JPH10255231A - Magneto-resistive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-resistive element, where a sufficient amount of tunnel current can be applied to a ferromagnetic tunnel junction, and high rate of change of MR (magneto-resistive) can be obtained. SOLUTION: The element has a ferromagnetic tunnel junction 21, and domain control films 214 and 215. The ferromagnetic tunnel junction 21 includes an insulating film 210, a first ferromagnetic film 211, and a second ferromagnetic film 212. The first ferromagnetic film 211 and the second ferromagnetic film 212 are laminated with the insulating layer 210 therebetween. The domain control films 214 and 215 are provided adjacent to both ends of the first ferromagnetic film 211.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element using a ferromagnetic tunnel junction in a magnetic sensing portion and a magnetic head using the same.

[0002]

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

[0003] In recent years, a new phenomenon called the giant magnetoresistance effect (GMR effect) has been found as a technique to meet such demands, and a higher magnetoresistance change rate than the conventional AMR effect has been obtained. Have been.
Among them, the GMR effect using a spin valve (SV) film has attracted attention. The spin valve film is a multilayer film composed of a ferromagnetic film, a non-magnetic metal film, a ferromagnetic film, and an antiferromagnetic film, and has a high sensitivity of 2 to 5% / Oe. Attention has been paid to a reproducing element in a head, and research for 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 film / insulating film / ferromagnetic film, and a tunnel effect appears depending on a relative angle of magnetization of both ferromagnetic films. Have been found, and research and development of a magnetoresistive element utilizing this phenomenon have been promoted. Since the ferromagnetic tunnel effect film has a very high magnetic field sensitivity, it has a potential as a reproducing magnetic head in ultra-high density magnetic recording of 10 Gbit / inch ² or more. S.Maekawa and V.Ga
fvert et al. in IEEE Trans. Magn., MAG-18, 707 (1982) are expected to show a tunnel effect depending on the relative angle of magnetization of both magnetic films at the magnetic / insulator / magnetic junction. That was shown theoretically and experimentally.

Japanese Patent Laid-Open No. 4-42417 discloses a magnetic head having a ferromagnetic tunnel effect film.
Compared to magnetic heads, high sensitivity to minute changes in leakage flux,
In addition, it discloses that detection can be performed with high resolution and that the probability of occurrence of pinholes in the insulating film can be reduced by reducing the bonding area to further improve 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 film and a magnetic head using the same.

Further, T. Miyazaki and N. Tezuka et al.
gn.Magn.Mater.139 (1995) L231, Fe / Al ₂ O ₃ / Fe
It is reported that a tunnel junction obtained an MR ratio of 18% at room temperature. Also, M. Pomerantz, JCSloczewski
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 when used as a magnetic head. For example, JP-A-4-
Known literature such as 42417 discloses several means for detecting a small change in magnetic flux with high sensitivity by using a magnetoresistive element using a ferromagnetic tunnel effect film and obtaining a high stable output. . As one of them, of a pair of magnetic layers forming a multi-layered magnetoresistive film, a magnetic layer whose magnetization direction changes due to leakage magnetic flux from a medium has an anisotropic dispersion angle such that magnetization rotation occurs simultaneously. Is required to be reduced and a single magnetic domain is required. Specifically, it is reported that a single magnetic domain is formed by inserting an intermediate layer such as BN into the magnetic layer.

However, even if a film having a small anisotropic dispersion angle is formed in this way, if the film is patterned to a size of several μm and operated with a high frequency magnetic field of several tens of MHz or more, a fine pattern film is formed. At the end, there is a problem that micro-turbulence in the spin direction occurs and a domain wall is formed, so that the single domain structure is broken and Barkhausen noise is generated.

Conventional AMR magnetic head and spin valve G
In the MR magnetic head, a method has been disclosed in which a magnetic domain control film is formed at both ends of a magnetoresistive film and a Barkhausen noise is prevented by applying a longitudinal bias (known literature: US Pat. No. 5,018,037, Japanese Patent Publication No. -21166 publication). In these cases, the magnetic domain control films are formed in direct contact with both end regions of the entire magnetic sensing portion. This is because, in an AMR magnetic head or a spin valve GMR magnetic head, a current is applied in a direction parallel to the surface of the magnetoresistive element, so that the magnetic domain control film is in contact with both ends of the magnetosensitive portion. Is not practically problematic.

However, a ferromagnetic tunnel junction has a first ferromagnetic film, an insulating film, and a second ferromagnetic film stacked vertically, and a tunnel current flows in the stacking direction to cause a change in magnetoresistance. Is what happens. Therefore, if the bias magnetic layer for controlling the magnetic domain comes into contact with the entire end of the magnetic sensing portion as in the conventional case, the upper and lower ferromagnetic layers separated by the insulating layer are electrically short-circuited, and the tunneling is performed. Since no current flows, a change in magnetoresistance cannot be obtained.

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

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive element capable of flowing a sufficiently large tunnel current through a ferromagnetic tunnel junction and obtaining a high MR ratio. That is.

Another object of the present invention is to provide a magnetoresistive element capable of obtaining a good output waveform without distortion.

Still another object of the present invention is to provide a magnetoresistive element capable of obtaining a stable output without noise.

[0016]

In order to solve the above-mentioned problems, a magnetoresistance effect element according to the present invention has a ferromagnetic tunnel junction and a magnetic domain control film. The ferromagnetic tunnel junction includes an insulating film, a first ferromagnetic film, and a second ferromagnetic film, wherein the first ferromagnetic film and the second ferromagnetic film are formed of the insulating film. Are laminated through. The magnetic domain control film is provided adjacent to both ends of one of the first ferromagnetic film and the second ferromagnetic film.

As described above, since the magnetic domain control film is provided adjacent to either end of either the first ferromagnetic film or the second ferromagnetic film, the first ferromagnetic film There is no room for an electrical short between the first ferromagnetic film and the second ferromagnetic film. Therefore, a sufficiently large tunnel current can flow through the ferromagnetic tunnel junction. For this reason, a large magnetoresistance change rate can be obtained.

Moreover, the ferromagnetic film provided with the magnetic domain control film can be brought into a single magnetic domain state by the magnetic domain control film. For this reason, the generation of Barkhausen noise that causes output waveform distortion can be suppressed, and a stable output without noise can be obtained.

Preferably, among the first ferromagnetic film and the second ferromagnetic film, the ferromagnetic film not provided with the magnetic domain control film has a magnetization fixed film.

According to this structure, one of the first ferromagnetic film and the second ferromagnetic film is operated as a pinned ferromagnetic film having a magnetization fixed film, and the other is operated as a free ferromagnetic film.
A relative angle change can be caused between the magnetization direction of the first ferromagnetic film and the magnetization direction of the second ferromagnetic film only by the movement of the magnetization of the free ferromagnetic film. In this case, the axis of easy magnetization of the free ferromagnetic film is perpendicular to the external magnetic field,
It is preferable to set the pinned ferromagnetic film so that the axis of easy magnetization is parallel. By doing so, when the external magnetic field is zero, the direction of magnetization of the free ferromagnetic film is perpendicular to the direction of magnetization of the pinned ferromagnetic film, so that an output waveform with good symmetry can be obtained. Moreover, the direction of magnetization of the free ferromagnetic film is
Since it changes in the magnetization rotation mode by the external magnetic field, high sensitivity is obtained, and smooth magnetization reversal is performed.
Generation of Barkhausen noise due to domain wall movement can be reduced.

