JPH1091925A - Ferromagnetic tunnel joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high MR changing factor with a good reproducibility by setting the barrier potential made by an insulation layer to the range of a specific eV in the ferromagnetic tunnel joint in which a first ferromagnetic layer, an insulation layer and a second ferromagnetic layer are successively laminated. SOLUTION: In the ferromagnetic tunnel joint, a first ferromagnetic layer 1, an insulation layer 3 and a second ferromagnetic layer 2 are successively laminated on an appropriate insulation supporting base plate 4. In this construction, the barrier potential made by the layer 3 is set in the range of 0.5 to 3eV. This potential is due to the fact that if the barrier potential exceeds 3eV, no high MR changing factor is obtained and it is estimated that no tunnel current flows. On the other hand, if the barrier potential becomes less than 0.5eV, not expected high MR changing factor is obtained. Thus, if the barrier potential is set within the range of 0.5 to 3eV, a stable and antiferromagnetic coupling is produced through the layer 3 between the layers 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistance effect element and a ferromagnetic tunnel junction used for a magnetic head.

[0002]

2. Description of the Related Art As a reproducing head for high-density magnetic recording, a magnetoresistive head (hereinafter, referred to as an MR magnetic head) using an anisotropic magnetoresistance (hereinafter, referred to as AMR) effect has been commercialized. However, AM such as NiFe
Since the R effect film is used, the magnetoresistance (MR) change rate is as low as about 2% and the sensitivity is as low as 0.5% / Oe. Therefore, an MR film having a higher MR change rate and higher sensitivity is desired.

In recent years, a new phenomenon called the giant magnetoresistance effect (GMR effect) has been discovered as a technology that meets such demands, and research has been conducted on the fact that a larger magnetoresistance change rate than the conventional AMR effect can be obtained. ing. A spin-valve (SV) film having a ferromagnetic layer / non-magnetic metal layer / ferromagnetic layer / antiferromagnetic layer, which causes the GMR effect, has a thickness of 2 to 5 mm.
Because of its high sensitivity of% / Oe, SV heads using the same have attracted attention as next-generation reproducing heads, and research on their practical use has begun.

On the other hand, apart from the GMR effect, a phenomenon called a ferromagnetic tunnel effect has a junction structure of a ferromagnetic layer / insulating layer / ferromagnetic layer, and a tunnel effect appears depending on a relative angle of magnetization of both ferromagnetic layers. Have been found, and research and development of a magnetoresistive element utilizing this phenomenon have been promoted. Since ferromagnetic tunnel effect films have very high magnetic field sensitivity,
There is a possibility as a reproducing head in ultra high density magnetic recording of 10 Gbit / inch ² or more. S. Maekawa and V. Gafvert et al. In IEEE Trans. Magn., MAG-18, 707 (1982)
It has been theoretically and experimentally shown that a tunnel effect is expected to appear depending on the relative angle of the magnetization of both magnetic layers in the magnetic / insulator / magnetic junction.

Japanese Patent Laid-Open No. 4-42417 discloses a magnetoresistive element having a ferromagnetic tunnel effect film.
In addition, it is described that detection can be performed with high resolution, and the probability of occurrence of pinholes can be reduced by reducing the bonding area to further improve the reproduction sensitivity.

Japanese Patent Application Laid-Open No. H4-103014 discloses a ferromagnetic tunnel effect film for applying a bias magnetic field from an antiferromagnetic material to a magnetic layer and a magnetoresistance effect element using the same.

Further, T. Miyazaki and N. Tezuka et al.
139 (1995) L231 reports that a Fe / Al ₂ O ₃ / Fe tunnel junction achieved an MR change rate of 18% at room temperature. M. Pomerantz, JCSlocczewski
And E. Spiller et al. Disclose Fe / a-Carbon / Fe films.

[0008] However, the ferromagnetic tunnel junctions reported so far have various problems to be solved.

The ferromagnetic tunnel junction of the present invention is the same as the above-described ferromagnetic tunnel effect film.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ferromagnetic tunnel junction capable of obtaining a high MR ratio with good reproducibility.

Another object of the present invention is to provide a ferromagnetic tunnel junction whose structure can be simplified when applied to a magnetoresistive element or a magnetic head.

