Patent Grant
7760473
This application claims the benefit of Japanese Patent Application No. 2006-048391 filed Feb. 24, 2006, which is hereby incorporated by reference.
1. Field
The present application relates to a magnetoresistance element with a Heusler alloy as the magnetic layer, capable of increasing a plateau magnetic field Hp1 while maintaining a high (RA.
2. Description of the Related art
The patent documents described below disclose a CPP magnetic detection device in which current flows in a direction perpendicular to a film surface of each layer constituting multi-layers (for example, see [0027], etc of JP-A-2004-146480).
In the patent documents, a Heusler alloy is used in at least one layer of a free magnetic layer and a fixed magnetic layer (both layers all are described as a term of a ferromagnetic layer in JP-A-2004-146480) disclosed (see claim 2 of JP-A-2004-146480, claim 9 of JP-A-2004-214251, and claim 10 of JP-A-2005-116703).
A spin polarizability may improve more when the free magnetic layer and the fixed magnetic layer are formed of the Heusler alloy, than when the free magnetic layer and the fixed magnetic layer are formed of a CoFe alloy or a NiFe alloy. The improved polarizability leads to an increased magnetoresistance variation ΔR. In a CPP magnetic detection device, the product ΔRA of the magnetoresistance variation ΔR and an element area A is a very important parameter for improving a high record density. Accordingly, it is preferable that the Heusler alloy is used in the free magnetic layer or the fixed magnetic layer.
In one embodiment, besides the ΔRA, a plateau magnetic field is also an important parameter.
The plateau magnetic field Hp1 refers to a strength of an exterior magnetic field, when an exterior magnetic field is applied in a direction antiparallel to magnetization direction of the fixed magnetic layer and the magnetization in the fixed magnetic layer begins to reverse due to the exterior magnetic field.
The more intense the plateau magnetic field is, the steadier the magnetization direction of the fixed magnetic layer remains. Accordingly, a producing property can improve.
In the above patent documents, other Heusler alloys, which several have different compositions, are exemplified, but Co2MnGe or Co2MnSi having a high spin polarizability has been considered to be an appropriate material for the fixed magnetic layer or the free magnetic layer.
However, when Co2MnGe or Co2MnSi is used in the fixed magnetic layer and the free magnetic layer, the plateau magnetic field Hp1 may not be properly intense.
Additionally, the plateau magnetic field Hp1 is not described and even not mentioned at all in the prior arts described above.
The present embodiments may obviate one or more of the drawbacks and limitations inherent in the related art. For example, in one embodiment, a magnetoresistance element is capable of increasing a plateau magnetic field Hp1 and maintaining a higher ΔRA than in the past art.
According to one embodiment, a magnetic detection device includes a fixed magnetic layer of which a direction of magnetization is fixed and a free magnetic layer which is formed on the fixed magnetic layer with a non-magnetic material layer interposed therebetween and of which the direction of magnetization varies by an exterior magnetic field. The fixed magnetic layer is formed of a first Heusler-alloy layer represented by CO2x(Mn(1-z)Fex)x(y (where an element is any one element of 3B group, 4B group, and 5B group, x and y all are in the unit of at %, and 3x+y=100 at %), and wherein the content y is in the range of about 20 to 30 at % and a Fe ratio z in MnFe is in the range of about 0.2 to 0.8.
The plateau magnetic field Hp1 may increase while maintaining high RA. Accordingly, the magnetization of the fixed magnetic layer according to one embodiment remains stable, thereby improving a reproducing quality.
It may be preferable that the element α is one of Ge, Si, and Al so as to maintain high ΔRA.
Additionally, it may be preferable that the first Heusler-alloy layer contacts the non-magnetic material layer so as to properly increase ΔRA.
In one embodiment, the fixed magnetic layer has a laminated ferri-structure that includes a first fixed magnetic layer, a second fixed magnetic layer, a non-magnetic intermediate layer interposed therebetween. The second fixed magnetic layer contacts the non-magnetic material layer and some of the second fixed magnetic layer is formed of the first Heusler-alloy layer. The second fixed magnetic layer constituting a spin-dependent scatter section may be formed of the first Heusler-alloy layer in which the spin polarizability is large so as to improving ΔRA, rather than the first fixed magnetic layer.
