JP2001284678A - Spin-valve magnetoresistive effect element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high output and improved thermal stability by assuring a good crystallinity even with a very thin antiferromagnetic layer, for larger exchange coupling magnetic field, resulting in higher recording density and smaller size of a magnetoresistive effect magnetic head. SOLUTION: The spin-valve magnetoresistive effect element comprises a magnetiresistive effect film 5 where there are laminated, on a base material layer 4 formed on a substrate 1, an untiferromagnetic layer 6 of Mn alloy such as PtMn which contains, as impurity, oxygen by 200 ppm or less, with 100 ppm or less preferred while 50 ppm or less more preferred, a pin magnetic layer 7, a non-magnetic conductive layer 8, and a free magnetic layer 11. The untiferromagnetic layer is formed by a vacuum melting process or vacuum metallurgy process using a pot of CaO (calcia) refractory while a molten Mn alloy target is used with, as impurity, oxygen concentration 200 ppm or less, with 100 ppm or less preferred while 50 ppm or less more preferred, for film- forming by sputtering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element used for, for example, a reproducing magnetic head or a magnetic field detecting sensor of a magnetic recording apparatus, and more particularly to a magnetoresistive element utilizing a spin valve magnetoresistive effect.

[0002]

2. Description of the Related Art Recently, magnetic recording devices such as hard disk devices are required to have higher recording densities.
As a reproducing magnetic head, a magnetoresistive (MR) sensor made of a spin valve film capable of increasing a magnetic field sensitivity by reducing a saturation magnetic field is used. The spin valve film has a sandwich structure in which a pair of magnetic layers are laminated on a substrate with a non-magnetic layer interposed therebetween, and one of the magnetic layers (pin magnetic layer)
Is fixed in the element height direction by the exchange coupling magnetic field Hex with the adjacent antiferromagnetic layer, whereas the magnetization of the other magnetic layer (free magnetic layer) generally uses the magnetic field of a permanent magnet. By the hard bias method described above, the element is formed into a single magnetic domain in the track width direction, and freely rotated by an external magnetic field.

In a spin-valve magnetic sensor, 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. The linearity of the magnetic response is secured, and the magnetic characteristics are improved. The antiferromagnetic material has properties such as a large exchange coupling magnetic field, excellent corrosion resistance, a high blocking temperature, and a low heat treatment (annealing) temperature as described in JP-A-9-35212. Various materials have been proposed in the past. However, the FeMn alloy generally used as an antiferromagnetic material has a problem that it is easily corroded, and the exchange anisotropic magnetic field Hex is unstable with respect to a temperature change.
Therefore, in the thin-film magnetic head described in Japanese Patent Application Laid-Open No. 9-35212, an X-Mn alloy (X = Ru, Rh, Ir, Pd, P) having an irregular crystal structure as the antiferromagnetic layer.
t).

Further, IrMn alloy, RhMn alloy, FeMn alloy,
Mn alloys and the like are easily affected by the underlayer, and have a feature that the vicinity of the upper surface of the antiferromagnetic layer is unlikely to exhibit antiferromagnetic properties. It is necessary to increase the film thickness or to provide a base film having a high (111) crystal orientation. In addition, the NiMn alloy has a thickness of 250 to ensure sufficient exchange coupling with the pinned magnetic layer.
It is necessary to perform heat treatment at a high temperature of not less than ° C., which may cause diffusion of a metal element between the pinned magnetic layer / non-magnetic layer / free magnetic layer, thereby lowering the MR ratio. In order to solve such a problem, Japanese Unexamined Patent Publication No. Hei 10-91921 discloses a PtMn alloy and a PtMn-X alloy (X = Ni, Pd, Rh, Ru, Ru, PtMn) having high thermal stability and good corrosion resistance.
An antiferromagnetic layer comprising Ir, Cr, Fe, Co) and a PdMn alloy has been proposed.

On the other hand, when the thickness of the antiferromagnetic layer is increased, the shunt to the antiferromagnetic layer is increased, so that not only the power consumption is increased, but also the MR ratio is reduced. Therefore, it is desirable that the antiferromagnetic layer be as thin as possible from the viewpoint of reducing the thickness of the magnetic sensor, reducing power consumption and improving output. JP-A-10-177706
Japanese Patent Application Laid-Open No. H11-157,199 discloses that the use of a PtMn film for the antiferromagnetic layer makes it possible to reduce the overall film thickness and the magnetic gap length, thereby increasing the detection sensitivity and supporting a high recording density. A spin-valve thin film element suitable for a multilayer GMR structure is disclosed.