[0021]

FIG. 1 is a perspective view schematically showing a magnetoresistive element according to the present invention, FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, and FIG. It is sectional drawing which followed the 3 line. As shown, the magnetoresistive element according to the present invention includes a ferromagnetic tunnel junction 21, a magnetic domain control film 214,
215. The ferromagnetic tunnel junction 21 includes an insulating film 210, a first ferromagnetic film 211, and a second ferromagnetic film 212. The first ferromagnetic film 211 and the second ferromagnetic film 212 are stacked on both sides of the insulating film 210. These are laminated on a suitable insulating support substrate 4. The magnetic domain control films 214 and 215 are provided adjacent to both ends of the first ferromagnetic film 211. In this embodiment, the first ferromagnetic film 211 is a free ferromagnetic film whose magnetization direction changes freely with respect to a minute external magnetic field, and the second ferromagnetic film 212 has a magnetization direction that changes with respect to a minute external magnetic field. The case where no pinned ferromagnetic film is used will be described.

<Magnetic Domain Control> In this type of magnetoresistance effect element, the ferromagnetic tunnel junction 21 is formed as a fine rectangular pattern. In such a pattern, it is not possible to avoid that a magnetically unstable portion is generated at the end of the pattern and a magnetic domain is formed. Therefore, the magnetization reversal in the domain wall motion mode is partially generated, and noise is generated. Therefore, magnetic domain control films 214 and 215 are formed on both ends of the first ferromagnetic film 211, and the first ferromagnetic film 21
1 is kept in a single magnetic domain state. The magnetic domain control films 214 and 215 shown in the embodiment are magnetic bias films.

FIG. 4 is a diagram for explaining the operation of the tunnel junction of the magnetoresistive element shown in FIGS. When the applied magnetic field H is zero, the magnetization direction M of the second ferromagnetic film 212
2 is pinned in a direction parallel to the magnetic field H to be applied. First ferromagnetic film 211
Is controlled by the magnetic domain control films 214 and 215 in a direction perpendicular to the magnetic field H to be applied. In this state, when a magnetic field H is applied from a magnetic recording medium such as a magnetic disk, the magnetization direction M2 of the pinned second ferromagnetic film 212 does not change, but the first magnetization direction M2 does not change.
The magnetization direction M1 of the ferromagnetic film 211 changes by, for example, the angle θ. This produces a magnetoresistance effect.

Since such magnetic domain control films 214 and 215 are provided adjacent to both ends of the first ferromagnetic film 211, the first ferromagnetic film 211 and the second ferromagnetic film 212 are provided.
There is no room for an electrical short between them. Therefore, a sufficiently large tunnel current can flow through the ferromagnetic tunnel junction 21. For this reason, a large magnetoresistance change rate can be obtained.

In addition, the first ferromagnetic film 211 provided with the magnetic domain control films 214 and 215 can be in a single magnetic domain state. For this reason, the generation of Barkhausen noise that causes output waveform distortion can be suppressed, and a stable output without noise can be obtained.

As the magnetic domain control films 214 and 215, a hard ferromagnetic film or an antiferromagnetic film can be used. As a hard ferromagnetic film constituting the magnetic domain control films 214 and 215, a ferromagnetic film having a coercive force of 1 kOe or more is preferable in order to prevent the influence of an external disturbance magnetic field. Although the thickness and material of the hard ferromagnetic film are not particularly limited, a product of the thickness t of the hard ferromagnetic film and the residual magnetic flux density Br to generate a bias magnetic field of a predetermined magnitude. t · Br needs to be a predetermined size. For this reason, a Co-based alloy is desirable as a material, and CoPt, CoPtCr, CoPtTa,
CoCrTa, CoPtTaCr, and the like are preferable because a high coercive force can be obtained even with a small film thickness.

An underlayer may be formed to increase the coercive force of these hard ferromagnetic films. These hard ferromagnetic films basically have a close-packed hexagonal crystal structure, and the axis of easy magnetization is the C-axis. Therefore, in order to efficiently apply a bias magnetic field in the in-plane direction of the film, it is preferable to set the C axis in the in-plane direction. In that case, some underlayer may be provided. By forming the underlayer, the coercive force can be further increased. The underlayer is preferably made of a material having the same lattice constant as that of the Co-based alloy. Among them, Cr, Mo, W, Ta, Zr and alloys thereof having a body-centered cubic structure are preferable.

When an antiferromagnetic film is used as the magnetic domain control films 214 and 215, an exchange bias magnetic field is generated by exchange coupling with the first ferromagnetic film 211. In order to generate a large exchange bias magnetic field, to achieve good flatness at the ferromagnetic layer / antiferromagnetic layer interface; and
It is important to suppress the formation of the mixing layer.

As the antiferromagnetic material, there are a metal material and an oxide material. As the metal antiferromagnetic material, FeMn, Ni
It is preferable to use a Mn-based alloy such as Mn or a Cr-based alloy such as CrAl or CrSb. In addition, as an oxide-based antiferromagnetic material, Ni
O, CoO, Fe ₂ O ₃ or the like may be used. Particularly preferred is a Mn-based antiferromagnetic material, which can provide a large exchange bias magnetic field. However, some Mn-based alloys cannot be obtained unless epitaxial growth is performed on a ferromagnetic film such as NiFe. In this case, as shown in FIGS. 5 and 6, an antiferromagnetic film is used. Magnetic domain control film 21
It is desirable that the first and second ferromagnetic tunnel junctions 4 and 215 be in contact with the first ferromagnetic film 211 which is to be brought into a single magnetic domain state. Alternatively, as shown in FIG. 7, a first ferromagnetic film 211 may be provided on the magnetic domain control films 214 and 215.

<Magnetization fixing means> Ferromagnetic tunnel junction 2
The change in magnetoresistance of 1 depends on the relative angle of magnetization of the first ferromagnetic film 211 and the second ferromagnetic film 212. Therefore,
In order to obtain a high output with a small magnetic field and a good symmetry waveform like a magnetic head, the magnetization direction M1 of the first ferromagnetic film 211 and the magnetization direction M2 of the second ferromagnetic film 212
It is desirable that they are not parallel to each other when the externally applied magnetic field is zero.

The easy axis of the first ferromagnetic film 211 which is a free ferromagnetic film is perpendicular to the external magnetic field, and the easy axis of the second ferromagnetic film 212 which is a pinned ferromagnetic film is parallel. There are the following two means for directing in such a manner.

The first magnetization fixing means uses a soft ferromagnetic film having a low coercive force for the first ferromagnetic film 211 which is a free ferromagnetic film and a second ferromagnetic film 212 which is a pinned ferromagnetic film. This method uses a hard magnetic film having a high coercive force.

FIG. 8 shows a case where the first magnetization fixing means is employed, that is, a soft ferromagnetic film having a low coercive force is used for the free ferromagnetic film, and a hard ferromagnetic film having a high coercive force is used for the pinned ferromagnetic film. It is a figure which shows the magnetic field-magnetoresistance (MR) change rate characteristic at the time of using. In FIG. 8, two arrows shown in a circle indicate the direction of magnetization of the first ferromagnetic film 211 and the direction of magnetization of the second ferromagnetic film 212, respectively. When the applied magnetic field H is gradually increased from a value lower than the magnetic field (-H2), the free ferromagnetic film 211 having a low coercive force undergoes magnetization reversal by the magnetic field (+ H1). When the applied magnetic field H is further increased, the pinned ferromagnetic film 212 having a high coercive force is magnetized by the magnetic field (+ H2). Similarly, the applied magnetic field H is
As the magnetic field is gradually decreased from a value higher than the magnetic field H2, the ferromagnetic films 211 and 212 are changed by the magnetic fields (-H1) and (-H2).
Undergoes magnetization reversal.

