Title: Magnetic head and magnetic reproducing apparatus
Abstract: In a magnetic head having magnetic yoke layers, each magnetic yoke layer includes a yoke projecting portion (2A) projected toward a recording medium, and yoke setback portions (2B) set back from the yoke projecting portion. A first bias magnetic field applying film (5) of an antiferromagnetic material is formed to cover the yoke projecting portion whereas a second bias magnetic field applying film (6) of a ferromagnetic material may be formed on opposite side surfaces of the yoke projecting portion.
Patent Number: 6,940,700 Issued on 09/06/2005 to Tateyama, et al.
| Inventors:
|
Tateyama; Kohichi (Kanagawa-ken, JP);
Hashimoto; Susumu (Kanagawa-ken, JP);
Takagishi; Masayuki (Kanagawa-ken, JP);
Funayama; Tomomi (Kanagawa-ken, JP);
Ohsawa; Yuichi (Kanagawa-ken, JP)
|
| Assignee:
|
Kabushiki Kaisha Toshiba (Tokyo, JP)
|
| Appl. No.:
|
176577 |
| Filed:
|
June 24, 2002 |
Foreign Application Priority Data
| Jun 22, 2001[JP] | 2001-190513 |
| Current U.S. Class: |
360/321 |
| Intern'l Class: |
G11B 005/33 |
| Field of Search: |
360/321,318,318.1
|
References Cited [Referenced By]
U.S. Patent Documents
| 6388846 | May., 2002 | Albertini et al.
| |
| 2004/0160705 | Aug., 2004 | Hara et al.
| |
| Foreign Patent Documents |
| 475397 | Mar., 1992 | EP.
| |
| 04121808 | Apr., 1992 | JP.
| |
| 7-235020 | Sep., 1995 | JP.
| |
| 2000285416 | Oct., 2000 | JP.
| |
Primary Examiner: Chen; Tianjie
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
1. A magnetic head for detecting a signal magnetic field from a recording medium, comprising:
a pair of magnetic yoke layers aligned via a magnetic gap, each said magnetic
yoke layer including a yoke projecting portion projected toward said recording
medium, and including yoke setback portions set back from said yoke projecting
portion;
a magnetoresistance effect film magnetically coupled to said magnetic yoke layers;
a pair of electrodes coupled to said magnetoresistance effect film to supply
a current thereto; and
first bias magnetic field applying films made of an antiferromagnetic material
provided at said yoke projecting portions,
wherein said first bias magnetic field applying films are stacked on a rear surface
of the yoke projecting portions opposite to the recording medium, and said first
bias magnetic field applying films are not provided at the yoke setback portions.
2. A magnetic head according to claim 1, further comprising a substrate whose
major surface is substantially in parallel with a surface of the recording medium,
said pair of magnetic yoke layers and said magnetoresistance effect film being
stacked on the major surface of the substrate.
3. A magnetic head according to claim 2, wherein said magnetic yoke projecting
portions are formed by skewing the magnetic yoke layers toward the recording medium.
4. A magnetic head according to claim 3, wherein one of said electrodes and said
first bias magnetic field applying films are stacked between said yoke projecting
portions and said magnetoresistance effect film.
5. A magnetic head according to claim 4, wherein said pair of electrodes supply
the current in a direction substantially perpendicular to the major surface.
6. A magnetic head according to claim 1, further comprising second bias magnetic
field applying films made of a ferromagnetic material and provided adjacent to
side faces of said yoke setback portions.
7. A magnetic head according to claim 1, further comprising a substrate whose
major surface is substantially perpendicular to a surface of the recording medium,
said pair of magnetic yoke layers and said magnetoresistance effect film being
stacked on the major surface of the substrate.
8. A magnetic head according to claim 7, further comprising second bias magnetic
field applying films made of a ferromagnetic material and provided adjacent to
side faces of said yoke setback portions.
9. A magnetic reproducing apparatus which reads information magnetically recorded
in a recording medium, comprising a magnetic head for detecting a signal magnetic
field from the recording medium,
said magnetic head having:
a pair of magnetic yoke layers aligned via a magnetic gap, each said magnetic
yoke layer including a yoke projecting portion projected toward said recording
medium, and including yoke setback portions set back from said yoke projecting
portion;
a magnetoresistance effect film magnetically coupled to said magnetic yoke layers;
a pair of electrodes coupled to said magnetoresistance effect film to supply
a current thereto; and
first bias magnetic field applying films made of an antiferromagnetic material
provided at said yoke projecting portions,
wherein said first bias magnetic field applying films are stacked on a rear surface
of the yoke projecting portions opposite to the recording medium, and said bias
magnetic field applying films are not provided at the yoke setback portions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior
Japanese Patent Application No. 2001-190513, filed on Jun. 22, 2001; the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a magnetic head and a magnetic reproducing apparatus,
and more particularly, to a magnetic head including a magnetic yoke having a projected
portion toward a recording medium, and a magnetic reproducing apparatus incorporating
the magnetic head.
