JP2010238332A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium which secures high quality by reducing noise caused by a non-recording part even when using ion implantation in forming a magnetic pattern comprising a magnetic recording part and the non-recording part. <P>SOLUTION: In the magnetic recording medium 100 including a magnetic recording layer 122 having at least the magnetic recording part formed in a prescribed pattern in an in-lane direction and the non-recording part 134 on a substrate, the magnetic recording layer includes a material having a perpendicular magnetic anisotropic constant Ku of 4&times;10<SP>6</SP>erg/cc or more, and the non-recording part is formed by implanting ion in the magnetic recording layer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a magnetic recording medium mounted on an HDD (Hard Disk Drive) or the like.

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, a 2.5-inch diameter magnetic recording medium used for HDDs or the like has been required to have an information recording capacity exceeding 200 GBytes per sheet. In order to meet such a demand, one square is required. It is required to realize an information recording density exceeding 400 GB per inch.

  In recent years, a perpendicular magnetic recording system has been proposed in order to achieve a high recording density in a magnetic recording medium used for an HDD or the like. The perpendicular magnetic recording medium used for the perpendicular magnetic recording system is adjusted so that the easy axis of magnetization of the magnetic recording layer is oriented in the direction perpendicular to the substrate surface. Compared to the conventional in-plane recording method, the perpendicular magnetic recording method can suppress the so-called thermal fluctuation phenomenon in which the thermal stability of the recording signal is lost due to the superparamagnetic phenomenon, and the recording signal disappears. Suitable for higher recording density.

  Furthermore, as a technology that improves recording density and thermal fluctuation resistance, patterning is performed so that non-magnetic tracks (non-recording portions) are parallel between recording magnetic tracks (magnetic recording portions), and interference between adjacent recording tracks is prevented. Magnetic recording media called discrete track media to prevent or bit pattern media in which arbitrary patterns are artificially arranged regularly have been proposed.

  Patterned media such as the discrete track media and bit pattern media described above are magnetically formed by forming a magnetic recording layer on a nonmagnetic substrate and then partially implanting ions to make them nonmagnetic or amorphous. After forming a magnetic recording layer on a non-magnetic substrate (for example, Patent Document 1) or by partially milling the magnetic recording layer to form irregularities, A technique for separating the magnetic recording layer and forming a magnetic pattern (for example, Patent Document 2) has been proposed.

  Specifically, first, a resist is formed on the magnetic recording layer, and a stamper on which a desired uneven pattern is formed is imprinted to transfer the uneven pattern to the resist, or a photoresist is applied on the magnetic recording layer. A desired concavo-convex pattern is formed on a photoresist by photolithography. Then, ions are implanted into the magnetic recording layer through the formed recess, or the magnetic recording layer exposed on the surface of the recess is milled by etching to separate the magnetic recording layer.

JP 2007-226862 A JP 2007-157111 A

  Among the above-described methods for producing patterned media, when irregularities are formed in the magnetic recording layer by milling, it is necessary to form a filling layer in order to fill the formed concave portions. At this time, when the filling layer is formed by sputtering, the filling layer is formed in the concave portion, but naturally a film (filling layer) is similarly formed on the convex portion. For this reason, a convex portion due to such a film is formed on the main surface of the magnetic recording medium. Therefore, in order to remove the film formed on the convex part, it has been conventionally necessary to remove the film formed on the convex part by etching to flatten the main surface.

  From the above reasons, when the manufacturing method by ion implantation as in Patent Document 1 is compared with the manufacturing method of milling the magnetic recording layer by etching as in Patent Document 2, the manufacturing method by ion implantation is more patterned media. Could be produced much more easily.

  However, the magnetic recording medium manufactured by ion implantation has a problem that the non-recording portion formed is not sufficiently demagnetized. In detail, in the manufacturing method by ion implantation, ions are implanted into the magnetic recording layer by using the ion beam method, so that the crystalline magnetic recording layer of the portion into which the ions are implanted is made amorphous, and the portion is Non-magnetic. Therefore, if the amount of ion implantation (dose amount) is insufficient, the magnetic recording layer that becomes the non-recording portion becomes insufficiently amorphous, and the portion cannot be completely demagnetized, and the non-recording portion is also magnetic. It will have. Then, the orientation direction of the easy axis of the non-recording portion becomes irregular and the magnetization direction is three-dimensional, so that the component perpendicular to the substrate surface (magnetic flux in the vertical direction) is included in the magnetization direction. End up. As a result, when reading with the magnetic head, the magnetic flux of the vertical component is picked up as noise together with the signal of the magnetic recording unit, leading to a decrease in read / write characteristics.

  Here, in order to completely demagnetize the non-recording portion, it is conceivable to increase the ion implantation amount. However, if the ion implantation amount is increased too much, amorphization is promoted too much, and not only the portion that becomes the non-recording portion of the magnetic recording layer but also the portion that becomes the magnetic track (non-magnetic). ). As a result, the overwrite characteristic is deteriorated. Further, when the ion implantation amount is increased, the time required for the ion implantation process is lengthened and there is a problem that the production efficiency is lowered.