[0006]

However, even when various Mn-based alloys other than the above-described FeMn alloy are used for the antiferromagnetic layer, it is necessary to secure a stable exchange coupling magnetic field Hex of a sufficient size for practical use. In order to achieve this, it is necessary to increase the thickness of the antiferromagnetic layer to at least 250 ° or more to enhance the (111) crystal orientation at the interface with the adjacent pinned magnetic layer. JP-A-10-177706 states that a relatively high exchange anisotropic magnetic field Hex can be obtained by using a PtMn film even if the thickness of the antiferromagnetic layer is reduced to about 100 °. The exchange anisotropic magnetic field is at most about 23.7 kA / m (300 Oe).

[0007] Takahashi Lab.'S paper "Ultra clean process and spin valve GMR thin film" (Journal of the Japan Society of Applied Magnetics Vol.2)
3, No. 7, 1999, pp. 1841 to 1847) point out that in order to further increase the density, it is essential to make the thickness of the spin valve GMR thin film element extremely thin. I have. Then, the impurity concentration is reduced to about 1 with respect to a normal sputtering process.
In a laminated film formed in an extremely clean atmosphere reduced to / 10,000, the growth of antiferromagnetic crystal grains is promoted by the reduction of impurities (oxygen) in the film, and the exchange magnetic anisotropy of the laminated film increases at room temperature. It has been reported that the method is extremely effective for producing an ultra-thin high-sensitivity spin valve GMR film. However, Takahashi et al. Also state that the flatness of the stacked film is degraded by the cleaning in the film formation atmosphere, and as a result, the GMR effect is extremely reduced.

Japanese Patent Application Laid-Open No. 10-284321 discloses a technique for purifying the antiferromagnetic film with high purity and low oxygen concentration.
By increasing the crystal grain size of the antiferromagnetic layer made of a Mn alloy having excellent corrosion resistance and thermal properties to 5 nm or more, and by aligning the crystal directions between in-plane crystal grains, a sufficient ferromagnetic film can be obtained. An exchange coupling film and a magnetoresistive element capable of obtaining an exchange coupling force are described. According to the publication, this antiferromagnetic layer can be formed with good reproducibility by forming a film using a Mn alloy target having an oxygen content of 1% by weight or less.

Japanese Patent Application Laid-Open No. 10-40813 discloses that an antiferromagnetic layer has a concentration of 1 to 2000 atom p as an impurity.
A spin-valve type magnetoresistive film and a magnetic head which are excellent in thermal stability by containing pm of oxygen and are composed of a magnetic multilayer film are disclosed. This antiferromagnetic layer is formed by a sputtering method. It is necessary to use a target having an oxygen content of 600 ppm or less and set the concentrations of impurities and H ₂ O in a sputtering gas atmosphere to a certain value or less. Furthermore, the ultimate pressure of the vacuum film forming apparatus used is 2 × 10
^-9 Torr (2.66 × 10 ^-7 Pa) or less is required. To achieve this, a metal gasket, a baking device, and an exhaust pump operating at 2 × 10 ^-9 Torr or less are included in the seal portion. A sputter device with special specifications is required.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a spin-valve magnetoresistive element using a Mn-based ordered alloy for an antiferromagnetic layer. Even if the antiferromagnetic layer is made extremely thin, good crystallinity can be ensured, and thereby a large exchange coupling magnetic field is ensured to achieve high output and remarkably improve thermal stability. It is a further object of the present invention to provide a high-performance spin-valve magnetoresistive head capable of achieving higher recording density and smaller size.

[0011]

According to the present invention, in order to achieve the above object, a pair of magnetic layers disposed on a substrate with a nonmagnetic conductive layer interposed therebetween, and a pair of magnetic layers adjacent to one of the magnetic layers A magnetoresistive film in which an antiferromagnetic layer,
It is formed by a vacuum melting method or a vacuum metallurgy method using a (calcia) refractory crucible, and has a concentration of 200 p as an impurity.
A spin-valve magnetoresistive element is provided, wherein the antiferromagnetic layer is formed by sputtering using a molten Mn-based alloy target containing oxygen of pm or less.

Further, according to the present invention, the antiferromagnetic layer comprises:
A spin-valve magnetoresistive element comprising a Mn-based alloy containing oxygen at a concentration of 200 ppm or less as an impurity is provided.

