JP2000132814A - Spin valve type magnetoresistance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the film thickness without decreasing the thermal stability of an exchange coupling layer by forming a first antiferromagnetic film having high exchange coupling energy per unit area with a second ferromagnetic film to produce a strong exchange bias magnetic field and forming the second antiferromagnetic film having a large anisotropic const. to thermally stabilize the magnetic moment. SOLUTION: An exchange coupling layer consisting of an antiferromagnetic material is formed on a fixing layer. In order to obtain an exchange coupling layer which is thermally stable and has a large pinning magnetic field, the exchange coupling layer is composed of plural antiferromagnetic films to increase the exchange coupling energy per unit area between the fixing layer and the antiferromagnetic film in contact with the fixing layer. Thus a large pinning magnetic field is obtd. and the anisotropic const. of the antiferromagnetic film not in contact with the fixing layer can be increased to secure desired thermal stability. Further, by introducing plural antiferromagnetic films, the thermal stability can be increased without decreasing the pinning magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetoresistive (MR) sensor based on the spin valve effect and a magnetoresistive head or magnetic recording apparatus using the sensor.

[0002]

2. Description of the Related Art With the recent increase in the density of magnetic recording devices, there are several types of reproducing sensors, from magnetoresistive (MR) sensors using the anisotropic magnetoresistive effect to giant magnetoresistive (GMR) sensors.
It is shifting to a spin-valve type magnetoresistive sensor utilizing the effect. A spin valve sensor is disclosed in US Pat.
No. 13 is disclosed.

An essential feature of a spin valve type magnetoresistive sensor is a first layer called a free layer.
, A second ferromagnetic layer called a pinned layer, a conductive non-magnetic spacer layer sandwiched immediately adjacent to these two layers, and an exchange in direct contact with the fixed layer. The coupling layer is a basic configuration, and an electrode that passes current through these layers and a Barkhausen noise (Bar)
and a permanent magnet layer for applying a longitudinal bias magnetic field for suppressing noise caused by non-uniformity of magnetization of the free layer, which is referred to as “khausen noise”. This sensor is usually provided in a minute space between two ferromagnetic materials called a magnetic shield, and reproduces a magnetization signal of a recording medium with high resolution.

The fixed layer has its magnetization fixed in a direction perpendicular to the surface facing the recording medium, and does not easily change its magnetization direction with respect to an external magnetic field. Since the free layer magnetization changes its direction in accordance with the magnetic field from the recording medium, a change occurs in the angle between the fixed layer magnetization and the free layer magnetization, thereby causing a change in magnetoresistance. The principle of operation of the spin valve type head is to reproduce this resistance change as a signal.

[0005] An anti-ferromagnetic material is usually used for the exchange coupling layer. The anti-ferromagnetic material needs to have a sufficiently large exchange coupling magnetic field applied to the fixed layer in the operating temperature range of the sensor. Known antiferromagnetic materials include:
Nickel oxide (NiO), iron-manganese alloy (FeM
n), nickel-manganese alloys (NiMn) and the like. Nickel oxide and iron-manganese alloys have a temperature at which exchange coupling disappears (blocking temperature), which is almost the same as the sensor temperature during operation of the magnetic recording apparatus. Not practical.

The nickel-manganese alloy has sufficient exchange coupling characteristics for practical use.
Long-term heat treatment at a high temperature of 240 degrees Celsius or higher is required, and during this heat treatment, diffusion of other materials into the free layer occurs,
The disadvantage is that the magnetoresistance effect is reduced.

Japanese Unexamined Patent Publication No. Hei 8-102417 discloses the use of a chromium-manganese-platinum alloy as an antiferromagnetic film material under such a demand. In a spin valve sensor having an antiferromagnetic film made of this material, the blocking temperature of the fixed layer can be about 300 ° C., and sufficient stability can be obtained even in an actual operating environment. The heat treatment temperature for obtaining exchange coupling characteristics is 200 to 23.
At 0 ° C., the holding time need only be one hour or more, and the GMR effect does not deteriorate.

