JP2010165398A - Magnetic recording medium and magnetic recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium with high thermal fluctuation resistance and magnetic recording and reproducing device. <P>SOLUTION: The adopted magnetic recording medium 10 is characterized in that a magnetic layer 2 comprises a plurality of magnetic regions 2a formed by magnetically separating the magnetic layer 2 with boundary regions 8 arranged on a surface opposite to a nonmagnetic substrate 1, and a lower region 2b arranged on a surface facing the nonmagnetic substrate 1, and the magnetic regions 2a adjacent to each other are magnetically continuous to each other via the lower region 2b, wherein a saturation magnetization (MsL) and a residual magnetization (MrL) of the lower region 2b and a saturation magnetization (MsU) and a residual magnetization (MrU) of the magnetic region 2a have relations of 0.05×MsU<MsL<0.4×MsU, and 0.01×MrU<MrL<0.2×MrU. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium and a magnetic recording / reproducing apparatus.

  In recent years, the application range of magnetic recording devices such as hard disk devices, flexible disk devices, and magnetic tape devices has been remarkably increased, and the importance has increased, and the recording density of magnetic recording media used in these devices has been significantly improved. It is being planned. In particular, since the introduction of the MR (magnet reactive) head and the PRML technology, the increase in recording density per unit area has become more intense. In recent years, GMR (Giant Magnet Resistive) heads, TMR (Tunneling Magnet Resistive) heads, etc. have been introduced, and the recording density continues to increase at a rate of about 100% per year. These magnetic recording media are required to achieve a higher recording density in the future, and for that purpose, it is required to achieve a high signal-to-noise ratio (SNR) and high resolution of the magnetic layer. In recent years, efforts have been made to increase the recording density by increasing the track density as well as improving the linear recording density.

  In the latest magnetic recording apparatus, the track density has reached 300 kTPI. However, as the track density is increased, the magnetic recording information between adjacent tracks interfere with each other, and the magnetization transition region in the boundary region becomes a noise source, which tends to cause a problem that the SNR is impaired. This directly deteriorates the bit error rate, which is an obstacle to the improvement of recording density.

  On the other hand, in order to increase the recording density of the magnetic recording medium, the size of each recording bit on the magnetic recording medium is made finer, and as much saturation magnetization and magnetic film thickness as possible are secured for each recording bit. There is a need. However, when the recording bit is miniaturized, the minimum magnetization volume per bit is reduced, and there arises a problem that the recording data is lost due to magnetization reversal due to thermal fluctuation.

  Further, as the track density increases, the track-to-track distance approaches, so that there is a problem that the magnetic recording apparatus is required to have a highly accurate track servo technology. On the other hand, a method is generally used in which recording is performed with a wide track width and reproduction is performed with a narrower track width than at the time of recording, thereby eliminating the influence from adjacent tracks as much as possible. However, this method can minimize the influence between tracks, but it is difficult to obtain a sufficient reproduction output, and it is difficult to secure a sufficient SNR.

As one of the methods for solving the above-mentioned thermal fluctuation problem and achieving the SNR and sufficient output, the recording tracks can be formed by forming irregularities along the tracks on the surface of the recording medium. Attempts have been made to increase the track density by physically or magnetically separating the tracks to suppress interference between adjacent tracks. Hereinafter, such a technique is referred to as a discrete track method, and a magnetic recording medium manufactured thereby is referred to as a discrete track medium.
Furthermore, an attempt has been made to manufacture a bit pattern medium in which the track portion of the discrete track medium is further separated in bit units.

  As an example of a discrete track medium, a magnetic recording medium in which a physically separated magnetic recording track and a servo signal pattern are formed by forming a magnetic layer on a nonmagnetic substrate having a concavo-convex pattern formed on the surface is known. (For example, refer to Patent Document 1).

JP 2004-164692 A

  With the development of discrete media and bit pattern media, it has become possible to separate adjacent recording tracks and recording bits physically or magnetically, suppress interference between adjacent tracks and bits, and increase the SNR of the media. However, in order to increase the recording density even in discrete media, etc., it is necessary to make the size of each recording track and recording bit on the magnetic recording medium fine and to ensure as large saturation magnetization as possible in each recording bit etc. Has occurred. That is, even in a discrete medium or the like, when the recording track is made finer for increasing the recording density, there is a problem that the magnetization volume is reduced and the recorded data is lost due to the magnetization reversal due to the thermal fluctuation.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a magnetic recording medium having high thermal fluctuation resistance in order to cope with an increase in recording density of discrete media and bit pattern media.

As a result of diligent efforts to solve the above problems, the inventor of the present application has found that a magnetic recording pattern such as a discrete medium or a bit pattern medium is a recording area and a boundary area that magnetically separates the magnetic area. It has been found that a magnetic recording medium having high thermal fluctuation resistance can be provided by making the saturation magnetization (MsL) and the residual magnetization (MrL) of the boundary region arranged between adjacent magnetic regions within a specific range, The present invention has been completed.
That is, the present invention employs the following configuration.
[1] A magnetic recording medium having a magnetic layer on at least one surface of a non-magnetic substrate, wherein the magnetic layer has alternating magnetic regions serving as recording regions and boundary regions separating the magnetic regions adjacent to each other. The saturation magnetization (MsL) and the residual magnetization (MrL) of the boundary region, and the saturation magnetization (MsU) and the residual magnetization (MrU) of the magnetic region are represented by the following formula (1) and the following formula ( A magnetic recording medium having the relationship 2).
0.05 × MsU <MsL <0.4 × MsU (1)
0.01 × MrU <MrL <0.2 × MrU (2)
[2] The boundary region is a stacked structure of a lower region made of a magnetic layer provided on the nonmagnetic substrate side and a nonmagnetic region provided on the lower region, and the saturation magnetization ( MsL) and remanent magnetization (MrL), and the saturation magnetization (MsU) and remanent magnetization (MrU) of the magnetic region have the relationship of the above formula (1) and the above formula (2). 1].
[3] The magnetic recording medium according to [2], wherein the magnetic region and the lower region are magnetically continuous.
[4] The magnetic recording medium according to [1], wherein the boundary region is a region in which the magnetic characteristics of the magnetic layer are modified.
[5] The magnetic recording medium according to any one of [1] to [4], wherein the magnetic region forms a convex portion and the boundary region forms a concave portion on a magnetic recording surface of the magnetic recording medium. Magnetic recording media.
[6] The magnetic recording medium according to [5], wherein a step between the magnetic region and the boundary region is in a range of 1 nm to 10 nm.
[7] Any one of [1] to [6], wherein the magnetic recording pattern including the magnetic region and the boundary region is at least one of a recording track, a recording bit, and a servo signal. 2. A magnetic recording medium according to 1.
[8] A magnetic head comprising the magnetic recording medium according to any one of [1] to [7], medium driving means for driving the magnetic recording medium in a recording track direction, a recording unit, and a reproducing unit. And a head moving means for moving the magnetic head relative to the magnetic recording medium, and a recording / reproducing signal processing means for reproducing a signal input to the magnetic head and an output signal from the magnetic head. A magnetic recording / reproducing apparatus.

