JP4611847B2 - Magnetic recording medium and magnetic recording / reproducing apparatus - Google Patents

Description

  The present invention relates to a magnetic recording medium, a manufacturing method thereof, and a magnetic recording / reproducing apparatus using the magnetic recording medium.

  In the perpendicular magnetic recording method, the demagnetizing field in the vicinity of the magnetization transition region, which is the boundary between recording bits, is achieved by orienting the easy axis of the magnetic recording layer that has been oriented in the in-plane direction of the medium in the perpendicular direction of the medium. Therefore, the higher the recording density, the more stable the magnetic field and the higher the resistance to thermal fluctuation, so that the method is suitable for improving the surface recording density.

  Further, when a backing layer made of a soft magnetic material is provided between the substrate and the perpendicular magnetic recording film, it functions as a so-called perpendicular two-layer medium, and high recording ability can be obtained. At this time, the soft magnetic underlayer plays a role of refluxing the recording magnetic field from the magnetic head, so that the recording / reproducing efficiency can be improved.

  In general, amorphous materials such as CoZrNb, CoTaZr, and FeCoB have been proposed as soft magnetic materials for forming the backing layer. Various materials have been proposed for the base film provided on the backing layer. For example, an hcp structure or fcc structure such as a Ti alloy (see Patent Document 1) or NiFeCr (see Patent Document 2), an amorphous structure such as Ta, or the like can be given.

When CoZrNb or CoTaZr is used as the material for the backing layer, a saturation magnetic flux density of only about 1.2 (T) can be obtained at maximum, and in order to have a sufficient role as the backing layer, 100 (nm) The above-described film thickness is required, and providing a backing layer having a film thickness of 100 nm or more is not preferable for producing a medium because it causes a decrease in throughput and a decrease in yield.
Furthermore, AFC (Anti-Ferro-Coupling) coupling is used in order to suppress external magnetic field resistance and the phenomenon of erasing a signal of a certain distance from a track (WATE, Wide-Area-Track-Erasure) when repeated signal recording is performed. When the structure is formed, the two layers of soft magnetic films that are AFC-bonded have a weak binding force, and thus cannot have sufficient resistance. A material mainly composed of Fe, such as FeCoB, can have a sufficient saturation magnetic field and, accordingly, external magnetic field resistance and WATE resistance, but there is a problem that corrosion of Fe occurs under high temperature and high humidity.

When a material having no magnetism is used for the base film, the distance between the magnetic head and the surface of the backing layer becomes longer due to the thickness of the base film, and it is necessary to increase the thickness of the backing layer in order to perform sufficient writing. By using a material having soft magnetic properties for the base film, both the role of the backing layer and the crystal orientation of the intermediate layer provided on the upper side can be controlled. However, according to studies by the present inventors, it has been found that when a Ni alloy or NiFe alloy material is used for the underlying film, the crystal orientation varies greatly depending on the Ni composition, the NiFe composition, and the material of the backing layer. I came.
Japanese Patent No. 2669529 JP 2003-123239 A

  Conventionally proposed media configurations are insufficient to obtain a magnetic recording medium with excellent recording / reproduction characteristics and productivity, and there is a demand for a magnetic recording medium that solves this problem and can be easily manufactured. It was.

  The present invention has been made in view of the above circumstances, and a magnetic recording medium capable of recording and reproducing high-density information by optimizing the material of the soft magnetic film and the material of the base film that form the backing layer, and An object of the present invention is to provide a magnetic recording / reproducing apparatus.

