Magnetic recording and playback device

Abstract

This invention provides a magnetic recording and playback device that enables high recording density by further improving the assist effect of microwave magnetic fields. [Solution] The magnetic recording and reproducing apparatus according to the present disclosure comprises a magnetic recording medium including a plurality of magnetic recording layers on a non-magnetic substrate, and a magnetic recording and reproducing head including a high-frequency magnetic field generating element, wherein the magnetic recording and reproducing head is equipped with recording poles that generate a recording magnetic field for writing information to the magnetic recording medium, the width of the recording poles is in the range of 30 to 80 nm in the radial direction of the magnetic recording medium, the width of the high-frequency magnetic field generating element is narrower than the width of the recording poles, and the magnetic recording layer closest to the high-frequency magnetic field generating element is a granular magnetic layer having isolated magnetic particles containing Co and Pt, oriented along the c axis in an hcp structure.

Description

Technical Field

[0001] The present disclosure relates to a magnetic recording and reproducing apparatus.

Background Art

[0002] In recent years, a microwave assisted recording method for performing recording by irradiating a magnetic recording medium with microwaves, which achieves a high areal recording density of 2 Tbit / inch 2 or so, has attracted attention as a next-generation recording method.

[0003] The microwave assisted recording method utilizes the fact that the coercivity is effectively reduced as magnetic particles absorb the energy of a high-frequency magnetic field, and can perform writing even on a magnetic layer with high coercivity under a low magnetic field.

[0004] For example, Patent Documents 1 and 2 describe magnetic recording and reproducing apparatuses of the microwave assisted recording method that are capable of achieving high recording density.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The demand for higher recording density for magnetic recording and reproducing apparatuses never ceases.

[0007] One aspect of the present disclosure is directed to providing a magnetic recording and reproducing apparatus that further improves the assist effect by a microwave magnetic field and enables high recording density.

Means for Solving the Problems

[0008] To address the above issues, this disclosure provides the following configuration. [1] A magnetic recording medium comprising a plurality of magnetic recording layers on a non-magnetic substrate, A magnetic recording / playback head including a high-frequency magnetic field generating element, It has, The magnetic recording and playback head includes recording poles that generate a recording magnetic field for writing information to the magnetic recording medium, The width of the recording magnetic pole is in the range of 30 to 80 nm in the radial direction of the magnetic recording medium. The width of the high-frequency magnetic field generating element is narrower than the width of the recording magnetic pole. A magnetic recording and playback device, wherein the magnetic recording layer closest to the high-frequency magnetic field generating element is a granular magnetic layer having isolated magnetic particles containing Co and Pt, oriented along the c axis in an hcp structure. [2] The magnetic recording and reproducing apparatus according to [1], wherein the distance between the high-frequency magnetic field generating element and the magnetic particle is 10 nm or less. [3] The magnetic recording and reproducing apparatus according to [1] or [2], wherein the particle size of the magnetic particles is 7 nm or less. [4] A magnetic recording and reproducing apparatus according to any one of [1] to [3], wherein a plurality of the magnetic recording layers are laminated on the non-magnetic substrate. [5] A rotational drive unit for rotating the magnetic recording medium, A head drive unit that moves the magnetic recording / reproduction head in the radial direction of the magnetic recording medium, A recording and playback signal processing system that processes the signal input to the magnetic recording and playback head and the output signal from the magnetic recording and playback head, A magnetic recording and reproducing apparatus according to any one of [1] to [3], having the following: [Effects of the Invention]

[0009] According to one aspect of this disclosure, it is possible to provide a magnetic recording and playback device that enables high recording density by further improving the assist effect of a microwave magnetic field. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic perspective view showing a magnetic recording and playback apparatus according to an embodiment of the present disclosure. [Figure 2] This is a schematic vertical cross-sectional view showing the magnetic recording / playback head and the magnetic recording medium. [Figure 3] This is a schematic cross-sectional view showing an example of the configuration of a magnetic recording medium. [Figure 4] The relationship between the particle size of magnetic particles contained in the second magnetic recording layer and the ADC gain in Examples 1-3 and Comparative Example 1 is shown. [Figure 5] The relationship between the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second magnetic recording layer and the ADC gain is shown for Examples 1, 4-6 and Comparative Examples 2 and 3. [Figure 6] The relationship between the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second or third magnetic recording layer and the ADC gain is shown for Examples 1, 4-6 and Comparative Examples 4-1-4-6. [Figure 7] The relationship between the particle size of magnetic particles contained in the second or third magnetic recording layer and the ADC gain in Examples 1-3 and Comparative Examples 5-1-5-4 is shown. [Modes for carrying out the invention]

[0011] The embodiments of this disclosure will be described in detail below. For ease of understanding, the same reference numerals are used for identical components in each drawing, and redundant explanations are omitted. Also, the scale of each component in the drawings may differ from the actual scale. In this specification, the "~" indicating a numerical range means that the values ​​before and after it are included as the lower and upper limits, respectively, unless otherwise specified. Furthermore, if only the upper limit of a numerical range represented by "~" has a unit specified, it means that the lower limit also has the same unit.

