U.S. patent application number 09/262314 was filed with the patent office on 2002-09-05 for magnetoresistive effect multi-layered structure and thin-film magnetic head with the magnetoresistive effect multi-layered structure.
Invention is credited to OHTA, MANABU, SASAKI, TETSURO, SHIMAZAWA, KOJI.
Application Number | 20020122278 09/262314 |
Document ID | / |
Family ID | 13938501 |
Filed Date | 2002-09-05 |
United States Patent
Application |
20020122278 |
Kind Code |
A1 |
SHIMAZAWA, KOJI ; et
al. |
September 5, 2002 |
MAGNETORESISTIVE EFFECT MULTI-LAYERED STRUCTURE AND THIN-FILM
MAGNETIC HEAD WITH THE MAGNETORESISTIVE EFFECT MULTI-LAYERED
STRUCTURE
Abstract
A MR multi-layered structure or a thin-film magnetic head with
the MR multi-layered structure includes a non-magnetic electrically
conductive material layer, first and second ferromagnetic material
layer separated by the non-magnetic electrically conductive
material layer, and an anti-ferromagnetic material layer formed
adjacent to and in physical contact with one surface of the second
ferromagnetic material layer, the one surface being in opposite
side of the non-magnetic electrically conductive material layer.
The second ferromagnetic material layer includes a first layer of a
ferromagnetic material containing Co, and a second layer of a
ferromagnetic material with a smaller magnetic anisotropy than that
of Co.
Inventors: |
SHIMAZAWA, KOJI; (TOKYO,
JP) ; SASAKI, TETSURO; (TOKYO, JP) ; OHTA,
MANABU; (TOKYO, JP) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN
1050 CONNECTICUT AVENUE, N.W.
SUITE 600
WASHINGTON
DC
20036-5339
US
|
Family ID: |
13938501 |
Appl. No.: |
09/262314 |
Filed: |
March 4, 1999 |
Current U.S.
Class: |
360/324.11 ;
G9B/5.241 |
Current CPC
Class: |
Y10T 428/1121 20150115;
G11B 5/66 20130101 |
Class at
Publication: |
360/324.11 |
International
Class: |
G11B 005/39 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 1998 |
JP |
88280/1998 |
Claims
What is claimed is:
1. A magnetoresistive effect multi-layered structure, comprising: a
non-magnetic electrically conductive material layer; first and
second ferromagnetic material layer separated by said non-magnetic
electrically conductive material layer; and an anti-ferromagnetic
material layer formed adjacent to and in physical contact with one
surface of said second ferromagnetic material layer, said one
surface being in opposite side of said non-magnetic electrically
conductive material layer, said second ferromagnetic material layer
including a first layer of a ferromagnetic material containing Co,
said first layer being stacked on said non-magnetic electrically
conductive material layer, and a second layer of a ferromagnetic
material with a smaller magnetic anisotropy than that of Co, said
second layer being stacked on said first layer.
2. The structure as claimed in claim 1, wherein said second layer
is made of a ferromagnetic material of Fe alloy.
3. The structure as claimed in claim 2, wherein said ferromagnetic
material of Fe alloy is selected one of ferromagnetic materials of
CoFe, FeSi and NiFe.
4. The structure as claimed in claim 1, wherein said second layer
is made of a ferromagnetic material of Ni alloy.
5. The structure as claimed in claim 4, wherein said ferromagnetic
material of Ni alloy is selected one of ferromagnetic materials of
FeNi, NiCo and NiCu.
6. The structure as claimed in claim 1, wherein said second layer
is made of an amorphous magnetic material alloy.
7. The structure as claimed in claim 1, wherein said second layer
has a thickness of 0.5 nm or more.
8. The structure as claimed in claim 1, wherein said first layer is
made of a ferromagnetic material of Co or CoFe.
9. A thin-film magnetic head with a magnetoresistive effect
multi-layered structure, said structure comprising: a non-magnetic
electrically conductive material layer; first and second
ferromagnetic material layer separated by said non-magnetic
electrically conductive material layer; and an anti-ferromagnetic
material layer formed adjacent to and in physical contact with one
surface of said second ferromagnetic material layer, said one
surface being in opposite side of said non-magnetic electrically
conductive material layer, said second ferromagnetic material layer
including a first layer of a ferromagnetic material containing Co,
said first layer being stacked on said non-magnetic electrically
conductive material layer, and a second layer of a ferromagnetic
material with a smaller magnetic anisotropy than that of Co, said
second layer being stacked on said first layer.
10. The head as claimed in claim 9, wherein said second layer is
made of a ferromagnetic material of Fe alloy.
11. The head as claimed in claim 10, wherein said ferromagnetic
material of Fe alloy is selected one of ferromagnetic materials of
CoFe, FeSi and NiFe.
12. The head as claimed in claim 9, wherein said second layer is
made of a ferromagnetic material of Ni alloy.
13. The head as claimed in claim 12, wherein said ferromagnetic
material of Ni alloy is selected one of ferromagnetic materials of
FeNi, NiCo and NiCu.
14. The head as claimed in claim 9, wherein said second layer is
made of an amorphous magnetic material alloy.
15. The head as claimed in claim 9, wherein said second layer has a
thickness of 0.5 nm or more.
16. The head as claimed in claim 9, wherein said first layer is
made of a ferromagnetic material of Co or CoFe.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a magnetoresistive effect
(MR) multi-layered structure especially using giant
magnetoresistive effect (GMR) such as spin valve effect, and a
thin-film magnetic head with the MR multi-layered structure used
for a HDD (Hard Disk Drive) unit.
DESCRIPTION OF THE RELATED ART
[0002] Recently, thin-film magnetic heads with MR sensors based on
spin valve effect of GMR characteristics are proposed (U.S. Pat.