  According to the discrete medium and the bit pattern medium of the present invention, the magnetic recording pattern is composed of a magnetic region that becomes a recording region and a boundary region that magnetically separates the magnetic region, and is arranged between adjacent magnetic regions. Since the saturation magnetization and residual magnetization in the boundary region are within a specific range, the magnetization volume per data bit is increased, and a magnetic recording medium having high thermal fluctuation resistance can be provided.

1A and 1B are diagrams for explaining a magnetic recording medium according to a first embodiment of the present invention. FIG. 1A is a plan view showing the whole, FIG. 1B is an enlarged plan view of a magnetic recording pattern, and FIG. FIG. 4 is a cross-sectional view taken along line AA ′ shown in FIG. FIG. 2 is a process cross-sectional view illustrating the method of manufacturing the magnetic recording medium according to the first embodiment of the present invention. 3A and 3B are views for explaining a magnetic recording medium according to a second embodiment of the present invention. FIG. 3A is a plan view showing the whole, FIG. 3B is an enlarged plan view of a magnetic recording pattern, and FIG. FIG. 6 is a cross-sectional view taken along line BB ′ shown in FIG. FIG. 4 is a process cross-sectional view illustrating a method of manufacturing a magnetic recording medium according to the second embodiment of the present invention. FIG. 5 is a perspective view showing a magnetic recording / reproducing apparatus according to the third embodiment of the present invention. FIG. 6 is a magnetic hysteresis curve of the magnetic recording pattern (magnetic region) and the boundary region of the example.

  Hereinafter, a magnetic recording medium and a magnetic recording / reproducing apparatus to which the present invention is applied will be described in detail with reference to the drawings. The magnetic recording medium of the present invention has a structure in which, for example, a soft magnetic layer, an intermediate layer, a magnetic layer with a magnetic pattern formed thereon, and a protective film are laminated on the surface of a nonmagnetic substrate, and a lubricating film is formed on the outermost surface. Is formed. In the magnetic recording medium according to the embodiment of the present invention, it is possible to provide other than the nonmagnetic substrate and the magnetic layer as appropriate.

<First Embodiment>
First, a configuration of a magnetic recording medium 10 as shown in FIG. 1 will be described as a first embodiment to which the present invention is applied. FIG. 1 is for explaining the configuration of the perpendicular magnetic recording medium 10 of the present embodiment. The size, thickness, dimensions, etc. of the respective parts shown in the figure are the actual dimensional relationships of the perpendicular magnetic recording medium 10. May be different.

  As shown in FIGS. 1A to 1C, the perpendicular magnetic recording medium 10 of the present embodiment is formed on a nonmagnetic substrate 1 from a soft magnetic backing layer (backing layer), an underlayer, an intermediate layer, and the like. A layer 11 to be formed, a magnetic layer 2 to be a magnetic recording layer, a protective layer, and a lubricant layer are formed and roughly configured. More specifically, in the magnetic layer 2, magnetic regions 2 a serving as recording regions and boundary regions 8 that magnetically separate the magnetic regions 2 a are adjacently disposed alternately. Further, as shown in FIG. 1C, the boundary region 8 includes a lower region 2b made of the magnetic layer 2 provided on the nonmagnetic substrate 1 side, and a nonmagnetic region 8a provided on the lower region 2b. It has a laminated structure. Adjacent magnetic regions 2a are configured to be magnetically continuous via the lower region 2b.

  The nonmagnetic substrate 1 is made of an Al alloy substrate such as an Al—Mg alloy mainly composed of Al, ordinary soda glass, aluminosilicate glass, crystallized glass, silicon, titanium, ceramics, and various resins. Any substrate can be used as long as it is a non-magnetic substrate. Among them, it is preferable to use a glass substrate such as an Al alloy substrate or crystallized glass, or a silicon substrate. The average surface roughness (Ra) of these substrates is preferably 1 nm or less, more preferably 0.5 nm or less, and particularly preferably 0.1 nm or less.

  The magnetic layer 2 may be an in-plane magnetic layer or a perpendicular magnetic layer, but a perpendicular magnetic layer is preferable in order to achieve a higher recording density. These magnetic layers 2 are preferably formed from an alloy mainly containing Co as a main component. As the magnetic layer for the in-plane magnetic recording medium, for example, a laminated structure including a nonmagnetic CrMo underlayer and a ferromagnetic CoCrPtTa recording layer can be used.

Examples of the magnetic layer 2 for perpendicular magnetic recording media include soft magnetic FeCo alloys (FeCoB, FeCoSiB, FeCoZr, FeCoZrB, FeCoZrBCu, etc.), FeTa alloys (FeTaN, FeTaC, etc.), Co alloys (CoTaZr, CoZrNB, CoB, etc.). A backing layer made of, etc., an orientation control film such as Pt, Pd, NiCr, NiFeCr, an intermediate film such as Ru, if necessary, and a recording layer made of 70Co-15Cr-15Pt alloy or 70Co-5Cr-15Pt-10SiO ₂ alloy Can be used.

  The magnetic layer 2 has a thickness of 3 nm to 20 nm, preferably 5 nm to 18 nm. The magnetic layer 2 may be formed so as to obtain sufficient head input / output according to the type of magnetic alloy used and the laminated structure. The film thickness of the magnetic layer 2 requires a recording layer thickness of a certain level or more in order to obtain a certain level of output during reproduction, while parameters indicating recording / reproduction characteristics usually deteriorate as the output increases. Therefore, it is necessary to set an optimum film thickness.

