WO2010053106A1

WO2010053106A1 - Perpendicular magnetic recording medium and magnetic storage device

Info

Publication number: WO2010053106A1
Application number: PCT/JP2009/068866
Authority: WO
Inventors: 廣常朱美
Original assignee: 株式会社日立製作所
Priority date: 2008-11-06
Filing date: 2009-11-05
Publication date: 2010-05-14
Also published as: JP2010113763A; JP5301953B2

Abstract

Provided is a medium that has high perpendicular magnetic anisotropy energy and high coercivity at room temperature, that has a low Curie temperature, and that enables recording even at low power with the perpendicular magnetic anisotropy energy and coercivity lowered. The perpendicular magnetic recording medium comprises a ground layer (102) and an intermediate layer (103) provided on a substrate (101) and a magnetic recording layer (104) that has perpendicular magnetic anisotropy at room temperature, and provides recording with the perpendicular magnetic anisotropy of the magnetic recording layer lowered by irradiation with energy. The intermediate layer comprises Ru and/or Pd. The magnetic recording layer is a laminate of a ferromagnetic metal layer (108) having Co as the principal component and a nonmagnetic metal layer (109) having Pd as the principal component. The ferromagnetic metal layer is from 0.15‑0.25 nm thick, the nonmagnetic metal layer is from 0.45‑0.8 nm thick, the thickness ratio of the ferromagnetic metal layer and the nonmagnetic metal layer is from 2‑4, and the difference in magnetic coercivity with energy irradiation and without irradiation is at least 8 kOe.

Description

Perpendicular magnetic recording medium and magnetic storage device

The present invention relates to an energy-assisted perpendicular magnetic recording medium and a magnetic storage device.

As of 2008, the surface recording density of a magnetic disk device (HDD) has become several hundred Gbit / inch ² or more, and the recording system has changed from the in-plane magnetic recording system to the perpendicular magnetic recording system as the density increases. This method has been found to be more effective for higher density than in-plane magnetic recording because the leakage flux from adjacent bits works in a direction to stabilize the magnetization when performing high-density recording. . However, in order to increase the density to 1 Tbit / inch ² or more, it is necessary to solve the problem of the stability against the environmental temperature, that is, the thermal demagnetization phenomenon even when the bit is reduced.

In order to solve this problem, it is necessary to apply a recording layer having larger perpendicular magnetic anisotropy energy and coercive force at room temperature. Realization of a recording magnetic head that generates a magnetic field is very difficult. Therefore, recording is performed by lowering the perpendicular magnetic anisotropy energy and coercive force to cause magnetization reversal only during recording by energy assist such as generating heat by light irradiation, and at other times perpendicular magnetic anisotropy energy The groundbreaking recording method that keeps the coercive force high was started. In particular, the energy assist method using near-field light can make the light spot extremely small in size below the wavelength as compared with a method of forming a diaphragm light spot with a laser beam using a lens or the like. For this reason, energy can be locally irradiated in a very narrow range with a diameter of a region heated by energy assist of several + nm or less, and it is considered suitable for high density recording of 1 Tbit / inch ² or more (Non-patent Document 1). ).

On the other hand, the energy assist method using near-field light has a characteristic that the intensity of the near-field light rapidly decreases with respect to the distance from the light source, so when the recording layer exists at a distance away from the light source, The intensity of light applied to the recording layer is reduced, and there is a problem that the recording layer cannot be heated practically. Further, when the magnetic spacing is reduced by bringing the recording layer close to the light source, the flying characteristics of the head are not stable. Furthermore, a recording layer having a large perpendicular magnetic anisotropy energy and coercive force at room temperature has a high Curie temperature, and irreversible deterioration occurs in the protective layer, the recording layer, etc. when the energy is irradiated many times up to the recording temperature. Therefore, it is difficult to record many times. The recording layer having a low Curie temperature has a problem that the perpendicular magnetic anisotropy energy and the coercive force are too small.

In this way, it has a large perpendicular magnetic anisotropy energy and coercive force, a low Curie temperature, good flying characteristics even with a small magnetic spacing, and perpendicular recording that can perform energy-assisted magnetic recording using near-field light. It was difficult to obtain a magnetic recording medium.

As described above, in order to realize high-density energy-assisted perpendicular magnetic recording, it is necessary to comprehensively overcome various problems as described below. First, the recording layer cannot be heated practically enough for energy assist using near-field light. Second, it is difficult to obtain a medium having a large perpendicular magnetic anisotropy energy and a high coercive force at room temperature and a low Curie temperature. Third, it is difficult to obtain a medium having good flying characteristics when the magnetic spacing is small.

An object of the present invention is to provide a perpendicular magnetic recording medium and a magnetic storage device that can solve the above-described problems and realize high-density energy-assisted perpendicular magnetic recording.

The following means were used as means for solving the above problems.

(1) It has a substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, and a protective layer, and the perpendicular magnetization of the magnetic recording layer by energy irradiation (assist) A perpendicular magnetic recording medium that performs recording in a state where anisotropy is reduced, wherein an intermediate layer is made of Ru and / or Pd, and the magnetic recording layer is mainly composed of a ferromagnetic metal layer mainly composed of Co and Pd. It is a laminate with a nonmagnetic metal layer as a component, the film thickness of the ferromagnetic metal layer is 0.15 or more and 0.25 nm or less, and the film thickness of the nonmagnetic metal layer is 0.45 or more and 0.8 nm or less. The film thickness ratio between the ferromagnetic metal layer and the nonmagnetic metal layer is 2 or more and 4 or less, and the difference in coercive force between energy irradiation and non-irradiation is 8 kOe or more.

This enables high-density perpendicular magnetic recording by energy irradiation (assist).

(2) A substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, a cap layer, and a protective layer. A perpendicular magnetic recording medium which performs recording in a state where the anisotropy is reduced, wherein the intermediate layer is made of Ru and / or Pdu, and the magnetic recording layer is mainly composed of a ferromagnetic metal layer mainly composed of Co and Pd. A non-magnetic metal layer as a component, and the cap layer is composed of a ferromagnetic metal layer mainly composed of Co and a non-magnetic metal layer mainly composed of Pd. Energy is 0.15 or more and 0.25 nm or less, the nonmagnetic metal layer is 0.45 or more and 0.8 nm or less, and the film thickness ratio of the ferromagnetic metal layer and the nonmagnetic metal layer is 2 or more and 4 or less. The difference in coercive force between time and non-irradiation is 8 kOe or more It was.

This makes it possible to further improve the flying characteristics of the perpendicular magnetic recording medium described in (1).

