Patent Application
20080057348
Specifically, this magnetic recording medium is structured by forming in sequence on a non-magnetic substrate 1 the soft magnetic undercoat film 2 that consists of soft magnetic material, the first undercoat film 3, the second undercoat film 4, the perpendicular magnetic recording film S, the protective film 6, and the lubricating film 7.
A metal substrate consisting of a metal material such as aluminum or an aluminum alloy can be used as the non-magnetic substrate 1, or a non-magnetic substrate consisting of non-metallic material such as glass, ceramic, silicon, silicon carbide, or carbon can also be used.
An amorphous glass or a crystallized glass can be used as the glass substrate. A general-purpose soda-lime glass or aluminosilicate glass can be used as the amorphous glass, and a lithium-based crystallized glass can be used as the crystallized glass. A sintered body having as a main component, for example, a general-purpose aluminum oxide, aluminum nitride, silicon nitride, or the fiber-reinforced products thereof, can be used as the ceramic substrate.
The non-magnetic substrate 1 has a mean surface roughness Ra equal to or less than 2 nm (20 Å), and preferably equal to or less than 1 nm, which is desirable in terms of the application to high density recording because it is possible decrease the flying height of the magnetic head during reading and writing.
The non-magnetic substrate 1 has a minute waviness (Wa) equal to or less than 0.3 nm (more preferably, equal to or less than 0.25 nm), which is desirable in terms of the application to high density recording because it is possible to decrease the flying height of the magnetic head during reading and writing.
In addition, at least one among the chamfered edge portion and the side portion of the chamfer portion has a mean surface roughness equal to or less than 10 nm (more preferably, equal to or less than 9.5 nm), which is preferable in terms of the flying stability of the magnetic head.
The waviness (Wa) can be measured as the mean surface roughness in a measuring range of 80 μm using, for example, a surface roughness measuring apparatus P-12 (KLA-Tencor Co.).
The soft magnetic undercoat film 2 is provided in order to increase the perpendicular direction component of the magnetic flux generated from the magnetic head and in order to establish the direction of the magnetic flux of the perpendicular magnetic recording film 5, on which the data is recorded, more firmly in the perpendicular direction. This action becomes more significant in particular when a single pole head for perpendicular recording is used as the magnetic read/write head.
The soft magnetic undercoat film 2 consists of a soft magnetic material, and a material that includes Fe, Ni, or Co can be used for this material.
The following are Examples of this material: FeCo alloys (FeCo, FeCoB, and the like), FiNi alloys (FeNi, FeNiMo, FeNiCr, FeNiSi and the like), FeAl alloys (FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, FeAlO and the like), FeCr alloys (FeCr, FeCrTi, FeCrCu and the like), FeTa alloys (FeTa, FeTaC, FeTaN and the like), FeMg alloys (FeMgO and the like), FeZr alloys (FeZrN and the like), FeC alloys, FeN alloys, FeSi alloys, FeP alloys, FeNb alloys, FeHf alloys, and FeB alloys, CoB alloys, CoP alloys, CoNi alloys (CoNi, CoNiB, CoNiP and the like), and FeCoNi alloys (FeCoNi, FeCoNiP, FeCoNiB and the like).
In addition, a material can be used that has a microcrystalline structure consisting of FeAlO, FeMgO, FeTaN, FeZrN or the like and that incorporates Fe at 60 at % or greater, or a granular structure in which fine crystal particles are dispersed in a matrix.
In addition to those cited above, it is also possible to use as the material for the soft magnetic undercoat film 2 a Co alloy that incorporates Co at 80 at % or greater and incorporates at least one or more selected from Zr, Nb, Ta, Cr, Mo or the like.
A CoZr alloy, CoZrNb alloy, CoZrTa alloy, CoZrCr alloy, CoZrMo alloy or the like can be suitably used as this material.
The coercive force Hc of the soft magnetic undercoat film 2 is preferably equal to or less than 100 Oe (and more preferably equal to or less than 20 Oe).
The coercive force Hc exceeding the above range is not preferable because the soft magnetic properties become insufficient and the read back waveform is not what is termed a rectangular wave, but becomes a distorted waveform.
The saturated magnetic flux density Bs of the soft magnetic undercoat film 2 is preferably equal to or greater than 0.6 T (more preferably, equal to or greater than 1 T). The Bs falling below this range is not preferable because the read back waveform is not what is termed a rectangular wave, but becomes a distorted waveform.
The product of the saturated magnetic flux density Bs and the thickness t of the soft magnetic undercoat film 2, Bs·t, is preferably equal to or greater than 40 T·nm (more preferably, equal to or greater than 60 T·nm). The product Bs·t falling below this range is not preferable because the read back waveform becomes a distorted waveform, and the OW properties (overwrite properties) deteriorate.
Sputtering methods, plating methods and the like can be used as the formation method of the soft magnetic undercoat film 2.
The soft magnetic undercoat film 2 can be have a form such that the material that forms it is partially or completely oxidized at the surface (the surface on the undercoat film 3 side).
Specifically, in the region of a predetermined depth from the surface of the soft magnetic undercoat film 2, it is possible that the material that forms the soft magnetic undercoat film 2 is locally oxidized or that this region consists of an oxide of this material.