The free magnetic layer may be formed of a second Heusler-alloy layer represented by Co2vMnvGew (v and w are in the unit of at % and 3v+w=100 at %). The content w in the formula is preferable if in the range of about 21 to 27 at % so as to improve ΔRA.
The plateau magnetic field Hp1 may increase while maintaining a high ΔRA. Accordingly, the magnetization of the fixed magnetic layer may remain stable so as to improve a reproducing quality.
In one embodiment, as shown in
In one embodiment, the single spin-valve thin film element is provided in an end section of a trailing side of a floating slider so as to detect a recording field of a hard disk and the like. An X direction of the drawing indicates a direction of a track width, an Y direction indicates a direction (height direction) of a leakage field from the a magnetic recording medium, and a Z direction indicates a moving direction of a magnetic recording medium such as a hard disk and a laminated direction of the single spin-valve thin film element of each layer. Each direction is in perpendicular relation to the other two directions.
A sign indicates a lower shield layer. The single spin-valve thin film element 20 is formed on the lower shield layer. The single spin-valve thin film element 20 has a laminated body 21 in the middle of the direction of the track width (the X direction).
In the laminated body 21, a under layer 1, a seed layer 2, an antiferromagnetic layer 3, a fixed magnetic layer 4, a non-magnetic material layer 5, a free magnetic layer 6, and a protecting layer 7 are sequentially laminated.
The free magnetic layer 6 is arranged in the direction of the track width (the X direction). The fixed magnetic layer 4 has a magnetization fixed in the height direction (the Y direction). In one embodiment, as shown in
As shown in
In both side of the track width direction of the laminated body 21, an insulating layer 31, a hard bias layer 40, and an insulating layer 32 are sequentially laminated from the bottom. An upper shield layer 11 is formed on the insulating layer 32 and the protecting layer 7.
A multilayered structure structured from the lower shield layer 10 to the upper shield layer 11 refers to a reproducing head (thin film magnetic head). The single spin-valve thin film element 20 includes the laminated body 21, the insulating layer 31, the hard bias layer 40, and the insulating layer 32. In the single spin-valve thin film element 20, the lower shield layer 10 and the upper shield layer 11 may serve as an electrode of the single spin-valve thin film element 20 and flow electric current in a direction perpendicular to interfaces constituting the laminated body 21. The structure is generally called a CCP (current perpendicular to the plane).
Each layer in
The antiferromagnetic layer 3 is formed of an antiferromagnetic material including an element X (where X is at least one element selected from Pt, Pd, Ir, Rh, Ru, and Os.) and Mn or an antiferromagnetic material including the element X, an element X′ (where X′ is at least one selected from Ne, Ar, Kr, Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, Cd, Sn, Hf, Ta, W, Re, Au, Pb, and the rare-earth elements), and Mn. The antiferromagnetic layer 3 is formed of, for example, an IrMn alloy or a PtMn alloy.
The first fixed magnetic layer 4a is formed of a ferromagnetic material such as CoFe, NiFe, and CoFeNi and the non-magnetic intermediate layer 4b is formed of a non-magnetic material such as Ru, Rh, Ir, Cr, Re, and Cu. A structure and a material of the second fixed magnetic layer 4c will be described below.
The non-magnetic material layer 5 is formed of Cu, Au or Ag. A structure and a material of the free magnetic layer 6 will be described below. The protecting layer 17 may be formed of Ta and the like.
The insulating layers 31 and 32 are formed of an insulating material such as Al2O3 or SiO2. The hard bias layer 40 is formed of, for example, a Co—Pt (cobalt-platinum) alloy, a Co—Cr—Pt (cobalt-chrome-platinum) alloy, or the like. The lower shield layer 10 or the upper shield layer 11 is formed of NiFe alloy or the like.
A characteristics of a spin-valve thin film element illustrated in
As shown in
The “Fe ratio z” is represented by Fe at %/(Fe at %+Mn at %).
When analyzing the composition, an SIMS analysis equipment or a nano-beam X-ray analysis (Nano-beam EDX) using a field-emission transmission electron microscopy (FE-TEM) is employed.
According to the experiment described below, and with above structure, a plateau magnetic field Hp1 can increase while maintaining a high product ΔRA of a magnetoresistance variation ΔR and an element area A.
