U.S. patent application number 13/934164 was filed with the patent office on 2013-11-07 for magnetic recording medium and manufacturing method thereof.
The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Takeshi Iwasaki, Yoshiyuki Kamata, Kaori Kimura, Masatoshi Sakurai.
Application Number | 20130295299 13/934164 |
Document ID | / |
Family ID | 45527048 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130295299 |
Kind Code |
A1 |
Iwasaki; Takeshi ; et
al. |
November 7, 2013 |
MAGNETIC RECORDING MEDIUM AND MANUFACTURING METHOD THEREOF
Abstract
According to one embodiment, a magnetic recording medium
includes a substrate, a soft magnetic layer, an underlayer, a
magnetic recording layer, and a protective layer, wherein the
magnetic recording layer is provided with a pattern including
recording portions and non-recording portions, the non-recording
portions have a composition that is equal to a composition obtained
by demagnetizing the recording portions, the non-recording portions
contain at least one metal element selected from the group
consisting of vanadium and zirconium and at least one element
selected from the group consisting of nitrogen, carbon, boron and
oxygen, and the at least one element selected from the group
consisting of nitrogen, carbon, boron and oxygen is contained in
the non-recording portions at a higher content than the content of
the at least one element selected from the group consisting of
nitrogen, carbon, boron and oxygen in the recording portions.
Inventors: |
Iwasaki; Takeshi;
(Inagi-shi, JP) ; Kimura; Kaori; (Yokohama-shi,
JP) ; Kamata; Yoshiyuki; (Tokyo, JP) ;
Sakurai; Masatoshi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Tokyo |
|
JP |
|
|
Family ID: |
45527048 |
Appl. No.: |
13/934164 |
Filed: |
July 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13175485 |
Jul 1, 2011 |
8507116 |
|
|
13934164 |
|
|
|
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Current U.S.
Class: |
427/595 |
Current CPC
Class: |
Y10T 428/11 20150115;
G11B 5/746 20130101; G11B 5/855 20130101; G11B 5/82 20130101; G11B
5/8404 20130101 |
Class at
Publication: |
427/595 |
International
Class: |
G11B 5/84 20060101
G11B005/84 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2010 |
JP |
2010-171136 |
Claims
1. A method of manufacturing a magnetic recording medium
comprising: forming a patterned mask layer and a
magnetism-deactivating layer comprising at least one metal element
selected from the group consisting of vanadium and zirconium on a
magnetic recording layer; and diffusing the metal element from the
magnetism-deactivating layer into the magnetic recording layer
through recessed portions of the pattern of the mask layer by ion
beam irradiation using a gas comprising at least one second element
selected from the group consisting of nitrogen, carbon, boron, and
oxygen.
2. The method of claim 1, wherein the gas comprises at least one of
gas selected from the group consisting of N.sub.2, CH.sub.4,
B.sub.2H.sub.6, O.sub.2, and O.sub.3.
3. The method of claim 2, wherein the gas further comprises He.
4. The method of claim 1, wherein the magnetism-deactivating layer
comprises, as a major component, a simple substance, nitride,
carbide, oxide, or boride of the at least one metal element or a
mixture of any of these materials.
5. The method of claim 1, wherein the metal element is
vanadium.
6. The method of claim 1, wherein the metal element is
zirconium.
7. The method of claim 1, wherein the second element is nitrogen.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 13/175,485, filed Jul. 1, 2011, which is based upon and claims
the benefit of priority from Japanese Patent Application No.
2010-171136, filed Jul. 29, 2010, the entire contents of each which
are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a magnetic
recording medium such as a patterned medium and to a manufacturing
method thereof.
BACKGROUND
[0003] In the information-oriented society in recent years, the
amount of data to be stored in a recording medium is continually
increasing. For this reason, a recording apparatus and a recording
medium with an outstandingly high recording capacity have been
desired. Also, hard disks, which are currently in an increasing
demand as an economical recording medium of high capacity, are
expected to be required to have recording density of 1 tera-bit or
more per square inch, which is ten times the current density, in
coming years.
[0004] In a magnetic recording medium used in conventional hard
disks, a predetermined region of a thin film including polycrystals
of magnetic fine particles is used as one bit for recording. In
order to increase recording capacity of a magnetic recording
medium, the recording density should be increased. In other words,
it is necessary to reduce the recording mark size which is usable
for recording of one bit. However, when the recording mark size is
simply reduced, the influence of noise which depends on the shapes
of magnetic fine particles becomes nonnegligible. If the particle
size of magnetic fine particles is reduced to lower the noise, a
problem of thermal fluctuation occurs, which makes it impossible to
maintain recorded data at a room temperature.
[0005] In order to avoid these problems, a bit patterned medium
(BPM) has been proposed, in which the recording material is
separated by a non-magnetic material in advance, and a single
magnetic dot is used as a single recording cell to perform read and
write.
[0006] In magnetic recording media installed in HDDs, there is an
arising problem of the interference between adjacent tracks which
inhibits improvement in track density. Particularly, reducing a
fringe effect of a write head field is a significant technical
problem to be solved. To solve this problem, there has been
developed a discrete track recording-type patterned medium (DTM),
in which the magnetic recording layer is processed so that the
recording tracks are physically separated from each other. In the
DTM, it is possible to reduce side erase which erases information
in the adjacent tracks in writing and side read which reads
information in the adjacent tracks in reading. On this account, the
DTM is promising as a magnetic recording medium capable of
providing a high recording density. Incidentally, it should be
noted that the term "patterned medium" as used herein in a broad
sense includes the bit patterned medium and DTM.
[0007] With respect to methods for manufacturing the BPM and the
DTM as described above, there are known a method wherein a pattern
of protrusions and recesses is formed on the surface of a magnetic
recording layer by way of fine working such as etching, and a
method wherein a pattern consisting of magnetic regions and
non-magnetic regions of a magnetic layer is formed by way of
chemical treatment. With respect to the latter method, various
methods are known, including, for example, a method wherein
specific regions of the magnetic recording layer are exposed to a
magnetically deactivating gas to thereby deactivate the magnetism
of the specific regions, a method wherein specific regions are
deactivated by the injection of an ionized element by making use of
a plasma beam, etc., and a method wherein a deactivating material
is deposited on specific regions to thereby allow the material to
diffuse into the specific regions.
[0008] In spite of these conventional techniques now available, it
is still demanded to manufacture a magnetic recording medium
wherein the magnetism of non-recording regions of the magnetic
recording medium can be efficiently and sufficiently
deactivated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A general architecture that implements the various features
of the embodiments will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate the embodiments and not to limit the scope of the
invention.
[0010] FIG. 1 is a plan view taken along the circumferential
direction of a bit-patterned medium according to one
embodiment;
[0011] FIG. 2 is a plan view taken along the circumferential
direction of a DTR medium according to one embodiment;
[0012] FIG. 3 is a cross-sectional view showing one example of a
magnetic recording medium according to one embodiment;
[0013] FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 4I, 4J and 4K
respectively show a cross-sectional view illustrating a
manufacturing method of a magnetic recording medium according to a
first embodiment;
[0014] FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, 5J and 5K
respectively show a cross-sectional view illustrating a
manufacturing method of a magnetic recording medium according to a
second embodiment; and
[0015] FIG. 6 is a perspective view showing a magnetic recording
apparatus mounting a magnetic recording medium manufactured
according to one embodiment.
DETAILED DESCRIPTION
[0016] Various embodiments will be described hereinafter with
reference to the accompanying drawings.
[0017] In general, according to one embodiment, a magnetic
recording medium comprises a substrate, a soft magnetic layer on
the substrate, an underlayer on the soft magnetic layer, a magnetic
recording layer on the underlayer, and a protective layer on the
magnetic recording layer, wherein the magnetic recording layer is
provided with a pattern including recording portions and
non-recording portions, the non-recording portions have a
composition that is equal to a composition obtained by
demagnetizing the recording portions, the non-recording portions
contain at least one metal element selected from the group
consisting of vanadium and zirconium and at least one element
selected from the group consisting of nitrogen, carbon, boron and
oxygen, and the at least one element selected from the group
consisting of nitrogen, carbon, boron and oxygen is contained in
the non-recording portions at a higher content than the content of
the at least one element selected from the group consisting of
nitrogen, carbon, boron and oxygen in the recording portions.
[0018] <Magnetic Recording Medium>
[0019] FIG. 1 shows a plan view of a bit patterned recording medium
(BPM) which is an example of the patterned medium 100 of the
embodiment along the circumferential direction. As shown in FIG. 1,
servo regions 110 and data regions 120 are alternately formed along
the circumferential direction of the medium. The servo region 110
includes a preamble section 111, an address section 112 and a burst
section 113. In this patterned medium, magnetic dots 121 are formed
in the data region 120.
[0020] FIG. 2 shows a plan view of a discrete track recording
medium (DTM) which is another example of the patterned medium
manufactured of the embodiment along the circumferential direction.
The data region 120 includes discrete tracks 120 wherein adjacent
tracks are separated from each other.
[0021] FIG. 3 shows a cross-sectional view of one example of a
magnetic recording medium 100 according to one embodiment. The
magnetic recording medium 100 according to this embodiment
comprises a stacked layer including a soft magnetic layer (CoTaZr)
having a thickness of 40 nm and an underlayer (Ru) for orientation
control having a thickness of 20 nm (in FIG. 3, both layers are
inclusively shown as an underlayer 2), a magnetic recording layer 3
(CoPtCr) having a thickness of 20 nm and including recording
regions 31 having magnetism and non-recording regions 32 having no
magnetism, a protective layer 10 formed of diamond-like carbon
(DLC) and having a thickness of 4 nm, and a lubricating layer (not
shown), all of these layers being formed on the surface of a glass
substrate 1.