Within the range where the applied magnetic field H satisfies | H1 | <H <| H2 |, the direction of magnetization of the first ferromagnetic film 211 and the direction of the second
The magnetization directions of the ferromagnetic films are antiparallel, and the magnetization directions are parallel when the applied magnetic field H is in the range of | H1 |> H and H> | H2 |. 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.
The ratio (ΔR / Rs) of the resistance value Rs when the magnetization direction is parallel to the resistance change ΔR when the magnetization direction changes from antiparallel to parallel (MR / Rs) becomes the MR change rate. Can be detected.

The second magnetization fixing means comprises the first ferromagnetic film 2
11 and the second ferromagnetic film 212 are both made of a soft ferromagnetic film, and a pinned ferromagnetic film is laminated on the second ferromagnetic film 212 with a fixed magnetization film.
This is a method of fixing the direction of magnetization. FIG. 9 shows the case where the second magnetization fixed means is adopted, that is, both the free ferromagnetic film and the pinned ferromagnetic film use a soft ferromagnetic film, and the magnetization fixed film is adjacent to the pinned ferromagnetic film. It is a figure which shows the magnetic field-MR change rate characteristic at the time of lamination. In the vicinity of zero magnetic field, only the free ferromagnetic film reverses magnetization, and the pinned ferromagnetic film exchange-coupled to the fixed magnetization film does not reverse magnetization. When the magnetic field is further increased and pinning cannot be performed by exchange coupling, the magnetization of the pinned ferromagnetic film is also reversed. In this case, the magnetic field H is + H5 <
A high MR ratio can be obtained in the range of H <+ H6.

Next, a specific example of the magnetization fixing means for satisfying the above requirements will be described.

As the magnetization fixed film 216, either a hard ferromagnetic film having a high coercive force or an antiferromagnetic film can be used. When a hard ferromagnetic film is used as the magnetization fixed film 216, the magnetization fixed film 216 and the second ferromagnetic film 212 are used.
The exchange coupling between the ferromagnetic film and the ferromagnetic film occurs between
The magnetization direction of the ferromagnetic film 212 is fixed, and the ferromagnetic film 212 becomes a pinned ferromagnetic film. When an antiferromagnetic film is used as the magnetization fixed film 216, exchange coupling between the magnetization fixed film 216 and the second ferromagnetic film 212 occurs due to the antiferromagnetic film-ferromagnetic film, and the second strong magnetic film is formed. The magnetization direction of the magnetic film 212 is fixed, and the magnetic film 212 becomes a pinned ferromagnetic film.

As the hard ferromagnetic film, a Co alloy, for example, CoPt, CoPtCr, CoPtTa, CoCrTa, CoPtTaCr or the like can be used. As the antiferromagnetic film, a metal antiferromagnetic material or an oxide antiferromagnetic material can be used. An example of a metallic antiferromagnetic material is a Mn alloy. Available Mn alloys include FeMn, NiMn, PtMn, RuMn, RhM
n, IrMn, PdMn and alloys thereof. Examples of oxide-based antiferromagnetic materials include NiO, NiCoO, Fe ₂ O ₃ ,
CoO.

FIG. 10 is a sectional view showing another example of the ferromagnetic tunnel junction 21 in the magnetoresistive element according to the present invention, FIG. 11 is a sectional view taken along line 11-11 of FIG. 10, and FIG. 10 is a cross-sectional view taken along line 12-12 of FIG. 10, and FIG. 13 is a view for explaining the operation of the tunnel junction of the magnetoresistive element shown in FIGS. In the drawings, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the second ferromagnetic film 212 is a free ferromagnetic film, and the first ferromagnetic film 211 is a pinned ferromagnetic film. At both ends of the second ferromagnetic film 212, magnetic domain control films 214 and 215 to be magnetic domain control films are formed. The first ferromagnetic film 211 is formed such that the easy axis of magnetization is parallel to the externally applied magnetic field H, and the easy axis of magnetization of the second ferromagnetic film 212 is vertical. In this case, the magnetization M1 of the first ferromagnetic film 211 is fixed with respect to the external magnetic field H, and the magnetization direction M2 of the second ferromagnetic film 212 can be freely changed with respect to the external magnetic field H. In this case, the same operation and effect as those of the embodiment shown in FIGS.

FIG. 14 is a sectional view showing another example of the ferromagnetic tunnel junction 21 of the magnetic head according to the present invention, FIG. 15 is a sectional view taken along line 15-15 of FIG. 14, and FIG. FIG. 17 is a cross-sectional view taken along line 16-16. In this example,
A fixed magnetization film 216 is provided on the surface of the second ferromagnetic film 212. Therefore, the second ferromagnetic film 212 becomes a pinned ferromagnetic film, and the first ferromagnetic film 211 becomes a free ferromagnetic film.
Although not shown, the magnetization fixed film 216 may be provided on the first ferromagnetic film 211. In this case, the first ferromagnetic film 211 becomes a pinned ferromagnetic film, and the second ferromagnetic film 212 becomes a free ferromagnetic film.

FIG. 17 is a diagram for explaining the operation of the tunnel junction of the magnetoresistive element shown in FIGS.
In the embodiment, when the applied magnetic field is zero, the direction of magnetization M1 of the first ferromagnetic film 211 is perpendicular to the magnetic field H to be applied, and the direction of magnetization M of the second ferromagnetic film 212 is M.
2 is fixed in a direction parallel to the magnetic field H to be applied. In this state, when a magnetic field H is applied from a magnetic recording medium such as a magnetic disk or the like, the magnetization direction M2 of the second ferromagnetic film 212 pinned by the magnetization fixed film 216 does not change, but the first magnetization direction M2 does not change. The direction M1 of the magnetization of the ferromagnetic film 211 changes, for example, by the angle θ. This produces a magnetoresistance effect.

Thus, a relative angle change is caused between the two ferromagnetic films 211 and 212 with respect to the direction of the magnetization only by the motion of the magnetization of the first ferromagnetic film 211 which is a free ferromagnetic film. be able to. In this case, the external magnetic field H
In contrast, the pinned ferromagnetic film in which the easy axis of magnetization of the first ferromagnetic film 211 constituting the free ferromagnetic film in which the direction of the magnetization M1 freely changes becomes perpendicular and the direction of the magnetization M2 is fixed. Is preferably set so that the axis of easy magnetization of the second ferromagnetic film 212 constituting the above is parallel. By doing so, the magnetization direction of the first ferromagnetic film 211, which is a free ferromagnetic film, changes in the magnetization rotation mode due to the external magnetic field, so that high MR sensitivity is obtained and smooth magnetization reversal is performed. In addition, generation of Barkhausen noise due to domain wall movement can be reduced.

<Insulating Film> The first ferromagnetic film 211 and the second
The insulating film 210 provided between the ferromagnetic films 212 has a very important role to obtain a high MR ratio with good reproducibility and to simplify the structure of a magnetoresistive element such as a magnetic head. Is responsible for. In particular, when the barrier potential of the insulating film 210 is set in the range of 0.5 to 3 eV, a high MR ratio can be obtained with good reproducibility, and the structure of the magnetoresistive element can be simplified. Next, this point will be described.

In the ferromagnetic tunnel junction, while the electron e maintains the spin direction, the first ferromagnetic film 211
When passing through the second ferromagnetic film 212 via the insulating film 210, 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, The tunnel conductance G is expressed as G = G ₀ ′ (1 + P ₁ ′ · P ₂ ′) COS θ. _{Here, 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 ′: wave numbers K _{1 電子} , K _{1 ↓} , K ₂ of electrons in both ferromagnetic layers
_↑, K _{2 ↓} and constants alpha ₁ determined by the height of the barrier potential, alpha _2: coefficient P ₁ which depends on the height of the barrier potential ', P _2': effective spin polarization P of the two ferromagnetic films 1,2 ₁ , P ₂ : the spin polarizations of the ferromagnetic films 1 and 2 (fractions of the effective spin polarizations P ₁ ′ and P ₂ ′). Change rate of tunnel conductance ΔG / G
₀ is ΔG / G ₀ = 2 · P ₁ ′ · P ₂ ′. The rate of change ΔG / G ₀ of the tunnel conductance is synonymous with the rate of change of MR.