  Therefore, at present, the ion implantation amount must be stopped to a certain extent, and when a manufacturing method using ion implantation is used, a slight decrease in read / write characteristics has to be allowed. For this reason, it has been desired to develop a technique capable of reducing noise caused by the non-recording portion without depending on the ion implantation amount.

  In view of such problems, the present invention ensures high quality by reducing noise caused by non-recording portions even when ion implantation is used to form a magnetic pattern composed of magnetic recording portions and non-recording portions. An object of the present invention is to provide a magnetic recording medium that can be used.

In order to solve the above problems, a typical configuration of a magnetic recording medium according to the present invention is a magnetic recording having a magnetic recording portion and a non-recording portion formed in a predetermined pattern in the in-plane direction on a substrate. In the magnetic recording medium provided with the layer, the magnetic recording layer is made of a material having a perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more, and the non-recording portion implants ions into the magnetic recording layer. It is formed by these.

The perpendicular magnetic anisotropy constant Ku represents the stability of the orientation of the easy axis of magnetization, and the larger the value, the less likely the easy axis of magnetization oriented in the vertical direction will fluctuate. In the above configuration, ions are implanted into the magnetic recording layer made of a material having the perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more. Then, the crystal structure of the portion of the magnetic recording layer into which ions are implanted is disordered, and the crystal orientation is significantly lowered. As a result, the easy axis of magnetization of the non-recording portion of the magnetic recording layer is in the in-plane direction (horizontal direction). Thereby, noise caused by the non-recording portion is reduced, and the quality of the magnetic recording medium can be improved.

Examples of the material that can satisfy the high perpendicular magnetic anisotropy constant Ku include a material in which SiO ₂ or TiO ₂ is contained in a CoPt-based alloy containing 20 to 40 at% Pt. As another means for satisfying the high perpendicular magnetic anisotropy constant Ku, the magnetic recording layer is composed of a Co / Pt multilayer film or a Co / Pd multilayer film and contains SiO ₂ or TiO _2. But you can. Furthermore, high Ku can also be realized by using SmCo ₅ , FePt, NdFeB, or the like for the magnetic recording layer.

The magnetic recording layer may be made of a material having a perpendicular magnetic anisotropy constant Ku of 1 × 10 ⁷ erg / cc or more.

  According to this configuration, as described above, the easy magnetization axis of the portion that becomes the non-recording portion of the magnetic recording layer is oriented in the horizontal direction by ion implantation, and the easy magnetization axis of the portion that becomes the magnetic recording portion is aligned more vertically. Can be made. Further, the higher the perpendicular magnetic anisotropy constant Ku is, the higher the saturation magnetization Ms is. Accordingly, the demagnetizing field is also proportional to this, and the above effect can be obtained remarkably.

The film thickness of the magnetic recording layer is preferably 4 nm to 8 nm. As described above, by using a material having a perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more, that is, a material having a high perpendicular magnetic anisotropy constant Ku, for the magnetic recording layer, The easy magnetization axes in the portion to be the magnetic recording portion are aligned in the vertical direction with high accuracy. Therefore, since the magnetic recording layer has high strength as a magnet, the thickness of the magnetic recording layer can be reduced to such a range. Moreover, about 8 nm of upper limit, since a strong demagnetizing field can be obtained, so that a film thickness is thin, it is preferable that it is the film thickness below this. The lower limit of 4 nm is preferably larger than this in order to obtain high Ku.

The dose amount of the ions is preferably 1 × 10 ¹⁵ atoms / cm ² to 1 × 10 ¹⁷ atoms / cm ² . As described above, the film thickness of the magnetic recording layer can be reduced by using a material having a high perpendicular magnetic anisotropy constant Ku for the magnetic recording layer. Therefore, the ion dose during ion implantation for forming the non-recording portion in the magnetic recording layer can be reduced to the above range.

  The above ions may be N ions. As a result, it is possible to reduce the crystal orientation of the portion that becomes the non-recording portion of the magnetic recording layer, and to suitably reduce the perpendicular magnetic anisotropy constant Ku.

  According to the present invention, even when ion implantation is used to form a magnetic pattern composed of a magnetic recording portion and a non-recording portion, noise caused by the non-recording portion is reduced and high quality of the magnetic recording medium is ensured. It becomes possible.

It is a figure explaining the structure of the perpendicular magnetic recording medium as a magnetic recording medium. It is a figure for demonstrating magnetic pattern formation. It is a figure explaining the hysteresis loop of an Example and a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  An embodiment of a magnetic recording medium according to the present invention will be described. FIG. 1 is a diagram illustrating a configuration of a perpendicular magnetic recording medium 100 as a magnetic recording medium. The perpendicular magnetic recording medium 100 according to the present embodiment is a patterned medium. As a result, the thermal fluctuation resistance of the perpendicular magnetic recording medium 100 can be improved, and a higher recording density can be promoted.

