JP2002123912A - Magneto-resistive effect element and magnetic disk unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply a sufficient magnetic field to a free layer without setting the thickness of a magnetic domain control film so large in a magneto-resistive effect element and a magnetic disk device. SOLUTION: A pair of hard magnetic films 2 are joined to both ends of a spin valve film 1, soft magnetic films 3 are joined to the ends of sides opposite to the joined parts with the spin valve film 1, bulged parts 4 are provided in the side ends of sides opposite to the joined parts of the soft magnetic films 3 with the soft magnetic films 2, and these bulged parts 4 are set close to each other so as to form a magnetic circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element and a magnetic disk drive, and more particularly to a spin valve film used for a reproducing head (read head) of a magnetic disk drive such as a hard disk drive (HDD). The present invention relates to a magnetoresistive element and a magnetic disk device having a magnetic field application structure for converting a free layer into a single magnetic domain.

[0002]

2. Description of the Related Art In recent years, with the increasing demand for downsizing and increasing the capacity of hard disk devices and the like, which are external storage devices for computers, read head elements are required to have higher sensitivity and finer design. MR using isotropic magnetoresistance effect
There is a limit in a head, and a giant magnetoresistance effect (GMR: Giant Magnetoresistance) is a new physical phenomenon that is expected to have a sensitivity several times higher than that of an MR head.
use of a GMR head utilizing a G.h.

This GMR film is formed in a multilayer structure of a ferromagnetic film and a non-magnetic film, and has a spin structure when the magnetization arrangement of the adjacent ferromagnetic films sandwiching the non-magnetic film is parallel or antiparallel. The fact that the electric conductivity differs due to the scattering depending on the resistance and the resistance value changes.

Among the films exhibiting such a giant magnetoresistive effect, a spin valve type magnetoresistive element having a simple structure and capable of easily obtaining a linear operation in a low magnetic field has been put to practical use. Has a laminated structure of a ferromagnetic film serving as a free layer, a nonmagnetic intermediate layer, a ferromagnetic film serving as a pinned layer, and an antiferromagnetic layer,
The magnetic moment of the pinned layer is fixed by the exchange coupling magnetic field from the adjacent antiferromagnetic layer.

The principle of reproduction in a read head using this spin valve film is that, when an external magnetic field is applied from a magnetic recording medium or the like, the magnetization direction of the free layer whose magnetization is not fixed coincides with the external magnetic field and freely. Due to the rotation, an angle difference occurs between the magnetization direction of the pinned layer whose magnetization is fixed and the magnetization direction.

[0006] As described above, the scattering depending on the spin of the conduction electrons changes depending on the angle difference, and the electric resistance changes. Therefore, the change in the electric resistance changes and the lead electrode connected to the spin valve film. By detecting a change in the voltage value by passing a constant current sense current from, a state of the external magnetic field, that is, a signal magnetic field from the magnetic recording medium is acquired, and a read head using the spin valve film is used. The rate of change in magnetoresistance is about 5%.

In order to increase the sensitivity of such a magnetoresistive element, if the free layer constituting the spin valve film does not form a single magnetic domain, Barkhausen noise occurs and the reproduction output fluctuates greatly. In order to eliminate the domain wall of the layer, a hard ferromagnetic film called a magnetic domain control film or a hard bias film is provided at both ends of the free layer.

Here, a conventional magnetoresistive element using a spin valve film will be described with reference to FIG. FIG. 7 is a schematic plan view of a conventional magnetoresistive effect element, in which a lower portion made of a NiFe alloy or the like is interposed on an Al ₂ O ₃ —TiC substrate serving as a slider base via an Al ₂ O ₃ film. A spin valve film 31 including a free layer, a non-magnetic intermediate layer, a pinned layer, and an antiferromagnetic layer is provided with a magnetic shield layer and a lower read gap layer (not shown) of Al ₂ O ₃ or the like. After patterning the spin valve film 31 into a predetermined shape, a magnetic domain control film 32 made of a hard magnetic film having a high coercive force such as CoCrPt is provided at both ends of the spin valve film 31, and then the magnetic domain control film 32 is covered. The electrode terminal 33 is formed by depositing a conductive film composed of a W / Ti / Ta multilayer film or the like as described above.

