JP2015001996A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having a large magnetic anisotropy constant Kand a magnetic recording layer including a ferromagnetic material in which a magnetization axis is inclined by 45° from a vertical direction to a magnetic recording medium main plane.SOLUTION: The magnetic recording medium comprises: a non-magnetic substrate; a seed layer; and a magnetic recording layer formed on the seed layer. The seed layer includes MnO, and the magnetic recording layer is formed of one or more magnetic layers. The magnetic layer contacting to the seed layer comprises a granular structure including: a magnetic crystal particles formed of an L1type regular alloy which are oriented (110); and a nonmagnetic crystal particle field surrounding the magnetic crystal particles and including carbon.

Description

The present invention relates to a magnetic recording medium. In particular, the present invention relates to a magnetic recording medium having a magnetic recording layer containing a formed on MnO seed layer (110) orientation L1 ₀ type ordered alloy.

  2. Description of the Related Art In recent years, a perpendicular magnetic recording method that magnetizes perpendicularly to a main plane of a magnetic recording medium has been used as a recording method of a magnetic recording apparatus. A magnetic recording medium (hereinafter referred to as “perpendicular magnetic recording medium”) used in a perpendicular magnetic recording system includes a nonmagnetic substrate and a magnetic recording layer formed of a magnetic material.

  In order to improve the recording density, the characteristics of the magnetic recording medium are continuously changed and improved. The main attempt is a gradual reduction in the size of the magnetic crystal grains in the magnetic recording layer. As a result, the size of today's magnetic crystal grains is approaching a physical property limit called the superparamagnetic limit, at which magnetization (recording information) cannot be kept stable due to the influence of ambient heat.

The thermal stability of the magnetic recording medium can be improved by forming the magnetic recording layer using a material having a large magnetic anisotropy. The thermal stability index of the magnetic recording medium is expressed as K _u V / k _b T. Wherein, K _u represents the magnetic anisotropy constant of the magnetic crystal grains of the material, V is represents the volume of the magnetic crystal grains, k _b represents a Boltzmann constant, and T is the environmental temperature using magnetic recording medium Represent. The ambient temperature is usually 280 to 300K. In order to keep the magnetization recorded on the magnetic recording medium stable for 10 years, it is estimated that K _u V / k _b T needs to be 60 or more. For this reason, for example, in a magnetic recording medium having a recording density of 1 Tbits / inch ² , K _u is required to be a large value exceeding 1 × 10 ⁷ erg / cm ³ (1 J / cm ³ ).

One means of overcoming the above-mentioned superparamagnetic limit problems, have been studied to create a magnetic crystal grains of a material having a large magnetic anisotropy constant K _u. However, magnetic crystal grains formed of a material having a large magnetic anisotropy constant K _u have a large coercive force, and there is a problem that magnetization reversal necessary for information recording becomes difficult only with a normal head magnetic field. . In order to overcome this problem, energy-assisted magnetic recording methods such as heat-assisted magnetic recording and microwave-assisted magnetic recording have been studied. In this regard, it has been proposed (100) thermally assisted magnetic recording for a magnetic recording medium having a magnetic recording layer composed mainly of (001) -oriented L1 ₀ type ordered alloy on the MnO underlayer orientation ( Patent Document 1). However, many problems remain in realizing the energy-assisted magnetic recording system.

As another means of overcoming the problem of the superparamagnetic limit described above, there has been proposed a method for facilitating magnetization reversal by applying a write magnetic field in an oblique direction with respect to the easy axis of magnetization of the magnetic crystal grains. Yes. In this regard, it has been reported that magnetization reversal is most easily performed when the angle between the easy magnetization axis and the write magnetic field is 45 degrees (see Non-Patent Document 1). Further, in the bit pattern medium, by using a tilted anisotropic magnetic recording medium in which the easy axis of magnetization of the magnetic recording layer is tilted from a direction perpendicular to the main plane of the magnetic recording medium, recording signal characteristics can be improved and recording can be performed. A simulation result indicating that the density can be increased has been reported (see Non-Patent Document 2). Furthermore, for the purpose of manufacturing a gradient anisotropic magnetic recording medium, a method of forming a gradient alignment layer containing a Co—Cr alloy using a collimator sputtering method has been proposed (see Non-Patent Document 3). Alternatively, (111) orientation of the fcc material, (100) hcp material orientation, or on the intermediate layer of amorphous material such as SiO _2, mainly L1 ₀ type ordered alloy (111) orientation A magnetic recording medium having a magnetic recording layer as a component has been proposed (see Patent Document 2).

