JP2738295B2 - Magnetoresistive film and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive film for use in a magnetoresistive element for reading a magnetic field intensity as a signal in a magnetic medium or the like, and more particularly to a magnetoresistive film having a large resistance change rate with a small external magnetic field. And a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the sensitivity of magnetic sensors has been increased and the density of magnetic recording has been increased. Accordingly, a magnetoresistive magnetic sensor (hereinafter referred to as an MR sensor) and a magnetoresistive magnetic head have been developed. (Hereinafter referred to as MR head) is being actively developed. Similarly, the MR sensor and the MR head read an external magnetic field signal by a change in resistance of a reading sensor portion made of a magnetic material. However, since the relative speed with respect to the recording medium does not depend on the reproduction output, the MR sensor and the MR head have a high reading. Sensitivity is M
The R head has a feature that a high output can be obtained even in high-density magnetic recording.

[0003] In recent years, exchange sintered by made with a magnetic thin film of at least two layers are laminated through a non-magnetic thin film provided adjacent the antiferromagnetic thin film on one of the soft magnetic thin film
There is a magnetoresistive film that changes resistance by applying a combined magnetic field and rotating the magnetization by an external magnetic field different from that of the adjacent soft magnetic thin film via the nonmagnetic thin film (Physical Review B (Phys. Rev. B) No. 43). Volume, 1297 pages, 1
991).

[0004]

However, although the conventional magnetoresistive element can be operated with a small external magnetic field, when used as a practical magnetic sensor or magnetic head, the magnetoresistive effect element can be moved up and down. It is necessary to provide a lateral bias layer or to apply a bias magnetic field from the outside.

An object of the present invention is to provide a magnetoresistive film made of an artificial lattice film which does not require a lateral bias mechanism and whose resistance changes around zero magnetic field, and a method of manufacturing the same.

[0006]

The present invention comprises a plurality of magnetic thin films laminated on a substrate via a non-magnetic thin film, and an antiferromagnetic thin film is provided on one of the adjacent soft magnetic thin films via the non-magnetic thin film. The exchange coupling magnetic field of the antiferromagnetic thin film is H _r , the coercive force of the other soft magnetic thin film is H _C2 , and the anisotropic magnetic field in the direction of applying an external magnetic field is H _K2 . When H _C2 <H
A magnetoresistive film which is a _K2 <H _r.

[0007] The type of magnetic material used for the magnetoresistive film of the present invention is not particularly limited, but specifically, Fe, Co,
Mn, Cr, Dy, Er, Nd, Tb, Tm, Ge, G
d and the like are preferable. Examples of alloys and compounds containing these elements include, for example, Fe-Si, Fe-Ni, Fe-
Co, Fe-Gd, Ni-Fe-Co, Ni-Fe-M
o, Fe-Al-Si (Sendust), Fe-Y, Fe
-Mn, Cr-Sb, Co-based amorphous, Co-P
t, Fe-Al, Fe-C, Mn-Sb, Ni-Mn,
Co-O, Ni-O, Fe-O, Ni-F, ferrite and the like are preferable.

In the present invention, a magnetic thin film is formed by selecting from these magnetic materials. In particular, this can be realized by selecting a material in which the anisotropic magnetic field H _{K2 of the} magnetic thin film not adjacent to the antiferromagnetic thin film is larger than the coercive force H _C2 . Further, the anisotropic magnetic field can be increased by reducing the film thickness.
For example, when NiFe has a thickness of about 10 angstroms, the anisotropic magnetic field H _K2 can be made larger than the coercive force H _C2 .

Further, generally the magnetic thin film, when a narrow pattern width by patterning, shape anisotropy H _d by demagnetizing field appears. The shape anisotropy H _d is inversely proportional to the pattern width W, and increases as the pattern width W decreases.
In the case of the artificial lattice magnetic thin Similarly shape anisotropy H _d appears. In addition, in the case of an artificial lattice magnetic thin film, magnetic layers and non-magnetic layers are alternately laminated, and the magnetic layers are magnetostatically coupled at the film ends. The effect of the magnetostatic coupling also increases as the pattern width W decreases. Actually, by reducing the pattern width W due to these effects, the magnetic field region of the magnetic layer where the magnetization is reversed is shifted, and the anisotropic magnetic field H _K2 can be made larger than the coercive force H _C2 .

