I 1111111111111111 11111 111111111111111 1111111111 11111 111111111111111 11111111
`US007968219Bl
`
`c12) United States Patent
`Jiang et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,968,219 Bl
`Jun. 28, 2011
`
`(54) MAGNETICALLY SOFT, HIGH SATURATION
`MAGNETIZATION LAMINATE OF
`IRON-COBALT-NITROGEN AND
`IRON-NICKEL FOR PERPENDICULAR
`MEDIA UNDERLAYERS
`
`(75)
`
`Inventors: Hai Jiang, Fremont, CA (US); Kyusik
`Sin, Pleasanton, CA (US); Yingjian
`Chen, Fremont, CA (US)
`
`(73) Assignee: Western Digital (Fremont), LLC,
`Fremont, CA (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 62 days.
`
`(21) Appl. No.: 12/033,991
`
`(22) Filed:
`
`Feb.20,2008
`
`Related U.S. Application Data
`
`(60) Division of application No. 10/854,119, filed on May
`25, 2004, now Pat. No. 7,354,664, which is a
`continuation-in-part of application No. 10/137,030,
`filed on May 1, 2002, now Pat. No. 6,778,358.
`
`(51)
`
`Int. Cl.
`GllB 5166
`(2006.01)
`(52) U.S. Cl. ......................... 428/829; 428/821; 428/827
`(58) Field of Classification Search ........................ None
`See application file for complete search history.
`
`(56)
`
`References Cited
`
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`11/2003 Litvinov et al.
`(Continued)
`
`OTHER PUBLICATIONS
`
`Soft High Saturation Magnetization (Fe0.7Co0.3)1-xNx Thin Films
`for Inductive Write Heads, Sun et al, IEEE Transactions on Magnet(cid:173)
`ics, vol. 36, No. 5 Sep. 2000.*
`
`(Continued)
`
`Primary Examiner - Mark Ruthkosky
`Assistant Examiner - Gary Harris
`
`ABSTRACT
`(57)
`A magnetic disk includes a substrate, a soft magnetic under(cid:173)
`layer disposed over the substrate, and a media layer disposed
`over the underlayer. The underlayer includes a first plurality
`oflayers each containing NiFe having an atomic concentra(cid:173)
`tion of iron that is at least about thirty percent. The underlay er
`further includes a second plurality oflayers that is interleaved
`with the first plurality oflayers. The second plurality oflayers
`each contain FeCoN having an atomic concentration of iron
`that is greater than an atomic concentration of cobalt, and
`having an atomic concentration of nitrogen that is less than
`the atomic concentration of cobalt. The atomic concentration
`of nitrogen is less than eight percent. The media layer con(cid:173)
`tains a magnetically hard material having an easy axis of
`magnetization oriented substantially perpendicular to both
`the media layer and the underlayer.
`
`6 Claims, 4 Drawing Sheets
`
`44
`
`42
`
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`US 7,968,219 Bl
`Page 2
`
`360/125.5
`
`U.S. PATENT DOCUMENTS
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`11/2004 Girt
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`6,943,041 B2
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`8/2006 Haginoya et al.
`7,177,117 Bl
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`4/2008 Jiang et al.
`2001/0008712 Al
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`2002/0109947 Al * 8/2002 Khizroev et al.
`360/319
`2003/0022023 Al *
`1/2003 Carey et al . ........... 428/694 MM
`2003/0197988 Al
`10/2003 Hasegawa et al.
`2005/0011590 Al
`1/2005 Kawasaki et al.
`OTHER PUBLICATIONS
`
`B. Viala, et al., "Microstructure and Magnetism in FeTaN Films
`Deposited in the Nanocrystalline State", Journal of Applied Physics,
`80(7), Oct. 1996, pp. 3941-3956.
`N.X. Sun, et al., "Microstructure and Soft Magnetic Properties of
`High Saturation Magnetization Fe-Co-N alloy Thin Films", Materi(cid:173)
`als Research Society Symposium, vol. 614, Apr. 2000, pp. F9.2.l(cid:173)
`F9.2.12.
`S. Nakagawa, et al., "Improvement of soft magnetism of Fe90Co 10
`sputtered films by addition ofN and Ta", Journal of Applied Physics,
`79(8), Apr. 1996, pp. 5156-5158.