Nos. 5,206,590 and 5,422,571) in order to satisfy the requirement
for ever increasing data storage densities in today's magnetic
storage systems like HDD units. The spin valve effect thin-film
structure includes first and second thin-film layers of a
ferromagnetic material separated by a thin-film layer of
non-magnetic metallic material, and an adjacent layer of
anti-ferromagnetic material is formed in physical contact with the
second ferromagnetic layer to provide exchange bias magnetic field
by exchange coupling at the interface of the layers. The
magnetization direction in the second ferromagnetic layer is
constrained or maintained by the exchange coupling, hereinafter the
second layer is called "pinned layer". On the other hand the
magnetization direction of the first ferromagnetic layer is free to
rotate in response to an externally applied magnetic field,
hereinafter the first layer is called "free layer". The direction
of the magnetization in the free layer changes between parallel and
anti-parallel against the direction of the magnetization in the
pinned layer, and hence the magneto-resistance greatly changes and
giant magneto-resistance characteristics are obtained.
[0003] The output characteristic of the spin valve MR sensor
depends upon the angular difference of magnetization between the
free and pinned ferromagnetic layers. The direction of the
magnetization of the free layer is free to rotate in accordance
with an external magnetic field. That of the pinned layer is fixed
to a specific direction (called as "pinned direction") by the
exchange coupling between this layer and adjacently formed
anti-ferromagnetic layer.
[0004] In this kind of spin valve effect MR sensor, the direction
of the magnetization of the pinned layer may change in some cases
by various reasons. If the direction of the magnetization changes,
the angular difference between the pinned and free layers changes
too and therefore the output characteristic also changes.
Consequently stabilizing the direction of the magnetization in the
pinned layer is very important.
[0005] In order to stabilize the direction of the magnetization by
the strong exchange coupling between the pinned and
anti-ferromagnetic layers, a process of temperature-annealing (pin
anneal process) is implemented under an external magnetic field
with a specific direction. The pin annealing is done by elevating
the temperature up to the Neel point and then cooling down to room
temperature under the magnetic field in the direction to be pinned.
By this pin anneal process, the exchange coupling is regulated at
the interface of the pinned and anti-ferromagnetic layers toward
the direction of the externally applied magnetic field.
[0006] However, the magnetoresistance characteristics may be
changed under actual high temperature operation of a HDD unit, even
if the pin anneal processing is properly implemented. This
degradation is caused by the high temperature stress during
operation of the HDD unit and by the magnetic field by a hard
magnet layer used for giving a bias magnetic field to the free
layer.
[0007] The detail of this degradation is as follows. The pinned
direction of the magnetization in the pinned layer is different
from that of the magnetic field (H.sub.HM) by the hard magnet. And
hence the direction of the magnetization of pinned layer which is
contacted with the anti-ferromagnetic layer is slightly rotated
toward the direction of H.sub.HM (hereinafter this direction of the
magnetization of the pinned layer is expressed as .nu..sub.p). In
the anti-ferromagnetic material layer, the Neel point temperature
differs from location to location inside the layer from macroscopic
point of view, and it is distributed in a certain range of
temperature. Even if the temperature is less than the "bulk" Neel
point (average Neel point), there could be small area whose micro
Neel point temperature is low and where the exchange coupling with
the pinned layer disappears. When such spin valve effect MR sensor
is operated at a high temperature T, which is less than the
blocking temperature at which the exchange couplings of all
microscopic areas disappear, and then cooled down to usual room
temperature, some microscopic area whose Neel temperatures are less
than T is effectively annealed again and the direction of the
magnetization is rotated in the direction of .theta..sub.p. The
total amount of the .theta..sub.p and the rotated amount component
will change the exchange coupling state between the
anti-ferromagnetic layer and the adjacent ferromagnetic layer to
determine the new pinned direction of the magnetization of the
magnetic structure. The new pinned direction will vary depending
upon the period of time kept at high temperature because the
magnetic characteristics of the ferromagnetic layer is changing
over with time under the high temperature.
[0008] As stated in the above paragraph, usage of such spin valve
MR sensor at high temperature may cause a change of the pinned
direction of the magnetization in the pinned layer, and the
electrical output characteristics of the sensor are degraded in
signal levels, and waveform symmetry.
[0009] In order to prevent the above-mentioned problems from
occurring, it had been desired that material having a high blocking
temperature and possible to provide smaller Neel temperature
distribution is used for the anti-ferromagnetic layer.
[0010] Japanese Patent Unexamined Publication No. 6(1994)-314617
discloses usage of a specific material for the anti-ferromagnetic
layer to obtain improved exchange coupling. Also, Japanese Patent
Unexamined Publication No. 9(1997)-82524 discloses insertion of an
intermediate layer for improving lattice matching between the
anti-ferromagnetic and pinned layers in order to obtain strong
exchange coupling in the interface.
[0011] As disclosed in these publications, usage of the specific
material for the anti-ferromagnetic layer and usage of intermediate
layer between the interface of the anti-ferromagnetic and pinned
layers have been proposed to enhance the exchange coupling and to
stabilize the pinned direction. However, no one has approached to
control the magnetic characteristics of the pinned ferromagnetic
layer itself to stabilize the pinned direction.
SUMMARY OF THE INVENTION
[0012] It is therefore an object of the present invention to
resolve the aforementioned problems by using a new approach, and to
provide a MR multi-layered structure and a thin-film magnetic head
with the MR multi-layered structure, whereby pinned direction can
be kept in stable at high temperature.
[0013] According to the present invention, a MR multi-layered
structure or a thin-film magnetic head with the MR multi-layered
structure includes a non-magnetic electrically conductive material
layer, first and second ferromagnetic material layer separated by
the non-magnetic electrically conductive material layer, and an
anti-ferromagnetic material layer formed adjacent to and in
physical contact with one surface of the second ferromagnetic
material layer, the one surface being in opposite side of the
non-magnetic electrically conductive material layer. The second
ferromagnetic material layer includes a first layer of a
ferromagnetic material containing Co, and a second layer of a
ferromagnetic material with a smaller magnetic anisotropy than that
of Co. The first layer is stacked on the non-magnetic electrically
conductive material layer, and the second layer is stacked on the
first layer.