  The boundary region 8 is a nonmagnetic region, for example, a region that magnetically separates the magnetic recording track and the servo signal pattern portion. As shown in FIG. 1B, the boundary region 8 only needs to be separated when the magnetic layer 2 is viewed from the surface side. Therefore, it is sufficient that at least the surface side of the magnetic layer 2 is demagnetized, The magnetic layer 2 may not be demagnetized on the bottom side.

  The nonmagnetic region 8a is provided on the surface side of the magnetic layer 2 as described above. The nonmagnetic region 8a may be a magnetically modified magnetic layer 2 or may be formed by embedding a nonmagnetic material. The thickness of the nonmagnetic region 8a is 2 nm to 15 nm, preferably 8 nm to 12 nm. If the thickness of the nonmagnetic region 8a is less than 2 nm, it is not preferable because the magnetic separation of the magnetic recording pattern becomes insufficient. On the other hand, when the thickness of the nonmagnetic region 8a exceeds 15 nm, the optimum thickness of the magnetic layer 2 is determined, so that the thickness of the lower region 2b is reduced and the thermal stability of the magnetic recording bit is lowered. Therefore, it is not preferable. On the other hand, if it is within the above range, a magnetic recording bit having a sufficient volume can be secured, so that a magnetic recording medium having high thermal fluctuation resistance can be provided.

  The thickness of the lower region 2b is 5 nm or more and 18 nm or less, preferably 8 or more and 12 or less. If the thickness of the lower region 2b is less than 5 nm, it is not preferable because a sufficient volume of magnetic recording bits cannot be secured. On the other hand, when the thickness of the lower region 2b exceeds 18 nm, the optimum film thickness of the magnetic layer 2 is determined. Therefore, the thickness of the nonmagnetic layer 8a is reduced and the magnetic separation of the magnetic recording pattern is insufficient. Therefore, it is not preferable. On the other hand, if it is within the above range, a magnetic recording bit having a sufficient volume can be secured, so that a magnetic recording medium having high thermal fluctuation resistance can be provided.

In the magnetic recording medium 10 of the present embodiment, the saturation magnetization (MsL) and the residual magnetization (MrL) of the lower region 2b constituting the boundary region 8, and the saturation magnetization (MsU) and the residual magnetization (MrU) of the magnetic region 2a. The following formula (3) and the following formula (4) are configured.
0.05 × MsU <MsL <0.4 × MsU (3)
0.01 × MrU <MrL <0.2 × MrU (4)

  The magnetic recording medium 10 of the present embodiment can increase the magnetization volume per data bit by adopting the above configuration, and the distance between adjacent tracks and bits can be reduced for higher recording density. Even in such a case, it is possible to provide the magnetic recording medium 10A having high thermal fluctuation resistance. In the present embodiment, when MsL is 0.05 × MsU or less, the magnetic coupling between each data bit and the adjacent data bit is reduced, and the thermal fluctuation resistance is reduced. On the other hand, when MsL is 0.4 × MsU or more, magnetic separation of data tracks and data bits becomes insufficient, and crosstalk occurs. Similarly, when MrL is 0.05 × MrU or less, the magnetic coupling between each data bit and the adjacent data bit is reduced, and the thermal fluctuation resistance is reduced. When MrL becomes 0.2 × MrU or more, magnetic separation of data tracks and data bits becomes insufficient, and crosstalk occurs. For example, a reverse signal is recorded on an adjacent track. If so, both signals cancel each other, and the signal strength decreases.

  The magnetic recording pattern of the present embodiment is composed of a magnetic region 2a and a boundary region 8, and so-called patterned media in which the magnetic recording pattern is arranged with a certain regularity for each bit, or magnetic recording. The pattern includes a medium arranged in a track shape, a servo signal pattern, and the like. In this embodiment, the magnetically separated magnetic recording pattern is a magnetic recording track, a recording bit, and a servo signal pattern, and is applied to a so-called discrete type magnetic recording medium because of its simplicity in manufacturing. preferable.

  A method for manufacturing the magnetic recording medium 10 described above will be described in detail with reference to FIG. In FIG. 2, layers other than the nonmagnetic substrate 1, the magnetic layer 2, and the protective layer 9 constituting the magnetic recording medium 10 are omitted.

  In this embodiment, as shown in FIGS. 2A to 2I, at least the magnetic layer 2 is formed on the nonmagnetic substrate 1 in step A (FIG. 2A), on the magnetic layer 2. Step B (FIG. 2 (b)) for forming the mask layer 3, Step C (FIG. 2 (c)) for forming the resist layer 4 on the mask layer 3, and a negative pattern of the magnetic recording pattern on the resist layer 4, Step D for transferring using stamp 5 (FIG. 2 (d); arrow in the figure indicates movement of stamp 5), Step E for removing portion corresponding to negative pattern of magnetic recording pattern using mask layer 3 (FIG. 2 (e)), a step F in which the surface layer portion of the magnetic layer 2 is partially ion milled from the surface on the resist layer 4 side (FIG. 2 (f); reference numeral 7 is a partial ion milling in the magnetic layer 2). The symbol d indicates the depth of ion milling in the magnetic layer 2), the magnetic layer Step G in which the magnetic properties of the magnetic layer 2 are modified by exposing the ion milled portion to reactive plasma or reactive ions (FIG. 2 (g); 8 is a boundary region in which the magnetic properties of the magnetic layer 2 are modified) Step H (FIG. 2 (h)) for removing the resist layer 4 and the mask layer 3, and Step I (FIG. 2 (i)) for covering the surface of the magnetic layer 2 with the protective layer 9 in this order. In this way, the magnetic recording medium 10 can be manufactured.

(Process A)
In this embodiment, first, a soft magnetic layer and an intermediate layer (not shown) are formed on the nonmagnetic substrate 1 as necessary using conventionally known materials and methods.
Next, as shown in Step A of FIG. 2A, the magnetic layer 2 made of the above-described material is formed on the nonmagnetic substrate 1, or on the soft magnetic layer or the intermediate layer. The magnetic layer 2 is usually formed as a thin film using a sputtering method.