(3) In the perpendicular magnetic recording medium according to (1) or (2), the Curie temperature of the magnetic recording layer is 220 ° C. or higher and 400 ° C. or lower.

Thereby, the flying characteristics of the perpendicular magnetic recording medium described in (1) or (2) can be further improved.

(4) The perpendicular magnetic recording medium according to (1) or (2) is characterized in that the average oxygen concentration in the magnetic recording layer is 5 atomic% or more and 15 atomic% or less.

This makes it possible to reduce the magnetic interaction in the in-plane direction and to reduce the recording noise.

(5) The perpendicular magnetic recording medium according to (1) or (2) is characterized in that the average boron concentration in the ferromagnetic metal layer is 5 atomic% or more and 15 atomic% or less.

This makes it possible to reduce the grain size in the in-plane direction and to reduce the reproduction noise.

(6) In the perpendicular magnetic recording medium according to (1) or (2), the thickness of the magnetic recording layer is 6 nm or more and 15 nm or less.

This makes it possible to reduce the temperature distribution in the film thickness direction during recording of the magnetic recording layer and to record a stable domain.

(7) The perpendicular magnetic recording medium according to (2) is characterized in that the average oxygen concentration in the cap layer is lower than the average oxygen concentration in the magnetic recording layer.

This improves the flatness of the lubricating layer and makes it possible to obtain a medium with good flying characteristics.

(8) In the perpendicular magnetic recording medium according to (2), the cap layer has a thickness of 1 nm to 4 nm.

This makes it possible to obtain a medium having both good flying characteristics and magnetic characteristics.

(9) The intermediate layer according to (1) or (2) is characterized by being made of Pd.

This shortened the film formation time and improved productivity.

(10) The intermediate layer according to (1) or (2) is characterized by being made of Ru.

This reduces surface roughness and improves flying characteristics.

(11) The intermediate layer described in (1) or (2) is characterized by being made of Ru and Pd.

This improved productivity and levitation characteristics little by little.

(12) A substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, and a protective layer, and perpendicular magnetic anisotropy of the magnetic recording layer by energy irradiation A magnetic storage device comprising: a perpendicular magnetic recording medium for recording in a state of reduced performance; a magnetic recording head having an energy irradiation function using near-field light; and a magnetic head having a signal reproducing head. In the perpendicular magnetic recording medium, the intermediate layer is made of Ru and / or Pd, and the magnetic recording layer is a laminate of a ferromagnetic metal layer mainly containing Co and a nonmagnetic metal layer mainly containing Pd. The film thickness of the ferromagnetic metal layer is 0.15 nm or more and 0.25 nm or less, the film thickness of the nonmagnetic metal layer is 0.45 nm or more and 0.8 nm or less, and the film of the ferromagnetic metal layer and the nonmagnetic metal layer The thickness ratio is 2 or more and 4 or less, and energy The difference in coercivity at and during non-irradiation morphism There are more than 8 kOe, the distance from the energy radiation source of the magnetic head during recording to the magnetic recording layer surface of the perpendicular magnetic recording medium is characterized in that it is 8nm or less.

As a result, a high-density magnetic storage device can be obtained.

According to the present invention, it is possible to obtain a perpendicular magnetic recording medium and a magnetic storage device suitable for high-density heat-assisted recording, capable of recording at a temperature rise by heat assist, and having a high coercive force at room temperature.

1 is a schematic cross-sectional view showing the overall layer configuration of a perpendicular magnetic recording medium of the present invention. The expanded sectional view of a recording layer. FIG. 3 is a diagram showing a detailed cross-sectional structure of an intermediate layer and a recording layer of a perpendicular magnetic recording medium according to the present invention, and shows a state in which the intermediate layer is laminated. FIG. 3 is a diagram showing a detailed cross-sectional structure of the intermediate layer and the recording layer of the perpendicular magnetic recording medium of the present invention, and shows a state in which the recording layer is laminated on the intermediate layer. The expanded sectional view of a recording layer. The figure which shows the relationship between the ferromagnetic metal layer film thickness, a floating characteristic, and a magnetic characteristic in the perpendicular magnetic recording medium of this invention. The figure which shows the relationship between the film thickness of a nonmagnetic metal layer, a temperature characteristic, and a magnetic characteristic in the perpendicular magnetic recording medium of this invention. The figure which shows the relationship between the film thickness ratio of a nonmagnetic metal layer and a ferromagnetic metal layer, and a magnetic characteristic in the perpendicular magnetic recording medium of this invention. The figure which shows the relationship between the coercive force difference of the perpendicular magnetic recording medium of this invention, and signal degradation amount. The figure which shows the relationship between the amount of oxygen in a recording layer, and the crystallization characteristic in the perpendicular magnetic recording medium of this invention. The figure which shows the relationship between the amount of boron in a ferromagnetic metal layer, a magnetic characteristic, and a crystal grain diameter in the perpendicular magnetic recording medium of this invention. FIG. 2 is a schematic cross-sectional view showing the entire layer structure of a perpendicular magnetic recording medium having a cap layer of the present invention. The enlarged view of a cap layer. The figure which shows the detailed cross-section of the perpendicular magnetic recording medium which has a cap layer of this invention. The expanded sectional view of a recording layer. The figure which shows the magnetic characteristic in the perpendicular magnetic recording medium which has a cap layer of this invention, and the medium of a comparative example. 1 is a schematic plan view showing a configuration example of a magnetic storage device of the present invention. FIG. 12A is a cross-sectional view taken along the line A-A ′ of FIG. 12A. 1 is a schematic view of a head mounted on a magnetic storage device of the present invention. Schematic view seen from the side of the main part of the head. The figure which shows the relationship between the distance from an energy source to the surface of a recording layer, and an absorptance in the magnetic memory device of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Example 1]
As one embodiment of the present invention, a perpendicular magnetic recording medium having a magnetic recording layer having perpendicular magnetic anisotropy at room temperature and performing recording in a state where the perpendicular magnetic anisotropy is reduced by energy irradiation (assist) is provided. explain. Here, energy assist was performed using near-field light. As a result, energy can be locally irradiated in a very narrow range in which the diameter of the heated region in the medium is several + nm or less. The energy dose was optimized and evaluated so that the temperature of the medium was about 70% or more of the Curie point.