[0014] In other words, according to the present invention, the
second ferromagnetic material layer (pinned layer) has a first
layer which is made of a ferromagnetic material containing Co and
stacked on the non-magnetic electrically conductive material layer,
and a second layer which is made of a ferromagnetic material with a
smaller magnetic anisotropy factor than that of Co and stacked on a
surface of the first layer that faces to the anti-ferromagnetic
material layer. Thus, the total magnetic anisotropy factor of the
pinned layer is reduced to realize smaller magnetic variations
under high temperature atmosphere, and hence a spin valve effect MR
sensor with more stable direction of the magnetization of the
pinned layer under high temperature atmosphere is realized. By
stabilizing the direction of the magnetization of the pinned layer,
the degradations of signal level and waveform symmetry of output
waveforms under high temperature atmosphere (for example at about
125.degree. C.) can be greatly reduced.
[0015] It is preferred that the second layer is made of a
ferromagnetic material of Fe alloy. In one embodiment according to
the present invention, the ferromagnetic material of Fe alloy may
be selected one of ferromagnetic materials of CoFe, FeSi and
NiFe.
[0016] It is also preferred that the second layer is made of a
ferromagnetic material of Ni alloy. In one embodiment according to
the present invention, the ferromagnetic material of Ni alloy may
be selected one of ferromagnetic materials of FeNi, NiCo and
NiCu.
[0017] It is preferred that the second layer is made of an
amorphous magnetic material alloy.
[0018] Preferably, the second layer has a thickness of 0.5 nm or
more.
[0019] It is also preferred that the first layer is made of a
ferromagnetic material of Co or CoFe.
[0020] Further objects and advantages of the present invention will
be apparent from the following description of the preferred
embodiments of the invention as illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows a cross-sectional view of a spin valve effect
multi-layered structure formed in a spin valve effect MR sensor of
a thin-film magnetic head as a preferred embodiment according to
the present invention; and
[0022] FIGS. 2a to 2c illustrate a method to measure the rotation
angle of the direction of the magnetization of the pinned
layer.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] FIG. 1 illustrates stacked thin-film layers of a spin valve
effect MR sensor. Referring to FIG. 1, reference numerals 10 and 12
denote first and second ferromagnetic thin-film layers respectively
which are separated by a thin-film layer 11 of a non-magnetic
electrically conductive metallic material. On the second
ferromagnetic thin-film layer 12, a thin-film layer 13 of
anti-ferromagnetic material is stacked, and a magnetic field
generated by the exchange coupling at the interface of the
thin-film layers 12 and 13 magnetizes the ferromagnetic layer 12,
and so to speak the layer is pinned. Thus, the second ferromagnetic
layer 12 is called as a pinned layer. The first ferromagnetic
thin-film layer 10 is a free layer in which there is no effect of
exchange coupling and hence the magnetization is free to rotate in
response to an externally applied magnetic field.
[0024] In this embodiment, the pinned layer 12 has two layered
structure composed of a second thin-film layer 12b of ferromagnetic
material containing Co and a first layer 12a of ferromagnetic
material with a smaller magnetic anisotropy than that of Co. The
first layer 12a is stacked on the surface of the second layer 12b,
which surface is opposed to the anti-ferromagnetic layer 13.
[0025] An example of the ferromagnetic material containing Co for
the second layer 12b is CoFe or Co. An example of the ferromagnetic
material with the smaller magnetic anisotropy than that of Co for
the first layer 12a is Fe alloy such as CoFe, FeSi or NiFe, or Ni
alloy such as FeNi, NiCo or NiCu. As for the composition of CoFe,
preferably Co is 0-90 at %, and more preferably Co is 40 at % where
its anisotropy factor becomes zero. As for the composition of FeSi,
preferably Si is 0-40 at %, and more preferably Si is 20 at % where
its anisotropy factor becomes zero. As for the composition of NiFe
or FeNi, preferably Fe is 0-80 at %, and more preferably Fe is 20
at % where its anisotropy factor becomes zero. As for the
composition of NiCo, preferably Co is 0-70 at %, and more
preferably Co is 5 at % where its anisotropy factor becomes zero.
As for the composition of NiCu, preferably Cu is 0-50 at %, and
more preferably Cu is 35 at % where its anisotropy factor becomes
zero.
[0026] It is preferred that the thickness of the first layer 12a of
the ferromagnetic material with the smaller magnetic anisotropy
than that of Co is 0.5 nm or more. Actually, if the layer of NiFe
is formed with a thickness less than 0.5 nm, the layer may be
shaped in islands and thus proper anisotropy control cannot be
expected. As for the ferromagnetic material with the smaller
magnetic anisotropy than that of Co for the first layer 12a,
amorphous magnetic alloy can be used as well as the aforementioned
Fe alloy or Ni alloy.
FIRST EXAMPLE
[0027] A first example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co.sub.90Fe.sub.10 (Co is 90 at % and Fe is 10 at %) with
the thickness of 1.0 or 2.0 nm and a ferromagnetic material layer
12a of Ni.sub.80Fe.sub.20 (Ni is 80 at % and Fe is 20 at %) with
the thickness of 0-4.0 nm, which has a smaller magnetic anisotropy
than that of Co, and an anti-ferromagnetic material layer 13 of
RuRhMn with the thickness of 10.0 nm, in this order.
[0028] Tables 1 and 2 show measured result of heat stability of the
pinned direction when the thickness of the NiFe layer 12a of the
pinned layer 12 is changed. In these Tables, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer.
Table 1 is in a case that the thickness of the CoFe layer 12b of
the pinned layer 12 is 1.0 nm, whereas Table 2 is in a case that
the thickness is 2.0 nm. The heat stability of the pinned direction
was detected by measuring the rotated angle of the pinned direction
of the multi-layered spin valve effect structure after the stress
of 125.degree. C. temperature which will be the maximum temperature
of the MR sensor actually operating in the HDD under the
application of simulated magnetic field from the hard magnets of
190 Oe toward perpendicular to the original pinned direction
provided during the annealing process.