However, the thermal stability of this material greatly depends on the film thickness, and a thin film thickness causes a remarkable decrease in the blocking temperature. For example, according to an experiment, the Pt amount was 4 at%.
In order to achieve a blocking temperature of 250 ° C. or higher with the composition described above, a film thickness of 30 nm or more is required. This film thickness accounts for 50% or more of the total film thickness of a normal spin valve film (the layer from the base film 42 to the cap layer 46 in FIG. 5), and the spin valve film has a total thickness of 50 nm. To the extent.

A read spin valve film for a magnetic recording device is sandwiched between two magnetic shields. The insulation between the shield and the spin valve film is provided by providing an insulating film such as alumina between them. Is secured. However, due to the recent trend toward higher recording densities, the shield interval is currently smaller than 200 nm, and will tend to be smaller in the future. If the distance between the shields is reduced while keeping the spin valve film thickness as it is, the thickness of the insulating film becomes thinner, and poor insulation between the shield and the spin valve film occurs.

Therefore, it is necessary to reduce the thickness of the spin valve film in order to secure the required film thickness of the insulating film. That is, it is necessary to reduce the thickness of the antiferromagnetic film that occupies most of the film thickness. However, as described above, when the antiferromagnetic film is made thinner, the thermal stability of the film deteriorates (for example, the blocking temperature decreases). Therefore, it is necessary to improve the thermal stability of the antiferromagnetic film.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the thickness of an exchange coupling layer, particularly an exchange coupling layer using a chromium-manganese-platinum antiferromagnetic film, without impairing its thermal stability. And

[0012]

In order to solve the above problems, the present invention mainly employs the following configuration.

A first ferromagnetic layer, a second ferromagnetic layer, a conductive non-magnetic spacer layer between the first and second ferromagnetic layers, and a second ferromagnetic layer. An exchange bias layer adjacent to the nonmagnetic spacer layer on the side opposite to the nonmagnetic spacer layer, wherein the exchange bias layer has a first antiferromagnetic property on the side in contact with the second ferromagnetic film. A plurality of antiferromagnetic films each including a film and a second antiferromagnetic film on a side not in contact with the second ferromagnetic film;
The antiferromagnetic film increases the exchange coupling energy per unit area with the second ferromagnetic film to give a strong exchange bias magnetic field, and the second antiferromagnetic film increases the anisotropy constant. A spin valve type magnetoresistive sensor whose magnetic moment is thermally stable.

In the spin-valve magnetoresistive sensor, the exchange coupling energy of the first antiferromagnetic film with the second ferromagnetic film per unit area is 1.0 × 10 ^−4.
J / m ² , a spin-valve magnetoresistive sensor.

In the spin-valve magnetoresistive sensor, the exchange bias layer is made of an alloy of chromium, manganese, and platinum, and the first antiferromagnetic film has a platinum composition of 3 at% or more. A spin-valve magnetoresistive sensor having a thickness of at least 10 at% and a thickness of at least 5 nm, and wherein the second antiferromagnetic film has a platinum composition of at least 9 at% and at most 15 at%.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A spin valve type magnetoresistive sensor according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 4 shows a read head according to an embodiment of the present invention. It is shown that a portion of the magnetic medium 13 has a direction of motion 14 of the magnetic medium relative to the read head that moves relatively along the Z axis. The tracks of the magnetic domains on the magnetic medium typically move along the Z axis adjacent to the read head. The magnetic medium 13 has a plurality of magnetic domains along the Z-axis direction, and its magnetic field h changes as the magnetic medium 13 moves relative to the head. This change in the magnetic field is read out as a change in the magnetic resistance of the sensor film.

The write head and the read head are composed of several layers, some of which are shown in FIG. 4, but some of the conventional layers, such as coupling layers, passivation layers, etc., are not shown. . In the manufacturing process, first, a substrate 16 is prepared, then a shield 17 is deposited thereon, and then a readout sensor film (spin valve film) 18 is further grown thereon. The read voltage output electrodes 19 and 20 are deposited thereon to form a read head integrally.

Further, an upper shield / lower core 21 is deposited, then a coil 22 is deposited, and an upper magnetic core 24 is formed thereon. For example, a dielectric layer 23 made of alumina is formed between the sensor film 18 and the lower shield 17 and between the sensor film 18 and the upper shield. Permanent magnet films 31 and 32 for applying a longitudinal bias magnetic field are arranged on both sides of the spin valve film 18 which is a read sensor film.

