U.S. patent application number 15/339094 was filed with the patent office on 2017-03-30 for current-perpendicular-to-plane magneto-resistance effect element.
This patent application is currently assigned to NATIONAL INSTITUTE FOR MATERIALS SCIENCE. The applicant listed for this patent is NATIONAL INSTITUTE FOR MATERIALS SCIENCE. Invention is credited to Ye DU, Takao FURUBAYASHI, Kazuhiro HONO, Yukiko TAKAHASHI.
Application Number | 20170092307 15/339094 |
Document ID | / |
Family ID | 51658412 |
Filed Date | 2017-03-30 |
United States Patent
Application |
20170092307 |
Kind Code |
A1 |
DU; Ye ; et al. |
March 30, 2017 |
CURRENT-PERPENDICULAR-TO-PLANE MAGNETO-RESISTANCE EFFECT
ELEMENT
Abstract
The CPPGMR element of the present invention has an orientation
layer 12 formed on a substrate 11 to texture a Heusler alloy into a
(100) direction, an underlying layer 13 that is an electrode for
magneto-resistance measurement stacked on the orientation layer 12,
a lower ferromagnetic layer 14 and an upper ferromagnetic layer 16
each stacked on the underlying layer 13 and made of a Heusler
alloy, a spacer layer 15 sandwiched between the lower ferromagnetic
layers 14 and the upper ferromagnetic layers 16, and a cap layer 17
stacked on the upper ferromagnetic layer 16 for surface-protection.
This manner makes it possible to provide, inexpensively, an element
using a current-perpendicular-to-plane giant magneto-resistance
effect (CPPGMR) of a thin film having a trilayered structure of a
ferromagnetic metal/a nonmagnetic metal/a ferromagnetic metal,
thereby showing excellent performances.
Inventors: |
DU; Ye; (Ibaraki, JP)
; FURUBAYASHI; Takao; (Ibaraki, JP) ; TAKAHASHI;
Yukiko; (Ibaraki, JP) ; HONO; Kazuhiro;
(Ibaraki, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NATIONAL INSTITUTE FOR MATERIALS SCIENCE |
Ibaraki |
|
JP |
|
|
Assignee: |
NATIONAL INSTITUTE FOR MATERIALS
SCIENCE
Ibaraki
JP
|
Family ID: |
51658412 |
Appl. No.: |
15/339094 |
Filed: |
October 31, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14774987 |
Sep 11, 2015 |
9558767 |
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PCT/JP2014/059778 |
Apr 2, 2014 |
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15339094 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B82Y 10/00 20130101;
G11B 5/3906 20130101; G11B 5/1278 20130101; G11B 5/39 20130101;
H01L 43/10 20130101; H01L 43/08 20130101; G11B 2005/3996 20130101;
G11B 5/3932 20130101; G01R 33/093 20130101; G11B 5/09 20130101 |
International
Class: |
G11B 5/39 20060101
G11B005/39; G01R 33/09 20060101 G01R033/09; B82Y 10/00 20060101
B82Y010/00; G11B 5/127 20060101 G11B005/127 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2013 |
JP |
2013-079344 |
Claims
1. A current-perpendicular-to-plane magneto-resistance effect
element, comprising: a substrate comprising at least one of a
surface-oxidized Si substrate, a silicon substrate, a glass
substrate, and a metal substrate; an orientation layer formed on
the substrate to texture Heusler alloy into a (100) direction; a
lower ferromagnetic layer and an upper ferromagnetic layer that
each comprises a polycrystalline thin film of a Heusler alloy
textured into a (100) direction, and that are each formed on the
orientation layer; and a spacer layer sandwiched between the lower
ferromagnetic layer and the upper ferromagnetic layer,. wherein the
orientation layer comprises at least one of MgO, TiN, and NiTa
alloys, thereby improving a variation of the electric resistance
per unit area of the element, compared with that of a (110)
textured polycrystalline element not using an orientation
layer.
2-3. (canceled)
4. The current-perpendicular-to-plane magneto-resistance effect
element according to claim 1, wherein the spacer layer is at least
one metal selected from the group consisting of Ag, Al, Cu, Au, and
Cr, or any alloys of the selected metal(s).