[0022] The patterns shown in FIGS. 1 and 2 are constituted by the
recording regions 31 and non-recording regions 32 shown in FIG. 3.
Namely, the structure represented by a rectangle in FIGS. 1 and 2
corresponds to the recording regions 31 of FIG. 3.
[0023] <Manufacturing Method of a Magnetic Recording Medium
According to a First Embodiment>
[0024] FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 4I, 4J and 4K
respectively illustrate a manufacturing method of a magnetic
recording medium according to a first embodiment. The following is
an explanation of this manufacturing method.
[0025] As shown in FIG. 4A, a soft magnetic layer (CoTaZr) having a
thickness of 40 nm (not shown), an underlayer (Ru) for orientation
control having a thickness of 20 nm (not shown), a magnetic
recording layer 3 (CoPtCr) having a thickness of 20 nm and a DLC
layer 4 having a thickness of 4 nm are successively deposited on
the surface of a glass substrate 1. Furthermore, a first hard mask
5 made of Mo and having a thickness of 5 nm, a second hard mask 6
made of C and having a thickness of 25 nm, and a third hard mask 7
made of Si and having a thickness of 3 nm are successively
deposited on the DLC layer 4. Furthermore, a resist 8 is
spin-coated on the third hard mask (Si) 7 to a thickness of 50 nm.
Meanwhile, a stamper provided with a pattern of protrusions and
recesses corresponding to the pattern shown in FIG. 1 or FIG. 2 for
example is prepared. This stamper can be manufactured by a series
of processes including EB drawing, Ni electrocasting and injection
molding. The stamper is disposed in a manner to make the pattern
thereof face the resist 8.
[0026] As shown in FIG. 4B, the stamper is imprinted in the resist
8, thereby transferring the pattern of protrusions and recesses of
the stamper to the resist 8. Thereafter, the stamper is taken out.
A residue of the resist is left on the bottom of the recessed
portions of the pattern that has been transferred to the resist
8.
[0027] As shown in FIG. 4C, by way of dry etching, the residual
resist existing in the recessed portions is removed to allow the
surface of the third hard mask 7 (Si) to be exposed. This step can
be carried out, for example, by making use of an inductively
coupled plasma (IPC)-reactive ion etching (RIE) apparatus, wherein
CF.sub.4 is used as a process gas, the pressure inside the chamber
is set to 0.1 Pa, the coil RF power and the platen (bias) RF power
are set to 100 W and 50 W, respectively, and the etching time is
set to 60 seconds.
[0028] As shown in FIG. 4D, by making use of the patterned resist
as a mask, the pattern is transferred to the third hard mask 7 (Si)
by means of ion beam etching, thereby allowing the second hard mask
6 (C) to be exposed at the recessed portions. This step can be
carried out, for example, by making use of the IPC-RIE apparatus,
wherein CF.sub.4 is used as a process gas, the pressure inside the
chamber is set to 0.1 Pa, the coil RF power and the platen RF power
are set to 100 W and 50 W, respectively, and the etching time is
set to 20 seconds.
[0029] As shown in FIG. 4E, by making use of the patterned third
hard mask 7 (Si) as a mask, the second hard mask 6 made of C is
etched to transfer the pattern to the second hard mask 6, thereby
allowing the surface of the first hard mask 5 (Mo) to be exposed at
the recessed portions. This step can be carried out, for example,
by making use of the IPC-RIE apparatus, wherein O.sub.2 is used as
a process gas, the pressure inside the chamber is set to 0.1 Pa,
the coil RF power and the platen RF power are set to 100 W and 50
W, respectively, and the etching time is set to 20 seconds.
[0030] As shown in FIG. 4F, by making use of the patterned second
hard mask 6 (C) as a mask, the first hard mask 5 made of Mo is
etched to transfer the pattern to the first hard mask 5, thereby
allowing the surface of the DLC layer 4 to be exposed at the
recessed portions. This step can be carried out, for example, by
making use of an ion-milling apparatus, wherein Ar gas is used, the
gas pressure is set to 0.06 Pa, accelerating voltage is set to 400
W, and the etching time is set to 10 seconds.
[0031] As shown in FIG. 4G, by making use of the patterned first
hard mask 5 (Mo) as a mask, the DLC layer 4 is etched to transfer
the pattern to the DLC layer 4, thereby allowing the surface of the
magnetic recording layer 3 to be exposed at the recessed portions.
This step can be carried out, for example, by making use of the
IPC-RIE apparatus, wherein O.sub.2 is used as a process gas, the
pressure inside the chamber is set to 0.1 Pa, the coil RF power and
the platen RF power are set to 100 W and 50 W, respectively, and
the etching time is set to 5 seconds.
[0032] As shown in FIG. 4H, as a magnetism-deactivating layer 9, a
vanadium layer having a thickness of 10 nm is deposited on the
surfaces of the mask and the magnetic recording layer 3. This
deposition can be carried out, for example, by means of DC
sputtering using Ar gas, wherein the pressure inside the chamber is
set to 0.7 Pa, the power is set to 500 W, and the deposition time
is set to 10 seconds. As a result of this step, the
magnetism-deactivating layer 9 is allowed to deposit on the surface
of the mask at the portions where the mask exists and also on the
surface of the magnetic recording layer 3 at the portions where the
mask does not exist.
[0033] As shown in FIG. 4I, the vanadium element contained in the
magnetism-deactivating layer 9 is allowed to diffuse into the
magnetic recording layer 3. This step can be carried out, for
example, by making use of an electron cyclotron resonance (ECR) ion
gun, wherein N.sub.2 gas is used, the gas pressure is set to 0.1
Pa, the microwave power is set to 1000 W, accelerating voltage is
set to 5000V, and treating time is set to 10 seconds. As a result,
the vanadium is allowed to diffuse selectively into specific
regions of magnetic recording layer 3 which are not covered with
the mask, thereby creating non-recording portions 32 exhibiting
non-magnetism. On the other hand, the regions of magnetic recording
layer 3 covered with the mask are turned into recording portions 31
retaining magnetism. In the processes described with reference to
FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 4I, 4J and 4K, the volume of
the non-recording portions 32 is kept almost the same before and
after the diffusion of vanadium. As a result, the thickness of the
recording portions 31 is approximately the same as that of the
non-recording portions 32 even after the diffusion of vanadium.
[0034] As shown in FIG. 4J, the first hard mask 5 (Mo) which has
been left is removed together with the layers deposited thereon.
This step can be carried out, for example, by dipping the medium in
a stripping solvent and then by separating the mask from the DLC
layer 4. With respect to the stripping solvent, it is possible to
employ, for example, an aqueous solution of hydrogen peroxide. When
the medium is dipped into this aqueous solution of hydrogen
peroxide and left to stand for one minute, the first hard mask 5
(Mo) as well as the masks thereon can be entirely separated from
the DLC layer 4.
[0035] Thereafter, as shown in FIG. 4K, by means of a chemical
deposition method (CVD), the protective layer 10 formed of
diamond-like carbon (DLC) and having a thickness of 4 nm is
deposited and then a lubricating agent (not shown) is coated
thereon to obtain a magnetic recording medium.
[0036] <Manufacturing Method of a Magnetic Recording Medium
According to a Second Embodiment>
[0037] FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, 5J and 5K
respectively illustrate a manufacturing method of a magnetic
recording medium according to a second embodiment. In the method
shown in FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, 5J and 5K, the
steps of FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G and 5H can be carried out
in the same manner as described in the steps of FIGS. 4A, 4B, 4C,
4D, 4E, 4F, 4G and 4H. Therefore, the step of FIG. 5I and the steps
following the step of FIG. 5I will be explained below.
[0038] As shown in FIG. 5I, the vanadium element contained in the
magnetism-deactivating layer 9 is allowed to diffuse into the
magnetic recording layer 3. This step differs from the step of FIG.
4I in the respect that the conditions for carrying out the
diffusion of vanadium are adjusted so as to reduce the density of
the non-recording portions 32, thereby expanding the volume of
non-recording portions 32. This step can be carried out, for
example, by making use of an ECR ion gun, wherein N.sub.2 gas is
used, gas pressure is set to 0.1 Pa, the microwave power is set to
1000 W, accelerating voltage is set to 5000V, and treating time is
set to 100 seconds. As a result, the volume of non-recording
portions 32 is enabled to increase and hence the height of
non-recording portions 32 from the substrate 1 increases to almost
the same height as that of the DLC layer 4 as measured from the
substrate 1.
[0039] As shown in FIG. 5J, the first hard mask 5 (Mo) which is
left is removed together with the layers deposited thereon. This
step can be carried out, for example, by dipping the medium in a
stripping solvent and then by separating the mask from the DLC
layer 4. With respect to the stripping solvent, it is possible to
employ, for example, an aqueous solution of hydrogen peroxide. When
the medium is dipped into this aqueous solution of hydrogen
peroxide and left to stand for one minute, the first hard mask 5
(Mo) as well as the masks thereon can be entirely separated from
the DLC layer 4.
