JP4522052B2 - Perpendicular magnetic recording medium and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a perpendicular magnetic recording medium and a manufacturing method thereof, and more particularly to a perpendicular magnetic recording medium that is mounted on various magnetic recording apparatuses and forms recording magnetization in a film thickness direction of the recording medium and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, with an increase in capacity of various magnetic disk recording devices such as an external storage device of a computer, a higher recording density of a magnetic recording medium is required. In the conventional magnetic recording system, the longitudinal magnetic recording system is the mainstream, but recently, the perpendicular magnetic recording system has been attracting attention as a technique for realizing high recording density of magnetic recording.
A recording medium using a perpendicular magnetic recording system (hereinafter referred to as “perpendicular magnetic recording medium”) plays a role of concentrating a magnetic recording layer of a hard magnetic material and a magnetic flux generated by a magnetic head used for recording on the magnetic recording layer. A backing layer made of a soft magnetic material is included as a constituent element. As a material of a magnetic recording layer for a perpendicular magnetic recording medium, currently a CoCr-based alloy crystalline film is mainly used. (For example, see Patent Document 1)
On the other hand, an amorphous film using a rare earth-transition metal alloy used as a magneto-optical recording material has a large perpendicular magnetic anisotropy constant Ku, and is a material of a magnetic recording layer in a perpendicular magnetic recording medium. As very promising. In the case of magneto-optical recording, an amorphous film having a composition near the compensation point is used. The coercive force Hc in such a composition range is considerably larger than Hc required as a material for perpendicular magnetic recording, and as such is difficult to use as a perpendicular magnetic recording medium.
[0003]
[Patent Document 1]
JP 2001-291224 A [Patent Document 2]
JP-A-7-296357 [0004]
[Problems to be solved by the invention]
At present, for a CoCr-based alloy crystalline magnetic recording material mainly used for perpendicular recording media, studies are being made to reduce the noise of the magnetic recording media in order to cope with the higher recording density in the future. Methods for reducing noise in the magnetic recording medium include thinning the magnetic recording layer, reducing the CoCr crystal grain size, and promoting grain boundary segregation. However, these methods deteriorate the thermal stability of the recorded signal, and in some cases, the recorded signal disappears, so-called thermal fluctuation occurs.
[0005]
For example, Patent Document 2 discloses that a perpendicular magnetic recording medium is provided with a high coercive force layer made of R—Fe—B (R represents Nd and / or Pr among rare earth elements) to obtain high magnetic characteristics. It is described. However, there is a limit to increasing the density of a perpendicular magnetic recording medium having grain boundaries in the magnetic recording layer as described above, and in reality, only reading / writing at a low density can be performed.
On the other hand, when an amorphous film of a rare earth-transition metal alloy is used, since it is amorphous, there is no so-called crystal grain boundary as found in a CoCr-based crystalline film. For this reason, there is no core for keeping the written signal in place, and the signal may shift or disappear. In particular, this phenomenon is likely to occur during signal recording at a high frequency. For this reason, there has been a problem that an amorphous film of a rare earth-transition metal alloy cannot be used as it is as a perpendicular magnetic recording material aiming at higher recording density.
[0006]
The present invention has been made in view of such a problem, and an object of the present invention is to make a perpendicular magnetic recording medium excellent in productivity without shifting or disappearance of written signals even at a high recording density. And a manufacturing method thereof.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, it has been found that by depositing Ag in an amorphous film of a rare earth-transition metal alloy, the domain wall can be fixed and good characteristics can be obtained.
Specifically, the perpendicular magnetic recording medium of the present invention is a perpendicular magnetic recording medium in which at least an intermediate layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate. And an amorphous film of a rare earth-transition metal alloy to which 2 at% or more and 15 at% or less of Ag is added.
[0008]
Here, between the before and Symbol nonmagnetic substrate intermediate layer, it is preferable to provide a backing layer made of a soft magnetic material.
In addition, it is preferable that one or a plurality of underlayers and a magnetic domain control layer for controlling the magnetic domains of the backing layer are sequentially laminated between the nonmagnetic substrate and the backing layer.
Furthermore, it is preferable to provide a nonmagnetic layer containing Ag between the magnetic recording layer and the protective layer.
[0009]
Here, the thickness of the nonmagnetic layer containing Ag is preferably 0.2 nm or more and 2 nm or less.
