JP3204871B2 - Magnetoresistive head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive head provided with a three-layer element including a magnetoresistive layer and a hard bias layer for applying a longitudinal bias magnetic field to the magnetoresistive layer. More particularly, the present invention relates to a magnetoresistive head in which the material of a hard bias layer is improved.

[0002]

2. Description of the Related Art FIG. 6 is an enlarged view showing a magnetoresistive head using a hard bias layer as a vertical bias layer as viewed from a side facing a recording medium. The three-layer element 4 includes a soft magnetic layer (SAL layer) 4a, a non-magnetic layer (SHUNT layer) 4
b, a magnetoresistive layer (MR layer) 4c. Normally, the magnetoresistive layer 4c is a layer of Fe—Ni alloy (permalloy), the nonmagnetic layer 4b is a layer of tantalum (Ta), and the soft magnetic layer 4a is formed of a Ni—Fe—Nb alloy. You.

[0006] In the magnetoresistive head shown in FIG. 6, an A layer is formed on a lower shield layer 2 formed of sendust or the like.
A lower gap layer 11 of l ₂ O ₃ or the like is formed, and the three-layer element 4 is provided thereon. On both sides of the three-layer element 4, hard bias layers 9 are formed as vertical bias layers. In the film in the height direction (Y direction), the main electrode layer 5 made of a non-magnetic conductive material having a small electric resistance such as Cu (copper) or W (tungsten) is formed on the hard bias layer 9. An upper gap layer 12 made of Al ₂ O ₃ or the like is formed on the three-layer element 4, the hard bias layer 9, and the main electrode layer 5, and an underlayer 3 a and an upper shield layer 3 such as a sendust are formed thereon. Have been. This head is opposed to a magnetic recording medium such as a hard disk in the Y direction. The Y direction is the direction of the leakage magnetic field from the recording medium. The relative movement direction between the magnetoresistive head and the magnetic recording medium is the Z direction.

The hard bias layer 9 is magnetized by applying a magnetic field in the track width Tw direction (X direction) after film formation.
A longitudinal bias magnetic field is applied to the magnetoresistive layer 4c by the residual magnetization, so that the magnetoresistive layer 4c is converted into a single magnetic domain in the X direction. The detection current flows from the main electrode layer 5 to the vertical bias layer 9.
Is applied to the three-layer element 4 in the X direction. When a detection current is applied to the magnetoresistive element 4c, the soft magnetic layer 4a is magnetized in the height direction (Y direction) by the magnetic field from the magnetoresistive layer 4c. Due to the magnetization of the soft magnetic layer 4a,
A lateral bias magnetic field is applied to the magnetoresistive layer 4c, and the magnetic domain direction of the magnetoresistive layer 4c is approximately 4 with respect to the height direction.
The angle is set to 5 degrees, so that in the magnetoresistive layer 4c,
The change in resistance due to the leakage magnetic field (external magnetic field) given from the magnetic recording medium in the Y direction becomes linear. In the hard bias type magnetoresistive head, the residual magnetization of the hard bias layer 9 causes the magnetoresistive layer 4 c
A single magnetic domain is stably formed in the direction, and Barkhausen noise can be reduced.

[0005]

As for the material of the conventional hard bias layer 9, research has been conducted mainly on magnetic material films used as magnetic recording media such as hard disks because of the necessity of increasing the residual magnetization to some extent. Have been. The conditions required for a magnetic material film used as a magnetic recording medium are as follows. FIG. 7 is an MH curve showing the relationship between the external magnetic field H (horizontal axis) and the magnetization M (vertical axis) given to the magnetic material in order to explain the magnetic characteristics.

Residual magnetization (Mr) A magnetic film for a magnetic recording medium has a residual magnetization of 0.8 T
(Tesla) Before and after is considered preferable. That is, while a certain amount of remanent magnetization is required for magnetic recording, the remanent magnetization cannot be increased without limit due to overwriting, and a magnetic material film having a thickness of about 0.8 T is used.

Coercive force (Hc) In a magnetic film for a magnetic recording medium, in-plane 2000 (Oe)
A certain coercive force (Hc) is required, and it is preferable to impart magnetic anisotropy.