FIG. 1A schematically shows a cross-sectional structure of a perpendicular magnetic recording medium having a recording layer 104 composed of a multilayer film of a ferromagnetic metal layer 108 and a nonmagnetic metal layer 109 as one embodiment of the present invention. It is. On the substrate 101, a Ni ₆₃ Ta ₃₈ layer of about 30 nm and a Ni ₉₄ W ₆ layer of about 7 nm as the underlayer 102, a Ru layer of about 16 nm as the intermediate layer 103, a recording layer 104 of about 12 nm, and a protective layer 106 of about 3 nm CN layers were sequentially formed. Film formation was performed by DC sputtering. Thereafter, about 107 nm of the lubricant 107 was applied on the CN layer. FIG. 1B is an enlarged conceptual diagram of the recording layer 104. For the recording layer 104, Co ₉₀ B ₁₀ was used for the ferromagnetic metal layer 108, and Pd was used for the nonmagnetic metal layer 109. The multilayer film was formed by alternately forming both layers while fixing the substrate and rotating the Co ₉₀ B ₁₀ target and the Pd target using a rotating cathode, and formed a total film of about 12 nm. Although simplified in FIG. 1B, in the recording layer 104, the ferromagnetic metal layer 108 and the nonmagnetic metal layer 109 are alternately laminated 15 times as the constituent layers by 0.2 nm and 0.6 nm, respectively. Yes. Since the origin of perpendicular magnetic anisotropy in the case of a multilayer film is mainly the interface, it is important that the two layers are alternately stacked to form an interface, and a ferromagnetic metal layer and a nonmagnetic metal layer Either of these may be formed first. A similar multilayer film can be formed by fixing the target and rotating the substrate. The film thickness of each constituent layer was changed by changing the power input to each target. Further, in order to form a grain boundary structure in the multilayer recording layer, a small amount of oxygen was added during film formation.

As shown in FIG. 2, the intermediate layer 103 is formed with 8 nm of Ru as the first intermediate layer 201 at a low gas pressure (1.4 Pa), and then 8 nm of Ru as the second intermediate layer 202 at a high gas pressure (5 Pa). Formed. In this way, a flat film is formed at a low gas pressure to adjust the crystallinity, and a film is formed thereon at a high gas pressure to form a concavo-convex shape (FIG. 2A). A multilayer recording layer 104 having good crystal orientation in the vertical direction can be formed on the shape in which the grains are separated (FIG. 2B). The multilayer film of the ferromagnetic metal layer 108 and the nonmagnetic metal layer 109 is mainly formed in the crystal grains 203 (FIG. 2C). As the range of gas pressure during intermediate layer deposition, when the low gas pressure is 1 to 2 Pa and the high gas pressure is 4 to 10 Pa, the uneven shape is formed, and the separation of the recording layer is promoted and the crystal orientation is improved. The effect to do was obtained.

First, the recording layer was examined. The thickness of the nonmagnetic metal layer was kept constant at 0.6 nm, and the floating characteristics of the ferromagnetic metal layer and the thickness dependence of the saturation magnetization were investigated. The results are shown in FIG.

Table 1
Ferromagnetic metal layer thickness (nm) Flying characteristics (mV) Saturation magnetization (emu / cc)
0.05 31.3-
0.1 31.3 212
0.15 31.3 301
0.17 31.3 320
0.2 31.3 336
0.23 31.4 359
0.25 31.5-
0.3 31.8 403
0.4 32.7 413

In this case, the number of constituent layers is 18 to 12, but since the magnetic moment is proportional to the recording layer thickness, the total thickness of the recording layer was constant at about 12 nm. The flying characteristics were measured by plotting the output of the piezoelectric terminal vibration when the head floated with a tester having a magnetic head with a dedicated piezoelectric sensor terminal attached to the head. The flatter the lubricant surface of the medium and the more stable the head flies without colliding with the medium, the smaller the output, and the smaller the output. When the levitation is stable, the piezo output is 31.5 mV or less, and the vibration becomes larger as the levitation becomes unstable, such as hitting or colliding, and the output increases. In order for the medium to be used practically, a head collision or the like should not occur, so it is important that the piezo output is 31.5 mV or less. Furthermore, 31.4 mV or less is more preferable because it is a level at which the medium and the head do not collide even when a disturbance such as external vibration occurs. The saturation magnetization was measured using a vibrating magnetic magnetometer (VSM) after the medium was cut into small pieces. In the present specification, evaluations not particularly described in temperature were all performed at room temperature. If the saturation magnetization is small, the signal level when the bit is recorded becomes low, the SNR becomes low, and the correctly recorded information cannot be reproduced. For this reason, it is important that the saturation magnetization is 290 emu / cc or more.

3 and Table 1, it can be seen that the thinner the ferromagnetic metal layer, the smaller the piezo output at the time of flying the head, and the better the flying characteristics, and the thicker the saturation magnetization becomes. When the thickness of the ferromagnetic metal layer is 0.15 nm or more and 0.25 nm or less, the piezoelectric output is 31.5 mV or less and the saturation magnetization is 290 emu / cc or more. It was. Furthermore, when the thickness of the ferromagnetic metal layer is 0.17 nm or more and 0.23 nm or less, the piezo output is 31.4 mV or less, the saturation magnetization is 310 emu / cc or more, and both the floating characteristics and the magnetic characteristics are better. Results were obtained.

The film thickness of the ferromagnetic metal layer was kept constant at 0.2 nm, and the dependence of the temperature characteristics and saturation magnetization on the film thickness of the nonmagnetic metal layer was investigated. The results are shown in FIG.

Table 2
Nonmagnetic metal layer thickness (nm) Saturation magnetization (emu / cc) Curie temperature (° C)
1.0 210 150
0.8 296 220
0.7 310 280
0.6 336 320
0.5-370
0.45 385 400
0.4 405 420
0.3 425-

In this case, the number of constituent layers is 10 to 24, but since the magnetic moment is proportional to the thickness of the recording layer, the total thickness of the recording layer was kept constant at about 12 nm. The temperature characteristics were obtained by measuring the saturation magnetization at each temperature while heating with a heater after cutting the medium into small pieces, and the temperature at which the saturation magnetization was sufficiently small at 20 emu / cc or less was taken as the Curie temperature. In the method of recording by reducing the perpendicular magnetic anisotropy by energy irradiation, the temperature characteristic is also an important physical property. When the Curie temperature is too low, the saturation magnetization is lowered by a small amount of energy irradiation, so that it is difficult to control the energy irradiation amount. Therefore, it is necessary to set the temperature sufficiently away from room temperature, and a Curie temperature of 220 ° C. or higher is preferable. On the other hand, when the Curie temperature is high, it is necessary to make the recording layer higher for recording. However, when the recording layer reaches 400 ° C. or more, the protective layer and the lubricant are thermally deteriorated. When the protective layer or the like deteriorates, the recording layer is exposed to the atmosphere and the magnetic characteristics deteriorate, or the surface of the protective layer or the lubricant material becomes uneven and the flying characteristics deteriorate. Therefore, the Curie temperature is preferably 400 ° C. or lower.