Although HDDs (hard disk drives) have recently experienced epoch-making
improvement in magnetic recording density, further enhancement of their recording
density is still demanded. Along with the progressive downsizing of recording bits
to cope with the continuous demand for higher and higher recording densities, conventional
thin-film heads became insufficient in reproduction sensitivity, and surrendered
its position as the main current to magnetoresistance effect (MR) heads making
use of a magnetoresistance effect. Among these MR heads, spin valve giant magnetoresistance
(SVGMR) heads are being remarked as exhibiting an especially large magnetoresistance effect.
On the other hand, along with enhancement of the recording density, floating
amounts
of thin-film magnetic heads during traveling are decreasing for detecting smaller
medium bit magnetic fields. It is therefore predicted that magnetic heads will
be inevitably driven in intermittent or continuous contact with recording mediums.
Also from various viewpoints other than enhancement of the recording density, HDDs
will be brought into use in AV (audio-visual) devices (such as video and/or audio
recorders) as the multimedia era matures. When a HDD is borne in an AV device,
reliability of HDD, especially its durability against external impact, is an important
issue. If an external impact (such as mechanical shock or vibration) is applied,
then the magnetic head may unexpectedly hit the medium surface. Therefore, there
is a demand for development of magnetic heads resistant to physical contacts.
However, the above-indicated SVGMR heads are well known as exhibiting abnormal
changes of resistance due to the heat generated by contact with recording mediums
during reproduction (thermal asperity). Therefore, conventional MR heads and SVGMR
heads whose magnetic detector portions are exposed on medium-facing surfaces of
the magnetic heads may fail to follow the future enhancement of recording density.
In contrast, the use of a yoke-type magnetic head that includes a magnetic yoke
for leading the signal magnetic field from the recording medium to an MR element
is considered effective. Since the yoke-type magnetic head is so configured that
the magnetic detector portion of the MR device is not exposed on the medium-facing
surface, it is resistant to thermal asperity.
Taking those situations into consideration, it will be effective toward future
enhancement of magnetic recording density to combine a yoke-type magnetic head
and an MR element.
However, to ensure a signal magnetic flux from a minute recording bit to
be read out with a high resolution, a projecting portion must be made at the tip
of the magnetic yoke, that is, on the medium-facing surface. In other words, it
is necessary to provide a minute projecting portion on the medium-facing surface
of the magnetic yoke so as to draw up there the signal magnetic flux from the recording
bit with a high resolution.
However, as a result of the Inventors' own researches, the yoke-type magnetic
head having such a projecting portion was found to involve the magnetic domain
generated at the projecting portion of the magnetic yoke as another large factor
of noise in addition to the MR element.
FIGS. 18A and 18B are schematic diagrams that show the structure of a yoke-type
magnetic head prepared and evaluated by the Inventors in the way toward the present
invention. FIG. 18A is its perspective view, and FIG. 18B is its longitudinal cross-sectional view.
The magnetic head shown here includes a pair of magnetic yoke layers 2,
2 formed on a substrate 12 to face to a recording medium, not shown,
in alignment with each other via a magnetic gap 1. A magnetoresistance effect
film 4 underlies the magnetic yoke layers 2, 2, and a lower
electrode 7 and an upper electrode 8 are connected to supply a sense
current perpendicularly to the film plane.
In this yoke-type magnetic head, the pair of magnetic yoke layers are magnetically
coupled to the magnetoresistance effect film 4 to form a magnetic circuit,
and detect a signal magnetic flux led from the recording medium to the magnetoresistance
effect film.
For the purpose of detecting a signal from a minute recording bit of a recording
medium, not shown, while distinguishing it from those of adjacent recording bits,
each magnetic yoke layer 2 has a projecting portion 2A of a predetermined
size. More specifically, as shown in FIGS. 18A and 18B, the magnetic yoke layer
2 has the yoke projecting portion 2A projecting toward the recording
medium and a yoke setback portion 2B formed to set back from the yoke projecting
portion 2A. Thus the spatial resolution of magnetic detection of the yoke-type
magnetic head can be determined by adjusting the width and projecting amount of
the projecting portion 2A.
In case of a CPP (current perpendicular to the plane) magnetoresistance effect
element as shown in FIGS. 18A and 18B, the projecting portion 2A may be
formed in agreement with an electrode formed on the magnetoresistance effect film 4.
In this type of yoke-type magnetic head, when a magnetic domain is generated
in
the magnetic yoke layers 2 and irregularly moves in response to a signal
magnetic field, it produces noise. Therefore, a bias magnetic field is preferably
applied to control the magnetic domain generated in the yokes 2. In case
of the magnet head shown in FIGS. 18A and 18B, bias magnetic field applying films
6, 6 of a hard magnetic material are formed on opposite side surfaces
of the magnetic yoke layers 2 to control the magnetic domain of the magnetic
yoke layers 2.
The Inventors however, have found through their researches that a bias magnetic
field from the bias magnetic field applying films 6 on opposite side surfaces
of the yoke setback portions 2B may occasionally fail to reach the yoke
projections 2A of the magnetic yoke layers 2 sufficiently. If the
bias magnetic field is not applied sufficiently, then the magnetic domain irregularly
moves in response to the signal magnetic field especially near the medium-facing
surface, and noise is liable to occur.
