(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2001/0031383 A1
`Sakawaki et al.
`(43) Pub. Date:
`Oct. 18, 2001
`
`US 20010031383A1
`
`(54) MAGNETIC RECORDING MEDIUM,
`PRODUCTION PROCESS THEREOF,
`MAGNETIC RECORDING AND
`REPRODUCING APPARATUS, AND
`SPUTTERING TARGET
`(76) Inventors: Akira Sakawaki, Chiba (JP); Masato
`Kokubu, Chiba (JP); Ryuji Sakaguchi,
`Chiba (JP); Hiroshi Sakai, Chiba (JP)
`Correspondence Address:
`SUGHRUE, MION, ZINN,
`MACPEAK & SEAS, PLLC
`2100 Pennsylvania Avenue, N.W.
`Washington, DC 20037-3213 (US)
`(21) Appl. No.:
`09/810,193
`y
`- - -
`9
`Mar. 19, 2001
`
`(22) Filed:
`
`Related U.S. Application Data
`(63) Non-provisional of provisional application No.
`60/230,810, filed on Sep. 7, 2000.
`
`(30)
`
`Foreign Application Priority Data
`
`Mar. 17, 2000 (JP).................................... P2000-077034
`
`Publication Classification
`
`(51) Int. Cl. ................................................... G11B 5/66
`
`(52) U.S. Cl. ...................................................... 428/694 TS
`
`(57)
`
`ABSTRACT
`
`An object of the present invention is to provide a process for
`easily producing a magnetic recording medium exhibiting
`excellent magnetic characteristics. In the present invention,
`an orientation-determining film is formed on a non-metallic
`Substrate which has undergone texturing, the orientation
`determining film is Subjected to oxidation or nitridation, and
`a non-magnetic undercoat film and a magnetic film are
`formed on the film.
`
`
`
`ZZZZZZZZZZZZZZZZZ K
`ZZZZZZZZZZZZZZZZZZ
`N
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`
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`G 2
`N 2
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`Page 1 of 15
`
`APPLIED MATERIALS EXHIBIT 1043
`
`

`

`Patent Application Publication Oct. 18, 2001
`Fig. 1
`
`
`
`US 2001/0031383 A1
`
`44444444444444444 5 NY
`ZZZZZZZZZZZZZZZZZZ 3
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`NN-2 S D 2
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`fig. 3
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`Page 2 of 15
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`

`

`US 2001/0031383 A1
`
`Oct. 18, 2001
`
`MAGNETIC RECORDING MEDIUM,
`PRODUCTION PROCESS THEREOF, MAGNETIC
`RECORDING AND REPRODUCING APPARATUS,
`AND SPUTTERING TARGET
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`0001. This application is an application filed under 35
`U.S.C. S111(a) claiming benefit pursuant to 35 U.S.C.
`$119(e)(1) of the filing date of Provisional application No.
`60/230,810 filed Sep. 7, 2000 pursuant to 35 U.S.C. S111(b).
`
`FIELD OF THE INVENTION
`0002 The present invention relates to a magnetic record
`ing medium employed in an apparatuS Such as a magnetic
`disk apparatus, a process for producing the magnetic record
`ing medium; a Sputtering target employed for producing the
`magnetic recording medium; and a magnetic recording and
`reproducing apparatus comprising the magnetic recording
`medium.
`
`BACKGROUND OF THE INVENTION
`Conventionally, a metallic Substrate formed of, for
`0.003
`example, an aluminum alloy is widely employed as a
`Substrate for producing a magnetic recording medium. USu
`ally, Such a metallic Substrate undergoes texturing, and is
`employed for producing a magnetic recording medium.
`0004 Texturing is a process for forming an irregular
`Surface on a Substrate along a predetermined direction
`(usually in a circumferential direction) of the Substrate.
`When the Surface of a Substrate undergoes texturing, the
`crystalline orientation of an undercoat film and a magnetic
`film, which are formed on the Substrate, is enhanced, and the
`magnetic film exhibits magnetic anisotropy. Thus magnetic
`characteristics, Such as thermal Stability and resolution, of a
`magnetic recording medium can be enhanced.