In one embodiment, the plateau magnetic field Hp1 refers to an strength of an exterior magnetic field, when an exterior magnetic field is applied in a direction antiparallel to magnetization direction of the fixed magnetic layer and the magnetization in the fixed magnetic layer begins to reverse due to the exterior magnetic field. As shown in
The higher the plateau is, the steadier the magnetization direction of the fixed magnetic layer 4 remains. Accordingly, a producing property can improve.
In one embodiment, in a first Heusler-alloy layer, some of Mn in Co2MnGe, for example, used as the prior Heusler alloy are substituted by Fe. Since the substitution of Fe for some of Mn makes a magnetostriction or a coercivity increase, it is considered that the plateau magnetic field Hp1 increases.
As described above, the Fe ratio z is in the range of about 0.2 to 0.8. When the Fe ratio z is below 0.2, the plateau magnetic field Hp1 cannot effectively increase. In one embodiment, the Fe ratio z is above 0.8, a deterioration in ΔRA increases. Accordingly, the Fe ratio z is set in the range of about 0.2 to 0.8.
According to one embodiment, the content y is set in the range of about 20 to 30 at %, but a high ΔRA may remain by using the content y. Additionally, it is preferable that the content y is about 25 at % so as to obtain a stable and high ΔRA.
The element α is any one of the 3B group, the 4B group, and the 5B group. In particular, Ge, Si, or Al may be preferably selected in the 3B group, the 4B group, and the 5B group so as to maintain the high ΔRA.
In one embodiment, as shown in
When the free magnetic layer 6 is formed of a second Heusler-alloy layer represented in the formula Co2vMnvGew (where v and w all are at % and 3v+w=100 at %.), ΔRA may preferably increase more effectively. The content w represented by the composition formula is set in the range of about 21 to 27 at %.
The free magnetic layer 6 may be formed of, for example, a Co2MnSi alloy, but in this case, a crystallization temperature of the Co2MnSi alloy is high, and specifically, an annealing process of 300° C. is required. The crystallization temperature of the second Heusler-alloy layer represented by Co2MnSi is not as high as that of the Co2MnSi alloy.
By appropriately crystallizing the Heusler alloy, the spin polarizability may increase so as to improve the ΔRA. However, when a high-temperature anneal is performed, for example, a exchanged-coupled magnetic field (Hex) between the antiferromagnetic layer 3 and the first fixed magnetic layer 4a may be degraded. Accordingly, the second Heusler-alloy layer is preferably employed in the free magnetic layer 6 so as to keep the annealing temperature low.
The crystallization temperature of the first Heusler-alloy layer employed in the magnetic layer 4c2 adjacent to the non-magnetic material layer of the fixed magnetic layer 4 become lower than that of Co2MnSi by substituting Fe for some of Mn even when Si is selected as the element α. However, in order to lower the crystallization temperature, it is better to select Ge as the element α.
For example, even when the first Heusler-alloy layer is employed in the free magnetic layer 6, the anneal temperature may be low so as to prevent the exchange-coupling magnetic field (Hex) between the antiferromagnetic layer 3 and the first fixed magnetic layer 4a, from being degraded. In contrast, the magnetostriction and coercivity of the free magnetic layer 6 may increase. Additionally, the second Heusler-alloy layer is thought to have higher spin polarization than the first Heusler-alloy layer. In order to increase the plateau magnetic field Hp1, it is important to employ the first Heusler-alloy layer in the fixed magnetic layer 4, particularly (Even when the first Heusler-alloy layer is not employed in the free magnetic layer 6, the plateau magnetic field Hp1 is not much degraded).
In one embodiment, the first Heusler-alloy layer is employed in the fixed magnetic layer 4 and the second Heusler-alloy layer is employed in the free magnetic layer 6.
The free magnetic layer 6 is formed of a single layer, but for example, the free magnetic layer 6 may be formed of a laminated structure or the laminated ferri structure as the same as the fixed magnetic layer 4. When the free magnetic layer 6 is formed of the laminated structure of the magnetic layer, it is preferable that the second Heusler-alloy layer is employed at least on the side adjacent to the non-magnetic material 5 so as to increase ΔRA. It is preferable that a soft magnetic material such as a NiFe alloy is employed in the parts except for the second Heusler-alloy layer of the free magnetic layer 6 so as to improve a reproducing sensitivity.
As shown in
In one embodiment, as shown in
The lower antiferromagnetic layer 103 and the upper antiferromagnetic layer 111 shown in
In the dual spin-valve thin film element 100 shown in
In one embodiment, the plateau magnetic field Hp1 may increase, while maintaining the ΔRA high. Accordingly, magnetization of the fixed magnetic layers 104 and 109 may be maintained in a stable state.