JP 2012-169017 A JP 2006-19000 A

Kryder et al., Journal of Magnetism and Magnetic Materials, 287 (2005) pp.449-458 Honda et al., IEICE Technical Report, 109 (2009), pp. 9-14 Honda et al., IEICE Technical Report, 110 (2010), pp. 65-72

  However, in the formation of the tilted alignment layer by the above-described collimator sputtering method, even if the collimator angle is 45 degrees, the orientation tilt angle of the resulting layer (that is, the angle formed by the perpendicular direction to the main plane of the substrate and the easy axis of magnetization) is several. Degrees, not far from 45 degrees, which is considered to be the most effective. Further, the obtained tilted alignment layer has only a small magnetic anisotropy constant Ku, which is insufficient for high-density recording. The present invention aims to solve these problems. Specifically, an object of the present invention is to provide a magnetic recording layer comprising a ferromagnetic material having a large magnetic anisotropy constant Ku and having an easy axis of magnetization inclined by 45 degrees from the direction perpendicular to the main plane of the magnetic recording medium. It is to provide a magnetic recording medium having the same. Another object of the present invention is to provide a method for easily manufacturing the aforementioned magnetic recording medium.

The magnetic recording medium of the present invention includes a nonmagnetic substrate, a seed layer, and a magnetic recording layer formed on the seed layer, the seed layer includes MnO, and the magnetic recording layer includes one or more magnetic recording layers. made of a magnetic layer, the magnetic layer in contact with the seed layer (110) and the magnetic crystal grains consisting of oriented L1 ₀ type ordered alloy surrounds the magnetic crystal grains, and a non-magnetic grain boundary containing carbon It has a granular structure. Here, L1 ₀ type ordered alloy may include Fe and Pt. Moreover, the L1 ₀ type ordered alloy, Ni, Mn, Cu, Ag, may further comprise at least one element selected from the group consisting of Au and Cr. In addition, the seed layer preferably includes (002) -oriented MnO.

Furthermore, the magnetic recording medium of the present invention may have a magnetic recording layer composed of one magnetic layer or a magnetic recording layer composed of a plurality of magnetic layers. In the magnetic recording medium having a magnetic recording layer composed of a plurality of magnetic layers, the magnetic layer not in contact with the seed layer (110) and the magnetic crystal grains consisting of oriented L1 ₀ type ordered alloy, carbon, Ta oxide, Si It can have a granular structure including at least one material selected from the group consisting of oxides, Ge oxides, Al oxides, and Ti oxides and having nonmagnetic crystal grain boundaries surrounding the magnetic crystal grains. . Here, the nonmagnetic crystal grain boundary of each layer of the plurality of magnetic layers is formed of a material different from the nonmagnetic crystal grain boundary of the magnetic layer immediately below it.

The method for producing a magnetic recording medium of the present invention includes a step of forming a seed layer containing MnO on a nonmagnetic substrate in a state where the nonmagnetic substrate is heated to a temperature in the range of 250 to 400 ° C. Forming a magnetic recording layer composed of one or more magnetic layers on the seed layer in a state where the nonmagnetic substrate is heated to a temperature in the range of 250 to 450 ° C., and magnetic layer in contact is characterized by having a granular structure having a (110) and the magnetic crystal grains consisting of oriented L1 ₀ type ordered alloy surrounds the magnetic crystal grains, the non-magnetic grain boundary containing carbon .