Next, although not shown, A
By providing an upper magnetic shield layer made of a NiFe alloy or the like via an upper read gap layer such as l ₂ O ₃ , the basic configuration of the read head is completed. In this case, the shape of the magnetic domain control film 32 is substantially similar to the shape of the electrode terminal 33.

However, in the GMR head using such a spin valve film, the magnetic domain control film 32 has a large leakage of magnetic flux and the magnetic domain control film 32 has a weak single magnetic domain to the free layer. It has been attempted to increase the magnetic field generated by increasing the thickness of the magnetic domain control film for generation and increasing the volume of the magnetic domain control film.

[0011]

However, when the thickness of the magnetic domain control film is increased, the shape anisotropy of the magnetic domain control film is weakened, and the magnetization rises from the film surface. Since the application of the single-domain magnetic field is stopped and the increase in the magnetic field caused by increasing the volume of the magnetic domain control film is smaller than an expected value, this state will be described with reference to FIGS.

FIG. 8 shows a magnetic domain control film 3 of a conventional magnetoresistive effect element referred to for easy understanding of an MFM (Magnetic Force Microscope) image.
2 is an AFM (Atomic Force Microscope) image of the vicinity of the spin valve film 31 after magnetization in the direction of the arrow in the figure, and a shape similar to the schematic plan view shown in FIG. 7 is confirmed.

FIG. 9 is an MFM image of the vicinity of the spin valve film 31 after the magnetic domain control film 32 of the conventional magnetoresistive element has been magnetized. , And a black portion indicates an N pole and a white portion indicates an S pole.

As is apparent from the figure, the spin valve film 3
1, the left junction end of the magnetic domain control film 32 has an N pole, while the right junction end has an S pole, and the free layer forming the spin valve film 31 is shifted to the right. It is understood that the magnet is magnetized in the left direction from.

However, magnetic poles also appear at the side ends 34 of the magnetic domain control film 32 other than the junction ends, and it is considered that magnetic flux leaks from this portion. If such a phenomenon occurs, the spin valve film 31 A sufficient magnetic field is not applied to the junction end, and the single layer of the free layer is incompletely formed, and Barkhausen noise is included in the read signal.

Therefore, conventionally, the magnetic domain control film 3
In order to compensate for the leakage of magnetic flux by increasing the film thickness of layer 2 and increasing the volume, the effect of shape anisotropy decreases as the film thickness increases, and the magnetic flux in the plane of the magnetic domain control film increases. Is leaked to the surface, which does not result in an improvement in magnetic flux.

In the figure, black and white spots appearing on the entire surface of the magnetic domain control film 32 represent magnetic poles caused by the magnetic flux rising in the plane, and the magnetic flux is leaking on the surface of the magnetic domain control film 32. Is understood.

Accordingly, an object of the present invention is to apply a sufficient magnetic field to the free layer without increasing the thickness of the magnetic domain control film.

[0019]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. In addition, FIG.
It is a schematic plan view of a magnetoresistive effect element using a spin valve film. Referring to FIG. 1, in order to achieve the above-described object, according to the present invention, a pair of hard magnetic films 2 are joined to both ends of a spin valve film 1 and a soft magnetic film is attached to an end opposite to the joint with the spin valve film 1. The magnetic film 3 is bonded, and the hard magnetic film 2
The overhanging portion 4 is provided at the side end opposite to the junction with the base member, and the overhanging portion 4 is formed such that the distance d between the side ends is 0 <d ≦ 3 μm to the extent that a magnetic circuit is formed. It is characterized by being brought close to each other.

As described above, the soft magnetic film 3 is joined to the pair of hard magnetic films 2 serving as the magnetic domain control films, and the projecting portion 4 is provided at the side end opposite to the joining portion. The magnetic circuit shown by the arrow in the figure, that is, close enough to form a closed magnetic circuit, to suppress the leakage of magnetic flux,
As a result, the magnetic flux can be concentrated at the junction with the spin valve film 1, and a sufficient magnetic field can be applied to the free layer constituting the spin valve film 1.

