U.S. patent number RE33,949 [Application Number 07/613,469] was granted by the patent office on 1992-06-02 for vertical magnetic recording arrangement.
This patent grant is currently assigned to Digital Equipment Corporation. Invention is credited to Shyam C. Das, Michael L. Mallary.
United States Patent |
RE33,949 |
Mallary , et al. |
June 2, 1992 |
**Please see images for:
( Certificate of Correction ) ** |
Vertical magnetic recording arrangement
Abstract
The present device provides a downstream magnetic shield which
is integrally formed with a write pole section having a tip to make
up a magnetic recording head. The shield and the write pole tip are
located with small gap therebetween, so that magnetic flux which
fringes from the magnetic write pole tip is intercepted by the
shield. Accordingly such fringing flux does not pass through the
recording medium, and hence if a data bit has been written into the
recording medium its dipole identity will not be weakened by the
fringing flux of a subsequent data bit being written into the
magnetic recording medium. In addition, the magnetic recording
medium is made up of a first layer of material having perpendicular
uniaxial anisotropy and an underlying layer made of a material
which has a low magnetic flux reluctance characteristic.
Accordingly, the magnetic flux passes vertically through the first
layer, along the second layer and finally passes vertically from
the second layer through the first layer into the shield. The face
of the shield is designed to be many times as large as the face of
the write pole section so that the density of the flux from the tip
is sufficient to effect a vertical recording while the density of
the flux passing into the downstream magnetic shield is low and
hence a previously recorded pattern is not reversed.
Inventors: |
Mallary; Michael L. (Berlin,
MA), Das; Shyam C. (Sudbury, MA) |
Assignee: |
Digital Equipment Corporation
(Maynard, MA)
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Family
ID: |
24785015 |
Appl.
No.: |
07/613,469 |
Filed: |
November 7, 1990 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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334936 |
Apr 7, 1989 |
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Reissue of: |
693522 |
Jan 22, 1985 |
04656546 |
Apr 7, 1987 |
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Current U.S.
Class: |
360/110; 360/122;
360/123.05; 360/125.03 |
Current CPC
Class: |
G11B
5/1278 (20130101); G11B 5/315 (20130101); G11B
5/00 (20130101); G11B 5/02 (20130101); Y10T
74/20822 (20150115) |
Current International
Class: |
G11B
5/127 (20060101); G11B 5/02 (20060101); G11B
005/127 (); G11B 005/23 (); G11B 005/147 () |
Field of
Search: |
;360/110,113,119,125,126,121,122 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Iwasaki, et al., "An Analysis For The Magnetization Mode For High
Density Magnetic Recording", IEEE Trans. on Magnetics, V MAG-13,
No. 5, Sep. 1977 pp. 1272-1277. .
Potter, et al., "Self-Consistent Computer Calculations For
Perpendicular Magnetic Recording", IEEE Trans. on Magnetics, vol.
MAG-16, No. 5, Sep. 1980, pp. 967-972. .
Lazzari, et al., "Thin-Film Head Study For Perpendicular
Recording", IEEE Trans. on Magnetics, vol. MAG-17, No. 6, Nov.
1981, pp. 3120-3121. .
Hanazono, et al., "Fabrication Of A Thin Film Head Using Polyimide
Resin And Sputtered Ni-Fe Films.sup.a) ", J. Appl. Phys. 53(3),
Mar. 1982, pp. 2608-2610. .
Shinagawa, et al., "Simulation Of Perpendicular Recording On Co-Cr
Media With A Thin Permalloy Film-Ferrite Composite Head", J. Appl.
Phys. 53(3), Mar. 1982, pp. 2585-2587. .
Oshiki, et al., "A Thin Film Head For Perpendicular Magnetic
Recording", J. Appl. Phys. 53(3), Mar. 1982, pp.
2593-2595..
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Primary Examiner: Heinz; A. J.
Attorney, Agent or Firm: Fish & Richardson
Parent Case Text
.Iadd.This is a continuation of copending application Ser. No.