[0012] A magnetic recording and reproducing apparatus according to an embodiment of the present disclosure (hereinafter, may be simply referred to as "the present embodiment") includes a magnetic recording medium and a magnetic recording and reproducing head including a high-frequency magnetic field generating element. The magnetic recording and reproducing head includes a recording magnetic pole that generates a recording magnetic field for writing information to the magnetic recording medium, the width of the recording magnetic pole is in the range of 30 to 80 nm in the radial direction of the magnetic recording medium, and the width of the high-frequency magnetic field generating element is narrower than the width of the recording magnetic pole. The magnetic recording layer closest to the high-frequency magnetic field generating element is a magnetic layer with a granular structure having isolated magnetic particles containing Co and Pt that are c-axis oriented in an hcp structure.

[0013] In the magnetic recording and reproducing apparatus according to the present embodiment, the width of the recording magnetic pole is set within the range of 30 to 80 nm in the radial direction of the magnetic recording medium, and the width of the high-frequency magnetic field generating element is made narrower than the width of the recording magnetic pole. Further, in the magnetic recording and reproducing apparatus according to the present embodiment, a magnetic layer with a granular structure having isolated magnetic particles containing Co and Pt that are c-axis oriented in an hcp structure is used for the magnetic recording layer provided in the magnetic recording medium, which is located closest to the high-frequency magnetic field generating element. Thereby, the magnetic recording and reproducing apparatus according to the present embodiment can further improve the assist effect by the microwave magnetic field, and can improve the recording density.

[0014] In order to increase the recording density of the magnetic recording medium incorporated in the magnetic recording and reproducing apparatus, it is necessary to reduce the width of the recording magnetic pole of the magnetic head that writes information to the magnetic recording medium. However, when the width of the recording magnetic pole is reduced, the strength of the recording magnetic field decreases, and the strength distribution in the recording surface also increases, so that the strength of the signal written in the magnetic recording layer decreases and becomes unstable, which may increase the error rate when reading information from the magnetic recording medium.

[0015] Therefore, while ensuring sufficient width for the recording poles of the magnetic head, the high-frequency magnetic field generating elements of the magnetic head are arranged so that they are narrower than the width of the recording poles. This allows magnetization reversal to occur only in the region where the assisting magnetic field from the high-frequency magnetic field generating elements is superimposed, even under conditions where magnetization reversal of the magnetic recording layer does not occur with the recording magnetic field alone. However, in the case of conventional magnetic recording media with a CAP layer, the strength of the microwave magnetic field from the high-frequency magnetic field generating elements decreases, and in particular, the attenuation in the direction of the thickness of the magnetic recording layer becomes significant, reducing the assisting effect of the microwave magnetic field and hindering magnetization reversal of the magnetic recording layer.

[0016] The inventors have adopted a granular structure for the magnetic particles in the magnetic recording layer closest to the high-frequency magnetic field generating element in order to enhance the assist effect of the high-frequency magnetic field. This is because granular magnetic particles can reduce the exchange interaction between particles, thereby reducing the magnetization reversal unit in the assist region and easily making the magnetization transition region smaller and more uniform. In other words, the assistance of microwave magnetic fields in magnetization reversal of magnetic particles is due to the precession of the magnetic particles caused by ferromagnetic resonance. This is because granular magnetic particles can reduce the exchange interaction between particles, making precession more likely to occur for magnetic particles with a small magnetization transition region.

[0017] Furthermore, in a granular magnetic recording layer, the magnetic particles are surrounded by oxides, nitrides, borides, or carbides. These materials surrounding the magnetic particles have a higher dielectric constant and higher transmittance to high-frequency magnetic fields compared to the magnetic particles themselves, thus preventing the high-frequency magnetic field from attenuating in the direction of the magnetic recording layer's thickness. Therefore, by making the magnetic particles in the magnetic recording layer closest to the high-frequency magnetic field generating element a granular structure, it becomes possible to enhance the assist effect of the microwave magnetic field.

