JP2000251226A - Spin valve magneto-resistance sensor and thin-film magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the magneto-resistance sensor in spin valve structure having an antiferromagnetic layer which produces an exchange coupling magnetic field between a ferromagnetic material and a pin magnetic layer even after a heat treatment, effectively suppresses the rotation of the magnetism of the spin magnetic layer due to the bias magnetic field of a magnetic head, and can obtain a high MR output. SOLUTION: The spin valve magneto-resistance sensor has a magneto- resistance effect film 3 formed by stacking on a substrate a ferromagnetic layer 4 and a pin magnetic layer 6 arranged across a nonmagnetic conductive layer 5 and an antiferromagnetic layer 7 adjacent to the pin magnetic layer. In this case, 2 to 10 at% added to PtMn alloy, and 45 to 55 at% Mn and Pt for the rest are added; and the antiferromagnetic layer is formed of the PtMcCr and thermally treated at 250 to 300 deg.C. In this case, the antiferromagnetic layer is formed of PdPtMnCr alloy obtained by adding 2 to 10 at% Cr, 45 to 55 at% Mn, 20 to 35 at% Pd, and Pt for the rest to PdPtMn alloy and thermally treated at 250 to 300 deg.C in a vacuum magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive sensor used in a magnetic recording apparatus, and more particularly to a magnetic sensor and a thin film magnetic head utilizing a spin valve magnetoresistance effect.

[0002]

2. Description of the Related Art Recently, in order to reduce the saturation magnetic field and enhance the magnetic field sensitivity in a reproducing magnetic head, the reproducing magnetic head comprises a sandwich-structured spin-valve film in which a pair of magnetic layers are laminated with a non-magnetic layer interposed therebetween. Magnetoresistive (MR) sensors have been developed. In a spin valve film, the magnetization of one magnetic layer (pinned magnetic layer) is fixed in the element height direction by an exchange coupling magnetic field with an adjacent antiferromagnetic layer, whereas the other magnetic layer (free magnetic layer) is fixed. The magnetization of the layer) is generally converted into a single magnetic domain in the track width direction of the element by a hard bias method using a magnetic field of a permanent magnet, and is freely rotated by an external magnetic field.

[0003] The larger the unidirectional anisotropic magnetic field due to the antiferromagnetic layer, the better the pinned magnetic layer can be made into a single magnetic domain.
Also, as the magnetization is sufficiently fixed, the linearity of the magnetic response to an external magnetic field is secured, and the magnetic characteristics of the magnetic sensor are improved. Examples of antiferromagnetic materials include, for example,
As described in Japanese Patent No. 35212, characteristics such as a large exchange coupling magnetic field, a high blocking temperature, excellent corrosion resistance, a low heat treatment (annealing) temperature, and a small film thickness are required. Conventionally, various materials have been proposed.

[0004]

However, there is a problem that the FeMn alloy conventionally used generally as an antiferromagnetic material is easily corroded. In addition, IrMn alloys, RhMn alloys, FeMn alloys, and the like are easily affected by the underlayer. Therefore, a so-called bottom type spin valve structure in which an antiferromagnetic layer is disposed on the substrate side and a pinned magnetic layer is laminated thereon is particularly used. , (111) It is necessary to provide a base film having high crystal orientation or to increase the film thickness. Also, NiMn
In the case of an alloy, it is necessary to perform heat treatment (annealing) at a high temperature of 250 ° C. or higher in order to sufficiently secure exchange coupling with the pinned magnetic layer. However, the NiMn alloy is a PtMn to be described later.
Alloy and PdMn alloy, Mn is easy to diffuse,
There is a possibility that the diffusion of the metal element occurs between the pin layer / non-magnetic layer / free layer, thereby lowering the MR ratio.

In order to solve such a problem, for example, in Japanese Patent Application Laid-Open No. Hei 9-147325, Pt is 5 to 54 at%,
There has been proposed a magnetoresistive read head in which an antiferromagnetic layer is formed using a PtMn alloy having Mn of 46 to 95 at% and heat-treated at a temperature of 200 ° C. to 350 ° C. Further, JP-A-10-91921 preferably discloses P
PtMn with t of 44 to 51 at% and Mn of 49 to 56 at%
Alloy or a Pt-Mn-X alloy (X
= Ni, Pd, Rh, Ru, Ir, Cr, Fe, C
o) A dual spin-valve thin film magnetic head in which an antiferromagnetic layer is formed using a PdMn alloy is disclosed.
According to both publications, a PtMn alloy has good corrosion resistance, a large exchange anisotropic magnetic field, is thermally stable, and exhibits an effective exchange anisotropic magnetic field regardless of whether it is laminated above or below a pinned magnetic layer. And a good thin-film magnetic head having a high blocking temperature, excellent linear response of the magnetoresistance effect, and excellent thermal stability can be obtained.

