U.S. patent application number 12/824102 was filed with the patent office on 2010-10-21 for ferromagnetically coupled magnetic recording media.
This patent application is currently assigned to SEAGATE TECHNOLOGY LLC. Invention is credited to Erol Girt, Mariana Rodica Munteanu, Hans Jurgen Richter, Felix Trejo.
Application Number | 20100266755 12/824102 |
Document ID | / |
Family ID | 37083498 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100266755 |
Kind Code |
A1 |
Girt; Erol ; et al. |
October 21, 2010 |
FERROMAGNETICALLY COUPLED MAGNETIC RECORDING MEDIA
Abstract
A ferromagnetically coupled magnetic recording medium having a
first ferromagnetic layer, a second ferromagnetic layer, and a
ferromagnetic coupling layer to ferromagnetically couple the first
ferromagnetic layer to the second ferromagnetic layer is used as
stable magnetic media with high MrT in high density recording hard
drives. The first ferromagnetic layer is the stabilization layer
and the second ferromagnetic layer is the main recording layer. The
ferromagnetic coupling layer comprises a conductive material having
a thickness which produces ferromagnetic coupling between said
first ferromagnetic layer and said second ferromagnetic layer via
the RKKY interaction.
Inventors: |
Girt; Erol; (Berkeley,
CA) ; Munteanu; Mariana Rodica; (Santa Clara, CA)
; Richter; Hans Jurgen; (Palo Alto, CA) ; Trejo;
Felix; (Fremont, CA) |
Correspondence
Address: |
SEAGATE TECHNOLOGY LLC;C/O Murabito Hao & Barnes LLP
Two North Market Street, Third Floor
San Jose
CA
95113
US
|
Assignee: |
SEAGATE TECHNOLOGY LLC
Scotts Valley
CA
|
Family ID: |
37083498 |
Appl. No.: |
12/824102 |
Filed: |
June 25, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11101068 |
Apr 6, 2005 |
|
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12824102 |
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Current U.S.
Class: |
427/131 |
Current CPC
Class: |
G11B 5/65 20130101; G11B
5/66 20130101; G11B 5/656 20130101 |
Class at
Publication: |
427/131 |
International
Class: |
G11B 5/84 20060101
G11B005/84 |
Claims
1-30. (canceled)
31. A method comprising: forming a first layer overlying a
substrate; forming a coupling layer overlying said first layer; and
forming said second layer overlying said coupling layer, wherein
said coupling layer ferromagnetically couples said first layer and
said second layer, wherein the first layer and the second layer are
not ferromagnetically coupled without the coupling layer.
32. The method as in claim 31 wherein said forming a coupling layer
comprises: forming a first interface layer; forming a spacer layer;
and forming a second interface layer, wherein said spacer layer
consists of Ru with a thickness of between 0 to 2 angstroms, or
between 11 to 17 angstroms, or between 25 to 31 angstroms, to
produce said ferromagnetic coupling of said first layer and said
second layer.
33. The method as in claim 31 wherein said layer is non-magnetic,
conductive and less than 6 nanometers in thickness, to produce said
ferromagnetic coupling of said first layer and said second
layer.
34. The method as in claim 33 wherein said coupling layer is one of
Pt, Pd, and alloys thereof.
35. The method as in claim 31 wherein said first interface layer
and said second interface layer have magnetic moments with magnetic
saturations greater than 300 emu/cm.sup.3.
36. The method as in claim 31 wherein said forming a coupling layer
comprises: forming a first interface layer; forming a spacer layer;
and forming a second interface layer, wherein said first interface
layer and said second interface layer are made from a material
selected from the group consisting of Fe, Co and alloys made of Fe
or Co mixed with one or more added elements selected from the group
consisting of Cr, Pt, Ta, B, Mo, Pd, Cu, Au, Ti, W, Ru, Si, Ge, Nb,
and Ni.
37. The method as in claim 31 wherein said first ferromagnetic
layer and said second ferromagnetic layer are selected from the
group consisting of alloys containing Co and Cr, and alloys
containing CoCr with one or more added elements selected from the
group consisting of Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe and Ni.
38. A method comprising: increasing remanence
squareness-thickness-product (Mrt) of a perpendicular magnetic
recording media by ferromagnetically coupling a ferromagnetic
recording layer and a ferromagnetic stabilization layer, wherein
said perpendicular magnetic recording media comprises: a substrate;
a seed layer or an underlayer; said ferromagnetic stabilization
layer; a ferromagnetic coupling layer; and said ferromagnetic
recording layer; and wherein further said ferromagnetic coupling
layer comprises, in overlying sequence: a first interface layer; a
spacer layer; and a second interface layer.
39. The method as in claim 38 wherein said spacer layer consists of
Ru with a thickness of between 0 to 2 angstroms, or between 11 to
17 angstroms, or between 25 to 31 angstroms, to produce said
ferromagnetic coupling of said ferromagnetic recording layer and
said ferromagnetic stabilization layer.
40. The method as in claim 38 wherein said ferromagnetic coupling
layer is non-magnetic, conductive and less than 6 nanometers in
thickness, to produce said ferromagnetic coupling of said
ferromagnetic recording layer and said ferromagnetic stabilization
layer.
41. The method as in claim 40 wherein said ferromagnetic coupling
layer is one of Pt, Pd, and alloys thereof.
42. The method as in claim 38 wherein said first interface layer
and said second interface layer have magnetic moments with magnetic
saturations greater than 300 emu/cm.sup.3.