[0040] Thereafter, as shown in FIG. 5K, by means of CVD, the
protective layer 10 formed of DLC and having a thickness of 4 nm is
deposited and then a lubricating agent (not shown) is coated
thereon to obtain a magnetic recording medium. The medium to be
obtained from the method shown in FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G,
5H, 5I, 5J and 5K would not be so influenced by the pattern of
protrusions and recesses originating from the recording portions 31
and non-recording portions 32 and hence the surface smoothness of
the medium can be more enhanced.
[0041] <Magnetism-Deactivating Layer and Non-Recording
Portions>
[0042] Next, the magnetism-deactivating layer 9 will be further
explained in detail.
[0043] The magnetism-deactivating layer 9 contains at least one
metal element selected from the group consisting of vanadium and
zirconium. More specifically, the magnetism-deactivating layer 9
comprises, as a major component, at least one metal element
selected from the group consisting of vanadium and zirconium each
in a form of elementary substance, nitride, carbide, oxide or
boride, or a mixture of any of these materials.
[0044] In the manufacturing method according to the embodiment, as
shown in FIG. 4H or FIG. 5H for example, the magnetism-deactivating
layer 9 is deposited on a patterned mask after the patterned mask
has been formed on the surface of the magnetic recording layer 3.
The deposition of the magnetism-deactivating layer 9 can be carried
out, for example, by means of DC sputtering using Ar gas, wherein
the pressure inside the chamber is set to 0.7 Pa, the power is set
to 500 W, and the deposition time is set to 10 seconds. Further, in
order to obtain the nitrides or oxides of vanadium or zirconium, it
is possible to employ a reactive sputtering wherein Ar gas is mixed
with nitrogen gas or oxygen gas. In this manner, the
magnetism-deactivating layer 9 having a thickness of 10 nm can be
deposited on the surface of the magnetic recording layer 3 or on
the surface of the mask. In this case, the magnetism-deactivating
layer 9 is deposited on the surface of the mask in the regions
where the mask exists and also on the surface of the magnetic
recording layer 3 in the regions where the mask does not exist.
[0045] After finishing the deposition of the magnetism-deactivating
layer 9, the magnetism-deactivating layer 9 is allowed to diffuse
into the magnetic recording layer 3. This diffusion can be
executed, for example, by means of ion beam irradiation using a gas
containing at least one element selected from the group consisting
of nitrogen, carbon, boron and oxygen. In this case, the diffusion
to the magnetic recording layer 3 is effected from the
magnetism-deactivating layer 9 existing at the recessed portions of
the mask pattern. Incidentally, by the term "diffusion", it is
intended to include not only the phenomenon of the migration of
elements constituting the magnetism-deactivating layer 9 into the
magnetic recording layer 3 but also a phenomenon of forming a solid
solution or an alloy through an interaction between an element
contained in the magnetism-deactivating layer 9 and an element
constituting the magnetic recording layer 3 or a phenomenon of
forming a compound through the reaction between an element
contained in the magnetism-deactivating layer 9 and an element
constituting the magnetic recording layer 3.
[0046] With respect to the gas to be used for the ion beam
irradiation, it is possible to use a gas containing at least one
element selected from the group consisting of nitrogen, carbon,
boron and oxygen. For example, it is possible to use a gas
containing at least one gas selected from the group consisting of
N.sub.2, CH.sub.4, B.sub.2H.sub.6, O.sub.2 and O.sub.3. The gas
useful in this case may contain He. With respect to the time of
irradiating the ion beam, it may be suitably selected from a period
of time ranging from 5 seconds to 1200 seconds for example. With
respect to the conditions for the ion beam irradiation, it is
possible to employ, as one example, a method using an ECR ion gun
wherein N.sub.2 gas is used, gas pressure is set to 0.1 Pa, the
microwave power is set to 1000 W, accelerating voltage is set to
5000V, and treating time is set to 100 seconds.
[0047] Next, the features of non-recording portions 32 will be
explained in detail.
[0048] The non-recording portions 32 are formed through the
diffusion of the magnetism-deactivating layer 9 into the magnetic
recording layer 3. Owing to the effects of diffusion of the
magnetism-deactivating layer 9, the magnetism of non-recording
portions 32 is deactivated. These non-magnetic non-recording
portions 32 are designed, together with the recording portions 31
retaining magnetism, to form a pattern as shown in FIG. 1 or FIG.
2.
[0049] The non-recording portions 32 contain not only an element
contained in the magnetic recording layer 3 but also an element
contained in the magnetism-deactivating layer 9. Under some
circumstances, the non-recording portions 32 may contain an element
contained in the gas to be used in the ion beam irradiation to be
performed for the diffusion. More specifically, the non-recording
portions 32 contain at least one metal element selected from the
group consisting of vanadium and zirconium and at least one element
selected from the group consisting of nitrogen, carbon, boron and
oxygen.
[0050] The content of at least one metal element selected from the
group consisting of vanadium and zirconium and contained in the
non-recording portions 32 is preferably not less than 10 atomic %
(at %), more preferably not less than 20 at %.
[0051] The content of at least one element selected from the group
consisting of nitrogen, carbon, boron and oxygen, which is to be
contained in the non-recording portions 32 should preferably be
controlled such that it is at least 2 at %, more preferably at
least 5 at % higher than the content of at least one element
selected from the group consisting of nitrogen, carbon, boron and
oxygen, which is to be contained in the recording portions 31.
[0052] Next, advantages to be derived from the formation of the
non-recording portions 32 by way of the diffusion of the
magnetism-deactivating layer 9 will be explained below.
[0053] (Advantages of Selecting Vanadium or Zirconium)
[0054] It is possible, through the diffusion of
magnetism-deactivating layer 9 into the magnetic recording layer 3,
to efficiently and sufficiently deactivate the magnetism of the
non-recording portions 32. Namely, since vanadium is capable of
forming a solid solution (solid solution regions are partially
formed) together with any one of Co, Cr and Pt constituting the
magnetic recording layer 3, it is relatively easy to enable
vanadium to diffuse into the magnetic recording layer 3. On the
other hand, in the case of zirconium, since the enthalpy of
formation (.DELTA.H) of zirconium with Co bearing the magnetism of
the magnetic recording layer 3 is higher in the negative direction,
zirconium can be easily formed into an alloy together with Co.
Because of this, zirconium is enabled to easily diffuse into the
magnetic recording layer 3 of Co type. Further, nitrogen, carbon,
boron and oxygen are provided in themselves with an effect of
deactivating the magnetism of Co and, at the same time, are capable
of forming a compound together with vanadium or zirconium and
further together with chromium. As a result, it is possible to
promote the diffusion of vanadium or zirconium, thereby making it
possible to sufficiently demagnetize the magnetic recording layer
3.
[0055] Whereas, when metals other than vanadium and zirconium are
used as in the case of the prior art, it is impossible to
sufficiently solid-solubilize them in the magnetic recording layer
because of the reasons that the solid-solubilizing effects thereof
to Co, Cr and Pt are weak and the enthalpy of formation in the
negative direction is not sufficiently high. Further, since the
diffusing effect of them is weak, it is impossible to sufficiently
deactivate the magnetism of the magnetic recording layer. For
example, in the cases of Cr and Mn, although the solid solution
zone thereof is relatively high, the diffusing effect of Cr is weak
and Mn itself may exhibit magnetism, thereby making it impossible
to sufficiently deactivate the magnetism. Furthermore, when it is
tried to deactivate the magnetism by using only vanadium or
zirconium as in the case of the prior art, the effect of diffusion,
especially the solid-solubilizing effect, would be weak and, hence,
it would be impossible to sufficiently deactivate the
magnetism.
[0056] (Advantages of Selecting the Kinds of Gas)
[0057] The execution of the diffusion of magnetism-deactivating
layer 9 containing vanadium or zirconium by making use of a gas
containing at least one element selected from the group consisting
of nitrogen, carbon, boron and oxygen is effective in deriving
magnetism-deactivating effects of these gases as well as in
obtaining the effects of achieving enhanced diffusivity due to the
crystal destruction resulting from the creation of compounds to be
formed between vanadium or zirconium and the gas.
[0058] Further, the inclusion of He in the aforementioned gas (for
example, N.sub.2-He mixed gas) is effective in promoting the
diffusion of vanadium or zirconium in the non-recording portions
due to the additional effect of He to enhance amorphousness, thus
making it possible to increase the degree of the deactivation of
magnetism. Additionally, owing to the decrease of density due to
the enhanced amorphousness, the volume of the non-recording
portions is caused to expand. Since it is possible to create
recording portions having a relatively high density and
non-recording portions having a relatively low density as described
above, a difference in height between the recessed portions and the
protruded portions originating from the recording portions and the
non-recording portions can be minimized or avoided.
[0059] Moreover, if a compound is formed through a reaction between
at least one element selected from the group consisting of
nitrogen, carbon, boron and oxygen and vanadium or zirconium
contained in the magnetic recording layer 3, the density of the
non-recording portions can be decreased relatively and hence the
volume thereof will be expanded. As a result, a difference in
height between the recessed portions and the protruded portions
originating from the recording portions and the non-recording
portions can be minimized or avoided.