The free magnetic layer 107 may be formed of the first Heusler-alloy layer, but is preferably formed of the second Heusler-alloy layer represented in the formula Co2vMnvGew (where v and w are at %, and 3v plus w equals 100 at %). The content w represented in the formula the composition formula is set in the range of about 21 to 27 at %, thereby more effectively increasing ΔRA.
A method of manufacturing the spin-valve thin film element 20 illustrated in
The under layer 1, the seed layer 2, the antiferromagnetic layer 3, the fixed magnetic layer 4, the non-magnetic material layer 5, the free magnetic layer 6, and the protecting layer 7 are sequentially laminated from the bottom on the lower shield 10 shown in
When the fixed magnetic layer 4 shown in
The free magnetic layer 6 may be formed of the first Heusler-alloy layer, but is preferably formed of the second Heusler-alloy layer represented by Co2vMnvGew (where v and w are at %, and 3v plus w equals 100 at %). The content w represented in the composition formula is set in the range of 21 to 27 at %.
After the laminated body 21 from the under layer 1 to the protecting layer 8 is formed, a thermal treatment in the magnetic field (for example, at 290° C. for 3 to 4 hours or so). Accordingly, the exchange-coupling magnetic field (Hex) occurs between the antiferromagnetic layer 3 and the first fixed magnetic layer 4a. Further, an RKKY interaction between the first fixed magnetic layer 4a and the second fixed magnetic layer 4c occurs, and then the first fixed magnetic layer 4a and the second fixed magnetic layer 4c are magnetized antiparallel with each other in a direction parallel to the height (the Y direction)
According to one embodiment, a crystallization and crystal orderization of the magnetic layer 4c2 adjacent to the non-magnetic material layer formed of the first Heusler-alloy layer and the free magnetic layer 5 formed of the second Heusler-alloy layer may be accelerated.
As shown in
In the method of manufacturing the spin-valve thin film element 20 according to one embodiment, the Heusler alloy may be appropriately crystallized and ordered at an anneal temperature less than 300° C. so as to prevent the exchange-coupling magnetic field (Hex) between the antiferromagnetic layer 3 and the fixed magnetic layer 4, from being degraded.
Additionally, since the plateau magnetic field Hp1 may increase, even when an unintentional high exterior magnetic field affects in the middle of manufacturing, the magnetization of the fixed magnetic layer 4 remains in a stable state.
The spin-valve thin film element 20 capable of maintaining a high ΔRA and increasing the plateau magnetic field Hp1 may be manufactured briefly or appropriately.
In the embodiment shown in
Films were configured below. The films were as follows: an under layer was formed of Ta(30), a seed layer was formed of NiFeCr(50), an antiferromagnetic layer was formed of IrMn(70), a lower fixed magnetic layer [a lower first fixed magnetic layer] was formed of Fe10 at %Co70at %(30), a lower non-magnetic intermediate layer was formed of Ru(9.1), a magnetic layer adjacent to a non-magnetic material layer was formed of Co2(Mn1-zFez)α(40), a lower non-magnetic material layer was formed of Cu(50), a free magnetic layer was formed of Co2(Mn1-zFez)α(80), an upper non-magnetic material layer was formed of Cu(50), a free magnetic layer was formed of C02(Mn1-zFez)α(80), an upper non-magnetic material layer was formed of Cu(50), an upper fixed magnetic layer [a magnetic layer adjacent to a non-magnetic material layer] was formed of Co2(Mn1-zFez)α(40), a magnetic layer adjacent to a non-magnetic intermediate layer was formed of Fe10 at %Co60 at %(30), an upper antiferromagnetic layer was formed of IrMn, and a protecting layer was formed of Ta(200). In this embodiment, Ge or Si was used as an element α. The numbers in the parentheses referred to a thickness of the films and a unit was Å. A thermal treatment for a configuration of the films was performed at 290° C. for 3.5 hours in a magnetic field of 10 kOe (about 790 kA/m).