[0018] <Magnetic recording and playback device> A magnetic recording and playback apparatus according to an embodiment of the present disclosure (hereinafter sometimes simply referred to as "this embodiment") will be described with reference to Figures 1 and 2. Figure 1 is a schematic perspective view showing an example of a magnetic recording and playback apparatus according to this embodiment, and Figure 2 is a schematic vertical cross-sectional view showing a magnetic recording and playback head and a magnetic recording medium. In Figure 2, the arrows indicate the rotational direction (circumferential direction) of the magnetic recording medium, and the direction perpendicular to the arrows and perpendicular to the plane of the paper indicates the radial direction of the magnetic recording medium.

[0019] As shown in Figure 1, the magnetic recording and playback apparatus 1 includes a magnetic recording medium 10 having one or more magnetic recording layers on a non-magnetic substrate, a rotation drive unit 20 for rotating the magnetic recording medium 10, a magnetic recording and playback head 30 including a high-frequency magnetic field generating element, a head drive unit 40 for moving the magnetic recording and playback head 30 in the radial direction of the magnetic recording medium 10, and a recording and playback signal processing system 50 for processing signal input to the magnetic recording and playback head 30 and output signals from the magnetic recording and playback head 30. The magnetic recording and playback apparatus 1 is a magnetic recording and playback apparatus using a microwave-assisted recording method.

[0020] An example of a magnetic recording and playback head 30 is shown in Figure 2. As shown in Figure 2, the magnetic recording and playback head 30 is a magnetic head for microwave-assisted recording and has a recording head 31 and a playback head 32.

[0021] The recording head 31 includes a recording magnetic pole 311 that generates a recording magnetic field for writing information to the magnetic recording medium 10, an auxiliary magnetic pole 312, a coil 313 that generates a magnetic field, and a high-frequency magnetic field generating element 314.

[0022] The width of the recording pole 311 is in the range of 30 to 80 nm in the radial direction of the magnetic recording medium 10, and the upper limit of the width of the recording pole 311 is preferably 60 nm, more preferably 50 nm, and even more preferably 40 nm. If the width of the recording pole 311 is within the above preferred range, magnetization reversal can be caused only in the assist region provided by the high-frequency magnetic field generating element 314.

[0023] The width of the high-frequency magnetic field generating element 314 is narrower than the width of the recording magnetic pole 311.

[0024] The magnetic recording layer of the magnetic recording medium 10, which is closest to the high-frequency magnetic field generating element 314, is a granular magnetic layer having isolated magnetic particles containing Co and Pt, which are c-axis oriented in an hcp structure, as described later.

[0025] The distance between the high-frequency magnetic field generating element and the magnetic particles contained in the magnetic recording layer is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 6 nm or less. If the distance between the high-frequency magnetic field generating element and the magnetic particles is 10 nm or less, the assist effect of the microwave magnetic field on the magnetic recording layer can be increased, thereby increasing the recording density of the magnetic recording layer 15.

[0026] The distance between the high-frequency magnetic field generating element and the magnetic particles contained in the magnetic recording layer is the shortest distance between the high-frequency magnetic field generating element and the magnetic particles contained in the magnetic recording layer. In other words, the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the magnetic recording layer is the distance between the tip of the high-frequency magnetic field generating element and the magnetic particle located closest to the tip of the high-frequency magnetic field generating element among the magnetic particles located on the outermost surface of the magnetic recording layer. Alternatively, the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the magnetic recording layer may be the average value of the distances between multiple magnetic particles contained in the magnetic recording layer.

[0027] The distance between the high-frequency magnetic field generating element and the magnetic particles contained in the magnetic recording layer can be measured, for example, by utilizing the write frequency dependence of the harmonic ratio of the reproduced signal.

[0028] The playback head 32 has a shield 321 and a playback element 322 sandwiched between the shields 321.

[0029] As shown in Figure 1, the magnetic recording and playback device 1 attaches the center of the magnetic recording medium 10 to the rotation axis of the spindle motor, and the magnetic recording and playback head 30 levitates and travels on the surface of the magnetic recording medium 10, which is rotated by the spindle motor, while writing or reading information from the magnetic recording medium 10.

[0030] The magnetic recording and playback device 1 ensures sufficient width for the recording magnetic poles 311 of the recording head 31, while making the width of the high-frequency magnetic field generating element 314 narrower than the width of the recording magnetic poles 311. Furthermore, the magnetic recording and playback device 1 uses a granular magnetic layer having isolated magnetic particles containing Co and Pt, oriented along the c axis in an hcp structure, in the magnetic recording layer of the magnetic recording medium 10 that is closest to the high-frequency magnetic field generating element 314 of the magnetic recording and playback head 30. As a result, the magnetic recording and playback device 1 can further improve the assist effect of the microwave magnetic field and increase the recording density, thereby improving the recording density.