1TABLE 1 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co.sub.90Fe.sub.10(1
nm)/Ni.sub.80Fe.sub.20(x)/ RuRhMn(10 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 6 3 5 7 3.5
7 4 6 8 3.0 9 4 5 8 2.5 13 5 7 10 2.0 15 6 9 12 1.5 17 6 11 15 1.0
20 7 13 18 0.5 22 10 14 22 No NiFe 24 12 16 25 Layer
[0029]
2TABLE 2 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co.sub.90Fe.sub.10(2
nm)/Ni.sub.80Fe.sub.20(x)/ RuRhMn(10 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 8 5 7 9 3.5
10 6 8 10 3.0 12 6 7 10 2.5 16 7 9 12 2.0 18 8 11 14 1.5 20 8 13 17
1.0 23 9 15 20 0.5 25 12 16 24 No NiFe 26 13 24 34 Layer
[0030] As will be apparent from these Tables 1 and 2, the rotated
angle of the pinned direction decreased, namely the heat stability
of the pinned direction improved by forming the NiFe layer 12a in
the pinned layer 12. Also, as will be understood from Table 1, in
case the thickness of the CoFe layer 12b is 1.0 nm, if the NiFe
layer 12a is formed with a thickness of 2.5 nm or more, the rotated
angle of the pinned direction after 1000 hours stress of heat and
magnetic field becomes 10 degrees or less. Furthermore, as will be
noted from Table 2, in case the thickness of the CoFe layer 12b is
2.0 nm, if the NiFe layer 12a is formed with a thickness of 3.0 nm
or more, the rotated angle of the pinned direction after 1000 hours
stress of heat and magnetic field becomes 10 degrees or less. As a
result, degradation of the electrical output characteristics of the
MR sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature can be kept
1.5% or less.
[0031] The rotated angle of the pinned direction can be easily
calculated from the output level of the spin valve effect sensor.
Namely, as shown in FIG. 2a, first a magnetic field 22, which is
perpendicular to the original pinned direction 21 provided at the
annealing process, is applied to the wafer 20, then .rho.-H loop is
measured. If there is no rotation of the pinned direction, the
measured .rho.-H loop is horizontally symmetrical as shown in FIG.
2b. If there is definite rotation of the pinned direction, the
measured .rho.-H loop becomes horizontally unsymmetrical as shown
in FIG. 2c. Assuming .theta..sub.p as the angle difference between
the rotated pinned direction 23 and the applied measurement field
direction 22, the following equation is formulated,
(E.sub.1-E.sub.0)/(E.sub.2-E.sub.0)={(1-cos
.theta..sub.p)/2}/{(1+cos .theta..sub.p)/2}. Consequently
.theta..sub.p is given the next equation,
.theta..sub.p=cos.sup.-1{(E.sub.1-E.sub.0)/(E-
.sub.2-E.sub.1+2E.sub.0)}. The rotation angle of the pinned
direction is given by 90.degree.-.theta..sub.p.
SECOND EXAMPLE
[0032] A second example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co.sub.90Fe.sub.10 (Co is 90 at % and Fe is 10 at %) with
the thickness of 1.0 or 2.0 nm and a ferromagnetic material layer
12a of Ni.sub.80Fe.sub.20 (Ni is 80 at % and Fe is 20 at %) with
the thickness of 0-4.0 nm, which has a smaller magnetic anisotropy
than that of Co, and an anti-ferromagnetic material layer 13 of
FeMn with the thickness of 12.0 nm, in this order.
[0033] Tables 3 and 4 show measured result of heat stability of the
pinned direction when the thickness of the NiFe layer 12a of the
pinned layer 12 is changed. In these Tables, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer.
Table 3 is in a case that the thickness of the CoFe layer 12b of
the pinned layer 12 is 1.0 nm, whereas Table 4 is in a case that
the thickness is 2.0 nm. The heat stability of the pinned direction
was detected by measuring the rotated angle of the pinned direction
of the multi-layered spin valve effect structure after the stress
of 125.degree. C. temperature which will be the maximum temperature
of the MR sensor actually operating in the HDD under the
application of simulated magnetic field from the hard magnets of
190 Oe toward perpendicular to the original pinned direction
provided during the annealing process.
3TABLE 3 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co.sub.90Fe.sub.10(1
nm)/Ni.sub.80Fe.sub.20(x)/ FeMn(12 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 6 8 13 15
3.5 7 9 13 16 3.0 9 9 12 16 2.5 13 10 14 18 2.0 15 11 16 20 1.5 17
11 18 23 1.0 20 12 20 26 0.5 22 15 23 30 No NiFe 24 16 24 32
Layer
[0034]
4TABLE 4 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co.sub.90Fe.sub.10(2
nm)/Ni.sub.80Fe.sub.20(x)/ FeMn(12 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 8 10 14 17
3.5 10 11 15 18 3.0 12 12 16 18 2.5 16 12 16 20 2.0 18 13 19 22 1.5
20 14 21 25 1.0 23 15 22 28 0.5 25 17 23 32 No NiFe 26 20 27 37
Layer
[0035] As will be apparent from these Tables 3 and 4, the rotated
angle of the pinned direction decreased, namely the heat stability
of the pinned direction improved by forming the NiFe layer 12a in
the pinned layer 12. Also, as will be understood from Table 3, in
case the thickness of the CoFe layer 12b is 1.0 nm, if the NiFe
layer 12a is formed with a thickness of 2.0 nm or more, the rotated
angle of the pinned direction after 1000 hours stress of heat and
magnetic field becomes 20 degrees or less. Furthermore, as will be
noted from Table 4, in case the thickness of the CoFe layer 12b is
2.0 nm, if the NiFe layer 12a is formed with a thickness of 2.5 nm
or more, the rotated angle of the pinned direction after 1000 hours
stress of heat and magnetic field becomes 20 degrees or less. As a
result, degradation of the electrical output characteristics of the
MR sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature can be kept
6.0% or less.