  The perpendicular magnetic recording medium 100 shown in FIG. 1 includes a disk substrate 110, an adhesion layer 112, a first soft magnetic layer 114a, a spacer layer 114b, a second soft magnetic layer 114c, a pre-underlayer 116, a first underlayer 118a, and a second layer. The underlayer 118b, the nonmagnetic granular layer 120, the first magnetic recording layer 122a, the second magnetic recording layer 122b, the auxiliary recording layer 124, the protective layer 126, and the lubricating layer 128 are included. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c together constitute the soft magnetic layer 114. The first base layer 118a and the second base layer 118b together constitute the base layer 118. The first magnetic recording layer 122a and the second magnetic recording layer 122b together constitute the magnetic recording layer 122.

(Disc base 110)
As the disk substrate 110, a glass disk obtained by forming amorphous (amorphous) aluminosilicate glass into a disk shape by direct pressing can be used. The type, size, thickness, etc. of the glass disk are not particularly limited. Examples of the material of the glass disk include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or glass ceramic such as crystallized glass. It is done. The glass disk is subjected to grinding, polishing, and chemical strengthening sequentially to obtain a smooth non-magnetic disk base 110 made of a chemically strengthened glass disk.

  On the disk substrate 110, a film is sequentially formed from the adhesion layer 112 to the auxiliary recording layer 124 by a DC magnetron sputtering method, and the protective layer 126 can be formed by a CVD method. Thereafter, the lubricating layer 128 can be formed by dip coating. Note that it is also preferable to use an in-line film forming method in terms of high productivity.

  Hereinafter, the configuration of each layer and the formation of a magnetic pattern in which a magnetic recording portion and a non-recording portion are formed in the magnetic recording layer 122 by performing resist layer deposition, patterning, ion implantation, and resist layer removal will be described.

  The adhesion layer 112 is formed in contact with the disk substrate 110, and has a function of increasing the peel strength between the soft magnetic layer 114 formed on the disk substrate 110 and the disk substrate 110, and the crystal grains of each layer formed thereon are finely divided. It has a function to make it uniform and uniform. When the disk substrate 110 is made of amorphous glass, the adhesion layer 112 is preferably an amorphous alloy film so as to correspond to the amorphous glass surface.

  The adhesion layer 112 can be selected from, for example, a CrTi amorphous layer, a CoW amorphous layer, a CrW amorphous layer, a CrTa amorphous layer, and a CrNb amorphous layer. Among these, a CoW alloy film is particularly preferable because it forms an amorphous metal film containing microcrystals. The adhesion layer 112 may be a single layer made of a single material, or may be formed by laminating a plurality of layers. For example, a CoW layer or a CrW layer may be formed on the CrTi layer. These adhesion layers 112 are preferably formed by sputtering with a material containing carbon dioxide, carbon monoxide, nitrogen, or oxygen, or the surface layer is exposed with these gases.

  The soft magnetic layer 114 is a layer that temporarily forms a magnetic path during recording in order to pass magnetic flux in a direction perpendicular to the recording layer in the perpendicular magnetic recording method. The soft magnetic layer 114 can be configured to have an AFC coupling by interposing a nonmagnetic spacer layer 114b between the first soft magnetic layer 114a and the second soft magnetic layer 114c. As a result, the magnetization direction of the soft magnetic layer 114 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and the vertical component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 114 is reduced. Can do. The composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c includes a Co-based alloy such as CoTaZr, a Co—Fe based alloy such as CoCrFeB and CoFeTaZr, and a Ni like a [Ni—Fe / Sn] n multilayer structure. A Fe alloy or the like can be used.

  The pre-underlayer 116 is a non-magnetic alloy layer, and has an effect of protecting the soft magnetic layer 114 and the easy axis of the hexagonal close-packed structure (hcp structure) included in the underlayer 118 formed thereon. It has a function of orienting the disk in the vertical direction. The pre-underlayer 116 preferably has a (111) plane of a face-centered cubic structure (fcc structure) parallel to the main surface of the disk substrate 110. Further, the pre-underlayer 116 may have a configuration in which these crystal structures and amorphous are mixed. The material of the pre-underlayer 116 can be selected from Ni, Cu, Pt, Pd, Zr, Hf, Nb, and Ta. Furthermore, it is good also as an alloy which has these metals as a main component and contains any one or more additional elements of Ti, V, Cr, Mo, and W. For example, NiW, CuW, or CuCr can be suitably selected as an alloy having an fcc structure.

  The underlayer 118 has an hcp structure, and has a function of growing a Co hcp crystal of the magnetic recording layer 122 as a granular structure. Therefore, the higher the crystal orientation of the underlayer 118, that is, the more the (0001) plane of the crystal of the underlayer 118 is parallel to the main surface of the disk substrate 110, the more the orientation of the magnetic recording layer 122 is improved. Can do. Ru is a typical material for the underlayer 118, but in addition, it can be selected from RuCr and RuCo. Since Ru has an hcp structure and the lattice spacing of crystals is close to Co, the magnetic recording layer 122 containing Co as a main component can be well oriented.

  When the underlayer 118 is made of Ru, a two-layer structure made of Ru can be obtained by changing the gas pressure during sputtering. Specifically, when forming the first underlayer 118a on the lower layer side, the Ar gas pressure is set to a predetermined pressure, that is, a low pressure, and when forming the second underlayer 118b on the upper layer side, the first lower layer 118b on the lower layer side is formed. The gas pressure of Ar is set higher than when forming the first underlayer 118a, that is, the pressure is increased. Thereby, the crystal orientation of the magnetic recording layer 122 can be improved by the first underlayer 118a, and the grain size of the magnetic particles of the magnetic recording layer 122 can be reduced by the second underlayer 118b.