`0005. In recent years, instead of a metallic substrate
`formed of aluminum or Similar metal, a non-metallic Sub
`Strate formed of material Such as glass or ceramic has been
`widely employed as a Substrate for producing a magnetic
`recording medium. Such a non-metallic Substrate has an
`advantage that head Slap does not easily occur in the
`Substrate, because of the high hardness of the Substrate.
`0006. However, in the case in which a non-metallic
`Substrate Such as a glass Substrate is employed, the magnetic
`film may not be imparted with Satisfactory magnetic anisot
`ropy even when the Substrate undergoes texturing. AS a
`result, the resultant magnetic recording medium may exhibit
`unsatisfactory magnetic characteristics.
`0007. In order to solve such problems, formation of a
`hard film which can be easily textured on a non-metallic
`Substrate formed of material Such as glass or ceramic has
`been proposed.
`0008 For example, Japanese Patent Application Laid
`Open (kokai) No. 5-197941 discloses a magnetic recording
`medium including a non-metallic Substrate formed of mate
`rial Such as glass or ceramic, and the Substrate is coated
`through sputtering with NiP film serving as a hard film
`which is easily textured.
`
`0009 Japanese Patent Application Laid-Open (kokai)
`Nos. 4-29561 and 9-167337 disclose a magnetic recording
`medium including a non-metallic Substrate which is plated
`with film Such as electroless plating film, and the film Serves
`as a hard film.
`0010. A magnetic recording medium including a hard
`film formed on a non-metallic Substrate is produced through
`the following process: the hard film is formed on the
`Substrate in a film formation apparatus Such as a Sputtering
`apparatus, the Substrate is temporarily removed from the
`apparatus and is Subjected to texturing by use of a texturing
`apparatus, the resultant Substrate is again placed in the
`apparatus, and then an undercoat film and a magnetic film
`are formed on the Substrate.
`0011. However, the aforementioned conventional pro
`duction proceSS for a magnetic recording medium includes
`complicated production Steps, resulting in high production
`costs. Therefore, there has been keen demand for a produc
`tion process for a magnetic recording medium, which
`encompasses a Simplified production procedure.
`
`SUMMARY OF THE INVENTION
`0012. In view of the foregoing, an object of the present
`invention is to provide a process for easily producing a
`magnetic recording medium exhibiting excellent magnetic
`characteristics.
`0013 The present invention provides a process for pro
`ducing a magnetic recording medium characterized by form
`ing an orientation-determining film, which determines the
`crystalline orientation of a film provided directly on the
`orientation-determining film, on a non-metallic Substrate
`which has undergone texturing, Subjecting the orientation
`determining film to oxidation or nitridation; and forming a
`non-magnetic undercoat film and a magnetic film on the
`orientation-determining film.
`0014. The oxidation or nitridation is carried out by bring
`ing the orientation-determining film into contact with an
`OXygen-containing gas or a nitrogen-containing gas.
`0015 The present invention also provides a process for
`producing a magnetic recording medium, which comprises
`forming an orientation-determining film, which determines
`the crystal orientation of a film provided directly on the
`orientation-determining film, on a non-metallic Substrate
`which has undergone texturing, and forming a non-magnetic
`undercoat film and a magnetic film on the orientation
`determining film, wherein the orientation-determining film
`is formed through Sputtering by use of a Sputtering gas
`containing nitrogen or a Sputtering gas containing oxygen.
`0016 Preferably, the orientation-determining film com
`prises NiP (the content of P is 10-40 at %) as a primary
`component.
`0017 Preferably, the orientation-determining film com
`prises NiPX (wherein X is one or more species of Cr, Mo,
`Si, Mn, W, Nb, Ti, and Zr, and the content of X is 0-25 at
`%) as a primary component.
`0018. The present invention also provides a sputtering
`target for forming the orientation-determining film, which
`comprises NiPX (wherein X is one or more species of Cr,
`Mo, Si, Mn, W, Nb, Ti, and Zr, and the content of X is 0-25
`at %) as a primary component.