[0031] <Magnetic recording medium> A magnetic recording medium used in the magnetic recording and playback apparatus according to this embodiment will be described with reference to Figure 3. Figure 3 is a schematic cross-sectional view showing an example of the configuration of a magnetic recording medium. As shown in Figure 3, the magnetic recording medium 10 comprises a non-magnetic substrate 11, a soft magnetic layer 12, a seed layer 13, a base layer 14, a magnetic recording layer 15, a protective layer 16, and a lubricant layer 17, which are laminated in this order from the non-magnetic substrate 11 side.

[0032] Examples of materials constituting the non-magnetic substrate 11 include Al alloys such as AlMg alloy, soda glass, aluminosilicate glass, amorphous glass, silicon, titanium, ceramics, sapphire, quartz, and resin. Among these, Al alloys and glass such as crystallized glass and amorphous glass are preferred.

[0033] The soft magnetic layer 12 is provided on the non-magnetic substrate 11 and has the function of guiding the recording magnetic field from the magnetic head when recording a signal on the magnetic recording medium 10, and efficiently applying the perpendicular component of the recording magnetic field to the magnetic recording layer 15.

[0034] Examples of materials that make up the soft magnetic layer 12 include soft magnetic alloys such as FeCo-based alloys, CoZrNb-based alloys, and CoTaZr-based alloys.

[0035] The soft magnetic layer 12 preferably has an amorphous structure. This improves the surface smoothness of the soft magnetic layer 12 and reduces signal noise caused by the soft magnetic layer 12, thereby reducing the amount of magnetic head levitation and further improving the recording density of the magnetic recording medium 10.

[0036] Alternatively, multiple soft magnetic layers 12 may be formed via a non-magnetic layer such as a Ru film to create an antiferromagnetic exchange-coupled (AFC) film.

[0037] The total thickness of the soft magnetic layer 12 is appropriately determined based on the balance between the recording and playback characteristics and the OW (Over Write) characteristics of the magnetic recording medium 10, but is preferably 20 to 120 nm.

[0038] The seed layer 13 is provided on top of the soft magnetic layer 12 and has the function of improving the (002) plane orientation of the base layer 14.

[0039] The material constituting the seed layer 13 is preferably a material with an hcp structure, fcc structure, or amorphous structure, and examples include Ru-based alloys, Ni-based alloys, Co-based alloys, Pt-based alloys, and Cu-based alloys.

[0040] The thickness of the seed layer 13 is preferably in the range of 0.5 to 20 nm, and more preferably in the range of 3 to 10 nm. By setting the thickness of the seed layer 13 within the above preferred range, the base layer 14 can be stably oriented in the (002) plane.

[0041] The base layer 14 is provided on top of the seed layer 13 and has the function of improving the (002) plane orientation of the magnetic recording layer 15.

[0042] As the material constituting the base layer 14, Ru or an alloy thereof having an hcp structure can be used.

[0043] The average grain size of the underlayer 14 is preferably in the range of 6 to 20 nm, and more preferably in the range of 6 to 8 nm.

[0044] The thickness of the underlayer 14 can be selected as appropriate, and is preferably 5 to 30 nm.

[0045] The magnetic recording layer 15 is provided on the base layer 14, and information is recorded on it. The magnetic recording layer 15 has a multilayer structure consisting of an uppermost layer 151 and layers 152 other than the uppermost layer. In this embodiment, the magnetic recording layer closest to the high-frequency magnetic field generating element 314, i.e., the uppermost layer 151 of the magnetic recording layer 15, has a granular structure with isolated magnetic particles containing Co and Pt, oriented along the c axis in an hcp structure.

[0046] By configuring the uppermost layer 151 in this way, the assist effect of the high-frequency magnetic field from the high-frequency magnetic field generating element 314 can be enhanced. As mentioned above, granular magnetic particles can reduce the exchange interaction between particles, which facilitates magnetization reversal in the assist region.

[0047] In other words, the assistance of microwave magnetic fields in reversing the magnetization of magnetic particles lies in inducing precession in the magnetic particles through ferromagnetic resonance. However, granular magnetic particles have a smaller exchange interaction between particles, making precession in the magnetic particles more likely to occur. Furthermore, a magnetic recording layer with a granular structure has a structure in which the magnetic particles are covered with oxides, nitrides, borides, or carbides. These materials covering the magnetic particles have a higher dielectric constant and higher transmittance to high-frequency magnetic fields compared to the magnetic particles themselves, thus suppressing the attenuation of the high-frequency magnetic field in the direction of the magnetic recording layer's thickness.