Further, Japanese Patent Application Laid-Open No. 9-16923 discloses that
A spin valve sensor is described in which a magnetic domain control layer formed adjacent to both ends of a spin valve sensor layer is formed by a laminated structure of a Ta film, a ferromagnetic NiFe film, and an antiferromagnetic CrMnPt film. According to the publication, the antiferromagnetic film has a composition of 30 to 70 at% Cr and 30 to 7 Mn.
0 at%, Pt 3.0 to 30.0 at%, and the high Cr content significantly improves the corrosion resistance.
By the addition of Pt, good exchange coupling characteristics with the NiFe ferromagnetic film formed thereunder are exhibited, and the blocking temperature is high.

[0007] Japanese Patent Application Laid-Open No. 9-81915 discloses a PtM
An antiferromagnetic layer is formed by using a PdPtMn alloy having higher corrosion resistance than an n alloy, and is subjected to a heat treatment at a relatively low temperature of about 230 ° C. so as to impart antiferromagnetism without deteriorating magnetoresistance characteristics. And a spin-valve magnetoresistive element with improved reliability. According to the same publication, the PdPtMn alloy contains M
A particularly high bias magnetic field amount is obtained when the atomic fraction of n is 48 to 54 at%.

In addition, a paper by Kenichi Aoshima et al., “Study on Underlayer of PdPtMn Spin Valve Film” (Journal of the Japan Society of Applied Magnetics, Vol.
22, No. 4-2, 1998, pp. 501-504) include PdPtMn.
In a spin valve film in which an antiferromagnetic layer of an alloy is disposed on the substrate side, the base material is not NiFe but NiFeCr.
Is used, the (111) of the PdPtMn antiferromagnetic layer
It is reported that the exchange coupling magnetic field is increased and the MR ratio is improved by improving the crystal orientation.

However, in the above-mentioned PdPtMn-based alloy, the corrosion resistance is improved, but the unidirectional anisotropic magnetic field after the heat treatment for ordering is not sufficiently large, so that the bias magnetic field inside the magnetic head or the like is reduced. There is a possibility that the anisotropic direction rotates by the action. For this reason, there has been a problem that the MR output of the spin valve sensor gradually decreases, so that a high reproduction output cannot be maintained and the reliability of the magnetic head is impaired.

Accordingly, an object of the present invention is to provide a high exchange coupling magnetic field with a pinned magnetic layer made of a ferromagnetic material even after heat treatment in view of the above-mentioned conventional problems, and to provide a magnetic head with a bias magnetic field. An object of the present invention is to provide a magnetoresistive sensor having a spin valve structure provided with an antiferromagnetic layer capable of effectively suppressing rotation of magnetization of a pinned magnetic layer and obtaining a high MR output.

Another object of the present invention is to provide such a spin-valve magnetoresistive sensor, which has excellent magnetic characteristics and high reliability, and is capable of achieving higher recording density. The purpose is to provide a head.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and comprises a pair of magnetic layers disposed on a substrate with a non-magnetic conductive layer interposed therebetween, and one of the magnetic layers A spin valve magnetoresistive sensor comprising a magnetoresistive film laminated with an antiferromagnetic layer adjacent to the antiferromagnetic layer, wherein the antiferromagnetic layer is made of a Pd-Pt-Mn-Cr alloy, and heat-treated for ordering the same. A spin valve magnetoresistive sensor is provided.

The inventor of the present application can increase the exchange coupling magnetic field Hex by adding an appropriate amount of Cr to the PdPtMn alloy and heat-treating the crystal structure to thereby increase the exchange coupling magnetic field Hex. In particular, the inventors have found that the rotation of the magnetization of the pinned magnetic layer is small and therefore the MR output does not decrease, and the present invention has been achieved. PdPtM
In selecting Cr as the metal X to be added to the n alloy, Zr, Nb, Ti, Cr, Ta, Mo, W, V, A
l as a candidate, the glass substrate Ta100Ｆｅ / CoFe
PdPtMnX is formed on a base film made of 100 °,
After heat-treating them in a vacuum magnetic field, their magnetic properties were evaluated. As a result, it was found that the exchange coupling magnetic field Hex decreased when an element other than Cr was added, whereas the exchange coupling magnetic field Hex increased only when Cr was added.

