JPH11251141A - Laminating film and element comprising high exchange-combination magnetic field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminating film, wherein stronger exchange-combination magnetic field used for magnetization control of a ferry-magnetics layer of thin-film type MR element and spin-valve element is stably obtained, and the spin-valve element using the laminating structure. SOLUTION: A laminating film wherein a base material layer, wherein the value of a surface roughness Ra is 90-110% of the value of inter-lattice surface distance of a (111) surface of a ferro-magnetics body, a ferro-magnetics layer, and an antiferromagnetics layer are sequentially laminated, is provided, and on a base material layer wherein the value of surface roughness Ra is 90-110% of inter-lattice surface distance of (111) surface of ferro-magnetics of a first ferro-magnetics layer, the first ferro-magnetics layer, a non-magnetics layer, a second ferro-magnetics layer, and the anti-ferromagnetics layer are sequentially laminated to constitute a magnetoresistance element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, a magnetic encoder, and other magnetic heads.
The present invention relates to an element utilizing the magnetoresistance effect.

[0002]

2. Description of the Related Art A hard disk is a magnetic recording device capable of recording and reading a large amount of information at high speed. The recording density of hard disks used in personal computers and the like has increased by about 60% in one year, and this trend is expected to continue in the future. As an element of a head for reading information recorded on a magnetic medium of this hard disk,
Magnetoresistance effect elements have come to be used frequently.

[0003] The magnetoresistance effect is an effect in which the electric resistance changes when a magnetic field is applied to a conductive magnetic material. A change in the magnetic field is detected using an element having this effect, and information recorded on a magnetic medium is read. Read. The magnetoresistive effect element includes a conventional MR (magnetoresistance) element that detects a resistance change due to an angle between a current direction of a ferromagnetic substance and a magnetization axis, and a recently developed nonmagnetic conductive layer composed of two ferromagnetic layers. There is a spin valve element which has a film structure in which an antiferromagnetic layer is in contact with the outside of one ferromagnetic layer sandwiched between body layers and which exhibits a large magnetoresistance effect. These elements have the advantage that they are not affected by the moving speed of the magnetic medium, can be miniaturized, and can easily identify and retrieve information recorded on the magnetic medium with a very high linear density. is there.

In these thin film type MR elements and spin valve elements, the magnetization of a ferromagnetic thin film due to a change in the magnetic field of a magnetic recording medium is used. However, a bias magnetic field is applied to suppress Barkhausen noise during magnetization. In order to control the magnetization direction, for example, to fix the magnetization direction of the ferromagnetic layer, an exchange coupling magnetic field at the interface formed by joining the antiferromagnetic films is used. In that case, it is extremely important to sufficiently increase the strength of the exchange coupling magnetic field in order to properly extract the magnetoresistance effect of the MR element or the spin valve element and to operate the element stably.

A method for increasing the strength of the exchange coupling magnetic field is as follows.
Various studies have been made so far, and it is said that the crystal structure and its specific orientation are effective. For example, Japanese Patent Application Laid-Open No. 6-314617 discloses that a composition of a Mn-based alloy in contact with a ferromagnetic film is N _100-Z Mn _Z (where N is Cu, Ru, Rh, Re, A
at least one selected from g, Au, Os, and Ir
There is disclosed an invention in which a good exchange coupling property can be obtained by forming a stack of antiferromagnetic films having a tetragonal crystal structure with 24 ≦ Z ≦ 75. Also, the ferromagnetic material NiF
In order to obtain an exchange coupling magnetic field between the e (Ni ₈₀ Fe ₂₀ : subscript atomic concentration%) layer and the antiferromagnetic FeMn (Fe ₅₀ Mn ₅₀ ) layer, the {111} plane of the NiFe crystal is used. It is also known that γ-Fe-Mn exhibiting strong antiferromagnetism can be easily obtained if a FeMn layer is formed on a plane oriented parallel to the surface.