The undercoat film 3 controls the orientation and crystal diameter of the second undercoat film 4 provided directly above and the perpendicular magnetic recording film 5.
The material that is used in the first undercoat film 3 is Pt, Pd, or an alloy including at least one thereof. Specifically, Pt, Pd, a Pt alloy, Pd alloy, or PtPd alloy can be used.
By using Pt, Pd, or an alloy including at least one thereof in the first undercoat film 3, the orientation of the second undercoat film 4 and the perpendicular magnetic recording film 5 provided on the first undercoat film 3 can be made advantageous.
With the object of making the crystal particles of the first undercoat film 3 microcrystalline, in the first undercoat film 3 it is preferable to use a Pt alloy in which the Pt has another element added or a Pd alloy in which the Pd has another element added.
B, C, P, Si, Al, Cr, Co, Ta, W, Pr, Nd, Sm and the like are preferable additive elements.
Among these, adding C is desirable. By incorporating C into the first undercoat film 3, the crystallinity of the second undercoat film 4 and the perpendicular magnetic recording film 5 can be made advantageous.
In addition, it is possible to use an alloy material having the additional elements given above in an alloy that includes Pt and Pd (PtPd alloy).
It is particular preferable that the first undercoat film 3 consists of any among a Pt—C alloy, Pt—Fe—C alloy, Pt—Ni—C alloy, Pt—Co—C alloy, Pt—Cr—C alloy, Pd—C alloy, Pd—Fe—C alloy, Pd—Ni—C alloy, Pd—Co—C alloy, Pd—Cr—C alloy, or Pt—Pd—C alloy.
The thickness of the first undercoat film 3 is preferably equal to or greater than 0.5 nm and equal to or less than 10 nm (in particular, 1-7 nm). When the thickness of the first undercoat film 3 is within this range, the perpendicular orientation of the perpendicular magnetic recording film S is particularly high and the distance between the magnetic head and the soft magnetic undercoat film 2 during reading and writing can be decreased. Thereby, there is no decrease in the resolution of the read signal and thus it is possible to improve the read/write properties.
When the thickness falls below this range, the perpendicular orientation of the perpendicular magnetic recording film 5 decreases, and the read/write properties and the thermal stability deteriorate.
In addition, when this thickness exceeds this range, the crystal particles become coarse and the distance between the magnetic head and the soft magnetic undercoat film 2 during reading and writing becomes large. As a consequence, the resolution of the read back signal and the read back output decrease.
The first undercoat film 3 preferably has a fcc structure. When the first undercoat film 3 has a fcc structure, the orientation of the second undercoat film 4 provided directly above and/or the perpendicular magnetic recording film 5 is favorable, and it is possible to make the crystal particles microcrystalline. The state of the crystal can be confirmed, for example, by X-ray diffraction or TEM (transmission electron microscopy).
The first undercoat film 3 can have a granular structure consisting of Pt and an oxide. In addition, it can have a granular structure consisting of Pd and an oxide.
SiO2, Al2O3, Cr2O3, CoO, or Ta2O5 can be used as the oxide.
The average diameter of the crystal particles of the first undercoat film 3 is preferably equal to or greater than 5 nm and equal to or less than 12 nm. The average diameter can be found by observing the crystal particles of the first undercoat film 3 using TEM (transmission electron microscopy) and processing the observed image.
The surface profile of the first undercoat film 3 influences the surface profile of the perpendicular magnetic recording film 5 and the protective film 6, and thus in order to make the surface irregularities of the magnetic recording medium small and reduce the magnetic head flying height during reading and writing, preferably the mean surface roughness Ra of the first undercoat film 3 is equal to or less than 2 nm.
Because the mean surface roughness Ra is equal to or less than 2 nm, the surface irregularities in the magnetic recording medium can be made small, the magnetic head flying height during reading and writing can be made sufficiently low, and thus the recording density can be increased.
When forming the first undercoat film 3, with the object of making the crystal particles of the perpendicular magnetic recording film 5 microcrystalline, a process gas that includes oxygen or nitrogen can be used as the film developing gas. For example, in the case that the first undercoat film 3 is formed by using a sputtering method, preferably a gas that is a mixture consisting of oxygen mixed into argon at a volume of approximately 0.05 to 10% (preferably, 0.1 to 3%) or a gas that is a mixture consisting of nitrogen mixed into argon at a volume of approximately 0.01 to 20% (preferably, 0.02 to 5% ) is used.
The second undercoat film 4 is for preventing distortion in the crystal structure of the perpendicular magnetic recording film 5 that occur due to the difference in the crystal lattice size between the first undercoat film 3 and the perpendicular magnetic recording film 5 and for decreasing the exchange coupling of the magnetic particles (crystal particles) of the perpendicular magnetic recording film 5.
Ru or an Ru alloy are materials that can be used in the second undercoat film 4.
By using Ru or an Ru alloy in the second undercoat film 4, it is possible to improve the read/write properties.
With the object of decreasing both the crystal lattice size of the second undercoat film 4 and the exchange coupling in the perpendicular magnetic recording film 5, an Ru alloy having another element added to the Ru is preferably used in the second undercoat film 4.
