JPH0888118A - Exchange coupled film and magnetoresistance effective element - Google Patents

Abstract

PURPOSE: To obtain an exchange coupled film having an excellent exchange coupling force and corrosion resistance by a method wherein an antiferromagnetic body film is composition modulated structured. CONSTITUTION: The switched connection film is provided with antiferromagnetic body films 3, 4 in the composition represented by M100-x Mnx as well as a ferromagnetic body film 2 lamination formed on these antiferromagnetic body films 3, 4 wherein M in the antiferromagnetic body film 3 is at least one kind of element selected from Fe, Co, Pd, Pt while the value of x: 40<x<=60 near the interface of the ferromagnetic body film 2 side but 20<=x<=40 near the opposite side to the interface. Besides, the composition of the antiferromagnetic body film changes within the range of 20<=x<=80 through the film thickness direction or the composition of antiferromagnetic body film is continuously changes or the composition of the antiferromagnetic body film changes stepwise. Furthermore, an electrode for current supply to at least the antiferromagnetic body film out of these exchange coupled films is formed on a substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exchange coupling film using exchange coupling between an antiferromagnetic material film and a ferromagnetic material film, and a magnetic field detecting sensor or reproducing magnetic field provided with this exchange coupling film. The present invention relates to a magnetoresistive element such as a head.

[0002]

2. Description of the Related Art As a reproducing head for high density magnetic recording, a magnetic head using a magnetoresistive effect element has been researched for some time. Currently, 80 at% Ni-20 at% Fe (commonly known as permalloy) alloy thin film is used as a magnetoresistive element material. In recent years, artificial lattice films such as (Co / Cu) _n exhibiting a giant magnetoresistive effect and spin valve films have been attracting attention as alternative materials.

However, since the magnetoresistive effect film using these materials has magnetic domains, Barkhausen noise resulting from this is a big problem in practical use, and the magnetoresistive effect film is made into a single magnetic domain. Various methods have been studied. One of them is a method of controlling the magnetic domain of the magnetoresistive film in a specific direction by using exchange coupling between the magnetoresistive film and the antiferromagnetic film, which are ferromagnetic materials. Γ-FeMn alloys have been widely known as the above (for example, US Pat. No. 4,103,315 and US Pat.
No. 014147). However, the γ-FeMn alloy has a problem of corrosion resistance, particularly corrosion with respect to water, and the exchange coupling force with the magnetoresistive effect film is deteriorated over time due to corrosion in the processing step as a magnetoresistive effect element or corrosion due to moisture in the atmosphere. There is a problem of deterioration.

Further, MnPt and Mn are used as an antiferromagnetic material film.
U.S. Pat. No. 4,103,315 also discloses examples using other .gamma.-Mn alloys such as Rh alloys and examples using oxide NiO. However, these γ-Mn alloys do not have sufficient exchange coupling force with the ferromagnetic material, and oxide systems such as NiO have poor thermal stability and exchange with the ferromagnetic material film at a high temperature of 100 ° C or higher. The binding force is unstable. Further, in the case of an insulating oxide system having a high electric resistance such as NiO, there is a problem that the element structure becomes complicated because the electrode cannot be directly taken out from this portion.

[0005]

As described above, the conventional antiferromagnetic material film used for obtaining exchange coupling with the ferromagnetic material film, for example, reduction of Barkhausen noise of the magnetoresistive effect element. Had a problem with its corrosion resistance.

The present invention has been made in order to solve such a problem, and has a good exchange coupling force and an exchange coupling film provided with an antiferromagnetic material film excellent in corrosion resistance, and the exchange coupling film thereof. An object of the present invention is to provide a magnetoresistive effect element including a film and capable of obtaining stable output over a long period of time.

[0007]

The exchange-coupling film of the present invention comprises an antiferromagnetic film having a composition represented by M _100-x Mn _x , and a strong layer formed with this antiferromagnetic film. And a magnetic film, M in the antiferromagnetic film is Fe, Co, Ni,
It consists of at least one selected from Pd and Pt, and the value of x is 40 <x ≤ 60 near the interface on the ferromagnetic film side.
And 20 ≤ x ≤ 40 near the surface opposite to the interface.
Is characterized in that.