THIRD EXAMPLE
[0036] A third example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 or 2.0 nm and a ferromagnetic
material layer 12a of Ni.sub.80Fe.sub.20 (Ni is 80 at % and Fe is
20 at %) with the thickness of 0-4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of RuRhMn with the thickness of 10.0 nm, in this
order.
[0037] Tables 5 and 6 show measured result of heat stability of the
pinned direction when the thickness of the NiFe layer 12a of the
pinned layer 12 is changed. In these Tables, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer.
Table 5 is in a case that the thickness of the Co layer 12b of the
pinned layer 12 is 1.0 nm, whereas Table 6 is in a case that the
thickness is 2.0 nm. The heat stability of the pinned direction was
detected by measuring the rotated angle of the pinned direction of
the multi-layered spin valve effect structure after the stress of
125.degree. C. temperature which will be the maximum temperature of
the MR sensor actually operating in the HDD under the application
of simulated magnetic field from the hard magnets of 190 Oe toward
perpendicular to the original pinned direction provided during the
annealing process.
5TABLE 5 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co(1
nm)/Ni.sub.80Fe.sub.20(x)/ RuRhMn(10 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 5 2 2 3 3.5
9 4 5 8 3.0 12 5 8 10 2.5 15 6 9 12 2.0 17 6 11 15 1.5 19 7 13 18
1.0 23 10 14 22 0.5 26 12 16 25 No NiFe 28 18 23 34 Layer
[0038]
6TABLE 6 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co(2
nm)/Ni.sub.80Fe.sub.20(x)/ RuRhMn(10 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 10 4 5 7
3.5 12 6 7 10 3.0 16 7 9 12 2.5 18 8 11 14 2.0 21 8 13 17 1.5 23 9
15 20 1.0 27 12 16 24 0.5 29 14 18 27 No NiFe 30 20 26 37 Layer
[0039] As will be apparent from these Tables 5 and 6, the rotated
angle of the pinned direction decreased, namely the heat stability
of the pinned direction improved by forming the NiFe layer 12a in
the pinned layer 12. Also, as will be understood from Table 5, in
case the thickness of the Co layer 12b is 1.0 nm, if the NiFe layer
12a is formed with a thickness of 3.0 nm or more, the rotated angle
of the pinned direction after 1000 hours stress of heat and
magnetic field becomes 10 degrees or less. Furthermore, as will be
noted from Table 6, in case the thickness of the Co layer 12b is
2.0 nm, if the NiFe layer 12a is formed with a thickness of 3.5 nm
or more, the rotated angle of the pinned direction after 1000 hours
stress of heat and magnetic field becomes 10 degrees or less. As a
result, degradation of the electrical output characteristics of the
MR sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature can be kept
1.5% or less.
FOURTH EXAMPLE
[0040] A fourth example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 or 2.0 nm and a ferromagnetic
material layer 12a of Ni.sub.80Fe.sub.20 (Ni is 80 at % and Fe is
20 at %) with the thickness of 0-4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of FeMn with the thickness of 10.0 nm, in this
order.
[0041] Tables 7 and 8 show measured result of heat stability of the
pinned direction when the thickness of the NiFe layer 12a of the
pinned layer 12 is changed. In these Tables, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer.
Table 7 is in a case that the thickness of the Co layer 12b of the
pinned layer 12 is 1.0 nm, whereas Table 8 is in a case that the
thickness is 2.0 nm. The heat stability of the pinned direction was
detected by measuring the rotated angle of the pinned direction of
the multi-layered spin valve effect structure after the stress of
125.degree. C. temperature which will be the maximum temperature of
the MR sensor actually operating in the HDD under the application
of simulated magnetic field from the hard magnets of 190 Oe toward
perpendicular to the original pinned direction provided during the
annealing process.
7TABLE 7 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co(1
nm)/Ni.sub.80Fe.sub.20(x)/ FeMn(10 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 5 5 5 6 3.5
9 9 12 17 3.0 12 10 14 18 2.5 15 11 16 20 2.0 17 11 19 23 1.5 19 12
21 26 1.0 23 15 21 30 0.5 26 17 24 34 No NiFe 28 23 29 38 Layer
[0042]
8TABLE 8 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/Co(2
nm)/Ni.sub.80Fe.sub.20(x)/ FeMn(10 nm) Thickness of NiFe Layer of
Hk of Rotated angle of Pinned Direction Pinned Pinned (Degrees)
Layer (nm) Layer (Oe) 24 Hours 100 Hours 1000 Hours 4.0 10 11 15 18
3.5 12 12 16 19 3.0 16 12 17 20 2.5 18 13 19 22 2.0 21 14 21 26 1.5
23 15 22 28 1.0 27 17 23 32 0.5 29 19 25 36 No NiFe 30 25 31 40
Layer
[0043] As will be apparent from these Tables 7 and 8, the rotated
angle of the pinned direction decreased, namely the heat stability
of the pinned direction improved by forming the NiFe layer 12a in
the pinned layer 12. Also, as will be understood from Table 7, in
case the thickness of the Co layer 12b is 1.0 nm, if the NiFe layer
12a is formed with a thickness of 2.5 nm or more, the rotated angle
of the pinned direction after 1000 hours stress of heat and
magnetic field becomes 20 degrees or less. Furthermore, as will be
noted from Table 8, in case the thickness of the Co layer 12b is
2.0 nm, if the NiFe layer 12a is formed with a thickness of 3.0 nm
or more, the rotated angle of the pinned direction after 1000 hours
stress of heat and magnetic field becomes 20 degrees or less. As a
result, degradation of the electrical output characteristics of the
MR sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature can be kept
6.0% or less.