[0060] Whereas, if it is tried to diffuse vanadium or zirconium by
making use of an inert gas mainly containing a rare gas as in the
case of the prior art, it is impossible to expect the
aforementioned magnetism-deactivating effects to be brought about
by at least one element selected from the group consisting of
nitrogen, carbon, boron and oxygen. Furthermore, it is impossible
to expect the effect of promoting the diffusion as well as the
effect of expansion that can be derived from the formation of a
compound. In the case of the method to diffuse a compound directly
into the magnetic recording layer as seen in the prior art, it is
impossible to expect the effects of creating a solid solution or an
alloy through an interaction between vanadium or zirconium and Co,
Cr or Pt to thereby make it impossible to achieve a sufficient
demagnetization. Additionally, it is impossible to expect the
effects to be brought about by the formation of a compound from a
reaction between nitrogen, carbon, boron or oxygen and other
elements contained in the magnetic recording layer.
[0061] <Other Materials and Process>
[0062] Next, each of the constituent elements contained in a
magnetic recording medium according to the embodiments will be
explained.
[0063] (Magnetic Recording Layer and Recording Portions)
[0064] A perpendicular magnetic recording layer contains, for
example, Co, Cr and Pt. In the case BPM, the perpendicular magnetic
recording layer should preferably be constructed such that the
grain boundary thereof is as small as possible. If constructed in
this manner, the recording bit can be reversed almost as a single
grain on the occasion of forming recording bits through working. In
the case DPM, it may contain oxides in addition to Co, Cr and Pt.
As the oxide, silicon oxide or titanium oxide is particularly
preferable. The perpendicular magnetic recording layer preferably
has a structure in which magnetic grains, i.e., crystal grains
having magnetism, are dispersed in the layer. The magnetic grains
preferably have a columnar structure which penetrates the
perpendicular magnetic recording layer in the thickness direction.
The formation of such a structure improves the orientation and
crystallinity of the magnetic grains of the perpendicular magnetic
recording layer, with the result that a signal-to-noise ratio (SN
ratio) suitable to high-density recording can be provided. The
amount of the oxide to be contained is important to provide such a
structure.
[0065] The content of the oxide in the perpendicular magnetic
recording layer is preferably 5 mol % or more and 15 mol % or less
and more preferably 8 mol % or more and 12 mol % or less based on
the total amount of Co, Cr and Pt. The reason why the content of
the oxide in the perpendicular magnetic recording layer is
preferably in the above range is that, when the perpendicular
magnetic recording layer is formed, the oxide precipitates around
the magnetic grains, and can separate fine magnetic grains. If the
oxide content exceeds the above range, the oxide remains in the
magnetic grains and damages the orientation and crystallinity of
the magnetic grains. Moreover, the oxide precipitates on the upper
and lower parts of the magnetic grains, with an undesirable result
that the columnar structure, in which the magnetic grains penetrate
the perpendicular magnetic recording layer in the thickness
direction, is not formed. The oxide content less than the above
range is undesirable because the fine magnetic grains are
insufficiently separated, resulting in increased noise when
information is reproduced, and therefore, a signal-to-noise ratio
(SN ratio) suitable to high-density recording is not provided.
[0066] The content of Cr in the perpendicular magnetic recording
layer is preferably 0 at % or more and 16 at % or less and more
preferably 5 at % or more and 14 at % or less. The reason why the
content of the Cr is preferably in the above range is that the
uniaxial crystal magnetic anisotropic constant Ku of the magnetic
grains is not too much reduced and high magnetization is retained,
with the result that read/write characteristics suitable to
high-density recording and sufficient thermal fluctuation
characteristics are provided. The Cr content exceeding the above
range is undesirable because Ku of the magnetic grains is lowered,
and therefore, the thermal fluctuation characteristics are
degraded, and also, the crystallinity and orientation of the
magnetic grains are impaired, resulting in deterioration in
read/write characteristics.
[0067] The content of Pt in the perpendicular magnetic recording
layer is preferably 10 at % or more and 25 at % or less. The reason
why the content of Pt is preferably in the above range is that the
Ku value required for the perpendicular magnetic layer is provided,
and further, the crystallinity and orientation of the magnetic
grains are improved, with the result that the thermal fluctuation
characteristics and read/write characteristics suitable to
high-density recording are provided. The Pt content exceeding the
above range is undesirable because a layer having an fcc structure
is formed in the magnetic grains and there is a risk that the
crystallinity and orientation are impaired. The Pt content less
than the above range is undesirable because a Ku value satisfactory
for the thermal fluctuation characteristics suitable to
high-density recording is not provided.
[0068] The perpendicular magnetic recording layer may contain one
or more types of elements selected from B, Ta, Mo, Cu, Nd, W, Nb,
Ti, Ru and Mn besides Co, Cr, Pt and the oxides. When the above
elements are contained, formation of fine magnetic grains is
promoted or the crystallinity and orientation can be improved and
read/write characteristics and thermal fluctuation characteristics
suitable to high-density recording can be provided. The total
content of the above elements is preferably 8 at % or less. The
content exceeding 8 at % is undesirable because phases other than
the hcp phase are formed in the magnetic grains and the
crystallinity and orientation of the magnetic grains are disturbed,
with the result that read/write characteristics and thermal
fluctuation characteristics suitable to high-density recording are
not provided.
[0069] As the perpendicular magnetic recording layer, a CoPt-based
alloy, CoCr-based alloy, CoPtCr-based alloy, CoPtO, CoPtCrO,
CoPtSi, CoPtCrSi, a multilayer structure of an alloy layer
containing at least one type selected from the group consisting of
Pt, Pd, Rh and Ru and a Co layer, and materials obtained by adding
Cr, B or O to these layers, for example, CoCr/PtCr, CoB/PdB and
CoO/RhO may be used.
[0070] The thickness of the perpendicular magnetic recording layer
is preferably 3 to 30 nm and more preferably 5 to 20 nm. When the
thickness is in this range, a magnetic recording apparatus suitable
to higher recording density can be manufactured. If the thickness
of the perpendicular magnetic recording layer is less than 3 nm,
read outputs are too low and noise components tend to be higher. If
the thickness of the perpendicular magnetic recording layer exceeds
30 nm, read outputs are too high and the waveform tends to be
distorted. The coercivity of the perpendicular magnetic recording
layer is preferably 237000 A/m (3000 Oe) or more. If the coercivity
is less than 237000 A/m (3000 Oe), thermal fluctuation resistance
tends to be degraded. The perpendicular squareness of the
perpendicular magnetic recording layer is preferably 0.8 or more.
If the perpendicular squareness is less than 0.8, the thermal
fluctuation resistance tends to be degraded.
[0071] (Substrate)
[0072] As the substrate, for example, a glass substrate, an
Al-based alloy substrate, a ceramic substrate, a carbon substrate
or an Si single crystal substrate having an oxide surface may be
used. As the glass substrate, an amorphous glass and a crystallized
glass are used. Examples of the amorphous glass may include a
general-purpose soda lime glass and an alumino-silicate glass. As
the crystallized glass, a lithium-based crystallized glass may be
exemplified. Examples of the ceramic substrate may include a
sintered material containing, as a major component, a
general-purpose aluminum oxide, an aluminum nitride, silicon
nitride or the like, and fiber-reinforced materials thereof. As the
substrate, it is also possible to use the above-described metal
substrates or nonmetal substrates with a NiP layer formed thereon
by plating or sputtering.
[0073] (Soft Magnetic Underlayer and Underlayer)
[0074] The soft magnetic underlayer (SUL) serves a part of such a
function of a magnetic head as to pass a recording magnetic field
from a single-pole head for magnetizing a perpendicular magnetic
recording layer in a horizontal direction and to circulate the
magnetic field to the side of the magnetic head, and applies a
sharp and sufficient perpendicular magnetic field to the recording
layer, thereby improving read/write efficiency. For the soft
magnetic underlayer, a material containing Fe, Ni or Co may be
used. Examples of such a material may include FeCo-based alloys
such as FeCo and FeCoV, FeNi-based alloys such as FeNi, FeNiMo,
FeNiCr and FeNiSi, FeAl-based alloys and FeSi-based alloys such as
FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu and FeAlO, FeTa-based alloys
such as FeTa, FeTaC and FeTaN and FeZr-based alloys such as FeZrN.
Materials having a microcrystalline structure such as FeAlO, FeMgO,
FeTaN and FeZrN containing Fe in an amount of 60 at % or more or a
granular structure in which fine crystal grains are dispersed in a
matrix may also be used. As other materials to be used for the soft
magnetic underlayer, Co alloys containing Co and at least one of
Zr, Hf, Nb, Ta, Ti and Y may also be used. Such a Co alloy
preferably contains 80 at % or more of Co. In the case of such a Co
alloy, an amorphous layer is easily formed when it is deposited by
sputtering. Because the amorphous soft magnetic material is not
provided with crystalline anisotropy, crystal defects and grain
boundaries, it exhibits excellent soft magnetism and is capable of
reducing medium noise. Preferable examples of the amorphous soft
magnetic material may include CoZr-, CoZrNb- and CoZrTa-based
alloys.
[0075] An underlayer may further be formed beneath the soft
magnetic underlayer to improve the crystallinity of the soft
magnetic underlayer or to improve the adhesion of the soft magnetic
underlayer to the substrate. As the material of such an underlayer,
Ti, Ta, W, Cr, Pt, alloys containing these metals or oxides or
nitrides of these metals may be used. An interlayer made of a
nonmagnetic material may be formed between the soft magnetic
underlayer and the recording layer. The interlayer has two
functions including the function to cut the exchange coupling
interaction between the soft magnetic underlayer and the recording
layer and the function to control the crystallinity of the
recording layer. As the material for the interlayer Ru, Pt, Pd, W,
Ti, Ta, Cr, Si, alloys containing these metals or oxides or
nitrides of these metals may be used.