When this magnetoresistive film is used as an MR head for reading a magnetic field signal in a hard disk drive (HDD) or the like, the MR element portion is formed to a very small size by etching. At this time, the aspect ratio (W / T) defined by the ratio between the pattern width W of the MR element portion and the track width T _W.
W ) also shifts the magnetic field region of the magnetic layer where the magnetization is reversed, so that the anisotropic magnetic field H _K2 can be made larger than the coercive force H _C2 .

Further, in such a magnetoresistive film, the axis of easy magnetization of the magnetic thin film is perpendicular to the direction of the applied signal magnetic field, and the coercive force of the magnetic thin film in the applied signal magnetic field direction is H. _C2 <the magnetic thin film such that H _K2 <H _r can be produced by film formation in a magnetic field. This film formation is performed by a method such as a vapor deposition method, a sputtering method, and a molecular beam epitaxy method (MBE). Further, as the substrate, glass, Si, MgO, GaAs, ferrite, CaTi
O or the like can be used.

The upper limit of the thickness of each magnetic thin film is 200 angstroms. On the other hand, there is no particular lower limit on the thickness of the magnetic thin film. Further, when the thickness of the magnetic thin film is 4 Å or more, it is easy to keep the film thickness uniform, the film thickness becomes good, and the magnitude of the saturation magnetization does not become too small. Further, even if the thickness of the magnetic thin film is 200 Å or more, the effect does not decrease. However, the effect does not increase with an increase in the film thickness, and waste of the film is increased, which is uneconomical.

Since it is impossible to directly measure the magnetic properties of the magnetic thin film existing in the magnetoresistive element, it is usually measured as follows.

First, a magnetic thin film to be measured is alternately deposited with a non-magnetic thin film until the total thickness of the magnetic thin film becomes about 200 to 400 angstroms to prepare a measurement sample.
The magnetic properties are measured for this. In this case, the thickness of the magnetic thin film, the thickness of the non-magnetic thin film and the composition of the non-magnetic thin film are as follows:
The same as that in the magnetoresistance effect measuring element is used.

The non-magnetic thin film is a material that plays a role in weakening magnetic interaction between films of magnetic thin films having different coercive forces.
The type is not particularly limited, and may be appropriately selected from various metals or semimetal non-magnetic materials and non-metal non-magnetic materials.

For example, as the metal non-magnetic material, Au, A
g, Cu, Pt, Al, Mg, Mo, Zn, Nb, T
a, V, Hf, Sb, Zr, Ga, Ti, Sn, Pb, and the like, and alloys thereof are preferable. As the non-metallic nonmagnetic material, SiO ₂ , SiO, SiN, Al ₂ O ₃ , Z
nO, MgO, TiN, etc. and those obtained by adding another element to them are preferable.

The thickness of the non-magnetic thin film is desirably 200 Å or less. In general, when the thickness of the non-magnetic thin film exceeds 200 angstroms, the resistance is determined by the non-magnetic thin film, and the spin-dependent scattering effect becomes relatively small. As a result, the magnetoresistance change rate becomes small. . On the other hand, if the thickness of the non-magnetic thin film is less than 4 angstroms, the magnetic interaction between the magnetic thin films becomes too large, and the occurrence of a magnetic direct contact state (pinhole) is inevitable. A state in which the magnetization directions of the thin films are different from each other is less likely to occur.

The thicknesses of the magnetic thin film and the non-magnetic thin film can be measured by a transmission electron microscope, a scanning electron microscope, Auger electron spectroscopy, or the like. The crystal structures of these thin films can be confirmed by X-ray diffraction, high-speed electron beam diffraction, or the like.

The number of repetitive laminations N of the artificial lattice film of the magnetoresistive film of the present invention is not particularly limited, and may be appropriately selected according to a desired magnetoresistance change rate. However, the rate of change in magnetoresistance also increases, but productivity decreases. Further, if the number N of repeated laminations is too large, the resistance value of the entire element becomes low and practical inconvenience occurs. Therefore, the number N of repeated laminations is usually preferably 50 or less.