07/334,936 filed on Apr. 7, 1989, now abandoned. .Iaddend.
Claims
I claim:
1. An arrangement for effecting vertical magnetic recording of
information comprising in combination: movable magnetizable
recording means formed to have first and second layers which lie
substantially parallel to the movement of said magnetizable
recording means, said first layer comprised of magnetizable
material which is characterized by perpendicular uniaxial
anisotropy and said second layer comprised of material
characterized by low magnetic reluctance, said magnetizable
recording means arranged to be moved in a downstream direction;
magnetic recording head means including magnetic flux generating
means, formed to have a write pole section and a downstream
magnetic shield section which is integrally connected to said write
pole section so that magnetic flux can readily pass,
bi-directionally, through said write pole section and said
downstream magnetic shield section; said downstream magnetic shield
section formed and disposed to have a relatively large face lying
in close proximity to said first layer; said write pole section
fashioned, while extending in an upstream direction from said
downstream magnetic shield section, to form a partial loop
configuration defining an opening and ending in a pole tip which is
disposed to lie in close proximity to said first layer so that the
magnetic flux passing into and alternatively out of said write pole
section will pass from said first layer through said pole tip and
alternatively from said pole tip into said first layer, said write
pole section being further formed and disposed such that a small
gap having a sufficiently small width is formed between said pole
tip and said downstream magnetic shield section so that, when said
pole tip has magnetic flux passing therethrough, fringing flux in
the downstream direction will substantially pass across said small
gap into said downstream magnetic shield face without passing
through said first layer, and whereby the remainder of said
magnetic flux passing through said pole tip passes substantially
vertically through said first layer into said second layer,
substantially parallel to and through said second layer, and
substantially vertically from said second layer through said first
layer into said downstream magnetic shield face, thereby effecting
vertical magnetic recording of information in said first layer.
2. An arrangement for effecting vertical magnetic recording
according to claim 1 wherein there is a distance from where said
magnetic flux leaves said pole tip and enters said second layer and
wherein said distance is G and wherein the width of said small gap
is between G/2 and 2G.
3. An arrangement for effecting vertical magnetic recording
according to claim 1 wherein said magnetic flux generating means is
a wire coil which in part passes through the opening in said
partial loop configuration of said write pole section.
4. An arrangement for effecting vertical magnetic recording
according to claim 1 wherein said write pole tip defines a track on
said magnetic recording means and wherein there is further included
side magnetic shield means which are disposed to lie in close
proximity to said write pole section along at least one adjacent
track position to form at least one side gap therebetween to enable
said side shield means to intercept magnetic flux which is fringing
from said magnetic write pole tip in the direction of tracks
adjacent to said track defined by the passage of said magnetic
recording means relative to said write pole tip.
5. An arrangement for effecting magnetic recording according to
claim 4 wherein said side magnetic shield means includes first and
second side magnetic shield means each of which is disposed to lie
on opposite sides of, and in close proximity to, said write pole
section to respectively form first and second gaps between said
first and second side magnetic shield means and said write pole
section to enable said first and second side shield means to
intercept magnetic flux .[.while.]. .Iadd.which .Iaddend.is
fringing from said magnetic write pole tip in the direction of
tracks adjacent to said track defined by the extension of said
write pole tip onto said magnetic recording means. .Iadd.