`
`C.L. Platt, et al., "Magnetic and Structural Properties ofFeCoB Thin
`Films", IEEE Transactions on Magnetics, vol. 37, No. 4, Jul. 2001,
`pp. 2302-2304.
`E.J. Yun, et al., "Magnetic Properties of RF Diode Sputtered
`CoxFelO0-x Alloy Thin Films", IEEE Transactions on Magnetics,
`vol. 32, No. 5, Sep. 1996, pp. 4535-4537.
`N.X. Sun, et al., "Soft High Saturation Magnetization (Fe0.7 Co0.
`3)1-xNx Thin Films for Inductive Write Heads", IEEE Transactions
`on Magnetics, vol. 36, No. 5, Sep. 2000, pp. 2506-2508.
`T. Nozawa, et al., "Magnetic Properties ofFeCoV Film Sandwiched
`by Thin Soft-Magnetic Films", IEEE Transactions on Magnetics, vol.
`37, No. 4, Jul. 2001, pp. 3033-3038.
`X. Liu, et al., "High Moment FeCoNi Alloy Thin Films Fabricated by
`Pulsed-Current Electrodeposition", IEEE Transactions on Magnet(cid:173)
`ics, vol. 37, No. 4, Jul. 2001, pp. 1764-1766.
`S. Wang et al., Improved high moment FeAIN/Si02 Laminated Mate(cid:173)
`rials for Thin Film Recording Heads, IEEE Transactions on Magnet(cid:173)
`ics, vol. 27, Nov. 1991, pp. 4879-4881.
`B.D. Cullity, "Introduction to Magnetic Materials", Addison-Wesley,
`1972, pp. 148.
`Rigano et al., "Magnetic Properties of Re-TM-N System", vol .
`Mag-23, No. 5, Sep. 1987.
`T. Ichihara et al., "Improvement of the Magnetic Characteristic of
`Multilayered Ni-Fe thin Films by Supplying External In-Plane
`Field during Sputtering", IEEE Transactions on Magnetics, vol. 32,
`No. 5, Sep. 1996, pp. 4582-4584.
`S. Nakagawa et al., "Soft Magnetic and Crystallographic Properties
`of Ni.sub.81Fe.sub.19/Co.sub.67Cr.sub.33 Multilayers as Backlay(cid:173)
`ers in Perpendicular Recording", IEEE Transactions on Magnetics,
`vol. 30, No. 4, 1994, pp. 4020-4022.
`N.R. Darragh et al., "Observation ofUnderlayer Domain Noise in
`Perpendicular Recording Disks", IEEE Transactions on Magnetics,
`vol. 29, No. 6, Nov. 1993, pp. 3742-3744.
`Parkin et al.,
`"Oscillations
`in Exchange Coupling and
`Magnetoresistance in Metallic Superlattice Structures: Co/Ru, Co/Cr
`and Fe/Cr", Phys. Rev. Lett., vol. 64, 1990, pp. 2034.
`
`* cited by examiner
`
`Ex.1033 / IPR2022-00117 / Page 2 of 10
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`

`U.S. Patent
`
`Jun.28,2011
`
`Sheet 1 of 4
`
`US 7,968,219 Bl
`
`20 ----.
`
`24
`
`22
`
`28
`
`FIG. 1
`
`44
`
`42
`
`46
`FIG. 2
`
`1.5
`
`0.5
`
`(Normalized
`Magnetization) 0
`
`-0.5
`
`-1.5
`-40
`
`-30
`
`20
`10
`0
`-10
`-20
`(Applied Field; Oersted)
`FIG. 3
`
`30
`
`40
`
`Ex.1033 / IPR2022-00117 / Page 3 of 10
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`

`

`U.S. Patent
`
`Jun.28,2011
`
`Sheet 2 of 4
`
`US 7,968,219 Bl
`
`-~
`
`"d
`(I)
`.!:::
`""@
`E
`!-
`0
`b
`
`1.05
`
`1.00
`
`0.95
`
`0
`
`2
`
`4
`
`6
`
`8
`
`10
`
`(N%)
`
`FIG. 4
`
`\
`I
`(
`_ _ _ _ _ J.... _ _ _ _ _ _ _ _ _
`
`153
`
`155
`
`158
`
`180
`
`171
`
`152
`
`170
`
`166
`
`156
`
`159
`
`FIG. 6
`
`,150
`
`Ex.1033 / IPR2022-00117 / Page 4 of 10
`APPLE INC. v. SCRAMOGE TECHNOLOGY, LTD.