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 polarizations P ₁ ′ and P ₂ ′ of both ferromagnetic films 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 ′ approach the spin polarizations P ₁ and P ₂ , and a high MR change rate is obtained.

When 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 that the barrier potential is set to 0.
It is presumed that by maintaining the range of 5 to 3 eV, the uniformity is good and the formation of the insulating film 210 with very few pinholes is guaranteed.

Particularly favorable results were obtained when the barrier potential was in the range of 1.5 to 2.5 eV.

When the barrier potential is in the range of 1.5 to 2.5 eV, the first ferromagnetic film 211 and the second ferromagnetic film 21
It is presumed that stable antiferromagnetic coupling occurs between the layer 2 and the insulating layer 210 via the insulating film 210.

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, it is impossible to obtain the high MR ratio expected in this type of ferromagnetic tunnel junction. The reason is presumed to be that the uniformity of the insulating film 210 deteriorates and pinholes increase.

Next, when the barrier potential is 0.5 to 3 eV
The possibility that stable antiferromagnetic coupling can be generated between the first ferromagnetic film 211 and the second ferromagnetic film 212 via the insulating film 210 in the range where A great advantage is obtained when the bonding is used for a read magnetic transducer of a magnetic head.

FIG. 18 is a graph showing the relationship between the magnetic field and the magnetoresistance ratio when antiferromagnetic coupling occurs. As shown in FIG. 18, when antiferromagnetic coupling occurs, the magnetic field-magnetoresistive curves L1 and L2 are in a region ΔH near zero magnetic field, and M
The R change rate shows the highest value. Therefore, when this ferromagnetic tunnel junction is used as a magnetic transducer for reading a magnetic head, there is no need to apply a bias magnetic field, and the diamagnetism due to the element shape and the effect of the magnetic domain control film cause a linear region near zero magnetic field. can get. Therefore, the structure of the magnetic head can be simplified.

An example of the insulating film 210 that can secure the above barrier potential is an aluminum oxide film that has been annealed at 40 to 100 ° C. in the air. In such an aluminum oxide film, a bridge between the upper and lower ferromagnetic films 211 to 212 cannot be formed because metal aluminum is not locally present, and as a result, a ferromagnetic tunnel having an extremely thin insulating film 210 having a high barrier potential is formed. Joining can be realized.

As another example of the insulating film 210, a diamond-like carbon film (hereinafter, referred to as a DLC film) is also effective for realizing an extremely thin insulating film 210 having a high barrier potential. is there. In particular, even if the DLC film formed by the plasma CVD method has a very small thickness of several tens of millimeters, a good insulating film 210 having no pinhole can be obtained.

Note that M. Pomerantz, JCSloczewski and
The intermediate C film disclosed by E. Spiller et al. Is an amorphous-C film produced by the MBE method and is different from the DLC film produced by the plasma CVD method. Specifically, the amorphous-C film is a film in which carbon is bonded to each other in a network. However, the DLC film of the present invention has carbon and hydrogen bonded to each other in a network. Are different.

Next, the junction area of the ferromagnetic tunnel junction 21 and the insulating film 210 will be described with reference to examples.

Example 1 In the manufacturing method, the insulating film 210 made of an aluminum oxide film was formed by heat-treating an aluminum film at 60 ° C. for 24 hours in the air. The junction area of the ferromagnetic tunnel junction is 0.25 to 25
It was set to 00 μm ² .

Twenty ferromagnetic tunnel junctions each having the above-described junction area were formed, 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, as the first ferromagnetic film 211, a Ni ₈₀ Fe ₂₀ film having a thickness of 10 nm is formed by RF sputtering, and the resist is subjected to a fine processing technique of resist photolithography, Ar ion milling, and resist stripping. It was patterned in a rectangular shape of 0.5 to 50 μm × 0.5 mm.

After that, resist patterning is performed to remove the surface oxide film of the Ni ₈₀ Fe ₂₀ film constituting the first ferromagnetic film 211 by reverse sputtering, and then the film thickness is 5 nm by electron beam heating vacuum evaporation. Was formed.

Thereafter, the sample was taken out of the vacuum evaporation apparatus and subjected to a heat treatment at 60 ° C. for 24 hours in the air, and then an insulating film 210 made of an aluminum oxide film was formed through a lift-off process.

Next, after resist patterning is performed again, a second ferromagnetic film 212 having a film thickness of 100 nm is formed.
An o film is formed by an RF sputtering method, and subsequently, a 0. 0 in the direction perpendicular to the first ferromagnetic film 211 through a lift-off process.
A second ferromagnetic film 212 having a rectangular pattern of 5 to 50 μm × 0.5 mm was formed. As a result, the bonding area is reduced to 0.
A ferromagnetic tunnel junction of 25 to 2500 μm ² was obtained.

For comparison, a Ni ₈₀ Fe ₂₀ / aluminum oxide / Co ferromagnetic tunnel junction in which a conventionally used native aluminum oxide film (after being formed and left in the air for 24 hours) is used as the insulating film 210 is the same. Prepared.

The first example employed in the examples and comparative examples
The conditions for forming the ferromagnetic film 211 and the second ferromagnetic film 212 are as follows. The aluminum film is
It was produced at an ultimate pressure of 3 × 10 ⁻⁵ Pa and a deposition rate of 0.05 nm / sec.

<Ferromagnetic Film Deposition Conditions> Ultimate pressure: 1 × 10 ⁻⁵ Pa Target: Ni-20 at% Fe (4 inch φ) Sputter gas: Ar 5 sccm Sputter pressure: 0.5 Pa Input power: 150 W Narumakure - _{DOO: Ni 80 Fe 20, 45nm /} min, Co 40nm / min substrate temperature: water cooling for the samples prepared in this manner was measured magnetoresistive (MR) curve by a DC 4-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. 19 shows a junction area 50 × 50 according to the present invention.
3 shows a magnetoresistance curve of a μm ² ferromagnetic tunnel junction. When the applied magnetic field is made larger than -1 kOe, at +5 Oe, the magnetization reversal of the first ferromagnetic film 211 occurs, and the spins of the first ferromagnetic film 211 and the second ferromagnetic film 212 become antiparallel. Therefore, the electric resistance increases. The barrier potential was determined to be 0.5 eV, and a similar MR curve was obtained in 16 of the 20 fabricated devices. The MR ratio was 6.6 to 8.1%, the average value of the MR ratio was 7.6%, and the variation ratio was ± 7%.

On the other hand, the natural aluminum oxide film is
In the ferromagnetic tunnel junction of Comparative Example having a barrier potential of 10, a barrier potential of only 0.2 eV was obtained. In addition, only four MR curves could be observed, the average MR change rate was as low as 1.5%, and the average value variation was as very large as ± 88%. 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, the aluminum oxide film formed by the heat treatment at 60 ° C. in the air was replaced with the insulating film 210.
As a result, a high barrier potential of 0.5 to 3 eV and a high MR change rate can be obtained, and further, there is little variation 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, 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 in the range of 30 to 250 ° C. as an insulating film 210, when the heat treatment was performed at 40 to 100 ° C. It was found that the rate of change was obtained, the variation was small, and a high yield was obtained.