5. The current-perpendicular-to-plane magneto-resistance effect
element according to claim 1, wherein at least one of the
orientation layer, the lower ferromagnetic layer, the upper
ferromagnetic layer, and the spacer layer is formed by a sputtering
method.
6. The current-perpendicular-to-plane magneto-resistance effect
element according to claim 1, wherein an underlying layer that is
an electrode for magneto-resistance measurement is laid to be
sandwiched between the orientation layer and the lower
ferromagnetic layer.
7. The current-perpendicular-to-plane magneto-resistance effect
element according to claim 6, wherein the underlying layer
comprises a metal or an alloy.
8. The current-perpendicular-to-plane magneto-resistance effect
element according to claim 1, further comprising a cap layer
stacked on the upper ferromagnetic layer for
surface-protection.
9. The current-perpendicular-to-plane magneto-resistance effect
element according to claim 8, wherein the cap layer comprises at
least one metal selected from the group consisting of Ag, Al, Cu,
Au, Ru, and Pt, or any alloys of the selected metal(s).
Description
TECHNICAL FIELD
[0001] The present invention relates to an element using a
current-perpendicular-to-plane giant magneto-resistance effect
(CPPGMR) of a thin film having a trilayered structure of a
ferromagnetic metal/a nonmagnetic metal/a ferromagnetic metal, in
particular, a current-perpendicular-to-plane giant
magneto-resistance effect element using an ordinarily usable
surface-oxidized Si substrate, silicon substrate, glass substrate,
metal substrate or the like instead of an expensive MgO
monocrystalline substrate.
BACKGROUND ART
[0002] Elements each using a current-perpendicular-to-plane giant
magneto-resistance effect (referred to also as a CPPGMR
hereinafter) of a thin film having a trilayered structure of a
ferromagnetic metal/a nonmagnetic metal/a ferromagnetic metal have
been expected for readout heads for magnetic disks. Researches have
been made about elements each using a Heusler alloy, which is large
in spin polarizability, as each of the ferromagnetic metals. A
development has been made about a CPPGMR element using a
polycrystalline thin film having a crystal orientation textured
into a (110) direction as a layer of the Heusler alloy (for
example, Patent Literatures 1 to 3).
[0003] By contrast, it is demonstrated that in a CPPGMR element,
the use of a monocrystalline thin film textured into a (100)
direction makes it possible to improve performances of the element
(for example, Non Patent Literatures 1 and 2). However, for the
production of the monocrystalline thin film, an expensive MgO
monocrystalline substrate is required, and thus such methods are
impracticable from the viewpoint of costs.
CITATION LIST
Patent Literatures
[0004] Patent Literature 1: JP 2010-212631 A
[0005] Patent Literature 2: JP 2011-35336 A
[0006] Patent Literature 3: JP 2005-116701 A
Non Patent Literatures
[0007] Non Patent Literature 1: Appl. Phys. Lett. 100, 052405
(2012).
[0008] Non Patent Literature 2: Appl. Phys. Lett. 101, 252408
(2012).
SUMMARY OF INVENTION
Technical Problem
[0009] The present invention has been made in light of actual
situations of the above-mentioned conventional techniques, and an
object of the invention is to provide, without using any MgO
monocrystalline substrates, a CPPGMR element more inexpensive and
better in performances than CPPGMR elements each using a
polycrystalline thin film having a crystal orientation textured to
a (110) direction.
Solution to Problem
[0010] In order to solve the above-mentioned problems, the present
invention provides a CPPGMR element having structural requirements
described below.
[0011] For example, as illustrated in FIG. 1, the CPPGMR element of
the present invention includes, an orientation layer 12 on a
substrate 11 to texture Heusler alloy into a (100) direction, a
lower ferromagnetic layer 14 and an upper ferromagnetic layer 16
that each includes a polycrystalline thin film of a Heusler alloy
textured into a (100) direction, and that are each stacked on the
orientation layer 12, and a spacer layer 15 sandwiched between the
lower ferromagnetic layer 14 and the upper ferromagnetic layer
16.