In order to achieve the above object, the present invention employs the following configuration.
(1) The magnetic recording medium of the present invention is a perpendicular magnetic recording medium having at least a backing layer, a base film, an intermediate film, and a perpendicular magnetic recording film on a nonmagnetic substrate, and the saturation of the soft magnetic film constituting the backing layer. The magnetic flux density Bs is 1.4 (T) or more, the soft magnetic film is made of an alloy obtained by adding at least one of Ta and Nb to CoFeHf, and the base film contains 80 at% or more of Ni. It is made of Ni alloy or NiFe alloy containing Ni of 50 at% or more , and an intermediate film of Ru or Ru alloy is provided thereon, and the Hf content of the soft magnetic film is 1 at% or more and 12 at% or less. To do.
(2) The magnetic recording medium of the present invention is characterized in that the soft magnetic film has an Hf content of 2 at% or more and 8 at% or less.
(3) The magnetic recording medium of the present invention is characterized in that the soft magnetic film further contains at least one of Al, Ni, and Cr.
(4) In the magnetic recording medium of the present invention, the backing layer is composed of two soft magnetic films and a nonmagnetic intermediate layer formed therebetween, and the two soft magnetic films are AFC (Anti-Ferro-Coupling). It is characterized by being connected.
(5) The magnetic recording medium of the present invention is characterized in that the nonmagnetic intermediate layer is made of Ru or a Ru alloy.

(6) The magnetic recording medium of the present invention is characterized in that the soft magnetic film has an amorphous structure.
(7) The magnetic recording medium of the present invention is characterized in that the content of Fe in the soft magnetic film is 5 at% or more and 40 at% or less.
(8) The magnetic recording medium of the present invention is characterized in that the thickness of the backing layer is 20 nm or more and 80 nm or less.
(9) The magnetic recording medium of the present invention is characterized in that the intermediate film has a thickness of 16 nm or less.
(10) The magnetic recording medium of the present invention is characterized in that the soft magnetic film is either CoFeHfTaAl or CoFeHfNbAl.
(11) A magnetic recording / reproducing apparatus of the present invention is a magnetic recording / reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording / reproducing information on the magnetic recording medium, wherein the magnetic head is a single pole head. The magnetic recording medium is the magnetic recording medium according to any one of the preceding items.

As described above, according to the present invention, in the perpendicular magnetic recording medium having at least the backing layer, the base film, the intermediate film, and the perpendicular magnetic recording film on the nonmagnetic substrate, the saturation of the soft magnetic film constituting the backing layer is achieved. The magnetic flux density Bs is 1.4 (T) or more, the soft magnetic film is made of an alloy obtained by adding at least one of Ta and Nb to CoFeHf, and the base film contains 80 at% or more of Ni. It is made of a Ni alloy or a NiFe alloy containing Ni at 50 at% or more , and an Ru or Ru alloy intermediate film is provided thereon, and the Hf content of the soft magnetic film is 1 at% or more and 12 at% or less. It is possible to provide a magnetic recording medium and a magnetic recording / reproducing apparatus that are excellent in performance and capable of recording and reproducing high-density information.

FIG. 1 shows an example of the first embodiment of the magnetic recording medium of the present invention.
The magnetic recording medium A shown here is a backing comprising a first soft magnetic film 2, a nonmagnetic intermediate layer 3 made of Ru, and a second soft magnetic film 4 on a nonmagnetic substrate 1. A layer a is provided, and a base film 5, an intermediate film 6, a perpendicular magnetic recording film 7, a protective film 8, and a lubricating film 9 are sequentially formed.

In the present embodiment, the nonmagnetic substrate 1 may be a metal substrate made of a metal material such as aluminum or an aluminum alloy, or a nonmetal substrate made of a nonmetal material such as glass, ceramic, silicon, silicon carbide, or carbon. May be used.
In this embodiment mode, amorphous glass and crystallized glass can be used as the glass substrate, and general-purpose soda lime glass and aluminosilicate glass can be used as the amorphous glass. Further, as the crystallized glass, lithium-based crystallized glass can be used.

The nonmagnetic substrate 1 preferably has an average surface roughness Ra of 0.8 nm or less, preferably 0.5 nm or less in order to improve the crystal orientation of the nonmagnetic intermediate layer 3 and the perpendicular magnetic recording film 7. The recording / reproducing characteristics can be improved, and it is desirable that the magnetic head is suitable for high recording density recording, which preferably has a low flying height.
Further, the fine waviness (Wa) on the surface of the nonmagnetic substrate 1 is preferably 0.3 nm or less (more preferably 0.25 nm or less) from the viewpoint of suitable for high recording density recording with a magnetic head flying low. .

