JPH076915A - Magnetic multilayered film, magnetoresistive element, and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the magnetic field sensitivity while reducing the hysteresis by a method wherein the coersive force of adjacent magnetic thin film are changed from one another through the intermediary of non-magnetic thin films. CONSTITUTION:The coersive forces of adjacent magnetic thin films M1, M2, Mn-1, Mn-2 throught the intermediary of non-magnetic thin films N1, N2, Nn-2, Nn-1 are changed from one another while securing the thickness of the first magnetic thin films M1, Mn-1 having small coersive force, the thickness of the second magnetic thin films M2, Mn-2 having large coersive force and the thickness of the non-magnetic thin films N1, N2, Nn-2, Nn-1 respectively to be t1, t2 and t3, 4Angstrom <t2<20Angstrom , 5Angstrom <t1<=20Angstrom , t1<t2, 32Angstrom <3t<50Angstrom . On the other hand, the squareness ratio of the first magnetic thin films M1, Mn-1 having small coersive force is to be 0.7-1.0 while that of the second magnetic thin films M2, Mn-2 having large coersive force is to be 0.1-0.8. Through these specifications, the large gradient of the magnetoresistive variation within the magnetic field range of -500e-+500e, the high magnetic sensitivity and the reduced hysteresis can be assured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive change element capable of reading a particularly small magnetic field change as a large electric resistance change signal, among magnetoresistive change elements for reading the magnetic field strength of a magnetic recording medium or the like as a signal. The present invention relates to a magnetic multilayer film suitable for it, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, magnetic sensors have been made highly sensitive and magnetic recording has been made highly dense. Along with this, magnetoresistive effect type magnetic sensors (hereinafter referred to as M
It is called R sensor. ) Or a magnetoresistive effect type magnetic head (hereinafter referred to as an MR head) is being actively developed. Both the MR sensor and the MR head read the external magnetic field signal by the resistance change of the reading sensor section using a magnetic material. However, in the MR sensor and the MR head, the relative speed with the recording medium does not depend on the reproduction output. From MR
The sensor has high sensitivity, and the MR head has a feature that high output can be obtained even in high-density magnetic recording.

However, in a conventional MR sensor using a magnetic material such as Ni _0.8 Fe _0.2 (permalloy) or NiCo due to the anisotropic magnetoresistive effect, the resistance change rate ΔR / R is as small as about 2 to 4%, The sensitivity is insufficient as a read MR head material for ultra-high density recording on the order of several GBPI.

By the way, an artificial lattice having a structure in which thin films having a thickness on the order of atomic diameter of metal are periodically laminated has attracted attention in recent years because it exhibits characteristics different from those of bulk metal. As one type of such an artificial lattice, there is a magnetic multilayer film in which ferromagnetic metal thin films and antiferromagnetic metal thin films are alternately laminated on a substrate. So far, iron-chromium type, nickel-chromium type and iron- Manganese type (JP-A-60-1)
No. 89906), a magnetic multilayer film is known. Among them, it is reported that the iron-chromium type (Fe / Cr) exhibits a magnetoresistance change of more than 40% at ultralow temperature (4.2K) (Phys. Rev. Lett, Vol. 61, 2).
472, 1988). However, in this artificial lattice magnetic multilayer film, the external magnetic field (operating magnetic field strength) at which the maximum resistance change occurs is as large as ten dozen kOe to several dozen kOe, and it is not practical as it is. In addition to these, artificial lattice magnetic multilayer films of Co / Cu, Co / Ag, etc. have been proposed, but these have too high operating magnetic field strength.

Under these circumstances, therefore, there has been proposed a ternary artificial lattice magnetic multilayer film which exhibits a giant MR change due to induced ferrimagnetism by laminating two magnetic layers having different coercive forces via a non-magnetic layer. . For example, the Hc of adjacent magnetic thin films are different via the non-magnetic layer, and the thickness of each layer is 200.
The following documents, such as those of A or less (Japanese Patent Laid-Open No. 4-218982; c below), have been published.

A. Journal of The Physical Society of
Japan, 59 (1990) 3061T. Shinjo and H. Yamamoto [Co (30) / Cu (50) / NiFe (30) / C
u (50)] × 15 [() indicates the film thickness of each layer (A), ×
Is the number of repetitions, the same applies below] in the applied magnetic field 3 kOe
The MR change rate was about 9.9% at 500 Oe, and about 8.5% at 500 Oe.

B. Journal of Magnetism and Magnetic
Materials, 99 (1991) 243 H.Ymamamoto, T.Okuyama, H.Do
In addition to hnomae, and T. Shinjo a, structural analysis results, temperature change of MR change rate and resistivity, change with angle of external magnetic field, minor loop of MR curve, dependence of stacking number, dependence of Cu layer thickness, magnetization curve The changes are discussed.

C. [Patent Document 1] JP-A-4-218982 [Patent Document 1] Japanese Patent Application Laid-Open No. 4-218982 SUMMARY OF THE INVENTION The present invention relates to a magnetic multilayer film in which magnetic thin films having different coercive forces are laminated via a non-magnetic thin film. Laminated examples are disclosed.

