JP2850866B2 - Magnetoresistive sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetoresistive sensor for reading magnetic information.

[0002]

2. Description of the Related Art Conventionally, magnetoresistive sensors ("MR sensors")
Also called. ) Or magneto-resistive heads, which are known to read data from magnetic surfaces with a large linear density. Magnetoresistance sensors detect magnetic field signals via the strength of the magnetic flux sensed by the reading element and the change in resistance as a function of direction. Such a conventional magnetoresistive sensor has an anisotropic magnetoresistance (1) in which one component of the resistance of the reading element changes in proportion to the square of the cosine of the angle between the magnetization direction and the direction of the sense current flowing through the element. It operates based on the (AMR) effect. A more detailed description of the AMR effect can be found in DA Thomson (Th
omson) et al. “Memory, Storage, and Related Applica
tions "IEEE Trans.on Mag.MAG-11, p.1039 (1975).

[0003] In a more recent paper, the resistance change of a laminated magnetic sensor is attributable to the spin-dependent conduction of conduction electrons between the magnetic layers through the non-magnetic layer and the associated spin-dependent scattering at the layer interface. , A more pronounced magnetoresistance effect is described. This magnetoresistance effect is called by various names such as “giant magnetoresistance effect” and “spin valve effect”. Such a magnetoresistive sensor is made of a suitable material, and has improved sensitivity and a large change in resistance as compared to a sensor using the AMR effect. In this type of magnetoresistive sensor, the in-plane resistance between a pair of ferromagnetic layers separated by a nonmagnetic layer changes in proportion to the cosine of the angle between the magnetization directions of the two layers.

Japanese Unexamined Patent Publication No. 2-61572 describes a laminated magnetic structure which produces a high MR change caused by antiparallel alignment of magnetization in a magnetic layer. As the materials that can be used in the laminated structure, the above publication discloses ferromagnetic transition metals and alloys. It also discloses a structure in which an antiferromagnetic layer is added to one of at least two ferromagnetic layers separated by an intermediate layer, and FeMn is suitable as the antiferromagnetic layer.

Japanese Patent Application Laid-Open No. 4-358310 discloses a ferromagnetic thin film having two ferromagnetic thin film layers separated by a nonmagnetic metal thin film layer. The magnetization directions of the layers are orthogonal, the resistance between the two uncoupled ferromagnetic layers varies in proportion to the cosine of the angle between the magnetization directions of the two layers, and is independent of the direction of the current passing through the sensor. A resistance sensor is disclosed.

Japanese Patent Application Laid-Open No. Hei 6-203340 discloses two ferromagnetic thin film layers separated by a nonmagnetic metal material thin film layer. When an externally applied magnetic field is zero, an adjacent antiferromagnetic material layer is formed. A magnetoresistive sensor based on the above effect is disclosed in which the magnetization is kept perpendicular to the other ferromagnetic layer.

FIG. 8 shows a partial sectional view of a conventional magnetoresistive sensor. In FIG. 8, a base layer 22 is laminated on a substrate 21 to form a magnetoresistive sensor. That is, the underlayer 22
A FeMn layer 23 as an exchange bias layer is stacked on the second ferromagnetic layer 24, a non-magnetic spacer layer 25,
The first ferromagnetic layers 26 are sequentially laminated to form a magnetoresistive sensor.

[0008]

Conventionally, an FeMn film, a NiMn film, and a NiO film have been used for the anti-ferromagnetic exchange bias layer. The FeMn film is easy to manufacture and has been widely used as an exchange bias layer, but has a disadvantage that it is easily corroded. The NiMn film has a large exchange coupling magnetic field, which is a magnetic field for fixing the magnetization direction of the ferromagnetic layer, and has high corrosion resistance, but requires a high synthesis temperature, so that the magnetoresistance effect (M
R) The disadvantage is that the ratio is low. NiO is more effective than FeMn or NiMn because it has high corrosion resistance and is an insulator, but when laminated with a ferromagnetic layer, the coercive force of the ferromagnetic material becomes larger than the exchange coupling magnetic field, There is a problem that normal operation cannot be expected as a magnetoresistive sensor.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetoresistive sensor using an antiferromagnetic exchange bias layer having high corrosion resistance and low synthesis temperature. To provide.