6. A magnetic transducing head device, operable in conjunction with
and from a preferred side of a layered vertical recording medium
arranged to be moved in a downstream direction for effecting
vertical recording of bits of information in tracks thereon, the
device comprising
magnetic flux generating means including
a write pole section, and
a downstream magnetic shield section which is integrally connected
to said write pole section so that magnetic flux can readily pass
through said write pole section and said downstream magnetic shield
section,
said downstream magnetic shield section formed and disposed to have
a relatively large face defining an air bearing surface which can
be operated in close proximity to said preferred side of said
medium,
said write pole section and said downstream magnetic shield section
being constructed so that said write pole section is disposed in an
upstream direction with respect to said downstream magnetic shield
section so that said write pole section and said downstream
magnetic shield section form a partial loop configuration that
defines an opening between said write pole section and said
downstream magnetic shield section, said write pole section ending
in a pole tip which is disposed to be operated in close proximity
to said medium so that the magnetic flux passing through said write
pole section will pass from said pole tip into said medium,
said opening defining a gap at a midsection of said write pole
section and said downstream magnetic shield section and a
relatively smaller gap between said pole tip and said downstream
magnetic shield section, said smaller gap having a sufficiently
small width so that, when said pole tip has magnetic flux passing
therethrough, fringing flux in the downstream direction will be
substantially directed to pass from said pole tip across said
smaller gap into said downstream magnetic shield, such that
substantially all of the remainder of said magnetic flux is
presented for passing through said pole tip substantially
vertically into said medium and then to said downstream magnetic
shield face, and
whereby sharply defined bits of information may be vertically
recorded at said pole tip in tracks on said medium. .Iaddend.
.Iadd.
7. The device of claim 6 wherein said magnetic flux generating
means is a wire coil which in part passes through the opening in
said partial loop configuration. .Iaddend. .Iadd.
8. The head device of claim 6 further including side magnetic
shield means disposed to lie in close proximity to said write pole
section along at least one track adjacent to a track to be written
on said medium at said pole tip to form at least one side gap
between said side shield means and said write pole section to
enable said side shield means to intercept magnetic flux which is
fringing from said pole tip in the direction of said at least one
adjacent track. .Iaddend. .Iadd.
9. The head device of claim 8 wherein said side shield means
includes first and second side magnetic shield means each of which
is disposed to lie on opposite side of, and in close proximity to,
said write pole section to respectively form first and second gaps
between said first and second side magnetic shield means and said
write pole section to enable said first and second side shield
means to intercept magnetic flux from said magnetic write pole tip
in the direction of tracks adjacent to a track to be written at
said pole tip on said medium. .Iaddend. .Iadd.
10. The device of claim 6 wherein said write pole section is
constructed with a bowed region to define said partial loop
configuration. .Iaddend. .Iadd.
11. A magnetic transducing head device having at least one pole for
effecting vertical recording of magnetic transitions on and from a
preferred side of a layered vertical magnetic recording medium
arranged to be moved in a downstream direction, the device
comprising
a write pole terminating in a write pole tip,
a downstream shield integrally connected to the write pole and
having a large shield tip area relative to the area of the write
pole tip,
the write pole cooperating with the downstream shield to engage
flux from a write flux source,
the write pole tip configured to present write flux from the write
flux source to the medium for recording information on the medium,
and
the write pole and said downstream shield being constructed to
define a gap between them, said gap being smaller in the area of
the write pole tip and the downstream shield tip than it is in an
area closer to where the downstream shield is integrally connected
to said write pole,
said gap between the write pole tip and the downstream shield tip
being sufficiently small to substantially transfer to the
downstream shield downstream fringing flux emanating from the write
pole tip to minimize presentation of downstream fringing flux to
the medium when presenting write flux from the pole tip to the
medium for recording information on the medium, whereby a write
field gradient generated by the write flux in the recording medium
is increased and recorded transitions are sharper, as a result of
such minimization. .Iaddend. .Iadd.
12. The device of claim 11 wherein the write flux source is a wire
coil, that passes through at least a portion of said gap. .Iaddend.
.Iadd.
13. The head device of claim 11 further including side magnetic
shield means disposed to lie in close proximity to the write pole
section along at least one track adjacent to a track to be written
on the medium at the pole tip to form at least one side gap
therebetween to enable the side shield means to intercept magnetic
flux fringing from the pole tip in the direction of the at least
one adjacent track. .Iaddend. .Iadd.
14. The head device of claim 13 wherein the side shield means
includes first and second side magnetic shield means each of which
is disposed to lie on opposite sides of, and in close proximity to,
the write pole section to respectively form first and second gaps
between the first and second side magnetic shield means and the
write pole section to enable the first and second side shield means
to intercept magnetic flux from the magnetic write pole tip in the
direction of tracks adjacent to a track to be written at the pole
tip on the medium. .Iaddend. .Iadd.