`
`Page 3 of 15
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`

`US 2001/0031383 A1
`
`Oct. 18, 2001
`
`0019. The present invention also provides a magnetic
`recording medium comprising a non-metallic Substrate
`which has undergone texturing, an orientation-determining
`film formed on the non-metallic Substrate; and a non
`magnetic undercoat film and a magnetic film, which are
`formed on the orientation-determining film, characterized in
`that the ratio of a coercive force in a circumferential direc
`tion of the medium (Hec) to a coercive force in a radial
`direction of the medium (Hcr); i.e., Hcc/Hcr, is 1.1 or more.
`0020. The orientation-determining film has an average
`Surface roughness (Ra) of less than 0.5 nm.
`0021. The magnetic recording medium of the present
`invention comprises a structure wherein a non-magnetic
`adhesive film, which prevents exfoliation of the orientation
`determining film from the substrate, is formed between the
`non-metallic Substrate and the orientation-determining film,
`and the non-magnetic adhesive film comprises one or more
`species of Cr, Mo, Nb, V, Re, Zr, W, and Ti.
`0022. The present invention also provides a magnetic
`recording and reproducing apparatus comprising the mag
`netic recording medium and a magnetic head for recording
`data onto the medium and reproducing the data therefrom.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0023 FIG. 1 is a partially cross-sectional view of one
`embodiment of the magnetic recording medium of the
`present invention.
`0024 FIG. 2 is a partially cross-sectional view of one
`embodiment of the magnetic recording and reproducing
`apparatus of the present invention.
`0.025
`FIG. 3 is a partially cross-sectional view of another
`embodiment of the magnetic recording medium of the
`present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`FIG. 1 is a schematic representation showing an
`0.026
`example embodiment of the magnetic recording medium of
`the present invention. The magnetic recording medium
`comprises a non-metallic Substrate 1 which has undergone
`texturing, an orientation-determining film 2 formed on the
`Substrate, a non-magnetic undercoat film 3, a magnetic film
`4, and a protective film 5, the films 3 to 5 being successively
`formed on the film 2. Hereinafter, the structure of the
`non-metallic Substrate 1 and the orientation-determining
`film 2 will be called a medium Substrate 6.
`0027. The non-metallic substrate 1 is formed from a
`non-metallic material Such as glass, ceramic, Silicon, Silicon
`carbide, or carbon. Particularly, from the viewpoint of
`durability and cost, a glass Substrate is preferably employed.
`0028. The glass substrate is formed from amorphous
`glass or crystallized glass. The amorphous glass may be
`widely-used Soda-lime glass, aluminocate glass, or alumi
`nosilicate glass. The crystallized glass may be lithium-based
`crystallized glass.
`0029 Particularly, amorphous glass exhibiting uniform
`physical properties Such as hardneSS is preferably employed
`as a material of the Substrate, Since the Substrate can be
`Subjected to uniform texturing.
`
`0030. Meanwhile, a ceramic substrate may be a widely
`used sintered compact predominantly containing aluminum
`oxide, aluminum nitride, and Silicon nitride, or fiber-rein
`forced material thereof.
`0031. The non-metallic substrate 1 is subjected to
`mechanical texturing or Similar processing by use of a
`lapping tape containing fixed abrasive grains or by use of
`free abrasive grains, to have a textured Surface.
`0032 Texture lines formed on the non-metallic substrate
`1 through texturing are preferably along the circumferential
`direction of the Substrate.
`(0033) The average surface roughness (Ra) of the non
`metallic substrate 1 is 0.1-1 nm (1-10 A), preferably 0.3-0.8
`nm (3-8 A).
`0034) When the average surface roughness (Ra) is below
`the above range, the non-metallic Substrate 1 is excessively
`Smooth, and thus the Substrate encounters difficulty in
`enhancing the magnetic anisotropy of the magnetic film 4. In
`contrast, when the average Surface roughness (Ra) is in
`excess of the above range, the evenness of the medium is
`lowered, resulting in poor glide height characteristics. AS a
`result, reducing the flying height of a magnetic head during
`reproduction of data becomes difficult.