43. The method as in claim 38 wherein said first interface layer
and said second interface layer are made from a material selected
from the group consisting of Fe, Co and alloys made of Fe or Co
mixed with one or more added elements selected from the group
consisting of Cr, Pt, Ta, B, Mo, Pd, Cu, Au, Ti, W, Ru, Si, Ge, Nb,
and Ni.
44. The method as in claim 38 wherein said ferromagnetic recording
layer and said ferromagnetic stabilization layer are selected from
the group consisting of alloys containing Co and Cr, and alloys
containing CoCr with one or more added elements selected from the
group consisting of Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe and Ni.
45. A method comprising: increasing remanence
squareness-thickness-product (Mrt) of a perpendicular magnetic
recording media by ferromagnetically coupling a ferromagnetic
recording layer and a ferromagnetic stabilization layer using a
ferromagnetic coupling layer; and utilizing said ferromagnetic
coupling of said ferromagnetic recording layer and said
ferromagnetic stabilization layer to lower coercivity of said
perpendicular magnetic recording media, and increase stability of
said ferromagnetic recording layer between writing processes;
wherein said perpendicular magnetic recording media comprises: a
substrate; a seed layer or an underlayer; said ferromagnetic
stabilization layer; said ferromagnetic coupling layer; and said
ferromagnetic recording layer.
46. The method as in claim 45 wherein said ferromagnetic recording
layer and said ferromagnetic stabilization layer are selected from
the group consisting of alloys containing Co and Cr, and alloys
containing CoCr with one or more added elements selected from the
group consisting of Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe and Ni.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to the field of disc
drive storage, and more particularly to ferromagnetically coupled
magnetic recording media.
[0003] 2. Description of the Related Art
[0004] Conventional disc drives are used to magnetically record,
store and retrieve digital data. Data is recorded to and retrieved
from one or more discs that are rotated at more than one thousand
revolutions per minute (rpm) by a motor. The data is recorded and
retrieved from the discs by an array of vertically aligned
read/write head assemblies, which are controllably moved from data
track to data track by an actuator assembly.
[0005] The three major components making up a conventional hard
disc drive are magnetic media, read/write head assemblies and
motors. Magnetic media, which is used as a medium to magnetically
store digital data, typically includes a layered structure, of
which at least one of the layers is made of a magnetic material,
such as CoCrPtB, having high coercivity and high remnant moment.
The read/write head assemblies typically include a read sensor and
a writing coil carried on an air bearing slider attached to an
actuator. This slider acts in a cooperative hydrodynamic
relationship with a thin layer of air dragged along by the spinning
discs to fly the head assembly in a closely spaced relationship to
the disc surface. The actuator is used to move the heads from track
to track and is of the type usually referred to as a rotary voice
coil actuator. A typical rotary voice coil actuator consists of a
pivot shaft fixedly attached to the disc drive housing closely
adjacent to the outer diameter of the discs. Motors, which are used
to spin the magnetic media at rates of higher than 1,000
revolutions per minute (rpm), typically include brushless direct
current (DC) motors. The structure of disc drives is well
known.
[0006] Magnetic media can be locally magnetized by a read/write
head, which creates a highly concentrated magnetic field that
alternates direction based upon bits of the information being
stored. The highly concentrated localized magnetic field produced
by the read/write head magnetizes the grains of the magnetic media
at that location, provided the magnetic field is greater than the
coercivity of the magnetic media. The grains retain a remnant
magnetization after the magnetic field is removed, which points in
the same direction of the magnetic field. A read/write head that
produces an electrical response to a magnetic signal can then read
the magnetization of the magnetic media.
[0007] Magnetic media structures are typically made to include a
series of thin films deposited on top of aluminum substrates,
ceramic substrates or glass substrates. FIG. 1 illustrates a
conventional anti-ferromagnetically coupled magnetic media
structure having a substrate 110, a seed layer 115, a first
ferromagnetic layer 120, an anti-ferromagnetic coupling layer 125,
a second ferromagnetic layer 130, and a protective overcoat
140.
[0008] Substrate 110 is typically made of Aluminum (Al),
nickel-phosphorus plated aluminum, glass or ceramic. Seed layer 115
is typically made of Cr or a Cr alloy and can be less than 200
angstroms. First ferromagnetic layer 120 is the stabilization layer
and can be made of a ferromagnetic material such as Co. Second
ferromagnetic layer 130 is the main recording layer and is also
made of a ferromagnetic material such as Co. Anti-ferromagnetic
coupling (AFC) layer 125 is made of Ru and is used to
anti-ferromagnetically couple the main recording layer with the
stabilization layer.
[0009] In AFC media the main recording layer is
anti-ferromagnetically coupled across a Ru spacer layer with the
thin magnetic stabilization layer. The stability of the main
recording layer increases because of the coupling with the
stabilization layer 120 and because of the decrease of the
demagnetization field that the main recording layer experiences.
This increase in stability of the main recording layer can be
traded off against the decreasing average magnetic grain volume in
the main recording layer. However, in this AFC structure the net
MrT of this media is reduced (net
MrT=(M.sub.rT).sub.ML-(M.sub.rT).sub.SL) causing an increase in the
effective electronic noise and a reduction in total signal-to-noise
ratio (SNR) (total SNR=Media SNR+Electronic SNR).
[0010] The magnetic media structure of FIG. 1 lacks optimal
magnetic properties because of high noise resulting from high
magnetic exchange coupling between grains. Therefore what is needed
is a magnetic media structure that is useable for high-density
recording, has a high MrT and is stable.