Next, PdPtMnCr is used as an antiferromagnetic layer.
In determining the amount of Cr added in the alloy, first, the film thickness was deposited Ta30Å / NiFe100Å on a glass substrate, a PdPtMnCr thereon by sputtering by placing a Cr chip on Pd ₃₀ Pt ₂₀ Mn ₅₀ on the target 35
0 °, and a Ta film is further formed thereon as a protective film by 30 °.
A film was formed. This was heat-treated at 280 ° C. for 10 hours in a magnetic field of 1 kOe in a heating furnace having a degree of vacuum of 1 × 10 ⁻⁶ Torr or less, and the exchange coupling magnetic field Hex was evaluated. The Cr content is
Similarly, Cr placed on the target during sputtering
It was adjusted according to the number of chips, and the actual Cr content was determined by ICP analysis. The lattice constant (a,
Table 1 shows changes in c) and the exchange coupling magnetic field Hex.

[0015]

[Table 1]

From the table, it can be seen that the exchange coupling magnetic field Hex increases when the Cr content is 2 at% or more, and decreases when the Cr content exceeds 10 at%. The reason for this is that the addition of Cr replaces the Pt and Pd atoms in the PdPtMn alloy with Cr having a smaller atomic radius, the lattice constant becomes smaller, and M
It is considered that the distance between n atoms became shorter, and antiferromagnetic coupling was strengthened. If the Cr content exceeds 10 at%, it is considered that the exchange coupling magnetic field Hex is lowered because Cr atoms also enter Mn sites in the PdPtMn alloy.
As a result, the Cr content of the PdPtMnCr alloy as the antiferromagnetic layer is optimally in the range of 2 to 10 at%. Further, in a PdPtMn-based alloy, the Pd content is 20 to 35 at%.
This range is desirable because the exchange coupling magnetic field Hex becomes large in the range.

Further, the heat treatment temperature is 250 ° C. to 300 ° C.
Is desirable. For sufficient ordering, it is necessary to heat-treat at a temperature of at least 250 ° C.
Is exceeded, the diffusion between the antiferromagnetic layer and the adjacent ferromagnetic layer and / or between the ferromagnetic layers sandwiching the nonmagnetic conductive layer becomes large, resulting in deterioration of MR characteristics and the pin magnetic layer / free magnetic layer. It is not preferable because the interaction becomes large.

According to still another aspect of the present invention, there is provided a thin-film magnetic head having the above-described spin-valve magnetoresistive sensor, excellent in magnetoresistance change rate and linear response thereof, and capable of increasing recording density. You.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
1 shows a sectional view of a magnetoresistive sensor having a spin valve structure to which the present invention is applied, as viewed from an ABS (air bearing surface) side. The spin-valve magnetoresistive sensor, bottom made of glass or silicon, Al ₂ O ₃ · Alumina provided on a substrate made of a ceramic material such as TiC (Al ₂ O ₃₎ Ta having a thickness of 30Å on the insulating layer 1 A ground layer 2 is formed, and a magnetoresistive (MR) film 3 having a so-called top spin valve structure in which an antiferromagnetic layer is disposed on the side opposite to the substrate is laminated thereon.

The MR film 3 is made of Ni laminated on the underlayer 2.
A free magnetic layer 4 composed of an Fe film 41 and a Co film 42;
Nonmagnetic conductive layer 5 made of Cu film, pinned magnetic layer 6 made of Co film, and antiferromagnetic layer 7 made of PdPtMnCr film
And The MR film 3 is formed at 250 ° C.
By performing heat treatment in a unidirectional magnetic field at a temperature of 300 ° C., the crystal structure of the antiferromagnetic layer 7 is regularized, and the pinned magnetic layer 6 is given unidirectional anisotropy to fix its magnetization orientation. A protective film 8 made of Ta is formed on the MR film 3. Each of the film layers is continuously formed by, for example, DC sputtering.

Both sides of the MR film 3 are removed by etching in accordance with a predetermined track width to form a hard bias layer and conductive leads (both not shown) as electrodes for flowing a sense current. Further, the entire laminated structure is covered with an alumina insulating layer, and the spin valve M of the present invention is provided.
The R sensor is completed.

The composition of the antiferromagnetic layer 7 is such that Pd is 20 at% or less.
35 at%, Mn is 45 at% -55 at%, Cr is 2 at%-
The range is 10 at%, and the balance is Pt. With this film composition, a high exchange coupling magnetic field can be obtained between the antiferromagnetic layer and the pinned magnetic layer after the heat treatment.

The present invention provides a so-called bottom spin valve structure in which an antiferromagnetic layer is arranged on the substrate side, as well as the top spin valve structure described above with reference to FIG. A dual spin valve structure in which the pinned magnetic layer is symmetrically arranged with the free magnetic layer interposed therebetween. An antiferromagnetic layer and one of its adjacent ferromagnetic films are exchange-coupled (synthetic).
The present invention can be similarly applied to spin valve MR sensors having various known structures such as a tic) type spin valve structure.