BRIEF SUMMARY OF THE INVENTION
According to an embodiment of the invention, there is provided a magnetic
head for detecting a signal magnetic field from a recording medium, comprising:
a pair of magnetic yoke layers aligned via a magnetic gap, each said magnetic yoke
layer including a yoke projecting portion projected toward said recording medium,
and including yoke setback portions set back from said yoke projecting portion;
a magnetoresistance effect film magnetically coupled to said magnetic yoke layers;
a pair of electrodes coupled to said magnetoresistance effect film to supply a
current thereto; and first bias magnetic field applying films made of an antiferromagnetic
material provided at said yoke projecting portions.
According to another embodiment of the invention, there is provided a magnetic
head for detecting a signal magnetic field from a recording medium, comprising:
a pair of magnetic yoke layers aligned via a magnetic gap, each said magnetic yoke
layer including a yoke projecting portion projected toward said recording medium,
and including yoke setback portions set back from said yoke projecting portion;
a magnetoresistance effect film magnetically coupled to said magnetic yoke layers;
a pair of electrodes coupled to said magnetoresistance effect film to supply a
current thereto; and second bias magnetic field applying films made of an ferromagnetic
material and covering at least a part of opposite side surfaces of said yoke projecting portions.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the detailed description
given herebelow and from the accompanying drawings of the embodiments of the invention.
However, the drawings are not intended to imply limitation of the invention to
a specific embodiment, but are for explanation and understanding only.
In the drawings:
FIG. 1 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to an embodiment of the invention;
FIG. 2 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the second specific example of
the invention;
FIG. 3 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the third specific example of invention;
FIG. 4 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the fourth specific example of
the invention;
FIG. 5 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the fifth specific example of
the invention;
FIG. 6 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the sixth specific example of
the invention;
FIG. 7 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the seventh specific example of
the invention;
FIG. 8 is a schematic diagram that shows a perspective view of the substantial
part of a magnetic head according to the eighth specific example of the invention;
FIGS. 9A through 9D are cross-sectional views of the substantial part of the
magnetic head according to the fourth specific example under a manufacturing process;
FIGS. 10A through 10C are cross-sectional views of the substantial part of
the magnetic head according to the fourth specific example under the manufacturing process;
FIGS. 11A through 11D are cross-sectional views of the substantial part of
the magnetic head according to the fourth specific example under the manufacturing process;
FIGS. 12A through 12C are cross-sectional views of the substantial part of
the magnetic head according to the fourth specific example under the manufacturing process;
FIGS. 13A through 13D are cross-sectional views of the substantial part of
the magnetic head according to the fourth specific example under the manufacturing process;
FIGS. 14A through 14C are cross-sectional views of the substantial part of
the magnetic head according to the seventh specific example under the manufacturing process;
FIG. 15 is a schematic diagram that shows a magnetic head according to a further
specific example of the invention;
FIG. 16 is a perspective view of the substantial part of a magnetic reproducing
apparatus according to an embodiment of the invention, which roughly illustrates
its configuration;
FIG. 17 is an enlarged perspective view of a magnetic head assembly at the distal
end of an actuator arm 155, viewed from the disk side; and
FIGS. 18A and 18B are schematic diagrams that show the structure of a yoke-type
magnetic head prepared and evaluated by the Inventors in the way toward the present
invention, in which FIG. 18A is a perspective view and FIG. 18B is its longitudinal
cross-sectional view.
DETAILED DESCRIPTION OF THE INVENTION
Some embodiments of the invention will now be explained below with reference
to the drawings.
FIG. 1 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to an embodiment of the invention.
This is a cross-sectional view taken along a plane vertical to a medium-facing
surface S facing to a recording medium, not shown, corresponding to FIG.
18B.
Similarly to the magnetic head shown in FIGS. 18A and 18B, the magnetic
head shown in FIG. 1 has a pair of magnetic yoke layers
2,
2 formed
to lie on the medium-facing surface S and aligned to each other via a magnetic
gap in the direction vertical to the plane of the drawing sheet. FIG. 1 is a cross-sectional
view taken by cutting one of the yokes along its lengthwise direction.
On a substrate
12, a magnetoresistance effect film
4 underlies
each
magnetic yoke layer
2, and a lower electrode
7 and an upper electrode
8 are connected thereto to supply a sense current substantially vertically
to the plane of the film
4. That is, the magnetoresistance effect element
shown here has a CPP (current perpendicular to the plane) structure.
Explanation is continued about the magnetoresistance effect element.
CIP (current in-plane) GMR elements that need regulation of the reproducing track
width between electrodes to cope with the recent rapid progress of microminiaturization
will soon make microprocessing (for a track width not exceeding 0.2 μm) thereof
very difficult with the current manufacturing process. In this respect, CPP GMR
elements configured to supply a sense current perpendicularly to the film plane
of the MR film are more advantageous.
Japanese Patent Laid-Open Publication No. H10-55512 is one of publications
disclosing a CPP MR element, the entire contents of this reference being incorporated
herein by reference. A representative CPP MR element is a tunneling magnetoresistance
effect (TMR) element that has recently attained a giant magnetoresistance effect
by making use of the tunneling effect of electrons.