B, C, P, Ta, W, Mo and the like are preferable additive elements.
Preferably the thickness of the second undercoat film 4 is equal to or greater than 0.5 nm and equal to or less than 10 nm (particularly, 1 to 6 nm). When the thickness of the second undercoat film 4 is within this range, the effects of the second undercoat film 4 (preventing distortion in the crystal structure of the perpendicular magnetic recording film 5 and decreasing the exchange coupling of magnetic particles) is increased and the distance between the magnetic head and the soft magnetic undercoat film 2 during reading and writing can be made small. Thereby, it is possible to improve the read/write properties without decreasing the resolution of the read back signal.
When this thickness falls below this range, the effects of the second undercoat film 4 decrease and the read/write properties deteriorate. In addition, when the thickness greatly exceeds this range, the crystal particles become coarse and the distance between the magnetic head and the soft magnetic undercoat film 2 during reading and writing increases. Thereby, the resolution of the read back signal and the read back output decrease.
The thickness of the second undercoat film 4 can be a value that exceeds 10 nm (for example, equal to or greater than 15 nm).
Preferably, the second undercoat film 4 has a hcp structure. The crystal structure can be confirmed by using, for example, X-ray diffraction or transmission electron microscopy (TEM).
The second undercoat film 4 can have a granular structure consisting of Ru and an oxide. SiO2, Al2O3, Cr2O3, CoO, or Ta2O5 can be used as the oxide.
Preferably, the average diameter of the crystal particles of the second undercoat film 4 is equal to or greater than 5 nm and equal to or less than 12 nm. This average diameter can be found, for example, by observing the crystal particles of the second undercoat film 4 using TEM (transmission electron microscopy) and processing the observed image.
The easy magnetization axis of the perpendicular magnetic recording film 5 is oriented generally in the direction perpendicular to the substrate, and the perpendicular magnetic recording film S preferably consists of a material that includes at least Co and Pt.
For example, it is possible to use a CoPt alloy or a CoCrPt alloy. In addition, it is possible to use a material that has at least one of SiO2, Al2O3, ZrO2, Cr2O3, and Ta2O5 added to the CoPt alloy or the CoCrPt alloy.
In particular, preferably a CoCrPt alloy or a material having an oxide such as SiO2, Al2O3, ZrO2, or Cr2O3 added to the CoCrPt alloy is used.
In the case that a CoCrPt alloy that does not have an oxide added is used, preferably, the Cr content is equal to or greater than 14 at % and equal to or less than 24 at % (preferably, equal to or greater than 15 at % and equal to or less than 22 at % ), and the Pt content is equal to or greater than 14 at % and equal to or less than 24 at % (preferably, equal to or greater than 15 at % and equal to or less than 20 at % ).
The Cr content falling below this range is not preferable because below this range the exchange coupling between magnetic particles becomes large, which in turn results in the magnetic cluster diameter becoming large and the noise increasing. In addition, the Cr content exceeding this range is not preferable because above this range the coercive force and the ratio of the residual magnetization (Mr) and the saturation magnetization (Ms), that is, Mr/Ms, are reduced.
The Pt content falling below this range is not preferable because the effect of improving the read/write properties becomes insufficient, and at the same time, the ratio between the residual magnetization (Mr) and the saturation magnetization (Ms), that is, Mr/Ms, is reduced and the thermal stability deteriorates. In addition, the Pt content exceeding this range is not preferable because the noise increases.
In the case that a material having an oxide added to CoCrPt is used, the total Cr and oxide content is preferably equal to or greater than 12 at % and equal to or less than 22 at % (more preferably, equal to or greater than 14 at % and equal to or less than 20 at % ), and the Pt content is equal to or greater than 13 at % and equal to or less than 20 at % (more preferably, equal to or greater than 14 at % and equal to or less than 20 at % ).
The total Cr and oxide content falling below this range is not preferable because below this range the exchange coupling between magnetic particles becomes large, which in turn results in the magnetic cluster diameter becoming large and the noise increasing. In addition, the total Cr and oxide content exceeding this range is not preferable because above this range the coercive force and the ratio of the residual magnetization (Mr) and the saturation magnetization (Ms), that is, Mr/Ms, are reduced.
The Pt content falling below this range is not preferable because the effect of improving the read/write properties becomes insufficient, and at the same time, the ratio between the residual magnetization (Mr) and the saturation magnetization (Ms), that is, the Mr/Ms, is reduced and the thermal stability deteriorates. In addition, the Pt content exceeding this range is not preferable because the noise increases.
Note that “the easy magnetization axis is oriented generally in the direction perpendicular to the substrate” means that the coercive force Hc(P) in the perpendicular direction and the coercive force Hc(L) in the in-plane direction are such that Hc(P) >Hc(L).
The perpendicular magnetic recording film 5 can have a one-layer structure comprising a CoCrPt material or the like, or may have a two or more layer structure comprising different components.
The thickness of the perpendicular magnetic recording film 5 is preferably 7 to 30 nm (more preferably, 10 to 25 nm). When the perpendicular magnetic recording film 5 is equal to or greater than 7 nm, a sufficient magnetic flux can be obtained, the output during read back does not decrease, and it is possible to prevent the confirmation of the output waveform from becoming difficult due to the noise component. Thereby, a magnetic read/write apparatus that can be applied to an increased recording density can be obtained.