  According to the present invention, a magnetic recording medium having a high magnetic anisotropy constant Ku can be provided. According to the present invention, it is possible to provide a magnetic recording medium having a magnetic recording layer made of magnetic grains whose easy axis of magnetization is inclined 45 degrees from the film surface perpendicular.

It is the schematic of the vertical cross section which shows 1st Embodiment of the magnetic recording medium of this invention. It is the schematic of the horizontal cross section of the magnetic-recording layer of this invention. It is the schematic of the vertical cross section which shows 2nd Embodiment of the magnetic recording medium of this invention. 2 is a diagram showing an X-ray diffraction profile of the magnetic recording medium obtained in Example 1. FIG. 6 is a diagram showing an X-ray diffraction profile of a magnetic recording medium obtained in Comparative Example 1. FIG.

The magnetic recording medium of the present invention includes a nonmagnetic substrate, a seed layer, and a magnetic recording layer formed on the seed layer, the seed layer includes MnO, and the magnetic recording layer includes one or more magnetic recording layers. It consists of component layer, component layer in contact with the seed layer, and the magnetic crystal grains consisting of (110) oriented L1 ₀ type ordered alloy surrounds the magnetic crystal grains and a nonmagnetic grain boundary containing carbon It has the granular structure which has. FIG. 1 shows a first embodiment of the magnetic recording medium of the present invention. FIG. 1 is a cross-sectional view of a cross section perpendicular to the main plane of the magnetic recording medium 100 (also referred to as “vertical cross section” in this specification). A magnetic recording medium 100 in FIG. 1 includes a nonmagnetic substrate 10, an adhesion layer 20, an underlayer 30, a seed layer 40, a magnetic recording layer 50, and a protective layer 60 in this order. The magnetic recording layer 50 shown in FIG. 1 is composed of a single magnetic layer. Here, the adhesion layer 20, the base layer 30, and the protective layer 60 are layers that are optionally formed.

  The nonmagnetic substrate 10 is a substrate having a smooth surface on which each constituent layer is formed. For example, the nonmagnetic substrate 10 can be formed using a material generally used for magnetic recording media (Al alloy plated with NiP, tempered glass, crystallized glass, etc.). In all the examples shown below, a glass substrate is used as the nonmagnetic substrate 10, but the examples shown below do not limit the material of the nonmagnetic substrate of the present invention.

  The adhesion layer 20 that can be optionally provided is a layer for ensuring adhesion between the nonmagnetic substrate 10 and the underlayer 30 or the seed layer 40. The material for forming the adhesion layer 20 can be selected from metals such as Ta, Ni, W, Ta, Cr, Ru, and alloys containing the aforementioned metals. The adhesion layer 20 may be formed from a single layer or may have a laminated structure of a plurality of layers. The adhesion layer 20 can be formed by a conventional method known in the art, such as a DC magnetron sputtering method or a vacuum evaporation method.

  The underlayer 30 that can be optionally provided controls the crystallinity and crystal axis orientation of the seed layer 40 formed thereon, and as a result, the magnetic recording layer 50 formed on the seed layer 40. This is a layer for controlling the grain size and crystal orientation of the magnetic crystal grains 50a. The underlayer 30 may be formed from a single layer or may have a stacked structure of a plurality of layers. The underlayer 30 is preferably a nonmagnetic film formed from Cr, a Cr alloy, or a mixture thereof. In the present invention, “Cr alloy” means an alloy containing Cr as a main component and further containing at least one metal selected from the group consisting of Mo, W, Ti, V, and Mn. The material constituting the underlayer 30 preferably has a crystal lattice close to the crystal lattice of the magnetic recording layer 50. It is preferable to appropriately select the constituent material of the underlayer 30 according to the composition of the magnetic recording layer 50. The underlayer 30 can be formed by a conventional method known in the art, such as a DC magnetron sputtering method or a vacuum evaporation method.