`
`

`

`U.S. Patent
`
`Jun.28,2011
`
`Sheet 3 of 4
`
`US 7,968,219 Bl
`
`If)
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`
`Ex.1033 / IPR2022-00117 / Page 5 of 10
`APPLE INC. v. SCRAMOGE TECHNOLOGY, LTD.
`
`

`

`U.S. Patent
`
`Jun.28,2011
`
`Sheet 4 of 4
`
`US 7,968,219 Bl
`
`1.5
`
`1.0
`
`,,
`
`,
`
`0. 5 c - - - - - - - - - -4-----
`C - - - - - - - - i- 12 _ __l_ __ _
`
`(N ormalized
`Magnetization) 0
`
`'
`
`- - - - - -~ - -~ - - - - - - - - , - - - - - - - - - ~ - - - - - - - - - - -
`
`'
`
`'------~--~--~-1 __ 2 ___ -±-__ ---------
`
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`
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`
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`
`50
`25
`0
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`-50
`(Applied Field; Oersted)
`FIG. 7 (Prior Art)
`
`75
`
`100
`
`Ex.1033 / IPR2022-00117 / Page 6 of 10
`APPLE INC. v. SCRAMOGE TECHNOLOGY, LTD.
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`

`US 7,968,219 Bl
`
`1
`MAGNETICALLY SOFT, HIGH SATURATION
`MAGNETIZATION LAMINATE OF
`IRON-COBALT-NITROGEN AND
`IRON-NICKEL FOR PERPENDICULAR
`MEDIA UNDERLAYERS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a divisional of U.S. patent application
`Ser. No. 10/854,119, filed May 25, 2004, which is a continu(cid:173)
`ation-in-part of U.S. patent application Ser. No. 10/137,030,
`filed May 1, 2002, now U.S. Pat. No. 6,778,358, granted Aug.
`17, 2004, both of which are incorporated by reference herein
`in their entirety. Also incorporated by reference is U.S. patent
`application Ser. No. 10/853,416, filed May 24, 2004.
`
`TECHNICAL FIELD
`
`The present invention relates to magnetic media, for
`example magnetic disks or tapes for information storage sys(cid:173)
`tems such as disk or tape drives.
`
`BACKGROUND
`
`Electromagnetic transducers such as heads for disk or tape
`drives commonly include Permalloy (approximately Ni_ 81
`Fe 19), which is formed in thin layers to create magnetic
`fe~tures. Permalloy is known to be magnetically "soft," that
`is, to have high permeability and low coercivity, allowing
`structures made of Permalloy to act like good conductors of
`magnetic flux. Disks having a media layer that stores mag(cid:173)
`netic bits in a direction substantially perpendicular to the
`media surface, sometimes termed "perpendicular recording,"
`have been proposed to have a soft magnetic underlayer of
`permalloy or the like.
`For example, an inductive head may have conductive coils
`that induce magnetic flux in an adjacent Permalloy core, that
`flux employed to magnetize a portion or bit of an adjacent
`media. That same inductive head may read signals from the
`media by bringing the core near the magnetized media por(cid:173)
`tion so that the flux from the media portion induces a flux in
`the core, the changing flux in the core inducing an electric
`current in the coils. Alternatively, instead of inductively sens(cid:173)
`ing media fields, magnetoresistive (MR) sensors or merged
`heads that include MR or giant magnetoresistive (GMR) sen(cid:173)
`sors may use thinner layers of Permalloy to read signals, by
`sensing a change in electrical resistance of the sensor that is
`caused by the magnetic signal. For perpendicular recording,
`the soft magnetic underlay er of the disk as well as the soft
`magnetic core of the head may together form a magnetic
`circuit for flux that travels across the media layer to write or
`read information.