In addition, the thickness of the perpendicular magnetic recording film 5 is preferably equal to or less than 30 nm because it is thereby possible to suppress the increasing coarseness of the magnetic particles in the perpendicular magnetic recording film 5 and there is no concern that the read/write properties will deteriorate due to an increase in noise.
The coercive force of the perpendicular magnetic recording film 5 is preferably equal to or greater than 3000 Oe. The coercive force being less than 3000 Oe is not preferable because the necessary resolution for high recording density cannot be obtained, and in addition, the thermal stability deteriorates.
The ratio of the residual magnetization (Ms) saturation magnetization (Ms), that is, Mr/Ms, of the perpendicular magnetic recording film 5 is preferably equal to or greater than 0.9. The Mr/Ms being less than 0.9 is not preferable because the thermal stability deteriorates.
The negative nucleation field (−Hn) of the perpendicular magnetic recording film 5 is preferably equal to or greater than 0. The negative nucleation field (−Hn) being less than 0 is not preferable because the thermal stability deteriorates.
The average diameter of the crystal particles of the perpendicular magnetic recording film 5 is preferably equal to or greater than 5 nm and equal to or less than 12 nm. The average diameter can be found by observing the crystal particles of the perpendicular magnetic recording film 5 using TEM (transmission electron microscopy) and processing the observed image.
ΔHc/Hc of the perpendicular magnetic recording film 5 is preferably equal to or less than 0.25. ΔHc/Hc being equal to or less than 0.25 is preferable because the variation in the diameter of the magnetic particles (crystal particles) is small, the coercive force in the perpendicular direction of the perpendicular magnetic recording film 5 becomes uniform, and thereby it is possible improve the resolution.
The protective film 6 prevents the corrosion of the perpendicular magnetic recording film 5, and at the same time prevents damage to the medium surface when the magnetic head contacts the medium. Thus, it is possible to use conventional well known materials such as C, SiO2, or ZrO2.
When the thickness of the protective film 6 is equal to or greater than 1 nm and equal to or less than 7 nm, the distance between the magnetic head and the medium becomes small, and thus is desirable in terms of high recording density.
Preferably, conventional a well known material such as perfluoropolyether, fluorinated alcohols, fluorinated carbons or the like are used in the lubricating film 7.
To manufacture the magnetic recording medium, it is possible to use a method in which the non-magnetic substrate 1, soft magnetic undercoat film 2, first undercoat film 3, second undercoat film 4, and perpendicular magnetic recording film 5 are formed in sequence by sputtering and the like, the protective film 6 is formed by sputtering or CVD, and the lubricating film 7 is formed by dipping or the like.
In the magnetic recording medium of the present embodiment, the first undercoat film 3 consists of Pt, Pd, or an alloy of at least one among them, and the second undercoat film 4 consists of Ru or an Ru alloy. Thereby, the read/write properties and the thermal stability are improved, and it is possible to read and write high density data.
Using an alloy including at least one selected from among Fe, Co, and Ni, and at least one selected from among Ta, Nb, Zr, Si, B, C, N, and O is advantageous.
By providing the seed film 8, the first undercoat film 3 can be formed without being influenced by the crystallinity, crystal diameter, or surface state of the soft magnetic undercoat film 2.
It is particularly preferable to use a material for the seed film 8 that has a saturated magnetic flux density Bs equal to or greater than 0.3 T and a coercive force Hc equal to or less than 100 Oe. By using this material for the seed film 8, it is possible to prevent the resolution from deteriorating due to the distance between the magnetic head and the soft magnetic undercoat film 2.
It is advantageous to use a CoCr alloy that includes one selected from among Pt, Ta, Nb, Zr, Si, B, C, and O in the intermediate film 9.
By providing the intermediate film 9, it is possible to prevent the crystallinity of the perpendicular magnetic recording film 5 from deteriorating due to the disorder in the crystallinity in the interface between the second undercoat film 4 and the perpendicular magnetic recording film 5.
The thickness of the intermediate film 9 is preferably equal to or less than 5 nm (more preferably, equal to or less than 3 nm). When the thickness of the intermediate film 9 is within this range, the effect of the intermediate film 9 (preventing the deterioration of the crystallinity of the perpendicular magnetic recording film 5) is increased and the distance between the magnetic head and the soft magnetic undercoat film 2 during reading and writing can be reduced. Thereby, the read/write properties can be improved without decreasing the resolution of the read back signal.
The non-magnetic substrate 1, soft magnetic undercoat film 2, perpendicular magnetic recording film 5, protective film 6 and the lubricating film 7 can have the same composition as those in the first embodiment.
The undercoat film 23 controls the orientation and the crystal diameter of the intermediate film 24 provided directly above or the intermediate film 24 and the perpendicular magnetic recording film 5 provided directly above.
The material used in the intermediate film 23 is an alloy that includes at least Pt and C.
Using Pt without C is not preferable because the crystal diameter becomes large, and thus the crystal diameter in the perpendicular magnetic recording film 5 that is grown epitaxially becomes large due to the influence of the undercoat film 23, and thereby the noise increases.