[0012]

According to the present invention, there is provided a ferromagnetic tunnel junction comprising a first ferromagnetic layer, an insulating layer, and a second ferromagnetic layer which are sequentially stacked. 0.5-3 eV barrier potential by the insulating layer
Is set in the range of.

[0013]

FIG. 1 is a perspective view conceptually showing a ferromagnetic tunnel junction, and FIG. 2 is a sectional view taken along line A2-A2 in FIG. As shown, the ferromagnetic tunnel junction is
The first ferromagnetic layer 1, the insulating layer 3, and the second ferromagnetic layer 2 are sequentially laminated. These are laminated on a suitable insulating support substrate 4. The present invention is characterized in that in such a structure, the barrier potential by the insulating layer 3 is set in a range of 0.5 to 3 eV.

In the ferromagnetic tunnel junction, the electrons e pass from the first ferromagnetic layer 1 to the second ferromagnetic layer 2 via the insulating layer 3 while maintaining the spin direction (FIGS. 1 and 2).
At this time, the transmittance of the electron e is obtained from the amplitude square ratio of the incident wave and the transmitted wave using the wave function obtained in consideration of the spin, and the tunnel conductance G is given by G = G ₀ ′ (1+ P ₁ ′ · P ₂ ′) COSθ. Where P ₁ ′ = [(K _{1 ↑} -K _{1 ↓} ) / (K _{1 ↑} + K _{1 ↓} )] α ₁ P ₂ ′ = [(K _{2 ↑} -K _{2 ↓} ) / (K _{2 ↑} + K _{2 ↓} )] α ₂ G ₀ ′: electron wave numbers K _{1 ↑} , K _{1 ↓} , K _{2 ↑} , K in both ferromagnetic layers
_{2 ↓} and constants determined by the height of the barrier potential α ₁ , α ₂ : Coefficients dependent on the height of the barrier potential P ₁ ′, P ₂ ′: Effective spin polarization P ₁ , P of both ferromagnetic layers 1 and 2 ₂ : The spin polarization of both ferromagnetic layers 1 and 2 (fractional portions of effective spin polarizations P ₁ ′ and P ₂ ′). The rate of change ΔG / G ₀ of the tunnel conductance is ΔG / G ₀ = 2 · P ₁ ′ · P ₂ ′. The rate of change of tunnel conductance ΔG / G ₀ is MR
Synonymous with change rate.

When the height of the barrier potential is low, the coefficients α ₁ and α ₂ depending on the barrier potential become small, so that the effective spin polarization degrees P ₁ ′ and P ₂ ′ of both ferromagnetic layers also become small, and the MR change rate becomes small. Lower. Conversely, if the barrier potential is sufficiently high, the effective spin polarizations P ₁ ′ and P ₂ ′ become spin polarizations P ₁ and P 2.
₂ and a high MR ratio is obtained.

In the case of the present invention in which the barrier potential is in the range of 0.5 to 3 eV, a high MR ratio can be obtained with good reproducibility. One of the reasons is presumed that by maintaining the barrier potential in the range of 0.5 to 3 eV, the uniformity is good and the formation of the insulating layer 3 with very few pinholes is guaranteed.

Another reason is that stable anti-ferromagnetic coupling occurs between the first ferromagnetic layer 1 and the second ferromagnetic layer 2 via the insulating layer 3 in the range of the barrier potential described above. It is supposed to be. Barrier potential 1.5-2.5
Particularly favorable results were obtained in the eV range.

If the barrier potential exceeds 3 eV, a high MR ratio cannot be obtained. Although the cause is not clear, it is assumed that the tunnel current stops flowing in the range of the barrier potential exceeding 3 eV.

If the barrier potential is smaller than 0.5 eV, the high MR ratio expected in such a ferromagnetic tunnel junction cannot be obtained. The reason is presumed to be that the uniformity of the insulating layer 3 deteriorates and pinholes increase.

Next, in the range where the barrier potential is 0.5 to 3 eV, stable antiferromagnetic coupling is generated between the first ferromagnetic layer 1 and the second ferromagnetic layer 2 via the insulating layer 3. This possibility brings a great advantage when this ferromagnetic tunnel junction is used for a magnetic transducer for reading a magnetic head.