[0076] In order to prevent spike noise, the soft magnetic
underlayer may be divided into plural layers and Ru layers with a
thickness of 0.5 to 1.5 nm are interposed therebetween to attain
anti-ferromagnetic coupling. Also, a soft magnetic layer may be
exchange-coupled with a pinning layer of a hard magnetic film such
as CoCrPt, SmCo or FePt having longitudinal anisotropy or an
anti-ferromagnetic film such as IrMn and PtMn. A magnetic film
(such as Co) and a nonmagnetic film (such as Pt) may be provided
under and on the Ru layer to control exchange coupling force.
[0077] (Nonmagnetic Interlayer)
[0078] In the embodiments, an interlayer made of a nonmagnetic
material may be formed between the soft magnetic underlayer and
magnetic recording layer. The interlayer has two functions, i.e., a
function to interrupt the exchange coupling interaction between the
soft magnetic underlayer and recording layer, and a function to
control the crystallinity of the recording layer. The interlayer is
preferably a layer of Ru, Re, Pt, Pd, Ti, or a crystalline alloy
containing one of these elements. To improve the crystal
orientation of the perpendicular magnetic recording layer, the film
thickness of the interlayer is preferably 1 to 30 nm. Also, the
crystal orientation plane is preferably (0002) for Ru, Re, and Ti,
and (111) for Pt and Pd. This makes it possible to obtain a high Ku
value and high thermal stability.
[0079] The above-mentioned materials except for Ti are favorable as
the interlayer material because they have a corrosion resistance
against dry etching gases such as CF.sub.4 and SF.sub.6. In the
manufacture of the medium, a dry etching step using a gas such as
CF.sub.4 or SF.sub.6 as an etching gas may be performed. In this
case, the material of the interlayer preferably has a corrosion
resistance against the etching gas, in order to prevent
characteristic deterioration caused by deterioration of the
interlayer, e.g., magnetic characteristic deterioration or
microstructure shape deterioration due to corrosion. Note that Ti
is corroded by etching gases such as CF.sub.4 and SF.sub.6, but
usable as the interlayer material when selecting, e.g., O.sub.2 as
an etching gas because Ti has a corrosion resistance against
O.sub.2. Note also that the interlayer may be a multilayered film
including two or more layers.
[0080] (Protective Layer)
[0081] The protective layer is provided for the purpose of
preventing corrosion of the perpendicular magnetic recording layer
and also preventing the surface of a medium from being damaged when
the magnetic head is brought into contact with the medium. Examples
of the material of the protective layer include those containing C,
Si, B, SiO.sub.2 or ZrO.sub.2. It is preferable to set the
thickness of the protective layer from 1 to 10 nm. Since such a
thin protective layer enables to reduce the spacing between the
head and medium, it is suitable for high-density recording. Carbon
may be classified into sp.sup.2-bonded carbon (graphite) and
sp.sup.3-bonded carbon (diamond). Though sp3-bonded carbon is
superior in durability and corrosion resistance to graphite, it is
inferior in surface smoothness to graphite because it is
crystalline material. Usually, carbon is deposited by sputtering
using a graphite target. In this method, amorphous carbon in which
sp.sup.2-bonded carbon and sp3-bonded carbon are mixed is formed.
Carbon in which the ratio of sp.sup.3-bonded carbon is larger is
called diamond-like carbon (DLC). DLC is superior in durability and
corrosion resistance and also in surface smoothness because it is
amorphous and therefore utilized as the surface protective layer
for magnetic recording media. The deposition of DLC by chemical
vapor deposition (CVD) produces DLC through excitation and
decomposition of raw gas in plasma and chemical reactions, and
therefore, DLC richer in sp3-bonded carbon can be formed by
adjusting the conditions.
[0082] Next, preferable conditions and other matters required in
each of the steps in the manufacturing method will be
explained.
[0083] (Formation of Mask)
[0084] A first hard mask, a second hard mask and a third hard mask
are sequentially deposited on the surface of the DLC layer 4.
[0085] As for the first hard mask, it can be formed by depositing,
for example, Mo to a thickness of 5 nm. Alternatively, it is also
possible to employ Cr, Zn, Al, etc. As for the second hard mask, it
can be formed by depositing, for example, C to a thickness of 25
nm. Alternatively, it is also possible to employ an ordinary
photoresist such as PMMA, ZEP, etc. As for the third hard mask, it
can be formed by depositing, for example, Si to a thickness of 3
nm. Alternatively, it is also possible to employ SiC, Ti,
SiO.sub.2, SOG (Spin-on-glass), Ta, etc.
[0086] Incidentally, in the manufacturing method of the embodiments
described herein, the aforementioned first hard mask, second hard
mask and third hard mask may not be necessarily required to be
used. It is possible, in place of these hard masks, to employ a
mask which is capable of forming any optional pattern on the
surface of the magnetic recording layer and of being separated from
the magnetic recording layer after finishing the diffusion of the
magnetism-deactivating layer.
[0087] (Imprinting)
[0088] A stamper having patterns of recording tracks and servo data
is pressed against a substrate on which a resist is applied and
then the resist is cured, thereby to transfer the patterns of
protrusions and recesses.
[0089] As the resist, for example, a UV curing resist or a general
novolak-type photoresist may be used. When the UV curing resist is
used, the stamper is preferably made of a transparent material such
as quartz or resin. The UV curing resist is cured by applying
ultraviolet ray. A high-pressure mercury lamp, for example, can be
used as a light source of the ultraviolet ray. When the general
novolak-type photoresist is used, the stamper may be made of a
material such as Ni, quartz, Si and SiC. The resist can be cured by
applying heat or pressure.
[0090] (Residue Removal)
[0091] The resist residue is removed by gaseous O.sub.2 reactive
ion etching (RIE) after the imprint. Although an inductively
coupled plasma-RIE (ICP-RIE), which can generate a plasma at a high
density at a low pressure, is preferable, an electron cyclotron
resonance-RIE (ECR-RIE) or a general capacitive coupled plasma-RIE
(CCP-RIE) may also be used.
[0092] (Deposition of Protective Layer and Post-Treatment)
[0093] The carbon protective layer may be deposited to obtain good
coverage over the protrusions and recesses preferably by means of
CVD, but it may be deposited also by means of sputtering or vacuum
deposition. When CVD is used, a DLC film containing a large amount
of sp.sup.3 bonded carbon is formed. A lubricant is applied to the
surface of the protective layer. As the lubricant, for example, a
perfluoropolyether, fluorinated alcohol, fluorinated carboxylic
acid or the like may be used.
[0094] (Stripping)
[0095] After the patterning of the magnetic recording layer is
finished, the stripping of the first hard mask is executed. By the
expression "stripping of the first hard mask", it is intended to
mean a treatment for exposing the surface of an underlayer disposed
on the underside of the first hard mask. The second hard mask and
the third hard mask remaining on the surface of the first hard mask
can be removed together with the stripping of the first hard mask.
The stripping of the first hard mask can be carried out by way of a
wet process. With respect to the stripping solvent, it is possible
to employ, for example, an aqueous solution of hydrogen peroxide,
hydrochloric acid, sulfuric acid, nitric acid, etc. In order to
prevent the magnetic recording layer from being damaged, it is more
preferable to employ a dilute acid exhibiting a pH of not less than
4. The first hard mask can be stripped off by simply dipping the
recording medium in this stripping solvent for around one minute.
According to this stripping method, it is possible to strip off the
first hard mask without giving any damage to the magnetic recording
layer. It is preferable to wash the magnetic recording layer with
water or a solvent after the stripping thereof so as to completely
remove the stripping solvent.
[0096] <Magnetic Recording Apparatus>
[0097] Now, the magnetic recording apparatus (HDD) comprising the
magnetic recording medium of the embodiment will be described
below. FIG. 6 is a perspective view of a magnetic recording
apparatus in which the magnetic recording medium manufactured
according to the embodiment is installed.
[0098] As shown in FIG. 6, the magnetic recording apparatus 150
according to the embodiment is of a type using a rotary actuator.
The magnetic recording medium is attached to the spindle 140, and
is rotated in the direction of arrow A by a motor (not shown) that
responds to control signals from a drive controller (not shown).
The magnetic recording apparatus 150 may comprise a plurality of
magnetic recording medium.
[0099] The head slider 130 configured to read from and write to the
magnetic recording medium is attached to the tip of the film-like
suspension 154. The head slider 130 has a magnetic head mounted
near the tip thereof. When the magnetic recording medium rotates,
the air bearing surface (ABS) of the head slider 130 is held at a
predetermined height so as to fly over the surface of the magnetic
recording medium under a balance of pressing force of the
suspension 154 and the pressure produce on the air bearing surface
(ABS) of head slider 130.
[0100] The suspension 154 is connected to one end of an actuator
arm 155. A voice coil motor 156, a kind of linear motor, is
provided on the other end of the actuator arm 155. The voice coil
motor 156 is formed of a magnetic circuit including a driving coil
(not shown) wound around a bobbin and a permanent magnet and a
counter yoke arranged opposite to each other so as to sandwich the
coil therebetween. The actuator arm 155 is held by ball bearings
(not shown) provided at two vertical positions of the pivot 157.
The actuator arm 155 can be rotatably slid by the voice coil motor
156. As a result, the magnetic head can be accessed any position on
the magnetic recording medium.