The magnetoresistive effect element of the present invention is characterized in that the above-mentioned exchange coupling film and an electrode for passing a current through at least a ferromagnetic film of this exchange coupling film are formed on a substrate. And

The present invention will be described in detail below. First, the composition of the antiferromagnetic material film in the exchange coupling film of the present invention is M
_100-x Mn _x (M is at least one selected from Fe, Co, Ni, Pd, and Pt), and M using Fe, Co, Ni, Pd, or Pt as M
The n alloy generally has a large exchange coupling force. Here, the value of x is 40 <in the vicinity of the interface on the ferromagnetic film side.
x ≤ 60, 20 ≤ near the surface on the opposite side of the interface
x ≦ 40. In the present invention, the numerical value of x represents atomic%, and the vicinity means a range within 2 nm from the interface, for example. In this way, by changing the composition of the antiferromagnetic material film in the vicinity of the interface and in the vicinity of the surface on the opposite side within the above range, it is possible to improve corrosion resistance while maintaining excellent exchange coupling force. A preferable composition in the vicinity of the interface on the ferromagnetic film side is a composition ratio of M to Mn of 1: 1. This composition is particularly preferable in terms of exchange coupling force and blocking temperature.

Further, in the exchange coupling film of the present invention, the composition is not particularly limited in the vicinity of the central portion in the film thickness direction of the antiferromagnetic material film. However, it is preferable that the composition of the antiferromagnetic material film is set within the range of 20 ≦ x ≦ 80 over the film thickness direction. What makes M for 80 <x composition
This is because if the amount of n is too large, the corrosion resistance is reduced, and if the composition is x <20, the Neel temperature may be lower than room temperature and exchange coupling may not be obtained. More preferably, it is a composition-modulation type antiferromagnetic material film in which the amount of Mn decreases as it moves away from the laminated interface with the ferromagnetic material film within the above range. In addition, although this composition-modulated form is preferably a continuous composition change, it may be a step-form composition change, that is, a laminated film of films having different compositions. The continuous composition change can be formed by forming a multilayer film having a composition which is changed stepwise and performing an annealing treatment, or by multi-element simultaneous film formation. However, the composition modulation mode may be such that the exchange coupling of the present invention becomes maximum or minimum in the vicinity of the central portion in the film thickness direction of the antiferromagnetic material film, that is, in the vicinity of the interface with the ferromagnetic material and If the surface on the opposite side is in the above range, good corrosion resistance and exchange coupling force can be exhibited. The ferromagnetic film relating to the exchange coupling film of the present invention is a film that exhibits ferromagnetism, and is not particularly limited, but when used in a magnetoresistive effect element, a magnetoresistive effect element such as permalloy having a small saturation magnetic field or a giant magnetoresistive effect element is used. Ferromagnetic metals such as Fe, Ni and Co, which exhibit a magnetoresistive effect, and alloys of these, Fe _m Ni _100-m and Fe _m Co.
_{100-m, Fe m Co n} Ni 100-mn (m, n numerical values represents. Atomic%) was added a third element and a fourth element for the purpose of improving and magnetic properties of these ferromagnetic metal alloy Examples include artificial lattices composed of alloys and non-magnetic metal alloys, spin valve films, granular magnetic alloy films, and the like.

In particular, Fe _m Co _100-m , Fe _m Co _n
Co based ferromagnetic material such as _{Ni 100-mn, Fe m Co} n Pd 10 0-mn film is preferable since it is possible to increase the blocking temperature is the temperature at which the exchange coupling disappears. When the blocking temperature is high, it is effective in preventing the deterioration of the exchange coupling force in the process involving a thermal cycle when forming the device structure.

At least a part of the ferromagnetic film and the antiferromagnetic film according to the present invention may be laminated and exchange-coupled.

In the composition-modulation type antiferromagnetic material film relating to the exchange coupling film of the present invention, it is preferable to add Cu as an additional element for the purpose of lattice matching and improvement of corrosion resistance. That is, by using an antiferromagnetic film having a composition of (MMn) _100-y Cu _y (0 <y ≦ 50), lattice matching and corrosion resistance are further improved. Here, M represents at least one selected from Fe, Co, Ni, Pd, and Pt, and when the composition of each component in MMn alone is M _100-x Mn _x as described above, 20 ≤ x ≤ A compositional range of 80 is preferred. The numerical value of y represents atomic%. Here, Cu may be added in a constant amount from the interface to the surface, or may be concentration-modulated. Further, for example, it may be added only in the vicinity of the surface on the opposite side of the interface from the viewpoint of maintaining the exchange coupling force and improving the corrosion resistance. In this (MMn) _100-y Cu _y composition, 50
In the case of <y, the amount of Cu is too large to obtain sufficient exchange coupling. The preferred range for obtaining sufficient exchange coupling is 0 <
y ≦ 20. The composition-modulation type antiferromagnetic material film relating to the exchange coupling film of the present invention is (MMn) _100-y Cu
It is also possible to use a composition modulation type in which only the amount of Cu is changed in the composition of _y (0 <y ≦ 50).