[0048] It is preferable to keep the distance between the high-frequency magnetic field generating element 314 and the magnetic particles contained in the uppermost layer 151 of the magnetic recording layer 15 as close as possible. The distance between the high-frequency magnetic field generating element 314 and the magnetic particles contained in the uppermost layer 151 of the magnetic recording layer 15 is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 6 nm or less. By keeping the distance between the high-frequency magnetic field generating element 314 and the magnetic particles contained in the uppermost layer 151 of the magnetic recording layer 15 as close as possible, the assist effect of the microwave magnetic field on the uppermost layer 151 of the magnetic recording layer 15 can be increased, thereby increasing the recording density of the magnetic recording layer 15.

[0049] The particle size of the magnetic particles constituting the uppermost layer 151 of the magnetic recording layer 15 is preferably as small as possible. The particle size of the magnetic particles is preferably 7 nm or less, and more preferably 6 nm or less. By doing so, the bit size of the magnetic recording medium 10 can be reduced, and thus the recording density of the magnetic recording layer 15 can be increased.

[0050] The particle size of magnetic particles (hereinafter also referred to as "particle diameter") is the average particle diameter of the magnetic particles. The particle size of magnetic particles can be measured by observing the plane of the magnetic particles with a transmission electron microscope (TEM). Observe any number of magnetic particles (for example, 200 to 300) with a TEM, and the average value of the major axis and minor axis of the magnetic particles is taken as the particle size of the magnetic particles. If the magnetic particles are spherical, determine the diameter of the magnetic particles; if the magnetic particles are elliptical, determine the midpoint between the minor axis and major axis of the magnetic particles; and if the magnetic particles have an irregular shape, determine the midpoint between the short side and long side of the magnetic particles. Then, create a particle diameter distribution of the magnetic particles, and based on that particle diameter distribution, determine the average value of the particle diameter of the magnetic particles, and this average value is taken as the particle size of the magnetic particles. The same measurement method can be used for the particle sizes of magnetic particles contained in layers 152 other than the uppermost layer.

[0051] The material constituting the uppermost layer 151 is preferably one in which CoCrPt-based magnetic particles are covered with an oxide, nitride, boride, or carbide. Examples of materials constituting the uppermost layer 151 include CoCrPt-B2O3, CoCrPt-SiO2, CoCrPt-Cr2O3, CoCrPt-TiO2, CoCrPt-ZrO2, CoCrPt-Nb2O5, CoCrPt-Ta2O5, and CoCrPt-TiO2.

[0052] Examples of materials that make up layers 152 other than the top layer include CoCrPt-B2O3, CoCrPt-SiO2, CoCrPt-Cr2O3, CoCrPt-TiO2, CoCrPt-ZrO2, CoCrPt-Nb2O5, CoCrPt-Ta2O5, and CoCrPt-TiO2 when layers 152 other than the top layer have a granular structure. When layers 152 other than the top layer have a structure other than a granular structure, examples of materials that make up layers 152 other than the top layer include CoCr, CoCrPt, and CoCrPtB.

[0053] For the deposition methods of the soft magnetic layer 12, seed layer 13, underlayer 14, and magnetic recording layer 15, general deposition methods such as DC magnetron sputtering or RF sputtering can be used.

[0054] When forming the soft magnetic layer 12, seed layer 13, underlayer 14, and magnetic recording layer 15, RF (Radio Frequency) bias, DC bias, pulsed DC, pulsed DC bias, etc. may be used as needed.

[0055] As the reactive gas, O2 gas, H2O gas, or N2 gas may be used.

[0056] The sputtering gas pressure is adjusted as needed to optimize the characteristics of each layer, but it is usually within the range of 0.1 to 30 Pa.

[0057] The protective layer 16 has the function of protecting the magnetic recording medium 10 from damage caused by contact between the magnetic head and the magnetic recording medium 10.

[0058] The protective layer 16 may contain carbon.

[0059] For example, sputtering, plasma CVD, and ion beam methods can be used to deposit the protective layer 16.

[0060] The thickness of the protective layer 16 is preferably 1 to 5 nm, and more preferably 1 to 3 nm.

[0061] The lubricant layer 17 can be formed using a liquid lubricant. Preferably, the liquid lubricant is chemically stable, has low friction, and low adsorption. Examples of liquid lubricants include fluororesin-based lubricants such as perfluoropolyether-based lubricants containing compounds with a perfluoropolyether structure.

[0062] The thickness of the lubricant layer 17 is not particularly limited, but may be, for example, 0.5 to 2.0 nm.