D. JP-4-247607 discloses _{(Ni x Co 1-x)} x 'Fe 1-x' and _{(Co y Ni 1-y)} z
Fe _1-z (x = 0.6 to 1.0, x ′ = 0.7 to 1.
0, y = 0.4 to 1.0, and z = 0.8 to 1.0) are disclosed via a non-magnetic layer, and in the embodiment, two kinds of 30A are used. The magnetic layers are laminated via a 50 A non-magnetic layer.

E. The Institute of Electrical Engineers of Japan Magnetics Research Material,
MAG-91-161 Hoshino, Hosoe, Jinbo, Kanda, Tsunashima, Uchiyama a, b. Additional studies are being made on the dependence on the Cu layer thickness and the NiFe layer thickness. In addition, there is a result of the Cu layer thickness dependency of Hc of Co obtained by extrapolation from the magnetization curve. In addition, NiFe (30) -Cu (320) and Co
NiFe (30) -Cu (160) -Co was synthesized by combining the respective magnetization curves obtained from (30) -Cu (320).
It is compared with the magnetization curve of (30) -Cu (160).
In this case, since the Cu intermediate thickness is different from that of the ternary artificial lattice, it is not possible to directly compare the squareness ratio and Hc.

In addition, as shown in FIG. 7 and FIG. In 8,
The dependence of the NiFe layer thickness t ₁ and the Co layer thickness t ₂ when the nonmagnetic layer is fixed at 80 A is shown. Of these, FIG. 7 has a Co layer thickness t ₂ fixed at 30 A,
The MR change rate when the iFe layer thickness t ₁ is changed to ₅ to 50 A is shown. In addition, FIG. 8 has (t ₁ , t
₂ ) = There are data points of (20,10) and (20,5). However, these MR change rates are all less than 4%.

F. The Institute of Electrical Engineers of Japan Magnetics Research Material,
MAG-91-242 Okuyama, Yamamoto, Shinjo Developmental analysis of giant MR changes due to induced ferrimagnetism is described. It has been confirmed that the MR similarly changes with the rotation of the magnetic moment of the NiFe layer having a small Hc, and a giant MR phenomenon appears due to the antiparallel state of the artificially generated spins. Also, this development is N
It has been proved that it is different from the anisotropic MR effect of iFe by the difference in the applied magnetic field angle of MR.

G. Journal of Japan Applied Magnetics, 17 (199)
3) 365. (Issue date 1993.4.1) Miyauchi, Araki, Narimiya The present inventors' paper. A multilayer film in which three kinds of materials using NiFe, Co, and Cu are laminated (hereinafter, such a film is referred to as a ternary magnetic multilayer film). Fig. 8 for C
r (50) [Cu (50) -Co (10) -Cu (5
0) -NiFe (10)] × 10 MR change curve in the range of −10 to 10 Oe is shown. In addition, FIG. 7
(NiFe thickness t ₁ , Co thickness t ₂ ) = (10, 1
0), (20,10), (30,10), (30,1)
5) and (20, 20) data points, and FIG.
3 has (t ₁ , t ₂ ) = (10, 10), (15, 1
0), (20, 10), and (30, 10) have data on the gradient of the change in magnetoresistance, but the Cu layer thickness is all 50 A.

In such a ternary artificial lattice magnetic multilayer film, the magnitude of the MR change rate is inferior to that of Fe / Cr, Co / Cu, Co / Ag, etc., but it is 10 at an applied magnetic field of several 100 Oe or less. It shows a huge MR change rate of about%.
However, the contents disclosed in these documents are several tens.
Only for MR changes with an applied magnetic field of about 100 Oe.

By the way, as an MR head material in actual ultra-high density magnetic recording, an applied magnetic field of -50 Oe to 50 is used.
The MR change curve up to Oe is important. However, in these conventional ternary artificial lattices, the MR change at an applied magnetic field of 0 does not increase so much and is almost zero. The rate of increase in MR change reaches a maximum at about 60 Oe, at which time MR is about 9%.
The rate of change is shown. That is, the rising of the change curve is slow. On the other hand, in the case of permalloy (NiFe), the gradient of MR change in a 0 magnetic field is almost 0, the MR change rate is almost unchanged, and the differential value of the MR change rate is close to 0.

As a means for solving such a characteristic, N
With iFe or the like, a shunt layer having a small specific resistance such as Ti is provided to shift the operating point. In addition to this shunt layer, a soft film bias layer made of a soft magnetic material having a large specific resistance such as CoZrMo or NiFeRh is provided to apply a bias magnetic field. However, the structure having such a bias layer complicates the process, makes it difficult to stabilize the characteristics, and causes an increase in cost. In addition, since a gentle portion of the MR change curve is used, the S / N is lowered.

Further, the MR head or the like requires a heat treatment such as baking or curing of the resist material in the steps of patterning, flattening, etc. in a complicated laminated structure, and the temperature is 250 ° C.
Some heat resistance is required. However, in the conventional ternary artificial lattice magnetic multilayer film, such heat treatment deteriorates the characteristics.