(Process B)
Next, a mask layer 3 is formed on the magnetic layer 2 in Step B shown in FIG. The mask layer 3 is made of C, Ta, W, Ta nitride, W nitride, Si, SiO ₂ , Ta ₂ O ₅ , Re, Mo, Ti, V, Nb, Sn, Ga, Ge, As, Ni. It is preferable to form with the material containing any 1 or more types chosen from the group which consists of. By using such a material, the shielding property against the milling ions 6 of the mask layer 3 can be improved, and the magnetic recording pattern formation characteristics by the mask layer 3 can be improved. Furthermore, since these materials are easy to dry-etch using a reactive gas, residues can be reduced in step H of FIG. 2H, and contamination on the surface of the magnetic recording medium 10 can be reduced. .

  In this embodiment, among these materials, As, Ge, Sn, and Ga are preferably used as the mask layer 3, and Ni, Ti, V, and Nb are more preferably used, and C, Mo, and Ta are used. , W is most preferable.

(Process C-Process D-Process E)
Next, in step C shown in FIG. 2C, a resist layer 4 made of the above material is formed.
Next, in step D shown in FIG. 2D, the negative pattern of the magnetic recording pattern is transferred by pressing the stamp 5 against the resist layer 4.
Next, in step E shown in FIG. 2E, the portion of the mask layer 3 corresponding to the negative pattern of the magnetic recording pattern is removed.

  In the manufacturing method of the present embodiment, the thickness of the concave portion of the resist layer 4 after transferring the negative pattern of the magnetic recording pattern to the resist layer 4 as shown in Step D of FIG. It is preferable to be within the range. By setting the thickness of the concave portion of the resist layer 4 within this range, it is possible to prevent sagging of the edge portion of the mask layer 3 in the etching process of the mask layer 3 shown in the step E of FIG. Become. Further, the shielding property against the milling ions 6 of the mask layer 3 can be improved, and the magnetic recording pattern forming characteristics by the mask layer 3 can be improved.

  In the manufacturing method of the present embodiment, the material used for the resist layer 4 in the step C of FIG. 2C and the step D of FIG. It is preferable to irradiate the resist layer 4 with radiation when the pattern is transferred using the stamp 5 or after the pattern transfer step. By adopting such a method, the shape of the stamp 5 can be accurately transferred to the resist layer 4. This prevents sagging of the edge portion of the mask layer 3 in the etching process of the mask layer 3 shown in the step E of FIG. 2E, improves the shielding property against the implanted ions of the mask layer 3, It is possible to improve the formation characteristics of the magnetic recording pattern by the mask layer 3. In addition, the radiation demonstrated by this embodiment is an electromagnetic wave of wide concepts, such as a heat ray, visible light, an ultraviolet-ray, an X-ray, a gamma ray, for example. Moreover, the material which has curability by radiation irradiation is, for example, a thermosetting resin for heat rays and an ultraviolet curable resin for ultraviolet rays.

  In the manufacturing method of the present embodiment, in particular, in the step of transferring the pattern to the resist layer 4 using the stamp 5, the stamp layer 5 is pressed against the resist layer 4 in a state where the fluidity of the resist layer 4 is high. It is preferable to irradiate the resist layer 4 with radiation in a state. As a result, the resist layer 4 is cured, and then the stamp 5 is separated from the resist layer 4 so that the shape of the stamp 5 can be transferred to the resist layer 4 with high accuracy. As a method of irradiating the resist layer 4 with radiation while the stamp 5 is pressed against the resist layer 4, a method of irradiating radiation from the opposite side of the stamp 5, that is, the non-magnetic substrate 1 side, radiation as a material of the stamp 5 is used. The material of the stamp 5 or the method of irradiating radiation from the stamp 5 side, the method of irradiating radiation from the side of the stamp 5, the radiation having high conductivity with respect to the solid like heat rays, or the like A method of irradiating radiation by heat conduction from the nonmagnetic substrate 1 can be used. In the manufacturing method of the present embodiment, among the above methods, in particular, an ultraviolet curable resin such as a novolak resin, an acrylate ester, and an alicyclic epoxy is used as a resist material. It is preferable to use highly transparent glass or resin.

  By transferring the pattern to the resist layer 4 using the method as described above, the coercive force and the residual magnetization in the region between the magnetic tracks can be reduced to the utmost, writing blur at the time of magnetic recording is eliminated, and a high surface It is possible to provide a magnetic recording medium having a recording density.

  As the stamper (stamp 5) used in the above process, for example, a metal plate formed with a fine track pattern using a method such as electron beam drawing can be used. Hardness and durability that can be withstood are required. As such a material, for example, Ni or the like can be used, but the type of the material is not limited as long as it meets the above-described purpose. Such a stamper can also form servo signal patterns such as a burst pattern, a gray code pattern, and a preamble pattern in addition to a track on which normal data is recorded.

(Process F)
Next, in step F shown in FIG. 2F, a part of the surface layer of the magnetic layer 2 is removed by ion milling or the like.
In the present embodiment, the magnetic layer 2 is formed by removing a part of the surface layer of the magnetic layer 2 and then modifying the magnetic properties of the magnetic layer 2 by exposing the surface to reactive plasma or reactive ions. As compared with the case where a part of the magnetic recording medium is not removed, the contrast of the magnetic recording pattern becomes clearer and the S / N of the magnetic recording medium 10 is improved. The reason for this may be that by removing the surface layer portion of the magnetic layer 2, the surface is cleaned and activated, and the reactivity with reactive plasma and reactive ions is increased. Another possible reason is that defects such as vacancies are introduced into the surface layer of the magnetic layer 2 and reactive ions easily enter the magnetic layer 2 through the defects.

In the manufacturing method of the present embodiment, the depth d when part of the surface layer of the magnetic layer 2 is removed by ion milling or the like is preferably in the range of 0.1 nm to 15 nm, more preferably in the range of 1 to 10 nm. And When the removal depth by ion milling is smaller than 0.1 nm, the above-mentioned effect of removing the magnetic layer does not appear, and when the removal depth is larger than 15 nm, the surface smoothness of the magnetic recording medium is deteriorated and magnetic recording is performed. There is a concern that the flying characteristics of the magnetic head when the reproducing apparatus is configured may be deteriorated.
In this embodiment, for example, the magnetic layer 2 already formed is exposed to a reactive plasma or a reactive ion in a region where the magnetic recording pattern and the servo signal pattern are magnetically separated, and the magnetic characteristics of the magnetic layer 2 are improved. It can be formed by a quality method.