That is, since the magnetization in the longitudinal direction of the soft magnetic film 3 is directed to the longitudinal direction by forming the closed magnetic path indicated by the arrow in the figure, the magnetic pole does not appear at the side end of the soft magnetic film 3. In addition, the leakage of the magnetic flux at the side end of the soft magnetic film 3 is suppressed.

By forming the closed magnetic circuit in this manner, it is not necessary to increase the thickness of the hard magnetic film 2. For example, the critical thickness at which the magnetic flux rises is 300 °.
By setting the thickness of the hard magnetic film 2 to 300 ° or less, shape anisotropy can be sufficiently utilized. In addition,
On the hard magnetic film 2 and the soft magnetic film 3, an electrode terminal film 5 for supplying a current to the spin valve film 1 is provided.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive element according to an embodiment of the present invention will now be described with reference to FIGS. FIG. 2 is a schematic plan view of the magnetoresistive effect element according to the embodiment of the present invention, and FIG.
FIG. 3B is a schematic cross-sectional view taken along a dashed-dotted line connecting −A ′, FIG. 3B is an enlarged view within a dashed circle in FIG. 3A, and FIG. FIG. 4 is a schematic cross-sectional view taken along a dashed line connecting BB ′.

Referring to FIGS. 2 and 3C, an Al ₂ O ₃ film 12 having a thickness of, for example, 2 μm is formed on an Al ₂ O ₃ —TiC substrate 11 by sputtering.
Is deposited, and then, using selective electrolytic plating, 100
While applying a magnetic field of [Oe], the thickness is 1 to 3 μm,
For example, a 3 μm NiFe film is formed as the lower magnetic shield layer 13, and then an Al ₂ O ₃ film having a thickness of, for example, 500 ° is deposited by sputtering, and then patterned into a predetermined shape. To form a lower read gap layer 14, and then deposit a spin valve film 15 for constituting a magnetoresistive element.

As the spin valve film 15, FIG.
As shown in (b), for example, after forming a Ta layer 21 having a thickness of, for example, 50 ° as a base layer by using a sputtering method while applying a magnetic field of 80 [Oe], the thickness becomes: For example, a NiFe free layer 22 of 40 ° and a thickness of, for example, a CoFe free layer 23 of 25 ° and a thickness of
For example, a Cu intermediate layer 24 of 25 °
5 ° CoFe pinned layer 25 and a thickness of 20 to 30
An antiferromagnetic layer 26 made of a PdPtMn film of 0 °, for example, 250 ° is sequentially laminated. The composition of NiFe in this case is, for example, Ni ₈₁ Fe ₁₉ and C
The composition of oFe is, for example, Co ₉₀ Fe ₁₀ ,
The composition of PdPtMn are, for example, Pd ₃₁ Pt ₁₇ Mn _52.

Next, in vacuum, 100 [Oe] or more in a direction orthogonal to the magnetic field applied during film formation, for example,
While applying a DC magnetic field of 2500 [Oe], heat treatment is performed in vacuum at 250 to 280 ° C, for example, 280 ° C for 0.5 to 5 hours, for example, 3 hours. By the heat treatment in a state where the magnetic field is applied, the magnetization direction of the CoFe pinned layer 25 is fixed as the direction of the applied DC magnetic field of the antiferromagnetic layer 26.

Next, a resist pattern (not shown) is provided, and the spin valve film 15 is patterned into a predetermined shape by performing ion milling using Ar ions. 3
The magnetic domain control film 16 made of a CoCrPt film having a thickness of 200 ° or less, for example, is deposited. In this case, the composition of CoCrPt constituting the magnetic domain control film 16 is, for example,
Co ₇₈ Cr ₁₀ Pt ₁₂ .

Next, CoCr deposited on the resist pattern together with the resist pattern by the lift-off method.
After removing the Pt film, a new resist pattern (not shown) is provided again, and then a Ni film having a thickness of 50 to 300 Å, for example, 200 Å is formed by sputtering.
A soft magnetic film 17 made of Fe is formed and joined to the magnetic domain control film 16 at a position indicated by a broken line in FIG.

In this case, an overhang 18 is provided at the opposite side end of the soft magnetic film 17, and the interval d between the overhangs 18 is 0 <.
The soft magnetic film 17 is formed so that d ≦ 3 μm, for example, d = 0.5 μm. In this case, in order to form a complete magnetic circuit, d = 0 may be set. However, if this is done, the electrode terminal 19 for flowing a current to the spin valve film 15 is electrically short-circuited. There is.