As described above, in the conventional ternary magnetic multilayer film, the gradient (M) of the magnetoresistance change in the magnetic field range of -50 to 50 Oe.
The R slope) is less than 0.15% / Oe, which is not satisfactory in terms of characteristics. However, FIG. 8 shows a linear resistance change at -10 to 10 Oe.

On the other hand, in the MR head, it is also important that the maximum hysteresis width of the magnetoresistance change curve (MR curve) is small. This maximum hysteresis width is preferably 10 Oe or less, particularly 6 Oe or less. However, most of the conventional ternary magnetic multilayer films cannot satisfy this requirement. However, FIG. In No. 8, the hysteresis width is extremely small.

Furthermore, the MR head is required to be used under a high frequency magnetic field of 1 MHz or more for high density recording / reproducing. However, in the film thickness structure of various conventional ternary magnetic multilayer films, the slope of the magnetoresistance change curve (MR slope at high frequency) in a high frequency magnetic field of 1 MHz or more is 0.03% / Oe.
As described above, it is difficult to obtain high high frequency sensitivity.

[0021]

The object of the present invention is to provide a magnetoresistive change curve having a maximum hysteresis width as small as 10 Oe or less, linearly in the magnetic field range of -50 to 50 Oe, for example, 0.15% / Oe or more. Large magnetic resistance change gradient (MR
Slope, which has a large magnetoresistance change rate of, for example, 5% or more, and has a large magnetoresistance change gradient (high-frequency MR slope) of, for example, 0.03% / Oe or more in a high-frequency magnetic field of 1 MHz or more, and a heat-resistant temperature. To provide a high magnetic multi-layer film, a magnetoresistive variable element using the same, and a manufacturing method thereof.

[0022]

The above object is achieved by the present invention described in (1) to (16) below. (1) A first magnetic thin film having a small coercive force, which has at least two layers of magnetic thin films laminated via a non-magnetic thin film, and adjacent magnetic thin films have different coercive forces via the non-magnetic thin film. Is set to be t ₁ , the thickness of the second magnetic thin film having a large coercive force is t ₂ , and the thickness of the nonmagnetic thin film is t ₃ , then 4 A <
t ₂ <20 A, 5 A <t ₁ ≦ 20 A, t ₁ > t ₂ , 32
A magnetic multilayer film with A <t ₃ <50A. (2) The squareness ratio SQ ₁ of the first magnetic thin film having a small coercive force is 0.7 to 1.0, and the squareness ratio SQ ₂ of the second magnetic thin film having a large coercive force is 0.1 to 0. The magnetic multilayer film according to (1) above, which is 0.8. (3) The magnetic multilayer film according to (1) or (2), wherein SQ ₂ / SQ ₁ is 0.3 to 1.0. (4) 6 A ≤t ₂ , t ₁ ≤18 A, t ₁ ≥1.05t
₂ , The magnetic multilayer film according to any one of (1) to (3) above, wherein 36 A ≤t ₃ ≤48 A. (5) The maximum hysteresis width of the magnetic resistance change curve is 10 Oe
The magnetic multilayer film according to any one of (1) to (4) below. (6) The magnetic multilayer film according to any one of the above (1) to (5), wherein the gradient of magnetoresistance change in the magnetic field range of −50 to −50 Oe is 0.15% / Oe or more. (7) [(maximum value of specific resistance-minimum value of specific resistance) / minimum value of specific resistance] × 100 The magnetoresistance change rate is 5% or more, any of the above (1) to (6) The magnetic multilayer film. (8) The nonmagnetic multilayer film according to any one of the above (1) to (7), wherein the gradient of change in magnetoresistance in a high frequency magnetic field at 1 MHz is 0.03% / Oe or more. (9) the first composition of the magnetic thin film (Ni _x Fe _1-x)
y Co _1-y (where 0.7 ≦ x ≦ 0.9, 0.5 ≦ y
≦ 1.0. ) The magnetic multilayer film according to any one of the above (1) to (8). (10) The composition of the second magnetic thin film is (Co _z Ni
_1-z ) _w Fe _1-w (where 0.4 ≦ z ≦ 1.0, 0.
5 ≦ w ≦ 1.0. The above (1) represented by
The magnetic multilayer film according to any one of (9). (11) The magnetic multilayer film according to any one of (1) to (10) above, wherein the non-magnetic thin film is selected from Au, Ag or Cu or an alloy containing 70% or more of 1 to 3 of them. (12) The method for producing a magnetic multilayer film according to any one of (1) to (11) above, wherein after the film formation, heat treatment is performed at a temperature of 400 ° C. or lower. (13) The film is formed at a pressure of 10 ^-8 Torr or less (1)
(11) A method for manufacturing a magnetic multilayer film according to any one of (11). (14) A magnetoresistive effect element having the magnetic multilayer film according to any one of (1) to (11) above on a substrate. (15) The magnetoresistive effect element according to the above (14), which does not have a bias magnetic field applying mechanism. (16) According to the manufacturing method of (12) or (13), at least two magnetic thin films are formed on a substrate via a non-magnetic thin film, and the magnetic multilayer film according to any one of (1) to (11) above. And a method for manufacturing a magnetoresistive effect element.