  Further, when the gas pressure is increased, the mean free path of the plasma ions to be sputtered is shortened, so that the film formation rate is slow and the film becomes rough, so that separation and refinement of Ru crystal particles can be promoted, Co crystal grains can also be made finer.

  Further, a small amount of oxygen may be contained in Ru of the base layer 118. As a result, the separation and refinement of the Ru crystal grains can be further promoted, and the magnetic grains of the magnetic recording layer 122 can be further isolated and refined. Note that oxygen may be contained by reactive sputtering, but it is preferable to use a target containing oxygen at the time of sputtering film formation.

  The nonmagnetic granular layer 120 is a nonmagnetic layer having a granular structure. A nonmagnetic granular layer 120 is formed on the hcp crystal structure of the underlayer 118, and a granular layer of the first magnetic recording layer 122a (or the magnetic recording layer 122) is grown thereon, whereby the magnetic granular layer is initially formed. It has the effect of separating from the growth stage (rise). Thereby, isolation of the magnetic particles of the magnetic recording layer 122 can be promoted. The composition of the nonmagnetic granular layer 120 can be a granular structure by forming a grain boundary by segregating a nonmagnetic substance between nonmagnetic crystal grains made of a Co-based alloy.

In the present embodiment, CoCr—SiO ₂ is used for the nonmagnetic granular layer 120. As a result, SiO ₂ (nonmagnetic substance) segregates between Co-based alloys (nonmagnetic crystal grains) to form grain boundaries, and the nonmagnetic granular layer 120 has a granular structure. Note that CoCr—SiO ₂ is an example, and the present invention is not limited to this. In addition, CoCrRu—SiO ₂ can be preferably used, and Rh (rhodium), Pd (palladium), Ag (silver), Os (osmium), Ir (iridium), Au (gold) can be used instead of Ru. Can also be used. A non-magnetic substance is a substance that can form a grain boundary around magnetic particles so that exchange interaction between magnetic particles (magnetic grains) is suppressed or blocked, and cobalt (Co). Any non-magnetic substance that does not dissolve in solution can be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (CrO ₂ , Cr ₂ O ₃ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

  In this embodiment, the nonmagnetic granular layer 120 is provided on the underlayer 118 (second underlayer 118b). However, the present invention is not limited to this, and the vertical direction is not provided without providing the nonmagnetic granular layer 120. It is also possible to configure the magnetic recording medium 100.

  The magnetic recording layer 122 has a columnar granular structure in which a nonmagnetic substance is segregated around a magnetic particle of a hard magnetic material selected from a Co-based alloy, an Fe-based alloy, and a Ni-based alloy to form a grain boundary. It is a magnetic layer. By providing the nonmagnetic granular layer 120, the magnetic particles can be epitaxially grown continuously from the granular structure. In particular, when the perpendicular magnetic recording medium 100 according to the present embodiment is a discrete track medium, the configuration in which the magnetic recording layer 122 has a granular structure can improve the SNR (Signal to Noise Ratio). .

  In this embodiment, the magnetic recording layer 122 includes a first magnetic recording layer 122a and a second magnetic recording layer 122b having different compositions and film thicknesses. As a result, small crystal grains of the second magnetic recording layer 122b continue to grow from the crystal grains of the first magnetic recording layer 122a, and the second magnetic recording layer 122b, which is the main recording layer, can be miniaturized. Can be improved.

  Further, the first magnetic recording layer 122a and the second magnetic recording layer 122b constituting the magnetic recording layer 122 are formed with a magnetic pattern portion and a non-recording portion in a predetermined pattern by forming a magnetic pattern described later. The As a result, the perpendicular magnetic recording medium 100 can be a patterned medium, which can improve thermal fluctuation resistance and promote higher recording density. As such a patterned medium, the perpendicular magnetic recording medium 100 may be a bit pattern medium in which magnetic recording portions are scattered on the main surface, or a linearly formed magnetic recording portion and a non-recording portion are formed on the main surface. Discrete track media arranged alternately in the radial direction may be used.

  The relative magnetic permeability of the first magnetic recording layer 122a and the second magnetic recording layer 122b existing in the non-recording portion is preferably about 2 to 100. That is, it is said that the magnetism of the first magnetic recording layer 122a and the second magnetic recording layer 122b becomes a magnetism between the hard magnetism and the soft magnetism (non-hard magnetism). As a result, it is possible to improve the read / write characteristics of the magnetic recording portion while ensuring a high SNR.

In this embodiment, CoCrPt—SiO ₂ —TiO ₂ is used for the first magnetic recording layer 122a. In CoCrPt—SiO ₂ —TiO ₂ , nonmagnetic materials such as SiO ₂ and TiO ₂ (composite oxide) segregate around magnetic particles (grains) made of CoCrPt to form grain boundaries, and the magnetic particles are columnar. A granular structure was formed. The magnetic particles were epitaxially grown continuously from the granular structure of the nonmagnetic granular layer 120.