  The seed layer 40 is a layer for controlling the grain size and crystal orientation of the magnetic crystal grains 50a of the magnetic recording layer 50 as an upper layer while ensuring adhesion between the underlayer 30 and the magnetic recording layer 50. . The seed layer 40 includes MnO. Preferably, the seed layer 40 includes (002) -oriented MnO. The seed layer 40 can be formed using any method known in the art, such as an RF magnetron sputtering method or a vacuum deposition method, which enables epitaxial growth of MnO on the underlayer 30. The seed layer 40 can be formed in a state where the nonmagnetic substrate 10 is heated to a temperature within the range of 250 to 400 ° C.

  The magnetic recording layer 50 has a granular structure. Specifically, as shown in FIG. 2, which is a schematic diagram of the magnetic recording layer 50 in a cross section (also referred to as “horizontal cross section” in the present specification) parallel to the main plane of the magnetic recording medium 100, the magnetic recording layer 50 Is composed of magnetic crystal grains 50a and nonmagnetic crystal grain boundaries 50b surrounding the magnetic crystal grains 50a.

The magnetic crystal grain 50a is formed from a ferromagnetic material. The ferromagnetic material that can be used includes at least one element selected from the group consisting of Fe, Co, and Ni and at least one element selected from the group consisting of Pt, Pd, Ir, and Ni. including an L1 ₀ type ordered alloy containing. Preferred L1 ₀ type ordered alloy include FePt, FePd, CoPt, FeNi, and the like. More preferred L1 ₀ type ordered alloy includes Fe and Pt. For the purpose of characteristic modulation of the magnetic crystal grains 50a, with respect to L1 ₀ type ordered alloy, Mn, Cu, Ag, Au , may be added a metal such as Cr. Desirable characteristic modulation comprises a reduction in the temperature required for ordering of the L1 ₀ type ordered alloy.

L1 ₀ type ordered alloy in the magnetic crystal grains 50a are oriented (110). That is, the surface on the magnetic crystal grains 50a is (110) plane of L1 ₀ type ordered alloys, the magnetization easy axis of the L1 ₀ type ordered alloy ([002] axis) is on the magnetic crystal grains 50a surfaces and magnetic recording The medium 100 is inclined from the direction perpendicular to the main plane. The tilt angle of the easy axis with respect to the perpendicular direction is 35 to 45 degrees, preferably 45 degrees.

  The nonmagnetic grain boundary 50b is C (carbon) or at least one oxide material selected from the group consisting of Ta oxide, Si oxide, Ge oxide, Al oxide and Ti oxide, and C. And a mixture containing In the present embodiment in which the magnetic recording layer 50 is a single layer, it is essential that the nonmagnetic crystal grain boundary 50b contains C. This is because C is important for realizing good separation of the magnetic crystal grains 50a. If good separation of the magnetic crystal grains 50a is not achieved, the crystal growth direction of the magnetic crystal grains 50a (that is, the orientation of the magnetic crystal grains 50a) is not expected.

  Preferably, the volume fraction of the magnetic crystal grains 50a in the magnetic recording layer 50 is in the range of 80 to 50% by volume. Correspondingly, the volume fraction of the nonmagnetic crystal grain boundaries 50b in the magnetic recording layer 50 is in the range of 20 to 50% by volume. When the volume fraction of the magnetic crystal grains 50a is 50% by volume or more, the magnetic recording layer 50 has high magnetic anisotropy. Further, when the volume fraction of the magnetic crystal grains 50a is 80% by volume or less, the magnetic crystal grains 50a are sufficiently separated.

  In this embodiment in which the magnetic recording layer 50 is composed of a single magnetic layer, the magnetic recording layer 50 preferably has a thickness of 4 to 16 nm, typically 10 nm. When the magnetic recording layer 50 has a thickness of 6 nm or more, a magnetic moment amount necessary for signal reproduction can be secured. Moreover, when the magnetic recording layer 50 has a film thickness of 16 nm or less, simultaneous reversal of magnetization is performed. Furthermore, the single magnetic recording layer 50 in this embodiment has an advantage that the continuity of the magnetic crystal grains 50a is maintained.