`In order to store more information in smaller spaces, trans(cid:173)
`ducer elements have decreased in size for many years. One
`difficulty with this deceased size is that the amount of flux that
`needs to be transmitted may saturate elements such as mag(cid:173)
`netic pole layers, which becomes particularly troublesome
`when ends of the pole layers closest to the media, commonly
`termed pole tips, are saturated. Magnetic saturation in this
`case limits the amount of flux that is transmitted through the
`pole tips, limiting writing or reading of signals. Moreover,
`such saturation may blur that writing or reading, as the flux
`may be evenly dispersed over an entire pole tip instead of 65
`being focused in a corner that has relatively high flux density.
`For these reasons the use of high magnetic saturation mate-
`
`2
`rials (also known as high moment or high Bs materials) in
`magnetic core elements has been known for many years.
`For instance, iron is known to have a higher magnetic
`moment than nickel, so increasing the proportion of iron
`compared to nickel generally yields a higher moment alloy.
`Iron, however, is also more corrosive than nickel, which
`imposes a limit to the concentration of iron that is feasible for
`many applications. Also, it is difficult to achieve soft mag(cid:173)
`netic properties for primarily-iron NiFe compared to prima-
`10 rily-nickel NiFe. Anderson et al., in U.S. Pat. No. 4,589,042,
`teach the use of high moment Ni.45Fe_ 55 for pole tips. Ander(cid:173)
`son et al. do not use Ni.45 Fe_ 55 throughout the core due to
`problems with permeability of that material, which Anderson
`et al. suggest is due to relatively high magnetostriction of
`15 Ni.45 Fe_ 55 .
`As noted in U.S. Pat. No. 5,606,478 to Chen et al., the use
`ofhighmoment materials has also been proposed for layers of
`magnetic cores located closest to a gap region separating the
`cores. Also noted by Chen et al. are some of the difficulties
`20 presented by these high moment materials, including chal(cid:173)
`lenges in forming desired elements and corrosion of the ele(cid:173)
`ments once formed. Chen et al. state that magnetostriction is
`another problem with Ni.4 6Fe_ 55 , and teach the importance of
`constructing of heads having Permalloy material layers that
`25 counteract the effects of that magnetostriction. This balanc(cid:173)
`ing of positive and negative magnetostriction with plural
`NiFealloys is also described in U.S. Pat. No. 5,874,0l0to Tao
`et al.
`Primarily iron FeCo alloys are known to have a very high
`30 saturation magnetization but also high magnetostriction that
`makes them unsuitable for many head applications. That is,
`mechanical stress during slider fabrication or use may perturb
`desirable magnetic domain patterns of the head. FIG. 7 shows
`a B/H loop 12 ofa FeCoN layer that was formed by sputtering
`35 deposition at room temperature, the layer having a thickness
`of approximately 500 A and having a composition of approxi(cid:173)
`mately Fe_ 66Co_ 28N_ 06 . The applied H-field is shown in oer(cid:173)
`sted (Oe) across the horizontal axis while the magnetization
`of the layer is plotted in normalized units along the vertical
`40 axis, with unity defined as the saturation magnetization for a
`given material. The FeCoN layer has a saturation magnetiza(cid:173)
`tion (BJ of approximately 24.0 kilogauss and is magnetically
`isotropic, as shown by the single B/H loop 12. B/H loop 12
`also indicates a relatively high coercivity of about 80 oersted,
`45 which may be unsuitable for applications requiring soft mag(cid:173)
`netic properties.
`In an article entitled "Microstructures and Soft Magnetic
`Properties of High Saturation Magnetization Fe----Co-N
`alloy Thin Films," Materials Research Society, Spring meet-
`50 ing, Section F, April 2000, N. X. Sun et al. report the forma(cid:173)
`tion ofFeCoN films having high magnetic saturation but also
`high magnetostriction and moderate coercivity. Sun et al. also
`report the formation of a thin film structure in which FeCoN
`is grown on and capped by Permalloy, to create a sandwich
`55 structure having reduced coercivity but compressive stress.