[0063] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present disclosure is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, or modifications are possible without departing from the spirit of the invention. The above embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Examples]

[0064] The embodiments will be described in more detail below with reference to examples and comparative examples, but the embodiments are not limited to these examples and comparative examples.

[0065] <Example 1> [Manufacturing of magnetic recording media] A magnetic recording medium was fabricated using the following method.

[0066] A cleaned 3.5-inch outer diameter glass non-magnetic substrate (manufactured by HOYA) is placed in the deposition chamber of a DC magnetron sputtering system (C-3040, manufactured by Anelva), and the ultimate vacuum level is 1 × 10⁻⁶. -5 The deposition chamber was evacuated until the pressure dropped to Pa.

[0067] Next, a 10 nm thick adhesion layer was formed on a non-magnetic substrate using a Cr-50at%Ti target (50 at% Ti content, the remainder being Cr).

[0068] Next, using a target of Co-30at%Fe-9at%Zr-9at%Ta (Fe content 30at%, Zr content 9at%, Ta content 9at%, remainder Co), a soft magnetic layer with a thickness of 25 nm was formed on the adhesion layer by lowering the temperature of the non-magnetic substrate to below 100°C.

[0069] Next, using a Ni-3at%W target (3at% W content, the remainder being Ni) and a Ru target, a 5nm thick Ni-3at%W layer and a 20nm thick Ru layer were formed on the soft magnetic substrate in that order, creating an orientation-controlled substrate.

[0070] Next, a target with a granular structure and a thickness of 9 nm was formed on an orientation-controlled substrate using a target containing 82 mol% (Co-24 at% Pt)-2 mol% SiO2-7 mol% B2O3-9 mol% TiO2 (24 at% Pt, 82 mol% Co alloy, 2 mol% SiO2, 7 mol% B2O3, and 9 mol% TiO2). The sputtering pressure was set to 2 Pa.

[0071] Next, a non-magnetic layer having a granular structure with a thickness of 0.3 nm was formed on the first magnetic recording layer using a target of 91 mol% (Ru-48 at% Co)-9 mol% TiO2 (48 at% Co content, 91 mol% alloy content with the remainder being Ru, and 9 mol% TiO2 content).

[0072] Next, a second magnetic recording layer with a 6 nm thick granular structure was formed on a non-magnetic layer using a target of 92 mol% (Co-4 at%Cr-18 at%Pt)-5 mol%SiO2-3 mol%TiO2 (92 mol% alloy content with 4 at% Cr, 18 at% Pt, and the remainder being Co, 5 mol% SiO2, and 3 mol% TiO2). The sputtering pressure was 2 Pa. The particle size of the magnetic particles in the resulting second magnetic recording layer was 7 nm.

[0073] Next, a protective layer of hard carbon was formed on the second magnetic recording layer using an ion beam method. The thickness of the protective layer was set to 2 nm.

[0074] Next, a 1.0 nm thick lubricant layer made of perfluoropolyether was formed on the protective layer using a dipping method. This resulted in the manufacture of a magnetic recording medium.

[0075] In this embodiment, the first magnetic recording layer is the "magnetic recording layer other than the top layer," and the second magnetic recording layer is the "top layer of the magnetic recording layers." In this embodiment, the particle size of the magnetic particles contained in the second magnetic recording layer and the distance between the high-frequency magnetic field generating element and the magnetic particles are as follows. (Particle size of magnetic particles contained in the magnetic recording layer) • Example 1: 7nm (Distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second magnetic recording layer) Example 1: 10nm

[0076] [evaluation] The ADC (Areal Density Capability) was measured for the manufactured magnetic recording medium. The ADC was measured using a MAMR head and a spin stand tester. The width of the MAMR head's recording poles was 40 nm in the radial direction of the magnetic recording medium, and the width of the high-frequency magnetic field generating element was 35 nm in the radial direction of the magnetic recording medium. The measurement was performed with a distance of 10 nm between the high-frequency magnetic field generating element and the magnetic particles of the second magnetic recording layer. The ADC was calculated as the product of the maximum track density (Tracks per Inch, TPI) and the maximum bit density (BPI) of the manufactured magnetic recording medium. A higher ADC value indicates higher recording density. The ADC was measured both with the high-frequency magnetic field generating element turned on (microwave-assisted recording method) and with it turned off (conventional recording method). The ADC measurement results are shown in Figures 4 and 5.