  The magnetic recording layer 50 can be epitaxially grown on the seed layer 40 of a ferromagnetic material constituting the magnetic crystal grains 50a, including sputtering (including DC magnetron sputtering and RF magnetron sputtering), and vacuum deposition. It can be formed using any method known in the art. The magnetic recording layer 50 can be formed in a state where the nonmagnetic substrate 10 is heated to a temperature in the range of 250 to # 450 ° C., preferably 350 to 450 ° C.

  The protective layer 60 is a layer for protecting the constituent layers below the magnetic recording layer 50. The protective layer 60 may be a single layer or may have a multilayer structure. The protective layer 60 composed of a single layer can be formed of a material mainly composed of carbon that is conventionally used in the field of magnetic recording media. The protective layer 60 having a laminated structure is, for example, a laminated structure of two types of carbon materials having different characteristics, a laminated structure of a metal and a carbon material, or a laminated structure of a metal oxide film and a carbon material. Also good. The protective layer 60 can be formed using any method known in the art such as CVD, sputtering (including DC magnetron sputtering), and vacuum deposition.

  A vertical section of a second embodiment of the magnetic recording medium of the present invention is shown in FIG. The magnetic recording medium 200 of the second embodiment is different from that of the first embodiment in that the magnetic recording layer 50 is composed of two layers (a first magnetic layer 51 and a second magnetic layer 52). This is different from 100. The nonmagnetic substrate 10, the adhesion layer 20, the underlayer 30, the seed layer 40, and the protective layer 60 have the same material and configuration as in the first embodiment.

In the present embodiment, the first magnetic layer 51 in contact with the seed layer 40 has a granular structure. Specifically, and a (110) and the first magnetic crystal grains 51a made of oriented L1 ₀ type ordered alloys, the first non-magnetic grain boundary 51b surrounding the first magnetic crystal grains 51a. The first magnetic crystal grain 51a and the first nonmagnetic crystal grain boundary 51b have the same material and configuration as the magnetic crystal grain 50a and the nonmagnetic crystal grain boundary 50b of the first embodiment, respectively.

  The first magnetic layer 51 preferably has a thickness of 1 to 4 nm, typically 2 nm. Since the first magnetic layer 51 has a thickness of 1 nm or more, the first magnetic crystal grains 51a are sufficiently ordered. Further, since the first magnetic layer 51 has a film thickness of 4 nm or less, the regrowth of the first magnetic crystal grains 51a can be suppressed. “Magnetic grain regrowth” means that a thin film of a material other than a ferromagnetic material (for example, a material of a nonmagnetic grain boundary) is formed on the upper surface of a magnetic crystal grain, and the magnetic crystal grain is again formed on the thin film. It means to grow up. Since the regrown magnetic crystal grains have random orientation, the orientation of the ordered alloy in the magnetic crystal grains and the magnetic anisotropy of the magnetic recording layer are reduced. The suppression of the regrowth of the first magnetic crystal grains 51a is achieved by epitaxially growing the second magnetic crystal grains 52a in the second magnetic layer 52 formed on the first magnetic layer 51 according to the orientation of the first magnetic crystal grains 51a. It is also preferable in terms of making it.

  The volume fraction of the first magnetic crystal grain 51a and the first nonmagnetic crystal grain boundary 51b in the first magnetic layer 51 is equal to the volume fraction of the magnetic crystal grain 50 and the nonmagnetic crystal grain boundary 50b of the first embodiment. The same is preferable.

In the present embodiment, the second magnetic layer 52 formed on the first magnetic layer 51 has a granular structure. Specifically, composed of (110) and the second magnetic crystal grains 52a made of oriented L1 ₀ type ordered alloy, and a second non-magnetic grain boundary 52b surrounding the periphery of the second magnetic crystal grains 52a. The second magnetic crystal grain 52a has the same material and configuration as the magnetic crystal grain 50a of the first embodiment.