`The magnetostriction of this sandwich structure, while some(cid:173)
`what less than that of the single film ofFeCoN, may still be
`problematic for head applications. Such issues would be
`expected to grow with increased length of a magnetostrictive
`60 layer, so that disk layers that extend many times as far as head
`layers would appear to be poor candidates for magnetostric(cid:173)
`tive materials.
`
`SUMMARY
`
`In one embodiment, a magnetic disk is disclosed, compris(cid:173)
`ing a self-supporting substrate; a soft magnetic underlayer
`
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`US 7,968,219 Bl
`
`3
`disposed over the substrate, the underlayer including a first
`layer containing NiFe having an atomic concentration of iron
`that is at least thirty percent and not more than seventy per(cid:173)
`cent, a second layer that adjoins the first layer and contains
`FeCoN having an atomic concentration of iron that is greater
`than the second layer's atomic concentration of cobalt, hav(cid:173)
`ing an atomic concentration of nitrogen that is less than the
`second layer's atomic concentration of cobalt and less than
`about three percent; and a media layer disposed over the
`underlayer and containing a magnetically hard material hav(cid:173)
`ing an easy axis of magnetization oriented substantially per(cid:173)
`pendicular to both the media layer and the underlay er.
`The underlayer may include a first plurality oflayers each
`containing NiFe having an atomic concentration ofiron that is
`at least about thirty percent; a second plurality oflayers that is
`interleaved with the first plurality of layers, the second plu(cid:173)
`rality of layers each containing FeCoN having an atomic
`concentration of iron that is greater than an atomic concen(cid:173)
`tration of cobalt, and having an atomic concentration of nitro(cid:173)
`gen that is less than the atomic concentration of cobalt, the
`atomic concentration of nitrogen being less than eight per(cid:173)
`cent.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a cutaway cross-sectional view of a sandwich
`structure made of a primarily iron FeCoN layer affixed
`between a pair ofFeNi layers.
`FIG. 2 is a cutaway cross-sectional view of a laminated
`structure made of a plurality of primarily iron FeCoN layers
`interleaved with a plurality of primarily iron FeNi layers.
`FIG. 3 is plot of a B/H loop of the laminated structure of
`FIG. 2.
`FIG. 4 is a plot of saturation magnetization as a function of
`nitrogen content for (Fe_ 70Co_ 30)N.
`FIG. 5 is a cutaway cross-sectional view of a magnetic disk
`for perpendicular recording including a soft magnetic under(cid:173)
`layer formed of the laminated structure of FIG. 2.
`FIG. 6 is a cutaway cross-sectional view of a perpendicular
`recording head interacting with the disk of FIG. 5.
`FIG. 7 is plot of a B/H loop of a prior art FeCoN layer.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`FIG. 1 is a cutaway cross-sectional view of a sandwich
`structure 20 made of an iron-cobalt-nitride (FeCoN) layer 22
`affixed between a pair of iron-nickel (FeNi) layers 24 and 26.
`The sandwich structure 20 is formed on a substrate 28 that
`provides a smooth surface promoting favorable crystallo(cid:173)
`graphic growth oflayers 22, 24 and 26. The FeCoN layer 22
`has a thickness of approximately 4 7 5 A and has a composition
`of approximately Fe_ 69Co_ 30N_ 01 . The FeNi layers 24 and 26
`each have a thickness of approximately 25 A and have a
`composition of approximately Ni_ 55Fe.45 . Layers 22, 24 and
`26 were formed by DC magnetron sputtering deposition at
`room temperature. Magnetron sputtering has a deposition
`rate that is approximately ten times faster than that of RF
`sputtering, which is an advantage in commercial applications
`such as magnetic head production. The substrate may be a 60
`silicon dioxide, alumina, chromium, tantalum or titanium, for
`example.