(Process G)
Next, in the manufacturing method of the present embodiment, the magnetic properties of the magnetic layer 2 are improved by exposing the ion milled portion of the magnetic layer 2 to reactive plasma or reactive ions in Step G shown in FIG. Thus, the magnetic layer 2 is magnetically separated.

  Here, the magnetically separated magnetic recording pattern described in the present embodiment refers to the magnetic layer 2 when the magnetic recording medium 10 is viewed from the surface side, as shown in Step G of FIG. Is a state separated by a non-magnetic region 8a that has been made non-magnetic (see also FIG. 1B). That is, if the magnetic layer 2 is separated from the surface side, the object of the present invention can be achieved even if it is not separated at the bottom of the boundary region 8, which will be described in the present invention. This is included in the concept of the boundary region 8 that magnetically separates the magnetic layer 2a that is a so-called recording region.

  Further, the modification of the magnetic layer 2 for forming the nonmagnetic region 8a described in the present embodiment means that the coercive force, residual magnetization, etc. of the magnetic layer 2 are partially changed in order to pattern the magnetic layer 2. The change refers to lowering the coercive force and lowering the remanent magnetization. In the present embodiment, in particular, the modification of the magnetic characteristics as described above can be performed by exposing the magnetic layer 2 to reactive plasma or reactive ions, or by ion implantation.

Examples of the reactive plasma used in the present embodiment include inductively coupled plasma (ICP) and reactive ion plasma (RIE).
Examples of the reactive ions described here include the above-described inductively coupled plasma and reactive ions present in the reactive ion plasma.

The inductively coupled plasma described in the present embodiment is a high-temperature gas obtained by generating a Joule heat due to an eddy current in the plasma by generating a plasma by applying a high voltage to a gas and applying a high-frequency fluctuating magnetic field. Plasma. Such an inductively coupled plasma has a high electron density, and can improve the magnetic properties with high efficiency in a magnetic film having a large area compared to the case of manufacturing a discrete track medium using a conventional ion beam. . The reactive ion plasma is a highly reactive plasma in which a reactive gas such as O ₂ , SF ₆ , CHF ₃ , CF ₄ , or CCl ₄ is added to the plasma. By adopting such plasma as the reactive plasma used in this embodiment, the magnetic alloy of the magnetic film 2 can be halogenated and oxidized to improve the magnetic characteristics or make it non-magnetic with higher efficiency. It becomes possible.

In the manufacturing method of the present embodiment, a method of modifying the magnetic layer 2 by exposing the formed magnetic layer 2 to reactive plasma is exemplified. However, such modification treatment is performed using the magnetic layer 2. It is preferable to realize this by a reaction between the magnetic metal constituting the element and atoms or ions in the reactive plasma.
The reaction described here means that the atoms in the reactive plasma enter the magnetic metal and the crystal structure of the magnetic metal changes, the composition of the magnetic metal changes, or the magnetic metal oxidizes. Examples include nitriding of magnetic metal, silicidation of magnetic metal, and the like.

In the present embodiment, in particular, the oxygen layer or the nitrogen atom is contained as the reactive plasma, and the magnetic layer 2 is reacted with the magnetic metal constituting the magnetic layer 2 and the oxygen atom or the nitrogen atom in the reactive plasma. Is preferably oxidized. For example, by partially oxidizing the magnetic layer 2, it becomes possible to efficiently reduce the remanent magnetization, coercive force, etc. of this oxidized portion, so that the magnetic layer 2 is magnetically separated by a short reactive plasma treatment. The magnetic recording medium 10 having a magnetic recording pattern can be manufactured.
In the manufacturing method of the present embodiment, a part of the magnetic layer 2 can be made amorphous and non-magnetic by performing ion implantation on the formed magnetic layer 2. As the implanted ions, argon, neon, helium inert gas, nitrogen gas, oxygen gas, hydrogen gas, etc., or a mixed gas thereof can be used.

(Process H)
Next, in the present embodiment, the resist layer 4 and the mask layer 3 are removed as shown in Step H of FIG.
Here, as a specific method for removing the resist layer 4 and the mask layer 3 after the reactive plasma treatment, for example, a technique such as dry etching, reactive ion etching, ion milling, or wet etching is appropriately employed. be able to.
Further, in the present embodiment, in order to eliminate a step generated between the magnetic recording pattern 2 and the boundary region 8 formed of the nonmagnetic region 8a, a nonmagnetic material or the like is further embedded in the concave portion of the boundary region 8 and smoothed. good.

(Process I)
Next, as shown in Step I of FIG. 2 (i), in the manufacturing method of this embodiment, the protective layer 9 is formed, and further, a lubricant is applied thereon, whereby the magnetic recording medium 10 is formed. It is preferable to employ a manufacturing process.

As a method for forming the protective layer 9, a method of forming a diamond like carbon thin film using a P-CVD method or the like is generally used, but the method is not particularly limited. The material of the protective layer 9, carbon (C), hydrogenated carbon (hxc), nitrogenated carbon (CN), almotriptan amorphous carbon, carbonaceous layer such as silicon carbide (SiC) or, _SiO 2, Zr ₂ Commonly used protective film materials such as O ₃ and TiN can be used. Further, the protective layer 9 may be formed as a single layer or a two-layer structure. In addition, the film thickness of the protective film 9 needs to be less than 10 nm. This is because if the thickness of the protective film exceeds 10 nm, the distance between the head and the magnetic layer increases, and sufficient input / output signal strength cannot be obtained.

  Further, as described above, an unillustrated lubricating layer made of, for example, a fluorine-based lubricant, a hydrocarbon-based lubricant, a mixture thereof, or the like is usually formed on the protective layer 9 with a thickness of 1 to 4 nm. More preferably.