  The backing layer a includes two soft magnetic films 2 and 4 and a Ru nonmagnetic intermediate layer 3 formed between the two soft magnetic films 2 and 4. . The soft magnetic films 2 and 4 above and below the Ru non-magnetic intermediate layer 3 are AFC (Anti-Ferro-Coupling) coupled via the non-magnetic intermediate layer 3. With this configuration, an external magnetic field is prevented. And resistance to a WATE (Wide-Area-Track-Erasure) phenomenon, which is a problem peculiar to perpendicular magnetic recording.

In the structure of this embodiment, the soft magnetic films 2 and 4 are made of a CoFeHf alloy and have a saturation magnetic flux density Bs of 1.4 (T) or more. By using this material, a high saturation magnetic flux density and high corrosion resistance can be obtained, and excellent recording / reproducing characteristics can be obtained when NiFe having a predetermined composition is used for the base film.
In the soft magnetic films 2 and 4, the amount of Hf added is preferably 1 at% or more and 12 at% or less (preferably 2 at% or more and 8 at% or less). If the amount of Hf added in the soft magnetic films 2 and 4 is less than 1 at%, the orientation of NiFe becomes insufficient and excellent recording / reproducing characteristics cannot be obtained, which is not preferable. Conversely, if the amount of Hf added exceeds 12 at%, the saturation magnetic flux density Bs is not preferable.

Furthermore, it is preferable to add either Ta or Nb to CoFeHf constituting the soft magnetic films 2 and 4. These elements are preferable for promoting the amorphization of the soft magnetic films 2 and 4. Moreover, it is preferable because the orientation of the nonmagnetic intermediate layer 3 provided between them is improved.
The amount of Ta and Nb added to CoFeHf constituting the soft magnetic films 2 and 4 is preferably 7 at% or less. Addition exceeding 7 at% is not preferable because the saturation magnetic flux density Bs decreases. The total amount of Hf, Ta and Nb is preferably 15 at% (preferably 12 at% or less, more preferably 10 at% or less).

Al, Ni, and Cr added to the soft magnetic films 2 and 4 are added to improve the corrosivity of the soft magnetic films 2 and 4 themselves, and the addition amount is preferably less than 5 at%. Although the corrosion resistance improves as the amount added increases, it is not preferable that the amount added be 5 at% or more because the saturation magnetic flux density decreases.
The Fe content of the soft magnetic films 2 and 4 is preferably 5 at% or more and 40 at% or less. If the Fe content is less than 5 at%, the saturation magnetic flux density Bs is low, which is not preferable. If the Fe content exceeds 40 at%, the corrosivity deteriorates, which is not preferable.

  The thickness of the backing layer a (the total thickness of the first soft magnetic film 2, the nonmagnetic intermediate layer 3, and the second soft magnetic film 4) is preferably 20 nm or more and 80 nm or less. If the thickness of the backing layer a is less than 20 nm, it is not preferable because the magnetic flux from the magnetic head cannot be sufficiently absorbed, writing becomes insufficient and the recording / reproducing characteristics deteriorate. When the thickness of the backing layer a exceeds 80 nm, productivity is remarkably lowered, which is not preferable.

  When CoFeHfTaAl, CoFeHfTaCr, CoFeHfNbAl, or CoFeHfNbCr is used as the material of the soft magnetic films 2 and 4, the orientation of NiFe having a predetermined composition provided thereon can be increased and the thickness of the intermediate film 6 can be increased. As a result, the thickness of the soft magnetic films 2 and 4 can be reduced. Therefore, it is possible to achieve both good recording / reproduction characteristics and productivity.