A plateau magnetic field Hp1 was measured, in relation to a varied Fe ratio z of Co2(Mn1-zFez)α constituting a magnetic layer adjacent to non-magnetic material layer. When the element α is formed of Ge, an unidirectional exchange-bias field (Hex*) and magnetization λS were measured. The result of each experiment is shown in
As shown in
Alternatively, the increase in the Fe ratio z led to an increase in the plateau magnetic field Hp1. The reason that the plateau magnetic field Hp1 increased was because a magnetostrition or a coercivity of a second fixed magnetic layer constituting the fixed magnetic layer increased.
Additionally, as shown in
As shown in
The above-experiment was performed by using Ge or Si as the element α, and besides Ge or Si, an experiment was also performed by using Al.
When the magnetic layer adjacent to the non-magnetic material layer and the free magnetic layer were formed of Co2xFexAly, Co2xFexSiy, or Co2xFexGey (however, in a case of a Heusler alloy, 3x plus y equals 100 at %), a relationship between a composition ratio y and ΔRA was measured in the experiment.
As shown in
A three element system of CoFeα was used in
As described in
That is, iIt is preferable to select the Heusler alloy in the free magnetic layer, in that the Heusler alloy has a high spin polarization and has a capability of decreasing the magnetostriction and coercivity of the free magnetic layer.
The free magnetic layer was formed of CoMnGe, and the magnetic layer adjacent to the non-magnetic material layer was formed of CoMnFecα such that ΔRA and the plateau magnetic field Hp1 were measured. The films in the experiment were as follows: the under layer was formed of Ta(30), the seed layer was formed of NiFeCr(50), the antiferromagnetic layer was formed of IrMn(70), the lower fixed magnetic layer [a lower first fixed magnetic layer] was formed of Fe10 at %Co70at %(30), the lower non-magnetic intermediate layer was formed of Ru(9.1), the magnetic layer adjacent to a non-magnetic material layer was formed of Co2(Mn1-zFez)α(40), the lower non-magnetic material layer was formed of Cu(50), the free magnetic layer was formed of Co2(Mn1-zFez)α(80), the upper non-magnetic material layer was formed of Cu(50), the free magnetic layer was formed of Co2(Mn1-zFez)α(80), the upper non-magnetic material layer was formed of Cu(50), the upper fixed magnetic layer [the magnetic layer adjacent to a non-magnetic material layer] was formed of Co2(Mn1-zFez)α(40), the magnetic layer adjacent to the non-magnetic intermediate layer was formed of Fe10 at %Co60 at % (30), the upper antiferromagnetic layer was formed of IrMn, and the protecting layer was formed of Ta(200). In this case, as an element α, Ge or Si was used. The numbers in the parentheses referred to a thickness of the films and a unit was Å. A thermal treatment for a configuration of the films was performed at 290° C. for 3.5 hours in a magnetic field of 10 kOe(about 790 kA/m).
A plateau magnetic field Hp1 was measured, in relation to a varied Fe ratio z of Co2(Mn1-zFez)α constituting a magnetic layer adjacent to non-magnetic material layer. Each of the results is shown in
As shown in
Alternatively, as shown in
On the basis of the
As shown in
A more preferred method of maintaining a high ΔRA, while increasing the plateau magnetic field Hp1 was that the magnetic layer adjacent to the non-magnetic material layer constituting the fixed magnetic layer was formed of the Co2x(Mn(1-z)Fez)xα alloy and the free magnetic layer was formed of Co2vMnvGew in the experiment results in
Various embodiments described herein can be used alone or in combination with one another. The forgoing detailed description has described only a few of the many possible implementations of the present invention. For this reason, this detailed description is intended by way of illustration, and not by way of limitation. It is only the following claims, including all equivalents that are intended to define the scope of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-048391 | Feb 2006 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7310207 | Hasegawa et al. | Dec 2007 | B2 |
| 7336453 | Hasegawa et al. | Feb 2008 | B2 |
| 7466525 | Hasegawa et al. | Dec 2008 | B2 |
| 7480122 | Ide et al. | Jan 2009 | B2 |
| 7554776 | Hasegawa et al. | Jun 2009 | B2 |
| 7558028 | Carey et al. | Jul 2009 | B2 |
| 20050266274 | Hasegawa et al. | Dec 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 2004-146480 | May 2004 | JP |
| 2004-214251 | Jul 2004 | JP |
| 2004-524689 | Aug 2004 | JP |
| 2005-116703 | Apr 2005 | JP |
| 2005-347418 | Dec 2005 | JP |
| 02069356 | Sep 2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20070201169 A1 | Aug 2007 | US |