As the substrate 16, ceramics or a material obtained by depositing a dielectric film on ceramics can be used. For the upper and lower magnetic shields 21 and 17, a permalloy, sendust, a Co-based amorphous material showing soft magnetism, a microcrystalline ferromagnetic material showing soft magnetism, or the like can be used.

FIG. 5 shows the preferred configuration of the preferred sensor between the upper and lower shields. In the sensor film, the sensor is formed in a space between two magnetic shields, but FIG. 5 omits the magnetic shield. In this embodiment, a base film Ta film 42 is formed on the insulating film 41 formed between the magnetic shields. Other examples of this film include Ru, Pd, Pt, Au, Ag, Cu, Ir,
A Ru film or an alloy film of two or more of these films can also be used.

On top of this, a first ferromagnetic layer (free layer) 45
To form As the first ferromagnetic layer, a NiFe alloy film or a stacked film of a NiFe film and a Co or CoFe film can be used. At the time of formation, a unidirectional magnetic field is applied in the x direction to induce the magnetic anisotropy in the x direction. Next, a non-magnetic spacer layer 43 is formed. As the nonmagnetic spacer layer, a Cu film 43 having a thickness of 2.0 to 3.5 nm is used.
Au or Ag may be used instead of Cu as the material of this film. Next, the fixed layer 52 made of a ferromagnetic layer material is formed on the non-magnetic spacer. Co as the fixed layer
A film, a CoFe alloy or a CoFeNi alloy film can be used.

Next, an exchange coupling layer 50 made of an antiferromagnetic material is formed on the fixed layer. Next, a cap layer 46 is formed on the exchange coupling layer. As a cap layer, a Ta film,
Ru, Pd, Pt, Au, Ag, Cu, Ir, Rh or an alloy film of two or more of these can also be used. These films are formed in the same vacuum by, for example, an RF magnetron sputtering method. In order to fix the magnetization of the fixed layer in the direction of 56 shown in FIG. 5, a magnetic field is applied in the direction of 56, the temperature is kept at 200 to 230 ° C. for 30 minutes or more, and cooling in the magnetic field is performed (exchange bias is changed). The cooling is performed while applying a magnetic field by the exchange coupling layer 50 in the direction to be applied, that is, the Y direction in FIG. 5).

Underlayer films 60 and 61 made of Cr are formed on both sides of the spin valve film made of 42, 45, 43, 52, 50 and 46, and Co-based permanent magnet films 62 and 63 are formed thereon. create. Further, electrode films 64 and 65 for passing a current through the spin valve film are formed thereon.
Here, as the permanent magnet film, CoCrPt, CoP
An alloy such as t, CoCrPtTa or CoCrTa is used. In addition, when a sufficient coercive force is provided without a base film as in the case of CoCrPt-ZrO2, the Cr base film can be omitted. After completion of the sensor, the permanent magnet film is magnetized by applying a magnetic field in the x direction.

Although not shown, the spin-valve magnetoresistive sensor may have a stacked structure opposite to the stacked structure shown in FIG. That is, an underlayer formed on the substrate, an exchange bias layer made of an antiferromagnetic material formed on the underlayer,
A second layer formed adjacent to the exchange bias layer on the film surface;
A non-magnetic spacer layer formed adjacent to the second ferromagnetic layer, a first ferromagnetic layer formed adjacent to the non-magnetic spacer layer on the film surface, A capping layer formed on the ferromagnetic layer, the spin valve film processed into a fixed shape formed of a capping layer; and the first ferromagnetic film of the spin valve film processed into the fixed shape is adjacent in two film cross sections. A Co-based permanent magnet film having a base film formed so as to perform, an electrode film adjacent to the permanent magnet film on the film surface,
A spin valve type magnetoresistive sensor provided with

The structure shown in FIGS. 4 and 5 (where the exchange coupling layer is a single layer instead of two layers) is generally known, and the present invention provides a read sensor film ( The spin valve film 18 has a specific configuration and a method for forming the same.