[0077] Figure 4 shows the relationship between the particle size of the magnetic particles contained in the second magnetic recording layer and the ADC gain. The ADC gain on the vertical axis of Figure 4 is expressed as the ratio of the ADC gain of Example 1 to the reference value (ADC gain of Comparative Example 1) multiplied by 100, as shown in the following formula (I), with the ADC gain of the case where the particle size of the magnetic particles is 8 nm (Comparative Example 1), as described later, as the reference value, and represents the amount of improvement (difference) in the ADC gain. ADC Gain [%] = (ADC Gain of Example 1) / (ADC Gain of Comparative Example 1) × 100 ... (I)

[0078] Figure 5 shows the relationship between the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second magnetic recording layer and the ADC gain. The ADC gain on the vertical axis of Figure 5 is expressed as the ratio of the ADC gain of Example 1 to the reference value (ADC gain of Comparative Example 3) multiplied by 100, as shown in the following formula (II), with the ADC gain of the case where the distance between the high-frequency magnetic field generating element and the magnetic particles is 12 nm (Comparative Example 3), as described later, as the reference value, and represents the amount of improvement (difference) in the ADC gain. ADC gain [%] = (ADC gain of Example 1) / (ADC gain of Comparative Example 3) × 100 ... (II)

[0079] <Examples 2 and 3, Comparative Example 1> In Example 1, the grain size of the Ru layer was changed by varying the thickness of the Ni-3at%W layer, and the grain size of the magnetic particles in the second magnetic recording layer was varied within the range of 5 to 8 nm, as described below. The procedure was the same as in Example 1. The measurement results of the ADCs in Examples 2 and 3 and Comparative Example 1 are shown in Figure 4. (Particle size of magnetic particles contained in the second magnetic recording layer) Example 2: 6nm Example 3: 5nm ·Comparative example 1: 8nm

[0080] As shown in Figure 4, the ADC gains of Examples 1 to 3 were higher than those of Comparative Example 1. Therefore, it was confirmed that the smaller the magnetic particles contained in the second magnetic recording layer, the higher the ADC gain, and that the ADC gain improved more significantly when the high-frequency magnetic field generating element was turned on (microwave-assisted recording method) than when it was turned off (conventional recording method).

[0081] <Examples 4-6, Comparative Examples 2 and 3> In Example 1, the procedure was the same as in Example 1, except that the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second magnetic recording layer was varied within the range of 6 to 12 nm, as described below. The measurement results of the ADCs in Examples 4 to 6 and Comparative Examples 2 and 3 are shown in Figure 5. (Distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second magnetic recording layer) Example 4: 9nm • Example 5: 8nm Example 6: 7nm ·Comparative example 2: 11nm ·Comparative example 3: 12nm

[0082] [evaluation] As shown in Figure 5, the ADC gains of Examples 1, 4-6 were higher than those of Comparative Examples 2 and 3. Therefore, it was confirmed that the closer the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the second magnetic recording layer, the higher the ADC gain, and that the ADC gain improved more significantly when the high-frequency magnetic field generating element was turned on (microwave-assisted recording method) than when it was turned off (conventional recording method).

[0083] <Comparative Examples 4-1 to 4-6> In Example 1, a 1.3 nm thick film of 52at%Co-18at%Cr-20at%Pt-10at%B was provided as a third magnetic recording layer between the second magnetic recording layer and the protective layer. The third magnetic recording layer is a magnetic recording layer having a non-granular structure. The particle size of the magnetic particles contained in the third magnetic recording layer was set to 7.3 nm. The ADC measurement was performed by changing the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the third magnetic recording layer in 1 nm increments within the range of 7 to 12 nm, as follows. Otherwise, the procedure was the same as in Example 1. The ADC measurement results for Comparative Examples 4-1 to 4-6 are shown in Figure 6. (Distance between the high-frequency magnetic field generating element and the magnetic particles contained in the third magnetic recording layer) • Example 4-1: 7nm • Example 4-2: 8nm • Example 4-3: 9nm ·Comparative example 4-4: 10nm ·Comparative example 4-5: 11nm ·Comparative example 4-6: 12nm

[0084] In Figure 6, the ADC gain on the vertical axis is expressed as the ratio of the ADC gain of any of Comparative Examples 4-1 to 4-5 to the reference value (ADC gain of Comparative Example 4-6), multiplied by 100, as shown in the following formula (III). The ADC gain when the distance between the high-frequency magnetic field generating element and the magnetic particles contained in the third magnetic recording layer is 12 nm (Comparative Example 4-6) is used as the reference value. In other words, the ADC gain on the vertical axis shows the amount of improvement (difference) in the ADC gain of Comparative Examples 4-1 to 4-5 relative to the ADC gain of Comparative Example 4-6. Figure 6 also shows the results for magnetic recording media without a third magnetic recording layer, i.e., Examples 1, 4 to 6 and Comparative Examples 2 and 3. ADC Gain [%] = (ADC Gain of any of Comparative Examples 4-1 to 4-5) / (ADC Gain of Comparative Example 4-6) × 100 ... (III)

[0085] As shown in Figure 6, the ADC gains of Examples 1 and 4-6 were higher than those of Comparative Examples 4-1 to 4-3. Therefore, it was confirmed that the ADC gain improves as the magnetic recording layer closest to the high-frequency magnetic field generating element is made into a granular structure and the distance between the high-frequency magnetic field generating element and the magnetic recording layer is shortened.

