JPH11283830A - Magnetoresistance effect film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resistance varying rate, which can be larger than that of a GMR film, namely capable of reaching even 30%, by showing the behavior of magnetic resistance which differs from a normal GMR film, namely a reverse magnetoresistance effect. SOLUTION: A magnetoresistance effect film is obtained by laminating a multilayer film, which is provided with plural ferromagnetic body layers 12 and 14 which are laminated through a nonmagnetic film and an antiferromagnetic body layer 15 laminated adjacent to a ferromagnetic body layer on one side of a nonmagnetic layer 13 among these layers 12 and 14, adjacent to a semiconductor. It is preferable that one of B, Al and Sb is doped to an Si layer as this semiconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a read head for high density magnetic recording, and more particularly to a magnetoresistive film using a giant magnetoresistance effect.

[0002]

2. Description of the Related Art A read head for high-density magnetic recording generally uses an anisotropic magnetoresistance effect. In this method, a bias magnetic field is applied to a NiFe alloy thin film in the vertical and horizontal directions, magnetization is oriented in a direction of about 45 ° from the vertical direction of the thin film, and the magnetization direction is changed by a signal magnetic field from a magnetic recording medium. Since the electric resistance of the thin film changes when it is changed, a signal is detected based on the change. According to such an anisotropic magnetoresistive element, the rate of change in resistance is at most about 3%.

As the magnetic recording density increases, the area of the magnetic recording medium per unit bit decreases, and the signal magnetic field weakens. Therefore, a method with a large resistance change rate is being studied. According to a magnetoresistive film using the giant magnetoresistance effect (GMR) (hereinafter sometimes referred to as “GMR film”), the resistance change rate is about As large as 7 to 8% are obtained.

A GMR film is generally formed on a substrate of Al ₂ O ₃ or the like via an insulating film of Al ₂ O _3. The structure of the GMR film is generally a plurality of ferromagnetic layers separated by a non-magnetic layer. Are laminated. The ferromagnetic layer on one side of the nonmagnetic layer among the plurality of ferromagnetic layers is adjacent to the antiferromagnetic layer,
The magnetization direction is fixed. This ferromagnetic layer is called a fixed layer. The magnetization direction of the ferromagnetic layer on the other side of the nonmagnetic layer among the plurality of ferromagnetic layers changes depending on an external magnetic field, for example, a signal magnetic field of the magnetic recording film. This ferromagnetic layer is called a free layer. The resistance of the GMR film changes depending on the magnetization direction of the free layer and the magnetization direction of the fixed layer. That is, since the resistance of the GMR film changes according to the signal magnetic field of the magnetic recording film, the signal of the magnetic recording film can be detected by the resistance of the GMR film.

In the GMR film, the resistance is small when an external magnetic field is applied in the direction of magnetization of the antiferromagnetic layer and the magnetization of the free layer is arranged in parallel with the magnetization of the fixed layer. In a state where the external magnetic field is zero and a state where a weak external magnetic field is applied in a direction opposite to the magnetization of the antiferromagnetic layer, the magnetization of the fixed layer and the magnetization of the free layer are antiparallel. . In this state,
The resistance is about 7 to 8% greater than when the magnetization is parallel. When the external magnetic field applied in the direction opposite to the magnetization direction of the antiferromagnetic layer becomes larger than the magnitude of the exchange coupling magnetic field between the antiferromagnetic layer and the ferromagnetic layer, the magnetization of the fixed layer is reversed. As a result, the magnetizations of the fixed layer and the free layer become parallel to each other. When it is parallel, the resistance drops by about 7 to 8% compared to when it is antiparallel.

[0006]

SUMMARY OF THE INVENTION It has been discovered that a magnetoresistive film formed on a semiconductor exhibits a magnetoresistive behavior different from that of a normal GMR, that is, a magnetoresistive effect opposite to that of a normal GMR. This has led to the present invention.

[0007] It is an object of the present invention to provide a magnetoresistive film exhibiting a unique magnetoresistive effect. Furthermore,
It is another object of the present invention to provide a magnetoresistive film having a higher resistance change rate than a normal GMR film. The magnetoresistive film of the present invention has a very large resistance change rate, for example, as high as 30%. There is a possibility that a large resistance change rate that can be achieved may be obtained.

[0008]

According to the present invention, there is provided a magnetoresistive film comprising: a plurality of ferromagnetic layers stacked via a nonmagnetic layer;
A multilayer film having an antiferromagnetic layer stacked adjacent to a ferromagnetic layer on one side of the nonmagnetic layer among the plurality of ferromagnetic layers is stacked adjacent to the semiconductor. Features.