SUMMARY OF THE INVENTION
[0011] This limitation is overcome by using ferromagnetically
coupled magnetic recording media instead of anti-ferromagnetically
coupled magnetic recording media. A ferromagnetically coupled
magnetic recording medium comprises a first ferromagnetic layer, a
second ferromagnetic layer, and a ferromagnetic coupling layer to
ferromagnetically couple the first ferromagnetic layer to the
second ferromagnetic layer. The first ferromagnetic layer is the
stabilization layer and the second ferromagnetic layer is the main
recording layer. The ferromagnetic coupling layer comprises a
conductive material having a thickness which produces ferromagnetic
coupling between the first ferromagnetic layer and the second
ferromagnetic layer via the RKKY interaction.
[0012] In one embodiment of the magnetic recording medium the
conductive material of the ferromagnetic coupling layer can be Ru,
Rh, Ir, Cr, Cu, Re, V or alloys made of these elements.
[0013] In another embodiment, the first ferromagnetic layer and the
second ferromagnetic layer are made of Co-based alloys.
Additionally the ferromagnetic coupling layer is made of Ru and has
a thickness range which is between about 0 and 2 angstroms, or
between about 11 angstroms and 17 angstroms, or between about 25
angstroms and 31 angstroms. This thickness range produces
ferromagnetic coupling between the first ferromagnetic layer and
the second ferromagnetic layer according to the RKKY
interaction.
[0014] In another embodiment of the magnetic recording medium, the
ferromagnetic coupling layer includes a non-magnetic conductive
layer, which is ferromagnetically polarized in the presence of the
first ferromagnetic layer and the second ferromagnetic layer. In
this embodiment the ferromagnetic coupling layer has a thickness
less than 6 nanometers and can be made of Pt, Pd, Pt-alloys, or
Pd-alloys.
[0015] In another embodiment of the magnetic recording medium, the
ferromagnetic coupling layer includes a weekly ferromagnetic layer
that provides direct exchange interaction coupling between the
first ferromagnetic layer and the second ferromagnetic layer. The
ferromagnetic coupling layer can have a magnetization less than 300
emu/cm.sup.3 and preferably has a magnetization less than 100
emu/cm.sup.3. Additionally, the ferromagnetic coupling layer can be
made of Co, Ni, Fe or alloys thereof.
[0016] In other embodiments of the invention, the first
ferromagnetic layer and the second ferromagnetic layer of the
magnetic recording medium are made of Co, Cr, or alloys containing
Co or Cr. The alloys containing Co or Cr can have one or more of
elements Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe or Ni added to the
alloy.
[0017] In other embodiments of the invention, the first
ferromagnetic layer and the second ferromagnetic layer of the
magnetic recording medium are made of Si, Al, Ti, Hf, W, Mg, Nb,
Fe, B, V, Mn, Ge, Mo, Ru, Rh, Re, Pt, Zr, Y, Cr, Sm, Co, Ni or Ta.
Some examples include TiO.sub.2, Al.sub.2O.sub.3, MgO, WO.sub.3,
Cr.sub.2O.sub.3, Nb.sub.2O5, ZrO2, Ta2O5, MoO3, Y2O3, Sm2O3, CoO
and CoCrPt+SiO.sub.2.
[0018] Another embodiment of the invention includes a magnetic
recording medium, comprising, a first ferromagnetic layer, a first
interface layer, a ferromagnetic coupling layer, a second interface
layer, a second ferromagnetic layer, wherein the ferromagnetic
coupling layer is used to ferromagnetically couple the first
ferromagnetic layer and the second ferromagnetic layer. The first
interface layer and the second interface layer can have magnetic
moments with magnetic saturations greater than 300 emu/cm.sup.3 and
preferably greater than 500 emu/cm.sup.3. The first interface layer
and the second interface layer can be made of Fe, Co or alloys made
of Fe or Co. The alloys made of Fe or Co can be mixed with one or
more added elements which include Cr, Pt, Ta, B, Mo, Pd, Cu, Au,
Ti, W, Ru, Si, Ge, Nb, or Ni.
[0019] Another embodiment of the invention includes a magnetic
recording medium, comprising, a first ferromagnetic layer, a second
ferromagnetic layer, a ferromagnetic coupling layer for
ferromagnetically coupling the first ferromagnetic layer to the
second ferromagnetic layer, wherein the ferromagnetic coupling
layer is anti-ferromagnetically coupled to both the first
ferromagnetic layer and the second ferromagnetic layer. The
ferromagnetic coupling layer can further include two non-magnetic
spacer layers separated by a magnetic interface layer. The magnetic
interface layer can include Fe, Co, FeX, or CoX where X is one or
more of Cr, Pt, Ta, B, Mo, Ru, Si, Ge, Nb, or Ni. Additionally, the
magnetic interface layer can have a magnetic saturation greater
than 300 emu/cm.sup.3 and preferably greater than 500
emu/cm.sup.3.
[0020] Another embodiment of the invention includes a magnetic
recording medium comprising a first ferromagnetic structure further
comprising a CoCrPtB layer and a Co layer, a second ferromagnetic
structure further comprising a Co layer and a CoCrPtB layer, and a
ferromagnetic coupling structure for ferromagnetically coupling the
first ferromagnetic layer to the second ferromagnetic layer,
wherein the ferromagnetic coupling structure further comprises a
first Ru layer, a Co layer, and a second Ru layer.