4 and Table 2, it can be seen that the saturation magnetization increases as the film thickness of the nonmagnetic metal layer decreases, and the Curie temperature decreases as the film thickness increases. When the film thickness of the nonmagnetic metal layer is 0.45 nm or more and 0.8 nm or less, the Curie temperature is 400 ° C. or less and the saturation magnetization is 290 emu / cc or more. It was. Furthermore, when the film thickness of the nonmagnetic metal layer is 0.5 nm or more and 0.7 nm or less, the Curie temperature is 370 ° C. or less, the saturation magnetization is 310 emu / cc or more, and both the temperature characteristics and the magnetic characteristics are better. was gotten.

FIG. 5 and Table 3 show the results of examining the magnetic characteristics while changing the film thickness ratio between the nonmagnetic metal layer and the ferromagnetic metal layer.

Table 3
Film thickness of ferromagnetic metal layer Film thickness of nonmagnetic metal layer Film thickness ratio Coercive force (nm) (nm) (kOe)
0.9 0.15 6 7.1
0.75 0.15 5 8.0
0.8 0.2 4 9.1
0.7 0.2 3.5 10.5
0.6 0.2 3 11.7
0.5 0.2 2.5 10.5
0.5 0.25 2 9.4
0.45 0.3 1.5 7.2

Here, the coercive force was examined using a Kerr effect measuring device. If the coercive force is low, an unstable region of the recorded region disappears due to a head magnetic field, a rise in the temperature around the head, or the like. . From FIG. 5 and Table 3, it can be seen that the coercive force increases when the film thickness ratio between the nonmagnetic metal layer and the ferromagnetic metal layer is in an appropriate range. When the film thickness ratio between the nonmagnetic metal layer and the ferromagnetic metal layer was 2 or more and 4 or less, a coercive force of 9 kOe or more was obtained. Furthermore, when the film thickness ratio between the nonmagnetic metal layer and the ferromagnetic metal layer was 2.5 or more and 3.5 or less, a better result was obtained with a coercive force of 10.5 kOe or more.

Table 4 shows a result of comparing the case where the film thickness ratio is constant and the film thickness of the magnetic metal layer and the ferromagnetic metal layer is within the above-mentioned preferable range and the case outside the range.

Table 4
Number Thickness of ferromagnetic metal layer Thickness of nonmagnetic metal layer Thickness ratio Coercivity
(Nm) (nm) (kOe)
41 0.4 1.2 3 7.1
42 0.2 0.6 3 11.7
43 0.1 0.3 3 3.5
44 0.08 0.24 3 2.7

Thus, even when the film thickness ratio between the nonmagnetic metal layer and the ferromagnetic metal layer is in an appropriate range, when the film thickness of the constituent layer is out of the appropriate range (numbers 41, 43, 44), that is, here When the thickness of the ferromagnetic metal layer is 0.4, 0.1, 0.08 nm, the coercive force is smaller than 9 kOe. In summary, only when the film thickness and the film thickness ratio of each constituent layer are in a good range, good results of flying characteristics, magnetic characteristics, and temperature characteristics could be obtained.

Fig. 6 and Table 5 show the results of examining the relationship between the difference in coercive force during energy irradiation and non-irradiation and the signal degradation amount.

Table 5
Coercive force Coercive force difference Signal degradation (kOe) (kOe) (dB)
4.7 3.7 5
7.1 6.1 1
9.0 8.0 0.2
10.5 9.5 0
11.7 10.7 0

The energy light source wavelength during recording was 780 nm, the emission power of the energy light source was 100 mW, the energy irradiation time was 2 ns, the recording magnetic field was about 6 kOe, and the medium shown in FIG. 1 was used. The measurement was performed according to the following procedure. After recording with energy assist at a linear recording density of 1500 fci, the signal level was measured. Next, recording was performed on the adjacent tracks at a linear recording density of 1000 fci, and the level of the signal recorded first was measured again. When recording on the tracks on both sides, the already recorded track is also exposed to the head magnetic field and temperature rise leaked from the adjacent track. For this reason, in a medium having a low coercive force difference and insufficient, a part of the recording bit area disappears and signal degradation occurs. The signal degradation amount was calculated as the signal degradation amount by the difference in signal level between the first recording and the recording on both sides.

If signal degradation occurs more than 1%, it becomes difficult to save the degradation signal by error correction. Further, since error correction requires recording extra codes for error correction, the smaller the deterioration signal, the lower the recording density can be suppressed, and the signal deterioration is more preferably 0%. From FIG. 6 and Table 5, it can be seen that signal deterioration does not occur as the coercive force difference increases. When the difference in coercive force between energy irradiation and non-irradiation was 8 kOe or more, the signal deterioration amount was suppressed to 0.2 dB or less, and good results were obtained. Furthermore, when the difference in coercive force between energy irradiation and non-irradiation was 9.5 kOe or more, the signal deterioration amount was suppressed to 0 dB, and a better result was obtained.

Next, the intermediate layer material dependency was examined. The ferromagnetic metal layer thickness is 0.2 nm, the non-magnetic metal layer thickness is 0.6 nm, the total recording layer thickness is 12 nm, and the combination of the intermediate layer material and the film forming process is changed. The magnetic force was examined. A comparison was also made between the case where the intermediate layer was formed by the low gas pressure and high gas pressure film forming processes and the case where the intermediate layer was formed by a single film forming process. Table 6 summarizes the results.

Table 6
No.
(KOe)
61 Pd (low gas pressure, 8 nm) / Pd (high gas pressure, 8 nm) 13.5
62 Ru (low gas pressure, 8 nm) / Pd (high gas pressure, 8 nm) 12.2
63 Ru (low gas pressure, 8 nm) / Ru (high gas pressure, 8 nm) 11.7
64 Pd (low gas pressure, 8 nm) / Ru (high gas pressure, 8 nm) 11.5
65 Pd (low gas pressure, 16 nm) 11.1
66 Ru (low gas pressure, 16 nm) 10.6
67 None 6.4
68 Co (low gas pressure, 16 nm) 4.4
69 Co (low gas pressure, 8 nm) / Pd (high gas pressure, 8 nm) 4.1

Thus, when the intermediate layer material was Ru and / or Pd, a large coercive force of 9 kOe was obtained. However, although the composition of the recording layer was good, the coercive force was as small as 4 to 6 kOe when the intermediate layer material was other than Ru and Pd, or when the intermediate layer was not formed. Moreover, when the intermediate layer is a single layer, the coercive force is low because the crystal grains are not sufficiently separated. As an intermediate layer material, Ru has good characteristics because the hcp structure crystal improves the c-axis of the Co layer or the (111) orientation of the Pd layer, and forms an uneven shape. This is probably because the perpendicular magnetic anisotropy of the recording layer is easily formed. Co having the same hcp structure has little formation of uneven shapes and a good coercive force could not be obtained. Although Pd has an fcc structure, it is considered that the coercive force is increased because the uneven shape is large and the separation of crystal grains is promoted. Further, since Pd has a high film formation rate, mass production can be improved by using Pd for film formation at a high gas pressure. However, the surface roughness was large, the roughness of number 61 was 1.5 times that of number 63, and number 62 was 1.3 times that of number 63.