[0023]

In the ternary artificial lattice magnetic multilayer film, the magnetoresistance change curve (MR curve) having a small hysteresis width, good linearity in the magnetic field range of -50 to 50 Oe and a large MR slope, and a high magnetoresistance change. In order to obtain a high rate, a large gradient of the magnetoresistance change in a high frequency magnetic field of 1 MHz or more, and good heat resistance, the difference between Hc shown in a to g in the above-mentioned literature, and the difference there. The structure of the film is not enough. In order to satisfy all of these characteristics, the film thicknesses t ₁ , t ₂ and t ₃ of the first and second magnetic thin films and the non-magnetic thin film must be controlled according to the present invention. And, such film thicknesses t ₁ , t ₂ , t _{3 of the} present invention
Are not described in documents a to g and the like.

[0024]

Specific Structure The specific structure of the present invention will be described in detail below.

In the present invention, it is necessary that the coercive force of the magnetic thin films adjacent to each other with the non-magnetic thin film interposed therebetween be different from each other. The reason is that the principle of the present invention is that when the magnetization directions of the adjacent magnetic layers are deviated, conduction electrons are scattered depending on spin, resistance increases, and the magnetization directions are opposite to each other. This is because the maximum resistance is sometimes exhibited. That is, in the present invention, is between the external magnetic field of a coercive force Hc ₂ of coercive force Hc ₁ and the second magnetic thin film layer of the first magnetic thin film _{(Hc 1 <H <Hc 2} ) as shown in Figure 2 When
The components in which the magnetization directions of the adjacent magnetic layers are opposite to each other are generated, and the resistance increases.

The relationship among the external magnetic field, coercive force, and magnetization direction of the ternary artificial lattice multilayer magnetic film will be described. Figure 1
FIG. 3 is a cross-sectional view of an artificial lattice magnetic multilayer film 1 that is an example of the present invention. In FIG. 1, an artificial lattice magnetic multilayer film 1 has magnetic thin films M ₁ , M _2, ..., M _n-1 , M _n on a substrate 4,
Between the two adjacent magnetic thin films, the non-magnetic thin films N ₁ , N ₂
, N _n-2 and N _n-1 .

Now, a case in which only two kinds of magnetic thin films having different coercive forces are provided will be described in a simplified manner. As shown in FIG. 2, Hc of the two types of magnetic thin film layers is Hc ₁ and Hc ₂ , respectively (0 <Hc ₁ <Hc
₂ ). First, the external magnetic field H is changed to H <-Hm (Hm is the second
Is an external magnetic field at which the magnetization of the magnetic thin film is saturated. ). First and second magnetic thin film layers,
The magnetization direction of is the same as that of H in the- (negative) direction. Next, when the external magnetic field is increased, in the region (I) where H <Hc ₁ , the magnetization directions of both magnetic thin films are still in one direction.
When the external magnetic field is increased to reach the region (II) where Hc ₁ <H <Hm, the magnetization direction of a part of the magnetic thin film begins to reverse, and the magnetization directions of the magnetic thin film and the magnetization direction of the magnetic thin film have mutually opposite components.
Further, in the region (III) where Hm <H in which the external magnetic field is increased, the magnetization direction of the magnetic thin film is aligned with the + direction.

Next, when the external magnetic field H is reduced, Hc₂ 
In the <H region (IV), the magnetization direction of the magnetic thin film is +
It is still facing, but -Hc₂ <H <Hc₂ Area (V)
Then, the magnetization direction of the magnetic thin film layer is reversed in one direction.
Therefore, there is a component in which the magnetization directions of the magnetic thin film are opposite to each other.
Occurs. Furthermore, in the region H <−Hm (VI), the magnetic thinness is
The magnetization directions of the film are aligned in one direction. This magnetic thin
Region where the magnetization directions of the film are opposite to each other
In (II) and (V), conduction electrons are scattered depending on spin.
The resistance increases due to the disturbance. For example, the first magnetic thin film
For example, Ni with a small Hc _0.8 Fe_0.2 Select (Hc number Oe),
For example, Co (Hc
By selecting several tens Oe), the external magnetic field Hc₂ Small outside
An MR element that exhibits a large resistance change rate in a partial magnetic field can be obtained.

The type of magnetic material used in the magnetic thin film of the present invention is not particularly limited, but specifically, Fe, Ni, Co,
Mn, Cr, Dy, Er, Nd, Tb, Tm, Ce, G
d and the like are preferable. Examples of alloys and compounds containing these elements include Fe-Si, Fe-Ni, and Fe-.
Co, Fe-Al, Fe-Al-Si (Sendust etc.), Fe-Y, Fe-Gd, Fe-Mn, Co-N
i, Cr-Sb, Fe-based amorphous alloy, Co-based amorphous alloy, Co-Pt, Fe-Al, Fe-C, M
n-Sb, Ni-Mn, Co-O, Ni-O, Fe-
O, Fe-Al-Si-N, Ni-F, ferrite and the like are preferable. In the present invention, two or more of these magnetic materials having different coercive forces are selected to form the magnetic thin film.