<Embodiment 2> The first ferromagnetic film 211 is made of Co.
-50% at, and the second ferromagnetic film 212 has C
o and the insulating film 210 were composed of a DLC film. Co
_{A 50} Fe ₅₀ / DLC / Co ferromagnetic tunnel junction is formed, the first ferromagnetic film 211 has a thickness of 10 nm, and the second ferromagnetic film 212 has a thickness of 10 nm.
Was 5 nm in thickness. The bonding area is 0.25 to 2500μ
It was m ^2. First ferromagnetic film 211 and second ferromagnetic film 2
12 was produced in the same manner as in Example 1. Insulating film 210
Was formed to a film thickness of 5 nm by a plasma CVD method and 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 film 210 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 clear from Table 2, plasma CVD
It can be seen that, by using the DLC film manufactured by the method as the insulating film 210, a high barrier potential and a high MR change rate can be obtained, and further, there is little variation and a high yield can be obtained. For example, for a sample having a bonding area of 50 × 50 μm ² according to the present embodiment, 20
The MR curve was obtained for 15 of the pieces. The average value of the MR change rate was 18.9%, and the variation of the change rate was ± 12%. Further, as in Example 1, the yield was particularly high when the barrier potential was 1.5 to 2.5 eV. On the other hand, in the ferromagnetic tunnel junction of the comparative example using the natural aluminum oxide film as the insulating film 210, the barrier potential is small, and only five MR curves can be observed.
The average rate of change was as low as 3.3%, and the variation was as large as ± 88%.

Next, the relationship between the junction area and the switching 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 film 210, and thus 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.

Further, it was found that the magnetic field Hab shown in FIG. 19, that is, the magnetic field in which the magnetization of the first ferromagnetic film 211 is reversed shifts in the negative direction. In particular, when the bonding area is 1
Less than 0 μm ² and barrier potential of 1.5 to 2.5
In the case of eV, the first ferromagnetic film 211 and the second
Are in an antiparallel state. This indicates that an antiferromagnetic coupling force is acting between the two magnetic films. When the junction area is smaller than 10 μm ² , a high MR ratio and a high yield were obtained because the insulating film 210 having a uniform and very few pinholes was used, and by reducing the junction area, the two magnetic films were formed. It is considered that antiferromagnetic coupling occurred between them. Example 1
-7 and Example 2-8, the bonding area was 10 μm.
If the barrier potential is greater than 2.5 eV even at m ² or less, an antiferromagnetic junction cannot be obtained between the two magnetic films, and the yield will slightly decrease.

<Combined Use of Fixed Magnetization and Domain Control> FIG.
In the embodiment shown in FIG. 17, the magnetization fixed film 216 is provided on the second ferromagnetic film 212 and the first ferromagnetic film 2
Magnetic domain control films 214 and 215 are provided at both ends of the magnetic field control device 11. Therefore, both the action of controlling the magnetic domain and the action of fixing the magnetization can be obtained.

Next, an example in which the ferromagnetic tunnel junction according to the present invention is applied to a magnetic head will be described.

FIG. 20 is a perspective view of a magnetic head according to the present invention. In the figures, the dimensions are exaggerated. The illustrated magnetic head according to the present invention includes a slider 1, a magnetic transducer using a ferromagnetic tunnel junction (hereinafter referred to as a ferromagnetic tunnel junction magnetic transducer) 2, and an inductive magnetic transducer 3. including. The slider 1 has rails 11 and 12 on the medium facing surface side, and the surfaces of the rails 11 and 12 constitute air bearing surfaces 13 and 14. The number of rails 11 and 12 is not limited to two. It may have one to three rails and may be a flat surface without rails. In addition, various geometrical shapes may be added to an air bearing surface (hereinafter, referred to as an ABS surface) in order to improve flying characteristics. The present invention can be applied to any type of slider.

The magnetic transducers 2 and 3 include rails 11 and 1
One or both of them are provided at the end of the medium moving direction a1. The medium moving direction a1 coincides with the outflow direction of air that moves when the medium moves at high speed. At the end face of the slider 1 in the medium moving direction a1, extraction electrodes 41 and 42 connected to the ferromagnetic tunnel junction type magnetic conversion element 2 and extraction electrodes 43 and 44 connected to the magnetic conversion element 3 are provided.

FIG. 21 is an enlarged sectional view of a magnetic transducer element of the magnetic head shown in FIG. The ferromagnetic tunnel junction type magnetic transducer 2 is a reproducing element, and the inductive magnetic transducer 3 is a writing element. The ferromagnetic tunnel junction type magnetic conversion element 2 and the induction type magnetic conversion element 3 are laminated on an insulating film 102 provided on a ceramic base 101 constituting the slider 1. Ceramic base 101
Is usually composed of Al ₂ O ₃ —TiC. Since Al ₂ O ₃ -TiC is conductive, for example, Al ₂ O 3
_An insulating film 102 of ₃ is attached. When the ceramic base 101 has a high insulating property, the insulating film 102 can be omitted.

FIG. 22 is an enlarged sectional view of a portion of the ferromagnetic tunnel junction type magnetic transducer 2, FIG. 23 is an enlarged perspective view thereof, and FIG. 24 is a sectional view taken along line 24-24 in FIG. The ferromagnetic tunnel junction type magnetic transducer 2 has a structure of the ferromagnetic tunnel junction 21 that is substantially the same as the magnetoresistive element shown in FIGS. That is, the ferromagnetic tunnel junction type magnetic transducer 2 includes the ferromagnetic tunnel junction 21 and the electrode films 22 and 23 and is supported by the insulating support films 24 and 25 which constitute a part of the slider 1. The ferromagnetic tunnel junction 21 includes an insulating film 210
, A first ferromagnetic film 211, and a second ferromagnetic film 212. The first ferromagnetic film 211 and the second ferromagnetic film 212 are stacked via an insulating film 210. The magnetic domain control films 214 and 215 are provided adjacent to both ends of the first ferromagnetic film 211.

The electrode films 22 and 23 are the first electrode film 22
And a second electrode film 23. First electrode film 2
2 is connected to the first ferromagnetic film 211 and the second electrode film 2
Reference numeral 3 is connected to the second ferromagnetic film 212.

The first electrode film 22 and the second electrode film 23 are provided so as not to be exposed on the ABS 13 (or 14). As a specific means, in the embodiment, in the embodiment, the front end surface of the ferromagnetic tunnel junction 21 is formed by the ABS 13
(Or 14) and the first electrode film 22
In addition, the second electrode film 23 is set back from the ABS 13 (or 14) at the tip end surface of the ferromagnetic tunnel junction 21 by a distance D1.

The ferromagnetic tunnel junction type magnetic transducer 2 comprises
The lower magnetic shield film 51 and the upper magnetic shield film 52 are disposed inside the insulating support films 24 and 25. The lower magnetic shield film 51 is formed of the ceramic base 10.
1 and the insulating support film 24 is attached on the lower magnetic shield film 51.

As described above, the ABS 13 (or 1)
4) By forming a structure in which the first electrode film 22 and the second electrode film 23 are not exposed, the lower magnetic shield film 51 and the upper magnetic shield film 52 and the ferromagnetic tunnel junction type magnetic transducer 2, particularly, It has been found that electrostatic breakdown hardly occurs between the first electrode film 22 and the second electrode film 23, and the withstand voltage is improved.

Further, the lower magnetic shield film 51 and the upper magnetic shield film 5 on the ABS 13 (or 14)
2 and the ferromagnetic tunnel junction 21 serving as a magnetic sensing part can be narrowed, so that high-density recording and reproduction can be performed as compared with the related art.