First Conventional Example
[0044] A first conventional example for comparison of the
multi-layered spin valve effect structure with a pinned layer in a
single layered structure was actually fabricated by depositing
multi-layers under application of magnetic field without heating
the substrate. Concretely, the multi-layered structure was formed
by sequentially depositing, on the substrate of AlTiC, an under
layer of Ta with the thickness of 5.0 nm, a ferromagnetic material
layer (free layer) composed of a Ni.sub.80Fe.sub.20 (Ni is 80 at %
and Fe is 20 at %) layer with the thickness of 9.0 nm and a Co
layer with the thickness of 1.0 nm, a non-magnetic metallic
material layer of Cu with the thickness of 3.0 nm, a ferromagnetic
material layer (pinned layer) having the single layered structure
of FeCo alloy with the thickness of 2.0 nm, and an
anti-ferromagnetic material layer of FeMn with the thickness of
12.0 nm, in this order.
[0045] Table 9 shows measured result of heat stability of the
pinned direction when the composition of Co in the FeCo alloy of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned of the multi-layered spin valve
effect structure stress of 125.degree. C. temperature which will be
the temperature of the MR sensor actually operating in the
application of simulated magnetic field from the hard magnets of
190 Oe toward perpendicular to the original pinned direction
provided during the annealing process.
9TABLE 9 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/FeCo(2 nm)/FeMn(12
nm) Composition of Co in Hk of Rotated angle of Pinned Direction
Pinned Pinned (Degrees) Layer (at %) Layer (Oe) 24 Hours 100 Hours
1000 Hours 0 20 15 25 30 10 19 15 24 29 20 17 14 22 26 30 15 14 19
23 40 12 12 16 19 50 15 14 19 23 60 17 14 22 26 70 19 15 24 29 80
23 18 24 33 90 26 20 27 37 100 30 23 29 40
[0046] As will be apparent from Table 9, if the pinned layer is
formed in the single layered structure, the rotated angle of the
spinned direction after 1000 hours stress of heat and magnetic
field will never become 20 degrees or less in most cases. As a
result, degradation of the electrical output characteristics of the
MR sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature seriously
increases.
Second Conventional Example
[0047] Similarly, a second conventional example for comparison of
the multi-layered spin valve effect structure with a pinned layer
in a single layered structure was actually fabricated by depositing
multi-layers under application of magnetic field without heating
the substrate. Concretely, the multi-layered structure was formed
by sequentially depositing, on the substrate of AlTiC, an under
layer of Ta with the thickness of 5.0 nm, a ferromagnetic material
layer (free layer) composed of a Ni.sub.80Fe.sub.20 (Ni is 80 at %
and Fe is 20 at %) layer with the thickness of 9.0 nm and a Co
layer with the thickness of 1.0 nm, a non-magnetic metallic
material layer of Cu with the thickness of 3.0 nm, a ferromagnetic
material layer (pinned layer) having the single layered structure
of FeCo alloy with the thickness of 2.0 nm, and an
anti-ferromagnetic material layer of RuRhMn with the thickness of
10.0 nm, in this order.
[0048] Table 10 shows measured result of heat stability of the
pinned direction when the composition of Co in the FeCo alloy of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
10TABLE 10 Ta(5 nm)/NiFe(9 nm)/Co(1 nm)/Cu(3 nm)/FeCo(2
nm)/RuRhMn(10 nm) Composition of Co in Hk of Rotated angle of
Pinned Direction Pinned Pinned (Degrees) Layer (at %) Layer (Oe) 24
Hours 100 Hours 1000 Hours 0 20 12 22 27 10 19 12 21 26 20 17 11 19
23 30 15 11 16 20 40 12 9 13 16 50 15 11 16 20 60 17 11 19 23 70 19
12 21 26 80 23 15 21 30 90 26 17 24 34 100 30 20 26 37
[0049] As will be apparent from Table 10, if the pinned layer is
formed in the single layered structure, the rotated angle of the
pinned direction after 1000 hours stress of heat and magnetic field
will never become 20 degrees or less in most cases. As a result,
degradation of the electrical output characteristics of the MR
sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature seriously
increases.
FIFTH EXAMPLE
[0050] A fifth example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 nm and a ferromagnetic material
layer 12a of FeSi with the thickness of 4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of FeMn with the thickness of 10.0 nm, in this
order.
[0051] Table 11 shows measured result of heat stability of the
pinned direction when the composition of Si in the FeSi layer of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
11TABLE 11 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/FeSi (4
nm)/FeMn (10 nm) Composition of Si in Hk of Rotated angle of Pinned
Direction FeSi Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 20 15 25 30 4 19 15 24 29 8 17 14 22 26 12
15 14 19 23 16 12 12 16 19 20 10 11 14 17 24 12 12 16 19 28 15 14
19 23 32 16 14 20 24 36 18 15 23 28 40 20 15 25 30
[0052] As will be apparent from Table 11, the rotated angle of the
pinned direction decreased, namely the heat stability of the pinned
direction improved by forming the FeSi layer 12a in the pinned
layer 12. Also, as will be understood from Table 11, if the
composition of Si in the FeSi layer 12a is 16-24 at %, the rotated
angle of the pinned direction after 1000 hours stress of heat and
magnetic field becomes 20 degrees or less. As a result, degradation
of the electrical output characteristics of the MR sensor due to
rotation of the pinned direction during operation under the stress
of about 125.degree. C. temperature can be kept at sufficiently low
degree.
SIXTH EXAMPLE
[0053] A sixth example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 nm and a ferromagnetic material
layer 12a of FeSi with the thickness of 4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of RuRhMn with the thickness of 10.0 nm, in this
order.