The undercoat film 23 particularly preferably consists of any among a Pt—C alloy, Pt—Fe—C alloy, Pt—Ni—C alloy, Pt—Co—C alloy, or a Pt—Cr—C alloy.
The material used in the undercoat film 23 can be an alloy that includes at least Pd and C.
In the case that Pd is used without C, the crystal diameter becomes large, and thus the crystal diameter in the perpendicular magnetic recording film 5 that is grown epitaxially becomes large due to the influence of the undercoat film 23, and thereby the noise increases.
In the case that an alloy that includes Pd and C is used, the undercoat film 23 particularly preferably consists of any selected from among a Pd—C alloy, Pd—Fe—C alloy, Pd—Ni—C alloy, Pd—Co—C alloy, or Pd—Cr—C alloy.
The C content of the undercoat film 23 is preferably equal to or greater than 1 at % and equal to or less than 40 at % (more preferably, equal to or greater than 5 at % and equal to or less than 30 at %).
As shown in
The thickness of the undercoat film 23 is preferably equal to or greater than 0.5 nm and equal to or less than 15 nm (in particular, 1 to 10 nm). When the thickness of the undercoat film 23 is within this range, the perpendicular orientation of the perpendicular magnetic recording film 5 is particularly high and the distance between the magnetic head and the soft magnetic undercoat film 2 during reading and writing becomes small. Thus, it is possible to increase the read/write properties without lowering the resolution of the read back signal.
When this thickness falls below the above range, the perpendicular orientation in the perpendicular magnetic recording film 5 is reduced, and the read/write properties and the thermal stability deteriorates.
In addition, when this thickness exceeds the above range, the crystal particles become course and the distance between the magnetic head an the soft magnetic undercoat film 2 during reading and writing increases. Thus, the resolution of the read back signal and the read back output decrease.
The undercoat film 23 preferably has a fcc structure. Due to the undercoat film 23 having a fcc structure, the orientation of the intermediate film 24 provided directly above and/or the perpendicular magnetic recording film 5 is good, and it is possible to make the crystal particles microcrystalline. The state of the particles can be confirmed, for example, by X-ray diffraction or transmission electron microscopy (TEM).
The average diameter of the crystal particles in the undercoat film 23 is equal to or greater than 5 nm and equal to or less than 12 nm. This average diameter can be found, for example, by observing the crystal particles of the undercoat film 23 using TEM (transmission electron microscopy) and processing the observed image.
The surface profile of the undercoat film 23 influences the surface profile of the perpendicular magnetic recording film 5 and the protective film 6, and thus in order to make the surface irregularities of the magnetic recording medium small and decrease the magnetic head flying height during reading and writing, the mean surface roughness Ra of the undercoat film 23 is preferably equal to or less than 2 nm.
Because this mean surface roughness Ra is equal to or less than 2 nm, the surface irregularities of the magnetic recording medium are reduced, the magnetic head flying height during reading and writing is sufficiently decreased, and thereby it is possible to increase the recording density.
When forming the undercoat film 23, with the object of making the crystal particles of the perpendicular magnetic recording film 5 microcrystalline, it is possible to use a process gas that includes oxygen or nitrogen as the gas for film formation. For example, in the case that the undercoat film 23 is formed using a sputtering method, preferably a gas that is a mixture consisting of oxygen mixed into argon at a volume of approximately 0.05 to 10% (preferably, 0.1 to 3%) or a gas that is a mixture consisting of nitrogen mixed into argon at a volume of approximately 0.01 to 20% (preferably, 0.02 to 5%) is used.
The intermediate film 24 prevents distortion in the crystal structure of the perpendicular magnetic recording film 5 due to the difference in the crystal lattice size between the undercoat film 23 and the perpendicular magnetic recording film 5, and at the same time, decreases the exchange coupling of the magnetic particles (crystal particles) in the perpendicular magnetic recording film 5.
Preferably a material having a hcp structure or a fcc structure is used in the intermediate film 24.
The intermediate film 24 preferably includes at least one among Ru and Co.
The thickness of the intermediate film 24 is preferably equal to or less than 10 nm (preferably equal to or less than 6 nm) so as not to cause a deterioration in the read/write properties due to the magnetic particles (crystal particles) in the perpendicular magnetic recording film 5 becoming coarse or a decrease in the resolution because of increase in the distance between the magnetic head and the undercoat film 2.
The thickness of the intermediate film 24 can be made a value that exceeds 10 nm (for example, equal to or greater than 15 nm).
Note that in the present invention a structure that does not provide the intermediate film 24 is also possible.
To manufacture the magnetic recording medium described above, a method used in which the soft magnetic undercoat film 2, the undercoat film 23, intermediate film 24, and the perpendicular magnetic recording film 5 are formed in sequence on the non-magnetic substrate 1 by a sputtering method or the like, the protective film 6 is formed by a sputtering method, a CVD method or the like, and the lubricating film 7 is formed by a dipping method or the like.
Preferably, the undercoat film 23 is formed at a temperature of 150 to 400° C.
Superior read/write properties can be obtained when the temperature is in this range.