In the operating temperature range of the sensor, the fixed layer 5
2 must be stably fixed in a direction 56 perpendicular to the medium facing surface. Therefore, in order to evaluate the stability of the magnetization of the fixed layer, several types of samples having different configurations of the exchange coupling layer were prepared, and a magnetic field of 240 kA / m was applied in a direction of 56 to fix the magnetization of the fixed layer. 230 with applied
After holding at 3 ° C. for 3 hours, cooling in a magnetic field (cooling while applying the magnetic field) was performed, and then the thermal stability of the magnetization of the fixed layer was evaluated.

The sample was prepared by mounting Ta5 / NiF on a glass substrate.
e5 / Co1 / Cu2.3 / Co3 / exchange coupling layer / Ta
A structure having a configuration of 3 (nm) was prepared. As the exchange coupling layer, (1) (Cr _0.5 Mn _0.5 ) ₉₆ Pt _{4 having a} thickness of 30 nm
(2) (Cr _0.5 Mn _0.5 ) ₉₀ Pt _{10 having a} thickness of 30 nm
(3) (Cr _0.5 Mn _0.5 ) ₉₀ Pt _{13 having a} thickness of 30 nm
(4) 10 nm thick (Cr _0.5 Mn _0.5 ) ₉₀ Pt ₁₀
A film and a laminated film of a (Cr _0.5 Mn _0.5 ) ₉₀ Pt ₁₃ film having a thickness of 18 nm were used (attributes of four curves in FIGS. 1 and 2).

The thermal stability was evaluated as follows. First, the initial hysteresis curves measured at 35 ° C, pinning magnetic field H _p ⁰ at this time, i.e., H _P (T = 35 °
C). Then, after raising the temperature to temperature T ₁ of in no magnetic field, the easy magnetization direction (Pin direction) and opposite direction of the fixed layer 2
After maintaining the fixed layer magnetization in the direction of the magnetic field by applying a magnetic field of 40 kA / m and maintaining the magnetization in the magnetic field direction for 10 minutes, the sample is cooled down to 35 ° C under the same magnetic field, and a hysteresis curve is measured at 35 ° C. . The pinning magnetic field at this time is _defined as H _p (T ₁ ).

Next, in the same manner, the heat history is held at the holding temperature T _2.
After performing at a temperature of (> T ₁ ), the pinning magnetic field H _p (T ₂ ) at 35 ° C. is measured. The heat history up to the maximum temperature of 275 ° C. is added while sequentially increasing the holding temperature, and the pinning magnetic field H _p at 35 ° C. is measured. A film in which the pinning magnetic field is greatly reduced due to the thermal history has a lower thermal stability.

FIG. 1 shows the relationship between the holding temperature T of the thermal history and the pinning magnetic field at room temperature (for example, 35 ° C.) after the thermal history. That is, the vertical axis H _P in FIG. 1 represents the strength of the pinning magnetic field at room temperature (eg, 35 ° C.) after cooling after applying the magnetic field at the holding temperature. As the holding temperature T increases, the pinning field decreases and crosses zero and becomes negatively large. The amount of decrease in the pinning magnetic field tends to decrease as the amount of Pt increases (compare curves (1), (2) and (3) in FIG. 1). The temperature at which the pinning magnetic field crosses zero is 170 ° C for Pt4at% of curve (1), (2)
Pt10at% at 220 ° C, (3) Pt13a
At t%, the temperature was 245 ° C., and increased with an increase in the amount of Pt. According to FIG. 1, a curve (1) having a small amount of Pt is shown.
Is 35 ° C after cooling when the holding temperature is 170 °
The pinning magnetic field at the point is reversed.