`FIG. 2 is a cutaway cross-sectional view of a laminated
`structure 40 made of a plurality of primarily iron FeCoN
`layers 42 interleaved with a plurality of primarily iron FeNi 65
`layers 44. The sandwich structure 20 is formed on a substrate
`46 that provides a surface promoting favorable microstruc-
`
`4
`tural growth oflayers 42 and 44. The FeCoN layers 42 each
`have a thickness of approximately 475 A and a composition
`of approximately Fe_ 69Co_ 30N_ 01 . The FeNi layers 42 each
`have a thickness of approximately 25 A and have a composi(cid:173)
`tion of approximately Ni_ 55Fe.45 . Layers 42 and 44 were
`formed by magnetron sputtering deposition on substrate 46 at
`room temperature. Various other compositions and thick(cid:173)
`nesses may also be suitable. For example, the FeCoN layers
`may have atomic concentrations of iron in a range between
`10 50% and 80%, atomic concentrations of cobalt in a range
`between 17% and 50%, and atomic concentrations of nitro(cid:173)
`gen in a range between 0.01 % and 3%. As another example,
`the NiFe layers may have atomic concentrations of iron in a
`range between 30% and 70%, and atomic concentrations of
`15 nickel in a range between 70% and 30%. The thickness of any
`of the layers may for example be in a range between a few
`angstroms and one hundred nanometers.
`FIG. 3 shows B/H loops 30 and 33 for the laminated struc(cid:173)
`ture 40 of FIG. 2 having an overall thickness of about 2500 A.
`20 The laminated structure has a saturation magnetization (Bs)
`of approximately 2.4 tesla (T), nearly that of the single layer
`ofFeCoN. The coercivity of the hard axis, which is defined as
`the applied field of the loop 30 at which the magnetization is
`zero, is about 4 oersted (Oe) while the coercivity of the easy
`25 axis is about 12 Oe as shown by loop 33. The permeability is
`approximately 2000, and the laminate has been found to be
`suitable for applications such as soft magnetic underlayers for
`magnetic disks.
`FIG. 4 is a plot 60 of experimentally determined saturation
`30 magnetization Bs of FeCoN for various concentrations of
`nitrogen gas, normalized for zero nitrogen. The plot 60 was
`generated using a sputtering target ofFe_ 70Co_ 30 and varying
`the amount of nitrogen gas. The concentration of nitrogen in
`the solid layer ofFeCoN has been found to be about the same
`35 as that in the gas. At the wafer formation level, the concen(cid:173)
`tration of various elements can be determined by Auger Elec(cid:173)
`tron Spectroscopy (AES) or Electron Energy Loss Spectros(cid:173)
`copy (EELS), while concentrations of various elements of a
`layer in a completed device such as a magnetic disk can be
`40 determined by Transmission Electron Microscopy (TEM).
`The plot 60 has a peak saturation magnetization Bs at about
`1 % nitrogen, with Bs generally declining as the nitrogen con(cid:173)
`tent is increased above 1 %. The coercivity generally increases
`as the nitrogen content of FeCoN layers declines from
`45 approximately 7%, however, arguing against the use of low
`nitrogen content FeCoN in magnetic disks.
`A laminated structure of FeCoN/NiFe having a coercivity
`below 12 Oe and a Bs above 2.3 T may be desirable for
`applications such as soft magnetic underlayers for disks. In
`50 this case, the magnetically soft, high Bs laminate 40 used in a
`soft magnetic underlayer of a perpendicular recording disk
`may include FeCoN with a nitrogen concentration as high as
`about eight percent. Such a laminated soft magnetic under(cid:173)
`layer may be formed entirely of alternating layers ofFeCoN
`55 and NiFe, which, because of the high Bs compared to tradi(cid:173)
`tional underlayers, may have an overall thickness of about
`2000 A or less.
`A media layer 158 is disposed over the underlay er 155, the
`media layer having an easy axis of magnetization that is
`substantially perpendicular to a major surface 153 of the
`medium. A thin, physically hard overcoat 156 separates the
`media layer 158 from the medium surface 153. The medium
`150, which may for example be a rigid disk, is moving relative
`to the head in a direction shown by arrow 159. The head 100
`may be spaced from the medium 150 by a nanoscale air
`bearing, or the head may be in frequent or continuous contact
`with the medium during operation. The word nanoscale as
`
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`US 7,968,219 Bl
`
`5
`used herein is meant to represent a size that is most conve(cid:173)
`niently described in terms of nanometers, e.g., between about
`one nanometer and about two hundred nanometers.