Turning back to the embodiment shown in FIG. 1, each magnetic yoke layer
2 includes a yoke projecting portion
2A projected toward a recording
medium, and yoke setback portion
2B formed to set back from the yoke projecting
portion
2A. In this specific example, the yoke projecting portion
2A
is formed by skewing the magnetic yoke layer
2 toward the recording medium.
The yoke projecting portion
2A can regulate the detecting resolution of
a signal magnetic field from a recording bit. In this specific example, the upper
electrode
8 of the magnetoresistance effect film
4 is formed in agreement
with the projecting portion
2A.
The gap between the upper electrode
8 and the magnetoresistance effect
film
4 is buried with an insulating layer
9. A bias magnetic field
applying film
5 made of an antiferromagnetic material is formed to extend
to cover the upper electrode
8 and upper surfaces of opposite end portions
of the magnetoresistance effect film
4. An insulating film, not shown, may
be inserted between the magnetoresistance effect film
4 and the bias applying
film
5 to prevent the shunt of the sense current.
An exchanging bias magnetic field applied from the bias applying film
5
to the magnetic yoke layer
2 aligns magnetization in the magnetic yoke layer
2 and prevents generation of magnetic domains therein. Once any magnetic
domain is produced in the magnetic yoke layer
2, it will become a noise-generating
factor upon movements of the magnetic wall relative to the signal magnetic field
during reproduction.
In shield type magnetoresistance effect (MR or GMR) heads not having magnetic
yoke layers, noise could be prevented by controlling magnetic domains only in the
portion of the magnetoresistance effect element. In yoke-type magnetic heads, however,
since a signal magnetic field is guided to the element portion through the magnetic
yoke layers, control of magnetic domains in the magnetic yoke layers themselves
is a very important issue.
In the yoke-type magnetic head according to the embodiment of the invention, a
bias applying film
5 of an antiferromagnetic material is formed on the entire
back surface of the magnetic yoke layer
2. As a result, the bias magnetic
field can be sufficiently applied to both the yoke projecting portion
2A
and the yoke setback portion
2B. That is, since the embodiment of the invention
can apply a sufficient bias magnetic field to the entirety of the magnetic yoke
layer having the three-dimensional shape including the projecting portion
2A,
it can produce low-noise, stable reproduced signals.
FIG. 2 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the second specific example of
the invention. This is also a cross-sectional view taken by cutting one of the
magnetic yoke layers
2 along its lengthwise direction. Some of components
shown here, which are common to those of FIG. 1, are labeled with common reference
numerals, and their detailed explanation is omitted here.
This specific example also includes the bias magnetic field applying film
5
made of an antiferromagnetic material on the back surface of the magnetic yoke
layer
2. Additionally, a bias magnetic field applying film
6 of a
ferromagnetic material having a high coercive force is formed to lie on opposite
side surfaces of the magnetic yoke layer
2 to generate a bias magnetic field
for controlling magnetic domains in the magnetic yoke.
The bias magnetic field applying film
5 of an antiferromagnetic material,
when getting into exchanging coupling with the magnetic yoke layer
2, can
apply a static bias magnetic field even to portions where it is difficult to exert
a magnetostatic field bias because of their three-dimensional geometries. In this
specific example, by additionally providing the bias magnetic field applying film
6 of a ferromagnetic material having a high coercive force on opposite side
surfaces of the magnetic yoke layer
2, it is possible to obtain a bias magnetic
field for further stabilization and to cancel influences of a demagnetizing field
by magnetic charges generated there, thereby to accomplish a more stable state.
FIG. 3 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the third specific example of
invention. Here again, some of components shown here, which are common to those
of FIGS. 1 and 2, are labeled with common reference numerals, and their detailed
explanation is omitted here.
In this specific example, the bias magnetic field applying film
5 of an
antiferromagnetic material is locally formed only on the back surface of the magnetic
yoke projecting portion
2A projecting toward a recording medium.
In the magnetic yoke layer
2, magnetic domains are most likely to generate
in the flat portions
2A
1 and the sloping surfaces
2A
2
of the magnetic yoke projecting portions, which are nearest to the recording medium.
In this specific example, since the bias magnetic field applying film
5
of an antiferromagnetic material is formed on the back surface of those portions
and gets into exchanging coupling with the yoke projecting portion
2A, magnetic
domains can be stabilized. At the same time, since the bias magnetic field applying
film
5 does not exist on back surfaces of the yoke setback portions
2B
of the magnetic circuit, which form a path of a signal magnetic flux, magnetic
domains can be stabilized without degrading the magnetic efficiency.
FIG. 4 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the fourth specific example of
the invention. Here again, some of components shown here, which are common to those
of FIGS. 1 to
3, are labeled with common reference numerals, and their detailed
explanation is omitted here.
Also in this specific example, the bias magnetic field applying film
5
of an antiferromagnetic material is locally formed exclusively on the back surface
of the magnetic yoke projecting portion
2A projecting toward a recording
medium. Additionally, a bias magnetic applying film
6 of a ferromagnetic
material having a high coercive force is formed to lie on opposite side surfaces
of the magnetic yoke layer
2 to generate a bias magnetic field for controlling
magnetic domains in the magnetic yoke layer.