The upper limit of the thickness of each magnetic thin film is 20A.
On the other hand, there is no particular lower limit to the thickness of the magnetic thin film, but if it is 4 A or less, the Curie point becomes lower than room temperature and the practicality is lost. Further, if the thickness exceeds 4A, it becomes easy to keep the film thickness uniform and the film quality becomes good. Further, the magnitude of saturation magnetization does not become too small. Film thickness 20
If it is larger than A, it becomes impossible to fabricate a structure satisfying all of the above properties.

The coercive force Hc of each magnetic thin film is, for example, 0.001 Oe to 10 kOe, especially 0.01 to 10 kOe, depending on the external magnetic field strength of the applied element and the required resistance change rate.
It may be appropriately selected from the range of 1000 Oe. Further, the coercive force ratio of the adjacent magnetic thin films is 1.2: 1 to 100 :.
1, particularly 1.5: 1 to 100: 1, more preferably 2: 1
It is preferably ˜80: 1, especially 3: 1 to 60: 1, more preferably 5: 1 to 50: 1, especially 6: 1 to 30: 1. If the ratio is too large, the MR curve becomes broad, and if it is too small, the difference in Hc becomes too close, and the antiparallel state does not work effectively.

When measuring Hc, the magnetic characteristics of the magnetic thin film present in the magnetoresistive effect element cannot be directly measured, and therefore, it is usually measured as follows. That is, 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 reaches about 200 to 400 A to prepare a measurement sample, and the magnetic characteristics of the sample are measured. At this time, 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 the same as those in the magnetoresistive effect measuring element.

In the present invention, in order to obtain a high linearity MR curve and a high heat resistance from a zero magnetic field, the residual magnetization Mr of the first magnetic thin film having a small Hc and the second magnetic thin film having a large Hc in the zero magnetic field is Mr. , That is, the squareness ratio SQ = Mr / Ms
To control.

In the first magnetic thin film, 0.7 ≦ SQ ₁ ≦
1.0, more preferably 0.8 ≦ SQ ₁ ≦ 1.0,
In the second magnetic thin film, it is preferable that 0.1 ≦ SQ ₂ ≦ 0.8, and more preferably 0.3 ≦ SQ ₂ ≦ 0.8.

Since the first magnetic thin film regulates the rise of MR change in the vicinity of 0 magnetic field, the squareness ratio should be closer to 1.0. When it becomes smaller than 0.7, the rising edge of the MR change curve becomes broad, and as a result, the MR change rate becomes small. On the other hand, 0 for the second magnetic thin film
It is better that the magnetization is smaller than the residual magnetization (Mr) near the magnetic field. For example, when the squareness ratio is 0.7, the magnetization of both magnetic thin films aligned in one direction is reversed in magnetization by 30% of the second magnetic thin film at 0 magnetic field. As a result, a portion that partially shows an antiparallel state is generated in the 0 magnetic field, and this spin-dependent MR change occurs. Therefore, by selecting the squareness ratio of the second magnetic thin film, it is possible to freely design the MR curve that linearly changes with zero magnetic field.

As the magnetic thin film satisfying such characteristics, the first magnetic thin film is (Ni _x Fe _1-x ) _y Co.
_1-y (however, 0.7 ≦ x ≦ 0.9, 0.5 ≦ y ≦ 1.
0) and (Co _z Ni _1-z ) _w as the first magnetic thin film.
Fe _1-w (however, 0.4 ≦ z ≦ 1.0, 0.5 ≦ w ≦
Those having a composition of 1.0) are preferable.

In the present invention, the film thicknesses of the first and second magnetic thin films and the non-magnetic thin film are optimized. Now, as in most of the concrete examples shown in the above-mentioned documents a to g, when the thickness of the first and second magnetic thin films is the same, the squareness ratio of both thin films becomes 1. It approaches 0. Therefore, the magnetization curve does not show a clear bending of the magnetization. As a result, the MR change curve has a poor linearity in the 0 magnetic field which rises first at several 10 Oe.
Therefore, the thinner the magnetic thin film is, the better the linearity is, and the good rising characteristics are exhibited. Also, both thin films
Even when the thickness is as thin as about 10 A or less, even if it is heated in a vacuum at about 250 ° C., it is not significantly affected by the deterioration of the squareness ratio, and there is no problem in heat resistance. When the first magnetic thin film is made thicker, the rectangular shape approaches 1.0. Therefore, if the first magnetic thin film is made slightly thicker independently of the second magnetic thin film, the MR characteristic after the heat treatment in the process is better.

SQ ₂ / SQ ₁ is 0.3 to 1.0,
It is particularly preferably 0.3 to 0.8.

In the present invention, when the film thicknesses of the first and second magnetic thin films and the nonmagnetic thin film are t _1, t ₂ and t ₃ , respectively, 4A <t ₂ <20A, 5A <t ₁
≦ 20A, in particular _{5A <t 1 <20A, t} 2 <t 1, and 32A <t ₃ <50A, more preferably, 6A ≦ t ₂ <
18A, 6A <t ₁ ≤ 18A, 1.05t ₂ <t ₁ to 36A ≤ t ₃ ≤ 48A. When t ₂ is 20 A or more, the squareness of the second magnetic thin film becomes large, the linearity is lost, and the rising characteristics deteriorate.