[0054] Table 12 shows measured result of heat stability of the
pinned direction when the composition of Si in the FeSi layer of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
12TABLE 12 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/FeSi (4 nm)/
RuRhMn (10 nm) Composition of Si in Hk of Rotated angle of Pinned
Direction FeSi Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 20 12 22 27 4 19 12 21 26 8 17 11 19 23 12
15 11 16 20 16 12 9 13 16 20 10 8 11 14 24 12 9 13 16 28 15 12 16
20 32 16 15 17 21 36 18 16 20 25 40 20 20 22 27
[0055] As will be apparent from Table 12, the rotated angle of the
pinned direction decreased, namely the heat stability of the pinned
direction improved by forming the FeSi layer 12a in the pinned
layer 12. Also, as will be understood from Table 11, if the
composition of Si in the FeSi layer 12a is 16-24 at %, the rotated
angle of the pinned direction after 1000 hours stress of heat and
magnetic field becomes 20 degrees or less. As a result, degradation
of the electrical output characteristics of the MR sensor due to
rotation of the pinned direction during operation under the stress
of about 125.degree. C. temperature can be kept at sufficiently low
degree.
SEVENTH EXAMPLE
[0056] A seventh example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 nm and a ferromagnetic material
layer 12a of FeNi with the thickness of 4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of FeMn with the thickness of 12.0 nm, in this
order.
[0057] Table 13 shows measured result of heat stability of the
pinned direction when the composition of Ni in the FeNi layer of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree.0 C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
13TABLE 13 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/FeNi (4
nm)/FeMn (12 nm) Composition of Ni in Hk of Rotated angle of Pinned
Direction FeNi Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 22 17 25 32 10 12 12 16 19 20 5 5 5 6 30 8 9
9 11 40 10 11 14 17 50 12 12 18 19 60 13 13 17 21 70 10 11 14 17 80
5 5 5 8 90 9 10 11 14 100 14 13 18 22
[0058] As will be apparent from Table 13, the rotated angle of the
pinned direction decreased, namely the heat stability of the pinned
direction improved by forming the FeNi layer 12a in the pinned
layer 12. Also, as will be understood from Table 13, if Ni is
contained in the layer 12a, the rotated angle of the pinned
direction after 1000 hours stress of heat and magnetic field
becomes 20 degrees or less. Particularly, if the composition of Ni
in the FeNi layer 12a is 20-80 at %, the rotated angle becomes very
small as 6 degrees. As a result, degradation of the electrical
output characteristics of the MR sensor due to rotation of the
pinned direction during operation under the stress of about
125.degree. C. temperature can be extremely low degree.
EIGHTH EXAMPLE
[0059] A eighth example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 nm and a ferromagnetic material
layer 12a of FeNi with the thickness of 4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of RuRhMn with the thickness of 10.0 nm, in this
order.
[0060] Table 14 shows measured result of heat stability of the
pinned direction when the composition of Ni in the FeNi layer of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
14TABLE 14 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/FeNi (4 nm)/
RuRhMn (10 nm) Composition of Ni in Hk of Rotated angle of Pinned
Direction FeNi Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 22 14 22 29 10 12 9 13 16 20 5 2 2 3 30 8 5
6 8 40 10 8 11 14 50 12 9 13 16 60 13 10 14 16 70 10 8 11 14 80 5 2
2 3 90 9 7 8 11 100 14 10 15 19
[0061] As will be apparent from Table 14, the rotated angle of the
pinned direction decreased, namely the heat stability of the pinned
direction improved by forming the FeNi layer 12a in the pinned
layer 12. Also, as will be understood from Table 14, if Ni is
contained in the layer 12a, the rotated angle of the pinned
direction after 1000 hours stress of heat and magnetic field
becomes 20 degrees or less. Particularly, if the composition of Ni
in the FeNi layer 12a is 20-80 at %, the rotated angle becomes very
small as 3 degrees. As a result, degradation of the electrical
output characteristics of the MR sensor due to rotation of the
pinned direction during operation under the stress of about
125.degree. C. temperature can be kept at extremely low degree.
Third Conventional Example
[0062] A third conventional example for comparison of the
multi-layered spin valve effect structure with a pinned layer in a
single layered structure was actually fabricated by depositing
multi-layers under application of magnetic field without heating
the substrate. Concretely, the multi-layered structure was formed
by sequentially depositing, on the substrate of AlTiC, an under
layer of Ta with the thickness of 5.0 nm, a ferromagnetic material
layer (free layer) composed of a NiFe layer with the thickness of
9.0 nm and a Co layer with the thickness of 1.0 nm, a non-magnetic
metallic material layer of Cu with the thickness of 3.0 nm, a
ferromagnetic material layer (pinned layer) having the single
layered structure of NiCo alloy with the thickness of 2.0 nm, and
an anti-ferromagnetic material layer of FeMn with the thickness of
12.0 nm, in this order.
[0063] Table 15 shows measured result of heat stability of the
pinned direction when the composition of Co in the NiCo alloy of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after stress of 125.degree. C. temperature
which will be the maximum temperature of the MR sensor actually
operating in the HDD under the application of simulated magnetic
field from the hard magnets of 190 Oe toward perpendicular to the
original pinned direction provided during the annealing
process.
15TABLE 15 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/ NiCo (2
nm)/FeMn (12 nm) Composition of Co in Hk of Rotated angle of Pinned
Direction Pinned Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 14 13 18 22 10 9 10 11 14 20 13 13 17 21 30
16 14 20 24 40 19 15 24 29 50 20 15 25 30 60 22 17 25 32 70 24 18
25 35 80 27 21 27 37 90 28 22 28 38 100 30 23 29 40
[0064] As will be apparent from Table 15, if the pinned layer is
formed in the single layered structure, the rotated angle of the
pinned direction after 1000 hours stress of heat and magnetic field
will never become 20 degrees or less in most cases. As a result,
degradation of the electrical output characteristics of the MR
sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature seriously
increases.