In the magnetoresistive film according to the present invention, the semiconductor is preferably made of a Si layer and doped with impurities. Here, the impurities are preferably any of B, Al, and Sb. The thickness of this Si layer is 5 to 1
It is preferably 00 nm. The specific resistance of the semiconductor is
It is desirable to have 0.5 × 10 ⁻² Ωcm to 20 × 10 ⁻² Ωcm.

[0010] The resistance change rate (Δ
(ρ / ρ) is preferably 7% or more.

[0011]

In the magnetoresistive film of the present invention, the magnetization directions of the two ferromagnetic layers are antiparallel to each other when no external magnetic field is applied. When a small external magnetic field is applied in a direction opposite to the magnetization direction of the antiferromagnetic layers, the magnetizations of both ferromagnetic layers are maintained antiparallel to each other.

A magnetic field applied in a direction opposite to the magnetization direction of the antiferromagnetic layer causes an exchange coupling magnetic field between the antiferromagnetic layer and an adjacent ferromagnetic layer (fixed layer). Hex
, The magnetization of the fixed layer is reversed, and the magnetizations of both ferromagnetic layers become parallel to each other.

In the magnetoresistive film of the present invention, when the magnetizations of both ferromagnetic layers are antiparallel to each other, the resistance of the magnetoresistive film is small, but the magnetizations of both ferromagnetic layers are parallel to each other. Then, the resistance increases. This phenomenon of the magnetoresistance effect is opposite to that seen in a general GMR film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the magnetoresistive film of the present invention, and FIG. 2 is a sectional view showing another embodiment of the magnetoresistive film of the present invention. FIG. 3 is a cross-sectional view of the embodiment, FIG. 4 is a graph showing the relationship between the resistance change rate of the magnetoresistive film of the present invention shown in FIG. 3 and the intensity of the applied magnetic field, and FIG. FIG. 6 is a graph showing the relationship between the resistance change rate and the thickness of the Si layer, and FIG. 6 is a graph showing the relationship between the resistance change rate of the magnetoresistive film of the present invention and the specific resistance of the Si layer. FIG. 7 is a cross-sectional view of an example of a general magnetoresistive film (GMR film). FIG. 8 shows the relationship between the resistance change rate of the general magnetoresistive film (GMR film) shown in FIG. It is a graph which shows a relationship. In these drawings, the same parts are denoted by the same reference numerals.

The magnetoresistive film of the present invention has a semiconductor layer 11, for example, an impurity-doped Si layer on an insulating substrate 10, as shown in FIG.
Layer is formed on top of it. A ferromagnetic layer 12, which is a free layer, a nonmagnetic layer 13, a ferromagnetic layer 14, and an antiferromagnetic layer 15, are formed on the semiconductor layer 11 in this order. The ferromagnetic layer 14 is a fixed layer whose magnetization direction is fixed by an adjacent antiferromagnetic layer 15. In FIG. 1, the semiconductor layer 11 is formed on the substrate 10, but in another embodiment of FIG. 2, the magnetoresistance effect from the ferromagnetic layer 12 to the antiferromagnetic layer 15 is formed on the substrate 10. A laminated structure of a film is formed, and a semiconductor layer 1 is formed thereon.
1 is formed.

FIG. 3 is a sectional view showing an embodiment of the magnetoresistive film of the present invention. A glass substrate is used as the substrate 30, and a Si layer 3 doped with Sb as a semiconductor is formed thereon.
1 is formed to a thickness of 50 nm. Thereon, a Ta underlayer 32 having a thickness of 5 nm and a Ni ₈₀ Fe ₂₀ (a
t. %) Of the free layer 33 and the CoFe layer 34 of 1 nm.
nm, the Cu nonmagnetic layer 35 is 2.3 nm, the CoFe fixed layer 36 as the ferromagnetic layer is 3 nm, and Ir ₂₀ Mn ₈₀ (at.
%) Of an antiferromagnetic layer 37 having a thickness of 8 nm, and a Ta
The protective layer 38 has a thickness of 3 nm.