Next, after removing the resist pattern, a lead electrode is formed by sputtering, for example, to a thickness of 100 nm (= 1000 °), for example.
An Al film is deposited on the entire surface, and then ion-milling using Ar ions is performed by using a resist pattern having an opening corresponding to the core width as a mask, thereby removing the exposed portion of the Al film to remove the magnetic domain control film 16. And an electrode terminal 19 for applying a current to the spin valve film 15 while covering the diamagnetic film 17.

After that, although not shown, an Al ₂ O ₃ film having a thickness of, for example, 500 ° is deposited again by the sputtering method, and then patterned into a predetermined shape by the ion milling method. A single spin valve element is formed by forming a read gap layer and then forming an upper magnetic shield layer by forming a NiFe film having a thickness of 1 to 3 μm, for example, 3 μm, by a selective electrolytic plating method. Thus, the basic configuration of the MR head is completed.

As described above, in the embodiment of the present invention, since the magnetic circuit is formed by providing the soft magnetic film 17 having the overhang portion 18, the leakage of the magnetic flux at the side end of the electrode terminal 19 is prevented. Since the thickness of the magnetic domain control film 16 can be reduced to 300 ° or less, the shape anisotropy acts strongly and the magnetization does not rise in the plane.

Here, the film thickness dependence of the magnetic pole distribution in the film plane of the magnetic domain control film 16 will be described with reference to FIGS. 4 to 6. FIG. It is a six-fold enlargement. FIG. 4 is an MFM image showing the magnetic pole distribution in the film surface after magnetization when the thickness of the magnetic domain control film is set to 504 °, and the shape is anisotropic so that black and white spots are clearly seen. The magnetic properties are weakened and the magnetic pole is exposed on the surface. In this case, a 202 ° Cr film is provided as a base, and the same applies hereinafter.

FIG. 5 is an MFM image showing the magnetic pole distribution in the film surface after magnetization when the thickness of the magnetic domain control film is set to 203 °. Black and white spots are blurred compared to FIG. Thus, it is understood that the shape anisotropy is acting by reducing the film thickness.

FIG. 6 is an MFM image showing the magnetic pole distribution in the film surface after magnetization when the thickness of the magnetic domain control film is 58 °. It is understood that the shape anisotropy is strongly acting by making the thickness extremely thin.
Therefore, the effect of reducing the thickness of the magnetic domain control film 16 is apparent.

Although the embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the embodiment, and various modifications are possible. For example, in the description of the embodiment, NiFe
Although a single spin-valve element composed of / CoFe / Cu / CoFe / PdPtMn is used, the present invention is not limited to such a single spin-valve element, and for example, other laminated structures such as NiFe / Cu / NiFe / FeMn. A single spin valve element may be used, and further, a dual spin valve element may be used.

In the description of the above embodiment, CoCrPt is used as the magnetic domain control film 16, but it is not limited to CoCrPt.
A hard magnetic film having another high coercive force such as CoCr may be used.

In the above embodiment, Ni
Fe, CoFe, PdPtMn, and CoCrPt, respectively, Ni ₈₁ Fe ₁₉ , Co ₉₀ Fe ₁₀ , and Pd ₃₁ Pt
₁₇ Mn ₅₂ and Co ₇₈ Cr ₁₀ Pt ₁₂ are used,
The composition ratio is not limited to such a composition ratio, and the composition ratio may be appropriately selected according to required magnetic characteristics, processing characteristics, and the like.

Further, in the above embodiment, the magnetic domain control film 16 and the soft magnetic film 17 are shown as being joined together neatly, but the magnetic domain control film 16 and the soft magnetic film 17 are Therefore, the magnetic domain control film 16 and the soft magnetic film 17 may be overlapped at the junction, thereby improving the alignment accuracy in the resist pattern forming process. Can be eased.

Further, in the above embodiment, although using NiFe as a soft magnetic film 17, as the composition ratio of Ni ₈₀ Fe ₂₀ or Ni ₅₀ Fe any composition ratio, such as ₅₀ N
An iFe film may be used, and a soft magnetic film other than NiFe may be used.