The surface of the uppermost magnetic thin film may be provided with an antioxidant film such as silicon nitride or silicon oxide for protection, or a metal conductive layer for leading out electrodes.

[0021]

In the magnetoresistive film of the present invention, it is essential that an antiferromagnetic thin film is formed adjacent to one soft magnetic thin film via a nonmagnetic thin film, and that an exchange coupling magnetic field works. The reason is that the principle of the present invention is to exhibit the maximum resistance value when the magnetization directions of adjacent magnetic thin films are opposite to each other. That is, in the magnetoresistive film of the present invention, as shown in FIG. 1, the strength of the external magnetic field H is such that the coercive force H _{C2 of} the soft magnetic thin film 5 (see FIG. 3) and the exchange coupling of the antiferromagnetic thin film.
When it is between the combined magnetic field H _r (H _C2 <H <H _r ), the directions of magnetization of the adjacent soft magnetic thin films are opposite to each other,
The resistance value of the magnetoresistive film increases.

Further, it is essential that the anisotropic magnetic field H _{K2 in the} direction of the applied signal magnetic field is larger than the coercive force H _C2 of the soft magnetic thin film. However, the coercive force H _C2 is the exchange coupling magnetic field H
_If it is larger than _r , an antiparallel state of the magnetization direction cannot be obtained, and a sufficient resistance change cannot be obtained, which is not preferable.

Next, the relationship among the external magnetic field, the coercive force, and the direction of magnetization will be described. As described above, the exchange coupling magnetic field of the antiferromagnetic thin film is H _r , and the coercive force of the soft magnetic thin film 5 is H _r .
_C2 , the anisotropic magnetic field in the direction of the applied signal magnetic field is H _K2 (where 0 <H _C2 <H _K2 <H _r ). First, the external magnetic field H is applied so that H <−H _K2. (See FIG. 1). In this [region A], the magnetization directions of the soft magnetic thin film 3 and the soft magnetic thin film 5 shown in FIG.
They are aligned in the (negative) direction. Note that arrows 3 and 5 shown in FIG. 1 represent the magnetization directions of the soft magnetic thin film 3 and the soft magnetic thin film 5 shown in FIG. 3, respectively.

Here, when the external magnetic field is weakened, -H _K2
In [region B] of <H <H _K2 , the magnetization of the soft magnetic thin film 5 starts to rotate continuously. Subsequently, in [region C] of H _K2 <H <H _r , the soft magnetic thin film 5 is completely rotated. Upon completion of the magnetization reversal, the magnetization directions of the soft magnetic thin film 3 and the soft magnetic thin film 5 become opposite to each other. Further, in the [region D] of H _r <H where the external magnetic field is increased, the magnetization of the soft magnetic thin film 3 is also reversed, and the magnetization directions of the soft magnetic thin film 3 and the soft magnetic thin film 5 are aligned in the + (positive) direction. .

The resistance of the magnetoresistive film changes depending on the relative magnetization direction of the soft magnetic thin film 3 and the soft magnetic thin film 5, and changes linearly around a zero magnetic field in [region B], and changes in [region C]. ] Has the maximum value (R _MAX ). That is, with such a film, a magnetoresistive film having a linear change in resistance around zero magnetic field and requiring no lateral bias mechanism can be obtained.

[0026]

Next, the present invention will be described with reference to the drawings.

FIG. 2 is a sectional view showing the structure of a magnetoresistive film according to one embodiment of the present invention. Magnetoresistive film of the present embodiment, as shown in FIG. 2, the artificial lattice film 1 on the glass substrate 7 forming a metal thin film 6 is formed, an artificial lattice film 1, the soft magnetic thin film M _1, M ₂ , ..., M _n-1 , M _n
And a non-magnetic thin film N ₁ between two adjacent soft magnetic thin films,
N _2, ......, and _{N n-2, N n-} 1, and an antiferromagnetic film AM. These are stacked in the order of a magnetic thin film M ₁ , a non-magnetic thin film N ₁ , a magnetic thin film M ₂ ,..., A non-magnetic thin film N _n−1 , a magnetic thin film M _n , and an antiferromagnetic film AM.