The Mn alloy used for the antiferromagnetic layer is usually an XMn alloy (X is Pt, Ni, Ru, Pd, Ir, C
r or any two or more of these), which generally have the property of being easily oxidized. Conventionally, a target generally used for sputtering an antiferromagnetic layer is a sintered target obtained by sintering a metal or alloy powder, so that the oxygen content as an impurity tends to increase, particularly It is difficult to reduce the oxygen concentration of the Mn-based alloy target. Also, conventional magnesium oxide,
Similarly, it is difficult to significantly reduce the oxygen concentration of a target obtained by melting a metal or alloy powder using a crucible such as an alumina or silica refractory.

On the other hand, the vacuum melting method using a crucible made of a CaO refractory is performed by adding an appropriate amount of an Al-based alloy and melting a Mn-based alloy at a high temperature in the crucible under a vacuum or Ar atmosphere. By refining, impurities such as oxygen and sulfur can be removed to an extremely low level, whereby a Mn-based alloy target in which the concentration of oxygen contained as impurities is 200 ppm or less can be formed. According to the present invention, by using this alloy target, the impurity oxygen concentration of the antiferromagnetic layer can be reduced to 200 ppm or less, preferably to 50 ppm or less. Good crystallinity can be ensured even with a thin film, and a large exchange coupling magnetic field can be ensured between adjacent magnetic layers.

[0015]

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 is a sectional view of a bottom spin valve magnetoresistive element to which the present invention is applied, as viewed from an ABS (air bearing surface) side. This magnetoresistive element is made of glass, silicon, A
An underlayer 4 made of a Ta film 2 and a (NiFe) 75Cr25 film 3 is formed on a substrate 1 made of a ceramic material such as l2O3.TiC and covered with an insulating layer such as alumina (Al2O3). A magnetoresistive (MR) film 5 having a bottom spin valve structure is laminated thereon.

The MR film 5 is made of Pt laminated on the underlayer 4.
An antiferromagnetic layer 6 made of a Mn alloy, a pinned magnetic layer 7 made of a Co alloy film, a nonmagnetic conductive layer 8 made of a Cu film,
and a free magnetic layer 11 composed of an o-alloy film 9 and a Ni80Fe20 film 10. The MR film 5 is subjected to a predetermined heat treatment in a vacuum magnetic field after film formation, thereby ordering the antiferromagnetic layer 6 and imparting unidirectional anisotropy to the pinned magnetic layer 7 to fix its magnetization orientation. . On the MR film 5, a protective film 12 made of Ta is formed. Both sides of the MR film 5 are removed by etching according to a predetermined track width, and a hard bias layer and conductive leads (both not shown) as electrodes for flowing a sense current are formed. Further, when the entire laminated structure is covered with an alumina insulating layer, a spin valve MR sensor is completed.

Each of the above film layers is continuously formed by, for example, DC sputtering. In particular, the antiferromagnetic layer 6 is made of PtM containing oxygen having a concentration of 200 ppm or less as an impurity.
It is formed by sputtering using an n-alloy target. Such a target from which oxygen has been removed to an extremely low level is formed by using a CaO refractory crucible and using a vacuum melting method in which an appropriate amount of an Al-based alloy is added and refined in a vacuum or Ar atmosphere. can do. Further, this method can remove impurities such as sulfur in addition to oxygen to an extremely low level.

By using this molten PtMn alloy target, the antiferromagnetic layer 6 has an oxygen content of 200 ppm or less as an impurity. More preferably, by using a PtMn alloy target having an oxygen concentration of 100 ppm or less, more preferably 50 ppm or less, the oxygen concentration of the antiferromagnetic layer is reduced to 100 ppm or less, or 50 ppm or less.
Thus, the exchange coupling with the pinned magnetic layer 7 can be increased. Naturally, the sputtering apparatus is required to have a performance capable of sufficiently reducing the degree of vacuum in the vacuum chamber during film formation. However, Japanese Patent Laid-Open No.
No. 10 ^-7 Pa (1) as in the case of
An apparatus for creating an ultra-high vacuum of the order of 0 ^-9 Torr is not required, and the formation of the antiferromagnetic layer is carried out by using a normally used 1.33 × 1
0 ^{-6 to} 6.65 × 10 ^-6 Pa (1 × 10 ^{-8 to} 5 × 10 ^-8
It is preferable to perform sputtering at a degree of vacuum of about Torr). According to the present invention, since the impurity concentration of the molten Mn-based alloy target is sufficiently low, a sufficiently large exchange coupling can be obtained even at such a degree of vacuum. Further, it is necessary to sufficiently increase the purity of Ar gas and the like used as a sputtering gas so as to reduce the concentration of oxygen and other impurities. In this example, the concentration of the oxygen impurity is measured by a known inert gas carrier melting infrared absorption method.