The second magnetic recording layer _122b, using _{CoCrPt-SiO 2 -TiO 2 -Co 3} O 4. Also in the second magnetic recording layer 122b, SiO ₂ , TiO ₂ , and Co ₃ O ₄ (composite oxide) that are nonmagnetic substances are segregated around the magnetic particles (grains) made of CoCrPt to form grain boundaries, A granular structure in which magnetic particles were grown in a columnar shape was formed.

In this embodiment, the magnetic recording layer 122, particularly the second magnetic recording layer 122b, is made of a material having a perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more. The perpendicular magnetic anisotropy constant Ku is a value representing the stability of the orientation of the easy axis of magnetization, and the larger the value, the less likely the easy axis of magnetization oriented in the vertical direction will fluctuate. Accordingly, the magnetic recording layer 122 (in particular, the second magnetic recording layer 122b in the present embodiment) made of a material having a perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more as in the above-described configuration will be described later. When ions are implanted when forming a pattern, the crystal structure of the magnetic recording layer 122 in the ion-implanted portion is disturbed, and the crystal orientation is significantly lowered. As a result, the easy axis of magnetization of the non-recording portion of the magnetic recording layer 122 faces in the in-plane direction (horizontal direction).

  The above phenomenon is considered to be due to the fact that the perpendicular magnetic anisotropy constant Ku is remarkably lowered by ion implantation, so that the magnetization axis is defeated by the demagnetizing field and faces in the in-plane direction. That is, before the ions are implanted, the easy axis of magnetization of the magnetic recording layer 122 is stronger than the demagnetizing field, and thus is oriented in the vertical direction. Further, Ku is weakened by ion implantation, but saturation magnetization Ms is less decreased by ion implantation (when Ku is reduced by about 90%, Ms is reduced only by about 30%), and a demagnetizing field proportional to saturation magnetization Ms. There is little decline. As a result, it is considered that the easy magnetization axis is defeated by the demagnetizing field and cannot be directed in the vertical direction, and is directed in the horizontal direction. Therefore, in the non-recording portion formed by ion implantation, the magnetic flux in the vertical direction that becomes noise when reading with the magnetic head is eliminated, so that noise caused by the non-recording portion is reduced and the magnetic recording medium Quality can be improved.

More preferably, the magnetic recording layer 122, particularly the second magnetic recording layer 122b, may be made of a material having a perpendicular magnetic anisotropy constant Ku of 1 × 10 ⁷ erg / cc or more. According to such a configuration, as described above, the easy magnetization axis of the portion that becomes the non-recording portion of the magnetic recording layer 122 is oriented in the horizontal direction by ion implantation, and the easy magnetization axis of the portion that becomes the magnetic recording portion is made more vertical. Can be aligned. Further, the higher the perpendicular magnetic anisotropy constant Ku is, the higher the saturation magnetization Ms is. Accordingly, the demagnetizing field is also proportional to this, and the above effect can be obtained remarkably.

As a material capable of meeting the high perpendicular magnetic anisotropy constant Ku, it may be exemplified material containing SiO ₂ and TiO ₂ and Pt in CoPt-based alloy containing 40 at% of 20at%. In addition, the Pt content itself is usually added to the magnetic material of the magnetic recording medium in order to improve the coercive force Hc. However, the peak at which the coercive force is improved is about 17 at%, and noise is higher than this. Not added to increase. Therefore, it can be said that the inclusion of a large amount of Pt as much as 20 at% to 40 at% as described above is a range that is not normally performed, and is a special range for satisfying high Ku.

As another means for satisfying high Ku, the magnetic recording layer may be formed of a Co / Pt multilayer film or a Co / Pd multilayer film, and may contain SiO ₂ or TiO ₂ . Furthermore, high Ku can also be realized by using SmCo ₅ , FePt, NdFeB, or the like for the magnetic recording layer.

  In the present embodiment, since the magnetic recording layer 122 is composed of two layers, the first magnetic recording layer 122a and the second magnetic recording layer 122b, the second magnetic recording layer 122b is made to have a high perpendicular magnetic anisotropy constant Ku. However, when the magnetic recording layer 122 is composed of a single layer, the single magnetic recording layer 122 is composed of a material having a high perpendicular magnetic anisotropy constant Ku. Needless to say.

  Furthermore, in this embodiment, the film thickness of the magnetic recording layer 122, that is, the total film thickness of the first magnetic recording layer 122a and the second magnetic recording layer 122b can be set within a range of 4 nm to 8 nm. The total film thickness of the magnetic recording layer 122 and the auxiliary recording layer 124 is preferably set in the range of 8 nm to 15 nm. As described above, by using a material having a high perpendicular magnetic anisotropy constant Ku for the magnetic recording layer 122 (second magnetic recording layer 122b), the easy axis of magnetization in the portion of the magnetic recording layer 122 that becomes the magnetic recording portion is , It is aligned in the vertical direction with high accuracy. Therefore, since the magnetic recording layer 122 has high strength as a magnet, the thickness of the magnetic recording layer 122 can be reduced to such a range. Moreover, about 8 nm of upper limit, since a strong demagnetizing field can be obtained, so that a film thickness is thin, it is preferable that it is the film thickness below this. The lower limit of 4 nm is preferably larger than this in order to obtain a high perpendicular magnetic anisotropy constant Ku. Unlike the present embodiment, when the magnetic recording layer 122 is composed of one layer, it goes without saying that the film thickness of the single magnetic recording layer 122 is set within the above range.