[0021] All of these embodiments can be implemented in both
longitudinal and perpendicular magnetic recording medium. For
example, other embodiments can include the combinations of mixing a
first ferromagnetic layer that is perpendicular or longitudinal
with a second ferromagnetic layer can also be perpendicular or
longitudinal.
[0022] All of these embodiments of the magnetic recording medium
can be used in a hard disc drive, which comprises the magnetic
recording medium described in the embodiments above, a motor for
spinning the magnetic recording medium about its center and a
transducer for reading and writing on the magnetic recording medium
while the magnetic recording medium is rotated about by the
motor.
[0023] Other embodiments of the perpendicular magnetic media
structure can include various thicknesses and compositions.
BRIEF DESCRIPTION OF THE INVENTION
[0024] FIG. 1 is a block diagram showing a prior art
anti-ferromagnetically coupled magnetic media structure.
[0025] FIG. 2A is a block diagram showing a ferromagnetically
coupled longitudinal magnetic media structure in accordance with
one embodiment of the invention.
[0026] FIG. 2B is a block diagram showing a perpendicular magnetic
media structure similar to the one shown in FIG. 2A in accordance
with one embodiment of the invention.
[0027] FIG. 3A is a block diagram showing a ferromagnetically
coupled longitudinal magnetic media structure having interface
layers in accordance with another embodiment of the invention.
[0028] FIG. 3B is a block diagram showing a perpendicular magnetic
media structure similar to the one shown in FIG. 3A in accordance
with one embodiment of the invention.
[0029] FIG. 4A is a block diagram showing a ferromagnetically
coupled longitudinal magnetic media structure having interface
layers in accordance with another embodiment of the invention.
[0030] FIG. 4B is a schematic drawing showing a ferromagnetically
coupled longitudinal magnetic media structure with magnetic grains
in the interface layer in accordance with another embodiment of the
invention.
[0031] FIG. 4C is a schematic drawing showing a ferromagnetically
coupled longitudinal magnetic media structure with canted magnetic
grains in the interface layer in accordance with another embodiment
of the invention.
[0032] FIG. 5A-5C are illustrations showing perpendicular
multilayer magnetic media structures similar to the ones shown in
FIG. 4A-4C.
[0033] FIG. 6-7 are graphs showing vibrating sample magnetometer
(VSM) data for samples having different thickness of magnetic
layers containing cobalt (Co).
[0034] FIG. 8 is a block diagram showing a hard drive using the
magnetic recording media described with reference to FIG. 2A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] The invention provides a system and method for high areal
density magnetic recording which includes a magnetic media
structure that has a high MrT while still being stable:
[0036] FIG. 2A illustrates a multilayer magnetic media structure
200 having a ferromagnetic coupling layer used to make stable media
with high MrT, in accordance with one embodiment of the invention.
Magnetic media structure 200 includes a substrate 210, a seed layer
and or under layer substructure 215 including one or more layers, a
first ferromagnetic layer 220, a ferromagnetic coupling layer 225,
a second ferromagnetic layer 230, a magnetic written bit boundary
235 and a protective overcoat 240.
[0037] Substrate 210 of magnetic media structure 200 is a
non-magnetic material sufficiently thick to provide sufficient
rigidity. Substrate 210 can be made out of Aluminum (Al),
nickel-phosphorus plated aluminum, Al--Mg based alloys, other
aluminum based alloys, other non-magnetic metals, other
non-magnetic alloys, glass, ceramic, polymers, glass-ceramics,
chemically treated glass, and composites and/or laminates thereof.
The seed layer and or under layer substructure 215 can vary
depending on the type of magnetic media 200. For example, if the
magnetic media 200 is longitudinal media then the seed layer and or
under layer substructure 215 includes non-magnetic seed and under
layers capable of controlling the crystallographic texture of
cobalt based alloys. More specifically, the seed layers may include
amorphous or fine grain material such as NiAl, NiP, CoW, CrTa, or
CrTi. The under layers may include Cr-based alloys. However, if the
magnetic media 200 is perpendicular media then the seed layer and
or under layer substructure 215 can include cohesive layers, soft
magnetic underlayers and interlayers. Specifically, the cohesive
layer can include Ti, Cr, CrTa, or Ta, and the soft magnetic
underlayers can include Fe or Co rich magnetic layers whereas the
interlayer structure could consist of at least one amorphous layer
such as Ta, TaCr, TiCr, or/and face-centered-cubic (FCC) layer such
as Cu, Ag, Au, Pt and hexagonal-closed-packed (HCP) layer such as
Ru, Re alloys.
[0038] First ferromagnetic layer 220 and second ferromagnetic layer
230 are magnetic materials exhibiting ferromagnetic properties.
First ferromagnetic layer refers to the ferromagnetic layer closer
to the substrate and is a stabilization layer whereas second
ferromagnetic layer refers to the ferromagnetic layer further away
from the substrate and is a main recording layer. Therefore,
throughout this specification. the terms first ferromagnetic layer
220 and second ferromagnetic layer 230 may be interchanged with
stabilization layer and main recording layer, respectively. Each of
the stabilization layer and main recording layer can exhibit
ferromagnetic or superparamagnetic properties While the entire
magnetic media structure 200 exhibits ferromagnetic properties.
First ferromagnetic layer 220 and second ferromagnetic layer 230
can be a single layer or a multi-layered ferromagnetic structure.
Some examples of first ferromagnetic layer 220 and second
ferromagnetic layer 230 are alloys containing Co, Cr, or CoCr.