The magnetoresistive element is made of glass, Si, Al
Although it is formed on a substrate such as TiC, if a ferromagnetic thin film such as Ni-Fe or Co-Fe is formed directly, the interface energy difference between the substrate and the ferromagnetic material is large, so that the arrangement of metal atoms is not sufficient. In some cases, a uniform film cannot be obtained. Therefore, usually, Ti,
A metal film such as Zr, Hf, V, Nb, Ta, Cr, Mo, and W is formed as a base layer on a substrate, and a ferromagnetic layer is formed thereon. In a laminated thin film having a structure in which an underlayer is formed on a Si substrate and then NiFe, Cu, NiFe and FeMn, that is, a spin-valve film, a face-centered cubic lattice (fcc) As a result of comparison using metal of each crystal system of the centered cubic lattice (bcc) or dense hexagonal lattice (fcc), when the crystal orientation of the laminated thin film differs depending on the underlying layer, and the thin film has a strong {111} plane texture, There are reports that a strong exchange coupling magnetic field can be obtained (R. Nakatani et al., Jpn. J. Ap
pl.Phys., vol. 33 (1994), pp. 133-137).

However, there are many unknown factors that influence other than the crystal orientation of the laminated film. If the factors are clarified and applied to a manufacturing method, a more stable and strong exchange coupling magnetic field can be obtained. There is.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an
An object of the present invention is to improve the performance of a device by obtaining a stronger and more stable exchange coupling magnetic field used for controlling the magnetization of the ferromagnetic layer of the device or the spin valve device.

[0009]

Means for Solving the Problems The present inventor has made various studies on the above-mentioned magnetoresistive effect element with respect to the factor affecting the strength Hex of the exchange coupling magnetic field by the antiferromagnetic layer in contact with the ferromagnetic layer. . As a result, it was found that the state of the underlayer greatly affected Hex even in an element having the same configuration. However, the crystal orientation of the ferromagnetic layer showed that the Factors other than the crystal structure of the metal were considered to have a stronger effect. Therefore, as a result of further investigation, the effect of the surface roughness of the underlayer was found.

[0010] An underlayer having a varied thickness is formed on a glass substrate, NiFe and MnFe are further formed thereon, and Hex is obtained by a vibrating sample magnetometer (VSM). Hex changes accordingly. Therefore, as a result of examining the effect by changing the thickness of the underlayer variously, it was found that the thickness did not directly affect Hex. However, when the surface roughness of the underlayer was measured by an AFM (Atomic Force Microscope) and the value was compared with the Hex of the device obtained by forming a film thereon, it was found that there was a good correlation. I found it.
That is, the surface roughness is determined by AFM center plane average roughness Ra.
When the value of Ra is substantially equal to the distance between lattice planes of the {111} plane of the ferromagnetic crystal formed thereon, Hex becomes the largest.

Although the surface roughness of the underlayer can be controlled by changing the film thickness at the time of film formation, such a film can be controlled to a required thickness by a method such as ion milling or reverse sputtering after film formation. The same effect can be obtained even if the roughness is high.

Further, an underlayer, a ferromagnetic layer,
Not only the MR element in which the antiferromagnetic layer and the antiferromagnetic layer are sequentially stacked, but also the underlayer, the first ferromagnetic layer, the nonmagnetic layer, the second ferromagnetic layer, and the antiferromagnetic layer. The surface roughness of the underlayer was also effective in increasing the exchange coupling magnetic field strength Hex formed by the second ferromagnetic layer and the antiferromagnetic layer also in the spin valve element of the multilayer stack in which the layers were sequentially stacked. .
However, if the element in contact with the underlayer, which is an underlayer, an antiferromagnetic layer, and a ferromagnetic layer sequentially laminated on the substrate, is an antiferromagnetic material, the surface roughness of the underlayer will reduce the above-mentioned effect. The effect of increasing Hex was not obtained even with the same value of Ra as when it brought.