FIG. 4 shows the magnetoresistance effect of this magnetoresistance effect film.
Is shown in the graph. In this graph, the direction opposite to the magnetization of the Ir ₂₀ Mn ₈₀ antiferromagnetic layer 37 is positive. When the external magnetic field is zero, the magnetization of the Ni ₈₀ Fe ₂₀ free layer 33 is C
The direction of the magnetization of the oFe fixed layer 36 is opposite to the direction of magnetization. When a small magnetic field is applied to the magnetoresistive film in a direction opposite to the direction of magnetization of the Ir ₂₀ Mn ₈₀ antiferromagnetic layer 37, the magnetization of the Ni ₈₀ Fe ₂₀ free layer 33 is also opposite to the magnetization of the CoFe fixed layer 36. They are arranged in parallel. In such a state, the electric resistance of the magnetoresistive film has a small value. This applied magnetic field was gradually increased to Ir ₂₀ M
When the exchange coupling magnetic field Hex between the n ₈₀ antiferromagnetic layer 37 and the adjacent CoFe fixed layer 36 becomes larger than the magnitude of the exchange coupling magnetic field Hex, the magnetization direction of the CoFe fixed layer 36 is reversed and Ni ₈₀ Fe ₂₀ free Magnetization of layer 33 and CoFe fixed layer 3
6 are aligned in the same direction. At this time, the electric resistance of the magnetoresistive film rapidly increases.

Next, by gradually reducing the applied magnetic field,
When it becomes smaller than the magnitude of the exchange coupling magnetic field Hex,
The magnetization direction of the CoFe pinned layer 36 reverses and returns to its original state,
Ni ₈₀Fe₂₀The magnetization of the free layer 33 and the magnetization of the CoFe pinned layer 36
The magnetization becomes antiparallel. At this time, the electrical resistance of the magnetoresistive film is
The resistance drops sharply. As shown in the figure,
The change in resistance between when it was done and when it was made smaller
Hysteresis was observed in the rates but not shown in the figure.
No.

The external magnetic field is further reduced so that the intensity of the external magnetic field is in the opposite direction from zero, ie, in the CoFe fixed layer 36.
The magnetization of the Ni ₈₀ Fe ₂₀ free layer 33 is easily inverted if the magnetization is directed in the same direction as the magnetization of the Ni ₈₀ Fe ₂₀ free layer 33, so that the magnetization of the CoFe fixed layer 36 and the magnetization of the Ni ₈₀ Fe ₂₀ free layer 33 are parallel to each other. As such, the resistance rises sharply.

For comparison, a GMR film having a general structure is shown in FIG. The difference between this GMR film and the magnetoresistive effect film of the present invention shown in FIG. 3 is that the present invention has a general difference from the Sb-doped Si layer 31 under the Ta underlayer of the magnetoresistive effect film. Is that there is no Si layer 31 in the GMR film. The magnetoresistance change rate (Δ
FIG. 8 shows the relationship between (ρ / ρ) and the applied magnetic field strength. Also in this figure, the Ir ₂₀ Mn ₈₀ antiferromagnetic layer 37
The direction opposite to the magnetization is shown as positive.

Referring to FIGS. 7 and 8, the GMR film is made of Co.
When an external magnetic field is applied in the same direction as the magnetization of the Fe fixed layer 36, the magnetization of the Ni ₈₀ Fe ₂₀ free layer 33 is aligned in the same direction as the magnetization of the CoFe fixed layer 36. This state is set to Δρ / ρ = 0 in FIG. In a state where the external magnetic field applied to the GMR film is zero and a state where a small magnetic field is applied in the opposite direction to the magnetization of the Ir ₂₀ Mn ₈₀ antiferromagnetic layer 37, Ni ₈₀ F
magnetization of e ₂₀ free layer 33 is arranged in parallel reaction to the magnetization of the CoFe pinned layer 36, the electrical resistance of the GMR film rises rapidly. By gradually increasing the applied magnetic field, the Ir ₂₀ Mn ₈₀ antiferromagnetic layer 37 and the CoFe fixed layer 3
6, the magnetization direction of the CoFe fixed layer 36 is reversed, and the exchange coupling magnetic field Hex becomes larger.
The magnetization of the ₈₀ Fe free layer 33 and the magnetization of the CoFe fixed layer 36 are aligned in the same direction. At this time, the electric resistance of the magnetoresistive film rapidly decreases. The magnitude of the applied magnetic field is the exchange coupling magnetic field Hex
Before and after the magnitude of the hysteresis, hysteresis appears in the relationship between the resistance change rate and the magnitude of the external magnetic field due to the increase and decrease of the applied magnetic field (not shown). In the GMR film of FIG. 7, the magnitude of the rate of change in resistance was about 6.8% as shown in FIG.
On the other hand, in the magnetoresistive film of the present invention shown in FIG. 3, the resistance change rate is sharply reduced by applying the magnetic field in the positive direction, and as shown in FIG.

A current, for example, a sense current of 10 mA is applied to the magnetoresistive film to measure the resistance change rate. Since the magnetoresistive film is provided adjacent to the semiconductor, when the specific resistance of the semiconductor is small, or As the thickness of the semiconductor increases, the current flowing through the semiconductor layer increases, so that even if the resistance change rate of the magnetoresistive film increases, the detection sensitivity may be deteriorated.