In the magnetic recording medium of the present embodiment, the undercoat film 23 consists of an alloy that includes at least Pt and C or an alloy that includes at least Pd and C, and thus the read/write properties and the thermal stability improve, and the reading and writing of high density data becomes possible.
The seed film 8 can be formed identically to that shown in the second embodiment.
By providing the seed film 8, it is possible to form the undercoat film 23 without being influenced by the crystallinity, the crystal grain diameter, or the surface condition of the soft magnetic undercoat film 2.
A single pole head for perpendicular magnetic recording can be used as the magnetic head 12.
As shown in
According to the magnetic read/write apparatus described above, because of using the magnetic recording medium 10 described above, it is possible to increase both the thermal stability and the read/write properties.
Therefore, according to the magnetic read/write apparatus, troubles such as data loss due to thermal fluctuation can be prevented from occurring, and at the same time it is possible to implement high recording density.
The operational effect of the present invention will now be clarified by way of examples. However, the present invention is not limited to the following examples.
A cleaned glass substrate 1 (Ohara Co. of JAPAN, external diameter: 2.5 inches) was accommodated in the film formation chamber of a DC magnetron sputtering apparatus (ANELVA of JAPAN, C-3010). After air was expelled from the film formation chamber until an ultimate vacuum of 1×10−5 Pa was attained, a soft magnetic undercoat film 2 having a thickness of 180 nm was formed on the substrate 1 using a sputtering method by using a target consisting of 89Co-4Zr-7Nb (a Co content of 89 at % , a Zr content of 4 at % , and an Nb content of 7 at % ). It was confirmed by using a vibrating sample magnetometer (VSM) that the product of the saturation magnetic flux Bs and the film thickness t, that is, B·t, of this film was 200 T·nm.
Next, at 240° C., a first undercoat film 3 having a thickness of 5 nm was formed on the soft magnetic undercoat film 2 described above by using a 75Pt-25C (Pt content of 75 at % and a C content of 25 at % ) target. At this point in time, the crystal particles of the surface of the first undercoat film 3 were observed using TEM, and found to have an average diameter of 8 nm.
On the first undercoat film 3, the second undercoat film 4 having a thickness of 5 nm was formed by using a Ru target, and the perpendicular magnetic recording film 5 having a thickness of 20 nm was formed by using a 64Co-17Cr-17Pt-2B (Co content at 64 at % , Cr content at 17 at % , Pt content at 17 at % and B content at 2 at % ) target. Note that in the sputtering step described above, argon was used as the processing gas for film formation, and the film was formed under a pressure of 0.6 Pa.
Next, a protective film 6 having a thickness of 5 nm was formed by using CVD.
After that, a lubricating film 7 consisting of a perfluoropolyether was formed using a dipping method, and a magnetic recording medium was obtained. The composition of this magnetic recording medium is shown in Table 1.
Except for the first undercoat film 3 not being provided, the magnetic recording medium was fabricated according to Example 1. The composition of this magnetic recording medium is shown in Table 1.
Except for the second undercoat film 4 not being provided, the magnetic recording media were fabricated according to Example 1. The compositions of these magnetic recording media are shown in Table 1.
The magnetic recording media in the Example and the Comparative Examples were evaluated. The evaluation of the read/write properties was carried out by using a read/write analyzer RWA1632 and a spin stand S1701MP manufactured by GIZIK Co. (USA).
In the evaluation of the read/write properties, a magnetic head using a single pole electrode in the write portion and using a GMR element in the read back portion were employed, and the recording frequency conditions were measured as a track recording density of 600 kFCI.
In the evaluation of the thermal fluctuation properties, the spin stand described above, and the magnetic head described above were used. After writing at a track recording density of 50 kFCI at a temperature of 70° C., the rate of decrease (%/decade) of the output with respect to the read back output after writing 1 second was calculated based on (S-So)×100/(S0×3). In this equation, So denotes the read back output after the passage of 1 second after writing the signal on the magnetic recording medium, and S denotes the read back output after 1000 seconds. The results of the test are shown in Table 1.
As shown in Table 1, the Examples providing the first undercoat film 3 and the second undercoat film 4 showed read/write properties that were superior compared to the comparative Example.
Except for the composition of the first undercoat film 3 shown in Table 2, the magnetic recording media were fabricated according to Example 1.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 2.
As shown in Table 2, the Examples in which the first undercoat film 3 consists of Pt or a Pt alloy showed superior read/write properties.
Except for the thickness of the first undercoat film 3 shown in Table 3, the magnetic recording media were fabricated according to Example 1.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 3.
As shown in Table 3, the Examples in which the thickness of the first undercoat film 3 was equal to or greater than 0.5 nm and equal to or less than 10 nm (in particular, 1 to 7 nm) showed superior read/write properties.
Except for the composition of the second undercoat film 4 shown in Table 4, the magnetic recording media were fabricated according to Example 1.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 4.
As shown in Table 4, the Examples in which the second undercoat film 4 consisted of Ru or an Ru alloy showed superior read/write properties.
Except for the thickness of the second undercoat film 4 shown in Table 5, the magnetic recording media were fabricated according to Example 1.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 5.