As described above, it has a substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, and a protective layer, and the perpendicular magnetic anisotropy is reduced by energy irradiation. In a perpendicular magnetic recording medium that performs recording in a state, an intermediate layer is formed of Ru and / or Pd, and the magnetic recording layer includes a ferromagnetic metal layer mainly containing Co and a nonmagnetic metal layer mainly containing Pd. The ferromagnetic metal layer has a thickness of 0.15 nm to 0.25 nm and the nonmagnetic metal layer has a thickness of 0.45 nm to 0.8 nm. By setting the film thickness ratio to 2 to 4 and the difference in coercivity between energy irradiation and non-irradiation to 8 kOe or more, an energy-assisted perpendicular magnetic recording medium having good recording / reproducing characteristics can be obtained. It becomes possible.

In addition, for the substrate 101, tempered glass having a diameter of 2.5 inches, a thickness of 0.6 mm, and a surface roughness Ra of 0.3 nm or less was used, but the diameter was 3.5 inches, 5 inches, or 1.8 inches. For example, a substrate having a different size such as 1 mm, 0.8 mm, or 0.5 mm may be used. The material of the substrate may be other than tempered glass, but a material such as Si or aluminum that does not deform or change even when the surface is exposed to about 500 ° C. is preferable.

Although the Ni ₆₃ Ta ₃₈ layer and the Ni ₉₄ W ₆ layer were used for the underlayer 102, other materials and film thicknesses may be used as long as adhesion and flatness with the substrate and the intermediate layer can be secured. The protective layer 106 may have a different composition ratio or other materials as long as adhesion to the recording layer, transparency at the wavelength of the heat-assisted light source, and surface flatness can be ensured.

Further, the film thickness of the ferromagnetic metal layer is 0.2 nm, the film thickness of the nonmagnetic metal layer is 0.6 nm, the total film thickness of the recording layer is 12 nm, and the amount of oxygen added to the Ar gas during film formation is changed. When the relationship between the amount of oxygen in the film, the crystal orientation of the recording layer, and the grain boundary width of the crystal was examined, the results shown in FIG. 7 and Table 7 were obtained.

Table 7
Number Oxygen content (atomic%) Crystal orientation (°) Grain boundary width (nm)
71 0 3.19 0
72 5 3.21 0.3
73 8 3.25 0.4
74 10 3.28 0.5
75 13 3.3 0.55
76 15 3.32 0.6
77 19 3.43 0.8

The oxygen amount was analyzed using an energy dispersive X-ray analyzer (EDX). The crystal orientation was examined using an X-ray diffractometer. The better the crystal orientation, the more uniform the magnetic properties of each crystal. When the crystal orientation deteriorates, the dispersion of magnetic characteristics increases and causes noise. Therefore, the crystal orientation is preferably 3.35 ° or less. The grain boundary width was determined by observing 100 grains and grain boundaries with a transmission electron microscope (TEM), and obtaining an average value of the grain boundaries. The larger the grain boundary width, the less magnetic influence of adjacent particles. That is, the magnetic correlation distance is reduced and the recording error rate is reduced. Therefore, the crystal grain boundary needs to be large, and is preferably at least 0.3 nm or more. When the grain boundary is not formed, the magnetic correlation distance is too large, and a high-density bit such as a bit length of 25 nm cannot be formed.

7 and Table 7 that the crystal orientation deteriorates and the grain boundary width increases as the amount of oxygen increases. When the amount of oxygen in the recording layer was 5 atom% or more and 15 atom% or less, the crystal orientation was 3.35 ° or less and the grain boundary width was 0.3 nm or more, and good results were obtained. Further, when the oxygen content in the recording layer is 8 atomic% or more and 13 atomic% or less, the crystal orientation can be 3.3 ° or less and the grain boundary width can be 0.4 nm or more, and a better result is obtained. .

Furthermore, it has become possible to reduce the crystal grain size by adding B (boron) into the ferromagnetic metal layer. As for the crystal grain size, 100 particles were observed with a transmission electron microscope (TEM), and the average value and dispersion of the grain size were obtained. When the crystal grain size is reduced, noise during recording can be reduced. When recording with a bit length of 25 nm at the shortest, if there is a crystal grain of 12.5 nm or more, which is half of the shortest bit length, noise during recording increases rapidly. For this reason, since the dispersion of the crystal grain size is about 20%, the average grain size is preferably 11.4 nm or less. On the other hand, if B is added too much, the recording layer deteriorates during heating. Although the heating time of the medium during actual recording is several ns, the deterioration of the saturation magnetization when heated at 400 ° C. for 1 h was examined as an acceleration test. When the amount of deterioration is large, the number of rewritable times decreases, and therefore it is preferably 200 emu / cc or less. Prepare targets with different boron (B) contents in the ferromagnetic metal layer, the ferromagnetic metal layer thickness is 0.2 nm, the nonmagnetic metal layer thickness is 0.6 nm, and the total recording layer thickness is 12 nm. As shown in FIG. 8 and Table 8, when recording layers having different B addition amounts in the ferromagnetic metal layer were formed and the boron content and crystal grain size in the film and the saturation magnetization deterioration amount during the acceleration test were examined. The result was obtained.

Table 8
Number Boron amount Saturation magnetization deterioration Crystal grain size
(Atom%) (emu / cc) (nm)
81 0 20 12.5
82 5 20 11.0
83 8 30 10.8
84 10 50 10.6
85 13 100 10.5
86 15 180 10.3
87 19 250 10.2

From this, it can be seen that as the amount of boron in the ferromagnetic metal layer increases, the amount of saturation magnetization deterioration increases and the crystal grain size decreases. When the boron content in the ferromagnetic metal layer was 5 atomic% or more and 15 atomic% or less, the saturation magnetization deterioration amount could be 200 emu / cc or less, the crystal grain size could be 11 nm or less, and good results were obtained. Further, when the boron content is 8 atomic% or more and 13 atomic% or less, the saturation magnetization deterioration amount can be 100 emu / cc or less and the crystal grain size can be 10.8 nm or less, and a better result is obtained.