FIG. 3 is a graph showing the relationship between the magnetic field and the magnetoresistance ratio when antiferromagnetic coupling occurs. As shown in FIG. 3, when antiferromagnetic coupling occurs, the magnetic field-magnetoresistive curves L1 and L2 show the highest MR change rate in a region ΔH near zero magnetic field. Therefore, when this ferromagnetic tunnel junction is used as a magnetic transducer for reading of a magnetic head, it is not necessary to apply a bias magnetic field, and a linear region near zero magnetic field can be obtained only by the shape effect. Therefore, the structure of the magnetic head can be simplified.

An example of the insulating layer 3 that can secure the above-mentioned barrier potential is an aluminum oxide film annealed at 40 to 100 ° C. in the air. In such an aluminum oxide film, since metallic aluminum is not present locally, a bridge cannot be formed between the upper and lower ferromagnetic layers 1-2, and as a result, a ferromagnetic tunnel having an extremely thin insulating layer 3 having a high barrier potential is obtained. Joining can be realized.

Another example of the insulating film is a diamond-like carbon film (hereinafter referred to as a DLC film).
This is also effective in realizing an ultra-thin insulating layer 3 having a high barrier potential. In particular, the DLC film manufactured by the plasma CVD method has an extremely thin layer thickness of several tens of
A good insulating layer 3 which is uniform and free from pinholes can be obtained.

The intermediate C film disclosed by M. Pomerantz, JCSlocczewski, and E. Spiller is an amorphous-C film produced by MBE, and is different from a DLC film produced by plasma CVD. Specifically, amorphous-C
The film is a film in which carbon is bonded to each other in a network, but the DLC film of the present invention is essentially different in that carbon and hydrogen are bonded in a network.

In the present invention, the coercive force of the first ferromagnetic layer 1 and the coercive force of the second ferromagnetic layer 2 are usually different from each other. FIG. 4 shows that the coercive force H1 of the first ferromagnetic layer 1 and the coercive force H2 of the second ferromagnetic layer 2 are H1> H2 (or H2> H
A magnetization curve in the case of different values as in 1) is shown.
As shown, the magnetization curve has a two-step loop.
In FIG. 4, two arrows shown inside the circle indicate the direction of magnetization of the first ferromagnetic layer 1 and the direction of magnetization of the second ferromagnetic layer 2, respectively.

The direction of magnetization of the first ferromagnetic layer 1 and the direction of magnetization of the second ferromagnetic layer 2 are such that the applied magnetic field is larger than the coercive force H2 (absolute value) and larger than the coercive force H1 (absolute value). When the applied magnetic field is smaller than the coercive force H1, the parallelism occurs. The electric resistance is large when the direction of magnetization is in an antiparallel state, and becomes small when the direction of magnetization is in a parallel state. Assuming that the resistance value is Rs when the magnetization direction is parallel and ΔR is the change in resistance when the magnetization direction changes from antiparallel to parallel, the MR change rate is ΔR / Rs
Becomes Thereby, an externally applied magnetic field can be detected.

Next, an embodiment will be described. Example 1 On an insulating support substrate 4 made of a 3 inch φ glass substrate, Ni
A first ferromagnetic layer 1 made of Fe, an insulating layer 3 made of an aluminum oxide film, and a second ferromagnetic layer 2 made of Co were laminated to obtain a ferromagnetic tunnel junction shown in FIGS. The insulating layer 3 made of an aluminum oxide film was formed by performing a heat treatment on the aluminum film at 60 ° C. for 24 hours in the air.
The junction area of the ferromagnetic tunnel junction was set to 0.25 to 2500 μm ² .

Twenty ferromagnetic tunnel junctions each having the above-described junction area were manufactured, and the barrier potential, the average value of the MR change rate, and the variation thereof were examined for each junction area. The yield was also examined. Next, a method for manufacturing a ferromagnetic tunnel junction will be specifically described.

First, a coning 7059 having a size of 3 inches φ
A 10 nm-thick NiFe film is formed as a first ferromagnetic layer 1 on a supporting substrate 4 made of a glass substrate by RF sputtering, and is subjected to 0.5 micron processing using resist photolithography, Ar ion milling, and resist stripping. It was patterned into a rectangular shape of 〜50 μm × 0.5 mm.