As shown in Table 5, the Examples in which the thickness of the second undercoat film 4 was equal to or greater than 0.5 nm and equal to or less than 10 nm (in particular, 1 to 7 nm) showed superior read/write properties.
Except for the material and thickness of the soft magnetic undercoat film 2 shown in Table 6, the magnetic recording media were fabricated according to Example 1.
Except for providing the seed film 8 between the soft magnetic undercoat film 2 and the first undercoat film 3, the magnetic recording media were fabricated according to Example 1.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 6.
As shown in Table 6, the Examples show superior read/write properties. In particular, in the Examples in which the seed film 8 was provided, superior read/write properties were obtained.
Except for providing the intermediate film 9 between the second undercoat film 4 and the perpendicular magnetic recording film 5, the magnetic recording media were fabricated according to Example 1.
Except for the material and thickness of the perpendicular magnetic recording film 5 shown in Table 7, the magnetic recording media were fabricated according to Example 1.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the test are shown in Table 7.
As shown in Table 7, the Examples showed superior read/write properties.
Except for forming the first undercoat film 3 as explained below, the magnetic recording media were fabricated according to Example 1.
Specifically, a first undercoat film 3 having a thickness of 5 nm was formed on the soft magnetic undercoat film 2 by using a 75Pd-25C (Pd content at 75 at % and C content at 25 at % ) target. At this point in time, the crystal particles of the surface of the undercoat film 3 were observed using TEM, and found to have an average diameter of 8.3 nm.
The read/write properties of the magnetic recording medium in this Example were evaluated. The results of the tests are shown in Table 8.
Except for not providing the second undercoat film 4, the magnetic recording media were fabricated according to Example 45. The read/write properties of the magnetic recording media were evaluated. The results of the tests are shown in
Except for the composition and thickness of the first undercoat film 3 shown in Table 8, the magnetic recording media were fabricated according to Example 45.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 8.
As shown in Table 8, the Examples in which the first undercoat film 3 consists of Pd or a Pd alloy showed superior read/write properties. Superior read/write properties were obtained in the case of using an alloy that included Pt and Pd as well.
Except for the composition and thickness of the first undercoat film 3, the second undercoat film 4, and the perpendicular magnetic recording film 5 shown in Table 9, the magnetic recording media were fabricated according to Example 1.
The read/write properties of magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 9.
As shown in Table 9, the Examples in which a material that included an oxide was used in the first undercoat film 3, the second undercoat film 4, and the perpendicular magnetic recording film 5 showed superior read/write properties.
A cleaned glass substrate 1 (Ohara Co. of JAPAN, external diameter 2.5 inches) was accommodated in the film formation chamber of a DC magnetron sputter apparatus (ANELVA of JAPAN, C-3010). After air was expelled from the film formation chamber until an ultimate vacuum of 1×10−5 Pa was attained, a soft magnetic undercoat film 2 having a thickness of 180 nm was formed on the substrate 1 using a sputtering method using a target consisting of 89Co-4Zr-7Nb (Co content of 89 at % , a Zr content of 4 at %, and an Nb content of 7 at % ). It was confirmed by using a vibrating sample magnetometer (VSM) that the product of the saturation magnetic flux Bs and the film thickness t, that is, B·t, of this film was 200T·nm.
Next, at 240° C., the undercoat film 23 having a thickness of 5 nm was formed on the soft magnetic undercoat film 2 described above by using a 75Pt-25C (Pt content of 75 at % and a C content of 25 at % ) target. At this point in time, the crystal particles of the surface of the undercoat film 23 were observed using TEM, and found to have an average diameter of 8 nm.
On the undercoat film 23, the intermediate film 24 having a thickness of 2 nm was formed by using a Ru target, and the perpendicular magnetic recording film 5 having a thickness of 20 nm was formed by using a 64Co-17Cr-17Pt-2B (Co content at 64 at % , Cr content at 17 at % , Pt content at 17 at % and B content at 2 at % ) target. Note that in the sputtering step described above, argon was used as the processing gas for film formation, and the film was formed under a pressure of 0.6 Pa.
Next, a protective film 6 having a thickness of 5 nm was formed by using a CVD method.
Next, a lubricating film 7 consisting or a perfluoropolyether was formed by using a dipping method, and a magnetic recording medium was obtained.
Except for forming the undercoat film 23 by using targets consisting of Pt. Ru, or C, the magnetic recording media were formed according to Example 78. The compositions of these magnetic recording media are shown in Table 10.
The read/write properties of the magnetic recording media in these Examples and Comparative Examples were evaluated. The evaluation of the read/write properties was carried out by using a read/write analyzer RWA1632 and a spin stand S1701MP manufactured by GIZIK Co. (USA).
In the evaluation of the read/write properties, a magnetic head using a single pole electrode in the write portion and using a GMR element in the read back portion was employed, and the recording frequency conditions were measured as a track recording density of 600 kFCI.
In the evaluation of the thermal fluctuation properties, the spin stand described above and the magnetic head described above were used, and after writing at a track recording density of 50 kFCI at a temperature of 70° C., the rate of decrease (%/decade) of the output with respect to the read back output after writing 1 second was calculated based on (S-So)×100/(S0×3). In this equation, So indicates the read back output after the passage of 1 second after writing the signal on the magnetic recording medium, and S indicates the read back output after 1000 seconds. The results of the test are shown in Table 10.