The reason why the appropriate surface roughness of the underlayer increases the strength of the exchange coupling magnetic field between the ferromagnetic layer and the antiferromagnetic layer thus formed thereon is not necessarily obvious. is not. However, one guess is as follows. Ferromagnetic thin films deposited by sputtering are usually
In the fcc structure, the {111} plane tends to be oriented parallel to the plane on which it is deposited. Here, when the roughness of the underlayer surface is exactly equal to the {111} plane interval of the ferromagnetic material at the value of Ra, the ferromagnetic material atoms that have arrived at the surface first adhere to the surface in such a way as to fill the concave portions. Distribution facilitates the arrangement of the atoms to be deposited next to form the {111} plane, and as the deposition proceeds, the entire surface of the ferromagnetic film is almost completely oriented in the {111} plane. Then the antiferromagnetic material deposited on it will also be {111}
The resulting film has a plane-oriented fcc structure, and a strong exchange coupling magnetic field is formed at the interface. In the case of a spin valve element,
If the first ferromagnetic layer is sufficiently oriented in the {111} plane, both the nonmagnetic layer above it and the second ferromagnetic layer
The surface on which the {111} plane is deposited and the antiferromagnetic layer is stacked has a nearly perfect {111} plane orientation. The result is a strong exchange-coupling magnetic field, as also shown in the report by R. Nakatani et al. Of Jpn. J. Appl. Phys. On the other hand, the roughness of the underlayer surface is {111} as the value of Ra.
When the distance is shifted from the plane spacing, the distribution of the attached atoms is not preferable for the {111} plane orientation of the subsequently deposited atoms. It will not reach, and a strong exchange coupling magnetic field will not be obtained. When an antiferromagnetic layer is formed directly on the underlayer, for example, FeMn does not form a film having an fcc structure.
Even if a ferromagnetic material is formed thereon, strong Hex cannot be obtained.

The present invention was completed by further examining the limits of the surface roughness of the underlayer. That is, the gist of the present invention is as follows.

(1) A laminated film having a configuration in which an underlayer, a ferromagnetic layer, and an antiferromagnetic layer are sequentially laminated on a substrate, wherein the surface roughness Ra of the underlayer is ferromagnetic. {111} of the body
A laminated film characterized by being 90 to 110% of the value of the distance between lattice planes of the plane.

(2) A magnetoresistive device having a structure in which an underlayer, a first ferromagnetic layer, a nonmagnetic layer, a second ferromagnetic layer, and an antiferromagnetic layer are sequentially stacked on a substrate. In the device, the value of the surface roughness Ra of the underlayer is 90 to 110% of the distance between the {111} plane lattice planes of the first ferromagnetic layer in contact with the underlayer.
A magnetoresistive element, characterized in that:

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the present invention, the underlayer is made of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo,
Any commonly used metal film such as W may be used, and there is no particular limitation.

However, the surface has a center plane average roughness value represented by Ra, and an anti-ferromagnetic material layer is formed thereon to form an exchange coupling magnetic field in a subsequent film forming and laminating step. It is assumed that the distance between the {111} plane lattice planes of the ferromagnetic material is 90 to 110%. This is because when the measured value of the surface roughness Ra of the underlayer by AFM or the like is substantially equal to the distance between the {111} plane lattice planes of the ferromagnetic material, the strength Hex of the obtained exchange coupling magnetic field becomes largest. If the value is less than 10% or less than 10%, it becomes H
This is because ex becomes smaller.

Since the surface roughness of the underlayer changes depending on the thickness of the metal film, it can be controlled by changing the film thickness. This is because when a metal is deposited by ordinary sputtering or the like, it becomes an amorphous film at the very thin initial stage and is smooth, for example, following the surface of the substrate. Since the structure changes, surface irregularities based on the formation of crystal grains and grain boundaries appear. However, as the deposition proceeds further, the irregularities are filled and smoothed. In order for the unevenness to increase and the surface roughness to change, the film thickness needs to be about 50 or more, and when it exceeds 200, it becomes smooth again.