By thus controlling the film thickness of the first and second magnetic thin films and the non-magnetic thin film, the magnetic multilayer film immediately after film formation has a high MR change rate of 5% or more, particularly 6 to 10%. At the same time, the linearity is high at 0 magnetic field, and the MR change with a large MR slope is shown. More specifically, the MR gradient from the applied magnetic field of −50 Oe to +50 Oe is 0.
15% / Oe or more, usually about 0.2 to 0.5%, and sufficient characteristics can be obtained as a read MR head for ultrahigh density recording.

In the present invention, as described above, t ₁ , t
_{Since 2} and t ₃ are regulated, good heat resistance can be obtained, and deterioration of characteristics due to heat treatment, especially deterioration of MR change rate is extremely reduced. That is, for example, the MR change rate can be maintained at 75% or more before the heat treatment even by heat treatment up to 250 ° C. in vacuum, and the MR change rate of 4.5% or more, particularly 5% or more.
The rate of change is shown. After heat treatment, SQ ₁ is 0.7 to
1.0, particularly 0.8 to 1.0, and SQ ₂ is 0.1 to 0.
A value of 8, in particular 0.3-0.8 is maintained.

Furthermore, the maximum hysteresis width of the magnetic resistance change curve can be set to 10 Oe or less, generally 4 to 6 Oe, which is extremely advantageous in practical use. And, the MR gradient in a high frequency magnetic field of 1 MHz is 0.03% / Oe or more, and is usually 0.
It can be set to 05 to 0.5% / Oe, which is suitable for a read MR head for high density magnetic recording.

The MR change rate is (ρmax −ρs) when the maximum and minimum values of the specific resistance are ρmax and ρsat.
ρsat) × 100 / ρsat (%). Further, the maximum hysteresis width is the maximum value of the hysteresis calculated by measuring the magnetoresistance change curve (MR curve) at -50 to +50 Oe. Furthermore, for the MR slope, measure the MR curve,
It is the maximum value of the differential value at −50 to +50 Oe obtained by obtaining the differential curve. And the high frequency MR tilt is 1MH
-3 when measuring the MR change rate in an alternating magnetic field of z 30 Oe
It is the inclination between +3 Oe.

The non-magnetic thin film used is a material that weakens magnetic interaction between magnetic thin films having different coercive forces, and the kind thereof is not particularly limited, and various metals or semi-metal non-magnetic materials or non-metal non-magnetic materials are used. Can be selected as appropriate. As the metal non-magnetic material, Au, Ag, Cu, Pt, Al, M
g, Mo, Zn, Nb, Ta, V, Hf, Sb, Zr,
Ga, Ti, Sn, Pb and the like and alloys thereof are preferable.
As the semi-metal non-magnetic material, Si, Ge, C, B, etc., or those obtained by adding another element to these are preferable. As non-metal non-magnetic materials, SiO ₂ , SiO, SiN, Al ₂ O ₃ ,
It is preferable to use ZnO, MgO, TiN, or the like, or those to which another element is added. Among these, Au, Ag or Cu, or an alloy containing 70% or more of 1 to 3 of these is preferable.

Generally reported Cu layer thickness of 50A
In the following thin cases, only a small MR change rate of 3 to 4% or less is shown. Further, the magnetic layer thickness at this time is as thick as about 30A. However, the present invention exhibits a linear MR change by combining a non-magnetic thin film of less than 50 A with a thin magnetic thin film of less than 20 A. In particular, when the thickness t _{3 of the} non-magnetic thin film is 32 A <t ₃ <50 A, a linear MR change curve centered at 0 magnetic field can be realized. When it is 50 A or more, the magnetic coupling between the layers is completely broken and the linear region is narrowed, which is not suitable for the head characteristics. Also 32A
Below, the magnetic coupling between layers becomes strong, and as a result,
The linearity that the MR curve rises largely deviates from the zero magnetic field in the positive direction, resulting in poor linearity. The thickness 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 structure of the thin film can be confirmed by X-ray diffraction, high-speed electron beam diffraction, or the like.

In the present invention, the number of times n of repeated lamination of the artificial lattice magnetic multilayer film is not particularly limited and may be appropriately selected according to the target magnetoresistance change rate, etc., but in order to obtain a sufficient magnetoresistance change rate. It is preferable that n is 3 or more. Further, as the number of laminated layers increases, the rate of change in resistance also increases, but productivity deteriorates. Further, if n is too large, the resistance of the entire device becomes too low, which causes practical inconvenience. Is preferably 50 or less.
The long-period structure can be confirmed by a small-angle X-ray diffraction pattern from the appearance of primary and secondary peaks according to the repeating period.

In the above description, only two kinds of magnetic thin films having different coercive forces are used as the magnetic thin film, but if three or more kinds of magnetic thin films having different coercive forces are used,
The external magnetic field in which the magnetization direction is reversed can be set at two or more places, and the range of operating magnetic field strength can be expanded.