Specific Resistance (ρ) In a magnetic film for a magnetic recording medium, the specific resistance (ρ) does not matter.

Squareness ratio (S, S ^* ) Regarding the squareness ratio represented by S = Mr / Ms and S ^* = a / Hc, S is larger than 0.8 and S ^* is larger than 0.95. is needed.

Media Noise In a magnetic film for a magnetic recording medium, it is necessary to reduce media noise, and optimization of the crystal structure of the magnetic film is required.

On the other hand, when the characteristics required for the hard bias layer 9 of the magnetoresistive head are compared with the above, the first is the remanent magnetization (Mr).
Since the hard bias layer 9 applies a longitudinal bias magnetic field in the X direction to the magnetoresistive layer 4c to make it a single magnetic domain, the larger the residual magnetization, the better. Further, in the future magnetoresistive head, it is required to read a signal recorded at a high density, and as a result, it is necessary to further narrow the read gap. Therefore, it is required to further improve (film thickness x residual magnetization).

The hard bias layer 9 has a certain magnitude of in-plane coercivity when Ni is overlaid on the Ni—Fe film of the magnetoresistive layer 4c. -It is necessary to show exchange coupling with the Fe film. Therefore, the hard bias layer 9 requires a certain coercive force (Hc). However, a large coercive force such as that of a magnetic recording medium is not required. If the in-plane coercive force is at least 200 (Oe) or more, there is no practical problem.
(Oe) or more is sufficient. It is preferable that the hard bias layer 9 be easily magnetized and saturated in the X direction. Therefore, a magnetically isotropic material is preferable.

Regarding the specific resistance (ρ), in the magnetoresistive head, a detection current is applied from the main electrode layer 5 to the magnetoresistive layer 4c through the hard bias layer 9, and a detection output is given by the detection current. Therefore, it is necessary that the specific resistance (ρ) of the hard bias layer 9 serving as the path of the detection current be small.

In the hard bias layer, it is not necessary to be particular about the squareness ratio, and it does not matter about the noise of the medium. That is, it is not necessary to optimize the crystal structure for suppressing the media noise.

In the conventional magnetoresistive head, among the magnetic materials for magnetic recording media developed to satisfy the above conditions, the specific resistance (ρ) required as the condition of the hard bias layer 9 is low. Focus on materials such as
A typical example is Co-Pt (cobalt-platinum).
It has been studied to use a base alloy or a Co-Cr-Pt (cobalt-chromium-platinum) base alloy.

Here, in a Co—Pt alloy, the coercive force can be increased by increasing the concentration of Pt. Further, in the magnetoresistive head, corrosion resistance is required, and it is possible to increase the corrosion resistance to some extent by increasing the concentration of Pt. However, as the Pt concentration increases, the residual magnetization (Mr) decreases.
Thus, in the Co-Pt alloy, there is a trade-off between the corrosion resistance and the magnetic properties.

[0017] In addition, C in which Cr is added to a Co-Pt alloy
An o-Cr-Pt-based alloy can improve corrosion resistance as compared with Co-Pt. However, when Cr is added, the remanence (Mr) decreases and the specific resistance (ρ) increases even if the concentration is slight.

When a conventional magnetic film material for a magnetic recording medium such as a Co-Pt-based alloy or a Co-Cr-Pt-based alloy is diverted to a hard bias layer, both magnetic properties and corrosion resistance can be improved. difficult. Further, as a material for a hard bias layer having a small film thickness and appropriate magnetic properties, such as a future narrow gap magnetoresistive head, a Co-Pt alloy or a Co-Cr-Pt alloy is used. The development of magnetic materials that are changing is desired.

The present invention solves the above-mentioned conventional problems, and provides a magnetoresistive head in which a hard bias layer is formed by a magnetic material film capable of improving magnetic characteristics and improving corrosion resistance as compared with the prior art. It is intended to be.

[0020]

According to the present invention, there is provided a magnetoresistive head having a hard bias layer provided on both sides of the magnetoresistive layer for applying a longitudinal bias magnetic field to the magnetoresistive layer. If the layer is Co-Ni-
It is formed of a Pt-based alloy and has a Ni concentration of 10 to 10.
20 (at%), the concentration of Pt is 13 to 19 (at%)
It is characterized by being.