However, since the thickness of the underlayer is not directly related to Hex, the thickness of the underlayer is adjusted to a required thickness, and the surface roughness is adjusted by a method such as ion milling or reverse sputtering to obtain a Ra.
May be within the above range.

According to the present invention, whether the magnetoresistive element is an MR element or a spin valve element, the exchange coupling magnetic field used therein can be strong and stabilized. However, the layer directly formed on the underlayer must be a ferromagnetic layer, and the exchange coupling magnetic field obtained in this order is an antiferromagnetic layer on the underlayer, and a ferromagnetic layer on it. However, even if the Ra value of the surface roughness of the underlayer is in the above range, a sufficient effect of increasing Hex cannot be obtained. In the case of an MR element, a ferromagnetic layer and an antiferromagnetic layer may be formed on the underlayer. In the case of a spin valve element, there are two ferromagnetic layers sandwiching a non-magnetic layer, but these two layers may be the same ferromagnetic substance,
Different ferromagnetic materials may be used. In the case of different ferromagnetic materials, the Ra value of the surface roughness of the underlayer must be 90 to 110% of the distance between the ferromagnetic {111} planes of the first layer in contact therewith. If the thickness is out of this range, a state in which the entire laminated film is {111} -oriented cannot be obtained. Even if the distance between the {111} planes of the ferromagnetic material in the second layer is out of this range, a sufficient Hex can be obtained, but it is preferable that the distance be in the same range.

[0022]

EXAMPLES Example 1 Underlayers of various thicknesses of Ta as shown in Table 1 were formed on a glass substrate by RF sputtering. Table 1 shows the surface roughness of the underlayer as A
The results measured using FM are also shown. in this case,
The reference area was 0.5 μm square. Thickness on these underlayers
200 NiFe (Ni ₈₀ Fe ₂₀ ) layers, 200
Of FeMn (Fe ₅₀ Mn ₅₀ ) was formed to produce MR elements having an exchange coupling magnetic field. With respect to these devices, an MR curve was drawn by a magnetoresistive measuring device, and Hex was obtained from the curves.

[0023]

[Table 1]

Table 1 also shows the measurement results of the strength Hex of the exchange coupling magnetic field. From now on, the surface roughness Ra of the underlayer and H
FIG. 1 shows the relationship between ex and the measurement result. The ferromagnetic material NiFe is face-centered cubic, and its {111} -plane lattice plane distance is 2.04. In FIG. 1, Hex
The range of Ra at which is greatly improved is 1.83 to 2.25,
It can be seen that the distance between the {111} plane lattice planes is 90 to 110%.

[Example 2] A Zr underlayer was formed on a glass substrate by RF sputtering to form 0, 30, 50, 80, 100, 140, 1
Films were formed to a thickness of 80 and 220, respectively. The results of measuring these surface roughnesses using AFM were 1.5
6, 1.76, 1.86, 1.98, 2.05, 1.82, 1.62 and 1.49
Met. Spin valve elements on these underlayers
60-CoFe, 25-Cu, 35-CoFe, and 250
-NiMn was sequentially formed and heat-treated at 250 ° C. for 3 hours in a unidirectional magnetic field of 1000 Oersted. In addition,
This CoFe is Co ₉₀ Fe ₁₀ . For each of the obtained devices, an MR curve was drawn by a magnetic resistance measuring device, and Hex was determined.

FIG. 2 shows the relationship between the surface roughness Ra of the underlayer of the obtained device and Hex. Co that is face-centered cubic
The distance between the {111} -plane lattice planes of Fe is 2.05, and it can be seen from this figure that when the Ra value becomes 90% or more of this distance, that is, when the Ra value becomes 1.85 or more, Hex greatly increases.

[0027]

According to the present invention, the exchange coupling magnetic field used for controlling the magnetization of the ferromagnetic layer of the thin film type MR element or spin valve element can be obtained more strongly and stably. By applying this, the performance of a magnetoresistive element used for a magnetic head, particularly a spin valve element, can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the surface roughness Ra of an underlayer of an MR type magnetoresistive element and the strength Hex of an exchange coupling magnetic field.