The thickness of the antiferromagnetic layer 6 is about 10 to 400 °
, Preferably set to 150 ° or less, more preferably 100 ° or less. According to the present invention, even if the thickness of the antiferromagnetic layer is made extremely thin, good crystallinity can be ensured, and therefore a sufficiently large exchange coupling magnetic field with the pinned magnetic layer 7 is exhibited. Can be done. Furthermore, the extra and useless current flowing in the film layer not related to the magnetoresistance effect such as the antiferromagnetic layer 6 is reduced by making it extremely thin, so that the power consumption of the magnetoresistance effect element is reduced and the output is improved. Can be achieved.

The antiferromagnetic layer 6 preferably has an average crystal grain size of 20 ° or more in a layer portion having a thickness of at least 50 ° from the interface on the substrate side. In particular, when the PtMn antiferromagnetic layer has an fcc (face-centered cubic) or fct (face-centered tetragonal) crystal structure, a strong (111) orientation at the interface with the pinned magnetic layer 7 can be obtained, which is advantageous. It is. Further, when the (NiFe) 75Cr25 film 3 of the adjacent underlayer has an average crystal grain size of 20 ° or more, an antiferromagnetic layer can be epitaxially grown thereon, so that a good (111) crystal can be obtained. This is preferable because the orientation can be ensured.

The material of the antiferromagnetic layer of the present invention is PtMn.
The alloy is particularly preferable because Pt is a material that is relatively hard to be oxidized. In addition, Pt, Ni, and R are elements that form an alloy with Mn and exhibit antiferromagnetism.
u, Pd, Ir, Cr or a Mn-based alloy with any two or more of these can be used. Also in this case, by performing sputtering using a melting target in the same manner, good crystallinity can be secured even when the film thickness is extremely thin, and an antiferromagnetic layer exhibiting a large exchange coupling magnetic field can be obtained. .

The present invention has a so-called top spin valve structure in which an antiferromagnetic layer is arranged on the side opposite to the substrate, in addition to the bottom spin valve structure described above with reference to FIG. A dual spin valve structure in which a ferromagnetic layer and a free magnetic layer are arranged symmetrically, a pinned magnetic layer is composed of a pair of ferromagnetic films antiferromagnetically coupled with a nonmagnetic film interposed, and an applied magnetic field The present invention can be similarly applied to spin valve MR elements having various known structures, such as a synthetic type spin valve structure in which an antiferromagnetic layer and one of the adjacent ferromagnetic films are exchange-coupled in the presence of.

[0023]

(Embodiment 1) In the spin-valve MR element shown in FIG. 1, Ta30 @ / (NiFe) 75 was formed on a glass substrate.
Cr2540Å / PtMntÅ / Co alloy 21Å / Cu2
6Å / Co alloy 10Å / Ni80Fe2050Å / Ta30
The spin valve MR film of Å was continuously formed by DC sputtering while changing the thickness t of the PtMn layer,
2 in a vacuum magnetic field of 1.1 T (Tesla) for layer ordering.
Heat treatment was performed at 70 ° C. × 10 hours. The PtMn layer was formed by using a melted PtMn alloy target and a PtMn layer using a conventional sintered target as a comparative example.
Was measured. The film thickness t of the antiferromagnetic layer was 5 in Example 1.
0, 75, 100, 150, 200, 250, 300,
400 °, and 150, 200, 25 for the comparative example.
0, 300, and 400 °.

FIG. 2 shows the results. In this figure, in each case, as the thickness t of the antiferromagnetic layer becomes smaller,
The exchange coupling magnetic field Hex has decreased. However, when the molten PtMn alloy target of this example was used, the degree of decrease in Hex was much smaller than in the comparative example using the conventional target, and the Hex was relatively high even at a film thickness t = 100 ° or less. It can be seen that the value can be maintained.

(Example 2) A synthetic spin valve film in which the pin magnetic layer in Example 1 was formed of a laminated film of Co alloy 20% / Ru 8.5% / Co alloy 26% was similarly formed by changing the thickness t of the PtMn layer. Instead, a film was continuously formed by DC sputtering, and a heat treatment was performed at 270 ° C. × 10 hours in a vacuum magnetic field of 1.1 T (tesla) for ordering the PtMn layer. The PtMn layer was formed using a molten PtMn alloy target and a PtMn layer using a conventional sintered target as a comparative example, and the exchange coupling magnetic field Hex with respect to the antiferromagnetic layer thickness t was measured for each. The thickness t of the antiferromagnetic layer was 75, 100, 15 for Example 1.
0, 200, 250 °, and 75, 10 for the comparative example.
0, 150, 200, 250, 300 °.