  As described above, according to the magnetic recording medium 10 of the present embodiment, the magnetic recording pattern is composed of the magnetic region 2a serving as a recording region and the boundary region 8 that magnetically separates the magnetic region 2a. Saturation magnetization (MsL) and residual magnetization (MrL) of the lower region 2b constituting the boundary region 8 arranged between the magnetic regions 2a to be performed, and saturation magnetization (MsU) and residual magnetization (MrU) of the magnetic region 2a, Since the relations of the above formulas (3) and (4) are satisfied, it is possible to provide a magnetic recording medium having a high magnetization volume per data bit and high resistance to thermal fluctuation.

<Second Embodiment>
Next, a configuration of a magnetic recording medium 20 as shown in FIG. 3 will be described as a second embodiment to which the present invention is applied. As shown in FIGS. 3A to 3C, in the magnetic recording medium 20 of the present embodiment, the configuration of the magnetic layer 22 is different from the configuration of the magnetic layer 2 of the first embodiment described above. There are other configurations which are the same as those of the first embodiment. Therefore, for the magnetic recording medium of the present embodiment, the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. In FIGS. 3A to 3C, layers other than the nonmagnetic substrate 1, the layer 11, and the magnetic layer 22 constituting the magnetic recording medium 30 are omitted.

  As shown in FIGS. 3A to 3C, the magnetic recording medium 20 of the present embodiment is schematically configured by laminating a magnetic layer 22 on at least one surface of the nonmagnetic substrate 1. In the magnetic layer 22, magnetic regions 22a serving as recording regions and boundary regions 28 separating the magnetic regions 22a are alternately arranged adjacent to each other. Here, the boundary region 28 of the present embodiment is configured to completely separate the adjacent magnetic regions 22 a to the bottom of the magnetic layer 22. A magnetic recording pattern is formed by the magnetic region 22 a and the boundary region 28. In the magnetic recording pattern, as shown in FIG. 3C, the magnetic region 22a forms a convex portion and the boundary region 28 forms a concave portion on the magnetic recording surface of the magnetic recording medium 20.

  Even in the case where the magnetic region 22a on the surface of the magnetic recording medium forms a convex portion and the boundary region 28 adjacent to the magnetic region 22a forms a concave portion as in the present embodiment, The magnetic head can be made to fly above. In this case, since the magnetic area 22a has a small distance from the magnetic head, reading and writing can be performed by the magnetic head. On the other hand, the boundary area 28 of the magnetic recording pattern has a large distance from the magnetic head. And writing becomes difficult.

  In the magnetic recording medium 20 of this embodiment, the uneven step d formed by the magnetic region 22a and the boundary region 28 is preferably in the range of 1 to 10 nm, and more preferably in the range of 3 to 5 μm. If the level difference d is less than 1 nm, reading and writing by the magnetic head to the boundary region 28 are possible, and magnetic separation of the magnetic recording pattern becomes impossible, and it is not preferable. This is not preferable because the surface smoothness of the recording medium 20 deteriorates and the flying characteristics of the magnetic head when the magnetic recording / reproducing apparatus is manufactured deteriorates.

  The boundary region 28 of the present embodiment is obtained by modifying the magnetic characteristics of the magnetic layer 22. Specifically, the modification of the magnetism and characteristics of the boundary region 28 is such that the saturation magnetization of the boundary region 28 is more than 5% and less than 40%, more preferably 10% to 30% of the saturation magnetization of the unprocessed magnetic layer 22. It is preferable to do. Similarly, it is preferable that the residual magnetization of the boundary region 28 be more than 1% and 20% or less, more preferably 5% or more and 15% or less of the residual magnetization of the unprocessed magnetic layer 22.

That is, the saturation magnetization (MsL) and the residual magnetization (MrL) of the boundary region 28 and the saturation magnetization (MsU) and the residual magnetization (MrU) of the magnetic region 22a are represented by the following expressions (5) and (6). Have
0.05 × MsU <MsL <0.4 × MsU (5)
0.01 × MrU <MrL <0.2 × MrU (6)

  Next, a method for manufacturing the magnetic recording medium 20 according to the second embodiment will be described. Note that the manufacturing method of the magnetic recording medium 20 of the present embodiment is different from the manufacturing method of the magnetic recording medium of the first embodiment in the formation method of the boundary region 28, and the other steps are the same. Since it is the same as the manufacturing method of 1 embodiment, description is abbreviate | omitted.

  In this embodiment, similarly to the first embodiment, after performing the step F (see FIG. 2F) of partially ion milling the surface layer portion of the magnetic layer 2 from the surface on the resist layer 4 side, FIG. As shown in FIGS. 4A to 4C, the step G ′ for modifying the magnetic properties of the magnetic layer 22 by exposing the ion milled portion of the magnetic layer 22 to reactive plasma or reactive ions (FIG. 4 ( a); 28 denotes a boundary region in which the magnetic properties of the magnetic layer 22 are modified), a step H ′ for removing the resist layer 4 and the mask layer 3 (FIG. 4B), and protecting the surface of the magnetic layer 22 The magnetic recording medium 20 can be manufactured by a method having the steps I ′ (FIG. 4C) covered with the layer 9 in this order.

(Process F)
Also in this embodiment, as in the first embodiment, in step F, a part of the surface layer of the magnetic layer 22 is removed by ion milling or the like to form irregularities. By providing irregularities in the magnetic layer 22 in this manner, the distance between the boundary region 28 corresponding to the concave portion of the magnetic recording pattern and the magnetic head can be increased, and reading / writing of information to the boundary region 28 by the magnetic head can be prevented. .

(Process G ')
Next, in the manufacturing method of this embodiment, the magnetic properties of the magnetic layer 22 are exposed by exposing the ion milled portion of the magnetic layer 22 to reactive plasma or reactive ions in the step G ′ shown in FIG. Reform. As a result, magnetic regions 22a and boundary regions 28 as shown in FIGS. 3A to 3C are formed. Further, the boundary region 28 can be formed by performing ion implantation on the magnetic layer 22 to modify the magnetic characteristics of the implanted portion.