[0086] <Comparative Examples 5-1 to 5-4> In Example 1, a 1.3 nm thick film of 52at%Co-18at%Cr-20at%Pt-10at%B was provided as a third magnetic recording layer between the second magnetic recording layer and the protective layer. The third magnetic recording layer is a magnetic recording layer having a non-granular structure. By changing the thickness of the Ni-3at%W layer, the particle size of the Ru layer was changed, and the particle size of the magnetic particles in the second magnetic recording layer was changed in 1 nm increments within the range of 5 to 8 nm, as follows. The rest of the procedure was the same as in Example 1. The ADC measurement results for Comparative Examples 5-1 to 5-4 are shown in Figure 7. (Particle size of magnetic particles contained in the third magnetic recording layer) Example 5-1: 5nm • Example 5-2: 6nm ·Comparative example 5-3: 7nm ·Comparative example 5-4: 8nm

[0087] In Figure 7, the ADC gain on the vertical axis is expressed as the ratio of the ADC gain of any of Comparative Examples 5-1 to 5-3 to (the ADC gain of Comparative Example 5-4) multiplied by 100, using the ADC gain of the case where the particle size of the magnetic particles contained in the third magnetic recording layer is 8 nm (Comparative Example 5-4) as the reference value, as shown in the following formula (IV). In other words, the ADC gain on the vertical axis shows the amount of improvement (difference) in the ADC gain of Comparative Examples 5-1 to 5-3 relative to the ADC gain of Comparative Example 5-4. Figure 7 also shows the results for magnetic recording media without a third magnetic recording layer, i.e., Examples 1 to 3 and Comparative Examples 2 and 3.

[0088] As shown in Figure 7, the ADC gains of Examples 1-3 were higher than those of Comparative Examples 5-1-5-3. Therefore, it was confirmed that the ADC gain improves as the magnetic recording layer closest to the high-frequency magnetic field generating element is made into a granular structure and the particle size of the magnetic particles contained in that magnetic recording layer is reduced. [Explanation of Symbols]

[0089] 1. Magnetic recording and playback device 10 Magnetic recording media 11 Non-magnetic substrate 12 Soft magnetic layer 13 Seed Layer 14 Base layer 15 Magnetic recording layer 16 Protective layer 17 Lubricant layer 20 Rotary drive unit 30 Magnetic recording and playback heads 31 Recording head 32 playback heads 40 Head drive unit 50 Recording and Playback Signal Processing System 151 Top Floor 152 Layers other than the top layer 311 Recording Magnetic Poles 312 Auxiliary magnetic pole 314 High-frequency magnetic field generating element

Claims

1. A magnetic recording medium comprising multiple magnetic recording layers on a non-magnetic substrate, A magnetic recording / playback head including a high-frequency magnetic field generating element, It has, The magnetic recording and playback head includes recording poles that generate a recording magnetic field for writing information to the magnetic recording medium, The width of the recording magnetic pole is in the range of 30 to 80 nm in the radial direction of the magnetic recording medium. The width of the high-frequency magnetic field generating element is narrower than the width of the recording magnetic pole. A magnetic recording and playback device, wherein the magnetic recording layer closest to the high-frequency magnetic field generating element is a granular magnetic layer having isolated magnetic particles containing Co and Pt, oriented along the c axis in an hcp structure.

2. The magnetic recording and regeneration apparatus according to claim 1, wherein the distance between the high-frequency magnetic field generating element and the magnetic particle is 10 nm or less.

3. The magnetic recording and regeneration apparatus according to claim 1 or 2, wherein the particle size of the magnetic particles is 7 nm or less.

4. The magnetic recording and playback apparatus according to claim 1 or 2, wherein a plurality of the magnetic recording layers are laminated on the non-magnetic substrate.

5. A rotational drive unit for rotating the magnetic recording medium, A head drive unit that moves the magnetic recording / reproduction head in the radial direction of the magnetic recording medium, A recording and playback signal processing system that processes the signal input to the magnetic recording and playback head and the output signal from the magnetic recording and playback head, A magnetic recording and reproducing apparatus according to claim 1 or 2, having the following features.

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