In this test, that is, the reduction of the pinning magnetic field due to the heat history in the reverse magnetic field was confirmed by the Journal of Applied Physics.
physics) vol. 80, pp 4528-4553
(1996) and the Journal of Applied Physics
ics) vol. 80, pp3233-3238 (19
According to the model shown in (98), the magnetization of the antiferromagnetic grains in the exchange coupling layer made of polycrystal is reversed by thermal excitation first from the one having the smaller grain size. Volume ratio R (hereinafter, referred to as reversal rate) for the antiferromagnetic particle overall antiferromagnetic grains caused the magnetization reversal by an opposing magnetic field in the thermal history of the ^{_{study, R = {(H p 0}} -Hp) / ( 2H _p ⁰ )｝ × 100 (%) (1)

FIG. 2 is a graph plotting the reversal rate R of the antiferromagnetic grains with respect to the holding temperature T. As the amount of Pt increases, the reversal rate decreases, indicating that the magnetization of the antiferromagnetic grains is thermally stable. This is because the anisotropy constant of the antiferromagnetic film increases as the Pt composition increases. The inversion ratio at a holding temperature of 150 ° C. is 37% for a Pt amount of 4 at%, 12% for a Pt amount of 10 at%, and as small as 4% for a Pt amount of 13 at%.
The stability of the antiferromagnetic film having a t amount of 13 at% is remarkably high.

However, when the Pt amount is 13 at%, FIG.
As can be seen from FIG. 1, the initial (35 ° C.) pinning magnetic field is as small as 12 kA / m (see curve (3) in FIG. 1). To function as a spin valve sensor, I Triple E Transaction Magnetics (IEEE T
rans. Magn. ), 32, 3374 (199
As shown in 6), since the pinning magnetic field needs to be 16 kA / m or more, the Pt amount of 13 at% cannot be used as a sensor in terms of the pinning magnetic field.

Therefore, in order to obtain an exchange coupling layer that is thermally stable and has a large pinning magnetic field, the exchange coupling layer is composed of a plurality of antiferromagnetic films, and the fixed layer of the antiferromagnetic film that is in contact with the fixed layer. By increasing the exchange coupling energy per unit area, a large pinning magnetic field was obtained, and the thermal stability was ensured by increasing the anisotropic constant of the antiferromagnetic film not in contact with the fixed layer.

Specifically, the Pt amount of the antiferromagnetic film in contact with the fixed layer is set to 10 at% or less, the film thickness is set to 5 nm or more, and the Pt amount of the antiferromagnetic film not in contact with the fixed layer is set to 10 at%.
% Or more. For example, as the exchange coupling layer, a film thickness of 10 n
The curve (4) in FIG. 1 and the curve in FIG. 2 show the results when a laminated film of a (Cr _0.5 Mn _0.5 ) ₉₀ Pt ₁₀ film and a (Cr _0.5 Mn _0.5 ) ₉₀ Pt ₁₃ film having a thickness of 18 nm was used. This is shown in (8).

As can be seen from FIG. 2, in this laminated structure, the reversal rate is smaller than the result of a single layer of Pt 10 at%, and as can be seen from FIG. 1, the pinning magnetic field is smaller than the pinning magnetic field of Pt 10 at%. It is equal or higher. Therefore, the thermal stability could be improved without lowering the pinning magnetic field by laminating the antiferromagnetic films.

FIG. 3 shows that a magnetic field of 240 kA / m is applied in the opposite direction to the direction of easy magnetization of the fixed layer to maintain the ambient temperature at 110 ° C., and then cooled in the magnetic field to 35 ° C. and pinned at 35 ° C. The retention time dependence of the pinning magnetic field when measuring the magnetic field is shown. The test sample was placed on a glass substrate with T
a5 / NiFe5 / Co1 / Cu2.3 / Co3 / exchange coupling layer / Ta3 nm, and a single layer film of Pt10at% 30 nm, Pt10at% 4
0 nm single layer film, Pt10at% 10nm / Pt13at
% 18nm laminated film and Pt10at% 11nm / Pt1
A 3 at% 13 nm laminated film was used.

[0038] The retention time pinning magnetic field when the logarithmic axis decreases linearly, pinning magnetic field after 10 ⁵ minutes, Pt1
0at% 30nm single layer film, 16kA / m, Pt10at
It is 20 kA / m in the case of a% 40 nm single layer film. On the other hand, Pt
In the laminated film of 10 at% 10 nm / Pt 13 at% 18 nm, the pinning magnetic field after 10 ⁵ minutes is 22 kA / m, and although the film thickness is small, Pt 10 at% 40
It becomes larger than the value of the nm single layer film.