In the method of manufacturing the magnetic recording medium of the present invention, it is preferable that the gas pressure at the time of laminating the magnetic recording layer is less 100mTorr than 10 mTorr.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic sectional view of a perpendicular magnetic recording medium according to the first embodiment of the present invention. The magnetic recording medium according to the present embodiment has a structure in which at least an intermediate layer 5, a magnetic recording layer 6, and a protective layer 8 are formed in this order on a nonmagnetic substrate 1, and a liquid lubricant layer 9 is further formed thereon. Is formed.
The nonmagnetic substrate 1 is a disk-shaped carrier for laminating magnetic films. As this nonmagnetic substrate 1, there can be used an Al alloy plated with NiP, tempered glass, crystallized glass or the like, which is used for a normal magnetic recording medium.
[0011]
The intermediate layer 5 is used for controlling the characteristics of the magnetic recording layer 6, and a nonmagnetic element or a nonmagnetic alloy is appropriately used. The film thickness is preferably 5 nm or more and 30 nm or less.
The magnetic recording layer 6 is made of an amorphous film of a rare earth-transition metal alloy. Examples of the rare earth-transition metal alloy amorphous film include, but are not limited to, TbCo and TbFeCo. A major feature of the present invention is that the amorphous film of the rare earth-transition metal alloy contains Ag. By adding Ag, the domain wall existing between the recorded bits is fixed at the position when the bits are written. Therefore, when a signal is recorded at a high recording density, the recorded bit is prevented from shifting or disappearing due to the movement of the domain wall.
[0012]
Examples of a method for adding Ag to an amorphous film of a rare earth-transition metal alloy include a method of forming a target containing Ag and forming a film together with the rare earth-transition metal alloy, and an amorphous target of a rare earth-transition metal alloy. A method of forming a film by placing an Ag chip on the top can be used.
Here, when the concentration of Ag in the thin film is less than 1 at%, the amount of the additive is too small to sufficiently fix the domain wall. On the other hand, if the concentration of Ag is higher than 15 at%, sufficient perpendicular magnetic anisotropy cannot be obtained, so that it does not function as a perpendicular magnetic recording medium. Therefore, in order to obtain sufficient characteristics as a perpendicular magnetic recording medium, it is desirable that the Ag concentration is 1 at% or more and 15 at% or less.
[0013]
If the pressure of the gas used when forming the magnetic recording layer 6 is lower than 10 mTorr, it is difficult to write a signal because the magnetic interaction is too strong. On the other hand, if it is higher than 100 mTorr, the perpendicular magnetic anisotropy is lowered, so that it is not suitable for use as a magnetic recording layer. Therefore, in the process of forming the magnetic recording layer 6, it is desirable that the pressure of the gas used at the time of film formation is 10 mTorr or more and 100 mTorr or less.
As the protective layer 8, a conventionally used protective film such as a protective film mainly composed of carbon can be used. The conditions such as the film thickness of the protective layer 8 can be the same as those used for ordinary magnetic recording media. The liquid lubricant layer 9 can also be made of a conventionally used material, for example, a perfluoropolyether lubricant. Conditions such as the film thickness of the liquid lubricant layer 9 can be the same as those used in ordinary magnetic recording media.
[0014]
(Second Embodiment)
In this embodiment, a soft magnetic backing layer for concentrating magnetic flux generated by a magnetic head used for recording on the magnetic recording layer is provided between the nonmagnetic substrate and the intermediate layer. FIG. 2 is a schematic cross-sectional view of the perpendicular magnetic recording medium according to the present embodiment. The magnetic recording medium has a structure in which at least a soft magnetic backing layer 4, an intermediate layer 5, a magnetic recording layer 6, and a protective layer 8 are sequentially formed on a nonmagnetic substrate 1, and further a liquid lubricant layer is formed thereon. 9 is formed. Among these, the nonmagnetic substrate 1, the intermediate layer 5, the magnetic recording layer 6, the protective layer 8, and the liquid lubricant layer 9 can have the same configuration as in the first embodiment described above.
[0015]
The soft magnetic backing layer 4 plays a role of concentrating the magnetic flux generated by the magnetic head used for recording on the magnetic recording layer 6. NiFe alloy, Sendust (FeSiAl) alloy or the like can be used as the soft magnetic backing layer 4. However, when an amorphous Co alloy such as CoNbZr or CoTaZr is used, good electromagnetic conversion characteristics can be obtained. it can. The optimum value of the thickness of the soft magnetic underlayer 4 varies depending on the structure and characteristics of the magnetic head used for recording, but it is preferably 10 nm or more and 300 nm or less in view of productivity.