As shown in Table 10, the Examples in which the undercoat film 23 consists of 75Pt-25C shows superior read/write properties compared to the Comparative Examples.
Except for the compositions of the undercoat film 23 shown in Table 11, the magnetic recording media were fabricated according to Example 78.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 11.
As shown in Table 11, the Examples in which the undercoat film 23 included at least Pt or C, superior read/write properties were shown. In particular, the Examples in which the C content of the undercoat film 23 was equal to or greater than 1 at % and equal to or less than 40 at % (in particular, equal to or greater than 5 at % and equal to or less than 30 at % ) showed superior properties.
Except for the thickness of the undercoat film 23 shown in Table 12, the magnetic recording media were fabricated according to Example 78.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 12.
As shown in Table 12, the Examples in which the thickness of the undercoat film 23 was equal to or greater than 0.5 nm and equal to or less than 15 nm (in particular 1 to 10 nm) showed superior read/write properties.
Except for the temperature during formation of the undercoat film 23 shown in Table 13, the magnetic recording media were fabricated according to Example 78.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 13.
As shown in Table 13, the Examples for which the temperature during the formation of the undercoat film 23 was from 150 to 400° C. showed superior read/write properties.
Except for the material and thickness of the soft magnetic undercoat film 2 shown in
Except for providing the seed film 8 between the soft magnetic undercoat film 2 and the undercoat film 23, the magnetic recording media were fabricated according to Example 78.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 14.
As shown in Table 14, the Examples showed superior read/write properties. In particular, superior read/write properties were obtained in the Examples providing the seed film 8 obtained.
Except for the material and thickness of the intermediate film 24 and the perpendicular magnetic recording film 5 shown in Table 15, the magnetic recording media were fabricated according to Example 78.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results are shown in Table 15.
Note that in the Table, Ru/CoCr indicates having a two-layer structure in which the intermediate film 24 provides a second layer consisting of CoCr on the first layer that consists of Ru. The thickness of the intermediate films 24 are all 2 nm, and this is denoted by 2/2.
As shown in Table 15, the Examples showed superior read/write properties.
Except for forming the undercoat film 23 as follows, the magnetic recording medium was fabricated according to Example 78.
Specifically, the undercoat film 23 having a thickness of 5 nm was formed on a soft magnetic undercoat film 2 by using a 75Pd-25C (Pd content at 75 at % and C content at 25 at % ) target. At this point in time, the crystal particles of the surface of the undercoat film 23 were observed using TEM, and found to have an average diameter of 8.3 nm.
The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 16.
Except for forming the undercoat film 23 using the target consisting of Pd, the magnetic recording media were fabricated according to Example 117. The read/write properties of this magnetic recording medium were evaluated. The results of the tests are shown in Table 16.
Except for the composition and thickness of the undercoat film 23 shown in Table 16, the magnetic recording media were fabricated according to Example 117. The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 16.
As shown in Table 16, Examples in which the undercoat film 23 included at least Pd and C showed superior read/write properties.
Magnetic recording media were fabricated in which the material and the thickness of the intermediate film 24 and the perpendicular magnetic recording film 5 were as shown in Table 17. The other conditions were according to Example 78. The read/write properties of the magnetic recording media in these Examples were evaluated. The results of the tests are shown in Table 17.
As shown in Table 17, the Examples in which the perpendicular magnetic recording film S included an oxide showed superior read/write properties.
In the magnetic recording media of the present invention, at least a soft magnetic undercoat film, a first undercoat film, a second undercoat film, a perpendicular magnetic recording film, and a protective film are provided on a non-magnetic substrate; the first undercoat film consists of Pt, Pd, or an alloy including at least one among them; and the second undercoat film consists of Ru or an Ru alloy. Thereby, it is possible to improve the read/write properties and the thermal stability.
In addition, a soft magnetic undercoat film, an undercoat film that controls the orientation and crystal diameter of the film directly above, a perpendicular magnetic recording film in which the easy magnetization axis is generally oriented perpendicular to the substrate, and a protective film are provided; the undercoat film consists of an alloy that includes at least Pt and C or an alloy that includes at least Pd and C are provided on a non-magnetic substrate. Thereby, it is possible to improve the read/write properties and the thermal stability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-6188 | Jan 2003 | JP | national |
| 2003-6189 | Jan 2003 | JP | national |
| 2003-103452 | Apr 2003 | JP | national |
| 2003-103453 | Apr 2003 | JP | national |
This application claims the benefit of Japanese Unexamined Patent Application, First Publication No. 2003-6188 filed Jan. 14, 2003; Japanese Unexamined Patent Application, First Publication No. 2003-6189 filed Jan. 14, 2003; Japanese Unexamined Patent Application, First Publication No. 2003-103452 filed Apr. 7, 2003; Japanese Unexamined Patent Application, First Publication No. 2003-103453 filed Apr. 7, 2003; and U.S. Provisional Application No. 60/440,631, the contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/00205 | 1/14/2004 | WO | 00 | 5/17/2006 |
| Number | Date | Country | |
|---|---|---|---|
| 60440631 | Jan 2003 | US |