It is particularly preferable that the soft magnetic films 2 and 4 have an amorphous structure. This is because the amorphous structure prevents the surface roughness Ra from increasing, reduces the flying height of the magnetic head, and further increases the recording density.
Hbias, which is an index indicating the magnitude of AFC coupling between the two soft magnetic films 2 and 4 constituting the backing layer a, is preferably 80 (Oe) or more.
This Hbias will be described below with reference to FIG.
FIG. 2 shows the MH loop of the substrate in-plane component of the backing layer a (the direction of easy magnetization of the soft magnetic films 2 and 4 forming the backing layer). A saturation magnetic flux density is defined as Ms, and a magnetic field that is Ms / 2 that is half of the saturation magnetic flux density Ms is defined as Hbias. Using the above materials as the soft magnetic films 2 and 4, the nonmagnetic intermediate layer 3 of Ru provided between the two soft magnetic films has a predetermined thickness (0.6 to 0.8 nm). Thus, Hbias of 80 (Oe) or more can be obtained. As a result, it is possible to increase external magnetic field resistance and WATE resistance.

The coercive force Hc of the soft magnetic films 2 and 4 is preferably 10 (Oe) or less (preferably 10 (Oe) or less). Note that 1 (Oe) is about 79 A / m.
As a method of forming the soft magnetic films 2 and 4, a sputtering method can be used.
When the soft magnetic films 2 and 4 constituting the backing layer a are formed, it is preferable to form the films while applying a magnetic field in the radial direction of the substrate.

  The base film 5 is for controlling the orientation and crystal size of the perpendicular magnetic recording film 7 provided thereon. The undercoat film 5 is preferably a Ni alloy containing 80 at% or more of Ni or a NiFe alloy containing 50% or more of Ni. If the Ni content is less than 50 at%, the value of Δθ50 indicating the (111) crystal orientation of NiFe increases and crystal orientation deteriorates. As a result, recording / reproduction characteristics deteriorate, which is not preferable.

An element can be added to the Ni alloy or NiFe alloy constituting the base film 5 for the purpose of reducing the crystal size and improving the matching of the crystal lattice size with the intermediate film 6. B and Mn are particularly preferable for the purpose of reducing the crystal size. The content of B and Mn is preferably 6 (at%) or less. Further, Ru, Pt, W, Mo, Ta, Nb, etc. may be added for the purpose of improving the consistency of the crystal lattice size with the intermediate film 6.
The saturation magnetic flux density Bs of the Ni alloy or the NiFe alloy constituting the base film 5 is preferably 0.4 (T) or more. If it is less than 0.4 (T), the function as a part of the backing layer becomes weak at the time of writing, which is not preferable because the recording / reproducing characteristics are deteriorated.
The film thickness of the base film 5 is preferably 1 (nm) or more and 10 (nm) or less. If the base film 5 is less than 1 (nm), the effect as the base film 5 becomes insufficient, the effect of reducing the grain size cannot be obtained, and the orientation deteriorates, which is not preferable. On the other hand, if the thickness of the base film 5 exceeds 10 (nm), the crystal size increases, which is not preferable.

The intermediate film 6 is preferably made of Ru or a Ru alloy.
The thickness of the intermediate film 6 is preferably 16 nm or less (preferably 12 nm or less). This thickness can be achieved by using a CoFeHf alloy for the soft magnetic films 2 and 4 and a Ni alloy or NiFe alloy having a predetermined composition for the base film 5. By making the intermediate film 6 thin, the distance between the magnetic head and the backing layer a is reduced, and the magnetic flux can be made steep. As a result, if the magnetic flux equivalent to the conventional one is sufficient, the thickness of the soft magnetic films 2 and 4 can be further reduced, and the productivity can be improved.

The perpendicular magnetic recording film 7 has an easy magnetization axis perpendicular to the substrate surface. The perpendicular magnetic recording film 7 contains at least Co and Pt as constituent elements, and oxides, Cr, B, Cu, Ta, and Zr can be added for the purpose of improving SNR characteristics.
Examples of the oxide constituting the perpendicular magnetic recording film 7 include SiO ₂ , SiO, Cr ₂ O ₃ , CoO, Ta ₂ O ₃ , and TiO ₂ . The volume ratio of the oxide is preferably 15 to 40% by volume. If the volume ratio of the oxide is less than 15% by volume, the SNR characteristic becomes insufficient, which is not preferable. When the volume ratio of the oxide exceeds 40% by volume, it is not preferable because a coercive force sufficient for a high recording density cannot be obtained.
The nucleation magnetic field (-Hn) of the perpendicular magnetic recording film 7 is preferably 2.0 (kOe) or more. It is not preferable that -Hn is less than 2.0 (kOe) because thermal fluctuation occurs.
The thickness of the perpendicular magnetic recording film 7 is preferably 6 to 20 nm. When the thickness of the perpendicular magnetic recording film 7 when viewed as an oxide granular layer is within this range, it is preferable because sufficient output can be secured and OW (overwrite) characteristics do not deteriorate.
The perpendicular magnetic recording film 7 can have a single-layer structure or a structure of two or more layers made of materials having different compositions.