The materials used for the first magnetic recording layer 122a and the second magnetic recording layer 122b described above are examples, and the present invention is not limited to these. Furthermore, in the present embodiment, the first magnetic recording layer 122a and the second magnetic recording layer 122b are different materials (targets), but the present invention is not limited to this, and the same composition and type may be used. Examples of the nonmagnetic substance for forming the nonmagnetic region include silicon oxide (SiO _x ), chromium (Cr), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), Examples thereof include oxides such as tantalum oxide (Ta ₂ O ₅ ), iron oxide (Fe ₂ O ₃ ), and boron oxide (B ₂ O ₃ ). Further, nitrides such as _BN, a carbide such as B 4 _{C 3} can also be suitably used.

Further, in the present embodiment, two types of non-magnetic substances (oxides) are used in the first magnetic recording layer 122a and three types of non-magnetic substances (oxides) in the second magnetic recording layer 122b. However, the present invention is not limited to this. For example, in one or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b, one type of nonmagnetic material may be used, or two or more types of nonmagnetic materials may be used in combination. It is. Although there is no limitation on the kind of nonmagnetic substance contained at this time, it is particularly preferable to contain SiO ₂ and TiO ₂ as in this embodiment. Therefore, unlike the present embodiment, when the magnetic recording layer 122 is composed of only one layer, the magnetic recording layer 122 is preferably made of CoCrPt—SiO ₂ —TiO ₂ .

  When the perpendicular magnetic recording medium 100 according to the present embodiment is a bit pattern medium, each recording bit is separated and independent, so that the magnetic recording layer 122 does not necessarily have a granular structure. However, the SNR can be improved by the configuration in which the magnetic recording layer 122 has a granular structure.

  The auxiliary recording layer 124 is a magnetic layer that is substantially magnetically continuous in the in-plane direction of the main surface of the substrate. The auxiliary recording layer 124 needs to be adjacent or close to the magnetic recording layer 122 so as to have a magnetic interaction. As a material of the auxiliary recording layer 124, for example, CoCrPt, CoCrPtB, or a small amount of oxides can be contained in these. The purpose of the auxiliary recording layer 124 is to adjust the reverse magnetic domain nucleation magnetic field Hn and the coercive force Hc, thereby improving the heat resistance fluctuation characteristic, the OW characteristic, and the SNR. In order to achieve this object, it is desirable that the auxiliary recording layer 124 has high perpendicular magnetic anisotropy Ku and saturation magnetization Ms. In the present embodiment, the auxiliary recording layer 124 is provided above the magnetic recording layer 122, but may be provided below.

  Note that “magnetically continuous” means that magnetism is continuous. “Substantially continuous” means that the magnetism may be discontinuous not by a single magnet but by grain boundaries of crystal grains when observed in the entire auxiliary recording layer 124. The grain boundaries are not limited to crystal discontinuities, and Cr may be segregated, and further, a minute amount of oxide may be contained and segregated. However, even when a grain boundary containing an oxide is formed in the auxiliary recording layer 124, it is preferable that the area is smaller than the grain boundary of the magnetic recording layer 122 (the content of the oxide is small). The function and action of the auxiliary recording layer 124 are not necessarily clear, but Hn and Hc can be adjusted by having magnetic interaction with the granular magnetic grains of the magnetic recording layer 122 (with exchange coupling), and heat resistance. It is thought that fluctuation characteristics and SNR are improved. In addition, since the crystal grains connected to the granular magnetic grains (crystal grains having magnetic interaction) have a larger area than the cross section of the granular magnetic grains, the magnetization is easily reversed by receiving a large amount of magnetic flux from the magnetic head. It is thought to improve the characteristics.

  In the present embodiment, the perpendicular magnetic recording medium 100 is configured to include the auxiliary recording layer 124. However, when the perpendicular magnetic recording medium 100 is a bit pattern medium, the auxiliary recording layer 124 may not be provided. Good.

  The protective layer 126 can be formed by depositing carbon by a CVD method while maintaining a vacuum. The protective layer 126 is a layer for protecting the perpendicular magnetic recording medium 100 from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness compared to that deposited by the sputtering method, so that the perpendicular magnetic recording medium 100 can be more effectively protected against the impact from the magnetic head.

(Magnetic pattern formation)
Next, magnetic pattern formation for forming a magnetic recording portion and a non-recording portion in a predetermined pattern on the magnetic recording layer 122 of this embodiment will be described in detail. Here, the magnetic pattern formation may be performed immediately after the magnetic recording layer 122 is formed, or may be performed after the auxiliary recording layer 124 or the protective layer 126 is formed.