The instant specific example can reliably apply the exchanging coupling bias
magnetic field to the magnetic yoke projecting portions
2A difficult to
apply the bias magnetic field from the bias magnetic field applying films
6
of a ferromagnetic material having a high coercive force, by using the bias magnetic
field applying film
5 of an antiferromagnetic material in association with
those difficult portions, and can simultaneously prevent generation of magnetic
charges in the magnetic yoke setback portions
2B by using the bias magnetic
field applying films
6. Moreover, since the bias magnetic field applying
film
5 of an antiferromagnetic material does not exist on the magnetic circuit,
the specific example can meet the requirement of stabilization without degrading
the magnetic efficiency. Therefore, this specific example of the invention realizes
a head satisfying both the requirement of stable reproduction signals and the requirement
of a high efficiency or a high output.
FIG. 5 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the fifth specific example of
the invention. Here again, some of components shown here, which are common to those
of FIGS. 1 to
4, are labeled with common reference numerals, and their detailed
explanation is omitted here.
In this specific example, the bias magnetic field applying film
6 of a
ferromagnetic material having a high coercive force is formed to cover the opposite
side surfaces of the magnetic yoke layer and the top surfaces of the yoke setback
portions
2B and to additionally cover lower parts of the sloping surfaces
of the yoke projecting portions
2A.
This specific example can sufficiently exert the hard biasing effect also to
the yoke projecting portions
2A by extending the bias applying film
6
of a ferromagnetic material closely to the foots of the yoke projecting portion
2A. As a result, the control of magnetic domains by the bias magnetic field
is exercised also on the medium-facing surface of the yoke projecting portion
2A.
FIG. 6 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the sixth specific example of
the invention. Here again, some of components shown here, which are common to those
of FIGS. 1 to
5, are labeled with common reference numerals, and their detailed
explanation is omitted here.
In this specific example, the bias magnetic field applying film
6 of a
ferromagnetic material having a high coercive force covers opposite side surfaces
of the magnetic yoke layer and upper surfaces of the yoke setback portions
2B,
and additionally lies on lower portions of sloping surfaces of the yoke projecting
portion
2A.
In this case, the bias magnetic field applying film
6 exerts its hard
biasing
effect to the yoke projecting portion
2A as well, and enables the control
of magnetic domains by the bias magnetic field even on the medium-facing surface
of the yoke projecting portion
2A.
It can be determined appropriately whether the bias magnetic field applying film
6 should be formed exclusively on the top surfaces of the yoke setback portions
2B as shown in FIG. 5 or should be formed to extend until partly covering
the sloping surfaces of the yoke projecting portions
2A, taking account
of parameters such as the projecting amount and width of the yoke projecting portion
2A, thickness and material of the yoke
2, and intensity of the signal
magnetic field from the recording medium.
FIG. 7 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the seventh specific example of
the invention. Here again, some of components shown here, which are common to those
of FIGS. 1 to
6, are labeled with common reference numerals, and their detailed
explanation is omitted here.
In this specific example, the bias magnetic field applying film
6 of a
ferromagnetic material having a high coercive force is extended to cover sloping
surfaces of the yoke projecting portions
2A up to substantially the same
level as the top surface of the yoke projecting portion
2A.
The bias magnetic field applying film
6 shown here enables more sufficient
exertion of the hard biasing effect thereof to the yoke projecting portion
2A,
and hence enables more effective control of magnetic domains by the bias magnetic
field even on the medium-facing surface of the yoke projecting portion
2A.
It can be adequately determined which of the levels shown in FIGS. 5 through 7
the bias magnetic field applying film
6 should be extended to, taking account
of parameters such as the projecting amount and width of the yoke projecting portion
2A, thickness and material of the yoke
2, and intensity of the signal
magnetic field from the recording medium. In case the signal magnetic field from
the recording medium is not sufficiently intensive, the bias magnetic field applying
film
6 is preferably formed to slightly set back from the top surface of
the yoke projecting portion
2A for the purpose of preventing turbulence
of the signal magnetic field by the magnetic field from the bias magnetic field
applying film
6.
FIG. 8 is a schematic diagram that shows a cross-sectional structure of the
substantial part of a magnetic head according to the eighth specific example of
the invention. Here again, some of components shown here, which are common to those
of FIGS. 1 to
7, are labeled with common reference numerals, and their detailed
explanation is omitted here.
In this specific example, the bias magnetic field applying film
6 of a
ferromagnetic material having a high coercive force is formed to cover sloping
surfaces of the yoke projecting portion
2A up to substantially the same
level as the top surface of the yoke projecting portion
2A. Additionally,
the bias magnetic field applying film
5 of an antiferromagnetic material
is formed on the back surface of the yoke projecting portion
2A.
By combining the bias magnetic field applying film
6 of a ferromagnetic
material and the bias magnetic field applying film
5 of an antiferromagnetic
material, a sufficient bias magnetic field can be easily applied to the entirety
of the projecting portion and the setback portions
2B of the magnetic yoke
layer
2.