In order to alleviate the difference in surface energy between the substrate material and the material constituting the artificial lattice, improve the wettability of both materials, and realize a laminated structure having a flat interface in a wide range, a magnetic multilayer As a base layer of the film, 10-100A
A thin film of Cr, Fe, Co, Ni, W, Ti, V, Mn or their alloys may be provided. Furthermore, an anti-oxidation film such as silicon nitride or silicon oxide may be provided on the surface of the uppermost magnetic thin film, or a metal conductive layer for leading out electrodes may be provided. The magnetic multilayer film is formed by vapor deposition, sputtering, molecular beam epitaxy (MB
Use the method such as E). At this time, it is preferable to perform the vapor deposition method, especially the MBE method, at an operating pressure of 10 ^-8 Torr or less. Further, as the substrate, glass, silicon, MgO, G
It is possible to use aAs, ferrite, CaTiO, or the like.

FIGS. 3 and 4 show an example in which a magnetoresistive variable element, for example, an MR head is constructed using the magnetic multilayer film of the present invention. Magnetoresistive change element 1 shown in both figures
0 is, for example, Cu, Ag, or the like for forming the above-mentioned magnetic multilayer film 1 in the insulating layer 5 and supplying a measurement current to the magnetic multilayer film 1.
The electrodes 3 and 3 made of Au or the like are connected to the shunt layer 2 made of Ti or the like. The magnetic multilayer film 1 is covered with shields 6 and 6 such as Sendust and Permalloy.
Further, in the example of FIG. 4, under the shunt layer 2, for example, Co
A bias magnetic field applying layer 7 made of a soft magnetic material having a large specific resistance such as ZrMo and NiFeRh is provided. However, since the magnetic multilayer film of the present invention has a good rising characteristic in a zero magnetic field, this shunt layer and bias magnetic field applying means may not be provided.

In manufacturing such a magnetoresistive variable element, heat treatment such as baking, annealing, and curing of resist is required in the steps such as patterning and planarization during the process. However, since the multilayer film of the present invention has good heat resistance, it is 400 ° C. or lower, generally 50 to 300 ° C., especially 5 ° C.
It can fully support heat treatment between 0 and 250 ° C. The heat treatment may be performed usually in vacuum, in an inert gas atmosphere, in the air, or the like.

[0051]

EXAMPLES The present invention will now be described in more detail with reference to specific examples.

Example 1 Using the glass substrate 4 as a substrate, the glass substrate 4 was placed in an ultrahigh vacuum vapor deposition apparatus and vacuumed to 10 ^-9 to 10 ^-10 Torr.
An artificial lattice magnetic multilayer film 1 having the following composition was prepared while rotating the substrate while keeping the substrate temperature at room temperature. At this time, vapor deposition was performed by a molecular beam epitaxy method (MBE) at a film forming rate of about 0.3 A / sec.

Table 1 below shows the structure of the multilayer film of the magnetic thin film and the non-magnetic thin film and the magnetoresistance change rate. In Table 1, for example, Sample No. 1 is [Ni _0.8 Fe _0.2 (1
3) / Cu (45) / Co (10) / Cu (45)] ×
A 10, t ₁ = a 13A thick Ni80% -Fe20
% Permalloy magnetic (NiFe) alloy first magnetic thin film, t ₃ = 45 A thick Cu non-magnetic thin film, t ₂ = 10 A
Thick second magnetic thin film of Co and t ₃ = 45 A thick Cu
This means that the step of sequentially depositing the non-magnetic thin film of 10 was repeated 10 times. The number of repeats for each sample was set to 10 times, so this was set to (Cu / t ₃ , Co / t ₂ , NiF
(45, 10, 13) in the order of e / t ₁ ) are shown in Table 1. In each sample, 50 A of Cr was used as the underlayer.
Intervening layers.

The magnetization and BH loop were measured by a vibrating magnetometer. For resistance measurement, a sample with a shape of 0.5 × 10 mm was prepared from the sample having the constitution shown in Table 1,
The resistance when changing from -300 to 300 Oe while applying an external magnetic field in the plane perpendicular to the current is 4
The minimum value of the specific resistance and the MR change rate were obtained from the resistance measured by the terminal method. MR change rate (MR,%), the maximum value of resistivity is ρmax, the minimum value of resistivity is ρsat,
Calculated by the following formula: MR = (ρ _m −ρ sat) × 100
/ Ρsat (%). Further, the MR gradient (% / Oe) from the applied magnetic field of −50 Oe to 50 Oe was obtained. This value must be 0.15% / Oe or more as described above. Furthermore, B
The maximum hysteresis width of the H loop was obtained. Also, the MR slope (% / Oe) in a high frequency magnetic field of 1 MHz (magnetic field strength of 3 Oe) was obtained.

Separately from this, the first magnetic thin film (Co) or the second magnetic thin film (NiFe) and the non-magnetic thin film (C
u) and were used to prepare a binary system artificial lattice under the above conditions, and the respective squareness ratios SQ ₁ and SQ ₂ and their relative ratios SQ ₂ / SQ ₁ were determined. The results (initial characteristics) are also shown in Table 1.