FIG. 21 shows a composite magnetic head having a ferromagnetic tunnel junction type magnetic transducer 2 serving as a reproducing element and an inductive magnetic transducer 3 serving as a writing element. The inductive magnetic transducer 3 includes a lower magnetic film 52, an upper magnetic film 32, and a coil film 3, which also serve as an upper magnetic shield film for the ferromagnetic tunnel junction magnetic transducer 2.
3, a gap film 34 made of alumina or the like, an insulating film 35 made of an organic resin such as a novolak resin, and a protective film 36 made of alumina or the like. The tip portions of the lower magnetic film 52 and the upper magnetic film 32 are opposed to each other with a gap film 34 having a small thickness therebetween.
The lower pole part P1 and the upper pole part P2
The writing is performed in. The lower magnetic film 52 and the upper magnetic film 32 are coupled to each other so as to complete a magnetic circuit at a back gap portion whose yoke portion is on the opposite side of the lower pole portion P1 and the upper pole portion P2.
A coil film 33 is formed inside the insulating film 35 so as to spiral around the joint of the yoke. Both ends of the coil film 33 are electrically connected to the extraction electrodes 43 and 44. The number of turns and the number of films of the coil film 33 are arbitrary.

FIG. 25 shows another embodiment of the ferromagnetic tunnel junction type magnetic transducer. In the ferromagnetic tunnel junction type magnetic conversion element 2 shown in the embodiment, the structure of the ferromagnetic tunnel junction 21 is substantially the same as the magnetoresistance effect element shown in FIGS. . That is, the ferromagnetic tunnel junction 21 includes the insulating film 210, the first ferromagnetic film 211, and the second ferromagnetic film 212.
The first ferromagnetic film 211 and the second ferromagnetic film 212 are stacked via an insulating film 210. Magnetic domain control film 21
Reference numerals 4 and 215 are provided adjacent to both ends of the second ferromagnetic film 212.

FIG. 26 is an enlarged sectional view of a portion of the ferromagnetic tunnel junction type magnetic conversion element 2 when the magnetization fixed film 216 is provided, and FIG. 27 is an enlarged perspective view thereof. In the drawings, the same components as those in FIGS. 22 to 24 are denoted by the same reference numerals, and description thereof will be omitted. In the embodiment, the ferromagnetic tunnel junction type magnetic transducer 2 includes a ferromagnetic tunnel junction 2.
The structure 1 is substantially the same as the magnetoresistive element shown in FIGS. That is, the ferromagnetic tunnel junction type magnetic transducer 2 includes the ferromagnetic tunnel junction 21 and the electrode films 22 and 23 and is supported by the insulating support films 24 and 25 which constitute a part of the slider 1. The ferromagnetic tunnel junction 21 includes an insulating film 210, a first ferromagnetic film 211, and a second ferromagnetic film 212. First ferromagnetic film 211 and second ferromagnetic film 212
Are stacked with the insulating film 210 interposed therebetween. The magnetic domain control films 214 and 215 are provided adjacent to both ends of the first ferromagnetic film 211. The magnetization fixed film 216 is provided on the second ferromagnetic film 212.

The electrode films 22 and 23 are the first electrode film 22
And a second electrode film 23. First electrode film 2
2 is connected to the first ferromagnetic film 211 and the second electrode film 2
Reference numeral 3 is connected to the second ferromagnetic film 212 via the magnetization fixed film 216. Next, an example in which the ferromagnetic tunnel junction according to the present invention is applied to a magnetic head using a magnetoresistive film will be described.

<Embodiment 3> A reproducing magnetoresistive magnetic head provided with a magnetic domain control film using the Ni ₈₀ Fe ₂₀ / thermally oxidized alumina film / Co ferromagnetic tunnel junction according to the embodiment 1 as a magnetoresistive film, A non-magnetic head was manufactured, a recording signal written on a magnetic recording medium was read, and reproduction characteristics were compared. In this embodiment, the first ferromagnetic film 211 is made of Ni ₈₀ Fe
₂₀ film, the intermediate insulating film 210 thermally oxidized alumina layer, the second ferromagnetic film 212 and the Co film, each film thickness, Ni ₈₀ Fe ₂₀
The film thickness is 20 nm, the alumina oxide film is 5 nm, and the Co film thickness is 5 nm.
I tried to be. Next, a method for manufacturing a magnetic head will be described. First, a 30 μm-thick alumina insulating film 10
A 2 μm thick sendust film is formed as a lower magnetic shield film 51 on the Al ₂ O ₃ —TiC substrate 101 (not shown) on which DC 2 has been formed using a DC sputtering method. A predetermined shape was formed by etching.

Next, an alumina film having a film thickness of 80 nm is formed thereon by RF sputtering as a lower insulating support film 24. Subsequently, as a first electrode film 22, after resist patterning, Ta (10 nm) is formed. ) / Cu (100nm) / Ta (1
0 nm) was formed by a DC sputtering method, and processed into a predetermined shape by a lift-off method.

Next, a first ₈₀ nm-thick Ni ₈₀ Fe ₂₀ film was used.
Ferromagnetic film 211, an intermediate insulating film 210 made of a thermal oxide alumina film having a thickness of 5 nm, and a second insulating film 210 made of a Co film having a thickness of 5 nm.
The ferromagnetic tunnel junction 21 in which the ferromagnetic films 212 are stacked is formed. For the formation of the ferromagnetic tunnel junction, a combined sputtering / electron beam evaporation film forming apparatus capable of continuously forming the sputtered film and the vapor-deposited film without exposing to the atmosphere was used. Next, formation of a ferromagnetic tunnel junction will be described.

First, after resist patterning on the first electrode film 22, Ni ₈₀ Fe is used as the first ferromagnetic film 211.
₂₀ (film thickness: 20 nm) was formed by film formation in a magnetic field by RF sputtering. Subsequently, a 5 nm-thick aluminum film was continuously formed by electron beam evaporation without being exposed to the air. After that, heat treatment was performed at 60 ° C. for 24 hours in the air, and then an insulating film 210 made of a thermal aluminum oxide film was formed through a lift-off process. Then, a resist is patterned on the entire surface excluding the portions where the magnetic domain control films 214 and 215 are formed, and unnecessary Ni ₈₀ Fe ₂₀
(20 nm) / The aluminum oxide film (5 nm) was removed by Ar ion etching. Then, an underlayer Ti ₁₀ W ₉₀ (5 nm) / hard ferromagnetic layer Co ₈₀ Pt ₂₀ (15 nm) is used as a magnetic domain control film.
The magnetic domain control films 214 and 215 were formed by forming a film by the C sputtering method and removing the resist by the lift-off method. Thereafter, resist patterning was performed again, and the first ferromagnetic film 211, the intermediate insulating film 210, and the magnetic domain control films 214 and 215 were processed into predetermined shapes by Ar ion etching and resist peeling.

Next, in order to form the insulating film 213 for preventing short circuit, a resist cover is formed on the ferromagnetic tunnel junction 21 to be formed, and the alumina insulating layer is formed by RF sputtering.
After forming the film (layer thickness: 50 nm), the resist was lifted off to form an insulating film 213 for preventing short circuit. The insulating film 213 for short-circuit prevention makes the ferromagnetic tunnel junction portion 21 have a prescribed size so that a tunnel current does not flow in portions other than the ferromagnetic tunnel junction portion 21.
Insulation between the first electrode film 23 and the first ferromagnetic film 21
It is provided to insulate the first and second ferromagnetic films 212.
Then, resist patterning is performed to form a second ferromagnetic film 212, and a film thickness of 10
A Co film of nm was formed in a magnetic field by an RF sputtering method, and a second ferromagnetic film 212 was formed by a lift-off method. At this time, the direction of the applied magnetic field when forming the second ferromagnetic film is the first direction.
And in the direction perpendicular to the time when the ferromagnetic film was formed.