  The second nonmagnetic grain boundary 52b is formed of at least one oxide material selected from the group consisting of Ta oxide, Si oxide, Ge oxide, Al oxide, and Ti oxide. By forming the second nonmagnetic crystal grain boundary 52b from a material different from the first nonmagnetic crystal grain boundary 51b or a material that is the same material but having a different composition ratio of constituent elements, magnetic crystal grains can be regrown. While suppressing, it is possible to increase the film thickness of the entire magnetic recording layer 50 and to secure the amount of magnetic moment necessary for signal reproduction. The material of the second nonmagnetic crystal grain boundary 52b is preferably a material different from that of the first nonmagnetic crystal grain boundary 51b.

  Preferably, the volume fraction of the second magnetic crystal grains 52a in the second magnetic layer 52 is in the range of 80 to 50% by volume. Correspondingly, the volume fraction of the second nonmagnetic crystal grain boundary 52b in the second magnetic layer 52 is in the range of 20 to 50% by volume. When the volume fraction of the second magnetic crystal grains 52a is 50% by volume or more, the second magnetic layer 52 has high magnetic anisotropy. Further, when the volume fraction of the second magnetic crystal grains 52a is 80% by volume or less, the second magnetic crystal grains 52a are sufficiently separated.

  Preferably, the volume fraction of the second magnetic crystal grains 52 a in the second magnetic layer 52 is in the range of −10 to 0% with respect to the volume fraction of the first magnetic crystal grains 51 a in the first magnetic layer 51. It can be. By setting the volume fraction within the above-described range, the epitaxial growth from the first magnetic crystal grain 51a to the second magnetic crystal grain 52a is promoted, and at the same time, the second magnetic crystal grain 52a is formed by the second nonmagnetic crystal grain boundary 52b. Separation can be ensured.

  Moreover, it is preferable that the 1st magnetic crystal grain 51a and the 2nd magnetic crystal grain 52a consist of the same structural elements. This is because by using the same constituent element, epitaxial growth from the first magnetic crystal grain 51a to the second magnetic crystal grain 52a is promoted, and the degree of ordering of the ordered alloy is improved.

  The second magnetic layer 52 preferably has a thickness of 1 to 12 nm, typically 7 nm. When the second magnetic layer 52 has a thickness of 1 nm or more, the second magnetic crystal grains 52a are sufficiently ordered. Further, since the second magnetic layer 52 has a film thickness of 12 nm or less, the separation of the second magnetic crystal grains 52a can be ensured.

  Each magnetic layer in the magnetic recording layer 50 of the present embodiment can be used in the related art such as sputtering (including DC magnetron sputtering, RF magnetron sputtering, etc.), vacuum deposition, etc., which enables epitaxial growth of magnetic crystal grains. It can be formed using any known method. Each magnetic layer can be formed in a state where the nonmagnetic substrate 10 is heated to a temperature in the range of 250 to 450 ° C., preferably 350 to 450 ° C.

  By adopting the above configuration, in the magnetic recording medium 200 of the second embodiment, the magnetic crystal grains 51a of the first magnetic layer 51 and the magnetic crystal grains 52a of the second magnetic layer 52 are in a one-to-one columnar shape. Will grow. In other words, the magnetic crystal grains 52a of the second magnetic layer 52 take over the magnetic crystal grains 51a of the first magnetic layer 51 and grow. In this way, by suppressing the secondary growth of magnetic crystal grains in each layer, a magnetic recording layer having a large film thickness is obtained, and at the same time, excellent orientation of ordered alloys in the magnetic crystal grains and high magnetic anisotropy are obtained. A magnetic recording layer having a constant can be realized. As a result, a magnetic recording medium having excellent characteristics can be obtained.