[0024]

(Embodiment 1) In the MR sensor of FIG. 1, Ta30Å / NiFe50Å / Co10 was formed on a glass substrate.
{/ Cu25} / Co30} / PdPtMnCr300
A {/ Ta30} spin valve film is continuously formed by DC sputtering, and the spin valve film is formed in a vacuum magnetic field of 3000 Oe.
Heat treatment was performed at 50 ° C. × 10 hours. The composition of the PdPtMnCr antiferromagnetic layer 7 was changed, and the MR curve was measured for each of them. Table 2 shows the results.

[0025]

[Table 2]

From the table, it is found that Pd is 20 at% to 35 at%,
When Mn is in the range of 45 at% to 55 at% and Cr is in the range of 2 at% to 10 at%, the exchange coupling magnetic field Hex is remarkably large and M
It can be seen that the R ratio is significantly higher.

Example 2 In the MR sensor of FIG. 1, Ta30Å / NiFe60 was formed on a thermally oxidized Si substrate.
Å / Co10Å / Cu25Å / Co30Å / PdPtM
A spin valve film of nCr250 / Ta30 was continuously formed by DC sputtering. PdPtMnC
The composition of r antiferromagnetic layer 7 and the two types of Pd ₂₃ Pt ₂₂ Mn ₅₀ Cr ₅ and _{Pd 24 Pt 2 2.5 Mn 52 Cr} 1.5, and 30
Heat treatment was performed in a vacuum magnetic field of 00 Oe for 5 hours. Heat treatment temperature from 230 ° C to 250 ° C, 270 ° C, 300 ° C, 320
The temperature was varied in five steps up to ° C. For each of them, the MR curve was measured after the heat treatment, and changes in the exchange coupling magnetic field Hex and the MR ratio were examined. Table 3 shows the results.

[0028]

[Table 3]

From this table, it can be seen that when the Cr content is within the range of the present invention at 5 at%, the exchange coupling magnetic field Hex is remarkably large regardless of the heat treatment temperature, as compared with the case where the Cr content is 1.5 at%. And the MR ratio is remarkably high. Also,
The heat treatment temperature is set within the range of the present invention (250 ° C., 270 ° C., 30 ° C.).
0 ° C.), the exchange coupling magnetic field Hex and the MR ratio are high. On the other hand, when the heat treatment temperature is 230 ° C., both the exchange coupling magnetic field Hex and the MR ratio are small. Also, 3
At a heat treatment temperature of 20 ° C., the exchange coupling magnetic field Hex is large, but the MR ratio is low. Thus, the heat treatment temperature is from 250 ° C. to 3 ° C.
The range of 00 ° C is appropriate.

[0030]

As is apparent from the above description, according to the spin valve magnetoresistive sensor of the present invention, PdPtMn
Cr is added to the alloy in the range of 2 at% to 10 at%, Pd is in the range of 20 to 35 at%, Mn is in the range of 45 to 55 at%, and the balance is Pt. After the heat treatment, a larger exchange coupling magnetic field Hex is obtained after the heat treatment, whereby the magnetization of the pinned magnetic layer is not rotated even by the bias magnetic field of the magnetic head, the decrease in the MR output is suppressed, and the reproduction output is reduced. And its thermal and magnetic stability are achieved. Further, according to the present invention, such as high magnetoresistance change rate and linear response,
By obtaining a spin-valve magnetoresistive sensor having improved magnetic conversion characteristics, it is possible to realize a high-performance, high-reliability magnetic head capable of increasing the recording density.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a spin-valve magnetoresistive sensor to which the present invention is applied, as viewed from an ABS side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating layer 2 Underlayer 3 MR film 4 Free magnetic layer 41 NiFe film 42 Co film 5 Nonmagnetic conductive layer 6 Pinned magnetic layer 7 Antiferromagnetic layer 8 Protective layer

Claims (4)

[Claims] 1. A spin valve magnetoresistance comprising a magnetoresistive film in which a pair of magnetic layers disposed on a substrate with a nonmagnetic conductive layer interposed therebetween and an antiferromagnetic layer adjacent to one of the magnetic layers is stacked. A spin valve magnetoresistive sensor, wherein the antiferromagnetic layer is made of a Pd-Pt-Mn-Cr alloy, and is heat-treated for ordering the antiferromagnetic layer. 2. The film composition of the antiferromagnetic layer is such that Mn is 45
~ 55at%, Cr 2 ~ 10at%, Pd 20 ~ 35at
The spin valve magnetoresistive sensor according to claim 1, wherein the balance is Pt. 3. The temperature of the heat treatment is 250 ° C. to 300 ° C.
The spin valve magnetoresistive sensor according to claim 1 or 2, wherein the temperature is in the range of ° C. 4. A thin-film magnetic head comprising the spin-valve magnetoresistive sensor according to claim 1.