[0012] In the CPPGMR element of the present invention, it is
preferred that: the substrate 11 is at least one of a
surface-oxidized Si substrate, a silicon substrate, a glass
substrate, and a metal substrate; the orientation layer 12 includes
at least one of MgO, TiN, and NiTa alloys; the lower ferromagnetic
layer 14 and the upper ferromagnetic layer 16 each includes a
Heusler alloy represented by a composition formula of Co.sub.2AB
wherein A is Cr, Mn, or Fe, or a mixture obtained by mixing two or
more of these elements with each other to set the total quantity of
the mixed elements to 1, and B is Al, Si, Ga, Ge, In, or Sn, or a
mixture obtained by mixing two or more of these elements with each
other to set the total quantity of the mixed elements to 1; and the
spacer layer 15 is at least one metal selected from the group
consisting of Ag, Al, Cu, Au, and Cr, or any alloys of the selected
metal(s).
[0013] In the CPPGMR element of the present invention, it is
preferred that at least one of the orientation layer 12, the lower
ferromagnetic layer 14, the upper ferromagnetic layer 16, and the
spacer layer 15 is formed by a sputtering method.
[0014] In the CPPGMR element of the present invention, it is
further preferred that an underlying layer 13 for
magneto-resistance measurement is laid to be sandwiched between the
orientation layer 12 and the lower ferromagnetic layer 14. The
underlying layer 13 can be formed, using at least one metal
selected from the group consisting of Ag, Al, Cu, Au, and Cr, or
any alloys of the selected metal(s). It is advisable to form the
underlying layer 13 by a sputtering method.
[0015] In the CPPGMR element of the present invention, it is also
preferred that a cap layer 17 to be stacked on the upper
ferromagnetic layer 16 for surface protection. The cap layer 17 may
be formed, using at least one metal selected from the group
consisting of Ag, Al, Cu, Au, Ru, and Pt, or any alloys of the
selected metal(s). It is advisable to form the cap layer 17 by a
sputtering method.
Advantageous Effects of Invention
[0016] In the present invention, an orientation layer is laid over
a substrate including at least one of a surface-oxidized Si
substrate, a silicon substrate, a glass substrate, and a metal
substrate, which are inexpensive, without using any MgO
monocrystalline substrates to produce a CPPGMR element including a
(100)-textured polycrystalline thin film. It has been verified that
this production makes the resultant element better in properties
than any production using a (110)-textured polycrystalline thin
film. Such a structure makes it possible to produce a CPPGMR
element more inexpensive and higher in performances.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a schematic structural view of a CPPGMR element
according to an embodiment of the present invention.
[0018] FIG. 2 is a chart showing an X-ray diffraction pattern of a
film obtained by stacking, onto an oxidized Si substrate,
respective films of the following from below: MgO (10)/Cr (20)/Ag
(50)/CFGG (10)/Ag (7)/CFGG (10)/Ag (5)/Ru (8).
[0019] FIG. 3 is a schematic sectional view of a CPPGMR element
according to an embodiment of the present invention.
[0020] FIG. 4 is a graph demonstrating a change in the value of
"the area of an element".times."the electric resistance thereof"
versus a magnetic field applied thereto.
[0021] FIG. 5 is a graph demonstrating results of the value
.DELTA.RA of "the change of the magneto-resistance
thereof".times."the area of an element" versus annealing
temperature, in which black squares show results of a
(110)-textured orientation film according to a conventional
method.
DESCRIPTION OF EMBODIMENTS
[0022] Hereinafter, the present invention will be described,
referring to the drawings.
[0023] FIG. 1 is a schematic structural view of a
current-perpendicular-to-plane magneto-resistance effect (CPPGMR)
element according to an embodiment of the present invention. In the
figure, the CPPGMR element of the present embodiment is configured
by a substrate 11, an orientation layer 12, an underlying layer 13,
a lower ferromagnetic layer 14, a spacer layer 15, an upper
ferromagnetic layer 16, and a cap layer 17 stacked in this
order.