`0035. As compared with a metallic material, the non
`metallic Substrate 1 has a high hardneSS and is difficult to
`texture. Therefore, when the Substrate is subjected to tex
`turing, abnormal protrusions Such as fins are difficult to
`form, with the result that the maximum protrusion height
`(Rip) is lowered.
`0036) The orientation-determining film 2 is provided for
`determining the crystalline orientation of the non-magnetic
`undercoat film 3 formed on the film 2 and for determining
`the crystalline orientation of the magnetic film 4 formed on
`the film 3, to thereby enhance the magnetic anisotropy of the
`magnetic film 4. The orientation-determining film 2 deter
`mines the crystalline orientation of the non-magnetic under
`coat film 3 and the magnetic film 4, and also functions as a
`film for forming fine crystal grains, i.e., the film 2 forms fine
`magnetic grains in the films 3 and 4.
`0037. The orientation-determining film 2 is preferably
`formed from a material containing NiP as a primary com
`ponent. The content of P is 10-40 at %, preferably 15-35 at
`%.
`0038. The reasons for this are that, when the content of P
`is less than 10 at %, NiP is susceptible to magnetization. In
`contrast, when the content of P is in excess of 40 at %, the
`crystal orientation of the non-magnetic undercoat film 3 and
`the magnetic film 4 is easily impaired.
`0039. Alternatively, the orientation-determining film 2 is
`preferably formed from a material containing NiPX
`(wherein X is one or more species of Cr, Mo, Si, Mn, W, Nb,
`Ti, and Zr) as a primary component. The content of X is 0-25
`at %, preferably 5-25 at %, more preferably 10-25 at %.
`When the content of X is in excess of 25 at %, the crystalline
`orientation of the non-magnetic undercoat film 3 and the
`magnetic film 4 is impaired, and the magnetic anisotropy of
`the magnetic film 4 is lowered.
`0040 AS used herein, the term “primary component”
`refers to the case in which the content of the component is
`in excess of 50 at %.
`
`Page 4 of 15
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`

`US 2001/0031383 A1
`
`Oct. 18, 2001
`
`0041. The thickness of the orientation-determining film 2
`is preferably 2-100 nm (20-1,000 A). When the thickness is
`below the above range, the magnetic anisotropy of the
`magnetic film 4 is lowered, whereas when the thickneSS is in
`excess of the above range, the orientation-determining film
`2 is easily exfoliated and production costs increase, which is
`unsatisfactory.
`0042. The orientation-determining film 2 may be or may
`not be Subjected to texturing.
`0043. When orientation-determining film 2 is subjected
`to texturing, texture lines are preferably along the circum
`ferential direction of the Substrate.
`0044) The orientation-determining film 2 preferably has
`an average Surface roughness (Ra) of 1 nm or less, from the
`Viewpoint of glide height characteristics.
`004.5 The average surface roughness (Ra) of the orien
`tation-determining film 2 is more preferably less than 0.5 nm
`(5 A), much more preferably less than 0.3 nm.
`0046) The orientation-determining film 2 is formed from
`a metallic material which has a relatively low hardneSS and
`is easily processed, such as NiPX. Therefore, when the film
`2 is Subjected to texturing, large protrusions Such as fins and
`burrs are easily produced on the Surface of the film, and thus
`the maximum protrusion height (Rip) tends to increase.
`0047 When the average surface roughness (Ra) of the
`orientation-determining film 2 is less than 0.5 nm (5A), the
`amount of abraded Substance is reduced during texturing,
`and an increase in the maximum protrusion height (Rip) of
`the film 2 is prevented. Consequently, the maximum pro
`trusion height (Rip) of the medium can be reduced, and
`deterioration of the glide height characteristics can be pre
`vented.
`0.048. The non-magnetic undercoat film 3 may be formed
`from conventionally known materials for undercoat film.