The protective film 8 is for preventing corrosion of the perpendicular magnetic recording film 7 and preventing damage to the surface of the medium when the magnetic head comes into contact with the medium. A conventionally known material can be used, for example, C, SiO _2. And those containing ZrO ₂ can be used. The thickness of the protective film 8 is preferably 1 nm or more and 5 nm or less because the distance between the magnetic head and the medium can be reduced, so that a high recording density is achieved.
The lubricating film 9 is preferably made of a conventionally known material such as perfluoropolyether, fluorinated alcohol, fluorinated carboxylic acid or the like.

  In the magnetic recording medium A of the present embodiment, in the perpendicular magnetic recording medium having at least the backing layer a, the base film 5, the intermediate film 6, and the perpendicular magnetic recording film 7 on the nonmagnetic substrate 1, the backing layer is used. Since the soft magnetic films 2 and 4 constituting a are made of a CoFeHf alloy having a saturation magnetic flux density Bs of 1.4 (T) or more, and the base film 5 is made of a Ni alloy or a NiFe alloy, the productivity is excellent. A magnetic recording medium capable of recording and reproducing high-density information.

FIG. 3 shows an example of a magnetic recording / reproducing apparatus 12 using the magnetic recording medium A.
The magnetic recording / reproducing apparatus 12 shown here includes a magnetic recording medium 10, a medium driving unit 13 that rotationally drives the magnetic recording medium 10, a magnetic head 14 that records and reproduces information on the magnetic recording medium 10, and a head driving unit 15. And a recording / reproducing signal processing system 16. The recording / reproducing signal processing system 16 can process the input data and send the recording signal to the magnetic head 14, or can process the reproducing signal from the magnetic head 14 and output the data.

  According to the magnetic recording / reproducing apparatus 12 shown in FIG. 3, a perpendicular magnetic recording medium A having at least a backing layer a, a base film 5, an intermediate film 6 and a perpendicular magnetic recording film 7 is provided on a nonmagnetic substrate 1, and this perpendicular recording medium A is provided. Since the magnetic recording medium A is a magnetic recording medium A that is excellent in productivity as described above and can record and reproduce high-density information by the magnetic head 14, magnetic recording capable of recording and reproducing high-density information. A playback device 12 can be provided.

Hereinafter, an example is shown and the operation effect of the present invention is clarified. However, the present invention is not limited to the following examples.
(Example 1: Sample 1)
A glass substrate (MYG amorphous substrate MEL3, diameter 2.5 inches) is accommodated in a film formation chamber of a DC magnetron sputtering apparatus (Anelva C-3010), and the ultimate vacuum is 1 × 10 ⁻⁵ Pa. The inside of the film forming chamber was evacuated. 69Co-20Fe-5Hf-4Ta-2Al (Co content 69 at%, Fe content 20 at%, Hf content 5 at%, Ta content 4 at%, Al content 2 at% as a first soft magnetic film on this substrate. ) To a thickness of 30 nm, and then a Ru film as a nonmagnetic intermediate layer to a thickness of 0.8 nm, and then as a second soft magnetic film, 69Co-20Fe-5Hf-4Ta- A 2Al composition film was formed to a thickness of 30 nm to form a backing layer.
It was confirmed by XRD that the crystal structure of the obtained soft magnetic film was an amorphous structure.