  Here, the magnetic recording pattern of the present embodiment does not include only the case where the magnetic layer 22 is magnetically separated by the nonmagnetic region, but can be read and written by the magnetic head as described above. The case where it is provided in is also included. That is, in the present embodiment, when the recording surface of the magnetic recording medium 20 is viewed in plan (see FIG. 3B), the magnetic recording pattern portion may not be magnetically separated by the boundary region composed of the nonmagnetic region. The boundary region 28 may be separated from the magnetic head, the magnetic recording pattern portion may be provided close to the magnetic head, and the magnetic recording pattern may be provided in a state in which reading and writing can be performed by the magnetic head.

  Therefore, in this embodiment, the magnetic characteristics of the magnetic layer 22 at the location where the ion milling of the magnetic layer 22 is performed, that is, the location that becomes the boundary region 28, are modified, and the saturation magnetization (MsL) and the residual magnetization (MrL) at the location. Is adjusted so that the saturation magnetization (MsU) and the residual magnetization (MrU) of the magnetic layer 22 at the location to be the magnetic region 22a are in the relationship of the above formula (5) and the above formula (6).

(Process H ′ to Process I ′)
Next, in the present embodiment, the resist layer 4 and the mask layer 3 are removed as shown in Step H ′ of FIG.
Next, as shown in Step I ′ of FIG. 4C, in the manufacturing method of the present embodiment, the protective layer 9 is formed, and a lubricant is applied thereon, whereby the magnetic recording medium 20 is formed. It is preferable to employ a process for manufacturing.

  As described above, according to the magnetic recording medium 20 of the present embodiment, the magnetic recording pattern is composed of the magnetic region 22a serving as the recording region and the boundary region 28 in which the magnetic characteristics of the magnetic layer 22 are modified, The saturation magnetization (MsL) and residual magnetization (MrL) of the boundary region 28 arranged between the adjacent magnetic regions 22a, and the saturation magnetization (MsU) and residual magnetization (MrU) of the magnetic region 2a are expressed by the above equation (5). Since the relationship of the above equation (6) is satisfied, it is possible to provide a magnetic recording medium having a high magnetization volume per data bit and high resistance to thermal fluctuation.

<Third Embodiment>
Next, as a magnetic recording / reproducing apparatus to which the present invention is applied, a magnetic recording / reproducing apparatus including the magnetic recording media 10 and 20 shown in FIGS. 1 and 3 will be described as an example. FIG. 5 is a schematic configuration diagram showing an example of a magnetic recording / reproducing apparatus to which the present invention is applied. A magnetic recording / reproducing apparatus 30 shown in FIG. 5 includes a magnetic recording medium 10 (20) shown in FIGS. 1 and 3, and a medium driving unit 31 that rotates the magnetic recording medium 10 in the circumferential direction (drives in the recording track direction). , A magnetic head 32 composed of a read head and a write head, head movement means 33 for moving the magnetic head 32 relative to the magnetic recording medium 10, signal input to the magnetic head 32, and output signals from the magnetic head 32 Recording / reproduction signal processing means 34 for performing reproduction.

The recording / reproducing signal processing means 34 processes data input from the outside to generate a recording signal, inputs this recording signal to the magnetic head 32, and processes the reproducing signal from the magnetic head 32 to process the data. -Generate data and output this data to the outside.
The magnetic head 32 uses an AMR element using the anisotropic magnetoresistive effect (AMR) as a read element for the read head, a GMR element using the giant magnetoresistive effect (GMR), and a tunnel effect. A magnetic head having a TuMR element or the like suitable for high recording density can be used.

Since the magnetic recording / reproducing apparatus 30 of this embodiment includes the magnetic recording medium 10 (20) having excellent writing characteristics, a magnetic head 32 having a small writing magnetic field corresponding to a high recording density is used. Even if it exists, it can write in a magnetic recording pattern reliably and becomes the thing excellent in the high recording density characteristic.
Further, in the magnetic recording / reproducing apparatus 30 of this embodiment, the magnetic recording medium 10 (20) is less affected by the adjacent magnetic recording pattern at the time of reading, so that the magnetic head provided with a read head having the same width as the write head Using 32, sufficient reproduction output and high SNR can be obtained.

  Hereinafter, an example is shown and the effect of the present invention is explained concretely.

Example 1
A magnetic recording medium which is an example of the present invention was obtained by the following production method.
First, as the non-magnetic _substrate, a _{Li 2 Si 2 O 5, Al} 2 O 3 -K 2 O, Al 2 O 3 -K 2 O, MgO-P 2 O 5, Sb 2 O 3 -ZnO constituents A glass substrate for a hard disk made of crystallized glass and having an outer diameter of 65 mm, an inner diameter of 20 mm, and an average surface roughness (Ra) of 2 mm (0.2 nm) was prepared.

Next, such a nonmagnetic substrate is placed in the vacuum chamber of the film forming apparatus, the inside of the vacuum chamber is evacuated to 1.0 × 10 ⁻⁵ Pa or less, and a DC sputtering method is used to form a nonmagnetic substrate on A FeCoB film as a soft magnetic layer, a Ru film as an intermediate layer, and a ₂₅ Fe- ₃₀ Co- ₄₅ Pt film as a magnetic layer were sequentially formed. The thickness of each of the deposited layers was 60 nm for the soft magnetic layer, 10 nm for the intermediate layer, and 20 nm for the magnetic layer.

Next, a resist made of an ultraviolet curable resin was applied to the entire surface of the magnetic layer with a thickness of 60 nm to form a resist film. Thereafter, a Ni stamper prepared in advance was brought into close contact with the surface of the resist film and pressed. Thereby, the uneven pattern of the stamper was imprinted on the surface of the resist film. In the stamper, a groove having a depth of 30 nm and a width of 70 nm is engraved with a track pitch and a bit pitch of 100 nm. Thereafter, the resist film was irradiated with ultraviolet rays to cure the resist film to form a resist layer, and the concave portions of the resist layer were removed by dry etching to expose the surface of the magnetic layer to form a resist pattern. The dry etching conditions for the resist layer were O ₂ gas 40 sccm, pressure 0.3 Pa, high-frequency plasma power 300 W, DC bias 30 W, and etching time 15 seconds.