In the present embodiment, the intermediate layer 5 controls the characteristics of the magnetic recording layer 6 and plays a role of magnetically separating the soft magnetic underlayer 4 and the magnetic recording layer 6.
[0016]
(Third embodiment)
In this embodiment, an antiferromagnetic layer for controlling the magnetic domain of one or more underlayers and soft magnetic underlayers between the nonmagnetic substrate and the soft magnetic underlayer described in the second embodiment. (Magnetic domain control layer) is further sequentially laminated. FIG. 3 is a schematic cross-sectional view of the perpendicular magnetic recording medium according to this embodiment. In the magnetic recording medium, at least one or a plurality of underlayers 2, a magnetic domain control layer 3, a soft magnetic backing layer 4, an intermediate layer 5, a magnetic recording layer 6 and a protective layer 8 are sequentially formed on a nonmagnetic substrate 1. Further, a liquid lubricant layer 9 is formed thereon. Among these, the nonmagnetic substrate 1, the soft magnetic backing layer 4, the intermediate layer 5, the magnetic recording layer 6, the protective layer 8, and the liquid lubricant layer 9 have the same configuration as that of the second embodiment described above. it can.
[0017]
As the magnetic domain control layer 3, an antiferromagnetic film made of an alloy containing Mn or a hard magnetic film in which magnetization is oriented in the radial direction of the disk of the nonmagnetic substrate 1 can be used. The thickness of the magnetic domain control layer 3 is desirably 5 nm or more and 300 nm or less.
The underlayer 2 includes an orientation control layer for controlling the orientation of magnetization in at least the magnetic domain control layer 3. When a Mn alloy-based antiferromagnetic film is used as the magnetic domain control layer 3, it is desirable to use a single metal or alloy having a face-centered cubic structure as the underlayer 2. In that case, the underlayer 2 can include a further underlayer for controlling the fine structure of a layer made of a single metal or an alloy on the nonmagnetic substrate 1 side. When a hard magnetic film is used as the magnetic domain control layer 3, a Cr alloy or the like can be used as the underlayer 2. Also in this case, the underlayer 2 can include a plurality of further underlayers for controlling the fine structure of the layer made of a Cr alloy or the like on the nonmagnetic substrate 1 side.
[0018]
(Fourth embodiment)
In this embodiment, a nonmagnetic layer containing Ag is provided between the magnetic recording layer and the protective layer. FIG. 4 is a schematic cross-sectional view of a perpendicular magnetic recording medium according to this embodiment. The magnetic recording medium includes a nonmagnetic layer 7 including at least one or a plurality of underlayers 2, a magnetic domain control layer 3, a soft magnetic backing layer 4, an intermediate layer 5, a magnetic recording layer 6, and Ag on a nonmagnetic substrate 1. The protective layer 8 is formed in order, and the liquid lubricant layer 9 is further formed thereon. Among these, the nonmagnetic substrate 1, the underlayer 2, the magnetic domain control layer 3, the soft magnetic backing layer 4, the intermediate layer 5, the magnetic recording layer 6, the protective layer 8, and the liquid lubricant layer 9 are the third embodiment described above. It can be set as the structure similar to a form.
[0019]
The nonmagnetic layer 7 containing Ag is composed of an Ag single layer or an alloy layer mainly composed of Ag. By inserting the nonmagnetic layer 7 containing Ag, the recorded signal is further stabilized, so that higher density recording is possible. The film thickness of the nonmagnetic layer 7 containing Ag is preferably 0.5 nm or more and 2 nm or less. When the film thickness is thinner than 0.2 nm, the film thickness is too thin to obtain the effect of insertion sufficiently. On the other hand, when the thickness is greater than 2 nm, the distance between the magnetic recording head and the magnetic layer is too long, so that sufficient electromagnetic conversion characteristics cannot be realized.
Examples of the present invention will be described below. It should be noted that the following examples merely describe preferred representative examples of the present invention, and do not limit the present invention in any way.
[0020]
【Example】
Example 1
A chemically strengthened glass substrate (N-5 glass substrate manufactured by HOYA) having a smooth surface was used as a nonmagnetic substrate, and this was washed and introduced into a sputtering apparatus, and a Ti intermediate layer was formed to a thickness of 15 nm. Next, a magnetic recording layer was formed using a composite target in which an Ag chip was placed on a TbCo target. The ratio of adding Ag was adjusted by changing the number of chips placed on the target. When the magnetic recording layer is formed, the gas pressure in the vacuum apparatus is adjusted to 5 mTorr by adjusting the total flow rate of the film forming gas used during film formation and the opening of a valve provided between the vacuum apparatus and the vacuum pump. It was varied in the range of ~ 150 mTorr. The thickness of the magnetic recording layer was constant at 30 nm.