[0021]

[0022]

[0023]

[0024]

In the conventional hard bias layer, a magnetic film developed for a magnetic recording medium is used. However, according to the present invention, the characteristics required for a magnetic film for a magnetic recording medium and the characteristics of a magnetoresistive head can be improved. This is done by paying attention to the fact that the characteristics required for the magnetic film of the hard bias layer are not always the same. More specifically, the magnetic film forming the hard bias layer does not require a high coercive force (Hc) like a magnetic film for a magnetic recording medium, and rather the residual magnetization, the specific resistance and the corrosion resistance are more important factors. Focusing on something,
A Co-Ni-Pt-based alloy is used as a material satisfying this.

The Co—Ni—Pt alloy can increase the remanent magnetization (Mr) and the saturation magnetization (Mr) as compared with the Co—Pt alloy used for the conventional hard bias layer.
s) can also be slightly increased. Coercive force (Hc) is Co-Pt
200 (Oe) or more, which is required as a hard bias layer, and further 500 (Oe)
The above can be sufficiently secured. In addition, the Co—Ni—Pt-based alloy has better corrosion resistance than conventional materials.

First, regarding the residual magnetization required for the magnetic film of the hard bias layer, as shown in Table 1, the Ni concentration is 10 to 20 (at%) and the Pt concentration is 13 to 1 (at%).
If it is 9 (at%), the residual magnetization (Mr) becomes 10 (k
G; kilogauss) or more, and the residual magnetization can be improved by about 20 to 30% as compared with Co ₇₆ Pt ₂₄ (at%) used as a conventional hard bias layer. That is, a magnetic material capable of increasing the residual magnetization to 10 (kG) or more is Co
_(ax) Ni _(x) Pt _(b) , x = 10-20
(At%), b = 13-19 (at%), a-x = 61
７５75 (at%).

[0027]

Furthermore, when the magnetic film is left in a high temperature and high humidity environment or immersed in pure water and physiological saline,
As a result of examining the corrosion state of the magnetic film, as shown in Table 1, when the corrosion resistance was evaluated as “○” or “◎”, the Ni concentration x was 10 to 33 (at%) and the Pt concentration b Is 13 ~
24 (at%). However, a + b = 100 (at
%). With the composition in this range, the corrosion resistance of the hard bias layer can be improved as compared with the conventional one.

[0029]

EXAMPLE The structure of a hard bias layer using a magnetic film and the structure of a magnetoresistive head using this hard bias layer shown in the following examples are the same as those shown in FIG.
That is, on the lower gap layer 11 of Al ₂ O ₃ or the like,
Soft magnetic layer (SAL layer) 4a, non-magnetic layer (SHUNT layer)
4b and a three-layer element 4 in which a magnetoresistive layer (MR layer) 4c is laminated. A hard bias layer 9 is formed on the lower gap layer 11 so as to sandwich both sides of the three-layer element 4 in the X direction.
Are formed. The main electrode layer 5 is formed on the hard bias layer 9 in the height direction (Y direction) of the film.

The magnetic films shown in Table 1 as samples (a) to (m) were formed as magnetic materials to constitute the hard bias layer 9, and their magnetic properties, specific resistance, and corrosion resistance were examined. The film was formed using an RF conventional sputtering apparatus,
And the Ni and Pt chips were appropriately arranged to adjust the film composition. The sputtering gas pressure was 10 (mTorr) for samples (a) to (j), and sample (k) to
(M) is 1 (mTorr). The thickness of each sample described in Table 1 below was 500 Å.

Saturation magnetization (Ms), residual magnetization (Mr), M
Each magnetic property of the squareness ratio (S, S ^* ) and coercive force (Hc) of the −H curve was measured using a vibrating sample magnetometer (VSM). In this measurement, for each sample, ± 10 (kOe)
The MH curve at the applied magnetic field was determined, and the above-described characteristics were derived from the MH curve. The saturation magnetization (Ms) is the amount of magnetization in an external magnetic field of 10 (kOe). The specific resistance (ρ) was measured by a four-terminal method.