These alloys containing Co, Cr or CoCr can further have elements
selected from the group Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe and Ni
added in. Other examples of first ferromagnetic layer 220 and
second ferromagnetic layer 230 include alloys containing at least
one oxide material selected from the group consisting of Si, Al,
Ti, Hf, W, Mg, Nb, Fe, B, V, Mn, Ge, Mo, Ru, Rh, Re, Pt, Zr, Y, Cr,
Sm, Co, Ni and Ta.
[0039] Some example of an alloy containing an oxide are TiO.sub.2,
Al.sub.2O.sub.3, MgO, WO.sub.3, Cr.sub.2O.sub.3, Nb.sub.2O5, ZrO2,
Ta2O5, MoO3, Y2O3, Sm2O3, CoO, and CoCrPt+SiO.sub.2.
[0040] The ferromagnetic coupling layer 225, which
ferromagnetically couples the first ferromagnetic layer 220 and the
second ferromagnetic layer 230 can be a non-magnetic conductive
layer that provides RKKY coupling, a non-magnetic conductive layer
that is ferromagnetically polarized in the presence of the first
ferromagnetic layer 220 and the second ferromagnetic layer 230, or
a weekly ferromagnetic layer that provides direct exchange
interaction coupling. Although FIG. 2A shows that ferromagnetic
coupling layer 225 is a single layer, ferromagnetic coupling layer
225 can include multiple layers as further discussed with reference
to the examples FIGS. 3 and 4 below.
[0041] Ferromagnetic coupling via non-magnetic conductive layer
that provides RKKY coupling can be achieved if the ferromagnetic
coupling layer 225 falls within specific thickness ranges. Some
examples of materials used for RKKY coupling include Ru, Rh, Ir,
Cr, Cu, Re, V as well as alloys made of these elements. For example
if the RKKY coupling layer is Ru and the ferromagnetic layers are
Co-based alloys then the ferromagnetic coupling can be achieved for
Ru thicknesses ranging between 0 to 2 angstroms, and from about 11
angstroms to 17 angstroms, and from about 25 angstroms to 31
angstroms.
[0042] Ferromagnetic coupling via a non-magnetic conductive layer
that is ferromagnetically polarized in the presence of the first
ferromagnetic layer 220 and the second ferromagnetic layer 230 can
be achieved with a ferromagnetic coupling layer 225 made of
specific materials. Some examples of materials that are suitable
for use as a ferromagnetic coupling layer 235 include Pt, Pd, and
alloys thereof which are ferromagnetically polarized when in the
presence of a ferromagnetic layer, independent of thickness when
the thickness is less than 6 nm.
[0043] Ferromagnetic coupling via a weekly ferromagnetic layer that
provides direct exchange interaction coupling can be achieved with
a ferromagnetic coupling layer 225 made of specific materials. Some
examples of materials include Co, Ni, Fe and alloys thereof having
a magnetization less than 300 emu/cm.sup.3 and preferably less than
100 emu/cm.sup.3.
[0044] Magnetic written bit boundary 235 is a schematic demarcation
which separates magnetic bits aligned in one direction from
magnetic bits aligned in another direction. The position of the
magnetic written bit boundary is determined by the writing head,
which writes in a specific area depending on the design of the
magnetic media and the magnetic head. Protective overcoat 240 is a
protective layer deposited onto over the magnetic recording stack
to protect it both during the manufacture of the hard drive or
during operation of the hard drive. Protective overcoat 240 can be
a carbon containing layer such as diamond-like-carbon which is
sputtered onto the second ferromagnetic layer 230. The thickness of
protective overcoat 240 can be less than 50 angstroms and is
preferably less than 30 angstroms.
[0045] The magnetic media structure of FIG. 2A shows first
ferromagnetic layer 220 and second ferromagnetic layer 230 are
ferromagnetically coupled together through ferromagnetic coupling
layer 225. The arrows shown in first ferromagnetic layer 220 and
second ferromagnetic layer 230 represent the direction in which the
magnetic written bits within these layers are magnetized. The
arrows represent the direction of the magnetic written bit moments
in the absence of a magnetic field, which is also referred to as
the remnant moment. The right magnetic written bits in both first
ferromagnetic layer 220 and second ferromagnetic layer 230 are
coupled together ferromagnetically pointing in the same direction
towards the left of the FIG. 2A. Similarly, the left magnetic
written bits in both first ferromagnetic layer 220 and second
ferromagnetic layer 230 are coupled together ferromagnetically
pointing in the same direction towards the right of the FIG.
2A.
[0046] The magnetic media structure described with reference to
FIG. 2A above is made using magnetic media manufacturing processes
well known in the art. Conventional media manufacturing processes
include texturing substrate 210, cleaning substrate 210, and
depositing layers 215 through 240. The deposition process includes
sputtering target material of usually the same material as their
respective layers so that thin films of the sputtered material grow
on the substrate. The deposition process is usually done at ambient
temperatures and only after the deposition chamber has been
evacuated to low pressures.
[0047] The magnetic layers of the alloy perpendicular or
longitudinal recording media, which include a single or a couple of
magnetic layers wherein the thickness of each layer can range from
one atomic layer (monolayer) to thicknesses of about several
hundred angstroms, are typically deposited onto cold substrates or
substrates that have been heated to high temperatures, such as
250.degree. C.
[0048] FIG. 2B illustrates a perpendicular multilayer magnetic
media structure similar to the one shown in FIG. 2A except that it
shows perpendicular recording as oppose to longitudinal recording.