Pt 10 at% 11 nm / Pt 13
In the case of the at% 13 nm laminated film, the pinning magnetic field after 10 ⁵ minutes is 15 kA / m, which is almost the same value as the Pt 10 at% 30 nm single-layer film despite its small film thickness. . Therefore, by laminating films having different Pt compositions, thermal stability equivalent to that of a single-layer film of Pt 10 at% 30 nm can be realized with a film thickness of 24 nm, and about 2 nm.
It is possible to reduce the thickness to 0%.

Although an example in which chromium, manganese, and a platinum alloy are used as the exchange coupling layer has been described, in addition to the alloy composed of chromium and manganese, cobalt, gold,
An alloy containing one or more of silver, copper, platinum, palladium, rhodium, iridium, ruthenium, and osmium can also be used. In this case, the total sum of the additive element compositions on the fixed layer side may be smaller than the total sum of the additive element compositions on the opposite side of the fixed layer.

Also, in other antiferromagnetic materials, an antiferromagnetic film having a large exchange coupling constant is brought into contact with the interface with the fixed layer, and an antiferromagnetic film having a large anisotropic constant and a stable magnetic moment is obtained. Laminating a film thereon is also included in the present invention.

As described above, the embodiments of the present invention include those having the following structures, functions, and actions.

The exchange coupling layer is composed of a plurality of antiferromagnetic films, and the antiferromagnetic film in contact with the second ferromagnetic layer (fixed layer) has a unit area per unit area with the second ferromagnetic layer (fixed layer). The other antiferromagnetic films have a large exchange coupling energy and a large anisotropy constant, and their magnetic moments are thermally stable. As a result, the exchange bias layer is thermally stable and gives a large exchange bias magnetic field.

As a specific configuration, the exchange coupling layer is composed of a plurality of chromium-manganese-platinum alloy films having different compositions, and the platinum composition of the antiferromagnetic film in contact with the fixed layer is changed to the antiferromagnetic film separated from the fixed layer. (To increase the exchange coupling energy per unit area). Preferably, the platinum composition of the antiferromagnetic film in contact with the fixed layer is 3 at%.
10 at% or less and the film thickness is 5 nm or more. The platinum composition on the side away from the fixed layer should be at least 10 at%
It is set to 5 at% or less (H _P approaches 0 at 15 at% or more).

Here, instead of platinum, cobalt, gold,
A silver, copper, platinum, palladium, rhodium, iridium, ruthenium, osmium film or an alloy film of two or more of these films can also be used.

In order to increase the exchange coupling energy between the fixed layer and the antiferromagnetic film in contact with the fixed layer of the exchange coupling layer, the exchange bias magnetic field applied to the fixed layer by the exchange coupling layer, that is, the fixed bias layer, This is for increasing the pinning magnetic field. Further, the anisotropy constant of the antiferromagnetic film that does not directly contact the fixed layer is increased by increasing the anisotropy constant (J / m ³ ) of the entire exchange coupling layer. This is for improving the property (reducing the rate at which the magnetization reversal of the antiferromagnetic grains occurs).

As a specific method, in the above-described structure, the platinum composition on the side adjacent to the fixed layer is set to 3 to 10 at% and the film thickness is set to 5 nm or more because the unit area between the fixed layer and the antiferromagnetic layer is Exchange exchange energy of 1.0 × 1
This is because the pinning magnetic field of the fixed layer functions as a sensor film by setting the pinning magnetic field to 0 ^-4 J / m ² or more.

The reason why the platinum composition of the antiferromagnetic film remote from the fixed layer is made larger than that of the antiferromagnetic film in contact with the fixed layer (preferably 10 at% or more) is that the more the amount of Pt is, the more the antiferromagnetic film becomes. Is increased, and the antiferromagnetic magnetic moment becomes thermally stable (see FIG. 2).

By adopting this structure, the thermal stability of the exchange coupling layer can be improved without lowering the pinning magnetic field as compared with the current single layer film of chromium-manganese-platinum alloy.
The exchange coupling layer can be made thinner.

[0050]

According to the present invention, the exchange coupling layer is composed of a plurality of antiferromagnetic films having different elements or compositions, and the exchange coupling energy per unit area of the antiferromagnetic film in contact with the fixed layer is increased. By increasing the anisotropy constant of the pinned layer, the thermal stability can be improved without lowering the pinning magnetic field of the fixed layer, and as a result, the antiferromagnetic film thickness can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the thermal stability of a fixed layer of a spin valve sensor film.