The thickness of the antiferromagnetic material film relating to the exchange coupling film of the present invention is not particularly limited as long as it is in the range where antiferromagnetism is exhibited. However, in order to obtain a large exchange coupling force,
It is desirable that the thickness of the antiferromagnetic material film be thicker than the thickness of the ferromagnetic material film. Further, it is preferable that the M _100-x Mn _x (40 ≤ x ≤ 60) antiferromagnetic material film, which is a composition near the laminated interface with the ferromagnetic material, has a film thickness of 15 nm or less.

The exchange coupling film of the present invention is formed on, for example, a substrate by using a known film forming method such as a vapor deposition method, a sputtering method and an MBE method. At this time, in order to impart unidirectional anisotropy to the antiferromagnetic film, film formation and heat treatment may be performed in a magnetic field.

The substrate is not particularly limited, and is not particularly limited to amorphous substrates such as glass and resin, single crystal substrates such as Si, MgO, Al ₂ O ₃ and various ferrites, oriented substrates, and sintered substrates. An underlayer having a thickness of 1 to 100 nm may be provided on the substrate in order to improve the crystallinity of the antiferromagnetic material film or the ferromagnetic material film. The underlayer is not particularly limited as long as it improves crystallinity, but for example, a noble metal such as Pd or Pt, an amorphous metal such as CoZrNb, a metal having a face-centered cubic structure, an alloy, or the like can be used.

Further, in the above-mentioned exchange coupling film of the present invention, at least an electrode for passing a current through the ferromagnetic film is formed of, for example, Cu, Ag, Au, Al or an alloy thereof, so that the present invention can be realized. The magnetoresistive effect element can be easily obtained. Here, the electrode may be in a form of being in direct contact with the ferromagnetic film or a form of interposing an antiferromagnetic film.

As described above, the exchange coupling film of the present invention can be applied to various devices using a magnetoresistive effect element such as a magnetic field detecting sensor and a reproducing magnetic head.

In the magnetoresistive element of the present invention, the exchange coupling force between the antiferromagnetic material film and the ferromagnetic material film is not limited to the Barkhausen noise removal in the ferromagnetic material film, but is also an artificial lattice film or spin valve film. It can also be used for fixing the magnetization to.

[0020]

The present invention will be described below with reference to the drawings. Example 1 An exchange coupling film of the present invention composed of an antiferromagnetic material film and a ferromagnetic material film was produced using an RF magnetron sputtering apparatus.
A cross-sectional view of the exchange coupling membrane is shown in FIG. Specifically, on the sapphire C face 1, a ferromagnetic film 2 having a composition of CoFePd is formed with a thickness of 5 nm and a composition of Fe ₅₀ Mn ₅₀ (50 at% F
The antiferromagnetic film 3 represented by e-50 at% Mn) has a thickness of 10 nm, and the antiferromagnetic film 4 having a composition of Fe ₆₅ Mn ₃₅ has a thickness of 5 nm. The film was formed in a magnetic field. At this time, the substrate was not particularly heated. The crystal structure and the orientation of the exchange-coupled film thus obtained were examined by X-ray diffraction, and the crystal structure was a face-centered cubic structure.
11) It was confirmed that the film was oriented.

This film was allowed to stand in pure water for 1 hour, and the occurrence of corrosion pits was examined. The result is shown in FIG. As shown in FIG. 2, the exchange coupling film of this example had a significantly low probability of corrosion pits, and almost no corrosion pits were found. As Comparative Example 1, 15 nm thick Fe prepared in the same manner as in Example 1 was used.
FIG. 2 shows the result of leaving the same in the pure water for 1 hour for the exchange coupling film having only ₅₀ Mn ₅₀ as the antiferromagnetic film. As shown in FIG. 2, the probability of occurrence of corrosion pits was significantly high. Incidentally, FIG. 3 shows a situation of occurrence of corrosion pits observed by an optical microscope. FIG. 3A shows the results of this example, and FIG. 3B shows the results of Comparative Example 1. Corrosion pits are indicated by black dots in the figure. As described above, it can be seen that the corrosion resistance of the FeMn film is significantly improved by forming the FeMn film with the composition changed into the laminated film.

Example 2 An exchange coupling membrane was prepared in the same manner as in Example 1. FIG. 4 shows the magnetization curves of the easy-axis direction a (magnetic field direction during film formation) and the hard-axis direction b of the exchange-coupling film produced here. At this time, the value of c in FIG. 4 becomes the exchange bias magnetic field (Hua). In the exchange-coupling film of the present invention, an exchange-coupling bias magnetic field equivalent to that of the exchange-coupling film having only Fe ₅₀ Mn ₅₀ as the antiferromagnetic film was obtained.