An Si layer (Sb-doped) having a specific resistance of 1.4 × 10 ^-2 Ωcm in the magnetoresistive film of the embodiment of the present invention shown in FIG.
The resistance change rate (%) of the magnetoresistive film when the thickness was changed was measured, and the result is shown in FIG.
As can be seen from this figure, the resistance change rate Δρ /
It is clear that ρ is obtained between 5 and 100 nm.

Next, the Sb doping amount of the Si layer (Sb doping) in the magnetoresistive film of the embodiment shown in FIG.
The semiconductor layer whose specific resistance was changed from 0.2 × 10 ⁻² Ωcm to 40 × 10 ⁻² Ωcm was set to a thickness of 50 nm, and the resistance change rate was measured at that time. The result is shown in FIG. As can be seen from this figure, the resistance change rate Δρ / ρ of 7% or more is 0.5
× It is clear that obtained when the 10 ^-2 Ωcm~20 × 10 ^-2 Ωcm.

5 and 6, the rate of change of resistance Δρ / ρ
Is set to be 7% or more,
It is considered that a higher resistance change rate can be obtained by further increasing the resistance of the Si layer to eliminate the shunt loss. However, as the specific resistance increases, the Si layer becomes an insulator instead of a semiconductor. As the properties of the insulator become stronger, the rate of change in resistance gradually decreases, and consequently the rate of change in resistance becomes positive as in a general GMR film. For that, S
It is considered that there is a lower limit of the thickness of the i-layer and an upper limit of the specific resistance.

In the above description, the semiconductor is Sb
Although the description has been given of the Si layer doped with, it has been clarified by experiments that the Si layer which can be used can be a layer doped with either B or Al instead of Sb.

Although Ir ₂₀ Mn ₈₀ is used as the antiferromagnetic layer, the effects of the present invention can be similarly obtained with Fe ₅₀ Mn ₅₀ and others.

[0028]

As described above, the magnetoresistive film of the present invention formed adjacent to a semiconductor film exhibits a magnetoresistive behavior different from that of a normal GMR film, that is, a reverse magnetoresistive effect. The resistance change rate is larger than that of a normal GMR film, and there is a possibility that a resistance change rate as high as 30% can be obtained, a more sensitive read head can be obtained, and a higher magnetic recording density can be achieved. It can contribute to its potential.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a magnetoresistive film of the present invention.

FIG. 2 is a sectional view showing another embodiment of the magnetoresistive film of the present invention.

FIG. 3 is a sectional view of an embodiment of a magnetoresistive film of the present invention.

4 is a graph showing a relationship between a resistance change rate of the magnetoresistive film of the present invention shown in FIG. 3 and an applied magnetic field intensity.

FIG. 5 is a graph showing the relationship between the resistance change rate of the magnetoresistive film of the present invention and the thickness of the Si layer.

FIG. 6 is a graph showing a relationship between a resistance change rate of a magnetoresistive film of the present invention and a specific resistance of a Si layer.

FIG. 7 is a cross-sectional view of an example of a general magneto-resistance effect film (GMR film).

8 is a general magnetoresistive film (GMR film) shown in FIG. 7;
5 is a graph showing the relationship between the rate of change in resistance and the applied magnetic field strength.

[Explanation of symbols]

10,30 substrate 11 semiconductor layer 12, 14 ferromagnetic substance layers 13 nonmagnetic layer 15 antiferromagnetic layer 31 Si layer 32 Ta underlayer 33 Ni ₈₀ Fe ₂₀ free layer 34 CoFe layer 35 Cu nonmagnetic layer 36 CoFe pinned layer 37 Ir ₂₀ Mn ₈₀ antiferromagnetic layer 38 Ta protective layer

Claims (5)

[Claims] 1. A plurality of ferromagnetic layers laminated via a nonmagnetic layer, and a plurality of ferromagnetic layers laminated adjacent to a ferromagnetic layer on one side of the nonmagnetic layer among the plurality of ferromagnetic layers. A multilayer film having an antiferromagnetic layer is laminated adjacent to a semiconductor. 2. The magnetoresistive film according to claim 1, wherein said semiconductor is made of a Si layer and is doped with an impurity. 3. The magnetoresistive film according to claim 2, wherein said impurity is one of B, Al, and Sb. 4. The magnetoresistive film according to claim 2, wherein said Si layer has a thickness of 5 to 100 nm. 5. The semiconductor according to claim 1, wherein said semiconductor has a specific resistance of 0.5 × 10 ^-2 Ωcm.
5. The magnetoresistive film according to claim 1, wherein said magnetoresistive film has a thickness of about 20 * 10 ^<-2 > [Omega] cm.