[0024] The substrate 11 is most preferably a surface-oxidized Si
substrate from the viewpoint of costs, but may be a silicon
substrate for semiconductor-production, or may be a glass substrate
or a metal substrate. It is sufficient for the orientation layer 12
to be a layer having an effect of texturing a Heusler alloy into a
(100) direction. Thus, the orientation layer 12 is preferably a
layer containing at least one of MgO, TiN, and NiTa alloys. Of
these components, MgO and TiN are crystalline. Such a crystalline
orientation layer is textured into a (100) direction to grow
easily, so that the layer itself undergoes (100) orientation to
induce the (100) orientation of a Heusler alloy. Although NiTa is
amorphous, NiTa induces the (100) orientation of a Heusler alloy
growing on this component. When the substrate 11 has a crystal
orientation, NiTa simultaneously has an effect of breaking off any
effect of the crystal orientation. The underlying layer 13 is made
of a metal or an alloy, and is to be an electrode for
magneto-resistance measurement. For the underlying layer 13, the
following is usable: a metal containing at least one of Ag, Al, Cu,
Au Cr and others; or any alloys of one or more of these metal
elements. A different underlying layer may be added below the
orientation layer 12.
[0025] The lower ferromagnetic layer 14 and the upper ferromagnetic
layer 16 each contains a polycrystalline Heusler alloy textured to
a (100) direction represented by a composition formula of
Co.sub.2AB wherein A is Cr, Mn, or Fe, or a mixture obtained by
mixing two or more of these elements with each other to set the
total quantity of the mixed elements to 1, and B is Al, Si, Ga, Ge,
In, or Sn, or a mixture obtained by mixing two or more of these
elements with each other to set the total quantity of the mixed
elements to 1. The Heusler alloy is in particular preferably a
Co.sub.2FeGa.sub.0.5Ge.sub.0.5 (CFGG) polycrystalline thin film,
but may be a Co.sub.2FeAl.sub.1-xSi.sub.x, Co.sub.2MnSi or
Co.sub.2Fe.sub.1-xMn.sub.xSi polycrystalline thin film. For the
upper ferromagnetic layer and the lower ferromagnetic layer, one
Heusler alloy may be used. Alternatively, any combination of two or
more Heusler alloys may be used, as well as any combination of one
or more Heusler alloys with one or more different metals or
alloys.
[0026] The spacer layer 15 is made of a metal or an alloy. The cap
layer 17 is made of a metal or an alloy for surface-protection. For
the spacer layer 15, the following is usable: for example, a metal
containing at least one of Ag, Al, Cu, Au, Cr, and others; or any
alloys of one or more of these metal elements. For the cap layer
17, the following is usable: for example, a metal containing at
least one of Ag, Al, Cu, Au, Ru, Pt, and others; or any alloys of
one or more of these metal elements.
[0027] For each of the orientation layer 12, the underlying layer
13, the spacer layer 15, and the cap layer 17, a single material
may be used, or two or more materials stacked onto each other may
be used.
[0028] It is preferred to form at least one of the orientation
layer 12, the lower ferromagnetic layer 14, the upper ferromagnetic
layer 16, and the spacer layer by a sputtering method. It is also
preferred to anneal the stacked-film at a temperature of 200 to
450.degree. C. for about 15 to 60 minutes to be improved in crystal
structure.
EXAMPLES
[0029] The following will describe examples of the present
invention.
[0030] FIG. 3 is a schematic sectional view of a CPPGMR element
according to an example of the present invention. In the figure, a
surface-oxidized Si substrate is used as a substrate 11; MgO is
used as an orientation layer 12; a stacked Cr layer 13a and Ag
layer 13b, the Cr layer 13a being positioned below, as an
underlying layer 13; a polycrystalline (0001)-textured Heusler
alloy, Co.sub.2FeGa.sub.0.5Ge.sub.0.5 (CFGG), as an upper
ferromagnetic layer 14 and a lower ferromagnetic layer 16; Ag as a
spacer layer 15; and a stacked Ag layer 17a and Ru layer 17b, the
Ag layer 17a being positioned below, as a cap layer 17.
[0031] The CPPGMR element of the present example is an element
obtained by forming, onto the oxidized Si substrate, respective
films of the following from below: MgO (10)/Cr (20)/Ag (50)/CFGG
(10)/Ag (7)/CFGG (10)/Ag (5)/Ru (8). The number in each pair of
parentheses represents the film thickness (nm). By a sputtering
method, the film-formation of the layer structure is attained.
[0032] FIG. 2 is an X-ray diffraction pattern of the stack having
the film structure illustrated in FIG. 3. According to the X-ray
diffraction, the structure of the crystal was examined. As a
result, it was understood from the results shown in FIG. 2 that the
layer of each of Cr, Ag, and CFGG was textured into a (100)
direction. In order to improve the thin film in crystal structure,
the sample was annealed at 400.degree. C. for 30 minutes.