The corrosion resistance test was conducted by forming a magnetic film of each sample on an Al ₂ O ₃ substrate with a thickness of 500 Å in an environment of high temperature and high humidity of 80 ° C. and 90% relative humidity. The corrosion state of the surface was observed with an optical microscope in each of the samples left for a period of time, those immersed in pure water for 24 hours, and those immersed in physiological saline for 24 hours. In any one of these, “×” indicates that the corrosion area occupies 20% or more, “、” indicates that the corrosion area is 5% or more and less than 20%, and “○” indicates that the corrosion area is less than 5%. Those having a corrosion area of 0% were evaluated as “◎”.

In Table 1, (a) shows that Co is 100
% (B) and (c) are Co-Pt alloys and (k) is a Co-Ni alloy. Others are magnetic films used for a hard bias layer of a Co-Ni-Pt-based alloy according to an embodiment of the present invention. Co-Ni-
In each of the magnetic films of the Pt alloy, the concentration of Ni and the concentration of Pt are randomly changed. The concentration x of Ni is in the range of 10 to 33 (at%), and the concentration b of Pt is 13
２４24 (at%).

[0034]

[Table 1]

Among the samples shown in Table 1, Co-Ni-Pt alloys capable of making the remanent magnetization (Mr) 10 kG or more are as follows:
When Co _(ax) Ni _(x) Pt _(b) , x = 10 to 2
0 (at%), b = 13 to 19 (at%), and ax = 61 to 80 (at%). Samples of the corresponding Co—Ni—Pt alloys are (e), (f), and (i).
(L) (m), all of which are evaluated by the corrosion resistance test as “○” and “◎”. Here, (b) of Table 1
(C) are all Co-Pt alloys, but the evaluation results in the corrosion resistance test are all “Δ” because the Pt concentration is low. The Co—Pt-based alloy used as the conventional hard bias layer has a high Pt concentration in order to improve the corrosion resistance. For example, Co ₇₆ Pt ₂₄ (at
%) Was used. In this Co ₇₆ Pt ₂₄ (at%), the remanent magnetization (Mr) measured in the same manner as in the sample is about 7 to 8 (kG).

Therefore, x = 10 to 20 (at%),
b = 13 to 19 (at%), ax = 61 to 80 (at
In Co having a composition in the range _{of%) (ax) Ni (x} ) Pt (b), residual magnetization than the magnetic film of the conventional hard bias layer (Mr) can be increased by about 20-30%, the residual magnetization 10
(KG) or higher. Further, in the samples (e), (f), (i), (l) and (m) in this range, the saturation magnetization (Ms) becomes a high value of 12.3 (kG) or more, and the coercive force (Hc ) Is 435 (Oe) or more and the specific resistance (ρ) is 58.3 (μΩ · cm) or less.
And it will be excellent in corrosion resistance. Therefore, when a Co—Ni—Pt alloy is used as the hard bias layer,
x = 10 to 20 (at%), b = 13 to 19 (at
%) And a−x = 61 to 80 (at%).

Next, samples (e) to (j) and (l)
Each of the Co—Ni—Pt-based alloys (m) has an excellent corrosion resistance rating of “○” or “◎”. Focusing on the fact that corrosion resistance can be improved, Co _(ax) Ni _(x) P
At t _(b) , the concentration x of Ni is set to 10 to 33 (at%).
It is preferable that the concentration b of Pt is 13 to 24 (at%). That is, when forming a hard bias layer having excellent corrosion resistance, the concentration x of Ni is set to 10 to 33 (at
%), And the concentration b of Pt was set to 13 to 24 (at%).
It is preferable to use an o-Ni-Pt alloy. Samples (e) to (j) and (l) having this composition range
(M) is a relatively high value when the remanent magnetization (Mr) is 9.4 (kG) or more, and the coercive force (Hc) is 110 (Og).
e) and the specific resistance (ρ) is 58.3 (μ)
Ω · cm) or less. Therefore, the concentration x of Ni is 10 to 33 (at%) and the concentration b of Pt is 13 to 2 (at%).
4 (at%) of samples (e)-(j) and (l) (m)
Has excellent corrosion resistance and is suitable as a magnetic film of a hard bias layer from the viewpoint of magnetic properties.