Next, the magnetization fixed layer 216 and the second electrode film 2
The resist patterning is performed to form
The oxide layer on the surface of the Co film, which is a ferromagnetic film, is removed by reverse sputtering, so that the final second ferromagnetic film 212 has a thickness of 5
nm, followed by PtMn (15 nm) / Ta (10 n
m) / Cu (100 nm) / Ta (10 nm) films were continuously formed by DC sputtering, and the PtMn magnetization fixed layer 216 and the second electrode film 23 were formed by lift-off. Note that Ta (10 nm) was formed as an oxidation preventing layer during the process.

Next, a film thickness of 80 was formed by RF bias sputtering.
A nanometer alumina film was formed, and an upper insulating support film 25 was formed. Next, a NiFe film (thickness: 2 μm) was formed as an upper magnetic shield film 52 by DC sputtering, and was patterned into a predetermined shape by photolithography and etching techniques.
Finally, after a Cu pump electrode film was formed by a plating method, a 30-μm-thick alumina film was covered as a protective film.
Then, the ferromagnetic tunnel junction 21 was exposed to the ABS by processing and polishing to a predetermined size. As described above, a reproducing magnetoresistive head having a junction area of 1 μm in width and 1 μm in length was obtained. That is, the track width of the magnetic head was 1 μm, the MR height was 1 μm, and the MR shield interval was 0.19 μm.

In the magnetic head having no magnetic domain control film, the first ferromagnetic film 211 and the insulating film 210 are formed into a predetermined shape by a lift-off method, and then the short-circuit preventing insulating film 213 is formed.
Is formed in a similar manner. Other processes are the same as the case of providing the magnetic domain control film.

The MR curve and output waveform of the magnetoresistive head for reproduction manufactured as described above were examined. FIG. 28 shows the MR curve (measured magnetic field: ± 40 Oe) of the magnetic head provided with the magnetic domain control film, and FIG. 29 shows the MR curve of the magnetic head not provided with the magnetic domain control film. As can be seen from the figure, the magnetic head provided with the magnetic domain control film can obtain a smooth MR curve, whereas the magnetic head without the magnetic domain control film provides an unstable MR curve in which hysteresis and stepwise changes are observed. It became.

FIG. 30 shows an output waveform of a magnetic head provided with a magnetic domain control film, and FIG. 31 shows an output waveform of a magnetic head not provided with a magnetic domain control film. As shown in FIG. 31, the magnetic head without a magnetic domain control film is unstable due to a change in the baseline or the output amplitude and has a large noise. By doing so, a stable output waveform is obtained as shown in FIG.

From the above results, it can be seen that by providing the magnetic domain control film, a stable and noise-free MR curve or output waveform can be obtained.

<Embodiment 4> Next, characteristics of the magnetic head according to the present invention and a conventional AMR magnetic head were examined.

<Magnetic Head of the Present Invention>
A magnetic head using a Fe / DLC / Co ferromagnetic tunnel junction as a magnetoresistive film was fabricated, read sensitivity and read output were examined, and compared with a conventional magnetic head using a NiFe film (AMR) as a magnetoresistive film. . Regarding the film configuration of the ferromagnetic tunnel junction, the first ferromagnetic film 211 is Co-50 at% Fe, the second ferromagnetic film 212 is a Co film, and the intermediate insulating film 210 is a D-type.
An LC film was obtained. At this time, the thickness of the first ferromagnetic film 211 was 15 nm, the thickness of the second ferromagnetic film 212 was 20 nm, and the thickness of the intermediate insulating film 210 was 5 nm.

Next, a method for manufacturing a magnetic head will be described. The ferromagnetic tunnel junction was formed by the method described in the second embodiment, and the other steps were the same as in the third embodiment, up to the formation of the upper magnetic shield film. The thickness of the lower insulating support film 24 is 100
nm, and the thickness of the upper insulating support film 25 is 120 nm.
The shield interval was 0.26 μm. The track width and the MR height of the ferromagnetic tunnel junction conversion element were each set to 1 μm.

Thereafter, as shown in FIG. 21, an inductive magnetic transducer element serving as a write element was formed on the upper magnetic shield film. As described above, the magnetic head using the ferromagnetic tunnel junction as the magnetoresistive film was manufactured.

<Conventional AMR Magnetic Head: Comparative Example> For comparison, a track width of 1 μm, an MR height of 1 μm, and an MR magnetic head using a SAL bias type NiFe film as a magnetoresistive film.
A magnetic head having a gap interval of 0.26 μm was also manufactured. The fabrication method is described below. The structure up to the lower insulating support film 24 is the same as that of the magnetic head using the ferromagnetic tunnel junction of the present invention.
After forming the lower insulating support film 24, first, a Ni ₇₃ Fe ₁₈ Rh ₉ film (10 nm thick) as a SAL film and Ta as a magnetic separation film.
Film (film thickness 8 nm), MR film Ni ₈₀ Fe ₂₀ (film thickness 17 nm),
A Ta film (film thickness: 5 nm) was sequentially laminated as a protective film by DC sputtering, and processed into a predetermined shape by photolithography and etching. After that, Ti ₁₀ W as a domain control film
₉₀ (10 nm) / Co ₈₀ Pt ₂₀ (50 nm), Ta (1
0 nm) / Cu (100 nm) / Ta (10 nm) were formed by a DC sputtering method, and processed into a predetermined shape by a lift-off method. Thereafter, the formation of the upper insulating support film 25 is the same as that of the magnetic head using the ferromagnetic tunnel junction of the present invention.

Using the manufactured magnetic head, a coercive force of 25
Signals were recorded and reproduced on a magnetic recording medium having a thickness of 00 Oe and a thickness of 50 nm, and the output waveform was examined. As a result, as shown in FIG. 32, in the magnetic head of the present invention using the ferromagnetic tunnel junction, a good waveform without distortion was obtained.

FIG. 33 is a diagram showing the relationship between the reproduction output per unit track width and the recording density. A curve L3 indicates the characteristics of the magnetic head using the ferromagnetic tunnel junction according to the present invention,
A curve L4 shows the characteristics of a magnetic head using a conventional AMR film manufactured as a comparative example. That is, the magnetic head according to the present invention obtained a reproduction output 4 to 5 times higher than the magnetic head using the conventional AMR film.

[0109]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a magnetoresistance effect element capable of obtaining a high MR ratio. (B) It is possible to provide a magnetoresistive element capable of obtaining a stable output without noise.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a magnetoresistive element according to the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is a diagram illustrating an operation of a tunnel junction of the magnetoresistive element shown in FIGS.

FIG. 5 is a perspective view schematically showing another embodiment of the magnetoresistance effect element according to the present invention.

6 is a sectional view taken along line 6-6 in FIG.

FIG. 7 is a cross-sectional view schematically showing another embodiment of the magnetoresistance effect element according to the present invention.

FIG. 8 shows a magnetic field-magnetic resistance (MR) change rate characteristic when a soft ferromagnetic film having a low coercive force is used as a free ferromagnetic film and a hard ferromagnetic film having a high coercive force is used as a pinned ferromagnetic film. FIG.

FIG. 9 shows the magnetic field-MR ratio characteristics when a soft ferromagnetic film is used for both a free ferromagnetic film and a pinned ferromagnetic film and a magnetization fixed film is stacked adjacent to the pinned ferromagnetic film. FIG.

FIG. 10 is a sectional view showing another example of the ferromagnetic tunnel junction in the magnetoresistance effect element according to the present invention.

FIG. 11 is a sectional view taken along the line 11-11 in FIG. 10;

FIG. 12 is a sectional view taken along line 12-12 of FIG. 10;

FIG. 13 is a diagram for explaining the operation of the tunnel junction of the magnetoresistive element shown in FIGS.

FIG. 14 is a sectional view showing another example of the ferromagnetic tunnel junction of the magnetic head according to the present invention.