`For example, the film may be formed from an alloy of one
`or more species of Cr, Ti, Ni, Si, Ta, W, Mo, V, and Nb.
`Alternatively, the film 3 may be formed from an alloy of one
`or more of the above elements and other elements, So long
`as such “other elements” do not impede the crystallinity of
`the film.
`0049 Particularly, the film 3 is preferably formed from
`Cr or a Cr alloy (e.g., CrTi, CrW, CrMo, CrV, or CrSi).
`0050. The non-magnetic undercoat film 3 may be of a
`Single-layer Structure, or of a multi-layer Structure formed of
`a plurality of films which are of the same composition or of
`different compositions. The thickness of the non-magnetic
`undercoat film 3 is 1-100 nm (10-1,000 A), preferably 2-50
`nm (20-500 A).
`0051. The crystalline orientation of the non-magnetic
`undercoat film 3 is preferably (002).
`0.052 The magnetic film 4 is preferably formed from a
`material containing Co as a primary component. The mate
`rial may be, for example, an alloy of Co and one or more
`species of Cr, Pt, Ta, B, Ti, Ag, Cu, Al, Au, W, Nb, Zr, V, Ni,
`Fe, and Mo.
`0.053
`Preferable specific examples of the above material
`include materials predominantly containing a CoCrTa-,
`
`CoCrPt-, CoCrPtB- or CoCrPtTa-based alloy. Of these
`alloys, in particular, a CoCrPtTa-based alloy is preferably
`employed.
`(0054) The thickness of the magnetic film 4 may be 5-30
`nm (50-300 A).
`0055. The crystalline orientation of the magnetic film 4 is
`preferably (110).
`0056. The magnetic film 4 may be of a single-layer
`Structure, or of a multi-layer Structure formed of a plurality
`of films which are of the same composition or of different
`compositions.
`0057 Preferably, a non-magnetic intermediate layer is
`provided between the non-magnetic undercoat film and the
`magnetic film, in order to further improve the crystal ori
`entation of the magnetic film and to further enhance the
`effects of the present invention.
`0058. The non-magnetic intermediate layer may be
`formed from a CoCr alloy (content of Cr: 20-40 at %).
`0059) The protective film 5 may be formed from conven
`tionally known materials. For example, the film may be
`formed from a material containing a single component Such
`as carbon, Silicon oxide, Silicon nitride, or Zirconium oxide;
`or a material predominantly containing Such components.
`(0060) The thickness of the protective film 5 is preferably
`2-10 nm (20-100 A).
`0061. If necessary, a lubrication film formed from a
`lubricant Such as a fluorine-based liquid lubricant (e.g.,
`perfluoropolyether) may be provided on the protective film
`5.
`0062. In the magnetic recording medium of the present
`invention, the ratio of a coercive force in a circumferential
`direction of the medium (Hec) to a coercive force in a radial
`direction of the medium (Hcr); i.e., Hcc/Hcr, is 1.1 or more,
`preferably 1.2 or more.
`0063) When the ratio Hec/Hcr is below the above range,
`the magnetic anisotropy a of the magnetic recording medium
`is insufficient, and magnetic characteristics of the medium,
`Such as thermal Stability, are unsatisfactory.
`0064. A first embodiment of the production process for a
`magnetic recording medium of the present invention will
`next be described by taking, as an example, production of
`the aforementioned magnetic recording medium.
`0065. Firstly, the non-metallic Substrate 1 is subjected to
`texturing. Preferably, the Substrate 1 is subjected to
`mechanical texturing by use of lapping tape containing fixed
`abrasive grains, or by use of free abrasive grains. During
`texturing, texture lines are preferably formed in the circum
`ferential direction of the Substrate.
`0066. The substrate may be subjected to chemical etching
`after mechanical texturing, in order to remove fine fins,
`burrs, and the like which are produced on the Surface during
`mechanical texturing, and to obtain excellent Surface even
`CSS.
`0067 Subsequently, the orientation-determining film 2 is
`formed on the non-metallic substrate 1, to thereby form the
`medium Substrate 6.