`FIG. 5 is a cutaway cross-sectional view of a portion of a
`medium 150 such as a disk designed for perpendicular stor(cid:173)
`age of data that is written and read by a relatively moving head
`containing an electromagnetic or electrooptical transducer.
`The medium 150 includes a substrate 152 that, for the case in
`which the medium is a disk for a hard disk drive, may be made
`of glass, aluminum or other materials. The substrate 152 may
`be textured, or an optional texture layer 151 may provided
`that promotes favorable growth of a soft magnetic underlayer
`155. For example, a substrate 152 of an aluminum-magne(cid:173)
`sium (AlMg) alloy may be plated with a layer of nickel
`phosphorous (NiP) to a thickness of about 15 microns that
`increases the hardness of the substrate and provides a surface
`suitable for polishing to provide a desired roughness or tex(cid:173)
`ture.
`A soft magnetic underlay er 155 has been formed of inter(cid:173)
`leaved layers of FeCoN 162 and NiFe 160 similar to that
`described above, formed to an overall thickness that is in a
`range between about 1000 A and 4000 A. The NiFe layers 160
`may contain Ni,~eci-XJ, wherein 0.3~X~0.7 and FeCoN
`layers 162 may containFeyCo2 N(l-Y-Z), wherein 0.5~Y~0.8
`and 0<(l-Y-Z)~0.03. The underlayer may be thinner than is
`conventional for perpendicular media, for example less than
`2000 A, due to the relatively high Bs of over 2.3 T. The
`coercivity of the underlay er 155 may be in a range between
`about twelve oersted and two oersted.
`The soft magnetic underlay er 155 may alternatively contain a
`plurality of magnetic layers each containing F eCoN that are
`interleaved with a plurality of much thinner nonmagnetic
`layers. For example, the underlay er may include a plurality of
`magnetic layers each containing FeCoN having an atomic
`concentration of iron that is greater than its atomic concen(cid:173)
`tration of cobalt, and having an atomic concentration of nitro(cid:173)
`gen that is less than eight percent and less than the atomic
`concentration of cobalt, the underlayer including a plurality
`of nonmagnetic layers that are interleaved with the magnetic 40
`layers, each of the nonmagnetic layers having a thickness that
`is less than one-tenth that of an adjoining layer of the mag(cid:173)
`netic layers. The coupling between adjacent magnetic layers
`that is provided by the nonmagnetic layers may reduce noise
`in the underlayer that may otherwise reduce signal integrity. 45
`As an example, the nonmagnetic layers may have a thick(cid:173)
`ness in a range between about eight angstroms and twelve
`angstroms, although a greater or smaller thickness is possible.
`The FeCoN layers may each have a thickness in a range
`between about one hundred angstroms and five hundred ang- 50
`stroms, although a greater or smaller thickness is possible.
`The underlayer may be thinner than is conventional for per(cid:173)
`pendicular media, for example less than 2000 A, due to the
`relatively high Bs of over 2.3 T. The coercivity of the under(cid:173)
`layer 155 may be in a range between about twenty oersted and 55
`two oersted.
`In one embodiment, the nonmagnetic layers may be chro(cid:173)
`mium or ruthenium, formed to a thickness in a range between
`about eight angstroms and twelve angstroms so that adjacent
`magnetic layers are exchange coupled in an antiparallel ori(cid:173)
`entations. This may be termed antiferromagnetic exchange
`coupling. In this embodiment the underlayer may have a
`substantially zero net magnetic moment, provided that an
`even number of magnetic layers of equal thickness is formed,
`or that the overall thickness of the layers having one magnetic
`orientation is substantially equal to the overall thickness of
`the magnetic layers having the opposite orientation.
`
`6
`In one embodiment, the nonmagnetic layers are made of a
`metal oxide or nitride that induces antiparallel magnetostatic
`coupling between a pair of adjacent magnetic layers. As an
`example, the metal oxide or nitride is AlxOu-XJ, Ta~(l-YJ or
`Al2 N(l-Z)· In another embodiment, to induce antiparallel
`magnetostatic coupling between a pair of adjacent magnetic
`layers, the nonmagnetic layer can be made of a metal such as
`Cu, Ti, Ta or NiCr.