[0010]

A magnetoresistive sensor according to the present invention comprises a non-magnetic spacer layer, a first ferromagnetic layer and a second ferromagnetic layer separated from each other by the non-magnetic spacer layer. And an exchange bias layer for maintaining the magnetization of the second ferromagnetic layer in a desired direction.
The exchange bias layer is composed of a laminated film of a nickel oxide and an interface control layer, and the interface control layer is in contact with the second ferromagnetic layer. As the interface control layer, a nonmagnetic metal, Cr or Mn or an oxide thereof, an iron oxide, or the like is used. Non-magnetic metals include Al, Ti, V, Cu, Zn,
Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, H
f, Ta, W, Re, Pt, Au, Pb, Bi, La,
Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
One metal selected from o and Er or an alloy composed of two or more metals. The thickness t of the nonmagnetic metal is 0.
The range is 3 nm ≦ t ≦ 1.0 nm. The interface control layer is C
In the case of r or Mn or its oxide, iron oxide, etc.,
The thickness t is in the range of 0.3 nm ≦ t ≦ 2.0 nm.

When a nickel oxide layer is used as the exchange bias layer, a thin layer made of a non-magnetic metal or antiferromagnetic (hereinafter, referred to as an “interface control layer”) is laminated between the ferromagnetic material to be laminated. Therefore, the coercive force of the ferromagnetic material is reduced,
This time, it was made clear by the present inventors.

FIG. 2 shows a glass substrate using Cu for the interface control layer / NiO (50 nm) / Cu (0.5 nm) / Ni
7 shows a magnetization curve of a sample having an Fe (6 nm) configuration and a magnetization curve of a NiO single layer for comparison. Since a single layer of NiO has a large coercive force and takes two values at zero magnetic field, it cannot be used for a spin valve film. In contrast, Cu as an interface control layer
By using the (0.5 nm) layer, the coercive force is reduced to 1/3 or less, and the spin valve operation becomes possible.

FIG. 3 shows a glass substrate / NiO (50 nm).
In the sample having the structure of / interfacial control layer (tnm) / NiFe (6 nm), the change in the exchange coupling magnetic field and the coercive force depending on the layer thickness t is shown, and this is an example in which Cu or Ag is used as the nonmagnetic metal for the interface control layer. . 41 is the coercive force of the sample with Cu as the interface control layer, 42 is the coercive force of the sample with Ag as the interface control layer, 43 is the exchange coupling magnetic field of the sample with Cu as the interface control layer, 44 is the Ag 4 shows the exchange coupling magnetic field of the sample. As the thickness of the interface control layer increases, the values of the coercive force and the exchange coupling magnetic field decrease, but the coercive force decreases more than the exchange coupling magnetic field decreases. Therefore, by selecting the thickness of the interface control layer to be 0.3 nm or more and 1.0 nm or less, the exchange coupling magnetic field becomes larger than the coercive force, and normal operation as a magnetoresistive sensor becomes possible. A suitable thickness of the interface control layer is 0.3 nm or more and 1.0 n
m or less, and 0.3 nm or more and 2.0
nm or less.

[0014]

FIG. 1 is a sectional view partially showing a block diagram of an embodiment of a magnetoresistive sensor according to the present invention. Hereinafter, description will be made based on this drawing.

An underlayer 12 is laminated on a substrate 11 to form a magnetoresistive sensor. That is, a two-layer film of the NiO layer 13 and the interface control layer 14 is laminated on the underlayer 12 as an exchange bias layer, and the second ferromagnetic layer 15, the non-magnetic spacer layer 16, the first ferromagnetic layer The layers 17 are sequentially laminated to form a magnetoresistive sensor. The magnetoresistive sensor is patterned into an appropriate size and shape by a photolithography process,
The electrode layers 18a and 18b are laminated so as to be in contact with the end. A current source 19 and a sensing means 20 are connected to the electrode layers 18a and 18b, and constitute a magnetic detector capable of detecting a change in an external magnetic field as a change in resistivity.

The underlayer 12 is made of a dielectric such as alumina, SiO ₂ , aluminum nitride, silicon nitride or the like, or Zr, T
Materials having an fcc structure such as a, Hf, and Mo are suitable. Non-magnetic metal, Cr or M
n or their oxides, iron oxides and the like are used. Non-magnetic metals include Al, Ti, V, Cu, Zn, Y, Z
r, Nb, Mo, Ru, Rh, Pd, Ag, Hf, T
a, W, Re, Pt, Au, Pb, Bi, La, Ce,
Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
It is preferable to use one metal selected from r or an alloy composed of two or more metals. The thickness t of the nonmagnetic metal is preferably in the range of 0.3 nm ≦ t ≦ 1.0 m. The thickness t when Cr or Mn or their oxides or iron oxides is 0.3 nm ≦ t ≦ 2.0 n
The range of m is preferred. The first and second ferromagnetic layers 15,
17 include NiFe, NiFeCo, CoZr-based materials, FeCoB, Sendust, iron nitride-based materials, FeCo
Etc. can be used. First and second ferromagnetic layers 1
The film thickness of 5, 17 is desirably about 1 to 10 nm. It is also possible that the first and second ferromagnetic layers 15 and 17 have a thin Co film adjacent to the nonmagnetic spacer layer 16.
The nonmagnetic spacer layer 16 can be made of one metal selected from silver, gold and copper, or an alloy composed of two or more metals. The thickness of the nonmagnetic spacer layer 16 is 2 to
3 nm is preferred. Nickel oxide composition ratio O / (Ni
+ O) is preferably in the range of 0.4 ≦ O / (Ni + O) ≦ 0.6.