FIG. 2 is a graph showing the thermal stability of an exchange coupling layer of a spin valve sensor film.

FIG. 3 is another graph showing the thermal stability of the fixed layer of the spin valve sensor film.

FIG. 4 is a structural diagram of a magnetic head for a magnetic recording device using the spin valve sensor of the present invention.

FIG. 5 is a structural diagram of a spin valve sensor of the present invention.

[Explanation of symbols]

1,5 The exchange coupling layer has a thickness of 30 nm (Cr _0.5 M
n _0.5 ) Line showing characteristics in the case of ₉₆ Pt ₄ 2,6,9 The exchange coupling layer has a thickness of 30 nm (Cr _0.5 M
Lines showing characteristics in the case of (n _0.5 ) ₉₀ Pt ₁₀ 3,7 (Cr _0.5 M
Lines showing characteristics in the case of n _0.5 ) ₉₀ Pt ₁₃ 4,8,11 The exchange coupling layer has a thickness of 10 nm (Cr _0.5
(Mn _0.5 ) ₉₀ Pt ₁₀ film and 18 nm thick (Cr _0.5 Mn)
_0.5 ) Line showing characteristics in the case of a laminated film of ₉₀ Pt ₁₃ films 10 (Cr _0.5 Mn _0.5 ) in which the exchange coupling layer has a thickness of 40 nm
Line showing characteristics in the case of ₉₀ Pt ₁₀ 12 (Cr _0.5 Mn _0.5 ) with an exchange coupling layer having a film thickness of 11 nm
₉₀ Pt ₁₀ film and 13 nm thick (Cr _0.5 Mn _0.5 ) ₉₀ Pt
Line showing characteristics in the case of a _13- layer film 16 Substrate 17, 21 Magnetic shield 23 Reproduction gap 24 Magnetic core 22 Coil 18 Spin valve film 31, 32 Permanent magnet film 19, 20 Electrode 41 Insulating film 42 Base film 43 Non-magnetic Conductive film film 45 first ferromagnetic layer 46 cap film 52 fixed layer 50 exchange coupling layer 56, 57 magnetization direction 60, 61 base film 62, 63 permanent magnet film 64, 65 electrode,

Claims (11)