Thereafter, resist patterning is performed to remove the surface oxide layer of the NiFe layer constituting the first ferromagnetic layer 1 by reverse sputtering, and then an aluminum film having a thickness of 5 nm is formed by electron beam heating vacuum evaporation. A film was formed.

Thereafter, the sample was taken out of the vacuum deposition apparatus, and subjected to a heat treatment at 60 ° C. for 24 hours in the air, followed by a lift-off process to obtain a sample having a diameter of 3 mmφ.
An insulating layer 3 made of an aluminum oxide film was formed.

Next, after the resist patterning is performed again, a Co film having a thickness of 100 nm is formed as the second ferromagnetic layer 2 by RF sputtering, and then the first ferromagnetic layer is subjected to a lift-off process. 0.5 ～ 50μm × 0.5m in the direction perpendicular to 1
A second ferromagnetic layer 2 having a rectangular pattern of m was formed.
As a result, a ferromagnetic tunnel junction having a junction area of 0.25 to 2500 μm ² was obtained.

For comparison, a NiFe / aluminum oxide / Co ferromagnetic tunnel junction using a conventionally used native aluminum oxide film (after film formation and left in the air for 24 hours) as an insulating layer 3 was also prepared. .

The first example employed in Examples and Comparative Examples
The conditions for forming the ferromagnetic layer 1 and the second ferromagnetic layer 2 are as follows. In addition, the ultimate pressure of the aluminum film is 3 ×
It was produced at 10 ⁻⁵ Pa at a deposition rate of 0.05 nm / sec. <Ferromagnetic layer deposition conditions> Ultimate pressure: 1 × 10 ^-5 Pa Target: Ni ₈₀ Fe ₂₀ at%, Co (4 inch φ) Sputter gas: Ar 5 sccm Sputter pressure: 0.5 Pa Input power: 150 W Film formation rate: NiFe 45 nm / min, Co 40 nm / min Substrate temperature: water-cooled The samples prepared in this manner were measured for magnetoresistance (MR) curve by a DC four-terminal method. The maximum applied magnetic field at the time of measurement was ± 1 kOe. After applying a magnetic field of −1 kOe, the magnetic field was gradually increased to +1 kOe, and returned to −1 kOe again. As for the barrier potential, the VI characteristic of the tunnel junction was measured, and the deviation from the linear region was determined.

FIG. 5 shows a magnetoresistance curve of a ferromagnetic tunnel junction having a junction area of 50 × 50 μm ^{2 according} to the present invention. As the applied magnetic field is increased beyond -1 kOe, the first
Since the magnetization reversal of the ferromagnetic layer 1 occurs and the spins of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 become antiparallel, the electric resistance increases. 0.5 eV as a result of calculating barrier potential
, And the same M was obtained in 16 of the 20
An R curve was obtained. The MR change rate is 6.6 to 8.1%,
The average value of the R change rate is 7.6%, and the change rate variation is ± 7%
Met.

On the other hand, the natural aluminum oxide film is
In the ferromagnetic tunnel junction of the comparative example, the barrier potential was only obtained at 0.2 eV. Also, only four MR curves could be observed, and the average MR change rate was 1.5%.
The average value variation was ± 88%, which was very large.
Similar evaluations were made for various bonding areas. The results are shown in Tables 1-1 and 1-2.

As is apparent from Table 1, by using the aluminum oxide film formed by the heat treatment at 60 ° C. in the atmosphere as the insulating layer 3, a high barrier potential of 0.5 to 3 eV and a high MR change rate can be obtained, and the variation can be improved. And a high yield can be obtained. In particular, the yield is high when the barrier potential is 1.5 to 2.5 eV. Also, 30-25
As a result of examining the MR characteristics of a ferromagnetic tunnel junction using an aluminum oxide film obtained by heat treatment in the air at a temperature of 0 ° C. as an insulating layer 3, a high MR ratio was obtained when the heat treatment was performed at 40 to 100 ° C. It was also found that there was little variation and a high yield was obtained.