FIG. 4 is an RH curve of a spin valve film using 0.5 nm of Cu, which is a nonmagnetic metal, as an interface control layer. The structure is NiO (50 nm) / Cu (0.5 n
m) / NiFe (3 nm) / Cu (2.5 nm) / Ni
Fe (6 nm). For the NiO film formation, an rf sputtering method using a sintered target was used. The sputtering gas was Ar, the gas pressure was 0.3 Pa, and the input power was 200 W. Cu and NiFe were formed by dc magnetron sputtering. The sputtering gas was Ar, the gas pressure was 0.3 Pa, and the input power was Cu7W and NiFe35W. A normal MR operation is performed, and an MR ratio of 5.5% is obtained. When the Cu layer thickness was 0.3 nm or less, the spin valve did not operate normally because the coercive force of the fixed layer was large. If the thickness is 1.0 nm or more, the exchange coupling magnetic field becomes small, so that it is not suitable for a magnetoresistive sensor. On the other hand, NiO (50 nm) / NiFe (3 nm) without using the interface control layer
In the spin valve film having the structure of / Cu (2.5 nm) / NiFe (6 nm), a normal spin valve operation was not performed because the coercive force of the fixed layer was large.

FIG. 5 is an RH curve of a spin valve film using 0.5 nm of nonmagnetic metal Ag as an interface control layer. The composition is NiO (50 nm) / Ag (0.5 n
m) / NiFe (3 nm) / Cu (2.5 nm) / Ni
Fe (6 nm). Normal MR with an MR ratio of 5.5%
You can see that it is working. The film forming conditions are the same as those for Cu. When the thickness of the Ag layer was 0.3 nm or less, a normal spin valve operation was not performed because the coercive force of the fixed layer was large. If the thickness is 1.0 nm or more, the exchange coupling magnetic field becomes small, so that it is not suitable for a magnetoresistive sensor. As the interface control layer, other nonmagnetic metals, namely, Al, Ti, V, Zn,
Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, T
a, W, Re, Pt, Au, Pb, Bi, La, Ce,
When one metal selected from Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er or an alloy composed of two or more metals is used, the same as when Cu or Ag is used. The result was obtained.

FIG. 6 shows a glass substrate / NiO (50 nm).
/ Interface control layer (tnm) In a sample having a structure of NiFe (6 nm), the change in the exchange coupling magnetic field Hex and the coercive force Hc depending on the layer thickness t is shown.
These are the results using n or Cr. 71 is the coercive force of the sample in which Mn is the interface control layer, 72 is the coercive force of the sample in which Cr is the interface control layer, 73 is the exchange coupling magnetic field of the sample in which Mn is the interface control layer, and 74 is Cr the interface control layer. 4 shows the exchange coupling magnetic field of the sample. As the thickness of the interface control layer increases, the coercive force monotonously decreases, but the exchange coupling magnetic field once increases and then decreases. When the thickness of the interface control layer is selected to be 0.3 nm or more, the exchange coupling magnetic field becomes larger than the coercive force, and normal operation as a magnetoresistive sensor becomes possible. NiO (50) using the antiferromagnetic metal Cr or Mn for the interface control layer
nm) / Cr or Mn (0.5 nm) / NiFe (3n
m) / Cu (2.5 nm) / NiFe (6 nm) sample was prepared, and the RH curve was measured. As a result, a normal MR operation was performed at an MR ratio of 5.5%. When the layer thickness of Cr or Mn is 0.3 nm or less, a normal spin valve operation was not performed because the coercive force of the fixed layer was large. If the thickness is 2.0 nm or more, the exchange coupling magnetic field becomes small, so that it is not suitable for a magnetic resistance sensor. When the oxide of Cr or Mn was used as the interface control layer, the same result as in the case of Cr or Mn was obtained.