Next, specific experimental results of the magnetoresistive film of the present invention will be described with reference to FIG. FIG.
It is a side view which shows the structure of the specific example of the magnetoresistive film of this invention. (Example 1) First, a glass substrate 7 was used as a substrate, placed in an ultra-high vacuum evaporation apparatus, and 10 ^-9 to 10 ^-10 t.
Vacuum to orr. The substrate temperature is kept at room temperature, while rotating the glass substrate 7, a Cr thin film is formed as the metal thin film 6 to a thickness of 50 angstroms, and then the artificial lattice film 1 having the following composition is formed at about 0.3 angstroms / sec. Film formation was performed at a film formation speed of.

The artificial lattice film 1 is formed of a soft magnetic thin film 5, a nonmagnetic thin film 4, a soft magnetic thin film 3, and an antiferromagnetic film 2 in the order of, for example, Cr (50) / NiFe (20) / Cu When (55) / NiFe (20) / FeMn (50) is displayed, the metal thin film 6
After forming a 50 Å thick Cr film as
20 angstrom thick Ni80% -Fe20% soft magnetic thin film 5, 55 angstrom thick nonmagnetic thin film 4, 20 angstrom thick Ni80% -Fe20
% Soft magnetic thin film 3 and 50 Å thick F
This means that the antiferromagnetic thin film 2 of eMn is sequentially deposited.

The magnetization was measured by a vibrating magnetometer, and the resistance was measured by 0.3 × 10 mm from the sample.
While applying an external magnetic field H in the plane so as to be perpendicular to the direction of the current, -500 to 50
The resistance when changing to 0 Oe (Oersted) is 4
Measured by the terminal method, the rate of change in magnetoresistance Δ
R / R was determined. The magnetoresistance change rate ΔR / R was calculated by the following equation, with the maximum resistance value being R _MAX and the minimum resistance value being R _MIN .

[0031]

Here, the manufactured artificial lattice film is composed of Cr (50) / NiFe (8) / Cu (55) / NiFe (20) / FeMn (50) Cr (50) / NiFe (10) / Cu (55) / NiFe (20) / FeMn (50) Cr (50) / NiFe (20) / Cu (55) / NiFe (20) / FeMn (50) Cr (50) / NiFe (25) / Cu (55) / NiFe (20) / FeMn (50). In an artificial lattice film in which the soft magnetic NiFe layer has a thickness of 8 to 15 angstroms, a soft magnetic layer in which the anisotropic magnetic field H _K of the NiFe layer is larger than the coercive force H _C is obtained. The BH curve of this artificial lattice film was as shown in FIG. 1, and a film having a linearly changing resistance around a zero magnetic field was obtained.

Further, in the NiFe layer 25 angstrom sample, the anisotropy of the NiFe layer magnetic field H _K is the coercive force H
_C was almost the same, and a film having a linearly variable resistance before and after the zero magnetic field was not obtained. (Example 2) As in the case of Example 1, the following artificial lattice film was prepared.

Cr (50) / NiFe (10) / Cu (22) / NiFe (20) / FeMn (50) Then, Au is formed on this to form an electrode 2400
Angstrom was deposited. Further, a resist is applied on the artificial lattice film, and the MR patterns having various MR pattern widths are subjected to fine processing using a dry etching apparatus. Then, the Au layer of the MR sensing part is removed to obtain a resistance measurement sample. And

The sizes of the sensing portions of the artificial lattice film whose magnetoresistance was measured are four types of 3 × 200 μm 5 × 200 μm 10 × 200 μm 20 × 200 μm. In an artificial lattice film having an MR pattern width of 30 μm or less, the apparent anisotropic magnetic field H _K of the NiFe layer is larger than the coercive force H _C due to the demagnetizing field of the film and the effect of the magnetostatic coupling between the magnetic layers of the artificial lattice film. growing. It was found that the MR curve of the artificial lattice film continuously shifted in the region where the resistance was linearly changed according to the MR pattern width.