  Furthermore, the magnetic recording medium of the present invention may have a magnetic recording layer composed of three or more magnetic layers. In this case, the lowermost magnetic layer in contact with the seed layer has the same configuration as the first magnetic layer of the second embodiment, and the magnetic layers other than the lowermost layer are carbon, Ta oxide, Si oxide. A nonmagnetic crystal grain boundary including at least one material selected from the group consisting of Ge oxide, Al oxide, and Ti oxide, and the nonmagnetic crystal grain boundary is a nonmagnetic crystal grain of the magnetic layer immediately below the nonmagnetic crystal grain boundary The structure is the same as that of the second magnetic layer of the second embodiment except that it is made of a material different from the field. For example, in the second magnetic layer from the bottom formed on the lowermost magnetic layer including the nonmagnetic crystal grain boundary containing carbon, the nonmagnetic crystal grain boundary includes Ta oxide, Si oxide, and Ge oxide. And at least one material selected from the group consisting of Al oxide and Ti oxide. In addition, by suppressing secondary growth of magnetic crystal grains in each layer, a magnetic recording layer having a large film thickness is obtained, and at the same time, an excellent orientation of ordered alloys in the magnetic crystal grains and a high magnetic anisotropy constant are obtained. A magnetic recording layer can be realized. As a result, a magnetic recording medium having excellent characteristics can be obtained.

Example 1
A chemically strengthened glass substrate (N-10 glass substrate manufactured by HOYA) having a smooth surface was washed to prepare a nonmagnetic substrate 10. The nonmagnetic substrate 10 after cleaning was introduced into an in-line type sputtering apparatus. The following constituent layers were formed without releasing the laminate from the atmosphere.

  An adhesion layer 20 made of Ta having a thickness of 5 nm was formed by a DC magnetron sputtering method using a pure Ta target in an Ar atmosphere. Next, an underlayer 30 made of Cr having a thickness of 20 nm was formed by DC magnetron sputtering using a pure Cr target in an Ar atmosphere.

  Next, the seed layer 40 made of MnO having a thickness of 10 nm is formed by RF sputtering using a MnO target in an Ar gas having a pressure of 0.02 Pa in a state where the laminated body on which the base layer 30 is formed is heated to 300 ° C. Got. In the formation of the seed layer 40, 200 W of RF power was used.

  Next, in a state where the layered body on which the seed layer 40 is formed is heated to 450 ° C., a 4 nm-thick FePt—C film is formed by DC magnetron sputtering using an FePt—C target in an Ar gas having a pressure of 1.0 Pa. A magnetic recording layer 50 made of was obtained. In the formation of the magnetic recording layer 50, 25 W DC power was used. The composition ratio of FePt and C in the FePt—C target used was adjusted so as to obtain a magnetic recording layer 50 containing 75 volume% FePt magnetic crystal grains and 25 volume percent C nonmagnetic crystal grain boundaries. .

  Finally, a protective layer 60 made of C having a thickness of 3 nm was formed by DC magnetron sputtering using a carbon target in an Ar atmosphere.

(Comparative Example 1)
A magnetic recording medium was obtained by repeating the procedure of Example 1 except that the magnetic recording layer 50 made of FePt having a thickness of 10 nm was formed using an FePt target instead of the FePt-C target.

(Evaluation)
The magnetic recording media obtained in Example 1 and Comparative Example 1 were analyzed using an X-ray diffractometer manufactured by Philips. FIG. 4 shows an X-ray diffraction profile of the magnetic recording medium of Example 1. FIG. 5 shows an X-ray diffraction profile of the magnetic recording medium of Comparative Example 1.

  In general, when FePt is deposited without performing orientation control, a (111) -oriented FePt film is obtained. Further, when FePt-C is deposited on an MgO film generally used in magnetic recording media, the FePt film grows at random, and a plurality of diffraction peaks such as FePt (001) and FePt (002) are observed. Be done

  In the X-ray diffraction profile of the magnetic recording medium of Example 1 shown in FIG. 4, a diffraction peak of FePt (110) indicating that the FePt magnetic crystal grains are (110) oriented was observed. On the other hand, diffraction peaks of FePt (001), FePt (002), and FePt (111) indicating the presence of other orientations were not observed. From this, it can be seen that in the magnetic recording medium of Example 1, FePt magnetic crystal grains having a good (110) orientation were obtained.

  On the other hand, in the X-ray diffraction profile of the magnetic recording medium of Comparative Example 1 shown in FIG. 5, the diffraction peaks of FePt (110) were not observed, but the diffraction peaks of FePt (001) and FePt (002) were observed. . This shows that in the magnetic recording medium of Example 1, randomly oriented FePt magnetic crystal grains are obtained instead of FePt magnetic crystal grains having a good (110) orientation.