If the bias magnetic field applying film is formed of a ferromagnetic material
having a high coercive force, a bias magnetic field for more reliable stability
can be obtained, and simultaneously, influences of a demagnetizing field by magnetic
charges generated in that portion can be cancelled. Thus a more stable state can
be attained.
Next explained is a magnetic head manufacturing method according to an embodiment
of the invention, taking the magnetic head having the structure according to the
fourth specific example.
FIGS. 9A through 14C are cross-sectional views of the substantial part of the
magnetic head according to the fourth specific example under a manufacturing process.
First as shown in FIG. 9A, the lower electrode
7 is formed on the substrate
12. More specifically, while introducing Ar (argon) gas up to the pressure
of 1 mTorr, electrically conductive Cu (copper) is deposited on the substrate
12
already having an insulating film of SiO
2 or Al
2O
3,
for example, by DC magnetron sputtering until a 200 nm thick film is obtained.
As a cohesion layer for the purpose of preventing exfoliation of the electrode
from the substrate, a Ta (tantalum) film of a thickness around 5 nm may be formed
beforehand. As the material of the electrode, any of electrically conductive metals
such as Au (gold), Mo (molybdenum), W (tungsten), Ag (silver) and their alloys
(like Au—Cu alloy, Ag—Cu alloy, Au—Ag—Cu alloy, Mo—W
alloy, etc) may be used alternatively.
As the material of the cohesion layer, any of metals such as Ti (titanium), Cr
(chromium) and their alloys may be used in lieu of Ta.
In the next step, a resist is coated by a thickness around 400 nm, and its pattern
defining the width of 500 nm for the electrode is exposed and developed with I
rays. Then, etching is carried out in an ion milling apparatus introducing Ar gas
up to the pressure of 0.2 mTorr. Then the resist is removed, thereby to obtain
the Cu electrode 500 nm wide and 200 nm high.
After that, as shown in FIG. 9B, the insulating layer
9 of a thickness
around 300 nm is formed. In this specific example, SiO
2 can be used
as the insulator, and reactive RF sputtering using Si (silicon) as the target and
introducing oxygen can be used as the film-forming process. As to the material
of the insulator, any material having an insulating property may be used.
After that, as shown in FIG. 9C, a contact hole for access to the electrode
7 is formed. For example, after a resist for EB (electron beam) is coated
up to a thickness around 200 nm, it is patterned by EB exposure to define a 200
nm contact hole in diameter. There is no limitation for the size and shape of this
contact hole, and they may be determined appropriately in accordance with the specification
of the head to be made.
As next shown in FIG. 9D, etching is carried out by RIE (reactive ion etching)
to make the contact hole. For the etching, CHF
3 may be used as the gas
seed, and the degree of vacuum during etching may be 1 Pa, for example. The etching
speed of SiO
2 used here is approximately 60 nm/minute. However, as the
process for the etching carried out in this step, ICP or RIBE, for example, may
be used in lieu of RIE, provided the selectivity of the etching speed between the
patterned resist and insulator is sufficiently large.
As next shown in FIG. 10A, the electrode
7 is buried in the contact hole
made in FIG. 9D, and the patterned resist and an overlying electrode film are removed
by lift-off technique used in a typical semiconductor process. More specifically,
this structure can be made by using 400 nm thick Cu as the electrode to buried
in the contact hole and using DC sputtering while introducing Ar until making a
degree of vacuum around 1 mTorr during deposition and applying a bias.
As next shown in FIG. 10B, after the insulating layer
9, 300 nm thick,
is formed, a low-viscosity resist (for example, a product from Tokyo Ohka Corporation
under the trade name "OFR") is coated, and a thickness around 100 nm of the insulating
film
9 is etched off by etch-back technique used in a typical semiconductor
process. Thereafter, the structure is smoothed by CMP (chemical mechanical polishing),
there by obtain a flat surface as shown in FIG.
10C.
The electrode obtained in this process is 100 nm high and 100 nm in diameter.
A sample of this structure was actually prepared and its surface quality was measured
by AFM (atomic force micrography). As a result, its surface roughness was within
10 nm, and the electrode was confirmed to be very excellent in flatness and smoothness.
As next shown in FIG. 11A, a CPP GMR film
4 is formed on the substrate
already obtained as shown in FIG.
10C. Then a resist pattern
10 having
a T-shaped section is formed. In this case, a T-shaped pattern is simultaneously
formed for later use also at he position of an alignment marker M.
As next shown in FIG. 11B, the CPP GMR film
4 is etched by ion milling
to define the shape of the reproducing element. This shape may be approximately
500 nm×500 nm square, for example.
As next shown in FIG. 11C, the insulating film
9, approximately 150 nm
thick, is formed on the entire surface.
Then as shown in FIG. 11D, using the alignment marker M as the reference, patterning
of a contact hole for connection of the upper electrode is carried out by EB lithography,
and etching such as RIE for example is carried out, thereby to make out the electrode
hole for contact with the CPP GMR film
4.
As next shown in FIG. 12A, after the Cu upper electrode, approximately 200 nm
thick, is formed, a mask
10 having a pattern width around 200 nm is formed.