FIG. 2 is a diagram showing the relationship between the surface roughness Ra of an underlayer of the element and the strength Hex of an exchange coupling magnetic field in a spin-valve magnetoresistive element.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 7, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

Since the surface roughness of the underlayer changes depending on the thickness of the metal film, it can be controlled by changing the film thickness. This is because when a metal is deposited by ordinary sputtering or the like, it becomes an amorphous film at the very thin initial stage and is smooth, for example, following the surface of the substrate. Since the structure changes, surface irregularities based on the formation of crystal grains and grain boundaries appear. However, as the deposition proceeds further, the irregularities are filled and smoothed. In order to increase the irregularities and change the surface roughness, the film thickness needs to be about 50 mm or more, and if it exceeds 200 mm , it becomes smooth again.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

[0022]

EXAMPLES Example 1 Underlayers of various thicknesses of Ta as shown in Table 1 were formed on a glass substrate by RF sputtering. Table 1 shows the surface roughness of the underlayer as A
The results measured using FM are also shown. in this case,
The reference area was 0.5 μm square. Thickness on these underlayers
200 mm NiFe (Ni ₈₀ Fe ₂₀ ) layer, 200 mm thick
Of FeMn (Fe ₅₀ Mn ₅₀ ) was formed to produce MR elements having an exchange coupling magnetic field. With respect to these devices, an MR curve was drawn by a magnetoresistive measuring device, and Hex was obtained from the curves.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

Table 1 also shows the measurement results of the strength Hex of the exchange coupling magnetic field. From now on, the surface roughness Ra of the underlayer and H
FIG. 1 shows the relationship between ex and the measurement result. The ferromagnetic material NiFe is face-centered cubic and its {111} -plane lattice plane distance is 2.04 ° . In FIG. 1, Hex
Range of Ra which is significantly improved is from 1.83 to 2.25 Å,
It can be seen that the distance between the {111} plane lattice planes is 90 to 110%.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

Example 2 A Zr Underlayer on a Glass Substrate
By RF sputtering, 0, 30, 50, 80, 100, 140, 1
80 and 220Å, Respectively. These tables
The results of measuring the surface roughness using AFM were 1.5
6, 1.76, 1.86, 1.98, 2.05, 1.82, 1.62 and 1.49Å
Met. Spin valve elements on these underlayers
60Å-CoFe, 25Å-Cu, 35Å-CoFe, and 250
Å-NiMn deposited sequentially, one direction of 1000 Oersted
Heat treatment was performed at 250 ° C for 3 hours in a magnetic field. In addition,
This CoFe is Co₉₀Fe_TenIt is. The obtained device is
Let them draw an MR curve with a magnetic resistance measurement device,
Hex was sought more.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

FIG. 2 shows the relationship between the surface roughness Ra of the underlayer of the obtained device and Hex. Co that is face-centered cubic
The distance between the lattice planes of the {111} plane of Fe is 2.05 ° , and it can be seen from this figure that when the Ra value becomes 90% or more of this distance, that is, when the Ra value becomes 1.85 ° or more, Hex greatly increases.

Claims (2)

[Claims] 1. A laminated film having a structure in which an underlayer, a ferromagnetic layer, and an antiferromagnetic layer are sequentially laminated on a substrate, wherein the surface roughness Ra of the underlayer is a ferromagnetic material. A laminated film characterized by being 90 to 110% of the value of the distance between lattice planes of the {111} plane. 2. A magnetoresistive element having a configuration in which an underlayer, a first ferromagnetic layer, a nonmagnetic layer, a second ferromagnetic layer, and an antiferromagnetic layer are sequentially stacked on a substrate. Wherein the value of the surface roughness Ra of the underlayer is 90 to 110% of the distance between the {111} plane lattice planes of the first ferromagnetic layer in contact with the underlayer. Resistance element.