[Claims] A first ferromagnetic layer, a second ferromagnetic layer,
A spin valve comprising: a conductive non-magnetic spacer layer between the first and second ferromagnetic layers; and an exchange bias layer adjacent to the second ferromagnetic layer on the side opposite to the non-magnetic spacer layer. A magnetoresistive sensor, wherein the exchange bias layer has a first antiferromagnetic film on a side in contact with the second ferromagnetic film and a second antiferromagnetic film on a side not in contact with the second ferromagnetic film. And a plurality of antiferromagnetic films comprising a magnetic film, wherein the first antiferromagnetic film has a strong exchange bias magnetic field by increasing exchange coupling energy per unit area with the second ferromagnetic film. Wherein the second antiferromagnetic film has a large anisotropy constant and its magnetic moment is thermally stable. 2. The spin-valve magnetoresistive sensor according to claim 1, wherein the exchange coupling energy per unit area of the first antiferromagnetic film with the second ferromagnetic film is 1.0 × 10 ⁻⁴ J. / M ² or more, a spin valve type magnetoresistive sensor. 3. The spin valve type magnetoresistive sensor according to claim 1, wherein the exchange bias layer is made of an alloy composed of chromium, manganese, and platinum, and a platinum composition of the first antiferromagnetic film. Is smaller than the platinum composition of the second antiferromagnetic film. 4. The spin valve type magnetoresistive sensor according to claim 1, wherein the exchange bias layer is made of an alloy composed of chromium, manganese, and platinum, and the first antiferromagnetic film is The platinum composition is 3 at% or more and 10 at% or less and the film thickness is 5 nm or more, and the second antiferromagnetic film has a platinum composition of 9 at% or more and 15 at% or less. Spin valve type magnetoresistive sensor. 5. The spin valve type magnetoresistive sensor according to claim 1, wherein the exchange bias layer is formed by adding cobalt, gold, silver, copper, platinum, palladium, rhodium, as an additive element to an alloy composed of chromium and manganese. One or more of iridium, ruthenium, and osmium are included, and the total sum of the additive element compositions of the first antiferromagnetic film is the second antiferromagnetic film.
A spin valve type magnetoresistive sensor, wherein the total amount of the additive element compositions of the antiferromagnetic film is less than the total. 6. A buffer layer formed on a substrate, a first ferromagnetic layer formed on the buffer layer, a non-magnetic spacer layer formed adjacent to the first ferromagnetic layer, A second ferromagnetic layer formed adjacent to the magnetic spacer layer on the film surface, an exchange bias layer made of an antiferromagnetic material formed adjacent to the second ferromagnetic layer, and A Co-based permanent magnet having a spin-valve film formed into a fixed shape composed of the formed capping layer, and a base film formed so as to be adjacent to the spin-valve film processed into the fixed shape in two film cross sections. A spin-valve magnetoresistive sensor comprising: a magnet film; and an electrode film adjacent to the permanent magnet film on the film surface, wherein the exchange bias layer is disposed on a first side in contact with the second ferromagnetic film. And the second ferromagnetic film And a second antiferromagnetic film on the non-existing side, wherein the first antiferromagnetic film has an exchange coupling energy per unit area with the second ferromagnetic film. Wherein the second antiferromagnetic film has a large anisotropy constant and its magnetic moment is thermally stable. . 7. An underlayer formed on a substrate, an exchange bias layer made of an antiferromagnetic material formed on the underlayer,
A second layer formed adjacent to the exchange bias layer on the film surface;
A non-magnetic spacer layer formed adjacent to the second ferromagnetic layer; a first ferromagnetic layer formed adjacent to the non-magnetic spacer layer on the film surface; A spin-valve film processed into a fixed shape comprising a capping layer formed on a ferromagnetic layer; and a first ferromagnetic film of the spin-valve film processed into a fixed shape, adjacent to the first ferromagnetic film in two cross sections of the film. A Co-based permanent magnet film having a base film formed so as to perform, an electrode film adjacent to the permanent magnet film on the film surface,
Wherein the exchange bias layer has a first antiferromagnetic film on a side in contact with the second ferromagnetic film and a first antiferromagnetic film on a side not in contact with the second ferromagnetic film. A second antiferromagnetic film, and a plurality of antiferromagnetic films, wherein the first antiferromagnetic film increases exchange coupling energy per unit area with the second ferromagnetic film. Wherein the second anti-ferromagnetic film has a large anisotropy constant and its magnetic moment is thermally stable. 8. The spin-valve magnetoresistive sensor according to claim 6, wherein an exchange coupling energy per unit area of the first antiferromagnetic film with the second ferromagnetic film is 1.0 × 10 ^−. A spin-valve type magnetoresistive sensor, wherein the magnetoresistance sensor is ⁴ J / m ² or more. 9. The spin-valve magnetoresistive sensor according to claim 6, wherein the exchange bias layer is made of an alloy composed of chromium, manganese, and platinum. A spin valve type magnetoresistive sensor, wherein a platinum composition is smaller than a platinum composition of the second antiferromagnetic film. 10. The spin valve type magnetoresistive sensor according to claim 6, wherein the exchange bias layer is made of an alloy composed of chromium, manganese, and platinum, and the first antiferromagnetic film is The second antiferromagnetic film has a platinum composition of 3 at% or more and 10 at% or less and a film thickness of 5 nm or more, and the second antiferromagnetic film has a platinum composition of 10 at% or more and 15 at% or less. Spin valve type magnetoresistive sensor. 11. The spin valve type magnetoresistive sensor according to claim 6, wherein the exchange bias layer is formed by adding cobalt, gold, silver, copper, platinum, palladium, as an additive element to an alloy comprising chromium and manganese. It contains one or more of rhodium, iridium, ruthenium, and osmium, and the sum of the additive element compositions of the first antiferromagnetic film is the second.
A spin valve type magnetoresistive sensor, wherein the total amount of the additive element compositions of the antiferromagnetic film is less than the total.