  In this embodiment, the magnetic pattern is formed after the protective layer 126 is formed. This prevents the alkaline solution immersed in the resist layer from coming into direct contact with the magnetic recording layer 122, thereby preventing the alkaline solution from penetrating into the magnetic recording portion of the magnetic recording layer 122 and demagnetizing the portion. Can be prevented. Further, since it is not necessary to form the protective layer 126 after the magnetic pattern is formed, the manufacturing process is simplified. Therefore, productivity can be improved and contamination in the manufacturing process of the perpendicular magnetic recording medium 100 can be reduced.

  FIG. 2 is a diagram for explaining magnetic pattern formation. In FIG. 2, the description of the layer closer to the disk substrate 110 than the magnetic recording layer 122 is omitted for easy understanding. In the magnetic pattern formation, resist layer deposition, patterning, ion implantation, and resist layer removal are performed. Details of the magnetic pattern formation will be described below.

<Resist layer deposition>
As shown in FIG. 2A, a resist layer 130 is formed on the magnetic recording layer 122 via the auxiliary recording layer 124 and the protective layer 126 by using a spin coating method. As the resist layer 130, SOG (Spin On Glass) mainly composed of silica, a general novolac-based photoresist, or the like can be suitably used.

<Patterning>
As shown in FIG. 2B, the magnetic pattern is transferred by impressing a stamper 132 against the resist layer 130 (imprint method). Thereby, the resist layer 130 is processed, and the thickness of the resist layer 130 partially changes. The stamper 132 has a concavo-convex pattern corresponding to a predetermined pattern of a magnetic recording portion and a non-recording portion to be transferred. In addition to the predetermined pattern of the magnetic recording portion and the non-recording portion, the stamper can be provided with a concave / convex pattern corresponding to a servo pattern for storing servo information such as preamble, address, and burst.

  After the magnetic pattern is transferred to the resist layer 130 by the stamper 132, the stamper 132 is removed from the resist layer 130, thereby forming a concavo-convex pattern consisting of convex portions and concave portions of a predetermined pattern (magnetic pattern) on the resist layer 130. . In this embodiment, a fluorine-based release agent is applied to the surface of the stamper 132. Thereby, the stamper 132 can be favorably peeled from the resist layer 130.

  In this embodiment, the imprint method using the stamper 132 is used for patterning, but a photolithography method can also be used suitably. However, when the photolithography method is used, the photoresist is formed as the resist layer 130 in the above-described formation of the resist layer 130, and the formed photoresist is exposed and developed using a mask to form a magnetic layer. A predetermined pattern as a recording unit is transferred.

<Ion implantation>
As shown in FIG. 2C, the first magnetic recording layer 122a and the second magnetic recording layer 122b are formed from the concave portion of the resist layer 130 with the resist layer 130 having a predetermined pattern formed by patterning interposed therebetween. Ions are implanted into the magnetic recording layer 122 made of using the ion beam method. As a result, the crystal in the portion where the ions are implanted in the magnetic recording layer 122 is made amorphous, so that the first magnetic recording layer 122a and the second magnetic recording layer 122b in that portion are made non-magnetic, and the non-recording portion 134 is made. (Indicated by hatching in FIG. 2). Therefore, the portion of the magnetic recording layer 122 under the convex portion of the resist layer 130 can be a magnetically separated magnetic recording portion.

In the present embodiment, the material having a high perpendicular magnetic anisotropy constant Ku (4 × 10 ⁶ erg / cc or more) is used for the magnetic recording layer 122, particularly the second magnetic recording layer 122b. In the magnetic recording layer 122 in which ions are implanted, that is, in the portion that has become the non-recording portion 134, the crystal orientation is remarkably lowered, and the easy axis of magnetization is in the in-plane direction (horizontal direction). Accordingly, the magnetic flux in the vertical direction, which becomes a noise source at the time of reading by the magnetic head, is reduced. Therefore, even if the non-recording part 134 is not sufficiently demagnetized in the ion implantation, the noise caused by the non-recording part 134 Can be reduced.

In this embodiment, N ions are used as ions to be implanted. As a result, the crystal orientation of the portion that becomes the non-recording portion 134 of the magnetic recording layer 122 can be reduced, and the perpendicular magnetic anisotropy constant Ku can be suitably reduced. Other examples of ions that can be used include B, P, Si, F, C, In, Bi, Kr, Ar, Xe, W, As, Ge, Mo, Sn, N ₂ , and O ₂ . It is also possible to implant any one or more ions selected from these groups.

  The amount of energy for implanting ions is 1 to 50 keV. If the amount of energy for ion implantation is less than 1 keV, magnetic separation of the magnetic recording portion in the magnetic recording layer 122 is not performed properly, which causes noise when reading by the head. As a result, the perpendicular magnetic recording medium 100 cannot be configured as a patterned medium. On the other hand, if it is 50 keV or more, demagnetization or amorphization of the magnetic recording layer 122 is promoted too much, the read / write characteristics are deteriorated, or the magnetic recording portion under the convex portion of the resist layer 130 Even the magnetic recording layer 122 is demagnetized.