Next, a film having a composition of 80Ni-20Fe as a base film is 5 nm thick, a film of Ru as an intermediate film is 12 nm thick, and a film of a composition of 60Co-10Cr-20Pt-10SiO ₂ as a perpendicular magnetic recording film is 10 nm thick, A film having a composition of 65Co-18Cr-14Pt-3B was formed to a thickness of 6 nm.
Next, a protective film having a thickness of 4 nm was formed by a CVD method.
Next, a lubricating film made of perfluoropolyether was formed by a dipping method to obtain a perpendicular magnetic recording medium.

(Comparative Example 1-3)
Of the films formed in Example 1, a magnetic recording medium was manufactured in accordance with Example 1 except that the material of the soft magnetic film was CoZrNb, CoTaZr, or CoFeB.
(Comparative Examples 4 and 5)
Of the films formed in Example 1, a magnetic recording medium was manufactured according to Example 1 except that Ta and Pt were used as the material for the base film.

Each sample of these examples and the magnetic recording medium of the comparative example were evaluated for magnetostatic characteristics and recording / reproducing characteristics. The Kerr effect measuring device manufactured by Neoarc was used for evaluation of the magnetostatic characteristics, and the recording / reproducing characteristics were measured using a read / write analyzer RWA1632 manufactured by GUZIK, USA, and a spin stand S1701MP.
For the evaluation of the recording / reproducing characteristics, the recording frequency condition was measured at a linear recording density of 1000 kFCI using a magnetic head using a single pole magnetic pole for writing and a GMR element for the reproducing part. The overwrite characteristic (OW) characteristic was evaluated by measuring the remainder of the first signal after writing a signal of 67 kFCI after writing a signal of 500 kFCI. The evaluation results are shown in Table 1 below.

In Example (Sample) 1 shown in Table 1, the holding power (Hc) was increased as compared with Comparative Example 1-2, and it was confirmed that it exceeded the SNR. It was found that excellent recording / reproducing characteristics can be obtained even when the Ru intermediate film is as thin as 12 nm. Further, it was found that when a material with low Bs such as CoZrNb or CoTaZr was used, the overwrite (OW) characteristics were lowered, suggesting that the thickness was insufficient.
Sample 1 has an increased holding force (Hc) as compared to Comparative Example 3-4, an SNR exceeding, an excellent overwrite (OW) characteristic, and an excellent recording signal width. Was confirmed. In addition, it was found that the distance between the magnetic head and the backing layer was reduced by using the NiFe alloy base film, which is a soft magnetic material, so that the NiFe alloy as the base functioned as a soft magnetic film. Further, from the comparison of the track widths of the sample 1 using the NiFe alloy base film and the samples of Comparative Examples 3 and 4 using the Ta or Pt base film, the sample 1 using the NiFe alloy base film was obtained. It was found that the sample can increase the number of signals in the track direction and increase the signal density per area by reducing the width of the recording signal.

(Samples 2-11)
A magnetic recording medium was manufactured according to Example 1 except that the composition of the soft magnetic film was changed. The evaluation results are shown in Table 2 below.

Samples having any composition of Samples 2 to 12 listed in Table 2 were able to obtain excellent characteristics.
Comparing samples 2 to 5, a saturation magnetic flux density of 1.42 to 1.63 (T) can be obtained by setting the content of Hf in the range of 1 to 12 at%, but as the content of Hf increases, The saturation magnetic flux density decreases to 1.42 (T) at 12 at%, and the recording / reproduction characteristic SNR also tends to decrease. Therefore, the upper limit of the Hf content is the saturation magnetic flux density 1.4 (T) intended by the present invention. It can be seen that it is 12 at% from the condition that it is necessary. It can be seen that the saturation magnetic flux density is higher and the recording / reproducing characteristic SNR is also better if the Hf content is in the range of 2-8 at% even within the range of 1-12 at%.
Further, from the results shown in Table 2, it has been clarified that excellent magnetic properties can be obtained even when Ta, Al, Nb, Cr, and Ni are added to the Co—Fe—Hf alloy constituting the soft magnetic film. .