FIG. 7 shows a glass substrate / NiO (50 nm).
6 shows changes in the exchange coupling magnetic field Hex and the coercive force Hc depending on the layer thickness t in a sample having a configuration of / FeO (tnm) / NiFe (6 nm). 81 is a coercive force and 82 is an exchange coupling magnetic field. As the thickness of the interface control layer increases, the coercive force monotonously decreases, but the exchange coupling magnetic field once increases and then decreases. By selecting the thickness of the interface control layer to be 0.3 nm or more, the exchange coupling magnetic field becomes larger than the coercive force, and normal operation as a magnetoresistive sensor becomes possible. NiO (50 nm) / iron oxide (0.5 n) using iron oxide for interface control layer
m) / NiFe (3 nm) / Cu (2.5 nm) / Ni
When a sample having an Fe (6 nm) configuration was prepared and an RH curve was measured, a normal MR operation was performed at an MR ratio of 5.5%. When the thickness of the iron oxide layer was 0.3 nm or less, the spin valve did not operate normally because the coercive force of the fixed layer was large. If the thickness is 2.0 nm or more, the exchange coupling magnetic field becomes small, so that it is not suitable for a magnetic resistance sensor.

In addition, using the magnetoresistive sensor according to the present invention (the magnetoresistive sensor according to claim 1, 2, 3, 4, 5, 6, or 7), a shield layer, a lower gap layer, A resistance sensor is stacked, a shield layer is patterned, a magnetoresistive sensor is patterned, a vertical bias layer and a lower electrode layer are sequentially stacked so as to be in contact with an end thereof, and , A shield type magnetoresistive sensor in which a gap layer and an upper shield layer are sequentially laminated.

Further, using a magnetoresistive sensor according to the present invention (a magnetoresistive sensor according to claims 1, 2, 3, 4, 5, 6, or 7), a shield layer, a lower gap layer, The resistance sensor is stacked, the shield layer is patterned, the magnetoresistive sensor is patterned, the vertical bias layer and the lower electrode layer are sequentially stacked so as to partially overlap the upper part, A shield-type magnetoresistive sensor in which an upper gap layer and an upper shield layer are sequentially stacked on top of each other can also be configured.

Further, means for generating a current through the shielded magnetoresistive sensor using one of the above two shielded magnetoresistive sensors, and a resistance of the shielded magnetoresistive sensor as a function of a magnetic field to be detected. It is also possible to configure a magnetoresistive detector including means for detecting a rate change.

Further, a magnetic storage medium having a plurality of tracks for recording data using the magnetoresistive detection device, a magnetic recording device for storing data on the magnetic storage medium, Configuring a magnetic storage system comprising: a magnetic recording device and actuator means coupled to the magnetoresistive transducer to move the recording device and the magnetoresistive detector to a selected track of the magnetic storage medium. Can also.

[0025]

According to the present invention, the exchange bias layer is a laminated film of nickel oxide and an interface control layer, and the interface control layer is formed of a nonmagnetic metal, Cr or Mn, or an oxide thereof.
The use of iron oxide or the like enables the holding force of the ferromagnetic layer to be kept low even when nickel oxide is used, so that it has an anti-ferromagnetic exchange bias layer having high corrosion resistance and a low synthesis temperature. A magnetoresistive sensor can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view partially showing a block diagram of an embodiment of a magnetoresistive sensor according to the present invention.

FIG. 2 shows a glass substrate / NiO (50 nm) / C using Cu for an interface control layer in a magnetoresistive sensor according to the present invention.
The magnetization curves of a sample of u (0.5 nm) / NiFe (6 nm) and a sample of glass substrate / NiO (50 nm) / NiFe (6 nm) without using Cu for the interface control layer for comparison are shown. It is a graph shown.

FIG. 3 shows a magnetoresistive sensor according to the present invention, in which Cu or Ag is used for an interface control layer, and a glass substrate / NiO (50 n
7 is a graph showing the relationship between the thickness of the interface control layer, the exchange coupling magnetic field, and the coercive force in a sample of m) / Cu or Ag (tnm) / NiFe (6 nm).

FIG. 4 is a graph showing an RH curve of a spin valve film using Cu for an interface control layer in the magnetoresistive sensor according to the present invention.

FIG. 5 is a graph showing an RH curve of a spin valve film using Ag for the interface control layer in the magnetoresistive sensor according to the present invention.