Then the upper electrode
8 is etched by ion milling using the mask
10.
When the mask
10 is removed thereafter, the cross-sectional configuration
as shown in FIG. 12B is obtained.
A sample of the CPP GMR film
4 and the upper and lower electrodes
8,
7 was actually prepared by the same process, and confirmed to have upper
and lower alignment accuracy not larger than 20 nm, that is, to have remarkably
excellent accuracy, by cross-sectional TEM (transmission electron microscopy).
After that, as shown in FIG. 12C, the bias magnetic field applying film
5
of an antiferromagnetic material, which is the core of the embodiment of the invention,
is formed on the entire surface. The antiferromagnetic material of the bias magnetic
filed applying film
5 may be, for example, approximately 10 nm thick NiO.
As the antiferromagnetic material, oxides like NiO and CrO, and alloys of Mn and
precious metals, such as IrMn, PtMn, PdMn, (Pt, Pd)Mn, FeMn, etc., are usable.
Thickness and shape of the film can be adequately determined as well.
Subsequently, a resist pattern is formed on a region above the upper
electrode
8, and the bias magnetic field applying film
5 is partly
removed by etching, thereby to obtain the cross-sectional configuration shown in
FIG.
13A.
As next shown in FIG. 13B, Ni
80Fe
20 (in atomic %) is deposited
on the entire substrate surface up to a thickness around 200 nm as the magnetic
yoke film, and a resist mask
10 patterned into an approximately 500 nm×500
nm square (substantially the same size as the CPP GMR film
4) is formed.
As next shown in FIG. 13C, the substrate having formed the mask
10 undergoes
etching by ion milling, for example, to define the yoke film pattern.
Then as shown in FIG. 13D, after approximately 50 nm thick CoPt is deposited
as the bias magnetic field applying film
6, the resist mask
10 is
removed by lift-off technique. Material and thickness of the bias magnetic field
applying film
6 formed here can be adequately determined in accordance with
the specification of the magnetic head to be made.
After that, although not shown, there follow some steps of forming the protective
film, processing the gap, polishing the medium-facing surface, and so on. In a
magnetic head actually prepared through those steps, magnetic domains along the
medium-facing surface of the magnetic head were evaluated while applying an external
magnetic field (corresponding to the magnetic field of a medium). As a result,
turbulence of magnetic domains in the yoke projecting portions
2A was very
small along the medium-facing surface, and the embodiment of the invention was
confirmed to be effective for stabilizing magnetic domains in the magnetic yoke
layers
2.
Next explained is a manufacturing process of the substantial part of the magnetic
head according to the seventh specific example explained above.
FIGS. 14A through 14C are cross-sectional views of the substantial part of
the magnetic head according to the seventh specific example under the manufacturing process.
The aspect shown in FIG. 14A corresponds to the aspect just after removal of
the resist mask
10 from the semi product shown in FIG. 13C except that the
bias magnetic field applying film
5 is not formed.
From this aspect, as next shown in FIG. 14B, the bias magnetic field applying
film
6 of a ferromagnetic material is formed, patterned, and processed for
making the gap.
After that, Al
2O
3 is once deposited as the protective
film
11 on the entire substrate surface, pattered, and next polished by
CMP for adjusting the medium-facing surface. As a result, as shown in FIG. 14C,
the magnetic head whose yoke projecting portions
2A and the top surface
of the bias magnetic field applying film
6 are exposed on the top surface
of the protective film can be obtained.
A sample magnetic head was actually prepared by the same process, and a magnetic
field was applied to observe magnetic domains along the medium-facing surface.
As a result, turbulence of magnetic domains on the distal end of the magnetic pole
was very small, and the magnetic head was confirmed to significantly reduce magnetic
wall noise caused by turbulence of magnetic domains.
Heretofore, some embodiments of the invention have been explained with
reference to FIGS. 1 through 14C. The invention, however, is not limited to the
embodiments or specific examples.
FIG. 15 is a schematic diagram that shows a magnetic head according to a further
specific example of the invention. In the magnetic head shown here, a pair of magnetic
yoke layers
2 are aligned side-by-side on a substrate, not shown, located
deeper of the plane of the drawing sheet. On these magnetic yoke layers
2,
2, a magnetoresistance effect film
4 is formed to bridge them. The
magnetoresistance effect film
4 may be either of the CIP type or of the
CPP type.
Each magnetic yoke layer
2 includes a projecting portion
2A forming
the distal end thereof and projected toward a recording medium
200, and
yoke setback portions
2B formed in opposite sides of the projecting portion
2A to set back therefrom.
The bias magnetic field applying film
6 of a ferromagnetic material is
formed to lie next to opposite side surfaces of the yoke setback portions
2B.
The bias magnetic field applying film of an antiferromagnetic material is formed
to overlie the surfaces of the yoke projecting portions
2A.
In this configuration, the yoke projecting portions
2A projected toward
the recording medium
200 are controlled in magnetic domain by an exchanging
coupling magnetic field by the bias magnetic applying film
5, whereas the
yoke setback portions
2B are controlled by a hard bias from the bias magnetic
field applying film
6 on their opposite side surfaces.