In FIG. 2A the magnetic domains found within first ferromagnetic
layer 220 and second ferromagnetic layer 220 are aligned parallel
to the substrate 210 and longitudinal to the plane of the film
whereas in FIG. 2B the magnetic domains of first ferromagnetic
layer 220 and second ferromagnetic layer 220 are aligned
perpendicular to the substrate 210 and perpendicular to the plane
of the film. The magnetic media structure of FIG. 2B shows first
ferromagnetic layer 220 and second ferromagnetic layer 230 are
ferromagnetically coupled together through ferromagnetic coupling
layer 225. The arrows shown in first ferromagnetic layer 220 and
second ferromagnetic layer 230 represent the direction in which the
magnetic written bits within these layers are magnetized in the
absence of an external magnetic field. The right magnetic written
bits in both first ferromagnetic layer 220 and second ferromagnetic
layer 230 are coupled together ferromagnetically pointing in the
same direction towards the substrate 210. Similarly, the left
magnetic written bits in both first ferromagnetic layer 220 and
second ferromagnetic layer 230 are coupled together
ferromagnetically pointing in the same direction away from the
substrate 210.
[0049] FIG. 3A illustrates another magnetic media structure 300
having a ferromagnetic coupling layer in accordance with another
embodiment of the invention. Magnetic media structure 300 includes
a substrate 210, a seed layer and or under layer substructure 215
including one or more layers, a first ferromagnetic layer 220, a
first interface layer 310, a ferromagnetic coupling layer 225, a
second interface layer 315, a second ferromagnetic layer 230, a
magnetic written bit boundary 235, and a protective overcoat 240.
In magnetic media structure 300 there is an interface layer between
the first ferromagnetic layer 220 and the ferromagnetic coupling
layer 225 as well as between the second ferromagnetic layer 230 and
the ferromagnetic coupling layer 225. First interface layer 310 and
the second interface layer 315 can be made of materials having
large magnetic moments with magnetic saturations greater than 300
emu/cm.sup.3 (M.sub.5>300 emu/cm.sup.3) and preferably greater
than 500 emu/cm.sup.3 (M.sub.s>500 emu/cm.sup.3). Some examples
of materials that can be used for first interface layer 310 and
second interface layer 315 include materials having high moment
elements such as Fe or Co or alloys made of Fe or Co mixed with one
or more added elements including Cr, Pt, Ta, B, Mo, Pd, Cu, Au, Ti,
W, Ru, Si, Ge, Nb, or Ni.
[0050] FIG. 3B illustrates a perpendicular multilayer magnetic
media structure similar to the one shown in FIG. 3A except that it
shows perpendicular recording as oppose to longitudinal recording.
In FIG. 3A the magnetic domains found within first ferromagnetic
layer 220, second ferromagnetic layer 230, first interface layer
310, and second interface layer 315 are aligned parallel to the
substrate 210 and longitudinal to the plane of the film whereas in
FIG. 3B the magnetic domains of first ferromagnetic layer 220,
second ferromagnetic layer 230, first interface layer 310, and
second interface layer 315 are aligned perpendicular to the
substrate 210 and perpendicular to the plane of the film. The
magnetic media structure of FIG. 3B shows first ferromagnetic layer
220 and second ferromagnetic layer 230 are ferromagnetically
coupled together through first interface layer 310, second
interface layer 315, and spacer layer 330. The arrows shown in
first ferromagnetic layer 220 and second ferromagnetic layer 230
represent the direction in which the magnetic written bits within
these layers are magnetized in the absence of an external magnetic
field. The right magnetic written bits in both first ferromagnetic
layer 220 and second ferromagnetic layer 230 are coupled together
ferromagnetically pointing in the same direction toward the
substrate 210. Similarly, the left magnetic written bits in both
first ferromagnetic layer 220 and second ferromagnetic layer 230
are coupled together ferromagnetically pointing in the same
direction away from the substrate 210.
[0051] FIG. 4A-4C illustrate three other longitudinal magnetic
media structures having ferromagnetic coupling in accordance with
other embodiments of the invention. In the embodiments of FIG.
4A-4C, the two ferromagnetic layers are ferromagnetically coupled
indirectly by two anti-ferromagnetically coupled layers. The
ferromagnetic coupling section can be a) two non-magnetic spacer
layers separated by a magnetic interface layer as further discussed
with reference to FIG. 4A, or b) a non-magnetic spacer layer with a
magnetic grain structure located in the middle of the layer as
further discussed with reference to FIG. 4B, or c) a non-magnetic
spacer layer with magnetic grains substantially uniformly
distributed across a non-magnetic spacer layer as further discussed
with reference to FIG. 4C. In the three embodiments of FIG. 4A-4C,
the interaction between the first ferromagnetic layer and second
ferromagnetic layer is provided via RICKY coupling across the
ferromagnetic coupling layer.
[0052] FIG. 4A is a block diagram showing a ferromagnetically
coupled longitudinal magnetic media structure having interface
layers in accordance with an embodiment of the invention. FIG. 4A
shows a first ferromagnetic layer 220, a second ferromagnetic layer
230 and a ferromagnetic coupling layer which further includes an
interface layer 410, a first spacer layer 415, and a second spacer
layer 420. Interface layer 410 can be made of materials having
large magnetic moments with magnetic saturations greater than 300
emu/cm.sup.3 (M.sub.s>300 emu/cm.sup.3) and preferably greater
than 500 emu/cm.sup.3 (M.sub.s>500 emu/cm.sup.3). Some examples
of materials that can be used for interface layer 410 include
materials having high moment elements such as Fe or Co or alloys
made of Fe or Co mixed with one or more added elements including
Cr, Pt, Ta, B, Mo, Ru, Si, Ge, Nb, or Ni. Additionally, interface
layer 410 can be a continuous film or discontinuous film depending
on the material used or the conditions used to deposit the film.