Example 3 In the same manner as in Example 1, a ferromagnetic film made of CoFePd having a thickness of 5 nm and an antiferromagnetic film made of N having a thickness of 10 nm were used.
i ₅₀ Mn ₅₀ and 5 nm of Ni ₆₅ Mn ₃₅ were heat-treated in a magnetic field and in a magnetic field to form an exchange coupling film.

As a result of leaving the obtained exchange-coupled membrane in pure water for 1 hour, almost no corrosion pits were found. As Comparative Example 2, an N film having a thickness of 15 nm was prepared in the same manner as in Example 1.
Similarly, with respect to the exchange-coupling film having only i ₅₀ Mn ₅₀ as the antiferromagnetic film, many corrosion pits were formed when the film was left in pure water for 1 hour. The probability of occurrence of corrosion pits is shown in FIG. As described above, it can be seen that the corrosion resistance of the NiMn film is significantly improved by forming the NiMn film with the composition changed into the laminated film.

Example 4 to Example 9 In the same manner as in Example 1, the ferromagnetic film and antiferromagnetic film shown in Table 1 were formed to form an exchange coupling film. In addition,
In Example 7, an antiferromagnetic film was formed by simultaneous multi-component film formation so that the composition changed continuously, and the film thickness shown in Table 1 represents the distance from the interface with the ferromagnetic film. The composition indicates the composition at that distance.

As a result of leaving the obtained exchange-coupled film in pure water for 1 hour, almost no corrosion pits were found. Also, exchange coupling films using only the antiferromagnetic material film near the interface were prepared as Comparative Example 3 to Comparative Example 6 in the same manner as in Example 1 and left in pure water for 1 hour in the same manner. There was a corrosion pit. Figure 2 shows the probability of corrosion pits
Shown in In addition, Example 4 and Comparative Example 3 correspond to Example 5, Comparative Example 4, Example 6 and Comparative Example 5, and Example 7 and Comparative Example 6, respectively. As described above, it can be understood that the corrosion resistance of the film is significantly improved by forming the laminated film in which the composition of the antiferromagnetic film is changed.

[0027]

[Table 1] Example 10 In the same manner as in Example 1, CoFePd having a film thickness of 5 nm was used as the ferromagnetic film and F having a film thickness of 10 nm was used as the antiferromagnetic film.
e ₅₀ Mn ₅₀ and Fe _63.7 Mn _34.3 Cu ₂ having a thickness of 5 nm were formed to form an exchange coupling film. When the crystal structure and the orientation of the exchange-exchanged film thus obtained were examined by X-ray diffraction, it was confirmed that the crystal structure was a face-centered cubic structure and was a (111) -oriented film.

This film was allowed to stand in pure water to examine the state of corrosion pit formation. As a result of observing with an optical microscope after standing for 1 hour, almost no corrosion pits were found. Again 18
As a result of standing for a time, the exchange-coupling film of Comparative Example 1 was almost completely corroded and peeled off, whereas the exchange-coupling film of the present Example had corrosion progressed but part of the film. Remained on the substrate except. Thus, the addition of Cu significantly improved the corrosion resistance of the FeMn film.

Example 11 In the same manner as in Example 8, a ferromagnetic film made of CoFePd having a film thickness of 5 nm and an antiferromagnetic film made of F having a film thickness of 10 nm were used.
e ₅₀ Mn ₅₀ and 5 nm (Fe _0.65 Mn _0.35 ) _100-y C
u _y (y = 0,1,2,5,10,15) was formed into an exchange coupling film. The obtained exchange-bonded film was left in the same pure water for 3 hours, and the probability of occurrence of corrosion pits was examined by an optical microscope. The result is shown in FIG. From Figure 5, 1at% C
Even with the addition of u, the corrosion resistance was significantly improved. Also, the exchange bias magnetic field (Hua) after standing was 90% or more compared with the initial value.