In particular, in this sample, the MR pattern width is 5
At the time of μm, a film having a linearly changing resistance before and after the zero magnetic field was obtained. On the other hand, in a sample having an MR pattern width of 30 μm or more, the influence of the demagnetizing field and the magnetostatic coupling becomes relatively small.
A film with a linearly changing resistance before and after the zero magnetic field was not obtained. (Example 3) It is generally known that a NiFe film has uniaxial anisotropy by being deposited (formed) in a magnetic field. NiFe having uniaxial anisotropy by deposition in this magnetic field
When an external magnetic field is applied in the hard axis direction of the film, this NiFe
The BH curve of the layer also shows that the anisotropic magnetic field H _K has a coercive force H _C
The shape becomes larger than that. Therefore, even with an artificial lattice film in which the direction of application of the external magnetic field is a hard axis due to deposition in a magnetic field, a magnetoresistive film having a linearly variable resistance around a zero magnetic field can be obtained.

More specifically, SmC
An o-magnet was arranged, and the artificial lattice film was deposited in a state where an external magnetic field of about several tens of Oe (Oersted) was applied in parallel with the glass substrate 7. When the BH curve of this sample is measured, the direction of application of the magnetic field during vapor deposition becomes the axis of easy magnetization of the NiFe layer, and the anisotropic magnetic field H _K does not become much larger than the coercive force H _C. However, the magnetization direction of the film is perpendicular to the direction in which the magnetic field is applied during deposition, and when an external magnetic field is applied in the direction of the hard axis, the resistance of the artificial lattice film has good linearity around the zero magnetic field. It turned out to change.

The anisotropic magnetic field H _K and the coercive force H _C change depending on the soft magnetic properties and the anisotropy coefficient of the soft magnetic material. NiF
The eMo material shows soft magnetic properties that are several steps better than the NiFe material. The coercive force H _C is better than that of the NiFe material,
In the eMo material, the anisotropic magnetic field H _K is larger than the coercive force H _C , and is, for example, Cr (50) / NiFeMo (2
0) / Cu (55) / NiFe (20) / FeMn (5
It can be seen that a magnetoresistive film which does not require a lateral bias mechanism which similarly changes resistance around zero magnetic field can be obtained with the artificial lattice film composed of 0).

[0039]

As described above, according to the present invention, the horizontal
It is possible to obtain a magnetoresistive film made of an artificial lattice that does not require a bias mechanism and changes its resistance around zero magnetic field.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the operation principle of a magnetoresistive film according to the present invention.

FIG. 2 is a side view showing a configuration of a magnetoresistive film of the present invention.

FIG. 3 is a side view showing a configuration of a specific example of a magnetoresistive film of the present invention.

[Explanation of symbols]

1 superlattice 2, AM antiferromagnetic thin _{3,5, M 1, M 2,} ..., M n-1, M n soft magnetic thin film _{4, N 1, N 2,} ..., N n-2, N n _-1 Non-magnetic thin film 6 Metal thin film 7 Glass substrate

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 43/12 G01R 33/06 R

Claims (6)

(57) [Claims] An antiferromagnetic thin film is provided adjacent to one of the soft magnetic thin films adjacent to the soft magnetic thin film via the nonmagnetic thin film. When the exchange coupling magnetic field of the ferromagnetic thin film is H _r , the coercive force of the other soft magnetic thin film is H _C2 , and the anisotropic magnetic field in the direction of the applied signal magnetic field is H _K2 , H _C2 <H _K2 <H _r A magnetoresistive effect film, characterized in that: 2. A magnetoresistive film according to claim 1, wherein the pattern width of the magnetoresistive film is 30 μm or less . 3. The magnetic device according to claim 1, wherein an aspect ratio defined by (pattern width / track width) of the magnetoresistive element portion of the magnetoresistive film is 0.1 to 100. Resistive film. 4. A magnetoresistive film, wherein the soft magnetic thin film according to claim 1 is made of a NiFe alloy, a NiFeMo alloy, or an alloy containing these as a main component. 5. The method of manufacturing a magnetoresistive film according to claim 1, wherein the axis of easy magnetization of the magnetic thin film is perpendicular to the direction of the applied signal magnetic field and is in the direction of the applied signal magnetic field. Forming the magnetic thin film in a magnetic field such that the coercive force of each of the above is H _C2 <H _K2 <H _r . 6. The method according to claim 5, wherein the coercive force of each of the magnetic thin films is H _C2 <H _K2.
<Method of manufacturing the magnetoresistive film, wherein etching the pattern width to 30μm or less so that H _r.