`
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`

`US 2001/0031383 A1
`
`Oct. 18, 2001
`
`0068 The orientation-determining film 2 is preferably
`formed through Sputtering by use of a Sputtering apparatus
`Serving as a film formation apparatus.
`0069. When the orientation-determining film 2 is formed
`through Sputtering, the aforementioned material constituting
`the film 2 is employed as a Sputtering target.
`0070 The sputtering target is desirably a material con
`taining, as a primary component, NiPX (wherein X is one or
`more species of Cr, Mo, Si, Mn, W, Nb, Ti, and Zr; and the
`content of X is 0-25 at %, preferably 5-25 at %, more
`preferably 10-25 at %).
`0071. When the content of X is in excess of the above
`range, the crystalline orientation of the non-magnetic under
`coat film 3 and the magnetic film 4 is impaired, and the
`magnetic anisotropy of the film 4 is lowered.
`0.072 The target may be a sintered alloy target or an alloy
`target produced through a casting method. Particularly, a
`Sintered alloy target is preferably employed. Such a sintered
`alloy target may be produced by means of a conventionally
`known Sintering method Such as hot isostatic pressing (HIP)
`or hot pressing, from alloy powder of the aforementioned
`composition, a plurality of alloy powders which are mixed
`to obtain the aforementioned composition, or a mixture of
`mono-metallic powders. The aforementioned alloy powder
`and metallic powder may be produced by means of a
`conventionally known method Such as a gas-atomizing
`method.
`0073. In order to form the orientation-determining film 2,
`the non-metallic Substrate 1 is placed in a chamber of a
`Sputtering apparatus, a Sputtering gas Such as argon gas is
`introduced into the chamber, and electricity is applied to the
`target, thereby depositing the target material onto the non
`metallic Substrate 1 through Sputtering.
`0.074 The orientation-determining film 2 may be formed
`through, instead of Sputtering, plating (such as electroless
`plating), vacuum deposition, ion plating, or a similar pro
`
`CCSS.
`0075. In the production process for the magnetic record
`ing medium of the embodiment, after completion of the
`formation of the orientation-determining film 2, the film is
`Subjected to oxidation.
`0.076. Oxidation of the orientation-determining film 2
`may be carried out by bringing the film 2 into contact with
`an oxygen-containing gas.
`0077. The oxygen-containing gas may be air, pure oxy
`gen, or Steam. Alternatively, the oxygen-containing gas may
`be an oxygen-enriched gas which consists of air containing
`a large amount of oxygen.
`0078. In order to bring the orientation-determining film 2
`into contact with the oxygen-containing gas, after the film 2
`is formed on the Substrate 1 in the film formation apparatus
`(Sputtering apparatus) to form the medium Substrate 6 as
`described above, the oxygen-containing gas is introduced
`into the chamber of the film formation apparatus in which
`the medium Substrate 6 is placed.
`0079. In this case, the content of oxygen in the gas to
`which the orientation-determining film 2 is exposed; i.e., the
`gas in the chamber, may be 1-100 vol%.
`
`0080. By use of such an oxygen-containing gas, oxida
`tion of the film 2 can be easily carried out.
`0081. The process for bringing the orientation-determin
`ing film 2 into contact with the oxygen-containing gas is
`preferably carried out at a temperature lower than the
`temperature at which the material constituting the film 2 is
`crystallized; for example, at 280 C. or lower, in order to
`prevent the possibility that the orientation of the non
`magnetic undercoat film 3 and the magnetic film 4 might be
`adversely affected by crystallization of the film 2. The
`temperature at which the process is carried out may be
`determined to be ambient temperature or higher. The period
`of time for the process to be carried out (i.e., the time during
`which the film 2 is exposed to the oxygen-containing gas)
`may be appropriately determined in accordance with, for
`example, the content of oxygen in the oxygen-containing
`gaS.
`0082 Through this process, at least the area in proximity
`to the Surface of the orientation-determining film 2 is
`oxidized.