First spacer layer 415 and a second spacer layer 420 can generally
consist of most non-magnetic material or composition. Some specific
examples of materials useable for first spacer layer 415 and second
spacer layer 420 include Ru, Rh, Ir, Cr, Cu, Re, V and alloys made
of these elements. The thickness of first spacer layer 415 and
second spacer layer 420 are chosen to maximize anti-ferromagnetic
coupling between the magnetic interface layer 410 and both first
ferromagnetic layer 220 and second ferromagnetic layer 230. The
thickness of first spacer layer 415 and second spacer layer 420
ranges from 4 to 10 angstroms, which is approximately 2-3
monolayers.
[0053] FIG. 4B is a schematic drawing showing a ferromagnetically
coupled longitudinal magnetic media structure with magnetic grains
in the interface layer in accordance with another embodiment of the
invention. Some examples of materials that can be used for magnetic
grains in the interface layer 225 include materials having high
moment elements such as Fe or Co or alloys made of Fe or Co mixed
with one or more added elements including Cr, Pt, Ta, B, Mo, Ru,
Si, Ge, Nb, or Ni.
[0054] FIG. 4C is a schematic drawing showing a ferromagnetically
coupled longitudinal magnetic media structure with canted magnetic
grains in the interface layer in accordance with another embodiment
of the invention. Some examples of materials that can be used for
magnetic grains in the interface layer 225 include materials having
high moment elements such as Fe or Co or alloys made of Fe or Co
mixed with one or more added elements including Cr, Pt, Ta, B, Mo,
Ru, Si, Ge, Nb or Ni.
[0055] FIG. 5A-5C illustrate perpendicular multilayer magnetic
media structures similar to the ones shown in FIG. 4A-4C with the
exception that these show perpendicular recording as oppose to
longitudinal recording. In FIG. 4A-4C the magnetic domains found
within first ferromagnetic layer 220, second ferromagnetic layer
230 and the interface layer 410 are aligned parallel to the
substrate 210 and longitudinal to the plane of the film whereas in
FIG. 5A-5C the magnetic domains of first ferromagnetic layer 220,
second ferromagnetic layer 230, and the interface layer 410 are
aligned perpendicular to the substrate 210 and perpendicular to the
plane of the film. The magnetic media embodiments illustrated in
FIG. 5A-5C show the first ferromagnetic layer 220 and the second
ferromagnetic layer 230 ferromagnetically coupled together through
the interface layer 410. The arrows shown in first ferromagnetic
layer 220 and second ferromagnetic layer 230 represent the
direction in which the magnetic written bits within these layers
are magnetized in the absence of an external magnetic field. The
right magnetic written bits in both first ferromagnetic layer 220
and second ferromagnetic layer 230 are coupled together
ferromagnetically pointing in the same direction toward the
substrate 210. Similarly, the left magnetic written bits in both
first ferromagnetic layer 220 and second ferromagnetic layer 230
are coupled together ferromagnetically pointing in the same
direction away from the substrate 210.
[0056] In addition to magnetic media structures with first
ferromagnetic layer 220 and second ferromagnetic layer 230 having
the same magnetic orientation, as described above with reference to
FIGS. 2-5C, other combinations are possible. Other combinations
include a mixture of a first ferromagnetic layer that is
perpendicular or longitudinal with a second ferromagnetic layer can
also be perpendicular or longitudinal. The first of these
combinations is a magnetic recording medium having a first
ferromagnetic layer, a second ferromagnetic layer, and a
ferromagnetic coupling layer to ferromagnetically couple the first
ferromagnetic layer to the second ferromagnetic layer wherein the
magnetocrystalline anisotropy of the first and second ferromagnetic
layers are perpendicular to the film plane. The second of these
combinations is a magnetic recording medium having a first
ferromagnetic layer, a second ferromagnetic layer, and a
ferromagnetic coupling layer to ferromagnetically couple the first
ferromagnetic layer to the second ferromagnetic layer wherein the
magnetocrystalline anisotropy of the first and second ferromagnetic
layers are parallel to the film plane. The third of these
combinations is a magnetic recording medium having a first
ferromagnetic layer, a second ferromagnetic layer, and a
ferromagnetic coupling layer to ferromagnetically couple the first
ferromagnetic layer to the second ferromagnetic layer wherein the
magnetocrystalline anisotropy of the first ferromagnetic layer is
perpendicular to the film plane and the magnetocrystalline
anisotropy of the second ferromagnetic layer is parallel to the
film plane. The fourth of these combinations is a magnetic
recording medium having a first ferromagnetic layer, a second
ferromagnetic layer, and a ferromagnetic coupling layer to
ferromagnetically couple the first ferromagnetic layer to the
second ferromagnetic layer, wherein the magnetocrystalline
anisotropy of the first ferromagnetic layer is parallel to the film
plane and the magnetocrystalline anisotropy of the second
ferromagnetic layer is perpendicular to the film plane.