FIG. 3 shows the results. As in the first embodiment, in each case, the exchange coupling magnetic field Hex decreases as the thickness t of the antiferromagnetic layer decreases, but the exchange coupling magnetic field Hex decreases when the molten PtMn alloy target of the present invention is used. However, the degree of decrease of Hex is much smaller than the conventional one, and the film thickness t
It can be seen that a relatively high Hex value can be maintained even when = 100 ° or less.

(Embodiment 3) The same spin valve MR element as in Embodiment 1 was formed by DC sputtering using a molten PtMn alloy target for the PtMn layer and changing the thickness t of the PtMn layer. ) In a vacuum magnetic field of 270 ° C. × 10 hours. As a comparative example, a spin valve MR element having the same film configuration was formed on a PtMn layer using a conventional sintered target. The thickness t of the antiferromagnetic layer is set to 100, 150, 200, and 250 °, and the temperature of each is changed (25 ° C. to 400 ° C.
(At intervals of ° C).

FIG. 4 shows the measurement results of Example 3 and FIG. 5 shows the measurement results of Comparative Example. In these figures, the difference between the two is particularly noticeable when the thickness of the antiferromagnetic layer is t = 100, 150 °. That is, when the molten PtMn alloy target of this embodiment is used, a relatively high Hex
It can be seen that the value is maintained.

[0029]

According to the present invention, as described above, CaO
By using a Mn-based alloy target formed by a vacuum melting method using a (calcia) refractory crucible,
Since the impurity oxygen concentration of the antiferromagnetic layer can be remarkably reduced and excellent crystallinity can be ensured even when the film thickness is extremely thin, a large exchange coupling magnetic field and excellent thermal stability can be ensured. Accordingly, a high-performance spin-valve magnetoresistive magnetic head capable of achieving higher recording density and smaller size can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a main part of a bottom spin-valve magnetoresistive element to which the present invention is applied, viewed from the ABS side.

FIG. 2 is a diagram showing the relationship between the exchange coupling magnetic field Hex and the thickness of a PtMn antiferromagnetic layer of the bottom spin valve magnetoresistive film of FIG.

FIG. 3 is a diagram showing the relationship between the exchange coupling magnetic field Hex and the thickness of a PtMn antiferromagnetic layer of a synthetic type bottom spin valve magnetoresistive film.

FIG. 4 is a diagram showing a relationship between exchange coupling magnetic field Hex and temperature of the bottom spin valve magnetoresistive film of FIG. 1;

FIG. 5 shows a PtM film formed using a conventional sintered target.
FIG. 4 is a diagram showing a relationship between exchange coupling magnetic field Hex and temperature of a bottom spin valve magnetoresistive film having an n antiferromagnetic layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Ta film 3 NiFeCr film 4 Underlayer 5 MR film 6 Antiferromagnetic layer 7 Pin magnetic layer 8 Nonmagnetic conductive layer 9 CoFe film 10 NiFe film 11 Free magnetic layer 12 Protective film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 10/32 H01L 43/12 H01L 43/12 G01R 33/06 R (72) Inventor Jitao Osaka 2-15-17 Egawa, Shimamoto-cho, Mishima-gun Reedlight SMI Co., Ltd. (72) Inventor Masaki Ueno 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Pref. Hiroshi Nishida 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture (72) Inventor Fuminori Higami 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka F: Inside readlight SMI Term (reference) 2G017 AD55 AD63 AD65 4K029 AA09 BA02 BA21 BB02 BD11 CA05 DC04 DC08 5D034 BA05 BA21 CA00 CA08 DA05 5E049 AA10 BA12 BA16 CB02 CC01 DB02 DB12 GC02

Claims (2)

[Claims] 1. A spin valve magnet 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 resistance effect element, formed by a vacuum melting method using a crucible of CaO (calcia) refractory and using a molten Mn-based alloy target containing oxygen having a concentration of 200 ppm or less as an impurity,
A spin-valve magnetoresistive element, wherein the antiferromagnetic layer is formed by sputtering. 2. The spin-valve magnetoresistive element according to claim 1, wherein the antiferromagnetic layer is made of a Mn-based alloy containing oxygen as an impurity at a concentration of 200 ppm or less.