(Samples 12, 13)
A magnetic recording medium was prepared according to Sample 1 except that the thickness of the soft magnetic film was changed. The evaluation results are shown in Table 3 below.

  From the results shown in Table 3, Samples 1, 13, and 14 (thicknesses 60, 20, and 80 nm) having a soft magnetic film thickness of 20 nm or more were able to obtain excellent characteristics, but the thickness was 15 nm. Sample b was slightly degraded in properties.

(Sample 14-20)
A magnetic recording medium was prepared according to Sample 1 except that the composition and thickness of the NiFe alloy as the underlayer were changed. The evaluation results are shown in Table 4 below.

  From Table 4, all the samples 15 to 21 which are NiFe alloys containing Ni at 50 at% or more were able to obtain excellent characteristics. In addition, samples 22 to 26, which are Ni alloys containing 80 at% or more of Ni, also obtained excellent characteristics.

(Samples 21-32)
A magnetic recording medium was prepared according to Sample 1 except that the material and thickness of the intermediate film were changed. The evaluation results are shown in Table 5 below.

  From Table 5, it replaces with 100at% Ru, the intermediate film of the composition which substituted 10-20at% of Ru for either Co, Cr, Mn, Al, and Mo, or the thickness of an intermediate film is 8-25 nm Although the samples were changed in the range, excellent characteristics could be obtained in any case.

FIG. 1 is a cross-sectional view showing a first embodiment of a magnetic recording medium according to the present invention. FIG. 2 is a diagram showing an MH loop of an in-plane component of the backing layer applied to the magnetic recording medium according to the present invention. FIG. 3 is a block diagram showing an example of a magnetic recording / reproducing apparatus provided with a magnetic recording medium according to the present invention.

Explanation of symbols

A magnetic recording medium a backing layer 1 nonmagnetic substrate 2 first soft magnetic film 3 intermediate film 4 second soft magnetic film 5 underlayer 6 intermediate film 7 perpendicular magnetic recording film 8 protective film

Claims (11)

In a perpendicular magnetic recording medium having at least a backing layer, a base film, an intermediate film, and a perpendicular magnetic recording film on a nonmagnetic substrate, the saturation magnetic flux density Bs of the soft magnetic film constituting the backing layer is 1.4 (T) or more. And the soft magnetic film is made of an alloy obtained by adding at least one of Ta and Nb to CoFeHf, and the base film is a Ni alloy containing 80 at% or more of Ni or a NiFe alloy containing 50 at% or more of Ni. A magnetic recording medium comprising: an intermediate film of Ru or Ru alloy formed thereon, wherein the soft magnetic film has an Hf content of 1 at% to 12 at%.   2. The magnetic recording medium according to claim 1, wherein the soft magnetic film has an Hf content of 2 at% or more and 8 at% or less.   The magnetic recording medium according to claim 1, wherein the soft magnetic film further contains at least one of Al, Ni, and Cr.   The backing layer is composed of two soft magnetic films and a nonmagnetic intermediate layer formed therebetween, and the two soft magnetic films are AFC (Anti-Ferro-Coupling) coupled. The magnetic recording medium according to any one of 1 to 3.   The magnetic recording medium according to claim 4, wherein the nonmagnetic intermediate layer is made of Ru or a Ru alloy.   The magnetic recording medium according to claim 1, wherein the soft magnetic film has an amorphous structure.   The magnetic recording medium according to claim 1, wherein the soft magnetic film has an Fe content of 5 at% or more and 40 at% or less.   The magnetic recording medium according to any one of claims 1 to 7, wherein the thickness of the backing layer is 20 nm or more and 80 nm or less.   The magnetic recording medium according to claim 1, wherein the intermediate film has a thickness of 16 nm or less.   10. The magnetic recording medium according to claim 1, wherein the soft magnetic film is one of CoFeHfTaAl or CoFeHfNbAl.   11. A magnetic recording / reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording / reproducing information on / from the magnetic recording medium, wherein the magnetic head is a single pole head, and the magnetic recording medium comprises: A magnetic recording / reproducing apparatus according to any one of the above.

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