15. The device of claim 11 wherein said write pole is constructed
with a bowed region to define said gap and said smaller gap.
.Iaddend. .Iadd.
16. A magnetic transducing head device, operable in conjunction
with and from a preferred side of a layered vertical recording
medium arranged to be moved in a downstream direction for effecting
vertical recording of bits of information in tracks thereon,
comprising
magnetic flux generating means, including
a write pole section, and
a downstream magnetic shield section which is integrally connected
to said write pole section so that magnetic flux can readily pass
through said write pole section and said downstream magnetic shield
section,
said downstream magnetic shield section formed and disposed to have
a relatively large face defining an air bearing surface which can
be operated in close proximity to said preferred side of said
medium, said write pole section fashioned, while extending in an
upstream direction from said downstream magnetic shield section, to
form a partial loop configuration defining an opening and ending in
a pole tip which is disposed to be operated in close proximity to
said medium so that the magnetic flux passing through said write
pole section will pass from said pole tip into said medium,
said write pole section being further formed and disposed with a
bowed out midsection with a small gap having a sufficiently small
width formed between said pole tip and said downstream magnetic
shield section so that, when said pole tip has magnetic flux
passing therethrough, fringing flux in the downstream direction
will be substantially directed to pass from the side of said pole
tip across said small gap into said downstream magnetic shield,
such that substantially all of the remainder of said magnetic flux
is presented for passing through said pole tip substantially
vertically into said medium and then to said downstream magnetic
shield face,
whereby sharply defined bits of information may be vertically
recorded at said pole tip in tracks on said medium, and further
including side magnetic shield means disposed to lie in close
proximity to said write pole section along at least one track
adjacent to a track to be written on said medium at said pole tip
to form at least one side gap between said side shield means and
said write pole section to enable said side shield means to
intercept magnetic flux which is fringing from said pole tip in the
direction of said at least one adjacent track. .Iaddend. .Iadd.17.
The device of claim 16 wherein said side shield means includes
first and second side magnetic shield means each of which is
disposed to lie on opposite sides of, and in close proximity to,
said write pole section to respectively form first and second gaps
between said first and second side magnetic shield means and said
write pole section to enable said first and second side shield
means to intercept magnetic flux from said magnetic write pole tip
in the direction of tracks adjacent to a track to be written at
said pole tip on said medium. .Iaddend. .Iadd.18. A magnetic head
having at least one pole for effecting downstream vertical
recording of magnetic transitions on a layered vertical magnetic
recording medium via a write field gradient comprising
a write pole terminating in a write pole tip,
a downstream shield integrally connected to the write pole and
having a large shield tip area relative to the area of the write
pole tip,
the write pole cooperating with the downstream shield to engage
flux from a write flux source,
the write pole tip configured to present write flux from the write
flux source to the medium for recording information on the
medium,
the write pole proximally coupled to the downstream shield to
substantially capture downstream fringing flux emanating from the
write pole to minimize presentation of downstream fringing flux to
the medium when presenting write flux from the pole tip to the
medium for recording information on the medium, whereby the write
field gradient at the pole tip is increased and recorded
transitions are sharper, as a result of such minimization, and
further including side magnetic shield means disposed to lie in
close proximity to the write pole section along at least one track
adjacent to a track to be written on the medium at the pole tip to
form at least one side gap therebetween to enable the side shield
means to intercept magnetic flux fringing from the pole tip in the
direction of the at least
one adjacent track. .Iaddend. .Iadd.19. The head of claim 18
wherein the side shield means includes first and second side
magnetic shield means each of which is disposed to lie on opposite
sides of, and in close proximity to, the write pole section to
respectively form first and second gaps between the first and
second side magnetic shield means and the write pole section to
enable the first and second side shield means to intercept magnetic
flux from the magnetic write pole tip in the direction of tracks
adjacent to a track to be written at the pole tip on the medium.