[0021]
Finally, a protective layer made of carbon was formed to a thickness of 5 nm, and then taken out from the vacuum apparatus. All the films other than the magnetic recording layer were formed by a DC magnetron sputtering method under a gas pressure of 5 mTorr. Thereafter, a liquid lubricant layer 2 nm made of perfluoropolyether was formed by a dip method to obtain a perpendicular magnetic recording medium.
The magnetic properties were calculated by measuring the magnetization curve with a vibrating sample magnetometer. The perpendicular magnetic anisotropy constant Ku was calculated from a magnetic torque curve measured in a plane including the normal direction of the substrate surface.
FIG. 5 shows changes in the coercive force Hc and the squareness ratio S of a medium manufactured by changing the addition amount of Ag. By adding 1 at% or more of Ag to the rare earth-transition metal alloy amorphous film, Hc increases rapidly, and a high value of 5000 Oe or more is obtained at an addition amount of about 5 at%. Further, by adding Ag, Hc gradually decreases, and by adding 20 at% or more, it becomes a small value of 3000 Oe or less. On the other hand, the squareness ratio S shows a good value of almost 1 until the addition amount of Ag is 15 at%, but it is understood that if the addition amount is more than that, the squareness ratio S decreases rapidly.
[0022]
FIG. 6 shows the dependence of the perpendicular magnetic anisotropy constant Ku of the same medium on the Ag addition amount. When Ag is not added, it is about 2 × 10 ⁶ erg / cc. However, when Ag is added, Ku rapidly increases, and when the added amount of Ag at which Hc reaches a maximum value is about 5 at%. It shows a considerably large value of 5 × 10 ⁶ erg / cc or more. Further, as the amount of Ag added increases, Ku decreases monotonously, and when 20 at% is added, it becomes a small value for a vertical medium of 1.5 × 10 ⁶ erg / cc or less. It can be seen that the tendency of the change in Hc with respect to the added amount of Ag shown in FIG. 5 reflects the change in Ku.
[0023]
Thus, it can be seen that good magnetic properties can be obtained by adding Ag to the amorphous film of the rare earth-transition metal alloy and making the addition amount 15 at% or less. FIG. 7 shows changes in coercivity Hc and squareness ratio S with respect to gas pressure. In the region where the gas pressure is 100 mTorr or less, a high value of Hc of 3000 Oe or more is obtained. The squareness ratio S also shows a good characteristic of almost 1 in a gas pressure region of 100 mTorr or less.
FIG. 8 shows the gas pressure dependence of the perpendicular magnetic anisotropy constant Ku of the same medium. At a gas pressure of 5 mTorr, a high value of 5.7 × 10 ⁶ erg / cc is shown. However, as the gas pressure increases, Ku decreases monotonously, and at 100 mTorr, it becomes 2.7 × 10 ⁶ erg / cc. Become. When the gas pressure becomes 150 mTorr, Ku becomes a small value of 1 × 10 ⁶ erg / cc or less.
[0024]
(Example 2)
The same nonmagnetic substrate as in Example 1 was used, and after cleaning, it was introduced into a sputtering apparatus. First, a soft magnetic backing layer having a thickness of 200 nm was formed using a CoZrNb target. Thereafter, an intermediate layer, a magnetic recording layer, a protective layer and a liquid lubricant layer were formed in the same manner as in Example 1 to produce a perpendicular magnetic recording medium having a structure as shown in FIG. The electromagnetic conversion characteristics of the perpendicular magnetic recording medium were measured with a GMR head using a spin stand tester.
FIG. 9 shows SNR (ratio of noise and signal of electromagnetic conversion characteristics) at a linear recording density of 350 kFCI of a perpendicular magnetic recording medium manufactured by changing the addition amount of Ag. When Ag is not added, the SNR is a low value of about 12 dB. This is because the signal is shifted because there is no nucleus for keeping the written signal in place. On the other hand, by adding 1 at% or more of Ag, nuclei are generated, and the SNR increases rapidly, showing a good value of 15 dB or more. However, when the addition amount is more than 15 at%, the SNR is drastically decreased. This is because the perpendicular magnetic anisotropy has been reduced by adding too much Ag. Therefore, it can be seen that the addition amount of Ag is preferably 1 at% or more and 15 at% or less.