Next, ion etching of the surface layer portion of the magnetic layer was performed on the region on the magnetic layer exposed from the resist pattern, and at the same time, the magnetic properties of the portion below the magnetic layer were modified. This step was performed by ion implantation simultaneously with ion beam etching using a mixed gas of nitrogen and hydrogen (mixing ratio is 1: 1 and the flow rate of each gas is 40 sccm) as a process gas. Processing of this step, the acceleration voltage 1000V, a current density of 0.4 mA / cm ^2, carried out under the conditions of the etching rate 0.08 nm / sec, the etching depth was set to 10nm, the magnetic layer of the ion-implanted 10nm thereunder Modified the magnetic properties. FIG. 6 shows the magnetic hysteresis curve of the magnetic recording region (magnetic region) and its boundary region. A curve U is a magnetic recording pattern portion, and a curve L is a magnetic hysteresis curve in the boundary region. The saturation magnetization (MsL) and residual magnetization (MrL) of the boundary region and the saturation magnetization (MsU) and residual magnetization (MrU) of the magnetic recording pattern portion are 0.33 × MsU = MsL, 0.05 × MrU = MrL There was a relationship.

  Thereafter, the resist pattern was removed from the surface of the magnetic layer by dry etching. Next, a protective layer made of carbon having an average film thickness of 40 mm is formed on the magnetic layer by plasma CVD, and further, a lubricating film is formed by applying a fluorine-based lubricant on the protective layer. did. Through the above steps, the magnetic recording medium of the example having the configuration of the magnetic recording medium 20 of the second embodiment was manufactured.

The magnetic conversion characteristics (SNR and 3T-squash) of the magnetic recording media of the examples obtained in this way were measured. The evaluation of electromagnetic conversion characteristics was performed using a spin stand. The evaluation head uses a perpendicular recording head for recording, and a TuMR head (Tunneling Magneto Resistive Head, manufactured by TDK Corporation) for reading. The SNR value and 3T-squash when a 750 kFCI signal is recorded are used. It was measured.
As a result, it was found that the SNR was 13.7 dB, the 3T-squash (fringe) was 96%, and the recording / reproduction characteristics were excellent. Here, 3T-squash (3-track squash) refers to the ratio of the signal strength of the center track before and after recording the signal on both sides of the center after recording the signal on the center track ( %).

(Example 2)
A magnetic recording medium was manufactured in the same manner as in Example 1. In Example 2, the ion-implanted magnetic layer was set to 0.39 × MsU = MsL and 0.19 × MrU = MrL. As a result, SNR was 13.3 dB and 3T-squash (fringe) was 90%.

(Example 3)
A magnetic recording medium was manufactured in the same manner as in Example 1. In Example 3, the ion-implanted magnetic layer was set to 0.06 × MsU = MsL and 0.02 × MrU = MrL. As a result, SNR was 13.4 dB and 3T-squash (fringe) was 97%.

(Comparative Example 1)
A magnetic recording medium was manufactured in the same manner as in Example 1. However, in Comparative Example 1, the etching depth during ion etching of the surface layer portion of the magnetic layer with respect to the region on the magnetic layer exposed from the resist pattern and the modification of the magnetic properties were performed. Was 10 nm as in the example, but the magnetic layer below it was completely demagnetized. That is, MsL = MrL = 0. As a result, SNR was 13.1 dB and 3T-squash (fringe) was 97%.

(Comparative Example 2)
A magnetic recording medium was manufactured in the same manner as in Example 1. However, in Comparative Example 2, the etching depth during ion etching of the surface layer portion of the magnetic layer with respect to the region on the magnetic layer exposed from the resist pattern and the modification of the magnetic properties were performed. Was 10 nm as in the example, but the ion-implanted magnetic layer below it was set to 0.45 × MsU = MsL and 0.24 × MrU = MrL. As a result, SNR was 12.8 dB and 3T-squash (fringe) was 83%.

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic board | substrate 2,22 ... Magnetic layer 2a, 22a ... Magnetic area | region 2b ... Lower area | region 8,28 ... Boundary area 8a ... Nonmagnetic area | region 10,20 ... Magnetic recording medium 30 ... Magnetic recording / reproducing apparatus 31 ... Medium drive part 32 ... Magnetic head 33 ... Head movement means 34 ... Recording / reproduction signal processing means

Claims (8)

A magnetic recording medium comprising a magnetic layer on at least one surface of a nonmagnetic substrate,
In the magnetic layer, a magnetic region to be a recording region and a boundary region that separates the magnetic region are alternately arranged adjacent to each other,
The saturation magnetization (MsL) and remanent magnetization (MrL) of the boundary region and the saturation magnetization (MsU) and remanent magnetization (MrU) of the magnetic region have the relationship of the following formula (1) and the following formula (2). A magnetic recording medium characterized by the above.
0.05 × MsU <MsL <0.4 × MsU (1)
0.01 × MrU <MrL <0.2 × MrU (2) The boundary region is a laminated structure of a lower region made of a magnetic layer provided on the nonmagnetic substrate side and a nonmagnetic region provided on the lower region,
The saturation magnetization (MsL) and remanent magnetization (MrL) of the lower region and the saturation magnetization (MsU) and remanent magnetization (MrU) of the magnetic region have the relationship of the above formulas (1) and (2). The magnetic recording medium according to claim 1.   The magnetic recording medium according to claim 2, wherein the magnetic region and the lower region are magnetically continuous.   The magnetic recording medium according to claim 1, wherein the boundary region is a region in which the magnetic characteristics of the magnetic layer are modified.   5. The magnetic recording medium according to claim 1, wherein the magnetic region forms a convex portion and the boundary region forms a concave portion on a magnetic recording surface of the magnetic recording medium.   The magnetic recording medium according to claim 5, wherein a step between the magnetic region and the boundary region is in a range of 1 nm to 10 nm.   The magnetic recording medium according to any one of claims 1 to 6, wherein the magnetic recording pattern including the magnetic region and the boundary region is at least one of a recording track, a recording bit, and a servo signal. . A magnetic recording medium according to any one of claims 1 to 7,
Medium driving means for driving the magnetic recording medium in a recording track direction;
A magnetic head comprising a recording unit and a reproducing unit;
Head moving means for moving the magnetic head relative to the magnetic recording medium;
A magnetic recording / reproducing apparatus comprising: a recording / reproducing signal processing means for reproducing a signal input to the magnetic head and an output signal from the magnetic head.

Images