Fourth Conventional Example
[0065] A fourth conventional example for comparison of the
multi-layered spin valve effect structure with a pinned layer in a
single layered structure was actually fabricated by depositing
multi-layers under application of magnetic field without heating
the substrate. Concretely, the multi-layered structure was formed
by sequentially depositing, on the substrate of AlTiC, an under
layer of Ta with the thickness of 5.0 nm, a ferromagnetic material
layer (free layer) composed of a NiFe layer with the thickness of
9.0 nm and a Co layer with the thickness of 1.0 nm, a non-magnetic
metallic material layer of Cu with the thickness of 3.0 nm, a
ferromagnetic material layer (pinned layer) having the single
layered structure of NiCo alloy with the thickness of 2.0 nm, and
an anti-ferromagnetic material layer of RuRhMn with the thickness
of 10.0 nm, in this order.
[0066] Table 16 shows measured result of heat stability of the
pinned direction when the composition of Co in the NiCo alloy of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
16TABLE 16 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/NiCo (2 nm)/
RuRhMn (10 nm) Composition of Co in Hk of Rotated angle of Pinned
Direction Pinned Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 14 10 15 19 10 9 7 8 11 20 13 10 14 18 30 16
11 17 21 40 19 12 21 26 50 20 12 22 27 60 22 14 22 29 70 24 15 22
32 80 27 18 24 34 90 28 19 25 35 100 30 20 26 37
[0067] As will be apparent from Table 16, if the pinned layer is
formed in the single layered structure, the rotated angle of the
pinned direction after 1000 hours stress of heat and magnetic field
will never become 20 degrees or less in most cases. As a result,
degradation of the electrical output characteristics of the MR
sensor due to rotation of the pinned direction during operation
under the stress of about 125.degree. C. temperature seriously
increases.
NINTH EXAMPLE
[0068] A ninth example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 nm and a ferromagnetic material
layer 12a of NiCu with the thickness of 4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of FeMn with the thickness of 12.0 nm, in this
order.
[0069] Table 17 shows measured result of heat stability of the
pinned direction when the composition of Cu in the NiCu layer of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
17TABLE 17 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/NiCu (4
nm)/FeMn (12 nm) Composition of Cu in Hk of Rotated angle of Pinned
Direction NiCu Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 14 13 18 22 5 13 13 17 21 10 13 13 17 21 15
12 12 16 19 20 11 11 15 18 25 11 11 15 18 30 10 11 14 17 35 9 10 11
14 40 10 11 14 17 45 11 11 15 18 50 13 13 17 21
[0070] As will be apparent from Table 17, the rotated angle of the
pinned direction decreased, namely the heat stability of the pinned
direction improved by forming the NiCu layer 12a in the pinned
layer 12. Also, as will be understood from Table 13, if Cu is
contained in the layer 12a, the rotated angle of the, pinned
direction after 1000 hours stress of heat and magnetic field
becomes 20 degrees or less. Particularly, if the composition of Cu
in the NiCu layer 12a is 15-45 at %, the rotated angle becomes very
small. As a result, degradation of the electrical output
characteristics of the MR sensor due to rotation of the pinned
direction during operation under the stress of about 125.degree. C.
temperature can be kept at extremely low degree.
TENTH EXAMPLE
[0071] A tenth example of the multi-layered spin valve effect
structure as illustrated in FIG. 1 was actually fabricated by
depositing multi-layers under application of magnetic field without
heating the substrate. Concretely, the multi-layered structure was
formed by sequentially depositing, on the substrate of AlTiC, an
under layer of Ta with the thickness of 5.0 nm, a ferromagnetic
material layer (free layer) 10 composed of a NiFe layer with the
thickness of 9.0 nm and a Co layer with the thickness of 1.0 nm, a
non-magnetic metallic material layer 11 of Cu with the thickness of
3.0 nm, a ferromagnetic material layer (pinned layer) 12 having a
two layered structure composed of a ferromagnetic material layer
12b of Co with the thickness of 1.0 nm and a ferromagnetic material
layer 12a of NiCu with the thickness of 4.0 nm, which has a smaller
magnetic anisotropy than that of Co, and an anti-ferromagnetic
material layer 13 of RuRhMn with the thickness of 10.0 nm, in this
order.
[0072] Table 18 shows measured result of heat stability of the
pinned direction when the composition of Cu in the NiCu layer of
the pinned layer is changed. In this Table, Hk of the pinned layer
corresponds to magnetic anisotropy factor of the pinned layer. The
heat stability of the pinned direction was detected by measuring
the rotated angle of the pinned direction of the multi-layered spin
valve effect structure after the stress of 125.degree. C.
temperature which will be the maximum temperature of the MR sensor
actually operating in the HDD under the application of simulated
magnetic field from the hard magnets of 190 Oe toward perpendicular
to the original pinned direction provided during the annealing
process.
18TABLE 18 Ta (5 nm)/NiFe (9 nm)/Co (1 nm)/Cu (3 nm)/NiCu (4 nm)/
RuRhMn (10 nm) Composition of Cu in Hk of Rotated angle of Pinned
Direction NiCu Layer Pinned (Degrees) (at %) Layer (Oe) 24 Hours
100 Hours 1000 Hours 0 14 10 15 19 5 13 10 14 18 10 13 10 14 18 15
12 9 13 16 20 11 8 12 15 25 11 8 12 15 30 10 8 11 14 35 9 7 8 11 40
10 8 11 14 45 11 8 12 15 50 13 10 14 18
[0073] As will be apparent from Table 18, the rotated angle of the
pinned direction decreased, namely the heat stability of the pinned
direction improved by forming the NiCu layer 12a in the pinned
layer 12. Also, as will be understood from Table 13, if Cu is
contained in the layer 12a, the rotated angle of the pinned
direction after 1000 hours stress of heat and magnetic field
becomes 20 degrees or less. As a result, degradation of the
electrical output characteristics of the MR sensor due to rotation
of the pinned direction during operation under the stress of about
125.degree. C. temperature can be keep at extremely low degree.
[0074] Many widely different embodiments of the present invention
may be constructed without departing from the spirit and scope of
the present invention. It should be understood that the present
invention is not limited to the specific embodiments described in
the specification, except as defined in the appended claims.
* * * * *