Furthermore, the total amount (dose amount) of ions to be implanted is 1 × 10 ¹⁵ atoms / cm ² to 1 × 10 ¹⁷ atoms / cm ² . As described above, in this embodiment, a material having a high perpendicular magnetic anisotropy constant Ku is used for the magnetic recording layer 122. Accordingly, since the film thickness of the magnetic recording layer 122 can be reduced, the dose amount of ions for forming the non-recording portion 134 can be reduced to the above range. In the above range, the read / write characteristics of the magnetic recording portion can be improved while maintaining the good SNR of the perpendicular magnetic recording medium 100.

<Resist layer removal>
As shown in FIG. 2D, by immersing the resist layer 130 in the alkaline solution 140, the resist layer 130 can be easily removed without etching as shown in FIG. In this embodiment, a KOH solution is used as the alkaline solution. Since KOH is a strong base, the KOH solution exhibits strong alkalinity, and the resist layer 130 can be suitably removed.

  As described above, by performing resist layer deposition, patterning, ion implantation, and resist layer removal, a magnetic recording portion and a non-recording portion 134 having a predetermined pattern in the in-plane direction on the perpendicular magnetic recording medium 100, that is, a magnetic pattern Is formed. Thereby, the perpendicular magnetic recording medium 100 can be a patterned medium.

(Lubrication layer formation)
After removing the resist layer 130 as shown in FIG. 2 (e), a lubricating layer 128 is formed on the perpendicular magnetic recording medium 100 (on the protective layer 126). The lubricating layer 128 can be formed of PFPE (perfluoropolyether) by dip coating. PFPE has a long chain molecular structure and binds with high affinity to N atoms on the surface of the protective layer 126. Due to the action of the lubricating layer 128, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 100, damage or loss of the protective layer 126 can be prevented.

FIG. 3 is a diagram illustrating hysteresis loops of the example and the comparative example. As an example, a magnetic recording layer having a perpendicular magnetic anisotropy constant Ku of 5.8 × 10 ⁶ erg / cc and a comparative example of Ku of less than 3.5 × 10 ⁶ erg / cc was used. As can be seen from FIG. 3, when the ion implantation energy is made equal, the decrease in Hc and the shift in Hn are large. Further, it can be seen that the residual magnetization in the vertical direction is reduced and is directed in the in-plane direction. The reason why the saturation magnetization Ms is greatly reduced is considered to be because the residual magnetization in the vertical direction is reduced. From these facts, it was confirmed that by performing ion implantation using a material having a high Ku, the magnetization direction can be directed in the in-plane direction, and noise can be greatly reduced.

As described above, according to the magnetic recording medium according to the present embodiment, by implanting ions into the magnetic recording layer 122 made of a material having a perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more, The portion of the magnetic recording layer 122 into which ions are implanted has a disordered crystal structure, and crystal orientation is significantly lowered. Thereby, since the easy axis of magnetization of the non-recording part 134 of the magnetic recording layer 122 faces in the in-plane direction (horizontal direction), noise caused by the non-recording part is reduced, and the quality of the magnetic recording medium can be improved. It becomes possible.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  In the above embodiment, the magnetic recording layer 122 is composed of two layers having a granular structure. However, the present invention is not limited to this, and it may be composed of one layer or a plurality of layers. Also good. In the above-described embodiment, the magnetic recording medium according to the present invention has been described as the perpendicular magnetic recording medium 100. However, the present invention is not limited to this, and the present invention can also be suitably used for an in-plane magnetic recording medium. .

  The present invention can be used as a magnetic recording medium mounted on a magnetic recording type HDD or the like.

DESCRIPTION OF SYMBOLS 100 ... Perpendicular magnetic recording medium 110 ... Disk base | substrate 112 ... Adhesion layer 114 ... Soft magnetic layer 114a ... First soft magnetic layer 114b ... Spacer layer 114c ... Second soft magnetic layer 116 ... Pre-underlayer 118 ... Underlayer 118a ... First Underlayer 118b ... second underlayer 120 ... nonmagnetic granular layer 122 ... magnetic recording layer 122a ... first magnetic recording layer 122b ... second magnetic recording layer 124 ... auxiliary recording layer 126 ... protective layer 128 ... lubricating layer 130 ... resist layer 134 ... non-recording part 140 ... alkaline solution

Claims (5)

In a magnetic recording medium comprising a magnetic recording layer having a magnetic recording portion and a non-recording portion formed in a predetermined pattern in the in-plane direction on the substrate,
The magnetic recording layer is made of a material having a perpendicular magnetic anisotropy constant Ku of 4 × 10 ⁶ erg / cc or more,
The non-recording portion is formed by implanting ions into the magnetic recording layer. The magnetic recording medium according to claim 1, wherein the magnetic recording layer is made of a material having a perpendicular magnetic anisotropy constant Ku of 5 × 10 ⁶ erg / cc or more.   The magnetic recording medium according to claim 1, wherein the magnetic recording layer has a thickness of 4 nm to 8 nm. ^2. The magnetic recording medium according to claim 1, wherein a dose amount of the ions is 1 × 10 ¹⁵ atoms / cm ² to 1 × 10 ¹⁷ atoms / cm ² .   The magnetic recording medium according to claim 1, wherein the ions are N ions.

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