[0025]
Next, FIG. 10 shows the SNR at a linear recording density of 350 kFCI of a perpendicular magnetic recording medium manufactured by changing the gas pressure. A good SNR of 15 dB or more is obtained when the deposition gas pressure is in the range of 10 mTorr to 100 mTorr. When the gas pressure is lower than 10 mTorr, the exchange interaction inside the magnetic recording layer is too strong, so that a signal cannot be written or a shift or the like occurs particularly at a high recording density, resulting in a poor SNR. On the other hand, when the gas pressure is higher than 100 mTorr, the perpendicular magnetic anisotropy is lowered, so that the SNR is deteriorated.
From these results, it can be seen that it is desirable that the addition amount of Ag in the amorphous film of the rare earth-transition metal alloy is 1 at% to 15 at% and the gas pressure is 10 mTorr to 100 mTorr.
[0026]
(Example 3)
The same nonmagnetic substrate as in Example 2 was used and introduced into the sputtering apparatus after cleaning. Then, before forming the soft magnetic backing layer, a 5 nm Ta film was formed on the nonmagnetic substrate as the first underlayer. Next, 5 nm of NiFeCr was formed as a second underlayer on the first underlayer. Next, IrMn was deposited to a thickness of 10 nm as a magnetic domain control layer on the second underlayer. Thereafter, in the same manner as in Example 2, a soft magnetic backing layer, an intermediate layer, a magnetic recording layer, a protective layer and a liquid lubricant layer were formed, and a perpendicular magnetic recording medium having a structure as shown in FIG. 3 was produced.
[0027]
FIG. 11 shows an output waveform for one round by a spin stand tester of a perpendicular magnetic recording medium. Among these, the waveform 1002 shows the output waveform for one round by the spin stand tester of the perpendicular magnetic recording medium according to the present embodiment. As a comparative example, an output waveform 1004 of a perpendicular magnetic recording medium according to Example 2 in which the underlayer and the magnetic domain control layer are not provided is also shown in the drawing. In the absence of the underlayer and the magnetic domain control layer, spike noise occurs non-uniformly over the entire circumference. On the other hand, it can be seen that spike noise is not generated at all by providing the base layer and the magnetic domain control layer. This is because in the case of the present embodiment, the domain wall is not formed in the soft magnetic underlayer by providing the underlayer and the magnetic domain control layer.
[0028]
Example 4
After using the same nonmagnetic substrate as in Example 3 and introducing it into the sputtering apparatus after cleaning, after forming the first underlayer, the second underlayer, the magnetic domain control layer, the soft magnetic backing layer, the intermediate layer, and the magnetic recording layer, An Ag layer was formed using an Ag target. Thereafter, in the same manner as in Example 3, a protective layer and a liquid lubricant layer were formed, and a perpendicular magnetic recording medium having a configuration as shown in FIG. 4 was produced. The film thickness of the Ag layer was changed from 0 to 5 nm.
FIG. 12 shows the SNR at a linear recording density of 350 kFCI of a perpendicular magnetic recording medium manufactured by changing the thickness of the Ag layer. When the Ag film thickness is thinner than 0.2 nm, only an SNR comparable to that obtained when no Ag film is inserted is obtained. This is because the effect of inserting the Ag film is not obtained because the film thickness is too thin. When the film thickness is 0.2 nm or more, the SNR increases rapidly and shows a maximum value of about 22 dB at 0.5 nm. This is an increase of about 1.5 dB compared to the case where no Ag layer is inserted. When the Ag film thickness is further increased, the SNR monotonously decreases. When the Ag film thickness is greater than 2 nm, the SNR value is smaller than when no Ag film is inserted. This is because the distance between the magnetic layer and the head is increased by inserting the Ag layer. Therefore, it can be seen that when the Ag layer is provided, the film thickness must be 0.2 nm or more and 2 nm or less.
[0029]
【The invention's effect】
As described above, according to the present invention, in a perpendicular magnetic recording medium in which at least an intermediate layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate, the magnetic recording layer has 2 at % Is a rare earth-transition metal alloy amorphous film to which 15 to 15 at% of Ag is added. Therefore , the coercive force Hc, the squareness ratio S, the perpendicular magnetic anisotropy constant Ku, and the SNR have good characteristics. A magnetic recording medium can be provided.