Next, the relationship between the Curie temperature of the recording layer, the flying characteristics, and the recording characteristics was examined. As for the flying characteristics, an acceleration test was conducted, and the number of times the glide head hits when flying with the glide tester after irradiating the medium with far-field laser light (wavelength 780 nm, spot diameter 1 μm) 10 ns for 1000 times. As for the recording characteristics, recording was performed with near-field light at a bit length of 50 nm, and 100 recording domains were observed with a magnetic microscope (MFM) to determine the bit length dispersion. The measurement was compared with the dispersion at the optimum power of each medium while changing the recording power. Table 9 summarizes the results.

Table 9
Number Curie temperature (° C) Number of head hits (times) Bit length dispersion (%)
91 200 0 25
92 220 0 14
93 240 0 10
94 300 1 8
95 370 2 6
96 400 5 6
97 450 10 6

From this, it can be seen that the higher the Curie temperature of the recording layer, the greater the number of head hits. This is because, since the Curie temperature is high, recording cannot be performed unless the temperature of the recording layer is increased during recording, and the protective layer and the lubricant are thermally deteriorated by the heat at this time. It is considered that irregularities are formed on the surface, the floating characteristics are deteriorated, and the number of hits is increased. Further, the lower the Curie temperature of the recording layer, the larger the bit length dispersion. This is because the temperature at the time of recording is low, that is, the output power is low and the difference from room temperature is small, so that the variation in temperature control increases. When the recording layer Curie temperature was 220 ° C. or higher and 400 ° C. or lower, the number of head hits was as small as 5 or less, and good results were obtained with a bit length dispersion of 15% or less. Further, when the recording layer Curie temperature was 250 ° C. or higher and 370 ° C. or lower, the number of hits of the head was very small, 2 times or less, and a better result was obtained with a bit length dispersion of 10% or less.

The relationship between the film thickness of the recording layer, temperature characteristics, and magnetic characteristics was examined. The results are shown in Table 10. As for the temperature characteristics, the temperature difference between the energy incident side (upper surface) of the recording layer and the opposite substrate side (lower surface) was examined. When the temperature difference is large, when the recording layer is irradiated with energy for recording, the perpendicular magnetic anisotropy is decreased by heating only the upper surface and the magnetization is reversed, but the lower surface remains low in temperature and high in perpendicular magnetic anisotropy. For this reason, magnetization reversal does not occur, and the rate at which recording bits are not formed increases. Therefore, the temperature difference between the upper and lower recording layers is preferably 125 ° C. or less, which is sufficiently small with respect to the recording temperature. As the magnetic characteristics, the magnitude of the magnetic moment is shown as a ratio with the nominal recording layer 12 nm being 1. When the magnetic moment is lowered, the signal strength is deteriorated. Therefore, the magnitude of the magnetic moment needs to be 0.5 or more of the nominal value.

Table 10
Number Recording layer thickness Temperature difference between upper and lower recording layers Magnetic moment
(Nm) (℃)
101 4 5 0.3
102 6 20 0.5
103 8.4 45 0.7
104 12 90 1
105 13 105 1.1
106 15 125 1.25
107 18 153 1.5

Table 10 shows that the temperature difference between the upper and lower recording layers increases as the recording layer thickness increases. This is because the light intensity decreases where the near-field light is separated from the light source. In addition, the magnetic moment decreases as the recording layer thickness decreases. This is because it is related to the magnetization of the recording layer and its volume. When the thickness of the recording layer was 6 nm or more and 15 nm or less, good results were obtained in which the temperature difference between the upper and lower recording layers was 125 ° C. and the magnetic moment was 0.5 or more. Furthermore, when the recording layer thickness was 8.4 nm or more and 13 nm or less, a better result was obtained in which the temperature difference between the upper and lower recording layers was 105 ° C. and the magnetic moment was 0.7 or more.

[Example 2]
In Example 2, as one example of the present invention, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature and a cap layer are provided, and the perpendicular magnetic anisotropy is lowered by energy irradiation (assist). A perpendicular magnetic recording medium for recording will be described.

FIG. 9A shows a recording layer 104 composed of a multilayer film of a ferromagnetic metal layer 108 and a nonmagnetic metal layer 109, a cap layer ferromagnetic metal layer 901, and a cap layer nonmagnetic as an embodiment of the present invention. 1 schematically shows a cross-sectional structure of a perpendicular magnetic recording medium having a cap layer 105 formed of a multilayer film of metal layers 902. On the substrate 101, a Ni ₆₃ Ta ₃₈ layer and a Ni ₉₄ W ₆ layer of about 30 nm as the underlayer 102, a Ru layer of about 16 nm as the intermediate layer 103, a recording layer 104 of about 12 nm, and a cap layer 105 of about 3 nm. Then, a CN layer of about 3 nm was sequentially formed as the protective layer 106. Film formation was performed by DC sputtering. Thereafter, about 107 nm of the lubricant 107 was applied on the CN layer.

The recording layer 104 was laminated using Co ₉₀ B ₁₀ of 0.2 nm for the ferromagnetic metal layer 108 and Pd of 0.6 nm for the nonmagnetic metal layer 109, and a trace amount of oxygen was added. Details are as described in Example 1. FIG. 9B is an enlarged view of the cap layer 105. The cap layer 105 was laminated by using 0.2 nm of Co for the ferromagnetic metal layer 901 for the cap layer and 0.6 nm of Pd for the nonmagnetic metal layer 902 for the cap layer. When the cap layer is 3 nm, the number of layers is about 4 times. The cap layer having the multilayer structure was formed by alternately forming both layers while fixing the substrate and rotating the Co target and the Pd target. A similar multilayer film can be formed by fixing the target and rotating the substrate. The film thickness of each constituent layer was changed by changing the power input to each target. The gas pressure during cap layer deposition was 5 Pa.

In the comparative example, media different in composition and structure of the cap layer were prepared, and the flying characteristics and magnetic characteristics were compared. A comparison was made using a Co ₆₅ Cr ₁₅ Pt ₁₂ B ₈ composition for the cap layer.

First, a medium having a multi-layered cap layer and a comparative cap layer was formed, and the flying characteristics of the perpendicular magnetic recording medium were examined and compared in Table 11. Here, the yield at which a medium with good flying characteristics was obtained was examined. For the yield, 20 media having the same configuration were prepared, and those with a piezoelectric output of 31.3 mV or less were Class A products, those with 31.4 to 31.5 mV were Class B products, and those with 31.6 mV or more were used. Each percentage was examined by counting as NG.