EXAMPLES
Examples 1-10
[0101] Bit-patterned media of Examples 1-10 and Comparative
Examples 1-9 were manufactured and various characteristics thereof
were investigated.
[0102] The general features of these media manufactured herein will
be described below. In the cases of the media of Examples 1-10 and
Comparative Examples 5-9, a magnetism-deactivating layer comprising
vanadium, etc. was stacked on a magnetic recording layer and then
the diffusion of the magnetism-deactivating layer was performed by
the ion beam irradiation using various kinds of gas. In the cases
of the media of Comparative Examples 1-4, ion injection of various
kinds of elements was conducted to a magnetic recording layer.
[0103] Each of these media was manufactured as described below.
[0104] A glass substrate (amorphous substrate MEL 5, 2.5 inches in
diameter; Konica Minolta Co.) was placed in a deposition chamber of
a DC magnetron sputtering apparatus (C-3010; Anelver Co.) and then
the interior of the deposition chamber was evacuated until the
degree of vacuum was increased to 1.times.10.sup.-5 Pa. Then, a
film of Co-7 at % Ta-5 at % Zr having a thickness of 40 nm was
deposited, as a soft magnetic layer, on the surface of the
substrate, thereby forming a soft magnetic underlayer. Then, an
interlayer (Ru) having a thickness of 20 nm and a perpendicular
magnetic recording layer of Co-20 at % Pt-10 at % Cr having a
thickness of 20 nm were deposited. Next, by means of a CVD method,
a DLC protective layer having a thickness of 4 nm was deposited.
Thereafter, a first hard mask formed of Mo and having a thickness
of 5 nm, a second hard mask formed of C and having a thickness of
25 nm and a third hard mask formed of Si and having a thickness of
3 nm were successively deposited. Furthermore, a resist was
spin-coated on the surface of the third hard mask (Si) to a
thickness of 50 nm.
[0105] Then, a patterned mask was formed on the surface of a
magnetic recording layer as described below. First of all, a
stamper having a predetermined pattern of protrusions and recesses
formed by means of EB drawing, Ni electrocasting or injection
molding was imprinted in the resist, thereby transferring the
pattern of the stamper to the resist. Thereafter, the stamper was
taken out. Since a residue of the resist was left on the bottom of
the recessed portions of the pattern transferred to the resist, dry
etching was performed by making use of an IPC-RIE apparatus,
wherein CF.sub.4 was used as a process gas, the chamber pressure
was set to 0.1 Pa, the coil RF power and the platen (bias) RF power
were set to 100 W and 50 W, respectively, and the etching time was
set to 60 seconds. As a result, the residue of the resist left
remaining in the recessed portions was removed, thereby allowing
the surface of third hard mask (Si) to be exposed. Then, by making
use of the patterned resist as a mask and by means of the IPC-RIE
apparatus, ion beam etching was performed, wherein CF.sub.4 was
used as a process gas, the pressure inside the chamber was set to
0.1 Pa, the coil RF power and the platen RF power were set to 100 W
and 50 W, respectively, and etching time was set to 20 seconds. As
a result, the pattern was transferred to the third hard mask (Si)
and the surface of the second hard mask (C) was exposed at the
recessed portions. Then, by making use of the patterned third hard
mask (Si) as a mask and by means of the IPC-RIE apparatus, the
etching of the second hard mask formed of C was performed, wherein
O.sub.2 was used as a process gas, the pressure inside the chamber
was set to 0.1 Pa, the coil RF power and the platen RF power were
set to 100 W and 50 W, respectively, and etching time was set to 20
seconds. As a result, the pattern of the third hard mask (Si) was
transferred to the second hard mask (C) and the surface of the
first hard mask (Mo) was exposed at the recessed portions. Then, by
making use of the patterned second hard mask (C) as a mask and by
making use of an ion milling apparatus, the etching of the first
hard mask formed of Mo was performed, wherein Ar gas was used, the
gas pressure was set to 0.06 Pa, the accelerating voltage was set
to 400V, and etching time was set to 10 seconds. As a result, the
pattern was transferred to the first hard mask and the surface of
the DLC layer was exposed at the recessed portions. Then, by making
use of the patterned first hard mask (Mo) as a mask and by means of
the ICP-RIE apparatus, the etching of the DLC layer was performed,
wherein O.sub.2 gas was used as a process gas, the pressure inside
the chamber was set to 0.1 Pa, the coil RF power and the platen RF
power were set to 100 W and 50 W, and etching time was set to 5
seconds. As a result, the pattern was transferred to the DLC layer
and the surface of the magnetic recording layer was exposed at the
recessed portions.
[0106] Thereafter, the demagnetization of the non-recording
portions and the processes succeeding thereto were performed.
[0107] As a representative example, in the case of the recording
medium of Example 1, the demagnetization was performed as described
below. By means of DC sputtering using Ar gas, vanadium was
deposited as a magnetism-deactivating layer on the surface of the
magnetic recording layer to a thickness of 10 nm, wherein the
pressure inside the chamber was set to 0.7 Pa, the power was set to
500 W and the depositing time was set to 10 seconds. Then, by
making use of an ECR ion gun using N.sub.2 gas, diffusion of the
vanadium element to the magnetic recording layer was performed,
wherein the gas pressure was set to 0.1 Pa, the microwave power was
set to 1000 W, the accelerating voltage was set to 5000V, and
treating time was set to 100 seconds. In the cases of the recording
media of Examples 2-10 and Comparative Examples 5-9, the
demagnetization was performed in the same manner as described in
Example 1 except that the compound to be used as the
magnetism-deactivating layer and the kind of gas to be used for the
diffusion were changed. In the cases of Comparative Examples 1-4,
the demagnetization was performed by irradiating a plasma beam to
the magnetic recording layer using various kinds of elements.
[0108] As a post treatment following the aforementioned
demagnetization, the medium was dipped in an aqueous solution of
hydrogen peroxide for one minute, thereby entirely removing the
first hard mask (Mo) and layers deposited thereon. Then, by means
of the CVD method, the DLC protective layer was deposited to a
thickness of 4 nm and then a lubricating agent was coated thereon
by means of a dipping method, thus obtaining various kinds of
patterned perpendicular magnetic recording medium.
[0109] The media thus manufactured were measured in terms of
read/write characteristics, static magnetic characteristics,
surface roughness and the content of vanadium in the magnetic
recording layer.
[0110] In order to assess the read/write characteristics, the
electromagnetic conversion characteristics of the medium was
measured by making use of a read/write analyzer RWA1632 and a spin
stand S1701 MP (both available from GUZIK Co. USA). More
specifically, by making use of a head provided, at the writing
portion thereof, with a shielded pole type magnetic pole which is a
shield-attached single pole type magnetic pole (the shield acts to
converge the magnetic flux to be emitted from a magnetic head) and
also provided, at the reading portion thereof, with a TMR element,
the signal-to-noise ratio (SNR) was measured with the condition of
recording frequency being set to 1400 kBPI in linear recording
density.
[0111] The measurement of surface roughness was performed by making
use of an AFM (Veeco Co.). Specifically, the measurement was
performed with the tapping mode of 256.times.256 resolution in a
view-field of 10 .mu.m.
[0112] The assessment of static magnetic characteristics was
performed by making use of a vibration sample type magnetometer
(VSM) (available from Riken Denshi Co.). Further, in order to
investigate the magnetization corresponding to the non-recording
portions, a medium having the magnetic recording layer thereof
subjected, through its entire top surface, to diffusion treatment
without using a mask (a medium whose top surface is entirely
constituted by non-recording portions) was separately prepared and
the magnetization thereof was measured.
[0113] Further, the observation and measurement of these media were
performed, through their cross-sections, by making use of a
transmission electron microscope (TEM) and energy dispersive X-ray
spectroscopy (EDX) to thereby measure the content of vanadium in
their magnetic recording layers.
[0114] The results thus measured are summarized in Table 1. In this
Table 1, the read/write characteristics are shown as SNR, the
static magnetic characteristics as Ms, and the surface roughness as
Ra.
TABLE-US-00001 TABLE 1 Content (at %) of Ms of Demagnetizing V in
non-recording non-recording SNR Ra layer Gas portions portions
(emu/cc) (dB) (nm) Ex. 1 Vanadium N.sub.2 30 0 13.6 0.3 Ex. 2
Vanadium He--N.sub.2 30 0 13.8 0.2 Ex. 3 Vanadium nitride N.sub.2
30 0 12.5 0.4 Ex. 4 Vanadium nitride He--N.sub.2 30 0 12.7 0.2 Ex.
5 Vanadium carbide N.sub.2 30 0 11.3 0.4 Ex. 6 Vanadium carbide
He--N.sub.2 30 0 11.8 0.3 Ex. 7 Vanadium oxide N.sub.2 30 0 11.5
0.5 Ex. 8 Vanadium oxide He--N.sub.2 30 0 11.9 0.3 Ex. 9 Vanadium
boride N.sub.2 30 0 11.2 0.5 Ex. 10 Vanadium boride He--N.sub.2 30
0 11.4 0.4 Comp. Ex. 1 Chromium (Ion injection) 30 110 9.5 1.8
Comp. Ex. 2 Vanadium (Ion injection) 30 100 9.8 1.7 Comp. Ex. 3
Zirconium (Ion injection) 30 120 9.7 1.9 Comp. Ex. 4 Tantalum (Ion
injection) 30 250 6.5 1.9 Comp. Ex. 5 Chromium Ar 30 130 8.8 2.3
Comp. Ex. 6 Vanadium Ar 30 100 9.0 2.2 Comp. Ex. 7 Zirconium Ar 30
110 9.3 2.4 Comp. Ex. 8 Tantalum Ar 30 300 6.3 2.4 Comp. Ex. 9
Vanadium Kr 30 120 9.1 2.8
[0115] As seen from Table 1, the media of Examples 1-10 indicated
excellent SNR as compared with the media of Comparative Examples.