In addition, since the soft magnetic backing layer is provided between the nonmagnetic substrate and the intermediate layer, the magnetic flux generated by the magnetic head can be concentrated, and a steep magnetic field gradient can be formed in the magnetic recording layer. As a result, even better characteristics can be obtained.
[0030]
Further, since one or more underlayers and magnetic domain control layers are sequentially laminated between the nonmagnetic substrate and the soft magnetic backing layer, spike noise caused by the formation of the domain wall of the soft magnetic layer is completely eliminated. It can be suppressed, and is very preferable for practical use of a perpendicular magnetic recording medium.
Further, since the gas pressure when laminating the magnetic recording layers is 10 mTorr or more and 100 mTorr or less, a perpendicular magnetic recording medium exhibiting good characteristics can be manufactured.
Furthermore, better electromagnetic conversion characteristics can be obtained by inserting a nonmagnetic layer containing Ag between the magnetic recording layer and the protective layer.
Furthermore, the method for manufacturing a perpendicular magnetic recording medium according to the present invention can be performed using an existing manufacturing apparatus, and is therefore suitable for mass production of a large-capacity magnetic recording medium.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the configuration of a magnetic recording medium according to a first embodiment of the invention.
FIG. 2 is a schematic cross-sectional view showing a configuration of a magnetic recording medium according to a second embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing the configuration of a magnetic recording medium according to a third embodiment of the invention.
FIG. 4 is a schematic cross-sectional view showing a configuration of a magnetic recording medium according to a fourth embodiment of the present invention.
FIG. 5 is a graph showing the Ag concentration dependence of the magnetic characteristics of the perpendicular magnetic recording medium according to Example 1 of the present invention.
FIG. 6 is a graph showing the Ag concentration dependence of the perpendicular magnetic anisotropy constant of the perpendicular magnetic recording medium according to Example 1 of the present invention.
FIG. 7 is a graph showing the film formation gas pressure dependence of the magnetic characteristics of the perpendicular magnetic recording medium according to Example 1 of the present invention.
FIG. 8 is a graph showing the dependency of the perpendicular magnetic anisotropy constant of the perpendicular magnetic recording medium according to Example 1 of the present invention on the deposition gas pressure.
FIG. 9 is a graph showing the Ag concentration dependence of SNR of a perpendicular magnetic recording medium according to Example 2 of the present invention.
FIG. 10 is a graph showing the dependency of SNR on the deposition gas pressure of the perpendicular magnetic recording medium according to Example 2 of the present invention.
FIG. 11 is a diagram showing output waveforms for one round by a spin stand tester of a perpendicular magnetic recording medium according to Embodiment 3 of the present invention and a perpendicular magnetic recording medium according to Embodiment 2;
FIG. 12 is a graph showing the dependency of SNR on the Ag layer thickness of a perpendicular magnetic recording medium according to Example 4 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nonmagnetic base | substrate 2 Underlayer 3 Magnetic domain control layer 4 Soft magnetic backing layer 5 Intermediate layer 6 Magnetic recording layer 7 Nonmagnetic layer 8 containing Ag 8 Protective layer 9 Liquid lubricant layers 1002, 1004 Output waveform

Claims (6)

In a perpendicular magnetic recording medium in which at least an intermediate layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate , Ag of 2 at% or more and 15 at% or less is added to the magnetic recording layer. A perpendicular magnetic recording medium comprising an amorphous film of a rare earth-transition metal alloy. 2. The perpendicular magnetic recording medium according to claim 1, wherein a backing layer made of a soft magnetic material is provided between the nonmagnetic substrate and the intermediate layer. Wherein between the nonmagnetic substrate and the backing layer, to claim 2 in which one or more layers domain control layer for controlling the magnetic domain of the base layer and the backing layer is characterized by comprising sequentially laminated The perpendicular magnetic recording medium described. Said magnetic between the recording layer and the protective layer, a perpendicular magnetic recording medium according to any one of claims 1 to 3, characterized in that a nonmagnetic layer containing Ag. The perpendicular magnetic recording medium according to claim 4 , wherein a film thickness of the nonmagnetic layer containing Ag is not less than 0.2 nm and not more than 2 nm. The method of manufacturing the perpendicular magnetic recording medium according to any one of claims 1 to 5, the vertical magnetic recording medium you wherein gas pressure at the time of laminating the magnetic recording layer is less 100mTorr than 10mTorr Production method.

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