Example 2 A ferromagnetic tunnel junction in which an insulating layer 3 was formed of a DLC film was formed on a supporting substrate 4 made of a glass substrate. The first ferromagnetic layer 1 was made of Co ₅₀ Fe ₅₀ , and the second ferromagnetic layer 2 was made of Co. The bonding area was 0.25 to 2500 μm ² . The first ferromagnetic layer 1 and the second ferromagnetic layer 2 were manufactured in the same manner as in Example 1. The DLC film forming the insulating film 3 was formed by a plasma CVD method so as to have a layer thickness of 5 nm and a diameter of 3 mmφ, and was patterned by a lift-off method. The conditions for forming the DLC film are shown below.

<DLC film deposition conditions> Ultimate pressure: 2 × 10 ^-3 Pa Introduced gas: methane 5 sccm Sputter pressure: 3.5 Pa RF power: 50 W Self-bias: -150 V Film deposition rate: 10 nm / min Substrate temperature: no heating and no water cooling As a comparative example, a Co ₅₀ Fe ₅₀ / aluminum oxide / Co ferromagnetic tunnel junction using a natural aluminum oxide film as the insulating layer 3 was produced.

Tables 2-1 and 2-2 show the results obtained by measuring the MR characteristics of the samples of the above Examples and Comparative Examples by the DC four-terminal method.

As is apparent from Table 2, by using the DLC film produced by the plasma CVD method as the insulating layer 3, a high barrier potential and a high MR ratio can be obtained, and further, there is little variation and a high yield. It can be seen that it can be obtained. For example, the bonding area 50 according to this embodiment is
× 20 μm ² sample
An MR curve was obtained with 15 pieces. The average value of MR change rate is 1
At 8.9%, the variation in the rate of change was ± 12%. Further, similarly to the first embodiment, the barrier potential is 1.5 to 2.5 eV
In particular, the yield was high. On the other hand, in the ferromagnetic tunnel junction of the comparative example using the natural aluminum oxide film as the insulating layer 3, the barrier potential was small, and only five MR curves could be observed, and the average MR change rate was 3.3%.
And the variation was as large as ± 88%.

Next, the relationship between the junction area and the switching magnetic field will be described. It is reported that the smaller the bonding area, the smaller the number of defects such as pinholes in the insulating layer 3 and the higher the yield. As can be seen from Tables 1 and 2, in the ferromagnetic tunnel junction of this example, the smaller the junction area, the higher the MR ratio and the higher the yield. In particular, the yield increases when the barrier potential is 1.5 to 2.5 eV. The magnetic field Hab shown in FIG.
It has been found that the magnetic field at which the magnetization of the first ferromagnetic layer 1 is reversed shifts in the negative direction. In particular, when the bonding area is 10μ
When the barrier potential is smaller than m ² and the barrier potential is 1.5 to 2.5 eV,
In a zero magnetic field, the magnetizations of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 become antiparallel. This indicates that an antiferromagnetic coupling force is acting between the two magnetic layers. When the junction area is smaller than 10 μm ² , a high MR ratio and a high yield were obtained because the insulating layer 3 having a uniform and very few pinholes was used, and the joint area was reduced. It is considered that the antiferromagnetic coupling occurred in FIG. Also, as shown in Examples 1-7 and 2-8, if the barrier potential is larger than 2.5 eV even when the junction area is 10 μm ² or less, an antiferromagnetic junction cannot be obtained between the two magnetic layers, and the yield is slightly increased. descend.

Next, an example in which the ferromagnetic tunnel junction according to the present invention is applied to a magnetic head will be described. <MR head of the present invention> Co ₅₀ Fe ₅₀ / DLC / C according to Example 2
o Fabrication of a magnetoresistive head for reproduction using a ferromagnetic tunnel junction as a magnetoresistive film, reading of a recording signal written to a magnetic recording medium, examination of reproduction sensitivity and reproduction output, and the conventional AMR magnetoresistance effect Compared with the mold head. FIG. 6 is a schematic view of a reproducing magnetic head using a ferromagnetic tunnel junction according to the present invention. Next, a method for manufacturing the head will be described.

First, on an Al ₂ O ₃ —TiC substrate (not shown) on which a 30 μm-thick alumina insulating film was formed, a ₂ μm-thick film was formed as a lower shield film 71 by DC sputtering.
Is formed by photolithography and Ar
A predetermined shape was formed by ion etching.