Further, in the above embodiment, the length of the overhang provided on the soft magnetic film is set to one in the longitudinal direction of the electrode terminal.
However, since the length of the overhang does not significantly affect the magnetic characteristics, the length of the overhang is arbitrary, and the distance d between the overhangs is important. However, care must be taken because if the length of the overhang is too short, the magnetic flux is likely to leak.

Further, in the description of the embodiment of the present invention, a single MR head structure is described, but the present invention is not limited to such a single MR head, but an inductive type thin film magnetic head. It goes without saying that the present invention is also applied to a composite type thin film magnetic head laminated with a head.

Here, the detailed features of the present invention will be described with reference to FIG. 1 again. See FIG. 1 (Supplementary Note 1) A pair of hard magnetic films 2 are joined to both ends of the spin valve film 1, and a soft magnetic film 3 is joined to an end opposite to the joint with the spin valve film 1. An overhang 4 is provided at a side end of the soft magnetic film 3 opposite to a joint with the hard magnetic film 2, and the overhang 4 is brought close enough to form a magnetic circuit. Magneto-resistance effect element. (Supplementary Note 2) The distance d between the side ends of the overhang portion 4 is 0 <d.
The magnetoresistance effect element according to claim 1, wherein ≦ 3 μm. (Supplementary Note 3) The magnetoresistive element according to Supplementary Note 1 or 2, wherein the thickness of the hard magnetic film 2 is 300 ° or less. (Supplementary Note 4) A magnetic disk device comprising the magnetoresistance effect element according to any one of Supplementary Notes 1 to 3.

[0044]

According to the present invention, a soft magnetic film is joined to a hard magnetic film for making the free layer of the magnetoresistive element constituting the thin film magnetic head into a single magnetic domain, and the soft magnetic film is bonded to the opposite side of the soft magnetic film. Since a magnetic circuit is formed by providing an overhanging portion at the side end, a sufficient magnetic field can be applied to the free layer without increasing the thickness of the hard magnetic film so much. An information reading error due to Barkhausen noise of a read signal can be eliminated, and this greatly contributes to improvement in performance of the magnetic disk drive.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is a schematic plan view of the magnetoresistive element according to the embodiment of the present invention.

FIG. 3 is a schematic sectional view of a magnetoresistive element according to an embodiment of the present invention.

FIG. 4 shows M after magnetization when the magnetic domain control film is set at 504 °.
It is an FM image.

FIG. 5 shows M after magnetization when the magnetic domain control film is set to 203 °.
It is an FM image.

FIG. 6 shows MF after magnetization when the magnetic domain control film is set to 58 °.
It is an M image.

FIG. 7 is a schematic plan view of a conventional magnetoresistance effect element.

FIG. 8 is an AFM image of a conventional magnetoresistance effect element after magnetization of a magnetic domain control film.

FIG. 9 is an MFM image of a conventional magnetoresistance effect element after a magnetic domain control film is magnetized.

[Explanation of symbols]

1 spin valve film 2 hard magnetic film 3 soft magnetic film 4 protruding portion 5 the electrode terminal film 11 Al ₂ O ₃ -TiC substrate 12 Al ₂ O ₃ film 13 lower magnetic shield layer 14 lower read gap layer 15 spin-valve film 16 domain Control film 17 Soft magnetic film 18 Overhang 19 Electrode terminal 21 Ta film 22 NiFe free layer 23 CoFe free layer 24 Cu intermediate layer 25 CoFe pinned layer 26 Antiferromagnetic layer 31 Spin valve film 32 Magnetic domain control film 33 Electrode terminal 34 Magnetic domain Side edge of control membrane

Claims (3)

[Claims] 1. A pair of hard magnetic films are joined to both ends of a spin valve film, and a soft magnetic film is joined to an end opposite to a joint portion with the spin valve film. A magnetoresistive element, wherein an overhang portion is provided at a side end opposite to a junction with a magnetic film, and the overhang portion is brought close enough to form a magnetic circuit. 2. The distance d between the side ends of the overhanging portion is 0 <d.
The magnetoresistance effect element according to claim 1, wherein ≤ 3 µm. 3. A magnetic disk drive comprising the magnetoresistive element according to claim 1.