`0083) Subsequently, the non-magnetic undercoat film 3 is
`formed on the orientation-determining film 2. The non
`magnetic undercoat film 3 may be formed through Sputtering
`by use of a Sputtering apparatus.
`0084 Subsequently, the magnetic film 4 is formed on the
`non-magnetic undercoat film 3. The magnetic film 4 may be
`formed through Sputtering by use of a Sputtering apparatus.
`0085 Subsequently, the protective film 5 is formed on the
`magnetic film 4. The protective film 5 may be formed
`through, for example, plasma CVD or Sputtering.
`0086. In the production process for the magnetic record
`ing medium of the embodiment, the orientation-determining
`film 2 is formed on the non-metallic Substrate 1 which has
`undergone texturing, and then the film 2 is Subjected to
`oxidation. Therefore, even though the substrate 1 is formed
`from a non-metallic Substrate, which makes imparting high
`magnetic anisotropy to the magnetic film difficult, the crys
`talline orientation of the non-magnetic undercoat film 3 and
`the magnetic film 4, which are being formed over the
`Substrate 1, can be improved, and the magnetic anisotropy of
`the magnetic film 4 can be enhanced.
`0087. Therefore, magnetic characteristics of the magnetic
`recording medium, Such as thermal Stability, error rate, and
`S/N ratio, can be improved.
`0088. In general, thermal stability is excellent in a
`medium which has a high crystal magnetic anisotropy
`constant (Ku). In the magnetic recording medium of the
`embodiment of the present invention, thermal stability is
`thought to be enhanced, Since the crystal magnetic anisot
`ropy constant (Ku) is enhanced by enhancement of magnetic
`anisotropy in a circumferential direction.
`0089. As used herein, the term “thermal stability” refers
`to the degree of difficulty in occurrence of thermal decay.
`0090. As used herein, the term “thermal decay” refers to
`a phenomenon in which recording bits become unstable and
`recorded data are thermally lost. In a magnetic recording
`apparatus, thermal decay is manifested in the form of
`reduction in reproduction output of recorded data with the
`passage of time.
`
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`US 2001/0031383 A1
`
`Oct. 18, 2001
`
`According to the production process, the half
`0.091
`power width of a reproduction output peak is narrowed, and
`thus the resolution of the reproduction output can be
`enhanced. Therefore, a magnetic recording medium in
`which the error rate is improved can be produced.
`0092. When magnetic anisotropy is enhanced, coercive
`force and reproduction output (S) are improved, yielding an
`improvement in the S/N ratio.
`0093. In addition, crystal grains in the non-magnetic
`undercoat film 3 become fine. Consequently, magnetic
`grains in the magnetic film 4, which is grown under the
`influence of the film 3, may become fine and uniform,
`resulting in reduction in noise (N). Therefore, reproduction
`output per unit film thickness may be enhanced, and thus the
`film 4 may be thinned. When the film 4 is thinned, excessive
`growth of the magnetic grains is Suppressed, and the grains
`may become even finer, which results in further reduction in
`noise. Consequently, the S/N ratio can be further improved.
`0094.
`In the production process of the embodiment, the
`orientation-determining film 2 is formed on the non-metallic
`Substrate 1 which has undergone texturing in a film forma
`tion apparatus Such as a Sputtering apparatus, and Subse
`quently, the non-magnetic undercoat film 3 and the magnetic
`film 4 are formed on the orientation-determining film 2 in
`the same apparatus without removal of the thus-formed
`medium Substrate 6 from the apparatus.
`0.095
`Therefore, the production process can be simpli
`fied, and production costs can be reduced.
`0096. In contrast, when a conventional production pro
`cess is employed, after the film formation Step (in which a
`NiP hard film is formed on a substrate) is carried out, the
`resultant Substrate is temporarily removed from a film
`formation apparatus and is Subjected to texturing (i.e., the
`hard film is Subjected to texturing). Subsequently another
`film formation step (in which a non-magnetic undercoat film
`and a magnetic film are formed) is carried out, thus com
`plicating the production process.