That is, this configuration can apply a stable bias magnetic field to the entirety
of the magnetic yoke layers
2 having the projecting portions, and can effectively
prevent noise caused by generation of magnetic domains in the magnetic yoke layers.
Furthermore, by making the bias magnetic field applying film
6
with a ferromagnetic material having a high coercive force, a bias magnetic field
for more reliable stability can be obtained, and simultaneously, influences of
a demagnetizing field by magnetic charges generated in that portion
2B can
be cancelled. Thus a more stable state can be attained.
Heretofore, some forms of magnetic head according to embodiments of the
invention have been explained. As described above, embodiments of the invention
make it easy to sufficiently control magnetic domains even in the projecting portions
at the distal ends of the magnetic yoke layers in magnetic heads using the magnetic
yoke layers, and can significantly reduce magnetic wall noise caused by movements
of magnetic walls in the magnetic yoke layers. As a result, embodiments of the
invention can provide magnetic heads excellent in process controllability and having
high efficiency, high outputs and stable outputs.
This results in a great industrial advantage for realizing magnetic heads having
high resolution, high outputs and high S/N ratios, as well as magnetic reproducing
apparatuses incorporating them.
Next explained is a magnetic reproduing apparatus having inboard any of the
magnetic heads explained with reference to FIGS. 1 through 15.
FIG. 16 is a perspective view that shows outline configuration of this kind
of magnetic reproducing apparatus. The magnetic reproducing apparatus
150
shown here is of a type using a rotary actuator. A magnetic recording medium disk
200 is mounted on a spindle
152 and rotated in the arrow A direction
by a motor, not shown, which is responsive to a control signal from a controller
of a driving mechanism, not shown. The magnetic reproducing apparatus
150
shown here may have a plurality of medium disks
200 inboard.
The medium disk
200 may be of a "lateral recording type" in which directions
of the recording bits are substantially in parallel to the disk surface or may
be of a "perpendicular recording type" in which directions of the recording bits
are substantially perpendicular to the disk surface.
A head slider
153 for carrying out recording and reproduction of information
to be stored in the medium disk
200 is attached to the tip of a film-shaped
suspension
154. The head slider
153 supports a magnetic head, for
example, according to one of the foregoing embodiments of the invention, near the
distal end thereof.
Once the medium disk
200 rotates, the medium-facing surface (ABS) of
the head slider
153 is held floating by a predetermined distance above the
surface of the medium disk
200. Also acceptable is a so-called "contact-traveling
type" in which the slider contacts the medium disk
200.
The suspension
154 is connected to one end of an actuator arm
155
having a bobbin portion for holding a drive coil, not shown, and others. At the
opposite end of the actuator arm
155, a voice coil motor
156, a kind
of linear motor, is provided. The voice coil motor
156 comprises a drive
coil, not shown, wound on the bobbin portion of the actuator arm
155, and
a magnetic circuit made up of a permanent magnet and an opposed yoke that are opposed
to sandwich the drive coil.
The actuator arm
155 is supported by ball bearings, not shown, which are
located at upper and lower two positions of the spindle
157 and driven by
the voice coil motor
156 for rotating, sliding movements.
FIG. 17 is a perspective view of a magnetic head assembly at the distal end
from an actuator arm
155 involved, which is viewed from the disk. The magnetic
head assembly
160 includes the actuator arm
155 having the bobbin
portion supporting the drive coil, for example, and the suspension
154 is
connected to one end of the actuator arm
155.
At the distal end of the suspension
154, a head slider
153 carrying
the magnetic head as explained with reference to FIGS. 1 through 15 is attached.
The suspension
154 has a lead
164 for writing and reading signals,
and the lead line
164 is connected to electrodes of the magnetic head incorporated
in the head slider
153. Numeral
165 in FIG. 15 denotes an electrode
pad of the magnetic head assembly
160.
In this embodiment, one of the magnetic heads already explained in conjunction
with the aforementioned embodiments is used as the reading head, information magnetically
recorded on the medium disk
200 under a higher recording density than before
can be read reliably.
Heretofore, some embodiments of the invention have been explained with
reference to specific examples. However, the invention is not limited to these
specific examples.
For example, as to a specific structure of the magnetoresistance effect film
4, and the specific size, shape, material, or positional relationship of
the magnetic yoke layer
2, electrodes
7 and
8, bias magnetic
field applying films
5 and
6, insulating layer
9 can be selected
from the known art. The invention encompasses any such changes by persons skilled
in the art provided they attain the effects of respective embodiments of the invention.
When the magnetic head according to the present invention is combined with a
recording head, a recording-reproducing integrated magnetic head may be realized.
Further, the magnetic reproducing apparatus according to the present invention
may be of a fixed type in which specific magnetic recording medium is permanently
installed, while it may be of a removable type in which the magnetic recording
medium can be replaced easily.
While the present invention has been disclosed in terms of the embodiment in
order to facilitate better understanding thereof, it should be appreciated that
the invention can be embodied in various ways without departing from the principle
of the invention. Therefore, the invention should be understood to include all
possible embodiments and modification to the shown embodiments which can be embodied
without departing from the principle of the invention as set forth in the appended claims.
*