Example 12 A magnetoresistive effect element of the present invention was produced by using an exchange coupling film of an antiferromagnetic material film and a ferromagnetic material film, which had sufficient exchange bias magnetic field and corrosion resistance in Example 1. A sectional view of the magnetoresistive effect element is shown in FIG. The substrate 5 has a thermally oxidized Si wafer, and the ferromagnetic films 6 and 7 each have a thickness of 5 nm.
And 3 nm CoFePd, and the antiferromagnetic film 8 has a thickness of 1
Fe ₅₀ Mn ₅₀ having a thickness of 0 nm and Fe ₆₅ Mn ₃₅ having a thickness of 5 nm were used, and Cu having a thickness of 3 nm was used for the nonmagnetic film 9. Also,
A CoZrNb film having a thickness of 10 nm was formed as the high-resistance soft magnetic film 10. Further, Cu of 20 μm is used for the electrode 11,
A 4 nm CoPt film was used for the hard film 12. 6, 7,
The films Nos. 8, 9 and 12 are formed in a magnetic field, and further heat-treated in a magnetic field to impart unidirectional anisotropy to the antiferromagnetic film 8 and to magnetize the ferromagnetic film 7. Fixed. The high resistance soft magnetic material film 9 is also formed in a magnetic field to impart uniaxial anisotropy, and the hard film 12 is magnetized to further strengthen the uniaxiality of the high resistance soft magnetic material film. There is. After that, the element was processed using a normal semiconductor process to obtain a magnetoresistive element.

When a magnetic field was applied from the outside to the obtained magnetoresistive effect element and its magnetic field response was examined, a stable output comparable to that of the same magnetoresistive effect element was obtained, and magnetic domain wall movement was caused. There was no occurrence of Barkhausen noise accompanying it. In addition, the production yield obtained as a device was also improved.

Example 13 As an antiferromagnetic film, Fe ₅₀ Mn ₅₀ having a film thickness of 10 nm and
But using a laminated film composed of Fe _63.7 Mn _{34 .3} Cu ₂ of 5 nm, to prepare a magneto-resistance effect element of the present invention in the same manner as in Example 11.

A magnetic field was externally applied to the obtained magnetoresistive effect element, and its magnetic field response was examined.
The same stable output as that of the magnetoresistive effect element of No. 1 was obtained, and the Barkhausen noise accompanying the domain wall movement was not found. In addition, the production yield obtained as a device was also improved.

[0034]

As described above in detail, in the exchange coupling film of the present invention, the antiferromagnetic film has a composition modulation structure,
The magnetoresistive effect element of the present invention having a good exchange coupling force and excellent in corrosion resistance and comprising such an exchange coupling film can obtain a stable output for a long time, There is great value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an exchange coupling membrane according to a first embodiment.

FIG. 2 is a diagram showing a probability of occurrence of corrosion pits in an exchange coupling film left in pure water for 1 hour.

FIG. 3 is a diagram showing a situation of occurrence of corrosion pits observed by an optical microscope.

FIG. 4 is a diagram showing a magnetization curve in an easy-axis direction a and a hard-axis direction b of the exchange coupling film.

FIG. 5 is a diagram showing a Cu amount and a corrosion pit occurrence probability.

FIG. 6 is a sectional view of a magnetoresistive effect element of the present invention.

[Explanation of symbols]

1 ... Sapphire C plane, 2, 6, 7 ... Ferromagnetic material film, 3, 4, 8 ... Antiferromagnetic material film, 5 ......... Substrate, 9
……… Non-magnetic material film, 10 ………… High resistance soft magnetic material film, 11
……… Electrode, 12 ……… Hard film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomomi Funayama No. 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center (72) Inventor Hitoshi Iwasaki Komukai-Toshiba, Kawasaki-shi, Kanagawa Town No. 1 Incorporated company Toshiba Research and Development Center (72) Inventor Masashi Sahashi Komukai-shi, Kawasaki, Kanagawa Prefecture Komukai Toshiba Town No. 1 Incorporated company Toshiba Research and Development Center (72) Inventor Hiroyuki Hasebe Kawasaki, Kanagawa Prefecture Komukai-Toshiba-cho 1-ku, Toshiba Research & Development Center

Claims (5)

[Claims] 1. An exchange coupling film comprising an antiferromagnetic film having a composition represented by M _100-x Mn _x , and a ferromagnetic film laminated with the antiferromagnetic film. M in the antiferromagnetic material film is Fe, Co, Ni, P
It is composed of at least one selected from d and Pt, and the value of x is 40 <x ≤ 60 near the interface on the ferromagnetic film side.
And near the surface opposite to the interface, 20 ≤ x
An exchange-coupling membrane characterized in that ≦ 40. 2. The exchange coupling film according to claim 1, wherein the composition of the antiferromagnetic film is 20 ≦ x ≦ 8 throughout the film thickness direction.
An exchange-coupling membrane characterized by varying within the range of 0. 3. The exchange coupling film according to claim 1, wherein the composition of the antiferromagnetic film continuously changes. 4. The exchange coupling film according to claim 1, wherein the composition of the antiferromagnetic film changes stepwise. 5. The exchange coupling film according to claim 1, and an electrode for passing a current through at least a ferromagnetic film of the exchange coupling film is formed on a substrate. A magnetoresistive effect element characterized by being formed.