From Table 11, it can be seen that the thicker the cap layer, the higher the yield. When the cap layer thickness was 1 nm or more, the A-class product yield was 90%, and good results were obtained. Furthermore, when the cap layer thickness was 2 nm or more, the yield of Class A products was improved to 95%, and better results were obtained. The improvement of the flying characteristics was similarly improved in both the multilayer cap layer and the comparative cap layer. The reason why the flying characteristics are improved is considered to be that the unevenness formed by the formation of crystal grains on the surface of the recording layer was made smooth by forming the cap layer 105 as shown in FIG.

Next, the magnetic characteristics were compared. The coercive force of each medium was measured, and the amount of coercive force deterioration due to cap layer formation was examined. The magnetic characteristics when the cap layer is formed in the present invention and the comparative example are compared in FIG. In the comparative example having a Co ₆₅ Cr ₁₅ Pt ₁₂ B ₈ composition cap layer that is not multi-layered, the coercive force deterioration was extremely large, and even when 1 nm was formed, a large deterioration of 2 kOe or more was shown. This is because the cap layer having a small coercive force was formed on the recording layer having a large coercive force, so that the magnetic characteristics of the entire medium deteriorated. On the other hand, in the medium with a multilayer film cap layer of the present invention, even if a cap layer is formed to improve the floating characteristics, the deterioration of magnetic characteristics is extremely small, and even if a 4 nm cap layer is formed, the deterioration is as small as 1.5 kOe. I understand that. This is presumably because the cap layer also has a multilayer film structure so that layers having a large coercive force are stacked. Thus, by providing a cap layer having a multilayer structure comprising a ferromagnetic metal layer for a cap layer and a nonmagnetic metal layer for a cap layer on a recording layer having a high perpendicular magnetic anisotropy, it is possible to prevent deterioration of magnetic characteristics and As a result, the flying characteristics can be made extremely good.

Further, the composition and process dependency of the multilayer cap layer were investigated while keeping the conditions of the recording layer, etc., and are shown in Table 12. A medium in which Co ₉₀ B ₁₀ is 0.2 nm for the ferromagnetic metal layer 901 for the cap layer and Pd is 0.6 nm for the nonmagnetic metal layer 902 for the cap layer was manufactured (No. 121). The thickness of the cap layer was 2 nm. When B was added in this way, the yield of Class A products decreased to 85%. From this, it was found that it is better not to add B to the cap layer.

A medium in which the ferromagnetic metal layer 901 for the cap layer was laminated using Co of 0.2 nm and the nonmagnetic metal layer 902 for the cap layer was laminated using 0.6 nm of Pd was produced. Here, as with the recording layer, a small amount of oxygen was added. In the case where oxygen was added, when the amount of O in the cap layer was 10 atomic% (No. 122), the yield of the class A product decreased to 80%. When the amount of O in the cap layer was 5 atomic% (No. 123), the yield of the class A product was 85%. From this, it was found that a smaller amount of oxygen in the cap layer is better.

A medium (No. 124) was prepared by laminating Co ₉₀ B ₁₀ with 0.1 nm for the cap layer ferromagnetic metal layer 901 and Pd with 0.6 nm for the non-magnetic metal layer 902 for cap layer. The thickness of the cap layer was 2 nm. It has been found that when such a ferromagnetic metal layer is made thinner than the recording layer, the degradation of the coercive force can be reduced while the yield of the class A product remains 95%.

A medium (No. 125) was prepared by laminating Co for the cap layer ferromagnetic metal layer 901 with 0.1 nm of Co and for the cap layer nonmagnetic metal layer 902 with Pd of 0.6 nm. The thickness of the cap layer was 2 nm. Thus, it was found that when B was not added to the ferromagnetic metal layer and the constituent layer was made thinner than the recording layer, the yield of the class A product was improved to 97% and the coercive force deterioration could be further reduced.

A medium in which Co ₉₀ B ₁₀ is 0.2 nm for the ferromagnetic metal layer 901 for the cap layer, Pd is 0.6 nm for the non-magnetic metal layer 902 for the cap layer, and the sputtering gas pressure is 3.5 Pa. No. 126) was produced. The thickness of the cap layer was 2 nm. When the gas pressure is lowered in this way, the film forming rate is increased and the mass productivity is improved. The yield of class A products remained at 95%, and the coercivity deteriorated slightly.

A medium (No. 127) in which Co is 0.2 nm for the ferromagnetic metal layer 901 for the cap layer, Pd is 0.6 nm for the nonmagnetic metal layer 902 for the cap layer, and the sputtering gas pressure is 3.5 Pa. Was made. The thickness of the cap layer was 2 nm. When the gas pressure is lowered in this way, the film forming rate is increased and the mass productivity is improved. The yield of Class A products improved to 97%. The degradation of the coercive force was slightly increased.

Table 12
Number Class A product (%) Coercive force degradation (kOe)
114 95 0.8
121 85 0.8
122 80 0.8
123 85 0.8
124 95 0.6
125 97 0.6
126 95 0.9
127 97 0.9

The layer configuration, manufacturing method, material, evaluation method, etc. not described in this example were the same as in Example 1.

[Example 3]
An outline of a magnetic memory device according to an embodiment of the present invention is shown in FIG. (A) is a schematic plan view, and (b) is an AA ′ sectional view thereof. (C) is a schematic diagram of the head, and (d) is a schematic diagram viewed from the side of the main part of the head.

This apparatus has a perpendicular magnetic recording medium 1501, a driving unit 1502 for driving the medium 150, a magnetic head flying slider 1503, a magnetic head driving means 1504, and a magnetic head recording / reproducing signal processing means 1505. The magnetic head is a recording / reproducing separation type magnetic head formed on a magnetic head slider. The recording head is provided with means 1507 for forming a magnetic field and energy irradiation means 1506 using near-field light. Further, the magnetic head is provided with a reproducing current detecting means (reproducing head) 1508 to reproduce the recorded bit. Near-field light is supplied to an energy irradiation means 1506 using near-field light through an optical waveguide 1202 formed on the suspension 1201. The flying slider 1503 is attached to the suspension via the flexure 1203 in order to improve positioning accuracy.