Next, as a lower insulating layer 81, R
An alumina film having a film thickness of 80 nm is formed by the F sputtering method, and subsequently, a Cr (5 nm) / Cu (30 nm) / Cr (5 nm) film is DC-sputtered as a first electrode film 61 after resist patterning. A film was formed by a method and processed into a predetermined shape by a lift-off method.

Next, a first ₅₀ nm-thick Co ₅₀ Fe ₅₀ film is used.
A ferromagnetic layer 1, an insulating film 3 made of a DLC film having a thickness of 5 nm, and a second ferromagnetic layer 2 made of a Co film having a thickness of 5 nm were stacked, thereby forming a ferromagnetic tunnel junction 9. A method for forming a ferromagnetic tunnel junction will be described.

First, after the resist patterning, the first ferromagnetic
As layer 1, Co₅₀Fe₅₀(10nm) layer formed by RF sputtering
Then, a DLC (5 nm) layer is formed as an insulating layer 3 by a plasma CVD method.
did. Next, as the second ferromagnetic layer 2, a Co (10 nm) layer is RF-coated.
Formed by sputtering method, 1μm width by lift-off method X length
6μm Of the shape.

Finally, in the same manner as the first electrode film 61,
After the distaste patterning, Cr (5 nm) /
A Cu (30 nm) / Cr (5 nm) film is formed and lifted off to a specified shape.
Processed into a shape. Before forming the second electrode film, the second electrode film is formed.
Reverse the surface oxide layer formed on the ferromagnetic layer 2
And the final thickness of the second ferromagnetic layer is 5 μnm. become
I did it. On top of this, a film thickness 90
A nm alumina film was formed.

Next, as the upper shield film 72,
A μm NiFe film is formed by DC sputtering,
And a predetermined shape by Ar ion etching. Most
Later, after preparing a bump electrode film of Cu by plating method,
An alumina film having a thickness of 30 μm was covered as a protective film. That
After that, it is processed and polished to a predetermined size, and the bonding area is 1 μm in width. ,
Length 1μm Of the magnetoresistive head for reproduction. sand
That is, the track width of the head is 1 μm and the MR height is
1 μm and the MR shield interval was 0.27 μm. <Conventional AMR Head: Comparative Example> For comparison, FIG.
Such a SAL bias type NiFe layer is used as a MR film.
Lock width 1 μm, MR height 1 μm, MR shield interval 0.27
A μm conventional AMR head was also fabricated. The fabrication method is shown below.
You. Until the lower insulating layer 81 is formed, the ferromagnetic tunnel of the present invention is used.
This is the same as a multi-junction type MR head. Form the lower insulating layer 81
After the formation, first, a NiFeRh film 51 as a SAL film, a magnetic separation film
A Ta film 52 as a DC film and a NiFe film 53 as an MR film.
It is formed by the putter method and processed into a rectangular shape by the fine processing technology.
Was. Thereafter, the electrode films 61 and 62, the upper insulating layer 82 and the upper
The partial shield film 72 was formed by a thin film and fine processing technique.

Using this magnetic head, a coercive force of 2500 Oe
Then, a recording signal written on a magnetic recording medium having a thickness of 50 nm was reproduced, and its characteristics were examined. FIG. 8 is a diagram comparing the reproduction output per unit track width with the recording density. Curve L3
Represents the characteristic of the magnetic head using the ferromagnetic tunnel junction according to the present invention, and curve L4 represents the characteristic of the conventional AMR head. As shown in FIG. 8, according to the reproducing magnetoresistive head of the present invention, 4 to 5 times more than the conventional AMR head.
Double playback output was obtained.

[0051]

As described above, according to the present invention, the following effects can be obtained. (A) A ferromagnetic tunnel junction capable of obtaining a high MR ratio with good reproducibility can be provided. (B) A ferromagnetic tunnel capable of simplifying the structure in application to a magnetoresistive element or a magnetic head. Bonding can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a ferromagnetic tunnel junction according to the present invention.

FIG. 2 is a sectional view taken along line A2-A2 in FIG.

FIG. 3 is a diagram illustrating a magnetoresistance change rate characteristic of a ferromagnetic tunnel junction.

FIG. 4 is a diagram showing a magnetization curve of a ferromagnetic tunnel junction.