`A media layer 158 is disposed over the underlay er 155, the
`10 media layer having an easy axis of magnetization that is
`substantially perpendicular to a major surface 153 of the
`medium 150. The media layer 158 may be formed of a single
`layer or of multiple layers, for example of cobalt based mag(cid:173)
`netic alloy layers interleaved with platinum group nonmag-
`15 netic layers to enhance perpendicular anisotropy. A nonmag(cid:173)
`netic exchange decoupling material may be contained in the
`media layer or layers to decouple magnetic grains for reduc(cid:173)
`ing noise. A nonmagnetic decoupling layer 164, which also
`serves as a seed layer for the media layer 158, is disposed
`20 between the underlayer 155 and the media layer, and may
`contain for example chromium (Cr) or titanium (Ti). A thin,
`physically hard overcoat 156 of diamond-like carbon (DLC),
`tetrahedral-amorphous carbon (ta-C), silicon carbide (SiC) or
`the like separates the media layer 158 from the medium
`25 surface 153. Although not shown, a thin lubricant layer may
`coat the medium surface 153.
`FIG. 6 is a cutaway cross-sectional view of a magnetic head
`100 interacting with the medium 150, which is moving rela(cid:173)
`tive to the head in a direction shown by arrow 159. The head
`30 100 has a medium-facing surface 166 disposed adjacent to the
`medium surface 153. The head 100 may be spaced from the
`medium 150 by a nanoscale air bearing, or the head may be in
`frequent or continuous contact with the medium during
`operation. The word nanoscale as used herein is meant to
`35 represent a size that is most conveniently described in terms
`of nanometers, e.g., between about one nanometer and about
`two hundred nanometers. The head 100 in this embodiment is
`designed for perpendicular recording on the medium 150, and
`includes a laminated write pole layer 101 that terminates
`adjacent to the medium-facing surface in a first pole tip 170,
`which may sometimes be called a write pole tip. The write
`pole layer 101 may be formed of a plurality oflayers ofFeNi
`interleaved with a plurality of layers of FeCoN, similar to
`laminate 40 described above.
`A soft magnetic layer 188 adjoins the write pole layer 101
`but terminates further from the medium-facing surface 166
`than the first pole tip 170, layers 101 and 188 combining to
`form a write pole. Another soft magnetic layer 178 is mag(cid:173)
`netically coupled to the write pole layer 101 in a region that is
`removed from the medium-facing surface and not shown in
`this figure, and is magnetically coupled to the write pole layer
`101 adjacent to the medium-facing surface by a soft magnetic
`pedestal 175. The pedestal 175 may serve to deflect magnetic
`flux from traveling exactly perpendicular to the media layer
`158, so that perpendicularly oriented bits in the media layer
`can flip more easily. For this purpose write pole tip comer 171
`may be spaced a similar distance from the pedestal as it is
`from the soft underlay er 155, e.g., on the order of 50-200 nm.
`The soft magnetic layer 178 and pedestal 175 may be consid-
`60 ered to form a return pole layer that terminates adjacent to the
`medium-facing surface in a second pole tip 180. At least one
`electrically conductive coil section may be disposed between
`layers 101 and 178 and another coil section disposed
`upstream of layer 188, to induce magnetic flux in the pole
`layers.
`Although not apparent in this view, the return pole tip 180
`may have an area that is at least two or three orders of mag-
`
`65
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`US 7,968,219 Bl
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`7
`nitude greater than that of the write pole tip 170.Altematively,
`another return pole layer and return pole tip may additionally
`be provided, for example between the write pole layer and a
`MR sensor. The write pole tip 170 may have a substantially
`trapezoidal shape that has a maximum track width at a trailing
`corner 171. The trailing comer 171 of the write pole tip 170
`may be approximately equidistant from soft magnetic under(cid:173)
`layer 155 and soft magnetic pedestal 175 in this embodiment,
`to deflect magnetic flux from the write pole. The write pole
`layer 170 may have a Bs that is between about 2.35 T and 2.45 10
`T, while the soft magnetic pedestal 175 may have a Bs that is
`substantially less, e.g., less than 2.0 T. A magnetoresistive or
`magnetooptical sensor may also be included with the head,
`such a sensor not shown in this view.
`The invention claimed is:
`1. A magn