Next, FIG. 1 shows the Ni concentration, residual magnetization (Mr) and saturation magnetization (Ms) of the Co—Ni—Pt alloy.
And Co-Cr-Pt as a comparative example.
4 shows the relationship between the concentration of Cr and the residual magnetization (Mr) and the saturation magnetization (Ms) in a system alloy.

In Co _(ax) Ni _(x) Pt _(b) , b is 13
(At%) and x is changed from 0 (at%) to 12 (at%).
%), 20 (at%), and 33 (at%), respectively, and the samples (b), (e), and (f) in Table 1 are respectively shown.
(G). Co _(ax) Cr _{(x) as} a comparative example
In Pt _(b) , b was fixed at 13 (at%), and x
From 0 (at%) to 4 (at%), 6 (at%), 11
(At%) is measured. The measuring method of the magnetic properties for each of the Co-Ni-Pt-based alloy and the Co-Cr-Pt-based alloy is the same as the measuring method of each property shown in Table 1. In FIG. 1, those having a thickness of 500 angstroms are indicated by solid white circles, and those having a thickness of 1000 angstroms are indicated by intermediate solid circles.

(A) and (b) are Co-Ni-Pt, respectively.
Magnetization (Ms) and residual magnetization (Mr) of the base alloy, (c)
(D) shows the saturation magnetization (Ms) and residual magnetization (Mr) of the Co—Cr—Pt-based alloy, respectively. In FIG. 1, Co-
Although the saturation magnetization (c) and the remanent magnetization (d) decrease with only a slight increase in the Cr concentration of the Cr-Pt-based alloy, the Ni concentration increases in the Co-Ni-Pt-based alloy. However, the saturation magnetization (a) is not so small,
Is in the range of 5 to 10 (at%), the saturation magnetization increases. Further, in a Co—Ni—Pt-based alloy, when the concentration of Ni is increased, the residual magnetization (Mr) tends to increase. When the film thickness is 500 Å, the Ni concentration is 5 to 25 (at%). In the range, the residual magnetization (Mr)
Is a high value exceeding 1.0 (T; Tesla).

That is, when a hard bias layer having a thickness of about 500 Å or less is formed of a Co—Ni—Pt-based alloy and the Pt concentration is about 13 (at%), the Ni concentration is 5 to 5 at%. It is preferable to set the range to 25 (at%), and from FIG. 1, a more preferable range of the Ni concentration is 10 to 20 (at%).

FIG. 2 shows a film thickness of 500 Å (solid white circle) and 1000 Å of the same Co—Ni—Pt alloy as in FIG. 1 and a Co—Cr—Pt alloy as a comparative example.
In each of Angstroms (filled circles), when the concentration of Pt was fixed at 13 (at%), N
It shows the relationship between the concentration of i or Cr and the coercive force (Hc).

FIG. 2 shows that the Co—Cr—Pt alloy
The coercive force (Hc) increases as the concentration of
In an o-Ni-Pt alloy, when the concentration of Ni increases,
It can be seen that the coercive force (Hc) decreases. However, as described above, the magnetic film constituting the hard bias layer does not require a higher coercive force than the magnetic recording medium, and the coercive force (H
If c) is 200 (Oe) or more, there is no practical problem,
More preferably, it may be about 500 (Oe) or more. Co
-The thickness of the Ni-Pt alloy is about 500 Å or less, and the Pt concentration is 13 (at
%), The coercive force (Hc) can be increased to 200 (Oe) or more if the Ni concentration is 30 (at%) or less, and the coercive force (Hc) can be reduced to about 18 (at%) or less. 500
(Oe) or more.