FIG. 5 is a diagram showing a magnetoresistance change rate characteristic of the ferromagnetic tunnel junction according to the present invention.

FIG. 6 is a perspective view schematically showing a configuration of a magnetic head using a ferromagnetic tunnel junction according to the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a conventional magnetic head using the AMR effect.

FIG. 8 is a diagram showing the reproduction characteristics of the reproduction magnetic head of the present invention and a conventional AMR head.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first ferromagnetic layer 2 second ferromagnetic layer 3 insulating layer 4 substrate 51 SAL film 52 magnetic separation film 53 MR film 61, 62 electrode film 71 lower shield film 72 upper shield film 81 lower insulating layer 82 upper Insulation layer 9 Ferromagnetic tunnel junction

[Procedure amendment]

[Submission date] March 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

[0017] Another reason is that the range of the above-mentioned barrier potential between the first ferromagnetic layer 1 and the second ferromagnetic layer 2, through the insulating layer 3, a stable antiferromagnetic coupling It is presumed to occur. Barrier potential 1.5 ~
In the range of 2.5 eV, particularly preferable results were obtained.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

Next, to the extent that the barrier potential is 0.5～3EV, between the first ferromagnetic layer 1 and the second ferromagnetic layer 2, through the insulating layer 3, a stable antiferromagnetic coupling The possibility that can be created brings a great advantage when this ferromagnetic tunnel junction is used for a read magnetic transducer of a magnetic head.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

On the other hand, the natural aluminum oxide film is
In the ferromagnetic tunnel junction of the comparative example, the barrier potential was only obtained at 0.2 eV. Also, only four MR curves could be observed, and the average MR change rate was 1.5%.
The average value variation was ± 88%, which was very large.
Similar evaluations were made for various bonding areas. The results are shown in Tables 1-1 and 1-2.

[Procedure amendment]

[Submission date] May 22, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 9

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

Further, T. Miyazaki and N. Tezuka et al.
139 (1995) L231 reports that a Fe / Al ₂ O ₃ / Fe tunnel junction achieved an MR change rate of 18% at room temperature. Also, M. Pomerantz, JCSloczewski , E. Spiller and the like disclose Fe / a-Carbon / Fe films.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

Incidentally, M. Pomerantz, JCSloczewski and E.
The intermediate C film disclosed by Spiller et al. Is an amorphous-C film manufactured by the MBE method, and is different from the DLC film manufactured by the plasma CVD method. Specifically, the amorphous-C film is a film in which carbons are bonded to each other in a network, while the DLC film of the present invention is formed by combining carbon and hydrogen in a network.
And are essentially different.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Manabu Ota 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Satoru Araki 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Inside the corporation

Claims (9)

[Claims] 1. A ferromagnetic tunnel junction in which a first ferromagnetic layer, an insulating layer, and a second ferromagnetic layer are sequentially stacked, wherein a barrier potential of the insulating layer is in a range of 0.5 to 3 eV. Ferromagnetic tunnel junction. 2. The ferromagnetic tunnel junction according to claim 1, wherein a barrier potential of the insulating layer is in a range of 1.5 to 2.5 eV. 3. The ferromagnetic tunnel junction according to claim 1, wherein the coercive force of the first ferromagnetic layer is different from the coercive force of the second ferromagnetic layer. 4. The ferromagnetic tunnel junction according to claim 1, wherein said first ferromagnetic layer and said second ferromagnetic layer are antiferromagnetically coupled via said insulating layer. Magnetic tunnel junction. 5. The ferromagnetic tunnel junction according to claim 1, wherein the insulating layer is formed at 40 to 100 ° C. in air after being formed.
Ferromagnetic tunnel junction, an aluminum oxide film formed by heat treatment at 6. The ferromagnetic tunnel junction according to claim 1, wherein the insulating layer is a diamond-like carbon film. 7. The ferromagnetic tunnel junction according to claim 1, wherein the area of the tunnel junction is 10 μm ² or less. 8. A magnetoresistive element using a ferromagnetic tunnel junction as a magneto-sensitive portion, wherein the ferromagnetic tunnel junction is any one of claims 1 to 7. 9. A magnetoresistive head having a magnetoresistive element, wherein the magnetoresistive element is as described in claim 7.