Thereafter, to measure the electric resistance in the direction
perpendicular to the plane of the film, the workpiece was finely
worked, as illustrated in FIG. 3, and a silicon oxide (SiO.sub.2)
layer 19 was laid adjacently to the stack composed of the upper
ferromagnetic layer 14, the spacer layer 15, the lower
ferromagnetic layer 16, and the cap layer 17. Next, a Cu electrode
layer 18 was attached onto the cap layer 17 and the silicon oxide
layer 19. A constant-current source 20 was connected between the
underlying layer 13 and the Cu electrode layer 18, and a voltmeter
21 was connected between the underlying layer 13 and the Cu
electrode layer 18. The constant-current source 20 and the
voltmeter 21 were used to examine a change in the electric
resistance of the CPPGMR element versus the magnetic field.
Furthermore, while the temperature for annealing the sample was
varied between 300.degree. C. and 450.degree. C., the variation
.DELTA.RA of the electric resistance per unit area of the element
was examined.
[0033] FIG. 4 shows a change in the electric resistance of the
CPPGMR element versus the magnetic field. When the magnetic field
was in the range of about .+-.200 [Oe](=1000/(4.pi.)A)/m), the
following variation of the electric resistance was obtained per
unit area of the element: a variation .DELTA.RA of 4.6
[m.OMEGA..mu.m.sup.2].
[0034] For comparison, without using any MgOs (orientation layers),
a sample was produced to have a film structure having, over an
oxidized Si substrate, respective films of the following: Ta (5)/Cu
(250)/Ta (5)/CFGG (5)/Ag (7)/CFGG (5)/Ag (5)/Ru (6), T (2) and Ru
(2). The sample was measured in the same way. It was verified about
this sample that the crystal orientation of CFGG was textured to
(110).
[0035] FIG. 5 is a graph obtained by plotting the variation
.DELTA.RA of the electric resistance per unit area of each of the
elements versus the annealing temperature T.sub.an. About the
(110)-textured sample according to the conventional technique, the
variation .DELTA.RA was lowered in the case of
T.sub.an>400.degree. C. By contrast, about the (100)-textured
sample according to the present invention, at a T.sub.an of
400.degree. C., a variation .DELTA.RA of 4.3 [m.OMEGA..mu.m.sup.2]
was obtained as the average value, which was a value larger than
the maximum value 3.5 [m.OMEGA..mu.m.sup.2] according to the
conventional technique.
[0036] In a modified example of the present invention, a layer of
an antiferromagnetic material may be further added, as a pinning
layer, onto the upper ferromagnetic layer in the structure
illustrated in FIG. 3. The antiferromagnetic material is, for
example, any IrMn alloys or PtMn alloys. This layer structure,
which has the upper ferromagnetic layer to which the pinning layer
is added, makes it possible to restrain magnetization inversion in
the upper ferromagnetic layer by exchange anisotropy to stabilize a
state that the upper ferromagnetic layer and the lower
ferromagnetic layer are magnetized in antiparallel to each other.
The pinning layer may be inserted below the lower ferromagnetic
layer.
[0037] In the above-mentioned embodiment, a case has been
illustrated which has a film structure of MgO (10)/Cr (20)/Ag
(50)/CFGG (10)/Ag (7)/CFGG (10)/Ag (5)/Ru (8). However, the present
invention is not limited to this structure. Of course, the film
material and the film thickness of each of the layers can be
appropriately selected from scopes anticipated by those skilled in
the art as far as the selected material and film thickness do not
depart from the subject matters of the present invention.
INDUSTRIAL APPLICABILITY
[0038] current-perpendicular-to-plane magneto-resistance effect
(CPPGMR), is suitable for being used for a read head for a magnetic
disk, and is usable for detecting fine magnetic information
pieces.
REFERENCE SIGNS LIST
[0039] 11: substrate [0040] 12: orientation layer [0041] 13:
underlying layer [0042] 14: lower ferromagnetic layer [0043] 15:
spacer layer [0044] 16: upper ferromagnetic layer [0045] 17: cap
layer
* * * * *