[0056]

[Table 1]

From the results shown in Table 1, it can be seen that according to the present invention, a large MR change rate, a large MR slope, a large high frequency MR slope, and a small hysteresis can be obtained. The sample No. 2 was annealed in vacuum (10 ⁻⁷ Torr) at the temperature shown in FIG. 5 for 1 hour. From this figure, it can be seen that the heat resistance is also good.

[0058]

According to the present invention, a large magnetic resistance change rate is exhibited, a large magnetic resistance change gradient is obtained in the magnetic field range of -50 Oe to +50 Oe, magnetic field sensitivity is high, hysteresis is small, and a magnetic multilayer film is obtained. To be Moreover, it has high detection sensitivity in a high frequency magnetic field and exhibits good heat resistance. Therefore, a highly sensitive MR sensor and high-density magnetic recording are possible, and an excellent magnetoresistive variable element such as an MR head that does not require a bias applying material structure can be provided.

[Brief description of drawings]

FIG. 1 is a partially omitted cross-sectional view of a magnetic multilayer film of the present invention.

FIG. 2 is a schematic diagram of a BH curve explaining the operation of the present invention.

FIG. 3 is a partially omitted front view showing an example of a magnetoresistive variable element of the present invention.

FIG. 4 is a partially omitted front view showing another example of the magnetoresistive variable element of the present invention.

FIG. 5 is a graph showing changes in MR change rate and MR slope when a magnetic multilayer film of the present invention is heat-treated.

[Explanation of symbols]

 1 Artificial lattice film 10 Magnetoresistive change element 4 Substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 43/08 Z 9274-4M

Claims (16)

[Claims] 1. A first magnetic film having a small coercive force, which has at least two layers of magnetic thin films laminated with a nonmagnetic thin film interposed therebetween, and adjacent magnetic thin films have different coercive forces via the nonmagnetic thin film. When the thickness of the magnetic thin film is t ₁ , the thickness of the second magnetic thin film having a large coercive force is t ₂ , and the thickness of the nonmagnetic thin film is t ₃ , 4 A <t ₂ <20 A, 5 A <t ₁ ≤
A magnetic multilayer film in which 20 A, t ₁ > t ₂ , and 32 A <t ₃ <50 A. 2. The squareness ratio SQ ₁ of the first magnetic thin film having a small coercive force is 0.7 to 1.0, and the squareness ratio SQ ₂ of the second magnetic thin film having a large coercive force is 0.1. The magnetic multi-layer film according to claim 1, which is about 0.8. 3. The magnetic multilayer film according to claim ₁ , wherein SQ ₂ / SQ ₁ is 0.3 to 1.0. 4. 6 A ≤t ₂ , t ₁ ≤18 A, t ₁ ≥1.
The magnetic multilayer film according to any one of claims 1 to ₃ , wherein 05t ₂ and 36 A ≤t ₃ ≤48 A. 5. The magnetic multilayer film according to claim 1, wherein the maximum hysteresis width of the magnetic resistance change curve is 10 Oe or less. 6. The gradient of magnetoresistance change in a magnetic field range of −50 to −50 Oe is 0.15% / Oe or more.
Any of the magnetic multilayer film. 7. [(maximum specific resistance-minimum specific resistance)]
/ Minimum value of specific resistance] × 100, the rate of change in magnetoresistance is 5% or more, and the magnetic multilayer film according to claim 1. 8. The non-magnetic multilayer film according to claim 1, wherein the gradient of magnetoresistance change in a high frequency magnetic field at 1 MHz is 0.03% / Oe or more. 9. The composition of the first magnetic thin film is (Ni _x F
e _1-x ) _y Co _1-y (where 0.7 ≦ x ≦ 0.9,
0.5 ≦ y ≦ 1.0. ) Claims 1-8 represented by
Any of the magnetic multilayer film. 10. The composition of the second magnetic thin film is (Co_z 
Ni_1-z )_w Fe_{1- w} (However, 0.4 ≦ z ≦ 1.0,
0.5 ≦ w ≦ 1.0. ) Represented by 1) to 9
Any of the magnetic multilayer film. 11. The magnetic multilayer film according to claim 1, wherein the non-magnetic thin film is selected from Au, Ag or Cu or an alloy containing 70% or more of 1 to 3 of them. 12. The method for producing a magnetic multilayer film according to claim 1, wherein after the film formation, heat treatment is performed at a temperature of 400 ° C. or lower. 13. The method for producing a magnetic multilayer film according to claim 1, wherein the film formation is performed at a pressure of 10 ⁻⁸ Torr or less. 14. A magnetoresistive element having a magnetic multilayer film according to claim 1 on a substrate. 15. The magnetoresistive effect element according to claim 14, which does not have a bias magnetic field applying mechanism. 16. A magnetic film having at least two magnetic thin films formed on a substrate via a non-magnetic thin film by the manufacturing method according to claim 12 or 13, and the magnetic multilayer film according to claim 1. Method of manufacturing resistance effect element.