FIG. 6 is a diagram illustrating a glass substrate / NiO (50n) using Mn or Cr for the interface control layer in the magnetoresistive sensor according to the present invention.
10 is a graph showing the relationship between the thickness of the interface control layer, the exchange coupling magnetic field, and the coercive force in a sample of m) / Mn or Cr (tnm) / NiFe (6 nm).

FIG. 7 shows a magnetoresistive sensor according to the present invention, in which an iron oxide is used for an interface control layer, and a glass substrate / NiO (50 nm) /
4 is a graph showing the relationship between the thickness of the interface control layer, the exchange coupling magnetic field, and the coercive force in a sample of iron oxide (tnm) / NiFe (6 nm).

FIG. 8 is a sectional view showing a conventional magnetoresistive sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Underlayer 13 NiO layer 14 Interface control layer 15 Second ferromagnetic layer 16 Non-magnetic spacer layer 17 First ferromagnetic layer 41 Coercive force of sample using Cu as interface control layer 42 Ag as interface Coercive force of sample 43 used as control layer 43 Exchange coupling magnetic field of sample using Cu as interface control layer 44 Exchange coupling magnetic field of sample using Ag as interface control layer 71 Coercive force of sample using Mn as interface control layer 72 Cr at interface Coercive force of sample with control layer 73 Exchange coupling magnetic field of sample with Mn as interface control layer 74 Exchange coupling magnetic field of sample with Cr as interface control layer 81 Coercive force 82 Exchange coupling magnetic field

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidefumi Yamamoto 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Kunihiko Ishihara 5-7-1 Shiba, Minato-ku, Tokyo NEC (56) References JP-A-8-127864 (JP, A) JP-A-7-202292 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/39

Claims (11)

(57) [Claims] 1. A non-magnetic spacer layer, a first ferromagnetic layer and a second ferromagnetic layer separated from each other by the non-magnetic spacer layer, and a magnetization of the second ferromagnetic layer Wherein the exchange bias layer comprises a laminated film of nickel oxide and a non-magnetic metal, and the non-magnetic metal comprises the second A magnetoresistive sensor in contact with a ferromagnetic layer. 2. The method according to claim 1, wherein the non-magnetic metal is Al, Ti, V, C
u, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd,
Ag, Hf, Ta, W, Re, Pt, Au, Pb, B
i, La, Ce, Pr, Nd, Sm, Eu, Gd, T
The magnetoresistive sensor according to claim 1, wherein the magnetoresistive sensor is one metal selected from b, Dy, Ho, and Er or an alloy including two or more metals. 3. The thickness t of the non-magnetic metal is 0.3 nm.
The magnetoresistive sensor according to claim 1, wherein ≦ t ≦ 1.0 nm. 4. A nonmagnetic spacer layer, a first ferromagnetic layer and a second ferromagnetic layer separated from each other by the nonmagnetic spacer layer, and a magnetization of the second ferromagnetic layer. Wherein the exchange bias layer comprises nickel oxide and Cr or Mn.
A magnetoresistive sensor comprising a laminated film of n or its oxide, and wherein said Cr or Mn or its oxide is in contact with said second ferromagnetic layer. 5. The thickness t of Cr or Mn or an oxide thereof is in the range of 0.3 nm ≦ t ≦ 2.0 nm.
The magnetoresistive sensor according to claim 4. 6. A non-magnetic spacer layer, a first ferromagnetic layer and a second ferromagnetic layer separated from each other by the non-magnetic spacer layer, and a magnetization of the second ferromagnetic layer. Wherein the exchange bias layer comprises a laminated film of nickel oxide and iron oxide, and the iron oxide is A magnetoresistive sensor in contact with a magnetic layer. 7. The thickness t of the iron oxide is 0.3 nm ≦
7. The magnetoresistive sensor according to claim 6, wherein t ≦ 2.0 nm. 8. The method according to claim 1, wherein the first and second ferromagnetic layers are C
4. An alloy comprising one metal selected from the group consisting of o, Fe and Ni or an alloy comprising two or more metals.
8. The magnetoresistive sensor according to 4, 5, 6, or 7. 9. The method according to claim 1, wherein the first and second ferromagnetic layers have a thin Co film adjacent to the non-magnetic spacer layer. Magnetoresistive sensor. 10. The non-magnetic spacer layer includes one metal selected from gold, silver and copper, or an alloy composed of two or more metals. , 6 or 7. 11. The composition ratio of the nickel oxide, O / (N
The magnetoresistive sensor according to claim 1, 2, 3, 4, 5, 6, or 7, wherein (i + O) satisfies 0.4 ≦ O / (Ni + O) ≦ 0.6.