickness of the magnetic domain control layer 34 becomes 38 nm, the height of the magnetic domain control layer 34 becomes almost equal to the height of the MR layer 31 (FIG. 5). Therefore, the amount of magnetic flux entering the MR layer 31 is sufficient for controlling the magnetic domain of the MR layer. Even in the case of such a configuration of the MR head, output fluctuation can be suppressed. However, in this case, the output is reduced to about two thirds of the configuration of the MR head described in the first embodiment. This is because the magnetically active region of the MR layer decreases, and the magnetic flux of the magnetic domain control layer 34 directly enters the soft magnetic layer 32 and is magnetostatically coupled thereto.

When the thickness of the magnetic domain control layer 34 becomes 48 or 58 nm, the height of the magnetic domain control layer 34 exceeds the height of the MR layer 31 (FIG. 6). Therefore, although the amount of magnetic flux entering the MR layer 31 is sufficient for controlling the magnetic domains of the MR layer 31, more magnetic flux is supplied from the magnetic domain control layer. This extra magnetic flux becomes an unstable factor that fluctuates the magnetically active region of the MR layer 31 and causes an increase in output fluctuation of the MR head. Also, the output of the MR head decreases at a rate of about 1% / nm with respect to the configuration of the MR head described in the first embodiment. However, the denominator is an increment of the film thickness exceeding the height of the MR layer 31 of the magnetic domain control layer 34.

Conversely, when the thickness of the magnetic domain control layer 34 is kept constant at 45 nm and the thickness of the underlying metal layer 35 is made thinner than 5 nm, the output of the MR head rapidly decreases. This is MR
This is because ferromagnetic exchange coupling starts to appear between the layer 31 and the magnetic domain control layer 34. Therefore, the thickness of the magnetic domain control layer 34 must be 5 nm or more.

In the above embodiment, the width of the magnetic sensing portion 38 of the MR head, that is, the reproduction width of the data track is 2.5 μm or less, and the magnetic domain control method of the present invention is different from the conventional magnetic domain control method. In comparison, it has been confirmed that the smaller the width of the magnetic sensing unit 38, the greater the effect of suppressing the decrease in output.

[0024]

According to the present invention, it is possible to reduce the output fluctuation and the asymmetry of the waveform of an MR head used as a magnetic sensor in a magnetic storage system. A storage system is presented.

[Brief description of the drawings]

FIG. 1 is a read-only MR used in a magnetic storage system.
A bird's-eye view of a composite magnetic head including a head and a recording-only inductive head.

FIG. 2 is a cross-sectional view of a functional portion of a conventional magnetoresistive head to which a longitudinal bias magnetic field is applied by a magnetic domain control layer using a nonmagnetic or magnetic metal layer as a base.

FIG. 3 is a sectional view of a functional portion of a magnetoresistive head based on the principle of the present invention in Embodiment 1.

FIG. 4 is a cross-sectional view of a functional portion of a magnetoresistive head based on the principle of the present invention when the thickness of a magnetic domain control layer according to a second embodiment is 28 nm.

FIG. 5 is a cross-sectional view of a functional portion of a magnetoresistive head based on the principle of the present invention when the thickness of a magnetic domain control layer according to a second embodiment is 38 nm.

FIG. 6 shows the magnetic domain control layer of Example 2 having a film thickness of 48 or 58 nm.
FIG. 3 is a cross-sectional view of a functional portion of a magnetoresistive head based on the principle of the present invention in the case of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Magnetoresistive head (MR head) 12 Inductive head 21, 31 MR layer 22, 32 Soft magnetic layer 23, 33 Nonmagnetic layer 24, 34 Magnetic domain control layer 25 Nonmagnetic or magnetic base metal layer 26, 36 Electrode layer 27 , 37 Junction 28, 38 Magnetic sensing part 29, 39 End region 35 (Magnetic) Base metal layer 40 Taper angle 41 Film thickness separating magnetic domain control layer 34 of base metal layer 35 and MR layer 31

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsuya Mitsuoka 2880 Kozu, Kozuhara-shi, Kanagawa Prefecture, Ltd.Storage Systems Division, Hitachi, Ltd. (72) Inventor Takashi Kawabe 2880 Kozu, Kozu, Hitachi, Ltd. Storage, Hitachi Ltd. System Division

Claims (5)

[Claims] 1. The method of claim 1, wherein the M uses anisotropic magnetoresistance effect of a ferromagnetic material.
An R layer 31, a soft magnetic layer 32 for applying a lateral bias magnetic field to the MR layer 31, a nonmagnetic layer 33 for cutting off exchange coupling between the MR layer 31 and the soft magnetic layer 32;
A hard magnetic layer (magnetic domain control layer) 34 which is formed in an end region 39 of the magnetic sensing portion 38 and applies a longitudinal bias magnetic field to the MR layer 31; and stabilizes the magnetic characteristics of the magnetic domain control layer 34. The magnetic domain control layer 34 comprises a non-magnetic underlayer metal layer 35 laminated under the magnetic domain control layer 34.
Is in the magnetic sensing portion 38 via the base metal layer 35.
The underlayer metal layer 35 that includes the junction 37 in contact with the R layer 31, the soft magnetic layer 32 and the nonmagnetic layer 33 and separates the magnetic domain control layer 34 and the MR layer 31 has a thickness 41 of 5 nm.
A magnetoresistive head (MR head) characterized by the above. 2. The film thickness of the soft magnetic layer 32 and the non-magnetic layer 33 is less than half the film thickness of the soft magnetic layer 32 in the edge region 39 of the base metal layer 35. 2. The MR head according to claim 1, wherein the MR head has a thickness equivalent to that of the combined MR head. 3. The thickness of the magnetic domain control layer 34 in the end region 39 is determined by the height of the MR layer 31 and the magnetic domain control layer 34.
2. The magnetic domain control layer 34 has a film thickness such that the height of the magnetic domain control layer 34 is the same, and the magnitude of the residual magnetization of the magnetic domain control layer 34 is equal to or greater than the magnitude of the saturation magnetization of the MR layer 31. MR head. 4. The junction 37 includes a tapered edge extending over the MR layer 31, the soft magnetic layer 32 and the non-magnetic layer 33, and the angle (taper angle) 40 of the tapered edge is 60 °.
2. The MR head according to claim 1, wherein the angle is in a range of about to 90 [deg.]. 5. A magnetic storage system using the MR head according to claim 1 as a reproducing head.