FIG. 15 is a sectional view taken along the line 15-15 in FIG. 14;

FIG. 16 is a sectional view taken along line 16-16 of FIG. 14;

FIG. 17 is a view for explaining the operation of the tunnel junction of the magnetoresistive element shown in FIGS. 14 to 16;

FIG. 18 is a diagram showing a magnetic field-magnetic resistance change rate characteristic when antiferromagnetic coupling occurs.

FIG. 19 shows a magnetoresistance curve of a ferromagnetic tunnel junction having a junction area of 50 × 50 μm ² .

FIG. 20 is a perspective view of a magnetic head including a magnetoresistive element according to the present invention.

FIG. 21 is an enlarged sectional view of a magnetic transducer element of the magnetic head shown in FIG. 20;

FIG. 22 shows the MR of the magnetic head shown in FIGS. 20 and 21;
It is an expanded sectional view of a magnetic transducer element part.

FIG. 23 is an enlarged perspective view of the MR magnetic transducer shown in FIG. 22;

FIG. 24 is a sectional view taken along the line 24-24 in FIG. 23;

FIG. 25 is a sectional view showing another example of the MR magnetic transducer.

FIG. 26 is an enlarged cross-sectional view of a portion of a ferromagnetic tunnel junction type magnetic transducer when a magnetization fixed film is provided.

27 is an enlarged perspective view of the ferromagnetic tunnel junction type magnetic transducer shown in FIG. 26.

FIG. 28 is a diagram showing an MR curve of a magnetic head provided with a magnetic domain control film.

FIG. 29 is a diagram showing an MR curve of a magnetic head without a magnetic domain control film.

FIG. 30 is a diagram showing an output waveform of a magnetic head provided with a magnetic domain control film.

FIG. 31 is a diagram showing an output waveform of a magnetic head to which a magnetic domain control film is not provided.

FIG. 32 is a diagram showing an output waveform of a magnetic head according to the present invention using a ferromagnetic tunnel junction.

FIG. 33 is a diagram showing, in comparison, the relationship between the reproduction output per unit track width and the recording density of the magnetic head according to the present invention and a conventional magnetic head.

[Explanation of symbols]

 Reference Signs List 1 slider 4 substrate 21 ferromagnetic tunnel junction 211 first ferromagnetic film 212 second ferromagnetic film 210 insulating film 214, 215 domain control film 216 magnetization fixed film 22 first electrode film 23 second electrode film 24 , 25 Insulating support film 13, 14 ABS surface

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

Claims (27)

[Claims] 1. A magnetoresistive element having a ferromagnetic tunnel junction and a magnetic domain control film, wherein the ferromagnetic tunnel junction includes an insulating film, a first ferromagnetic film, and a second ferromagnetic film. A magnetic film, wherein the first ferromagnetic film and the second ferromagnetic film are stacked with the insulating film interposed therebetween, and wherein the magnetic domain control film comprises the first ferromagnetic film and the second A magnetoresistive element provided adjacent to either end of one of the two ferromagnetic films. 2. The magnetoresistance effect element according to claim 1, wherein the magnetic domain control film is a hard ferromagnetic film. 3. The magnetoresistive element according to claim 2, wherein the hard ferromagnetic film is made of a Co alloy. 4. The magnetoresistance effect element according to claim 3, wherein the Co alloy is CoPt, CoPtCr, CoPtTa, CoCrTa or
At least one type of magnetoresistive element selected from CoPtTaCr. 5. The magnetoresistance effect element according to claim 1, wherein said magnetic domain control film is an antiferromagnetic film. 6. The magnetoresistive element according to claim 5, wherein the antiferromagnetic film is made of one of a metal antiferromagnetic material and an oxide antiferromagnetic material. . 7. The magnetoresistance effect element according to claim 6, wherein the metal-based antiferromagnetic material is a Mn alloy. 8. The magnetoresistance effect element according to claim 7, wherein the Mn alloy is FeMn, NiMn, PtMn, RuMn, RhMn, IrM.
A magnetoresistive element made of at least one selected from n, PdMn, or an alloy thereof. 9. The magnetoresistance effect element according to claim 6, wherein the oxide-based antiferromagnetic material is NiO, NiCoO, or Fe ₂ O _3.
At least one type of magnetoresistive element selected from the group consisting of: 10. The magnetoresistance effect element according to claim 1, wherein the magnetization direction of the first ferromagnetic film and the magnetization direction of the second ferromagnetic film are such that an externally applied magnetic field is zero. Magneto-resistance effect elements that are not parallel to each other in the case of. 11. The magnetoresistive element according to claim 10, wherein the magnetization direction of the first ferromagnetic film and the magnetization direction of the second ferromagnetic film are perpendicular to each other. Resistance effect element. 12. The magnetoresistive element according to claim 1, wherein an easy axis of said first ferromagnetic film and an easy axis of said second ferromagnetic film are not parallel to each other. Magnetoresistive element. 13. The magnetoresistive element according to claim 12, wherein an easy axis of the first ferromagnetic film and an easy axis of the second ferromagnetic film are perpendicular to each other. Magnetoresistive element. 14. The magnetoresistive element according to claim 1, wherein one of the first ferromagnetic film and the second ferromagnetic film has an easy axis of magnetization. A magnetoresistive element perpendicular to an externally applied magnetic field and having an easy axis of magnetization of the other ferromagnetic film parallel to the externally applied magnetic field. 15. The magnetoresistive effect element according to claim 1, wherein the magnetic domain control film is provided among the first ferromagnetic film and the second ferromagnetic film. The magnetoresistive element, wherein the non-ferromagnetic film is a hard ferromagnetic film having a higher coercive force than the ferromagnetic film provided with the magnetic domain control film. 16. The magnetoresistive element according to claim 14, wherein an easy axis of the ferromagnetic film including the magnetic domain control film is perpendicular to a direction of an externally applied magnetic field. 17. The magnetoresistance effect element according to claim 1, wherein the magnetic domain control film is provided among the first ferromagnetic film and the second ferromagnetic film. The magnetoresistive element having a fixed magnetization film without the ferromagnetic film. 18. The magnetoresistive element according to claim 17, wherein the magnetization fixed film is a hard ferromagnetic film. 19. The magnetoresistive element according to claim 17, wherein the magnetization fixed film is an antiferromagnetic film. 20. The magnetoresistive element according to claim 17, wherein, of the first ferromagnetic film and the second ferromagnetic film, a ferromagnetic film including the magnetic domain control film is easily magnetized. A magnetoresistive element whose axis is perpendicular to the direction of the externally applied magnetic field and whose easy axis of magnetization of the ferromagnetic film including the magnetization fixed film is parallel to the direction of the externally applied magnetic field. 21. The magnetoresistive element according to claim 1, wherein a barrier potential of the ferromagnetic tunnel junction due to the insulating film is in a range of 0.5 to 3 eV. Effect element. 22. The magnetoresistance effect element according to claim 21, wherein a barrier potential of the insulating film is 1.5 to 2.5.
A magnetoresistive element in the eV range. 23. The magnetoresistive element according to claim 21, wherein the first ferromagnetic film and the second ferromagnetic film have antiferromagnetic coupling via the insulating film. The magnetoresistive effect element. 24. The magnetoresistive element according to claim 21, wherein the insulating film is formed at 40 to 100 ° C. in air after being formed.
A magnetoresistive element, which is an aluminum oxide film formed by heat treatment in step 1. 25. The magnetoresistive element according to claim 21, wherein the insulating film is a diamond-like carbon film. 26. The magnetoresistance effect element according to claim 21, wherein the area of the ferromagnetic tunnel junction is 10 μm ² or less. 27. A magnetic head having a magneto-resistance effect element, wherein the magneto-resistance effect element is any one of claims 1 to 26.