Next, the thermal and magnetic characteristics during recording were examined. The light source wavelength is 780 nm, and the perpendicular magnetic recording medium 1501 has the structure shown in FIG. FIG. 13 shows the relationship between the distance (magnetic spacing) from the near-field light source, which is the energy irradiation source, to the recording layer surface and the energy absorption rate in the perpendicular magnetic recording medium. This was calculated from the intensity of near-field light and the absorptance of the medium at that wavelength, and normalized when the distance was 4 nm. From this, it can be seen that the smaller the distance, the larger the absorption rate of the medium. When the absorptance is small, the medium cannot be heated sufficiently with near-field light and recording cannot be performed. Therefore, the absorptance is preferably 25% or more. When the distance from the energy irradiation source to the recording layer surface was 8 nm or less, an absorptivity of 25% or more was obtained. Furthermore, when the distance from the energy irradiation source to the surface of the recording layer was 7 nm or less, an absorptivity was 32% or more and a better result was obtained.

Furthermore, after incorporating the medium described in Example 1 into the magnetic storage device and confirming that the head stably floats at a head flying height of 4 nm, a head equipped with the energy irradiation means using the near-field light is mounted. And recorded. When the domain was evaluated by MFM, it was found that a domain having a linear density direction of about 25 nm and a track width direction of 50 nm could be formed.

From the above, it has a substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, and a protective layer, and the perpendicular magnetic anisotropy is lowered by energy irradiation. As a perpendicular magnetic recording medium for recording in a state, an intermediate layer is formed of Ru and / or Pd, and a magnetic recording layer is composed of a ferromagnetic metal layer mainly containing Co and a nonmagnetic metal layer mainly containing Pd. The ferromagnetic metal layer has a thickness of 0.15 nm to 0.25 nm, the nonmagnetic metal layer has a thickness of 0.45 nm to 0.8 nm, and the ferromagnetic metal layer is nonmagnetic. A magnetic layer having a metal layer thickness ratio of 2 to 4 and a perpendicular magnetic recording medium in which the difference in coercivity between energy irradiation and non-irradiation is 8 kOe or more, and further has an energy irradiation function using near-field light. Includes a recording head and a signal playback head , The distance from the energy radiation source during recording to the magnetic recording layer surface by a 8nm or less, it is possible to obtain an energy-assisted magnetic memory device having good recording and reproduction characteristics.

101 Substrate 102 Underlayer 103 Intermediate layer 104 Recording layer 105 Cap layer 106 Protective layer 107 Lubricant 108 Ferromagnetic metal layer 109 Nonmagnetic metal layer 201 First intermediate layer 202 Second intermediate layer 203 Crystal grain 204 Grain boundary 901 For cap layer Ferromagnetic metal layer 902 Non-magnetic metal layer for cap layer 1201 Suspension 1202 Optical waveguide 1203 Flexure 1501 Perpendicular magnetic recording medium 1502 Medium drive unit 1503 Flying slider 1504 Magnetic head drive means 1505 Recording / reproduction signal processing means 1506 Energy using near-field light Irradiation means 1507 Means 1508 for forming a magnetic field Reproducing head

Claims

A substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, and a protective layer, and the perpendicular magnetic anisotropy of the magnetic recording layer by energy irradiation; A perpendicular magnetic recording medium for recording in a lowered state,
The intermediate layer is made of Ru and / or Pd;
The magnetic recording layer is a laminate of a ferromagnetic metal layer mainly containing Co and a nonmagnetic metal layer mainly containing Pd,
The ferromagnetic metal layer has a thickness of 0.15 nm or more and 0.25 nm or less,
The nonmagnetic metal layer has a thickness of 0.45 nm or more and 0.8 nm or less,
The film thickness ratio of the ferromagnetic metal layer and the nonmagnetic metal layer is 2 or more and 4 or less,
A perpendicular magnetic recording medium characterized in that a difference in coercive force between energy irradiation and non-irradiation is 8 kOe or more.
A substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, a cap layer, and a protective layer. A perpendicular magnetic recording medium that performs recording in a state of reduced directionality,
The intermediate layer is made of Ru and / or Pd;
The magnetic recording layer is a laminate of a ferromagnetic metal layer mainly containing Co and a nonmagnetic metal layer mainly containing Pd,
The cap layer comprises a laminate of a ferromagnetic metal layer mainly composed of Co and a nonmagnetic metal layer mainly composed of Pd,
The ferromagnetic metal layer has a thickness of 0.15 nm or more and 0.25 nm or less,
The nonmagnetic metal layer has a thickness of 0.45 nm or more and 0.8 nm or less,
The film thickness ratio of the ferromagnetic metal layer and the nonmagnetic metal layer is 2 or more and 4 or less,
A perpendicular magnetic recording medium characterized in that a difference in coercive force between energy irradiation and non-irradiation is 8 kOe or more.
The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer has a Curie temperature of 220 ° C. or more and 400 ° C. or less.
3. The perpendicular magnetic recording medium according to claim 1, wherein an average oxygen concentration in the magnetic recording layer is 5 atomic% or more and 15 atomic% or less.
3. The perpendicular magnetic recording medium according to claim 1, wherein an average boron concentration in the ferromagnetic metal layer is 5 atomic% or more and 15 atomic% or less.
The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer has a thickness of 6 nm to 15 nm.
3. The perpendicular magnetic recording medium according to claim 2, wherein an average oxygen concentration in the cap layer is lower than an average oxygen concentration in the magnetic recording layer.
The perpendicular magnetic recording medium according to claim 2, wherein the cap layer has a thickness of 1 nm to 4 nm.
3. The perpendicular magnetic recording medium according to claim 1, wherein the intermediate layer is made of Pd.
3. The perpendicular magnetic recording medium according to claim 1, wherein the intermediate layer is made of Ru.
3. The perpendicular magnetic recording medium according to claim 1, wherein the intermediate layer is made of Ru and Pd.
A substrate, an underlayer and an intermediate layer provided on the substrate, a magnetic recording layer having a perpendicular magnetic anisotropy at room temperature, and a protective layer, and the perpendicular magnetic anisotropy of the magnetic recording layer by energy irradiation; A perpendicular magnetic recording medium for recording in a lowered state;
A magnetic head having a magnetic recording head having an energy irradiation function using near-field light and a signal reproducing head;
In the perpendicular magnetic recording medium, the intermediate layer is made of Ru and / or Pd, and the magnetic recording layer is a laminate of a ferromagnetic metal layer mainly containing Co and a nonmagnetic metal layer mainly containing Pd. The ferromagnetic metal layer has a thickness of 0.15 nm to 0.25 nm and the nonmagnetic metal layer has a thickness of 0.45 nm to 0.8 nm. The thickness ratio of the magnetic metal layer is 2 or more and 4 or less, and the difference in coercive force between the energy irradiation and non-irradiation is 8 kOe or more,
A magnetic storage device, wherein a distance from the energy irradiation source of the magnetic head to the surface of the magnetic recording layer of the perpendicular magnetic recording medium is 8 nm or less during recording.