FIG. 3 is a diagram similar to FIG. 1 and FIG.
For the Co-Ni-Pt-based alloy and the Co-Cr-Pt-based alloy where the concentration of t is 13 (at%), the change in specific resistance (ρ) when the concentration of Ni or Cr is changed is shown. . As shown in FIG. 3, in the Co—Cr—Pt alloy, when the concentration of Cr increases, the specific resistance (ρ) increases,
It turns out that it is not preferable as a material of a hard bias layer. On the other hand, it can be seen that the specific resistance (ρ) is stable at a low value in the Co—Ni—Pt alloy regardless of the concentration of Ni. When a Co—Ni—Pt-based alloy is used as the magnetic film of the hard bias layer, regardless of the concentration of Ni,
The specific resistance (ρ) decreases.

FIGS. 4 and 5 show the change in the concentration of Cr or Ni in the Co—Ni—Pt-based alloy and the Co—Cr—Pt-based alloy shown in each of the above figures, and the MH curves. The relationship with the squareness ratios S and S ^* is shown. 4 and 5 that the Co-Ni-Pt-based alloy has a constant angular system ratio S, S ^* regardless of the Ni concentration, and the Co-Cr-Pt
It turns out that it is equivalent to a system alloy.

[0046]

As described above, according to the present invention, the use of a Co—Ni—Pt alloy as the material of the magnetic film constituting the hard bias layer of the magnetoresistive head can increase the residual magnetization, The resistance effect layer can be stably formed into a single magnetic domain, and Barkhausen noise can be reduced.
It is also excellent in corrosion resistance and hardly causes film peeling of each layer of the magnetoresistive head.

Further, the concentration of Ni is 10 to 20 (at%).
And the Pt concentration is in the range of 13 to 19 (at%), the residual magnetization (M.sub.M) of the Co--Ni--Pt-based magnetic film
r) can be 10 (kG) or more, and the magnetic characteristics can be improved as compared with the conventional hard bias layer.

Further, when the Pt concentration is approximately 13 (at%), the residual magnetization can be increased to 1.0 T or more by setting the Ni concentration to 5 to 25 (at%), and the magnetic characteristics are also improved. It can be improved.

Further, the concentration of Ni is 10 to 33 (at
%), The hard bias layer excellent in corrosion resistance can be formed by setting the concentration of Pt to 13 to 24 (at%).

[Brief description of the drawings]

FIG. 1 shows Co—Ni—P used as a material for a hard bias layer.
FIG. 4 is a diagram showing the relationship between the concentration of Ni or Cr and the saturation magnetization (Ms) and the residual magnetization (Mr) in a t-based alloy and a Co—Cr—Pt-based alloy as a comparative example;

FIG. 2 shows Co—Ni—P used as a material for a hard bias layer.
FIG. 7 is a diagram showing the relationship between the coercive force (Hc) and the concentration of Ni or Cr in a t-based alloy and a Co—Cr—Pt-based alloy as a comparative example;

FIG. 3 shows Co—Ni—P used as a material for a hard bias layer.
FIG. 7 is a diagram showing the relationship between the concentration of Ni or Cr and the specific resistance (ρ) between a t-based alloy and a Co—Cr—Pt-based alloy as a comparative example;

FIG. 4 shows Co—Ni—P used as a material for a hard bias layer.
FIG. 7 is a diagram showing the relationship between the concentration of Ni or Cr and the squareness ratio S in a t-based alloy and a Co—Cr—Pt-based alloy as a comparative example;

FIG. 5 shows Co—Ni—P used as a material of a hard bias layer.
A diagram showing a relationship between the concentration of Ni or Cr and the squareness ratio S ^* in a t-based alloy and a Co—Cr—Pt-based alloy as a comparative example,

FIG. 6 is an enlarged front view showing a magnetoresistive head having a hard bias layer from a side facing a recording medium;

FIG. 7 is an MH curve diagram of a magnetic material,

[Explanation of symbols]

 Reference Signs List 4 trilayer element 4a soft magnetic layer 4b nonmagnetic layer 4c magnetoresistive layer 5 main electrode 9 hard bias layer

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/39

Claims (1)

(57) [Claims] 1. A magnetoresistive head provided with a hard bias layer for applying a longitudinal bias magnetic field to the magnetoresistive layer located on both sides of the magnetoresistive layer, wherein the hard bias layer is made of Co—Ni—Pt. A magnetoresistive head made of a base alloy having a Ni concentration of 10 to 20 (at%) and a Pt concentration of 13 to 19 (at%).