As described above, by stacking the FePt—C magnetic recording layer on the MnO seed layer, (110) -oriented FePt magnetic crystal grains could be obtained. The FePt ordered alloy has an easy axis of magnetization in the [002] direction. The [002] axis of FePt is inclined 45 degrees from the [110] axis. Therefore, the (110) -oriented FePt magnetic crystal grains have an easy axis of magnetization that is inclined by 45 degrees from the direction perpendicular to the surface of the magnetic recording layer (that is, the surface of the magnetic recording medium). When Ku in the easy axis direction of the magnetic recording medium of Example 1 was measured, a high value of 2.2 × 10 ⁷ erg / cm ³ (2.2 J / cm ³ ) was obtained. Therefore, the magnetic recording medium of the present invention includes an L1 ₀ type ordered alloy, and has a magnetic recording layer having an easy axis of magnetization tilted 45 degrees from the vertical high magnetic anisotropy constant Ku and the magnetic recording layer surface be able to.

  The above effect cannot be obtained by a combination of a MnO seed layer and a FePt magnetic layer, or a combination of a seed layer of a conventional material such as MgO and a FePt-C magnetic layer, and is predicted based on the prior art. It is difficult to do.

100, 200 Magnetic recording medium 10 Nonmagnetic substrate 20 Adhesion layer 30 Underlayer 40 Seed layer 50 Magnetic recording layer 50a Magnetic crystal grain 50b Nonmagnetic crystal grain boundary 51 First magnetic layer 51a First magnetic crystal grain 51b First nonmagnetic crystal Grain boundary 52 Second magnetic layer 52a Second magnetic crystal grain 52b Second nonmagnetic crystal grain boundary 60 Protective layer

Claims (7)

A non-magnetic substrate, a seed layer, and a magnetic recording layer formed on the seed layer;
The seed layer includes MnO;
The magnetic recording layer is composed of one or more magnetic layers,
Magnetic layer in contact with the seed layer (110) and oriented L1 consists ₀ ordered alloy magnetic crystal grains, surrounding the magnetic crystal grains, it has a granular structure including a non-magnetic grain boundary containing carbon A magnetic recording medium characterized by the above. The magnetic recording medium according to claim 1, wherein the L1 ₀ type ordered alloy contains Fe and Pt. The L1 ₀ type ordered alloy, Ni, Mn, Cu, Ag , magnetic recording medium according to claim 2, further comprising at least one element selected from the group consisting of Au and Cr.   The magnetic recording medium according to claim 1, wherein the magnetic recording layer includes one magnetic layer. The magnetic recording layer comprises a plurality of magnetic layers,
Magnetic layer not in contact with the seed layer is made of (110) and the magnetic crystal grains consisting of oriented L1 ₀ type ordered alloy, carbon, Ta oxide, Si oxide, Ge oxide, Al oxide and Ti oxide A granular structure comprising at least one material selected from the group and having a non-magnetic grain boundary surrounding the magnetic crystal grains;
2. The magnetic recording medium according to claim 1, wherein the nonmagnetic crystal grain boundary of each of the plurality of magnetic layers is formed of a material different from the nonmagnetic crystal grain boundary of the magnetic layer immediately below the magnetic layer. .   The magnetic recording medium according to claim 1, wherein the seed layer contains (002) -oriented MnO. Forming a seed layer containing MnO on the nonmagnetic substrate in a state where the nonmagnetic substrate is heated to a temperature in the range of 250 to 400 ° C .;
Forming a magnetic recording layer comprising one or more magnetic layers on the seed layer in a state where the nonmagnetic substrate is heated to a temperature in the range of 250 to 450 ° C .;
Wherein the magnetic layer in contact with the seed layer (110) oriented L1 ₀ type consisting ordered alloy magnetic crystal grains and surrounds the magnetic crystal grains, granular structure and a non-magnetic grain boundary containing carbon A method for producing a magnetic recording medium, comprising:

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