`0097 When a sputtering target containing, as a primary
`component, NiP (wherein the content of P is 0-25 at %) is
`employed, the orientation-determining film 2 can be easily
`formed.
`0.098 When a sputtering target containing, as a primary
`component, NiPX (wherein X is one or more species of Cr,
`Mo, Si, Mn, W, Nb, Ti, and Zr; and the content of X is 0-25
`at %) is employed, the orientation-determining film 2 can be
`easily formed.
`0099. The aforementioned magnetic recording medium
`includes the non-metallic Substrate 1 which has undergone
`texturing, the orientation-determining film 2 formed on the
`Substrate 1, and the non-magnetic undercoat film 3 and the
`magnetic film 4, which are formed on the film 2; and the
`ratio of a coercive force in a circumferential direction of the
`medium (Hec) to a coercive force in a radial direction of the
`medium (Hcr); i.e., Hcc/Hcr, is 1.1 or more. Therefore, the
`magnetic recording medium exhibits high magnetic anisot
`ropy and excellent magnetic characteristics with respect to
`Such parameters as thermal Stability, error rate, and S/N
`ratio. In addition, the production proceSS for the medium can
`be simplified, and production costs can be reduced.
`
`0100 When the orientation-determining film 2 included
`in the aforementioned magnetic recording medium is not
`Subjected to texturing, a texturing Step is not necessary
`during production of the medium. Thus the production
`process is Simplified and production costs can be reduced. In
`addition, deterioration of glide height characteristics can be
`prevented. The deterioration occurs when the film 2 is
`Subjected to texturing, because the Surface of the film 2
`becomes rough, and the maximum protrusion height (Rip) of
`the Surface of the medium increases.
`0101 Meanwhile, when the orientation-determining film
`2 is Subjected to texturing, the crystalline orientation of the
`non-magnetic undercoat film 3 and the magnetic film 4 can
`further be improved, and the magnetic anisotropy of the film
`4 can be further enhanced.
`0102 FIG. 2 shows an embodiment of the magnetic
`recording and reproducing apparatus including the magnetic
`recording medium. The apparatus includes a magnetic
`recording medium 7, the Structure of the medium being
`shown in FIG. 1; a medium-driving portion 8 which rotates
`the medium 7; a magnetic head 9 which is employed for
`recording of data onto the medium 7 and for reproduction of
`the data from the medium 7; a head-driving portion 10; and
`a recorded/reproduced signal-processing System 11. In the
`System 11, incoming external Signals are processed and Sent
`to the magnetic head 9, or reproduction signals from the
`head 9 are processed and Sent to the outside.
`0103) When the magnetic recording and reproducing
`apparatus is employed, recording density can be increased,
`Since the magnetic anisotropy of the magnetic recording
`medium can be enhanced. Thus S/N ratio and error rate can
`be improved. In addition, loss of recorded data which is
`attributed to thermal decay can be prevented.
`0104. A second embodiment of the production process
`for a magnetic recording medium of the present invention
`will next be described.
`0105 The production process of the second embodiment
`differs from that of the first embodiment in that an orienta
`tion-determining film 2 is Subjected to nitridation instead of
`oxidation.
`0106 Nitridation of the orientation-determining film 2
`may be carried out by bringing the film 2 into contact with
`a nitrogen-containing gas. For example, a nitrogen-contain
`ing gas may be introduced into a chamber of a film forma
`tion apparatus in which a medium Substrate 6 is placed.
`0107 The nitrogen-containing gas may be air or pure
`nitrogen. Alternatively, the nitrogen-containing gas may be
`a nitrogen-enriched gas which consists of air containing a
`large amount of nitrogen.
`0108. In this case, the nitrogen content of the gas to
`which the orientation-determining film 2 is exposed may be
`1-100 vol%. By use of Such a nitrogen-containing gas,
`nitridation of the film 2 can be easily carried out.
`0109 The process for bringing the orientation-determin
`ing film 2 into contact with the nitrogen-containing gas is
`preferably carried out at a t