The reason for this can be assumably attributed to the fact that
while the magnetization (Ms) of the non-recording portions was made
zero so that magnetic interference between bits was prevented in
the cases of the media of Examples 1-10, the Ms of the
non-recording portions was left so that magnetic interference
between bits was allowed to take place in the case of the media of
Comparative Examples, resulting in an increase in noise.
Furthermore, the surface roughness (Ra) of the media of Examples
1-10 was improved as compared with the media of Comparative
Examples 1-9. Owing to this improvement, it was assumed that the
head-floating characteristics of the medium of each of Examples was
improved as compared with the media of Comparative Examples.
Meanwhile, the existence of vanadium was not recognized in the
recording regions in the media of Examples 1-10. On the other hand,
the existence of vanadium was recognized in the non-recording
regions as shown in Table 1.
Examples 11-20
[0116] Bit-patterned media of Examples 11-20 and Comparative
Example 10 were manufactured and various characteristics thereof
were investigated.
[0117] The general features of these media manufactured herein will
be described below. A magnetism-deactivating layer comprising
zirconium, etc. was stacked on a magnetic recording layer in each
of these media and then the diffusion of the magnetism-deactivating
layer was performed by the ion beam irradiation using various kinds
of gas.
[0118] The manufacture of each of these media was performed in the
same manner as described in the case of the medium of Example 1.
However, the kind of compound to be used as the
magnetism-deactivating layer and the kind of gas to be used for the
diffusion were changed as indicated above.
[0119] The media thus manufactured were respectively measured in
terms of read/write characteristics, static magnetic
characteristics, surface roughness and the content of zirconium in
the magnetic recording layer. These measurements were performed in
the same manner as described in Example 1.
[0120] The results thus measured are summarized in Table 2. In this
Table 2, the read/write characteristics are shown as SNR, the
static magnetic characteristic as Ms, and the surface roughness as
Ra.
TABLE-US-00002 TABLE 2 Content (at %) of Ms of Demagnetizing Zr in
non-recording non-recording SNR Ra layer Gas portions portions
(emu/cc) (dB) (nm) Ex. 11 Zirconium N.sub.2 30 0 13.6 0.5 Ex. 12
Zirconium He--N.sub.2 30 0 13.9 0.2 Ex. 13 Zirconium N.sub.2 30 0
12.5 0.5 nitride Ex. 14 Zirconium He--N.sub.2 30 0 12.8 0.3 nitride
Ex. 15 Zirconium N.sub.2 30 0 11.4 0.5 carbide Ex. 16 Zirconium
He--N.sub.2 30 0 11.6 0.4 carbide Ex. 17 Zirconium N.sub.2 30 0
11.3 0.4 oxide Ex. 18 Zirconium He--N.sub.2 30 0 11.8 0.3 oxide Ex.
19 Zirconium N.sub.2 30 0 11.5 0.5 boride Ex. 20 Zirconium
He--N.sub.2 30 0 11.8 0.3 boride Comp. Ex. 10 Zirconium Kr 30 130
8.9 2.2
[0121] As seen from Table 2, the media of Examples 11-20 indicated
excellent SNR as compared with the medium of Comparative Example
10. The reason for this can be assumably attributed to the fact
that while the magnetization (Ms) of the non-recording portions was
made zero so that magnetic interference between bits was prevented
in the cases of the media of Examples 11-20, the Ms of the
non-recording portions was left so that magnetic interference
between bits was allowed to take place in the medium of Comparative
Example 10, resulting in an increase in noise. Furthermore, the
surface roughness (Ra) of the media of Examples 11-20 was improved
as compared with the medium of Comparative Example 10. Owing to
this improvement, it was assumed that the head-floating
characteristics of the medium of each of Examples was improved as
compared with the medium of Comparative Example 10. Meanwhile, the
existence of zirconium was not recognized in the recording regions
in the media of Examples 11-20. On the other hand, the existence of
zirconium was recognized in the non-recording regions as shown in
Table 2.
Examples 21-29
[0122] Bit-patterned media of Examples 21-29 and Comparative
Example 11 were manufactured and various characteristics thereof
were investigated.
[0123] The general features of these media manufactured herein will
be described below. A magnetism-deactivating layer comprising
vanadium was stacked on a magnetic recording layer in each of these
media and then the diffusion of the magnetism-deactivating layer
was performed by the ion beam irradiation using N.sub.2 gas.
[0124] The manufacture of each of these media was performed in the
same manner as described in the case of the medium of Example 1.
However, the treating time for the diffusion was changed as shown
in Table 3.
[0125] The media thus manufactured were measured in terms of
read/write characteristics, static magnetic characteristics,
surface roughness, the content of vanadium in the magnetic
recording layer, and the content of nitrogen. The measurements of
read/write characteristics, static magnetic characteristics,
surface roughness and the content of vanadium were performed in the
same manner as described in Example 1. With respect to the content
of nitrogen, together with the difference in height between
protrusions and recesses, it was measured along the cross-section
of the substrate using TEM and TEM-EDX.
[0126] The results thus measured are summarized in Table 3. In this
Table 3, the read/write characteristics are shown as SNR, the
static magnetic characteristics as Ms, and the surface roughness as
Ra.
TABLE-US-00003 TABLE 3 Ms of Diffusion Content (at %) of Content
(at %) of non-recording treating time V in non-recording N in
non-recording portions SNR Ra (sec.) using N.sub.2 portions
portions (emu/cc) (dB) (nm) Ex. 21 5 10 2 19 11.0 0.9 Ex. 22 15 15
2 18 11.1 0.9 Ex. 23 30 20 5 5 13.0 0.5 Ex. 24 60 25 6 3 13.3 0.4
Ex. 25 100 30 7 0 13.7 0.4 Ex. 26 300 35 8 0 13.6 0.3 Ex. 27 500 40
7 0 13.8 0.3 Ex. 28 800 45 8 0 13.6 0.4 Ex. 29 1000 50 10 0 13.5
0.5 Comp. 0 0 0 500 3.2 3.5 Ex. 11
[0127] It was found from the image obtained from the TEM
observation in the cross-sectional direction that, in the cases of
the media of Examples 21 and 22, the level of the non-recording
portions was lower than the level of the recording portions by
about 3-4 nm (see FIG. 4K), but in the cases of the media of
Examples 23-29, no difference in level could be recognized between
the non-recording portions and the recording portions (see FIG.
5K). This phenomenon can be assumably attributed to the fact that,
in the cases of the media of Examples 23-29, vanadium nitride was
formed at the non-recording portions and, due to the creation of
the nitride, the volume of the non-recording portions was caused to
expand. It is conceivable that, as a result of this phenomenon, the
floating characteristics of the head was enabled to be further
improved in the cases of, the media of Examples 23-29.
Incidentally, in the case of the medium of Comparative Example 11,
since the medium was not subjected to any diffusion treatment, the
non-recording portions were projected, thereby making them higher
than the recording portions by about 6 nm, resulting in the
deterioration of surface roughness.
[0128] As shown in Table 3, the media of Examples 21-29 indicated
more excellent SNR as compared with the medium of Comparative
Example 11. Especially, in the cases of the media where the content
of vanadium in the non-recording portions was 20 at % or more, the
Ms became approximately zero and the surface roughness thereof was
not more than 0.5 nm, conceivably also resulting in the improvement
of floating characteristics of the head. Further, it will be
recognized that the media of Examples 21-29 indicated especially
excellent SNR.
[0129] Furthermore, in the cases of the media of Examples 21-29,
not only was vanadium not recognized in the recording regions, but
also nitrogen. On the other hand, as shown in Table 3, it was
possible to recognize the existence of vanadium and nitrogen in the
non-recording regions.
Examples 30-38
[0130] Bit-patterned media of Examples 30-38 and Comparative
Example 12 were manufactured and various characteristics thereof
were investigated.
[0131] The general features of these media manufactured herein will
be described below. A magnetism-deactivating layer comprising
zirconium was stacked on a magnetic recording layer in each of
these media and then the diffusion of the magnetism-deactivating
layer was performed by the ion beam irradiation beam using N.sub.2
gas.
[0132] The manufacture of each of these media was performed in the
same manner as described in the case of the medium of Example 1.
However, the treating time for the diffusion was changed as shown
in Table 4.
[0133] The media thus manufactured were measured in terms of
read/write characteristics, static magnetic characteristics,
surface roughness, the content of zirconium in the magnetic
recording layer, and the content of nitrogen. The measurements of
read/write characteristics, static magnetic characteristics,
surface roughness and the content of zirconium were performed in
the same manner as described in Example 1. With respect to the
content of nitrogen, together with the difference in height between
protrusions and recesses, it was measured along the cross-section
of the substrate using TEM and TEM-EDX.
[0134] The results thus measured are summarized in Table 4. In this
Table 4, the read/write characteristics are shown as SNR, the
static magnetic characteristics as Ms, and the surface roughness as
Ra.