.Iaddend.
.Iadd.20. An arrangement for effecting vertical magnetic recording
of information comprising in combination:
movable magnetizable recording means formed to have first and
second layers which lie substantially parallel to the movement of
said magnetizable recording means, said first layer comprised of
magnetizable material which is characterized by perpendicular
uniaxial anisotropy and said second layer comprised of material
characterized by low magnetic reluctance, said magnetizable
recording means arranged to be moved in a downstream direction;
magnetic recording head means including magnetic flux generating
means, formed to have a write pole section and a downstream
magnetic shield section which is integrally connected to said write
pole section so that magnetic flux can readily pass,
bidirectionally, through said write pole section and said
downstream magnetic shield section;
said downstream magnetic shield section formed and disposed to have
a relatively large face lying in close proximity to said first
layer;
said write pole section and said downstream magnetic shield section
being constructed so that said write pole section is disposed in an
upstream direction with respect to said downstream magnetic shield
section so that said write pole section and said downstream
magnetic shield section form a partial loop configuration that
defines an opening between said write pole section and said
downstream magnetic shield section, said write pole section ending
in a pole tip which is disposed to lie in close proximity to said
first layer so that the magnetic flux passing into and
alternatively out of said write pole section will pass from said
first layer through said pole tip and alternatively from said pole
tip into said first layer,
said opening defining a small gap between said pole tip and said
downstream magnetic shield section that has a sufficiently small
width so that, when said pole tip has magnetic flux passing
therethrough, fringing flux in the downstream direction will
substantially pass across said small gap into said downstream
magnetic shield section without passing through said first layer,
and whereby the remainder of said magnetic flux passing through
said pole tip passes substantially vertically through said first
layer into said second layer, substantially parallel to and through
said second layer, and substantially vertically from said second
layer through said first layer into said downstream magnetic shield
face, thereby effecting vertical magnetic recording of information
in said first layer. .Iaddend.
.Iadd.21. The device of claim 20 wherein said write pole section is
constructed with a bowed region to define said partial loop
configuration.
.Iaddend. .Iadd.22. An arrangement for effecting vertical magnetic
recording of information comprising in combination:
movable magnetizable recording means formed to have first and
second layers which lie substantially parallel to the movement of
said magnetizable recording means, said first layer comprised of
magnetizable material which is characterized by perpendicular
uniaxial anisotropy and said second layer comprised of material
characterized by low magnetic reluctance, said magnetizable
recording means arranged to be moved in a downstream direction;
magnetic recording head means including magnetic flux generating
means, formed to have a write pole section and a downstream
magnetic shield section which is integrally connected to said write
pole section so that magnetic flux can readily pass,
bidirectionally, through said write pole section and said
downstream magnetic shield section;
said downstream magnetic shield section formed and disposed to have
a relatively large face lying in close proximity to said first
layer;
said write pole section and said downstream magnetic shield section
being constructed so that said write pole section is disposed in an
upstream direction with respect to said downstream magnetic shield
section so that said write pole section and said downstream
magnetic shield section form a partial loop configuration that
defines a first gap between said write pole section and said
downstream magnetic shield section, said write pole section ending
in a pole tip which is disposed to lie in close proximity to said
first layer so that the magnetic flux passing into and
alternatively out of said write pole section will pass from said
first layer through said pole tip and alternatively from said pole
tip into said first layer,
said partial loop configuration defining a second gap of narrower
width than said first gap between said pole tip and said downstream
magnetic shield section, said width of said second gap being
sufficiently small such that when said pole tip has magnetic flux
passing therethrough, fringing flux in the downstream direction
will substantially pass across said small gap into said downstream
magnetic shield without passing through said first layer, and
whereby the remainder of said magnetic flux passing through said
pole tip passes substantially vertically through said first layer
into said second layer, substantially parallel to and through said
second layer, and substantially vertically from said second layer
through said first layer into said downstream magnetic shield face,
thereby effecting vertical magnetic recording of information in
said first
layer. .Iaddend. .Iadd.23. The device of claim 22 wherein said
write pole section is constructed with a bowed region to define
said partial loop configuration. .Iaddend.
Description
BACKGROUND
While magnetic recording of information is enormously successful,
it has been found that in the prior art there is a limitation with
respect to recording density. In the present state of the art the
popular method of magnetic recording has been longitudinal
recording. Magnetic recording systems to date generally recognize
recorded bits of information by detecting pulse peaks within
certain timing windows. Unfortunately systems often inadvertently
shift pulse patterns, in time, with respect to the timing of the
windows and this of course results in errors. It follows that when
linear density is increased, the time windows in which the peak
must be detected necessarily narrows and the systems become more
sensitive to noise and there are resulting errors.
Magnetic recording techniques have turned to considering vertical
recording as compared to longitudinal recording as a means for
vastly improving the linear density of recorded information.
Vertical magnetic recording has been accomplished by having the
recording medium pass between two mirror image recording heads. The
magnetic flux from a first recording head passes vertically from a
first write tip through the magnetic recording medium to a second
write tip (the write tip of a second recording head). The shape of
the tips concentrate the flux and hence effect a magnetic
polarization within the recording medium to provide recorded
information. The magnetic flux having passed through the second tip
is routed upstream to a flux return path of the second write head.
The flux return head is designed to have a face which is many times
larger than the write tip so that the flux passing into the flux
return head is disbursed therealong and hence the flux density is
low. The low density flux passes through the recording medium,
upstream, to the flux return path of the first magnetic write head
and therealong to complete a magnetic flux circuit. Because the
density of the flux passing through the recording medium upstream
is low, there is very little effect by way of reversing or
weakening any patterns in the recording medium upstream.
In the prior art vertical recording technique there has been a
prerequisite in that there has been required a relatively large
distance between the write tip and the flux return path to prevent
leakage flux cross-over. In other words in such techniques the full
strength of the write flux is desired to effect a desired
recording. However in such arrangements, as the described in U.S.
Pat. No. 4,317,148 the downstream fringing flux, which is ignored,
acts to reverse or weaken, the magnetic polarity of information
having been previously recorded and to compensate therefor, the
packing density has had to be reduced.
The present device employs a two layered recording medium, places
the flux return section downstream and by specifically locating the
write tip close to the flux return path, uses the flux return path
as a magnetic shield to intercept downstream fringing flux and thus
prevent reversal or weakening, of the magnetic polarity at the
trailing edge of a recorded bit of information. As mentioned above
the prior art is exemplified by the structure described in U.S.
Pat. No. 4,317,148.
SUMMARY
The present device includes a two layered recording medium. The
upper layer is comprised of a material having perpendicular
uniaxial anisotropy, such as cobalt chromium, while the underlayer
is comprised of material having a low magnetic reluctance such as
nickel iron. In addition the present device includes a write pole
section of a single write head (no mirror image write head is
included) which is formed in a partial loop configuration, away
from the downstream flux return section, so that there is no
leakage along the height dimension of the write pole section.
However, the partial loop configuration is designed to place the
write tip X micro inches away from the flux section. Where X is in
the range from G/2 to 2G and where G is the distance from the write
tip face to the beginning of the low reluctance layer. The gap X is
a small gap and hence most of the downstream fringing flux is
intercepted by the flux return section so that the flux return
section acts as a magnetic shield. The interception of the
downstream fringing flux by the magnetic shield reduces the
undesirable effect of reversing, or weakening, a previously
recorded bit of information. The present device further provides
magnetic shielding means which lie parallel to the tracks on the
recording medium so that tracks which lie adjacent to the track
being presently written do not suffer from magnetic polarity
reversals or weakening of dipole identification by flux fringing in
a side direction or orthogonally to the track presently
written.
The objects and features of the present invention will be better
understood by considering the following description taken in
conjunction with the drawings wherein:
FIG. 1 is a side view of the write head depicting the write pole
section formed in a partial loop and with the coils in sectional
view form;
FIG. 2 is a view of the write head as seen looking at the excursion
direction of the recording medium; and
FIG. 3 is an underside view of FIG. 2.
Consider FIG. 1. In FIG. 1 there is shown a section of the magnetic
recording medium 11 which is made up of an upper layer 13 and a
lower layer 15. The upper layer 13 in a preferred embodiment is
cobalt chromium but it should be understood that any material which
has perpendicular uniaxial anisotropy could be employed. The lower
layer 15 in a preferred embodiment is nickel iron but it should be
understood that any material which has a low magnetic reluctance
could be employed. While it is not shown in FIG. 1, it should be
understood that there is means to move the magnetic recording
medium in a downstream direction, i.e. a disk drive or the like. As
can be seen in FIG. 1, located in close proximity but with an air
space in between, there is shown the write head 17. The write head
17 is made up of a write pole section 19 and downstream shield 21.
The write pole section 19 is formed integrally with the shield 21
and is formed to extend upstream into a partial loop as can be
gleaned from FIG. 1. By forming the write pole section 19 into a
partial loop there is provided a bay or open section 23. By having
the write pole section separated from the shield section 21 by the
bay 23 there is little fringing magnetic flux passing from the
write pole section 19 to the shield 21 through the bay 23, i.e.
along the height dimension of the write head.
As can be readily understood from the examination of FIG. 1 there
is a coil 25 shown with four sections in FIG. 1 and its
configuration can be better understood by examining FIG. 2. While
it is not shown in FIG. 1 it should be understood that the coil 25
is connected to a source of electrical power so that when the coil
25 is energized there is a magnetic flux generated in the write
pole section 19. It should be further understood that by forming
write pole section 19 into a partial loop, the pole tip portion 27
comes into close proximity to the downstream shield section 21.
Accordingly there is a gap 30 which is labeled in the drawing as
the shield gap located between the pole tip 27 and the lower
portion of the downstream shield section 21. The selection of the
width (X) of the gap 30 is important. It has been determined that
if the distance between the bottom of the face of the pole tip 27
and the start of the lower layer 15 of the magnetic recording
medium has a dimension of G then the width (X) of the shield gap 30
should not be any smaller than G/2. This concept is set forth in
the drawing wherein the drawing depicts the width of the shield gap
as being equal to or greater than G/2. In the preferred embodiment
the shield gap is equal to G/2 because at that dimension virtually
all of the fringing flux passes directly into the downstream shield
21 while there is still a sufficient amount of flux emanating from
the pole tip 27 to effect a vertical magnetization in the layer 13.
However, in order to obtain sufficient write field it may be
necessary to increase the gap from G/2 to as much as 2G.
It should be borne in mind that the magnetic recording medium is
moving from a left to right in FIG. 1 and that the data bit
recorded in the section 29 of the layer 13 has been recorded and
the user wants that data bit to remain recorded on the magnetic
recording medium 11. Accordingly the system does not want fringing
flux to disturb or weaken or even reverse the dipole identification
of the data recorded in section 29. As depicted for purposes of
illustration (and not with any scientific exactness) the flux
passes from the pole tip 27, through the hard layer 13 and through
the soft layer 15 and is concentrated, or sufficiently dense, to
align the dipoles of the layer 13 so as to effect a vertical
recording of information in sections along the layer 13, such as
sections 29 and section 31. It should also be noted in FIG. 1 that
fringing flux 33 is shown emanating from the left hand side from
the pole tip 27. Such fringing flux indeed may disturb the dipole
identification of a section of the magnetic recording medium
entering under the write head but since that section is going to be
rewritten it makes no difference that it is being disturbed. It is
the downstream fringing flux that is the underside fringing flux
and in accordance with the present device such fringing flux on the
write end of the pole tip is intercepted by the shield section
21.
In order to have the magnetic flux emanate from the pole tip 27 and
cause the write pattern to be developed, as shown in section 35,
electrical current must be passing through the electrical coil as
shown. In other words in the two upper legs 25a and 25b the current
is passing into the figure while in the two segments 25c and 25d
the current is passing out of the figure. In this way the flux will
pass from the top of the figure through the write pole section and
through the pole tip 27 as shown. As depicted in FIG. 1 the
relative strength of the magnetized areas is shown by the arrows.
It will be noted that the arrow 37 is somewhat shorter than the
rest of the arrows in section 29 indicating that there has been a
slight weakening of that dipole identification because of the
fringing flux 39 overlapping segment 29 before section 29 passes
from under the fringing flux 39. The reduction of this adverse
effect (downstream demagnetization) in one of the salient features
of the present invention. By way of comparison the arrow 42 is
shown as being a bit diminished even though it has not been under
the pole tip at the point in time shown in FIG. 1 but has been
diminished because of the conditions under which it was recorded at
some previous time.
As can be seen further in FIG. 1 there is a side shield 43 whose
role is to intercept fringing flux that would pass over adjacent
tracks, i.e. which are adjacent to the track on the magnetic
recording medium which is passing under the pole tip at the time
depicted in FIG. 1. The arrangement and the utility of the side
shield 43 will be better understood by an examination of FIG.
2.
In FIG. 2 the various pieces of structure described in FIG. 1 are
identified by the same numbers. As can be seen in FIG. 2 the pole
tip 27 provides fringing flux in the direction of the side tracks
45 and 47. That fringing flux is depicted in FIG. 2 as the fringing
flux 49 and fringing flux 51. The fringing flux 49 is intercepted
by the side shield 43 while the fringing flux 51 is intercepted by
the side shield 53. Accordingly the tracks 45 and 47 which lie
adjacent to the track 55, that is the track that is being presently
written upon in accordance with the arrangement depicted in FIG. 2,
are not adversely affected by fringing flux. The gap between the
pole tip 27 and the side shield 43 as well as the gap between the
pole 27 and the side shield 53 can be larger than the downstream
shield gap 30 so as to reduce the loss of flux to the shields.
FIG. 3 depicts the underside of the device shown in FIG. 2. The
identification numbers of the structure in FIG. 3 are the same as
the identification numbers in FIGS. 1 and 2 and no further
explanation thereof appears to be necessary. The arrangement of the
device shown in FIG. 3 however does enable a clear understanding of
the overall device particularly how the side shields are formed
with respect to the downstream shield and with respect to the
winged arrangements of the write pole section 19.
By arranging to have the shield extension of the write head located
downstream of the write tip and by arranging to have the gap there
between be relatively small, but not so small as to permit all of
the flux to be intercepted by the shield, the present structure
creates less of a diminishing effect on data information which has
been previously written into the magnetic recording medium. In
addition by having the write pole section formed into a partial
loop, the amount of fringing flux which jumps the separation
between the write pole section and the flux return section is
minimized and the bay portion of the partial loop configuration
provides a location for the magnetic flux generating coils. It is
important to note that the gap dimension in the preferred
embodiment is related to the distance between the bottom of the
pole tip and the beginning of the soft layer or the layer having
the low magnetic reluctance. If the air bearing, that is the
distance between the pole tip and the upper surface of the hard
layer 13, is decreased then the gap can be increased because there
will be a greater incentive for the flux to pass through the layer
13 as a result of the reduced air bearing. As can be readily seen
in FIG. 1 the vast majority of the flux passes through the layer 13
in a vertical direction and hence there is a vertical recording of
the data in the layer 13. It should be further noted from the
description and by examination of FIG. 1 that the face of the
downstream shield 21 is many times larger than the face of the pole
tip. In point of fact the pole tip 27 could have an even narrower
face than shown in FIG. 1. By providing a rather large downstream
shield face, the flux is dispersed along that face and hence is
relatively low in density. Because of the low density aspect of the
flux passing on the return path into the downstream shield 21 there
is very little effect on the magnetization condition in the layer
13 which lies under the shield. By not disturbing the magnetization
pattern under the shield face one of the major objectives of the
present system is accomplished.
* * * * *