[0057] FIG. 6 is a graph showing vibrating sample magnetometer
(VSM) data for samples having different thickness of magnetic
layers containing cobalt (Co) made in accordance with an embodiment
of this invention. FIG. 6 data is for a magnetic media structure
sputtered on Al/NiP substrates having a Cr underlayer, a
paramagnetic hexagonal intermediate layer, a CoCr magnetic layer,
CoCrPtB magnetic layers, Co interface layers, and a Ru/Co/Ru
ferromagnetically coupled (FC) layer. Specifically the magnetic
media structure of FIG. 6 is
Cr/CoCr/CoCrPtB/Co/Ru/Co(varied)/Ru/Co/CoCrPtB. The thickness of Ru
spacer layers is about 0.6 nm and is chosen to achieve maximum
anti-ferromagnetic coupling between CoCrPtB/Co and the Co that is
located in-between Ru spacer layers and is labeled as Co(varied) in
the above structure. A 35 .ANG. overcoat was applied using
magnetron sputtering to protect the films from corrosion.
[0058] FIGS. 6 and 7 data shows that when the thickness of the Co
layer in the Ru/Co/Ru ferromagnetic coupling layer increases, the
coercivity of the magnetic media structure decreases. Additionally,
the data shows that when the Co layer thickness in the Ru/Co/Ru
ferromagnetic coupling layer is larger than 0.15 nm, the coupling
constant J.sub.r first increases then decreases.
[0059] For simplicity the CoCrPtB/Co layers located between the
CoCr.sub.37 and Ru layers will be labeled as bottom layers (BL) and
the Co/CoCrPtB layers that are located above Ru will be labeled as
top layers (TL), in the
Cr/CoCr37/CoCrPtB/Co/Ru/Co(varied)/Ru/Co/CoCrPtB structure. When
the applied magnetic field is zero, both TL and BL point in the
same direction if the ferromagnetic coupling is large enough to
overcome the magnetostatic interaction between TL and BL. If the
applied external magnetic field is larger than the exchange field,
due to the ferromagnetic coupling between magnetic layers, then the
BL will orient in the direction of the applied external magnetic
field. Since TL experiences both the applied external magnetic
field and the field due to the interaction with the BL, there is a
reduction in the coercivity field of the TL.
[0060] FIGS. 6 and 7 data also shows that when the Co layer
thickness in the Ru/Co/Ru ferromagnetic coupling layer is less than
0.15 nm (Co<0.15 nm), the strength of the ferromagnetic
interaction is similar to the strength of the magnetostatic
interaction. When the thickness of the Co layer is approximately
0.7 nm, the ferromagnetic interaction is strong enough to overcome
the magnetostatic interaction and orient TL and BL parallel at a
zero applied external magnetic field.
[0061] There are several differences between anti-ferromagnetically
coupled (AFC) media and ferromagnetically coupled (FC) media. In
order to compare and contrast AFC media and FC media, AFC and FC
media having the substantially the same MrT are compared. The
coupling strength between the magnetic layers in AFC and FC media
is substantially similar. The stability of the main recording
layer, which is the second ferromagnetic layer 230, in both the AFC
and FC media increases as a result of the coupling with the
stabilization layer, which is the first ferromagnetic layer 220.
The increase in stability depends on the coupling strength between
main recording layer 230 and the stabilization layer 220. One
difference between AFC media and FC media, which makes AFC media
advantages, is that the remanent coercivity of the AFC media
increases as a result of the coupling while the remanent coercivity
of the FC media decreases as a result of the coupling. Another
difference is that AFC media has a better switching field
distribution (SFD) than FC media.
[0062] There are also several differences between conventional
media, which is not AFC, and ferromagnetically coupled (FC) media.
In order to compare and contrast conventional media and FC media,
conventional and FC media having substantially the same MrT are
compared. The remanent coercivity of the of the main recording
layer in FC media can be reduced via coupling whereas conventional
media does not have this advantage. Another difference is that the
main recording layer in FC media is thinner than it is in
conventional media, which is an advantage if the writing bubble in
BL is significantly bigger than in the main recording layer.
[0063] FIG. 8 is an exploded perspective view of a magnetic hard
drive, which uses a magnetic recording media made using a substrate
made in accordance with an embodiment of this invention. The
magnetic hard drive 800, illustrated in FIG. 8, includes a housing
805 further having a base 810 sealed to a cover 815 by a seal 820.
The hard drive 800 also includes a spindle 830 to which is attached
one or more magnetic recording media 200 having surfaces 840
covered with a magnetic recording media (not shown) for
magnetically storing information. Although FIG. 8 illustrates a
hard drive 800 using several magnetic recording media 200, only one
surface is required to make the hard drive 800 operational. A
spindle motor (not shown in this figure) rotates the plurality of
magnetic recording media 200 past read/write heads 845 that are
suspended above surfaces 840 of the magnetic recording media 200 by
a suspension arm assembly 850. Under normal operating conditions,
the spindle motor rotates the magnetic recording media 200 at high
speeds past the read/write heads 845 while the suspension arm
assembly 850 moves and positions the read/write heads over one of
several radially spaced tracks (not shown). This allows the
read/write heads 845 to read and write magnetically encoded
information to the surfaces 840 of the magnetic recording media 200
at selected locations.
[0064] It will also be recognized by those skilled in the art that,
while the invention has been described above in terms of preferred
embodiments, it is not limited thereto. Various features and
aspects of the above-described invention may be used individually
or jointly. Further, although the invention has been described in
the context of its implementation in a particular environment and
for particular applications, those skilled in the art will
recognize that its usefulness is not limited thereto and that the
present invention can be utilized in any number of environments and
implementations.
* * * * *