TABLE-US-00004 TABLE 4 Content (at %) Content (at %) Ms of
Diffusion of Zr in of N in non-recording treating time
non-recording non-recording portions SNR Ra (sec.) using N.sub.2
portions portions (emu/cc) (dB) (nm) Ex. 30 10 10 2 17 11.4 0.8 Ex.
31 20 15 2 16 11.8 0.7 Ex. 32 40 20 8 2 13.4 0.4 Ex. 33 70 25 9 1
13.5 0.3 Ex. 34 120 30 9 0 13.8 0.3 Ex. 35 330 35 10 0 13.9 0.2 Ex.
36 540 40 10 0 13.9 0.2 Ex. 37 850 45 10 0 13.8 0.3 Ex. 38 1200 50
11 0 13.8 0.4 Comp. 0 0 0 500 3.8 3.7 Ex. 12
[0135] It was found from the image obtained from the TEM
observation in the cross-sectional direction that, in the cases of
the media of Examples 30 and 31, the level of the non-recording
portions was lower than the level of the recording portions by
about 3-4 nm (see FIG. 4K), but in the cases of the media of
Examples 32-38, no difference in level could be recognized between
the non-recording portions and the recording portions (see FIG.
5K). This phenomenon can be assumably attributed to the fact that,
in the cases of the media of Examples 32-38, zirconium nitride was
formed at the non-recording portions and, due to the creation of
the nitride, the volume of the non-recording portions was caused to
expand. It is conceivable that, as a result of this phenomenon, the
floating characteristics of the head were enabled to be further
improved in the cases of the media of Examples 32-38. Incidentally,
in the case of the medium of Comparative Example 12, since the
medium was not subjected to any diffusion treatment, the
non-recording portions were projected, thereby making them higher
than the recording portions by about 6 nm, resulting in the
deterioration of surface roughness.
[0136] As shown in Table 4, the media of Examples 30-38 indicated
more excellent SNR as compared with the medium of Comparative
Example 12. Especially, in the cases of the media where the content
of zirconium in the non-recording portions was 20 at % or more, the
Ms became approximately zero and the surface roughness thereof was
not more than 0.5 nm, conceivably also resulting in the improvement
of floating characteristics of the head. Further, it will be
recognized that the media of Examples 30-38 indicated especially
excellent SNR.
[0137] Furthermore, in the cases of the media of Examples 30-38,
not only was zirconium not recognized in the recording regions, but
also nitrogen. On the other hand, as shown in Table 4, it was
possible to recognize the existence of zirconium and nitrogen in
the non-recording regions.
Examples 39-54
[0138] Bit-patterned media of Examples 39-54 were manufactured and
various characteristics thereof were investigated.
[0139] The general features of these media manufactured herein will
be described below. A magnetism-deactivating layer comprising
vanadium or zirconium was stacked on a magnetic recording layer in
each of these media and then the diffusion of the
magnetism-deactivating layer was performed by the ion beam
irradiation using various kinds of gas.
[0140] The manufacture of each of these media was performed in the
same manner as described in the case of the medium of Example 1.
However, the kind of compound to be used as the
magnetism-deactivating layer and the kind of gas to be used for the
diffusion were changed as indicated above.
[0141] The media thus manufactured were measured in terms of
read/write characteristics, static magnetic characteristics,
surface roughness, the content of the metal element (vanadium or
zirconium) in the magnetic recording layer and the content of the
gas used for the diffusion. These measurements were performed in
the same manner as described in Example 1. With respect to the
measurement of the content of gas, since it was difficult to detect
He through the measurement using TEM-EDX, the results described
hereinafter do not include the results measured of He.
[0142] The results thus measured are summarized in Table 5. In this
Table 5, the read/write characteristics are shown as SNR, the
static magnetic characteristics as Ms, and the surface roughness as
Ra.
TABLE-US-00005 TABLE 5 Content (at % or mol %) Content (at %) of Ms
of Demagnetizing of metal element gas in non-recording
non-recording layer in non-recording portions portions SNR Ra
(metal element) Gas portions (excluding He) (emu/cc) (dB) (nm) Ex.
39 Vanadium CH.sub.4 30 7 0 11.5 0.4 Ex. 40 Vanadium B.sub.2H.sub.6
30 9 0 11.7 0.5 Ex. 41 Vanadium O.sub.2 30 6 0 11.4 0.5 Ex. 42
Vanadium O.sub.3 30 9 0 11.9 0.5 Ex. 43 Vanadium CH.sub.4 + He 30 8
0 12.1 0.3 Ex. 44 Vanadium B.sub.2H.sub.6 + He 30 10 0 12.3 0.4 Ex.
45 Vanadium O.sub.2 + He 30 7 0 12.4 0.4 Ex. 46 Vanadium O.sub.3 +
He 30 9 0 12.6 0.4 Ex. 47 Zirconium CH.sub.4 30 8 0 11.6 0.5 Ex. 48
Zirconium B.sub.2H.sub.6 30 10 0 11.8 0.5 Ex. 49 Zirconium O.sub.2
30 7 0 11.7 0.4 Ex. 50 Zirconium O.sub.3 30 9 0 11.8 0.5 Ex. 51
Zirconium CH.sub.4 + He 30 9 0 12.3 0.3 Ex. 52 Zirconium
B.sub.2H.sub.6 + He 30 11 0 12.6 0.4 Ex. 53 Zirconium O.sub.2 + He
30 8 0 12.8 0.3 Ex. 54 Zirconium O.sub.3 + He 30 11 0 12.7 0.4
[0143] In the cases of Examples 39-54, it was impossible to
recognize the existence of a metal element (vanadium or zirconium),
carbon, oxygen or boron in the recording portions. Whereas, it was
possible to recognize, in the non-recording portions, the existence
of a metal element (vanadium or zirconium) and also the elements of
gas (carbon, oxygen and boron) used for the diffusion as shown in
Table 5.
[0144] Further, as shown in Table 5, the media of Examples 39-54
were found to be excellent in SNR, Ms of the non-recording portions
and surface roughness.
[0145] Incidentally, although CH.sub.4 was employed as a gas
containing carbon, O.sub.2 as a gas containing oxygen, and
B.sub.2H.sub.6 as a gas containing boron in these examples, it is
also possible to employ other kinds of gas in obtaining the same
effects as described above as long as the gas to be used contains
carbon, oxygen or boron.
Examples 55-62
[0146] Bit-patterned media of Examples 55-62 and Comparative
Examples 13 and 14 were manufactured and various characteristics
thereof were investigated.
[0147] The general features of these media manufactured herein will
be described below. A magnetism-deactivating layer comprising
vanadium was stacked on a magnetic recording layer
(CoCrPt--SiO.sub.2) in each of these media and then the diffusion
of the magnetism-deactivating layer was performed by the ion beam
irradiation using O.sub.2 gas.
[0148] The manufacture of each of these media was performed in the
same manner as described in the case of the medium of Example 1.
However, (Co-20 at % Pt-14 at % Cr)-10 mol % SiO.sub.2 was used as
a magnetic recording medium in place of Co-20 at % Pt-10 at % Cr,
oxygen gas was used as a gas for the diffusion, and the gas
pressure and the treating time for the diffusion were changed as
shown in Table 6.
[0149] The media thus manufactured were measured in terms of
read/write characteristics, static magnetic characteristics,
surface roughness, and the content of oxygen in the magnetic
recording layer. The measurements of read/write characteristics,
static magnetic characteristics, surface roughness and the content
of vanadium were performed in the same manner as described in
Example 1. With respect to the content of oxygen, it was measured
along the cross-section of the substrate by making use of TEM-EDX,
thereby measuring the content of oxygen in the cross-section of the
medium.
[0150] The results thus measured are summarized in Table 6. In this
Table 6, the read/write characteristics are shown as SNR, the
static magnetic characteristics as Ms, and the surface roughness as
Ra.
TABLE-US-00006 TABLE 6 Content (at %) Content (at %) Ms of
Diffusion Gas of O element of O element in non-recording treating
pressure in recording non-recording portions SNR Ra time (sec.)
(Pa) portions portions (emu/cc) (dB) (nm) Ex. 55 50 0.1 20 22 19
11.0 0.9 Ex. 56 80 0.1 20 23 5 11.3 0.8 Ex. 57 100 0.1 20 25 0 11.5
0.5 Ex. 58 100 0.2 20 28 0 11.7 0.5 Ex. 59 100 0.3 20 30 0 11.8 0.4
Ex. 60 100 0.5 20 32 0 11.9 0.3 Ex. 61 100 0.7 20 35 0 12.0 0.3 Ex.
62 100 1.0 20 40 0 12.1 0.3 Comp. 0 0.1 20 20 500 3.8 3.7 Ex. 13
Comp. 30 0.1 20 21 250 5.6 2.4 Ex. 14
[0151] The content of oxygen in the recording portions in each of
the media of Examples 55-62 was found to be the same as the
composition of the material and no dependence thereof on the
treating time of diffusion as well as on the gas pressure was
recognized. Whereas, in the non-recording portions, the content of
oxygen was increased in accordance with an increase in treating
time of diffusion or an increase in gas pressure.
[0152] Further, as shown in Table 6, the media of Examples 55-62
were found to be excellent in SNR, in Ms of the non-recording
portion and in surface roughness as compared with the media of
Comparative Examples 13 and 14.
[0153] The various modules of the systems described herein can be
implemented as software applications, hardware and/or software
modules, or components on one or more computers, such as servers.
While the various modules are illustrated separately, they may
share some or all of the same underlying logic or code.
[0154] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *